Mapping of chlorophyll a distributions in coastal zones

NASA Technical Reports Server (NTRS)

Johnson, R. W.

1978-01-01

It is pointed out that chlorophyll a is an important environmental parameter for monitoring water quality, nutrient loads, and pollution effects in coastal zones. High chlorophyll a concentrations occur in areas which have high nutrient inflows from sources such as sewage treatment plants and industrial wastes. Low chlorophyll a concentrations may be due to the addition of toxic substances from industrial wastes or other sources. Remote sensing provides an opportunity to assess distributions of water quality parameters, such as chlorophyll a. A description is presented of the chlorophyll a analysis and a quantitative mapping of the James River, Virginia. An approach considered by Johnson (1977) was used in the analysis. An application of the multiple regression analysis technique to a data set collected over the New York Bight, an environmentally different area of the coastal zone, is also discussed.

Monochromatic body waves excited by great subduction zone earthquakes

NASA Astrophysics Data System (ADS)

Ihmlé, Pierre F.; Madariaga, Raúl

Large quasi-monochromatic body waves were excited by the 1995 Chile Mw=8.1 and by the 1994 Kurile Mw=8.3 events. They are observed on vertical/radial component seismograms following the direct P and Pdiff arrivals, at all azimuths. We devise a slant stack algorithm to characterize the source of the oscillations. This technique aims at locating near-source isotropic scatterers using broadband data from global networks. For both events, we find that the oscillations emanate from the trench. We show that these monochromatic waves are due to localized oscillations of the water column. Their period corresponds to the gravest ID mode of a water layer for vertically traveling compressional waves. We suggest that these monochromatic body waves may yield additional constraints on the source process of great subduction zone earthquakes.

Unconsidered sporadic sources of carbon dioxide emission from soils in taiga forests.

PubMed

Karelin, D V; Zamolodchikov, D G; Isaev, A S

2017-07-01

Long-term monitoring in the Russian taiga zone has shown that all known extreme destructive effects resulting in the weakening and death of tree stands (windfalls, pest attacks, drought events, etc.) can be sporadic, but significant sources of CO 2 soil emission. Among them are (i) a recently found effect of the multiyear CO 2 emission from soil at the bottom of deadwood of spruce trees that died due to climate warming and subsequent pest outbreaks, (ii) increased soil CO 2 emissions due to to the fall of tree trunks during massive windfalls, and (iii) pulse CO 2 emission as a result of the so-called Birch effect after drought events in the taiga zone. According to the modeling, while depending on the spatial and temporal scales of their manifestation, the impact of these sporadic effects on the regional and global soil respiration fluxes could be significant and should be taken into consideration. This is due to continuing Climate Change, and further increase of local, regional and Global human impacts on the atmospheric greenhouse gases balance, and land use, as well.

Magnetospheric electrons

NASA Technical Reports Server (NTRS)

Coroniti, F. V.; Thorne, R. M.

1972-01-01

Coupling of source, transport, and sink processes produces a fairly accurate model for the macroscopic structure and dynamics of magnetospheric electrons. Auroral electrons are controlled by convective transport from a plasma sheet source coupled with a precipitation loss due to whistler and electrostatic plasma turbulence. Outer and inner zone electrons are governed by radial diffusion transport from convection and acceleration sources external to the plasmapause and by parasitic precipitation losses arising from cyclotron and Landau interactions with whistler and ion cyclotron turbulence.

Persulfate injection into a gasoline source zone.

PubMed

Sra, Kanwartej S; Thomson, Neil R; Barker, Jim F

2013-07-01

One pore volume of unactivated sodium persulfate was delivered into an emplaced gasoline residual source zone at CFB Borden. Concentrations of inorganic species (S2O8(2-), SO4(2-), Na(+), dissolved inorganic carbon (DIC)) and selected gasoline compounds (benzene, toluene, ethylbenzene, xylenes, trimethylbenzenes and naphthalene) were monitored across a transect equipped with 90 multilevel sampling points for >10months post-injection. Mass loading (M˙) of compounds constructed from the transect data was used for assessment purposes. Breakthrough of inorganic species was observed when the injection slug crossed the monitoring transect. An increase in [Formula: see text] indicated persulfate consumption during oxidation of gasoline compounds or degradation due to the interaction with aquifer materials. M˙DIC increased by >100% suggesting some mineralization of gasoline compounds during treatment. Mass loading for all the monitored gasoline compounds reduced by 46 to 86% as the inorganic slug crossed the monitoring transect. The cumulative mass discharge across the monitoring transect was 19 to 58% lower than that expected without persulfate injection. After the inorganic injection slug was flushed from the source zone a partial rebound (40 to 80% of baseline levels) of mass discharge of the monitored gasoline compounds was observed. The ensemble of data collected provides insight into the fate and transport of the injected persulfate solution, and the accompanying treatment of a gasoline the source zone. Copyright © 2013 Elsevier B.V. All rights reserved.

Modeling hyporheic zone processes

USGS Publications Warehouse

Runkel, Robert L.; McKnight, Diane M.; Rajaram, Harihar

2003-01-01

Stream biogeochemistry is influenced by the physical and chemical processes that occur in the surrounding watershed. These processes include the mass loading of solutes from terrestrial and atmospheric sources, the physical transport of solutes within the watershed, and the transformation of solutes due to biogeochemical reactions. Research over the last two decades has identified the hyporheic zone as an important part of the stream system in which these processes occur. The hyporheic zone may be loosely defined as the porous areas of the stream bed and stream bank in which stream water mixes with shallow groundwater. Exchange of water and solutes between the stream proper and the hyporheic zone has many biogeochemical implications, due to differences in the chemical composition of surface and groundwater. For example, surface waters are typically oxidized environments with relatively high dissolved oxygen concentrations. In contrast, reducing conditions are often present in groundwater systems leading to low dissolved oxygen concentrations. Further, microbial oxidation of organic materials in groundwater leads to supersaturated concentrations of dissolved carbon dioxide relative to the atmosphere. Differences in surface and groundwater pH and temperature are also common. The hyporheic zone is therefore a mixing zone in which there are gradients in the concentrations of dissolved gasses, the concentrations of oxidized and reduced species, pH, and temperature. These gradients lead to biogeochemical reactions that ultimately affect stream water quality. Due to the complexity of these natural systems, modeling techniques are frequently employed to quantify process dynamics.

Characteristics of large three-dimensional heaps of particles produced by ballistic deposition from extended sources

NASA Astrophysics Data System (ADS)

Topic, Nikola; Gallas, Jason A. C.; Pöschel, Thorsten

2013-11-01

This paper reports a detailed numerical investigation of the geometrical and structural properties of three-dimensional heaps of particles. Our goal is the characterization of very large heaps produced by ballistic deposition from extended circular dropping areas. First, we provide an in-depth study of the formation of monodisperse heaps of particles. We find very large heaps to contain three new geometrical characteristics: they may display two external angles of repose, one internal angle of repose, and four distinct packing fraction (density) regions. Such features are found to be directly connected with the size of the dropping zone. We derive a differential equation describing the boundary of an unexpected triangular packing fraction zone formed under the dropping area. We investigate the impact that noise during the deposition has on the final heap structure. In addition, we perform two complementary experiments designed to test the robustness of the novel features found. The first experiment considers changes due to polydispersity. The second checks what happens when letting the extended dropping zone to become a point-like source of particles, the more common type of source.

NAPL source zone depletion model and its application to railroad-tank-car spills.

PubMed

Marruffo, Amanda; Yoon, Hongkyu; Schaeffer, David J; Barkan, Christopher P L; Saat, Mohd Rapik; Werth, Charles J

2012-01-01

We developed a new semi-analytical source zone depletion model (SZDM) for multicomponent light nonaqueous phase liquids (LNAPLs) and incorporated this into an existing screening model for estimating cleanup times for chemical spills from railroad tank cars that previously considered only single-component LNAPLs. Results from the SZDM compare favorably to those from a three-dimensional numerical model, and from another semi-analytical model that does not consider source zone depletion. The model was used to evaluate groundwater contamination and cleanup times for four complex mixtures of concern in the railroad industry. Among the petroleum hydrocarbon mixtures considered, the cleanup time of diesel fuel was much longer than E95, gasoline, and crude oil. This is mainly due to the high fraction of low solubility components in diesel fuel. The results demonstrate that the updated screening model with the newly developed SZDM is computationally efficient, and provides valuable comparisons of cleanup times that can be used in assessing the health and financial risk associated with chemical mixture spills from railroad-tank-car accidents. © 2011, The Author(s). Ground Water © 2011, National Ground Water Association.

Review of unsaturated-zone transport and attenuation of volatile organic compound (VOC) plumes leached from shallow source zones

NASA Astrophysics Data System (ADS)

Rivett, Michael O.; Wealthall, Gary P.; Dearden, Rachel A.; McAlary, Todd A.

2011-04-01

Reliable prediction of the unsaturated zone transport and attenuation of dissolved-phase VOC (volatile organic compound) plumes leached from shallow source zones is a complex, multi-process, environmental problem. It is an important problem as sources, which include solid-waste landfills, aqueous-phase liquid discharge lagoons and NAPL releases partially penetrating the unsaturated zone, may persist for decades. Natural attenuation processes operating in the unsaturated zone that, uniquely for VOCs includes volatilisation, may, however, serve to protect underlying groundwater and potentially reduce the need for expensive remedial actions. Review of the literature indicates that only a few studies have focused upon the overall leached VOC source and plume scenario as a whole. These are mostly modelling studies that often involve high strength, non-aqueous phase liquid (NAPL) sources for which density-induced and diffusive vapour transport is significant. Occasional dissolved-phase aromatic hydrocarbon controlled infiltration field studies also exist. Despite this lack of focus on the overall problem, a wide range of process-based unsaturated zone — VOC research has been conducted that may be collated to build good conceptual model understanding of the scenario, particularly for the much studied aromatic hydrocarbons and chlorinated aliphatic hydrocarbons (CAHs). In general, the former group is likely to be attenuated in the unsaturated zone due to their ready aerobic biodegradation, albeit with rate variability across the literature, whereas the fate of the latter is far less likely to be dominated by a single mechanism and dependent upon the relative importance of the various attenuation processes within individual site — VOC scenarios. Analytical and numerical modelling tools permit effective process representation of the whole scenario, albeit with potential for inclusion of additional processes — e.g., multi-mechanistic sorption phase partitioning, and provide good opportunity for further sensitivity analysis and development to practitioner use. There remains a significant need to obtain intermediate laboratory-scale and particularly field-scale (actual site and controlled release) datasets that address the scenario as a whole and permit validation of the available models. Integrated assessment of the range of simultaneous processes that combine to influence leached plume generation, transport and attenuation in the unsaturated zone is required. Component process research needs are required across the problem scenario and include: the simultaneous volatilisation and dissolution of source zones; development of appropriate field-scale dispersion estimates for the unsaturated zone; assessment of transient VOC exchanges between aqueous, vapour and sorbed phases and their influence upon plume attenuation; development of improved field methods to recognise and quantify biodegradation of CAHs; establishment of the influence of co-contaminants; and, finally, translation of research findings into more robust practitioner practice.

GIS-Mapping and Statistical Analyses to Identify Climate-Vulnerable Communities and Populations Exposed to Superfund Sites

EPA Science Inventory

Climate change-related cumulative health risks are expected to be disproportionately greater for overburdened communities, due to differential proximity and exposures to chemical sources and flood zones. Communities and populations vulnerable to climate change-associated impacts ...

Characterization and Remediation of Chlorinated Volatile Organic Contaminants in the Vadose Zone: An Overview of Issues and Approaches

PubMed Central

Brusseau, Mark L.; Carroll, Kenneth C.; Truex, Michael J.; Becker, David J.

2014-01-01

Contamination of vadose-zone systems by chlorinated solvents is widespread, and poses significant potential risk to human health through impacts on groundwater quality and vapor intrusion. Soil vapor extraction (SVE) is the presumptive remedy for such contamination, and has been used successfully for innumerable sites. However, SVE operations typically exhibit reduced mass-removal effectiveness at some point due to the impact of poorly accessible contaminant mass and associated mass-transfer limitations. Assessment of SVE performance and closure is currently based on characterizing contaminant mass discharge associated with the vadose-zone source, and its impact on groundwater or vapor intrusion. These issues are addressed in this overview, with a focus on summarizing recent advances in our understanding of the transport, characterization, and remediation of chlorinated solvents in the vadose zone. The evolution of contaminant distribution over time and the associated impacts on remediation efficiency will be discussed, as will the potential impact of persistent sources on groundwater quality and vapor intrusion. In addition, alternative methods for site characterization and remediation will be addressed. PMID:25383058

Modeling the effects of source and path heterogeneity on ground motions of great earthquakes on the Cascadia Subduction Zone Using 3D simulations

USGS Publications Warehouse

Delorey, Andrew; Frankel, Arthur; Liu, Pengcheng; Stephenson, William J.

2014-01-01

We ran finite‐difference earthquake simulations for great subduction zone earthquakes in Cascadia to model the effects of source and path heterogeneity for the purpose of improving strong‐motion predictions. We developed a rupture model for large subduction zone earthquakes based on a k−2 slip spectrum and scale‐dependent rise times by representing the slip distribution as the sum of normal modes of a vibrating membrane.Finite source and path effects were important in determining the distribution of strong motions through the locations of the hypocenter, subevents, and crustal structures like sedimentary basins. Some regions in Cascadia appear to be at greater risk than others during an event due to the geometry of the Cascadia fault zone relative to the coast and populated regions. The southern Oregon coast appears to have increased risk because it is closer to the locked zone of the Cascadia fault than other coastal areas and is also in the path of directivity amplification from any rupture propagating north to south in that part of the subduction zone, and the basins in the Puget Sound area are efficiently amplified by both north and south propagating ruptures off the coast of western Washington. We find that the median spectral accelerations at 5 s period from the simulations are similar to that of the Zhao et al. (2006) ground‐motion prediction equation, although our simulations predict higher amplitudes near the region of greatest slip and in the sedimentary basins, such as the Seattle basin.

Damping Effect of an Unsaturated-Saturated System on Tempospatial Variations of Pressure Head and Specific Flux

NASA Astrophysics Data System (ADS)

Yang, C.; Zhang, Y. K.; Liang, X.

2014-12-01

Damping effect of an unsaturated-saturated system on tempospatialvariations of pressurehead and specificflux was investigated. The variance and covariance of both pressure head and specific flux in such a system due to a white noise infiltration were obtained by solving the moment equations of water flow in the system and verified with Monte Carlo simulations. It was found that both the pressure head and specific flux in this case are temporally non-stationary. The variance is zero at early time due to a deterministic initial condition used, then increases with time, and approaches anasymptotic limit at late time.Both pressure head and specific flux arealso non-stationary in space since the variance decreases from source to sink. The unsaturated-saturated systembehavesasa noise filterand it damps both the pressure head and specific flux, i.e., reduces their variations and enhances their correlation. The effect is stronger in upper unsaturated zone than in lower unsaturated zone and saturated zone. As a noise filter, the unsaturated-saturated system is mainly a low pass filter, filtering out the high frequency components in the time series of hydrological variables. The damping effect is much stronger in the saturated zone than in the saturated zone.

Biostimulation of anaerobic BTEX biodegradation under fermentative methanogenic conditions at source-zone groundwater contaminated with a biodiesel blend (B20).

PubMed

Ramos, Débora Toledo; da Silva, Márcio Luis Busi; Chiaranda, Helen Simone; Alvarez, Pedro J J; Corseuil, Henry Xavier

2013-06-01

Field experiments were conducted to assess the potential for anaerobic biostimulation to enhance BTEX biodegradation under fermentative methanogenic conditions in groundwater impacted by a biodiesel blend (B20, consisting of 20 % v/v biodiesel and 80 % v/v diesel). B20 (100 L) was released at each of two plots through an area of 1 m(2) that was excavated down to the water table, 1.6 m below ground surface. One release was biostimulated with ammonium acetate, which was added weekly through injection wells near the source zone over 15 months. The other release was not biostimulated and served as a baseline control simulating natural attenuation. Ammonium acetate addition stimulated the development of strongly anaerobic conditions, as indicated by near-saturation methane concentrations. BTEX removal began within 8 months in the biostimulated source zone, but not in the natural attenuation control, where BTEX concentrations were still increasing (due to source dissolution) 2 years after the release. Phylogenetic analysis using quantitative PCR indicated an increase in concentration and relative abundance of Archaea (Crenarchaeota and Euryarchaeota), Geobacteraceae (Geobacter and Pelobacter spp.) and sulfate-reducing bacteria (Desulfovibrio, Desulfomicrobium, Desulfuromusa, and Desulfuromonas) in the biostimulated plot relative to the control. Apparently, biostimulation fortuitously enhanced the growth of putative anaerobic BTEX degraders and associated commensal microorganisms that consume acetate and H2, and enhance the thermodynamic feasibility of BTEX fermentation. This is the first field study to suggest that anaerobic-methanogenic biostimulation could enhance source zone bioremediation of groundwater aquifers impacted by biodiesel blends.

Measurements and modeling of the impact of weak magnetic fields on the plasma properties of a planar slot antenna driven plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshikawa, Jun, E-mail: jun.yoshikawa@tel.com; Susa, Yoshio; Ventzek, Peter L. G.

The radial line slot antenna plasma source is a type of surface wave plasma source driven by a planar slot antenna. Microwave power is transmitted through a slot antenna structure and dielectric window to a plasma characterized by a generation zone adjacent to the window and a diffusion zone that contacts a substrate. The diffusion zone is characterized by a very low electron temperature. This renders the source useful for soft etch applications and thin film deposition processes requiring low ion energy. Another property of the diffusion zone is that the plasma density tends to decrease from the axis tomore » the walls under the action of ambipolar diffusion at distances far from where the plasma is generated. A previous simulation study [Yoshikawa and. Ventzek, J. Vac. Sci. Technol. A 31, 031306 (2013)] predicted that the anisotropy in transport parameters due to weak static magnetic fields less than 50 G could be leveraged to manipulate the plasma profile in the radial direction. These simulations motivated experimental tests in which weak magnetic fields were applied to a radial line slot antenna source. Plasma absorption probe measurements of electron density and etch rate showed that the magnetic fields remote from the wafer were able to manipulate both parameters. A summary of these results is presented in this paper. Argon plasma simulation trends are compared with experimental plasma and etch rate measurements. A test of the impact of magnetic fields on charge up damage showed no perceptible negative effect.« less

Isotropic source terms of San Jacinto fault zone earthquakes based on waveform inversions with a generalized CAP method

NASA Astrophysics Data System (ADS)

Ross, Z. E.; Ben-Zion, Y.; Zhu, L.

2015-02-01

We analyse source tensor properties of seven Mw > 4.2 earthquakes in the complex trifurcation area of the San Jacinto Fault Zone, CA, with a focus on isotropic radiation that may be produced by rock damage in the source volumes. The earthquake mechanisms are derived with generalized `Cut and Paste' (gCAP) inversions of three-component waveforms typically recorded by >70 stations at regional distances. The gCAP method includes parameters ζ and χ representing, respectively, the relative strength of the isotropic and CLVD source terms. The possible errors in the isotropic and CLVD components due to station variability is quantified with bootstrap resampling for each event. The results indicate statistically significant explosive isotropic components for at least six of the events, corresponding to ˜0.4-8 per cent of the total potency/moment of the sources. In contrast, the CLVD components for most events are not found to be statistically significant. Trade-off and correlation between the isotropic and CLVD components are studied using synthetic tests with realistic station configurations. The associated uncertainties are found to be generally smaller than the observed isotropic components. Two different tests with velocity model perturbation are conducted to quantify the uncertainty due to inaccuracies in the Green's functions. Applications of the Mann-Whitney U test indicate statistically significant explosive isotropic terms for most events consistent with brittle damage production at the source.

Earthquake Forecasting in Northeast India using Energy Blocked Model

NASA Astrophysics Data System (ADS)

Mohapatra, A. K.; Mohanty, D. K.

2009-12-01

In the present study, the cumulative seismic energy released by earthquakes (M ≥ 5) for a period 1897 to 2007 is analyzed for Northeast (NE) India. It is one of the most seismically active regions of the world. The occurrence of three great earthquakes like 1897 Shillong plateau earthquake (Mw= 8.7), 1934 Bihar Nepal earthquake with (Mw= 8.3) and 1950 Upper Assam earthquake (Mw= 8.7) signify the possibility of great earthquakes in future from this region. The regional seismicity map for the study region is prepared by plotting the earthquake data for the period 1897 to 2007 from the source like USGS,ISC catalogs, GCMT database, Indian Meteorological department (IMD). Based on the geology, tectonic and seismicity the study region is classified into three source zones such as Zone 1: Arakan-Yoma zone (AYZ), Zone 2: Himalayan Zone (HZ) and Zone 3: Shillong Plateau zone (SPZ). The Arakan-Yoma Range is characterized by the subduction zone, developed by the junction of the Indian Plate and the Eurasian Plate. It shows a dense clustering of earthquake events and the 1908 eastern boundary earthquake. The Himalayan tectonic zone depicts the subduction zone, and the Assam syntaxis. This zone suffered by the great earthquakes like the 1950 Assam, 1934 Bihar and the 1951 Upper Himalayan earthquakes with Mw > 8. The Shillong Plateau zone was affected by major faults like the Dauki fault and exhibits its own style of the prominent tectonic features. The seismicity and hazard potential of Shillong Plateau is distinct from the Himalayan thrust. Using energy blocked model by Tsuboi, the forecasting of major earthquakes for each source zone is estimated. As per the energy blocked model, the supply of energy for potential earthquakes in an area is remarkably uniform with respect to time and the difference between the supply energy and cumulative energy released for a span of time, is a good indicator of energy blocked and can be utilized for the forecasting of major earthquakes. The proposed process provides a more consistent model of gradual accumulation of strain and non-uniform release through large earthquakes and can be applied in the evaluation of seismic risk. The cumulative seismic energy released by major earthquakes throughout the period from 1897 to 2007 of last 110 years in the all the zones are calculated and plotted. The plot gives characteristics curve for each zone. Each curve is irregular, reflecting occasional high activity. The maximum earthquake energy available at a particular time in a given area is given by S. The difference between the theoretical upper limit given by S and the cumulative energy released up to that time is calculated to find out the maximum magnitude of an earthquake which can occur in future. Energy blocked of the three source regions are 1.35*1017 Joules, 4.25*1017 Joules and 0.12*1017 in Joules respectively for source zone 1, 2 and 3, as a supply for potential earthquakes in due course of time. The predicted maximum magnitude (mmax) obtained for each source zone AYZ, HZ, and SPZ are 8.2, 8.6, and 8.4 respectively by this model. This study is also consistent with the previous predicted results by other workers.

High-Resolution Source Parameter and Site Characteristics Using Near-Field Recordings - Decoding the Trade-off Problems Between Site and Source

NASA Astrophysics Data System (ADS)

Chen, X.; Abercrombie, R. E.; Pennington, C.

2017-12-01

Recorded seismic waveforms include contributions from earthquake source properties and propagation effects, leading to long-standing trade-off problems between site/path effects and source effects. With near-field recordings, the path effect is relatively small, so the trade-off problem can be simplified to between source and site effects (commonly referred as "kappa value"). This problem is especially significant for small earthquakes where the corner frequencies are within similar ranges of kappa values, so direct spectrum fitting often leads to systematic biases due to corner frequency and magnitude. In response to the significantly increased seismicity rate in Oklahoma, several local networks have been deployed following major earthquakes: the Prague, Pawnee and Fairview earthquakes. Each network provides dense observations within 20 km surrounding the fault zone, recording tens of thousands of aftershocks between M1 to M3. Using near-field recordings in the Prague area, we apply a stacking approach to separate path/site and source effects. The resulting source parameters are consistent with parameters derived from ground motion and spectral ratio methods from other studies; they exhibit spatial coherence within the fault zone for different fault patches. We apply these source parameter constraints in an analysis of kappa values for stations within 20 km of the fault zone. The resulting kappa values show significantly reduced variability compared to those from direct spectral fitting without constraints on the source spectrum; they are not biased by earthquake magnitudes. With these improvements, we plan to apply the stacking analysis to other local arrays to analyze source properties and site characteristics. For selected individual earthquakes, we will also use individual-pair empirical Green's function (EGF) analysis to validate the source parameter estimations.

Coupling Aggressive Mass Removal with Microbial Reductive Dechlorination for Remediation of DNAPL Source Zones: A Review and Assessment

PubMed Central

Christ, John A.; Ramsburg, C. Andrew; Abriola, Linda M.; Pennell, Kurt D.; Löffler, Frank E.

2005-01-01

The infiltration of dense non-aqueous-phase liquids (DNAPLs) into the saturated subsurface typically produces a highly contaminated zone that serves as a long-term source of dissolved-phase groundwater contamination. Applications of aggressive physical–chemical technologies to such source zones may remove > 90% of the contaminant mass under favorable conditions. The remaining contaminant mass, however, can create a rebounding of aqueous-phase concentrations within the treated zone. Stimulation of microbial reductive dechlorination within the source zone after aggressive mass removal has recently been proposed as a promising staged-treatment remediation technology for transforming the remaining contaminant mass. This article reviews available laboratory and field evidence that supports the development of a treatment strategy that combines aggressive source-zone removal technologies with subsequent promotion of sustained microbial reductive dechlorination. Physical–chemical source-zone treatment technologies compatible with posttreatment stimulation of microbial activity are identified, and studies examining the requirements and controls (i.e., limits) of reductive dechlorination of chlorinated ethenes are investigated. Illustrative calculations are presented to explore the potential effects of source-zone management alternatives. Results suggest that, for the favorable conditions assumed in these calculations (i.e., statistical homogeneity of aquifer properties, known source-zone DNAPL distribution, and successful bioenhancement in the source zone), source longevity may be reduced by as much as an order of magnitude when physical–chemical source-zone treatment is coupled with reductive dechlorination. PMID:15811838

Underwater Sound: Deep-Ocean Propagation: Variations of temperature and pressure have great influence on the propagation of sound in the ocean.

PubMed

Frosch, R A

1964-11-13

The absorption of sound in sea water varies markedly with frequency, being much greater at high than at low frequencies. It is sufficiently small at frequencies below several kilocycles per second, however, to permit propagation to thousands of miles. Oceanographic factors produce variations in sound velocity with depth, and these variations have a strong influence on long-range propagation. The deep ocean is characterized by a strong channel, generally at a depth of 500 to 1500 meters. In addition to guided propagation in this channel, the velocity structure gives rise to strongly peaked propagation from surface sources to surface receivers 48 to 56 kilometers away, with strong shadow zones of weak intensity in between. The near-surface shadow zone, in the latter case, may be filled in by bottom reflections or near-surface guided propagation due to a surface isothermal layer. The near-surface shadow zones can be avoided with certainty only through locating sources and receivers deep in the ocean.

Marine Biogeochemistry of Particulate Trace Elements in the Exclusive Economic Zone (eez) of the State of Qatar

NASA Astrophysics Data System (ADS)

Yigiterhan, O.; Al-Ansari, I. S.; Abdel-Moati, M.; Murray, J. W.; Al-Ansi, M.

2016-02-01

We focus on the trace element geochemistry of particulate matter in the Exclusive Economic Zone (EEZ) of Qatar. A main goal of this research was to analyze a complete suite of trace elements on particulate matter samples from the water column from different oceanographic biogeochemical zones of the EEZ around Qatar. The sample set also includes plankton samples which are the main source of biogenic particles, dust samples which are a source of abiological particles to surface seawater and surface sediments which can be a source of resuspended particles and a sink for settling particles. The 15 metals and 2 non-metals analyzed in this study will be Al, Ti, V, Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn, Mo, Ag, Ba, U and P, N. Many factors control the composition of trace elements in marine particles. Most of these are important in the EEZ of Qatar, including:1. Natural sources: These are rivers, atmospheric dust, sediment resuspension and leaks from oil beds. However, due to very limited rainfall rivers play no major role in Qatar but resuspension of shallow carbonate rich sediments and input of atmospheric dust are important due to strong currents and surrounding deserts.2. Adsorption/desorption: These chemical processes occur everywhere in the ocean and transfer metals between particles and the solution phase.3. Biological uptake: This process is likewise a universal ocean process and results in transport of metals from the solution phase to biological particles.4. Redox conditions: These are important chemical reactions in the oxic, suboxic and anoxic zones. This can be the dominant controlling mechanism in the northeastern hypoxic deeper waters of the Qatar EEZ.5. Anthropogenic sources: The eastern part of the Qatar contains numerous industrial sites, petroleum/gas platforms and refineries. There are numerous industrial sources but the main hot spots are the port of Doha and the industrial cities of Mesaieed, Khor Al-Odaid, and Ras Laffan. We aimed to determine the influence of the different current systems, water masses, and terrestrial inputs on the distribution, fractionation, and fate of trace metal contaminants and elemental pollutants. We have also observed the level of anthropogenic enrichments for some of the elements which have not been previously documented. This research should be viewed as the first stage of a complete study.

Local seismicity preceding the March 14, 1979, Petatlan, Mexico Earthquake (Ms = 7.6)

NASA Astrophysics Data System (ADS)

Hsu, Vindell; Gettrust, Joseph F.; Helsley, Charles E.; Berg, Eduard

1983-05-01

Local seismicity surrounding the epicenter of the March 14, 1979, Petatlan, Mexico earthquake was monitored by a network of portable seismographs of the Hawaii Institute of Geophysics from 6 weeks before to 4 weeks after the main shock. Prior to the main shock, the recorded local seismic activity was shallow and restricted within the continental plate above the Benioff zone. The relocated main shock hypocenter also lay above the Benioff zone, suggesting an initial failure within the continental lithosphere. Four zones can be recognized that showed relatively higher seismic activity than the background. Activity within these zones has followed a number of moderate earthquakes that occurred before or after the initial deployment of the network. Three of these moderate earthquakes were near the Mexican coastline and occurred sequentially from southeast to northwest during the three months before the Petatlan earthquake. The Petatlan event occurred along the northwestern extension of this trend. We infer a possible connection between this observed earthquake migration pattern and the subduction of a fracture zone because the 200-km segment that includes the aftershock zones of the Petatlan earthquake and the three preceding moderate earthquakes matches the intersection of the southeastern limb of the Orozco Fracture Zone and the Middle America Trench. The Petatlan earthquake source region includes the region of the last of the three near-coast seismic activities (zone A). Earthquakes of zone A migrated toward the Petatlan main shock epicenter and were separated from it by an aseismic zone about 10 km wide. We designate this group of earthquakes as the foreshocks of the Petatlan earthquake. These foreshocks occurred within the continental lithosphere and their observed characteristics are interpreted as due to the high-stress environment before the main shock. Pre-main shock seismicity of the Petatlan earthquake source region shows a good correlation with the aftershocks in their spatial distribution. This suggests that an asperity existing along the Benioff zone may have affected both the pre-main shock activity in the continental lithosphere and the aftershocks along the Benioff zone. Although major thrust earthquakes at trenches occur along Benioff zones, in the present study we find little activity on this interplate boundary before the Petatlan earthquake. The overlying continental block, on the contrary, is very active seismically. Our data suggest that the activity is probably governed by the stress transmitted from below due to coupling between two plates and the heterogeneity within the continental lithosphere. The continental material is probably the more likely place for precursors.

Flat slabs seen from above: aeromagnetic data in Central Mexico

NASA Astrophysics Data System (ADS)

Manea, M.; Manea, V. C.

2006-12-01

The aeromagnetic map of Mexico shows a magnetic "quiet zone" in Guerrero and Oaxaca (Central Mexico), characterized by a general lack of short-wavelength magnetic anomalies. In order to investigate the magnetic quiet zone in relation with the thermal sources, spectral analysis has been applied to the aeromagnetic data. The results show the existence of deep magnetic sources (30-40 km) which we consider to be the Currie depth (corresponding to a temperature of 575-600°). Above the Curie temperature spontaneous magnetization vanishes and the minerals exhibit only a small paramagnetic susceptibility. Our estimates of magnetic basal depth are consistent with the heat flow measurements in the area (20-30 mW/m2). In order to explain such deep magnetic source and small heat flow estimates, we infer the thermal structure associated with the subduction of the Cocos plate beneath Central Mexico, using a finite element approach. The modeling results show that the 575-600°C isotherm is subhorisontal due to the flat slab regime in the area. Also, the heat flow estimates from thermal models and spectral analysis of aeromagnetic anomalies are in good agreement. We conclude that the magnetic quiet zone is associated with a flat slab subduction regime in Central Mexico, and proved to be an important constraint for the thermal structure associated with subduction zones.

Evaluating four-dimensional time-lapse electrical resistivity tomography for monitoring DNAPL source zone remediation.

PubMed

Power, Christopher; Gerhard, Jason I; Karaoulis, Marios; Tsourlos, Panagiotis; Giannopoulos, Antonios

2014-07-01

Practical, non-invasive tools do not currently exist for mapping the remediation of dense non-aqueous phase liquids (DNAPLs). Electrical resistivity tomography (ERT) exhibits significant potential but has not yet become a practitioner's tool due to challenges in interpreting the survey results at real sites. This study explores the effectiveness of recently developed four-dimensional (4D, i.e., 3D space plus time) time-lapse surface ERT to monitor DNAPL source zone remediation. A laboratory experiment demonstrated the approach for mapping a changing NAPL distribution over time. A recently developed DNAPL-ERT numerical model was then employed to independently simulate the experiment, providing confidence that the DNAPL-ERT model is a reliable tool for simulating real systems. The numerical model was then used to evaluate the potential for this approach at the field scale. Four DNAPL source zones, exhibiting a range of complexity, were initially simulated, followed by modeled time-lapse ERT monitoring of complete DNAPL remediation by enhanced dissolution. 4D ERT inversion provided estimates of the regions of the source zone experiencing mass reduction with time. Results show that 4D time-lapse ERT has significant potential to map both the outline and the center of mass of the evolving treated portion of the source zone to within a few meters in each direction. In addition, the technique can provide a reasonable, albeit conservative, estimate of the DNAPL volume remediated with time: 25% underestimation in the upper 2m and up to 50% underestimation at late time between 2 and 4m depth. The technique is less reliable for identifying cleanup of DNAPL stringers outside the main DNAPL body. Overall, this study demonstrates that 4D time-lapse ERT has potential for mapping where and how quickly DNAPL mass changes in real time during site remediation. Copyright © 2014 Elsevier B.V. All rights reserved.

Mapping Site Remediation with Electrical Resistivity Tomography Explored via Coupled-Model Simulations

NASA Astrophysics Data System (ADS)

Power, C.; Gerhard, J. I.; Tsourlos, P.; Giannopoulos, A.

2011-12-01

Remediation programs for sites contaminated with dense non-aqueous phase liquids (DNAPLs) would benefit from an ability to non-intrusively map the evolving volume and extent of the DNAPL source zone. Electrical resistivity tomography (ERT) is a well-established geophysical tool, widely used outside the remediation industry, that has significant potential for mapping DNAPL source zones. However, that potential has not been realized due to challenges in data interpretation from contaminated sites - in either a qualitative or quantitative way. The objective of this study is to evaluate the potential of ERT to map realistic, evolving DNAPL source zones within complex subsurface environments during remedial efforts. For this purpose, a novel coupled model was developed that integrates a multiphase flow model (DNAPL3D-MT), which generates realistic DNAPL release scenarios, with 3DINV, an ERT model which calculates the corresponding resistivity response. This presentation will describe the developed model coupling methodology, which integrates published petrophysical relationships to generate an electrical resistivity field that accounts for both the spatial heterogeneity of subsurface soils and the evolving spatial distribution of fluids (including permeability, porosity, clay content and air/water/DNAPL saturation). It will also present an example in which the coupled model was employed to explore the ability of ERT to track the remediation of a DNAPL source zone. A field-scale, three-dimensional release of chlorinated solvent DNAPL into heterogeneous clayey sand was simulated, including the subsurface migration and subsequent removal of the DNAPL source zone via dissolution in groundwater. Periodic surveys of this site via ERT applied at the surface were then simulated and inversion programs were used to calculate the subsurface distribution of electrical properties. This presentation will summarize this approach and its potential as a research tool exploring the range of site conditions under which ERT may prove useful in aiding DNAPL site remediation. Moreover, it is expected to provide a cost-effective avenue to test optimum ERT data acquisition, inversion and interpretative tools at contaminated sites.

Climatically driven yield variability of major crops in Khakassia (South Siberia)

NASA Astrophysics Data System (ADS)

Babushkina, Elena A.; Belokopytova, Liliana V.; Zhirnova, Dina F.; Shah, Santosh K.; Kostyakova, Tatiana V.

2018-06-01

We investigated the variability of yield of the three main crop cultures in the Khakassia Republic: spring wheat, spring barley, and oats. In terms of yield values, variability characteristics, and climatic response, the agricultural territory of Khakassia can be divided into three zones: (1) the Northern Zone, where crops yield has a high positive response to the amount of precipitation, May-July, and a moderately negative one to the temperatures of the same period; (2) the Central Zone, where crops yield depends mainly on temperatures; and (3) the Southern Zone, where climate has the least expressed impact on yield. The dominant pattern in the crops yield is caused by water stress during periods of high temperatures and low moisture supply with heat stress as additional reason. Differences between zones are due to combinations of temperature latitudinal gradient, precipitation altitudinal gradient, and the presence of a well-developed hydrological network and the irrigational system as moisture sources in the Central Zone. More detailed analysis shows differences in the climatic sensitivity of crops during phases of their vegetative growth and grain development and, to a lesser extent, during harvesting period. Multifactor linear regression models were constructed to estimate climate- and autocorrelation-induced variability of the crops yield. These models allowed prediction of the possibility of yield decreasing by at least 2-11% in the next decade due to increasing of the regional summer temperatures.

Climatically driven yield variability of major crops in Khakassia (South Siberia)

NASA Astrophysics Data System (ADS)

Babushkina, Elena A.; Belokopytova, Liliana V.; Zhirnova, Dina F.; Shah, Santosh K.; Kostyakova, Tatiana V.

2017-12-01

We investigated the variability of yield of the three main crop cultures in the Khakassia Republic: spring wheat, spring barley, and oats. In terms of yield values, variability characteristics, and climatic response, the agricultural territory of Khakassia can be divided into three zones: (1) the Northern Zone, where crops yield has a high positive response to the amount of precipitation, May-July, and a moderately negative one to the temperatures of the same period; (2) the Central Zone, where crops yield depends mainly on temperatures; and (3) the Southern Zone, where climate has the least expressed impact on yield. The dominant pattern in the crops yield is caused by water stress during periods of high temperatures and low moisture supply with heat stress as additional reason. Differences between zones are due to combinations of temperature latitudinal gradient, precipitation altitudinal gradient, and the presence of a well-developed hydrological network and the irrigational system as moisture sources in the Central Zone. More detailed analysis shows differences in the climatic sensitivity of crops during phases of their vegetative growth and grain development and, to a lesser extent, during harvesting period. Multifactor linear regression models were constructed to estimate climate- and autocorrelation-induced variability of the crops yield. These models allowed prediction of the possibility of yield decreasing by at least 2-11% in the next decade due to increasing of the regional summer temperatures.

77 FR 2658 - Airworthiness Directives; Bombardier, Inc. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-19

... high pressure fuel lines due to improper installation of an expandable pin on the lower cowl assembly... chafing of the high pressure fuel lines, which if not corrected, could cause fuel leakage in a fire zone... on a high pressure (HP) fuel line. The source of chafing was related to the improper installation of...

Hydrologic Controls on Losses of Individual Components of Crude Oil in the Subsurface

NASA Astrophysics Data System (ADS)

Bekins, B. A.; Baedecker, M. J.; Eganhouse, R. P.; Drennan, D.; Herkelrath, W. N.; Warren, E.; Cozzarelli, I.

2011-12-01

The time frame for natural attenuation of crude oil contamination in the subsurface has been studied for the last 27 years at a spill site located near Bemidji, Minnesota, USA. Data from the groundwater contaminant plume show that dissolved benzene concentrations adjacent to the oil decreased by 50% between 1993 and 2007. Previous studies at the site showed that benzene and ethylbenzene undergo minimal degradation in the methanogenic zone of the plume while toluene and o-xylene degrade rapidly in this zone. Other studies have shown that degradation of benzene under methanogenic conditions occurs in some cases but is generally unreliable in the field. In this study concentrations of volatile components in the crude oil source were examined to determine if the observed benzene decrease near the oil source zone was due a change in the ability of the methanogenic microbial community to degrade benzene or long-term depletion of the oil source. Oil samples collected in 2008 had benzene concentrations ranging from 7-61% of values measured in archived oil representative of the spill consistent with depletion of the oil source. Several lines of evidence indicate that dissolution and conservative transport control the losses of benzene and ethylbenzene from the crude oil. Laboratory microcosms constructed using sediments from the methanogenic zone near the source and incubated for over 13 months with an anaerobic mineral salt solution spiked with ~2 mg/L benzene exhibited no benzene losses. Concentrations of benzene and ethylbenzene in oil samples collected from five wells were linearly correlated to interpolated maximum pore space oil saturations adjacent to each well (R2 =0.72 and 0.55 respectively), indicating that losses of these compounds from the oil were controlled by the relative permeability of groundwater through the oil body. Moreover benzene loss from the oil was greater than ethylbenzene, consistent with their relative aqueous solubilities. Losses of other oil compounds appear to be more strongly controlled by methanogenic degradation occurring in the source zone. Concentrations of these compounds, which include the n-alkanes, toluene, and o-xylene, correlate better with location in the oil body than with pore space oil saturation. Greater degradation rates occur below a topographic depression where focussing of surface runoff leads to an annual recharge rate of almost twice that of a nearby higher elevation site. The oxygen in the recharge over the source zone never reaches the oil at the water table because it is rapidly consumed in the vadose zone by aerobic methanotrophs oxidizing methane produced from oil degradation in the source zone. Other electron acceptors including nitrate and sulphate are insignificant at this site. The data suggest that transport by recharge of the growth nutrients phosphorus and nitrogen is the explanation for the higher degradation rates of the oil components in the focussed recharge area.

Changes in dissolved organic matter quality in a peatland and forest headwater stream as a function of seasonality and hydrologic conditions

NASA Astrophysics Data System (ADS)

Broder, Tanja; Knorr, Klaus-Holger; Biester, Harald

2017-04-01

Peatlands and peaty riparian zones are major sources of dissolved organic matter (DOM), but are poorly understood in terms of export dynamics and controls thereof. Thereby quality of DOM affects function and behavior of DOM in aquatic ecosystems, but DOM quality can also help to track DOM sources and their export dynamics under specific hydrologic preconditions. The objective of this study was to elucidate controls on temporal variability in DOM concentration and quality in stream water draining a bog and a forested peaty riparian zone, particularly considering drought and storm flow events. DOM quality was monitored using spectrofluorometric indices for aromaticity (SUVA254), apparent molecular size (SR) and precursor organic material (FI), as well as PARAFAC modeling of excitation emission matrices (EEMs). Indices for DOM quality exhibited major changes due to different hydrologic conditions, but patterns were also dependent on season. Stream water at the forested site with mineral, peaty soils generally exhibited higher variability in DOM concentrations and quality compared to the outflow of an ombrotrophic bog, where DOM was less susceptible to changes in hydrologic conditions. During snowmelt and spring events, near-surface protein-like DOM pools were exported. A microbial DOM fraction originating from groundwater and deep peat layers was increasing during drought, while a strongly microbially altered DOM fraction was also exported by discharge events with dry preconditions at the forested site. This might be due to accelerated microbial activity in the peaty riparian zone of the forested site under these preconditions. Our study demonstrated that DOM export dynamics are not only a passive mixing of different hydrological sources, but monitoring studies have to consider that DOM quality depends on hydrologic preconditions and season. Moreover, the forested peaty riparian zone generated the most variability in headwater DOM quantity and quality, as could be tracked by the used spectrofluorometric indices.

The efficiency evaluation of in situ remediation performed around the source zone of DNAPL contaminated site, Wonju, Korea

NASA Astrophysics Data System (ADS)

Lee, S. S.; Lee, S. H.; Lee, K. K.

2014-12-01

The location of DNAPL source and distribution of contaminant plume at an industrial complex, Wonju, Korea, was examined based on the combined results of seasonal impact analysis, historical approach, radon tracer approach, and chemical fingerprinting conducted from 2009 to 2013 (Yang et al., 2013). With regard to the amount of contaminants discharged at this study site, there is no exact information on disposal. Therefore, various remediation technologies such as soil vapor extraction, soil flushing, biostimulation, and pump-and-treatment have been performed to eliminate the contaminant sources of trichloroethylene (TCE) and to prevent the migration of TCE plume from remediation target zones. Also, dissolved TCE concentration and mass of residual TCE in the initial stage of disposal were estimated to evaluate the efficiency of in situ remediation. The remediation efficiency according to the remediation actions was evaluated by tracing a time-series of plume evolution and estimating the temporal mass discharge at three transects (Source, Transec-1, Transect-2) which was assigned along the groundwater flow path. From results of periodically monitored TCE concentration at main source zone, the TCE level (15.74 mg/L) before the remediation dramatically decreased up to 0.56 mg/L at the end of year 2012 due to the effect of remediation. During the intensive remediation period from 2012 to 2013, the early average mass discharge (26.58 g/day) at source transect was decreased to average 4.99 g/day. Especially, in case of surfactant flushing test which was conducted to eliminate the residual TCE, the efficiency of surfactant flushing test was evaluated using the recovery rate of chloride ion which was used as tracer. The results for recovery rate of chloride ion show that test wells observed the slow recovery rate represented more effective dissolution of TCE than wells showing the rapid recovery rate. By using the source zone monitoring data and analytical solution, initial dissolved concentration and residual mass of TCE in late 1980s at the main source zone were roughly estimated 150 mg/L and 1000 kg, respectively. These values decreased to 0.45 mg/L and 33.07 kg direct after an intensive remedial action in 2013 and then it expected to be continuously decreased to 0.29 mg/L and 25.41 kg from the end of remedial actions to 2020.

Water level changes affect carbon turnover and microbial community composition in lake sediments

Treesearch

Lukas Weise; Andreas Ulrich; Matilde Moreano; Arthur Gessler; Zachary E. Kayler; Kristin Steger; Bernd Zeller; Kristin Rudolph; Jelena Knezevic-Jaric

2016-01-01

Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-...

Bacterial production in the water column of small streams highly depends on terrestrial dissolved organic carbon

NASA Astrophysics Data System (ADS)

Graeber, Daniel; Poulsen, Jane R.; Rasmussen, Jes J.; Kronvang, Brian; Zak, Dominik; Kamjunke, Norbert

2016-04-01

In the recent years it has become clear that the largest part of the terrestrial dissolved organic carbon (DOC) pool is removed on the way from the land to the ocean. Yet it is still unclear, where in the freshwater systems terrestrial DOC is actually taken up, and for streams DOC uptake was assumed to happen mostly at the stream bottom (benthic zone). However, a recent monitoring study implies that water column but not benthic bacteria are strongly affected by the amount and composition of DOM entering streams from the terrestrial zone. We conducted an experiment to compare the reaction of the bacterial production and heterotrophic uptake in the water column and the benthic zone to a standardized source of terrestrial DOC (leaf leachate from Beech litter). In detail, we sampled gravel and water from eight streams with a gradient in stream size and land use. For each stream four different treatments were incubated at 16°C for three days and each stream: filtered stream water with gravel stones (representing benthic zone bacteria) or unfiltered stream water (representing water column bacteria), both either with (n = 5) or, without (n = 3) leaf leachate. We found that the bacterial uptake of leaf litter DOC was higher for the benthic zone likely due to the higher bacterial production compared to the water column. In contrast, the bacterial production per amount of leaf leachate DOC taken up was significantly higher for the bacteria in the water column than for those in the benthic zone. This clearly indicates a higher growth efficiency with the leaf leachate DOC for the bacteria in the water column than in the benthic zone. We found a high variability for the growth efficiency in the water column, which was best explained by a negative correlation of the DOC demand with stream width (R² = 0.86, linear correlation of log-transformed data). This was not the case for the benthic zone bacteria (R² = 0.02). This implies that water column bacteria in very small streams are more dependent on terrestrial DOC sources for their growth than those in larger streams. Based on this experiment and literature data we hypothesize that: I) The response of the bacterial production to terrestrial DOC in the water column is stronger than for the benthic zone and is decreasing with increasing stream size, likely due to the increase of autochthonous DOC production within the stream. II) Independent of stream size there is only a small reaction to terrestrial DOC for the bacterial production in the benthic zone, either due to internal DOC production or a stronger dependency on particulate organic carbon. We propose that this terrestrial DOC dependency concept is generally applicable, however, its potential underlying mechanisms and concept predictions need to be tested further for other stream and river ecosystems.

Carbonate cements indicate channeled fluid flow along a zone of vertical faults at the deformation front of the Cascadia accretionary wedge (northwest U.S. coast)

NASA Astrophysics Data System (ADS)

Sample, James C.; Reid, Mary R.; Tols, Harold J.; Moore, J. Casey

1993-06-01

To understand the relation between fluid seeps and structures, sedimentary rocks were collected with the DSRV Alvin from a vertical fault zone that transects the deformation front of the Cascadia accretionary wedge. The rocks contained diagenetic carbonate cement that was precipitated from fluids expelled during accretion. Carbon, oxygen, and strontium isotope data are consistent with a fluid source at >2 km depth. Most carbon isotopes range from -1‰ to -25‰ (PDB [Peedee belemnitel] standard) consistent with a thermogenic methane source. Oxygen isotopes show extreme 18O depletions (-4‰ to -13‰ PDB) that are consistent with precipitation from fluids with temperatures as high as 100 °C. 87Sr/86Sr values of 0.70975 to 0.71279 may be due to strontium in fluids derived from clay-rich parts of the stratigraphic section. The ubiquity of carbonate precipitates and the isotope data indicate that the vertical fault zone is an efficient conduit for fluid dewatering from deep levels of the accretionary wedge.

Aquitard contaminant storage and flux resulting from dense nonaqueous phase liquid source zone dissolution and remediation

EPA Science Inventory

A one-dimensional diffusion model was used to investigate the effects of dense non-aqueous phase liquid (DNAPL) source zone dissolution and remediation on the storage and release of contaminants from aquitards. Source zone dissolution was represented by a power-law source depleti...

Preliminary vulnerability evaluation by local tsunami and flood by Puerto Vallarta

NASA Astrophysics Data System (ADS)

Trejo-Gómez, E.; Nunez-Cornu, F. J.; Ortiz, M.; Escudero, C. R.; CA-UdG-276 Sisvoc

2013-05-01

Jalisco coast is susceptible to local tsunami due to the occurrence of large earthquakes. In 1932 occurred three by largest earthquakes. Evidence suggests that one of them caused by offshore subsidence of sediments deposited by Armeria River. For the tsunamis 1932 have not been studied the seismic source. On October 9, 1995, occurred a large earthquake (Mw= 8.0) producing a tsunami with run up height up ≤ 5 m. This event affected Tenacatita Bay and many small villages along the coast of Jalisco and Colima. Using seismic source parameters, we simulated 1995 tsunami and estimated the maximum wave height. We compared the our results with 20 field measures 20 taked during 1995 along the south cost of Jalisco State, from Chalacatepec to Barra de Navidad. Similar seismic source parameters used for tsunami 1995 simulation was used as reference for simulating a hypothetical seismic source front Puerto Vallarta. We assumed that the fracture occurs in the gap for the north cost of Jalisco. Ten sites were distributed to cover the Banderas Bay, as theoretical pressure sensors, were estimated the maximum wave height and time to arrived at cost. After we delimited zones hazard zones by floods on digital model terrain, a graphic scale 1:20,000. At the moment, we have already included information by hazard caused by hypothetical tsunami in Puerto Vallarta. The hazard zones by flood were the north of Puerto Vallarta, as Ameca, El Salado, El Pitillal and Camarones. The initial wave height could be ≤ 1 m, 15 minutes after earthquake, in Pitillal zone. We estimated for Puerto Vallarta the maximum flood area was in El Salado zone, ≤ 2 km, with the maximum wave height > 3 m to ≤ 4.8 m at 25 and 75 minutes. We estimated a previous vulnerability evaluation by local tsunami and flood; it was based on the spatial distribution of socio-economic data from INEGI. We estimated a low vulnerability in El Salado and height vulnerability for El Pitillal and Ameca.

Root-zone acidity affects relative uptake of nitrate and ammonium from mixed nitrogen sources

NASA Technical Reports Server (NTRS)

Vessey, J. K.; Henry, L. T.; Chaillou, S.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1990-01-01

Soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 21 days on 4 sources of N (1.0 mM NO3-, 0.67 mM NO3- plus 0.33 mM NH4+, 0.33 mM NO3- plus 0.67 mM NH4+, and 1.0 mM NH4+) in hydroponic culture with the acidity of the nutrient solution controlled at pH 6.0, 5.5, 5.0, and 4.5. Dry matter and total N accumulation of the plants was not significantly affected by N-source at any of the pH levels except for decreases in these parameters in plants supplied solely with NH4+ at pH 4.5. Shoot-to-root ratios increased in plants which had an increased proportion [correction of proporiton] of NH4(+)-N in their nutrient solutions at all levels of root-zone pH. Uptake of NO3- and NH4+ was monitored daily by ion chromatography as depletion of these ions from the replenished hydroponic solutions. At all pH levels the proportion of either ion that was absorbed increased as the ratio of that ion increased in the nutrient solution. In plants which were supplied with sources of NO3- plus NH4+, NH4+ was absorbed at a ratio of 2:1 over NO3- at pH 6.0. As the pH of the root-zone declined, however, NH4+ uptake decreased and NO3- uptake increased. Thus, the NH4+ to NO3- uptake ratio declined with decreases in root-zone pH. The data indicate a negative effect of declining root-zone pH on NH4+ uptake and supports a hypothesis that the inhibition of growth of plants dependent on NH4(+)-N at low pH is due to a decline in NH4+ uptake and a consequential limitation of growth by N stress.

Oxygen Fugacity Variation From Mantle Transition Zone To Ocean Ridges Recorded By In Situ Diamond-Bearing Peridotite Of Indus Ophiolite

NASA Astrophysics Data System (ADS)

Das, S.; Basu, A. R.

2017-12-01

Our recently discovered transition zone ( 410 - 660 Km) -derived peridotites in the Indus Ophiolite, Ladakh Himalaya [1] provide a unique opportunity to study changes in oxygen fugacity from shallow mantle beneath ocean ridges to mantle transition zone. We found in situ diamond, graphite pseudomorphs after diamond crystals, hydrocarbon (C - H) and hydrogen (H2) fluid inclusions in ultra-high pressure (UHP) peridotites that occur in the mantle - section of the Indus ophiolite and sourced from the mantle transition zone [2]. Diamond occurs as octahedral inclusion in orthoenstatite of one of these peridotites. The graphite pseudomorphs after diamond crystals and primary hydrocarbon (C-H), and hydrogen (H2) fluids are included in olivine of this rock. Hydrocarbon fluids are also present as inclusions in high pressure clinoenstatite (> 8 GPa). The association of primary hydrocarbon and hydrogen fluid inclusions in the UHP peridotites suggest that their source-environment was highly reduced at the base of the upper mantle. We suggest that during mantle upwelling beneath Neo Tethyan spreading center, the hydrocarbon fluid was oxidized and precipitated diamond. The smaller diamonds converted to graphite at shallower depth due to size, high temperature and elevated oxygen fugacity. This process explains how deep mantle upwelling can oxidize reduced fluid carried from the transition zone to produce H2O - CO2. The H2O - CO2 fluids induce deep melting in the source of the mid oceanic ridge basalts (MORB) that create the oceanic crust. References: [1] Das S, Mukherjee B K, Basu A R, Sen K, Geol Soc London, Sp 412, 271 - 286; 2015. [2] Das S, Basu A R, Mukherjee B K, Geology 45 (8), 755 - 758; 2017.

Scenario based tsunami wave height estimation towards hazard evaluation for the Hellenic coastline and examples of extreme inundation zones in South Aegean

NASA Astrophysics Data System (ADS)

Melis, Nikolaos S.; Barberopoulou, Aggeliki; Frentzos, Elias; Krassanakis, Vassilios

2016-04-01

A scenario based methodology for tsunami hazard assessment is used, by incorporating earthquake sources with the potential to produce extreme tsunamis (measured through their capacity to cause maximum wave height and inundation extent). In the present study we follow a two phase approach. In the first phase, existing earthquake hazard zoning in the greater Aegean region is used to derive representative maximum expected earthquake magnitude events, with realistic seismotectonic source characteristics, and of greatest tsunamigenic potential within each zone. By stacking the scenario produced maximum wave heights a global maximum map is constructed for the entire Hellenic coastline, corresponding to all expected extreme offshore earthquake sources. Further evaluation of the produced coastline categories based on the maximum expected wave heights emphasizes the tsunami hazard in selected coastal zones with important functions (i.e. touristic crowded zones, industrial zones, airports, power plants etc). Owing to its proximity to the Hellenic Arc, many urban centres and being a popular tourist destination, Crete Island and the South Aegean region are given a top priority to define extreme inundation zoning. In the second phase, a set of four large coastal cities (Kalamata, Chania, Heraklion and Rethymno), important for tsunami hazard, due i.e. to the crowded beaches during the summer season or industrial facilities, are explored towards preparedness and resilience for tsunami hazard in Greece. To simulate tsunamis in the Aegean region (generation, propagation and runup) the MOST - ComMIT NOAA code was used. High resolution DEMs for bathymetry and topography were joined via an interface, specifically developed for the inundation maps in this study and with similar products in mind. For the examples explored in the present study, we used 5m resolution for the topography and 30m resolution for the bathymetry, respectively. Although this study can be considered as preliminary, it can also form the basis to further develop a scenario based inundation model database that can be used as an operational tool, for fast assessing tsunami prone zones during a real tsunami crisis.

Relative contributions of microbial and infrastructure heat at a crude oil-contaminated site

NASA Astrophysics Data System (ADS)

Warren, Ean; Bekins, Barbara A.

2018-04-01

Biodegradation of contaminants can increase the temperature in the subsurface due to heat generated from exothermic reactions, making temperature observations a potentially low-cost approach for determining microbial activity. For this technique to gain more widespread acceptance, it is necessary to better understand all the factors affecting the measured temperatures. Biodegradation has been occurring at a crude oil-contaminated site near Bemidji, Minnesota for 39 years, creating a quasi-steady-state plume of contaminants and degradation products. A model of subsurface heat generation and transport helps elucidate the contribution of microbial and infrastructure heating to observed temperature increases at this site. We created a steady-state, two-dimensional, heat transport model using previous-published parameter values for physical, chemical and biodegradation properties. Simulated temperature distributions closely match the observed average annual temperatures measured in the contaminated area at the site within less than 0.2 °C in the unsaturated zone and 0.4 °C in the saturated zone. The model results confirm that the observed subsurface heat from microbial activity is due primarily to methane oxidation in the unsaturated zone resulting in a 3.6 °C increase in average annual temperature. Another important source of subsurface heat is from the active, crude-oil pipelines crossing the site. The pipelines impact temperatures for a distance of 200 m and contribute half the heat. Model results show that not accounting for the heat from the pipelines leads to overestimating the degradation rates by a factor of 1.7, demonstrating the importance of identifying and quantifying all heat sources. The model results also highlighted a zone where previously unknown microbial activity is occurring at the site.

Relative contributions of microbial and infrastructure heat at a crude oil-contaminated site.

PubMed

Warren, Ean; Bekins, Barbara A

2018-04-01

Biodegradation of contaminants can increase the temperature in the subsurface due to heat generated from exothermic reactions, making temperature observations a potentially low-cost approach for determining microbial activity. For this technique to gain more widespread acceptance, it is necessary to better understand all the factors affecting the measured temperatures. Biodegradation has been occurring at a crude oil-contaminated site near Bemidji, Minnesota for 39 years, creating a quasi-steady-state plume of contaminants and degradation products. A model of subsurface heat generation and transport helps elucidate the contribution of microbial and infrastructure heating to observed temperature increases at this site. We created a steady-state, two-dimensional, heat transport model using previous-published parameter values for physical, chemical and biodegradation properties. Simulated temperature distributions closely match the observed average annual temperatures measured in the contaminated area at the site within less than 0.2 °C in the unsaturated zone and 0.4 °C in the saturated zone. The model results confirm that the observed subsurface heat from microbial activity is due primarily to methane oxidation in the unsaturated zone resulting in a 3.6 °C increase in average annual temperature. Another important source of subsurface heat is from the active, crude-oil pipelines crossing the site. The pipelines impact temperatures for a distance of 200 m and contribute half the heat. Model results show that not accounting for the heat from the pipelines leads to overestimating the degradation rates by a factor of 1.7, demonstrating the importance of identifying and quantifying all heat sources. The model results also highlighted a zone where previously unknown microbial activity is occurring at the site. Published by Elsevier B.V.

Investigating the influence of DNAPL spill characteristics on source zone architecture and mass removal in pool-dominated source zones

NASA Astrophysics Data System (ADS)

Wallace, K. A.; Abriola, L.; Chen, M.; Ramsburg, A.; Pennell, K. D.; Christ, J.

2009-12-01

Multiphase, compositional simulators were employed to investigate the spill characteristics and subsurface properties that lead to pool-dominated, dense non-aqueous phase liquid (DNAPL) source zone architectures. DNAPL pools commonly form at textural interfaces where low permeability lenses restrict the vertical migration of DNAPL, allowing for DNAPL to accumulate, reaching high saturation. Significant pooling has been observed in bench-scale experiments and field settings. However, commonly employed numerical simulations rarely predict the pooling suspected in the field. Given the importance of pooling on the efficacy of mass recovery and the down-gradient contaminant signal, it is important to understand the predominant factors affecting the creation of pool-dominated source zones and their subsequent mass discharge. In this work, contaminant properties, spill characteristics and subsurface permeability were varied to investigate the factors contributing to the development of a pool-dominated source zone. DNAPL infiltration and entrapment simulations were conducted in two- and three-dimensional domains using the University of Texas Chemical Compositional (UTCHEM) simulator. A modified version of MT3DMS was then used to simulate DNAPL dissolution and mass discharge. Numerical mesh size was varied to investigate the importance of numerical model parameters on simulations results. The temporal evolution of commonly employed source zone architecture metrics, such as the maximum DNAPL saturation, first and second spatial moments, and fraction of DNAPL mass located in pools, was monitored to determine how the source zone architecture evolved with time. Mass discharge was monitored to identify the link between source zone architecture and down-gradient contaminant flux. Contaminant characteristics and the presence of extensive low permeability lenses appeared to have the most influence on the development of a pool-dominated source zone. The link between DNAPL mass recovery and contaminant mass discharge was significantly influenced by the fraction of mass residing in DNAPL pools. The greater the fraction of mass residing in DNAPL pools the greater the likelihood for significant reductions in contaminant mass discharge at modest levels of mass removal. These results will help guide numerical and experimental studies on the remediation of pool-dominated source zones and will likely guide future source zone characterization efforts.

Inhalation exposure to cleaning products: application of a two-zone model.

PubMed

Earnest, C Matt; Corsi, Richard L

2013-01-01

In this study, modifications were made to previously applied two-zone models to address important factors that can affect exposures during cleaning tasks. Specifically, we expand on previous applications of the two-zone model by (1) introducing the source in discrete elements (source-cells) as opposed to a complete instantaneous release, (2) placing source cells in both the inner (near person) and outer zones concurrently, (3) treating each source cell as an independent mixture of multiple constituents, and (4) tracking the time-varying liquid concentration and emission rate of each constituent in each source cell. Three experiments were performed in an environmentally controlled chamber with a thermal mannequin and a simplified pure chemical source to simulate emissions from a cleaning product. Gas phase concentration measurements were taken in the bulk air and in the breathing zone of the mannequin to evaluate the model. The mean ratio of the integrated concentration in the mannequin's breathing zone to the concentration in the outer zone was 4.3 (standard deviation, σ = 1.6). The mean ratio of measured concentration in the breathing zone to predicted concentrations in the inner zone was 0.81 (σ = 0.16). Intake fractions ranged from 1.9 × 10(-3) to 2.7 × 10(-3). Model results reasonably predict those of previous exposure monitoring studies and indicate the inadequacy of well-mixed single-zone model applications for some but not all cleaning events.

Methane emissions and contaminant degradation rates at sites affected by accidental releases of denatured fuel-grade ethanol

NASA Astrophysics Data System (ADS)

Sihota, Natasha J.; Mayer, K. Ulrich; Toso, Mark A.; Atwater, Joel F.

2013-08-01

The recent increase in the use of denatured fuel-grade ethanol (DFE) has enhanced the probability of its environmental release. Due to the highly labile nature of ethanol (EtOH), it is expected to rapidly biodegrade, increasing the potential for inducing methanogenic conditions in the subsurface. As environmental releases of DFE can be expected to occur at the ground surface or in the vadose zone (e.g., due to surficial spills from rail lines or tanker trucks and leaking underground storage tanks), the potential for methane (CH4) generation at DFE spill sites requires evaluation. An assessment is needed because high CH4 generation rates may lead to CH4 fluxes towards the ground surface, which is of particular concern if spills are located close to human habitation—related to concerns of soil vapor intrusion (SVI). This work demonstrates, for the first time, the measurement of surficial gas release rates at large volume DFE spill sites. Two study sites, near Cambria and Balaton, in MN are investigated. Total carbon emissions at the ground surface (summing carbon dioxide (CO2) and CH4 emissions) are used to quantify depth-integrated DFE degradation rates. Results from both sites demonstrate that substantial CO2 and CH4 emissions do occur—even years after a spill. However, large total carbon fluxes, and CH4 emissions in particular, were restricted to a localized area within the DFE source zone. At the Balaton site, estimates of total DFE carbon losses in the source zone ranged between 5 and 174 μmol m- 2 s- 1, and CH4 effluxes ranged between non-detect and 9 μmol m- 2 s- 1. At the Cambria site estimates of total DFE carbon losses in the source zone ranged between 8 and 500 μmol m- 2 s- 1, and CH4 effluxes ranged between non-detect and 393 μmol m- 2 s- 1. Substantial CH4 accumulation, coupled with oxygen (O2) depletion, measured in samples collected from custom-designed gas collection chambers at the Cambria site suggests that the development of explosion or asphyxiation hazards is possible in confined spaces above a rapidly degrading DFE release. However, the results also indicate that the development of such hazards is locally constrained, will require a high degree of soil moisture, close proximity to the source zone, a good connection between the soil and the confined space, and poorly aerated conditions.

Methane emissions and contaminant degradation rates at sites affected by accidental releases of denatured fuel-grade ethanol.

PubMed

Sihota, Natasha J; Mayer, K Ulrich; Toso, Mark A; Atwater, Joel F

2013-08-01

The recent increase in the use of denatured fuel-grade ethanol (DFE) has enhanced the probability of its environmental release. Due to the highly labile nature of ethanol (EtOH), it is expected to rapidly biodegrade, increasing the potential for inducing methanogenic conditions in the subsurface. As environmental releases of DFE can be expected to occur at the ground surface or in the vadose zone (e.g., due to surficial spills from rail lines or tanker trucks and leaking underground storage tanks), the potential for methane (CH4) generation at DFE spill sites requires evaluation. An assessment is needed because high CH4 generation rates may lead to CH4 fluxes towards the ground surface, which is of particular concern if spills are located close to human habitation-related to concerns of soil vapor intrusion (SVI). This work demonstrates, for the first time, the measurement of surficial gas release rates at large volume DFE spill sites. Two study sites, near Cambria and Balaton, in MN are investigated. Total carbon emissions at the ground surface (summing carbon dioxide (CO2) and CH4 emissions) are used to quantify depth-integrated DFE degradation rates. Results from both sites demonstrate that substantial CO2 and CH4 emissions do occur-even years after a spill. However, large total carbon fluxes, and CH4 emissions in particular, were restricted to a localized area within the DFE source zone. At the Balaton site, estimates of total DFE carbon losses in the source zone ranged between 5 and 174 μmol m(-2) s(-1), and CH4 effluxes ranged between non-detect and 9 μmol m(-2) s(-1). At the Cambria site estimates of total DFE carbon losses in the source zone ranged between 8 and 500 μmol m(-2) s(-1), and CH4 effluxes ranged between non-detect and 393 μmol m(-2) s(-1). Substantial CH4 accumulation, coupled with oxygen (O2) depletion, measured in samples collected from custom-designed gas collection chambers at the Cambria site suggests that the development of explosion or asphyxiation hazards is possible in confined spaces above a rapidly degrading DFE release. However, the results also indicate that the development of such hazards is locally constrained, will require a high degree of soil moisture, close proximity to the source zone, a good connection between the soil and the confined space, and poorly aerated conditions. Copyright © 2013 Elsevier B.V. All rights reserved.

Detrital Geochemical Fingerprints of Rivers Along Southern Tibet and Nepal: Implications for Erosion of the Indus-Yarlung Suture Zone and the Himalayas

NASA Astrophysics Data System (ADS)

Hassim, M. F. B.; Carrapa, B.; DeCelles, P. G.; Kapp, P. A.; Gehrels, G. E.

2014-12-01

Our detrital geochemical study of modern sand collected from tributaries of the Yarlung River in southern Tibet and the Kali Gandaki River and its tributaries in Nepal shed light on the ages and exhumation histories of source rocks within the Indus-Yarlung Suture (IYS) zone and the Himalayas. Seven sand samples from rivers along the suture zone in southern Tibet between Xigatze to the east and Mt. Kailas to the west were collected for detrital zircon U-Pb geochronologic and Apatite Fission Track (AFT) thermochronologic analyses. Zircon U-Pb ages for all rivers range between 15 and 3568 Ma. Rivers draining the northern side of the suture zone mainly yield ages between 40 and 60 Ma, similar to the age of the Gangdese magmatic arc. Samples from rivers draining the southern side of the suture zone record a Tethyan Himalayan signal characterized by age clusters at 500 Ma and 1050 Ma. Our results indicate that the ages and proportion of U-Pb zircons ages of downstream samples from tributaries of the Yarlung River directly reflect source area ages and relative area of source rock exposure in the catchment basin. Significant age components at 37 - 40 Ma, 47 - 50 Ma, 55 - 58 Ma and 94 - 97 Ma reflect episodicity in Gangdese arc magmatism. Our AFT ages show two main signals at 23-18 Ma and 12 Ma, which are in agreement with accelerated exhumation of the Gangdese batholith during these time intervals. The 23 - 18 Ma signal partly overlaps with deposition of the Kailas Formation along the suture zone and may be related to exhumation due to upper plate extension in southern Tibet in response to Indian slab rollback and/or break-off events. Detrital thermochronology of four sand samples from the Kali Gandaki River and some of its tributaries in Nepal is underway and will provide constraints on the timing of erosion of the central Nepal Himalaya.

Characterizing Mega-Earthquake Related Tsunami on Subduction Zones without Large Historical Events

NASA Astrophysics Data System (ADS)

Williams, C. R.; Lee, R.; Astill, S.; Farahani, R.; Wilson, P. S.; Mohammed, F.

2014-12-01

Due to recent large tsunami events (e.g., Chile 2010 and Japan 2011), the insurance industry is very aware of the importance of managing its exposure to tsunami risk. There are currently few tools available to help establish policies for managing and pricing tsunami risk globally. As a starting point and to help address this issue, Risk Management Solutions Inc. (RMS) is developing a global suite of tsunami inundation footprints. This dataset will include both representations of historical events as well as a series of M9 scenarios on subductions zones that have not historical generated mega earthquakes. The latter set is included to address concerns about the completeness of the historical record for mega earthquakes. This concern stems from the fact that the Tohoku Japan earthquake was considerably larger than had been observed in the historical record. Characterizing the source and rupture pattern for the subduction zones without historical events is a poorly constrained process. In many case, the subduction zones can be segmented based on changes in the characteristics of the subducting slab or major ridge systems. For this project, the unit sources from the NOAA propagation database are utilized to leverage the basin wide modeling included in this dataset. The length of the rupture is characterized based on subduction zone segmentation and the slip per unit source can be determined based on the event magnitude (i.e., M9) and moment balancing. As these events have not occurred historically, there is little to constrain the slip distribution. Sensitivity tests on the potential rupture pattern have been undertaken comparing uniform slip to higher shallow slip and tapered slip models. Subduction zones examined include the Makran Trench, the Lesser Antilles and the Hikurangi Trench. The ultimate goal is to create a series of tsunami footprints to help insurers understand their exposures at risk to tsunami inundation around the world.

Modeling Enhanced Storage of Groundwater Contaminants due to the Presence of Cracks in Low Permeability Zones Underlying Contaminant Source Areas

DTIC Science & Technology

2011-03-01

Approved: //signed// 11 Mar 2011 __________________________________ _________ Mark N. Goltz , Ph.D. (Chairman) Date...Acknowledgments I appreciate the opportunity my thesis adviser, Dr. Mark N. Goltz , gave me by allowing me to work with him on this thesis topic and...3.15 is used ( Goltz and Roberts, 1988). R D B R

The importance of the riparian zone and in-stream processes in nitrate attenuation in undisturbed and agricultural watersheds – a review of the scientific literature

USGS Publications Warehouse

Ranalli, Anthony J.; Macalady, Donald L.

2010-01-01

We reviewed published studies from primarily glaciated regions in the United States, Canada, and Europe of the (1) transport of nitrate from terrestrial ecosystems to aquatic ecosystems, (2) attenuation of nitrate in the riparian zone of undisturbed and agricultural watersheds, (3) processes contributing to nitrate attenuation in riparian zones, (4) variation in the attenuation of nitrate in the riparian zone, and (5) importance of in-stream and hyporheic processes for nitrate attenuation in the stream channel. Our objectives were to synthesize the results of these studies and suggest methodologies to (1) monitor regional trends in nitrate concentration in undisturbed 1st order watersheds and (2) reduce nitrate loads in streams draining agricultural watersheds. Our review reveals that undisturbed headwater watersheds have been shown to be very retentive of nitrogen, but the importance of biogeochemical and hydrological riparian zone processes in retaining nitrogen in these watersheds has not been demonstrated as it has for agricultural watersheds. An understanding of the role of the riparian zone in nitrate attenuation in undisturbed watersheds is crucial because these watersheds are increasingly subject to stressors, such as changes in land use and climate, wildfire, and increases in atmospheric nitrogen deposition. In general, understanding processes controlling the concentration and flux of nitrate is critical to identifying and mapping the vulnerability of watersheds to water quality changes due to a variety of stressors. In undisturbed and agricultural watersheds we propose that understanding the importance of riparian zone processes in 2nd order and larger watersheds is critical. Research is needed that addresses the relative importance of how the following sources of nitrate along any given stream reach might change as watersheds increase in size and with flow: (1) inputs upstream from the reach, (2) tributary inflow, (3) water derived from the riparian zone, (4) groundwater from outside the riparian zone (intermediate or regional sources), and (5) in-stream (hyporheic) processes.

Pyrolysis reactor and fluidized bed combustion chamber

DOEpatents

Green, Norman W.

1981-01-06

A solid carbonaceous material is pyrolyzed in a descending flow pyrolysis reactor in the presence of a particulate source of heat to yield a particulate carbon containing solid residue. The particulate source of heat is obtained by educting with a gaseous source of oxygen the particulate carbon containing solid residue from a fluidized bed into a first combustion zone coupled to a second combustion zone. A source of oxygen is introduced into the second combustion zone to oxidize carbon monoxide formed in the first combustion zone to heat the solid residue to the temperature of the particulate source of heat.

Tectonic Tremor along the San Jacinto Fault Zone near Anza, California

NASA Astrophysics Data System (ADS)

Brown, J. R.

2013-12-01

In several tectonic settings where it is observed, low frequency tremor is proven as a useful tool to probe slow fault slip at depth (e.g., southwest Japan, Cascadia, Parkfield). However, tremor is difficult to detect due to its long durations and low amplitudes close to the noise band. This is particularly true in southern California where cultural noise sources are both spatially and temporally pervasive. Visually scanning continuous seismic recordings of the Southern California Seismic Network from 2001-2011 we find three pervasive occurrences of tremor: fall 2001, summer 2005 and summer 2010. In this presentation we focus on our analysis of the summer 2010 tremors on account of the enhanced instrumentation from the EarthScope Plate Boundary Observatory. During summer 2010 we detect ~240 hours of tremor-like signals in vicinity of the San Jacinto fault zone (SJFZ) near Anza. Visual inspection of continuous recordings up to 100 km northeast and southwest of the SJFZ do not record tremor-like signals indicating the source is both weak and local. Tremor is discriminated from other noise sources by calculating their spectral shapes to assure the signals are distinct from local noise sources and earthquakes. Similar to tremor spectra in other settings, the tremor signals in vicinity of the SJFZ are spectrally flat up to 9 Hz. In order to characterize the tremor source, we employ a combination of running autocorrelation and matched-filter techniques to detect and locate low frequency earthquakes (LFE) along the SJFZ one hour at a time. The autocorrelation of the north and vertical components of 14 stations detects over 13500 LFEs. We identify S-wave arrivals using the cross-correlation of 6 s windows for event pairs using the north component. Preliminary analysis of S-waves reveals a localized swarm of LFE epicenters extending 5 to 10 km SE of the Anza Gap with a horizontal error of +/- 4 km. Tremor depths are poorly constrained due to the lack of clear P-wave arrivals. The LFE epicenters reveal a zone of slow slip activity to the SE of the Anza Gap during early summer of 2010.

Spatial distribution and source apportionment of water pollution in different administrative zones of Wen-Rui-Tang (WRT) river watershed, China.

PubMed

Yang, Liping; Mei, Kun; Liu, Xingmei; Wu, Laosheng; Zhang, Minghua; Xu, Jianming; Wang, Fan

2013-08-01

Water quality degradation in river systems has caused great concerns all over the world. Identifying the spatial distribution and sources of water pollutants is the very first step for efficient water quality management. A set of water samples collected bimonthly at 12 monitoring sites in 2009 and 2010 were analyzed to determine the spatial distribution of critical parameters and to apportion the sources of pollutants in Wen-Rui-Tang (WRT) river watershed, near the East China Sea. The 12 monitoring sites were divided into three administrative zones of urban, suburban, and rural zones considering differences in land use and population density. Multivariate statistical methods [one-way analysis of variance, principal component analysis (PCA), and absolute principal component score-multiple linear regression (APCS-MLR) methods] were used to investigate the spatial distribution of water quality and to apportion the pollution sources. Results showed that most water quality parameters had no significant difference between the urban and suburban zones, whereas these two zones showed worse water quality than the rural zone. Based on PCA and APCS-MLR analysis, urban domestic sewage and commercial/service pollution, suburban domestic sewage along with fluorine point source pollution, and agricultural nonpoint source pollution with rural domestic sewage pollution were identified to the main pollution sources in urban, suburban, and rural zones, respectively. Understanding the water pollution characteristics of different administrative zones could put insights into effective water management policy-making especially in the area across various administrative zones.

Multi-geophysical approaches to detect karst channels underground - A case study in Mengzi of Yunnan Province, China

NASA Astrophysics Data System (ADS)

Gan, Fuping; Han, Kai; Lan, Funing; Chen, Yuling; Zhang, Wei

2017-01-01

Mengzi locates in the south 20 km away from the outlet of Nandong subsurface river, and has been suffering from water deficiency in recent years. It is necessary to find out the water resources underground according to the geological characteristics such as the positions and buried depths of the underground river to improve the civil and industrial environments. Due to the adverse factors such as topographic relief, bare rocks in karst terrains, the geophysical approaches, such as Controlled Source Audio Magnetotellurics and Seismic Refraction Tomography, were used to roughly identify faults and fracture zones by the geophysical features of low resistivity and low velocity, and then used the mise-a-la-masse method to judge which faults and fracture zones should be the potential channels of the subsurface river. Five anomalies were recognized along the profile of 2.4 km long and showed that the northeast river system has several branches. Drilling data have proved that the first borehole indicated a water bearing channel by a characteristics of rock core of river sands and gravels deposition, the second one encountered water-filled fracture zone with abundant water, and the third one exposed mud-filled fracture zone without sustainable water. The results from this case study show that the combination of Controlled Source Audio Magnetotellurics, Seismic Refraction Tomography and mise-a-la-Masse is one of the effective methods to detect water-filled channels or fracture zones in karst terrains.

Reductive dechlorination of trichloroethene DNAPL source zones: source zone architecture versus electron donor availability

NASA Astrophysics Data System (ADS)

Krol, M.; Kokkinaki, A.; Sleep, B.

2014-12-01

The persistence of dense-non-aqueous-phase liquids (DNAPLs) in the subsurface has led practitioners and regulatory agencies to turn towards low-maintenance, low-cost remediation methods. Biological degradation has been suggested as a possible solution, based on the well-proven ability of certain microbial species to break down dissolved chlorinated ethenes under favorable conditions. However, the biodegradation of pure phase chlorinated ethenes is subject to additional constraints: the continuous release of electron acceptor at a rate governed by mass transfer kinetics, and the temporal and spatial heterogeneity of DNAPL source zones which leads to spatially and temporally variable availability of the reactants for reductive dechlorination. In this work, we investigate the relationship between various DNAPL source zone characteristics and reaction kinetics using COMPSIM, a multiphase groundwater model that considers non-equilibrium mass transfer and Monod-type kinetics for reductive dechlorination. Numerical simulations are performed for simple, homogeneous trichloroethene DNAPL source zones to demonstrate the effect of single source zone characteristics, as well as for larger, more realistic heterogeneous source zones. It is shown that source zone size, and mass transfer kinetics may have a decisive effect on the predicted bio-enhancement. Finally, we evaluate the performance of DNAPL bioremediation for realistic, thermodynamically constrained, concentrations of electron donor. Our results indicate that the latter may be the most important limitation for the success of DNAPL bioremediation, leading to reduced bio-enhancement and, in many cases, comparable performance with water flooding.

Palaeogeography of late Cambrian to early Ordovician sediments in the Amadeus Basin, central Australia

NASA Astrophysics Data System (ADS)

Gorter, John D.

The depositional history of 6 sequences encompassing 18 parasequence of the Late Cambrian to Early Ordovician age in the Amadeus Basin is presented in a seried of generalized paleogeographic maps. As some of the parasequence sets are known to host large deposits of oil and gas, a thorough understanding of the potential reservoir-source rock combinations in the Amadeus Basin is essential for the discovery of further oil and gas reserves in this vast, under-explored basin. The best reservoir rocks in the Pacoota Sandstone are concentrated above the major sequence boundary between the Wallaby and Tempe Vale sequences on the Central Ridge. Poorer reservoirs occur within other sequences (e.g., parasequence set 3 and 13). Parasequence set 3 reservoirs, localized on the Central Ridge, are generally poor but owe their reservoir character to weathering at the pre-Tempe Vale sequence unconformity. Parasequence set 13 reservoirs are also concenterated along the Central Ridge, where small-scale shoaling clastic cycles are better developed. Basal Stairway Sandstone reservoirs in the Mereenie area on the Central Ridge are generally very poor, due to the cementation of the clean sandstone, but should improve to the southwest due to lesser burial-induced silicification. The source potential of the major Arenig organic-rich sediments is concentrated in the transitional zone between parasequence sets 15 and 16. East of West Waterhouse 1 well, these parasequence sets have been eroded and there is no remaining source potential. The transitional source-rich zone is better developed on the Central Ridge than in the Missionary Plain Trough. The Central Ridge is therefore of prime importance in the localization of both reservoir and source rocks in the Late Cambrian and Early Ordovician section of the Amadeus Basin.

Bioenhanced DNAPL Dissolution: Understanding how Microbial Competition, Biostimulation, and Bioaugmentation Affect Source Zone Longevity

NASA Astrophysics Data System (ADS)

Becker, J. G.; Seagren, E. A.

2006-12-01

The presence of dense non-aqueous phase liquids (DNAPLs) at many chlorinated ethene-contaminated sites can greatly extend the time frames needed to reduce dissolved contaminants to regulatory levels using bioremediation. However, it has been demonstrated that mass removal from chlorinated ethene DNAPLs can potentially be enhanced through dehalorespiration of dissolved contaminants near the NAPL-water interface. Although promising, the amount of "bioenhancement" that can be achieved under optimal conditions is currently not known, and the real significance and engineering potential of this phenomenon currently are not well understood, in part because it can be influenced by a complex set of factors, including DNAPL properties, hydrodynamics, substrate concentrations, and microbial competition for growth substrates. In this study it is hypothesized that: (1) different chlorinated ethene-respiring strains may dominate within different zones of a contaminant plume emanating from a DNAPL source zone due to variations in substrate availability, and microbial competition for chlorinated ethenes and/or electron donors; and (2) the outcome of competitive interactions near the DNAPL source zone will affect the longevity of DNAPL source zones by influencing the degree of dissolution bioenhancement, while the outcome of competitive interactions further downgradient will determine the extent of contaminant dechlorination. To demonstrate the validity of the proposed hypothesis, a series of simple, "proof-of-concept," mathematical simulations evaluating the effects of competitive interactions on the distribution of dehalorespirers at the DNAPL-water interface, the dissolution of tetrachloroethene (PCE), and extent of PCE detoxification were performed in a model competition scenario, in which Dehalococcoides ethenogenes and another dehalorespirer (Desulfuromonas michiganensis) compete for the electron acceptor (PCE) and/or electron donor. The model domain for this evaluation simulates a contaminant-source zone consisting of DNAPL ganglia trapped in a subsurface porous medium that slowly releases organic pollutants into the groundwater flowing past it. The model used in the simulations was based on a biokinetic model recently developed by Becker [Environ. Sci. Technol. 40(14):4473-4480] to describe competition among PCE-respiring populations in a homogenous continuously-stirred tank reactor. Becker's model was expanded by adding terms for chlorinated ethene partitioning between the DNAPL and aqueous phases, as well as advection and dispersion of aqueous chlorinated ethenes. The results of these preliminary simulations demonstrate that the outcome of competition between populations for growth substrates can have a significant impact on bioenhancement and, thus, on DNAPL source zone longevity. Although these proof-of- concept simulations do not incorporate all of the complexity of actual field systems, the modeling results are useful for identifying which parameters are important in determining the outcome of competition in the different scenarios and its impact on DNAPL dissolution. This information is needed to understand how biostimulation and bioaugmentation affect bioenhancement by stimulating different populations and develop bioremediation strategies that incorporate these treatment technologies while balancing the twin clean-up goals of reduced source longevity and complete detoxification.

Influence of Intracranial Electrode Density and Spatial Configuration on Interictal Spike Localization: A Case Study.

PubMed

Lie, Octavian V; Papanastassiou, Alexander M; Cavazos, José E; Szabó, Ákos C

2015-10-01

Poor seizure outcomes after epilepsy surgery often reflect an incorrect localization of the epileptic sources by standard intracranial EEG interpretation because of limited electrode coverage of the epileptogenic zone. This study investigates whether, in such conditions, source modeling is able to provide more accurate source localization than the standard clinical method that can be used prospectively to improve surgical resection planning. Suboptimal epileptogenic zone sampling is simulated by subsets of the electrode configuration used to record intracranial EEG in a patient rendered seizure free after surgery. sLORETA and the clinical method solutions are applied to interictal spikes sampled with these electrode subsets and are compared for colocalization with the resection volume and displacement due to electrode downsampling. sLORETA provides often congruent and at times more accurate source localization when compared with the standard clinical method. However, with electrode downsampling, individual sLORETA solution locations can vary considerably and shift consistently toward the remaining electrodes. sLORETA application can improve source localization based on the clinical method but does not reliably compensate for suboptimal electrode placement. Incorporating sLORETA solutions based on intracranial EEG in surgical planning should proceed cautiously in cases where electrode repositioning is planned on clinical grounds.

Exploring for geothermal resource in a dormant volcanic system: The Haleakala Southwest Rift Zone, Maui, Hawai'i

NASA Astrophysics Data System (ADS)

Martini, B. A.; Lewicki, J. L.; Kennedy, B. M.; Lide, C.; Oppliger, G.; Drakos, P. S.

2011-12-01

Suites of new geophysical and geochemical surveys provide compelling evidence for geothermal resource at the Haleakala Southwest Rift Zone (HSWRZ) on Maui Island, Hawai'i. Ground-based gravity (~400 stations) coupled with heli-borne magnetics (~1500 line kilometers) define both deep and shallow fractures/faults while also delineating potentially widespread subsurface hydrothermal alteration on the lower flanks (below approximately 1800 feet a.s.l.). Multi-level, upward continuation calculations and 2-D gravity and magnetic modeling provide information on source depths, but lack of lithologic information leaves ambiguity in the estimates. Lithology and physical property data from future drilling will improve these interpretations. Additionally, several well-defined gravity lows (possibly vent zones) lie coincident with magnetic highs suggesting the presence of dike intrusions at depth; a potentially young source of heat for a modern geothermal system. Soil CO2 fluxes were measured along transects across geophysically-defined faults and fractures as well as young cinder cones along the HSWRZ; a weak anomalous flux signal was observed at one young cinder cone location. Dissolved inorganic carbon concentrations and δ13C compositions and 3He/4He values measured in several shallow groundwater samples indicate addition of magmatic CO2 and He to the groundwater system. The general lack of observed magmatic surface CO2 signals on the HSWRZ is therefore likely due to a combination of groundwater 'scrubbing' of CO2 and relatively high biogenic surface CO2 fluxes that mask magmatic CO2. Similar surveys at the Puna geothermal field on the Kilauea Lower East Rift Zone (KLERZ) also showed a lack of surface CO2 flux signals attributed to a magmatic source, while aqueous geochemistry indicated contribution of magmatic CO2 and He to shallow groundwaters at both Maui and Puna. As magma has been intercepted in geothermal drilling at the Puna field, the lack of measured surface CO2 flux associated with upflow of magmatic fluids here is likely due to the aforementioned 'scrubbing' from extensive groundwater flow, as well as high background biogenic CO2 flux. Deep, temperature gradient core holes have been sited based on these geophysical and geochemical datasets.

Predicting DNAPL Source Zone and Plume Response Using Site-Measured Characteristics

DTIC Science & Technology

2017-05-19

FINAL REPORT Predicting DNAPL Source Zone and Plume Response Using Site- Measured Characteristics SERDP Project ER-1613 MAY 2017...Final Report 3. DATES COVERED (From - To) 2007 - 2017 4. TITLE AND SUBTITLE PREDICTING DNAPL SOURCE ZONE AND PLUME RESPONSE USING SITE- MEASURED ...historical record of concentration and head measurements , particularly in the near-source region. For each site considered, currently available data

MEAN-FIELD SOLAR DYNAMO MODELS WITH A STRONG MERIDIONAL FLOW AT THE BOTTOM OF THE CONVECTION ZONE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pipin, V. V.; Kosovichev, A. G.

2011-09-01

This paper presents a study of kinematic axisymmetric mean-field dynamo models for the case of meridional circulation with a deep-seated stagnation point and a strong return flow at the bottom of the convection zone. This kind of circulation follows from mean-field models of the angular momentum balance in the solar convection zone. The dynamo models include turbulent sources of the large-scale poloidal magnetic field production due to kinetic helicity and a combined effect due to the Coriolis force and large-scale electric current. In these models the toroidal magnetic field, which is responsible for sunspot production, is concentrated at the bottommore » of the convection zone and is transported to low-latitude regions by a meridional flow. The meridional component of the poloidal field is also concentrated at the bottom of the convection zone, while the radial component is concentrated in near-polar regions. We show that it is possible for this type of meridional circulation to construct kinematic dynamo models that resemble in some aspects the sunspot magnetic activity cycle. However, in the near-equatorial regions the phase relation between the toroidal and poloidal components disagrees with observations. We also show that the period of the magnetic cycle may not always monotonically decrease with the increase of the meridional flow speed. Thus, for further progress it is important to determine the structure of the meridional circulation, which is one of the critical properties, from helioseismology observations.« less

Evaluation of Long-term Performance of Enhanced Anaerobic Source Zone Bioremediation using mass flux

NASA Astrophysics Data System (ADS)

Haluska, A.; Cho, J.; Hatzinger, P.; Annable, M. D.

2017-12-01

Chlorinated ethene DNAPL source zones in groundwater act as potential long term sources of contamination as they dissolve yielding concentrations well above MCLs, posing an on-going public health risk. Enhanced bioremediation has been applied to treat many source zones with significant promise, but long-term sustainability of this technology has not been thoroughly assessed. This study evaluated the long-term effectiveness of enhanced anaerobic source zone bioremediation at chloroethene contaminated sites to determine if the treatment prevented contaminant rebound and removed NAPL from the source zone. Long-term performance was evaluated based on achieving MCL-based contaminant mass fluxes in parent compound concentrations during different monitoring periods. Groundwater concertation versus time data was compiled for 6-sites and post-remedial contaminant mass flux data was then measured using passive flux meters at wells both within and down-gradient of the source zone. Post-remedial mass flux data was then combined with pre-remedial water quality data to estimate pre-remedial mass flux. This information was used to characterize a DNAPL dissolution source strength function, such as the Power Law Model and the Equilibrium Stream tube model. The six-sites characterized for this study were (1) Former Charleston Air Force Base, Charleston, SC; (2) Dover Air Force Base, Dover, DE; (3) Treasure Island Naval Station, San Francisco, CA; (4) Former Raritan Arsenal, Edison, NJ; (5) Naval Air Station, Jacksonville, FL; and, (6) Former Naval Air Station, Alameda, CA. Contaminant mass fluxes decreased for all the sites by the end of the post-treatment monitoring period and rebound was limited within the source zone. Post remedial source strength function estimates suggest that decreases in contaminant mass flux will continue to occur at these sites, but a mass flux based on MCL levels may never be exceeded. Thus, site clean-up goals should be evaluated as order-of-magnitude reductions. Additionally, sites may require monitoring for a minimum of 5-years in order to sufficiently evaluate remedial performance. The study shows that enhanced anaerobic source zone bioremediation contributed to a modest reduction of source zone contaminant mass discharge and appears to have mitigated rebound of chlorinated ethenes.

Rift Zone Abandonment and Reconfiguration in Hawaii: Evidence from Mauna Loa’s Ninole Rift Zone

NASA Astrophysics Data System (ADS)

Morgan, J. K.; Park, J.; Zelt, C. A.

2009-12-01

Large oceanic volcanoes commonly develop elongate rift zones that disperse viscous magmas to the distal reaches of the edifice. Intrusion and dike propagation occur under tension perpendicular to the rift zone, controlled by topography, magmatic pressures, and deformation of the edifice. However, as volcanoes grow and interact, the controlling stress fields can change, potentially altering the orientations and activities of rift zones. This phenomenon is probably common, and can produce complex internal structures that influence the evolution of a volcano and its neighbors. However, little direct evidence for such rift zone reconfiguration exists, primarily due to poor preservation or recognition of earlier volcanic configurations. A new onshore-offshore 3-D seismic velocity model for the Island of Hawaii, derived from a joint tomographic inversion of an offshore airgun shot - onshore receiver geometry and earthquake sources beneath the island, demonstrates a complicated history of rift zone reconfiguration on Mauna Loa volcano, Hawaii, including wholesale rift zone abandonment. Mauna Loa’s southeast flank contains a massive high velocity intrusive complex, now buried beneath flows derived from Mauna Loa’s active southwest rift zone (SWRZ). Introduced here as the Ninole Rift Zone, this feature extends more than 60 km south of Mauna Loa’s summit, spans a depth range of ~2-14 km below sea level, and is the probable source of the 100-200 ka Ninole volcanics in several prominent erosional hills. A lack of high velocities beneath the upper SWRZ and its separate zone of high velocities on the submarine flank, indicate that the younger rift zone was built upon a pre-existing edifice that emanated from the Ninole rift zone. The ancient Ninole rift zone may stabilize Mauna Loa’s southeast flank, focusing recent volcanic activity and deformation onto the unbuttressed west flank. The upper portion of the Ninole rift zone appears to have migrated westward over time, possibly triggered by landsliding, causing its eventual abandonment in preference to Mauna Loa’s present-day SWRZ. Subsequently, the lower SWRZ broke away, tracking rift intrusions along the trace of the Kahuku detachment fault. Similar rift zone migration is thought to be underway at Kilauea volcano, and may one-day lead to the abandonment of the east rift zone. Such rift zone reconfiguration is a reflection of changing stress conditions within growing volcanoes. It is probably much more common than previously assumed, and may enable the growth of very large volcanic edifices such as Mauna Loa.

Preparation of multilayered nanocrystalline thin films with composition-modulated interfaces

NASA Astrophysics Data System (ADS)

Biro, D.; Barna, P. B.; Székely, L.; Geszti, O.; Hattori, T.; Devenyi, A.

2008-06-01

The properties of multilayer thin film structures depend on the morphology and structure of interfaces. A broad interface, in which the composition is varying, can enhance, e.g., the hardness of multilayer thin films. In the present experiments multilayers of TiAlN and CrN as well as TiAlN, CrN and MoS 2 were studied by using unbalanced magnetron sputter sources. The sputter sources were arranged side by side on an arc. This arrangement permits development of a transition zone between the layers, where the composition changes continuously. The multilayer system was deposited by one-fold oscillating movement of substrates in front of sputter sources. Thicknesses of layers could be changed both by oscillation frequency and by the power applied to sputter sources. Ti/Al: 50/50 at%, pure chromium and MoS 2 targets were used in the sputter sources. The depositions were performed in an Ar-N 2 mixture at 0.22 Pa working pressure. The sputtering power of the TiAl source was feed-back adjusted in fuzzy-logic mode in order to avoid fluctuation of the TiAl target sputter rate due to poisoning of the target surface. Structure characterization of films deposited on <1 0 0> Si wafers covered by thermally grown SiO 2 was performed by cross-sectional transmission electron microscopy. At first a 100 nm thick Cr base layer was deposited on the substrate to improve adhesion, which was followed by a CrN transition layer. The CrN transition layer was followed by a 100 nm thick TiAlN/CrN multilayer system. The TiAlN/CrN/MoS 2 multilayer system was deposited on the surface of this underlayer system. The underlayer systems Cr, CrN and TiAlN/CrN were crystalline with columnar structure according to the morphology of zone T of the structure zone models. The column boundaries contained segregated phases showing up in the under-focused TEM images. The surface of the underlayer system was wavy due to dome-shaped columns. The nanometer-scaled TiAlN/CrN/MoS 2 multilayer system followed this waviness. Crystallinity of the TiAlN and CrN layers in the multilayer system decreases with increasing thickness of the MoS 2 layer.

Imaging the deep structures of the convergent plates along the Ecuadorian subduction zone through receiver function analysis

NASA Astrophysics Data System (ADS)

Galve, A.; Charvis, P.; Regnier, M. M.; Font, Y.; Nocquet, J. M.; Segovia, M.

2017-12-01

The Ecuadorian subduction zone was affected by several large M>7.5 earthquakes. While we have low resolution on the 1942, 1958 earthquakes rupture zones extension, the 2016 Pedernales earthquake, that occurs at the same location than the 1942 earthquake, give strong constraints on the deep limit of the seismogenic zone. This downdip limit is caused by the onset of plasticity at a critical temperature (> 350-450 °C for crustal materials, or serpentinized mantle wedge, and eventually > 700 °C for dry mantle). However we still don't know exactly where is the upper plate Moho and therefore what controls the downdip limit of Ecuadorian large earthquakes seismogenic zone. For several years Géoazur and IG-EPN have maintained permanent and temporary networks (ADN and JUAN projects) along the margin to register the subduction zone seismological activity. Although Ecuador is not a good place to perform receiver function due to its position with respect to the worldwide teleseismic sources, the very long time deployment compensate this issue. We performed a frequency dependent receiver function analysis to derive (1) the thickness of the downgoing plate, (2) the interplate depth and (3) the upper plate Moho. These constraints give the frame to interpretation on the seismogenic zone of the 2016 Pedernales earthquake.

Simulation Model of Mobile Detection Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edmunds, T; Faissol, D; Yao, Y

2009-01-27

In this paper, we consider a mobile source that we attempt to detect with man-portable, vehicle-mounted or boat-mounted radiation detectors. The source is assumed to transit an area populated with these mobile detectors, and the objective is to detect the source before it reaches a perimeter. We describe a simulation model developed to estimate the probability that one of the mobile detectors will come in to close proximity of the moving source and detect it. We illustrate with a maritime simulation example. Our simulation takes place in a 10 km by 5 km rectangular bay patrolled by boats equipped withmore » 2-inch x 4-inch x 16-inch NaI detectors. Boats to be inspected enter the bay and randomly proceed to one of seven harbors on the shore. A source-bearing boat enters the mouth of the bay and proceeds to a pier on the opposite side. We wish to determine the probability that the source is detected and its range from target when detected. Patrol boats select the nearest in-bound boat for inspection and initiate an intercept course. Once within an operational range for the detection system, a detection algorithm is started. If the patrol boat confirms the source is not present, it selects the next nearest boat for inspection. Each run of the simulation ends either when a patrol successfully detects a source or when the source reaches its target. Several statistical detection algorithms have been implemented in the simulation model. First, a simple k-sigma algorithm, which alarms with the counts in a time window exceeds the mean background plus k times the standard deviation of background, is available to the user. The time window used is optimized with respect to the signal-to-background ratio for that range and relative speed. Second, a sequential probability ratio test [Wald 1947] is available, and configured in this simulation with a target false positive probability of 0.001 and false negative probability of 0.1. This test is utilized when the mobile detector maintains a constant range to the vessel being inspected. Finally, a variation of the sequential probability ratio test that is more appropriate when source and detector are not at constant range is available [Nelson 2005]. Each patrol boat in the fleet can be assigned a particular zone of the bay, or all boats can be assigned to monitor the entire bay. Boats assigned to a zone will only intercept and inspect other boats when they enter their zone. In our example simulation, each of two patrol boats operate in a 5 km by 5 km zone. Other parameters for this example include: (1) Detection range - 15 m range maintained between patrol boat and inspected boat; (2) Inbound boat arrival rate - Poisson process with mean arrival rate of 30 boats per hour; (3) Speed of boats to be inspected - Random between 4.5 and 9 knots; (4) Patrol boat speed - 10 knots; (5) Number of detectors per patrol boat - 4-2-inch x 4-inch x 16-inch NaI detectors; (6) Background radiation - 40 counts/sec per detector; and (7) Detector response due to radiation source at 1 meter - 1,589 counts/sec per detector. Simulation results indicate that two patrol boats are able to detect the source 81% of the time without zones and 90% of the time with zones. The average distances between the source and target at the end of the simulation is 5,866 km and 5,712 km for non-zoned and zoned patrols, respectively. Of those that did not reach the target, the average distance to the target is 7,305 km and 6,441 km respectively. Note that a design trade-off exists. While zoned patrols provide a higher probability of detection, the nonzoned patrols tend to detect the source farther from its target. Figure 1 displays the location of the source at the end of 1,000 simulations for the 5 x 10 km bay simulation. The simulation model and analysis described here can be used to determine the number of mobile detectors one would need to deploy in order to have a have reasonable chance of detecting a source in transit. By fixing the source speed to zero, the same model could be used to estimate how long it would take to detect a stationary source. For example, the model could predict how long it would take plant staff performing assigned duties carrying dosimeters to discover a contaminated spot in the facility.« less

Slab Geometry and Segmentation on Seismogenic Subduction Zone; Insight from gravity gradients

NASA Astrophysics Data System (ADS)

Saraswati, A. T.; Mazzotti, S.; Cattin, R.; Cadio, C.

2017-12-01

Slab geometry is a key parameter to improve seismic hazard assessment in subduction zones. In many cases, information about structures beneath subduction are obtained from geophysical dedicated studies, including geodetic and seismic measurements. However, due to the lack of global information, both geometry and segmentation in seismogenic zone of many subductions remain badly-constrained. Here we propose an alternative approach based on satellite gravity observations. The GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission enables to probe Earth deep mass structures from gravity gradients, which are more sensitive to spatial structure geometry and directional properties than classical gravitational data. Gravity gradients forward modeling of modeled slab is performed by using horizontal and vertical gravity gradient components to better determine slab geophysical model rather than vertical gradient only. Using polyhedron method, topography correction on gravity gradient signal is undertaken to enhance the anomaly signal of lithospheric structures. Afterward, we compare residual gravity gradients with the calculated signals associated with slab geometry. In this preliminary study, straightforward models are used to better understand the characteristic of gravity gradient signals due to deep mass sources. We pay a special attention to the delineation of slab borders and dip angle variations.

Trading Time with Space - Development of subduction zone parameter database for a maximum magnitude correlation assessment

NASA Astrophysics Data System (ADS)

Schaefer, Andreas; Wenzel, Friedemann

2017-04-01

Subduction zones are generally the sources of the earthquakes with the highest magnitudes. Not only in Japan or Chile, but also in Pakistan, the Solomon Islands or for the Lesser Antilles, subduction zones pose a significant hazard for the people. To understand the behavior of subduction zones, especially to identify their capabilities to produce maximum magnitude earthquakes, various physical models have been developed leading to a large number of various datasets, e.g. from geodesy, geomagnetics, structural geology, etc. There have been various studies to utilize this data for the compilation of a subduction zone parameters database, but mostly concentrating on only the major zones. Here, we compile the largest dataset of subduction zone parameters both in parameter diversity but also in the number of considered subduction zones. In total, more than 70 individual sources have been assessed and the aforementioned parametric data have been combined with seismological data and many more sources have been compiled leading to more than 60 individual parameters. Not all parameters have been resolved for each zone, since the data completeness depends on the data availability and quality for each source. In addition, the 3D down-dip geometry of a majority of the subduction zones has been resolved using historical earthquake hypocenter data and centroid moment tensors where available and additionally compared and verified with results from previous studies. With such a database, a statistical study has been undertaken to identify not only correlations between those parameters to estimate a parametric driven way to identify potentials for maximum possible magnitudes, but also to identify similarities between the sources themselves. This identification of similarities leads to a classification system for subduction zones. Here, it could be expected if two sources share enough common characteristics, other characteristics of interest may be similar as well. This concept technically trades time with space, considering subduction zones where we have likely not observed the maximum possible event yet. However, by identifying sources of the same class, the not-yet observed temporal behavior can be replaced by spatial similarity among different subduction zones. This database aims to enhance the research and understanding of subduction zones and to quantify their potential in producing mega earthquakes considering potential strong motion impact on nearby cities and their tsunami potential.

Morphology of auroral zone radio wave scintillation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rino, C.L.; Matthews, S.J.

1980-08-01

This paper describes the morphology of midnight sector and morning sector auroral zone scintillation observations made over a two-year period using the Wideband satelite, which is in a sun-synchronous, low-altitude orbit. No definitive seasonal variation was found. The nighttime data showed the highest scintillation ocurrence levels, but significant amounts of morning scintillation were observed. For the most part the scintillation activity followed the general pattern of local magnetic activity. The most prominent feature in the nightime data is a localized amplitude and phase scintillation enhancement at the point where the propagation vector lies within an L shell. A geometrical effectmore » due to a dynamic slab of sheetlike structures in the F region is hypothesized as the source of his enhancement. The data have been sorted by magnetic activity, proximity to local midnight, and season. The general features of the data are in agreement with the accepted morphology of auroral zone scintillation.« less

Qualitative and semiquantitative Fourier transformation using a noncoherent system.

PubMed

Rogers, G L

1979-09-15

A number of authors have pointed out that a system of zone plates combined with a diffuse source, transparent input, lens, and focusing screen will display on the output screen the Fourier transform of the input. Strictly speaking, the transform normally displayed is the cosine transform, and the bipolar output is superimposed on a dc gray level to give a positive-only intensity variation. By phase-shifting one zone plate the sine transform is obtained. Temporal modulation is possible. It is also possible to redesign the system to accept a diffusely reflecting input at the cost of introducing a phase gradient in the output. Results are given of the sine and cosine transforms of a small circular aperture. As expected, the sine transform is a uniform gray. Both transforms show unwanted artifacts beyond 0.1 rad off-axis. An analysis shows this is due to unwanted circularly symmetrical moire patterns between the zone plates.

Sanitary protection zoning based on time-dependent vulnerability assessment model - case examples at two different type of aquifers

NASA Astrophysics Data System (ADS)

Živanović, Vladimir; Jemcov, Igor; Dragišić, Veselin; Atanacković, Nebojša

2017-04-01

Delineation of sanitary protection zones of groundwater source is a comprehensive and multidisciplinary task. Uniform methodology for protection zoning for various type of aquifers is not established. Currently applied methods mostly rely on horizontal groundwater travel time toward the tapping structure. On the other hand, groundwater vulnerability assessment methods evaluate the protective function of unsaturated zone as an important part of groundwater source protection. In some particular cases surface flow might also be important, because of rapid transfer of contaminants toward the zones with intense infiltration. For delineation of sanitary protection zones three major components should be analysed: vertical travel time through unsaturated zone, horizontal travel time through saturated zone and surface water travel time toward intense infiltration zones. Integrating the aforementioned components into one time-dependent model represents a basis of presented method for delineation of groundwater source protection zones in rocks and sediments of different porosity. The proposed model comprises of travel time components of surface water, as well as groundwater (horizontal and vertical component). The results obtained using the model, represent the groundwater vulnerability as the sum of the surface and groundwater travel time and corresponds to the travel time of potential contaminants from the ground surface to the tapping structure. This vulnerability assessment approach do not consider contaminant properties (intrinsic vulnerability) although it can be easily improved for evaluating the specific groundwater vulnerability. This concept of the sanitary protection zones was applied at two different type of aquifers: karstic aquifer of catchment area of Blederija springs and "Beli Timok" source of intergranular shallow aquifer. The first one represents a typical karst hydrogeological system with part of the catchment with allogenic recharge, and the second one, the groundwater source within shallow intergranular alluvial aquifer, dominantly recharged by river bank filtration. For sanitary protection zones delineation, the applied method has shown the importance of introducing all travel time components equally. In the case of the karstic source, the importance of the surface flow toward ponor zones has been emphasized, as a consequence of rapid travel time of water in relation to diffuse infiltration from autogenic part. When it comes to the shallow intergranular aquifer, the character of the unsaturated zone gets more prominent role in the source protection, as important buffer of the vertical movement downward. The applicability of proposed method has been shown regardless of the type of the aquifer, and at the same time intelligible results of the delineated sanitary protection zones are possible to validate with various methods. Key words: groundwater protection zoning, time dependent model, karst aquifer, intergranular aquifer, groundwater source protection

Anisotropy in subduction zones: Insights from new source side S wave splitting measurements from India

NASA Astrophysics Data System (ADS)

Roy, Sunil K.; Kumar, M. Ravi; Davuluri, Srinagesh

2017-08-01

This study presents 106 splitting and 40 null measurements of source side anisotropy in subduction zones, utilizing direct S waves registered at two stations sited on the Indian continent, which show null shear wave splitting measurements for SKS phases. Our results suggest that trench-parallel anisotropy is dominant beneath the Philippines, Mariana, Izu-Bonin, and edge of the Java slab, while plate motion-parallel anisotropy is observed beneath the Solomon, Aegean, Japan, and Java slabs. Results from Kuril and Aleutian regions reveal trench-oblique anisotropy. We chose to interpret these observations primarily in terms of mantle flow beneath a subduction zone. While the two-dimensional (2-D) slab entrained flow model offers a simple explanation for trench-normal fast polarization azimuths (FPA), the trench-parallel FPA can be reconciled by extension due to slab rollback. The model that invokes age of the subducting lithosphere can explain anisotropy in the subslab, derived from rays recorded at the updip stations. However, when downdip stations are used, contributions from the slab and supraslab need to be considered. In Japan, anisotropy in the subslab mantle shallower than 300 km might be associated with trench-parallel mantle flow resulting in the alignment of FPA in the same direction. Anisotropy in the deeper part, above the transition zone, is probably associated with 2-D flow resulting in trench-normal FPA. Anisotropy in the Mariana Trench might be associated with trench-parallel mantle flow in the supraslab region, with similar deformation in the upper mantle and the transition zone.

Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

USGS Publications Warehouse

Peacock, Jared R.; Selway, Katherine

2016-01-01

The Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time-frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind-blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2-D and 3-D produce similar resistivity models, where structures in the preferred 3-D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.

Determination of Antimicrobial Activity of Sorrel (Hibiscus sabdariffa) on Esherichia coli O157:H7 Isolated from Food, Veterinary, and Clinical Samples

PubMed Central

Fullerton, Marjorie; Khatiwada, Janak; Johnson, Jacqueline U.; Davis, Shurrita

2011-01-01

Abstract The use of medicinal plants as natural antimicrobial agents is gaining popularity. Sorrel (Hibiscus sabdariffa) is widely used for the treatment of diseases. The objective of this study was to investigate the antimicrobial activity of sorrel on Escherichia coli O157:H7 isolates from food, veterinary, and clinical samples. Phenolics of the calyces were extracted from 10 g of ground, freeze-dried samples using 100 mL of 80% aqueous methanol. Concentrations of 10%, 5%, and 2.5% methanol extract of sorrel were investigated for its antimicrobial activity. Inhibition zones were indicated by a lack of microbial growth due to inhibitory concentrations of sorrel diffused into semisolid culture medium beneath the sorrel-impregnated disk. The results of this experiment showed that the most potent sorrel concentration was 10%, then 5%, and finally 2.5%. The overall mean zone of inhibition for the sorrel extract was 12.66 mm for 10%, 10.75 mm for 5%, and 8.9 mm for 2.5%. The highest inhibition zones (11.16 mm) were observed in veterinary samples, and the lowest (10.57 mm) in the food samples. There were significant (P<.05) differences among mean zones of inhibition found in the food, veterinary, and clinical sources. Based on the source of samples and concentration of sorrel extract, the lowest mean inhibition was 7.00±0.04 mm from clinical samples, and the highest was 15.37±0.61 mm from a food source. These findings indicated that sorrel was effective at all levels in inhibiting E. coli O157:H7; thus it possesses antimicrobial activity and hold great promise as an antimicrobial agent. PMID:21548802

Determination of antimicrobial activity of sorrel (Hibiscus sabdariffa) on Escherichia coli O157:H7 isolated from food, veterinary, and clinical samples.

PubMed

Fullerton, Marjorie; Khatiwada, Janak; Johnson, Jacqueline U; Davis, Shurrita; Williams, Leonard L

2011-09-01

The use of medicinal plants as natural antimicrobial agents is gaining popularity. Sorrel (Hibiscus sabdariffa) is widely used for the treatment of diseases. The objective of this study was to investigate the antimicrobial activity of sorrel on Escherichia coli O157:H7 isolates from food, veterinary, and clinical samples. Phenolics of the calyces were extracted from 10 g of ground, freeze-dried samples using 100 mL of 80% aqueous methanol. Concentrations of 10%, 5%, and 2.5% methanol extract of sorrel were investigated for its antimicrobial activity. Inhibition zones were indicated by a lack of microbial growth due to inhibitory concentrations of sorrel diffused into semisolid culture medium beneath the sorrel-impregnated disk. The results of this experiment showed that the most potent sorrel concentration was 10%, then 5%, and finally 2.5%. The overall mean zone of inhibition for the sorrel extract was 12.66 mm for 10%, 10.75 mm for 5%, and 8.9 mm for 2.5%. The highest inhibition zones (11.16 mm) were observed in veterinary samples, and the lowest (10.57 mm) in the food samples. There were significant (P<.05) differences among mean zones of inhibition found in the food, veterinary, and clinical sources. Based on the source of samples and concentration of sorrel extract, the lowest mean inhibition was 7.00±0.04 mm from clinical samples, and the highest was 15.37±0.61 mm from a food source. These findings indicated that sorrel was effective at all levels in inhibiting E. coli O157:H7; thus it possesses antimicrobial activity and hold great promise as an antimicrobial agent.

Monitoring marine recreational water quality using multiple microbial indicators in an urban tropical environment

PubMed Central

Shibata, Tomoyuki; Solo-Gabriele, Helena M.; Fleming, Lora E.; Elmir, Samir

2008-01-01

The microbial water quality at two beaches, Hobie Beach and Crandon Beach, in Miami-Dade County, Florida, USA was measured using multiple microbial indicators for the purpose of evaluating correlations between microbes and for identifying possible sources of contamination. The indicator microbes chosen for this study (enterococci, Escherichia coli, fecal coliform, total coliform and C. perfringens) were evaluated through three different sampling efforts. These efforts included daily measurements at four locations during a wet season month and a dry season month, spatially intensive water sampling during low- and high-tide periods, and a sand sampling effort. Results indicated that concentrations did not vary in a consistent fashion between one indicator microbe and another. Daily water quality frequently exceeded guideline levels at Hobie Beach for all indicator microbes except for fecal coliform, which never exceeded the guideline. Except for total coliform, the concentrations of microbes did not change significantly between seasons in spite of the fact that the physical–chemical parameters (rainfall, temperature, pH, and salinity) changed significantly between the two monitoring periods. Spatially intense water sampling showed that the concentrations of microbes were significantly different with distance from the shoreline. The highest concentrations were observed at shoreline points and decreased at offshore points. Furthermore, the highest concentrations of indicator microbe concentrations were observed at high tide, when the wash zone area of the beach was submerged. Beach sands within the wash zone tested positive for all indicator microbes, thereby suggesting that this zone may serve as the source of indicator microbes. Ultimate sources of indicator microbes to this zone may include humans, animals, and possibly the survival and regrowth of indicator microbes due to the unique environmental conditions found within this zone. Overall, the results of this study indicated that the concentrations of indicator microbes do not necessarily correlate with one another. Exceedence of water quality guidelines, and thus the frequency of beach advisories, depends upon which indicator microbe is chosen. PMID:15261551

Assessing the joint impact of DNAPL source-zone behavior and degradation products on the probabilistic characterization of human health risk

NASA Astrophysics Data System (ADS)

Henri, Christopher V.; Fernàndez-Garcia, Daniel; de Barros, Felipe P. J.

2016-02-01

The release of industrial contaminants into the subsurface has led to a rapid degradation of groundwater resources. Contamination caused by Dense Non-Aqueous Phase Liquids (DNAPLs) is particularly severe owing to their limited solubility, slow dissolution and in many cases high toxicity. A greater insight into how the DNAPL source zone behavior and the contaminant release towards the aquifer impact human health risk is crucial for an appropriate risk management. Risk analysis is further complicated by the uncertainty in aquifer properties and contaminant conditions. This study focuses on the impact of the DNAPL release mode on the human health risk propagation along the aquifer under uncertain conditions. Contaminant concentrations released from the source zone are described using a screening approach with a set of parameters representing several scenarios of DNAPL architecture. The uncertainty in the hydraulic properties is systematically accounted for by high-resolution Monte Carlo simulations. We simulate the release and the transport of the chlorinated solvent perchloroethylene and its carcinogenic degradation products in randomly heterogeneous porous media. The human health risk posed by the chemical mixture of these contaminants is characterized by the low-order statistics and the probability density function of common risk metrics. We show that the zone of high risk (hot spot) is independent of the DNAPL mass release mode, and that the risk amplitude is mostly controlled by heterogeneities and by the source zone architecture. The risk is lower and less uncertain when the source zone is formed mostly by ganglia than by pools. We also illustrate how the source zone efficiency (intensity of the water flux crossing the source zone) affects the risk posed by an exposure to the chemical mixture. Results display that high source zone efficiencies are counter-intuitively beneficial, decreasing the risk because of a reduction in the time available for the production of the highly toxic subspecies.

Temporal trend and source apportionment of water pollution in different functional zones of Qiantang River, China.

PubMed

Su, Shiliang; Li, Dan; Zhang, Qi; Xiao, Rui; Huang, Fang; Wu, Jiaping

2011-02-01

The increasingly serious river water pollution in developing countries poses great threat to environmental health and human welfare. The assignment of river function to specific uses, known as zoning, is a useful tool to reveal variations of water environmental adaptability to human impact. Therefore, characterizing the temporal trend and identifying responsible pollution sources in different functional zones could greatly improve our knowledge about human impacts on the river water environment. The aim of this study is to obtain a deeper understanding of temporal trends and sources of water pollution in different functional zones with a case study of the Qiantang River, China. Measurement data were obtained and pretreated for 13 variables from 41 monitoring sites in four categories of functional zones during the period 1996-2004. An exploratory approach, which combines smoothing and non-parametric statistical tests, was applied to characterize trends of four significant parameters (permanganate index, ammonia nitrogen, total cadmium and fluoride) accounting for differences among different functional zones identified by discriminant analysis. Aided by GIS, yearly pollution index (PI) for each monitoring site was further mapped to compare the within-group variations in temporal dynamics for different functional zones. Rotated principal component analysis and receptor model (absolute principle component score-multiple linear regression, APCS-MLR) revealed that potential pollution sources and their corresponding contributions varied among the four functional zones. Variations of APCS values for each site of one functional zone as well as their annual average values highlighted the uncertainties associated with cross space-time effects in source apportionment. All these results reinforce the notion that the concept of zoning should be taken seriously in water pollution control. Being applicable to other rivers, the framework of management-oriented source apportionment is thus believed to have potentials to offer new insights into water management and advance the source apportionment framework as an operational basis for national and local governments. © 2010 Elsevier Ltd. All rights reserved.

Evaluating time-lapse ERT for monitoring DNAPL remediation via numerical simulation

NASA Astrophysics Data System (ADS)

Power, C.; Karaoulis, M.; Gerhard, J.; Tsourlos, P.; Giannopoulos, A.

2012-12-01

Dense non-aqueous phase liquids (DNAPLs) remain a challenging geoenvironmental problem in the near subsurface. Numerous thermal, chemical, and biological treatment methods are being applied at sites but without a non-destructive, rapid technique to map the evolution of DNAPL mass in space and time, the degree of remedial success is difficult to quantify. Electrical resistivity tomography (ERT) has long been presented as highly promising in this context but has not yet become a practitioner's tool due to challenges in interpreting the survey results at real sites where the initial condition (DNAPL mass, DNAPL distribution, subsurface heterogeneity) is typically unknown. Recently, a new numerical model was presented that couples DNAPL and ERT simulation at the field scale, providing a tool for optimizing ERT application and interpretation at DNAPL sites (Power et al., 2011, Fall AGU, H31D-1191). The objective of this study is to employ this tool to evaluate the effectiveness of time-lapse ERT to monitor DNAPL source zone remediation, taking advantage of new inversion methodologies that exploit the differences in the target over time. Several three-dimensional releases of chlorinated solvent DNAPLs into heterogeneous clayey sand at the field scale were generated, varying in the depth and complexity of the source zone (target). Over time, dissolution of the DNAPL in groundwater was simulated with simultaneous mapping via periodic ERT surveys. Both surface and borehole ERT surveys were conducted for comparison purposes. The latest four-dimensional ERT inversion algorithms were employed to generate time-lapse isosurfaces of the DNAPL source zone for all cases. This methodology provided a qualitative assessment of the ability of ERT to track DNAPL mass removal for complex source zones in realistically heterogeneous environments. In addition, it provided a quantitative comparison between the actual DNAPL mass removed and that interpreted by ERT as a function of depth below the water table, as well as an estimate of the minimum DNAPL saturation changes necessary for an observable response from ERT.

Plasma-catalyzed fuel reformer

DOEpatents

Hartvigsen, Joseph J.; Elangovan, S.; Czernichowski, Piotr; Hollist, Michele

2013-06-11

A reformer is disclosed that includes a plasma zone to receive a pre-heated mixture of reactants and ionize the reactants by applying an electrical potential thereto. A first thermally conductive surface surrounds the plasma zone and is configured to transfer heat from an external heat source into the plasma zone. The reformer further includes a reaction zone to chemically transform the ionized reactants into synthesis gas comprising hydrogen and carbon monoxide. A second thermally conductive surface surrounds the reaction zone and is configured to transfer heat from the external heat source into the reaction zone. The first thermally conductive surface and second thermally conductive surface are both directly exposed to the external heat source. A corresponding method and system are also disclosed and claimed herein.

Efficient growth of HTS films with volatile elements

DOEpatents

Siegal, M.P.; Overmyer, D.L.; Dominguez, F.

1998-12-22

A system is disclosed for applying a volatile element-HTS layer, such as Tl-HTS, to a substrate in a multiple zone furnace, said method includes heating at higher temperature, in one zone of the furnace, a substrate and adjacent first source of Tl-HTS material, to sublimate Tl-oxide from the source to the substrate; and heating at lower temperature, in a separate zone of the furnace, a second source of Tl-oxide to replenish the first source of Tl-oxide from the second source. 3 figs.

Magnetic Data Interpretation for the Source-Edge Locations in Parts of the Tectonically Active Transition Zone of the Narmada-Son Lineament in Central India

NASA Astrophysics Data System (ADS)

Ghosh, G. K.

2016-02-01

The study has been carried out in the transition zone of the Narmada-Son lineament (NSL) which is seismically active with various geological complexities, upwarp movement of the mantle material into the crust through fault, fractures lamination and upwelling. NSL is one of the most prominent lineaments in central India after the Himalaya in the Indian geology. The area of investigation extends from longitude 80.25°E to 81.50°E and latitude 23.50°N to 24.37°N in the central part of the Indian continent. Different types of subsurface geological formations viz. alluvial, Gondwana, Deccan traps, Vindhyan, Mahakoshal, Granite and Gneisses groups exist in this area with varying geological ages. In this study area tectonic movement and crustal variation have been taken place during the past time and which might be reason for the variation of magnetic field. Magnetic anomaly suggests that the area has been highly disturbed which causes the Narmada-Son lineament trending in the ENE-WSW direction. Magnetic anomaly variation has been taken place due to the lithological variations subject to the changes in the geological contacts like thrusts and faults in this area. Shallow and deeper sources have been distinguished using frequency domain analysis by applying different filters. To enhance the magnetic data, various types of derivatives to identify the source-edge locations of the causative source bodies. The present study carried out the interpretation using total horizontal derivative, tilt angle derivative, horizontal tilt angle derivative and Cos (θ) derivative map to get source-edge locations. The results derived from various derivatives of magnetic data have been compared with the basement depth solutions calculated from 3D Euler deconvolution. It is suggested that total horizontal derivative, tilt angle derivative and Cos (θ) derivative are the most useful tools for identifying the multiple source edge locations of the causative bodies in this tectonically active and transition zone area. As this area is highly prone to hydrocarbon bearing zone, hence, the integrated interpretation could reliably image various thrusts and faults boundaries and the source edge locations with dip and strike orientation along with the basement lineation in encouraging exploration for better understanding of the geo-scientific data.

Seismotectonics of the Eastern Himalayan System and Indo-Burman Convergence Zone Using Seismic Waveform Inversion

NASA Astrophysics Data System (ADS)

Kumar, A.; Mitra, S.; Suresh, G.

2014-12-01

The Eastern Himalayan System (east of 88°E) is distinct from the rest of the India-Eurasia continental collision, due to a wider zone of distributed deformation, oblique convergence across two orthogonal plate boundaries and near absence of foreland basin sedimentary strata. To understand the seismotectonics of this region we study the spatial distribution and source mechanism of earthquakes originating within Eastern Himalaya, northeast India and Indo-Burman Convergence Zone (IBCZ). We compute focal mechanism of 32 moderate-to-large earthquakes (mb >=5.4) by modeling teleseismic P- and SH-waveforms, from GDSN stations, using least-squares inversion algorithm; and 7 small-to-moderate earthquakes (3.5<= mb <5.4) by modeling local P- and S-waveforms, from the NorthEast India Telemetered Network, using non-linear grid search algorithm. We also include source mechanisms from previous studies, either computed by waveform inversion or by first motion polarity from analog data. Depth distribution of modeled earthquakes reveal that the seismogenic layer beneath northeast India is ~45km thick. From source mechanisms we observe that moderate earthquakes in northeast India are spatially clustered in five zones with distinct mechanisms: (a) thrust earthquakes within the Eastern Himalayan wedge, on north dipping low angle faults; (b) thrust earthquakes along the northern edge of Shillong Plateau, on high angle south dipping fault; (c) dextral strike-slip earthquakes along Kopili fault zone, between Shillong Plateau and Mikir Hills, extending southeast beneath Naga Fold belts; (d) dextral strike-slip earthquakes within Bengal Basin, immediately south of Shillong Plateau; and (e) deep focus (>50 km) thrust earthquakes within IBCZ. Combining with GPS geodetic observations, it is evident that the N20E convergence between India and Tibet is accommodated as elastic strain both within eastern Himalaya and regions surrounding the Shillong Plateau. We hypothesize that the strike-slip earthquakes south of the Plateau occur on re-activated continental rifts paralleling the Eocene hinge zone. Distribution of earthquake hypocenters across the IBCZ reveal active subduction of the Indian plate beneath Burma micro-plate.

Spontaneous Growth and Mobilization of a Gas Phase in the Presence of Dense Non- Aqueous Phase Liquid (DNAPL)

NASA Astrophysics Data System (ADS)

Roy, J. W.; Smith, J. E.

2006-12-01

A number of mechanisms can lead to the presence of disconnected bubbles or ganglia of gas phase in groundwater. When associated with or near a DNAPL phase, the disconnected gas phase experiences mass transfer of dissolved gases including the volatile components of the DNAPL. The properties of the gas phase interface, such as interfacial tension and contact angle, can also be affected. This work addresses the behavior of spontaneous continual growth of initially trapped seed gas bubbles within DNAPL source zones. Three different experiments were performed in a 2-dimensional transparent flow cell 15 cm by 20 cm by 1.5 cm. In each case, a DNAPL pool was created within larger glass beads over smaller glass beads that served as a capillary barrier. The DNAPL consisted of either a 1:2 (v/v) tetrachloroethene (PCE) to benzene mixture, single component PCE, or single component TCE. The experiments effectively demonstrate spontaneous gas phase expansion and vertical advective mobilization of gas bubbles and ganglia above the DNAPL source zone. A cycle of gas phase growth and mobilization was facilitated by the presence of secondary seed bubbles left behind due to snap-off during vertical bubble (ganglion) mobilization. This gas phase growth process was relatively slow but continuous and could be expected to continue until the NAPL is completely dissolved. Some implications of the demonstrated behavior for water flow and mass transfer within and near the DNAPL source zone are highlighted.

Modeling tidal exchange and dispersion in Boston Harbor

USGS Publications Warehouse

Signell, Richard P.; Butman, Bradford

1992-01-01

Tidal dispersion and the horizontal exchange of water between Boston Harbor and the surrounding ocean are examined with a high-resolution (200 m) depth-averaged numerical model. The strongly varying bathymetry and coastline geometry of the harbor generate complex spatial patterns in the modeled tidal currents which are verified by shipboard acoustic Doppler surveys. Lagrangian exchange experiments demonstrate that tidal currents rapidly exchange and mix material near the inlets of the harbor due to asymmetry in the ebb/flood response. This tidal mixing zone extends roughly a tidal excursion from the inlets and plays an important role in the overall flushing of the harbor. Because the tides can only efficiently mix material in this limited region, however, harbor flushing must be considered a two step process: rapid exchange in the tidal mixing zone, followed by flushing of the tidal mixing zone by nontidal residual currents. Estimates of embayment flushing based on tidal calculations alone therefore can significantly overestimate the flushing time that would be expected under typical environmental conditions. Particle-release simulations from point sources also demonstrate that while the tides efficiently exchange material in the vicinity of the inlets, the exact nature of dispersion from point sources is extremely sensitive to the timing and location of the release, and the distribution of particles is streaky and patchlike. This suggests that high-resolution modeling of dispersion from point sources in these regions must be performed explicitly and cannot be parameterized as a plume with Gaussian-spreading in a larger scale flow field.

Modeling the Impact of Cracking in Low Permeability Layers in a Groundwater Contamination Source Zone on Dissolved Contaminant Fate and Transport

NASA Astrophysics Data System (ADS)

Sievers, K. W.; Goltz, M. N.; Huang, J.; Demond, A. H.

2011-12-01

Dense Non-Aqueous Phase Liquids (DNAPLs), which are chemicals and chemical mixtures that are heavier than and only slightly soluble in water, are a significant source of groundwater contamination. Even with the removal or destruction of most DNAPL mass, small amounts of remaining DNAPL can dissolve into flowing groundwater and continue as a contamination source for decades. One category of DNAPLs is the chlorinated aliphatic hydrocarbons (CAHs). CAHs, such as trichloroethylene and carbon tetrachloride, are found to contaminate groundwater at numerous DoD and industrial sites. DNAPLs move through soils and groundwater leaving behind residual separate phase contamination as well as pools sitting atop low permeability layers. Recently developed models are based on the assumption that dissolved CAHs diffuse slowly from pooled DNAPL into the low permeability layers. Subsequently, when the DNAPL pools and residual DNAPL are depleted, perhaps as a result of a remediation effort, the dissolved CAHs in these low permeability layers still remain to serve as long-term sources of contamination, due to so-called "back diffusion." These recently developed models assume that transport in the low permeability zones is strictly diffusive; however field observations suggest that more DNAPL and/or dissolved CAH is stored in the low permeability zones than can be explained on the basis of diffusion alone. One explanation for these field observations is that there is enhanced transport of dissolved CAHs and/or DNAPL into the low permeability layers due to cracking. Cracks may allow for advective flow of water contaminated with dissolved CAHs into the layer as well as possible movement of pure phase DNAPL into the layer. In this study, a multiphase numerical flow and transport model is employed in a dual domain (high and low permeability layers) to investigate the impact of cracking on DNAPL and CAH movement. Using literature values, the crack geometry and spacing was varied to model and compare four scenarios: (1) CAH diffusion only into cracks, (2) CAH advection-dispersion into cracks, (3) separate phase DNAPL movement into the cracks, and (4) CAH diffusion into an uncracked low permeability clay layer. For each scenario, model simulations are used to show the evolution and persistence of groundwater contamination downgradient of the DNAPL source.

Tsunami hazard map in eastern Bali

NASA Astrophysics Data System (ADS)

Afif, Haunan; Cipta, Athanasius

2015-04-01

Bali is a popular tourist destination both for Indonesian and foreign visitors. However, Bali is located close to the collision zone between the Indo-Australian Plate and Eurasian Plate in the south and back-arc thrust off the northern coast of Bali resulted Bali prone to earthquake and tsunami. Tsunami hazard map is needed for better understanding of hazard level in a particular area and tsunami modeling is one of the most reliable techniques to produce hazard map. Tsunami modeling conducted using TUNAMI N2 and set for two tsunami sources scenarios which are subduction zone in the south of Bali and back thrust in the north of Bali. Tsunami hazard zone is divided into 3 zones, the first is a high hazard zones with inundation height of more than 3m. The second is a moderate hazard zone with inundation height 1 to 3m and the third is a low tsunami hazard zones with tsunami inundation heights less than 1m. Those 2 scenarios showed southern region has a greater potential of tsunami impact than the northern areas. This is obviously shown in the distribution of the inundated area in the south of Bali including the island of Nusa Penida, Nusa Lembongan and Nusa Ceningan is wider than in the northern coast of Bali although the northern region of the Nusa Penida Island more inundated due to the coastal topography.

Tsunami hazard map in eastern Bali

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afif, Haunan, E-mail: afif@vsi.esdm.go.id; Cipta, Athanasius; Australian National University, Canberra

Bali is a popular tourist destination both for Indonesian and foreign visitors. However, Bali is located close to the collision zone between the Indo-Australian Plate and Eurasian Plate in the south and back-arc thrust off the northern coast of Bali resulted Bali prone to earthquake and tsunami. Tsunami hazard map is needed for better understanding of hazard level in a particular area and tsunami modeling is one of the most reliable techniques to produce hazard map. Tsunami modeling conducted using TUNAMI N2 and set for two tsunami sources scenarios which are subduction zone in the south of Bali and backmore » thrust in the north of Bali. Tsunami hazard zone is divided into 3 zones, the first is a high hazard zones with inundation height of more than 3m. The second is a moderate hazard zone with inundation height 1 to 3m and the third is a low tsunami hazard zones with tsunami inundation heights less than 1m. Those 2 scenarios showed southern region has a greater potential of tsunami impact than the northern areas. This is obviously shown in the distribution of the inundated area in the south of Bali including the island of Nusa Penida, Nusa Lembongan and Nusa Ceningan is wider than in the northern coast of Bali although the northern region of the Nusa Penida Island more inundated due to the coastal topography.« less

Field-scale forward and back diffusion through low-permeability zones

NASA Astrophysics Data System (ADS)

Yang, Minjune; Annable, Michael D.; Jawitz, James W.

2017-07-01

Understanding the effects of back diffusion of groundwater contaminants from low-permeability zones to aquifers is critical to making site management decisions related to remedial actions. Here, we combine aquifer and aquitard data to develop recommended site characterization strategies using a three-stage classification of plume life cycle based on the solute origins: aquifer source zone dissolution, source zone dissolution combined with back diffusion from an aquitard, and only back diffusion. We use measured aquitard concentration profile data from three field sites to identify signature shapes that are characteristic of these three stages. We find good fits to the measured data with analytical solutions that include the effects of advection and forward and back diffusion through low-permeability zones, and linearly and exponentially decreasing flux resulting from source dissolution in the aquifer. Aquifer contaminant time series data at monitoring wells from a mature site were well described using analytical solutions representing the combined case of source zone and back diffusion, while data from a site where the source had been isolated were well described solely by back diffusion. The modeling approach presented in this study is designed to enable site managers to implement appropriate remediation technologies at a proper timing for high- and low-permeability zones, considering estimated plume life cycle.

Field-scale forward and back diffusion through low-permeability zones.

PubMed

Yang, Minjune; Annable, Michael D; Jawitz, James W

2017-07-01

Understanding the effects of back diffusion of groundwater contaminants from low-permeability zones to aquifers is critical to making site management decisions related to remedial actions. Here, we combine aquifer and aquitard data to develop recommended site characterization strategies using a three-stage classification of plume life cycle based on the solute origins: aquifer source zone dissolution, source zone dissolution combined with back diffusion from an aquitard, and only back diffusion. We use measured aquitard concentration profile data from three field sites to identify signature shapes that are characteristic of these three stages. We find good fits to the measured data with analytical solutions that include the effects of advection and forward and back diffusion through low-permeability zones, and linearly and exponentially decreasing flux resulting from source dissolution in the aquifer. Aquifer contaminant time series data at monitoring wells from a mature site were well described using analytical solutions representing the combined case of source zone and back diffusion, while data from a site where the source had been isolated were well described solely by back diffusion. The modeling approach presented in this study is designed to enable site managers to implement appropriate remediation technologies at a proper timing for high- and low-permeability zones, considering estimated plume life cycle. Copyright © 2017 Elsevier B.V. All rights reserved.

Know Your Enemy - Implementation of Bioremediation within a Suspected DNAPL Source Zone Following High-Resolution Site Characterization at Contractors Road Heavy Equipment Area, Kennedy Space Center, Florida

NASA Technical Reports Server (NTRS)

Chrest, Anne; Daprato, Rebecca; Burcham, Michael; Johnson, Jill

2018-01-01

The National Aeronautics and Space Administration (NASA), Kennedy Space Center (KSC), has adopted high-resolution site characterization (HRSC) sampling techniques during baseline sampling prior to implementation of remedies to confirm and refine the conceptual site model (CSM). HRSC sampling was performed at Contractors Road Heavy Equipment Area (CRHE) prior to bioremediation implementation to verify the extent of the trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) source area (defined as the area with TCE concentrations above 1% solubility) and its daughter product dissolved plume that had been identified during previous HRSC events. The results of HRSC pre-bioremediation implementation sampling suggested that the TCE source area was larger than originally identified during initial site characterization activities, leading to a design refinement to improve electron donor distribution and increase the likelihood of achieving remedial objectives. Approach/Activities: HRSC was conducted from 2009 through 2014 to delineate the vertical and horizontal extent of chlorinated volatile organic compounds (CVOCs) in the groundwater. Approximately 2,340 samples were collected from 363 locations using direct push technology (DPT) groundwater sampling techniques. Samples were collected from up to 14 depth intervals at each location using a 4-foot sampling screen. This HRSC approach identified a narrow (approx. 5 to 30 feet wide), approximately 3,000 square foot TCE DNAPL source area (maximum detected TCE concentration of 160,000 micrograms per liter [micro-g/L] at DPT sampling location DPT0225). Prior to implementation of a bioremediation interim measure, HRSC baseline sampling was conducted using DPT groundwater sampling techniques. Concentrations of TCE were an order of magnitude lower than previous reported (12,000 micro-g/L maximum at DPT sampling location DPT0225) at locations sampled adjacent to previous sampling locations. To further evaluate the variability in concentrations observed additional sampling was conducted in 2016. The results identified higher concentrations than originally detected within the previously defined source area and the presence of source zone concentrations upgradient of the previously defined source area (maximum concentration observed 570,000 micro-g/L). The HRSC baseline sampling data allowed for a revision of the bioremediation design prior to implementation. Bioremediation was implemented within the eastern portion of the source area in November and December 2016 and quarterly performance monitoring was completed in March and June 2017. Reductions in CVOC concentrations from baseline were observed at all performance monitoring wells in the treatment area, and by June 2017, an approximate 95% CVOC mass reduction was observed based on monitoring well sampling results. Results/Lessons Learned: The results of this project suggest that, due to the complexity of DNAPL source zones, HRSC during pre-implementation baseline sampling in the TCE source zone was an essential strategy for verifying the treatment area and depth prior to remedy implementation. If the upgradient source zone mass was not identified prior to bioremediation implementation, the mass would have served as a long-term source for the dissolved plume.

Assessment of spatial information for hyperspectral imaging of lesion

NASA Astrophysics Data System (ADS)

Yang, Xue; Li, Gang; Lin, Ling

2016-10-01

Multiple diseases such as breast tumor poses a great threat to women's health and life, while the traditional detection method is complex, costly and unsuitable for frequently self-examination, therefore, an inexpensive, convenient and efficient method for tumor self-inspection is needed urgently, and lesion localization is an important step. This paper proposes an self-examination method for positioning of a lesion. The method adopts transillumination to acquire the hyperspectral images and to assess the spatial information of lesion. Firstly, multi-wavelength sources are modulated with frequency division, which is advantageous to separate images of different wavelength, meanwhile, the source serves as fill light to each other to improve the sensitivity in the low-lightlevel imaging. Secondly, the signal-to-noise ratio of transmitted images after demodulation are improved by frame accumulation technology. Next, gray distributions of transmitted images are analyzed. The gray-level differences is constituted by the actual transmitted images and fitting transmitted images of tissue without lesion, which is to rule out individual differences. Due to scattering effect, there will be transition zones between tissue and lesion, and the zone changes with wavelength change, which will help to identify the structure details of lesion. Finally, image segmentation is adopted to extract the lesion and the transition zones, and the spatial features of lesion are confirmed according to the transition zones and the differences of transmitted light intensity distributions. Experiment using flat-shaped tissue as an example shows that the proposed method can extract the space information of lesion.

Pressurized magma reservoir within the east rift zone of Kīlauea Volcano, Hawai`i: Evidence for relaxed stress changes from the 1975 Kalapana earthquake

NASA Astrophysics Data System (ADS)

Baker, Scott; Amelung, Falk

2015-03-01

We use 2000-2012 InSAR data from multiple satellites to investigate magma storage in Kīlauea's east rift zone (ERZ). The study period includes a surge in magma supply rate and intrusion-eruptions in 2007 and 2011. The Kupaianaha area inflated by ~5 cm prior to the 2007 intrusion and the Nāpau Crater area by ~10 cm following the 2011 intrusion. For the Nāpau Crater area, elastic modeling suggests an inflation source at 5 ± 2 km depth or more below sea level. The reservoir is located in the deeper section of the rift zone for which secular magma intrusion was inferred for the period following the 1975 Mw7.7 décollement earthquake. Reservoir pressurization suggests that in this section of the ERZ, extensional stress changes due to the earthquake have largely been compensated for and that this section is approaching its pre-1975 state. Reservoir pressurization also puts the molten core model into question for this section of Kīlauea's rift zone.

Modeling the influence of coupled mass transfer processes on mass flux downgradient of heterogeneous DNAPL source zones

NASA Astrophysics Data System (ADS)

Yang, Lurong; Wang, Xinyu; Mendoza-Sanchez, Itza; Abriola, Linda M.

2018-04-01

Sequestered mass in low permeability zones has been increasingly recognized as an important source of organic chemical contamination that acts to sustain downgradient plume concentrations above regulated levels. However, few modeling studies have investigated the influence of this sequestered mass and associated (coupled) mass transfer processes on plume persistence in complex dense nonaqueous phase liquid (DNAPL) source zones. This paper employs a multiphase flow and transport simulator (a modified version of the modular transport simulator MT3DMS) to explore the two- and three-dimensional evolution of source zone mass distribution and near-source plume persistence for two ensembles of highly heterogeneous DNAPL source zone realizations. Simulations reveal the strong influence of subsurface heterogeneity on the complexity of DNAPL and sequestered (immobile/sorbed) mass distribution. Small zones of entrapped DNAPL are shown to serve as a persistent source of low concentration plumes, difficult to distinguish from other (sorbed and immobile dissolved) sequestered mass sources. Results suggest that the presence of DNAPL tends to control plume longevity in the near-source area; for the examined scenarios, a substantial fraction (43.3-99.2%) of plume life was sustained by DNAPL dissolution processes. The presence of sorptive media and the extent of sorption non-ideality are shown to greatly affect predictions of near-source plume persistence following DNAPL depletion, with plume persistence varying one to two orders of magnitude with the selected sorption model. Results demonstrate the importance of sorption-controlled back diffusion from low permeability zones and reveal the importance of selecting the appropriate sorption model for accurate prediction of plume longevity. Large discrepancies for both DNAPL depletion time and plume longevity were observed between 2-D and 3-D model simulations. Differences between 2- and 3-D predictions increased in the presence of sorption, especially for the case of non-ideal sorption, demonstrating the limitations of employing 2-D predictions for field-scale modeling.

Colour preference and light sensitivity in trilobite larvae of mangrove horseshoe crab, Carcinoscopius rotundicauda (Latreille, 1802).

PubMed

Srijayat, T C; Pradeep, P J; Hassan, A; Chatterji, A; Shaharom, F; Jeffs, Andrew

2014-03-01

The trilobite larvae of C. rotundicauda were tested to determine their colour preference and light sensitivity until their first moulting (25 days post hatching) under laboratory conditions. Maximum congregation size of the trilobite larvae was found in the white zone respectively where (n = 12) followed by yellow (n = 8) and orange (n = 8), which showed the larval preference for lighter zones. Morisita's index calculation showed a clumped/aggregated distribution (yellow, blue, orange and white) and uniform/hyper dispersed distribution (green, red and black) for various colours tested. Trilobite larvae showed least preference for brighter regions while tested in the experiment [black; (n = 4) and red; (n = 5)]. Experiments done to determine the light sensitivity of trilobite larvae showed that the larvae had more preference towards ultraviolet lights. The maximum congregation size of 38.8 and 40.7% of the larvae was encountered under ultraviolet light, when the light sources were kept horizontal and vertical, respectively. Overall, results suggested that the trilobite larvae of C. rotundicauda, preferred light source of shorter wavelengths (UV light) and colours of lighter zone (white, yellow, orange), which might be due to their adaptation to their natural habitat for predator avoidance, prey selection and water quality.

The Relationship Between Partial Contaminant Source Zone Remediation and Groundwater Plume Attenuation

NASA Astrophysics Data System (ADS)

Falta, R. W.

2004-05-01

Analytical solutions are developed that relate changes in the contaminant mass in a source area to the behavior of biologically reactive dissolved contaminant groundwater plumes. Based on data from field experiments, laboratory experiments, numerical streamtube models, and numerical multiphase flow models, the chemical discharge from a source region is assumed to be a nonlinear power function of the fraction of contaminant mass removed from the source zone. This function can approximately represent source zone mass discharge behavior over a wide range of site conditions ranging from simple homogeneous systems, to complex heterogeneous systems. A mass balance on the source zone with advective transport and first order decay leads to a nonlinear differential equation that is solved analytically to provide a prediction of the time-dependent contaminant mass discharge leaving the source zone. The solution for source zone mass discharge is coupled semi-analytically with a modified version of the Domenico (1987) analytical solution for three-dimensional reactive advective and dispersive transport in groundwater. The semi-analytical model then employs the BIOCHLOR (Aziz et al., 2000; Sun et al., 1999) transformations to model sequential first order parent-daughter biological decay reactions of chlorinated ethenes and ethanes in the groundwater plume. The resulting semi-analytic model thus allows for transient simulation of complex source zone behavior that is fully coupled to a dissolved contaminant plume undergoing sequential biological reactions. Analyses of several realistic scenarios show that substantial changes in the ground water plume can result from the partial removal of contaminant mass from the source zone. These results, however, are sensitive to the nature of the source mass reduction-source discharge reduction curve, and to the rates of degradation of the primary contaminant and its daughter products in the ground water plume. Aziz, C.E., C.J. Newell, J.R. Gonzales, P. Haas, T.P. Clement, and Y. Sun, 2000, BIOCHLOR Natural Attenuation Decision Support System User's Manual Version 1.0, US EPA Report EPA/600/R-00/008 Domenico, P.A., 1987, An analytical model for multidimensional transport of a decaying contaminant species, J. Hydrol., 91: 49-58. Sun, Y., J.N. Petersen, T.P. Clement, and R.S. Skeen, 1999, A new analytical solution for multi-species transport equations with serial and parallel reactions, Water Resour. Res., 35(1): 185-190.

Bench-scale biodegradation tests to assess natural attenuation potential of 1,4-dioxane at three sites in California.

PubMed

Li, Mengyan; Van Orden, E Tess; DeVries, David J; Xiong, Zhong; Hinchee, Rob; Alvarez, Pedro J

2015-02-01

1,4-Dioxane (dioxane) is relatively recalcitrant to biodegradation, and its physicochemical properties preclude effective removal from contaminated groundwater by volatilization or adsorption. Through this microcosm study, we assessed the biodegradation potential of dioxane for three sites in California. Groundwater and sediment samples were collected at various locations at each site, including the presumed source zone, middle and leading edge of the plume. A total of 16 monitoring wells were sampled to prepare the microcosms. Biodegradation of dioxane was observed in 12 of 16 microcosms mimicking natural attenuation within 28 weeks. Rates varied from as high as 3,449 ± 459 µg/L/week in source-zone microcosms to a low of 0.3 ± 0.1 µg/L/week in microcosms with trace level of dioxane (<10 µg/L as initial concentration). The microcosms were spiked with (14)C-labeled dioxane to assess the fate of dioxane. Biological oxidizer-liquid scintillation analysis of bound residue infers that 14C-dioxane was assimilated into cell material only in microcosms exhibiting significant dioxane biodegradation. Mineralization was also observed per (14)CO2 recovery (up to 44% of the amount degraded in 28 weeks of incubation). Degradation and mineralization activity significantly decreased with increasing distance from the contaminant source area (p < 0.05), possibly due to less acclimation. Furthermore, both respiked and repeated microcosms prepared with source-zone samples from Site 1 confirmed relatively rapid dioxane degradation (i.e., 100 % removal by 20 weeks). These results show that indigenous microorganisms capable of degrading dioxane are present at these three sites, and suggest that monitored natural attenuation should be considered as a remedial response.

Carbon dynamics in the Elbe land-ocean transition zone

NASA Astrophysics Data System (ADS)

Amann, Thorben; Weiss, Andreas; Hartmann, Jens

2010-05-01

Recent model data reveal a discrepancy between the mobilisation of carbon from the terrestrial system into the fluvial system and the amount of carbon reaching the ocean. It is estimated that of 1.9 Pg C yr-1 total terrestrial input (Cole et al., 2007), 0.12-0.41 Pg C yr-1 are lost through CO2-evasion from inner and outer estuaries to the atmosphere (Chen & Borges, 2009) while 0.9 Pg C yr-1 are exported to the ocean (Cole et al., 2007). Therefore estuaries can be considered as significant CO2 sources. To better understand temporal and spatial patterns of critical biogeochemical transformations in the land-ocean transition zone (LOTZ), an extensive historical hydrochemical dataset of the Elbe-river and -inner estuary system was analysed. The LOTZ of the river Elbe can be distinguished into four zones with respect to changes in carbon species abundance: the non-tidal river zone, the tidal harbour zone, the maximum turbidity zone (MTZ) and the river mouth zone. The concentrations of suspended matter and POC decrease from the non-tidal river zone reaching their minima in the harbour zone. The MTZ is characterised by maximum SPM and POC values, while both parameters decrease to a further minimum in the river mouth. Interestingly the POC concentration has nearly doubled in the period 1999-2007 if compared to the period 1985-1998. A possible cause may be the decrease in the general pollution of the river, despite of decreasing N and P loads in the past decades. This is supported by the observed reduction of DOC concentrations by 50% in the earlier period. In contrast the proportions of DOC and POC values within the four zones did not change. The doubling of POC concentrations between the two periods is not reflected in increasing SPM concentrations, resulting in higher POC (wt-% SPM) values. A decrease of POC (wt-% SPM) from the non-tidal river zone to the river mouth indicates loss of organic carbon due to respiration processes. This is supported by an increase of nitrate and phosphate concentrations as well as dissolved inorganic carbon. Presented analysis is used to develop a new spatial framework for quantification of carbon dynamics especially addressing sinks and sources of carbon in the land-ocean transition zone of the river Elbe. References Chen, C.-T.A. and Borges, A.V. (2009), „Reconciling opposing views on carbon cycling in the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2', Deep-Sea Research II (56), 578-590. Cole, J. and Prairie, Y. and Caraco, N. and McDowell, W. and Tranvik, L. and Striegl, R. and Duarte, C. and Kortelainen, P. and Downing, J. and Middelburg, J. and Melack, J. (2007), "Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget", Ecosystems 10 (1), 172-185.

The changing trend in nitrate concentrations in major aquifers due to historical nitrate loading from agricultural land across England and Wales from 1925 to 2150.

PubMed

Wang, L; Stuart, M E; Lewis, M A; Ward, R S; Skirvin, D; Naden, P S; Collins, A L; Ascott, M J

2016-01-15

Nitrate is necessary for agricultural productivity, but can cause considerable problems if released into aquatic systems. Agricultural land is the major source of nitrates in UK groundwater. Due to the long time-lag in the groundwater system, it could take decades for leached nitrate from the soil to discharge into freshwaters. However, this nitrate time-lag has rarely been considered in environmental water management. Against this background, this paper presents an approach to modelling groundwater nitrate at the national scale, to simulate the impacts of historical nitrate loading from agricultural land on the evolution of groundwater nitrate concentrations. An additional process-based component was constructed for the saturated zone of significant aquifers in England and Wales. This uses a simple flow model which requires modelled recharge values, together with published aquifer properties and thickness data. A spatially distributed and temporally variable nitrate input function was also introduced. The sensitivity of parameters was analysed using Monte Carlo simulations. The model was calibrated using national nitrate monitoring data. Time series of annual average nitrate concentrations along with annual spatially distributed nitrate concentration maps from 1925 to 2150 were generated for 28 selected aquifer zones. The results show that 16 aquifer zones have an increasing trend in nitrate concentration, while average nitrate concentrations in the remaining 12 are declining. The results are also indicative of the trend in the flux of groundwater nitrate entering rivers through baseflow. The model thus enables the magnitude and timescale of groundwater nitrate response to be factored into source apportionment tools and to be taken into account alongside current planning of land-management options for reducing nitrate losses. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Assessment of chloroethene degradation rates based on ratios of daughter/parent compounds in groundwater plumes

NASA Astrophysics Data System (ADS)

Höhener, Patrick

2014-05-01

Chlorinated solvent spills at industrial and urban sites create groundwater plumes where tetrachloro- and trichloroethene may degrade to their daughter compounds, dichloroethenes, vinyl chloride and ethane. The assessment of degradation and natural attenuation at such sites may be based on the analysis and inverse modelling of concentration data, on the calculation of mass fluxes in transsects, and/or on the analysis of stable isotope ratios in the ethenes. Relatively few work has investigated the possibility of using ratio of concentrations for gaining information on degradation rates. The use of ratios bears the advantage that dilution of a single sample with contaminant-free water does not matter. It will be shown that molar ratios of daughter to parent compounds measured along a plume streamline are a rapid and robust mean of determining whether degradation rates increase or decrease along the degradation chain, and allow furthermore a quantitation of the relative magnitude of degradation rates compared to the rate of the parent compound. Furthermore, ratios of concentration will become constant in zones where degradation is absent, and this allows to sketching the extension of actively degrading zones. The assessment is possible for pure sources and also for mixed sources. A quantification method is proposed in order to estimate first-order degradation rates in zones of constant degradation activity. This quantification method includes corrections that are needed due to longitudinal and transversal dispersivity. The method was tested on a number of real field sites from literature. At the majority of these sites, the first-order degradation rates were decreasing along the degradation chain from tetrachloroethene to vinyl chloride, meaning that the latter was often reaching important concentrations. This is bad news for site owners due to the increased toxicity of vinyl chloride compared to its parent compounds.

Method for forming synthesis gas using a plasma-catalyzed fuel reformer

DOEpatents

Hartvigsen, Joseph J; Elangovan, S; Czernichowski, Piotr; Hollist, Michele

2015-04-28

A method of forming a synthesis gas utilizing a reformer is disclosed. The method utilizes a reformer that includes a plasma zone to receive a pre-heated mixture of reactants and ionize the reactants by applying an electrical potential thereto. A first thermally conductive surface surrounds the plasma zone and is configured to transfer heat from an external heat source into the plasma zone. The reformer further includes a reaction zone to chemically transform the ionized reactants into synthesis gas comprising hydrogen and carbon monoxide. A second thermally conductive surface surrounds the reaction zone and is configured to transfer heat from the external heat source into the reaction zone. The first thermally conductive surface and second thermally conductive surface are both directly exposed to the external heat source. A corresponding apparatus and system are also disclosed herein.

Spherical loudspeaker array for local active control of sound.

PubMed

Rafaely, Boaz

2009-05-01

Active control of sound has been employed to reduce noise levels around listeners' head using destructive interference from noise-canceling sound sources. Recently, spherical loudspeaker arrays have been studied as multiple-channel sound sources, capable of generating sound fields with high complexity. In this paper, the potential use of a spherical loudspeaker array for local active control of sound is investigated. A theoretical analysis of the primary and secondary sound fields around a spherical sound source reveals that the natural quiet zones for the spherical source have a shell-shape. Using numerical optimization, quiet zones with other shapes are designed, showing potential for quiet zones with extents that are significantly larger than the well-known limit of a tenth of a wavelength for monopole sources. The paper presents several simulation examples showing quiet zones in various configurations.

An arthroscopic evaluation of the anatomical "critical zone".

PubMed

Naidoo, N; Lazarus, L; Osman, S A; Satyapal, K S

2017-01-01

The "critical zone", a region of speculated vascularity, is situated approximately 10 mm proximal to the insertion of the supraspinatus tendon. Despite its obvious role as an anatomical landmark demarcator, its patho-anatomic nature has been identified as the source of rotator cuff pathology. Although many studies have attempted to evaluate the vascularity of this region, the architecture regarding the exact length, width and shape of the critical zone, remains unreported. This study aimed to determine the shape and morphometry of the "critical zone" arthroscopically. The sample series, which was comprised of 38 cases (n = 38) specific to pathological types, employed an anatomical investigation of the critical zone during routine real-time arthroscopy. Demographic representation: i) sex: 19 males, 19 females; ii) age range: 18-76 years; iii) race: white (n = 29), Indian (n = 7) and coloured (n = 2). The incidence of shape and the mean lengths and widths of the critical zone were determined in accordance with the relevant demographic factors and patient history. Although the cresenteric shape was predominant, hemispheric and sail-shaped critical zones were also identified. The lengths and widths of the critical zone appeared markedly increased in male individuals. While the increase in age may account for the increased incidence of rotator cuff degeneration due to poor end-vascular supply, the additional factors of height and weight presented as major determinants of the increase in size of the critical zone. In addition, the comparisons of length and width with each other and shape yielded levels of significant difference, therefore indicating a directly proportional relationship between the length and width of the critical zone. This detailed understanding of the critical zone may prove beneficial for the success of post-operative rotator cuff healing.

Morphology and topography study of graphene synthesized from plant oil

NASA Astrophysics Data System (ADS)

Robaiah, M.; Rusop, M.; Abdullah, S.; Khusaimi, Z.; Azhan, H.; Laila, M. O.; Salifairus, M. J.; Asli, N. A.

2018-05-01

The graphene is material consists of bonded atom carbon atoms in sheet form one atom thick. The different types of carbon sources which are refined corn oil, palm oil and waste cooking palm oil were used as carbon feedstock to supply carbon atom for synthesizing graphene on the nickel substrate by thermal chemical vapour deposition. The substrate and carbon sources were placed in double zone furnaces. The carbon sources and the substrate were heated at 300 °C and 900 °C respectively. The both furnaces were switched off after synthesis time for cooling process finish. The formation of the graphene on the Ni surface appears due to segregation and precipitation of a high amount of carbon from the source material during the cooling process. FESEM, AFM, UV-VIS Spectroscopy and Raman Spectroscopy were used to characterize and synthesized graphene.

Intrinsic Controls of Groundwater-Surface Water Dissolved Organic Carbon Quality and Quantity on Hyporheic Carbon Oxidation.

NASA Astrophysics Data System (ADS)

Garayburu-Caruso, V. A.; Stegen, J.; Graham, E.

2017-12-01

Inputs of dissolved organic carbon (DOC) and nutrients from groundwater (GW) and surface water (SW) to the hyporheic zone strongly influence biogeochemical processes. Despite increased research efforts, we still lack a mechanistic understanding of the conditions driving elevated hyporheic metabolism. This work explores hyporheic carbon oxidation from a thermodynamic perspective by evaluating changes in metabolic rates within hyporheic zone sediments in response to changes on DOC concentration and thermodynamic profiles that are characteristic of GW and SW sources. We hypothesize that GW DOC is protected from microbial oxidation due to low concentration and that SW DOC is protected due low thermodynamic favorability. Further, we propose that GW-SW mixing can simultaneously overcome both limitations and stimulate carbon oxidation. Hyporheic sediments from the Hanford site in Richland, WA were exposed to ambient, 2-,5- and 10-fold concentrations of natural DOC from SW and GW sources, separately, and incubated at in-situ temperature. The two DOC sources supply contrasting thermodynamic profiles, with GW providing lower concentration but more thermodynamically favorable DOC and SW higher concentration, more recalcitrant DOC. Across DOC treatments we characterized time series of oxygen concentration, DOC concentration, and pH as well as endpoint measurements of DOC thermodynamics using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Our results suggest that hyporheic metabolism of distinct carbon pools (GW or SW) can be limited by concentration or thermodynamic favorability. Our work provides an experimental approach to contribute to mechanistic understanding of freshwater carbon oxidation, and a process-based foundation for the development of watershed-scale hydrobiogeochemical models.

Trace Element Composition of Phytoplankton Along the US GEOTRACES Pacific Zonal Transect: Comparing Single-Cell SXRF Quotas, Chemical Leaching, and Bulk Particle Digestion

NASA Astrophysics Data System (ADS)

Ohnemus, D.; Rauschenberg, S.; Twining, B. S.

2014-12-01

The elemental stoichiometries of phytoplankton are critical ecological and chemical parameters due to biological participation in, if not control over, the marine cycles of many GEOTRACES trace elements and isotopes (TEI). Elemental stoichiometries in euphotic zone protists can be used as end-members in biogeochemical models for bioactive elements (e.g. Fe, Si) and can provide insight into relationships found in the deep ocean and sediments (e.g. Cd:P, Zn:Si) due to broad and organism-specific geochemical links. Though sub-euphotic zone (e.g. hydrothermal, margin-sourced lateral) inputs and processes are also interesting aspects of these cycles, biological incorporation of TEIs in the euphotic zone is, fundamentally, where "the rubber meets the road." Using the 2013 Pacific GEOTRACES super stations and Peruvian coastal transect as ecological waypoints, we present and compare results from three methods for studying trace elemental composition of phytoplankton: single-cell synchrotron x-ray fluorescence (SXRF); weak chemical leaching (acetic acid/hydroxylamine); and total chemical digestion (HNO3/HCl/HF). This combination of techniques allows examination of taxon-specific trends in biotic stoichiometry across the Eastern Pacific and also provides traditional bulk chemical metrics for both biotic and bulk shallow particulate composition.

Assessing the Impact of Source-Zone Remediation Efforts at the Contaminant-Plume Scale Through Analysis of Contaminant Mass Discharge

PubMed Central

Brusseau, M. L.; Hatton, J.; DiGuiseppi, W.

2011-01-01

The long-term impact of source-zone remediation efforts was assessed for a large site contaminated by trichloroethene. The impact of the remediation efforts (soil vapor extraction and in-situ chemical oxidation) was assessed through analysis of plume-scale contaminant mass discharge, which was measured using a high-resolution data set obtained from 23 years of operation of a large pump-and-treat system. The initial contaminant mass discharge peaked at approximately 7 kg/d, and then declined to approximately 2 kg/d. This latter value was sustained for several years prior to the initiation of source-zone remediation efforts. The contaminant mass discharge in 2010, measured several years after completion of the two source-zone remediation actions, was approximately 0.2 kg/d, which is ten times lower than the value prior to source-zone remediation. The time-continuous contaminant mass discharge data can be used to evaluate the impact of the source-zone remediation efforts on reducing the time required to operate the pump-and-treat system, and to estimate the cost savings associated with the decreased operational period. While significant reductions have been achieved, it is evident that the remediation efforts have not completely eliminated contaminant mass discharge and associated risk. Remaining contaminant mass contributing to the current mass discharge is hypothesized to comprise poorly-accessible mass in the source zones, as well as aqueous (and sorbed) mass present in the extensive lower-permeability units located within and adjacent to the contaminant plume. The fate of these sources is an issue of critical import to the remediation of chlorinated-solvent contaminated sites, and development of methods to address these sources will be required to achieve successful long-term management of such sites and to ultimately transition them to closure. PMID:22115080

IMPACTS OF DNAPL SOURCE TREATMENT ON CONTAMINANT MASS FLUX

EPA Science Inventory

Current remedial techniques are unable to completely eliminate all dense nonaqueous phase liquid (DNAPL) from source zone areas at most sites, and conflicting views on the benefits of partial DNAPL source zone remediation exist in the literature. A comparison of contaminant flux...

The DNAPL challenge: Is there a case for partial source removal?

NASA Astrophysics Data System (ADS)

Kavanaugh, M. C.; Rao, P. S. C.

2003-04-01

Despite significant advances in the science and technology of DNAPL source zone characterization, and DNAPL removal technologies over the past two decades, source remediation has not become a standard objective at most DNAPL sites. Few documented cases of DNAPL source removal have been published, and achievement of the usual cleanup metric in these source zones, namely, meeting Maximum Contaminant Levels ("MCLs") is rare. At most DNAPL sites, removal of sufficient amounts of DNAPL from the source zones to achieve MCLs is considered technically impracticable, taking cost into consideration. Leaving substantial quantities of DNAPL in source zones and instituting appropriate technologies to eliminate continued migration of groundwater plumes emanating from these source zones requires long-term reliability of barrier technologies (hydraulic or physical), and the permanence institutional controls. This strategy runs the risk of technical or institutional failures and possible liabilities associated with natural resource damage claims. To address this challenge, the U.S. Environmental Protection Agency ("EPA") established a panel of experts ("Panel") on DNAPL issues to provide their opinions on the overarching question of whether DNAPL source remediation is feasible. This Panel, co-chaired by the authors of this paper, has now prepared a report summarizing the opinions of the Panel on the key question of whether DNAPL source removal is achievable. This paper will present the findings of the Panel, addressing such issues as the current status of DNAPL source characterization and remediation technologies, alternative metrics of success for DNAPL source remediation, the potential benefits of partial DNAPL source depletion, and research needs to address data gaps that hinder the more widespread implementation of source removal strategies.

Assessment of macroseismic intensity in the Nile basin, Egypt

NASA Astrophysics Data System (ADS)

Fergany, Elsayed

2018-01-01

This work intends to assess deterministic seismic hazard and risk analysis in terms of the maximum expected intensity map of the Egyptian Nile basin sector. Seismic source zone model of Egypt was delineated based on updated compatible earthquake catalog in 2015, focal mechanisms, and the common tectonic elements. Four effective seismic source zones were identified along the Nile basin. The observed macroseismic intensity data along the basin was used to develop intensity prediction equation defined in terms of moment magnitude. Expected maximum intensity map was proven based on the developed intensity prediction equation, identified effective seismic source zones, and maximum expected magnitude for each zone along the basin. The earthquake hazard and risk analysis was discussed and analyzed in view of the maximum expected moment magnitude and the maximum expected intensity values for each effective source zone. Moderate expected magnitudes are expected to put high risk at Cairo and Aswan regions. The results of this study could be a recommendation for the planners in charge to mitigate the seismic risk at these strategic zones of Egypt.

The May 29 2008 earthquake aftershock sequence within the South Iceland Seismic Zone: Fault locations and source parameters of aftershocks

NASA Astrophysics Data System (ADS)

Brandsdottir, B.; Parsons, M.; White, R. S.; Gudmundsson, O.; Drew, J.

2010-12-01

The mid-Atlantic plate boundary breaks up into a series of segments across Iceland. The South Iceland Seismic Zone (SISZ) is a complex transform zone where left-lateral E-W shear between the Reykjanes Peninsula Rift Zone and the Eastern Volcanic Zone is accommodated by bookshelf faulting along N-S lateral strike-slip faults. The SISZ is also a transient feature, migrating sideways in response to the southward propagation of the Eastern Volcanic Zone. Sequences of large earthquakes (M > 6) lasting from days to years and affecting most of the seismic zone have occurred repeatedly in historical time (last 1100 years), separated by intervals of relative quiescence lasting decades to more than a century. On May 29 2008, a Mw 6.1 earthquake struck the western part of the South Iceland Seismic Zone, followed within seconds by a slightly smaller event on a second fault ~5 km further west. Aftershocks, detected by a temporal array of 11 seismometers and three permanent Icelandic Meteorological Office stations were located using an automated Coalescence Microseismic Mapping technique. The epicenters delineate two major and several smaller N-S faults as well as an E-W zone of activity stretching further west into the Reykjanes Peninsula Rift Zone. Fault plane solutions show both right lateral and oblique strike slip mechanisms along the two major N-S faults. The aftershocks deepen from 3-5 km in the north to 8-9 km in the south, suggesting that the main faults dip southwards. The faulting is interpreted to be driven by the local stress due to transform motion between two parallel segments of the divergent plate boundary crossing Iceland.

Vibroseis Monitoring of San Andreas Fault in California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korneev, Valeri; Nadeau, Robert

2004-06-11

A unique data set of seismograms for 720 source-receiver paths has been collected as part of a controlled source Vibroseis experiment San Andreas Fault (SAF) at Parkfield. In the experiment, seismic waves repeatedly illuminated the epicentral region of the expected M6 event at Parkfield from June 1987 until November 1996. For this effort, a large shear-wave vibrator was interfaced with the 3-component (3-C) borehole High-Resolution Seismic Network (HRSN), providing precisely timed collection of data for detailed studies of changes in wave propagation associated with stress and strain accumulation in the fault zone (FZ). Data collected by the borehole network weremore » examined for evidence of changes associated with the nucleation process of the anticipated M6 earthquake at Parkfield. These investigations reported significant traveltime changes in the S coda for paths crossing the fault zone southeast of the epicenter and above the rupture zone of the 1966 M6 earthquake. Analysis and modeling of these data and comparison with observed changes in creep, water level, microseismicity, slip-at-depth and propagation from characteristic repeating microearthquakes showed temporal variations in a variety of wave propagation attributes that were synchronous with changes in deformation and local seismicity patterns. Numerical modeling suggests 200 meters as an effective thickness of SAF. The observed variations can be explained by velocity 6 percent velocity variation within SAF core. Numerical modeling studies and a growing number of observations have argued for the propagation of fault-zone guided waves (FZGW) within a SAF zone that is 100 to 200 m wide at seismogenic depths and with 20 to 40 percent lower shear-wave velocity than the adjacent unfaulted rock. Guided wave amplitude tomographic inversion for SAF using microearthquakes, shows clearly that FZGW are significantly less attenuated in a well-defined region of the FZ. This region plunges to the northwest along the northwest boundary of the region of highest moment release and separates locked and slipping sections of the SAF at depth, as determined independently from geodesy, seismicity and the recurrence rates of characteristically repeating microearthquakes. The mechanism for low FZGW attenuation in the zone is possibly due to dewatering by fracture closure and/or fault-normal compression, or changes in fracture orientation due to a complex stress or strain field at the boundary between creeping and locked zones of the San Andreas Fault. Temporal changes of FZGW correlates with changes in overall seismicity. Active monitoring of changes in FZGW has a potential for imaging and detecting of changes in stress within FZ cores. Since FZGW primarily propagate in the low-velocity core region of fault zones, they sample the most active zone of fault deformation and provide greater structural detail of the inner fault core than body waves which propagate primarily outside of the central core region. FZGW also can be used for FZ continuity studies.« less

Seismic Migration Imaging of the Mantle Transition Zone Beneath Continental US with Receiver Functions

NASA Astrophysics Data System (ADS)

Zhang, H.; Schmandt, B.

2017-12-01

The mantle transition zone has been widely studied by multiple sub-fields in geosciences including seismology, mineral physics and geodynamics. Due to the relatively high water storage capacity of olivine polymorphs (wadsleyite and ringwoodite) inside the transition zone, it is proposed to be a potential geochemical water reservoir that may contain one or more ocean masses of water. However, there is an ongoing debate about the hydration level of those minerals and how it varies from place to place. Considering that dehydration melting, which may happen during mantle flow across phase transitions between hydrated olivine polymorphs, may be seismically detectable, large-scale seismic imaging of heterogeneous scattering in the transition zone can contribute to the debate. To improve our understanding of the properties of the mantle transition zone and how they relate to mantle flow across its boundaries, it is important to gain an accurate image with large spatial coverage. The accuracy is primarily limited by the density of broadband seismic data and the imaging algorithms applied to the data, while the spatial coverage is limited by the availability of wide-aperture (>500 km) seismic arrays. Thus, the emergence of the USArray seismic data set (www.usarray.org) provides a nearly ideal data source for receiver side imaging of the mantle transition zone due to its large aperture ( 4000 km) with relatively small station spacing ( 70 km), which ensures that the transition zone beneath it is well sampled by teleseismic waves. In total, more than 200,000 P to S receiver functions will be used for imaging structures in depth range of 300 km to 800 km beneath the continental US with an improved 3D Kirchhoff pre-stacking migration method. The method uses 3-D wave fronts calculated for P and S tomography models to more accurately calculate point scattering coefficients and map receiver function lag times to 3-D position. The new images will help resolve any laterally sporadic or dipping interfaces that may be present at transition zone depths. The locations of sporadic velocity decreases will be compared with mantle flow models to evaluate the possibility of dehydration melting.

Vulnerability Assessment of Groundwater Resources by Nutrient Source Apportionment to Individual Groundwater Wells: A Case Study in North Carolina

NASA Astrophysics Data System (ADS)

Ayub, R.; Obenour, D. R.; Keyworth, A. J.; Genereux, D. P.; Mahinthakumar, K.

2016-12-01

Groundwater contamination by nutrients (nitrogen and phosphorus) is a major concern in water table aquifers that underlie agricultural areas in the mid-Atlantic Coastal Plain of the United States. High nutrient concentrations leaching into shallow groundwater can lead to human health problems and eutrophication of receiving surface waters. Liquid manure from concentrated animal feeding operations (CAFOs) stored in open-air lagoons and applied to spray fields can be a significant source of nutrients to groundwater, along with septic waste. In this study, we developed a model-based methodology for source apportionment and vulnerability assessment using sparse groundwater quality sampling measurements for Duplin County, North Carolina (NC), obtained by the NC Department of Environmental Quality (NC DEQ). This model provides information relevant to management by estimating the nutrient transport through the aquifer from different sources and addressing the uncertainty of nutrient contaminant propagation. First, the zones of influence (dependent on nutrient pathways) for individual groundwater monitoring wells were identified using a two-dimensional vertically averaged groundwater flow and transport model incorporating geologic uncertainty for the surficial aquifer system. A multiple linear regression approach is then applied to estimate the contribution weights for different nutrient source types using the nutrient measurements from monitoring wells and the potential sources within each zone of influence. Using the source contribution weights and their uncertainty, a probabilistic vulnerability assessment of the study area due to nutrient contamination is performed. Knowledge of the contribution of different nutrient sources to contamination at receptor locations (e.g., private wells, municipal wells, stream beds etc.) will be helpful in planning and implementation of appropriate mitigation measures.

Personal sound zone reproduction with room reflections

NASA Astrophysics Data System (ADS)

Olik, Marek

Loudspeaker-based sound systems, capable of a convincing reproduction of different audio streams to listeners in the same acoustic enclosure, are a convenient alternative to headphones. Such systems aim to generate "sound zones" in which target sound programmes are to be reproduced with minimum interference from any alternative programmes. This can be achieved with appropriate filtering of the source (loudspeaker) signals, so that the target sound's energy is directed to the chosen zone while being attenuated elsewhere. The existing methods are unable to produce the required sound energy ratio (acoustic contrast) between the zones with a small number of sources when strong room reflections are present. Optimization of parameters is therefore required for systems with practical limitations to improve their performance in reflective acoustic environments. One important parameter is positioning of sources with respect to the zones and room boundaries. The first contribution of this thesis is a comparison of the key sound zoning methods implemented on compact and distributed geometrical source arrangements. The study presents previously unpublished detailed evaluation and ranking of such arrangements for systems with a limited number of sources in a reflective acoustic environment similar to a domestic room. Motivated by the requirement to investigate the relationship between source positioning and performance in detail, the central contribution of this thesis is a study on optimizing source arrangements when strong individual room reflections occur. Small sound zone systems are studied analytically and numerically to reveal relationships between the geometry of source arrays and performance in terms of acoustic contrast and array effort (related to system efficiency). Three novel source position optimization techniques are proposed to increase the contrast, and geometrical means of reducing the effort are determined. Contrary to previously published case studies, this work presents a systematic examination of the key problem of first order reflections and proposes general optimization techniques, thus forming an important contribution. The remaining contribution considers evaluation and comparison of the proposed techniques with two alternative approaches to sound zone generation under reflective conditions: acoustic contrast control (ACC) combined with anechoic source optimization and sound power minimization (SPM). The study provides a ranking of the examined approaches which could serve as a guideline for method selection for rooms with strong individual reflections.

Solution of multi-element LED light sources development automation problem

NASA Astrophysics Data System (ADS)

Chertov, Aleksandr N.; Gorbunova, Elena V.; Korotaev, Valery V.; Peretyagin, Vladimir S.

2014-09-01

The intensive development of LED technologies resulted in the creation of multicomponent light sources in the form of controlled illumination devices based on usage of mentioned LED technologies. These light sources are used in different areas of production (for example, in the food industry for sorting products or in the textile industry for quality control, etc.). The use of LED lighting products in the devices used in specialized lighting, became possible due to wide range of colors of light, LED structures (which determines the direction of radiation, the spatial distribution and intensity of the radiation, electrical, heat, power and other characteristics), and of course, the possibility of obtaining any shade in a wide dynamic range of brightness values. LED-based lighting devices are notable for the diversity of parameters and characteristics, such as color radiation, location and number of emitters, etc. Although LED technologies have several advantages, however, they require more attention if you need to ensure a certain character of illumination distribution and/or distribution of the color picture at a predetermined distance (for example, at flat surface, work zone, area of analysis or observation). This paper presents software designed for the development of the multicomponent LED light sources. The possibility of obtaining the desired color and energy distribution at the zone of analysis by specifying the spatial parameters of the created multicomponent light source and using of real power, spectral and color parameters and characteristics of the LEDs is shown as well.

Using Spectral Losses to Map a Damage Zone for the Source Physics Experiments (SPE)

NASA Astrophysics Data System (ADS)

Knox, H. A.; Abbott, R. E.; Bonal, N.; Preston, L. A.

2013-12-01

We performed a series of cross-borehole seismic experiments in support of the Source Physics Experiments (SPE). These surveys, which were conducted in a granitic body using a sparker source and hydrophone string, were designed to image the damage zone from two underground explosions (SPE2 and SPE3). We present results here from a total of six boreholes (the explosive shot emplacement hole and 5 satellite holes, 20-35 meters away) where we found a marked loss of high frequency energy in ray paths traversing the region near the SPE explosions. Specifically, the frequencies above ~400 Hz were lost in a region centered around 45 meters depth, coincident with SPE2 and SPE3 shots. We further quantified these spectral losses, developed a map of where they occur, and evaluated the attenuation effects of raypath length (i.e. source-receiver offset). We attribute this severe attenuation to the inelastic damage (i.e. cracking and pulverizing) caused by the large chemical explosions and propose that frequency attenuation of this magnitude provides yet another tool for detecting the damage due to large underground explosions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

An innovative wood-chip-framework substrate used as slow-release carbon source to treat high-strength nitrogen wastewater.

PubMed

Li, Huai; Chi, Zifang; Yan, Baixing; Cheng, Long; Li, Jianzheng

2017-01-01

Removal of nitrogen in wastewater before discharge into receiving water courses is an important consideration in treatment systems. However, nitrogen removal efficiency is usually limited due to the low carbon/nitrogen (C/N) ratio. A common solution is to add external carbon sources, but amount of liquid is difficult to determine. Therefore, a combined wood-chip-framework substrate (with wood, slag and gravel) as a slow-release carbon source was constructed in baffled subsurface-flow constructed wetlands to overcome the problem. Results show that the removal rate of ammonia nitrogen (NH 4 + -N), total nitrogen (TN) and chemical oxygen demand (COD) could reach 37.5%-85%, 57.4%-86%, 32.4%-78%, respectively, indicating the combined substrate could diffuse sufficient oxygen for the nitrification process (slag and gravel zone) and provide carbon source for denitrification process (wood-chip zone). The nitrification and denitrification were determined according to the location of slag/gravel and wood-chip, respectively. Nitrogen removal was efficient at the steady phase before a shock loading using slag-wood-gravel combined substrate because of nitrification-denitrification process, while nitrogen removal was efficient under a shock loading with wood-slag-gravel combined substrate because of ANAMMOX process. This study provides a new idea for wetland treatment of high-strength nitrogen wastewater. Copyright © 2016. Published by Elsevier B.V.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freeze, R.A.; McWhorter, D.B.

Many emerging remediation technologies are designed to remove contaminant mass from source zones at DNAPL sites in response to regulatory requirements. There is often concern in the regulated community as to whether mass removal actually reduces risk, or whether the small risk reductions achieved warrant the large costs incurred. This paper sets out a proposed framework for quantifying the degree to which risk is reduced as mass is removed from DNAPL source areas in shallow, saturated, low-permeability media. Risk is defined in terms of meeting an alternate concentration limit (ACL) at a compliance well in an aquifer underlying the sourcemore » zone. The ACL is back-calculated from a carcinogenic health-risk characterization at a downgradient water-supply well. Source-zone mass-removal efficiencies are heavily dependent on the distribution of mass between media (fractures, matrix) and phase (aqueous, sorbed, NAPL). Due to the uncertainties in currently available technology performance data, the scope of the paper is limited to developing a framework for generic technologies rather than making specific risk-reduction calculations for individual technologies. Despite the qualitative nature of the exercise, results imply that very high total mass-removal efficiencies are required to achieve significant long-term risk reduction with technology applications of finite duration. This paper is not an argument for no action at contaminated sites. Rather, it provides support for the conclusions of Cherry et al. (1992) that the primary goal of current remediation should be short-term risk reduction through containment, with the aim to pass on to future generations site conditions that are well-suited to the future applications of emerging technologies with improved mass-removal capabilities.« less

Computerized Workstation for Tsunami Hazard Monitoring

NASA Astrophysics Data System (ADS)

Lavrentiev-Jr, Mikhail; Marchuk, Andrey; Romanenko, Alexey; Simonov, Konstantin; Titov, Vasiliy

2010-05-01

We present general structure and functionality of the proposed Computerized Workstation for Tsunami Hazard Monitoring (CWTHM). The tool allows interactive monitoring of hazard, tsunami risk assessment, and mitigation - at all stages, from the period of strong tsunamigenic earthquake preparation to inundation of the defended coastal areas. CWTHM is a software-hardware complex with a set of software applications, optimized to achieve best performance on hardware platforms in use. The complex is calibrated for selected tsunami source zone(s) and coastal zone(s) to be defended. The number of zones (both source and coastal) is determined, or restricted, by available hardware resources. The presented complex performs monitoring of selected tsunami source zone via the Internet. The authors developed original algorithms, which enable detection of the preparation zone of the strong underwater earthquake automatically. For the so-determined zone the event time, magnitude and spatial location of tsunami source are evaluated by means of energy of the seismic precursors (foreshocks) analysis. All the above parameters are updated after each foreshock. Once preparing event is detected, several scenarios are forecasted for wave amplitude parameters as well as the inundation zone. Estimations include the lowest and the highest wave amplitudes and the least and the most inundation zone. In addition to that, the most probable case is calculated. In case of multiple defended coastal zones, forecasts and estimates can be done in parallel. Each time the simulated model wave reaches deep ocean buoys or tidal gauge, expected values of wave parameters and inundation zones are updated with historical events information and pre-calculated scenarios. The Method of Splitting Tsunami (MOST) software package is used for mathematical simulation. The authors suggest code acceleration for deep water wave propagation. As a result, performance is 15 times faster compared to MOST, original version. Performance gain is achieved by compiler options, use of optimized libraries, and advantages of OpenMP parallel technology. Moreover, it is possible to achieve 100 times code acceleration by using modern Graphics Processing Units (GPU). Parallel evaluation of inundation zones for multiple coastal zones is also available. All computer codes can be easily assembled under MS Windows and Unix OS family. Although software is virtually platform independent, the most performance gain is achieved while using the recommended hardware components. When the seismic event occurs, all valuable parameters are updated with seismic data and wave propagation monitoring is enabled. As soon as the wave passes each deep ocean tsunameter, parameters of the initial displacement at source are updated from direct calculations based on original algorithms. For better source reconstruction, a combination of two methods is used: optimal unit source linear combination from preliminary calculated database and direct numerical inversion along the wave ray between real source and particular measurement buoys. Specific dissipation parameter along with the wave ray is also taken into account. During the entire wave propagation process the expected wave parameters and inundation zone(s) characteristics are updated with all available information. If recommended hardware components are used, monitoring results are available in real time. The suggested version of CWTHM has been tested by analyzing seismic precursors (foreshocks) and the measured tsunami waves at North Pacific for the Central Kuril's tsunamigenic earthquake of November 15, 2006.

ANALYTICAL ASSESSMENT OF THE IMPACTS OF PARTIAL MASS DEPLETION IN DNAPL SOURCE ZONES (SAN FRANCISCO, CA)

EPA Science Inventory

Analytical solutions describing the time-dependent DNAPL source-zone mass and contaminant discharge rate are used as a flux-boundary condition in a semi-analytical contaminant transport model. These analytical solutions assume a power relationship between the flow-averaged sourc...

Application of a Persistent Dissolved-phase Reactive Treatment Zone for Mitigation of Mass Discharge from Sources Located in Lower-Permeability Sediments

PubMed Central

Marble, J.C.; Brusseau, M.L.; Carroll, K.C.; Plaschke, M.; Fuhrig, L.; Brinker, F.

2015-01-01

The purpose of this study is to examine the development and effectiveness of a persistent dissolved-phase treatment zone, created by injecting potassium permanganate solution, for mitigating discharge of contaminant from a source zone located in a relatively deep, low-permeability formation. A localized 1,1-dichloroethene (DCE) source zone comprising dissolved- and sorbed-phase mass is present in lower permeability strata adjacent to a sand/gravel unit in a section of the Tucson International Airport Area (TIAA) Superfund Site. The results of bench-scale studies conducted using core material collected from boreholes drilled at the site indicated that natural oxidant demand was low, which would promote permanganate persistence. The reactive zone was created by injecting a permanganate solution into multiple wells screened across the interface between the lower-permeability and higher-permeability units. The site has been monitored for nine years to characterize the spatial distribution of DCE and permanganate. Permanganate continues to persist at the site, and a substantial and sustained decrease in DCE concentrations in groundwater has occurred after the permanganate injection.. These results demonstrate successful creation of a long-term, dissolved-phase reactive-treatment zone that reduced mass discharge from the source. This project illustrates the application of in-situ chemical oxidation as a persistent dissolved-phase reactive-treatment system for lower-permeability source zones, which appears to effectively mitigate persistent mass discharge into groundwater. PMID:26300570

System and method for investigating sub-surface features of a rock formation using compressional acoustic sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vu, Cung Khac; Skelt, Christopher; Nihei, Kurt

A system and method for investigating rock formations outside a borehole are provided. The method includes generating a first compressional acoustic wave at a first frequency by a first acoustic source; and generating a second compressional acoustic wave at a second frequency by a second acoustic source. The first and the second acoustic sources are arranged within a localized area of the borehole. The first and the second acoustic waves intersect in an intersection volume outside the borehole. The method further includes receiving a third shear acoustic wave at a third frequency, the third shear acoustic wave returning to themore » borehole due to a non-linear mixing process in a non-linear mixing zone within the intersection volume at a receiver arranged in the borehole. The third frequency is equal to a difference between the first frequency and the second frequency.« less

Mantle transition zone input to kimberlite magmatism near a subduction zone: Origin of anomalous Nd-Hf isotope systematics at Lac de Gras, Canada

NASA Astrophysics Data System (ADS)

Tappe, Sebastian; Graham Pearson, D.; Kjarsgaard, Bruce A.; Nowell, Geoff; Dowall, David

2013-06-01

Late Cretaceous-Eocene kimberlites from the Lac de Gras area, central Slave craton, show the most extreme Nd-Hf isotope decoupling observed for kimberlites worldwide. They are characterized by a narrow range of moderately enriched Nd isotope compositions (ɛNd(i)=-0.4 to -3.5) that contrasts strongly with their moderately depleted to highly enriched ɛHf(i) values (+3.9 to -9.9). Although digestion of cratonic mantle material in proto-kimberlite melt can theoretically produce steep arrays in Nd-Hf isotope space, the amount of contaminant required to explain the Lac de Gras data is unrealistic. Instead, it is more plausible that mixing of compositionally discrete melt components within an isotopically variable source region is responsible for the steep Nd-Hf isotope array. As development of strongly negative ΔɛHf requires isotopic aging of a precursor material with Sm/Nd≫Lu/Hf for billion-year timescales, a number of models have been proposed where ancient MORB crust trapped in the mantle transition zone is the ultimate source of the extreme Hf isotope signature. However, we provide a conceptual modification and demonstrate that OIB-type domains within ancient subducted oceanic lithosphere can produce much stronger negative ΔɛHf during long-term isolation. Provided that these OIB-type domains have lower melting points compared with associated MORB crust, they are among the first material to melt within the transition zone during thermal perturbations. The resulting hydrous alkali silicate melts react strongly with depleted peridotite at the top of the transition zone and transfer negative ΔɛHf signatures to less dense materials, which can be more easily entrained within upward flowing mantle. Once these entrained refertilized domains rise above 300 km depth, they may become involved in CO2- and H2O-fluxed redox melting of upper mantle peridotite beneath a thick cratonic lid. We argue that incorporation of ancient transition zone material, which includes ultradeep diamonds, into the convecting upper mantle source region of Lac de Gras kimberlites was due to vigorous mantle return flow. This occurred in direct response to fast and complex subduction along the western margin of North America during the Late Cretaceous.

78 FR 28742 - Safety Zone; Milwaukee Harbor, Milwaukee, WI

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-16

... inclement weather, then the zone will be enforced on June 9, 2013, from 9:15 p.m. until 10:15 p.m. This.... If the fireworks display is cancelled due to inclement weather, then the zone will be enforced on.... on June 8, 2013. If the fireworks display is cancelled due to inclement weather, then the zone will...

Variations in fluid transport and seismogenic properties in the Lesser Antilles subduction zone: constraints from joint active-source and local earthquake tomography

NASA Astrophysics Data System (ADS)

Paulatto, M.; Laigle, M.; Charvis, P.; Galve, A.

2015-12-01

The degree of coupling and the seismogenic properties of the plate interface at subduction zones are affected by the abundance of slab fluids and subducted sediments. High fluid input can cause high pore-fluid pressures in the subduction channel and decrease coupling leading to aseismic behaviour. Constraining fluid input and transfer is therefore important for understanding plate coupling and large earthquake hazard, particularly in places where geodetic and seismological constraints are scarce. We use P-wave traveltimes from several active source seismic experiments and P- and S-wave traveltimes from shallow and intermediate depth (< 150 km) local earthquakes recorded on a vast amphibious array of OBSs and land stations to recover the Vp and Vp/Vs structure of the central Lesser Antilles subduction zone. Our model extends between Martinique and Antigua from the prism to the arc and from the surface to a depth of 160 km. We find low Vp and high Vp/Vs ratio (> 1.80) on the top of the slab, at depths of up to 100 km. We interpret this high Vp/Vs ratio anomaly as evidence of elevated fluid content either as free fluids or as bound fluids in hydrated minerals (e.g. serpentinite). The strength and depth extent of the anomaly varies strongly from south to north along the subduction zone and correlates with variations in forearc morphology and with sediment input constrained by multi-channel seismic reflection profiles. The anomaly is stronger and extends to greater depth in the south, offshore Martinique, where sediment input is elevated due to the vicinity of the Orinoco delta. The gently dipping forearc slope observed in this region may be the result of weak coupling of the plate interface. A high Vp/Vs ratio is also observed in the forearc likely indicating a fractured and water-saturated overriding plate. On the other hand the anomaly is weaker and shallower offshore Guadeloupe, where sediment input is low due to subduction of the Barracuda ridge. Here a strong plate coupling is likely responsible for uplifting the inner forearc and formation of the Karukera spur. We infer that variations in plate coupling modulated by slab fluid transport and release are a major factor in determining the distribution of seismic slip in the Lesser Antilles subduction zone.

Effects of permafrost degradation on vegetation in the Source Area of the Yellow River NE Qinghai Tibetan Plateau

NASA Astrophysics Data System (ADS)

Xiaoying, Jin; Huijun, Jin

2017-04-01

Permafrost degradation caused by climate warming has markedly changed ecological environment in the Source Area of the Yellow River, in the northeast of the Qinghai Tibetan Plateau. However, related research about ecological impact of permafrost degradation is limited in this area. More attentions should be paid to the impact of permafrost degradation on alpine grassland. In this study vegetation characteristics (plant species composition, vegetation cover and biomass, etc.) at different permafrost degradation stages (as represented by the continuous and discontinuous permafrost zone, transitional zone, and seasonally frozen ground zone) is investigated. The results showed that (1) there are total 64 species in continuous and discontinuous permafrost zone, transitional zone, and seasonally frozen ground zone, and seasonally frozen ground zone has more species than transitional zone and permafrost zone, (2) sedge is the dominant species in three zones. But Shrub only presented in the seasonally frozen ground zone. These results suggest that permafrost degradation affect the species number and species composition of alpine grassland.

Environmental health aspects of drinking water-borne outbreak due to karst flooding: case study.

PubMed

Dura, Gyula; Pándics, Tamás; Kádár, Mihály; Krisztalovics, Katalin; Kiss, Zoltánné; Bodnár, Judit; Asztalos, Agnes; Papp, Erzsébet

2010-09-01

Climate change may increase the incidence of waterborne diseases due to extreme rainfall events, and consequent microbiological contamination of the water source and supply. As a result of the complexity of the pathways from the surface to the consumer, it is difficult to detect an association between rainfall and human disease. The water supply of a Hungarian city, Miskolc (174,000 inhabitant), is mainly based on karstic water, a vulnerable underground water body. A large amount of precipitation fell on the catchment area of the karstic water source, causing an unusually strong karstic water flow and flooding, and subsequent microbiological contamination. The presence of several potential sources of contamination in the protective zone of the karstic water source should be emphasized. The water supplier was unprepared to treat the risk of waterborne outbreak caused by an extreme weather event. Public health intervention and hygienic measures were taken in line with epidemiological actions, focusing on the protection of consumers by providing safe drinking water. The contamination was identified, and measures were taken for risk reduction and prevention. This case study underlines the increasing importance of preparedness for extreme water events in order to protect the karstic water sources and to avoid waterborne outbreaks.

Investigation of spherical loudspeaker arrays for local active control of sound.

PubMed

Peleg, Tomer; Rafaely, Boaz

2011-10-01

Active control of sound can be employed globally to reduce noise levels in an entire enclosure, or locally around a listener's head. Recently, spherical loudspeaker arrays have been studied as multiple-channel sources for local active control of sound, presenting the fundamental theory and several active control configurations. In this paper, important aspects of using a spherical loudspeaker array for local active control of sound are further investigated. First, the feasibility of creating sphere-shaped quiet zones away from the source is studied both theoretically and numerically, showing that these quiet zones are associated with sound amplification and poor system robustness. To mitigate the latter, the design of shell-shaped quiet zones around the source is investigated. A combination of two spherical sources is then studied with the aim of enlarging the quiet zone. The two sources are employed to generate quiet zones that surround a rigid sphere, investigating the application of active control around a listener's head. A significant improvement in performance is demonstrated in this case over a conventional headrest-type system that uses two monopole secondary sources. Finally, several simulations are presented to support the theoretical work and to demonstrate the performance and limitations of the system. © 2011 Acoustical Society of America

On the parameterization of interleaving and turbulent mixing using CTD data from the Azores Frontal Zone

NASA Astrophysics Data System (ADS)

Kuzmina, N. P.

2000-01-01

CTD-data obtained in the Azores Frontal Zone using a towed undulating vehicle are analyzed to study the relationship between characteristics of intrusions and mean parameters of the thermohaline field. A self-similar dependence between intrusion intensity and hydrological parameters is obtained. The most well-founded interpretation of the empirical dependence is as follows: (a) the main source supporting intrusive layering is the salt finger convection; (b) the abrupt decrease of intrusion intensity with the reduction of geostrophic Richardson number obtained from the analysis is explained by the beginning of turbulence when salt fingers do not work any longer, so the "driving force" for intrusive motion disappears. These results are consistent with the conclusions of the paper [Kuzmina N.P., Rodionov V.B., 1992. About the influence of baroclinicity upon generation of the thermohaline intrusions in the oceanic frontal zones. Izvestiya Akad. Nauk SSSR, Atmosperic and Oceanic Physics 28 (10-11), 1077-1086]. These conclusions imply that there are three main mechanisms of intrusive layering at oceanic fronts, namely the 2D baroclinic instability of geostrophic flow, the vertical shear instability and the thermohaline instability where the driving source of intrusive motion is double diffusive convection. The baroclinic and thermohaline instabilities can generate intrusions of large vertical scale, while vertical shear instability usually gives rise to thin turbulent layers. Turbulence in these thin layers can prevent salt finger convection and thus destroy the energy source of the intrusive motion conditioned by thermoclinicity. Therefore, the baroclinicity plays two parts in the processes of the intrusive layering: (1) it prevents double-diffusion interleaving by means of turbulence, and (2) it generates intrusions due to the 2D baroclinic instability of geostrophic current. Using features of thermohaline interleaving as a specific tracer of turbulent mixing, we have estimated turbulent mixing coefficient as k t˜ Ri-0.8 ( Ri>1), where Ri is the geostrophic Richardson number. Application of the proposed approach to other frontal zones is discussed.

Seismic anisotropy in the Hellenic subduction zone: Effects of slab segmentation and subslab mantle flow

NASA Astrophysics Data System (ADS)

Evangelidis, C. P.

2017-12-01

The segmentation and differentiation of subducting slabs have considerable effects on mantle convection and tectonics. The Hellenic subduction zone is a complex convergent margin with strong curvature and fast slab rollback. The upper mantle seismic anisotropy in the region is studied focusing at its western and eastern edges in order to explore the effects of possible slab segmentation on mantle flow and fabrics. Complementary to new SKS shear-wave splitting measurements in regions not adequately sampled so far, the source-side splitting technique is applied to constrain the depth of anisotropy and to densify measurements. In the western Hellenic arc, a trench-normal subslab anisotropy is observed near the trench. In the forearc domain, source-side and SKS measurements reveal a trench-parallel pattern. This indicates subslab trench-parallel mantle flow, associated with return flow due to the fast slab rollback. The passage from continental to oceanic subduction in the western Hellenic zone is illustrated by a forearc transitional anisotropy pattern. This indicates subslab mantle flow parallel to a NE-SW smooth ramp that possibly connects the two subducted slabs. A young tear fault initiated at the Kefalonia Transform Fault is likely not entirely developed, as this trench-parallel anisotropy pattern is observed along the entire western Hellenic subduction system, even following this horizontal offset between the two slabs. At the eastern side of the Hellenic subduction zone, subslab source-side anisotropy measurements show a general trench-normal pattern. These are associated with mantle flow through a possible ongoing tearing of the oceanic lithosphere in the area. Although the exact geometry of this slab tear is relatively unknown, SKS trench-parallel measurements imply that the tear has not reached the surface yet. Further exploration of the Hellenic subduction system is necessary; denser seismic networks should be deployed at both its edges in order to achieve a more definite image of the structure and geodynamics of this area.

Biodiesel presence in the source zone hinders aromatic hydrocarbons attenuation in a B20-contaminated groundwater

NASA Astrophysics Data System (ADS)

Ramos, Débora Toledo; Lazzarin, Helen Simone Chiaranda; Alvarez, Pedro J. J.; Vogel, Timothy M.; Fernandes, Marilda; do Rosário, Mário; Corseuil, Henry Xavier

2016-10-01

The behavior of biodiesel blend spills have received limited attention in spite of the increasing and widespread introduction of biodiesel to the transportation fuel matrix. In this work, a controlled field release of biodiesel B20 (100 L of 20:80 v/v soybean biodiesel and diesel) was monitored over 6.2 years to assess the behavior and natural attenuation of constituents of major concern (e.g., BTEX (benzene, toluene, ethyl-benzene and xylenes) and PAHs (polycyclic aromatic hydrocarbons)) in a sandy aquifer material. Biodiesel was preferentially biodegraded compared to diesel aromatic compounds with a concomitant increase in acetate, methane (near saturation limit (≈ 22 mg L- 1)) and dissolved BTEX and PAH concentrations in the source zone during the first 1.5 to 2.0 years after the release. Benzene and benzo(a)pyrene concentrations remained above regulatory limits in the source zone until the end of the experiment (6.2 years after the release). Compared to a previous adjacent 100-L release of ethanol-amended gasoline, biodiesel/diesel blend release resulted in a shorter BTEX plume, but with higher residual dissolved hydrocarbon concentrations near the source zone. This was attributed to greater persistence of viscous (and less mobile) biodiesel than the highly-soluble and mobile ethanol in the source zone. This persistence of biodiesel/diesel NAPL at the source zone slowed BTEX and PAH biodegradation (by the establishment of an anaerobic zone) but reduced the plume length by reducing mobility. This is the first field study to assess biodiesel/diesel blend (B20) behavior in groundwater and its effects on the biodegradation and plume length of priority groundwater pollutants.

Biodiesel presence in the source zone hinders aromatic hydrocarbons attenuation in a B20-contaminated groundwater.

PubMed

Ramos, Débora Toledo; Lazzarin, Helen Simone Chiaranda; Alvarez, Pedro J J; Vogel, Timothy M; Fernandes, Marilda; do Rosário, Mário; Corseuil, Henry Xavier

2016-10-01

The behavior of biodiesel blend spills have received limited attention in spite of the increasing and widespread introduction of biodiesel to the transportation fuel matrix. In this work, a controlled field release of biodiesel B20 (100L of 20:80 v/v soybean biodiesel and diesel) was monitored over 6.2years to assess the behavior and natural attenuation of constituents of major concern (e.g., BTEX (benzene, toluene, ethyl-benzene and xylenes) and PAHs (polycyclic aromatic hydrocarbons)) in a sandy aquifer material. Biodiesel was preferentially biodegraded compared to diesel aromatic compounds with a concomitant increase in acetate, methane (near saturation limit (≈22mgL -1 )) and dissolved BTEX and PAH concentrations in the source zone during the first 1.5 to 2.0years after the release. Benzene and benzo(a)pyrene concentrations remained above regulatory limits in the source zone until the end of the experiment (6.2years after the release). Compared to a previous adjacent 100-L release of ethanol-amended gasoline, biodiesel/diesel blend release resulted in a shorter BTEX plume, but with higher residual dissolved hydrocarbon concentrations near the source zone. This was attributed to greater persistence of viscous (and less mobile) biodiesel than the highly-soluble and mobile ethanol in the source zone. This persistence of biodiesel/diesel NAPL at the source zone slowed BTEX and PAH biodegradation (by the establishment of an anaerobic zone) but reduced the plume length by reducing mobility. This is the first field study to assess biodiesel/diesel blend (B20) behavior in groundwater and its effects on the biodegradation and plume length of priority groundwater pollutants. Copyright © 2016 Elsevier B.V. All rights reserved.

[Carbon source metabolic diversity of soil microbial community under different climate types in the area affected by Wenchuan earthquake].

PubMed

Zhang, Guang-Shuai; Lin, Yong-Ming; Ma, Rui-Feng; Deng, Hao-Jun; Du, Kun; Wu, Cheng-Zhen; Hong, Wei

2015-02-01

The MS8.0 Wenchuan earthquake in 2008 led to huge damage to land covers in northwest Sichuan, one of the critical fragile eco-regions in China which can be divided into Semi-arid dry hot climate zone (SDHC) and Subtropical humid monsoon climate zone (SHMC). Using the method of Bilog-ECO-microplate technique, this paper aimed to determine the functional diversity of soil microbial community in the earthquake-affected areas which can be divided into undamaged area (U), recover area (R) and damaged area without recovery (D) under different climate types, in order to provide scientific basis for ecological recovery. The results indicated that the average-well-color-development (AWCD) in undamaged area and recovery area showed SDHC > SHMC, which was contrary to the AWCD in the damaged area without recovery. The AWCD of damaged area without recovery was the lowest in both climate zones. The number of carbon source utilization types of soil microbial in SHMC zone was significantly higher than that in SDHC zone. The carbon source utilization types in both climate zones presented a trend of recover area > undamaged area > damaged area without recovery. The carbon source metabolic diversity characteristic of soil microbial community was significantly different in different climate zones. The diversity index and evenness index both showed a ranking of undamaged area > recover area > damaged area without recovery. In addition, the recovery area had the highest richness index. The soil microbial carbon sources metabolism characteristic was affected by soil nutrient, aboveground vegetation biomass and vegetation coverage to some extent. In conclusion, earthquake and its secondary disasters influenced the carbon source metabolic diversity characteristic of soil microbial community mainly through the change of aboveground vegetation and soil environmental factors.

Assessing controls on perched saturated zones beneath the Idaho Nuclear Technology and Engineering Center, Idaho

USGS Publications Warehouse

Mirus, Benjamin B.; Perkins, Kim S.; Nimmo, John R.

2011-01-01

Waste byproducts associated with operations at the Idaho Nuclear Technology and Engineering Center (INTEC) have the potential to contaminate the eastern Snake River Plain (ESRP) aquifer. Recharge to the ESRP aquifer is controlled largely by the alternating stratigraphy of fractured volcanic rocks and sedimentary interbeds within the overlying vadose zone and by the availability of water at the surface. Beneath the INTEC facilities, localized zones of saturation perched on the sedimentary interbeds are of particular concern because they may facilitate accelerated transport of contaminants. The sources and timing of natural and anthropogenic recharge to the perched zones are poorly understood. Simple approaches for quantitative characterization of this complex, variably saturated flow system are needed to assess potential scenarios for contaminant transport under alternative remediation strategies. During 2009-2011, the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, employed data analysis and numerical simulations with a recently developed model of preferential flow to evaluate the sources and quantity of recharge to the perched zones. Piezometer, tensiometer, temperature, precipitation, and stream-discharge data were analyzed, with particular focus on the possibility of contributions to the perched zones from snowmelt and flow in the neighboring Big Lost River (BLR). Analysis of the timing and magnitude of subsurface dynamics indicate that streamflow provides local recharge to the shallow, intermediate, and deep perched saturated zones within 150 m of the BLR; at greater distances from the BLR the influence of streamflow on recharge is unclear. Perched water-level dynamics in most wells analyzed are consistent with findings from previous geochemical analyses, which suggest that a combination of annual snowmelt and anthropogenic sources (for example, leaky pipes and drainage ditches) contribute to recharge of shallow and intermediate perched zones throughout much of INTEC. The source-responsive fluxes model was parameterized to simulate recharge via preferential flow associated with intermittent episodes of streamflow in the BLR. The simulations correspond reasonably well to the observed hydrologic response within the shallow perched zone. Good model performance indicates that source-responsive flow through a limited number of connected fractures contributes substantially to the perched-zone dynamics. The agreement between simulated and observed perched-zone dynamics suggest that the source-responsive fluxes model can provide a valuable tool for quantifying rapid preferential flow processes that may result from different land management scenarios.

Dominant seismic sources for the cities in South Sumatra

NASA Astrophysics Data System (ADS)

Sunardi, Bambang; Sakya, Andi Eka; Masturyono, Murjaya, Jaya; Rohadi, Supriyanto; Sulastri, Putra, Ade Surya

2017-07-01

Subduction zone along west of Sumatra and Sumatran fault zone are active seismic sources. Seismotectonically, South Sumatra could be affected by earthquakes triggered by these seismic sources. This paper discussed contribution of each seismic source to earthquake hazards for cities of Palembang, Prabumulih, Banyuasin, OganIlir, Ogan Komering Ilir, South Oku, Musi Rawas and Empat Lawang. These hazards are presented in form of seismic hazard curves. The study was conducted by using Probabilistic Seismic Hazard Analysis (PSHA) of 2% probability of exceedance in 50 years. Seismic sources used in analysis included megathrust zone M2 of Sumatra and South Sumatra, background seismic sources and shallow crustal seismic sources consist of Ketaun, Musi, Manna and Kumering faults. The results of the study showed that for cities relatively far from the seismic sources, subduction / megathrust seismic source with a depth ≤ 50 km greatly contributed to the seismic hazard and the other areas showed deep background seismic sources with a depth of more than 100 km dominate to seismic hazard respectively.

A systematic review of post-deployment injury-related mortality among military personnel deployed to conflict zones.

PubMed

Knapik, Joseph J; Marin, Roberto E; Grier, Tyson L; Jones, Bruce H

2009-07-13

This paper reports on a systematic review of the literature on the post-conflict injury-related mortality of service members who deployed to conflict zones. Literature databases, reference lists of articles, agencies, investigators, and other sources were examined to find studies comparing injury-related mortality of military veterans who had served in conflict zones with that of contemporary veterans who had not served in conflict zones. Injury-related mortality was defined as a cause of death indicated by International Classification of Diseases E-codes E800 to E999 (external causes) or subgroupings within this range of codes. Twenty studies met the review criteria; all involved veterans serving during either the Vietnam or Persian Gulf conflict. Meta-analysis indicated that, compared with non-conflict-zone veterans, injury-related mortality was elevated for veterans serving in Vietnam (summary mortality rate ratio (SMRR) = 1.26, 95% confidence interval (95%CI) = 1.08-1.46) during 9 to 18 years of follow-up. Similarly, injury-related mortality was elevated for veterans serving in the Persian Gulf War (SMRR = 1.26, 95%CI = 1.16-1.37) during 3 to 8 years of follow-up. Much of the excess mortality among conflict-zone veterans was associated with motor vehicle events. The excess mortality decreased over time. Hypotheses to account for the excess mortality in conflict-zone veterans included post-traumatic stress, coping behaviors such as substance abuse, ill-defined diseases and symptoms, lower survivability in injury events due to conflict-zone comorbidities, altered perceptions of risk, and/or selection processes leading to the deployment of individuals who were risk-takers. Further research on the etiology of the excess mortality in conflict-zone veterans is warranted to develop appropriate interventions.

A systematic review of post-deployment injury-related mortality among military personnel deployed to conflict zones

PubMed Central

Knapik, Joseph J; Marin, Roberto E; Grier, Tyson L; Jones, Bruce H

2009-01-01

Background This paper reports on a systematic review of the literature on the post-conflict injury-related mortality of service members who deployed to conflict zones. Methods Literature databases, reference lists of articles, agencies, investigators, and other sources were examined to find studies comparing injury-related mortality of military veterans who had served in conflict zones with that of contemporary veterans who had not served in conflict zones. Injury-related mortality was defined as a cause of death indicated by International Classification of Diseases E-codes E800 to E999 (external causes) or subgroupings within this range of codes. Results Twenty studies met the review criteria; all involved veterans serving during either the Vietnam or Persian Gulf conflict. Meta-analysis indicated that, compared with non-conflict-zone veterans, injury-related mortality was elevated for veterans serving in Vietnam (summary mortality rate ratio (SMRR) = 1.26, 95% confidence interval (95%CI) = 1.08–1.46) during 9 to 18 years of follow-up. Similarly, injury-related mortality was elevated for veterans serving in the Persian Gulf War (SMRR = 1.26, 95%CI = 1.16–1.37) during 3 to 8 years of follow-up. Much of the excess mortality among conflict-zone veterans was associated with motor vehicle events. The excess mortality decreased over time. Hypotheses to account for the excess mortality in conflict-zone veterans included post-traumatic stress, coping behaviors such as substance abuse, ill-defined diseases and symptoms, lower survivability in injury events due to conflict-zone comorbidities, altered perceptions of risk, and/or selection processes leading to the deployment of individuals who were risk-takers. Conclusion Further research on the etiology of the excess mortality in conflict-zone veterans is warranted to develop appropriate interventions. PMID:19594931

X-Ray Probes of Jupiter's Auroral Zones, Galilean Moons, and the Io Plasma Torus

NASA Technical Reports Server (NTRS)

Elsner, R. F.; Ramsey, B. D.; Swartz, D. A.; Rehak, P.; Waite, J. H., Jr.; Cooper, J. F.; Johnson, R. E.

2005-01-01

Remote observations from the Earth orbiting Chandra X-ray Observatory and the XMM-Newton Observatory have shown the the Jovian system is a rich and complex source of x-ray emission. The planet's auroral zones and its disk are powerful sources of x-ray emission, though with different origins. Chandra observations discovered x-ray emission from the Io plasma torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is due to bombardment of their surfaces by highly energetic magnetospheric protons, and oxygen and sulfur ions, producing fluorescent x-ray emission lines from the elements in their surfaces against an intense background continuum. Although very faint when observed from Earth orbit, an imaging x-ray spectrometer in orbit around the icy Galilean moons would provide a detail mapping of the elemental composition in their surfaces. Here we review the results of Chandra and XMM-Newton observations of the Jovian system and describe the characteristics of X-MIME, an imaging x-ray spectrometer undergoing study for possible application to future missions to Jupiter such as JIMO. X-MIME has the ultimate goal of providing detailed high-resolution maps of the elemental abundances of the surfaces of Jupiter's icy moons and Io, as well as detailed study of the x-ray mission from the Io plasma torus, Jupiter's auroral zones, and the planetary disk.

Methane Leakage From Hydrocarbon Wellbores into Overlying Groundwater: Numerical Investigation of the Multiphase Flow Processes Governing Migration

NASA Astrophysics Data System (ADS)

Rice, Amy K.; McCray, John E.; Singha, Kamini

2018-04-01

Methane leakage due to compromised hydrocarbon well integrity can lead to impaired groundwater quality. Here we use a three-dimensional, multiphase (vapor and aqueous), multicomponent (methane, water, salt), numerical model (TOUGH2 EOS7C) to investigate hydrogeological conditions that could result in groundwater contamination from natural gas wellbore leakage that migrates upward toward a freshwater aquifer. The conceptual model used for the simulations assumes methane leakage at 20-30 m below groundwater. We perform 180 simulations for a sensitivity analysis, examining (1) multiphase flow parameters related to storage, capillarity, and relative permeability, including porosity (ϕ), initial fluid-phase saturation (SL), and van Genuchten n and α, (2) geostatistical variations in intrinsic permeability (ki), and (3) methane source-zone pressure. Simulated mean ki values are 10-18 and 10-13 m2 with variances of 1 and 5 m4. Simulated source-zone pressures range from just over ambient hydrostatic pressure at the depth of leakage (100 kPa) to the maximum pressure that steel casings are commonly rated to withstand (20,340 kPa). ki, initial SL, ϕ, and van Genuchten's n and α were the most important parameters in determining the volume of methane reaching groundwater during a given time period. Multiphase parameterization of formations underlying freshwater aquifers and overlying hydrocarbon production zones is fundamental to assessing aquifer vulnerability to methane leakage.

Evaluating Long-Term Impacts of Soil-Mixing Source-Zone Treatment using Cryogenic Core Collection

DTIC Science & Technology

2017-06-01

to (a) coring equipment freezing downhole, (b) freezing or binding of the core sample in barrel, and ( c ) running out of LN in the vicinity of sampling...encountered due to (a) coring equipment freezing downhole, (b) freezing or binding of the core sample in barrel, and ( c ) running out of LN in the...equipment freezing downhole, (b) freezing or binding of the core sample in barrel, and ( c ) running out of LN in the vicinity of sampling. Downhole

Impacts of DNAPL Source Treatment: Experimental and Modeling Assessment of the Benefits of Partial DNAPL Source Removal

DTIC Science & Technology

2009-09-01

nuclear industry for conducting performance assessment calculations. The analytical FORTRAN code for the DNAPL source function, REMChlor, was...project. The first was to apply existing deterministic codes , such as T2VOC and UTCHEM, to the DNAPL source zone to simulate the remediation processes...but describe the spatial variability of source zones unlike one-dimensional flow and transport codes that assume homogeneity. The Lagrangian models

Development of a Persistent Reactive Treatment Zone for Containment of Sources Located in Lower-Permeability Strata

NASA Astrophysics Data System (ADS)

Marble, J.; Carroll, K. C.; Brusseau, M. L.; Plaschke, M.; Brinker, F.

2013-12-01

Source zones located in relatively deep, low-permeability formations provide special challenges for remediation. Application of permeable reactive barriers, in-situ thermal, or electrokinetic methods would be expensive and generally impractical. In addition, the use of enhanced mass-removal approaches based on reagent injection (e.g., ISCO, enhanced-solubility reagents) is likely to be ineffective. One possible approach for such conditions is to create a persistent treatment zone for purposes of containment. This study examines the efficacy of this approach for containment and treatment of contaminants in a lower permeability zone using potassium permanganate (KMnO4) as the reactant. A localized 1,1-dichloroethene (DCE) source zone is present in a section of the Tucson International Airport Area (TIAA) Superfund Site. Characterization studies identified the source of DCE to be located in lower-permeability strata adjacent to the water table. Bench-scale studies were conducted using core material collected from boreholes drilled at the site to measure DCE concentrations and determine natural oxidant demand. The reactive zone was created by injecting ~1.7% KMnO4 solution into multiple wells screened within the lower-permeability unit. The site has been monitored for ~8 years to characterize the spatial distribution of DCE and permanganate. KMnO4 continues to persist at the site, demonstrating successful creation of a long-term reactive zone. Additionally, the footprint of the DCE contaminant plume in groundwater has decreased continuously with time. This project illustrates the application of ISCO as a reactive-treatment system for lower-permeability source zones, which appears to effectively mitigate persistent mass flux into groundwater.

Integrated geophysical investigations for the delineation of source and subsurface structure associated with hydro-uranium anomaly: A case study from South Purulia Shear Zone (SPSZ), India

NASA Astrophysics Data System (ADS)

Sharma, S. P.; Biswas, A.

2012-12-01

South Purulia Shear Zone (SPSZ) is an important region for prospecting of uranium mineralization. Geological studies and hydro-uranium anomaly suggest the presence of Uranium deposit around Raghunathpur village which lies about 8 km north of SPSZ. However, detailed geophysical investigations have not been carried out in this region for investigation of uranium mineralization. Since surface signature of uranium mineralization is not depicted near the location, a deeper subsurface source is expected for hydro uranium anomaly. To delineate the subsurface structure and to investigate the origin of hydro-uranium anomaly present in the area, Vertical Electrical Sounding (VES) using Schlumberger array and Gradient Resistivity Profiling (GRP) were performed at different locations along a profile perpendicular to the South Purulia Shear Zone. Apparent resistivity computed from the measured sounding data at various locations shows a continuously increasing trend. As a result, conventional apparent resistivity data is not able to detect the possible source of hydro uranium anomaly. An innovative approach is applied which depicts the apparent conductivity in the subsurface revealed a possible connection from SPSZ to Raghunathpur. On the other hand resistivity profiling data suggests a low resistive zone which is also characterized by low Self-Potential (SP) anomaly zone. Since SPSZ is characterized by the source of uranium mineralization; hydro-uranium anomaly at Raghunathpur is connected with the SPSZ. The conducting zone has been delineated from SPSZ to Raghunathpur at deeper depths which could be uranium bearing. Since the location is also characterized by a low gravity and high magnetic anomaly zone, this conducting zone is likely to be mineralized zone. Keywords: Apparent resistivity; apparent conductivity; Self Potential; Uranium mineralization; shear zone; hydro-uranium anomaly.

Compressible Flow Phenomena at Inception of Lateral Density Currents Fed by Collapsing Gas-Particle Mixtures

NASA Astrophysics Data System (ADS)

Valentine, Greg A.; Sweeney, Matthew R.

2018-02-01

Many geological flows are sourced by falling gas-particle mixtures, such as during collapse of lava domes, and impulsive eruptive jets, and sustained columns, and rock falls. The transition from vertical to lateral flow is complex due to the range of coupling between particles of different sizes and densities and the carrier gas, and due to the potential for compressible flow phenomena. We use multiphase modeling to explore these dynamics. In mixtures with small particles, and with subsonic speeds, particles follow the gas such that outgoing lateral flows have similar particle concentration and speed as the vertical flows. Large particles concentrate immediately upon impact and move laterally away as granular flows overridden by a high-speed jet of expelled gas. When a falling flow is supersonic, a bow shock develops above the impact zone, and this produces a zone of high pressure from which lateral flows emerge as overpressured wall jets. The jets form complex structures as the mixtures expand and accelerate and then recompress through a recompression zone that mimics a Mach disk shock in ideal gas jets. In mixtures with moderate to high ratios of fine to coarse particles, the latter tend to follow fine particles through the expansion-recompression flow fields because of particle-particle drag. Expansion within the flow fields can lead to locally reduced gas pressure that could enhance substrate erosion in natural flows. The recompression zones form at distances, and have peak pressures, that are roughly proportional to the Mach numbers of impacting flows.

Physical transformations of iron oxide and silver nanoparticles from an intermediate scale field transport study

NASA Astrophysics Data System (ADS)

Emerson, Hilary P.; Hart, Ashley E.; Baldwin, Jonathon A.; Waterhouse, Tyler C.; Kitchens, Christopher L.; Mefford, O. Thompson; Powell, Brian A.

2014-02-01

In recent years, there has been increasing concern regarding the fate and transport of engineered nanoparticles (NPs) in environmental systems and the potential impacts on human and environmental health due to the exponential increase in commercial and industrial use worldwide. To date, there have been relatively few field-scale studies or laboratory-based studies on environmentally relevant soils examining the chemical/physical behavior of the NPs following release into natural systems. The objective of this research is to demonstrate the behavior and transformations of iron oxide and silver NPs with different capping ligands within the unsaturated zone. Here, we show that NP transport within the vadose zone is minimal primarily due to heteroaggregation with soil surface coatings with results that >99 % of the NPs remained within 5 cm of the original source after 1 year in intermediate-scale field lysimeters. These results suggest that transport may be overestimated when compared to previous laboratory-scale studies on pristine soils and pure minerals and that future work must incorporate more environmentally relevant parameters.

Mechanisms of electron acceptor utilization: Implications for simulating anaerobic biodegradation

USGS Publications Warehouse

Schreiber, M.E.; Carey, G.R.; Feinstein, D.T.; Bahr, J.M.

2004-01-01

Simulation of biodegradation reactions within a reactive transport framework requires information on mechanisms of terminal electron acceptor processes (TEAPs). In initial modeling efforts, TEAPs were approximated as occurring sequentially, with the highest energy-yielding electron acceptors (e.g. oxygen) consumed before those that yield less energy (e.g., sulfate). Within this framework in a steady state plume, sequential electron acceptor utilization would theoretically produce methane at an organic-rich source and Fe(II) further downgradient, resulting in a limited zone of Fe(II) and methane overlap. However, contaminant plumes often display much more extensive zones of overlapping Fe(II) and methane. The extensive overlap could be caused by several abiotic and biotic processes including vertical mixing of byproducts in long-screened monitoring wells, adsorption of Fe(II) onto aquifer solids, or microscale heterogeneity in Fe(III) concentrations. Alternatively, the overlap could be due to simultaneous utilization of terminal electron acceptors. Because biodegradation rates are controlled by TEAPs, evaluating the mechanisms of electron acceptor utilization is critical for improving prediction of contaminant mass losses due to biodegradation. Using BioRedox-MT3DMS, a three-dimensional, multi-species reactive transport code, we simulated the current configurations of a BTEX plume and TEAP zones at a petroleum- contaminated field site in Wisconsin. Simulation results suggest that BTEX mass loss due to biodegradation is greatest under oxygen-reducing conditions, with smaller but similar contributions to mass loss from biodegradation under Fe(III)-reducing, sulfate-reducing, and methanogenic conditions. Results of sensitivity calculations document that BTEX losses due to biodegradation are most sensitive to the age of the plume, while the shape of the BTEX plume is most sensitive to effective porosity and rate constants for biodegradation under Fe(III)-reducing and methanogenic conditions. Using this transport model, we had limited success in simulating overlap of redox products using reasonable ranges of parameters within a strictly sequential electron acceptor utilization framework. Simulation results indicate that overlap of redox products cannot be accurately simulated using the constructed model, suggesting either that Fe(III) reduction and methanogenesis are occurring simultaneously in the source area, or that heterogeneities in Fe(III) concentration and/or mineral type cause the observed overlap. Additional field, experimental, and modeling studies will be needed to address these questions. ?? 2004 Elsevier B.V. All rights reserved.

Barbados: Architecture and implications for accretion

NASA Astrophysics Data System (ADS)

Speed, R. C.; Larue, D. K.

1982-05-01

The island of Barbados exposes the crestal zone of the remarkably broad accretionary prism of the Lesser Antilles foreacrc. The architecture of Barbados is three-tiered: an upper arched cap of Pleistocene reefs that record rapid and differential uplift of the island, an intermediate zone of nappes of mainly abyssal or deep bathyal pelagic rocks, and a basal complex whose lithotypes extend to substantial depth and may be representative of the bulk of the western or inner accretionary prism. The exposed basal complex consists of generally steeply dipping ENE to NE-striking fault-bounded packets which contain rocks of one of three lithic suites: terrigenous (quartzose turbidite and mudstone), debris flow, and hemipelagic (chiefly radiolarite). Present but imcomplete rock dating indicates that the terrigenous and hemipelagic suites and the pelagic rocks of the intermediate zone are age overlapping in Early and Middle Eocene time. Deformation within packets of the basal complex is systematic, pre- or synfault, and indicative of shortening that is generally normal to packet boundaries. A unit of terrigenous materials that probably underwent local resedimentation in the Miocene is recognized in wells, but its relationship to exposed rocks is uncertain. The packet-bounding faults of the basal complex are interpreted to have been primary accretionary surfaces which may have been reactivated by later intraprism movements. Exposed sedimentary rocks of Barbados can be successfully assigned to contemporaneous depositional sites associated with an accretionary prism: terrigenous beds to a trench wedge that was connected to South American sediment sources, debris flow to trench floor or slope basin accumulations of material derived from the lower slope, hemipelagic to Atlantic plain strata, and pelagic rocks of the intermediate zone to deep outer forearc basin sites. The decollement at the base of the intermediate zone is probably due to uplift and arcward motion of the crestal zone of the accretionary prism with respect to the forearc basin during progressive prism growth. Principal uplift of the prism seems to have started, apparently abruptly, in the Miocene. Quaternary uplift of Barbados may be due partly to local diapirism. Paleogene subduction that created the arcward region of the prism probably occurred in a differently configured zone from the present one.

Sanitary survey of the drinking water supply of Kombinati suburb-Tirana, Albania.

PubMed

Angjeli, V; Reme, B; Leno, L; Bukli, R; Bushati, G

2000-01-01

Microbiological pollution of drinking water is a major health problem in the suburbs of the Albanian capital. Intermittent supply and contamination, resulting in several gastrointestinal manifestations, are the main concerns for the population and health workers. The risk of outbreaks of water-borne diseases is high. Pollution originates from contamination of drinking water with domestic sewage. This research investigated the drinking water cycle from its natural source to the consumer, analysing samples and verifying pollution levels in the microbiological and chemical setting. The most important pollution sources were found in the distribution network, due to cross-contamination with sewers and illegal connections. The second pollution source was found around the extraction wells. This is related to abusive constructions within the sanitary zone around the wells and maybe the highly sewage-contaminated river water which feeds the aquifer.

Measuring Spatial Variability of Vapor Flux to Characterize Vadose-zone VOC Sources: Flow-cell Experiments

DOE PAGES

Mainhagu, Jon; Morrison, C.; Truex, Michael J.; ...

2014-08-05

A method termed vapor-phase tomography has recently been proposed to characterize the distribution of volatile organic contaminant mass in vadose-zone source areas, and to measure associated three-dimensional distributions of local contaminant mass discharge. The method is based on measuring the spatial variability of vapor flux, and thus inherent to its effectiveness is the premise that the magnitudes and temporal variability of vapor concentrations measured at different monitoring points within the interrogated area will be a function of the geospatial positions of the points relative to the source location. A series of flow-cell experiments was conducted to evaluate this premise. Amore » well-defined source zone was created by injection and extraction of a non-reactive gas (SF6). Spatial and temporal concentration distributions obtained from the tests were compared to simulations produced with a mathematical model describing advective and diffusive transport. Tests were conducted to characterize both areal and vertical components of the application. Decreases in concentration over time were observed for monitoring points located on the opposite side of the source zone from the local–extraction point, whereas increases were observed for monitoring points located between the local–extraction point and the source zone. We found that the results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.« less

Optimizing the design of vertical seismic profiling (VSP) for imaging fracture zones over hardrock basement geothermal environments

NASA Astrophysics Data System (ADS)

Reiser, Fabienne; Schmelzbach, Cedric; Maurer, Hansruedi; Greenhalgh, Stewart; Hellwig, Olaf

2017-04-01

A primary focus of geothermal seismic imaging is to map dipping faults and fracture zones that control rock permeability and fluid flow. Vertical seismic profiling (VSP) is therefore a most valuable means to image the immediate surroundings of an existing borehole to guide, for example, the placing of new boreholes to optimize production from known faults and fractures. We simulated 2D and 3D acoustic synthetic seismic data and processed it through to pre-stack depth migration to optimize VSP survey layouts for mapping moderately to steeply dipping fracture zones within possible basement geothermal reservoirs. Our VSP survey optimization procedure for sequentially selecting source locations to define the area where source points are best located for optimal imaging makes use of a cross-correlation statistic, by which a subset of migrated shot gathers is compared with a target or reference image from a comprehensive set of source gathers. In geothermal exploration at established sites, it is reasonable to assume that sufficient à priori information is available to construct such a target image. We generally obtained good results with a relatively small number of optimally chosen source positions distributed over an ideal source location area for different fracture zone scenarios (different dips, azimuths, and distances from the surveying borehole). Adding further sources outside the optimal source area did not necessarily improve the results, but rather resulted in image distortions. It was found that fracture zones located at borehole-receiver depths and laterally offset from the borehole by 300 m can be imaged reliably for a range of the different dips, but more source positions and large offsets between sources and the borehole are required for imaging steeply dipping interfaces. When such features cross-cut the borehole, they are particularly difficult to image. For fracture zones with different azimuths, 3D effects are observed. Far offset source positions contribute less to the image quality as fracture zone azimuth increases. Our optimization methodology is best suited for designing future field surveys with a favorable benefit-cost ratio in areas with significant à priori knowledge. Moreover, our optimization workflow is valuable for selecting useful subsets of acquired data for optimum target-oriented processing.

Comparisons of Source Characteristics between Recent Inland Crustal Earthquake Sequences inside and outside of Niigata-Kobe Tectonic Zone, Japan

NASA Astrophysics Data System (ADS)

Somei, K.; Asano, K.; Iwata, T.; Miyakoshi, K.

2012-12-01

After the 1995 Kobe earthquake, many M7-class inland earthquakes occurred in Japan. Some of those events (e.g., the 2004 Chuetsu earthquake) occurred in a tectonic zone which is characterized as a high strain rate zone by the GPS observation (Sagiya et al., 2000) or dense distribution of active faults. That belt-like zone along the coast in Japan Sea side of Tohoku and Chubu districts, and north of Kinki district, is called as the Niigata-Kobe tectonic zone (NKTZ, Sagiya et al, 2000). We investigate seismic scaling relationship for recent inland crustal earthquake sequences in Japan and compare source characteristics between events occurring inside and outside of NKTZ. We used S-wave coda part for estimating source spectra. Source spectral ratio is obtained by S-wave coda spectral ratio between the records of large and small events occurring close to each other from nation-wide strong motion network (K-NET and KiK-net) and broad-band seismic network (F-net) to remove propagation-path and site effects. We carefully examined the commonality of the decay of coda envelopes between event-pair records and modeled the observed spectral ratio by the source spectral ratio function with assuming omega-square source model for large and small events. We estimated the corner frequencies and seismic moment (ratio) from those modeled spectral ratio function. We determined Brune's stress drops of 356 events (Mw: 3.1-6.9) in ten earthquake sequences occurring in NKTZ and six sequences occurring outside of NKTZ. Most of source spectra obey omega-square source spectra. There is no obvious systematic difference between stress drops of events in NKTZ zone and others. We may conclude that the systematic tendency of seismic source scaling of the events occurred inside and outside of NKTZ does not exist and the average source scaling relationship can be effective for inland crustal earthquakes. Acknowledgements: Waveform data were provided from K-NET, KiK-net and F-net operated by National Research Institute for Earth Science and Disaster Prevention Japan. This study is supported by Multidisciplinary research project for Niigata-Kobe tectonic zone promoted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Impacts of Oil and Gas Production on Winter Ozone Pollution in the Uintah Basin Using Model Source Apportionment

NASA Astrophysics Data System (ADS)

Tran, H. N. Q.; Tran, T. T.; Mansfield, M. L.; Lyman, S. N.

2014-12-01

Contributions of emissions from oil and gas activities to elevated ozone concentrations in the Uintah Basin - Utah were evaluated using the CMAQ Integrated Source Apportionment Method (CMAQ-ISAM) technique, and were compared with the results of traditional budgeting methods. Unlike the traditional budgeting method, which compares simulations with and without emissions of the source(s) in question to quantify its impacts, the CMAQ-ISAM technique assigns tags to emissions of each source and tracks their evolution through physical and chemical processes to quantify the final ozone product yield from the source. Model simulations were performed for two episodes in winter 2013 of low and high ozone to provide better understanding of source contributions under different weather conditions. Due to the highly nonlinear ozone chemistry, results obtained from the two methods differed significantly. The growing oil and gas industry in the Uintah Basin is the largest contributor to the elevated zone (>75 ppb) observed in the Basin. This study therefore provides an insight into the impact of oil and gas industry on the ozone issue, and helps in determining effective control strategies.

Architecture, persistence and dissolution of a 20 to 45 year old trichloroethene DNAPL source zone.

PubMed

Rivett, Michael O; Dearden, Rachel A; Wealthall, Gary P

2014-12-01

A detailed field-scale investigation of processes controlling the architecture, persistence and dissolution of a 20 to 45year old trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) source zone located within a heterogeneous sand/gravel aquifer at a UK industrial site is presented. The source zone was partially enclosed by a 3-sided cell that allowed detailed longitudinal/fence transect monitoring along/across a controlled streamtube of flow induced by an extraction well positioned at the cell closed end. Integrated analysis of high-resolution DNAPL saturation (Sn) (from cores), dissolved-phase plume concentration (from multilevel samplers), tracer test and permeability datasets was undertaken. DNAPL architecture was determined from soil concentration data using partitioning calculations. DNAPL threshold soil concentrations and low Sn values calculated were sensitive to sorption assumptions. An outcome of this was the uncertainty in demarcation of secondary source zone diffused and sorbed mass that is distinct from trace amounts of low Sn DNAPL mass. The majority of source mass occurred within discrete lenses or pools of DNAPL associated with low permeability geological units. High residual saturation (Sn>10-20%) and pools (Sn>20%) together accounted for almost 40% of the DNAPL mass, but only 3% of the sampled source volume. High-saturation DNAPL lenses/pools were supported by lower permeability layers, but with DNAPL still primarily present within slightly more permeable overlying units. These lenses/pools exhibited approximately linearly declining Sn profiles with increasing elevation ascribed to preferential dissolution of the uppermost DNAPL. Bi-component partitioning calculations on soil samples confirmed that the dechlorination product cDCE (cis-dichloroethene) was accumulating in the TCE DNAPL. Estimated cDCE mole fractions in the DNAPL increased towards the DNAPL interface with the uppermost mole fraction of 0.04 comparable to literature laboratory data. DNAPL dissolution yielded heterogeneous dissolved-phase plumes of TCE and its dechlorination products that exhibited orders of magnitude local concentration variation. TCE solubility concentrations were relatively localised, but coincident with high saturation DNAPL lens source areas. Biotic dechlorination in the source zone area, however, caused cDCE to be the dominant dissolved-phase plume. The conservative tracer test usefully confirmed the continuity of a permeable gravel unit at depth through the source zone. Although this unit offered significant opportunity for DNAPL bypassing and decreased timeframes for dechlorination, it still transmitted a significant proportion of the contaminant flux. This was attributed to dissolution of DNAPL-mudstone aquitard associated sources at the base of the continuous gravel as well as contaminated groundwater from surrounding less permeable sand and gravel horizons draining into this permeable conduit. The cell extraction well provided an integrated metric of source zone dissolution yielding a mean concentration of around 45% TCE solubility (taking into account dechlorination) that was equivalent to a DNAPL mass removal rate of 0.4tonnes per annum over a 16m(2) cell cross sectional area of flow. This is a significant flux considering the source age and observed occurrence of much of the source mass within discrete lenses/pools. We advocate the need for further detailed field-scale studies on old DNAPL source zones that better resolve persistent pool/lens features and are of prolonged duration to assess the ageing of source zones. Such studies would further underpin the application of more surgical remediation technologies. Copyright © 2014. Published by Elsevier B.V.

Architecture, persistence and dissolution of a 20 to 45 year old trichloroethene DNAPL source zone

NASA Astrophysics Data System (ADS)

Rivett, Michael O.; Dearden, Rachel A.; Wealthall, Gary P.

2014-12-01

A detailed field-scale investigation of processes controlling the architecture, persistence and dissolution of a 20 to 45 year old trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) source zone located within a heterogeneous sand/gravel aquifer at a UK industrial site is presented. The source zone was partially enclosed by a 3-sided cell that allowed detailed longitudinal/fence transect monitoring along/across a controlled streamtube of flow induced by an extraction well positioned at the cell closed end. Integrated analysis of high-resolution DNAPL saturation (Sn) (from cores), dissolved-phase plume concentration (from multilevel samplers), tracer test and permeability datasets was undertaken. DNAPL architecture was determined from soil concentration data using partitioning calculations. DNAPL threshold soil concentrations and low Sn values calculated were sensitive to sorption assumptions. An outcome of this was the uncertainty in demarcation of secondary source zone diffused and sorbed mass that is distinct from trace amounts of low Sn DNAPL mass. The majority of source mass occurred within discrete lenses or pools of DNAPL associated with low permeability geological units. High residual saturation (Sn > 10-20%) and pools (Sn > 20%) together accounted for almost 40% of the DNAPL mass, but only 3% of the sampled source volume. High-saturation DNAPL lenses/pools were supported by lower permeability layers, but with DNAPL still primarily present within slightly more permeable overlying units. These lenses/pools exhibited approximately linearly declining Sn profiles with increasing elevation ascribed to preferential dissolution of the uppermost DNAPL. Bi-component partitioning calculations on soil samples confirmed that the dechlorination product cDCE (cis-dichloroethene) was accumulating in the TCE DNAPL. Estimated cDCE mole fractions in the DNAPL increased towards the DNAPL interface with the uppermost mole fraction of 0.04 comparable to literature laboratory data. DNAPL dissolution yielded heterogeneous dissolved-phase plumes of TCE and its dechlorination products that exhibited orders of magnitude local concentration variation. TCE solubility concentrations were relatively localised, but coincident with high saturation DNAPL lens source areas. Biotic dechlorination in the source zone area, however, caused cDCE to be the dominant dissolved-phase plume. The conservative tracer test usefully confirmed the continuity of a permeable gravel unit at depth through the source zone. Although this unit offered significant opportunity for DNAPL bypassing and decreased timeframes for dechlorination, it still transmitted a significant proportion of the contaminant flux. This was attributed to dissolution of DNAPL-mudstone aquitard associated sources at the base of the continuous gravel as well as contaminated groundwater from surrounding less permeable sand and gravel horizons draining into this permeable conduit. The cell extraction well provided an integrated metric of source zone dissolution yielding a mean concentration of around 45% TCE solubility (taking into account dechlorination) that was equivalent to a DNAPL mass removal rate of 0.4 tonnes per annum over a 16 m2 cell cross sectional area of flow. This is a significant flux considering the source age and observed occurrence of much of the source mass within discrete lenses/pools. We advocate the need for further detailed field-scale studies on old DNAPL source zones that better resolve persistent pool/lens features and are of prolonged duration to assess the ageing of source zones. Such studies would further underpin the application of more surgical remediation technologies.

Transport and degradation of perchlorate in deep vadose zone: implications from direct observations during bioremediation treatment

NASA Astrophysics Data System (ADS)

Dahan, Ofer; Katz, Idan; Avishai, Lior; Ronen, Zeev

2017-08-01

An in situ bioremediation experiment of a deep vadose zone ( ˜ 40 m) contaminated with a high concentration of perchlorate (> 25 000 mg L-1) was conducted through a full-scale field operation. Favourable environmental conditions for microbiological reduction of perchlorate were sought by infiltrating an electron donor-enriched water solution using drip irrigation underlying an airtight sealing liner. A vadose zone monitoring system (VMS) was used for real-time tracking of the percolation process, the penetration depth of dissolved organic carbon (DOC), and the variation in perchlorate concentration across the entire soil depth. The experimental conditions for each infiltration event were adjusted according to insight gained from data obtained by the VMS in previous stages. Continuous monitoring of the vadose zone indicated that in the top 13 m of the cross section, perchlorate concentration is dramatically reduced from thousands of milligrams per litre to near-detection limits with a concurrent increase in chloride concentration. Nevertheless, in the deeper parts of the vadose zone (< 17 m), perchlorate concentration increased, suggesting its mobilization down through the cross section. Breakthrough of DOC and bromide at different depths across the unsaturated zone showed limited migration capacity of biologically consumable carbon and energy sources due to their enhanced biodegradation in the upper soil layers. Nevertheless, the increased DOC concentration with concurrent reduction in perchlorate and increase in the chloride-to-perchlorate ratio in the top 13 m indicate partial degradation of perchlorate in this zone. There was no evidence of improved degradation conditions in the deeper parts where the initial concentrations of perchlorate were significantly higher.

Source and transport controls on the movement of nitrate to public supply wells in selected principal aquifers of the United States

USGS Publications Warehouse

McMahon, P.B.; Böhlke, J.K.; Kauffman, L.J.; Kipp, K.L.; Landon, M.K.; Crandall, C.A.; Burow, K.R.; Brown, C.J.

2008-01-01

In 2003–2005, systematic studies in four contrasting hydrogeologic settings were undertaken to improve understanding of source and transport controls on nitrate movement to public supply wells (PSW) in principal aquifers of the United States. Chemical, isotopic, and age tracer data show that agricultural fertilizers and urban septic leachate were the primary sources of large nitrate concentrations in PSW capture zones at Modesto, California (Central Valley aquifer system) and York, Nebraska (High Plains aquifer). Urban septic leachate and fertilizer (possibly nonfarm) were the primary sources of large nitrate concentrations in PSW capture zones at Woodbury, Connecticut (glacial aquifer system), and Tampa, Florida (Floridan aquifer system), respectively. Nitrate fluxes to the water table were larger in agricultural settings than urban settings, indicating that it would be beneficial to reduce PSW capture zone areas in agricultural regions. Mixing calculations indicate that about 50 to 85% of the nitrate in water from the PSW could be from those modern anthropogenic sources, with the remainder coming from sources in old (>50 years) recharge or sources in young recharge in undisturbed settings such as forests. Excess N2 concentrations and age tracers showed that denitrification at Modesto occurred gradually (first‐order rate constant of 0.02/a) in a thick reaction zone following a ∼30‐year lag time after recharge. Denitrification generally was not an important nitrate sink at Woodbury. At York and Tampa, denitrification occurred rapidly (0.5 to 6/a) in thin reaction zones in fine‐grained sediments that separated the anoxic PSW producing zones from overlying oxic, high‐nitrate ground water. Particle tracking showed that a major pathway by which anthropogenic nitrate reached the York and Tampa PSW was by movement through long well screens crossing multiple hydrogeologic units (York) and by movement through karst features (Tampa), processes which reduced ground water residence times in the denitrifying zones. These results illustrate how PSW vulnerability to nitrate contamination depends on complex variations and interactions between contaminant sources, reaction rates, transit times, mixing, and perturbation of ground water flow in contrasting hydrogeologic settings.

Source and transport controls on the movement of nitrate to public supply wells in selected principal aquifers of the United States

NASA Astrophysics Data System (ADS)

McMahon, P. B.; BöHlke, J. K.; Kauffman, L. J.; Kipp, K. L.; Landon, M. K.; Crandall, C. A.; Burow, K. R.; Brown, C. J.

2008-04-01

In 2003-2005, systematic studies in four contrasting hydrogeologic settings were undertaken to improve understanding of source and transport controls on nitrate movement to public supply wells (PSW) in principal aquifers of the United States. Chemical, isotopic, and age tracer data show that agricultural fertilizers and urban septic leachate were the primary sources of large nitrate concentrations in PSW capture zones at Modesto, California (Central Valley aquifer system) and York, Nebraska (High Plains aquifer). Urban septic leachate and fertilizer (possibly nonfarm) were the primary sources of large nitrate concentrations in PSW capture zones at Woodbury, Connecticut (glacial aquifer system), and Tampa, Florida (Floridan aquifer system), respectively. Nitrate fluxes to the water table were larger in agricultural settings than urban settings, indicating that it would be beneficial to reduce PSW capture zone areas in agricultural regions. Mixing calculations indicate that about 50 to 85% of the nitrate in water from the PSW could be from those modern anthropogenic sources, with the remainder coming from sources in old (>50 years) recharge or sources in young recharge in undisturbed settings such as forests. Excess N2 concentrations and age tracers showed that denitrification at Modesto occurred gradually (first-order rate constant of 0.02/a) in a thick reaction zone following a ˜30-year lag time after recharge. Denitrification generally was not an important nitrate sink at Woodbury. At York and Tampa, denitrification occurred rapidly (0.5 to 6/a) in thin reaction zones in fine-grained sediments that separated the anoxic PSW producing zones from overlying oxic, high-nitrate ground water. Particle tracking showed that a major pathway by which anthropogenic nitrate reached the York and Tampa PSW was by movement through long well screens crossing multiple hydrogeologic units (York) and by movement through karst features (Tampa), processes which reduced ground water residence times in the denitrifying zones. These results illustrate how PSW vulnerability to nitrate contamination depends on complex variations and interactions between contaminant sources, reaction rates, transit times, mixing, and perturbation of ground water flow in contrasting hydrogeologic settings.

Stream-subsurface nutrient dynamics in a groundwater-fed stream

NASA Astrophysics Data System (ADS)

Rezanezhad, F.; Niederkorn, A.; Parsons, C. T.; Van Cappellen, P.

2015-12-01

The stream-riparian-aquifer interface plays a major role in the regional flow of nutrients and contaminants due to a strong physical-chemical gradient that promotes the transformation, retention, elimination or release of biogenic elements. To better understand the effect of the near-stream zones on stream biogeochemistry, we conducted a field study on a groundwater-fed stream located in the rare Charitable Research Reserve, Cambridge, Ontario, Canada. This study focused on monitoring the spatial and temporal distributions of nutrient elements within the riparian and hyporheic zones of the stream. Several piezometer nests and a series of passive (diffusion) water samplers, known as peepers, were installed along longitudinal and lateral transects centered on the stream to obtain data on the groundwater chemistry. Groundwater upwelling along the stream resulted in distinctly different groundwater types and associated nitrate concentrations between small distances in the riparian zone (<4m). After the upstream source of the stream surface water, concentrations of nutrients (NO3-, NH4+, SO42- and carbon) did not significantly change before the downstream outlet. Although reduction of nitrate and sulphate were found in the riparian zone of the stream, this did not significantly influence the chemistry of the adjacent stream water. Also, minimal retention in the hyporheic zones limited reduction of reactive compounds (NO3- and SO42-) within the stream channel. The results showed that the dissolved organic carbon (DOC) and residence time of water in the hyporheic zone and in surface water limited denitrification.

Heterogeneous distribution of water in the mantle transition zone beneath United States inferred from seismic observations

NASA Astrophysics Data System (ADS)

Wang, Y.; Pavlis, G. L.; Li, M.

2017-12-01

The amount of water in the Earth's deep mantle is critical for the evolution of the solid Earth and the atmosphere. Mineral physics studies have revealed that Wadsleyite and Ringwoodite in the mantle transition zone could store several times the volume of water in the ocean. However, the water content and its distribution in the transition zone remain enigmatic due to lack of direct observations. Here we use seismic data from the full deployment of the Earthscope Transportable Array to produce 3D image of P to S scattering of the mantle transition zone beneath the United States. We compute the image volume from 141,080 pairs of high quality receiver functions defined by the Earthscope Automated Receiver Survey, reprocessed by the generalized iterative deconvolution method and imaged by the plane wave migration method. We find that the transition zone is filled with previously unrecognized small-scale heterogeneities that produce pervasive, negative polarity P to S conversions. Seismic synthetic modeling using a point source simulation method suggests two possible structures for these objects: 1) a set of randomly distributed blobs of slight difference in size, and 2) near vertical diapir structures from small scale convections. Combining with geodynamic simulations, we interpret the observation as compositional heterogeneity from small-scale, low-velocity bodies that are water enriched. Our results indicate there is a heterogeneous distribution of water through the entire mantle transition zone beneath the contiguous United States.

Comparison of geoelectrical/tectonic models for suture zones in the western U.S.A. and eastern Europe: are black shales a possible source of high conductivities?

USGS Publications Warehouse

Stanley, W.D.

1989-01-01

Large-scale geoelectrical anomalies have been mapped with geomagnetic depth sounding (GDS) and magnetotelluric (MT) surveys in the Carpathian Mountains region. These anomalies are associated with the zone of closure between stable Europe and a complex of microplates in front of the converging African plate. The zone of closure, or suture zone, is largely occupied by an extensive deformed flysch belt. The models derived to fit the observed geoelectrical data are useful in the study of other suture zones, and Carpathian structures have been compared with areas currently being studied in the western Cordillera of the U.S.A. Models derived for a smaller-scale suture zone mapped in western Washington State have features that are similar to the Carpathian models. The geoelectrical models for both the Carpathian and Washington anomalies require dipping conductive slabs of 1-5 ?? m material that extends to depths > 20 km. In both instances there is evidence that these materials may merge with lower crustal-mantle conductors along the down-dip margins of the slab. The main conductive units are interpreted to be sedimentary rocks that have been partially subducted due to collisional processes. Heat flow is low in both regions and it is difficult to explain fully the deep conduction mechanisms; however, evidence suggests that the conduction at depth may include electronic conduction in sulfide mineral or carbon films as well as ionic conduction in fluids or partial melt. ?? 1989.

Nitrate in groundwater and water sources used by riparian trees in an agricultural watershed: A chemical and isotopic investigation in southern Minnesota

USGS Publications Warehouse

Komor, Stephen C.; Magner, Joseph A.

1996-01-01

This study evaluates processes that affect nitrate concentrations in groundwater beneath riparian zones in an agricultural watershed. Nitrate pathways in the upper 2 m of groundwater were investigated beneath wooded and grass-shrub riparian zones next to cultivated fields. Because trees can be important components of the overall nitrate pathway in wooded riparian zones, water sources used by riparian trees and possible effects of trees on nitrate concentrations in groundwater were also investigated. Average nitrate concentrations in shallow groundwater beneath the cultivated fields were 5.5 mg/L upgradient of the wooded riparian zone and 3.5 mg/L upgradient of the grass-shrub zone. Shallow groundwater beneath the fields passed through the riparian zones and discharged into streams that had average nitrate concentrations of 8.5 mg/L (as N). Lateral variations of δD values in groundwater showed that mixing among different water sources occurred beneath the riparian zones. In the wooded riparian zone, nitrate concentrations in shallow groundwater were diluted by upwelling, nitrate-poor, deep groundwater. Upwelling deep groundwater contained ammonium with a δ15N of 5‰ that upon nitrification and mixing with nitrate in shallow groundwater caused nitrate δ15N values in shallow groundwater to decrease by as much as 19.5‰. Stream water penetrated laterally beneath the wooded riparian zone as far as 19 m from the stream's edge and beneath the grass-shrub zone as far as 27 m from the stream's edge. Nitrate concentrations in shallow groundwater immediately upgradient of where it mixed with stream water averaged 0.4 mg/L in the wooded riparian zone and 0.8 mg/L near the grass-shrub riparian zone. Nitrate concentrations increased toward the streams because of mixing with nitrate-rich stream water. Because nitrate concentrations were larger in stream water than shallow groundwater, concentrated nitrate in the streams cannot have come from shallow groundwater at these sites. Water sources of riparian trees were identified by comparing δD values of sap water, soil water, groundwater, and stream water. Soil water was the main water source for trees in the outer 4 to 6 m of one part of the wooded riparian zone and outer 10 m of another part. Groundwater was a significant water source for trees closer to the streams where the water table was less than about 2.1 to 2.7 m below the surface. No evidence was found in the nitrate concentration profiles that trees close to the streams that took up groundwater through their roots also took up nitrate from groundwater. The lack of such evidence is attributed to the nitrate concentration profiles being insufficiently sensitive indicators of nitrate removal by trees.

Rupture Process During the Mw 8.1 2017 Chiapas Mexico Earthquake: Shallow Intraplate Normal Faulting by Slab Bending

NASA Astrophysics Data System (ADS)

Okuwaki, R.; Yagi, Y.

2017-12-01

A seismic source model for the Mw 8.1 2017 Chiapas, Mexico, earthquake was constructed by kinematic waveform inversion using globally observed teleseismic waveforms, suggesting that the earthquake was a normal-faulting event on a steeply dipping plane, with the major slip concentrated around a relatively shallow depth of 28 km. The modeled rupture evolution showed unilateral, downdip propagation northwestward from the hypocenter, and the downdip width of the main rupture was restricted to less than 30 km below the slab interface, suggesting that the downdip extensional stresses due to the slab bending were the primary cause of the earthquake. The rupture front abruptly decelerated at the northwestern end of the main rupture where it intersected the subducting Tehuantepec Fracture Zone, suggesting that the fracture zone may have inhibited further rupture propagation.

A proposed origin of the Olympus Mons escarpment. [Martian volcanic feature

NASA Technical Reports Server (NTRS)

King, J. S.; Riehle, J. R.

1974-01-01

Olympus Mons (Nix Olympica) on Mars is delimited by a unique steep, nearly circular scarp. A pyroclastic model is proposed for the construct's origin. It is postulated that the Olympus Mons plateau is constructed predominantly of numerous ash-flow tuffs which were erupted from central sources over an extended period of time. Lava flows may be intercalated with the tuffs. A schematic radial profile incorporating the inferred compaction zones for an ash sheet is proposed. Following emplacement, eolian (and possibly fluvial) erosion and abrasion during dust storms would act on the ash sheets. Interior portions of the sheets would spall and slump following eolian erosion, generating steep, relatively smooth boundary scarps. The scarp would be circular due to symmetrical distribution of compaction zones. The model implies further that the Olympus Mons plateau rests on a more resistant rock substrate.

The use of a geographic information system to identify a dairy goat farm as the most likely source of an urban Q-fever outbreak.

PubMed

Schimmer, Barbara; Ter Schegget, Ronald; Wegdam, Marjolijn; Züchner, Lothar; de Bruin, Arnout; Schneeberger, Peter M; Veenstra, Thijs; Vellema, Piet; van der Hoek, Wim

2010-03-16

A Q-fever outbreak occurred in an urban area in the south of the Netherlands in May 2008. The distribution and timing of cases suggested a common source. We studied the spatial relationship between the residence locations of human cases and nearby small ruminant farms, of which one dairy goat farm had experienced abortions due to Q-fever since mid April 2008. A generic geographic information system (GIS) was used to develop a method for source detection in the still evolving major epidemic of Q-fever in the Netherlands. All notified Q-fever cases in the area were interviewed. Postal codes of cases and of small ruminant farms (size >40 animals) located within 5 kilometres of the cluster area were geo-referenced as point locations in a GIS-model. For each farm, attack rates and relative risks were calculated for 5 concentric zones adding 1 kilometre at a time, using the 5-10 kilometres zone as reference. These data were linked to the results of veterinary investigations. Persons living within 2 kilometres of an affected dairy goat farm (>400 animals) had a much higher risk for Q-fever than those living more than 5 kilometres away (Relative risk 31.1 [95% CI 16.4-59.1]). The study supported the hypothesis that a single dairy goat farm was the source of the human outbreak. GIS-based attack rate analysis is a promising tool for source detection in outbreaks of human Q-fever.

Vapor Intrusion Estimation Tool for Unsaturated Zone Contaminant Sources. User’s Guide

DTIC Science & Technology

2016-08-30

324449 Page Intentionally Left Blank iii Executive Summary Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants...strength and location, vadose zone transport, and a model for estimating movement of soil -gas vapor contamination into buildings. The tool may be...framework for estimating the impact of a vadose zone contaminant source on soil gas concentrations and vapor intrusion into a building

Application of multiple tracers (SF6 and chloride) to identify the transport by characteristics of contaminant at two separate contaminated sites

NASA Astrophysics Data System (ADS)

Lee, K. K.; Lee, S. S.; Kim, H. H.; Koh, E. H.; Kim, M. O.; Lee, K.; Kim, H. J.

2016-12-01

Multiple tracers were applied for source and pathway detection at two different sites. CO2 gas injected in the subsurface for a shallow-depth CO2 injection and leak test can be regarded as a potential contaminant source. Therefore, it is necessary to identify the migration pattern of CO2 gas. Also, at a DNAPL contaminated site, it is important to figure out the characteristics of plume evolution from the source zone. In this study, multiple tracers (SF6 and chloride) were used to evaluate the applicability of volatile and non-volatile tracers and to identify the characteristics of contaminant transport at each CO2 injection and leak test site and DNAPL contaminated site. Firstly, at the CO2 test site, multiple tracers were used to perform the single well push-drift-pull tracer test at total 3 specific depth zones. As results of tests, volatile and non-volatile tracers showed different mass recovery percentage. Most of chloride mass was recovered but less than half of SF6 mass was recovered due to volatile property. This means that only gaseous SF6 leak out to unsaturated zone. However, breakthrough curves of both tracers indicated similar peak time, effective porosity, and regional groundwater velocity. Also, at both contaminated sites, natural gradient tracer tests were performed with multiple tracers. With the results of natural gradient tracer test, it was possible to confirm the applicability of multiple tracers and to understand the contaminant transport in highly heterogeneous aquifer systems through the long-term monitoring of tracers. Acknowledgement: financial support was provided by the R&D Project on Environmental Management of Geologic CO2 Storage)" from the KEITI (Project Number: 2014001810003) and Korea Ministry of Environment as "The GAIA project (2014000540010)".

Reactive transport modeling of geochemical controls on secondary water quality impacts at a crude oil spill site near Bemidji, MN

USGS Publications Warehouse

Ng, Gene-Hua Crystal.; Bekins, Barbara A.; Cozzarelli, Isabelle M.; Baedecker, Mary Jo; Bennett, Philip C.; Amos, Richard T.; Herkelrath, William N.

2015-01-01

Anaerobic biodegradation of organic amendments and contaminants in aquifers can trigger secondary water quality impacts that impair groundwater resources. Reactive transport models help elucidate how diverse geochemical reactions control the spatiotemporal evolution of these impacts. Using extensive monitoring data from a crude oil spill site near Bemidji, Minnesota (USA), we implemented a comprehensive model that simulates secondary plumes of depleted dissolved O2 and elevated concentrations of Mn2+, Fe2+, CH4, and Ca2+ over a two-dimensional cross section for 30 years following the spill. The model produces observed changes by representing multiple oil constituents and coupled carbonate and hydroxide chemistry. The model includes reactions with carbonates and Fe and Mn mineral phases, outgassing of CH4 and CO2 gas phases, and sorption of Fe, Mn, and H+. Model results demonstrate that most of the carbon loss from the oil (70%) occurs through direct outgassing from the oil source zone, greatly limiting the amount of CH4 cycled down-gradient. The vast majority of reduced Fe is strongly attenuated on sediments, with most (91%) in the sorbed form in the model. Ferrous carbonates constitute a small fraction of the reduced Fe in simulations, but may be important for furthering the reduction of ferric oxides. The combined effect of concomitant redox reactions, sorption, and dissolved CO2 inputs from source-zone degradation successfully reproduced observed pH. The model demonstrates that secondary water quality impacts may depend strongly on organic carbon properties, and impacts may decrease due to sorption and direct outgassing from the source zone.

Sources and pathways of artificial radionuclides to soils at a High Arctic site.

PubMed

Lokas, E; Bartmiński, P; Wachniew, P; Mietelski, J W; Kawiak, T; Srodoń, J

2014-11-01

Activity concentrations, inventories and activity ratios of (137)Cs, (238)Pu, (239 + 240)Pu and (241)Am in soil profiles were surveyed in the dry tundra and the adjoining proglacial zones of glaciers at a High Arctic site on Svalbard. Vertical profiles of radionuclide activities were determined in up to 14-cm-thick soil sequences. Additionally, soil properties (pH, organic matter, texture, mineral composition and sorption capacity) were analyzed. Results obtained in this study revealed a large range of activity concentrations and inventories of the fallout radionuclides from the undetectable to the uncommonly high levels (inventories of 30,900 ± 940, 47 ± 6, 886 ± 80 and 296 ± 19 Bq/m(2) for (137)Cs, (238)Pu, (239 + 240)Pu and (241)Am, respectively) found in two profiles from the proglacial zone. Concentration of these initially airborne radionuclides in the proglacial zone soils is related to their accumulation in cryoconites that have a large ability to concentrate trace metals. The cryoconites develop on the surface of glaciers, and the material they accumulate is deposited on land surface after the glaciers retreat. The radionuclide inventories in the tundra soils, which effectively retain radionuclides due to high organic matter contents, were comparable to the global fallout deposition for this region of the world. The (238)Pu/(239 + 240)Pu activity ratios for tundra soils suggested global fallout as the dominant source of Pu. The (238)Pu/(239 + 240)Pu and (239 + 240)Pu/(137)Cs activity ratios in the proglacial soils pointed to possible contributions of these radionuclides from other, unidentified sources.

The Seismotectonic Model of Southern Africa

NASA Astrophysics Data System (ADS)

Midzi, Vunganai; Mulabisana, Thifelimbulu; Manzunzu, Brassnavy

2013-04-01

Presented in this report is a summary of the major structures and seismotectonic zones in Southern Africa (Botswana, Lesotho, Namibia, South Africa and Swaziland), which includes available information on fault plane solutions and stress data. Reports published by several experts contributed much to the prepared zones. The work was prepared as part of the requirements for the SIDA/IGCP Project 601 titled "Seismotectonics and Seismic Hazards in Africa" as well as part of the seismic source characterisation of the GEM-Africa Seismic hazard study. The seismic data used are part of the earthquake catalogue being prepared for the GEM-Africa project, which includes historical and instrumental records as collected from various agencies. Seventeen seismic zones/sources were identified and demarcated using all the available information. Two of the identiied sources are faults with reliable evidence of their activity. Though more faults have been identified in unpublished material as being active, more work is being carried out to obtain information that can be used to characterise them before they are included in the seismotectonic model. Explanations for the selected boundaries of the zones are also given in the report. It should be noted that this information is the first draft of the seismic source zones of the region. Futher interpreation of the data is envisaged which might result in more than one version of the zones.

Phytoplankton bloom dynamics in temperate, turbid, stressed estuaries: a model study

NASA Astrophysics Data System (ADS)

de Swart, Huib E.; Liu, Bo; de Jonge, Victor

2017-04-01

To gain insight into mechanisms underlying phytoplankton bloom dynamics in temperature, turbid estuaries, experiments were conducted with an idealised model that couples physical and biological processes. Results show that the model is capable of producing the main features of the observed blooms in the Ems estuary (Northwest Germany), viz. in the lower reach a spring bloom occur, which is followed by a secondary bloom in autumn. The along-estuary distribution of suspended sediment concentration (SSC) and the along-estuary distance between the nutrient source and the seaward bound of the turbidity zone control both the along-estuary locations and intensities of the blooms. Results of further sensitivity studies reveal that in a shallow, well-mixed estuary, under temporally-constant suspended sediment conditions, the seasonally-varying water temperature has larger impact on the timing of spring blooms than the seasonally-varying incident light intensity. The occurrence of the secondary bloom is caused by the fact that the growth rate of phytoplankton attains a maximum at an optimum water temperature. Bloom intensities are also modulated by the advective processes related to subtidal current because the latter regulates the seaward transport of nutrient from riverine source. Large-scale deepening of navigation channels leads to later spring blooms due to increased mixing depth. Finally, phytoplankton blooms are unlikely to occur in the upper reach due to the elevated SSC and the landward expansion of turbidity zone related to large-scale deepening.

Geologic evolution of the Kastel trough and its implications on the Adiyaman oil fields, SE Turkey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coskun, Bu.

1990-05-01

Oil field developments of the Adiyaman area one of the main oil producing zones in southeast Turkey, have been highly influenced by geologic evolution of the Kastel trough which is situated in front of the suture zone between the Arabian and Anatolian plates. The Upper Cretaceous movements created many paleostructural trends in the Kastel trough where important dolomitic and porous reservoirs exist. The most important tectonic event, which appeared during the Upper Cretaceous movements, is the accumulation of the Kocali-Karadut ophiolitic complex, advancing from the north to the south in the Kastel trough, where heavy materials caused formation of amore » structural model favoring generation and migration and entrapment of oil in the reservoir rocks. Due to the presence of the Kocali-Karadut complex in the Kastel trough the following zones have been distinguished. (1) North Uplift Area. Situated under the allochthonous units, many thrust and reverse faults characterize this zone. The presence of paleohighs, where primary dolomites develop, allows the appearance of some oil fields in the region. This is the main future exploration zone in southeast Turkey. (2) Accumulation Area. Advancing from the north to the south, the allochthonous Kocali-Karadut complex filled the Kastel trough creating a deep graben whose flanks present generally normal faults. (3) Structural Belt. Important paleohighs constitute an exploration trend in this zone where dolomitic and porous carbonates contain actual oil fields. (4) South Accumulation Area. Distant from the Arabian-Anatolian suture zone, regional tectonics and sedimentology show this zone remained deeply buried during geologic time; good source rocks were deposited during the Cretaceous. (5) South Uplift Area. This area corresponds to the northern flank of the huge regional Mardin high in southeast Turkey where new oil fields have been discovered.« less

Bubble-facilitated VOC transport: Laboratory experiments and numerical modelling

NASA Astrophysics Data System (ADS)

Mumford, K. G.; Soucy, N. C.

2017-12-01

Most conceptual and numerical models of vapor intrusion assume that the transport of volatile organic compounds (VOCs) from the source to near the building foundation is a diffusion-limited processes. However, the transport of VOCs by mobilized gas bubbles through the saturated zone could lead to increased rates of transport and advection through the unsaturated zone, thereby increasing mass flux and risks associated with vapor intrusion. This mobilized gas could be biogenic (methanogenic) but could also result from the partitioning of VOC to trapped atmospheric gases in light non-aqueous phase liquid (LNAPL) smear zones. The potential for bubble-facilitated VOC transport to increase mass flux was investigated in a series of 1D and 2D laboratory experiments. Pentane source zones were emplaced in sand using sequential drainage and imbibition steps to mimic a water table fluctuation and trap air alongside LNAPL residual. This source was placed below an uncontaminated, water saturated sand (occlusion zone) and a gravel-sized (glass beads) unsaturated zone. Water was pumped laterally through the source zone and occlusion zone to deliver the dissolved gases (air) that are required for the expansion of trapped gas bubbles. Images from 2D flow cell experiments were used to demonstrate fluid rearrangement in the source zone and gas expansion to the occlusion zone, and 1D column experiments were used to measure gas-phase pentane mass flux. This flux was found to be 1-2 orders of magnitude greater than that measured in diffusion-dominated control columns, and showed intermittent behavior consistent with bubble transport by repeated expansion, mobilization, coalescence and trapping. Numerical simulation results under a variety of conditions using an approach that couples macroscopic invasion percolation with mass transfer (MIP-MT) between the aqueous and gas phases will also be presented. The results of this study demonstrate the potential for bubble-facilitated transport to increase transport rates linked to vapor intrusion, and will serve as a basis for further development of conceptual and numerical models to investigate the conditions under which this mechanism may play an important role.

CO2-efflux measurements for evaluating source zone natural attenuation rates in a petroleum hydrocarbon contaminated aquifer.

PubMed

Sihota, Natasha J; Singurindy, Olga; Mayer, K Ulrich

2011-01-15

In order to gain regulatory approval for source zone natural attenuation (SZNA) at hydrocarbon-contaminated sites, knowledge regarding the extent of the contamination, its tendency to spread, and its longevity is required. However, reliable quantification of biodegradation rates, an important component of SZNA, remains a challenge. If the rate of CO(2) gas generation associated with contaminant degradation can be determined, it may be used as a proxy for the overall rate of subsurface biodegradation. Here, the CO(2)-efflux at the ground surface is measured using a dynamic closed chamber (DCC) method to evaluate whether this technique can be used to assess the areal extent of the contaminant source zone and the depth-integrated rate of contaminant mineralization. To this end, a field test was conducted at the Bemidji, MN, crude oil spill site. Results indicate that at the Bemidji site the CO(2)-efflux method is able to both delineate the source zone and distinguish between the rates of natural soil respiration and contaminant mineralization. The average CO(2)-efflux associated with contaminant degradation in the source zone is estimated at 2.6 μmol m(-2) s(-1), corresponding to a total petroleum hydrocarbon mineralization rate (expressed as C(10)H(22)) of 3.3 g m(-2) day(-1).

Performance and Economic Modeling of Horizontally Drilled Ground-Source Heat Pumps in Select California Climates

NASA Astrophysics Data System (ADS)

Wiryadinata, Steven

Service life modeling was performed to gage the viability of unitary 3.5 kWt, ground-source terminal heat pumps (GTHP) employing horizontal directionally drilled geothermal heat exchangers (GHX) over air-source terminal heat pumps (PTHP) in hotels and motels and residential apartment building sectors in California's coastal and inland climates. Results suggest the GTHP can reduce hourly peak demand for the utility by 7%-25% compared to PTHP, depending on the climate and building type. The annual energy savings, which range from -1% to 5%, are highly dependent on the GTHP pump energy use relative to the energy savings attributed to the difference in ground and air temperatures (DeltaT). In mild climates with small ?T, the pump energy use may overcome any advantage to utilizing a GHX. The majority of total levelized cost savings - ranging from 0.18/ft2 to 0.3/ft 2 - are due to reduced maintenance and lifetime capital cost normally associated with geothermal heat pump systems. Without these reductions (not validated for the GTHP system studied), the GTHP technology does not appear to offer significant advantages over PTHP in the climate zones studied here. The GTHP levelized cost was most sensitive to variations in installed cost and in some cases, energy use (influenced by climate zone choice), which together highlights the importance of climate selection for installation, and the need for larger market penetration of ground-source systems in order to bring down installed costs as the technology matures.

Macroscopic Source Properties from Dynamic Rupture Styles in Plastic Media

NASA Astrophysics Data System (ADS)

Gabriel, A.; Ampuero, J. P.; Dalguer, L. A.; Mai, P. M.

2011-12-01

High stress concentrations at earthquake rupture fronts may generate an inelastic off-fault response at the rupture tip, leading to increased energy absorption in the damage zone. Furthermore, the induced asymmetric plastic strain field in in-plane rupture modes may produce bimaterial interfaces that can increase radiation efficiency and reduce frictional dissipation. Off-fault inelasticity thus plays an important role for realistic predictions of near-fault ground motion. Guided by our previous studies in the 2D elastic case, we perform rupture dynamics simulations including rate-and-state friction and off-fault plasticity to investigate the effects on the rupture properties. We quantitatively analyze macroscopic source properties for different rupture styles, ranging from cracks to pulses and subshear to supershear ruptures, and their transitional mechanisms. The energy dissipation due to off-fault inelasticity modifies the conditions to obtain each rupture style and alters macroscopic source properties. We examine apparent fracture energy, rupture and healing front speed, peak slip and peak slip velocity, dynamic stress drop and size of the process and plastic zones, slip and plastic seismic moment, and their connection to ground motion. This presentation focuses on the effects of rupture style and off-fault plasticity on the resulting ground motion patterns, especially on characteristic slip velocity function signatures and resulting seismic moments. We aim at developing scaling rules for equivalent elastic models, as function of background stress and frictional parameters, that may lead to improved "pseudo-dynamic" source parameterizations for ground-motion calculation. Moreover, our simulations provide quantitative relations between off-fault energy dissipation and macroscopic source properties. These relations might provide a self-consistent theoretical framework for the study of the earthquake energy balance based on observable earthquake source parameters.

How much does geometry of seismic sources matter in tsunami modeling? A sensitivity analysis for the Calabrian subduction interface

NASA Astrophysics Data System (ADS)

Tonini, R.; Maesano, F. E.; Tiberti, M. M.; Romano, F.; Scala, A.; Lorito, S.; Volpe, M.; Basili, R.

2017-12-01

The geometry of seismogenic sources could be one of the most important factors concurring to control the generation and the propagation of earthquake-generated tsunamis and their effects on the coasts. Since the majority of potentially tsunamigenic earthquakes occur offshore, the corresponding faults are generally poorly constrained and, consequently, their geometry is often oversimplified as a planar fault. The rupture area of mega-thrust earthquakes in subduction zones, where most of the greatest tsunamis have occurred, extends for tens to hundreds of kilometers both down dip and along strike, and generally deviates from the planar geometry. Therefore, the larger the earthquake size is, the weaker the planar fault assumption become. In this work, we present a sensitivity analysis aimed to explore the effects on modeled tsunamis generated by seismic sources with different degrees of geometric complexities. We focused on the Calabrian subduction zone, located in the Mediterranean Sea, which is characterized by the convergence between the African and European plates, with rates of up to 5 mm/yr. This subduction zone has been considered to have generated some past large earthquakes and tsunamis, despite it shows only in-slab significant seismic activity below 40 km depth and no relevant seismicity in the shallower portion of the interface. Our analysis is performed by defining and modeling an exhaustive set of tsunami scenarios located in the Calabrian subduction and using different models of the subduction interface with increasing geometrical complexity, from a planar surface to a highly detailed 3D surface. The latter was obtained from the interpretation of a dense network of seismic reflection profiles coupled with the analysis of the seismicity distribution. The more relevant effects due to the inclusion of 3D complexities in the seismic source geometry are finally highlighted in terms of the resulting tsunami impact.

Characterization of NAPL source zone architecture and dissolution kinetics in heterogeneous porous media using magnetic resonance imaging.

PubMed

Zhang, Changyong; Werth, Charles J; Webb, Andrew G

2007-05-15

A direct visualization method using magnetic resonance imaging (MRI) was developed to characterize sand grain size distribution, nonaqueous phase liquid (NAPL) source zone architecture, and aqueous flowpaths in a three-dimensional (3-D) flowcell (26.5 cm x 10.5 cm x 10.5 cm) packed with a heterogeneous distribution of five different sand fractions. All images were acquired at a resolution of 0.1875 cm x 0.1875 cm x 0.225 cm. A 1H image of pore water resolved the heterogeneous permeability field; grain size differences as small as 0.1 mm could be distinguished. A time series of 1H images of water doped with the paramagnetic tracer MnCl2 were acquired and used to obtain voxel-scale breakthrough curves. Water preferentially flowed through coarse sands before NAPL release. After NAPL release, the flow bypassed NAPLzones, and bypassing was more evident for high NAPL saturation zones. A time series of 19F images of NAPL were acquired and used to determine voxel-scale NAPL saturation (Sn) during dissolution. Results show that 93% of NAPL mass was in the coarsest sand, most NAPL was trapped as pools and not as residual ganglia, NAPL saturation increased with depth, and the NAPL dissolution front moved vertically from the top to the bottom of the flowcell during the first 170 pore volumes of waterflushed. NAPL component effluent concentrations initially increased due to the development of flow in zones with decreasing NAPL saturation. Flowpath images suggest that this occurs as NAPL transitions from pools (Sn > 0.15) to residual ganglia. The results highlight the importance of flow bypassing and provide the opportunity to develop more accurate NAPL dissolution models.

Joint geophysical investigation of a small scale magnetic anomaly near Gotha, Germany

NASA Astrophysics Data System (ADS)

Queitsch, Matthias; Schiffler, Markus; Goepel, Andreas; Stolz, Ronny; Guenther, Thomas; Malz, Alexander; Meyer, Matthias; Meyer, Hans-Georg; Kukowski, Nina

2014-05-01

In the framework of the multidisciplinary project INFLUINS (INtegrated FLUid Dynamics IN Sedimentary Basins) several airborne surveys using a full tensor magnetic gradiometer (FTMG) system were conducted in and around the Thuringian basin (central Germany). These sensors are based on highly sensitive superconducting quantum interference devices (SQUIDs) with a planar-type gradiometer setup. One of the main goals was to map magnetic anomalies along major fault zones in this sedimentary basin. In most survey areas low signal amplitudes were observed caused by very low magnetization of subsurface rocks. Due to the high lateral resolution of a magnetic gradiometer system and a flight line spacing of only 50m, however, we were able to detect even small magnetic lineaments. Especially close to Gotha a NW-SE striking strong magnetic anomaly with a length of 1.5 km was detected, which cannot be explained by the structure of the Eichenberg-Gotha-Saalfeld (EGS) fault zone and the rock-physical properties (low susceptibilities). Therefore, we hypothesize that the source of the anomaly must be related to an anomalous magnetization in the fault plane. To test this hypothesis, here we focus on the results of the 3D inversion of the airborne magnetic data set and compare them with existing structural geological models. In addition, we conducted several ground based measurements such as electrical resistivity tomography (ERT) and frequency domain electromagnetics (FDEM) to locate the fault. Especially, the geoelectrical measurements were able to image the fault zone. The result of the 2D electrical resistivity tomography shows a lower resistivity in the fault zone. Joint interpretation of airborne magnetics, geoelectrical and geological information let us propose that the source of the magnetization may be a fluid-flow induced impregnation with iron-oxide bearing minerals in the vicinity of the EGS fault plane.

Basin-centered asperities in great subduction zone earthquakes: A link between slip, subsidence, and subduction erosion?

USGS Publications Warehouse

Wells, R.E.; Blakely, R.J.; Sugiyama, Y.; Scholl, D. W.; Dinterman, P.A.

2003-01-01

Published areas of high coseismic slip, or asperities, for 29 of the largest Circum-Pacific megathrust earthquakes are compared to forearc structure revealed by satellite free-air gravity, bathymetry, and seismic profiling. On average, 71% of an earthquake's seismic moment and 79% of its asperity area occur beneath the prominent gravity low outlining the deep-sea terrace; 57% of an earthquake's asperity area, on average, occurs beneath the forearc basins that lie within the deep-sea terrace. In SW Japan, slip in the 1923, 1944, 1946, and 1968 earthquakes was largely centered beneath five forearc basins whose landward edge overlies the 350??C isotherm on the plate boundary, the inferred downdip limit of the locked zone. Basin-centered coseismic slip also occurred along the Aleutian, Mexico, Peru, and Chile subduction zones but was ambiguous for the great 1964 Alaska earthquake. Beneath intrabasin structural highs, seismic slip tends to be lower, possibly due to higher temperatures and fluid pressures. Kilometers of late Cenozoic subsidence and crustal thinning above some of the source zones are indicated by seismic profiling and drilling and are thought to be caused by basal subduction erosion. The deep-sea terraces and basins may evolve not just by growth of the outer arc high but also by interseismic subsidence not recovered during earthquakes. Basin-centered asperities could indicate a link between subsidence, subduction erosion, and seismogenesis. Whatever the cause, forearc basins may be useful indicators of long-term seismic moment release. The source zone for Cascadia's 1700 A.D. earthquake contains five large, basin-centered gravity lows that may indicate potential asperities at depth. The gravity gradient marking the inferred downdip limit to large coseismic slip lies offshore, except in northwestern Washington, where the low extends landward beneath the coast. Transverse gravity highs between the basins suggest that the margin is seismically segmented and could produce a variety of large earthquakes. Published in 2003 by the American Geophysical Union.

A possible source of water in seismogenic subduction zones

NASA Astrophysics Data System (ADS)

Kameda, J.; Yamaguchi, A.; Kimura, G.; Iodp Exp. 322 Scientists

2010-12-01

Recent works on the subduction megathrusts have emphasized the mechanical function of fluids contributing dynamic slip-weakening. Basalt-hosting fault zones in on-land accretionary complexes present several textures of seismic slip under fluid-assisted condition such as implosion breccia with carbonate matrix and decrepitation of fluid inclusion. In order to clarify initiation and evolution processes of such fault zones as well as possible source of fluid in the seismogenic subduction zone, we examined a mineralogical/geochemical feature of basaltic basement recovered by IODP Exp. 322 at C0012, that is a reference site for subduction input in the Nankai Trough. A total of 10 samples (about 4 m depth interval from the basement top) were analyzed in this study. XRD analyses indicate that all of the samples contain considerable amount of smectite. The smectite does not appear as a form of interstratified phase with illite or chlorite. Preliminary chemical analyses by EDS in TEM suggest that the smectite is trioctahedral saponite with Ca as a dominant interlayer cation. To determine the saponite content quantitatively, cation exchange capacity (CEC) of bulk samples was measured. The samples show almost similar CEC of around 30 meq/100g, implying that bulk rock contains about 30 wt% of saponite, considering a general CEC of 100 meq/100g for monomineralic saponite. Such abundance of saponite might be a result from intense alteration of oceanic crust due to sea water circulation at low temperature. Previous experimental work suggests that saponite might be highly hydrated (two to three water layer hydration form) at the seismogenic P-T condition. Hence, altered upper oceanic crust is a possible water sink in the seismogenic zone. The water stored in the smectite interlayer region will be expelled via smectite to chlorite transition reaction, that might contribute to the dynamic weakening of the seimogenic plate boundary between the basement basalt and overlying accretionary prism.

Numerical simulations of the impact of seasonal heat storage on source zone emission in a TCE contaminated aquifer

NASA Astrophysics Data System (ADS)

Popp, Steffi; Beyer, Christof; Dahmke, Andreas; Bauer, Sebastian

2016-04-01

In urban regions, with high population densities and heat demand, seasonal high temperature heat storage in the shallow subsurface represents an attractive and efficient option for a sustainable heat supply. In fact, the major fraction of energy consumed in German households is used for room heating and hot water production. Especially in urbanized areas, however, the installation of high temperature heat storage systems is currently restricted due to concerns on negative influences on groundwater quality caused e.g. by possible interactions between heat storages and subsurface contaminants, which are a common problem in the urban subsurface. Detailed studies on the overall impact of the operation of high temperature heat storages on groundwater quality are scarce. Therefore, this work investigates possible interactions between groundwater temperature changes induced by heat storage via borehole heat exchangers and subsurface contaminations by numerical scenario analysis. For the simulation of non-isothermal groundwater flow, and reactive transport processes the OpenGeoSys code is used. A 2D horizontal cross section of a shallow groundwater aquifer is assumed in the simulated scenario, consisting of a sandy sediment typical for Northern Germany. Within the aquifer a residual trichloroethene (TCE) contaminant source zone is present. Temperature changes are induced by a seasonal heat storage placed within the aquifer with scenarios of maximum temperatures of 20°C, 40°C and 60°C, respectively, during heat injection and minimum temperatures of 2°C during heat extraction. In the scenario analysis also the location of the heat storage relative to the TCE source zone and plume was modified. Simulations were performed in a homogeneous aquifer as well as in a set of heterogeneous aquifers with hydraulic conductivity as spatially correlated random fields. In both cases, results show that the temperature increase in the heat plume and the consequential reduction of water viscosity lead to locally increased groundwater flow. Depending on the positioning of the heat storage relative to the TCE contamination, groundwater fluxes hence may be induced to increase within or partially bypass the TCE source zone. At the same time, TCE solubility decreases between 10 and 40 °C, which reduces TCE emission and almost compensates for the effects of a temperature induced increase of groundwater flow through the source zone. In total, the numerical simulations thus show only minor influences of the heat plume on the TCE emission compared to a thermally undisturbed aquifer. Acknowledgments: This work is part of the ANGUS+ project (www.angusplus.de) and funded by the German Federal Ministry of Education and Research (BMBF) as part of the energy storage initiative "Energiespeicher".

Plume persistence caused by back diffusion from thin clay layers in a sand aquifer following TCE source-zone hydraulic isolation.

PubMed

Parker, Beth L; Chapman, Steven W; Guilbeault, Martin A

2008-11-14

This paper concludes that back diffusion from one or a few thin clayey beds in a sand aquifer can cause contaminant persistence above MCLs in a sand aquifer long after the source zone initially causing the plume is isolated or removed. This conclusion is based on an intensive case study of a TCE contaminated site in Florida, with the processes evaluated using numerical modeling. At this site, the TCE DNAPL zone formed decades ago, and was hydraulically isolated by means of an innovative system performing groundwater extraction, treatment and re-injection. Treated water is re-injected in a row of injection wells situated a short distance downgradient of the extraction wells, creating a clean-water displacement front to efficiently flush the downgradient plume. This scheme avoids the creation of stagnation zones typical of most groundwater pump-and-treat systems, thereby minimizing the time for aquifer flushing and therefore downgradient cleanup. The system began operation in August 2002 and although the performance monitoring shows substantial declines in concentrations, detectable levels of TCE and degradation products persist downgradient of the re-injection wells, long after the TCE should have disappeared based on calculations assuming a nearly homogenous sand aquifer. Three hypotheses were assessed for this plume persistence: 1) incomplete source-zone capture, 2) DNAPL occurrence downgradient of the re-injection wells, and 3) back diffusion from one or more thin clay beds in the aquifer. After careful consideration, the first two hypotheses were eliminated, leaving back diffusion as the only plausible hypothesis, supported by detailed measurements of VOC concentrations within and near the clay beds and also by numerical model simulations that closely represent the field site hydrogeologic conditions. The model was also used to simulate a more generalized, hypothetical situation where more thin clayey beds occur in a sand aquifer with an underlying aquitard. While there is no doubt that DNAPL source mass reduction can eventually improve downgradient groundwater quality, the magnitude and time scale over which the improvement occurs is the major uncertainty given current characterization approaches. This study shows that even one thin clay bed, less than 0.2 m thick, can cause plume persistence due to back diffusion for several years or even decades after the flux from the source is completely isolated. Thin clay beds, which have a large storage capacity for dissolved and sorbed contaminant mass, are common in many types of sandy aquifers. However, without careful inspection of continuous cores and sampling, such thin clay beds, and their potential for causing long-term back-diffusion effects, can easily go unnoticed during site characterization.

Secondary electron ion source neutron generator

DOEpatents

Brainard, John P.; McCollister, Daryl R.

1998-01-01

A neutron generator employing an electron emitter, an ion source bombarded by the electrons from the electron emitter, a plasma containment zone, and a target situated between the plasma containment zone and the electron emitter. The target contains occluded deuterium, tritium, or a mixture thereof

iTOUGH2-EOS1SC. Multiphase Reservoir Simulator for Water under Sub- and Supercritical Conditions. User's Guide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Magnusdottir, Lilja; Finsterle, Stefan

2015-03-01

Supercritical fluids exist near magmatic heat sources in geothermal reservoirs, and the high enthalpy fluid is becoming more desirable for energy production with advancing technology. In geothermal modeling, the roots of the geothermal systems are normally avoided but in order to accurately predict the thermal behavior when wells are drilled close to magmatic intrusions, it is necessary to incorporate the heat sources into the modeling scheme. Modeling supercritical conditions poses a variety of challenges due to the large gradients in fluid properties near the critical zone. This work focused on using the iTOUGH2 simulator to model the extreme temperature andmore » pressure conditions in magmatic geothermal systems.« less

Cornell Mixing Zone Expert System

EPA Pesticide Factsheets

This page provides an overview Cornell Mixing Zone Expert System water quality modeling and decision support system designed for environmental impact assessment of mixing zones resulting from wastewater discharge from point sources

Magnetic Anomalies Associated With Fracture Zones in the Cretaceous Magnetic Quiet Zone in the North Pacific Ocean

NASA Astrophysics Data System (ADS)

Ishihara, T.

2003-12-01

The existence of magnetic anomalies along east-west trending fracture zones in the north Pacific is well known. These anomalies are particularly prominent in the Cretaceous magnetic quiet zone, where no comparable anomalies are observed other than those associated with the Hawaiian Ridge and the Musician Seamounts in a newly compiled magnetic anomaly map. Model calculation was conducted using old magnetic and bathymetric data collected in the Cretaceous magnetic quiet zone. Two-dimensional simple models along north-south lines, which cross the Mendocino, Pioneer, Murray, Molokai and Clarion Fracture Zones, were constructed in order to clarify the sources of these magnetic anomalies. In these model calculations, it was assumed that the source bodies have normal remanent magnetizations with their inclinations of about 5 (for Mendocino FZ) to -25 degrees (for Clarion FZ), corresponding to the latitudes 40 degrees south of the present locations, as was suggested to have been in the late Cretaceous by some of paleomagnetic studies. This assumption is consistent with the dominance of negative anomalies in the observation. The model calculations suggest that under assumption of 0.5 km thick magnetic source bodies, remanent magnetizations more than 10 A/m should occur below some of the ridges and troughs in these fractures zones. Alternatively, in more plausible models with a remanent magnetization of 3 A/m, the magnetic source bodies should have thicknesses of up to about 5 km there.

Perforation and bacterial contamination of microscope covers in lumbar spinal decompressive surgery.

PubMed

Osterhoff, Georg; Spirig, José; Klasen, Jürgen; Kuster, Stefan P; Zinkernagel, Annelies S; Sax, Hugo; Min, Kan

2014-01-01

To determine the integrity of microscope covers and bacterial contamination at the end of lumbar spinal decompressive surgery. A prospective study of 25 consecutive lumbar spinal decompressions with the use of a surgical microscope was performed. For detection of perforations, the microscope covers were filled with water at the end of surgery and the presence of water leakage in 3 zones (objective, ocular and control panel) was examined. For detection of bacterial contamination, swabs were taken from the covers at the same locations before and after surgery. Among the 25 covers, 1 (4%) perforation was observed and no association between perforation and bacterial contamination was seen; 3 (4%) of 75 smears from the 25 covers showed post-operative bacterial contamination, i.e. 2 in the ocular zone and 1 in the optical zone, without a cover perforation. The incidence of microscope cover perforation was very low and was not shown to be associated with bacterial contamination. External sources of bacterial contamination seem to outweigh the problem of contamination due to failure of cover integrity. © 2014 S. Karger AG, Basel.

Perforation and Bacterial Contamination of Microscope Covers in Lumbar Spinal Decompressive Surgery

PubMed Central

Osterhoff, Georg; Spirig, José; Klasen, Jürgen; Kuster, Stefan P.; Zinkernagel, Annelies S.; Sax, Hugo; Min, Kan

2014-01-01

Objective To determine the integrity of microscope covers and bacterial contamination at the end of lumbar spinal decompressive surgery. Materials and Methods A prospective study of 25 consecutive lumbar spinal decompressions with the use of a surgical microscope was performed. For detection of perforations, the microscope covers were filled with water at the end of surgery and the presence of water leakage in 3 zones (objective, ocular and control panel) was examined. For detection of bacterial contamination, swabs were taken from the covers at the same locations before and after surgery. Results Among the 25 covers, 1 (4%) perforation was observed and no association between perforation and bacterial contamination was seen; 3 (4%) of 75 smears from the 25 covers showed post-operative bacterial contamination, i.e. 2 in the ocular zone and 1 in the optical zone, without a cover perforation. Conclusions The incidence of microscope cover perforation was very low and was not shown to be associated with bacterial contamination. External sources of bacterial contamination seem to outweigh the problem of contamination due to failure of cover integrity. PMID:24903448

Hurricane Wilma's impact on overall soil elevation and zones within the soil profile in a mangrove forest

USGS Publications Warehouse

Whelan, K.R.T.; Smith, T. J.; Anderson, G.H.; Ouellette, M.L.

2009-01-01

Soil elevation affects tidal inundation period, inundation frequency, and overall hydroperiod, all of which are important ecological factors affecting species recruitment, composition, and survival in wetlands. Hurricanes can dramatically affect a site's soil elevation. We assessed the impact of Hurricane Wilma (2005) on soil elevation at a mangrove forest location along the Shark River in Everglades National Park, Florida, USA. Using multiple depth surface elevation tables (SETs) and marker horizons we measured soil accretion, erosion, and soil elevation. We partitioned the effect of Hurricane Wilma's storm deposit into four constituent soil zones: surface (accretion) zone, shallow zone (0–0.35 m), middle zone (0.35–4 m), and deep zone (4–6 m). We report expansion and contraction of each soil zone. Hurricane Wilma deposited 37.0 (± 3.0 SE) mm of material; however, the absolute soil elevation change was + 42.8 mm due to expansion in the shallow soil zone. One year post-hurricane, the soil profile had lost 10.0 mm in soil elevation, with 8.5 mm of the loss due to erosion. The remaining soil elevation loss was due to compaction from shallow subsidence. We found prolific growth of new fine rootlets (209 ± 34 SE g m−2) in the storm deposited material suggesting that deposits may become more stable in the near future (i.e., erosion rate will decrease). Surficial erosion and belowground processes both played an important role in determining the overall soil elevation. Expansion and contraction in the shallow soil zone may be due to hydrology, and in the middle and bottom soil zones due to shallow subsidence. Findings thus far indicate that soil elevation has made substantial gains compared to site specific relative sea-level rise, but data trends suggest that belowground processes, which differ by soil zone, may come to dominate the long term ecological impact of storm deposit.

CONTROLLED FIELD STUDY ON THE USE OF NITRATE AND OXYGEN FOR BIOREMEDIATION OF A GASOLINE SOURCE ZONE

EPA Science Inventory

Controlled releases of unleaded gasoline were used to evaluate the biotransformation of the soluble aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylene isomers, trimethylbenzene isomers, and naphthalene) within a source zone using nitrate and oxygen as electron accepto...

Active hold-down for heat treating

NASA Technical Reports Server (NTRS)

Collins, E. R., Jr. (Inventor)

1986-01-01

The object of the disclosure is to provide a vacuum hold-down for holding thin sheets to a support surface, which permits the thin sheet to change dimensions as it is held down. The hold-down includes numerous holes in the support surface, through which a vacuum is applied from a vacuum source. The holes are arranged in zones. The vacuum is repeatedly interrupted at only one or a few zones, while it continues to be applied to other zones, to allow the workpiece to creep along that interrupted zone. The vacuum to different zones is interrupted at different times, as by a slowly turning valve number, to allow each zone of the workpiece to creep. A positive pressure may be applied from a pressured air source to a zone when the vacuum is interrupted there, to help lift the corresponding workpiece zone off the surface to aid in creeping. The workpiece may undergo dimensional changes because of heating, cooling, drying, or other procedure.

Water sources and mixing in riparian wetlands revealed by tracers and geospatial analysis.

PubMed

Lessels, Jason S; Tetzlaff, Doerthe; Birkel, Christian; Dick, Jonathan; Soulsby, Chris

2016-01-01

Mixing of waters within riparian zones has been identified as an important influence on runoff generation and water quality. Improved understanding of the controls on the spatial and temporal variability of water sources and how they mix in riparian zones is therefore of both fundamental and applied interest. In this study, we have combined topographic indices derived from a high-resolution Digital Elevation Model (DEM) with repeated spatially high-resolution synoptic sampling of multiple tracers to investigate such dynamics of source water mixing. We use geostatistics to estimate concentrations of three different tracers (deuterium, alkalinity, and dissolved organic carbon) across an extended riparian zone in a headwater catchment in NE Scotland, to identify spatial and temporal influences on mixing of source waters. The various biogeochemical tracers and stable isotopes helped constrain the sources of runoff and their temporal dynamics. Results show that spatial variability in all three tracers was evident in all sampling campaigns, but more pronounced in warmer dryer periods. The extent of mixing areas within the riparian area reflected strong hydroclimatic controls and showed large degrees of expansion and contraction that was not strongly related to topographic indices. The integrated approach of using multiple tracers, geospatial statistics, and topographic analysis allowed us to classify three main riparian source areas and mixing zones. This study underlines the importance of the riparian zones for mixing soil water and groundwater and introduces a novel approach how this mixing can be quantified and the effect on the downstream chemistry be assessed.

An integrated monitoring network for hydrologic, geochemical, and sediment fluxes to characterize carbon-mineral fate in the Christina River Basin Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Sawyer, A. H.; Karwan, D. L.; Lazareva, O.

2011-12-01

Organic carbon (C) -mineral complexation mechanism plays an important role in C sequestration within watersheds. The primary goal of the Christina River Basin Critical Zone Observatory in SE Pennsylvania and N Delaware, USA (one of six National Science Foundation-funded observatories) is to quantify net carbon sink or source due to mineral production and transport and its dependence on land use. This effort requires an interdisciplinary understanding of carbon and mineral fluxes across interfaces between soil, aquifer, floodplain, and river. We have established a monitoring network that targets hydrologic, geochemical, and sedimentological transport processes across channel-floodplain-aquifer interfaces within White Clay Creek Watershed. Within the channel, suspended material is sampled and analyzed for organic and mineral composition as well as geochemical fingerprints. Surface water and groundwater are analyzed for C, Fe, and Mn chemistry. Within the floodplain, in-situ sensors monitor soil moisture, pressure, temperature, conductivity, and redox potential. Integrated data analysis should yield estimates of water and solute fluxes between the vadose zone, riparian aquifer, and stream. Our preliminary data show that storm events are important for carbon and mineral fluxes-suspended material in surface water changes in source and composition throughout the storm. Meanwhile, the variation in stream stage drives surface water-groundwater exchange, facilitating changes in redox potential and providing opportunity for enhanced transport and reactions involving C, Fe, and Mn in the riparian aquifer.

Spectral, electron microscopic and chemical investigations of gamma-induced purple color zonings in amethyst crystals from the Dursunbey-Balıkesir region of Turkey

NASA Astrophysics Data System (ADS)

Hatipoğlu, Murat; Kibar, Rana; Çetin, Ahmet; Can, Nurdoğan; Helvacı, Cahit; Derin, H.

2011-07-01

Amethyst crystals on matrix specimens from the Dursunbey-Balıkesir region in Turkey have five representative purple color zonings: dark purple, light purple, lilac, orchid, and violet. The purple color zonings have been analyzed with optical absorption spectra in the visible wavelength region, chemical full trace element analyses (inductively coupled plasma-atomic emission spectroscopy and inductively coupled plasma-mass spectroscopy), and scanning electron microscopic images with high magnification. It can be proposed that the production of the purple color in amethyst crystals is due to three dominant absorption bands centered at 375, 530, and 675 nm, respectively. In addition, the purple color zonings are also due to four minor absorption bands centered at 435, 480, 620, and 760 nm. X-ray diffraction graphics of the investigated amethyst crystals indicate that these crystals are composed of a nearly pure alpha-quartz phase and do not include any moganite silica phase and/or other mineral implications. Trace element analyses of the amethyst crystals show five representative purple color zonings, suggesting that the absorption bands can be mainly attributed to extrinsic defects (chemical impurities). However, another important factor that influences all structural defects in amethyst is likely to be the gamma irradiation that exists during amethyst crystallization and its inclusion in host materials. This gamma irradiation originates from the large underlying intrusive granitoid body in the region of amethyst formation. Irradiation modifies the valence values of the impurity elements in the amethyst crystals. It is observed that the violet-colored amethyst crystals have the most stable and the least reversible coloration when exposed to strong light sources. This situation can be related to the higher impurity content of Fe (2.50 ppm), Co (3.1 ppm), Ni (38 ppm), Cu (17.9 ppm), Zn (10 ppm), Zr (3.9 ppm), and Mo (21.8 ppm).

A compact "water-window" microscope with 60-nm spatial resolution based on a double stream gas-puff target and Fresnel zone plate optics

NASA Astrophysics Data System (ADS)

Wachulak, Przemyslaw; Torrisi, Alfio; Nawaz, Muhammad F.; Adjei, Daniel; Bartnik, Andrzej; Kostecki, Jerzy; Wegrzynski, Łukasz; Vondrová, Šárka; Turňová, Jana; Fok, Tomasz; Jančarek, Alexandr; Fiedorowicz, Henryk

2015-05-01

Radiation with shorter illumination wavelength allows for extension of the diffraction limit towards nanometer scale, which is a straightforward way to significantly improve a spatial resolution in photon based microscopes. Soft X-ray (SXR) radiation, from the so called "water window" spectral range, λ=2.3-4.4 nm, which is particularly suitable for biological imaging due to natural optical contrast, providing much better spatial resolution than one obtained with visible light microscopes. The high contrast is obtained because of selective absorption of radiation by carbon and water, being constituents of the biological samples. We present a desk-top system, capable of resolving 60 nm features in few seconds exposure time. We exploit the advantages of a compact, laser-plasma SXR source, based on a double stream nitrogen gas puff target, developed at the Institute of Optoelectronics, Military University of Technology. The source, emitting quasi-monochromatic, incoherent radiation, in the "water widow" spectral range at λ = 2.88 nm, is coupled with ellipsoidal, grazing incidence condenser and Fresnel zone plate objective. The construction of the microscope with some recent images of test and real samples will be presented and discussed.

The Impact of State Enterprise Zones on Urban Manufacturing Establishments

ERIC Educational Resources Information Center

Greenbaum, Robert T.; Engberg, John B.

2004-01-01

Since the early 1980s, the vast majority of states have implemented enterprise zones. This paper analyzes urban zones in six states, examining the factors that states use to choose zone locations and the subsequent effect of the zones on business activity and employment. The source of outcome data is the U.S. Bureau of Census' longitudinal…

Relative role of intrinsic and scattering attenuation beneath the Andaman Islands, India and tectonic implications

NASA Astrophysics Data System (ADS)

Singh, Chandrani; Biswas, Rahul; Srijayanthi, G.; Ravi Kumar, M.

2017-10-01

The attenuation characteristics of seismic waves traversing the Andaman Nicobar subduction zone (ANSZ) are investigated using high quality data from a network of broadband stations operational since 2009. We initially studied the Coda wave attenuation (Qc-1) under the assumption of a single isotropic scattering model. Subsequently, following the multiple isotropic scattering hypothesis, we isolated the relative contributions of intrinsic (Qi-1) and scattering (Qsc-1) attenuation employing the Multiple Lapse Time Window Analysis (MLTWA) method within a frequency range 1.5-18 Hz. Results reveal a highly attenuative nature of the crust, with the values of Qc being frequency dependent. The intrinsic absorption is mostly found to be predominant compared to scattering attenuation. The dominance of Qi-1 in the crust may be attributed to the presence of fluids associated with the subducted slab. Our results are consistent with the low velocity zone reported for the region. A comparison of our results with those from other regions of the globe shows that the ANSZ falls under the category of high intrinsic attenuation zone. Interestingly, the character of ANSZ is identical to that of eastern Himalaya and southern Tibet, but entirely different from the Garhwal-Kumaun Himalaya and the source zone of Chamoli earthquake, due to the underlying mechanisms causing high attenuation.

Morphology and composition of gold in a lateritic profile, Fazenda Pison “Garimpo”, Amazon, Brazil

NASA Astrophysics Data System (ADS)

Larizzatti, J. H.; Oliveira, S. M. B.; Butt, C. R. M.

2008-05-01

This study describes the morphological evolution of gold grains in a lateritic weathering profile in an equatorial rainforest climate. Primary sources of gold are quartz veins associated with shallow granophyric intrusion. Gold grains were found in fresh ore, saprolite, transition zones, ferruginous duricrust, red latosol, and yellow latosol. Irregularly shaped grains predominate, with smaller proportions of dendritic and prismatic forms. Gold grains are weathered in the uppermost 10 m of the regolith. Mean gold grain size is maximum in the duricrust (>125 μm) and decreases progressively upward into the yellow latosol (<90 μm). Voids and corrosion pits appear on grain surfaces, and progressive rounding is observed from the bottom of the profile to the top. Gold grains can be classified as either homogeneous or zoned with respect to their chemical composition. Homogeneous grains contain 2-15% Ag (mean 8.3%). Zoned grains have more variable Ag contents; grain cores have means of approximately 10% or 23% Ag, with Ag-poor zones of approximately 3.7% Ag along internal discontinuities and/or outer rims. Formation of Ag-poor rims is due to preferential depletion of silver. Processes responsible for duricrust formation may preserve some grains as large aggregates, but subsequent transformation into latosol further modifies them.

Probabilistic Seismic Hazard Assessment of the Chiapas State (SE Mexico)

NASA Astrophysics Data System (ADS)

Rodríguez-Lomelí, Anabel Georgina; García-Mayordomo, Julián

2015-04-01

The Chiapas State, in southeastern Mexico, is a very active seismic region due to the interaction of three tectonic plates: Northamerica, Cocos and Caribe. We present a probabilistic seismic hazard assessment (PSHA) specifically performed to evaluate seismic hazard in the Chiapas state. The PSHA was based on a composited seismic catalogue homogenized to Mw and was used a logic tree procedure for the consideration of different seismogenic source models and ground motion prediction equations (GMPEs). The results were obtained in terms of peak ground acceleration as well as spectral accelerations. The earthquake catalogue was compiled from the International Seismological Center and the Servicio Sismológico Nacional de México sources. Two different seismogenic source zones (SSZ) models were devised based on a revision of the tectonics of the region and the available geomorphological and geological maps. The SSZ were finally defined by the analysis of geophysical data, resulting two main different SSZ models. The Gutenberg-Richter parameters for each SSZ were calculated from the declustered and homogenized catalogue, while the maximum expected earthquake was assessed from both the catalogue and geological criteria. Several worldwide and regional GMPEs for subduction and crustal zones were revised. For each SSZ model we considered four possible combinations of GMPEs. Finally, hazard was calculated in terms of PGA and SA for 500-, 1000-, and 2500-years return periods for each branch of the logic tree using the CRISIS2007 software. The final hazard maps represent the mean values obtained from the two seismogenic and four attenuation models considered in the logic tree. For the three return periods analyzed, the maps locate the most hazardous areas in the Chiapas Central Pacific Zone, the Pacific Coastal Plain and in the Motagua and Polochic Fault Zone; intermediate hazard values in the Chiapas Batholith Zone and in the Strike-Slip Faults Province. The hazard decreases towards the northeast across the Reverse Faults Province and up to Yucatan Platform, where the lowest values are reached. We also produced uniform hazard spectra (UHS) for the three main cities of Chiapas. Tapachula city presents the highest spectral accelerations, while Tuxtla Gutierrez and San Cristobal de las Casas cities show similar values. We conclude that seismic hazard in Chiapas is chiefly controlled by the subduction of the Cocos beneath Northamerica and Caribe tectonic plates, that makes the coastal areas the most hazardous. Additionally, the Motagua and Polochic Fault Zones are also important, increasing the hazard particularly in southeastern Chiapas.

Secondary electron ion source neutron generator

DOEpatents

Brainard, J.P.; McCollister, D.R.

1998-04-28

A neutron generator employing an electron emitter, an ion source bombarded by the electrons from the electron emitter, a plasma containment zone, and a target situated between the plasma containment zone and the electron emitter is disclosed. The target contains occluded deuterium, tritium, or a mixture thereof. 4 figs.

FIELD MEASUREMENTS OF CONTAMINANT FLUX BY INTEGRAL PUMPING TESTS (SAN FRANCISCO, CA)

EPA Science Inventory

Current remedial techniques are unable to completely eliminate all dense nonaqueous phase liquid (DNAPL) from source zone areas and conflicting views on the benefits of partial DNAPL source zone remediation exist in the literature. A comparison of flux measurements before and af...

CONTAMINANT FLUX RESPONSES TO THERMAL TREATMENT OF DNAPL SOURCE ZONES (ABSTRACT ONLY)

EPA Science Inventory

Contaminant flux is being proposed as a metric to help elucidate the benefits of DNAPL source-zone remedial efforts. While it is clear that aggressive remediation technologies can rapidly remove DNAPL mass, experience has shown that complete removal is often not practicable. H...

Investigating drought vulnerability using stable water isotopes and tritium in a montane system

NASA Astrophysics Data System (ADS)

Thaw, Melissa; Visser, Ate; Deinhart, Amanda; Bibby, Richard; Everhart, Anthony; Sharp, Mike; Conklin, Martha

2017-04-01

We combined measurements of water stable isotopes (d18O and d2H) with measurements of tritium (3H) to track water from precipitation through the subsurface and vegetation. Our study examined drought vulnerability in terms of vegetation water sources and subsurface storage in two montane sites, seasonally, using stable isotopes and tritium. Relative proportions of evapotranspiration sources were determined using two-tracer (d18O and 3H), three component mixing models. The two sites, located in the Southern Sierra Critical Zone Observatory, California, USA, are Mediterranean in climate, straddling the rain-snow transition zone where the upper elevation site receives most of its precipitation as winter snow. Over the study period, summer 2015 followed four years of severe snow drought; summer 2016 followed a slightly below average winter. The lower elevation site experienced severe drought-induced tree mortality over this time. Preliminary results show severe snow drought conditions and summer precipitation affected the proportions of source water used by vegetation due to the ability of vegetation to change sources when new water became available. Both stable isotopes and tritium reflect seasonal shifts in vegetation water sources, as well as species vulnerability and tolerance to drought. Xylem water sampled from Abies concolor (white fir) and Arctostaphylos patula (manzanita) responded the most quickly to changes in available water sources compared to Pinus jeffreyi (Jeffrey pine) and Calocedrus decurrens (incense cedar). Abies concolor and Arctostaphylos patula responded more dramatically to summer soil evaporation by accessing summer rain and deep water sources more quickly. Abies concolor also responded more dramatically to changes in snowpack during winter. During severe drought conditions, Arctostaphylos's ability to tap into a wide range of water sources coincided with drought tolerance (100% survival rate), while mortality for Pinus ponderosa and Calocedrus decurrens exceeded 50% and 70%, respectively. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-717437

Investigating Along-Strike Variations of Source Parameters for Relocated Thrust Earthquakes Along the Sumatra-Java Subduction Zone

NASA Astrophysics Data System (ADS)

El Hariri, M.; Bilek, S. L.; Deshon, H. R.; Engdahl, E. R.

2009-12-01

Some earthquakes generate anomalously large tsunami waves relative to their surface wave magnitudes (Ms). This class of events, known as tsunami earthquakes, is characterized by having a long rupture duration and low radiated energy at long periods. These earthquakes are relatively rare. There have been only 9 documented cases, including 2 in the Java subduction zone (1994 Mw=7.8 and the 2006 Mw=7.7). Several models have been proposed to explain the unexpectedly large tsunami, such as displacement along high-angle splay faults, landslide-induced tsunami due to coseismic shaking, or large seismic slip within low rigidity sediments or weaker material along the shallowest part of the subduction zone. Slow slip has also been suggested along portions of the 2004 Mw=9.2 Sumatra-Andaman earthquake zone. In this study we compute the source parameters of 90 relocated shallow thrust events (Mw 5.1-7.8) along the Sumatra-Java subduction zone including the two Java tsunami earthquakes. Events are relocated using a modification to the Engdahl, van der Hilst and Buland (EHB) earthquake relocation method that incorporates an automated frequency-dependent phase detector. This allows for the use of increased numbers of phase arrival times, especially depth phases, and improves hypocentral locations. Source time functions, rupture duration and depth estimates are determined using multi-station deconvolution of broadband teleseismic P and SH waves. We seek to correlate any along-strike variation in rupture characteristics with tectonic features and rupture characteristics of the previous slow earthquakes along this margin to gain a better understanding of the conditions resulting in slow ruptures. Preliminary results from the analysis of these events show that in addition to depth-dependent variations there are also along-strike variations in rupture duration. We find that along the Java segment, the longer duration event locates in a highly coupled region corresponding to the location of a proposed subducting seamount. This correlation is less clear along the southern Sumatran segment. One longer duration event is located within the high slip area of the Mw=8.4 2007 rupture, while another is located in the weakly coupled region of the 1935 Mw=7.7 rupture area.

Effect of shipping emissions on European ground-level ozone

NASA Astrophysics Data System (ADS)

Stergiou, Ioannis; -Eleni Sotiropoulou, Rafaella; Tagaris, Efthimios

2017-04-01

Shipping emissions contribution to the global nitrogen oxides emissions is about 15%, affecting ozone formation and the chemical composition of the atmosphere. The objective of this study is to assess the impact of shipping emissions on ozone levels over Europe suggesting regions where air quality degradation due to shipping emissions dominates against the rest of the anthropogenic source emissions. Ranking the importance of the Standard Nomenclature for Air Pollution (SNAP) categories on ozone mixing ratio, road transport has the major impact followed by other mobile sources, power generation, and industrial combustion sectors. All other sectors have a minor impact, therefor, our analysis is focused on these four emission categories. Results suggest that shipping emissions seem to play an important role on ozone levels compared to road transport sector near the coastal zone, while they could partly offset the benefits from the emissions reduction of other mobile sources, power generation and industrial combustion sources, over a great part of the European land.

Quake clamps down on slow slip

NASA Astrophysics Data System (ADS)

Wallace, Laura M.; Bartlow, Noel; Hamling, Ian; Fry, Bill

2014-12-01

Using continuous GPS (cGPS) data from the Hikurangi subduction zone in New Zealand, we show for the first time that stress changes induced by a local earthquake can arrest an ongoing slow slip event (SSE). The cGPS data show that the slip rate in the northern portion of the 2013/2014 Kapiti SSE decreased abruptly following a nearby intraslab earthquake. We suggest that deceleration of the Kapiti SSE in early 2014 occurred due to a tenfold increase in the normal stress relative to shear stress in the SSE source, induced by the nearby Mw 6.3 earthquake, consistent with expectations of rate and state friction. Our observation of an abrupt halting/slowing of the SSE in response to stress changes imposed by a local earthquake has implications for the strength of fault zones hosting SSEs and supports the premise that static stress changes are an important ingredient in triggering (or delaying) fault slip.

Volcano-tectonic implications of 3-D velocity structures derived from joint active and passive source tomography of the island of Hawaii

USGS Publications Warehouse

Park, J.; Morgan, J.K.; Zelt, C.A.; Okubo, P.G.

2009-01-01

We present a velocity model of the onshore and offshore regions around the southern part of the island of Hawaii, including southern Mauna Kea, southeastern Hualalai, and the active volcanoes of Mauna Loa, and Kilauea, and Loihi seamount. The velocity model was inverted from about 200,000 first-arrival traveltime picks of earthquakes and air gun shots recorded at the Hawaiian Volcano Observatory (HVO). Reconstructed volcanic structures of the island provide us with an improved understanding of the volcano-tectonic evolution of Hawaiian volcanoes and their interactions. The summits and upper rift zones of the active volcanoes are characterized by high-velocity materials, correlated with intrusive magma cumulates. These high-velocity materials often do not extend the full lengths of the rift zones, suggesting that rift zone intrusions may be spatially limited. Seismicity tends to be localized seaward of the most active intrusive bodies. Low-velocity materials beneath parts of the active rift zones of Kilauea and Mauna Loa suggest discontinuous rift zone intrusives, possibly due to the presence of a preexisting volcanic edifice, e.g., along Mauna Loa beneath Kilauea's southwest rift zone, or alternatively, removal of high-velocity materials by large-scale landsliding, e.g., along Mauna Loa's western flank. Both locations also show increased seismicity that may result from edifice interactions or reactivation of buried faults. New high-velocity regions are recognized and suggest the presence of buried, and in some cases, previously unknown rift zones, within the northwest flank of Mauna Loa, and the south flanks of Mauna Loa, Hualalai, and Mauna Kea. Copyright 2009 by the American Geophysical Union.

On the behavior of site effects in Central Mexico (the Mexican Volcanic Belt - MVB), based on records of shallow earthquakes that occurred in the zone between 1998 and 2011

NASA Astrophysics Data System (ADS)

Clemente-Chavez, A.; Zúñiga, F. R.; Lermo, J.; Figueroa-Soto, A.; Valdés, C.; Montiel, M.; Chavez, O.; Arroyo, M.

2013-11-01

The Mexican Volcanic Belt (MVB) is a seismogenic zone that transects the central part of Mexico with an east-west orientation. The risk and hazard seismic of this seismogenic zone has not been studied at detail due to the scarcity of instrumental data as well as because seismicity in the continental regimen of Central Mexico is not too frequent, however, it is known that there are precedents of large earthquakes (Mw > 6.0) that have taken place in this zone. The Valley of Mexico City (VM) is the sole zone, within the MVB, which has been studied in detail; mainly focusing on the ground amplification during large events such as the 1985 subduction earthquake that occurred in Michoacan. The purpose of this article is to analyze the behavior of site effects in the MVB zone based on records of shallow earthquakes (data not reported before) that occurred in the zone between 1998 and 2011. We present a general overview of site effects on the MVB, a classification of the stations in order to reduce the uncertainty in the data to obtain attenuation parameters in future works, and some comparisons between the information presented here and that presented in previous studies. A regional evaluation of site effects and Fourier Acceleration Spectrum (FAS) shape was estimated based on 80 records of 22 shallow earthquakes within the MVB zone. Data of 25 stations were analyzed. Site effects were estimated by using the Horizontal-to-Vertical Spectral Ratio (HVSR) methodology. The results show that seismic waves are less amplified in the northeast sites of the MVB with respect to the rest of the zone and that it is possible to classify two groups of stations: (1) stations with Negligible Site Amplification (NSA) and (2) stations with Significant Site Amplification (SSA). Most of the sites in the first group showed small (< 3) amplifications while the second group showed amplifications ranging from 4 to 6.5 at frequencies of about 0.35, 0.75, 15 and 23 Hz. With these groups of stations, average levels of amplification were contrasted for the first time with those caused by the subduction zone earthaquakes. With respect to the FAS shapes, most of them showed similarities at similar epicentral distances. Finally, some variations of site effects were found when compared to those obtained in previous studies on different seismicity regions. These variations were attributed to the location of the source. These aspects help to advance the understanding about the amplification behavior and of the expected seismic risk on the Central Mexico due to large earthquakes within the MVB seismogenic zone.

On the behavior of site effects in central Mexico (the Mexican volcanic belt - MVB), based on records of shallow earthquakes that occurred in the zone between 1998 and 2011

NASA Astrophysics Data System (ADS)

Clemente-Chavez, A.; Zúñiga, F. R.; Lermo, J.; Figueroa-Soto, A.; Valdés, C.; Montiel, M.; Chavez, O.; Arroyo, M.

2014-06-01

The Mexican volcanic belt (MVB) is a seismogenic zone that transects the central part of Mexico with an east-west orientation. The seismic risk and hazard of this seismogenic zone has not been studied in detail due to the scarcity of instrumental data as well as because seismicity in the continental regime of central Mexico is not too frequent. However, it is known that there are precedents of large earthquakes (Mw > 6.0) that have taken place in this zone. The valley of Mexico City (VM) is the sole zone, within the MVB, that has been studied in detail. Studies have mainly focused on the ground amplification during large events such as the 1985 subduction earthquake that occurred off coast of Michoacán. The purpose of this article is to analyze the behavior of site effects in the MVB zone based on records of shallow earthquakes (data not reported before) that occurred in the zone between 1998 and 2011. We present a general overview of site effects in the MVB, a classification of the stations in order to reduce the uncertainty in the data when obtaining attenuation parameters in future works, as well as some comparisons between the information presented here and that presented in previous studies. A regional evaluation of site effects and Fourier acceleration spectrum (FAS) shape was estimated based on 80 records of 22 shallow earthquakes within the MVB zone. Data of 25 stations were analyzed. Site effects were estimated by using the horizontal-to-vertical spectral ratio (HVSR) methodology. The results show that seismic waves are less amplified in the northeast sites of the MVB with respect to the rest of the zone and that it is possible to classify two groups of stations: (1) stations with negligible site amplification (NSA) and (2) stations with significant site amplification (SSA). Most of the sites in the first group showed small (<3) amplifications while the second group showed amplifications ranging from 4 to 6.5 at frequencies of about 0.35, 0.75, 15 and 23 Hz. With these groups of stations, average levels of amplification were contrasted for the first time with those caused by the subduction zone earthquakes. With respect to the FAS shapes, most of them showed similarities at similar epicentral distances. Finally, some variations of site effects were found when compared to those obtained in previous studies on different seismicity regions. These variations were attributed to the location of the source. These aspects help to advance the understanding about the amplification behavior and of the expected seismic risk on central Mexico due to large earthquakes within the MVB seismogenic zone.

Magnetic susceptibility as a proxy for the hydrobiogeochemical cycling of iron within the water table fluctuation zone at hydrocarbon contaminated sites

NASA Astrophysics Data System (ADS)

Atekwana, E. A.; Enright, A.; Atekwana, E. A.; Beaver, C. L.; Rossbach, S.; Slater, L. D.; Ntarlagiannis, D.

2016-12-01

Sharp redox gradients are indicative of enhanced biogeochemical activity and occur at or near the water table. Hydrologic forcing drives changes in redox state and oxygen levels, enhancing the elemental cycling of metals, and coupling different biogeochemical cycles. These coupled hydrobiogeochemical cycles are often difficult to study in the field using geochemical and microbial proxies because of direct sampling limitations, the costs associated with these techniques, and because the dynamic nature of these processes complicates the interpretation of single time point measurements, which may not give accurate representations of prevailing conditions. Geophysical techniques can provide both the spatial and temporal resolution needed to elucidate these processes. Here we investigated the use of magnetic susceptibility (c) as a viable proxy for understanding the biogeochemical cycling of iron at several hydrocarbon contaminated sites where active intrinsic bioremediation is occurring. We performed borehole c logging using a Bartington c probe in the field as well as made c measurements on core samples retrieved from the field sites. Our results show the following: (1) in both sulfate-rich and sulfate-poor aquifers, excursions in c are coincident with zones of free product contamination and are limited to the water table fluctuation (smear) zone; (2) c values within the free product plume and contamination source zones are higher compared to values within the dissolved product plume; (3) high c coincides with zones of elevated Fe (II) and Fe (III) concentrations extracted from aquifer solids; and (4) the mixed valence magnetite and greigite were the dominant magnetic minerals. The c excursions are limited to the water table fluctuation zones because fluctuating water level conditions are hot beds for microbial activity due to the steep hydrocarbon and nutrients and consequently redox gradients. High water levels during periods of recharge favor anaerobic conditions enhancing iron reduction, while low water conditions during drought periods favor iron oxidation due to increased oxygen penetration. Such conditions favor mixed valent iron minerals such as magnetite and greigite. We conclude that c measurements are a low cost, rapid monitoring tool for assessing the elemental cycling of iron.

Investigating Transition Zone Thickness Variation under the Arabian Plate: Evidence Lacking for Deep Mantle Upwellings

NASA Astrophysics Data System (ADS)

Juliá, J.; Tang, Z.; Mai, P. M.; Zahran, H.

2014-12-01

Cenozoic volcanic outcrops in Arabia - locally known as harrats - span more than 2000 km along the western half of the Arabian plate, from eastern Yemen to southern Syria. The magmatism is bimodal in character, with older volcanics (30 to 20 My) being tholeiitic-to-transitional and paralleling the Red Sea margin, and younger volcanics (12 Ma to Recent) being transitional-to-strongly-alkalic and aligning in a more north-south direction. The bimodal character has been attributed to a two-stage rifting process along the Red Sea, where the old volcanics would have produced from shallow sources related to an initial passive rifting stage, and young volcanics would have originated from one or more deep-seated mantle plumes driving present active rifting. Early models suggested the harrats would have resulted from either lateral flow from the Afar plume in Ethiopia, or more locally from a separate mantle plume directly located under the shield. Most recently, tomographic images of the Arabian mantle have suggested the northern harrats could be resulting from flow originating at a deep plume under Jordan. In this work, we investigate the location of deep mantle plumes under the Arabian plate by mapping transition zone thickness with teleseismic receiver functions. The transition zone is bounded by seismic discontinuities, nominally at 410 and 660 km depth, originating from phase transitions in the olivine-normative component of the mantle. The precise depth of the discontinuities is strongly dependent on temperature and, due to the opposing signs of the corresponding Clapeyron slopes, positive temperature anomalies are expected to result in thinning of the transition zone. Our dataset consists of ~5000 low-frequency (fc < 0.25 Hz) receiver function waveforms obtained at ~110 broadband stations belonging to a number of permanent and temporary seismic networks in the region. The receiver functions were migrated to depth and stacked along a ~2000 km long record section displaying P-to-S conversions at seismic discontinuities under Western Arabia. Our results display a normal to thicker-than-average transition zone under the study area, suggesting thermal perturbations of the transition zone due to deep mantle upwellings under the western shield and/or Jordan are unlikely.

Incidence of cancer in the area around Amsterdam Airport Schiphol in 1988-2003: a population-based ecological study.

PubMed

Visser, Otto; van Wijnen, Joop H; van Leeuwen, Flora E

2005-12-06

Amsterdam Airport Schiphol is a major source of complaints about aircraft noise, safety risks and concerns about long term adverse health effects, including cancer. We investigated whether residents of the area around Schiphol are at higher risk of developing cancer than the general Dutch population. In a population-based study using the regional cancer registry, we estimated the cancer incidence during 1988-2003 in residents of the area surrounding Schiphol. We defined a study area based on aircraft noise contours and 4-digit postal code areas, since historical data on ambient air pollution were not available and recent emission data did not differ from the background urban air quality. In residents of the study area 13 207 cancer cases were diagnosed, which was close to the expected number, using national incidence rates as a reference (standardized incidence ratio [SIR] 1.02). We found a statistically significantly increased incidence of hematological malignancies (SIR 1.12, 95% confidence interval [CI]: 1.05, 1.19), mainly due to high rates for non-Hodgkin lymphoma (SIR 1.22, 95% CI: 1.12, 1.33) and acute lymphoblastic leukemia (SIR 1.34, 95% CI: 0.95, 1.83). The incidence of cancer of the respiratory system was statistically significantly decreased (SIR 0.94, 95% CI: 0.90, 0.99), due to the low rate in males (SIR 0.89). In the core zone of the study area, cancer incidence was slightly higher than in the remaining ring zone (rate ratio of the core zone compared to the ring zone 1.05, 95% CI 1.01, 1.10). This was caused by the higher incidence of cancer of the respiratory system, prostate and the female genital organs in the core zone in comparison to the ring zone. The overall cancer incidence in the Schiphol area was similar to the national incidence. The moderately increased risk of hematological malignancies could not be explained by higher levels of ambient air pollution in the Schiphol area. This observation warrants further research, for example in a study with focus on substances in urban ambient air pollution, as similar findings were observed in Greater Amsterdam.

The energy release in earthquakes, and subduction zone seismicity and stress in slabs. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Vassiliou, M. S.

1983-01-01

Energy release in earthquakes is discussed. Dynamic energy from source time function, a simplified procedure for modeling deep focus events, static energy estimates, near source energy studies, and energy and magnitude are addressed. Subduction zone seismicity and stress in slabs are also discussed.

MEASUREMENT AND USE OF CONTAMINANT FLUX AS AN ASSESSMENT TOOL FOR DNAPL REMEDIAL PERFORMANCE

EPA Science Inventory

Current remedial techniques are unable to completely eliminate all dense nonaqueous phase liquid (DNAPL) from source zone areas at most sites, and conflicting views on the benefits of partial DNAPL source zone remediation exist in the literature. A comparison of contaminant flux...

THE MEASUREMENT AND USE OF CONTAMINANT FLUX AS AN ASSESSMENT TOOL FOR DNAPL REMEDIAL PERFORMANCE

EPA Science Inventory

Current remedial techniques are unable to completely eliminate all dense nonaqueous phase liquid (DNAPL) from source zone areas at most sites, and conflicting views on the benefits of partial DNAPL source zone remediation exist in the literature. A comparison of contaminant flux...

New insight into the relationships between stress, strain and mass change at Mt. Etna during the period between the 1993-94 and 2001 eruptions

NASA Astrophysics Data System (ADS)

Carbone, Daniele; Aloisi, Marco; Vinciguerra, Sergio; Puglisi, Giuseppe

2014-05-01

During the time interval between the 1991-93 and 2001 main flank eruptions of Mt. Etna, volcanic activity was confined to the summit vents. Ground deformation and tomography studies suggest that this activity was fed by a magma body located beneath the north-west flank of the volcano, at a depth of around 7 km b.s.l.. Conversely, gravity studies indicate that the most important mass redistributions during the same period took place within an elongated volume centered below the southeastern sector of the volcano, at depths of 2-4 km b.s.l.. The phases of gravity decrease during the 1994-2001 period coincide with phases of higher strain release rate. The coupling between gravity and seismic data could reflect changes in the rate of micro-fracturing along the NNW-SSE weakness zone that cuts the SE slope of the volcano. This interpretation allows to explain why the main pressure and mass sources active at Etna during the 1994-2001 period do not coincide. The extensional dynamics of the southeastern flank of Etna may represent a second-order effect, triggered by the pressure source below the western flank and accommodated along the NNW-SSE weakness zone. In order to gain quantitative insight into the relationship between stress, strain and mass changes at Etna during the 1994-2001 period, we use a finite element modeling approach. Relying on recent studies involving stress- and temperature-induced degradation of the mechanical properties of rocks, we hypothesize that the inferred NNW-SSE weakness zone is characterized by an anomalously low Young's modulus (E). Results of our analysis are summarized in the following two points. (i) The presence of the weakness zone creates a distortion of the displacements field induced by the deeper pressure source, locally resulting in a weak extensional regime. This finding supports the hypothesis of a cause-effect relation between deeper pressurization beneath the western flank and shallower extension across the fracture zone beneath the SE flank of the volcano. However, the bulk extension across the weakness zone which is only due to pressurization of the magma reservoir is not sufficient to induce the observed gravity changes through changes in the rate of microfracturing. We suggest that propagation of pressurized gas, enhanced by the extensional regime across the NNW-SSE weakness zone, may have exerted tensile stresses across it, in turn increasing the bulk extension. (ii) For a given tensile stress across the fracture zone, the bulk extension increases proportionally as the value of E in the weakness zone decreases, while the ground deformation remains almost the same. This provides an explanation to understand how, during the studied period, the inferred changes in the bulk rate of microfracturing along the NNW-SSE weakness zone could have occurred with an associated small ground deformation. Indeed, we found that, as the value of E in correspondence of the fracture zone decreases, the ratio between deep extension and maximum ground displacement increases and, for values of E equal or less than about 10 GPa, deep extension of 1-2 m can develop with deformation of the surface close to the detection limit of GPS measurements. Our results highlight the importance of performing gravity studies at at volcanoes where there exists a causal link between medium fracturing and volcanic activity.

Delivery and Establishing Slow Release Carbon Source to the Hanford Vadose Zone Using Colloidal Silica Suspension Injection and Subsequent Gelation - Laboratory Study

NASA Astrophysics Data System (ADS)

Zhong, L.; Lee, M. H.; Lee, B.; Yang, S.

2016-12-01

Delivery of nutrient to and establish a slow release carbon source in the vadose zone and capillary fringe zone is essential for setting up of a long-lasting bioremediation of contaminations in those zones. Conventional solution-based injection and infiltration approaches are facing challenges to achieve the delivery and remedial goals. Aqueous silica suspensions undergo a delayed gelation process under favorite geochemical conditions. The delay in gelation provides a time window for the injection of the suspension into the subsurface; and the gelation of the amendment-silica suspension enables the amendment-laden gel to stay in the target zone and slowly release the constituents for contaminant remediation. This approach can potentially be applied to deliver bio-nutrients to the vadose zone and capillary fringe zone for enhanced bioremediation and achieve remedial goals. This research was conducted to demonstrate delayed gelation of colloidal silica suspensions when carbon sources were added and to prove the gelation occurs in sediments under vadose conditions. Sodium lactate, vegetable oil, ethanol, and molasses were tested as the examples of carbon source (or nutrient) amendments. The rheological properties of the silica suspensions during the gelation were characterized. The influence of silica, salinity, nutrient concentrations, and the type of nutrients was studied. The kinetics of nutrient release from silica-nutrient gel was quantified using molasses as the example, and the influence of suspension gelation time was evaluated. The injection behavior of the suspensions was investigated by monitoring their viscosity changes and the injection pressures when the suspensions were delivered into sediment columns.

Impact of hydrological alterations on river-groundwater exchange and water quality in a semi-arid area: Nueces River, Texas.

PubMed

Murgulet, Dorina; Murgulet, Valeriu; Spalt, Nicholas; Douglas, Audrey; Hay, Richard G

2016-12-01

There is a lack of understanding and methods for assessing the effects of anthropogenic disruptions, (i.e. river fragmentation due to dam construction) on the extent and degree of groundwater-surface water interaction and geochemical processes affecting the quality of water in semi-arid, coastal catchments. This study applied a novel combination of electrical resistivity tomography (ERT) and elemental and isotope geochemistry in a coastal river disturbed by extended drought and periodic flooding due to the operation of multiple dams. Geochemical analyses show that the saltwater barrier causes an increase in salinity in surface water in the downstream river as a result of limited freshwater inflows, strong evaporation effects on shallow groundwater and mostly stagnant river water, and is not due to saltwater intrusion by tidal flooding. Discharge from bank storage is dominant (~84%) in the downstream fragment and its contribution could increase salinity levels within the hyporheic zone and surface water. When surface water levels go up due to upstream freshwater releases the river temporarily displaces high salinity water trapped in the hyporheic zone to the underlying aquifer. Geochemical modeling shows a higher contribution of distant and deeper groundwater (~40%) in the upstream river and lower discharge from bank storage (~13%) through the hyporheic zone. Recharge from bank storage is a source of high salt to both upstream and downstream portions of the river but its contribution is higher below the dam. Continuous ERT imaging of the river bed complements geochemistry findings and indicate that while lithologically similar, downstream of the dam, the shallow aquifer is affected by salinization while fresher water saturates the aquifer in the upstream fragment. The relative contribution of flows (i.e. surface water releases or groundwater discharge) as related to the river fragmentation control changes of streamwater chemistry and likely impact the interpretation of seasonal trends. Copyright © 2016 Elsevier B.V. All rights reserved.

S-wave attenuation in northeastern Sonora, Mexico, near the faults that ruptured during the earthquake of 3 May 1887 Mw 7.5.

PubMed

Villalobos-Escobar, Gina P; Castro, Raúl R

2014-01-01

We used a new data set of relocated earthquakes recorded by the Seismic Network of Northeastern Sonora, Mexico (RESNES) to characterize the attenuation of S-waves in the fault zone of the 1887 Sonora earthquake (M w 7.5). We determined spectral attenuation functions for hypocentral distances (r) between 10 and 140 km using a nonparametric approach and found that in this fault zone the spectral amplitudes decay slower with distance at low frequencies (f < 4 Hz) compared to those reported in previous studies in the region using more distant recordings. The attenuation functions obtained for 23 frequencies (0.4 ≤ f ≤ 63.1 Hz) permit us estimating the average quality factor Q S  = (141 ± 1.1 )f ((0.74 ± 0.04)) and a geometrical spreading term G(r) = 1/r (0.21). The values of Q estimated for S-wave paths traveling along the fault system that rupture during the 1887 event, in the north-south direction, are considerably lower than the average Q estimated using source-station paths from multiple stations and directions. These results indicate that near the fault zone S waves attenuate considerably more than at regional scale, particularly at low frequencies. This may be the result of strong scattering near the faults due to the fractured upper crust and higher intrinsic attenuation due to stress concentration near the faults.

Transient Point Infiltration In The Unsaturated Zone

NASA Astrophysics Data System (ADS)

Buecker-Gittel, M.; Mohrlok, U.

The risk assessment of leaking sewer pipes gets more and more important due to urban groundwater management and environmental as well as health safety. This requires the quantification and balancing of transport and transformation processes based on the water flow in the unsaturated zone. The water flow from a single sewer leakage could be described as a point infiltration with time varying hydraulic conditions externally and internally. External variations are caused by the discharge in the sewer pipe as well as the state of the leakage itself. Internal variations are the results of microbiological clogging effects associated with the transformation processes. Technical as well as small scale laboratory experiments were conducted in order to investigate the water transport from an transient point infiltration. From the technical scale experiment there was evidence that the water flow takes place under transient conditions when sewage infiltrates into an unsaturated soil. Whereas the small scale experiments investigated the hydraulics of the water transport and the associated so- lute and particle transport in unsaturated soils in detail. The small scale experiment was a two-dimensional representation of such a point infiltration source where the distributed water transport could be measured by several tensiometers in the soil as well as by a selective measurement of the discharge at the bottom of the experimental setup. Several series of experiments were conducted varying the boundary and initial con- ditions in order to derive the important parameters controlling the infiltration of pure water from the point source. The results showed that there is a significant difference between the infiltration rate in the point source and the discharge rate at the bottom, that could be explained by storage processes due to an outflow resistance at the bottom. This effect is overlayn by a decreasing water content decreases over time correlated with a decreasing infiltration rate. As expected the initial conditions mainly affects the time scale for the water transport. Additionally, the influence of preferential flow paths on the discharge distribution could be found due to the heterogenieties caused by the filling and compaction process of the sandy soil.

[Classification of Priority Area for Soil Environmental Protection Around Water Sources: Method Proposed and Case Demonstration].

PubMed

Li, Lei; Wang, Tie-yu; Wang, Xiaojun; Xiao, Rong-bo; Li, Qi-feng; Peng, Chi; Han, Cun-liang

2016-04-15

Based on comprehensive consideration of soil environmental quality, pollution status of river, environmental vulnerability and the stress of pollution sources, a technical method was established for classification of priority area of soil environmental protection around the river-style water sources. Shunde channel as an important drinking water sources of Foshan City, Guangdong province, was studied as a case, of which the classification evaluation system was set up. In detail, several evaluation factors were selected according to the local conditions of nature, society and economy, including the pollution degree of heavy metals in soil and sediment, soil characteristics, groundwater sensitivity, vegetation coverage, the type and location of pollution sources. Data information was mainly obtained by means of field survey, sampling analysis, and remote sensing interpretation. Afterwards, Analytical Hierarchy Process (AHP) was adopted to decide the weight of each factor. The basic spatial data layers were set up respectively and overlaid based on the weighted summation assessment model in Geographical Information System (GIS), resulting in a classification map of soil environmental protection level in priority area of Shunde channel. Accordingly, the area was classified to three levels named as polluted zone, risky zone and safe zone, which respectively accounted for 6.37%, 60.90% and 32.73% of the whole study area. Polluted zone and risky zone were mainly distributed in Lecong, Longjiang and Leliu towns, with pollutants mainly resulted from the long-term development of aquaculture and the industries containing furniture, plastic constructional materials and textile and clothing. In accordance with the main pollution sources of soil, targeted and differentiated strategies were put forward. The newly established evaluation method could be referenced for the protection and sustainable utilization of soil environment around the water sources.

What do data used to develop ground-motion prediction equations tell us about motions near faults?

USGS Publications Warehouse

Boore, David M.

2014-01-01

A large database of ground motions from shallow earthquakes occurring in active tectonic regions around the world, recently developed in the Pacific Earthquake Engineering Center’s NGA-West2 project, has been used to investigate what such a database can say about the properties and processes of crustal fault zones. There are a relatively small number of near-rupture records, implying that few recordings in the database are within crustal fault zones, but the records that do exist emphasize the complexity of ground-motion amplitudes and polarization close to individual faults. On average over the whole data set, however, the scaling of ground motions with magnitude at a fixed distance, and the distance dependence of the ground motions, seem to be largely consistent with simple seismological models of source scaling, path propagation effects, and local site amplification. The data show that ground motions close to large faults, as measured by elastic response spectra, tend to saturate and become essentially constant for short periods. This saturation seems to be primarily a geometrical effect, due to the increasing size of the rupture surface with magnitude, and not due to a breakdown in self similarity.

What Do Data Used to Develop Ground-Motion Prediction Equations Tell Us About Motions Near Faults?

NASA Astrophysics Data System (ADS)

Boore, David M.

2014-11-01

A large database of ground motions from shallow earthquakes occurring in active tectonic regions around the world, recently developed in the Pacific Earthquake Engineering Center's NGA-West2 project, has been used to investigate what such a database can say about the properties and processes of crustal fault zones. There are a relatively small number of near-rupture records, implying that few recordings in the database are within crustal fault zones, but the records that do exist emphasize the complexity of ground-motion amplitudes and polarization close to individual faults. On average over the whole data set, however, the scaling of ground motions with magnitude at a fixed distance, and the distance dependence of the ground motions, seem to be largely consistent with simple seismological models of source scaling, path propagation effects, and local site amplification. The data show that ground motions close to large faults, as measured by elastic response spectra, tend to saturate and become essentially constant for short periods. This saturation seems to be primarily a geometrical effect, due to the increasing size of the rupture surface with magnitude, and not due to a breakdown in self similarity.

Two-dimensional distribution of microbial activity and flow patterns within naturally fractured chalk.

PubMed

Arnon, Shai; Ronen, Zeev; Adar, Eilon; Yakirevich, Alexander; Nativ, Ronit

2005-10-01

The two-dimensional distribution of flow patterns and their dynamic change due to microbial activity were investigated in naturally fractured chalk cores. Long-term biodegradation experiments were conducted in two cores ( approximately 20 cm diameter, 31 and 44 cm long), intersected by a natural fracture. 2,4,6-tribromophenol (TBP) was used as a model contaminant and as the sole carbon source for aerobic microbial activity. The transmissivity of the fractures was continuously reduced due to biomass accumulation in the fracture concurrent with TBP biodegradation. From multi-tracer experiments conducted prior to and following the microbial activity, it was found that biomass accumulation causes redistribution of the preferential flow channels. Zones of slow flow near the fracture inlet were clogged, thus further diverting the flow through zones of fast flow, which were also partially clogged. Quantitative evaluation of biodegradation and bacterial counts supported the results of the multi-tracer tests, indicating that most of the bacterial activity occurs close to the inlet. The changing flow patterns, which control the nutrient supply, resulted in variations in the concentrations of the chemical constituents (TBP, bromide and oxygen), used as indicators of biodegradation.

Impacts of building geometry modeling methods on the simulation results of urban building energy models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yixing; Hong, Tianzhen

We present that urban-scale building energy modeling (UBEM)—using building modeling to understand how a group of buildings will perform together—is attracting increasing attention in the energy modeling field. Unlike modeling a single building, which will use detailed information, UBEM generally uses existing building stock data consisting of high-level building information. This study evaluated the impacts of three zoning methods and the use of floor multipliers on the simulated energy use of 940 office and retail buildings in three climate zones using City Building Energy Saver. The first zoning method, OneZone, creates one thermal zone per floor using the target building'smore » footprint. The second zoning method, AutoZone, splits the building's footprint into perimeter and core zones. A novel, pixel-based automatic zoning algorithm is developed for the AutoZone method. The third zoning method, Prototype, uses the U.S. Department of Energy's reference building prototype shapes. Results show that simulated source energy use of buildings with the floor multiplier are marginally higher by up to 2.6% than those modeling each floor explicitly, which take two to three times longer to run. Compared with the AutoZone method, the OneZone method results in decreased thermal loads and less equipment capacities: 15.2% smaller fan capacity, 11.1% smaller cooling capacity, 11.0% smaller heating capacity, 16.9% less heating loads, and 7.5% less cooling loads. Source energy use differences range from -7.6% to 5.1%. When comparing the Prototype method with the AutoZone method, source energy use differences range from -12.1% to 19.0%, and larger ranges of differences are found for the thermal loads and equipment capacities. This study demonstrated that zoning methods have a significant impact on the simulated energy use of UBEM. Finally, one recommendation resulting from this study is to use the AutoZone method with floor multiplier to obtain accurate results while balancing the simulation run time for UBEM.« less

Impacts of building geometry modeling methods on the simulation results of urban building energy models

DOE PAGES

Chen, Yixing; Hong, Tianzhen

2018-02-20

We present that urban-scale building energy modeling (UBEM)—using building modeling to understand how a group of buildings will perform together—is attracting increasing attention in the energy modeling field. Unlike modeling a single building, which will use detailed information, UBEM generally uses existing building stock data consisting of high-level building information. This study evaluated the impacts of three zoning methods and the use of floor multipliers on the simulated energy use of 940 office and retail buildings in three climate zones using City Building Energy Saver. The first zoning method, OneZone, creates one thermal zone per floor using the target building'smore » footprint. The second zoning method, AutoZone, splits the building's footprint into perimeter and core zones. A novel, pixel-based automatic zoning algorithm is developed for the AutoZone method. The third zoning method, Prototype, uses the U.S. Department of Energy's reference building prototype shapes. Results show that simulated source energy use of buildings with the floor multiplier are marginally higher by up to 2.6% than those modeling each floor explicitly, which take two to three times longer to run. Compared with the AutoZone method, the OneZone method results in decreased thermal loads and less equipment capacities: 15.2% smaller fan capacity, 11.1% smaller cooling capacity, 11.0% smaller heating capacity, 16.9% less heating loads, and 7.5% less cooling loads. Source energy use differences range from -7.6% to 5.1%. When comparing the Prototype method with the AutoZone method, source energy use differences range from -12.1% to 19.0%, and larger ranges of differences are found for the thermal loads and equipment capacities. This study demonstrated that zoning methods have a significant impact on the simulated energy use of UBEM. Finally, one recommendation resulting from this study is to use the AutoZone method with floor multiplier to obtain accurate results while balancing the simulation run time for UBEM.« less

Floodplain ecohydrology: Climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees.

PubMed

Singer, Michael Bliss; Sargeant, Christopher I; Piégay, Hervé; Riquier, Jérémie; Wilson, Rob J S; Evans, Cristina M

2014-05-01

Seasonal and annual partitioning of water within river floodplains has important implications for ecohydrologic links between the water cycle and tree growth. Climatic and hydrologic shifts alter water distribution between floodplain storage reservoirs (e.g., vadose, phreatic), affecting water availability to tree roots. Water partitioning is also dependent on the physical conditions that control tree rooting depth (e.g., gravel layers that impede root growth), the sources of contributing water, the rate of water drainage, and water residence times within particular storage reservoirs. We employ instrumental climate records alongside oxygen isotopes within tree rings and regional source waters, as well as topographic data and soil depth measurements, to infer the water sources used over several decades by two co-occurring tree species within a riparian floodplain along the Rhône River in France. We find that water partitioning to riparian trees is influenced by annual (wet versus dry years) and seasonal (spring snowmelt versus spring rainfall) fluctuations in climate. This influence depends strongly on local (tree level) conditions including floodplain surface elevation and subsurface gravel layer elevation. The latter represents the upper limit of the phreatic zone and therefore controls access to shallow groundwater. The difference between them, the thickness of the vadose zone, controls total soil moisture retention capacity. These factors thus modulate the climatic influence on tree ring isotopes. Additionally, we identified growth signatures and tree ring isotope changes associated with recent restoration of minimum streamflows in the Rhône, which made new phreatic water sources available to some trees in otherwise dry years. Water shifts due to climatic fluctuations between floodplain storage reservoirsAnthropogenic changes to hydrology directly impact water available to treesEcohydrologic approaches to integration of hydrology afford new possibilities.

Consideration of Treatment Performance Assessment Metrics for a TCE Source Area Bioremediation (SABRe project)

NASA Astrophysics Data System (ADS)

Cai, Z.; Wilson, R. D.

2009-05-01

Techniques for optimizing the removal of NAPL mass in source zones have advanced at a more rapid rate than strategies to assess treatment performance. Informed selection of remediation approaches would be easier if measurements of performance were more directly transferable. We developed a number of methods based on data generated from multilevel sampler (MLS) transects to assess the effectiveness of a bioaugmentation/biostimulation trial in a TCE source residing in a terrace gravel aquifer in the East Midlands, UK. In this spatially complex aquifer, treatment inferred from long screen monitoring well data was not as reliable as that from consideration of mass flux changes across transects installed in and downgradient of the source. Falling head tests were conducted in the MLS ports to generate the necessary hydraulic conductivity (K) data. Combining K with concentration provides a mass flux map that allows calculation of mass turnover and an assessment of where in the complex geology the greatest turnover occurred. Five snapshots over a 600-day period indicate a marked reduction in TCE flux, suggesting a significant reduction in DNAPL mass over that expected due to natural processes. However, persistence of daughter products suggested that complete dechlorination did not occur. The MLS fence data also revealed that delivery of both carbon source and pH buffer were not uniform across the test zone. This may have lead to the generation of niches of iron(III) and sulphate reduction as well as methanogenesis, which impacted on dechlorination processes. In the absence of this spatial data, it is difficult to reconcile apparent treatment as indicated in monitoring well data to on-going processes.

Recent Findings on Tsunami Hazards in the Makran Subduction Zone, NW Indian Ocean

NASA Astrophysics Data System (ADS)

Heidarzadeh, M.; Satake, K.

2014-12-01

We present recent findings on tsunami hazards in the Makran subduction zone (MSZ), NW Indian Ocean, based on the results of tsunami source analyses for two Makran tsunamis of 1945 and 2013. A re-analysis of the source of the 27 November 1945 tsunami in the MSZ showed that the slip needs to be extended to deep waters around the depth contour of 3000 m in order to reproduce the observed tide gauge waveforms at Karachi and Mumbai. On the other hand, coastal uplift report at Ormara (Pakistan) implies that the source fault needs to be extended inland. In comparison to other existing fault models, our fault model is longer and includes a heterogeneous slip with larger maximum slip. The recent tsunami on 24 September 2013 in the Makran region was triggered by an inland Mw 7.7 earthquake. While the main shock and all aftershocks were located inland, a tsunami with a dominant period of around 12 min was recorded on tide gauges and a DART station. We examined different possible sources for this tsunami including a mud volcano, a mud/shale diapir, and a landslide/slump through numerical modeling. Only a submarine slump with a source dimension of 10-15 km and a thickness of around 100 m, located 60-70 km offshore Jiwani (Pakistan) at the water depth of around 2000m, was able to reasonably reproduce the observed tsunami waveforms. In terms of tsunami hazards, analyses of the two tsunamis provide new insights: 1) large runup heights can be generated in the coastal areas due to slip in deep waters, and 2) even an inland earthquake may generate tsunamigenic submarine landslides.

Floodplain ecohydrology: Climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees

PubMed Central

Singer, Michael Bliss; Sargeant, Christopher I; Piégay, Hervé; Riquier, Jérémie; Wilson, Rob J S; Evans, Cristina M

2014-01-01

Seasonal and annual partitioning of water within river floodplains has important implications for ecohydrologic links between the water cycle and tree growth. Climatic and hydrologic shifts alter water distribution between floodplain storage reservoirs (e.g., vadose, phreatic), affecting water availability to tree roots. Water partitioning is also dependent on the physical conditions that control tree rooting depth (e.g., gravel layers that impede root growth), the sources of contributing water, the rate of water drainage, and water residence times within particular storage reservoirs. We employ instrumental climate records alongside oxygen isotopes within tree rings and regional source waters, as well as topographic data and soil depth measurements, to infer the water sources used over several decades by two co-occurring tree species within a riparian floodplain along the Rhône River in France. We find that water partitioning to riparian trees is influenced by annual (wet versus dry years) and seasonal (spring snowmelt versus spring rainfall) fluctuations in climate. This influence depends strongly on local (tree level) conditions including floodplain surface elevation and subsurface gravel layer elevation. The latter represents the upper limit of the phreatic zone and therefore controls access to shallow groundwater. The difference between them, the thickness of the vadose zone, controls total soil moisture retention capacity. These factors thus modulate the climatic influence on tree ring isotopes. Additionally, we identified growth signatures and tree ring isotope changes associated with recent restoration of minimum streamflows in the Rhône, which made new phreatic water sources available to some trees in otherwise dry years. Key Points Water shifts due to climatic fluctuations between floodplain storage reservoirs Anthropogenic changes to hydrology directly impact water available to trees Ecohydrologic approaches to integration of hydrology afford new possibilities PMID:25506099

Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in soils and groundwater of a U.S. metropolitan area: migration and implications for human exposure.

PubMed

Xiao, Feng; Simcik, Matt F; Halbach, Thomas R; Gulliver, John S

2015-04-01

Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are emerging anthropogenic compounds that have recently become the target of global concern due to their ubiquitous presence in the environment, persistence, and bioaccumulative properties. This study was carried out to investigate the migration of PFOS and PFOA in soils and groundwater in a U.S. metropolitan area. We observed elevated levels in surface soils (median: 12.2 ng PFOS/g dw and 8.0 ng PFOA/g dw), which were much higher than the soil-screening levels for groundwater protection developed in this study. The measured levels in subsurface soils show a general increase with depth, suggesting a downward movement toward the groundwater table and a potential risk of aquifer contamination. Furthermore, concentrations of PFOS and PFOA in monitoring wells in the source zone varied insignificantly over 5 years (2009-2013), suggesting limited or no change in either the source or the magnitude of the source. The analysis also shows that natural processes of dispersion and dilution can significantly attenuate the groundwater contamination; the adsorption on aquifer solids, on the other hand, appears to have limited effects on the transport of PFOS and PFOA in the aquifer. The probabilistic exposure assessment indicates that ingestion of contaminated groundwater constitutes a much more important exposure route than ingestion of contaminated soil. Overall, the results suggest that (i) the transport of PFOS and PFOA is retarded in the vadose zone, but not in the aquifer; (ii) the groundwater contamination of PFOS and PFOA often follows their release to surface soils by years, if not decades; and (iii) the aquifer can be a major source of exposure for communities living near point sources. Copyright © 2014 Elsevier Ltd. All rights reserved.

A steep peripheral ring in irregular cornea topography, real or an instrument error?

PubMed

Galindo-Ferreiro, Alicia; Galvez-Ruiz, Alberto; Schellini, Silvana A; Galindo-Alonso, Julio

2016-01-01

To demonstrate that the steep peripheral ring (red zone) on corneal topography after myopic laser in situ keratomileusis (LASIK) could possibly due to instrument error and not always to a real increase in corneal curvature. A spherical model for the corneal surface and modifying topography software was used to analyze the cause of an error due to instrument design. This study involved modification of the software of a commercially available topographer. A small modification of the topography image results in a red zone on the corneal topography color map. Corneal modeling indicates that the red zone could be an artifact due to an instrument-induced error. The steep curvature changes after LASIK, signified by the red zone, could be also an error due to the plotting algorithms of the corneal topographer, besides a steep curvature change.

Seismological investigation of earthquakes in the New Madrid Seismic Zone. Final report, September 1986--December 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herrmann, R.B.; Nguyen, B.

Earthquake activity in the New Madrid Seismic Zone had been monitored by regional seismic networks since 1975. During this time period, over 3,700 earthquakes have been located within the region bounded by latitudes 35{degrees}--39{degrees}N and longitudes 87{degrees}--92{degrees}W. Most of these earthquakes occur within a 1.5{degrees} x 2{degrees} zone centered on the Missouri Bootheel. Source parameters of larger earthquakes in the zone and in eastern North America are determined using surface-wave spectral amplitudes and broadband waveforms for the purpose of determining the focal mechanism, source depth and seismic moment. Waveform modeling of broadband data is shown to be a powerful toolmore » in defining these source parameters when used complementary with regional seismic network data, and in addition, in verifying the correctness of previously published focal mechanism solutions.« less

Trace elements in garnet reveal multiple fluid pulses in eclogite, Ring Mountain, CA

NASA Astrophysics Data System (ADS)

Cruz-Uribe, A. M.; Page, F. Z.; Lozier, E.; Feineman, M. D.; Zack, T.; Mertz-Kraus, R.

2017-12-01

Garnetite veins in a hornblende-eclogite block from Ring Mountain, CA, offer a unique opportunity to investigate the chemical composition of fluid interactions during mélange formation in subduction zones. Garnet occurs as matrix porphyroblasts (2-5 mm) and in 1-5 cm garnetite veins that are laterally continuous up to 10 m across the outcrop. Garnet at the vein edges is slightly larger (300-600 µm) than within the veins (5-50 µm), and records a protracted history of vein garnet growth. Major and trace element concentrations in garnet were determined using EPMA and LA-ICP-MS, respectively. Detailed rim-to-rim trace element traverses were performed using 12 µm spots at 15 µm spacing across one matrix garnet (2 mm) and three vein edge garnet grains (375-570 µm). Zoning in Mn, Ca, and rare earth elements (REE) reveal 5 distinct garnet growth zones. Zone 1, found only in matrix garnet cores, is characterized by decreasing Mn and increasing Ca and is interpreted to reflect prograde zoning. Zones 2-5 are found in the mantles and rims of matrix garnet, and comprise the entirety of vein garnet. Garnet growth in Zones 2-5 is likely heavily influenced by internally- and externally-derived fluids, based on texture and chemistry. One key fluid-related texture of Zones 2-5 is oscillatory birefringence zoning, likely the result of incorporation of small amounts of water into the garnet structure (i.e., hydrogrossular). Zones 2 and 3 are characterized by progressive enrichment in heavy to middle REE from Zone 2 outward into Zone 3. We attribute this to diffusion-limited uptake of REE, wherein the heaviest REE are incorporated first, followed by progressively lighter REE. Zone 3 is also characterized by a high-Mn annulus that appears decoupled from the trace elements. Zone 4 is characterized by a sudden drop in Ca and enrichment in MREE, particularly Dy and Tb, possibly due to epidote breakdown. Zone 5 is characterized by strong enrichment in Mn+REE, with high-HREE and high-MREE oscillatory zones. Oxygen isotope values (δ18O, VSMOW) in Zone 1 (matrix cores) and Zones 2-4 are consistently 10 ‰, indicating that the fluid source for Zones 2-4 is likely internally-derived, or derived from mélange of similar bulk composition. δ18O values for Zone 5 cluster at 7 ‰, which indicates the addition of an externally-derived fluid with low δ18O and high Mn+REE.

Seismic Sources and Recurrence Rates as Adopted by USGS Staff for the Production of the 1982 and 1990 Probabilistic Ground Motion Maps for Alaska and the Conterminous United States

USGS Publications Warehouse

Hanson, Stanley L.; Perkins, David M.

1995-01-01

The construction of a probabilistic ground-motion hazard map for a region follows a sequence of analyses beginning with the selection of an earthquake catalog and ending with the mapping of calculated probabilistic ground-motion values (Hanson and others, 1992). An integral part of this process is the creation of sources used for the calculation of earthquake recurrence rates and ground motions. These sources consist of areas and lines that are representative of geologic or tectonic features and faults. After the design of the sources, it is necessary to arrange the coordinate points in a particular order compatible with the input format for the SEISRISK-III program (Bender and Perkins, 1987). Source zones are usually modeled as a point-rupture source. Where applicable, linear rupture sources are modeled with articulated lines, representing known faults, or a field of parallel lines, representing a generalized distribution of hypothetical faults. Based on the distribution of earthquakes throughout the individual source zones (or a collection of several sources), earthquake recurrence rates are computed for each of the sources, and a minimum and maximum magnitude is assigned. Over a period of time from 1978 to 1980 several conferences were held by the USGS to solicit information on regions of the United States for the purpose of creating source zones for computation of probabilistic ground motions (Thenhaus, 1983). As a result of these regional meetings and previous work in the Pacific Northwest, (Perkins and others, 1980), California continental shelf, (Thenhaus and others, 1980), and the Eastern outer continental shelf, (Perkins and others, 1979) a consensus set of source zones was agreed upon and subsequently used to produce a national ground motion hazard map for the United States (Algermissen and others, 1982). In this report and on the accompanying disk we provide a complete list of source areas and line sources as used for the 1982 and later 1990 seismic hazard maps for the conterminous U.S. and Alaska. These source zones are represented in the input form required for the hazard program SEISRISK-III, and they include the attenuation table and several other input parameter lines normally found at the beginning of an input data set for SEISRISK-III.

Fluid geochemistry of a deep-seated geothermal resource in the Puna plateau (Jujuy Province, Argentina)

NASA Astrophysics Data System (ADS)

Peralta Arnold, Y.; Cabassi, J.; Tassi, F.; Caffe, P. J.; Vaselli, O.

2017-05-01

This study focused on the geochemical and isotopic features of thermal fluids discharged from five zones located in the high altitude Puna plateau (Jujuy Province between S 22°20‧-23°20‧ and W 66°-67°), i.e. Granada, Vilama, Pairique, Coranzulí and Olaroz. Partially mature waters with a Na+-Cl- composition were recognized in all the investigated zones, suggesting that a deep hydrothermal reservoir hosted within the Paleozoic crystalline basement represents the main hydrothermal fluid source. The hydrothermal reservoirs are mainly recharged by meteoric water, although based on the δ18O-H2O and δD-H2O values, some contribution of andesitic water cannot be completely ruled out. Regional S-oriented faulting systems, which generated a horst and graben tectonics, and NE-, NW- and WE-oriented transverse structures, likely act as preferentially uprising pathways for the deep-originated fluids, as also supported by the Rc/Ra values (up to 1.39) indicating the occurrence of significant amounts of mantle He (up to 16%). Carbon dioxide, the most abundant compound in the gas phase associated with the thermal waters, mostly originated from a crustal source, although the occurrence of CO2 from a mantle source, contaminated by organic-rich material due to the subduction process, is also possible. Relatively small and cold Na+-HCO3--type aquifers were produced by the interaction between meteoric water and Cretaceous, Palaeogene to Miocene sediments. Dissolution of evaporitic surficial deposits strongly affected the chemistry of the thermal springs in the peripheral zones of the study area. Geothermometry in the Na-K-Ca-Mg system suggested equilibrium temperatures up to 200 °C for the deep aquifer, whereas lower temperatures (from 105 to 155 °C) were inferred by applying the H2 geothermometer, likely due to re-equilibrium processes during the thermal fluid uprising within relatively shallow Na-HCO3 aquifers. The great depth of the geothermal resource (possibly > 5000 m b.g.l.) is likely preventing further studies aimed to evaluate possible exploitation, although the occurrence of Li- and Ba-rich deposits associated may attract financial investments, giving a pulse for the development of this remote region.

Magma-tectonic interactions in Kīlauea's Southwest Rift Zone in 2006 through coupled geodetic/seismological analysis

NASA Astrophysics Data System (ADS)

Wauthier, C.; Roman, D. C.; Poland, M. P.

2015-12-01

For much of the first 20 years of Kīlauea's 1983-present Pu'u 'Ō'ō eruption, deformation was characterized by subsidence at the volcano's summit and along both the East Rift Zone (ERZ) and Southwest Rift Zone (SWRZ). At the end of 2003, however, Kīlauea's summit began a 4-year period of inflation due to a surge in magma supply to the volcano. In 2006, the SWRZ also experienced atypical inflation, which was last observed in 1981-82 during a series of dike intrusions. To investigate the active magma sources and their interactions with faulting in the SWRZ during 2006, we integrate contemporary geodetic data from InSAR and GPS with double-couple fault-plane solutions for volcano-tectonic earthquakes and Coulomb stress modeling. According to the rate of deformation measured in daily GPS data, two distinct periods can be defined, spanning January to 15 March 2006 (period 1) and 16 March to 30 September 2006 (period 2). Geodetic models suggest that, during period 1, deformation, due to pressurization of magma in a vertical prolate-spheroidal conduit, in the south caldera area. In addition, a major seismic swarm occurred in both the SWRZ and ERZ. Our preliminary results also suggest that, during period 2, magma was still overpressurizing the same prolate-spheroid but a subhorizontal sill also intruded further to the southwest in the seismic SWRZ (SSWRZ). The beginning of period 2 also corresponds to a switch from subsidence to inflation of the SWRZ. Faulting in the upper ERZ is primarily strike-slip, with no obvious change in FPS orientation between periods 1 and 2. In contrast, faulting in the upper SSWRZ occurs as dip-slip motion on near-vertical faults. SSWRZ FPS show a mix of orientations including NW- and NE-striking faults, which along with relative earthquake locations, suggest a series of right-stepping fault segments, particularly during period 2. Calculated Coulomb stress changes indicate that faulting in the upper SSWRZ may result from stresses produced by inflation of the geodetically modeled sources described above, in particular the prolate spheroid located in the south caldera area. In contrast, earthquakes in the ERZ are generally inhibited by the geodetically modeled sources, suggesting that another process may be responsible for faulting along the ERZ.

Health risk assessment of arsenic from blended water in distribution systems.

PubMed

Zhang, Hui; Zhou, Xue; Wang, Kai; Wang, Wen D

2017-12-06

In a water distribution system with different sources, water blending occurs, causing specific variations of the arsenic level. This study was undertaken to investigate the concentration and cancer risk of arsenic in blended water in Xi'an city. A total of 672 tap water samples were collected from eight sampling points in the blending zones for arsenic determination. The risk was evaluated through oral ingestion and dermal absorption, separately for males and females, as well as with respect to seasons and blending zones. Although the arsenic concentrations always fulfilled the requirements of the World Health Organization (WHO) (≤10 μg L -1 ), the total cancer risk value was higher than the general guidance risk value of 1.00 × 10 -6 . In the blending zone of the Qujiang and No.3 WTPs (Z2), the total cancer risk value was over 1.00 × 10 -5 , indicating that public health would be affected to some extent. More than 99% of the total cancer risk was from oral ingestion, and dermal absorption had a little contribution. With higher exposure duration and lower body weight, women had a higher cancer risk. In addition, due to several influential factors, the total cancer risk in the four blending zones reached the maximum in different seasons. The sensitivity analysis by the tornado chart proved that body weight, arsenic concentration and ingestion rate significantly contributed to cancer risk. This study suggests the regular monitoring of water blending zones for improving risk management.

Assessment of groundwater quality by unsaturated zone study due to migration of leachate from Abloradjei waste disposal site, Ghana

NASA Astrophysics Data System (ADS)

Egbi, Courage Davidson; Akiti, Tetteh Thomas; Osae, Shiloh; Dampare, Samuel Boakye; Abass, Gibrilla; Adomako, Dickson

2017-05-01

Leachate generated by open solid waste disposal sites contains substances likely to contaminate groundwater. The impact of potential contaminants migrating from leachate on groundwater can be quantified by monitoring their concentration and soil properties at specific points in the unsaturated zone. In this study, physical and chemical analyses were carried out on leachate, soil and water samples within the vicinity of the municipal solid waste disposal site at Abloradjei, a suburb of Accra, Ghana. The area has seen a massive increase in population and the residents depend on groundwater as the main source of water supply. Results obtained indicate alkaline pH for leachate and acidic conditions for unsaturated zone water. High EC values were recorded for leachate and unsaturated zone water. Major ions (Ca2+, Na+, Mg2+, K+, NO3 -, SO4 2-, Cl-, PO4 3- were analysed in leachate, unsaturated zone water, soil solution and groundwater while trace metals (Al, Fe, Cu, Zn, Pb) were analysed in both soil and extracted soil solution. Concentrations of major ions were high in all samples indicating possible anthropogenic origin. Mean % gravel, % sand, % clay, bulk density, volumetric water content and porosity were 28.8, 63.93, 6.6, 1 g cm-3, 35 and 62.7 %, respectively. Distribution of trace elements showed Kd variation of Al > Cu > Fe > Pb > Zn in the order of sequential increasing solubility. It was observed that the quality of groundwater is not suitable for drinking.

Estimating organic maturity from well logs, Upper Cretaceous Austin Chalk, Texas Gulf coast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hines, G.A.; Berg, R.R.

1990-09-01

The Austin Chalk is both a source rock for oil and a fractured reservoir, and the evaluation of its organic maturity from well logs could be an aid to exploration and production. Geochemical measurements have shown three zones of organic maturity for source materials: (1) an immature zone to depths of 6,000 ft, (2) a peak-generation and accumulation zone from 6,000 to 6,500 ft, and (3) a mature, expulsion and migration zone below 6,500 ft. The response of common well logs identifies these zones. True resistivity (R{sub t}) is low in the immature zone, increases to a maximum in themore » peak-generation zone, and decreases to intermediate values in the expulsion zone. Density and neutron porosities are different in the immature zone but are nearly equal in the peak generation and expulsion zones. Correlations with conventional core analyses indicate that R{sub t} values between 9 and 40 ohm-m in the expulsion zone reflect a moveable oil saturation of 10 to 20% in the rock matrix. The moveable saturation provides oil from the matrix to fractures and is essential for sustained oil production. Therefore, the evaluation of moveable oil from well logs could be important in exploration.« less

Assessment of source of information for polio supplementary immunization activities in 2014 and 2015, Somali, Ethiopia.

PubMed

Bedada, Selamawit Yilma; Gallagher, Kathleen; Aregay, Aron Kassahun; Mohammed, Bashir; Maalin, Mohammed Adem; Hassen, Hassen Abdisemed; Ali, Yusuf Mohammed; Braka, Fiona; Kilebou, Pierre M'pele

2017-01-01

Communication is key for the successful implementation of polio vaccination campaigns. The purpose of this study is to review and analyse the sources of information utilized by caregivers during polio supplementary immunization activities (SIAs) in Somali, Ethiopia in 2014 and 2015. Data on sources of information about the polio campaign were collected post campaign from caregivers by trained data collectors as part of house to house independent monitoring. The sources of information analysed in this paper include town criers (via megaphones), health workers, religious leaders, kebele leaders (Kebele is the lowest administrative structure in Ethiopia), radio, television, text message and others. The repetition of these sources of information was analysed across years and zones for trends. Polio vaccination campaign coverage was also reviewed by year and zones within the Somali region in parallel with the major sources of information used in the respective year and zones. 57,745 responses were used for this analysis but the responses were received from < or = 57,745 individuals since some of them may provide more than one response. Moreover, because sampling of households is conducted independently during each round of independent monitoring, the same household may have been included more than once in our analysis. The methodology used for independent monitoring does not allow for the calculation of response rates. Monitors go from house to house until information from 20 households is received. From the total 57,745 responses reviewed, over 37% of respondents reported that town criers were their source for information about the 2014 and 2015 polio SIAs. Zonal trends in using town criers as a major source of information in both study years remained consistent except in two zones. 87.5% of zones that reported at least 90% coverage during both study years had utilized town criers as a major source of information while the rest (12.5%) used health workers. We found that town criers were consistently the major source of information about the polio campaigns for Somali region parents and caregivers during polio immunization days held in 2014 and 2015. Health workers and kebele leaders were also important sources of information about the polio campaign for parents.

The Impact of In-situ Chemical Oxidation on Contaminant Mass Discharge: Linking Source-Zone and Plume-Scale Characterizations of Remediation Performance

NASA Astrophysics Data System (ADS)

Brusseau, M. L.; Carroll, K. C.; Baker, J. B.; Allen, T.; DiGuiseppi, W.; Hatton, J.; Morrison, C.; Russo, A. E.; Berkompas, J. L.

2011-12-01

A large-scale permanganate-based in-situ chemical oxidation (ISCO) effort has been conducted over the past ten years at a federal Superfund site in Tucson, AZ, for which trichloroethene (TCE) is the primary contaminant of concern. Remediation performance was assessed by examining the impact of treatment on contaminant mass discharge, an approach that has been used for only a very few prior ISCO projects. Contaminant mass discharge tests were conducted before and after permanganate injection to measure the impact at the source-zone scale. The results indicate that ISCO caused a significant reduction in mass discharge (approximately 75%). The standard approach of characterizing discharge at the source-zone scale was supplemented with additional characterization at the plume scale, which was evaluated by examining the change in contaminant mass discharge associated with the pump-and-treat system. The integrated contaminant mass discharge decreased by approximately 70%, consistent with the source-zone-scale measurements. The integrated mass discharge rebounded from 0.1 to 0.2 Kg/d within one year after cessation of permanganate injections, after which it has been stable for several years. Collection of the integrated contaminant mass discharge data throughout the ISCO treatment period provided a high-resolution, real-time analysis of the site-wide impact of ISCO, thereby linking source-zone remediation to impacts on overall risk. The results indicate that ISCO was successful in reducing contaminant mass discharge at this site, which comprises a highly heterogeneous subsurface environment. Analysis of TCE sediment concentration data for core material collected before and after ISCO supports the hypothesis that the remaining mass discharge is associated in part with poorly-accessible contaminant mass residing within lower-permeability zones.

Impact of in situ chemical oxidation on contaminant mass discharge: linking source-zone and plume-scale characterizations of remediation performance.

PubMed

Brusseau, M L; Carroll, K C; Allen, T; Baker, J; Diguiseppi, W; Hatton, J; Morrison, C; Russo, A; Berkompas, J

2011-06-15

A large-scale permanganate-based in situ chemical oxidation (ISCO) effort has been conducted over the past ten years at a federal Superfund site in Tucson, AZ, for which trichloroethene (TCE) is the primary contaminant of concern. Remediation performance was assessed by examining the impact of treatment on contaminant mass discharge, an approach that has been used for only a very few prior ISCO projects. Contaminant mass discharge tests were conducted before and after permanganate injection to measure the impact at the source-zone scale. The results indicate that ISCO caused a significant reduction in mass discharge (approximately 75%). The standard approach of characterizing discharge at the source-zone scale was supplemented with additional characterization at the plume scale, which was evaluated by examining the change in contaminant mass discharge associated with the pump-and-treat system. The integrated contaminant mass discharge decreased by approximately 70%, consistent with the source-zone-scale measurements. The integrated mass discharge rebounded from 0.1 to 0.2 kg/d within one year after cessation of permanganate injections, after which it has been stable for several years. Collection of the integrated contaminant mass discharge data throughout the ISCO treatment period provided a high-resolution, real-time analysis of the site-wide impact of ISCO, thereby linking source-zone remediation to impacts on overall risk. The results indicate that ISCO was successful in reducing contaminant mass discharge at this site, which comprises a highly heterogeneous subsurface environment. Analysis of TCE sediment concentration data for core material collected before and after ISCO supports the hypothesis that the remaining mass discharge is associated in part with poorly accessible contaminant mass residing within lower-permeability zones.

Soil water nitrate concentrations in giant cane and forest riparian buffer zones

Treesearch

Jon E. Schoonover; Karl W. J. Williard; James J. Zaczek; Jean C. Mangun; Andrew D. Carver

2003-01-01

Soil water nitrate concentrations in giant cane and forest riparian buffer zones along Cypress Creek in southern Illinois were compared to determine if the riparian zones were sources or sinks for nitrogen in the rooting zone. Suction lysimeters were used to collect soil water samples from the lower rooting zone in each of the two vegetation types. The cane riparian...

PLANT INVASIONS IN RHODE ISLAND RIPARIAN ZONES

EPA Science Inventory

The vegetation in riparian zones provides valuable wildlife habitat while enhancing instream habitat and water quality. Forest fragmentation, sunlit edges, and nutrient additions from adjacent development may be sources of stress on riparian zones. Landscape plants may include no...

TREATMENT OF A SATURATED ZONE HEXAVALENT CHROMIUM SOURCE AREA USING A FERROUS SULFATE/SODIUM DITHIONITE MIXTURE: A FIELD PILOT STUDY

EPA Science Inventory

A field pilot study was conducted to evaluate the performance of a combined ferrous sulfate/sodium dithionite solution for in situ treatment of a saturated zone hexavalent chromium source area at a former ferrochromium alloy production facility in Charleston, S.C. The saturate...

Distributed watershed modeling of design storms to identify nonpoint source loading areas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Endreny, T.A.; Wood, E.F.

1999-03-01

Watershed areas that generate nonpoint source (NPS) polluted runoff need to be identified prior to the design of basin-wide water quality projects. Current watershed-scale NPS models lack a variable source area (VSA) hydrology routine, and are therefore unable to identify spatially dynamic runoff zones. The TOPLATS model used a watertable-driven VSA hydrology routine to identify runoff zones in a 17.5 km{sup 2} agricultural watershed in central Oklahoma. Runoff areas were identified in a static modeling framework as a function of prestorm watertable depth and also in a dynamic modeling framework by simulating basin response to 2, 10, and 25 yrmore » return period 6 h design storms. Variable source area expansion occurred throughout the duration of each 6 h storm and total runoff area increased with design storm intensity. Basin-average runoff rates of 1 mm h{sup {minus}1} provided little insight into runoff extremes while the spatially distributed analysis identified saturation excess zones with runoff rates equaling effective precipitation. The intersection of agricultural landcover areas with these saturation excess runoff zones targeted the priority potential NPS runoff zones that should be validated with field visits. These intersected areas, labeled as potential NPS runoff zones, were mapped within the watershed to demonstrate spatial analysis options available in TOPLATS for managing complex distributions of watershed runoff. TOPLATS concepts in spatial saturation excess runoff modelling should be incorporated into NPS management models.« less

Analytical method for optimal source reduction with monitored natural attenuation in contaminated aquifers

USGS Publications Warehouse

Widdowson, M.A.; Chapelle, F.H.; Brauner, J.S.; ,

2003-01-01

A method is developed for optimizing monitored natural attenuation (MNA) and the reduction in the aqueous source zone concentration (??C) required to meet a site-specific regulatory target concentration. The mathematical model consists of two one-dimensional equations of mass balance for the aqueous phase contaminant, to coincide with up to two distinct zones of transformation, and appropriate boundary and intermediate conditions. The solution is written in terms of zone-dependent Peclet and Damko??hler numbers. The model is illustrated at a chlorinated solvent site where MNA was implemented following source treatment using in-situ chemical oxidation. The results demonstrate that by not taking into account a variable natural attenuation capacity (NAC), a lower target ??C is predicted, resulting in unnecessary source concentration reduction and cost with little benefit to achieving site-specific remediation goals.

A Hyporheic Mesocosm Experiment: Influence of Quantity and Quality of stream-source DOC on Rates of Hyporheic Metabolism

NASA Astrophysics Data System (ADS)

Serchan, S. P.; Wondzell, S. M.; Haggerty, R.; Pennington, R.; Feris, K. P.; Sanfilippo, A. R.; Reeder, W. J.; Tonina, D.

2016-12-01

Hyporheic zone biogeochemical processes can influence stream water chemistry. Some estimates show that 50-90% stream water CO2 is produced in the hyporheic zone through heterotrophic metabolism of organic matter, usually supplied from the stream as dissolved organic carbon (DOC). Preliminary results from our well network at the HJ Andrews WS1, indicate that dissolved inorganic carbon (DIC) is 1.5-2 times higher in the hyporheic zone than in stream water. Conversely, DOC (mg/L) is 1.5 times higher in stream water than in the hyporheic zone throughout the year. Overall, the hyporheic zone appears to be a net source of DIC. However, the increase in DIC along hyporheic flow paths is approximately 10-times greater than the loss of DOC, suggesting that metabolism of buried particulate organic carbon (POC) is a major source of organic carbon for microbial metabolism. However, we cannot completely rule out alternative sources of DIC, especially those originating in the overlying riparian soil, because hyporheic processes are difficult to isolate in well networks. To study hyporheic zone biogeochemical processes, particularly the transformation of organic carbon to inorganic carbon species, we designed and built six replicate 2-m long hyporheic mesocosms in which we are conducting DOC amendment experiments. We examine the role of DOC quality and quantity on hyporheic respiration by injecting labile (acetate) and refractory (fulvic acid) organic carbon and comparing rates of O2 consumption, DOC loss, and DIC gains against a control. We expect that stream source DOC is limiting in this small headwater stream, forcing hyporheic metabolism to rely on buried POC. However, the long burial time of POC suggests it is likely of low quality so that supplying labile DOC in stream water should shift hyporheic metabolism away from POC rather than increase the overall rate of metabolism. Future experiments will examine natural sources of DOC (stream periphyton, leaf, and soil humic horizon leachates), the breakdown of wood buried in the hyporheic zone, and the role of temperature and nutrients in controlling the rate at which buried POC is metabolized.

The ZONMET thermodynamic and kinetic model of metal condensation

NASA Astrophysics Data System (ADS)

Petaev, Michail I.; Wood, John A.; Meibom, Anders; Krot, Alexander N.; Keil, Klaus

2003-05-01

The ZONMET model of metal condensation is a FORTRAN computer code that calculates condensation with partial isolation-type equilibrium partitioning of the 19 most abundant elements among 203 gaseous and 488 condensed phases and growth in the nebula of a zoned metal grain by condensation from the nebular gas accompanied by diffusional redistribution of Ni, Co, and Cr. Of five input parameters of the ZONMET model (chemical composition of the system expressed as the dust/gas [ D/ G] ratio, nebular pressure [ Ptot], isolation degree [ξ], cooling rate ( CR), and seed size), only two—the D/ G ratio and the CR of the nebular source region of a zoned Fe,Ni grain—are important in determining the grain radius and Ni, Co, and Cr zoning profiles. We found no evidence for the supercooling during condensation of Fe,Ni metal that is predicted by the homogeneous nucleation theory. The model allows estimates to be made of physicochemical parameters in the CH chondrite nebular source regions. Modeling growth and simultaneous diffusional redistribution of Ni, Co, and Cr in the zoned metal grains of CH chondrites reveals that the condensation zoning profiles were substantially modified by diffusion while the grains were growing in the nebula. This means that previous estimates of the physicochemical conditions in the nebular source regions of CH and CB chondrites, based on measured zoning profiles of Ni, Co, Cr, and platinum group elements in Fe,Ni metal grains, need to be corrected. The two zoned metal grains in the PAT 91456 and NWA 470 CH chondrites studied so far require nebular source regions with different chemical compositions ( D/ G = 1 and D/ G = 4, respectively) and thermal histories characterized by variable cooling rates ( CR = 0.011 + 0.0022 × Δ T K/h and CR = 0.05 + 0.0035 × Δ T K/h, respectively). It appears that the metal grains of the CH chondrites were formed in multiple nebular source regions or in different events within the same source region as the CB chondrite metal grains were formed.

Sources of groundwater based on Helium analyses in and near the freshwater/saline-water transition zone of the San Antonio segment of the Edwards Aquifer, South-Central Texas, 2002-03

USGS Publications Warehouse

Hunt, Andrew G.; Lambert, Rebecca B.; Fahlquist, Lynne

2010-01-01

This report evaluates dissolved noble gas data, specifically helium-3 and helium-4, collected by the U.S. Geological Survey, in cooperation with the San Antonio Water System, during 2002-03. Helium analyses are used to provide insight into the sources of groundwater in the freshwater/saline-water transition zone of the San Antonio segment of the Edwards aquifer. Sixty-nine dissolved gas samples were collected from 19 monitoring wells (categorized as fresh, transitional, or saline on the basis of dissolved solids concentration in samples from the wells or from fluid-profile logging of the boreholes) arranged in five transects, with one exception, across the freshwater/saline-water interface (the 1,000-milligrams-per-liter dissolved solids concentration threshold) of the Edwards aquifer. The concentration of helium-4 (the dominant isotope in atmospheric and terrigenic helium) in samples ranged from 63 microcubic centimeters per kilogram at standard temperature (20 degrees Celsius) and pressure (1 atmosphere) in a well in the East Uvalde transect to 160,587 microcubic centimeters per kilogram at standard temperature and pressure in a well in the Kyle transect. Helium-4 concentrations in the 10 saline wells generally increase from the western transects to the eastern transects. Increasing helium-4 concentrations from southwest to northeast in the transition zone, indicating increasing residence time of groundwater from southwest to northeast, is consistent with the longstanding conceptualization of the Edwards aquifer in which water recharges in the southwest, flows generally northeasterly (including in the transition zone, although more slowly than in the fresh-water zone), and discharges at major springs in the northeast. Excess helium-4 was greater than 1,000 percent for 60 of the 69 samples, indicating that terrigenic helium is largely present and that most of the excess helium-4 comes from sources other than the atmosphere. The helium data of this report cannot be used to identify sources of groundwater in and near the transition zone of the Edwards aquifer in terms of specific geologic (stratigraphic) units or hydrogeologic units (aquifers or confining units). However, the data indicate that the source or sources of the helium, and thus the water in which the helium is dissolved, in the transition zone are mostly terrigenic in origin rather than atmospheric. Whether most helium in and near the transition zone of the Edwards aquifer originated either in rocks outside the transition zone and at depth or in the adjacent Trinity aquifer is uncertain; but most of the helium in the transition zone had to enter the transition zone from the Trinity aquifer because the Trinity aquifer is the hydrogeologic unit immediately beneath and laterally adjacent to the transition zone of the Edwards aquifer. Thus the helium data support a hypothesis of sufficient hydraulic connection between the Trinity and Edwards aquifers to allow movement of water from the Trinity aquifer to the transition zone of the Edwards aquifer.

Coda Q Attenuation and Source Parameters Analysis in North East India Using Local Earthquakes

NASA Astrophysics Data System (ADS)

Mohapatra, A. K.; Mohanty, W. K.; Earthquake Seismology

2010-12-01

Alok Kumar Mohapatra1* and William Kumar Mohanty1 *Corresponding author: alokgpiitkgp@gmail.com 1Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, West Bengal, India. Pin-721302 ABSTRACT In the present study, the quality factor of coda waves (Qc) and the source parameters has been estimated for the Northeastern India, using the digital data of ten local earthquakes from April 2001 to November 2002. Earthquakes with magnitude range from 3.8 to 4.9 have been taken into account. The time domain coda decay method of a single back scattering model is used to calculate frequency dependent values of Coda Q (Qc) where as, the source parameters like seismic moment(Mo), stress drop, source radius(r), radiant energy(Wo),and strain drop are estimated using displacement amplitude spectrum of body wave using Brune's model. The earthquakes with magnitude range 3.8 to 4.9 have been used for estimation Qc at six central frequencies 1.5 Hz, 3.0 Hz, 6.0 Hz, 9.0 Hz, 12.0 Hz, and 18.0 Hz. In the present work, the Qc value of local earthquakes are estimated to understand the attenuation characteristic, source parameters and tectonic activity of the region. Based on a criteria of homogeneity in the geological characteristics and the constrains imposed by the distribution of available events the study region has been classified into three zones such as the Tibetan Plateau Zone (TPZ), Bengal Alluvium and Arakan-Yuma Zone (BAZ), Shillong Plateau Zone (SPZ). It follows the power law Qc= Qo (f/fo)n where, Qo is the quality factor at the reference frequency (1Hz) fo and n is the frequency parameter which varies from region to region. The mean values of Qc reveals a dependence on frequency, varying from 292.9 at 1.5 Hz to 4880.1 at 18 Hz. Average frequency dependent relationship Qc values obtained of the Northeastern India is 198 f 1.035, while this relationship varies from the region to region such as, Tibetan Plateau Zone (TPZ): Qc= 226 f 1.11, Bengal Alluvium and Arakan-Yuma Zone (BAZ) : Qc= 301 f 0.87, Shillong Plateau Zone (SPZ): Qc=126 fo 0.85. It indicates Northeastern India is seismically active but comparing of all zones in the study region the Shillong Plateau Zone (SPZ): Qc= 126 f 0.85 is seismically most active. Where as the Bengal Alluvium and Arakan-Yuma Zone (BAZ) are less active and out of three the Tibetan Plateau Zone (TPZ)is intermediate active. This study may be useful for the seismic hazard assessment. The estimated seismic moments (Mo), range from 5.98×1020 to 3.88×1023 dyne-cm. The source radii(r) are confined between 152 to 1750 meter, the stress drop ranges between 0.0003×103 bar to 1.04×103 bar, the average radiant energy is 82.57×1018 ergs and the strain drop for the earthquake ranges from 0.00602×10-9 to 2.48×10-9 respectively. The estimated stress drop values for NE India depicts scattered nature of the larger seismic moment value whereas, they show a more systematic nature for smaller seismic moment values. The estimated source parameters are in agreement to previous works in this type of tectonic set up. Key words: Coda wave, Seismic source parameters, Lapse time, single back scattering model, Brune's model, Stress drop and North East India.

Modeling Degradation Product Partitioning in Chlorinated-DNAPL Source Zones

NASA Astrophysics Data System (ADS)

Boroumand, A.; Ramsburg, A.; Christ, J.; Abriola, L.

2009-12-01

Metabolic reductive dechlorination degrades aqueous phase contaminant concentrations, increasing the driving force for DNAPL dissolution. Results from laboratory and field investigations suggest that accumulation of cis-dichloroethene (cis-DCE) and vinyl chloride (VC) may occur within DNAPL source zones. The lack of (or slow) degradation of cis-DCE and VC within bioactive DNAPL source zones may result in these dechlorination products becoming distributed among the solid, aqueous, and organic phases. Partitioning of cis-DCE and VC into the organic phase may reduce aqueous phase concentrations of these contaminants and result in the enrichment of these dechlorination products within the non-aqueous phase. Enrichment of degradation products within DNAPL may reduce some of the advantages associated with the application of bioremediation in DNAPL source zones. Thus, it is important to quantify how partitioning (between the aqueous and organic phases) influences the transport of cis-DCE and VC within bioactive DNAPL source zones. In this work, abiotic two-phase (PCE-water) one-dimensional column experiments are modeled using analytical and numerical methods to examine the rate of partitioning and the capacity of PCE-DNAPL to reversibly sequester cis-DCE. These models consider aqueous-phase, nonaqueous phase, and aqueous plus nonaqueous phase mass transfer resistance using linear driving force and spherical diffusion expressions. Model parameters are examined and compared for different experimental conditions to evaluate the mechanisms controlling partitioning. Biot number, a dimensionless number which is an index of the ratio of the aqueous phase mass transfer rate in boundary layer to the mass transfer rate within the NAPL, is used to characterize conditions in which either or both processes are controlling. Results show that application of a single aqueous resistance is capable to capture breakthrough curves when DNAPL is distributed in porous media as low-saturation ganglia, while diffusion within the DNAPL should be considered for larger NAPL pools. These results offer important insights to the monitoring and interpretation of bioremediation strategies employed within DNAPL source zones.

Relationship between mass-flux reduction and source-zone mass removal: analysis of field data.

PubMed

Difilippo, Erica L; Brusseau, Mark L

2008-05-26

The magnitude of contaminant mass-flux reduction associated with a specific amount of contaminant mass removed is a key consideration for evaluating the effectiveness of a source-zone remediation effort. Thus, there is great interest in characterizing, estimating, and predicting relationships between mass-flux reduction and mass removal. Published data collected for several field studies were examined to evaluate relationships between mass-flux reduction and source-zone mass removal. The studies analyzed herein represent a variety of source-zone architectures, immiscible-liquid compositions, and implemented remediation technologies. There are two general approaches to characterizing the mass-flux-reduction/mass-removal relationship, end-point analysis and time-continuous analysis. End-point analysis, based on comparing masses and mass fluxes measured before and after a source-zone remediation effort, was conducted for 21 remediation projects. Mass removals were greater than 60% for all but three of the studies. Mass-flux reductions ranging from slightly less than to slightly greater than one-to-one were observed for the majority of the sites. However, these single-snapshot characterizations are limited in that the antecedent behavior is indeterminate. Time-continuous analysis, based on continuous monitoring of mass removal and mass flux, was performed for two sites, both for which data were obtained under water-flushing conditions. The reductions in mass flux were significantly different for the two sites (90% vs. approximately 8%) for similar mass removals ( approximately 40%). These results illustrate the dependence of the mass-flux-reduction/mass-removal relationship on source-zone architecture and associated mass-transfer processes. Minimal mass-flux reduction was observed for a system wherein mass removal was relatively efficient (ideal mass-transfer and displacement). Conversely, a significant degree of mass-flux reduction was observed for a site wherein mass removal was inefficient (non-ideal mass-transfer and displacement). The mass-flux-reduction/mass-removal relationship for the latter site exhibited a multi-step behavior, which cannot be predicted using some of the available simple estimation functions.

Rebound of a coal tar creosote plume following partial source zone treatment with permanganate.

PubMed

Thomson, N R; Fraser, M J; Lamarche, C; Barker, J F; Forsey, S P

2008-11-14

The long-term management of dissolved plumes originating from a coal tar creosote source is a technical challenge. For some sites stabilization of the source may be the best practical solution to decrease the contaminant mass loading to the plume and associated off-site migration. At the bench-scale, the deposition of manganese oxides, a permanganate reaction byproduct, has been shown to cause pore plugging and the formation of a manganese oxide layer adjacent to the non-aqueous phase liquid creosote which reduces post-treatment mass transfer and hence mass loading from the source. The objective of this study was to investigate the potential of partial permanganate treatment to reduce the ability of a coal tar creosote source zone to generate a multi-component plume at the pilot-scale over both the short-term (weeks to months) and the long-term (years) at a site where there is >10 years of comprehensive synoptic plume baseline data available. A series of preliminary bench-scale experiments were conducted to support this pilot-scale investigation. The results from the bench-scale experiments indicated that if sufficient mass removal of the reactive compounds is achieved then the effective solubility, aqueous concentration and rate of mass removal of the more abundant non-reactive coal tar creosote compounds such as biphenyl and dibenzofuran can be increased. Manganese oxide formation and deposition caused an order-of-magnitude decrease in hydraulic conductivity. Approximately 125 kg of permanganate were delivered into the pilot-scale source zone over 35 days, and based on mass balance estimates <10% of the initial reactive coal tar creosote mass in the source zone was oxidized. Mass discharge estimated at a down-gradient fence line indicated >35% reduction for all monitored compounds except for biphenyl, dibenzofuran and fluoranthene 150 days after treatment, which is consistent with the bench-scale experimental results. Pre- and post-treatment soil core data indicated a highly variable and random spatial distribution of mass within the source zone and provided no insight into the mass removed of any of the monitored species. The down-gradient plume was monitored approximately 1, 2 and 4 years following treatment. The data collected at 1 and 2 years post-treatment showed a decrease in mass discharge (10 to 60%) and/or total plume mass (0 to 55%); however, by 4 years post-treatment there was a rebound in both mass discharge and total plume mass for all monitored compounds to pre-treatment values or higher. The variability of the data collected was too large to resolve subtle changes in plume morphology, particularly near the source zone, that would provide insight into the impact of the formation and deposition of manganese oxides that occurred during treatment on mass transfer and/or flow by-passing. Overall, the results from this pilot-scale investigation indicate that there was a significant but short-term (months) reduction of mass emanating from the source zone as a result of permanganate treatment but there was no long-term (years) impact on the ability of this coal tar creosote source zone to generate a multi-component plume.

Mass Transfer Limited Enhanced Bioremediation at Dnapl Source Zones: a Numerical Study

NASA Astrophysics Data System (ADS)

Kokkinaki, A.; Sleep, B. E.

2011-12-01

The success of enhanced bioremediation of dense non-aqueous phase liquids (DNAPLs) relies on accelerating contaminant mass transfer from the organic to the aqueous phase, thus enhancing the depletion of DNAPL source zones compared to natural dissolution. This is achieved by promoting biological activity that reduces the contaminant's aqueous phase concentration. Although laboratory studies have demonstrated that high reaction rates are attainable by specialized microbial cultures in DNAPL source zones, field applications of the technology report lower reaction rates and prolonged remediation times. One possible explanation for this phenomenon is that the reaction rates are limited by the rate at which the contaminant partitions from the DNAPL to the aqueous phase. In such cases, slow mass transfer to the aqueous phase reduces the bioavailability of the contaminant and consequently decreases the potential source zone depletion enhancement. In this work, the effect of rate limited mass transfer on bio-enhanced dissolution of DNAPL chlorinated ethenes is investigated through a numerical study. A multi-phase, multi-component groundwater transport model is employed to simulate DNAPL mass depletion for a range of source zone scenarios. Rate limited mass transfer is modeled by a linear driving force model, employing a thermodynamic approach for the calculation of the DNAPL - water interfacial area. Metabolic reductive dechlorination is modeled by Monod kinetics, considering microbial growth and self-inhibition. The model was utilized to identify conditions in which mass transfer, rather than reaction, is the limiting process, as indicated by the bioavailability number. In such cases, reaction is slower than expected, and further increase in the reaction rate does not enhance mass depletion. Mass transfer rate limitations were shown to affect both dechlorination and microbial growth kinetics. The complex dynamics between mass transfer, DNAPL transport and distribution, and dechlorination kinetics were reflected in a transient, spatially heterogeneous bioavailability number and dissolution enhancement. In agreement with the literature, source zone architecture largely determined the impact of mass transfer on potential dissolution enhancement, with bioavailability decreasing the most at high ganglia to pool ratios. The results of this study suggest that if mass transfer rate limitations are not considered in designing bioremediation applications at DNAPL source zones, the enhancement of DNAPL depletion and the overall effectiveness of enhanced bioremediation may be significantly overestimated.

Formulating a coastal zone health metric for landuse impact management in urban coastal zones.

PubMed

Anilkumar, P P; Varghese, Koshy; Ganesh, L S

2010-11-01

The need for ICZM arises often due to inadequate or inappropriate landuse planning practices and policies, especially in urban coastal zones which are more complex due to the larger number of components, their critical dimensions, attributes and interactions. A survey of literature shows that there is no holistic metric for assessing the impacts of landuse planning on the health of a coastal zone. Thus there is a need to define such a metric. The proposed metric, CHI (Coastal zone Health Indicator), developed on the basis of coastal system sustainability, attempts to gauge the health status of any coastal zone. It is formulated and modeled through an expert survey and pertains to the characteristic components of coastal zones, their critical dimensions, and relevant attributes. The proposed metric is applied to two urban coastal zones and validated. It can be used for more coast friendly and sustainable landuse planning/masterplan preparation and thereby for the better management of landuse impacts on coastal zones. Copyright 2010 Elsevier Ltd. All rights reserved.

Geographical mapping of fluoride levels in drinking water sources in Nigeria.

PubMed

Akpata, Enosakhare S; Danfillo, I S; Otoh, E C; Mafeni, J O

2009-12-01

Knowledge of fluoride levels in drinking water is of importance in dental public health, yet this information is lacking, at national level, in Nigeria. To map out fluoride levels in drinking water sources in Nigeria. Fluoride levels in drinking water sources from 109 randomly selected Local Government Areas (LGAs) in the 6 Nigerian geopolitical zones were determined. From the results, maps showing LGAs with fluoride concentrations exceeding 0.3 ppm, were drawn. ANOVA and t-test were used to determine the significance of the differences between the fluoride levels in the drinking water sources. Fluoride levels were low in most parts of the country, being 0.3 ppm or less in 62% of the LGAs. Fluoride concentrations were generally higher in North Central geopolitical zone, than the other zones in the country (p<0.05). In a few drinking water sources, fluoride concentrations exceeded 1.5 ppm, but was as high as 6.7 ppm in one well. Only 9% of the water sources were from waterworks. Most of the water sources in Nigeria contained low fluoride levels; but few had excessive concentrations and need to be partially defluoridated, or else alternative sources of drinking water provided for the community.

Mercury Cadmium Selenide for Infrared Detection

DTIC Science & Technology

2013-06-01

were grown using elemental mercury (Hg), cadmium (Cd), and selenium (Se) sources. The beam equiva- lent pressure ( BEP ) emanating from all sources was...flux), the BEP measured for the cracker source was found to vary with the cracking zone temperature, tracking with the data found in Ref. 7. This sug...The Se BEP measured for the typical cracking zone temperature of 800 C was found to be close to a factor of two lower than at the typical effusion cell

Seismic velocity structure in the western part of Nankai subduction zone

NASA Astrophysics Data System (ADS)

Yamamoto, Y.; Obana, K.; Takahashi, T.; Nakanishi, A.; Kodaira, S.; Kaneda, Y.

2011-12-01

In the Nankai Trough, three major seismogenic zones of megathrust earthquake exist (Tokai, Tonankai and Nankai earthquake regions). The Hyuga-nada region was distinguished from these seismogenic zones because of the lack of megathrust earthquake. However, recent studies show the possibility of simultaneous rupture of the Nankai and Hyuga-nada segments was also pointed out [e.g., Furumura et al, 2010 JGR]. Because seismic velocity structure is one of the useful and basic information for understanding the possibility of seismic linkage of Nankai and Hyuga-nada segments, Japan Agency for Marine-Earth Science and Technology has been carried out a series of wide-angle active source surveys and local seismic observations among the three major seismogenic zones and Hyuga-nada segment from 2008, as a part of "Research concerning Interaction Between the Tokai, Tonankai and Nankai Earthquakes' funded by Ministry of Education, Culture, Sports, Science and Technology, Japan". We are performing two set of three-dimensional seismic velocity tomographic inversions, one is in the Hyuga-nada region and the other is western part of the coseismic rupture area of 1946 Nankai earthquake, to discuss the relationship between the structural heterogeneities and the location of segment boundary between Hyuga-nada and Nankai segment. For the analysis of Hyuga-nada segment, we used both active and passive source data. The obtained velocity model clearly showed the subducted Kyushu-Palau ridge as thick low velocity Philippine Sea slab in the southwestern part. Our velocity image also indicates that "the thin oceanic crust zone" located between Nankai segment and Kyushu-Palau Ridge segment, founded by Nakanishi et al [2010, AGU] by analyzing of the active source survey, continuously exists from trough axis to near the coastline of Kyushu Island. The overriding plate just above the coseismic slip area of 1968 Hyuga-nada earthquake shows relatively high velocity. Although the tomographic study in the western part of Nankai seismogenic zone is still a preliminary stage and we used only a part of the passive source data, we found the anomalous high velocity zone in the overriding plate. This zone is located at just beneath the cape Ashizuri, corresponding to the boundary between the Nankai and Hyuga-nada segments. To clarify more detail structure, we will perform the joint inversion using both active and passive source data in the western Nankai seismogenic zone.

Provisional tree and shrub seed zones for the Great Plains

Treesearch

Richard A. Cunningham

1975-01-01

Seed collection zones are subdivisions of land areas established to identify seed sources and to control the movement of seed and planting stock. Seed zones are needed for many species because of the genetic variation associated with their geographic distribution. Zone boundaries may be delineated from experimental data that identify genetic variation, or by analysis...

[Effect of terracing project on temporal-spatial variation of non-point source pollution load in Hujiashan watershed, China].

PubMed

Han, Qiang; Yu, Xing Xiu; Wang, Wei; Xu, Miao Miao; Ren, Rui; Zhang, Jia Peng

2017-04-18

Taking Hujiashan small watershed as the study area, based on the classified result of Landsat TM/ETM images of 2005, 2010 and 2015, combined with long-term field observation data, and used the export coefficient model, our study explored the effect of small watershed management project on temporal and spatial variation of total nitrogen (TN) load of non-point source pollution under the support of GIS technology. The results indicated that, due to the implementation of slope modification project, the area of cultivated land was significantly increased, while forest and bareland were decreased. The load of non-point source TN increased from 63208 kg in 2005 to 72778 kg in 2010, but reduced to 46876 kg in 2015. The contribution rate from residential areas was higher, the average contribution rate of the three periods was 53.5%, but it showed a decreasing trend year by year. The contribution rate of land use types was 45%, which showed an increasing trend year by year. The contribution rate of livestock was always low. From the spatial distribution, TN loading intensity was changed obviously after the terracing project. High load intensity zone was mainly concentrated on the slope of 5°-15° before terracing project. Nevertheless, high load intensity zone was concentrated on the slope of 15°-35° after terracing project, and 5°-8° had become a low load strength area. The TN load intensity changed little with time on the slope of 0°-8°, and it increased first and then decreased on the slope above 8°. With the treatment of sewage, garbage and livestock manure in rural areas, the output of nitrogen in the living and livestock breeding were significantly reduced. Due to the implementation of the project, the cultivated land area increased by 31%.

Isotopic investigation of the discharge driven nitrogen dynamics in a mesoscale river catchment

NASA Astrophysics Data System (ADS)

Mueller, Christin; Zink, Matthias; Krieg, Ronald; Rode, Michael; Merz, Ralf; Knöller, Kay

2016-04-01

Nitrate in surface and groundwater has increased in the last decades due to landuse change, the application of different fertilizer for agricultural landuse and industrial dust in the atmospheric deposition. Increasing nitrate concentrations have a major impact on eutrophication, especially for coastal ecosystems. Therefore it is important to quantify potential nitrate sources and determine nitrate process dynamics with its drivers. The Bode River catchment (total size of 3200 m2) in the Harz Mountains in Germany was intensively investigated by a monitoring approach with 133 sampling points representing the same number of sub-catchments for a period of two years. The area is characterized by a strong anthropogenic gradient, with forest conservation areas in the mountain region, grassland, and intensively mixed farming in the lowlands. Consecutive discharge simulations by a mesoscale hydrological model (mhM) allow a quantitative analysis of nitrate fluxes for all observed tributaries. The investigation of nitrate isotopic signatures for characteristic landscape types allows the delineation of dominant NO3- sources: coniferous forests are characterized by recycled nitrified soil nitrogen; grassland is mainly impacted by organic fertilizer (manure) and nitrified soil-N; in agricultural land use areas nitrate predominantly derives from synthetic fertilizer application. Besides source delineation, the relationship between runoff and nitrate dynamics was analyzed for the entire Bode river catchment and, more detailed, for one major tributary with minor artificial reservoirs (Selke River). Thereby, it becomes apparent that nitrate isotopic variations increase with decreasing discharge. This effect might be due to a local, more intense impact of bacterial denitrification under low discharge conditions (higher residence time) in the anoxic soil zone, in the groundwater that discharges into the river and in the hyporheic zone. Generally, δ15N and δ18Oof nitrate decrease with increasing runoff, which can be caused by a preferential wash-out of more easily mobilizable, isotopically lighter fractions of the soil nitrate pool.

Prediction of Bicarbonate Requirements for Enhanced Reductive Bioremediation of Chlorinated Solvent-Contaminated Sites

NASA Astrophysics Data System (ADS)

Robinson, C.; Barry, D. A.

2008-12-01

Enhanced anaerobic dechlorination is a promising technology for in situ remediation of chlorinated ethene DNAPL source areas. However, the build-up of organic acids and HCl in the source zone can lead to significant groundwater acidification. The resulting pH drop inhibits the activity of the dechlorinating microorganisms and thus may stall the remediation process. Source zone remediation requires extensive dechlorination, such that it may be common for soil's natural buffering capacity to be exceeded, and for acidic conditions to develop. In these cases bicarbonate addition (e.g., NaHCO3, KHCO3) is required for pH control. As a design tool for treatment strategies, we have developed BUCHLORAC, a Windows Graphical User Interface based on an abiotic geochemical model that allows the user to predict the acidity generated during dechlorination and associated buffer requirements for their specific operating conditions. BUCHLORAC was motivated by the SABRE (Source Area BioREmediation) project, which aims to evaluate the effectiveness of enhanced reductive dechlorination in the treatment of chlorinated solvent source zones.

Assessment of the Natural Attenuation of NAPL Source Zones and Post-Treatment NAPL Source Zone Residuals

DTIC Science & Technology

2013-11-15

was conducted. As expected, a cylinder was formed similar to the one shown in Figure 5.9 using potassium permanganate , with slight elongation in the...clean water injections at 400 mg/L. This was not necessary during the ISCO disturbance test, as potassium permanganate (KMnO4), which forms a deep

Comparisons of Low-Strain Amplification at Soft-Sediment, Hard-Rock, Topographic, and Fault-Zone Sites in the Hayward Fault Zone, California

NASA Astrophysics Data System (ADS)

Catchings, R.; Strayer, L. M.; Goldman, M.

2014-12-01

We used a temporary network of approximately 600 seismographs to record a seismic source generated by the collapse of a 13-story building near the active trace of the Hayward Fault. These data allow us to evaluate variations in ground shaking across a series of 30 2-km-long radial arrays centered on the seismic source. Individual seismographs were spaced at 200-m intervals, forming a series of 360°concentric arrays around the seismic source. The data show variations in amplification caused by (1) soft sediments within the East Bay alluvial plain (EBAP), (2) hard rocks within the East Bay hills (EBH), (3) low-velocity rocks within the Hayward Fault zone (HFZ), and (4) topography. Given that ground shaking varies strongly with distance from the source, the concentric arrays allowed us to measure variations in ground shaking as a function of azimuth at fixed distances from the source. On individual linear profiles within the concentric arrays, we observed decreases in peak ground velocity (PGV) across the HFZ and other faults within the EBH. However, for a given distance from the source, we observe four to five fold amplification from the EBAP sites compared to most sites in the EBH. Topographic and fault-zone amplification effects within the EBH, however, are greater than the EBAP sediment amplification. Thus, for future earthquakes, shaking at many sites within the EBH may be significantly stronger than many sites within the EBAP. These observations suggest amplification can be expected in unconsolidated sediments, but topographic and fault-zone amplification can be larger. This confirms the importance of site effects for hazard mitigation and in interpreting MMI for future and historical earthquakes.

Genetic implications of the trace element distribution pattern in the upper knox carbonate rocks, copper ridge district, East Tennessee

NASA Astrophysics Data System (ADS)

Churnet, Habte G.; Misra, Kula C.

1981-11-01

The Lower Ordovician, Upper Knox Group rocks (the Kingsport and Mascot formations) in the Copper Ridge district consist predominantly of fine-grained dolostones, medium and coarser grained dolostones, and limestones. Dolomite crystals of medium and coarser grained dolostones show up to eight cathodoluminescent zones of variable width and intensity. Electron microprobe analyses indicate that the zoning is related to variation in Fe/Mn ratios, the brighter luminescent zones corresponding to lower ratios. Superposed on this growth zoning is a compositional zoning characterized by a general increase in Fe from core to rim of individual dolomite crystals. Field and petrographic studies (Churnet, 1979; Churnet et al., 1981) indicate that the fine-grained dolostones formed in supratidal to upper intratidal environments, whereas the precursor lime muds of the limestones as well as of the medium and coarser grained dolostones formed in shallow subtidal to lower intertidal environments. The large areal extent of the dolostones must have required a regionally abundant source of Mg such as marine water. Yet, both limestones and dolostones have low Na and Sr contents suggestive of their formation in solutions more dilute than normal marine water. It is proposed that the fine-grained dolostones formed by aggradation of initially very fine-grained dolostones in presence of fresh water, and that the limestones stabilized and the medium and coarser grained dolostones formed in environments of mixed marine and fresh waters. Considered in the light of ordering of partition coefficients, such a mixing model can account for the observed correlation pattern of trace elements (especially, SMn and SrFe) as well as the Fe distribution in the zoned dolomite crystals. Variation of the partition coefficient of Mn due to fluctuations in the relative proportions of fresh and marine waters in the diagenetic solution may explain the different Fe/Mn ratios observed in the growth zones (luminescence bands) of zoned dolomite crystals.

Natural attenuation of petroleum hydrocarbons-a study of biodegradation effects in groundwater (Vitanovac, Serbia).

PubMed

Marić, Nenad; Matić, Ivan; Papić, Petar; Beškoski, Vladimir P; Ilić, Mila; Gojgić-Cvijović, Gordana; Miletić, Srđan; Nikić, Zoran; Vrvić, Miroslav M

2018-01-20

The role of natural attenuation processes in groundwater contamination by petroleum hydrocarbons is of intense scientific and practical interest. This study provides insight into the biodegradation effects in groundwater at a site contaminated by kerosene (jet fuel) in 1993 (Vitanovac, Serbia). Total petroleum hydrocarbons (TPH), hydrochemical indicators (O 2 , NO 3 - , Mn, Fe, SO 4 2- , HCO 3 - ), δ 13 C of dissolved inorganic carbon (DIC), and other parameters were measured to demonstrate biodegradation effects in groundwater at the contaminated site. Due to different biodegradation mechanisms, the zone of the lowest concentrations of electron acceptors and the zone of the highest concentrations of metabolic products of biodegradation overlap. Based on the analysis of redox-sensitive compounds in groundwater samples, redox processes ranged from strictly anoxic (methanogenesis) to oxic (oxygen reduction) within a short distance. The dependence of groundwater redox conditions on the distance from the source of contamination was observed. δ 13 C values of DIC ranged from - 15.83 to - 2.75‰, and the most positive values correspond to the zone under anaerobic and methanogenic conditions. Overall, results obtained provide clear evidence on the effects of natural attenuation processes-the activity of biodegradation mechanisms in field conditions.

Research progress on reconstruction of meniscus in tissue engineering.

PubMed

Zhang, Yu; Li, Pengsong; Wang, Hai; Wang, Yiwei; Song, Kedong; Li, Tianqing

2017-05-01

Meniscus damages are most common in sports injuries and aged knees. One third of meniscus lesions are known as white-white zone or nonvascular zones, which are composed of chondrocyte and extracellular matrix composition only. Due to low vascularization the ability of regeneration in such zones is inherently limited, leading to impossible self-regeneration post damage. Meniscus tissue engineering is known for emerging techniques for treating meniscus damage, but there are questions that need to be answered, including an optimal and suitable cell source, the usability of growth factor, the selectivity of optimal biomaterial scaffolds as well as the technology for improving partial reconstruction of meniscus tears. This review focuses on current research on the in vitro reconstruction of the meniscus using tissue engineering methods with the expectation to develop a series of tissue engineering meniscus products for the benefit of sports injuries. With rapid growth of clinical demand, the key breakthrough of meniscus tissue engineering research foundation is enlarged to a great extent. This review discusses aspects of meniscus tissue engineering, which is relative to the clinical treatment of meniscus injuries for further support and establishment of fundamental and clinical studies.

Investigation on the reproduction performance versus acoustic contrast control in sound field synthesis.

PubMed

Bai, Mingsian R; Wen, Jheng-Ciang; Hsu, Hoshen; Hua, Yi-Hsin; Hsieh, Yu-Hao

2014-10-01

A sound reconstruction system is proposed for audio reproduction with extended sweet spot and reduced reflections. An equivalent source method (ESM)-based sound field synthesis (SFS) approach, with the aid of dark zone minimization is adopted in the study. Conventional SFS that is based on the free-field assumption suffers from synthesis error due to boundary reflections. To tackle the problem, the proposed system utilizes convex optimization in designing array filters with both reproduction performance and acoustic contrast taken into consideration. Control points are deployed in the dark zone to minimize the reflections from the walls. Two approaches are employed to constrain the pressure and velocity in the dark zone. Pressure matching error (PME) and acoustic contrast (AC) are used as performance measures in simulations and experiments for a rectangular loudspeaker array. Perceptual Evaluation of Audio Quality (PEAQ) is also used to assess the audio reproduction quality. The results show that the pressure-constrained (PC) method yields better acoustic contrast, but poorer reproduction performance than the pressure-velocity constrained (PVC) method. A subjective listening test also indicates that the PVC method is the preferred method in a live room.

76 FR 37647 - Safety Zone; Missouri River From the Border Between Montana and North Dakota

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-28

... destruction, loss or injury due to hazards associated with rising flood water. Operation in this zone is... vessels from destruction, loss or injury due to the hazards associated with rising flood water. The... destruction, loss or injury due to the hazards associated with rising flood water. If you are a small business...

Magneto- to electroactive transmutation of spin waves in ErMnO3.

PubMed

Chaix, L; de Brion, S; Petit, S; Ballou, R; Regnault, L-P; Ollivier, J; Brubach, J-B; Roy, P; Debray, J; Lejay, P; Cano, A; Ressouche, E; Simonet, V

2014-04-04

The low-energy dynamical properties of the multiferroic hexagonal perovskite ErMnO3 have been studied by inelastic neutron scattering as well as terahertz and far infrared spectroscopies on a synchrotron source. From these complementary techniques, we have determined the magnon and crystal field spectra and identified a zone center magnon excitable only by the electric field of an electromagnetic wave. Using a comparison with the isostructural YMnO3 compound and crystal field calculations, we propose that this dynamical magnetoelectric process is due to the hybridization of a magnon with an electroactive crystal field transition.

Slab1.0: A three-dimensional model of global subduction zone geometries

NASA Astrophysics Data System (ADS)

Hayes, Gavin P.; Wald, David J.; Johnson, Rebecca L.

2012-01-01

We describe and present a new model of global subduction zone geometries, called Slab1.0. An extension of previous efforts to constrain the two-dimensional non-planar geometry of subduction zones around the focus of large earthquakes, Slab1.0 describes the detailed, non-planar, three-dimensional geometry of approximately 85% of subduction zones worldwide. While the model focuses on the detailed form of each slab from their trenches through the seismogenic zone, where it combines data sets from active source and passive seismology, it also continues to the limits of their seismic extent in the upper-mid mantle, providing a uniform approach to the definition of the entire seismically active slab geometry. Examples are shown for two well-constrained global locations; models for many other regions are available and can be freely downloaded in several formats from our new Slab1.0 website, http://on.doi.gov/d9ARbS. We describe improvements in our two-dimensional geometry constraint inversion, including the use of `average' active source seismic data profiles in the shallow trench regions where data are otherwise lacking, derived from the interpolation between other active source seismic data along-strike in the same subduction zone. We include several analyses of the uncertainty and robustness of our three-dimensional interpolation methods. In addition, we use the filtered, subduction-related earthquake data sets compiled to build Slab1.0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far, concluding that the width of these seismogenic zones is on average 30% larger than previous studies have suggested.

Hydrogen peroxide in deep waters from the Mediterranean Sea, South Atlantic and South Pacific Oceans

NASA Astrophysics Data System (ADS)

Hopwood, Mark J.; Rapp, Insa; Schlosser, Christian; Achterberg, Eric P.

2017-03-01

Hydrogen peroxide (H2O2) is present ubiquitously in marine surface waters where it is a reactive intermediate in the cycling of many trace elements. Photochemical processes are considered the dominant natural H2O2 source, yet cannot explain nanomolar H2O2 concentrations below the photic zone. Here, we determined the concentration of H2O2 in full depth profiles across three ocean basins (Mediterranean Sea, South Atlantic and South Pacific Oceans). To determine the accuracy of H2O2 measurements in the deep ocean we also re-assessed the contribution of interfering species to ‘apparent H2O2’, as analysed by the luminol based chemiluminescence technique. Within the vicinity of coastal oxygen minimum zones, accurate measurement of H2O2 was not possible due to interference from Fe(II). Offshore, in deep (>1000 m) waters H2O2 concentrations ranged from 0.25 ± 0.27 nM (Mediterranean, Balearics-Algeria) to 2.9 ± 2.2 nM (Mediterranean, Corsica-France). Our results indicate that a dark, pelagic H2O2 production mechanism must occur throughout the deep ocean. A bacterial source of H2O2 is the most likely origin and we show that this source is likely sufficient to account for all of the observed H2O2 in the deep ocean.

Hydrogen peroxide in deep waters from the Mediterranean Sea, South Atlantic and South Pacific Oceans

PubMed Central

Hopwood, Mark J.; Rapp, Insa; Schlosser, Christian; Achterberg, Eric P.

2017-01-01

Hydrogen peroxide (H2O2) is present ubiquitously in marine surface waters where it is a reactive intermediate in the cycling of many trace elements. Photochemical processes are considered the dominant natural H2O2 source, yet cannot explain nanomolar H2O2 concentrations below the photic zone. Here, we determined the concentration of H2O2 in full depth profiles across three ocean basins (Mediterranean Sea, South Atlantic and South Pacific Oceans). To determine the accuracy of H2O2 measurements in the deep ocean we also re-assessed the contribution of interfering species to ‘apparent H2O2’, as analysed by the luminol based chemiluminescence technique. Within the vicinity of coastal oxygen minimum zones, accurate measurement of H2O2 was not possible due to interference from Fe(II). Offshore, in deep (>1000 m) waters H2O2 concentrations ranged from 0.25 ± 0.27 nM (Mediterranean, Balearics-Algeria) to 2.9 ± 2.2 nM (Mediterranean, Corsica-France). Our results indicate that a dark, pelagic H2O2 production mechanism must occur throughout the deep ocean. A bacterial source of H2O2 is the most likely origin and we show that this source is likely sufficient to account for all of the observed H2O2 in the deep ocean. PMID:28266529

Processes controlling the fate of chloroethenes emanating from DNAPL aged sources in river-aquifer contexts.

PubMed

Puigserver, Diana; Cortés, Amparo; Viladevall, Manuel; Nogueras, Xènia; Parker, Beth L; Carmona, José M

2014-11-01

This work dealt with the physical and biogeochemical processes that favored the natural attenuation of chloroethene plumes of aged sources located close to influent rivers in the presence of co-contaminants, such as nitrate and sulfate. Two working hypotheses were proposed: i) Reductive dechlorination is increased in areas where the river-aquifer relationship results in the groundwater dilution of electron acceptors, the reduction potential of which exceeds that of specific chloroethenes; ii) zones where silts predominate or where textural changes occur are zones in which biodegradation preferentially takes place. A field site on a Quaternary alluvial aquifer at Torelló, Catalonia (Spain) was selected to validate these hypotheses. This aquifer is adjacent to an influent river, and its redox conditions favor reductive dechlorination. The main findings showed that the low concentrations of nitrate and sulfate due to dilution caused by the input of surface water diminish the competition for electrons between microorganisms that reduce co-contaminants and chloroethenes. Under these conditions, the most bioavailable electron acceptors were PCE and metabolites, which meant that their biodegradation was favored. This led to the possibility of devising remediation strategies based on bioenhancing natural attenuation. The artificial recharge with water that is low in nitrates and sulfates may favor dechlorinating microorganisms if the redox conditions in the mixing water are sufficiently maintained as reducing and if there are nutrients, electron donors and carbon sources necessary for these microorganisms. Copyright © 2014 Elsevier B.V. All rights reserved.

Microbial Metabolic Response to Carbon Sources in a Uranium Contaminated Floodplain

NASA Astrophysics Data System (ADS)

Barragan, L.; Boye, K.; Bargar, J.; Fendorf, S. E.

2016-12-01

In Riverton, Wyoming, uranium (U) from a former ore processing plant, contaminated the groundwater and accumulated in Naturally Reduced Zones (NRZs). The NRZs have now become a secondary source of U and are releasing U into the ground water due to seasonal water table fluctuations. Microorganisms that mediate the mobilization and retention of U are likely to reside in these zones enriched with organic matter that comprises their energy source of carbon (C) for respiration. In this study, we are measuring microbial respiration (basal and substrate induced) by the MicroRespTM system, which is a quick screening method for respiratory activity in natural samples. This can provide information about the microbial community composition at certain depths and insight into their metabolic pathways which may explain U behavior in the ground water. In addition, we are determining elemental composition in the sediments by X-ray fluorescence spectroscopy (XRF) and elemental analysis (EA). Water soluble cations, anions and organic C is determined by inductively coupled plasma (ICP), mass spectrometry, ion chromatography (IC) and non-purgeable organic carbon (NPOC) analyses, respectively. If the behavior of the microbial community in the NRZ environment (enriched in both U and C) differs from that in unsaturated sediments, this can provide crucial clues to understand what causes U to be retained or released from the NRZs. This information will be used to develop and improve models aimed at predicting U mobility in the floodplain groundwater systems.

Eogenetic siderite as an indicator for fluctuations in sedimentation rate in the Oligocene Boom Clay Formation (Belgium)

NASA Astrophysics Data System (ADS)

Laenen, B.; De Craen, M.

2004-01-01

Horizons with septarian concretions are a salient feature of the marine Boom Clay Formation. At most horizons, the concretions consist of ferroan calcite with variable amounts of pyrite, but at stratigraphic level S60 they also contain siderite. S60 is situated at the centre of an intensely bioturbated zone that is underlain by a pyrite-rich layer. Furthermore, the enclosing clay is strongly enriched in iron, manganese and phosphorous. The sedimentological and chemical zoning is indicative for low sedimentation rates, which allowed the concentration of iron in the aerobic zone of the sediment. Concentration of iron was the prerequisite for the formation of the siderite-containing concretions. The co-precipitation with pyrite is an argument for a formation in the sulphate reduction zone, and is indicative for a high rate of iron-reduction. The latter was due to the rapid burial of the iron-enriched layer below the redox boundary. The abrupt fluctuations in sedimentation rate were a response to the maximum flooding event of the second Rupelian third-order relative sea-level cycle, which caused a brief pushback of the detrital sediment wedge to its source areas. As this response is logically explained by the general sequence stratigraphic model [Spec. Publ.-Soc. Econ. Paleontol. Mineral. 42 (1988) 109], early diagenetic siderite may be widespread at maximum flooding surfaces in rapidly prograding marine mudstones.

[Dynamics and combined injuries of main pest species in rice cropping zones of Yunnan, Southwest China].

PubMed

Dong, Kun; Dong, Yan; Wang, Hai-Long; Zhang, Li-Min; Zan, Qing-An; Chen, Bin; Li, Zheng-Yue

2014-01-01

A series of rice pest injuries (due to pathogens, insects, and weeds) were surveyed in 286 farmers' fields for major rice varieties of three rice cropping zones of Yunnan Province, Southwest China. The composition and dynamics of main pest species were analyzed, and the trend of rice pest succession in Yunnan was discussed based upon landmark publications. The results showed that the three rice cropping zones had different pest characteristics as regard to main species, dynamics and combined injuries. Sheath rot, bacterial leaf blight, rice stripe, leaf hoppers, armyworms and stem borers were serious in the japonica rice zone. Sheath blight and rice stripe were serious in the japonica-indica interlacing zone. Leaf blast, sheath blight, leaf folders and weeds above rice crop canopy were serious in the indica rice zone. False smut, plant hoppers and weeds below rice crop canopy were ubiquitous and serious in the three kinds of rice cropping zones. Many kinds of weed infestation emerged in the whole rice cropping seasons. Echinochloa crusgalli, Sagittaria pygmaea, Potamogeton distinctus and Spirodela polyrhiza were the main species of weeds in the rice cropping zones of Yunnan. Overall, levels of combined injuries due to pests in the japonica rice zone and the indica rice zone were higher than that in the japonica-indica interlacing zone. In terms of the trend of rice pest succession in Yunnan, injuries due to false smut, sheath blight and plant hoppers seemed to be in a worse tendency in all rice cropping zones of Yunnan, while dominants species of weeds in the paddy fields are shifting from the annual weeds to the perennial malignant weeds.

14C age reassessment of groundwater from the discharge zone due to cross-flow mixing in the deep confined aquifer

NASA Astrophysics Data System (ADS)

Mao, Xumei; Wang, Hua; Feng, Liang

2018-05-01

In a groundwater flow system, the age of groundwater should gradually increase from the recharge zone to the discharge zone within the same streamline. However, it is occasionally observed that the groundwater age becomes younger in the discharge zone in the piedmont alluvial plain, and the oldest age often appears in the middle of the plain. A new set of groundwater chemistry and isotopes was employed to reassess the groundwater 14C ages from the discharge zone in the North China Plain (NCP). Carbonate precipitation, organic matter oxidation and cross-flow mixing in the groundwater from the recharge zone to the discharge zone are recognized according to the corresponding changes of HCO3- (or DIC) and δ13C in the same streamline of the third aquifer of the NCP. The effects of carbonate precipitation and organic matter oxidation are calibrated with a 13C mixing model and DIC correction, but these corrected 14C ages seem unreasonable because they grow younger from the middle plain to the discharge zone in the NCP. The relationship of Cl- content and the recharge distance is used to estimate the expected Cl- content in the discharge zone, and ln(a14C)/Cl is proposed to correct the a14C in groundwater for the effect of cross-flow mixing. The 14C ages were reassessed with the corrected a14C due to the cross-flow mixing varying from 1.25 to 30.58 ka, and the groundwater becomes older gradually from the recharge zone to the discharge zone. The results suggest that the reassessed 14C ages are more reasonable for the groundwater from the discharge zone due to cross-flow mixing.

Airborne radioactivity survey of parts of Atlantic Ocean beach, Virginia to Florida

USGS Publications Warehouse

Moxham, R.M.; Johnson, R.W.

1953-01-01

The accompanying maps show the results of an airborne radioactivity survey along the Atlantic Ocean beach from Cape Henry, Virginia to Cape Fear, North Carolina and from Savannah Bach Georgia to Miami Beach, Florida. The survey was made March 23-24, 1953, as part of a cooperative program with the U.S. Atomic Energy Commission. The survey was made with scintillation detection equipment mounted in a Douglas DC-3 aircraft and consisted of one flight line, at a 500-foot altitude, parallel to the beach. The vertical projection of the flight line coincided approximately with the landward limit of the modern beach. The width of the zone on the ground from which anomalous radiation is measured at the normal 500 foot flight altitude varies with the areal extent radioactivity of the source. For strong sources of radioactivity the width of the zone would be as much as 1,400 feet. The location of the flight lines is shown on the index map below. No abnormal radioactivity was detected along the northern flight line between Cape Henry, Virginia and Cape Fear, North Carolina. Along the southern flight line fourteen areas of abnormal radioactivity were detected between Savannah Beach, Georgia and Anastasia Island, Florida as shown on the map on the left. The abnormal radioactivity is apparently due to radioactive minerals associated with "black sand" deposits with occur locally along the beach in this region. The present technique of airborne radioactivity measurement does not permit distinguishing between activity sue to thorium and that due to uranium. An anomaly, therefore, may represent radioactivity due entirely to one or to a combination of these elements. It is not possible to determine the extent or radioactive content of the materials responsible for the abnormal radioactivity. The information given on the accompanying map indicates only those localities of greater-than-average radioactivity and, therefore suggest areas in which uranium and thorium deposits are more likely to occur.

Two applications of the Recently Developed UZF-MT3DMS Model for Evaluating Nonpoint-Source Fluxes (Invited)

NASA Astrophysics Data System (ADS)

Morway, E. D.; Niswonger, R. G.; Nishikawa, T.

2013-12-01

The solute-transport model MT3DMS was modified to simulate transport in the unsaturated-zone by incorporating the additional flow terms calculated by the Unsaturated-Zone Flow (UZF) package developed for MODFLOW. Referred to as UZF-MT3DMS, the model simulates advection and dispersion of conservative and reactive solutes in unsaturated and saturated porous media. Significant time savings are realized owing to the efficiency of the kinematic -wave approximation used by the UZF1 package relative to Richards' equation-based approaches, facilitating the use of automated parameter-estimation routines wherein thousands of model runs may be required. Currently, UZF-MT3DMS is applied to two real-world applications of existing MODFLOW and MT3DMS models retro-fitted to use the UZF1 package for simulating the unsaturated component of the sub-surface system. In the first application, two regional-scale investigations located in Colorado's Lower Arkansas River Valley (LARV) are developed to evaluate the extent and severity of unsaturated-zone salinization contributing to crop yield loss. Preliminary results indicate root zone concentrations over both regions are at or above salinity-thresholds of most crop types grown in the LARV. Regional-scale modeling investigations of salinization found in the literature commonly use lumped-parameter models rather than physically-based distributed-parameter models. In the second application, located near Joshua Tree, CA, nitrate loading to the underlying unconfined aquifer from domestic septic systems is evaluated. Due to the region's thick unsaturated-zone and correspondingly long unsaturated-zone residence times (multi-decade), UZF-MT3DMS enabled direct simulation of spatially-varying concentration break-through curves at the water table.

Shallow subsurface structure of the Wasatch fault, Provo segment, Utah, from integrated compressional and shear-wave seismic reflection profiles with implications for fault structure and development

USGS Publications Warehouse

McBride, J.H.; Stephenson, W.J.; Williams, R.A.; Odum, J.K.; Worley, D.M.; South, J.V.; Brinkerhoff, A.R.; Keach, R.W.; Okojie-Ayoro, A. O.

2010-01-01

Integrated vibroseis compressional and experimental hammer-source, shear-wave, seismic reflection profiles across the Provo segment of the Wasatch fault zone in Utah reveal near-surface and shallow bedrock structures caused by geologically recent deformation. Combining information from the seismic surveys, geologic mapping, terrain analysis, and previous seismic first-arrival modeling provides a well-constrained cross section of the upper ~500 m of the subsurface. Faults are mapped from the surface, through shallow, poorly consolidated deltaic sediments, and cutting through a rigid bedrock surface. The new seismic data are used to test hypotheses on changing fault orientation with depth, the number of subsidiary faults within the fault zone and the width of the fault zone, and the utility of integrating separate elastic methods to provide information on a complex structural zone. Although previous surface mapping has indicated only a few faults, the seismic section shows a wider and more complex deformation zone with both synthetic and antithetic normal faults. Our study demonstrates the usefulness of a combined shallow and deeper penetrating geophysical survey, integrated with detailed geologic mapping to constrain subsurface fault structure. Due to the complexity of the fault zone, accurate seismic velocity information is essential and was obtained from a first-break tomography model. The new constraints on fault geometry can be used to refine estimates of vertical versus lateral tectonic movements and to improve seismic hazard assessment along the Wasatch fault through an urban area. We suggest that earthquake-hazard assessments made without seismic reflection imaging may be biased by the previous mapping of too few faults. ?? 2010 Geological Society of America.

Identifying Attributes of CO2 Leakage Zones in Shallow Aquifers Using a Parametric Level Set Method

NASA Astrophysics Data System (ADS)

Sun, A. Y.; Islam, A.; Wheeler, M.

2016-12-01

Leakage through abandoned wells and geologic faults poses the greatest risk to CO2 storage permanence. For shallow aquifers, secondary CO2 plumes emanating from the leak zones may go undetected for a sustained period of time and has the greatest potential to cause large-scale and long-term environmental impacts. Identification of the attributes of leak zones, including their shape, location, and strength, is required for proper environmental risk assessment. This study applies a parametric level set (PaLS) method to characterize the leakage zone. Level set methods are appealing for tracking topological changes and recovering unknown shapes of objects. However, level set evolution using the conventional level set methods is challenging. In PaLS, the level set function is approximated using a weighted sum of basis functions and the level set evolution problem is replaced by an optimization problem. The efficacy of PaLS is demonstrated through recovering the source zone created by CO2 leakage into a carbonate aquifer. Our results show that PaLS is a robust source identification method that can recover the approximate source locations in the presence of measurement errors, model parameter uncertainty, and inaccurate initial guesses of source flux strengths. The PaLS inversion framework introduced in this work is generic and can be adapted for any reactive transport model by switching the pre- and post-processing routines.

CO2 dynamics in the Amargosa Desert: Fluxes and isotopic speciation in a deep unsaturated zone

USGS Publications Warehouse

Walvoord, Michelle Ann; Striegl, Robert G.; Prudic, David E.; Stonestrom, David A.

2005-01-01

Natural unsaturated-zone gas profiles at the U.S. Geological Survey's Amargosa Desert Research Site, near Beatty, Nevada, reveal the presence of two physically and isotopically distinct CO2 sources, one shallow and one deep. The shallow source derives from seasonally variable autotrophic and heterotrophic respiration in the root zone. Scanning electron micrograph results indicate that at least part of the deep CO2 source is associated with calcite precipitation at the 110-m-deep water table. We use a geochemical gas-diffusion model to explore processes of CO2 production and behavior in the unsaturated zone. The individual isotopic species 12CO2, 13CO2, and 14CO2 are treated as separate chemical components that diffuse and react independently. Steady state model solutions, constrained by the measured δ13C (in CO2), and δ14C (in CO2) profiles, indicate that the shallow CO2 source from root and microbial respiration composes ∼97% of the annual average total CO2 production at this arid site. Despite the small contribution from deep CO2 production amounting to ∼0.1 mol m−2 yr−1, upward diffusion from depth strongly influences the distribution of CO2 and carbon isotopes in the deep unsaturated zone. In addition to diffusion from deep CO2 production, 14C exchange with a sorbed CO2 phase is indicated by the modeled δ14C profiles, confirming previous work. The new model of carbon-isotopic profiles provides a quantitative approach for evaluating fluxes of carbon under natural conditions in deep unsaturated zones.

Mass discharge assessment at a brominated DNAPL site: Effects of known DNAPL source mass removal

NASA Astrophysics Data System (ADS)

Johnston, C. D.; Davis, G. B.; Bastow, T. P.; Woodbury, R. J.; Rao, P. S. C.; Annable, M. D.; Rhodes, S.

2014-08-01

Management and closure of contaminated sites is increasingly being proposed on the basis of mass flux of dissolved contaminants in groundwater. Better understanding of the links between source mass removal and contaminant mass fluxes in groundwater would allow greater acceptance of this metric in dealing with contaminated sites. Our objectives here were to show how measurements of the distribution of contaminant mass flux and the overall mass discharge emanating from the source under undisturbed groundwater conditions could be related to the processes and extent of source mass depletion. In addition, these estimates of mass discharge were sought in the application of agreed remediation targets set in terms of pumped groundwater quality from offsite wells. Results are reported from field studies conducted over a 5-year period at a brominated DNAPL (tetrabromoethane, TBA; and tribromoethene, TriBE) site located in suburban Perth, Western Australia. Groundwater fluxes (qw; L3/L2/T) and mass fluxes (Jc; M/L2/T) of dissolved brominated compounds were simultaneously estimated by deploying Passive Flux Meters (PFMs) in wells in a heterogeneous layered aquifer. PFMs were deployed in control plane (CP) wells immediately down-gradient of the source zone, before (2006) and after (2011) 69-85% of the source mass was removed, mainly by groundwater pumping from the source zone. The high-resolution (26-cm depth interval) measures of qw and Jc along the source CP allowed investigation of the DNAPL source-zone architecture and impacts of source mass removal. Comparable estimates of total mass discharge (MD; M/T) across the source zone CP reduced from 104 g day- 1 to 24-31 g day- 1 (70-77% reductions). Importantly, this mass discharge reduction was consistent with the estimated proportion of source mass remaining at the site (15-31%). That is, a linear relationship between mass discharge and source mass is suggested. The spatial detail of groundwater and mass flux distributions also provided further evidence of the source zone architecture and DNAPL mass depletion processes. This was especially apparent in different mass-depletion rates from distinct parts of the CP. High mass fluxes and groundwater fluxes located near the base of the aquifer dominated in terms of the dissolved mass flux in the profile, although not in terms of concentrations. Reductions observed in Jc and MD were used to better target future remedial efforts. Integration of the observations from the PFM deployments and the source mass depletion provided a basis for establishing flux-based management criteria for the site.

Mass discharge assessment at a brominated DNAPL site: Effects of known DNAPL source mass removal.

PubMed

Johnston, C D; Davis, G B; Bastow, T P; Woodbury, R J; Rao, P S C; Annable, M D; Rhodes, S

2014-08-01

Management and closure of contaminated sites is increasingly being proposed on the basis of mass flux of dissolved contaminants in groundwater. Better understanding of the links between source mass removal and contaminant mass fluxes in groundwater would allow greater acceptance of this metric in dealing with contaminated sites. Our objectives here were to show how measurements of the distribution of contaminant mass flux and the overall mass discharge emanating from the source under undisturbed groundwater conditions could be related to the processes and extent of source mass depletion. In addition, these estimates of mass discharge were sought in the application of agreed remediation targets set in terms of pumped groundwater quality from offsite wells. Results are reported from field studies conducted over a 5-year period at a brominated DNAPL (tetrabromoethane, TBA; and tribromoethene, TriBE) site located in suburban Perth, Western Australia. Groundwater fluxes (qw; L(3)/L(2)/T) and mass fluxes (Jc; M/L(2)/T) of dissolved brominated compounds were simultaneously estimated by deploying Passive Flux Meters (PFMs) in wells in a heterogeneous layered aquifer. PFMs were deployed in control plane (CP) wells immediately down-gradient of the source zone, before (2006) and after (2011) 69-85% of the source mass was removed, mainly by groundwater pumping from the source zone. The high-resolution (26-cm depth interval) measures of qw and Jc along the source CP allowed investigation of the DNAPL source-zone architecture and impacts of source mass removal. Comparable estimates of total mass discharge (MD; M/T) across the source zone CP reduced from 104gday(-1) to 24-31gday(-1) (70-77% reductions). Importantly, this mass discharge reduction was consistent with the estimated proportion of source mass remaining at the site (15-31%). That is, a linear relationship between mass discharge and source mass is suggested. The spatial detail of groundwater and mass flux distributions also provided further evidence of the source zone architecture and DNAPL mass depletion processes. This was especially apparent in different mass-depletion rates from distinct parts of the CP. High mass fluxes and groundwater fluxes located near the base of the aquifer dominated in terms of the dissolved mass flux in the profile, although not in terms of concentrations. Reductions observed in Jc and MD were used to better target future remedial efforts. Integration of the observations from the PFM deployments and the source mass depletion provided a basis for establishing flux-based management criteria for the site. Copyright © 2013 Elsevier B.V. All rights reserved.

[Effect of schistosomiasis control strategy based on infection source control of Poyang Lake region in Yongxiu County promotion zone].

PubMed

Chen, Zhe; Rao, Xian-long; Li, Yi-feng; Gu, Xiao-nan; Xu, Mei-xin; Lin, Dan-dan

2015-12-01

To evaluate the effect of schistosomiasis control strategy with emphasis on infection source control in the Yongxiu County promotion zone of Poyang Lake region. The Wucheng Township of Yongxiu County was selected as the observation site, and the effect of the comprehensive control strategy was evaluated by using the method of field surveys combined with retrospective investigations. In 2010, there were 17 persons whose stool tests for schistosome infection were positive, and the number of calculated schistosomiasis patients was 2,331. The infection rate of cattle was 4.5%, and the area with infected Oncomelania hupensis snails was 10.00 hm². In 2011, the comprehensive control strategy was carried out, and in 2012, there were no cattle in the promotion zone. In 2013 and 2014, there were no schistosomiasis patients with positive stool tests. In 2014, no schistosome infected snails were found. The control strategy with emphasis on infection source control effectively controls the transmission of schistosomiasis in Yongxiu County promotion zone.

Probabilistic Seismic Hazard Analysis of Victoria, British Columbia, Canada: Considering an Active Leech River Fault

NASA Astrophysics Data System (ADS)

Kukovica, J.; Molnar, S.; Ghofrani, H.

2017-12-01

The Leech River fault is situated on Vancouver Island near the city of Victoria, British Columbia, Canada. The 60km transpressional reverse fault zone runs east to west along the southern tip of Vancouver Island, dividing the lithologic units of Jurassic-Cretaceous Leech River Complex schists to the north and Eocene Metchosin Formation basalts to the south. This fault system poses a considerable hazard due to its proximity to Victoria and 3 major hydroelectric dams. The Canadian seismic hazard model for the 2015 National Building Code of Canada (NBCC) considered the fault system to be inactive. However, recent paleoseismic evidence suggests there to be at least 2 surface-rupturing events to have exceeded a moment magnitude (M) of 6.5 within the last 15,000 years (Morell et al. 2017). We perform a Probabilistic Seismic Hazard Analysis (PSHA) for the city of Victoria with consideration of the Leech River fault as an active source. A PSHA for Victoria which replicates the 2015 NBCC estimates is accomplished to calibrate our PSHA procedure. The same seismic source zones, magnitude recurrence parameters, and Ground Motion Prediction Equations (GMPEs) are used. We replicate the uniform hazard spectrum for a probability of exceedance of 2% in 50 years for a 500 km radial area around Victoria. An active Leech River fault zone is then added; known length and dip. We are determining magnitude recurrence parameters based on a Gutenberg-Richter relationship for the Leech River fault from various catalogues of the recorded seismicity (M 2-3) within the fault's vicinity and the proposed paleoseismic events. We seek to understand whether inclusion of an active Leech River fault source will significantly increase the probabilistic seismic hazard for Victoria. Morell et al. 2017. Quaternary rupture of a crustal fault beneath Victoria, British Columbia, Canada. GSA Today, 27, doi: 10.1130/GSATG291A.1

Overview of seismic potential in the central and eastern United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schweig, E.S.

1995-12-31

The seismic potential of any region can be framed in terms the locations of source zones, the frequency of earthquake occurrence for each source, and the maximum size earthquake that can be expect from each source. As delineated by modern and historical seismicity, the most important seismic source zones affecting the eastern United States include the New Madrid and Wabash Valley seismic zones of the central U.S., the southern Appalachians and Charleston, South Carolina, areas in the southeast, and the northern Appalachians and Adirondacks in the northeast. The most prominant of these in terms of current seismicity and historical seismicmore » moment release in the New Madrid seismic zone, which produced three earthquakes of moment magnitude {ge} 8 in 1811 and 1812. The frequency of earthquake recurrence can be examined using the instrumental record, the historical record, and the geological record. Each record covers a unique time period and has a different scale of temporal resolution and completeness of the data set. The Wabash Valley is an example where the long-term geological record indicates a greater potential than the instrumental and historical records. This points to the need to examine all of the evidence in any region in order to obtain a credible estimates of earthquake hazards. Although earthquake hazards may be dominated by mid-magnitude 6 earthquakes within the mapped seismic source zones, the 1994 Northridge, California, earthquake is just the most recent example of the danger of assuming future events will occur on faults known to have had past events and how destructive such an earthquake can be.« less

[Transfer characteristic and source identification of soil heavy metals from water-level-fluctuating zone along Xiangxi River, three-Gorges Reservoir area].

PubMed

Xu, Tao; Wang, Fei; Guo, Qiang; Nie, Xiao-Qian; Huang, Ying-Ping; Chen, Jun

2014-04-01

Transfer characteristics of heavy metals and their evaluation of potential risk were studied based on determining concentration of heavy metal in soils from water-level-fluctuating zone (altitude:145-175 m) and bank (altitude: 175-185 m) along Xiangxi River, Three Gorges Reservoir area. Factor analysis-multiple linear regression (FA-MLR) was employed for heavy metal source identification and source apportionment. Results demonstrate that, during exposing season, the concentration of soil heavy metals in water-level-fluctuation zone and bank showed the variation, and the concentration of soil heavy metals reduced in shallow soil, but increased in deep soil at water-level-fluctuation zone. However, the concentration of soil heavy metals reduced in both shallow and deep soil at bank during the same period. According to the geoaccumulation index,the pollution extent of heavy metals followed the order: Cd > Pb > Cu > Cr, Cd is the primary pollutant. FA and FA-MLR reveal that in soils from water-level-fluctuation zone, 75.60% of Pb originates from traffic, 62.03% of Cd is from agriculture, 64.71% of Cu and 75.36% of Cr are from natural rock. In soils from bank, 82.26% of Pb originates from traffic, 68.63% of Cd is from agriculture, 65.72% of Cu and 69.33% of Cr are from natural rock. In conclusion, FA-MLR can successfully identify source of heavy metal and compute source apportionment of heavy metals, meanwhile the transfer characteristic is revealed. All these information can be a reference for heavy metal pollution control.

Model assessment of atmospheric pollution control schemes for critical emission regions

NASA Astrophysics Data System (ADS)

Zhai, Shixian; An, Xingqin; Liu, Zhao; Sun, Zhaobin; Hou, Qing

2016-01-01

In recent years, the atmospheric environment in portions of China has become significantly degraded and the need for emission controls has become urgent. Because more international events are being planned, it is important to implement air quality assurance targeted at significant events held over specific periods of time. This study sets Yanqihu (YQH), Beijing, the location of the 2014 Beijing APEC (Asia-Pacific Economic Cooperation) summit, as the target region. By using the atmospheric inversion model FLEXPART, we determined the sensitive source zones that had the greatest impact on the air quality of the YQH region in November 2012. We then used the air-quality model Models-3/CMAQ and a high-resolution emissions inventory of the Beijing-Tianjian-Hebei region to establish emission reduction tests for the entire source area and for specific sensitive source zones. This was achieved by initiating emission reduction schemes at different ratios and different times. The results showed that initiating a moderate reduction of emissions days prior to a potential event is more beneficial to the air quality of Beijing than initiating a high-strength reduction campaign on the day of the event. The sensitive source zone of Beijing (BJ-Sens) accounts for 54.2% of the total source area of Beijing (BJ), but its reduction effect reaches 89%-100% of the total area, with a reduction efficiency 1.6-1.9 times greater than that of the entire area. The sensitive source zone of Huabei (HuaB-Sens.) only represents 17.6% of the total area of Huabei (HuaB), but its emission reduction effect reaches 59%-97% of the entire area, with a reduction efficiency 4.2-5.5 times greater than that of the total area. The earlier that emission reduction measures are implemented, the greater the effect they have on preventing the transmission of pollutants. In addition, expanding the controlling areas to sensitive provinces and cities around Beijing (HuaB-sens) can significantly accelerate the reduction effects compared to controlling measures only in the Beijing sensitive source zone (BJ-Sens). Therefore, when enacting emission reduction schemes, cooperating with surrounding provinces and cities, as well as narrowing the reduction scope to specific sensitive source zones prior to unfavorable meteorological conditions, can help reduce emissions control costs and improve the efficiency and maneuverability of emission reduction schemes.

High-resolution x-ray imaging for microbiology at the Advanced Photon Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, B.; Kemner, K. M.; Maser, J.

1999-11-02

Exciting new applications of high-resolution x-ray imaging have emerged recently due to major advances in high-brilliance synchrotrons sources and high-performance zone plate optics. Imaging with submicron resolution is now routine with hard x-rays: the authors have demonstrated 150 run in the 6--10 keV range with x-ray microscopes at the Advanced Photon Source (APS), a third-generation synchrotrons radiation facility. This has fueled interest in using x-ray imaging in applications ranging from the biomedical, environmental, and materials science fields to the microelectronics industry. One important application they have pursued at the APS is a study of the microbiology of bacteria and theirmore » associated extracellular material (biofilms) using fluorescence microanalysis. No microscopy techniques were previously available with sufficient resolution to study live bacteria ({approx}1 {micro}m x 4 {micro}m in size) and biofilms in their natural hydrated state with better than part-per-million elemental sensitivity and the capability of determining g chemical speciation. In vivo x-ray imaging minimizes artifacts due to sample fixation, drying, and staining. This provides key insights into the transport of metal contaminants by bacteria in the environment and potential new designs for remediation and sequestration strategies.« less

Root-zone temperature and water availability affect early root growth of planted longleaf pine

Treesearch

M.A. Sword

1995-01-01

Longleaf pine seedlings from three seed sources were exposed to three root-zone temperatures and three levels of water availability for 28 days. Root growth declined as temperature and water availability decreased. Root growth differed by seed source. Results suggest that subtle changes in the regeneration environment may influence early root growth of longleaf pine...

A Two and Half-Year-Performance Evaluation of a Field Test on Treatment of Source Zone Tetrachloroethene and Its Chlorinated Daughter Products Using Emulsified Zaro Valent Iron Nanoparticles

EPA Science Inventory

A field test of emulsified zero valent iron (EZVI) nanoparticles was conducted at Parris Island, SC, USA and was monitored for two and half years to assess the treatment of subsurface-source zone chlorinated volatile organic compounds (CVOCs) dominated by tetrachloroethene (PCE) ...

DipTest: A litmus test for E. coli detection in water.

PubMed

Gunda, Naga Siva Kumar; Dasgupta, Saumyadeb; Mitra, Sushanta K

2017-01-01

We have developed a new litmus paper test (DipTest) for detecting Escherichia coli (E. coli) in water samples by performing enzymatic reactions directly on the porous paper substrate. The paper strip consists of a long narrow piece of cellulose blotting paper coated with chemoattractant (at bottom edge), wax hydrophobic barrier (at the top edge), and custom formulated chemical reagents (at reaction zone immediately below the wax hydrophobic barrier). When the paper strip is dipped in water, E. coli in the water sample is attracted toward the paper strip due to a chemotaxic mechanism followed by the ascent along the paper strip toward the reaction zone due to a capillary wicking mechanism, and finally the capillary motion is arrested at the top edge of the paper strip by the hydrophobic barrier. The E. coli concentrated at the reaction zone of the paper strip will react with custom formulated chemical reagents to produce a pinkish-red color. Such a color change on the paper strip when dipped into water samples indicates the presence of E. coli contamination in potable water. The performance of the DipTest device has been checked with different known concentrations of E. coli contaminated water samples using different dip and wait times. The DipTest device has also been tested with different interfering bacteria and chemical contaminants. It has been observed that the different interfering contaminants do not have any impact on the DipTest, and it can become a potential solution for screening water samples for E. coli contamination at the point of source.

DipTest: A litmus test for E. coli detection in water

PubMed Central

Gunda, Naga Siva Kumar; Dasgupta, Saumyadeb

2017-01-01

We have developed a new litmus paper test (DipTest) for detecting Escherichia coli (E. coli) in water samples by performing enzymatic reactions directly on the porous paper substrate. The paper strip consists of a long narrow piece of cellulose blotting paper coated with chemoattractant (at bottom edge), wax hydrophobic barrier (at the top edge), and custom formulated chemical reagents (at reaction zone immediately below the wax hydrophobic barrier). When the paper strip is dipped in water, E. coli in the water sample is attracted toward the paper strip due to a chemotaxic mechanism followed by the ascent along the paper strip toward the reaction zone due to a capillary wicking mechanism, and finally the capillary motion is arrested at the top edge of the paper strip by the hydrophobic barrier. The E. coli concentrated at the reaction zone of the paper strip will react with custom formulated chemical reagents to produce a pinkish-red color. Such a color change on the paper strip when dipped into water samples indicates the presence of E. coli contamination in potable water. The performance of the DipTest device has been checked with different known concentrations of E. coli contaminated water samples using different dip and wait times. The DipTest device has also been tested with different interfering bacteria and chemical contaminants. It has been observed that the different interfering contaminants do not have any impact on the DipTest, and it can become a potential solution for screening water samples for E. coli contamination at the point of source. PMID:28877199

Impact of kinetic mass transfer on free convection in a porous medium

NASA Astrophysics Data System (ADS)

Lu, Chunhui; Shi, Liangsheng; Chen, Yiming; Xie, Yueqing; Simmons, Craig T.

2016-05-01

We investigate kinetic mass transfer effects on unstable density-driven flow and transport processes by numerical simulations of a modified Elder problem. The first-order dual-domain mass transfer model coupled with a variable-density-flow model is employed to describe transport behavior in porous media. Results show that in comparison to the no-mass-transfer case, a higher degree of instability and more unstable system is developed in the mass transfer case due to the reduced effective porosity and correspondingly a larger Rayleigh number (assuming permeability is independent on the mobile porosity). Given a constant total porosity, the magnitude of capacity ratio (i.e., immobile porosity/mobile porosity) controls the macroscopic plume profile in the mobile domain, while the magnitude of mass transfer timescale (i.e., the reciprocal of the mass transfer rate coefficient) dominates its evolution rate. The magnitude of capacity ratio plays an important role on the mechanism driving the mass flux into the aquifer system. Specifically, for a small capacity ratio, solute loading is dominated by the density-driven transport, while with increasing capacity ratio local mass transfer dominated solute loading may occur at later times. At significantly large times, however, both mechanisms contribute comparably to solute loading. Sherwood Number could be a nonmonotonic function of mass transfer timescale due to complicated interactions of solute between source zone, mobile zone and immobile zone in the top boundary layer, resulting in accordingly a similar behavior of the total mass. The initial assessment provides important insights into unstable density-driven flow and transport in the presence of kinetic mass transfer.

Hydrogeophysical imaging of deposit heterogeneity and groundwater chemistry changes during DNAPL source zone bioremediation.

PubMed

Chambers, J E; Wilkinson, P B; Wealthall, G P; Loke, M H; Dearden, R; Wilson, R; Allen, D; Ogilvy, R D

2010-10-21

Robust characterization and monitoring of dense nonaqueous phase liquid (DNAPL) source zones is essential for designing effective remediation strategies, and for assessing the efficacy of treatment. In this study high-resolution cross-hole electrical resistivity tomography (ERT) was evaluated as a means of monitoring a field-scale in-situ bioremediation experiment, in which emulsified vegetable oil (EVO) electron donor was injected into a trichloroethene source zone. Baseline ERT scans delineated the geometry of the interface between the contaminated alluvial aquifer and the underlying mudstone bedrock, and also the extent of drilling-induced physical heterogeneity. Time-lapse ERT images revealed major preferential flow pathways in the source and plume zones, which were corroborated by multiple lines of evidence, including geochemical monitoring and hydraulic testing using high density multilevel sampler arrays within the geophysical imaging planes. These pathways were shown to control the spatial distribution of the injected EVO, and a bicarbonate buffer introduced into the cell for pH control. Resistivity signatures were observed within the preferential flow pathways that were consistent with elevated chloride levels, providing tentative evidence from ERT of the biodegradation of chlorinated solvents. Copyright © 2010 S. Yamamoto. Published by Elsevier B.V. All rights reserved.

Contrasts between source parameters of M [>=] 5. 5 earthquakes in northern Baja California and southern California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doser, D.I.

1993-04-01

Source parameters determined from the body waveform modeling of large (M [>=] 5.5) historic earthquakes occurring between 1915 and 1956 along the San Jacinto and Imperial fault zones of southern California and the Cerro Prieto, Tres Hermanas and San Miguel fault zones of Baja California have been combined with information from post-1960's events to study regional variations in source parameters. The results suggest that large earthquakes along the relatively young San Miguel and Tres Hermanas fault zones have complex rupture histories, small source dimensions (< 25 km), high stress drops (60 bar average), and a high incidence of foreshock activity.more » This may be a reflection of the rough, highly segmented nature of the young faults. In contrast, Imperial-Cerro Prieto events of similar magnitude have low stress drops (16 bar average) and longer rupture lengths (42 km average), reflecting rupture along older, smoother fault planes. Events along the San Jacinto fault zone appear to lie in between these two groups. These results suggest a relationship between the structural and seismological properties of strike-slip faults that should be considered during seismic risk studies.« less

Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

USGS Publications Warehouse

Amos, Richard T.; Mayer, K. Ulrich

2006-01-01

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O2 to waters otherwise depleted in O2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given conditions more than 50% of all produced CH4 partitions to the gas phase or is aerobically oxidised near the water table, suggesting that these processes should be accounted for when assessing the rate and extent of methanogenic degradation of hydrocarbons.

Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

NASA Astrophysics Data System (ADS)

Amos, Richard T.; Ulrich Mayer, K.

2006-09-01

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O 2 to waters otherwise depleted in O 2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given conditions more than 50% of all produced CH 4 partitions to the gas phase or is aerobically oxidised near the water table, suggesting that these processes should be accounted for when assessing the rate and extent of methanogenic degradation of hydrocarbons.

INEEL Source Water Assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sehlke, Gerald

2003-03-01

The Idaho National Engineering and Environmental Laboratory (INEEL) covers approximately 890 mi2 and includes 12 public water systems that must be evaluated for Source water protection purposes under the Safe Drinking Water Act. Because of its size and location, six watersheds and five aquifers could potentially affect the INEEL’s drinking water sources. Based on a preliminary evaluation of the available information, it was determined that the Big Lost River, Birch Creek, and Little Lost River Watersheds and the eastern Snake River Plain Aquifer needed to be assessed. These watersheds were delineated using the United States Geologic Survey’s Hydrological Unit scheme.more » Well capture zones were originally estimated using the RESSQC module of the Environmental Protection Agency’s Well Head Protection Area model, and the initial modeling assumptions and results were checked by running several scenarios using Modflow modeling. After a technical review, the resulting capture zones were expanded to account for the uncertainties associated with changing groundwater flow directions, a thick vadose zone, and other data uncertainties. Finally, all well capture zones at a given facility were merged to a single wellhead protection area at each facility. A contaminant source inventory was conducted, and the results were integrated with the well capture zones, watershed and aquifer information, and facility information using geographic information system technology to complete the INEEL’s Source Water Assessment. Of the INEEL’s 12 public water systems, three systems rated as low susceptibility (EBR-I, Main Gate, and Gun Range), and the remainder rated as moderate susceptibility. No INEEL public water system rated as high susceptibility. We are using this information to develop a source water management plan from which we will subsequently implement an INEEL-wide source water management program. The results are a very robust set of wellhead protection areas that will protect the INEEL’s public water systems yet not too conservative to inhibit the INEEL from carrying out its missions.« less

The Idaho National Engineering and Environmental Laboratory Source Water Assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sehlke, G.

2003-03-17

The Idaho National Engineering and Environmental Laboratory (INEEL) covers approximately 890 square miles and includes 12 public water systems that must be evaluated for Source water protection purposes under the Safe Drinking Water Act. Because of its size and location, six watersheds and five aquifers could potentially affect the INEEL's drinking water sources. Based on a preliminary evaluation of the available information, it was determined that the Big Lost River, Birch Creek, and Little Lost River Watersheds and the eastern Snake River Plain Aquifer needed to be assessed. These watersheds were delineated using the United States Geologic Survey's Hydrological Unitmore » scheme. Well capture zones were originally estimated using the RESSQC module of the Environmental Protection Agency's Well Head Protection Area model, and the initial modeling assumptions and results were checked by running several scenarios using Modflow modeling. After a technical review, the resulting capture zones were expanded to account for the uncertainties associated with changing groundwater flow directions, a this vadose zone, and other data uncertainties. Finally, all well capture zones at a given facility were merged to a single wellhead protection area at each facility. A contaminant source inventory was conducted, and the results were integrated with the well capture zones, watershed and aquifer information, and facility information using geographic information system technology to complete the INEEL's Source Water Assessment. Of the INEEL's 12 public water systems, three systems rated as low susceptibility (EBR-1, Main Gate, and Gun Range), and the remainder rated as moderate susceptibility. No INEEL public water system rated as high susceptibility. We are using this information to develop a source water management plan from which we will subsequently implement an INEEL-wide source water management program. The results are a very robust set of wellhead protection areas that will protect the INEEL's public water systems yet not too conservative to inhibit the INEEL from carrying out its missions.« less

Impact of cascadia subduction zone earthquake on the seismic evaluation criteria of bridges : technical report : SPR 770.

DOT National Transportation Integrated Search

2016-12-01

A large magnitude long duration subduction earthquake is impending in the Pacific Northwest, which lies near the : Cascadia Subduction Zone (CSZ). Great subduction zone earthquakes are the largest earthquakes in the world and are the sole source : zo...

Assessment of source of information for polio supplementary immunization activities in 2014 and 2015, Somali, Ethiopia

PubMed Central

Bedada, Selamawit Yilma; Gallagher, Kathleen; Aregay, Aron Kassahun; Mohammed, Bashir; Maalin, Mohammed Adem; Hassen, Hassen Abdisemed; Ali, Yusuf Mohammed; Braka, Fiona; Kilebou, Pierre M’pele

2017-01-01

Introduction Communication is key for the successful implementation of polio vaccination campaigns. The purpose of this study is to review and analyse the sources of information utilized by caregivers during polio supplementary immunization activities (SIAs) in Somali, Ethiopia in 2014 and 2015. Methods Data on sources of information about the polio campaign were collected post campaign from caregivers by trained data collectors as part of house to house independent monitoring. The sources of information analysed in this paper include town criers (via megaphones), health workers, religious leaders, kebele leaders (Kebele is the lowest administrative structure in Ethiopia), radio, television, text message and others. The repetition of these sources of information was analysed across years and zones for trends. Polio vaccination campaign coverage was also reviewed by year and zones within the Somali region in parallel with the major sources of information used in the respective year and zones. 57,745 responses were used for this analysis but the responses were received from < or = 57,745 individuals since some of them may provide more than one response. Moreover, because sampling of households is conducted independently during each round of independent monitoring, the same household may have been included more than once in our analysis. The methodology used for independent monitoring does not allow for the calculation of response rates. Monitors go from house to house until information from 20 households is received. Results From the total 57,745 responses reviewed, over 37% of respondents reported that town criers were their source for information about the 2014 and 2015 polio SIAs. Zonal trends in using town criers as a major source of information in both study years remained consistent except in two zones. 87.5% of zones that reported at least 90% coverage during both study years had utilized town criers as a major source of information while the rest (12.5%) used health workers. Conclusion We found that town criers were consistently the major source of information about the polio campaigns for Somali region parents and caregivers during polio immunization days held in 2014 and 2015. Health workers and kebele leaders were also important sources of information about the polio campaign for parents. PMID:28983395

Cross-Matching Source Observations from the Palomar Transient Factory (PTF)

NASA Astrophysics Data System (ADS)

Laher, Russ; Grillmair, C.; Surace, J.; Monkewitz, S.; Jackson, E.

2009-01-01

Over the four-year lifetime of the PTF project, approximately 40 billion instances of astronomical-source observations will be extracted from the image data. The instances will correspond to the same astronomical objects being observed at roughly 25-50 different times, and so a very large catalog containing important object-variability information will be the chief PTF product. Organizing astronomical-source catalogs is conventionally done by dividing the catalog into declination zones and sorting by right ascension within each zone (e.g., the USNOA star catalog), in order to facilitate catalog searches. This method was reincarnated as the "zones" algorithm in a SQL-Server database implementation (Szalay et al., MSR-TR-2004-32), with corrections given by Gray et al. (MSR-TR-2006-52). The primary advantage of this implementation is that all of the work is done entirely on the database server and client/server communication is eliminated. We implemented the methods outlined in Gray et al. for a PostgreSQL database. We programmed the methods as database functions in PL/pgSQL procedural language. The cross-matching is currently based on source positions, but we intend to extend it to use both positions and positional uncertainties to form a chi-square statistic for optimal thresholding. The database design includes three main tables, plus a handful of internal tables. The Sources table stores the SExtractor source extractions taken at various times; the MergedSources table stores statistics about the astronomical objects, which are the result of cross-matching records in the Sources table; and the Merges table, which associates cross-matched primary keys in the Sources table with primary keys in the MergedSoures table. Besides judicious database indexing, we have also internally partitioned the Sources table by declination zone, in order to speed up the population of Sources records and make the database more manageable. The catalog will be accessible to the public after the proprietary period through IRSA (irsa.ipac.caltech.edu).

Temporal and spatial patterns for surf zone bacteria before and after disinfection of the orange county sanitation district effluent

USGS Publications Warehouse

Robertson, G.L.; Noble, M.A.; Xu, J. P.; Rosenfeld, L.K.; McGee, C.D.

2005-01-01

Data from pre- and post-disinfection fecal indicator bacteria (FIB) samples from final effluent, an offshore ocean outfall, and surf zone stations off Huntington Beach, CA were compared. Analysis of the results from these data sets confirmed that the ocean outfall was not the FIB source responsible for the postings and closures of local beaches that have occurred each summer since 1999. While FIB counts in the final effluent and offshore showed several order of magnitude reductions after disinfection, there were no significant reductions at the nearby surf zone stations. Additionally, the FIB spectral patterns suggest different sources. The dominant fortnightly cycle suggested that the source was related to the wetting and draining of the land from large spring tide tidal excursions.

Determination of viable Salmonellae from potable and source water through PMA assisted qPCR.

PubMed

Singh, Gulshan; Vajpayee, Poornima; Bhatti, Saurabh; Ronnie, Nirmala; Shah, Nimish; McClure, Peter; Shanker, Rishi

2013-07-01

Resource constrained countries identified as endemic zones for pathogenicity of Salmonella bear an economic burden due to recurring expenditure on medical treatment. qPCR used for Salmonella detection could not discriminate between viable and nonviable cells. Propidium monoazide (PMA) that selectively penetrates nonviable cells to cross-link their DNA, was coupled with ttr gene specific qPCR for quantifying viable salmonellae in source/potable waters collected from a north Indian city. Source water (raw water for urban potable water supply) and urban potable water exhibited viable salmonellae in the range of 2.1×10(4)-2.6×10(6) and 2-7160CFU/100mL, respectively. Potable water at water works exhibited DNA from dead cells but no viable cells were detected. PMA assisted qPCR could specifically detect low numbers of live salmonellae in Source and potable waters. This strategy can be used in surveillance of urban potable water distribution networks to map contamination points for better microbial risk management. Copyright © 2013 Elsevier Inc. All rights reserved.

Role of natural attenuation in modeling the leaching of contaminants in the risk analysis framework.

PubMed

Verginelli, Iason; Baciocchi, Renato

2013-01-15

Natural attenuation (NA) processes occurring in the subsurface can significantly affect the impact on groundwater from contamination sources located in the vadose zone, especially when mobile and readily biodegradable compounds, such as BTEX, are present. Besides, in the last decades several studies have shown natural attenuation to take place also for more persistent compounds, such as Polycyclic Aromatic Hydrocarbons (PAHs). Nevertheless, common risk analysis frameworks, based on the ASTM RBCA (Risk Based Corrective Action) approach, do not include NA pathways in the fate and transport models, thus possibly leading to an overestimation of the calculated risk. The aim of this study was to provide an insight on the relevance of the different key natural attenuation processes usually taking place in the subsurface and to highlight for which contamination scenarios their inclusion in the risk-analysis framework could provide a more realistic risk assessment. To this end, an analytical model accounting for source depletion and biodegradation, dispersion and diffusion during leaching was developed and applied to several contamination scenarios. These scenarios included contamination by BTEX, characterized by relatively high mobility and biodegradation rate, and PAHs, i.e. a more persistent class of compounds. The obtained results showed that BTEX are likely to be attenuated in the source zone due to their mobility and ready biodegradation (assuming biodegradation constant rates in the order of 0.01-1 d(-1)). Instead, attenuation along transport through the vadose zone was found to be less important, as the residence time of the contaminant in the unsaturated zone is often too low with respect to the time required to get a relevant biodegradation of BTEX. On the other hand, heavier compounds such as PAHs, were found to be attenuated during leaching since the residence time in the vadose zone can reach values up to thousands of years. In these cases, even with the relatively slow biodegradation rate of PAHs, in the order of 0.0001-0.001 d(-1), attenuation can result significant. These conclusions were also confirmed by comparing the model results with experimental data collected at an hydrocarbon-contaminated site. The proposed model, that neglects the transport of NAPLs, could be easily included in the risk-analysis framework, allowing to get a more realistic assessment of risks, while keeping the intrinsic simplicity of the ASTM-RBCA approach. Copyright © 2012 Elsevier Ltd. All rights reserved.

Emergence and petrology of the Mendocino Ridge

NASA Astrophysics Data System (ADS)

Fisk, Martin R.; Duncan, Robert A.; Fox, Christopher G.; Witter, Jeffrey B.

1993-11-01

The Mendocino Fracture Zone, a 3,000-km-long transform fault, extends from the San Andreas Fault at Cape Mendocino, California due west into the central Pacific basin. The shallow crest of this fracture zone, known as the Mendocino Ridge, rises to within 1,100 m of the sea surface at 270 km west of the California Coast. Rounded basalt pebbles and cobbles, indicative of a beach environment, are the dominant lithology at two locations on the crest of Mendocino Ridge and a40Ar/39 Ar incremental heating age of 11.0 ± 1.0 million years was determined for one of the these cobbles. This basalt must have been erupted on the Gorda Ridge because the crust immediately to the south of the fracture zone is older than 27 Ma. This age also implies that the crest of Mendocino Ridge was at sea level and would have blocked Pacific Ocean eastern boundary currents and affected the climate of the North American continent at some time since the late Miocene. Basalts from the Mendocino Fracture Zone (MFZ) are FeTi basalts similar to those commonly found at intersections of mid-ocean ridges and fracture zones. These basalts are chemically distinct from the nearby Gorda Ridge but they could have been derived from the same mantle source as the Gorda Ridge basalts. The location of the 11 Ma basalt suggests that Mendocino Ridge was transferred from the Gorda Plate to the Pacific Plate and the southern end of Gorda Ridge was truncated by a northward jump in the transform fault of MFZ.

The new Central American seismic hazard zonation: Mutual consensus based on up to day seismotectonic framework

NASA Astrophysics Data System (ADS)

Alvarado, Guillermo E.; Benito, Belén; Staller, Alejandra; Climent, Álvaro; Camacho, Eduardo; Rojas, Wilfredo; Marroquín, Griselda; Molina, Enrique; Talavera, J. Emilio; Martínez-Cuevas, Sandra; Lindholm, Conrad

2017-11-01

Central America is one of the most active seismic zones in the World, due to the interaction of five tectonic plates (North America, Caribbean, Coco, Nazca and South America), and its internal deformation, which generates almost one destructive earthquakes (5.4 ≤ Mw ≤ 8.1) every year. A new seismological zonation for Central America is proposed based on seismotectonic framework, a geological context (tectonic and geological maps), geophysical and geodetic evidence (gravimetric maps, magnetometric, GPS observations), and previous works. As a main source of data a depurated earthquake catalog was collected covering the period from 1522 to 2015. This catalog was homogenized to a moment magnitude scale (Mw). After a careful analysis of all the integrated geological and seismological information, the seismogenic zones were established into seismic areas defined by similar patterns of faulting, seismicity, and rupture mechanism. The tectonic environment has required considering seismic zones in two particular seismological regimes: a) crustal faulting (including local faults, major fracture zones of plate boundary limits, and thrust fault of deformed belts) and b) subduction, taking into account the change in the subduction angle along the trench, and the type and location of the rupture. The seismicity in the subduction zone is divided into interplate and intraplate inslab seismicity. The regional seismic zonation proposed for the whole of Central America, include local seismic zonations, avoiding discontinuities at the national boundaries, because of a consensus between the 7 countries, based on the cooperative work of specialists on Central American seismotectonics and related topics.

Comment on Sub-15 nm Hard X-Ray Focusing with a New Total-Reflection Zone Plate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Specht, Eliot D

2011-01-01

Takano et al. report the focusing of 10-keV X-rays to a size of 14.4 nm using a total-reflection zone plate (TRZP). This focal size is at the diffraction limit for the optic's aperture. This would be a noteworthy result, since the TRZP was fabricated using conventional lithography techniques. Alternative nanofocusing optics require more demanding fabrication methods. However, as I will discuss in this Comment, the intensity distribution presented by Takano et al. (Fig. 4 of ref. 1) is more consistent with the random speckle pattern produced by the scattering of a coherent incident beam by a distorted optic than withmore » a diffraction-limited focus. When interpreted in this manner, the true focal spot size is {approx}70 nm: 5 times the diffraction limit. When a coherent photon beam illuminates an optic containing randomly distributed regions which introduce different phase shifts, the scattered diffraction pattern consists of a speckle pattern. Each speckle will be diffraction-limited: the peak width of a single speckle depends entirely on the source coherence and gives no information about the optic. The envelope of the speckle distribution corresponds to the focal spot which would be observed using incoherent illumination. The width of this envelope is due to the finite size of the coherently-diffracting domains produced by slope and position errors in the optic. The focal intensity distribution in Fig. 4 of ref. 1 indeed contains a diffraction-limited peak, but this peak contains only a fraction of the power in the focused, and forms part of a distribution of sharp peaks with an envelope {approx}70 nm in width, just as expected for a speckle pattern. At the 4mm focal distance, the 70 nm width corresponds to a slope error of 18 {micro}rad. To reach the 14 nm diffraction limit, the slope error must be reduced to 3 {micro}rad. Takano et al. have identified a likely source of this error: warping due to stress as a result of zone deposition. It will be interesting to see whether the use of a more rigid substrate gives improved results.« less

Global Source Parameters from Regional Spectral Ratios for Yield Transportability Studies

NASA Astrophysics Data System (ADS)

Phillips, W. S.; Fisk, M. D.; Stead, R. J.; Begnaud, M. L.; Rowe, C. A.

2016-12-01

We use source parameters such as moment, corner frequency and high frequency rolloff as constraints in amplitude tomography, ensuring that spectra of well-studied earthquakes are recovered using the ensuing attenuation and site term model. We correct explosion data for path and site effects using such models, which allows us to test transportability of yield estimation techniques based on our best source spectral estimates. To develop a background set of source parameters, we applied spectral ratio techniques to envelopes of a global set of regional distance recordings from over 180,000 crustal events. Corner frequencies and moment ratios were determined via inversion using all event pairs within predetermined clusters, shifting to absolute levels using independently determined regional and teleseismic moments. The moment and corner frequency results can be expressed as stress drop, which has considerable scatter, yet shows dramatic regional patterns. We observe high stress in subduction zones along S. America, S. Mexico, the Banda Sea, and associated with the Yakutat Block in Alaska. We also observe high stress at the Himalayan syntaxes, the Pamirs, eastern Iran, the Caspian, the Altai-Sayan, and the central African rift. Low stress is observed along mid ocean spreading centers, the Afar rift, patches of convergence zones such as Nicaragua, the Zagros, Tibet, and the Tien Shan, among others. Mine blasts appear as low stress events due to their low corners and steep rolloffs. Many of these anomalies have been noted by previous studies, and we plan to compare results directly. As mentioned, these results will be used to constrain tomographic imaging, but can also be used in model validation procedures similar to the use of ground truth in location problems, and, perhaps most importantly, figure heavily in quality control of local and regional distance amplitude measurements.

Where does streamwater come from in low-relief forested watersheds? A dual-isotope approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klaus, J.; McDonnell, J. J.; Jackson, C. R.

The time and geographic sources of streamwater in low-relief watersheds are poorly understood. This is partly due to the difficult combination of low runoff coefficients and often damped streamwater isotopic signals precluding traditional hydrograph separation and convolution integral approaches. Here we present a dual-isotope approach involving 18O and 2H of water in a low-angle forested watershed to determine streamwater source components and then build a conceptual model of streamflow generation. We focus on three headwater lowland sub-catchments draining the Savannah River Site in South Carolina, USA. Our results for a 3-year sampling period show that the slopes of the meteoricmore » water lines/evaporation water lines (MWLs/EWLs) of the catchment water sources can be used to extract information on runoff sources in ways not considered before. Our dual-isotope approach was able to identify unique hillslope, riparian and deep groundwater, and streamflow compositions. Thus, the streams showed strong evaporative enrichment compared to the local meteoric water line (δ 2H = 7.15 · δ 18O +9.28‰) with slopes of 2.52, 2.84, and 2.86. Based on the unique and unambiguous slopes of the EWLs of the different water cycle components and the isotopic time series of the individual components, we were able to show how the riparian zone controls baseflow in this system and how the riparian zone "resets" the stable isotope composition of the observed streams in our low-angle, forested watersheds. Although this approach is limited in terms of quantifying mixing percentages between different end-members, our dual-isotope approach enabled the extraction of hydrologically useful information in a region with little change in individual isotope time series.« less

Where does streamwater come from in low-relief forested watersheds? A dual-isotope approach

DOE PAGES

Klaus, J.; McDonnell, J. J.; Jackson, C. R.; ...

2015-01-08

The time and geographic sources of streamwater in low-relief watersheds are poorly understood. This is partly due to the difficult combination of low runoff coefficients and often damped streamwater isotopic signals precluding traditional hydrograph separation and convolution integral approaches. Here we present a dual-isotope approach involving 18O and 2H of water in a low-angle forested watershed to determine streamwater source components and then build a conceptual model of streamflow generation. We focus on three headwater lowland sub-catchments draining the Savannah River Site in South Carolina, USA. Our results for a 3-year sampling period show that the slopes of the meteoricmore » water lines/evaporation water lines (MWLs/EWLs) of the catchment water sources can be used to extract information on runoff sources in ways not considered before. Our dual-isotope approach was able to identify unique hillslope, riparian and deep groundwater, and streamflow compositions. Thus, the streams showed strong evaporative enrichment compared to the local meteoric water line (δ 2H = 7.15 · δ 18O +9.28‰) with slopes of 2.52, 2.84, and 2.86. Based on the unique and unambiguous slopes of the EWLs of the different water cycle components and the isotopic time series of the individual components, we were able to show how the riparian zone controls baseflow in this system and how the riparian zone "resets" the stable isotope composition of the observed streams in our low-angle, forested watersheds. Although this approach is limited in terms of quantifying mixing percentages between different end-members, our dual-isotope approach enabled the extraction of hydrologically useful information in a region with little change in individual isotope time series.« less

Evaluation of groundwater and soil pollution in a landfill area using electrical resistivity imaging survey.

PubMed

Ahmed, A M; Sulaiman, W N

2001-11-01

Landfills are sources of groundwater and soil pollution due to the production of leachate and its migration through refuse. This study was conducted in order to determine the extent of groundwater and soil pollution within and around the landfill of Seri Petaling located in the State of Selangor, Malaysia. The condition of nearby surface water was also determined. An electrical resistivity imaging survey was used to investigate the leachate production within the landfill. Groundwater geochemistry was carried out and chemical analysis of water samples was conducted upstream and downstream of the landfill. Surface water was also analyzed in order to determine its quality. Soil chemical analysis was performed on soil samples taken from different locations within and around the landfill in the vadose zone (unsaturated zone) and below the water table (in the soil saturated zone). The resistivity image along line L-L1 indicated the presence of large zones of decomposed waste bodies saturated with highly conducting leachate. Analysis of trace elements indicated their presence in very low concentrations and did not reflect any sign of heavy metal pollution of ground and surface water or of soil. Major ions represented by Na, K, and Cl were found in anomalous concentrations in the groundwater of the downstream bore hole, where they are 99.1%, 99.2%, and 99.4%, respectively, higher compared to the upstream bore hole. Electrical conductivity (EC) was also found in anomalous concentration downstream. Ca and Mg ions represent the water hardness (which is comparatively high downstream). There is a general trend of pollution towards the downstream area. Sulfates (SO4) and nitrates (NO3) are found in the area in low concentrations, even below the WHO standards for drinking water, but are significantly higher in the surface water compared to the groundwater. Phosphate (PO4) and nitrite (NO2), although present in low levels, are significantly higher at the downstream. There is no significant difference in the amount of fluoride (F) in the different locations. In the soil vadose zone, heavy metals were found to be in their typical normal ranges and within the background concentrations. Soil exchangeable bases were significantly higher in the soil saturated zone compared to the vadose zone, and no significant difference was obtained in the levels of inorganic pollutants. With the exception of Cd, the concentration ranges of all trace elements (Cu, Zn, Cr, Pb, and Ni) of Seri Petaling landfill soils were below the upper limits of baseline concentrations published from different sources.

78 FR 42016 - Safety Zone; Discovery World Fireworks, Milwaukee Harbor, Milwaukee, WI

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-15

...-AA00 Safety Zone; Discovery World Fireworks, Milwaukee Harbor, Milwaukee, WI AGENCY: Coast Guard, DHS... Milwaukee Harbor due to 4 fireworks displays at Discovery World Pier. This safety zone is necessary to... entitled, ``Safety Zone; Discovery World Fireworks, Milwaukee Harbor, Milwaukee, Wisconsin'' in the Federal...

Work zone simulator analysis : driver performance and acceptance of alternate merge sign configurations.

DOT National Transportation Integrated Search

2016-06-01

Improving work zone road safety is an issue of great interest due to the high number of crashes observed in work : zones. Departments of Transportation (DOTs) use a variety of methods to inform drivers of upcoming work zones. One method : used by DOT...

Estimating the Impact of Vadose Zone Sources on Groundwater to Support Performance Assessment of Soil Vapor Extraction

EPA Science Inventory

Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants in the vadose zone. To support selection of an appropriate endpoint for the SVE remedy, an evaluation is needed to determine whether vadose zone contamination has been diminished sufficient...

Evaluation of multidimensional transport through a field-scale compacted soil liner

USGS Publications Warehouse

Willingham, T.W.; Werth, C.J.; Valocchi, A.J.; Krapac, I.G.; Toupiol, C.; Stark, T.D.; Daniel, D.E.

2004-01-01

A field-scale compacted soil liner was constructed at the University of Illinois at Urbana-Champaign by the U.S. Environmental Protection Agency (USEPA) and Illinois State Geological Survey in 1988 to investigate chemical transport rates through low permeability compacted clay liners (CCLs). Four tracers (bromide and three benzoic acid tracers) were each added to one of four large ring infiltrometers (LRIs) while tritium was added to the pond water (excluding the infiltrometers). Results from the long-term transport of Br- from the localized source zone of LRI are presented in this paper. Core samples were taken radially outward from the center of the Br- LRI and concentration depth profiles were obtained. Transport properties were evaluated using an axially symmetric transport model. Results indicate that (1) transport was diffusion controlled; (2) transport due to advection was negligible and well within the regulatory limits of ksat???1 ?? 10-7 cm/s; (3) diffusion rates in the horizontal and vertical directions were the same; and (4) small positioning errors due to compression during soil sampling did not affect the best fit advection and diffusion values. The best-fit diffusion coefficient for bromide was equal to the molecular diffusion coefficient multiplied by a tortuosity factor of 0.27, which is within 8% of the tortuosity factor (0.25) found in a related study where tritium transport through the same liner was evaluated. This suggests that the governing mechanisms for the transport of tritium and bromide through the CCL were similar. These results are significant because they address transport through a composite liner from a localized source zone which occurs when defects or punctures in the geomembrane of a composite system are present. ?? ASCE.

33 CFR 165.918 - Safety Zones; Annual events requiring safety zones in the Captain of the Port Sault Sainte Marie...

Code of Federal Regulations, 2014 CFR

2014-07-01

... due to inclement weather, then this section will be enforced July 5 from 9 p.m. until 11 p.m. (2... zone will be enforced each year on July 4 from 9 p.m. until 12:30 a.m. on July 5. If the July 4 fireworks are cancelled due to inclement weather, then this section will be enforced on July 5 from 9 p.m...

33 CFR 165.918 - Safety Zones; Annual events requiring safety zones in the Captain of the Port Sault Sainte Marie...

Code of Federal Regulations, 2011 CFR

2011-07-01

... due to inclement weather, then this section will be enforced July 5 from 9 p.m. until 11 p.m. (2... zone will be enforced each year on July 4 from 9 p.m. until 12:30 a.m. on July 5. If the July 4 fireworks are cancelled due to inclement weather, then this section will be enforced on July 5 from 9 p.m...

33 CFR 165.918 - Safety Zones; Annual events requiring safety zones in the Captain of the Port Sault Sainte Marie...

Code of Federal Regulations, 2012 CFR

2012-07-01

... due to inclement weather, then this section will be enforced July 5 from 9 p.m. until 11 p.m. (2... zone will be enforced each year on July 4 from 9 p.m. until 12:30 a.m. on July 5. If the July 4 fireworks are cancelled due to inclement weather, then this section will be enforced on July 5 from 9 p.m...

Modeling water exchange and contaminant transport through a Baltic coastal region.

PubMed

Engqvist, Anders; Döös, Kristofer; Andrejev, Oleg

2006-12-01

The water exchange of the Baltic coastal zone is characterized by its seasonally varying regimes. In the safety assessment of a potential repository for spent nuclear fuel, it is important to assess the consequences of a hypothetical leak of radionuclides through the seabed into a waterborne transport phase. In particular, estimates of the associated residence times in the near-shore coastal zone are of interest. There are several methods to quantify such measures, of which three are presented here. Using the coastal location of Forsmark (Sweden) as an example, methods based on passive tracers, particle trajectories, and the average age distribution of exogeneous water parcels are compared for a representative one-year cycle. Tracer-based methods can simulate diffusivity more realistically than the other methods. Trajectory-based methods can handle Lagrangian dispersion processes due to advection but neglect diffusion on the sub-grid scale. The method based on the concept of average age (AvA) of exogeneous water can include all such sources simultaneously not only boundary water bodies but also various (fresh)-water discharges. Due to the inclusion of sub-grid diffusion this method gives a smoother measure of the water renewal. It is shown that backward in time trajectories and AvA-times are basically equipollent methods, yielding correlated results within the limits set by the diffusivity.

Studies on urban drinking water quality in a tropical zone.

PubMed

Mudiam, Mohana Krishna Reddy; Pathak, S P; Gopal, K; Murthy, R C

2012-01-01

Anthropogenic activities associated with industrialization, agriculture and urbanization have led to the deterioration in water quality due to various contaminants. To assess the status of urban drinking water quality, samples were collected from the piped supplies as well as groundwater sources from different localities of residential, commercial and industrial areas of Lucknow City in a tropical zone of India during pre-monsoon for estimation of coliform and faecal coliform bacteria, organochlorine pesticides (OCPs) and heavy metals. Bacterial contamination was found to be more in the samples from commercial areas than residential and industrial areas. OCPs like α,γ-hexachlorocyclohexane and 1,1 p,p-DDE {dichloro-2, 2-bis(p-chlorophenyl) ethene)} were found to be present in most of the samples from study area. The total organochlorine pesticide levels were found to be within the European Union limit (0.5 μg/L) in most of the samples. Most of the heavy metals estimated in the samples were also found to be within the permissible limits as prescribed by World Health Organization for drinking water. Thus, these observations show that contamination of drinking water in urban areas may be mainly due to municipal, industrial and agricultural activities along with improper disposal of solid waste. This is an alarm to safety of public health and aquatic environment in tropics.

In situ grazing experiments apply new technology to gain insights into deep-sea microbial food webs

NASA Astrophysics Data System (ADS)

Pachiadaki, Maria G.; Taylor, Craig; Oikonomou, Andreas; Yakimov, Michail M.; Stoeck, Thorsten; Edgcomb, Virginia

2016-07-01

Predation by grazing protists in aquatic habitats can influence prokaryotic community structure and provides a source of new, labile organic matter. Due to methodological difficulties associated with studies of deep-sea (below photic zone) microbiota, trophic interactions between eukaryotes and prokaryotes in mesopelagic and bathypelagic realms are largely obscured. Further complicating matters, examinations of trophic interactions using water samples that have been exposed to upwards of hundreds of atmospheres of pressure change prior to initiating experiments can potentially introduce significant artifacts. Here we present results of the first study of protistan grazing in water layers ranging from the euphotic zone to the bathypelagic, utilizing the Microbial Sampler-Submersible Incubation Device (MS-SID) that makes possible in situ studies of microbial activities. Protistan grazing in the mesopelagic and bathypelagic realm of the East Mediterranean Sea was quantified using fluorescently labeled prokaryotes (FLP) prepared from the naturally-occurring prokaryotic assemblages. These studies reveal daily prokaryotic removal due to grazing ranging from 31.3±5.9% at 40 m depth to 0.5±0.3% at 950 m. At 3540 m depth, where a chemocline habitat exists with abundant and active prokaryotes above Urania basin, the daily consumption of prokaryotes by protists was 19.9±6.6% of the in situ abundance.

Total Petroleum Systems of the Carpathian - Balkanian Basin Province of Romania and Bulgaria

USGS Publications Warehouse

Pawlewicz, Mark

2007-01-01

The U.S. Geological Survey defined the Moesian Platform Composite Total Petroleum System and the Dysodile Schist-Tertiary Total Petroleum System, which contain three assessment units, in the Carpathian-Balkanian Basin Province of Romania and Bulgaria. The Moesian Platform Assessment Unit, contained within the Moesian Platform Composite Total Petroleum System, is composed of Mesozoic and Cenozoic rocks within the Moesian platform region of southern Romania and northern Bulgaria and also within the Birlad depression in the northeastern platform area. In Romania, hydrocarbon sources are identified as carbonate rocks and bituminous claystones within the Middle Devonian, Middle Jurassic, Lower Cretaceous, and Neogene stratigraphic sequences. In the Birlad depression, Neogene pelitic strata have the best potential for generating hydrocarbons. In Bulgaria, Middle and Upper Jurassic shales are the most probable hydrocarbon sources. The Romania Flysch Zone Assessment Unit in the Dysodile Schist-Tertiary Total Petroleum System encompasses three structural and paleogeographic subunits within the Pre-Carpathian Mountains region: (1) the Getic depression, a segment of the Carpathian foredeep; (2) the flysch zone of the eastern Carpathian Mountains (also called the Marginal Fold nappe); and (3) the Miocene zone (also called the Sub-Carpathian nappe). Source rocks are interpreted to be Oligocene dysodile schist and black claystone, along with Miocene black claystone and marls. Also part of the Dysodile Schist-Tertiary Total Petroleum System is the Romania Ploiesti Zone Assessment Unit, which includes a zone of diapir folds. This zone lies between the Rimnicu Sarat and Dinibovita valleys and between the folds of the inner Carpathian Mountains and the external flanks of the Carpathian foredeep. The Oligocene Dysodile Schist is considered the main hydrocarbon source rock and Neogene black marls and claystones are likely secondary sources; all are thought to be at their maximum thermal maturation. Undiscovered resources in the Carpathian-Balkanian Basin Province are estimated, at the mean, to be 2,076 billion cubic feet of gas, 1,013 million barrels of oil, and 116 million barrels of natural gas liquids.

Monitoring well utility in a heterogeneous DNAPL source zone area: Insights from proximal multilevel sampler wells and sampling capture-zone modelling

NASA Astrophysics Data System (ADS)

McMillan, Lindsay A.; Rivett, Michael O.; Wealthall, Gary P.; Zeeb, Peter; Dumble, Peter

2018-03-01

Groundwater-quality assessment at contaminated sites often involves the use of short-screen (1.5 to 3 m) monitoring wells. However, even over these intervals considerable variation may occur in contaminant concentrations in groundwater adjacent to the well screen. This is especially true in heterogeneous dense non-aqueous phase liquid (DNAPL) source zones, where cm-scale contamination variability may call into question the effectiveness of monitoring wells to deliver representative data. The utility of monitoring wells in such settings is evaluated by reference to high-resolution multilevel sampler (MLS) wells located proximally to short-screen wells, together with sampling capture-zone modelling to explore controls upon well sample provenance and sensitivity to monitoring protocols. Field data are analysed from the highly instrumented SABRE research site that contained an old trichloroethene source zone within a shallow alluvial aquifer at a UK industrial facility. With increased purging, monitoring-well samples tend to a flow-weighted average concentration but may exhibit sensitivity to the implemented protocol and degree of purging. Formation heterogeneity adjacent to the well-screen particularly, alongside pump-intake position and water level, influence this sensitivity. Purging of low volumes is vulnerable to poor reproducibility arising from concentration variability predicted over the initial 1 to 2 screen volumes purged. Marked heterogeneity may also result in limited long-term sample concentration stabilization. Development of bespoke monitoring protocols, that consider screen volumes purged, alongside water-quality indicator parameter stabilization, is recommended to validate and reduce uncertainty when interpreting monitoring-well data within source zone areas. Generalised recommendations on monitoring well based protocols are also developed. A key monitoring well utility is their proportionately greater sample draw from permeable horizons constituting a significant contaminant flux pathway and hence representative fraction of source mass flux. Acquisition of complementary, high-resolution, site monitoring data, however, vitally underpins optimal interpretation of monitoring-well datasets and appropriate advancement of a site conceptual model and remedial implementation.

Denatured ethanol release into gasoline residuals, Part 1: source behaviour.

PubMed

Freitas, Juliana G; Barker, James F

2013-05-01

With the increasing use of ethanol in fuels, it is important to evaluate its fate when released into the environment. While ethanol is less toxic than other organic compounds present in fuels, one of the concerns is the impact ethanol might have on the fate of gasoline hydrocarbons in groundwater. One possible concern is the spill of denatured ethanol (E95: ethanol containing 5% denaturants, usually hydrocarbons) in sites with pre-existing gasoline contamination. In that scenario, ethanol is expected to increase the mobility of the NAPL phase by acting as a cosolvent and decreasing interfacial tension. To evaluate the E95 behaviour and its impacts on pre-existing gasoline, a field test was performed at the CFB-Borden aquifer. Initially gasoline contamination was created releasing 200 L of E10 (gasoline with 10% ethanol) into the unsaturated zone. One year later, 184 L of E95 was released on top of the gasoline contamination. The site was monitored using soil cores, multilevel wells and one glass access tube. At the end of the test, the source zone was excavated and the compounds remaining were quantified. E95 ethanol accumulated and remained within the capillary fringe and unsaturated zone for more than 200 days, despite ~1m oscillations in the water table. The gasoline mobility increased and it was redistributed in the source zone. Gasoline NAPL saturations in the soil increased two fold in the source zone. However, water table oscillations caused a separation between the NAPL and ethanol: NAPL was smeared and remained in deeper positions while ethanol moved upwards following the water table rise. Similarly, the E95 denaturants that initially were within the ethanol-rich phase became separated from ethanol after the water table oscillation, remaining below the ethanol rich zone. The separation between ethanol and hydrocarbons in the source after water table oscillation indicates that ethanol's impact on hydrocarbon residuals is likely limited to early times. Copyright © 2013 Elsevier B.V. All rights reserved.

Passive seismic imaging based on seismic interferometry: method and its application to image the structure around the 2013 Mw6.6 Lushan earthquake

NASA Astrophysics Data System (ADS)

Gu, N.; Zhang, H.

2017-12-01

Seismic imaging of fault zones generally involves seismic velocity tomography using first arrival times or full waveforms from earthquakes occurring around the fault zones. However, in most cases seismic velocity tomography only gives smooth image of the fault zone structure. To get high-resolution structure of the fault zones, seismic migration using active seismic data needs to be used. But it is generally too expensive to conduct active seismic surveys, even for 2D. Here we propose to apply the passive seismic imaging method based on seismic interferometry to image fault zone detailed structures. Seismic interferometry generally refers to the construction of new seismic records for virtual sources and receivers by cross correlating and stacking the seismic records on physical receivers from physical sources. In this study, we utilize seismic waveforms recorded on surface seismic stations for each earthquake to construct zero-offset seismic record at each earthquake location as if there was a virtual receiver at each earthquake location. We have applied this method to image the fault zone structure around the 2013 Mw6.6 Lushan earthquake. After the occurrence of the mainshock, a 29-station temporary array is installed to monitor aftershocks. In this study, we first select aftershocks along several vertical cross sections approximately normal to the fault strike. Then we create several zero-offset seismic reflection sections by seismic interferometry with seismic waveforms from aftershocks around each section. Finally we migrate these zero-offset sections to create seismic structures around the fault zones. From these migration images, we can clearly identify strong reflectors, which correspond to major reverse fault where the mainshock occurs. This application shows that it is possible to image detailed fault zone structures with passive seismic sources.

Incidence of cancer in the area around Amsterdam Airport Schiphol in 1988–2003: a population-based ecological study

PubMed Central

Visser, Otto; van Wijnen, Joop H; van Leeuwen, Flora E

2005-01-01

Background Amsterdam Airport Schiphol is a major source of complaints about aircraft noise, safety risks and concerns about long term adverse health effects, including cancer. We investigated whether residents of the area around Schiphol are at higher risk of developing cancer than the general Dutch population. Methods In a population-based study using the regional cancer registry, we estimated the cancer incidence during 1988–2003 in residents of the area surrounding Schiphol. We defined a study area based on aircraft noise contours and 4-digit postal code areas, since historical data on ambient air pollution were not available and recent emission data did not differ from the background urban air quality. Results In residents of the study area 13 207 cancer cases were diagnosed, which was close to the expected number, using national incidence rates as a reference (standardized incidence ratio [SIR] 1.02). We found a statistically significantly increased incidence of hematological malignancies (SIR 1.12, 95% confidence interval [CI]: 1.05, 1.19), mainly due to high rates for non-Hodgkin lymphoma (SIR 1.22, 95% CI: 1.12, 1.33) and acute lymphoblastic leukemia (SIR 1.34, 95% CI: 0.95, 1.83). The incidence of cancer of the respiratory system was statistically significantly decreased (SIR 0.94, 95% CI: 0.90, 0.99), due to the low rate in males (SIR 0.89). In the core zone of the study area, cancer incidence was slightly higher than in the remaining ring zone (rate ratio of the core zone compared to the ring zone 1.05, 95% CI 1.01, 1.10). This was caused by the higher incidence of cancer of the respiratory system, prostate and the female genital organs in the core zone in comparison to the ring zone. Conclusion The overall cancer incidence in the Schiphol area was similar to the national incidence. The moderately increased risk of hematological malignancies could not be explained by higher levels of ambient air pollution in the Schiphol area. This observation warrants further research, for example in a study with focus on substances in urban ambient air pollution, as similar findings were observed in Greater Amsterdam. PMID:16332253

Characterization of potential zones of dust generation at eleven stations in the southern Sahara

NASA Astrophysics Data System (ADS)

Clark, I.; Assamoi, P.; Bertrand, J.; Giorgi, F.

Synoptic wind data for multi-decadal periods at eleven stations located in the southern Sahara region (Agadez, Atar, Bilma, Dori, Gao, Kayes, Nema, Niamey, Nouadhibou, Ouagadougou and Tessalit) are used to study the monthly dust deflation power over the region. We found that, regardless of the conditions of the soil, the deflation power (or wind efficiency) is not sufficient to generate significant amounts of aerosols south of 15°N. North of this latitude, the deflation power is much larger, with potential zones of either very strong deflation (Nouadhibou and Bilma) or severe deflation (Gao, Tessalit, Nema, Atar, Agadez). Stations in the Sahel region such as Gao, Agadez and Tessalit are characterized by a gradual reinforcement of the deflation power between 1970 and 1984 in correspondence of increasing desertification over the region. During this same period, Bilma, a well know region of dust source, experienced a major reduction in deflation power due to shifts in large scale wind patterns.

Efficacy evaluation of managed population shift in Ukraine from zone of obligate (compulsory) resettlement as a measure of public radiation protection.

PubMed

Gunko, N V

2015-12-01

Evaluation of efficacy of the managed population transmigration from zone of obligate (compulsory) resettlement as a measure of civil protection after the Chernobyl NPP accident from the perspective of radiation biology. Legislative and statutory tutorial documents that regulate the managed population shift from radiologically contaminated territories of Ukraine and data from the Ukrainian State Service of Statistics on time limits and scopes of population transmigration from contaminated settlements were the informational back ground of the study. Data on retrospective and expected/anticipated radiation doses in population of settlements exposed to radiological contamination in Ukraine after the Chernobyl disaster summarized for the 1986-1997 peri od and up to 2055 were the information source for calculation of averted doses due to population shift. Battery of basic research empirical evidence review methods was applied under the calculation, systemic, and biomedical approach. Population shift from zone of obligate (compulsore) resettlement (hereafter referred to as Zone 2) to stop the radiation exposure as a tool of civil protection from emergency ionizing radiation after the Chernobyl NPP accident was scientifically substantiated and expedient from the perspective of radiation biology. Estimability of a managed population shift from "dose effect" perspective and "benefit/harm" principle is worse because of data absence on individual radiation doses to migrants in the country. Public shift in 1990 and 1991 was most effective from the viewpoint of level of averted lifetime dose. Due to transmigration the averted lifetime dose to the most vulnerable group of the Chernobyl disaster survivors i.e. children aged 0 years varied from 11.2 to 28.8 mSv (calculated for the Perejizdiv village council of Zhytomyr province). Since 2000 there was almost no public shift being not accomplished in the scheduled scope. Delay and incompleteness of transmigration have diminished the efficacy of this measure in the framework of radiological protection of population. N. V. Gunko.

Seismic Reflection Images of Deep Lithospheric Faults and Thin Crust at the Actively Deforming Indo-Australian Plate Boundary in the Indian Ocean

NASA Astrophysics Data System (ADS)

Singh, S. C.; Carton, H.; Chauhan, A.; Dyment, J.; Cannat, M.; Hananto, N.; Hartoyo, D.; Tapponnier, P.; Davaille, A.

2007-12-01

Recently, we acquired deep seismic reflection data using a state-of-the-art technology of Schlumberger having a powerful source (10,000 cubic inch) and a 12 km long streamer along a 250 km long trench parallel line offshore Sumatra in the Indian Ocean deformation zone that provides seismic reflection image down to 40 km depth over the old oceanic lithosphere formed at Wharton spreading centre about 55-57 Ma ago. We observe deep penetrating faults that go down to 37 km depth (~24 km in the oceanic mantle), providing the first direct evidence for full lithospheric-scale deformation in an intra-plate oceanic domain. These faults dip NE and have dips between 25 and 40 degrees. The majority of faults are present in the mantle and are spaced at about 5 km, and do not seem cut through the Moho. We have also imaged active strike-slip fault zones that seem to be associated with the re-activation of ancient fracture zones, which is consistent with previous seismological and seafloor observations. The geometries of the deep penetrating faults neither seem to correspond to faulting associated with the plate bending at the subduction front nor with the re-activation of fracture zone that initiated about 7.5 Ma ago, and therefore, we suggest that these deep mantle faults were formed due to compressive stress at the beginning of the hard collision between India and Eurasia, soon after the cessation of seafloor spreading in the Wharton basin. We also find that the crust generated at the fast Wharton spreading centre 55-57 Ma ago is only 3.5-4.5 km thick, the thinnest crust ever observed in a fast spreading environment. We suggest that this extremely thin crust is due to 40-50°C lower than normal mantle temperature in this part of the Indian Ocean during its formation.

Artificial soft sediment resuspension and high density opportunistic macroalgal mat fragmentation as method for increasing sediment zoobenthic assemblage diversity in a eutrophic lagoon.

PubMed

Martelloni, Tatiana; Tomassetti, Paolo; Gennaro, Paola; Vani, Danilo; Persia, Emma; Persiano, Marco; Falchi, Riccardo; Porrello, Salvatore; Lenzi, Mauro

2016-09-15

Superficial soft sediment resuspension and partial fragmentation of high density opportunistic macroalgal mats were investigated by boat to determine the impact on zoobenthic assemblages in a eutrophic Mediterranean lagoon. Sediment resuspension was used to oxidise superficial organic sediments as a method to counteract the effects of eutrophication. Likewise, artificial decay of macroalgal mat was calculated to reduce a permanent source of sediment organic matter. An area of 9ha was disturbed (zone D) and two other areas of the same size were left undisturbed (zones U). We measured chemical-physical variables, estimated algal biomass and sedimentary organic matter, and conducted qualitative and quantitative determinations of the zoobenthic species detected in sediment and among algal mats. The results showed a constant major reduction in labile organic matter (LOM) and algal biomass in D, whereas values in U remained stable or increased. In the three zones, however, bare patches of lagoon bed increased in size, either by direct effect of the boats in D or by anaerobic decay of the algal mass in U. Zoobenthic assemblages in algal mats reduced the number of species in D, probably due to the sharp reduction in biomass, but remained stable in U, whereas in all three areas abundance increased. Sediment zoobenthic assemblages increased the number of species in D, as expected, due to drastic reduction in LOM, whereas values in U remained stable and again abundance increased in all three zones. In conclusion, we confirmed that reduction of sediment organic load enabled an increase in the number of species, while the algal mats proved to be an important substrate in the lagoon environment for zoobenthic assemblages, especially when mat alternated with bare intermat areas of lagoon bed. Sediment resuspension is confirmed as a management criterion for counteracting the effects of eutrophication and improving the biodiversity of zoobenthic assemblages in eutrophic lagoon environments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Temperature and composition of carbonate cements record early structural control on cementation in a nascent deformation band fault zone: Moab Fault, Utah, USA

NASA Astrophysics Data System (ADS)

Hodson, Keith R.; Crider, Juliet G.; Huntington, Katharine W.

2016-10-01

Fluid-driven cementation and diagenesis within fault zones can influence host rock permeability and rheology, affecting subsequent fluid migration and rock strength. However, there are few constraints on the feedbacks between diagenetic conditions and structural deformation. We investigate the cementation history of a fault-intersection zone on the Moab Fault, a well-studied fault system within the exhumed reservoir rocks of the Paradox Basin, Utah, USA. The fault zone hosts brittle structures recording different stages of deformation, including joints and two types of deformation bands. Using stable isotopes of carbon and oxygen, clumped isotope thermometry, and cathodoluminescence, we identify distinct source fluid compositions for the carbonate cements within the fault damage zone. Each source fluid is associated with different carbonate precipitation temperatures, luminescence characteristics, and styles of structural deformation. Luminescent carbonates appear to be derived from meteoric waters mixing with an organic-rich or magmatic carbon source. These cements have warm precipitation temperatures and are closely associated with jointing, capitalizing on increases in permeability associated with fracturing during faulting and subsequent exhumation. Earlier-formed non-luminescent carbonates have source fluid compositions similar to marine waters, low precipitation temperatures, and are closely associated with deformation bands. The deformation bands formed at shallow depths very early in the burial history, preconditioning the rock for fracturing and associated increases in permeability. Carbonate clumped isotope temperatures allow us to associate structural and diagenetic features with burial history, revealing that structural controls on fluid distribution are established early in the evolution of the host rock and fault zone, before the onset of major displacement.

Computational studies for a multiple-frequency electron cyclotron resonance ion source (abstract)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alton, G.D.

1996-03-01

The number density of electrons, the energy (electron temperature), and energy distribution are three of the fundamental properties which govern the performance of electron cyclotron resonance (ECR) ion sources in terms of their capability to produce high charge state ions. The maximum electron energy is affected by several processes including the ability of the plasma to absorb power. In principle, the performances of an ECR ion source can be realized by increasing the physical size of the ECR zone in relation to the total plasma volume. The ECR zones can be increased either in the spatial or frequency domains inmore » any ECR ion source based on B-minimum plasma confinement principles. The former technique requires the design of a carefully tailored magnetic field geometry so that the central region of the plasma volume is a large, uniformly distributed plasma volume which surrounds the axis of symmetry, as proposed in Ref. . Present art forms of the ECR source utilize single frequency microwave power supplies to maintain the plasma discharge; because the magnetic field distribution continually changes in this source design, the ECR zones are relegated to thin {open_quote}{open_quote}surfaces{close_quote}{close_quote} which surround the axis of symmetry. As a consequence of the small ECR zone in relation to the total plasma volume, the probability for stochastic heating of the electrons is quite low, thereby compromising the source performance. This handicap can be overcome by use of broadband, multiple frequency microwave power as evidenced by the enhanced performances of the CAPRICE and AECR ion sources when two frequency microwave power was utilized. We have used particle-in-cell codes to simulate the magnetic field distributions in these sources and to demonstrate the advantages of using multiple, discrete frequencies over single frequencies to power conventional ECR ion sources. (Abstract Truncated)« less

Germanium layers grown by zone thermal crystallization from a discrete liquid source

NASA Astrophysics Data System (ADS)

Yatsenko, A. N.; Chebotarev, S. N.; Lozovskii, V. N.; Mohamed, A. A. A.; Erimeev, G. A.; Goncharova, L. M.; Varnavskaya, A. A.

2017-11-01

It is proposed and investigated a method for growing thin uniform germanium layers onto large silicon substrates. The technique uses the hexagonally arranged local sources filled with liquid germanium. Germanium evaporates on very close substrate and in these conditions the residual gases vapor pressure highly reduces. It is shown that to achieve uniformity of the deposited layer better than 97% the critical thickness of the vacuum zone must be equal to l cr = 1.2 mm for a hexagonal arranged system of round local sources with the radius of r = 0.75 mm and the distance between the sources of h = 0.5 mm.

Sr-Nd-Hf-O isotope geochemistry of the Ertaibei pluton, East Junggar, NW China: Implications for development of a crustal-scale granitoid pluton and crustal growth

NASA Astrophysics Data System (ADS)

Tang, Gong-Jian; Wang, Qiang; Zhang, Chunfu; Wyman, Derek A.; Dan, Wei; Xia, Xiao-Ping; Chen, Hong-Yi; Zhao, Zhen-Hua

2017-09-01

To better understand the compositional diversity of plutonic complexes and crustal growth of the Central Asian Orogenic Belt (CAOB), we conducted an integrated study of the Ertaibei pluton, which obtained geochronological, petrological, geochemical, and isotopic (including whole rock Sr-Nd, in situ zircon Hf-O) data. The pluton (ca. 300 Ma) is composed of granodiorites that contain mafic microgranular enclaves (MMEs), dolerite dikes, and granite dikes containing quartz-tourmaline orbicules. The dolerite dikes were possibly generated by melting of an asthenospheric mantle source, with discrete assimilation of lower crustal components in the MASH (melting, assimilation, storage, and homogenization) zone. The MMEs originated from hybridization between mantle and crust-derived magmas, which spanned a range of melting depths (˜25-30 km) in the MASH zone and were episodically tapped. Melting of the basaltic lower crust in the core of the MASH zone generated magmas to form the granodiorites. The granite dikes originated from melting of an arc-derived volcanogenic sedimentary source with a minor underplated basaltic source in the roof of the MASH zone (˜25 km). The compositional diversity reflects both the magma sources and the degree of maturation of the MASH zone. Although having mantle-like radiogenic isotope compositions, the Ertaibei and other postcollisional granitoids show high zircon δ18O values (mostly between +6 and +9‰), indicating a negligible contribution to the CAOB crustal growth during the postcollisional period.

Effect of Inverter Power Source Characteristics on Welding Stability and Heat Affected Zone Dimensions

NASA Astrophysics Data System (ADS)

Il'yaschenko, D. P.; Chinakhov, D. A.; Mamadaliev, R. A.

2018-01-01

The paper presents results the research in the effect of power sources dynamic characteristics on stability of melting and electrode metal transfer to the weld pool shielded metal arc welding. It is proved that when applying inverter-type welding power sources, heat and mass transfer characteristics change, arc gap short-circuit time and drop generation time are reduced. This leads to reduction of weld pool heat content and contraction of the heat-affected zone by 36% in comparison the same parameters obtained using a diode rectifier.

Microstructure and Mechanical Characterization of Friction-Stir-Welded Dual-Phase Brass

NASA Astrophysics Data System (ADS)

Ramesh, R.; Dinaharan, I.; Akinlabi, E. T.; Murugan, N.

2018-03-01

Friction stir welding (FSW) is an ideal process to join brass to avoid the evaporation of zinc. In the present investigation, 6-mm-thick dual-phase brass plates were joined efficiently using FSW at various tool rotational speeds. The microstructures were studied using optical microscopy, electron backscattered diffraction and transmission electron microscopy. The optical micrographs revealed the evolution of various zones across the joint line. The microstructure of the heat-affected zone was similar to that of base metal. The weld zone exhibited finer grains due to dynamic recrystallization. The recrystallization was inhomogeneous and the inhomogeneity reduced with increased tool rotational speed. The dual phase was preserved in the weld zone due to the retention of zinc. The severe plastic deformation created a lot of dislocations in the weld zone. The weld zone was strengthened after welding. The role of tool rotational speed on the joint strength is further reported.

Variations in population exposure and evacuation potential to multiple tsunami evacuation phases on Alameda and Bay Farm Islands, California

NASA Astrophysics Data System (ADS)

Peters, J.

2015-12-01

Planning for a tsunami evacuation is challenging for California communities due to the variety of earthquake sources that could generate a tsunami. A maximum tsunami inundation zone is currently the basis for all tsunami evacuations in California, although an Evacuation Playbook consisting of specific event-based evacuation phases relating to flooding severity is in development. We chose to investigate the Evacuation Playbook approach for the island community of Alameda, CA since past reports estimated a significant difference in numbers of residents in the maximum inundation zone when compared to an event-based inundation zone. In order to recognize variations in the types of residents and businesses within each phase, a population exposure analysis was conducted for each of the four Alameda evacuation phases. A pedestrian evacuation analysis using an anisotropic, path distance model was also conducted to understand the time it would take for populations to reach high ground by foot. Initial results suggest that the two islands of the City of Alameda have different situations when it comes to the four tsunami evacuation phases. Pedestrian evacuation results suggest that Bay Farm Island would have more success evacuating by vehicle due to limited nearby high ground for pedestrians to reach safety. Therefore, agent-based traffic simulation software was used to model vehicle evacuation off Bay Farm Island. Initial results show that Alameda Island could face challenges evacuating numerous boat docks and a large beach for phases 1 and 2, whereas Bay Farm Island is unaffected at these phases but might be challenged with evacuating by vehicle for phases 3 and maximum due to congestion on limited egress routes. A better understanding of the population exposure within each tsunami Evacuation Playbook phase and the time it would take to evacuate out of each phase by foot or vehicle will help emergency managers implement the evacuation phases during an actual tsunami event.

Effects of Contaminated Site Age on Dissolution Dynamics

NASA Astrophysics Data System (ADS)

Jawitz, J. W.

2004-12-01

This work presents a streamtube-based analytical approach to evaluate reduction in groundwater contaminant flux resulting from partial mass reduction in a nonaqueous phase liquid (NAPL) source zone. The reduction in contaminant flux, Rj, discharged from the source zone is a remediation performance metric that has a direct effect on the fundamental drivers of remediation: protection of human health risks and the environment. Spatial variability is described within a Lagrangian framework where aquifer hydrodynamic heterogeneities are characterized using nonreactive travel time distributions, while NAPL spatial distribution heterogeneity can be similarly described using reactive travel time distributions. The combined statistics of these distributions are used to evaluate the relationship between reduction in contaminant mass, Rm, and Rj. A portion of the contaminant mass in the source zone is assumed to be removed via in-situ flushing remediation, with the initial and final conditions defined as steady-state natural-gradient groundwater flow through the contaminant source zone. The combined effect of aquifer and NAPL heterogeneities are shown to be captured in a single parameter, reactive travel time variability, that was determined to be the most important factor controlling the relationship between Rm and Rj. Increased values of the following parameters are shown to result in more favorable contaminant elution dynamics (i.e., greater flux reduction for a given reduction in mass): aquifer hydrodynamic heterogeneity, NAPL source zone heterogeneity, positive correlation between travel time and NAPL content, and time since the contamination event. Less favorable elution behavior is shown to result from negative correlations between travel time and NAPL content and rate-limited dissolution. The specific emphasis of this presentation is on the effects of the length of time that has elapsed since the contamination event (site age) on the dissolution dynamics.

Using high-frequency sensors to identify hydroclimatological controls on storm-event variability in catchment nutrient fluxes and source zone activation

NASA Astrophysics Data System (ADS)

Blaen, Phillip; Khamis, Kieran; Lloyd, Charlotte; Krause, Stefan

2017-04-01

At the river catchment scale, storm events can drive highly variable behaviour in nutrient and water fluxes, yet short-term dynamics are frequently missed by low resolution sampling regimes. In addition, nutrient source contributions can vary significantly within and between storm events. Our inability to identify and characterise time dynamic source zone contributions severely hampers the adequate design of land use management practices in order to control nutrient exports from agricultural landscapes. Here, we utilise an 8-month high-frequency (hourly) time series of streamflow, nitrate concentration (NO3) and fluorescent dissolved organic matter concentration (FDOM) derived from optical in-situ sensors located in a headwater agricultural catchment. We characterised variability in flow and nutrient dynamics across 29 storm events. Storm events represented 31% of the time series and contributed disproportionately to nutrient loads (43% of NO3 and 36% of CDOM) relative to their duration. Principal components analysis of potential hydroclimatological controls on nutrient fluxes demonstrated that a small number of components, representing >90% of variance in the dataset, were highly significant model predictors of inter-event variability in catchment nutrient export. Hysteresis analysis of nutrient concentration-discharge relationships suggested spatially discrete source zones existed for NO3 and FDOM, and that activation of these zones varied on an event-specific basis. Our results highlight the benefits of high-frequency in-situ monitoring for characterising complex short-term nutrient dynamics and unravelling connections between hydroclimatological variability and river nutrient export and source zone activation under extreme flow conditions. These new process-based insights are fundamental to underpinning the development of targeted management measures to reduce nutrient loading of surface waters.

Imaging the crustal magma sources beneath Mauna Loa and Kilauea volcanoes, Hawaii

USGS Publications Warehouse

Okubo, Paul G.; Benz, Harley M.; Chouet, Bernard A.

1997-01-01

Three-dimensional seismic P-wave traveltime tomography is used to image the magma sources beneath Mauna Loa and Kilauea volcanoes, Hawaii. High-velocity bodies (>6.4 km/s) in the upper 9 km of the crust beneath the summits and rift zones of the volcanoes correlate with zones of high magnetic intensities and are interpreted as solidified gabbro-ultramafic cumulates from which the surface volcanism is derived. The proximity of these high-velocity features to the rift zones is consistent with a ridge-spreading model of the volcanic flank. Southeast of the Hilina fault zone, along the south flank of Kilauea, low-velocity material (<6.0 km/s) is observed extending to depths of 9–11 km, indicating that the Hilina fault may extend possibly as deep as the basal decollement. Along the southeast flank of Mauna Loa, a similar low-velocity zone associated with the Kaoiki fault zone is observed extending to depths of 6–8 km. These two upper crustal low-velocity zones suggest common stages in the evolution of the Hawaiian shield volcanoes in which these fault systems are formed as a result of upper crustal deformation in response to magma injection within the volcanic edifice.

Data requirements for simulation of hydrogeologic effects of liquid waste injection, Harrison and Jackson Counties, Mississippi

USGS Publications Warehouse

Rebich, Richard A.

1994-01-01

Available literature and data were reviewed to quantify data requirements for computer simulation of hydrogeologic effects of liquid waste injection in southeastern Mississippi. Emphasis of each review was placed on quantifying physical properties of current Class I injection zones in Harrison and Jackson Counties. Class I injection zones are zones that are used for injection of hazardous or non-hazardous liquid waste below a formation containing the lowermost underground source of drinking water located within one-quarter of a mile of the injection well. Several mathematical models have been developed to simulate injection effects. The Basic Plume Method was selected because it is commonly used in permit applications, and the Intercomp model was selected because it is generally accepted and used in injection-related research. The input data requirements of the two models were combined into a single data requirement list inclusive of physical properties of injection zones only; injected waste and well properties are not included because such information is site-specific by industry, which is beyond the scope of this report. Results of the reviews of available literature and data indicated that Class I permit applications and standard-reference chemistry and physics texts were the primary sources of information to quantify physical properties of injection zones in Harrison and Jackson Counties. With the exception of a few reports and supplementary data for one injection zone in Jackson County, very little additional information pertaining to physical properties of the injection zones was available in sources other than permit applications and standard-reference texts.

78 FR 21260 - Safety Zone; Lubbers Cup Regatta; Spring Lake, MI

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-10

...-AA00 Safety Zone; Lubbers Cup Regatta; Spring Lake, MI AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone on Spring Lake in Spring Lake, Michigan. This safety zone is intended to restrict vessels from a portion of Spring Lake due to...

Three-dimensional electrical resistivity model of the hydrothermal system in Long Valley Caldera, California, from magnetotellurics

USGS Publications Warehouse

Peacock, Jared R.; Mangan, Margaret T.; McPhee, Darcy K.; Wannamaker, Phil E.

2016-01-01

Though shallow flow of hydrothermal fluids in Long Valley Caldera, California, has been well studied, neither the hydrothermal source reservoir nor heat source has been well characterized. Here a grid of magnetotelluric data were collected around the Long Valley volcanic system and modeled in 3-D. The preferred electrical resistivity model suggests that the source reservoir is a narrow east-west elongated body 4 km below the west moat. The heat source could be a zone of 2–5% partial melt 8 km below Deer Mountain. Additionally, a collection of hypersaline fluids, not connected to the shallow hydrothermal system, is found 3 km below the medial graben, which could originate from a zone of 5–10% partial melt 8 km below the south moat. Below Mammoth Mountain is a 3 km thick isolated body containing fluids and gases originating from an 8 km deep zone of 5–10% basaltic partial melt.

Proposed seed collection zones for the central states

Treesearch

Gustaf A. Limstrom

1963-01-01

Seed collection zones have been established in several regions and countries to insure that the sources of seed used in tree planting are properly selected. Use of such zones has undoubtedly improved the survival and growth of trees in plantations and has also facilitated the establishment of specifications for seed procurement and seed certification.

Methyl tert‐butyl ether degradation in the unsaturated zone and the relation between MTBE in the atmosphere and shallow groundwater

USGS Publications Warehouse

Baehr, Arthur L.; Charles, Emmanuel G.; Baker, Ronald J.

2001-01-01

Atmospheric methyl tert‐butyl ether (MTBE) concentrations in southern New Jersey generally exceeded concentrations in samples taken from the unsaturated zone. A simple unsaturated zone transport model indicates that MTBE degradation can explain the attenuation with half‐lives from a few months to a couple of years. Tert‐butyl alcohol (TBA), a possible degradation product of MTBE, was detected in unsaturated‐zone samples at concentrations exceeding atmospheric levels at some sites, suggesting the possible conversion of MTBE to TBA. At sites where MTBE was detected in shallow groundwater, the concentration was typically higher than the overlying unsaturated‐zone concentration. This observation is consistent with outgassing from the aquifer and combined with the unsaturated‐zone attenuation suggests some of the MTBE detections in shallow groundwater are nonatmospheric in origin, coming from leaking tanks, road runoff, or other sources. The identification of sources of MTBE in groundwater and attenuation mechanisms through the hydrologic cycle is critical in developing an understanding of the long‐term effect of MTBE releases.

Method and apparatus for converting hydrocarbon fuel into hydrogen gas and carbon dioxide

DOEpatents

Clawson, Lawrence G.; Mitchell, William L.; Bentley, Jeffrey M.; Thijssen, Johannes H.J.

2000-01-01

An apparatus and a method are disclosed for converting hydrocarbon fuel or an alcohol into hydrogen gas and carbon dioxide. The apparatus includes a first vessel having a partial oxidation reaction zone and a separate steam reforming reaction zone that is distinct from the partial oxidation reaction zone. The first vessel has a first vessel inlet at the partial oxidation reaction zone and a first vessel outlet at the steam reforming zone. The reformer also includes a helical tube extending about the first vessel. The helical tube has a first end connected to an oxygen-containing source and a second end connected to the first vessel at the partial oxidation reaction zone. Oxygen gas from an oxygen-containing source can be directed through the helical tube to the first vessel. A second vessel having a second vessel inlet and second vessel outlet is annularly disposed about the first vessel. The helical tube is disposed between the first vessel and the second vessel and gases from the first vessel can be directed through second vessel.

Regional Characteristics of Stress State of Main Seismic Active Faults in Mid-Northern Part of Sichuan-Yunnan Block

NASA Astrophysics Data System (ADS)

Weiwei, W.; Yaling, W.

2017-12-01

We restore the seismic source spectrums of 1012 earthquakes(2.0 ≤ ML ≤ 5.0) in the mid-northern part of Sichuan-Yunnan seismic block(26 ° N-33 ° N, 99 ° E-104 ° E),then calculate the source parameters.Based on the regional seismic tectonic background, the distribution of active faults and seismicity, the study area is divided into four statistical units (Z1 Jinshajiang and Litang fault zone, Z2 Xianshuihe fault zone, Z3 Anninghe-Zemuhe fault zone, Z4 Lijiang-Xiaojinhe fault zone). Seismic source stress drop results show the following, (1)The stress at the end of the Jinshajiang fault is low, strong earthquake activity rare.Stress-strain loading deceases gradually from northwest to southeast along Litang fault, the northwest section which is relatively locked is more likely to accumulate strain than southeast section. (2)Stress drop of Z2 is divided by Kangding, the southern section is low and northern section is high. Southern section (Kangding-Shimian) is difficult to accumulate higher strain in the short term, but in northern section (Garzê-Kangding), moderate and strong earthquakes have not filled the gaps of seismic moment release, there is still a high stress accumulation in partial section. (3)High stress-drop events were concentrated on Z3, strain accumulation of this unit is strong, and stress level is the highest, earthquake risk is high. (4)On Z4, stress drop characteristics of different magnitude earthquakes are not the same, which is related to complex tectonic setting, the specific reasons still need to be discussed deeply.The study also show that, (1)Stress drops display a systematic change with different faults and locations, high stress-drop events occurs mostly on the fault intersection area. Faults without locking condition and mainly creep, are mainly characterized by low stress drop. (2)Contrasting to what is commonly thought that "strike-slip faults are not easy to accumulate stress ", Z2 and Z3 all exhibit high stress levels, which may be due to that the magnitude and intensity of medium-strong earthquakes are not enough to release the accumulated energy. On the other hand, when the tectonic unit blocking fault movement and its contribution to accumulation of stress play a key role, the earthquake of same magnitude will release higher stress drop.

Reinterpretation of the tectonics and formation of the Pernambuco Plateau Basin, NE Brazil.

NASA Astrophysics Data System (ADS)

Hoggett, Murray; Jones, Stephen M.; Dunkley Jones, Tom; Reston, Timothy; Barbosa, Antonio; Biondo, Vanessa; Mort, Haydon P.

2017-04-01

The continental margin from Alagoas to Natal represents arguably the most frontier region for exploration on the Brazillian margin. High quality seismic data was not collected in the region for many decades as it was believed that only a few kilometers of sediment existed, and thus there was no exploration potential. Here we present the results of work done as part of an IODP virtual site survey. The work has resulted in a total reinterpretation of the basin structure and tectonics, including finding sediment filled half grabens holding up to 8km thick stratigraphic sections. The two deepest grabens likely represent rift jumps during breakup, which may imply different age sediments in the different grabens. The basin is also found to contain a sizable salt accumulation, previously uninterpreted due to hard overlying carbonates hampering seismic imaging. This salt can be seen to have been highly mobile in the past, and has developed into kilometer scale diapirs flanked by typical rollover anticlines. For the first time we show the basin has all the elements needed for a working petroleum system, with the exception a source rock - which cannot be speculated on further as the basin is undrilled. However source rock sequences are present in the Alagoas basin to the south, and recent released seep data show evidence for both biogeneic and thermogenic seeps over the plateau basin, which could also signal source rock presence. We present seismic and potential fields data, including forward potential fields models and seismically derived crustal stretching and thinning estimates, to show that the half grabens terminate abruptly at the latitude of the Pernambuco Shear Zone, a major crustal scale Precambrian shear zone. Onshore boreholes, well away from the deep seismically imaged half grabens offshore, find crystalline basement to drop away rapidly across the shearzone, revealing a third graben to terminate at the shear zone. We interpret this as that the preexisting crustal structure has acted as a mechanical barrier to south to north rift propagation, which has controlled the basin's formation. The shear zone was likely reactivated with a sinistral sense of shear to accommodate rifting, which also helps explain the anomalously wide continental margin at the Pernambuco Plateau.

Seismic gaps and source zones of recent large earthquakes in coastal Peru

USGS Publications Warehouse

Dewey, J.W.; Spence, W.

1979-01-01

The earthquakes of central coastal Peru occur principally in two distinct zones of shallow earthquake activity that are inland of and parallel to the axis of the Peru Trench. The interface-thrust (IT) zone includes the great thrust-fault earthquakes of 17 October 1966 and 3 October 1974. The coastal-plate interior (CPI) zone includes the great earthquake of 31 May 1970, and is located about 50 km inland of and 30 km deeper than the interface thrust zone. The occurrence of a large earthquake in one zone may not relieve elastic strain in the adjoining zone, thus complicating the application of the seismic gap concept to central coastal Peru. However, recognition of two seismic zones may facilitate detection of seismicity precursory to a large earthquake in a given zone; removal of probable CPI-zone earthquakes from plots of seismicity prior to the 1974 main shock dramatically emphasizes the high seismic activity near the rupture zone of that earthquake in the five years preceding the main shock. Other conclusions on the seismicity of coastal Peru that affect the application of the seismic gap concept to this region are: (1) Aftershocks of the great earthquakes of 1966, 1970, and 1974 occurred in spatially separated clusters. Some clusters may represent distinct small source regions triggered by the main shock rather than delimiting the total extent of main-shock rupture. The uncertainty in the interpretation of aftershock clusters results in corresponding uncertainties in estimates of stress drop and estimates of the dimensions of the seismic gap that has been filled by a major earthquake. (2) Aftershocks of the great thrust-fault earthquakes of 1966 and 1974 generally did not extend seaward as far as the Peru Trench. (3) None of the three great earthquakes produced significant teleseismic activity in the following month in the source regions of the other two earthquakes. The earthquake hypocenters that form the basis of this study were relocated using station adjustments computed by the method of joint hypocenter determination. ?? 1979 Birkha??user Verlag.

Negative ion source

DOEpatents

Leung, Ka-Ngo; Ehlers, Kenneth W.

1984-01-01

An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid, positively biases the plasma in the extraction zone to thereby prevent positive ions from migrating from the ionizing zone to the extraction zone. Low-energy electrons, which would ordinarily be dragged by the positive ions into the extraction zone, are thereby prevented from being present in the extraction zone and being extracted along with negative ions by the extraction grid. Additional electrons are suppressed from the output flux using ExB drift provided by permanent magnets and the extractor grid electrical field.

Negative ion source

DOEpatents

Leung, K.N.; Ehlers, K.W.

1982-08-06

An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid, positively biases the plasma in the extraction zone to thereby prevent positive ions from migrating from the ionizing zone to the extraction zone. Low-energy electrons, which would ordinarily be dragged by the positive ions into the extraction zone, are thereby prevented from being present in the extraction zone and being extracted along with negative ions by the extraction grid. Additional electrons are suppressed from the output flux using ExB drift provided by permanent magnets and the extractor grid electrical field.

Negative ion source

DOEpatents

Leung, K.N.; Ehlers, K.W.

1984-12-04

An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid, positively biases the plasma in the extraction zone to thereby prevent positive ions from migrating from the ionizing zone to the extraction zone. Low-energy electrons, which would ordinarily be dragged by the positive ions into the extraction zone, are thereby prevented from being present in the extraction zone and being extracted along with negative ions by the extraction grid. Additional electrons are suppressed from the output flux using ExB drift provided by permanent magnets and the extractor grid electrical field. 14 figs.

Vertical intensity modulation for improved radiographic penetration and reduced exclusion zone

NASA Astrophysics Data System (ADS)

Bendahan, J.; Langeveld, W. G. J.; Bharadwaj, V.; Amann, J.; Limborg, C.; Nosochkov, Y.

2016-09-01

In the present work, a method to direct the X-ray beam in real time to the desired locations in the cargo to increase penetration and reduce exclusion zone is presented. Cargo scanners employ high energy X-rays to produce radiographic images of the cargo. Most new scanners employ dual-energy to produce, in addition to attenuation maps, atomic number information in order to facilitate the detection of contraband. The electron beam producing the bremsstrahlung X-ray beam is usually directed approximately to the center of the container, concentrating the highest X-ray intensity to that area. Other parts of the container are exposed to lower radiation levels due to the large drop-off of the bremsstrahlung radiation intensity as a function of angle, especially for high energies (>6 MV). This results in lower penetration in these areas, requiring higher power sources that increase the dose and exclusion zone. The capability to modulate the X-ray source intensity on a pulse-by-pulse basis to deliver only as much radiation as required to the cargo has been reported previously. This method is, however, controlled by the most attenuating part of the inspected slice, resulting in excessive radiation to other areas of the cargo. A method to direct a dual-energy beam has been developed to provide a more precisely controlled level of required radiation to highly attenuating areas. The present method is based on steering the dual-energy electron beam using magnetic components on a pulse-to-pulse basis to a fixed location on the X-ray production target, but incident at different angles so as to direct the maximum intensity of the produced bremsstrahlung to the desired locations. The details of the technique and subsystem and simulation results are presented.

Determining Volcanic Deformation at San Miguel Volcano, El Salvador by Integrating Radar Interferometry and Seismic Analyses

NASA Astrophysics Data System (ADS)

Schiek, C. G.; Hurtado, J. M.; Velasco, A. A.; Buckley, S. M.; Escobar, D.

2008-12-01

From the early 1900's to the present day, San Miguel volcano has experienced many small eruptions and several periods of heightened seismic activity, making it one of the most active volcanoes in the El Salvadoran volcanic chain. Prior to 1969, the volcano experienced many explosive eruptions with Volcano Explosivity Indices (VEI) of 2. Since then, eruptions have decreased in intensity to an average VEI of 1. Eruptions mostly consist of phreatic explosions and central vent eruptions. Due to the explosive nature of this volcano, it is important to study the origins of the volcanism and its relationship to surface deformation and earthquake activity. We analyze these interactions by integrating interferometric synthetic aperture radar (InSAR) results with earthquake source location data from a ten-month (March 2007-January 2008) seismic deployment. The InSAR results show a maximum of 7 cm of volcanic inflation from March 2007 to mid-October 2007. During this time, seismic activity increased to a Real-time Seismic-Amplitude Measurement (RSAM) value of >400. Normal RSAM values for this volcano are <50. A period of quiescence began in mid-October 2007, and a maximum of 6 cm of deflation was observed in the interferometry results from 19 October 2007 to 19 January 2008. A clustering of at least 25 earthquakes that occurred between March 2007 and January 2008 suggests a fault zone through the center of the San Miguel volcanic cone. This fault zone is most likely where dyke propagation is occurring. Source mechanisms will be determined for the earthquakes associated with this fault zone, and they will be compared to the InSAR deformation field to determine if the mid-October seismic activity and observed surface deformation are compatible.

Work Zone Intrusion Report Interface Design

DOT National Transportation Integrated Search

2018-02-02

While necessary for roadways, work zones present a safety risk to crew. Half of road workers deaths between 2005 and 2010 were due to collisions with motorists intruding on the work zone. Therefore, addressing intrusions is an important step for ensu...

Screening of antibacterial activity of lactic acid bacteria against different pathogens found in vacuum-packaged meat products.

PubMed

Awaisheh, Saddam S; Ibrahim, Salam A

2009-11-01

The objective of this work was to screen the antibacterial activity of lactic acid bacteria (LAB) isolated from different sources against different pathogens found in ready-to-eat vacuum-packaged meat products (RTE-VPMP). LAB were isolated from human, RTE-VPMP, fermented vegetables, and dairy samples. These isolates were assessed for their antibacterial activity against Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus using spot on lawn technique. Six LAB isolates-three from a human source, two from a RTE-VPMP source, and one from a fermented vegetable source-were found to be effective against all pathogenic strains. Antibacterial activities of cell-free neutral supernatant broths of these isolates were assessed against the different pathogenic strains to confirm bacteriocin production. All six isolates were effective against all pathogenic strains. LAB isolates from the human source had the highest antibacterial activity and were significantly more effective than other LAB isolates, with the inhibition zone ranging from 14 to 22 mm. Inhibition zones of RTE-VPMP LAB isolates were lower than those of human origin (inhibition zone range, 11-17 mm). The lowest activities were for the fermented vegetable isolate, for which inhibition zones ranged from 11 to 15 mm. The three isolates of human origin were identified as L. acidophilus, L. casei, and L. reuteri; the two isolates from RTE-VPMP source were both L. sake; and the one isolate of fermented vegetable origin was L. plantarum. Our results showed that nonmeat product-sourced LAB were effective against several foodborne pathogens, which suggests that they could be used as natural biopreservatives in many RTE-VPMP produced in Jordan.

Dynamic Imaging of Coherent Sources Reveals Different Network Connectivity Underlying the Generation and Perpetuation of Epileptic Seizures

PubMed Central

Anwar, Abdul Rauf; Deuschl, Günther; Stephani, Ulrich; Raethjen, Jan; Siniatchkin, Michael

2013-01-01

The concept of focal epilepsies includes a seizure origin in brain regions with hyper synchronous activity (epileptogenic zone and seizure onset zone) and a complex epileptic network of different brain areas involved in the generation, propagation, and modulation of seizures. The purpose of this work was to study functional and effective connectivity between regions involved in networks of epileptic seizures. The beginning and middle part of focal seizures from ictal surface EEG data were analyzed using dynamic imaging of coherent sources (DICS), an inverse solution in the frequency domain which describes neuronal networks and coherences of oscillatory brain activities. The information flow (effective connectivity) between coherent sources was investigated using the renormalized partial directed coherence (RPDC) method. In 8/11 patients, the first and second source of epileptic activity as found by DICS were concordant with the operative resection site; these patients became seizure free after epilepsy surgery. In the remaining 3 patients, the results of DICS / RPDC calculations and the resection site were discordant; these patients had a poorer post-operative outcome. The first sources as found by DICS were located predominantly in cortical structures; subsequent sources included some subcortical structures: thalamus, Nucl. Subthalamicus and cerebellum. DICS seems to be a powerful tool to define the seizure onset zone and the epileptic networks involved. Seizure generation seems to be related to the propagation of epileptic activity from the primary source in the seizure onset zone, and maintenance of seizures is attributed to the perpetuation of epileptic activity between nodes in the epileptic network. Despite of these promising results, this proof of principle study needs further confirmation prior to the use of the described methods in the clinical praxis. PMID:24194931

Acoustic Transients of the Marginal Sea Ice Zone: A Provisional Catalog

DTIC Science & Technology

1989-08-01

Arctic marine mammals is approximately 20 million individuals. Most of these inhabit the marginal sea ice zone (MIZ), but some species, such as ringed ...Food: molluscs, worms, sea urchins, Arctic cod, occasionally other marine mammals, e.g., ringed and bearded seals, narwhals. Dive: to 80 m...called for. TRANSIENT DESCRIPTION Recordings unavailable DATA SOURCE SERIAL _____ 21 SUPPORTING DATA SOURCE IRIS Ringed Seal, Phoca hispida Circumpolar

Evaluation of Sources and Patterns of Elemental Composition of PM2.5 at Three Low-Income Neighborhood Schools and Residences in Quito, Ecuador

PubMed Central

Raysoni, Amit U.; Armijos, Rodrigo X.; Weigel, M. Margaret; Echanique, Patricia; Racines, Marcia; Pingitore, Nicholas E.; Li, Wen-Whai

2017-01-01

Elemental characterization of fine particulate matter was undertaken at schools and residences in three low income neighborhoods in Quito, Ecuador. The three zones were located in the northern (Cotocollao), south central (El Camal), and south east (Los Chillos) neighborhoods and were classified as zones 1–3, respectively. Forty elements were quantified via ICP-MS analysis. Amongst the geogenic elements, the concentration of Si was the most abundant followed by S, Al, and Ca. Elements with predominantly anthropogenic sources such as Zn, V, and Ni were higher in zone 3 school followed by zone 2 and zone 1 schools. Enrichment factors were calculated to study the role of crustal sources in the elemental concentrations. Geogenic elements, except K, all had values <10 and anthropogenic elements such as Ni, V, Zn, Pb, As, Cr had >10. Principal Component Analysis suggested that Ni and V concentrations were strongly attributable to pet coke and heavy oil combustion. Strong associations between As and Pb could be attributed to traffic and other industrial emissions. Resuspended dust, soil erosion, vehicular emissions (tailpipe, brake and tire wear, and engine abrasion), pet coke, heavy oil combustion, and heavy industrial operations were major contributors to air pollution. PMID:28644400

Evaluation of Sources and Patterns of Elemental Composition of PM2.5 at Three Low-Income Neighborhood Schools and Residences in Quito, Ecuador.

PubMed

Raysoni, Amit U; Armijos, Rodrigo X; Weigel, M Margaret; Echanique, Patricia; Racines, Marcia; Pingitore, Nicholas E; Li, Wen-Whai

2017-06-23

Elemental characterization of fine particulate matter was undertaken at schools and residences in three low income neighborhoods in Quito, Ecuador. The three zones were located in the northern (Cotocollao), south central (El Camal), and south east (Los Chillos) neighborhoods and were classified as zones 1-3, respectively. Forty elements were quantified via ICP-MS analysis. Amongst the geogenic elements, the concentration of Si was the most abundant followed by S, Al, and Ca. Elements with predominantly anthropogenic sources such as Zn, V, and Ni were higher in zone 3 school followed by zone 2 and zone 1 schools. Enrichment factors were calculated to study the role of crustal sources in the elemental concentrations. Geogenic elements, except K, all had values <10 and anthropogenic elements such as Ni, V, Zn, Pb, As, Cr had >10. Principal Component Analysis suggested that Ni and V concentrations were strongly attributable to pet coke and heavy oil combustion. Strong associations between As and Pb could be attributed to traffic and other industrial emissions. Resuspended dust, soil erosion, vehicular emissions (tailpipe, brake and tire wear, and engine abrasion), pet coke, heavy oil combustion, and heavy industrial operations were major contributors to air pollution.

Controlled field study on the use of nitrate and oxygen for bioremediation of a gasoline source zone

USGS Publications Warehouse

Barbaro, J.R.; Barker, J.F.

2000-01-01

Controlled releases of unleaded gasoline were utilized to evaluate the biotransformation of the soluble aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylene isomers, trimethylbenzene isomers, and naphthalene) within a source zone using nitrate and oxygen as electron acceptors. Experiments were conducted within two 2 m ?? 2 m ?? 3.5 m deep sheet-piling cells. In each treatment cell, a gasoline-contaminated zone was created below the water table. Groundwater amended with electron acceptors was then flushed continuously through the cells for 174 day. Electron-acceptor utilization and hydrocarbon-metabolite formation were noted in both cells, indicating that some microbial activity had been induced in response to flushing. Relative to the cell residence time, nitrate utilization was slow and aromatic-hydrocarbon mass losses in response to microaerophilic dissolved oxygen addition were not obvious under these in situ conditions. There was relatively little biotransformation of the aromatic hydrocarbons over the 2-m flow path monitored in this experiment. A large denitrifying population capable of aromatic hydrocarbon biotransformation failed to develop within the gasoline source zone over a 14-mo period of nitrate exposure.

Impact of Groundwater-Lake Interaction on Levels of E. coli in Near-Shore Swimming Waters at Beaches of the Great Lakes

NASA Astrophysics Data System (ADS)

Crowe, A. S.

2009-12-01

Beaches throughout the Great Lakes frequently are under health advisories for swimming due to elevated levels of E. coli. Many studies have shown that there are several potential sources of this E. coli (e.g., livestock, sewage treatment facilities, gulls and geese), and several mechanisms for delivering E. coli to the shoreline (e.g., rivers, creeks, storm water drains, currents, waves). But, groundwater is a mechanism for E. coli transport to the shoreline that is typically overlooked. Field studies undertaken at beaches throughout the Great lakes have measured levels of E. coli in the groundwater and sand at the groundwater-lake interface that are commonly over a 1000 times above Recreational Water Quality Guidelines, and that these high levels of E. coli are restricted to a zone below the beach adjacent to and within a few metres of the lake. Groundwater flow below beaches is always towards the shoreline with almost all groundwater discharge occurring at the groundwater-lake interface (i.e., not several or a few metres off-shore). Thus, groundwater discharge of the E. coli from zone represents a substantial and long-term reservoir for E. coli loading to the near shore recreational waters, and presents a potential health risk to swimmers. The high levels of E. coli in the sand and groundwater adjacent to the lake is also due to groundwater-lake interaction. During storms, wave runup and subsequent infiltration of lake water containing E. coli at the swash zone is the primary mechanism for delivering E. coli to the groundwater and sand adjacent to the lake. Field and modeling experiments show that storm events as short as a few hours can introduce substantial levels of E. coli to the groundwater because of the high inward groundwater velocities. However, its migration into the beach away from the shoreline is restricted to a few metres beyond the maximum extent of wave runup because groundwater flow below the beach continues to flow towards the shoreline creating a hydraulic barrier to inland migration of E. coli. Because groundwater discharge velocities following a storm event are much lower than the recharging groundwater velocities during infiltration, E. coli will enter the groundwater and sand much faster than in will discharge. Hence groundwater discharge of E. coli from this zone into the lake represents a long-term and continuous source of E. coli that will challenge regulators and beach managers who are trying to reduce levels of E. coli at swimming beaches throughout the Great Lakes.

Current status of new SAGE project with 51Cr neutrino source

DOE PAGES

Gavrin, V.; Cleveland, B.; Danshin, S.; ...

2015-03-15

A very short-baseline neutrino oscillation experiment with an intense 51Cr neutrino source is currently under construction at the Baksan Neutrino Observatory of the Institute for Nuclear Research RAS (BNO). The experiment, which is based on the existing SAGE experiment, will use an upgraded Gallium-Germanium Neutrino Telescope (GGNT) and an artificial 51Cr neutrino source with activity ~3 MCi to search for transitions of active neutrinos to sterile states with Δm 2 ~1 eV 2. The neutrino source will be placed in the center of a liquid Ga metal target that is divided into two concentric zones, internal and external. The averagemore » path length of neutrinos in each zone will be the same and the neutrino capture rate will be measured separately in each zone. The oscillation signature, which comes from the ratio of events in the near and far gallium volumes, will be largely free of systematic errors, such as may occur from cross section and source strength uncertainties, and will provide a clean signal of electron neutrino disappearance into a sterile state at baselines of about 0.6 and 2.0 m. The sensitivity to the disappearance of electron neutrinos is expected to be a few percent. Construction of this set of new facilities, including a two-zone tank for irradiation of 50 tons of Ga metal with the intense 51Cr source, as well as additional modules of the GGNT counting and extraction systems, is close to completion. In order to check the new facilities they will first be used for SAGE solar neutrino measurements.« less

Current status of new SAGE project with 51Cr neutrino source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavrin, V.; Cleveland, B.; Danshin, S.

A very short-baseline neutrino oscillation experiment with an intense 51Cr neutrino source is currently under construction at the Baksan Neutrino Observatory of the Institute for Nuclear Research RAS (BNO). The experiment, which is based on the existing SAGE experiment, will use an upgraded Gallium-Germanium Neutrino Telescope (GGNT) and an artificial 51Cr neutrino source with activity ~3 MCi to search for transitions of active neutrinos to sterile states with Δm 2 ~1 eV 2. The neutrino source will be placed in the center of a liquid Ga metal target that is divided into two concentric zones, internal and external. The averagemore » path length of neutrinos in each zone will be the same and the neutrino capture rate will be measured separately in each zone. The oscillation signature, which comes from the ratio of events in the near and far gallium volumes, will be largely free of systematic errors, such as may occur from cross section and source strength uncertainties, and will provide a clean signal of electron neutrino disappearance into a sterile state at baselines of about 0.6 and 2.0 m. The sensitivity to the disappearance of electron neutrinos is expected to be a few percent. Construction of this set of new facilities, including a two-zone tank for irradiation of 50 tons of Ga metal with the intense 51Cr source, as well as additional modules of the GGNT counting and extraction systems, is close to completion. In order to check the new facilities they will first be used for SAGE solar neutrino measurements.« less

Predicting dense nonaqueous phase liquid dissolution using a simplified source depletion model parameterized with partitioning tracers

NASA Astrophysics Data System (ADS)

Basu, Nandita B.; Fure, Adrian D.; Jawitz, James W.

2008-07-01

Simulations of nonpartitioning and partitioning tracer tests were used to parameterize the equilibrium stream tube model (ESM) that predicts the dissolution dynamics of dense nonaqueous phase liquids (DNAPLs) as a function of the Lagrangian properties of DNAPL source zones. Lagrangian, or stream-tube-based, approaches characterize source zones with as few as two trajectory-integrated parameters, in contrast to the potentially thousands of parameters required to describe the point-by-point variability in permeability and DNAPL in traditional Eulerian modeling approaches. The spill and subsequent dissolution of DNAPLs were simulated in two-dimensional domains having different hydrologic characteristics (variance of the log conductivity field = 0.2, 1, and 3) using the multiphase flow and transport simulator UTCHEM. Nonpartitioning and partitioning tracers were used to characterize the Lagrangian properties (travel time and trajectory-integrated DNAPL content statistics) of DNAPL source zones, which were in turn shown to be sufficient for accurate prediction of source dissolution behavior using the ESM throughout the relatively broad range of hydraulic conductivity variances tested here. The results were found to be relatively insensitive to travel time variability, suggesting that dissolution could be accurately predicted even if the travel time variance was only coarsely estimated. Estimation of the ESM parameters was also demonstrated using an approximate technique based on Eulerian data in the absence of tracer data; however, determining the minimum amount of such data required remains for future work. Finally, the stream tube model was shown to be a more unique predictor of dissolution behavior than approaches based on the ganglia-to-pool model for source zone characterization.

Effect of ammonium sulfate, ammonium chloride and root-zone acidity on inorganic ion content of tobacco

NASA Technical Reports Server (NTRS)

Vessey, J. K.; Raper, C. D. Jr; Henry, L. T.; Raper CD, J. r. (Principal Investigator)

1990-01-01

Tobacco plants (Nicotiana tabacum L. cv NC82) were supplied with (NH4)2SO4 or NH4Cl at root-zone pH of 6.0 and 4.5 in hydroponic culture for 28 days. Dry matter accumulation, total N and C content, and leaf area and number were not affected by the NH4+ source or root-zone pH. Plants supplied with NH4Cl accumulated up to 1.2 mM Cl g DW-1, but accumulated 37% less inorganic H2PO4- and 47% less SO4(2-) than plants supplied with (NH4)2SO4. The large Cl- accumulation resulted in NH4Cl- supplied plants having a 31% higher inorganic anion (NO3-, H2, PO4-, SO4(2-), and Cl-) charge. This higher inorganic anion charge in the NH4Cl-supplied plants was balanced by a similar increase in K+ charge. Plants supplied with NH4Cl accumulated greater concentrations of Cl- in leaves (up to 5.1% of DW) than plants supplied with (NH4)2SO4 (less than -% DW). Despite the high Cl- concentration of leaves in NH4Cl supplied plants, these plants showed no symptoms of Cl- toxicity. This demonstrates that toxicity symptoms are not due solely to an interaction between high Cl- concentration in tissue and NH4+ nutrition. The increase in root-zone acidity to pH 4.5 from 6.0 did not induce toxicity symptoms.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parra, J.; Collier, H.; Angstman, B.

In low porosity, low permeability zones, natural fractures are the primary source of permeability which affect both production and injection of fluids. The open fractures do not contribute much to porosity, but they provide an increased drainage network to any porosity. An important approach to characterizing the fracture orientation and fracture permeability of reservoir formations is one based upon the effects of such conditions on the propagation of acoustic and seismic waves in the rock. We present the feasibility of using seismic measurement techniques to map the fracture zones between wells spaced 2400 ft at depths of about 1000 ft.more » For this purpose we constructed computer models (which include azimuthal anisotropy) using Lodgepole reservoir parameters to predict seismic signatures recorded at the borehole scale, crosswell scale, and 3 D seismic scale. We have integrated well logs with existing 2D surfaces seismic to produce petrophysical and geological cross sections to determine the reservoir parameters and geometry for the computer models. In particular, the model responses are used to evaluate if surface seismic and crosswell seismic measurements can capture the anisotropy due to vertical fractures. Preliminary results suggested that seismic waves transmitted between two wells will propagate in carbonate fracture reservoirs, and the signal can be received above the noise level at the distance of 2400 ft. In addition, the large velocities contrast between the main fracture zone and the underlying unfractured Boundary Ridge Member, suggested that borehole reflection imaging may be appropriate to map and fracture zone thickness variation and fracture distributions in the reservoir.« less

Investigation of the potential for concealed base-metal mineralization at the Drenchwater Creek Zn-Pb-Ag occurrence, northern Alaska, using geology, reconnaissance geochemistry, and airborne electromagnetic geophysics

USGS Publications Warehouse

Graham, Garth E.; Deszcz-Pan, Maria; Abraham, Jared E.; Kelley, Karen D.

2011-01-01

No drilling has taken place at the Drenchwater occurrence, so alternative data sources (for example, geophysics) are especially important in assessing possible indicators of mineralization. Data from the 2005 electromagnetic survey define the geophysical character of the rocks at Drenchwater and, in combination with geological and surface-geochemical data, can aid in assessing the possible shallow (up to about 50 m), subsurface lateral extent of base-metal sulfide accumulations at Drenchwater. A distinct >3-km-long electromagnetic conductive zone (observed in apparent resistivity maps) coincides with, and extends further westward than, mineralized shale outcrops and soils anomalously high in Pb concentrations within the Kuna Formation; this conductive zone may indicate sulfide-rich rock. Models of electrical resistivity with depth, generated from inversion of electromagnetic data, which provide alongflight-line conductivity-depth profiles to between 25 and 50 m below ground surface, show that the shallow subsurface conductive zone occurs in areas of known mineralized outcrops and thins to the east. Broader, more conductive rock along the western ~1 km of the geophysical anomaly does not reach ground surface. These data suggest that the Drenchwater deposit is more extensive than previously thought. The application of inversion modeling also was applied to another smaller geochemical anomaly in the Twistem Creek area. The results are inconclusive, but they suggest that there may be a local conductive zone, possibly due to sulfides.

Using stable isotopes of water and strontium to investigate the hydrology of a natural and a constructed wetland

USGS Publications Warehouse

Hunt, R.J.; Bullen, T.D.; Krabbenhoft, D.P.; Kendall, C.

1998-01-01

Wetlands cannot exist without water, but wetland hydrology is difficult to characterize. As a result, compensatory wetland mitigation often only assumes the proper hydrology has been created. In this study, water sources and mass transfer processes in a natural and constructed wetland complex were investigated using isotopes of water and strontium. Water isotope profiles in the saturated zone revealed that the natural wetland and one site in the constructed wetland were primarily fed by ground water; profiles in another constructed wetland site showed recent rain was the predominant source of water in the root zone. Water isotopes in the capillary fringe indicated that the residence time for rain is less in the natural wetland than in the constructed wetland, thus transpiration (an important water sink) was greater in the natural wetland. Strontium isotopes showed a systematic difference between the natural and constructed wetlands that we attribute to the presence or absence of peat. In the peat-rich natural wetland, ??87Sr in the pore water increased along the flowline due to preferential weathering of minerals containing radiogenic Sr in response to elevated Fe concentrations in the water. In the constructed wetland, where peat thickness was thin and Fe concentrations in water were negligible, ??87Sr did not increase along the flowline. The source of the peat (on-site or off-site derived) applied in the constructed wetland controlled the ??87Sr at the top of the profile, but the effects were restricted by strong cation exchange in the underlying fluvial sediments. Based on the results of this study, neither constructed wetland site duplicated the water source and weathering environment of the adjoining natural wetland. Moreover, stable isotopes were shown to be effective tools for investigating wetlands and gaining insight not easily obtained using non-isotopic techniques. These tools have potential widespread application to wetlands that have distinct isotopic endmember sources.

Geochemical Specific Characters of the Oil and the Origin of the Oil and Gas Fields

NASA Astrophysics Data System (ADS)

Gottikh, Rimma; Pisotskiy, Bogdan; Plotnikova, Irina

2010-05-01

It is generally assumed that the fluid regime of the basement of ancient platforms is not associated with that of the sedimentary cover. This assumption is mainly due to the substantial time gap between the formation of the crystalline and sedimentary rocks as well as the evolutionary differences between the thermal regime of the interior and the redox potentials of fluid systems. The presence of loosely aggregated zones filled with salt-water solutions, oil or gas in the upper basement is explained by downward fluid flows from sedimentary rocks through tectonic faults into the disintegrated crystalline rocks. The formation of such zones is believed to be due to the crustal stratification due to Earth's pulsation, periodic variations of its rotational rate, hydrogenic deconsolidation, burial of the post-Early Proterozoic disintegration zones, etc. This pattern suggests that the matter and energy exchange between the Earth's spheres in the late stages of the platform development could only take place with the help of magmatic melts and the associated fluids during the tectonomagmatic cycles of the Earth's crust transformation. Gas and liquid hydrocarbon components mainly occur in crystalline basement rocks of ancient platforms penetrated to a depth of more than 3000 m due to deep degassing processes. The traces of the upward migration of fluids are sealed in the geological sequence, including the sedimentary cover, within secondary inclusions of rocks and minerals. The fluids are complex, reduced, multicomponent systems that transport lithophilous, chalcophilous and siderophilous elements. The presence of microelements in the bituminous phase of inclusions indicates that metals mainly occur in the complexes containing organic ligands. During the evolution of the fluid systems under new pressure and temperature conditions, low-solubility substances were separated out of the fluid to form hard bitumen, and the lighter components migrated into the overlying fractured and porous rocks. The high metal content of carbonaceous substances and their compositional variations governed by homogenisation temperatures of the inclusions suggest that they are not the products of the decomposition of oil fields. The constant presence of uranium in the fluid and its differentiation products allows the tracing of the systems' migration ways from the crystalline basement to oil-saturated reservoir zones of the sedimentary cover The known geochemical properties of bitumen and oil - high platinum content, specific distributions of rare earth elements, that are not characteristic of the upper crust formations, as well as 143Nd/144Nd and 87Sr/86Sr isotopic compounds, which are out of balance with the organic matter of sedimentary rocks - suggest that hydrocarbons are accumulated in the presence of cooling high-alkalinity mafite-ultramafite intrusions. This logically corresponds to the distribution of seismic anomalies and magnetic and gravity fields in the consolidated crust below the various petroleum fields (for example, South Tatarstan and Nepsky arches of the Romashkino and Verkhne-Chonskoye oil fields). The acquired geochemical and thermodynamic characteristics of the reduced fluids and their differentiation products from the crystalline basement and the sedimentary cover of the southern Siberian and eastern East European platforms indicate that these were formed outside of the sedimentary cover and that the migration was directed upwards. The analysis of the magmatic evolution on platforms reveals its alkaline trend due to the impeded degassing of magmatic sources at depth and the inflow of new doses of alkaline fluids or melts into them. Further evolution of the zones of partial melting of the substratum led, in the authors' view, to the generation of oil-forming fluids and their transportation into the Earth's upper crust. Their interaction with the surrounding rocks in turn led to the formation of oil accumulations. Thus, oil is the product of the interaction of deep, reduced fluids. Oil, graphite of the Archaean crystalline complexes and hard bitumens are interrelated elements of the evolution of deep, high-enthalpy systems. These large-scale reduced palaeofluid phenomena are obviously related to geodynamic and tectonomagmatic processes. The source of these fluid systems, their impact on the geological environment and its consequences can be determined through additional integrated geochemical studies using the isotopes of heavy elements and through the correlation of the observed potential fields with the structure of the consolidated crust and the sedimentary cover for the identification of geodynamic processes in geophysically inhomogeneous zones of the geological medium.

Perchlorate in the Hydrologic Cycle - An Overview of Sources and Occurrence

NASA Astrophysics Data System (ADS)

Stonestrom, D. A.; Jackson, W.; Mayer, K.; Orris, G. J.

2007-12-01

Perchlorate (ClO4-) in water and food is of concern due to deleterious health affects associated with hypothyroidism. The presence of widespread perchlorate in 0-to-28 ka-old pristine ground water of the Middle Rio Grande Basin (Plummer et al., 2006, ES&T, DOI:10.1021/es051739h), in ground water >1 mile from agricultural activities in the Southern High Plains (Rajagapolan et al., 2006, ES&T, DOI:10.1021/es052155i), and in unsaturated zones throughout the arid and semiarid southwestern United States (Rao et al., 2007, ES&T, DOI:10.1021/es062853i) clearly indicates that perchlorate is a non-exotic component of the hydrologic cycle, at least in dry environments. The natural system has been greatly perturbed in places by human activities. Most anthropogenic inputs are associated with the manufacture and use of explosives and rocket fuel, providing concentrated sources of excess perchlorate to the hydrologic cycle. Perchlorate-containing fertilizers and irrigation provide dispersed sources within and down-gradient from agricultural areas. Natural sources include photochemically mediated reactions involving ozone at the land surface and in the lower atmosphere. A growing body of work indicates that a small, but persistent, meteoric source acting over thousands of years can explain observed accumulations of unsaturated-zone perchlorate in arid regions. In addition to meteoric sources, oxyanions produced during volcanogenic processes can include appreciable amounts of natural perchlorate. Terrestrial plants take up perchlorate in soil water, with some species of xerophytic succulents concentrating the anion to high levels. Similarly, perchlorate in marine plants indicates that perchlorate is part of marine biochemical cycles. Perchlorate-bearing marine sediments of late Tertiary age suggest that perchlorate has been part of global geochemical cycles for millions of years and, furthermore, can be preserved in the subsurface despite the nearly ubiquitous presence of perchlorate-reducing bacteria in natural environments. New methods involving various combinations of ion chromatography, mass spectroscopy, and molecular biology are providing improved tools for understanding perchlorate in natural and perturbed systems. With large-scale sampling underway, a better understanding of the sources, sinks, and transformations of perchlorate in the hydrologic cycle is starting to emerge.

77 FR 49349 - Safety Zone; Chicago Air and Water Show, Lake Michigan, Chicago, IL

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-16

... Zone; Chicago Air and Water Show, Lake Michigan, Chicago, IL AGENCY: Coast Guard, DHS. ACTION... Water Show safety zone on Lake Michigan near Lincoln Park. This action is necessary to accurately reflect the enforcement dates and times for this safety zone due to changes made in this year's air show...

Influence of Organic Amendment and Compaction on Nutrient Dynamics in a Saturated Saline-Sodic Soil from the Riparian Zone.

PubMed

Miller, J J; Bremer, E; Curtis, T

2016-07-01

Cattle grazing in wet riparian pastures may influence nutrient dynamics due to nutrient deposition in feces and urine, soil compaction, and vegetation loss. We conducted a lab incubation study with a saline-sodic riparian soil to study nutrient (N, P, S, Fe, Mn, Cu, and Zn) dynamics in soil pore water using Plant Root Simulator (PRS) probes and release of nutrients into the overlying ponded water during flooding. The treatment factors were organic amendment (manure, roots, and unamended control), compaction (compacted, uncompacted), and burial time (3, 7, and 14 d). Amendment treatment had the greatest impact on nutrient dynamics, followed by burial time, whereas compaction had little impact. The findings generally supported our hypothesis that organic amendments should first increase nitrate loss, then increase Mn mobility, then Fe mobility and associated release of P, and finally increase sulfate loss. Declines in nitrate due to amendment addition were small because nitrate was at low levels in all treatments due to high denitrification potential instead of being released to soil pore water or overlying water. Addition of organic amendment strongly increased Mn and Fe concentrations in overlying water and of adsorbed Fe on PRS probes but only increased Mn on PRS probes on Day 3 due to subsequent displacement from ion exchange membranes. Transport of P to overlying water was increased by organic amendment addition but less so for manure than roots despite higher P on PRS probes. The findings showed that saline-sodic soils in riparian zones are generally a nutrient source for P and are a nutrient sink for N as measured using PRS probes after 3 to 7 d of flooding. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

A seismic hazard uncertainty analysis for the New Madrid seismic zone

USGS Publications Warehouse

Cramer, C.H.

2001-01-01

A review of the scientific issues relevant to characterizing earthquake sources in the New Madrid seismic zone has led to the development of a logic tree of possible alternative parameters. A variability analysis, using Monte Carlo sampling of this consensus logic tree, is presented and discussed. The analysis shows that for 2%-exceedence-in-50-year hazard, the best-estimate seismic hazard map is similar to previously published seismic hazard maps for the area. For peak ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 s (0.2 and 1.0 s Sa), the coefficient of variation (COV) representing the knowledge-based uncertainty in seismic hazard can exceed 0.6 over the New Madrid seismic zone and diminishes to about 0.1 away from areas of seismic activity. Sensitivity analyses show that the largest contributor to PGA, 0.2 and 1.0 s Sa seismic hazard variability is the uncertainty in the location of future 1811-1812 New Madrid sized earthquakes. This is followed by the variability due to the choice of ground motion attenuation relation, the magnitude for the 1811-1812 New Madrid earthquakes, and the recurrence interval for M>6.5 events. Seismic hazard is not very sensitive to the variability in seismogenic width and length. Published by Elsevier Science B.V.

Fault Geometry and Slip Distribution at Depth of the 1997 Mw 7.2 Zirkuh Earthquake: Contribution of Near-Field Displacement Data

NASA Astrophysics Data System (ADS)

Marchandon, Mathilde; Vergnolle, Mathilde; Sudhaus, Henriette; Cavalié, Olivier

2018-02-01

In this study, we reestimate the source model of the 1997 Mw 7.2 Zirkuh earthquake (northeastern Iran) by jointly optimizing intermediate-field Interferometry Synthetic Aperture Radar data and near-field optical correlation data using a two-step fault modeling procedure. First, we estimate the geometry of the multisegmented Abiz fault using a genetic algorithm. Then, we discretize the fault segments into subfaults and invert the data to image the slip distribution on the fault. Our joint-data model, although similar to the Interferometry Synthetic Aperture Radar-based model to the first order, highlights differences in the fault dip and slip distribution. Our preferred model is ˜80° west dipping in the northern part of the fault, ˜75° east dipping in the southern part and shows three disconnected high slip zones separated by low slip zones. The low slip zones are located where the Abiz fault shows geometric complexities and where the aftershocks are located. We interpret this rough slip distribution as three asperities separated by geometrical barriers that impede the rupture propagation. Finally, no shallow slip deficit is found for the overall rupture except on the central segment where it could be due to off-fault deformation in quaternary deposits.

Effects of upper ocean sound-speed structure on deep acoustic shadow-zone arrivals at 500- and 1000-km range.

PubMed

Van Uffelen, Lora J; Worcester, Peter F; Dzieciuch, Matthew A; Rudnick, Daniel L; Colosi, John A

2010-04-01

Deep acoustic shadow-zone arrivals observed in the late 1990s in the North Pacific Ocean reveal significant acoustic energy penetrating the geometric shadow. Comparisons of acoustic data obtained from vertical line arrays deployed in conjunction with 250-Hz acoustic sources at ranges of 500 and 1000 km from June to November 2004 in the North Pacific, with simulations incorporating scattering consistent with the Garrett-Munk internal-wave spectrum, are able to describe both the energy contained in and vertical extent of deep shadow-zone arrivals. Incoherent monthly averages of acoustic timefronts indicate that lower cusps associated with acoustic rays with shallow upper turning points (UTPs), where sound-speed structure is most variable and seasonally dependent, deepen from June to October as the summer thermocline develops. Surface-reflected rays, or those with near-surface UTPs, exhibit less scattering due to internal waves than in later months when the UTP deepens. Data collected in November exhibit dramatically more vertical extension than previous months. The depth to which timefronts extend is a complex combination of deterministic changes in the depths of the lower cusps as the range-average profiles evolve with seasonal change and of the amount of scattering, which depends on the mean vertical gradients at the depths of the UTPs.

A molecular Debye-Hückel theory and its applications to electrolyte solutions: The size asymmetric case

DOE PAGES

Xiao, Tiejun; Song, Xueyu

2017-03-28

We developed a molecular Debye-Hückel theory for electrolyte solutions with size asymmetry, where the dielectric response of an electrolyte solution is described by a linear combination of Debye-Hückel-like response modes. Furthermore, as the size asymmetry of an electrolyte solution leads to a charge imbalanced border zone around a solute, the dielectric response to the solute is characterized by two types of charge sources, namely, a bare solute charge and a charge distribution due to size asymmetry. These two kinds of charge sources are screened by the solvent differently, our theory presents a method to calculate the mean electric potential asmore » well as the electrostatic contributions to thermodynamic properties. Finally, the theory was successfully applied to binary as well as multi-component primitive models of electrolyte solutions.« less

Industrial pollution and the management of river water quality: a model of Kelani River, Sri Lanka.

PubMed

Gunawardena, Asha; Wijeratne, E M S; White, Ben; Hailu, Atakelty; Pandit, Ram

2017-08-19

Water quality of the Kelani River has become a critical issue in Sri Lanka due to the high cost of maintaining drinking water standards and the market and non-market costs of deteriorating river ecosystem services. By integrating a catchment model with a river model of water quality, we developed a method to estimate the effect of pollution sources on ambient water quality. Using integrated model simulations, we estimate (1) the relative contribution from point (industrial and domestic) and non-point sources (river catchment) to river water quality and (2) pollutant transfer coefficients for zones along the lower section of the river. Transfer coefficients provide the basis for policy analyses in relation to the location of new industries and the setting of priorities for industrial pollution control. They also offer valuable information to design socially optimal economic policy to manage industrialized river catchments.

Variations in Gas and Water Pulses at an Arctic Seep: Fluid Sources and Methane Transport

NASA Astrophysics Data System (ADS)

Hong, W.-L.; Torres, M. E.; Portnov, A.; Waage, M.; Haley, B.; Lepland, A.

2018-05-01

Methane fluxes into the oceans are largely dependent on the methane phase as it migrates upward through the sediments. Here we document decoupled methane transport by gaseous and aqueous phases in Storfjordrenna (offshore Svalbard) and propose a three-stage evolution model for active seepage in the region where gas hydrates are present in the shallow subsurface. In a preactive seepage stage, solute diffusion is the primary transport mechanism for methane in the dissolved phase. Fluids containing dissolved methane have high 87Sr/86Sr ratios due to silicate weathering in the microbial methanogenesis zone. During the active seepage stage, migration of gaseous methane results in near-seafloor gas hydrate formation and vigorous seafloor gas discharge with a thermogenic fingerprint. In the postactive seepage stage, the high concentration of dissolved lithium points to the contribution of a deeper-sourced aqueous fluid, which we postulate advects upward following cessation of gas discharge.

Source Water Assessment for the Las Vegas Valley Surface Waters

NASA Astrophysics Data System (ADS)

Albuquerque, S. P.; Piechota, T. C.

2003-12-01

The 1996 amendment to the Safe Drinking Water Act of 1974 created the Source Water Assessment Program (SWAP) with an objective to evaluate potential sources of contamination to drinking water intakes. The development of a Source Water Assessment Plan for Las Vegas Valley surface water runoff into Lake Mead is important since it will guide future work on source water protection of the main source of water. The first step was the identification of the watershed boundary and source water protection area. Two protection zones were delineated. Zone A extends 500 ft around water bodies, and Zone B extends 3000 ft from the boundaries of Zone A. These Zones extend upstream to the limits of dry weather flows in the storm channels within the Las Vegas Valley. After the protection areas were identified, the potential sources of contamination in the protection area were inventoried. Field work was conducted to identify possible sources of contamination. A GIS coverage obtained from local data sources was used to identify the septic tank locations. Finally, the National Pollutant Discharge Elimination System (NPDES) Permits were obtained from the State of Nevada, and included in the inventory. After the inventory was completed, a level of risk was assigned to each potential contaminating activity (PCA). The contaminants of concern were grouped into five categories: volatile organic compounds (VOCs), synthetic organic compounds (SOCs), inorganic compounds (IOCs), microbiological, and radionuclides. The vulnerability of the water intake to each of the PCAs was assigned based on these five categories, and also on three other factors: the physical barrier effectiveness, the risk potential, and the time of travel. The vulnerability analysis shows that the PCAs with the highest vulnerability rating include septic systems, golf courses/parks, storm channels, gas stations, auto repair shops, construction, and the wastewater treatment plant discharges. Based on the current water quality data (prior to treatment), the proximity of Las Vegas Wash to the intake, and the results of the vulnerability analysis of potential contaminating activities, it is determined that the drinking water intake is at a Moderate level of risk for VOC, SOC, and microbiological contaminants. The drinking water intake is at a High level of risk for IOC contaminants. Vulnerability to radiological contamination is Moderate. Source water protection in the Las Vegas Valley is strongly encouraged because of the documented influence of the Las Vegas Wash on the quality of the water at the intake.

Magnetic properties changes due to hydrocarbon contaminated groundwater table fluctuations

NASA Astrophysics Data System (ADS)

Ameen, Nawrass

2013-04-01

This study aims to understand the mechanisms and conditions which control the formation and transformation of ferro(i)magnetic minerals caused by hydrocarbon contaminated groundwater, in particular in the zone of fluctuating water levels. The work extends previous studies conducted at the same site. The study area is a former military air base at Hradčany, Czech Republic (50°37'22.71"N, 14°45'2.24"E). The site was heavily contaminated with petroleum hydrocarbons, due to leaks in petroleum storage tanks and jet fuelling stations over years of active use by the Soviet Union, which closed the base in 1991. The site is one of the most important sources of high quality groundwater in the Czech Republic. In a previous study, Rijal et al. (2010) concluded that the contaminants could be flushed into the sediments as the water level rose due to remediation processes leading to new formation of magnetite. In this previous study three different locations were investigated; however, from each location only one core was obtained. In order to recognize significant magnetic signatures versus depth three cores from each of these three locations were drilled in early 2012, penetrating the unsaturated zone, the groundwater fluctuation (GWF) zone and extending to about one meter below the groundwater level (~2.3 m depth at the time of sampling). Magnetic susceptibility (MS) profiles combined with other magnetic properties were analyzed to obtain a significant depth distribution of the ferro(i)magnetic concentration. Sediment properties, hydrocarbon content and bacterial activity were additionally studied. The results show that the highest ferrimagnetic mineral concentrations exist between 1.4-1.9 m depth from the baseline which is interpreted as the top of the GWF zone. Spikes of MS detected in the previous studies turned out to represent small-scale isolated features, but the trend of increasing MS values from the lowermost position of the groundwater table upward was verified. Mineral magnetic parameters indicate that magnetite is responsible for the MS signal which confirms the previous results (Rijal et al., 2010). The so far existing uncertainty of the groundwater level position could be solved. Bacterial activity is studied at particular depth horizons as it is assumed to be responsible for iron mineralogy changes. References: Rijal M.L., Appel E., Petrovský E. and Blaha U., 2010. Change of magnetic properties due to fluctuations of hydrocarbon contaminated groundwater in unconsolidated sediments. Environ.Pollut., 158, 1756-1762.

Assessing TCE source bioremediation by geostatistical analysis of a flux fence.

PubMed

Cai, Zuansi; Wilson, Ryan D; Lerner, David N

2012-01-01

Mass discharge across transect planes is increasingly used as a metric for performance assessment of in situ groundwater remediation systems. Mass discharge estimates using concentrations measured in multilevel transects are often made by assuming a uniform flow field, and uncertainty contributions from spatial concentration and flow field variability are often overlooked. We extend our recently developed geostatistical approach to estimate mass discharge using transect data of concentration and hydraulic conductivity, so accounting for the spatial variability of both datasets. The magnitude and uncertainty of mass discharge were quantified by conditional simulation. An important benefit of the approach is that uncertainty is quantified as an integral part of the mass discharge estimate. We use this approach for performance assessment of a bioremediation experiment of a trichloroethene (TCE) source zone. Analyses of dissolved parent and daughter compounds demonstrated that the engineered bioremediation has elevated the degradation rate of TCE, resulting in a two-thirds reduction in the TCE mass discharge from the source zone. The biologically enhanced dissolution of TCE was not significant (~5%), and was less than expected. However, the discharges of the daughter products cis-1,2, dichloroethene (cDCE) and vinyl chloride (VC) increased, probably because of the rapid transformation of TCE from the source zone to the measurement transect. This suggests that enhancing the biodegradation of cDCE and VC will be crucial to successful engineered bioremediation of TCE source zones. © 2012, The Author(s). Ground Water © 2012, National Ground Water Association.

Mapping genetic variation and seed zones for Bromus carinatus in the Blue Mountains of eastern Oregon, USA

Treesearch

R.C. Johnson; Vicky J. Erickson; Nancy L. Mandel; J. Bradley St. Clair; Kenneth W. Vance-Borland

2010-01-01

Seed transfer zones ensure that germplasm selected for restoration is suitable and sustainable in diverse environments. In this study, seed zones were developed for mountain brome (Bromus carinatus Hook. & Arn.) in the Blue Mountains of northeastern Oregon and adjoining Washington. Plants from 148 Blue Mountain seed source locations were...

The Impact of DNAPL Source-Zone Architecture on Contaminant Mass Flux and Plume Evolution in Heterogeneous Porous Media

DTIC Science & Technology

2013-08-01

remediation, ISCO, permanganate , persistence, DNAPL 16. SECURITY CLASSIFICATION OF: U 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF...focus on the lower-K zone 2 and surrounding higher-K matrix sand during the constant permanganate injection………………………… 45 Figure 5.1.3-3...Photographic image of the lower-K zone 2 and surrounding area after permanganate injection, exhibiting the shadow zone downgradient of the lower-K zone

Ste. Genevieve, Missouri Feasibility Report (Flood Control Study for Historic Ste. Genevieve - 80061). Volume 2. Appendices.

DTIC Science & Technology

1984-06-01

A greater seismic risk may be posed by two other zones: the *-."Southern Illinois - Wabash Zone and the New Madrid Zone. Earthquake ground motions...A-3 S 0I The study area is located in the Ozark Random Source Zone. This *seismotectonic zone is a region of moderate seismicity ( earthquake activity...40 inches, so that the tops of the casings are now 57 inches above the 1973 flood height. The new well casings’ elevations are approximately 395 feet

Process for liquefying carbonaceous materials of high molecular weight and for separating liquefaction products

DOEpatents

Malek, John M.

1977-01-01

Process characterized by comprising successively a dissolution zone fed with carbonaceous solids and with a solvent, a high pressure hydrogenation zone provided with a source of hydrogen, and a hydrogenation products separation zone, wherein the improvement consists mainly in chemical upgrading of the liquidform products derived from the separation zone, and recycling a part of the upgraded products to the dissolution zone, this recycled part being of either positively acidic or positively basic properties for enhancing the dissolution - decomposition of base-acid structures present in the carbonaceous solid feed.

[Land layout for lake tourism based on ecological restraint].

PubMed

Wang, Jian-Ying; Li, Jiang-Feng; Zou, Li-Lin; Liu, Shi-Bin

2012-10-01

To avoid the decrease and deterioration of lake wetlands and the other ecological issues such as lake water pollution that were caused by the unreasonable exploration of lake tourism, a land layout for the tourism development of Liangzi Lake with the priority of ecological security pattern was proposed, based on the minimal cumulative resistance model and by using GIS technology. The study area was divided into four ecological function zones, i. e., core protection zone, ecological buffer zone, ecotone zone, and human activity zone. The core protection zone was the landscape region of ecological source. In the protection zone, new tourism land was forbidden to be increased, and some of the existing fundamental tourism facilities should be removed while some of them should be upgraded. The ecological buffer zone was the landscape region with resistance value ranged from 0 to 4562. In the buffer zone, expansion of tourism land should be forbidden, the existing tourism land should be downsized, and human activities should be isolated from ecological source by converting the human environment to the natural environment as far as possible. The ecotone zone was the landscape region with resistance value ranged from 4562 to 30797. In this zone, the existing tourism land was distributed in patches, tourism land could be expanded properly, and the lake forestry ecological tourism should be developed widely. The human activity zone was the landscape region with resistance value ranged from 30797 to 97334, which would be the key area for the land layout of lake tourism. It was suggested that the land layout for tourism with the priority of landscape ecological security pattern would be the best choice for the lake sustainable development.

Modelling the diurnal and seasonal dynamics of soil CO2 exchange in a semiarid ecosystem with high plant-interspace heterogeneity

NASA Astrophysics Data System (ADS)

Gong, Jinnan; Wang, Ben; Jia, Xin; Feng, Wei; Zha, Tianshan; Kellomäki, Seppo; Peltola, Heli

2018-01-01

We used process-based modelling to investigate the roles of carbon-flux (C-flux) components and plant-interspace heterogeneities in regulating soil CO2 exchanges (FS) in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation). The model was parameterized and validated with multivariate data measured during the years 2013-2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant-interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

Sedimentation and associated trace metal enrichment in the riparian zone of the Three Gorges Reservoir, China.

PubMed

Tang, Qiang; Bao, Yuhai; He, Xiubin; Zhou, Huaidong; Cao, Zhijing; Gao, Peng; Zhong, Ronghua; Hu, Yunhua; Zhang, Xinbao

2014-05-01

Impoundment of the Three Gorges Reservoir has created an artificial riparian zone with a vertical height of 30 m and a total area of 349 km(2), which has been subjected to seasonal inundation and exposure due to regular reservoir impoundment and the occurrence of natural floods. The significant alteration of hydrologic regime has caused numerous environmental changes. The present study investigated the magnitude and spatial pattern of sedimentation and metal enrichment in a typical section of the riparian zone, composed of bench terraces with previous agricultural land uses, and explored their links to the changed hydrologic regime. In particular, we measured the total sediment depths and collected surface riparian sediments and down-profile sectioned riparian soils (at 5 cm intervals) for trace metal determination. Our analysis showed that the annual average sedimentation rates varied from 0.5 to 10 cm·yr(-1) and they decreased significantly with increasing elevation. This lateral distribution was principally attributed to seasonal variations in water levels and suspended sediment concentrations. Enriched concentrations of trace metals were found both in the riparian sediments and soils, but they were generally higher in the riparian sediments than in riparian soils and followed a similar lateral decreasing trend. Metal contamination assessment showed that the riparian sediments were slightly contaminated by Ni, Zn, and Pb, moderately contaminated by Cu, and moderately to strongly contaminated by Cd; while riparian soils were slightly contaminated by As, and moderately contaminated by Cd. Trace metal enrichment in the riparian sediments may be attributed to external input of contaminated sediments produced from upstream anthropogenic sources and chemical adsorption from dissolved fractions during pure sediment mobilization and after sink for a prolonged flooding period due to reservoir impoundment. Copyright © 2014 Elsevier B.V. All rights reserved.

Do heavy metals existing in abandoned mining sites represent a real health risk? A study case in the SE Spain.

NASA Astrophysics Data System (ADS)

Martinez-Sanchez, Maria Jose; Perez-Sirvent, Carmen; García-Lorenzo, Mari Luz; Martínez-López, Salvadora; Perez-Espinosa, Victor; Hernández-Cordoba, Manuel; Bech, Jaime

2013-04-01

Mining activities have been carried out for centuries in Sierra Minera (SE Spain) giving rise to a large number of sites distributed throughout the zone in which residues are accumulated. This communication reports studies as regards metal mobilization and analysis of the health risk that could be posed by inhalation, dermic contact or occasional ingestion of this type of sediments. Lead was used as the metal for the studies due to its particular abundance in the zone. A large number of samples were taken and general analytical determinations (pH, particle size, organic matter, equivalent calcium carbonate content and mineralogical composition) were carried out in order its characterization. An in vitro method for obtaining formation on Pb bioaccessibility in these mine waste materials was also carried out. Our results prove that mineral associations, different alteration states and sorption/desorption processes play an important role in the bioavailability of lead. In addition, it is noteworthy that the metal fraction dissolved by the proposed in vitro methodology is lower than 100%, both in the stomach and intestinal phases. Finally an assessment of the risk posed by lead is achieved. To this respect it should be noted that the IRIS database provide cancer slope factor and reference dose, as a way to assess the risk caused by arsenic, cadmium and copper but no for lead, probably due to the wide variety of real situations, and the discrepancy of the sources. The way here suggested is a novelty in this sense, and the results could be extrapolated to other similar zones and be incorporated to the general protocol of risk assessment applied to contaminated sites.

Genetic profiling to determine potential origins of boll weevils (Coleoptera: Curculionidae) captured in a Texas eradication zone: endemicity, immigration, or sabotage?

PubMed

Kim, Kyung Seok; Sappington, Thomas W; Allen, Charles T

2008-12-01

Thirty-seven boll weevils, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), were captured in pheromone traps near Lubbock, TX, in the Southern High Plains/Caprock eradication zone during August-October 2006. No boll weevils had been captured in this zone or neighboring zones to the north earlier in the year, and only very low numbers had been captured in neighboring zones to the south and east. Therefore, the captures near Lubbock were unexpected. Five of the weevils captured the last week of August were preserved and genotyped at 10 microsatellite loci for comparison with a database of genotypes for 22 boll weevil populations sampled from eight U.S. states and four locations in Mexico. The Lubbock population itself is an unlikely source, suggesting that the captured weevils probably did not originate from a low-level endemic population. Populations from eastern states, Mexico, and Big Spring, TX, can be confidently excluded as potential source regions. Although the Weslaco and Kingsville, TX, areas cannot be statistically excluded, they are unlikely sources. The most likely sources are nearby areas in New Mexico, TX, or southwest Oklahoma, or from areas of eastern Texas represented by Waxahachie and El Campo populations. Together, genetic and circumstantial evidence suggest either that the trapped boll weevils are the offspring of alone mated female that immigrated from eastern Texas earlier in the summer or that weevils originally captured near Waxahachie but now long-dead were planted in the traps by a disgruntled employee of the eradication program.

Latitude Dependence of Low-Altitude O+ Ion Upflow: Statistical Results From FAST Observations

NASA Astrophysics Data System (ADS)

Zhao, K.; Chen, K. W.; Jiang, Y.; Chen, W. J.; Huang, L. F.; Fu, S.

2017-09-01

We introduce a statistical model to explain the latitudinal dependence of the occurrence rate and energy flux of the ionospheric escaping ions, taking advantage of advances in the spatial coverage and accuracy of FAST observations. We use a weighted piecewise Gaussian function to fit the dependence, because two probability peaks are located in the dayside polar cusp source region and the nightside auroral oval zone source region. The statistical results show that (1) the Gaussian Mixture Model suitably describes the dayside polar cusp upflows, and the dayside and the nightside auroral oval zone upflows. (2) The magnetic latitudes of the ionospheric upflow source regions expand toward the magnetic equator as Kp increases, from 81° magnetic latitude (MLAT) (cusp upflows) and 63° MLAT (auroral oval upflows) during quiet times to 76° MLAT and 61° MLAT, respectively. (3) The dayside polar cusp region provides only 3-5% O+ upflows among all the source regions, which include the dayside auroral oval zone, dayside polar cusp, nightside auroral oval zone, and even the polar cap. However, observations show that more than 70% of upflows occur in the auroral oval zone and that the occurrence probability increases at the altitudes of 3500-4200 km, which is considered to be the lower altitude boundary of ion beams. This observed result suggests that soft electron precipitation and transverse wave heating are the most efficient ion energization/acceleration mechanisms at the altitudes of FAST orbit, and that the parallel acceleration caused by field-aligned potential drops becomes effective above that altitude.

A geophysical investigation of shallow deformation along an anomalous section of the Wasatch fault zone, Utah, USA

USGS Publications Warehouse

McBride, J.H.; Stephenson, W.J.; Thompson, T.J.; Harper, M.P.; Eipert, A.A.; Hoopes, J.C.; Tingey, D.G.; Keach, R.W.; Okojie-Ayoro, A. O.; Gunderson, K.L.; Meirovitz, C.D.; Hicks, T.C.; Spencer, C.J.; Yaede, J.R.; Worley, D.M.

2008-01-01

We report the results of a geophysical study of the Wasatch fault zone near the Provo and Salt Lake City segment boundary. This area is anomalous because the fault zone strikes more east-west than north-south. Vibroseis was used to record a common mid-point (CMP) profile that provides information to depths of ???500 m. A tomographic velocity model, derived from first breaks, constrained source and receiver static corrections; this was required due to complex terrain and significant lateral velocity contrasts. The profile reveals an ???250-m-wide graben in the hanging wall of the main fault that is associated with both synthetic and antithetic faults. Faults defined by apparent reflector offsets propagate upward toward topographic gradients. Faults mapped from a nearby trench and the seismic profile also appear to correlate with topographic alignments on LiDAR gradient maps. The faults as measured in the trench show a wide range of apparent dips, 20??-90??, and appear to steepen with depth on the seismic section. Although the fault zone is likely composed of numerous small faults, the broad asymmetric structure in the hanging wall is fairly simple and dominated by two inward-facing ruptures. Our results indicate the feasibility of mapping fault zones in rugged terrain and complex near-surface geology using low-frequency vibroseis. Further, the integration of geologic mapping and seismic reflection can extend surface observations in areas where structural deformation is obscured by poorly stratified or otherwise unmappable deposits. Therefore, the vibroseis technique, when integrated with geological information, provides constraints for assessing geologic hazards in areas of potential development.

What role did the Hikurangi subduction zone play in the M7.8 Kaikoura earthquake?

NASA Astrophysics Data System (ADS)

Wallace, L. M.; Hamling, I. J.; Kaneko, Y.; Fry, B.; Clark, K.; Bannister, S. C.; Ellis, S. M.; Francois-Holden, C.; Hreinsdottir, S.; Mueller, C.

2017-12-01

The 2016 M7.8 Kaikoura earthquake ruptured at least a dozen faults in the northern South Island of New Zealand, within the transition from the Hikurangi subduction zone (in the North Island) to the transpressive Alpine Fault (in the central South Island). The role that the southern end of the Hikurangi subduction zone played (or did not play) in the Kaikoura earthquake remains one of the most controversial aspects of this spectacularly complex earthquake. Investigations using near-field seismological and geodetic data suggest a dominantly crustal faulting source for the event, while studies relying on teleseismic data propose that a large portion of the moment release is due to rupture of the Hikurangi subduction interface beneath the northern South Island. InSAR and GPS data also show that a large amount of afterslip (up to 0.5 m) occurred on the subduction interface beneath the crustal faults that ruptured in the M7.8 earthquake, during the months following the earthquake. Modeling of GPS velocities for the 20 year period prior to the earthquake indicate that interseismic coupling was occurring on the Hikurangi subduction interface beneath the northern South Island, in a similar location to the suggested coseismic and postseismic slip on the subduction interface. We will integrate geodetic, seismological, tsunami, and geological observations in an attempt to balance the seemingly conflicting views from local and teleseismic data regarding the role that the southern Hikurangi subduction zone played in the earthquake. We will also discuss the broader implications of the observed coseismic and postseismic deformation for understanding the kinematics of the southern termination of the Hikurangi subduction zone, and its role in the transition from subduction to strike-slip in the central New Zealand region.

Water quality effects of intermittent water supply in Arraiján, Panama.

PubMed

Erickson, John J; Smith, Charlotte D; Goodridge, Amador; Nelson, Kara L

2017-05-01

Intermittent drinking water supply is common in low- and middle-income countries throughout the world and can cause water quality to degrade in the distribution system. In this study, we characterized water quality in one study zone with continuous supply and three zones with intermittent supply in the drinking water distribution network in Arraiján, Panama. Low or zero pressures occurred in all zones, and negative pressures occurred in the continuous zone and two of the intermittent zones. Despite hydraulic conditions that created risks for backflow and contaminant intrusion, only four of 423 (0.9%) grab samples collected at random times were positive for total coliform bacteria and only one was positive for E. coli. Only nine of 496 (1.8%) samples had turbidity >1.0 NTU and all samples had ≥0.2 mg/L free chlorine residual. In contrast, water quality was often degraded during the first-flush period (when supply first returned after an outage). Still, routine and first-flush water quality under intermittent supply was much better in Arraiján than that reported in a previous study conducted in India. Better water quality in Arraiján could be due to better water quality leaving the treatment plant, shorter supply outages, higher supply pressures, a more consistent and higher chlorine residual, and fewer contaminant sources near pipes. The results illustrate that intermittent supply and its effects on water quality can vary greatly between and within distribution networks. The study also demonstrated that monitoring techniques designed specifically for intermittent supply, such as continuous pressure monitoring and sampling the first flush, can detect water quality threats and degradation that would not likely be detected with conventional monitoring. Copyright © 2017 Elsevier Ltd. All rights reserved.

Potential Seismic Signatures of Megathrust Preparatory Zones

NASA Astrophysics Data System (ADS)

Parameswaran, R. M.; Maheswari, K.; Rajendran, K.

2017-12-01

The Mw 9.2, 2004 Sumatra earthquake awakened the otherwise inactive Andaman-Sumatra subduction zone (ASSZ), pushing it into an era of amplified seismicity. The subduction zone has since witnessed an array of inter- and intra-plate events along and around its trench. Several intra-plate events like the 2012 Wharton Basin earthquakes (Mw 8.6 and 8.2), are believed to be the triggered response of the plateward transmission of stresses due to the 2004 earthquake (Ishii et al., 2013). On the other hand, the Mw 7.5, 2009 33-km-deep intra-plate normal-faulting event in the northern Andaman segment is an example of outer-rise seismicity resulting from the post-seismic relaxation of the subducting slab (Andrade and Rajendran, 2011). These are aftermaths of a drastic change in the stress regime from compressional to extensional, following the 2004 megathrust event. But, pre-megathrust, aside from the inter-plate thrust mechanisms that are widely observed along the trench, how does the plate-motion-driven compression manifest in the regional seismicity? What happens to the stresses accumulating within the bending subducting slab; does it source deeper compressional events prior to a megathrust? The 2009 normal outer-rise earthquake was preceded by the 13 September 2002, Mw 6.5 Diglipur outer-rise thrust earthquake (22 km depth), both occurring at the northern terminus of the 2004-rupture, in the compressing forearc that experienced surface uplift pre-megathrust (Rajendran et al., 2003; Rajendran et al., 2007). This work, therefore, examines the slip models of such pre-event outer-rise thrust earthquakes along the stretch of the 2004 rupture zone in the ASSZ. The work is also being extended to understand the preparatory zones of other global megathrust earthquakes.

Stable isotope hydrology in fractured and detritic aquifers at both sides of the South Atlantic Ocean: Mar del Plata (Argentina) and the Rawsonville and Sandspruit river catchment areas (South Africa)

NASA Astrophysics Data System (ADS)

Glok Galli, Melisa; Damons, Matthew E.; Siwawa, Sitembiso; Bocanegra, Emilia M.; Nel, Jacobus M.; Mazvimavi, Dominic; Martínez, Daniel E.

2017-01-01

The aim of this work is to characterize the isotope composition of water (2H and 18O) in order to establish the relationship between fractured and detritic aquifers in similar hydrological environments located at both sides of the Atlantic Ocean. The Mar del Plata zone, placed in the Argentine Buenos Aires province in South America, and the Rawsonville and Sandspruit river catchment areas, situated in the Western Cape province in South Africa were compared. Rainwater and groundwater samples from fractured and detritic aquifers were analyzed through laser spectroscopy. In both Argentina and South African study sites, stable isotopes data demonstrate an aquifers recharge source from rainfall. For the Mar del Plata region, two different groups of detritic aquifer's samples with distinct recharge processes can be identified due to the close relationship existing between the present hydrogeological environments, the aquifer's grain size sediments and the isotopes contents: one representing rapid infiltration in aquifer sediments of the creeks' palaeobeds and hills zones (sandy or silt sandy sediments) and the other with slow infiltration of evaporated water in plain zones with an aquitard behavior. In the last group, the evaporation process occurs previous infiltration or in the aquifer's non-saturated zone, because of the existence of very low topographic gradients and fine-grained sediments. The evaporation phenomenon is not evident in the Sandspruit river catchment site's detritic aquifer, because its sandy composition allows a faster infiltration rate than in the loess that compounds the Pampeano aquifer in the interfluves zones of the Argentinian study area.

Fine structure of Mytella falcata (Bivalvia) gill filaments.

PubMed

de Oliveira David, José Augusto; Salaroli, Renato B; Fontanetti, Carmem S

2008-01-01

Bivalve filter feeders are sessile animals that live in constant contact with water and its pollutants. Their gill is an organ highly exposed to these conditions due to its large surface and its involvement in gas exchanges and feeding. The bivalve Mytella falcata is found in estuaries of Latin America, on the Atlantic as well as the Pacific Coast. It is commonly consumed, and sometimes is the only source of protein of low-income communities. In this study, gill filaments of M. falcata were characterized using histology, histochemistry and transmission electron microscopy for future comparative studies among animals exposed to environmental pollutants. Gill filaments may be divided into abfrontal, intermediate and frontal zones. Filaments are interconnected by ciliary discs. In the center of filaments, haemocytes circulate through a haemolymph vessel internally lined by an endothelium and supported by an acellular connective tissue rich in polysaccharides and collagen. The abfrontal zone contains cuboidal cells, while the intermediate zone consists of a simple squamous epithelium. The frontal zone is composed of five columnar cell types: one absorptive, mainly characterized by the presence of pinocytic vesicles in the apical region of the cell; one secretory, rarely observed; and three ciliated with abundant mitochondria. All cells lining the filament exhibit numerous microvilli and seem to absorb substances from the environment. PAS staining was observed in mucous cells in the frontal and abfrontal zones. Bromophenol blue allowed the distinction of haemocytes and detection of a glycoprotein secretion in the secretory cells of the frontal region. The characteristics of M. falcata gill filaments observed in this study were very similar to those of other bivalves, especially other Mytilidae, and are suitable for histopathological studies on the effect of water-soluble pollutants.

Pronounced zonation of seismic anisotropy in the Western Hellenic subduction zone and its geodynamic significance

NASA Astrophysics Data System (ADS)

Olive, Jean-Arthur; Pearce, Frederick; Rondenay, Stéphane; Behn, Mark D.

2014-04-01

Many subduction zones exhibit significant retrograde motion of their arc and trench. The observation of fast shear-wave velocities parallel to the trench in such settings has been inferred to represent trench-parallel mantle flow beneath a retreating slab. Here, we investigate this process by measuring seismic anisotropy in the shallow Aegean mantle. We carry out shear-wave splitting analysis on a dense array of seismometers across the Western Hellenic Subduction Zone, and find a pronounced zonation of anisotropy at the scale of the subduction zone. Fast SKS splitting directions subparallel to the trench-retreat direction dominate the region nearest to the trench. Fast splitting directions abruptly transition to trench-parallel above the corner of the mantle wedge, and rotate back to trench-normal over the back-arc. We argue that the trench-normal anisotropy near the trench is explained by entrainment of an asthenospheric layer beneath the shallow-dipping portion of the slab. Toward the volcanic arc this signature is overprinted by trench-parallel anisotropy in the mantle wedge, likely caused by a layer of strained serpentine immediately above the slab. Arcward steepening of the slab and horizontal divergence of mantle flow due to rollback may generate an additional component of sub-slab trench-parallel anisotropy in this region. Poloidal flow above the retreating slab is likely the dominant source of back-arc trench-normal anisotropy. We hypothesize that trench-normal anisotropy associated with significant entrainment of the asthenospheric mantle near the trench may be widespread but only observable at shallow-dipping subduction zones where stations nearest the trench do not overlie the mantle wedge.

40 CFR 146.6 - Area of review.

Code of Federal Regulations, 2014 CFR

2014-07-01

... lateral distance in which the pressures in the injection zone may cause the migration of the injection and... injection zone may cause the migration of the injection and/or formation fluid into an underground source of...

40 CFR 146.6 - Area of review.

Code of Federal Regulations, 2013 CFR

2013-07-01

... lateral distance in which the pressures in the injection zone may cause the migration of the injection and... injection zone may cause the migration of the injection and/or formation fluid into an underground source of...

40 CFR 146.6 - Area of review.

Code of Federal Regulations, 2011 CFR

2011-07-01

... lateral distance in which the pressures in the injection zone may cause the migration of the injection and... injection zone may cause the migration of the injection and/or formation fluid into an underground source of...

Geochemical and hydrologic controls on phosphorus transport in a sewage-contaminated sand and gravel aquifer near Ashumet Pond, Cape Cod, Massachusetts

USGS Publications Warehouse

Walter, Donald A.; Rea, Brigid A.; Stollenwerk, Kenneth G.; Savoie, Jennifer G.

1996-01-01

Currently (1993), about 170 kg/yr of phosphorus discharges into Ashumet Pond on Cape Cod from a plume of sewage-contaminated ground water. Phosphorus in the plume is mobile in two distinct geochemical environments--an anoxic zone containing dissolved iron and a suboxic zone containing dissolved oxygen. Phosphorus mobility in the suboxic zone is due to saturation of available sorption sites. Phosphorus loading to Ashumet Pond may increase significantly after sewage disposal is stopped due to phosphorus desorption from sediment surfaces.

3D mapping, hydrodynamics and modelling of the freshwater-brine mixing zone in salt flats similar to the Salar de Atacama (Chile)

NASA Astrophysics Data System (ADS)

Marazuela, M. A.; Vázquez-Suñé, E.; Custodio, E.; Palma, T.; García-Gil, A.; Ayora, C.

2018-06-01

Salt flat brines are a major source of minerals and especially lithium. Moreover, valuable wetlands with delicate ecologies are also commonly present at the margins of salt flats. Therefore, the efficient and sustainable exploitation of the brines they contain requires detailed knowledge about the hydrogeology of the system. A critical issue is the freshwater-brine mixing zone, which develops as a result of the mass balance between the recharged freshwater and the evaporating brine. The complex processes occurring in salt flats require a three-dimensional (3D) approach to assess the mixing zone geometry. In this study, a 3D map of the mixing zone in a salt flat is presented, using the Salar de Atacama as an example. This mapping procedure is proposed as the basis of computationally efficient three-dimensional numerical models, provided that the hydraulic heads of freshwater and mixed waters are corrected based on their density variations to convert them into brine heads. After this correction, the locations of lagoons and wetlands that are characteristic of the marginal zones of the salt flats coincide with the regional minimum water (brine) heads. The different morphologies of the mixing zone resulting from this 3D mapping have been interpreted using a two-dimensional (2D) flow and transport numerical model of an idealized cross-section of the mixing zone. The result of the model shows a slope of the mixing zone that is similar to that obtained by 3D mapping and lower than in previous models. To explain this geometry, the 2D model was used to evaluate the effects of heterogeneity in the mixing zone geometry. The higher the permeability of the upper aquifer is, the lower the slope and the shallower the mixing zone become. This occurs because most of the freshwater lateral recharge flows through the upper aquifer due to its much higher transmissivity, thus reducing the freshwater head. The presence of a few meters of highly permeable materials in the upper part of these hydrogeological systems, such as alluvial fans or karstified evaporites that are frequently associated with the salt flats, is enough to greatly modify the geometry of the saline interface.

Overview of surface measurements and spatial characterization of submicrometer particulate matter during the DISCOVER-AQ 2013 campaign in Houston, TX.

PubMed

Leong, Y J; Sanchez, N P; Wallace, H W; Karakurt Cevik, B; Hernandez, C S; Han, Y; Flynn, J H; Massoli, P; Floerchinger, C; Fortner, E C; Herndon, S; Bean, J K; Hildebrandt Ruiz, L; Jeon, W; Choi, Y; Lefer, B; Griffin, R J

2017-08-01

The sources of submicrometer particulate matter (PM 1 ) remain poorly characterized in the industrialized city of Houston, TX. A mobile sampling approach was used to characterize PM 1 composition and concentration across Houston based on high-time-resolution measurements of nonrefractory PM 1 and trace gases during the DISCOVER-AQ Texas 2013 campaign. Two pollution zones with marked differences in PM 1 levels, character, and dynamics were established based on cluster analysis of organic aerosol mass loadings sampled at 16 sites. The highest PM 1 mass concentrations (average 11.6 ± 5.7 µg/m 3 ) were observed to the northwest of Houston (zone 1), dominated by secondary organic aerosol (SOA) mass likely driven by nighttime biogenic organonitrate formation. Zone 2, an industrial/urban area south/east of Houston, exhibited lower concentrations of PM 1 (average 4.4 ± 3.3 µg/m 3 ), significant organic aerosol (OA) aging, and evidence of primary sulfate emissions. Diurnal patterns and backward-trajectory analyses enable the classification of airmass clusters characterized by distinct PM sources: biogenic SOA, photochemical aged SOA, and primary sulfate emissions from the Houston Ship Channel. Principal component analysis (PCA) indicates that secondary biogenic organonitrates primarily related with monoterpenes are predominant in zone 1 (accounting for 34% of the variability in the data set). The relevance of photochemical processes and industrial and traffic emission sources in zone 2 also is highlighted by PCA, which identifies three factors related with these processes/sources (~50% of the aerosol/trace gas concentration variability). PCA reveals a relatively minor contribution of isoprene to SOA formation in zone 1 and the absence of isoprene-derived aerosol in zone 2. The relevance of industrial amine emissions and the likely contribution of chloride-displaced sea salt aerosol to the observed variability in pollution levels in zone 2 also are captured by PCA. This article describes an urban-scale mobile study to characterize spatial variations in submicrometer particulate matter (PM 1 ) in greater Houston. The data set indicates substantial spatial variations in PM 1 sources/chemistry and elucidates the importance of photochemistry and nighttime oxidant chemistry in producing secondary PM 1 . These results emphasize the potential benefits of effective control strategies throughout the region, not only to reduce primary emissions of PM 1 from automobiles and industry but also to reduce the emissions of important secondary PM 1 precursors, including sulfur oxides, nitrogen oxides, ammonia, and volatile organic compounds. Such efforts also could aid in efforts to reduce mixing ratios of ozone.

Sources, fluxes, and behaviors of fluorescent dissolved organic matter (FDOM) in the Nakdong River Estuary, Korea

NASA Astrophysics Data System (ADS)

Lee, Shin-Ah; Kim, Guebuem

2018-02-01

We monitored seasonal variations in dissolved organic carbon (DOC), the stable carbon isotope of DOC (δ13C-DOC), and fluorescent dissolved organic matter (FDOM) in water samples from a fixed station in the Nakdong River Estuary, Korea. Sampling was performed every hour during spring tide once a month from October 2014 to August 2015. The concentrations of DOC and humic-like FDOM showed significant negative correlations against salinity (r2 = 0.42-0.98, p < 0.0001), indicating that the river-originated DOM components were the major source and behave conservatively in the estuarine mixing zone. The extrapolated δ13C-DOC values (-27.5 to -24.5 ‰) in fresh water confirm that both components are mainly of terrestrial origin. The slopes of humic-like FDOM against salinity were 60-80 % higher in the summer and fall due to higher terrestrial production of humic-like FDOM. The slopes of protein-like FDOM against salinity, however, were 70-80 % higher in spring due to higher biological production in river water. Our results suggest that there are large seasonal changes in riverine fluxes of humic- and protein-like FDOM to the ocean.

Nonresponse patterns in the Federal Waterfowl Hunter Questionnaire Survey

USGS Publications Warehouse

Pendleton, G.W.

1992-01-01

I analyzed data from the 1984 and 1986 Federal Waterfowl Hunter Questionnaire Survey (WHQS) to estimate the rate of return of name and address contact cards, to evaluate the efficiency of the Survey's stratification scheme, and to investigate potential sources of bias due to nonresponse at the contact card and questionnaire stages of the Survey. Median response at the contact card stage was 0.200 in 1984 and 0.208 in 1986, but was lower than 0.100 for many sample post offices. Large portions of the intended sample contributed little to the final estimates in the Survey. Differences in response characteristics between post office size strata were detected, but size strata were confounded with contact card return rates; differences among geographic zones within states were more pronounced. Large biases in harvest and hunter activity due to nonresponse were not found; however, consistent smaller magnitude biases were found. Bias in estimates of the proportion of active hunters was the most pronounced effect of nonresponse. All of the sources of bias detected would produce overestimates of harvest and activity. Redesigning the WHQS, including use of a complete list of waterfowl hunters and resampling nonrespondents, would be needed to reduce nonresponse bias.

Analysis of Radiation Transport Due to Activated Coolant in the ITER Neutral Beam Injection Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Royston, Katherine; Wilson, Stephen C.; Risner, Joel M.

Detailed spatial distributions of the biological dose rate due to a variety of sources are required for the design of the ITER tokamak facility to ensure that all radiological zoning limits are met. During operation, water in the Integrated loop of Blanket, Edge-localized mode and vertical stabilization coils, and Divertor (IBED) cooling system will be activated by plasma neutrons and will flow out of the bioshield through a complex system of pipes and heat exchangers. This paper discusses the methods used to characterize the biological dose rate outside the tokamak complex due to 16N gamma radiation emitted by the activatedmore » coolant in the Neutral Beam Injection (NBI) cell of the tokamak building. Activated coolant will enter the NBI cell through the IBED Primary Heat Transfer System (PHTS), and the NBI PHTS will also become activated due to radiation streaming through the NBI system. To properly characterize these gamma sources, the production of 16N, the decay of 16N, and the flow of activated water through the coolant loops were modeled. The impact of conservative approximations on the solution was also examined. Once the source due to activated coolant was calculated, the resulting biological dose rate outside the north wall of the NBI cell was determined through the use of sophisticated variance reduction techniques. The AutomateD VAriaNce reducTion Generator (ADVANTG) software implements methods developed specifically to provide highly effective variance reduction for complex radiation transport simulations such as those encountered with ITER. Using ADVANTG with the Monte Carlo N-particle (MCNP) radiation transport code, radiation responses were calculated on a fine spatial mesh with a high degree of statistical accuracy. In conclusion, advanced visualization tools were also developed and used to determine pipe cell connectivity, to facilitate model checking, and to post-process the transport simulation results.« less

Analysis of Radiation Transport Due to Activated Coolant in the ITER Neutral Beam Injection Cell

DOE PAGES

Royston, Katherine; Wilson, Stephen C.; Risner, Joel M.; ...

2017-07-26

Detailed spatial distributions of the biological dose rate due to a variety of sources are required for the design of the ITER tokamak facility to ensure that all radiological zoning limits are met. During operation, water in the Integrated loop of Blanket, Edge-localized mode and vertical stabilization coils, and Divertor (IBED) cooling system will be activated by plasma neutrons and will flow out of the bioshield through a complex system of pipes and heat exchangers. This paper discusses the methods used to characterize the biological dose rate outside the tokamak complex due to 16N gamma radiation emitted by the activatedmore » coolant in the Neutral Beam Injection (NBI) cell of the tokamak building. Activated coolant will enter the NBI cell through the IBED Primary Heat Transfer System (PHTS), and the NBI PHTS will also become activated due to radiation streaming through the NBI system. To properly characterize these gamma sources, the production of 16N, the decay of 16N, and the flow of activated water through the coolant loops were modeled. The impact of conservative approximations on the solution was also examined. Once the source due to activated coolant was calculated, the resulting biological dose rate outside the north wall of the NBI cell was determined through the use of sophisticated variance reduction techniques. The AutomateD VAriaNce reducTion Generator (ADVANTG) software implements methods developed specifically to provide highly effective variance reduction for complex radiation transport simulations such as those encountered with ITER. Using ADVANTG with the Monte Carlo N-particle (MCNP) radiation transport code, radiation responses were calculated on a fine spatial mesh with a high degree of statistical accuracy. In conclusion, advanced visualization tools were also developed and used to determine pipe cell connectivity, to facilitate model checking, and to post-process the transport simulation results.« less

Pre-eruption recharge of the Bishop magma system

USGS Publications Warehouse

Wark, D.A.; Hildreth, W.; Spear, F.S.; Cherniak, D.J.; Watson, E.B.

2007-01-01

The 650 km3 rhyolitic Bishop Tuff (eastern California, USA), which is stratigraphically zoned with respect to temperatures of mineral equilibration, reflects a corresponding thermal gradient in the source magma chamber. Consistent with previous work, application of the new TitaniQ (Ti-in-quartz) thermometer to quartz phenocryst rims documents an ???100 ??C temperature increase with chamber depth at the time of eruption. Application of TitaniQ to quartz phenocryst cores, however, reveals lower temperatures and an earlier gradient that was less steep, with temperature increasing with depth by only ???30 ??C. In many late-erupted crystals, sharp boundaries that separate low-temperature cores from high-temperature rims cut internal cathodoluminescent growth zoning, indicating partial phenocryst dissolution prior to crystallization of the high-temperature rims. Rimward jumps in Ti concentration across these boundaries are too abrupt (e.g., 40 ppm across a distance of <10 ??m) to have survived magmatic temperatures for more than ???100 yr. We interpret these observations to indicate heating-induced partial dissolution of quartz, followed by growth of high-temperature rims (made possible by lowering of water activity due to addition of CO2) within 100 yr of the climactic 760 ka eruption. Hot mafic melts injected into deeper parts of the magma system were the likely source of heat and CO2, raising the possibility that eruption and caldera collapse owe their origin to a recharge event. ?? 2007 Geological Society of America.

Quantitative analysis of transverse bacterial migration induced by chemotaxis in a packed column with structured physical heterogeneity.

PubMed

Wang, Meng; Ford, Roseanne M

2010-01-15

A two-dimensional mathematical model was developed to simulate transport phenomena of chemotactic bacteria in a sand-packed column designed with structured physical heterogeneity in the presence of a localized chemical source. In contrast to mathematical models in previous research work, in which bacteria were typically treated as immobile colloids, this model incorporated a convective-like chemotaxis term to represent chemotactic migration. Consistency between experimental observation and model prediction supported the assertions that (1) dispersion-induced microbial transfer between adjacent conductive zones occurred at the interface and had little influence on bacterial transport in the bulk flow of the permeable layers and (2) the enhanced transverse bacterial migration in chemotactic experiments relative to nonchemotactic controls was mainly due to directed migration toward the chemical source zone. On the basis of parameter sensitivity analysis, chemotactic parameters determined in bulk aqueous fluid were adequate to predict the microbial transport in our intermediate-scale porous media system. Additionally, the analysis of adsorption coefficient values supported the observation of a previous study that microbial deposition to the surface of porous media might be decreased under the effect of chemoattractant gradients. By quantitatively describing bacterial transport and distribution in a heterogeneous system, this mathematical model serves to advance our understanding of chemotaxis and motility effects in granular media systems and provides insights for modeling microbial transport in in situ microbial processes.

Analytical model for BTEX natural attenuation in the presence of fuel ethanol and its anaerobic metabolite acetate.

PubMed

da Silva, Marcio L B; Gomez, Diego E; Alvarez, Pedro J J

2013-03-01

Flow-through column studies were conducted to mimic the natural attenuation of ethanol and BTEX mixtures, and to consider potential inhibitory effects of ethanol and its anaerobic metabolite acetate on BTEX biodegradation. Results were analyzed using a one-dimensional analytical model that was developed using consecutive reaction differential equations based on first-order kinetics. Decrease in pH due to acetogenesis was also modeled, using charge balance equations under CaCO(3) dissolution conditions. Delay in BTEX removal was observed and simulated in the presence of ethanol and acetate. Acetate was the major volatile fatty acid intermediate produced during anaerobic ethanol biodegradation (accounting for about 58% of the volatile fatty acid mass) as suggested by the model data fit. Acetate accumulation (up to 1.1 g/L) near the source zone contributed to a pH decrease by almost one unit. The anaerobic degradation of ethanol (2 g/L influent concentration) at the source zone produced methane at concentrations exceeding its solubility (~/=26mg/L). Overall, this simple analytical model adequately described ethanol degradation, acetate accumulation and methane production patterns, suggesting that it could be used as a screening tool to simulate lag times in BTEX biodegradation, changes in groundwater pH and methane generation following ethanol-blended fuel releases. Copyright © 2012 Elsevier B.V. All rights reserved.

Estimating the impact of natural and technogenic factors on the incidence of malignant neoplasms in Altai krai

NASA Astrophysics Data System (ADS)

Romanov, A. N.; Kovrigin, A. O.; Lazarev, A. F.; Lubennikov, V. A.

2016-12-01

Air pollution by industry and motor vehicles, the use of coal ash for the construction of residential and nonresidential buildings, and the presence of dead zones in the residential sector are the main factors of carcinogenic risk to human health. Natural factors (such as topography and prevailing wind directions) can weaken or strengthen technogenic factors. Based on the estimate of pollutant concentrations in the snow cover of Barnaul, we reveal residential areas that are located at the crossroads of atmospheric transport of carcinogenic substances and characterized by concentrations considerably exceeding the maximum allowable concentration. These areas are characterized by the integral accumulation of carcinogenic substances concurrently from multiple sources; for almost any wind rose, the impact of one of the pollution sources is observed throughout the year. The assessment of the carcinogenic risk for a territory depends much on the correlation between local topography and the height of apartments above ground level. Using cancer register data for Barnaul, we reveal an increased level of the incidence of malignant neoplasms in people living in high-rise buildings located in areas with a sharp change in topography (such as ledges, hills, and lowlands). This may occur due to stagnant zones and wind shadows; under certain correlation between topography and the height and shape of buildings, carcinogenic substances accumulate maximally.

The Multi-Layer Variable Absorbers in NGC 1365 Revealed by XMM-Newton and NuSTAR

NASA Technical Reports Server (NTRS)

Rivers, E.; Risaliti, G.; Walton, D. J.; Harrison, F.; Arevalo, P.; Baur, F. E.; Boggs, S. E.; Brenneman, L. W.; Brightman, M.; Zhang, W. W.

2015-01-01

Between 2012 July and 2013 February, NuSTAR and XMM-Newton performed four long-look joint observations of the type 1.8 Seyfert, NGC 1365. We have analyzed the variable absorption seen in these observations in order to characterize the geometry of the absorbing material. Two of the observations caught NGC 1365 in an unusually low absorption state, revealing complexity in the multi-layer absorber that had previously been hidden. We find the need for three distinct zones of neutral absorption in addition to the two zones of ionized absorption and the Compton-thick torus previously seen in this source. The most prominent absorber is likely associated with broad-line region clouds with column densities of around approximately 10 (sup 23) per square centimeter and a highly clumpy nature as evidenced by an occultation event in 2013 February. We also find evidence of a patchy absorber with a variable column around approximately 10 (sup 22) per square centimeter and a line-of-sight covering fraction of 0.3-0.9, which responds directly to the intrinsic source flux, possibly due to a wind geometry. A full-covering, constant absorber with a low column density of approximately 1 by 10 (sup 22) per square centimeter is also present, though the location of this low density haze is unknown.

Probabilistic seismic hazard analysis for Sumatra, Indonesia and across the Southern Malaysian Peninsula

USGS Publications Warehouse

Petersen, M.D.; Dewey, J.; Hartzell, S.; Mueller, C.; Harmsen, S.; Frankel, A.D.; Rukstales, K.

2004-01-01

The ground motion hazard for Sumatra and the Malaysian peninsula is calculated in a probabilistic framework, using procedures developed for the US National Seismic Hazard Maps. We constructed regional earthquake source models and used standard published and modified attenuation equations to calculate peak ground acceleration at 2% and 10% probability of exceedance in 50 years for rock site conditions. We developed or modified earthquake catalogs and declustered these catalogs to include only independent earthquakes. The resulting catalogs were used to define four source zones that characterize earthquakes in four tectonic environments: subduction zone interface earthquakes, subduction zone deep intraslab earthquakes, strike-slip transform earthquakes, and intraplate earthquakes. The recurrence rates and sizes of historical earthquakes on known faults and across zones were also determined from this modified catalog. In addition to the source zones, our seismic source model considers two major faults that are known historically to generate large earthquakes: the Sumatran subduction zone and the Sumatran transform fault. Several published studies were used to describe earthquakes along these faults during historical and pre-historical time, as well as to identify segmentation models of faults. Peak horizontal ground accelerations were calculated using ground motion prediction relations that were developed from seismic data obtained from the crustal interplate environment, crustal intraplate environment, along the subduction zone interface, and from deep intraslab earthquakes. Most of these relations, however, have not been developed for large distances that are needed for calculating the hazard across the Malaysian peninsula, and none were developed for earthquake ground motions generated in an interplate tectonic environment that are propagated into an intraplate tectonic environment. For the interplate and intraplate crustal earthquakes, we have applied ground-motion prediction relations that are consistent with California (interplate) and India (intraplate) strong motion data that we collected for distances beyond 200 km. For the subduction zone equations, we recognized that the published relationships at large distances were not consistent with global earthquake data that we collected and modified the relations to be compatible with the global subduction zone ground motions. In this analysis, we have used alternative source and attenuation models and weighted them to account for our uncertainty in which model is most appropriate for Sumatra or for the Malaysian peninsula. The resulting peak horizontal ground accelerations for 2% probability of exceedance in 50 years range from over 100% g to about 10% g across Sumatra and generally less than 20% g across most of the Malaysian peninsula. The ground motions at 10% probability of exceedance in 50 years are typically about 60% of the ground motions derived for a hazard level at 2% probability of exceedance in 50 years. The largest contributors to hazard are from the Sumatran faults.

Littoral lichens as a novel source of potentially bioactive Actinobacteria.

PubMed

Parrot, Delphine; Antony-Babu, Sanjay; Intertaglia, Laurent; Grube, Martin; Tomasi, Sophie; Suzuki, Marcelino T

2015-10-30

Cultivable Actinobacteria are the largest source of microbially derived bioactive molecules. The high demand for novel antibiotics highlights the need for exploring novel sources of these bacteria. Microbial symbioses with sessile macro-organisms, known to contain bioactive compounds likely of bacterial origin, represent an interesting and underexplored source of Actinobacteria. We studied the diversity and potential for bioactive-metabolite production of Actinobacteria associated with two marine lichens (Lichina confinis and L. pygmaea; from intertidal and subtidal zones) and one littoral lichen (Roccella fuciformis; from supratidal zone) from the Brittany coast (France), as well as the terrestrial lichen Collema auriforme (from a riparian zone, Austria). A total of 247 bacterial strains were isolated using two selective media. Isolates were identified and clustered into 101 OTUs (98% identity) including 51 actinobacterial OTUs. The actinobacterial families observed were: Brevibacteriaceae, Cellulomonadaceae, Gordoniaceae, Micrococcaceae, Mycobacteriaceae, Nocardioidaceae, Promicromonosporaceae, Pseudonocardiaceae, Sanguibacteraceae and Streptomycetaceae. Interestingly, the diversity was most influenced by the selective media rather than lichen species or the level of lichen thallus association. The potential for bioactive-metabolite biosynthesis of the isolates was confirmed by screening genes coding for polyketide synthases types I and II. These results show that littoral lichens are a source of diverse potentially bioactive Actinobacteria.

Littoral lichens as a novel source of potentially bioactive Actinobacteria

PubMed Central

Parrot, Delphine; Antony-Babu, Sanjay; Intertaglia, Laurent; Grube, Martin; Tomasi, Sophie; Suzuki, Marcelino T.

2015-01-01

Cultivable Actinobacteria are the largest source of microbially derived bioactive molecules. The high demand for novel antibiotics highlights the need for exploring novel sources of these bacteria. Microbial symbioses with sessile macro-organisms, known to contain bioactive compounds likely of bacterial origin, represent an interesting and underexplored source of Actinobacteria. We studied the diversity and potential for bioactive-metabolite production of Actinobacteria associated with two marine lichens (Lichina confinis and L. pygmaea; from intertidal and subtidal zones) and one littoral lichen (Roccella fuciformis; from supratidal zone) from the Brittany coast (France), as well as the terrestrial lichen Collema auriforme (from a riparian zone, Austria). A total of 247 bacterial strains were isolated using two selective media. Isolates were identified and clustered into 101 OTUs (98% identity) including 51 actinobacterial OTUs. The actinobacterial families observed were: Brevibacteriaceae, Cellulomonadaceae, Gordoniaceae, Micrococcaceae, Mycobacteriaceae, Nocardioidaceae, Promicromonosporaceae, Pseudonocardiaceae, Sanguibacteraceae and Streptomycetaceae. Interestingly, the diversity was most influenced by the selective media rather than lichen species or the level of lichen thallus association. The potential for bioactive-metabolite biosynthesis of the isolates was confirmed by screening genes coding for polyketide synthases types I and II. These results show that littoral lichens are a source of diverse potentially bioactive Actinobacteria. PMID:26514347

How Well Does Fracture Set Characterization Reduce Uncertainty in Capture Zone Size for Wells Situated in Sedimentary Bedrock Aquifers?

NASA Astrophysics Data System (ADS)

West, A. C.; Novakowski, K. S.

2005-12-01

Regional groundwater flow models are rife with uncertainty. The three-dimensional flux vector fields must generally be inferred using inverse modelling from sparse measurements of hydraulic head, from measurements of hydraulic parameters at a scale that is miniscule in comparison to that of the domain, and from none to a very few measurements of recharge or discharge rate. Despite the inherent uncertainty in these models they are routinely used to delineate steady-state or time-of-travel capture zones for the purpose of wellhead protection. The latter are defined as the volume of the aquifer within which released particles will arrive at the well within the specified time and their delineation requires the additional step of dividing the magnitudes of the flux vectors by the assumed porosity to arrive at the ``average linear groundwater velocity'' vector field. Since the porosity is usually assumed constant over the domain one could be forgiven for thinking that the uncertainty introduced at this step is minor in comparison to the flow model calibration step. We consider this question when the porosity in question is fracture porosity in flat-lying sedimentary bedrock. We also consider whether or not the diffusive uptake of solute into the rock matrix which lies between the source and the production well reduces or enhances the uncertainty. To evaluate the uncertainty an aquifer cross section is conceptualized as an array of horizontal, randomly-spaced, parallel-plate fractures of random aperture, with adjacent horizontal fractures connected by vertical fractures again of random spacing and aperture. The source is assumed to be a continuous concentration (i.e. a dirichlet boundary condition) representing a leaking tank or a DNAPL pool, and the receptor is a fully pentrating well located in the down-gradient direction. In this context the time-of-travel capture zone is defined as the separation distance required such that the source does not contaminate the well beyond a threshold concentration within the specified time. Aquifers are simulated by drawing the random spacings and apertures from specified distributions. Predictions are made of capture zone size assuming various degrees of knowledge of these distributions, with the parameters of the horizontal fractures being estimated using simulated hydraulic tests and a maximum likelihood estimator. The uncertainty is evaluated by calculating the variance in the capture zone size estimated in multiple realizations. The results show that despite good strategies to estimate the parameters of the horizontal fractures the uncertainty in capture zone size is enormous, mostly due to the lack of available information on vertical fractures. Also, at realistic distances (less than ten kilometers) and using realistic transmissivity distributions for the horizontal fractures the uptake of solute from fractures into matrix cannot be relied upon to protect the production well from contamination.

Linking major and trace element headwater stream concentrations to DOC release and hydrologic conditions in a bog and peaty riparian zone

NASA Astrophysics Data System (ADS)

Broder, Tanja; Biester, Harald

2017-04-01

Peatlands and organic-rich riparian zones are known to export large amounts of dissolved organic carbon (DOC) to surface water. In organic-rich, acidic headwater streams main carriers for element export are dissolved organic matter (DOM) and organic-iron complexes. In this environment DOM might also act as major carrier for metals, which otherwise may have a low solubility. This study examines annual and short term event-based variations of major and trace elements in a headwater catchment. Patterns are used to trace hydrological pathways and element sources under different hydrologic preconditions. Furthermore, it elucidates the importance of DOC as carrier of different elements in a bog and a peaty riparian catchment. The study was conducted in a small headwater stream draining an ombrotrophic peatland with an adjacent forested area with peaty riparian soils in the Harz Mountains (Germany). Discharge sampling was conducted weekly at two sites from snowmelt to begin of snowfall and in high resolution during selected discharge events in 2013 and 2014. Element concentrations were measured by means of ICP-MS and ICP-OES. A PCA was performed for each site and for annual and event datasets. Results show that a large number of element concentrations strongly correlate with DOC concentrations at the bog site. Even elements like Ca and Mg, which are known to have a low affinity to DOC. Congruently, the first principal component integrates the DOC pattern (element loadings > 0.8: Ca, Fe, Mg, Mn, Zn, As, Sr, Cd, DOC) and explained about 35 % of total variance and even 50 % during rain events (loadings > 0.8: Al, Ca, Fe, Mg, Mn, Zn, Li, Co, As, Sr, Cd, Pb, DOC). The study cannot verify that all correlating elements bind to DOC. It is likely that also a common mobilization pattern in the upper peat layer by plant decomposition causes the same response to changes in hydrologic pathways. Additionally, a low mineral content and an enrichment of elements like Fe and Mn in the upper peat layers due to prevailing redox conditions might play a major role in a bog environment. At the peaty riparian zone only Ca, Fe, and Sr strongly correlated with DOC over the annual record. The PCA of the annual record display no clear DOC component here, but indicates that DOC is influenced by Component one (element loadings > 0.8: Ca, Mg, Zn, Co, Sr) and two (Al, V, La, Pb, U) suggesting different DOC sources in the peaty riparian zone. A large number of elements correlate with DOC during rain event sampling at the riparian zone. In contrast to the bog site the event-based riparian zone PCA distinguished a clear discharge related component with mineral, groundwater related elements (K, Rb, In, Cs, NO3- and SO42-). Pattern of the mineral and DOC components prove that during base flow discharge is generated in a shallow groundwater layer and successively increases upward to the organic-rich upper soil layer with increasing discharge. Contrarily, bog element pattern confirm a dominating surface-near discharge, due to high hydraulic conductivities.

Fuel injection staged sectoral combustor for burning low-BTU fuel gas

DOEpatents

Vogt, Robert L.

1981-01-01

A high-temperature combustor for burning low-BTU coal gas in a gas turbine is described. The combustor comprises a plurality of individual combustor chambers. Each combustor chamber has a main burning zone and a pilot burning zone. A pipe for the low-BTU coal gas is connected to the upstream end of the pilot burning zone; this pipe surrounds a liquid fuel source and is in turn surrounded by an air supply pipe; swirling means are provided between the liquid fuel source and the coal gas pipe and between the gas pipe and the air pipe. Additional preheated air is provided by counter-current coolant air in passages formed by a double wall arrangement of the walls of the main burning zone communicating with passages of a double wall arrangement of the pilot burning zone; this preheated air is turned at the upstream end of the pilot burning zone through swirlers to mix with the original gas and air input (and the liquid fuel input when used) to provide more efficient combustion. One or more fuel injection stages (second stages) are provided for direct input of coal gas into the main burning zone. The countercurrent air coolant passages are connected to swirlers surrounding the input from each second stage to provide additional oxidant.

Fuel injection staged sectoral combustor for burning low-BTU fuel gas

DOEpatents

Vogt, Robert L.

1985-02-12

A high-temperature combustor for burning low-BTU coal gas in a gas turbine is described. The combustor comprises a plurality of individual combustor chambers. Each combustor chamber has a main burning zone and a pilot burning zone. A pipe for the low-BTU coal gas is connected to the upstream end of the pilot burning zone: this pipe surrounds a liquid fuel source and is in turn surrounded by an air supply pipe: swirling means are provided between the liquid fuel source and the coal gas pipe and between the gas pipe and the air pipe. Additional preheated air is provided by counter-current coolant air in passages formed by a double wall arrangement of the walls of the main burning zone communicating with passages of a double wall arrangement of the pilot burning zone: this preheated air is turned at the upstream end of the pilot burning zone through swirlers to mix with the original gas and air input (and the liquid fuel input when used) to provide more efficient combustion. One or more fuel injection stages (second stages) are provided for direct input of coal gas into the main burning zone. The countercurrent air coolant passages are connected to swirlers surrounding the input from each second stage to provide additional oxidant.

Collapse risk of buildings in the Pacific Northwest region due to subduction earthquakes

USGS Publications Warehouse

Raghunandan, Meera; Liel, Abbie B.; Luco, Nicolas

2015-01-01

Subduction earthquakes similar to the 2011 Japan and 2010 Chile events will occur in the future in the Cascadia subduction zone in the Pacific Northwest. In this paper, nonlinear dynamic analyses are carried out on 24 buildings designed according to outdated and modern building codes for the cities of Seattle, Washington, and Portland, Oregon. The results indicate that the median collapse capacity of the ductile (post-1970) buildings is approximately 40% less when subjected to ground motions from subduction, as compared to crustal earthquakes. Buildings are more susceptible to earthquake-induced collapse when shaken by subduction records (as compared to crustal records of the same intensity) because the subduction motions tend to be longer in duration due to their larger magnitude and the greater source-to-site distance. As a result, subduction earthquakes are shown to contribute to the majority of the collapse risk of the buildings analyzed.

Intra-community implications of implementing multiple tsunami-evacuation zones in Alameda, California

USGS Publications Warehouse

Peters, Jeff; Wood, Nathan J.; Wilson, Rick; Miller, Kevin

2016-01-01

Tsunami-evacuation planning in coastal communities is typically based on maximum evacuation zones for a single scenario or a composite of sources; however, this approach may over-evacuate a community and overly disrupt the local economy and strain emergency-service resources. To minimize the potential for future over-evacuations, multiple evacuation zones based on arrival time and inundation extent are being developed for California coastal communities. We use the coastal city of Alameda, California (USA), as a case study to explore population and evacuation implications associated with multiple tsunami-evacuation zones. We use geospatial analyses to estimate the number and type of people in each tsunami-evacuation zone and anisotropic pedestrian evacuation models to estimate pedestrian travel time out of each zone. Results demonstrate that there are tens of thousands of individuals in tsunami-evacuation zones on the two main islands of Alameda, but they will likely have sufficient time to evacuate before wave arrival. Quality of life could be impacted by the high number of government offices, schools, day-care centers, and medical offices in certain evacuation zones and by potentially high population density at one identified safe area after an evacuation. Multi-jurisdictional evacuation planning may be warranted, given that many at-risk individuals may need to evacuate to neighboring jurisdictions. The use of maximum evacuation zones for local tsunami sources may be warranted given the limited amount of available time to confidently recommend smaller zones which would result in fewer evacuees; however, this approach may also result in over-evacuation and the incorrect perception that successful evacuations are unlikely.

Evaluation of accuracy of synthetic waveforms for subduction-zone earthquakes by using a land-ocean unified 3D structure model

NASA Astrophysics Data System (ADS)

Okamoto, Taro; Takenaka, Hiroshi; Nakamura, Takeshi

2018-06-01

Seismic wave propagation from shallow subduction-zone earthquakes can be strongly affected by 3D heterogeneous structures, such as oceanic water and sedimentary layers with irregular thicknesses. Synthetic waveforms must incorporate these effects so that they reproduce the characteristics of the observed waveforms properly. In this paper, we evaluate the accuracy of synthetic waveforms for small earthquakes in the source area of the 2011 Tohoku-Oki earthquake ( M JMA 9.0) at the Japan Trench. We compute the synthetic waveforms on the basis of a land-ocean unified 3D structure model using our heterogeneity, oceanic layer, and topography finite-difference method. In estimating the source parameters, we apply the first-motion augmented moment tensor (FAMT) method that we have recently proposed to minimize biases due to inappropriate source parameters. We find that, among several estimates, only the FAMT solutions are located very near the plate interface, which demonstrates the importance of using a 3D model for ensuring the self-consistency of the structure model, source position, and source mechanisms. Using several different filter passbands, we find that the full waveforms with periods longer than about 10 s can be reproduced well, while the degree of waveform fitting becomes worse for periods shorter than about 10 s. At periods around 4 s, the initial body waveforms can be modeled, but the later large-amplitude surface waves are difficult to reproduce correctly. The degree of waveform fitting depends on the source location, with better fittings for deep sources near land. We further examine the 3D sensitivity kernels: for the period of 12.8 s, the kernel shows a symmetric pattern with respect to the straight path between the source and the station, while for the period of 6.1 s, a curved pattern is obtained. Also, the range of the sensitive area becomes shallower for the latter case. Such a 3D spatial pattern cannot be predicted by 1D Earth models and indicates the strong effects of 3D heterogeneity on short-period ( ≲ 10s) waveforms. Thus, it would be necessary to consider such 3D effects when improving the structure and source models.

Spatial and temporal dynamics of organohalide-respiring bacteria in a heterogeneous PCE-DNAPL source zone

NASA Astrophysics Data System (ADS)

Cápiro, Natalie L.; Löffler, Frank E.; Pennell, Kurt D.

2015-11-01

Effective treatment of sites contaminated with dense non-aqueous phase liquids (DNAPLs) requires detailed understanding of the microbial community responses to changes in source zone strength and architecture. Changes in the spatial and temporal distributions of the organohalide-respiring Dehalococcoides mccartyi (Dhc) strains and Geobacter lovleyi strain SZ (GeoSZ) were examined in a heterogeneous tetrachloroethene- (PCE-) DNAPL source zone within a two-dimensional laboratory-scale aquifer flow cell. As part of a combined remedy approach, flushing with 2.3 pore volumes (PVs) of 4% (w/w) solution of the nonionic, biodegradable surfactant Tween® 80 removed 55% of the initial contaminant mass, and resulted in a PCE-DNAPL distribution that contained 51% discrete ganglia and 49% pools (ganglia-to-pool ratio of 1.06). Subsequent bioaugmentation with the PCE-to-ethene-dechlorinating consortium BDI-SZ resulted in cis-1,2-dichloroethene (cis-DCE) formation after 1 PV (ca. 7 days), while vinyl chloride (VC) and ethene were detected 10 PVs after bioaugmentation. Maximum ethene yields (ca. 90 μM) within DNAPL pool and ganglia regions coincided with the detection of the vcrA reductive dehalogenase (RDase) gene that exceeded the Dhc 16S rRNA genes by 2.0 ± 1.3 and 4.0 ± 1.7 fold in the pool and ganglia regions, respectively. Dhc and GeoSZ cell abundance increased by up to 4 orders-of-magnitude after 28 PVs of steady-state operation, with 1 to 2 orders-of-magnitude increases observed in close proximity to residual PCE-DNAPL. These observations suggest the involvement of these dechlorinators the in observed PCE dissolution enhancements of up to 2.3 and 6.0-fold within pool and ganglia regions, respectively. Analysis of the solid and aqueous samples at the conclusion of the experiment revealed that the highest VC (≥ 155 μM) and ethene (≥ 65 μM) concentrations were measured in zones where Dhc and GeoSZ were predominately attached to the solids. These findings demonstrate dynamic responses of organohalide-respiring bacteria in a heterogeneous DNAPL source zone, and emphasize the influence of source zone architecture on bioremediation performance.

Field demonstration and evaluation of the Passive Flux Meter on a CAH groundwater plume.

PubMed

Verreydt, G; Annable, M D; Kaskassian, S; Van Keer, I; Bronders, J; Diels, L; Vanderauwera, P

2013-07-01

This study comprises the first application of the Passive Flux Meter (PFM) for the measurement of chlorinated aliphatic hydrocarbon (CAH) mass fluxes and Darcy water fluxes in groundwater at a European field site. The PFM was originally developed and applied to measurements near source zones. The focus of the PFM is extended from near source to plume zones. For this purpose, 48 PFMs of 1.4 m length were constructed and installed in eight different monitoring wells in the source and plume zone of a CAH-contaminated field site located in France. The PFMs were retrieved, sampled, and analyzed after 3 to 11 weeks of exposure time, depending on the expected contaminant flux. PFM evaluation criteria include analytical, technical, and practical aspects as well as conditions and applicability. PFM flux data were compared with so-called traditional soil and groundwater concentration data obtained using active sampling methods. The PFMs deliver reasonable results for source as well as plume zones. The limiting factor in the PFM applicability is the exposure time together with the groundwater flux. Measured groundwater velocities at the field site range from 2 to 41 cm/day. Measured contaminant flux data raise up to 13 g/m(2)/day for perchloroethylene in the plume zone. Calculated PFM flux averaged concentration data and traditional concentration data were of similar magnitude for most wells. However, both datasets need to be compared with reservation because of the different sampling nature and time. Two important issues are the PFM tracer loss during installation/extraction and the deviation of the groundwater flow field when passing the monitoring well and PFM. The demonstration of the PFM at a CAH-contaminated field site in Europe confirmed the efficiency of the flux measurement technique for source as well as plume zones. The PFM can be applied without concerns in monitoring wells with European standards. The acquired flux data are of great value for the purpose of site characterization and mass discharge modeling, and can be used in combination with traditional soil and groundwater sampling methods.

Monitoring well utility in a heterogeneous DNAPL source zone area: Insights from proximal multilevel sampler wells and sampling capture-zone modelling.

PubMed

McMillan, Lindsay A; Rivett, Michael O; Wealthall, Gary P; Zeeb, Peter; Dumble, Peter

2018-03-01

Groundwater-quality assessment at contaminated sites often involves the use of short-screen (1.5 to 3 m) monitoring wells. However, even over these intervals considerable variation may occur in contaminant concentrations in groundwater adjacent to the well screen. This is especially true in heterogeneous dense non-aqueous phase liquid (DNAPL) source zones, where cm-scale contamination variability may call into question the effectiveness of monitoring wells to deliver representative data. The utility of monitoring wells in such settings is evaluated by reference to high-resolution multilevel sampler (MLS) wells located proximally to short-screen wells, together with sampling capture-zone modelling to explore controls upon well sample provenance and sensitivity to monitoring protocols. Field data are analysed from the highly instrumented SABRE research site that contained an old trichloroethene source zone within a shallow alluvial aquifer at a UK industrial facility. With increased purging, monitoring-well samples tend to a flow-weighted average concentration but may exhibit sensitivity to the implemented protocol and degree of purging. Formation heterogeneity adjacent to the well-screen particularly, alongside pump-intake position and water level, influence this sensitivity. Purging of low volumes is vulnerable to poor reproducibility arising from concentration variability predicted over the initial 1 to 2 screen volumes purged. Marked heterogeneity may also result in limited long-term sample concentration stabilization. Development of bespoke monitoring protocols, that consider screen volumes purged, alongside water-quality indicator parameter stabilization, is recommended to validate and reduce uncertainty when interpreting monitoring-well data within source zone areas. Generalised recommendations on monitoring well based protocols are also developed. A key monitoring well utility is their proportionately greater sample draw from permeable horizons constituting a significant contaminant flux pathway and hence representative fraction of source mass flux. Acquisition of complementary, high-resolution, site monitoring data, however, vitally underpins optimal interpretation of monitoring-well datasets and appropriate advancement of a site conceptual model and remedial implementation. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Development of seed zones for the Eastern United States: Request for input and collaboration!

Treesearch

Carrie C. Pike; George Hernandez; Barbara Crane; Paul Berrang

2017-01-01

Artificial regeneration is necessary for meeting a variety of management objectives following timber harvests and other disturbances. While foresters use ecological classification to identify the most appropriate species to plant on a particular site, they generally use seed zones to identify the most suitable seed source of that species to plant. Seed zones have been...

Purification effect of two typical water source vegetation buffer zones on land-sourced pollutants

NASA Astrophysics Data System (ADS)

Li, Gang

2017-03-01

Two vegetation buffer zones (tree-shrub-grass pattern and tree-grass pattern) were selected as test objects around Siming reservoir in Yuyao City of China. The effect of the storm runoff intensity (low and high intensity) and the buffer zone width (1 m, 3 m, 5 m, 7 m, 9 m, 12 m, 16 m) on pollutants (suspended solids, ammonium nitrogen and total phosphorus) was studied by the artificial simulation runoff. The results showed that with the increase of the width of buffer zone, the pollutant concentration was decreased. The purification effect of the two buffer zones on suspended solids and total phosphorus was basically stable at 52-55% and 34-37%, respectively. But the purification effect on ammonium nitrogen was the tree-shrub-grass pattern (69.7%) significantly better than that of tree-grass pattern (52.1%). The purification rate at the low runoff intensity was 1.8-2.0 times that at the high runoff intensity. The relationship between the purification rate and buffer zone width can be expressed by the natural logarithm equation, and the model adjustment coefficient was greater than 0.92.

Municipal water supplies in Lee County, Florida, 1974

USGS Publications Warehouse

O'Donnell, T. H.

1977-01-01

In 1974 the total pumpage for Lee County, Fla., municipal supplies reached 5,700 Mgal (million gallons annually), an increase of 54 percent over 1970 levels. Pumpage from individual sources included: Caloosahatchee River, 1,312 Mgal; water-table aquifer, 2,171 Mgal; the water-bearing zone in the Tamiami Formation, 340 Mgal; the water-bearing zone in the upper part of the Hawthorn Formation, 1,399 Mgal; the saline water zones in the lower part of the Hawthorn Formation and the Suwannee Limestone, 483 Mgal. Among the various sources, the water-table aquifer showed the greatest increase in municipal pumpage over 1970 levels (60 percent) while the saline zones in the lower part of the Hawthorn Formation and Suwannee Limestone showed the least (40 percent). Intensive pumpage from the water bearing zone in the upper part of the Hawthorn Formation has caused a progressive decline in water levels in wells tapping that zone. The quality of fresh ground water in areas unaffected by intrusion of saline water, generally meets all the recommended limits of the Environmental Protection Agency. The chemical treatment processes utilized by water plants in the county are generally effective in producing finished water that meets EPA preliminary drinking water standards. (Woodard-USGS)

Probabilistic seismic hazard assessments of Sabah, east Malaysia: accounting for local earthquake activity near Ranau

NASA Astrophysics Data System (ADS)

Khalil, Amin E.; Abir, Ismail A.; Ginsos, Hanteh; Abdel Hafiez, Hesham E.; Khan, Sohail

2018-02-01

Sabah state in eastern Malaysia, unlike most of the other Malaysian states, is characterized by common seismological activity; generally an earthquake of moderate magnitude is experienced at an interval of roughly every 20 years, originating mainly from two major sources, either a local source (e.g. Ranau and Lahad Dato) or a regional source (e.g. Kalimantan and South Philippines subductions). The seismicity map of Sabah shows the presence of two zones of distinctive seismicity, these zones are near Ranau (near Kota Kinabalu) and Lahad Datu in the southeast of Sabah. The seismicity record of Ranau begins in 1991, according to the international seismicity bulletins (e.g. United States Geological Survey and the International Seismological Center), and this short record is not sufficient for seismic source characterization. Fortunately, active Quaternary fault systems are delineated in the area. Henceforth, the seismicity of the area is thus determined as line sources referring to these faults. Two main fault systems are believed to be the source of such activities; namely, the Mensaban fault zone and the Crocker fault zone in addition to some other faults in their vicinity. Seismic hazard assessments became a very important and needed study for the extensive developing projects in Sabah especially with the presence of earthquake activities. Probabilistic seismic hazard assessments are adopted for the present work since it can provide the probability of various ground motion levels during expected from future large earthquakes. The output results are presented in terms of spectral acceleration curves and uniform hazard curves for periods of 500, 1000 and 2500 years. Since this is the first time that a complete hazard study has been done for the area, the output will be a base and standard for any future strategic plans in the area.

Fusion of Tomography Tests for DNAPL Source Zone Characterization: Technology Development and Validation

DTIC Science & Technology

2011-07-01

alternative to the REV and fracture network concepts, pp. 533-561, Rock Mechanics : Proceedings of the 28th U.S. Symposium, Tucson, Arizona, edited by I.W...spatially integrated measure of residual DNAPL volume in the flow without causing disturbances to the source zone domain [ Jin et al., 1995; Nelson and...step. 6 Hydrological inversion has been a major focus of groundwater hydrology during the last three decades [see Yeh, 1986; Sun , 1994 and

Microstructure Evolution During Continuous Cooling in AISI 5140 Steel Processed by Induction Heating Chromizing

NASA Astrophysics Data System (ADS)

Hu, Jianjun; Ma, Chaoping; Yang, Xian; Xu, Hongbin; Guo, Ning; Yu, Hongbing

2017-11-01

In this study, induction heating chromizing (IHC) and box-type furnace heating chromizing (BFHC) were conducted on commercial AISI 5140 steels, respectively. Microstructure, microhardness and wear resistance of the chromized samples were characterized. The results show that the IHC samples have thicker Cr coating layer and stronger interface bond due to pre-compressive stress among the packed powders. Three kinds of microstructures including alloyed cementite (AC-layer), fine pearlite zone (FP-zone) and carbon-poor zone (CP-zone) are formed near the interface in the IHC samples. The main reason given for this is that different contents of Cr and C have different effects on pearlite phase and morphology. The IHC sample shows better wear properties due to its stronger interface bonding strength than that of the BFHC sample. The formation mechanism of CP-zone and its influences on microhardness and wear resistance are also discussed.

Mantle transition zone structure beneath India and Western China from migration of PP and SS precursors

NASA Astrophysics Data System (ADS)

Lessing, Stephan; Thomas, Christine; Rost, Sebastian; Cobden, Laura; Dobson, David P.

2014-04-01

We investigate the seismic structure of the upper-mantle and mantle transition zone beneath India and Western China using PP and SS underside reflections off seismic discontinuities, which arrive as precursors to the PP and SS arrival. We use high-resolution array seismic techniques to identify precursory energy and to map lateral variations of discontinuity depths. We find deep reflections off the 410 km discontinuity (P410P and S410S) beneath Tibet, Western China and India at depths of 410-440 km and elevated underside reflections of the 410 km discontinuity at 370-390 km depth beneath the Tien Shan region and Eastern Himalayas. These reflections likely correspond to the olivine to wadsleyite phase transition. The 410 km discontinuity appears to deepen in Central and Northern Tibet. We also find reflections off the 660 km discontinuity beneath Northern China at depths between 660 and 700 km (P660P and S660S) which could be attributed to the mineral transformation of ringwoodite to magnesiowuestite and perovskite. These observations could be consistent with the presence of cold material in the middle and lower part of the mantle transition zone in this region. We also find a deeper reflector between 700 and 740 km depth beneath Tibet which cannot be explained by a depressed 660 km discontinuity. This structure could, however, be explained by the segregation of oceanic crust and the formation of a neutrally buoyant garnet-rich layer beneath the mantle transition zone, due to subduction of oceanic crust of the Tethys Ocean. For several combinations of sources and receivers we do not detect arrivals of P660P and S660S although similar combinations of sources and receivers give well-developed P660P and S660S arrivals. Our thermodynamic modelling of seismic structure for a range of compositions and mantle geotherms shows that non-observations of P660P and S660S arrivals could be caused by the dependence of underside reflection coefficients on the incidence angle of the incoming seismic waves. Apart from reflections off the 410 and 660 km discontinuities, we observe intermittent reflectors at 300 and 520 km depth. The discontinuity structure of the study region likely reflects lateral thermal and chemical variations in the upper-mantle and mantle transition zone connected to past and present subduction and mantle convection processes.

Combining SAR with LANDSAT for Change Detection of Riparian Buffer Zone in a Semi-arid River Basin

NASA Astrophysics Data System (ADS)

Chang, N.

2006-12-01

A combination of RADARSAT-1 and Landsat 5 TM satellite images linking the soil moisture variation with Normalized Difference Vegetation Index (NDVI) measurements were used to accomplish remotely sensed change detection of riparian buffer zone in the Choke Canyon Reservoir Watershed (CCRW), South Texas. The CCRW was selected as the study area contributing to the reservoir, which is mostly agricultural and range land in a semi-arid coastal environment. This makes the study significant due to the interception capability of non-point source impact within the riparian buffer zone and the maintenance of ecosystem integrity region wide. First of all, an estimation of soil moisture using RADARSAT-1 Synthetic Aperture Radar (SAR) satellite imagery was conducted. With its all-weather capability, the RADARSAT-1 is a promising tool for measuring the surface soil moisture over seasons. The time constraint is almost negligible since the RADARSAT-1 is able to capture surface soil moisture over a large area in a matter of seconds, if the area is within its swath. RADARSAT-1 images presented at here were captured in two acquisitions, including April and September 2004. With the aid of five corner reflectors deployed by Alaska Satellite Facility (ASF), essential radiometric and geometric calibrations were performed to improve the accuracy of the SAR imagery. The horizontal errors were reduced from initially 560 meter down to less than 5 meter at the best try. Then two Landsat 5 TM satellite images were summarized based on its NDVI. The combination of and NDVI and SAR data obviously show that soil moisture and vegetation biomass wholly varies in space and time in the CCRW leading to identify the riparian buffer zone evolution over seasons. It is found that the seasonal soil moisture variation is highly tied with the NDVI values and the change detection of buffer zone is technically feasible. It will contribute to develop more effective management strategies for non-point source pollution control, bird habitat monitoring, and grazing and live stock handlings in the future. Future research focuses on comparison of soil moisture variability within RADARSAT-1 footprints and NDVI variations against interferometric SAR for studying riparian ecosystem functioning on a seasonal basis.

A coupled airflow and source/sink model for simulating indoor VOC exposures.

PubMed

Yang, X; Chen, Q

2001-12-01

In this paper, a numerical model is presented to study the indoor air quality (IAQ) in a room with different emission sources, sinks, and ventilation methods. A computer program, ACCESS-IAQ, is developed to simulate the airflow pattern, the time history of the contaminant concentrations in the occupied zone, and the inhalation exposures. The program developed may be useful for IAQ professional to design healthy and comfortable indoor environments. A numerical study has been carried out to predict the effectiveness of a displacement ventilation and a mixing ventilation on volatile organic compound (VOC) removal in a model office. Results from the numerical predictions show that when a "wet" emission source (a freshly painted wood stain) is distributed uniformly across the floor area with sinks (gypsum board) from the four vertical walls, displacement ventilation has consistently lower exposure at the breathing level of the occupant in the room. Such an effect is mainly due to the higher ventilation efficiency of displacement ventilation compared to the mixing ventilation. The simulation results also show that the walls adsorb significant amounts of VOCs during the first hour and act as secondary sources thereafter.

2,4,6-Trinitrotoluene in soil and groundwater under a waste lagoon at the former Explosives Factory Maribyrnong (EFM), Victoria, Australia

NASA Astrophysics Data System (ADS)

Martel, Richard; Robertson, Timothy James; Doan, Minh Quan; Thiboutot, Sonia; Ampleman, Guy; Provatas, Arthur; Jenkins, Thomas

2008-01-01

Energetic materials contamination was investigated at the former Explosives Factory Maribyrnong, Victoria, Australia. Spectrophotometric/high performance liquid chromatography (HPLC) analysis was utilised to delineate a 5 tonne crystalline 2,4,6-trinitrotoluene (TNT) source in a former process waste lagoon that was found to be supplying contaminant leachate to the surficial clay aquitard with a maximum-recorded concentration of 7.0 ppm TNT. Groundwater within underlying sand and gravel aquifers was found to be uncontaminated due to upward hydraulic gradients resulting in slow plume development and propagation. Adsorption and microcosm test results from a parallel study were used as input parameters to simulate aqueous TNT transport in the clay aquitard using ATRANS20 software. The simulated TNT plume was localised within a few metres of the source, and at steady state, though leaching rate calculations suggest that without mitigation or other changes to the system, persistence of the source would be approximately 2,000 years. Remediation strategies may involve removal of the near surface source zone and infilling with an impermeable capping to impede leaching while facilitating ongoing natural attenuation by anaerobic degradation.

Determining Source Attenuation History to Support Closure by Natural Attenuation

DTIC Science & Technology

2013-09-01

SUBTITLE 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 6. AUTHOR(S...Tortuosity Factor Exponent Bulk Density of Low-k Zone DistriDutlon Coemctent or FractiOn Organic Carbon In Low-k Zone o rgaric CarDon Pa-tnioning...Organic Carbon In Low-k Zone orgaric CarDon Pa-tnioning coemctent Constrtuent Half-Life in Low-k Zone 3. GEN ERA L Year Core sample Collected fran

Fault zone structure and seismic reflection characteristics in zones of slow slip and tsunami earthquakes

NASA Astrophysics Data System (ADS)

Bell, Rebecca; Henrys, Stuart; Sutherland, Rupert; Barker, Daniel; Wallace, Laura; Holden, Caroline; Power, William; Wang, Xiaoming; Morgan, Joanna; Warner, Michael; Downes, Gaye

2015-04-01

Over the last couple of decades we have learned that a whole spectrum of different fault slip behaviour takes place on subduction megathrust faults from stick-slip earthquakes to slow slip and stable sliding. Geophysical data, including seismic reflection data, can be used to characterise margins and fault zones that undergo different modes of slip. In this presentation we will focus on the Hikurangi margin, New Zealand, which exhibits marked along-strike changes in seismic behaviour and margin characteristics. Campaign and continuous GPS measurements reveal deep interseismic coupling and deep slow slip events (~30-60 km) at the southern Hikurangi margin. The northern margin, in contrast, experiences aseismic slip and shallow (<10-15 km) slow slip events (SSE) every 18-24 months with equivalent moment magnitudes of Mw 6.5-6.8. Updip of the SSE region two unusual megathrust earthquakes occurred in March and May 1947 with characteristics typical of tsunami earthquakes. The Hikurangi margin is therefore an excellent natural laboratory to study differential fault slip behaviour. Using 2D seismic reflection, magnetic anomaly and geodetic data we observe in the source areas of the 1947 tsunami earthquakes i) low amplitude interface reflectivity, ii) shallower interface relief, iii) bathymetric ridges, iv) magnetic anomaly highs and in the case of the March 1947 earthquake v) stronger geodetic coupling. We suggest that this is due to the subduction of seamounts, similar in dimensions to seamounts observed on the incoming Pacific plate, to depths of <10 km. We propose a source model for the 1947 tsunami earthquakes based on geophysical data and find that extremely low rupture velocities (c. 300 m/s) are required to model the observed large tsunami run-up heights (Bell et al. 2014, EPSL). Our study suggests that subducted topography can cause the nucleation of moderate earthquakes with complex, low velocity rupture scenarios that enhance tsunami waves, and the role of subducted rough topography in seismic hazard should not be under-estimated. 2D seismic reflection data along the northern Hikurangi margin also image thick (c. 2 km) high-amplitude reflectivity zones (HRZ) coinciding broadly with the source areas of shallow SSEs. The HRZ may be the result of high-fluid content within subduction sediments, suggesting fluids may exert an important control on the generation of SSEs by reducing effective stress (Bell et al. 2010, GJI). However, this hypothesis remains untested. In this presentation, using synthetic models, we will discuss planned future applications of an advanced seismic imaging technique called Full-waveform inversion, integrated with drilling, at subduction margins like Hikurangi to recover fault physical properties at high-resolution in 3D to examine the properties of heterogeneous fault zones.

Selective transport of palynomorphs in marine turbiditic deposits: An example from the Ascension-Monterey Canyon system offshore central California

USGS Publications Warehouse

McGann, Mary

2017-01-01

The pollen assemblage of a deep-sea core (15G) collected at lower bathyal depths (3491 m) on a levee of Monterey Canyon off central California was investigated to gain insights into the delivery processes of terrigenous material to submarine fans and the effect this transport has on the palynological record. Thirty-two samples were obtained down the length of the core, 19 from hemipelagic and mixed mud deposits considered to be the background record, and 13 others from displaced flow deposits. The pollen record obtained from the background samples documents variations in the terrestrial flora as it adapted to changing climatic conditions over the last 19,000 cal yrs BP. A Q-mode cluster analysis defined three pollen zones: a Glacial Pollen Zone (ca. 20,000–17,000 cal yr BP), an overlying Transitional Pollen Zone (ca. 17,000–11,500 cal yr BP), and an Interglacial Pollen Zone (ca. 11,500 cal yr BP to present). Another Q-mode cluster analysis, of both the background mud and flow deposits, also defined these three pollen zones, but four of the 13 turbiditic deposits were assigned to pollen zones older than expected by their stratigraphic position. This was due to these samples containing statistically significant fewer palynomorphs than the background muds as well as being enriched (∼10–35% in some cases) in hydraulically-efficient Pinus pollen. A selective bias in the pollen assemblage, such as demonstrated here, may result in incorrect interpretations (e.g., climatic shifts or environmental perturbations) based on the floral record, indicating turbiditic deposits should be avoided in marine palynological studies. Particularly in the case of fine-grained flow deposits that may not be visually distinct, granulometry and grain size frequency distribution curves may not be enough to identify these biased deposits. Determining the relative abundance and source of displaced shallow-water benthic foraminifera entrained in these sediments serves as an excellent additional tool to do so.

Flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone of the Three Gorges Reservoir, China.

PubMed

Tang, Qiang; Bao, Yuhai; He, Xiubin; Fu, Bojie; Collins, Adrian L; Zhang, Xinbao

2016-04-01

Since the launch of the Three Gorges Dam on the Yangtze River, a distinctive reservoir fluctuation zone has been created and significantly modified by regular dam operations. Sediment redistribution within this artificial landscape differs substantially from that in natural fluvial riparian zones, due to a specific hydrological regime comprising steps of water impoundment with increasing magnitudes and seasonal water level fluctuation holding a range of sediment fluxes. This study reinterpreted post-dam sedimentary dynamics in the reservoir fluctuation zone by stratigraphy determination of a 345-cm long sediment core, and related it to impact of the hydrological regime. Seasonality in absolute grain-size composition of suspended sediment was applied as a methodological basis for stratigraphic differentiation. Sedimentary laminations with relatively higher proportions of sandy fractions were ascribed to sedimentation during the dry season when proximal subsurface bank erosion dominates source contributions, while stratigraphy with a lower proportion of sandy fractions is possibly contributed by sedimentation during the wet season when distal upstream surface erosion prevails. Chronology determination revealed non-linear and high annual sedimentation rates ranging from 21.7 to 152.1cm/yr. Although channel geomorphology may primarily determine the spatial extent of sedimentation, seasonal sedimentary dynamics was predominantly governed by the frequency, magnitude, and duration of flooding. Summer inundation by natural floods with enhanced sediment loads produced from upstream basins induced higher sedimentation rates than water impoundment during the dry season when distal sediment supply was limited. We thus conclude that flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone, though little impact on total sediment retention rate was detected. Ongoing reductions in flow and sediment supply under human disturbance may have profound implications in affecting sedimentary equilibrium in the reservoir fluctuation zone. The results herein provide insights of how big dams have disrupted the sediment conveyance processes of large scale fluvial systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Metasomatism, Fluid Overpressure and Brecciation at the Slab-Mantle Interface: Insights from the Livingstone Fault, New Zealand

NASA Astrophysics Data System (ADS)

Tarling, M.; Smith, S. A. F.; Scott, J.

2017-12-01

Juxtaposition of mantle peridotite and serpentinite against quartzofeldspathic and mafic schists occurs along the shallow slab-mantle interface in some subduction zones. This part of the subduction interface has been invoked as a possible source region of episodic tremor and slow slip, yet geological observations of fault zone structures and chemical reactions pertinent to this region are quite rare. The >1000 km long Livingstone Fault in New Zealand is a superbly exposed fault zone that provides a suitable analogue (both in terms of scale and the rock types involved) for the shallow slab-mantle interface. The fault is characterized by a foliated and highly sheared serpentinite mélange tens to several hundreds of meters wide that separates (partially serpentinised) peridotites from quartzofeldspathic schists. Talc- and tremolite-forming metasomatic reactions occurred along the margins of the mélange and around entrained pods due to mixing of serpentinite with silica- and calcium-rich fluids derived from the adjacent quartzofeldspathic schist. The metasomatic reactions generated significant volumes of water at the melange-schist contact that became trapped between the two relatively impermeable fault zone lithologies. On the schist side of the contact, brittle faulting was promoted by the formation of a laterally-continuous silicified zone up to tens of metres wide. On the melange side, a zone up to tens of metres wide of `crackle-breccias' containing veined stockworks of tremolite indicates periodic increases of pore pressure sufficient to cause hydraulic fracture of serpentinite. The crackle-breccias are multi-generational indicating that this process was episodic. Sr and Nd isotope data and permeability calculations suggest that the episodic brecciation process was critical to the transfer of fluids across the melange. Our observations suggest that fluid-producing metasomatic reactions along the shallow slab-mantle interface may contribute to the tremor signal by triggering brecciation events and promoting brittle failure in serpentinite and schist.

The Africa South America Intercontinental Teleconnection.

NASA Astrophysics Data System (ADS)

Cook, K. H.; Hsieh, J.-S.; Hagos, S. M.

2004-07-01

The influence of heating over Africa on the South American precipitation climatology, and the influence of South America on Africa, is examined through the application of GCM simulations with idealized boundary conditions and perpetual solstice (January and July) conditions.The presence of Africa is associated with a pronounced (up to 4 mm day-1) decrease in precipitation in Brazil's Nordeste region during austral summer. Low-level moisture divergence and dry-air advection associated with the downbranch of a Walker circulation induced by heating over southern Africa is amplified over the Nordeste due to the response of the land surface. The response is much smaller during austral winter due to differences in the heat source over Africa and a reduced sensitivity in the surface heat balance over tropical South America. Forcing from South America in January shifts the position of the South Indian convergence zone (SICZ) to the southwest over southern Africa in association with the formation of the South Atlantic convergence zone (SACZ). In July, a Rossby wave train generated over South America induces a response in the surface temperature of Africa that leads to stronger precipitation in central and western Africa.This study suggests a zonal mode of variability for South American and African circulation and precipitation fields. The resulting perturbations depend as much on land surface atmosphere interactions as on the direct forcing from the adjacent continent, and the mechanisms are highly nonlinear.

Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones.

PubMed

Kalvelage, Tim; Lavik, Gaute; Jensen, Marlene M; Revsbech, Niels Peter; Löscher, Carolin; Schunck, Harald; Desai, Dhwani K; Hauss, Helena; Kiko, Rainer; Holtappels, Moritz; LaRoche, Julie; Schmitz, Ruth A; Graco, Michelle I; Kuypers, Marcel M M

2015-01-01

Oxygen minimum zones are major sites of fixed nitrogen loss in the ocean. Recent studies have highlighted the importance of anaerobic ammonium oxidation, anammox, in pelagic nitrogen removal. Sources of ammonium for the anammox reaction, however, remain controversial, as heterotrophic denitrification and alternative anaerobic pathways of organic matter remineralization cannot account for the ammonium requirements of reported anammox rates. Here, we explore the significance of microaerobic respiration as a source of ammonium during organic matter degradation in the oxygen-deficient waters off Namibia and Peru. Experiments with additions of double-labelled oxygen revealed high aerobic activity in the upper OMZs, likely controlled by surface organic matter export. Consistently observed oxygen consumption in samples retrieved throughout the lower OMZs hints at efficient exploitation of vertically and laterally advected, oxygenated waters in this zone by aerobic microorganisms. In accordance, metagenomic and metatranscriptomic analyses identified genes encoding for aerobic terminal oxidases and demonstrated their expression by diverse microbial communities, even in virtually anoxic waters. Our results suggest that microaerobic respiration is a major mode of organic matter remineralization and source of ammonium (~45-100%) in the upper oxygen minimum zones, and reconcile hitherto observed mismatches between ammonium producing and consuming processes therein.

Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones

PubMed Central

Kalvelage, Tim; Lavik, Gaute; Jensen, Marlene M.; Revsbech, Niels Peter; Löscher, Carolin; Schunck, Harald; Desai, Dhwani K.; Hauss, Helena; Kiko, Rainer; Holtappels, Moritz; LaRoche, Julie; Schmitz, Ruth A.; Graco, Michelle I.; Kuypers, Marcel M. M.

2015-01-01

Oxygen minimum zones are major sites of fixed nitrogen loss in the ocean. Recent studies have highlighted the importance of anaerobic ammonium oxidation, anammox, in pelagic nitrogen removal. Sources of ammonium for the anammox reaction, however, remain controversial, as heterotrophic denitrification and alternative anaerobic pathways of organic matter remineralization cannot account for the ammonium requirements of reported anammox rates. Here, we explore the significance of microaerobic respiration as a source of ammonium during organic matter degradation in the oxygen-deficient waters off Namibia and Peru. Experiments with additions of double-labelled oxygen revealed high aerobic activity in the upper OMZs, likely controlled by surface organic matter export. Consistently observed oxygen consumption in samples retrieved throughout the lower OMZs hints at efficient exploitation of vertically and laterally advected, oxygenated waters in this zone by aerobic microorganisms. In accordance, metagenomic and metatranscriptomic analyses identified genes encoding for aerobic terminal oxidases and demonstrated their expression by diverse microbial communities, even in virtually anoxic waters. Our results suggest that microaerobic respiration is a major mode of organic matter remineralization and source of ammonium (~45-100%) in the upper oxygen minimum zones, and reconcile hitherto observed mismatches between ammonium producing and consuming processes therein. PMID:26192623

Nitrogen Isotopic Composition of Proteinaceous Coral Skeletal Amino Acids Records Change in Source Nitrate to the Euphotic Zone in the Western Tropical Pacific

NASA Astrophysics Data System (ADS)

Williams, B.; Thibodeau, B.; Chikaraishi, Y.; Ohkouchi, N.; Grottoli, A. G.

2014-12-01

Instrumental and proxy data and global climate model experiments indicate a multi-decadal shoaling of the western tropical Pacific (WTP) thermocline potentially related to a shift in ENSO frequency. In the WTP, the nutricline coincides with the thermocline, and a shoaling of the nutricline brings more nitrate-rich seawater higher in the water column and within the sunlit euphotic zone. In the nutrient-poor WTP, this incursion of nitrate-rich water at the bottom of the euphotic zone may stimulate productivity in the water column. However, there is a general paucity of measurements below the surface with which to investigate recent changes in seawater chemistry. Nitrogen isotope (δ15N) measurements of particulate organic matter (POM) can elucidate the source of nitrogen to the WTP and related trophic dynamics. This POM is the food source to the long-lived proteinaceous corals, and drives the nitrogen isotopic composition of their skeleton. Here, we report time series δ15N values from the banded skeletons of proteinaceous corals from offshore Palau in the WTP that provide proxy information about past changes in euphotic zone nitrogen dynamics. Bulk skeletal δ15N values declined between 1977 and 2010 suggesting a progressively increasing contribution of deep water with isotopically-light nitrate to the euphotic zone and/or a shortening of the planktonic food web. Since only some amino acids are enriched in δ15N with each trophic transfer in a food web, we measured the δ15N composition of seven individual amino acids in the same coral skeleton. The δ15N time series of the individual amino acids also declined over time, mirroring the bulk values. These new data indicate that the changes in the source nitrogen to the base of the euphotic zone drives a decline in coral skeletal δ15N values, consistent with the shoaling nutricline, with no coinciding alteration of the trophic structure in the WTP.

Contribution of Fugitive Emissions for PM10 Concentrations in an Industrial Area of Portugal

NASA Astrophysics Data System (ADS)

Marta Almeida, Susana; Viana Silva, Alexandra; Garcia, Silvia; Miranda, Ana Isabel

2013-04-01

Significant atmospheric dust arises from the mechanical disturbance of granular material exposed to the air. Dust generated from these open sources is termed "fugitive" because it is not discharged to the atmosphere in a confined flow stream. Common sources of fugitive dust include unpaved roads, agricultural tilling operations, aggregate storage piles, heavy construction and harbor operations. The objective of this work was to identify the likeliness and extend of the PM10 limit value exceedences due to fugitive emissions in a particularly zone where PM fugitive emissions are a core of environmental concerns - Mitrena, Portugal. Mitrena, is an industrial area that coexists with a high-density urban region (Setúbal) and areas with an important environmental concern (Sado Estuary and Arrábida which belongs to the protected area Natura 2000 Network). Due to the typology of industry sited in Mitrena (e.g. power plant, paper mill, cement, pesticides and fertilized productions), there are a large uncontrolled PM fugitive emissions, providing from heavy traffic and handling and storage of raw material on uncover stockyards in the harbor and industries. Dispersion modeling was performed with the software TAPM (The Air Pollution Model) and results were mapped over the study area, using GIS (Geographic Information Systems). Results showed that managing local particles concentrations can be a frustrating affair because the weight of fugitive sources is very high comparing with the local anthropogenic stationary sources. In order to ensure that the industry can continue to meet its commitments in protecting air quality, it is essential to warrant that the characteristics of releases from all fugitive sources are fully understood in order to target future investments in those areas where maximum benefit will be achieved.

Coastal sources, sinks and strong organic complexation of dissolved cobalt within the US North Atlantic GEOTRACES transect GA03

NASA Astrophysics Data System (ADS)

Noble, Abigail E.; Ohnemus, Daniel C.; Hawco, Nicholas J.; Lam, Phoebe J.; Saito, Mak A.

2017-06-01

Cobalt is the scarcest of metallic micronutrients and displays a complex biogeochemical cycle. This study examines the distribution, chemical speciation, and biogeochemistry of dissolved cobalt during the US North Atlantic GEOTRACES transect expeditions (GA03/3_e), which took place in the fall of 2010 and 2011. Two major subsurface sources of cobalt to the North Atlantic were identified. The more prominent of the two was a large plume of cobalt emanating from the African coast off the eastern tropical North Atlantic coincident with the oxygen minimum zone (OMZ) likely due to reductive dissolution, biouptake and remineralization, and aeolian dust deposition. The occurrence of this plume in an OMZ with oxygen above suboxic levels implies a high threshold for persistence of dissolved cobalt plumes. The other major subsurface source came from Upper Labrador Seawater, which may carry high cobalt concentrations due to the interaction of this water mass with resuspended sediment at the western margin or from transport further upstream. Minor sources of cobalt came from dust, coastal surface waters and hydrothermal systems along the Mid-Atlantic Ridge. The full depth section of cobalt chemical speciation revealed near-complete complexation in surface waters, even within regions of high dust deposition. However, labile cobalt observed below the euphotic zone demonstrated that strong cobalt-binding ligands were not present in excess of the total cobalt concentration there, implying that mesopelagic labile cobalt was sourced from the remineralization of sinking organic matter. In the upper water column, correlations were observed between total cobalt and phosphate, and between labile cobalt and phosphate, demonstrating a strong biological influence on cobalt cycling. Along the western margin off the North American coast, this correlation with phosphate was no longer observed and instead a relationship between cobalt and salinity was observed, reflecting the importance of coastal input processes on cobalt distributions. In deep waters, both total and labile cobalt concentrations were lower than in intermediate depth waters, demonstrating that scavenging may remove labile cobalt from the water column. Total and labile cobalt distributions were also compared to a previously published South Atlantic GEOTRACES-compliant zonal transect (CoFeMUG, GAc01) to discern regional biogeochemical differences. Together, these Atlantic sectional studies highlight the dynamic ecological stoichiometry of total and labile cobalt. As increasing anthropogenic use and subsequent release of cobalt poses the potential to overpower natural cobalt signals in the oceans, it is more important than ever to establish a baseline understanding of cobalt distributions in the ocean.

Synthesis of Ti-Ta alloys with dual structure by incomplete diffusion between elemental powders.

PubMed

Liu, Yong; Li, Kaiyang; Wu, Hong; Song, Min; Wang, Wen; Li, Nianfeng; Tang, Huiping

2015-11-01

In this work, powder metallurgical (PM) Ti-Ta alloys were sintered using blended elemental powders. A dual structure, consisting of Ti-rich and Ta-rich zones, was formed due to the insufficient diffusion between Ti and Ta powders. The microstructure, mechanical properties and in vitro biological properties of the alloys were studied. Results indicated that the alloys have inhomogenous microstructures and compositions, but the grain structures were continuous from the Ti-rich zone to the Ta-rich zone. The Ta-rich zone exhibited a much finer grain size than the Ti-rich zone. The alloys had a high relative density in the range of 95-98%, with the porosity increasing with the content of Ta due to the increased difficulty in sintering and the formation of Kirkendall pores. The alloys had a good combination of low elastic modulus and high tensile strength. The strength of alloys was almost doubled compared to that of the ingot metallurgy alloys with the same compositions. The low elastic modulus was due to the residual pores and the alloying effect of Ta, while the high tensile strength resulted from the strengthening effects of solid solution, fine grain size and α phase. The alloys had a high biocompatibility due to the addition of Ta, and were suitable for the attachment of cells due to the surface porosity. It was also indicated that PM Ti-(20-30)Ta alloys are promising for biomedical applications after the evaluations of both the mechanical and the biological properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

Source and dynamics of a volcanic caldera unrest: Campi Flegrei, 1983-84.

PubMed

De Siena, Luca; Chiodini, Giovanni; Vilardo, Giuseppe; Del Pezzo, Edoardo; Castellano, Mario; Colombelli, Simona; Tisato, Nicola; Ventura, Guido

2017-08-14

Despite their importance for eruption forecasting the causes of seismic rupture processes during caldera unrest are still poorly reconstructed from seismic images. Seismic source locations and waveform attenuation analyses of earthquakes in the Campi Flegrei area (Southern Italy) during the 1983-1984 unrest have revealed a 4-4.5 km deep NW-SE striking aseismic zone of high attenuation offshore Pozzuoli. The lateral features and the principal axis of the attenuation anomaly correspond to the main source of ground uplift during the unrest. Seismic swarms correlate in space and time with fluid injections from a deep hot source, inferred to represent geochemical and temperature variations at Solfatara. These swarms struck a high-attenuation 3-4 km deep reservoir of supercritical fluids under Pozzuoli and migrated towards a shallower aseismic deformation source under Solfatara. The reservoir became aseismic for two months just after the main seismic swarm (April 1, 1984) due to a SE-to-NW directed input from the high-attenuation domain, possibly a dyke emplacement. The unrest ended after fluids migrated from Pozzuoli to the location of the last caldera eruption (Mt. Nuovo, 1538 AD). The results show that the high attenuation domain controls the largest monitored seismic, deformation, and geochemical unrest at the caldera.

Present Kinematic Regime and Recent Seismicity of Gulf Suez, Egypt

NASA Astrophysics Data System (ADS)

Mohamed, G.-E. A.; Abd El-Aal, A. K.

2018-01-01

In this study we computed recent seismicity and present kinematic regime in the northern and middle zones of Gulf of Suez as inferred from moment tensor settlings and focal mechanism of local earthquakes that happened in this region. On 18 and 22 of July, 2014 two moderate size earthquakes of local magnitudes 4.2 and 4.1 struck the northern zone of Gulf of Suez near Suez City. These events are instrumentally recorded by Egyptian National Seismic Network (ENSN). The earthquakes have been felt at Suez City and greater Cairo metropolitan zone while no losses were reported. The source mechanism and source parameters of the calculated events were considered by the near-source waveform data listed at very broadband stations of ENSN and supported by the P-wave polarity data of short period stations. The new settling method and software used deem the action of the source time function, which has been ignored in most of the program series of the moment tensor settling analysis with near source seismograms. The obtained results from settling technique indicate that the estimated seismic moments of both earthquakes are 0.6621E + 15 and 0.4447E + 15 Nm conforming to a moment magnitude Mw 3.8 and 3.7 respectively. The fault plan settlings obtained from both settling technique and polarity of first-arrival indicate the dominance of normal faulting. We also evaluated the stress field in north and middle zones of Gulf of Suez using a multiple inverse method. The prime strain axis shows that the deformation is taken up mainly as stretching in the E-W and NE-SW direction.

Probabilistic Seismic Hazard Assessment for Iraq Using Complete Earthquake Catalogue Files

NASA Astrophysics Data System (ADS)

Ameer, A. S.; Sharma, M. L.; Wason, H. R.; Alsinawi, S. A.

2005-05-01

Probabilistic seismic hazard analysis (PSHA) has been carried out for Iraq. The earthquake catalogue used in the present study covers an area between latitude 29° 38.5° N and longitude 39° 50° E containing more than a thousand events for the period 1905 2000. The entire Iraq region has been divided into thirteen seismogenic sources based on their seismic characteristics, geological setting and tectonic framework. The completeness of the seismicity catalogue has been checked using the method proposed by Stepp (1972). The analysis of completeness shows that the earthquake catalogue is not complete below Ms=4.8 for all of Iraq and seismic source zones S1, S4, S5, and S8, while it varies for the other seismic zones. A statistical treatment of completeness of the data file was carried out in each of the magnitude classes. The Frequency Magnitude Distributions (FMD) for the study area including all seismic source zones were established and the minimum magnitude of complete reporting (Mc) were then estimated. For the entire Iraq the Mc was estimated to be about Ms=4.0 while S11 shows the lowest Mc to be about Ms=3.5 and the highest Mc of about Ms=4.2 was observed for S4. The earthquake activity parameters (activity rate λ, b value, maximum regional magnitude mmax) as well as the mean return period (R) with a certain lower magnitude mmin ≥ m along with their probability of occurrence have been determined for all thirteen seismic source zones of Iraq. The maximum regional magnitude mmax was estimated as 7.87 ± 0.86 for entire Iraq. The return period for magnitude 6.0 is largest for source zone S3 which is estimated to be 705 years while the smallest value is estimated as 9.9 years for all of Iraq.

Quantitative evaluation of water quality in the coastal zone by remote sensing

NASA Technical Reports Server (NTRS)

James, W. P.

1971-01-01

Remote sensing as a tool in a waste management program is discussed. By monitoring both the pollution sources and the environmental quality, the interaction between the components of the exturaine system was observed. The need for in situ sampling is reduced with the development of improved calibrated, multichannel sensors. Remote sensing is used for: (1) pollution source determination, (2) mapping the influence zone of the waste source on water quality parameters, and (3) estimating the magnitude of the water quality parameters. Diffusion coefficients and circulation patterns can also be determined by remote sensing, along with subtle changes in vegetative patterns and density.

Permian arc-back-arc basin development along the Ailaoshan tectonic zone: Geochemical, isotopic and geochronological evidence from the Mojiang volcanic rocks, Southwest China

NASA Astrophysics Data System (ADS)

Fan, Weiming; Wang, Yuejun; Zhang, Aimei; Zhang, Feifei; Zhang, Yuzhi

2010-10-01

This paper presents a set of new SHRIMP zircon U-Pb geochronological, elemental and Sr-Nd-Pb isotopic data for the Wusu and Yaxuanqiao basaltic rocks (the Mojiang area) along the Ailaoshan tectonic zone. The Wusu basaltic sequence is dominated by SiO 2-poor, MgO- and TiO 2-rich basalts with a major mineral assemblage of plagioclase + clinopyroxene. These rocks gave a SHRIMP zircon U-Pb age of 287 ± 5 Ma (MSWD = 0.58). In contrast, the Yaxuanqiao basaltic sequence is predominantly composed of high-Al basaltic andesite, which gave a SHRIMP zircon U-Pb age of 265 ± 7 Ma (MSWD = 0.34). The analyzed samples for both sequences exhibit significant enrichment in LILEs and depletion in HFSEs with (Nb/La)n of 0.38-0.81, similar to arc-like volcanics. They have positive ɛNd(t) values (+ 3.52 to + 5.54). In comparison with MORB-derived magmatic rocks, the Wusu basalts are more enriched in LILEs and REEs, and the Yaxuanqiao samples are more enriched in LILEs but variably depleted in Ti, Y and HREE. The Wusu samples show high Pb isotopic ratios, similar to the Tethyan basalts, whereas the Yaxuanqiao samples plot in the field of the global pelagic sediments. The geochemical and Sr-Nd-Pb isotopic characteristics suggest that the Wusu basalts originated from a MORB-like source metasomatised by slab-derived fluids, while the Yaxuanqiao rocks have a fluid-modified MORB source with the input of subducted sediments. The geochemical affinity to both MORB- and arc-like sources, together with other geological observations, appears to support the development of a Permian arc-back-arc basin along the Ailaoshan-Song Ma tectonic zone in response to the northward subduction of the Paleotethys main Ocean. The final closure of the arc-back-arc basin took place in the uppermost Triassic due to the diachronous amalgamation between the Yangtze and Simao-Indochina Blocks.

Near-Road Exposure and Impact of Air Pollution on Allergic Diseases in Elementary School Children: A Cross-Sectional Study

PubMed Central

Kim, Ho Hyun; Lee, Chung Soo; Yu, Seung Do; Lee, Jung Sub; Chang, Jun Young; Jeon, Jun Min; Son, Hye Rim; Park, Chan Jung; Shin, Dong Chun

2016-01-01

Purpose The study aims to classify schools based on traffic pollutants and their complex sources, to assess the environment, to determine the state of allergic diseases among students using the International Study of Asthma and Allergies in children (ISAAC) questionnaire, and to assess their connection to air pollutants. Materials and Methods A total of seven schools were divided into three categories according to the characteristics of their surrounding environments: three schools in traffic-related zones, two schools in complex source zones I (urban), and two schools in complex source zones II (industrial complex). ISAAC questionnaires were administered and the 4404 completed questionnaires were analyzed. Results The frequency of asthma treatment during the past 12 months showed a significant increase (p<0.05) with exposure to NO2 [1.67, 95% confidence intervals (CIs) 1.03–2.71] in the complex source zones. The frequency of allergic rhinitis treatment during the past 12 months increased significantly with exposure to Black Carbon (1.60, 95% CIs 1.36–1.90) (p<0.001), SO2 (1.09, 95% CIs 1.01–1.17) (p<0.05), NO2 (1.18, 95% CIs 1.07–1.30) (p<0.01) for all subjects. Conclusion In terms of supporting children's health, care, and prevention related to major spaces for children, such as school zones, spaces used in coming to and leaving school, playgrounds, and classrooms are essential to ensuring not only the safety of children from traffic accidents but also their protection from local traffic pollutants and various hazardous environmental factors. PMID:26996571

In Situ Thermal Remediation of DNAPL Source Zones

DTIC Science & Technology

2011-12-01

electrode locations, the red Xs are injection and extraction .......... 20 Figure 3. 3. Photograph showing detail of the visualization tank...tank. The green circles are thermocouple locations, the blue squares are electrode locations, the red Xs are injection and extraction...through that zone. As water continues to move into that zone and outgas bubbles, the bubbles will move upward. In general terms, it has been

Seed origin and size of ponderosa pine planting stock grown at several California nurseries

Treesearch

Frank J. Baron; Gilbert H. Schubert

1963-01-01

Ponderosa pine planting stock (1-0 and 2-0) grown from five different seed collection zones in the California pine region differed noticeably in size. On the west side of the Sierra Nevada, seeds from zones above 4,000 feet yielded smaller seedlings than those from lower zones, but larger seedlings than those from east-side sources. Average dimensions (seedling weight...

Wildlife habitats in managed rangelands—the Great Basin of southeastern Oregon: riparian zones.

Treesearch

Jack Ward Thomas; Chris Maser; Jon E. Rodiek

1979-01-01

Riparian zones can be identified by the presence of vegetation that requires free or unbound water or conditions that are more moist than normal (fig. 1) (Franklin and Dyrness 1973, Minore and Smith 1971). Riparian zones can vary considerably in size and vegetative complex because of the many combinations that can be created between water sources (fig. 2) and physical...

Unintentional contaminant transfer from groundwater to the vadose zone during source zone remediation of volatile organic compounds.

PubMed

Chong, Andrea D; Mayer, K Ulrich

2017-09-01

Historical heavy use of chlorinated solvents in conjunction with improper disposal practices and accidental releases has resulted in widespread contamination of soils and groundwater in North America and worldwide. As a result, remediation of chlorinated solvents is required at many sites. For source zone treatment, common remediation strategies include in-situ chemical oxidation (ISCO) using potassium or sodium permanganate, and the enhancement of biodegradation by primary substrate addition. It is well known that these remediation methods tend to generate gas (carbon dioxide (CO 2 ) in the case of ISCO using permanganate, CO 2 and methane (CH 4 ) in the case of bioremediation). Vigorous gas generation in the presence of chlorinated solvents, which are categorized as volatile organic contaminants (VOCs), may cause gas exsolution, ebullition and stripping of the contaminants from the treatment zone. This process may lead to unintentional 'compartment transfer', whereby VOCs are transported away from the contaminated zone into overlying clean sediments and into the vadose zone. To this extent, benchtop column experiments were conducted to quantify the effect of gas generation during remediation of the common chlorinated solvent trichloroethylene (TCE/C 2 Cl 3 H). Both ISCO and enhanced bioremediation were considered as treatment methods. Results show that gas exsolution and ebullition occurs for both remediation technologies. Facilitated by ebullition, TCE was transported from the source zone into overlying clean groundwater and was subsequently released into the column headspace. For the case of enhanced bioremediation, the intermediate degradation product vinyl chloride (VC) was also stripped from the treatment zone. The concentrations measured in the headspace of the columns (TCE ∼300ppm in the ISCO column, TCE ∼500ppm and VC ∼1380ppm in the bioremediation column) indicate that substantial transfer of VOCs to the vadose zone is possible. These findings provide direct evidence for the unintended spreading of contaminants as a result of remediation efforts, which can, under some circumstances, result in enhanced risks for soil vapour intrusion. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhanced Amendment Delivery to Subsurface Using Shear Thinning Fluid and Aqueous Foam for Metal, Radionuclide, and NAPL Remediation

NASA Astrophysics Data System (ADS)

Zhong, L.; Szecsody, J.; Li, X.; Oostrom, M.; Truex, M.

2010-12-01

In many contamination sites, removal of contaminants by any active remediation efforts is not practical due to the high cost and technological limitations. Alternatively, in situ remediation is expected to be the most important remediation strategy. Delivery of reactive amendment to the contamination zone is essential for the reactions between the contaminants and remedial amendments to proceed in situ. It is a challenge to effectively deliver remedial amendment to the subsurface contamination source areas in both aquifer and vadose zone. In aquifer, heterogeneity induces fluid bypassing the low-permeability zones, resulting in certain contaminated areas inaccessible to the remedial amendment delivered by water injection, thus inhibiting the success of remedial operations. In vadose zone in situ remediation, conventional solution injection and infiltration for amendment delivery have difficulties to achieve successful lateral spreading and uniform distribution of the reactive media. These approaches also tend to displace highly mobile metal and radionuclide contaminants such as hexavalent chromium [Cr(VI)] and technetium (Tc-99), causing spreading of contaminations. Shear thinning fluid and aqueous foam can be applied to enhance the amendment delivery and improve in situ subsurface remediation efficiency under aquifer and vadose zone conditions, respectively. Column and 2-D flow cell experiments were conducted to demonstrate the enhanced delivery and improved remediation achieved by the application of shear thinning fluid and foam injection at the laboratory scale. Solutions of biopolymer xanthan gum were used as the shear thinning delivering fluids. Surfactant sodium lauryl ether sulfate (STEOL CS-330) was the foaming agent. The shear thinning fluid delivery (STFD) considerably improved the sweeping efficiency over a heterogeneous system and enhanced the non-aqueous liquid phase (NAPL) removal. The delivery of amendment into low-perm zones (LPZs) by STFD also increased the persistence of amendment solution in the LPZs after injection. Immobilization of Tc-99 was improved when a reductant was delivered by foam versus by water-based solution to contaminated vadose zone sediments. Foam delivery remarkably improved the lateral distribution of fluids compared to direct liquid injection. In heterogeneous vadose zone formation, foam injection increased the liquid flow in the high permeable zones into which very limited fluid was distributed during liquid infiltration, demonstrating improved amendment distribution uniformity in the heterogeneous system by foam delivery.

Antibacterial Properties of Endophytic Bacteria Isolated from a Fern Species Equisetum arvense L. Against Foodborne Pathogenic Bacteria Staphylococcus aureus and Escherichia coli O157:H7.

PubMed

Das, Gitishree; Patra, Jayanta Kumar; Baek, Kwang-Hyun

2017-01-01

Endophytic bacteria (EB) are a rich source of secondary metabolites with medicinal importance. In this study, EB were isolated from the bottle brush herb Equisetum arvense and identified based on 16S rRNA sequencing. Evaluation of its antibacterial potential was conducted using two common foodborne pathogenic bacteria, Staphylococcus aureus ATCC 12600 and Escherichia coli O157:H7 ATCC 43890. Out of 103 identified EB, three species, Streptomyces albolongus, Dermacoccus sp., and Mycobacterium sp., showed significant antibacterial activity against S. aureus with inhibition zones of 45.34 ± 0.15, 43.28 ± 0.19, and 22.98 ± 0.18 mm, respectively, whereas only two species, Streptomyces griseoaurantiacus (EAL196) and Paenibacillus sp. (EAS116), showed moderate antibacterial activity against E. coli O157:H7 with inhibition zones of 9.41 ± 0.29 and 10.44 ± 0.31 mm, respectively. Furthermore, ethyl acetate extract of S. albolongus, Mycobacterium sp., and Dermacoccus sp. showed antibacterial activity against S. aureus, with inhibition zones of 23.43 ± 0.21, 21.18 ± 0.22, and 19.72 ± 0.10 mm, respectively. The methanol extract of Dermacoccus sp. and Paenibacillus sp. showed antibacterial activity against S. aureus and E. coli O157:H7, with inhibition zones of 11.30 ± 0.17 and 10.01 ± 0.21 mm, respectively. Scanning electron microscopy indicated swollen and lysed cell membranes of pathogens treated with ethyl acetate extract. A possible reason might be, likely due to EB metabolites penetrating the bacterial cell membranes and affecting various metabolic functions resulting in lysis. To the best of our knowledge, this is the first study to report that EB from E. arvense can be used as a source of natural antibacterial compounds against foodborne pathogenic bacteria.

The carbonaceous phyllite rock-hosted Pedra Verde copper mine, Borborema Province, Brazil: Stable isotope constraints, structural controls and metallogenic evolution

NASA Astrophysics Data System (ADS)

da Silva Nogueira de Matos, José Henrique; Saraiva dos Santos, Ticiano José; Virgínia Soares Monteiro, Lena

2017-12-01

The Pedra Verde Copper Mine is located in the Viçosa do Ceará municipality, State of Ceará, NE Brazil. The copper mineralization is hosted by the Pedra Verde Phyllite, which is a carbonaceous chlorite-calcite phyllite with subordinate biotite. It belongs to the Neoproterozoic Martinópole Group of the Médio Coreaú Domain, Borborema Province. The Pedra Verde deposit is stratabound and its ore zoning is conspicuous, according to the following sequence, from bottom to top: marcasite/pyrite, native silver, chalcopyrite, bornite, chalcocite, native copper and hematite. Barite and carbonaceous material are reported in ore zones. Zoning reflects the ore formation within a redox boundary developed due to the interaction between oxidized copper- and sulfate-bearing fluids and the reduced phyllite. Structural control on mineralization is evidenced by the association of the ore minerals with veins, hinge folds, shadow pressures, and mylonitic foliation. It was mainly exercised by a dextral transcurrent shear zone developed during the third deformational stage identified in the Médio Coreaú Domain between 590 Ma and 570 Ma. This points to the importance of epigenetic, post-metamorphic deformational events for ore formation. Oxygen isotopic composition (δ18OH2O = 8.94 to 11.28‰, at 250 to 300 °C) estimated for the hydrothermal fluids in equilibrium with calcite indicates metamorphic or evolved meteoric isotopic signatures. The δ13CPDB values (-2.60 to -9.25‰) obtained for hydrothermal calcite indicate mixing of carbon sources derived from marine carbonate rocks and carbonaceous material. The δ34SCDT values (14.88 to 36.91‰) of sulfides suggest evaporites as sulfate sources or a closed system in relation to SO42- availability to form H2S. Carbonaceous matter had a key role in thermochemical sulfate processes and sulfide precipitation. The Pedra Verde Copper Mine is considered the first stratabound meta-sedimentary rock-hosted copper deposit described in Brazil and shares similarities with the syn-orogenic copper deposits of the Congo-Zambian Copperbelt formed during the Gondwana amalgamation.

Geodetic evidence for en echelon dike emplacement and concurrent slow slip during the June 2007 intrusion and eruption at Kīlauea volcano, Hawaii

USGS Publications Warehouse

Montgomery-Brown, E. K.; Sinnett, D.K.; Poland, M.; Segall, P.; Orr, T.; Zebker, H.; Miklius, Asta

2010-01-01

A series of complex events at Kīlauea Volcano, Hawaii, 17 June to 19 June 2007, began with an intrusion in the upper east rift zone (ERZ) and culminated with a small eruption (1500 m3). Surface deformation due to the intrusion was recorded in unprecedented detail by Global Positioning System (GPS) and tilt networks as well as interferometric synthetic aperture radar (InSAR) data acquired by the ENVISAT and ALOS satellites. A joint nonlinear inversion of GPS, tilt, and InSAR data yields a deflationary source beneath the summit caldera and an ENE-striking uniform-opening dislocation with ~2 m opening, a dip of ∼80° to the south, and extending from the surface to ~2 km depth. This simple model reasonably fits the overall pattern of deformation but significantly misfits data near the western end of an inferred dike-like source. Three more complex dike models are tested that allow for distributed opening including (1) a dike that follows the surface trace of the active rift zone, (2) a dike that follows the symmetry axis of InSAR deformation, and (3) two en echelon dike segments beneath mapped surface cracks and newly formed steaming areas. The en echelon dike model best fits near-field GPS and tilt data. Maximum opening of 2.4 m occurred on the eastern segment beneath the eruptive vent. Although this model represents the best fit to the ERZ data, it still fails to explain data from a coastal tiltmeter and GPS sites on Kīlauea's southwestern flank. The southwest flank GPS sites and the coastal tiltmeter exhibit deformation consistent with observations of previous slow slip events beneath Kīlauea's south flank, but inconsistent with observations of previous intrusions. Slow slip events at Kīlauea and elsewhere are thought to occur in a transition zone between locked and stably sliding zones of a fault. An inversion including slip on a basal decollement improves fit to these data and suggests a maximum of ~15 cm of seaward fault motion, comparable to previous slow-slip events.

Mass Balance of Multiyear Sea Ice in the Southern Beaufort Sea

DTIC Science & Technology

2012-09-30

datasets. Table 1 lists the primary data sources to be used. To determine sources and sinks of MY ice, we use a simple model of MY ice circulation, which is...shown in Figure 1. In this model , we consider the Beaufort Sea to consist of four zones defined by mean drift of sea ice in summer and winter, such...Healy/Louis S. St. Laurant cruises 1 Seasonal Ice Zone Observing Network 2 Polar Airborne Measurements and Arctic Regional Climate Model

Effect of medium electrophysical parameters and their temperature dependences on wideband electromagnetic pulse propagation

NASA Astrophysics Data System (ADS)

Volkomirskaya, L. B.; Gulevich, O. A.; Reznikov, A. E.

2017-03-01

The dielectric permittivity of fiery spoil tips (Shakhty town, Rostov Region) is studied with the use of a GROT 12E remote-controlled ground-penetrating radar (GPR). An anomalous zone in a combustion source is shown to be clearly pronounced in GPR data due to the temperature dependence of the dielectric permittivity of these spoil tips. To substantiate this statement, the GPR data are compared with direct measurements of soil temperatures at depths from 1.5 to 2.5 m. The experimental results are compared with the variable spectral range of a GPR sounding pulse. GPR is shown to be a promising tool for the mapping of temperature-contrast underground objects.

Time dependent deformation and stress in the lithosphere. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Yang, M.

1980-01-01

Efficient computer programs incorporating frontal solution and time stepping procedure were developed for the modelling of geodynamic problems. This scheme allows for investigating the quasi static phenomena including the effects of the rheological structure of a tectonically active region. From three dimensional models of strike slip earthquakes, it was found that lateral variation of viscosity affects the characteristics of surface deformations. The vertical deformation is especially informative about the viscosity structure in a strike slip fault zone. A three dimensional viscoelastic model of a thrust earthquake indicated that the transient disturbance on plate velocity due to a great plate boundary earthquake is significant at intermediate distances, but becomes barely measurable 1000 km away from the source.

Ultraviolet spectrometer experiment for the Voyager mission

NASA Technical Reports Server (NTRS)

Broadfoot, A. L.; Sandel, B. R.; Shemansky, D. E.; Atreya, S. K.; Donahue, T. M.; Moos, H. W.; Bertaux, J. L.; Blamont, J. E.; Ajello, J. M.; Strobel, D. F.

1977-01-01

An objective grating spectrometer covering the wavelength range of 500 to 1700 A with a 10-A resolution is employed for the Voyager ultraviolet spectrometer experiment. In determining the composition and structure of the atmospheres of Saturn, Jupiter and several satellites, the ultraviolet spectrometer will rely on airglow mode observations to measure radiation from the atmospheres due to resonant scattering of solar flux, and the occultation mode for assessments of the atmospheric extinction of solar or stellar radiation as the spacecraft enters shadow zones. Since it is capable of prolonged stellar observations in the 500 to 1000 A wavelength range, the spectrometer is expected to make important contributions to exploratory studies of UV sources.

Pollution of the sediments of the coastal zone of the Sambia Peninsula and the Curonian Spit (Southeastern Baltic Sea).

PubMed

Krek, Alexander; Krechik, Viktor; Danchenkov, Aleksandr; Krek, Elena

2018-01-01

The detailed environmental survey of the coastal zone of the Kaliningrad Region northern coast was carried out. The pollutants distribution in the silty clay fraction and calculation of ecological indexes allowed the evaluation of distribution of potentially harmful elements (PHEs). The sources of pollution in the most intensively used areas were identified, and transit and accumulation zones were allocated. A large area of anomalous content of PHEs was revealed on the underwater coastal slope of the Curonian Spit National Park, which is situated far from the sources of pollution. The alongshore bed load transport provides the contamination of the underwater slope whereas the beaches are less exposed to pollution.

Widespread natural perchlorate in unsaturated zones of the southwest United States

USGS Publications Warehouse

Rao, Balaji; Anderson, Todd A.; Orris, Greta J.; Rainwater, Ken A.; Rajagopalan, Srinath; Sandvig, Renee M.; Scanlon, Bridget R.; Stonestrom, David A.; Walvoord, Michelle Ann; Jackson, W Andrew

2007-01-01

A substantial reservoir (up to 1 kg ha-1) of natural perchlorate is present in diverse unsaturated zones of the arid and semi-arid southwestern United States. The perchlorate co-occurs with meteoric chloride that has accumulated in these soils throughout the Holocene [0 to 10−15 ka (thousand years ago)] and possibly longer periods. Previously, natural perchlorate widely believed to be limited to the Atacama Desert, now appears widespread in steppe-to-desert ecoregions. The perchlorate reservoir becomes sufficiently large to affect groundwater when recharge from irrigation or climate change flushes accumulated salts from the unsaturated zone. This new source may help explain increasing reports of perchlorate in dry region agricultural products and should be considered when evaluating overall source contributions.

Mapping of thermal injury in biologic tissues using quantitative pathologic techniques

NASA Astrophysics Data System (ADS)

Thomsen, Sharon L.

1999-05-01

Qualitative and quantitative pathologic techniques can be used for (1) mapping of thermal injury, (2) comparisons lesion sizes and configurations for different instruments or heating sources and (3) comparisons of treatment effects. Concentric zones of thermal damage form around a single volume heat source. The boundaries between some of these zones are distinct and measurable. Depending on the energy deposition, heating times and tissue type, the zones can include the following beginning at the hotter center and progressing to the cooler periphery: (1) tissue ablation, (2) carbonization, (3) tissue water vaporization, (4) structural protein denaturation (thermal coagulation), (5) vital enzyme protein denaturation, (6) cell membrane disruption, (7) hemorrhage, hemostasis and hyperhemia, (8) tissue necrosis and (9) wound organization and healing.

User's Guide and Download for IECCU- Indoor Environmental Concentrations in Buildings with Conditioned and Unconditioned Zones

EPA Pesticide Factsheets

This program serves two purposes: (1) as a general-purpose indoor exposure model in buildings with multiple zones, multiple chemicals and multiple sources and sinks, and (2) as a special-purpose concentration model

Spatial stress variations in the aftershock sequence following the 2008 M6 earthquake doublet in the South Iceland Seismic Zone

NASA Astrophysics Data System (ADS)

Hensch, M.; Árnadóttir, Th.; Lund, B.; Brandsdóttir, B.

2012-04-01

The South Iceland Seismic Zone (SISZ) is an approximately 80 km wide E-W transform zone, bridging the offset between the Eastern Volcanic Zone and the Hengill triple junction to the west. The plate motion is accommodated in the brittle crust by faulting on many N-S trending right-lateral strike-slip faults of 2-5 km separation. Major sequences of large earthquakes (M>6) has occurred repeatedly in the SISZ since the settlement in Iceland more than thousand years ago. On 29th May 2008, two M6 earthquakes hit the western part of the SISZ on two adjacent N-S faults within a few seconds. The intense aftershock sequence was recorded by the permanent Icelandic SIL network and a promptly installed temporary network of 11 portable seismometers in the source region. The network located thousands of aftershocks during the following days, illuminating a 12-17 km long region along both major fault ruptures as well as several smaller parallel faults along a diffuse E-W trending region west of the mainshock area without any preceding main rupture. This episode is suggested to be the continuation of an earthquake sequence which started with two M6.5 and several M5-6 events in June 2000. The time delay between the 2000 and 2008 events could be due to an inflation episode in Hengill during 1993-1998, that potentially locked N-S strike slip faults in the western part of the SISZ. Around 300 focal solutions for aftershocks have been derived by analyzing P-wave polarities, showing predominantly strike-slip movements with occasional normal faulting components (unstable P-axis direction), which suggests an extensional stress regime as their driving force. A subsequent stress inversion of four different aftershock clusters reveals slight variations of the directions of the average σ3 axes. While for both southern clusters, including the E-W cluster, the σ3 axes are rather elongated perpendicular to the overall plate spreading axis, they are more northerly trending for shallower clusters located further north. In this study we will try to shed light into whether the azimuth variations of σ3 is caused by stress changes due to the inflation-deflation episode in Hengill (NW of the activated fault zone) or solely depending to the depth of the aftershock clusters.

Distribution of Minor Elements in Calcite From the Unsaturated Zone at Yucca Mountain, Nevada

NASA Astrophysics Data System (ADS)

Marshall, B. D.; Whelan, J. F.

2001-12-01

Calcite is sporadically distributed in fractures and cavities in the volcanic rocks that form the 500- to 700-m-thick unsaturated zone at Yucca Mountain. Previous work has shown that the calcite precipitated from water moving downward through the unsaturated zone since the volcanic rocks were emplaced approximately 13 Ma. Calcite thus serves as a proxy for the chemistry and amounts of past percolation, two parameters that are important in predictions of the future behavior of the potential radioactive waste repository at Yucca Mountain. Latest calcite, which began forming between approximately 5 and 2 Ma, typically displays fine-scale growth zoning defined by distributions of Mn (inferred from cathodoluminescence), Mg, and Sr. Electron microprobe (EPMA) mapping of outermost calcite reveals Mg growth zoning1 and higher overall concentrations of Mg in late calcite than in older calcite. Micro X-ray fluorescence (micro-XRF) maps were obtained by slow rastering of the samples over a 100-watt X-ray source collimated through a final aperture of 100 μ m. Although the spatial resolution of the micro-XRF mapping is much less than that of EPMA, this technique reveals distributions of some elements to which EPMA is less sensitive. Micro-XRF maps show that Sr is spatially correlated with Mg; Sr concentrations range to 500 μ g/g at the resolution of the 100-μ m collimator. Because both Mg and Sr have similar calcite-water distribution coefficients much less than one, the Mg/Sr in calcite reflects the Mg/Sr of the water that precipitated the calcite. The distribution coefficient for Mn is greater than one and variations in Mn are not correlated with Mg and Sr. Covariation of Mg and Sr in the percolating water may be explained by reactions that affect the rate of uptake of chemical constituents from the overlying rock and soil, and/or evaporation. Late calcite has lower δ 13C values, probably due to a regional change from wetter to drier climate conditions. The higher Mg and Sr concentrations in the late calcite may record lower deposition rates and decreased percolation fluxes due to the drier climate. 1 Wilson, N.S.F., Cline, J.S., and Lundberg, S.A.W., 2000, Paragenesis and chemical composition of secondary mineralization at Yucca Mountain, Nevada, Geol. Soc. Am. Abs. Prog., v. 32, p. A260.

Groundwater-surface water interaction in the riparian zone of an incised channel, Walnut Creek, Iowa

USGS Publications Warehouse

Schilling, K.E.; Li, Z.; Zhang, Y.-K.

2006-01-01

Riparian zones of many incised channels in agricultural regions are cropped to the channel edge leaving them unvegetated for large portions of the year. In this study we evaluated surface and groundwater interaction in the riparian zone of an incised stream during a spring high flow period using detailed stream stage and hydraulic head data from six wells, and water quality sampling to determine whether the riparian zone can be a source of nitrate pollution to streams. Study results indicated that bank storage of stream water from Walnut Creek during a large storm water runoff event was limited to a narrow 1.6 m zone immediately adjacent to the channel. Nitrate concentrations in riparian groundwater were highest near the incised stream where the unsaturated zone was thickest. Nitrate and dissolved oxygen concentrations and nitrate-chloride ratios increased during a spring recharge period then decreased in the latter portion of the study. We used MODFLOW and MT3DMS to evaluate dilution and denitrification processes that would contribute to decreasing nitrate concentrations in riparian groundwater over time. MT3DMS model simulations were improved with a denitrification rate of 0.02 1/d assigned to the floodplain sediments implying that denitrification plays an important role in reducing nitrate concentrations in groundwater. We conclude that riparian zones of incised channels can potentially be a source of nitrate to streams during spring recharge periods when the near-stream riparian zone is largely unvegetated. ?? 2005 Elsevier B.V. All rights reserved.