Variation in surface water-groundwater exchange with land use in an urban stream

NASA Astrophysics Data System (ADS)

Ryan, Robert J.; Welty, Claire; Larson, Philip C.

2010-10-01

SummaryA suite of methods is being utilized in the Baltimore metropolitan area to develop an understanding of the interaction between groundwater and surface water at multiple space and time scales. As part of this effort, bromide tracer experiments were conducted over two 10-day periods in August 2007 and May 2008 along two sections (each approximately 900 m long) of Dead Run, a small urban stream located in Baltimore County, Maryland, to investigate the influence of distinct zones of riparian land cover on surface-subsurface exchange and transient storage under low and high baseflow conditions. Riparian land cover varied by reach along a gradient of land use spanning parkland, suburban/residential, commercial, institutional, and transportation, and included wooded, meadow, turf grass, and impervious cover. Under summer low baseflow conditions, surface water-groundwater exchange, defined by gross inflow and gross outflow, was larger and net inflow (gross inflow minus gross outflow) had greater spatial variability, than was observed under spring high baseflow conditions. In addition, the fraction of nominal travel time attributable to transient storage ( Fmed) was lower and was more spatially variable under high baseflow conditions than under low baseflow conditions. The influence of baseflow condition on surface water-ground water exchange and transient storage was most evident in the subreaches with the least riparian forest cover and these effects are attributed to a lack of shading in reaches with little riparian forest cover. We suggest that under summer low baseflow conditions, the lack of shading allowed excess in-channel vegetation growth which acted as a transient storage zone and a conduit for outflow (i.e. uptake and evapotranspiration). Under spring high baseflow conditions the transient storage capacity of the channel was reduced because there was little in-channel vegetation.

Changes in streambed sediment characteristics and solute transport in the headwaters of Valley Creek, an urbanizing watershed

NASA Astrophysics Data System (ADS)

Ryan, Robert J.; Packman, Aaron I.

2006-05-01

Changes in streambed sediments were monitored in conjunction with Q series of conservative solute tracer injections over a 2-year period to assess the effects of urbanization on two streams in the Valley Creek watershed, located in Chester County, Pennsylvania approximately 30 km west of Philadelphia. The modeling package OTIS was used to analyze the solute transport behavior. Comparison of the results from the two streams demonstrates that the fine sediment fraction of the streambed controls hydraulic conductivity and transient storage exchange in this gravel- and cobble-bed Piedmont system. One site had a narrow (10-40 m) riparian corridor of mowed lawn and woody brush. At this site, the silt-clay fraction ( d<50 μm) of the fine sediment ( d<2 mm) increased from 6 to 25% during the course of the study. The relationship between sediment characteristics and transient storage exchange was evaluated using the method of Wörman et al. [Wörman, A., Packman, A.I., Johansson, H., Jonsson, K., 2002a. Effect of flow-induced exchange in hyporheic zones on longitudinal transport of solutes in streams and rivers. Water Resources Research 38. doi: 10.1029/2001WR000769], who showed that the hyporheic residence time, scaled by the hydraulic conductivity and stream depth, is a function of stream velocity and physical channel characteristics. This analysis indicated that the observed change in fine sediment composition caused a two-fold reduction in the hydraulic conductivity, a four-fold reduction in the transient storage area, and an order of magnitude reduction in the exchange coefficient. The second study site had a wide (100-300 m) riparian corridor of deciduous forest. During the study period, a parcel of woodland encompassing 11% of the drainage area was cleared and nine homes were constructed on the site. Despite this prominent development of the watershed, there was no significant change in sediment characteristics or solute transport during the study period. The model-derived transient storage exchange parameters in our urbanizing study sites were found to be statistically similar to the values for forested mountain streams given in the literature. Thus, the relationship between urbanization and transient storage should be determined by examining the temporal change in the characteristics of individual stream reaches rather than by comparing the solute transport parameters obtained in different types of streams.

Importance of unsaturated zone flow for simulating recharge in a humid climate

USGS Publications Warehouse

Hunt, R.J.; Prudic, David E.; Walker, J.F.; Anderson, M.P.

2008-01-01

Transient recharge to the water table is often not well understood or quantified. Two approaches for simulating transient recharge in a ground water flow model were investigated using the Trout Lake watershed in north-central Wisconsin: (1) a traditional approach of adding recharge directly to the water table and (2) routing the same volume of water through an unsaturated zone column to the water table. Areas with thin (less than 1 m) unsaturated zones showed little difference in timing of recharge between the two approaches; when water was routed through the unsaturated zone, however, less recharge was delivered to the water table and more discharge occurred to the surface because recharge direction and magnitude changed when the water table rose to the land surface. Areas with a thick (15 to 26 m) unsaturated zone were characterized by multimonth lags between infiltration and recharge, and, in some cases, wetting fronts from precipitation events during the fall overtook and mixed with infiltration from the previous spring snowmelt. Thus, in thicker unsaturated zones, the volume of water infiltrated was properly simulated using the traditional approach, but the timing was different from simulations that included unsaturated zone flow. Routing of rejected recharge and ground water discharge at land surface to surface water features also provided a better simulation of the observed flow regime in a stream at the basin outlet. These results demonstrate that consideration of flow through the unsaturated zone may be important when simulating transient ground water flow in humid climates with shallow water tables.

Retention and transport of nutrients in a third-order stream in northwestern California; hyporheic processes

USGS Publications Warehouse

Triska, F.J.; Kennedy, V.C.; Avanzino, R.J.; Zellweger, G.W.; Bencala, K.E.

1989-01-01

Chloride and nitrate were coinjected into the surface waters of a third-order stream for 20 d to exmaine solute retention, and the fate of nitrate during subsurface transport. A series of wells (shallow pits) 0.5-10 m from the adjacent channel were sampled to estimate the lateral interflow of water. Two subsurface return flows beneath the wetted channel were also examined. Results indicated that the capacity of the hyporheic zone for transient solute storage and as potential biological habitat varies with channel morphology, bed roughness, and permeability. A conceptual model that considers the groundwater-stream water interface as the fluvial boundary is proposed. -from Authors

Coupled Spatio-Temporal Patterns of Solute Transport, Metabolism and Nutrient Uptake in Streams

NASA Astrophysics Data System (ADS)

Kurz, M. J.; Schmidt, C.

2017-12-01

Slower flow velocities and longer residence times within stream transient storage (TS) zones facilitate interaction between solutes and microbial communities, potentially increasing local rates of metabolic activity. Multiple factors, including channel morphology and substrate, variable hydrology, and seasonal changes in biological and physical parameters, result in changes in the solute transport dynamics and reactivity of TS zones over time and space. These changes would be expected to, in turn, influence rates of whole-stream ecosystem functions such as metabolism and nutrient uptake. However, the linkages between solute transport and ecosystem functioning within TS zones, and the contribution of TS zones to whole-stream functioning, are not always so straight forward. This may be due, in part, to methodological challenges. In this study we investigated the influence of stream channel hydro-morphology and substrate type on reach (103 m) and sub-reach (102 m) scale TS and ecosystem functioning. Patterns in solute transport, metabolism and nitrate uptake were tracked from April through October in two contrasting upland streams using several methods. The two streams, located in the Harz Mountains, Germany, are characterized by differing size (0.02 vs. 0.3 m3/s), dominant stream channel substrate (bedrock vs. alluvium) and sub-reach morphology (predominance of pools, riffles and glides). Solute transport parameters and respiration rates at the reach and sub-reach scale were estimated monthly from coupled pulse injections of the reactive tracer resazurin (Raz) and conservative tracers uranine and salt. Raz, a weakly fluorescent dye, irreversibly transforms to resorufin (Rru) under mildly reducing conditions, providing a proxy for aerobic respiration. Daily rates of primary productivity, respiration and nitrate retention at the reach scale were estimated using the diel cycles in dissolved oxygen and nitrate concentrations measured by in-situ sensors. Preliminary results indicate distinct differences in common metrics of TS and Raz transformation rates within and between the two streams. However, transformation rates and TS metrics are not well correlated, indicating complexities in the relationship between solute transport dynamics and metabolism in streams.

Quantifying hyporheic exchange at high spatial resolution using natural temperature variations along a first-order stream

NASA Astrophysics Data System (ADS)

Westhoff, M. C.; Gooseff, M. N.; Bogaard, T. A.; Savenije, H. H. G.

2011-10-01

Hyporheic exchange is an important process that underpins stream ecosystem function, and there have been numerous ways to characterize and quantify exchange flow rates and hyporheic zone size. The most common approach, using conservative stream tracer experiments and 1-D solute transport modeling, results in oversimplified representations of the system. Here we present a new approach to quantify hyporheic exchange and the size of the hyporheic zone (HZ) using high-resolution temperature measurements and a coupled 1-D transient storage and energy balance model to simulate in-stream water temperatures. Distributed temperature sensing was used to observe in-stream water temperatures with a spatial and temporal resolution of 2 and 3 min, respectively. The hyporheic exchange coefficient (which describes the rate of exchange) and the volume of the HZ were determined to range between 0 and 2.7 × 10-3 s-1 and 0 and 0.032 m3 m-1, respectively, at a spatial resolution of 1-10 m, by simulating a time series of in-stream water temperatures along a 565 m long stretch of a small first-order stream in central Luxembourg. As opposed to conventional stream tracer tests, two advantages of this approach are that exchange parameters can be determined for any stream segment over which data have been collected and that the depth of the HZ can be estimated as well. Although the presented method was tested on a small stream, it has potential for any stream where rapid (in regard to time) temperature change of a few degrees can be obtained.

Ground water stratification and delivery of nitrate to an incised stream under varying flow conditions.

PubMed

Böhlke, J K; O'Connell, Michael E; Prestegaard, Karen L

2007-01-01

Ground water processes affecting seasonal variations of surface water nitrate concentrations were investigated in an incised first-order stream in an agricultural watershed with a riparian forest in the coastal plain of Maryland. Aquifer characteristics including sediment stratigraphy, geochemistry, and hydraulic properties were examined in combination with chemical and isotopic analyses of ground water, macropore discharge, and stream water. The ground water flow system exhibits vertical stratification of hydraulic properties and redox conditions, with sub-horizontal boundaries that extend beneath the field and adjacent riparian forest. Below the minimum water table position, ground water age gradients indicate low recharge rates (2-5 cm yr(-1)) and long residence times (years to decades), whereas the transient ground water wedge between the maximum and minimum water table positions has a relatively short residence time (months to years), partly because of an upward increase in hydraulic conductivity. Oxygen reduction and denitrification in recharging ground waters are coupled with pyrite oxidation near the minimum water table elevation in a mottled weathering zone in Tertiary marine glauconitic sediments. The incised stream had high nitrate concentrations during high flow conditions when much of the ground water was transmitted rapidly across the riparian zone in a shallow oxic aquifer wedge with abundant outflow macropores, and low nitrate concentrations during low flow conditions when the oxic wedge was smaller and stream discharge was dominated by upwelling from the deeper denitrified parts of the aquifer. Results from this and similar studies illustrate the importance of near-stream geomorphology and subsurface geology as controls of riparian zone function and delivery of nitrate to streams in agricultural watersheds.

Ground water stratification and delivery of nitrate to an incised stream under varying flow conditions

USGS Publications Warehouse

Böhlke, J.K.; O'Connell, M. E.; Prestegaard, K.L.

2007-01-01

Ground water processes affecting seasonal variations of surface water nitrate concentrations were investigated in an incised first-order stream in an agricultural watershed with a riparian forest in the coastal plain of Maryland. Aquifer characteristics including sediment stratigraphy, geochemistry, and hydraulic properties were examined in combination with chemical and isotopic analyses of ground water, macropore discharge, and stream water. The ground water flow system exhibits vertical stratification of hydraulic properties and redox conditions, with sub-horizontal boundaries that extend beneath the field and adjacent riparian forest. Below the minimum water table position, ground water age gradients indicate low recharge rates (2-5 cm yr-1) and long residence times (years to decades), whereas the transient ground water wedge between the maximum and minimum water table positions has a relatively short residence time (months to years), partly because of an upward increase in hydraulic conductivity. Oxygen reduction and denitrification in recharging ground waters are coupled with pyrite oxidation near the minimum water table elevation in a mottled weathering zone in Tertiary marine glauconitic sediments. The incised stream had high nitrate concentrations during high flow conditions when much of the ground water was transmitted rapidly across the riparian zone in a shallow oxic aquifer wedge with abundant outflow macropores, and low nitrate concentrations during low flow conditions when the oxic wedge was smaller and stream discharge was dominated by upwelling from the deeper denitrified parts of the aquifer. Results from this and similar studies illustrate the importance of near-stream geomorphology and subsurface geology as controls of riparian zone function and delivery of nitrate to streams in agricultural watersheds. ?? ASA, CSSA, SSSA.

One-dimensional flow model of the river-hyporheic zone system

NASA Astrophysics Data System (ADS)

Pokrajac, D.

2016-12-01

The hyporheic zone is a shallow layer beneath natural streams that is characterized by intense exchange of water, nutrients, pollutants and thermal energy. Understanding these exchange processes is crucial for successful modelling of the river hydrodynamics and morphodynamics at various scales from the river corridor up to the river network scale (Cardenas, 2015). Existing simulation models of hyporheic exchange processes are either idealized models of the tracer movement through the river-hyporheic zone system (e.g. TSM, Bencala and Walters, 1983) or detailed models of turbulent flow in a stream, coupled with a conventional 2D Darcian groundwater model (e.g. Cardenas and Wilson, 2007). This paper presents an alternative approach which involves a simple 1-D simulation model of the hyporheic zone system based on the classical SWE equations coupled with the newly developed porous media analogue. This allows incorporating the effects of flow unsteadiness and non-Darcian parameterization od the drag term in the hyporheic zone model. The conceptual model of the stream-hyporheic zone system consists of a 1D model of the open channel flow in the river, coupled with a 1D model of the flow in the hyporheic zone via volume flux due to the difference in the water level in the river and the hyporheic zone. The interaction with the underlying groundwater aquifer is neglected, but coupling the present model with any conventional groundwater model is straightforward. The paper presents the derivation of the 1D flow equations for flow in the hyporheic zone, the details of the numerical scheme used for solving them and the model validation by comparison with published experimental data. References Bencala, K. E., and R. A. Walters (1983) "Simulation of solute transport in a mountain pool-and-riffle stream- a transient storage model", Water Resources Reseach 19(3): 718-724. Cardenas, M. B. (2015) "Hyporheic zone hydrologic science: A historical account of its emergence and a prospectus", Water Resources Research 51: 3601-3616 Cardenas, M. B., and J. L. Wilson (2007) "Dunes, turbulent eddies, and interfacial exchange with permeable sediments", Water Resour. Res. 43:W08412

Resazurin as a Proxy for Estimating Stream Respiration

NASA Astrophysics Data System (ADS)

Gonzalez Pinzon, R. A.; Haggerty, R.; Argerich, A.; Briggs, M.; Lautz, L. K.; Lemke, D.; Hare, D. K.

2010-12-01

Hydrologic retention in stream ecosystems favors the reactions of solutes and nutrients in metabolically active transient storage (MATS) zones. These zones are hot spots where metabolic activity is expected to contribute significantly to ecosystem respiration. We compare the results of a series of coinjections of resazurin (Raz) as a redox sensitive tracer, and NaCl as a conservative tracer to investigate the function of MATS zones. Raz is a dye that undergoes an irreversible reduction to resorufin (Rru) when exposed to aerobic respiration. To characterize the transformation of Raz we measured the BTC of the tracers at the boundary conditions, and during plateau concentrations we sampled the longitudinal profile of surface water. We also used the two-station diel technique to quantify gross primary production (GPP) and community respiration (CR) within the reaches. Injections have been performed in streams with different morphology, streambed composition, and riparian vegetation in Oregon-USA (WS 1 and WS 3 in the HJ Andrews Forest LTER, and Drift Creek), Spain (Riera de Santa Fe del Montseny, Catalonia) and Wyoming-USA (Cherry Creek). The results support the idea that under different ranges of community respiration, the transformation of Raz to Rru is a proxy for quantifying MATS, characterizing spatial heterogeneity in respiration rates, and ultimately, could be used to estimate ecosystem respiration in environments where direct measurement is challenging.

Impacts of different rainfall patterns on hyporheic zone under transient conditions

NASA Astrophysics Data System (ADS)

Liu, S.; Chui, T. F. M.

2017-12-01

The hyporheic zone (HZ), the region beneath or alongside a streambed, can play a vital role in stream ecology. Several previous studies have investigated the influential factors on the HZ in the steady state. However, the exchange between surface water and groundwater in the HZ can be dynamic and transient, during a transient event such as a storm. Therefore, this study investigates the changes of the HZ under the transient conditions of a storm, and examines the impacts of different rainfall patterns (i.e., intensity and duration) on the HZ. A two-dimensional groundwater-stream model is developed with a domain of 10-meter long and 2-meter deep. The streambed consists of a series of dunes that induce hyporheic exchanges. Brinkman-Darcy and Navier-Stokes equations are respectively employed for the subsurface and stream water, and the velocity and the pressure are coupled at the interface (i.e., the streambed). To compare the results from different rainfall patterns, the influential duration (IT) and the influential depth (ID) are proposed and evaluated. IT is the time required for the HZ to return to its intial stage, once it starts to change. ID is the maximum increment in the depth of the HZ. To accurately detect the region of the HZ in different situations, the moving split-window analysis method is used. The region of the HZ is found to vary significantly under different rainfall intensities. Rainfall intensity displays logarithmic relationships with both the IT and ID with high coefficients of determination (r2=0.98). The derived relationships can be used to predict the influrence of a rainfall event on the HZ. However, the influence of rainfall duration on the HZ depends on other factors such as groundwater response. Rainfall duration displays positive realionships with the IT and ID, but only between certain lower and upper thresholds of rainfall duration. If rainfall duration is shorter than the lower threshold value or longer than the upper value, the IT and ID will have little change with rainfall duration.

Sediment export, transient landscape response and catchment-scale connectivity following rapid climate warming and Alpine glacier recession

NASA Astrophysics Data System (ADS)

Lane, Stuart N.; Bakker, Maarten; Gabbud, Chrystelle; Micheletti, Natan; Saugy, Jean-Noël

2017-01-01

In the face of rapid climate warming, rapid glacier recession should lead to a marked increase in the spatial extent of the paraglacial zone in glaciated drainage basins. The extent of the paraglacial zone has been well established to be transient but there are very few studies of this transient response and what it means for sediment export. There is good reason to expect that glacier recession could increase basin-scale sediment connectivity as: sediment becomes less dependent on glacier surface transport; proglacial streams are more able to migrate laterally than subglacial streams and so access sediment for transport; and glacier debuttressing may aid the development of gullies that can dissect moraines and so aid hillslope to proglacial zone connectivity. By using records of the flushing of hydroelectric power installations we were able to develop a record of coarse sediment (sand and gravel) export from a basin with a rapidly retreating valley glacier, the Haut Glacier d'Arolla, from 1977 to 2014. Modelling suggested that these data could only be partially controlled by transport capacity implying an important role for sediment supply and potentially for the influence of changing sediment connectivity. Indeed, there was evidence of the effects of glacial debuttressing upon gullying processes and hence a possible increase in the ease of connection of upstream basins to the proglacial area. More recently, we were able to show possible temperature control on sediment export, which may only have become apparent because of the progressive development of better sediment connectivity. However, whilst rapid glacier recession should result in theory in a progressive increase in connectivity of sediment sources to the basin outlet, the supply to capacity ratio does not increase continually with glacier recession until maximum capacity is reached. We identified two possible examples of why. First, gullying was also accompanied by the sediment accumulation at the base of moraines that was too coarse to be transported by the proglacial stream, maintaining disconnection of the upper basins. Second, the sediment capacity ratio appeared to be elevated during periods of more rapid retreat and we attribute this to the importance of a continued supply of unworked glacial till before fluvial reworking and sorting of freshly exposed sediment increased the resistance of sediment to entrainment and hence export rates. Thus, the transient geomorphic response of glaciated basins to glacier recession may involve negative feedbacks that can reduce the extent to which increases in connectivity elsewhere in the basin lead to increased sediment export.

Longitudinal Stream Profile Morphology and Patterns of Knickpoint Propagation in the Bighorn Range

NASA Astrophysics Data System (ADS)

Safran, E. B.; Anderson, R. S.; Riihimaki, C. A.; Armstrong, J.

2005-12-01

The northern U. S. Rocky Mountains and the adjacent sedimentary basins are in a transient state of response to regional, Late Cenozoic exhumation. Assembling the history of landscape change there requires interpreting the morphology and genesis of transient landforms such as knickpoints in longitudinal stream profiles. We used concavity and normalized channel steepness indices to quantify the longitudinal profile morphology of >75 streams draining the east side of the Bighorn Range and the adjacent Powder River Basin. Our analyses show that individual units in the range-margin sedimentary cover rock exert a strong influence on longitudinal profile morphology. In the Tongue River and Crazy Woman Creek drainages, more than 50% of the streams examined had knickpoints localized within a resistant, siliceous dolomite. Knickpoints on most streams with drainage areas greater than ~100 km2 at the range front have migrated headward into the gneissic and plutonic core of the range. In the Clear Creek drainage, where the lateral extent of sedimentary cover rock is more restricted than in the adjacent drainages, knickpoints do not align with any particular unit. River profiles in the Powder River Basin beyond 10-20 km from the range front exhibit concavities of ~0.3-0.6 and normalized channel steepness indices of 40-60 (using 0.45 as a reference concavity). All profiles analyzed that extend into the mountain range exhibit at least one reach with exceptionally high (>2) concavity and relatively high (100-600) normalized channel steepness index, highlighting zones of transient adjustment to local base-level drop in the basin. Headwater reaches of range-draining streams exhibit variable but moderate values of concavity (0.15-0.9) and normalized channel steepness index (20-100). The varied morphology of these reaches reflects their passage across a relict surface of low relief but also the effects of glaciation and/or the signature of the narrow summit spine that caps the range.

On the use of rhodamine WT for the characterization of stream hydrodynamics and transient storage

USGS Publications Warehouse

Runkel, Robert L.

2015-01-01

Recent advances in fluorometry have led to increased use of rhodamine WT as a tracer in streams and rivers. In light of this increased use, a review of the dye's behavior in freshwater systems is presented. Studies in the groundwater literature indicate that rhodamine WT is transported nonconservatively, with sorption removing substantial amounts of tracer mass. Column studies document a two-step breakthrough curve in which two structural isomers are chromatographically separated. Although the potential for nonconservative transport is acknowledged in the surface water literature, many studies assume that sorptive losses will not affect the characterization of physical transport processes. A literature review and modeling analysis indicates that this assumption is valid for quantification of physical properties that are based on the bulk of the tracer mass (traveltime), and invalid for the characterization of processes represented by the tracer tail (transient storage attributable to hyporheic exchange). Rhodamine WT should be considered nonconservative in the hyporheic zone due to nonconservative behavior demonstrated for similar conditions in groundwater. As such, rhodamine WT should not be used as a quantitative tracer in hyporheic zone investigations, including the study of long flow paths and the development of models describing hyporheic zone processes. Rhodamine WT may be used to qualitatively characterize storage in large systems, where there are few practical alternatives. Qualitative investigations should rely on early portions of the tracer profile, making use of the temporal resolution afforded by in situ fluorometry, while discarding later parts of the tracer profile that are adversely affected by sorption.

Response of hyporheic zones to transient forcing

NASA Astrophysics Data System (ADS)

Singh, T.; Wu, L.; Gomez-Velez, J. D.; Krause, S.; Hannah, D. M.; Lewandowski, J.; Nuetzmann, G.

2017-12-01

Exchange of water, solutes, and energy between river channels and hyporheic zones (HZs) modulates biogeochemical cycling, regulates stream temperature and impacts ecological structure and function. Numerical modelling of HZ processes is required as field observations are challenging for transient flow. To gain a deeper mechanistic understanding of the effects of transient discharge on hyporheic exchange, we performed a systematic analysis using numerical experiments. In this case, we vary (i) the characteristics of time-varying flood events; (ii) river bedform geometry; (iii) river hydraulic geometry; and (iv) the magnitude and direction of groundwater fluxes (neutral, gaining and losing conditions). We conceptualize the stream bed as a two-dimensional system. Whereby the flow is driven by a dynamically changing head distribution at the water-sediment interface and is modulated by steady groundwater flow. Our model estimates both net values for a single bedform and spatial distributions of (i) the flow field; (ii) mean residence times; and (iii) the concentration of a conservative tracer. A detailed sensitivity analysis was performed by changing channel slope, flood characteristics, groundwater upwelling/downwelling fluxes and biogeochemical time-scales in different bedforms such as ripples, dunes and alternating bars. Results show that change of parameters can have a substantial impact on exchange fluxes which can lead to the expansion, contraction, emergence and/or dissipation of HZs . Our results also reveal that groundwater fluxes have different impacts on HZs during flood events, depending on the channel slope and bedform topography. It is found that topographies with smaller aspect ratios and shallower slopes are more affected by groundwater upwelling/downwelling fluxes during flood events. The analysis of biogeochemical transformations shows that discharge events can potentially affects the efficiencies of nitrate removal. Taking into consideration multiple morphological characteristics along with hydrological controls are important to improve model conceptualizations at the reach and watershed scale.

Residence times of transient riverbank exchanges traced by dissolved gases

NASA Astrophysics Data System (ADS)

Popp, A. L.; Brennwald, M. S.; Kipfer, R.

2016-12-01

Ecosystem functioning of streams heavily depends on nutrient and pollutant fluxes between the stream and the adjacent groundwater. To study potential reactions, we have to estimate the residence time of water exchanges through the streambed and bank sediment. These exchanges within the hyporheic zone have already been thoroughly investigated. However, most previous studies assumed steady-state conditions, despite the fact that the magnitude and timing of riverbank exchanges are highly dynamic. In this study, we estimate residence times of riverbank exchange under transient conditions at a restored river reach in Switzerland. In the stream and in two adjacent observation wells (in 1 m distance to the stream), we continuously analyzed dissolved gas concentrations (O2, N2, O2, Ar, He, Kr, Ne) with a portable mass spectrometer for five months on a 30 m river reach. Additionally, we continuously measured electric conductivity, water tables, and water and air temperatures at all sampling points. At the observation wells we also employed slug tests to estimate the hydraulic conductivity of the investigated stream reach. The obtained time series of tracer data reveals how residence times depend on changes in the hydraulic connectivity of the stream and the adjacent groundwater. Changes in the hydraulic state are induced by (i) different groundwater pumping rates of nearby groundwater abstraction wells, (ii) increased river discharge and (iii) subsequent changes in the hydraulic conductivity of the streambed as a result of unclogging the streambed after floods. Our results contribute to existing knowledge in this research area by identifying non-stationary processes such as the unclogging of the riverbed after flood events. In order to test our hypotheses, our next step is to use our experimental data to constrain a numerical model.

Quantifying hyporheic exchange in a karst stream using 222Rn

NASA Astrophysics Data System (ADS)

Khadka, M. B.; Martin, J. B.; Kurz, M. J.

2013-12-01

The hyporheic zone is a critical interface between groundwater and river water environments and is characterized by steep biogeochemical gradients. Understanding how this interface affects solute transport, nutrient cycling and contaminant attenuation is essential for better water resource management of streams. However, this understanding is constrained due to difficulty associated with quantification of exchange of water through the hyporheic zone. We tested a radon (222Rn) method to estimate the hyporheic water residence time and exchange rate in the bottom sediment of the spring-fed Ichetucknee River, north-central Florida. The river, which flows over the top of the unconfined karstic Floridan Aquifer, is characterized by a broad bedrock channel partially in-filled with unconsolidated sediments. Radon (222Rn) activity in the pore waters of the channel sediments differs from the amount expected from sediment production and decay. Although most radon in streams originates from sources in bottom sediments, the Ichetucknee River water has 222Rn activities (251×5 PCi/L) that are nearly twice that of the pore water (128×15 PCi/L). The river water 222Rn activity is consistent with that of the source springs, suggesting the source of Rn in the river is from deep within the aquifer rather than bottom sediments and that the excess 222Rn in the pore water results from hyporheic exchange. Profiles of radon concentrations with depth through the sediments show that the mixing of stream water and pore water extends 35-45 cm below the sediment and water interface. Based on a model that integrates the excess radon with depth, we estimate the water exchange rate to be between 1.1 and 1.6 cm/day with an average value of 1.3×0.2 cm/day. Water that exchanges across the sediment-water interface pumps oxygen into the sediments, thereby enhancing organic carbon remineralization, as well as the production of NH4+ and PO43- and their fluxes from sediments to the stream. As opposed to conventional in-stream tracer injection method which estimates exchange between the stream and both the hyporheic zone and the surface transient storage zone, the 222Rn approach measures the water exchange between stream and hyporheic sediments only. Although the present method is tested on a spring-fed karst stream, it has potential for any freshwater system (e.g. wetland, lake) where distinct radon activity and production between surface water and underlying sediments occur.

Fingerprinting Dissolved Organic Carbon (DOC) Sources with Specific UV Absorbance (SUVA) and Fluorescence

NASA Astrophysics Data System (ADS)

van Verseveld, W. J.; Lajtha, K.; McDonnell, J. J.

2007-12-01

DOC is an important water quality constituent because it is an important food source for stream biota, it plays a significant role in metal toxicity and transport, and protects aquatic organisms by absorbing visible and UV light. However, sources of stream DOC and changes in DOC quality at storm and seasonal scales remain poorly understood. We characterized DOC concentrations and SUVA (as an indicator of aromaticity) at the plot, hillslope and catchment scale during and between five storm events over the period Fall 2004 until Spring 2005, in WS10, H.J. Andrews, Oregon, USA. This study site has hillslopes that issue directly into the stream. This enabled us to compare a trenched hillslope response to the stream response without the influence of a riparian zone. The main result of this study was that SUVA in addition to DOC was needed to fingerprint sources of DOC. Stream water and lateral subsurface flow showed a clockwise DOC and SUVA hysteresis pattern. Both organic horizon water and transient groundwater were characterized by high DOC concentrations and SUVA values, while DOC concentrations and SUVA values in soil water decreased with depth in the soil profile. This indicates transient groundwater was an important contributor to high DOC concentrations and SUVA values during storm events. During the falling limb of the hydrograph deep soil water and seepage groundwater based on SUVA values contributed significantly to lateral subsurface flow and stream water. Preliminary results showed that fluorescence of stream water and lateral subsurface flow continuously measured with a fluorometer was significantly related to UV-absorbance during a December storm event. Finally, SUVA of lateral subsurface flow was lower than SUVA of stream water at the seasonal scale, indicating a difference in mixing of water sources at the hillslope and catchment scale. Overall, our results show that SUVA and fluorescence are useful tracers for fingerprinting DOC sources.

Two tales of legacy effects on stream nutrient behaviour

NASA Astrophysics Data System (ADS)

Bieroza, M.; Heathwaite, A. L.

2017-12-01

Intensive agriculture has led to large-scale land use conversion, shortening of flow pathways and increased loads of nutrients in streams. This legacy results in gradual build-up of nutrients in agricultural catchments: in soil for phosphorus (biogeochemical legacy) and in the unsaturated zone for nitrate (hydrologic legacy), controlling the water quality in the long-term. Here we investigate these effects on phosphorus and nitrate stream concentrations using high-frequency (10-5 - 100 Hz) sampling with in situ wet-chemistry analysers and optical sensors. Based on our 5 year study, we observe that storm flow responses differ for both nutrients: phosphorus shows rapid increases (up to 3 orders of magnitude) in concentrations with stream flow, whereas nitrate shows both dilution and concentration effects with increasing flow. However, the range of nitrate concentrations change is narrow (up to 2 times the mean) and reflects chemostatic behaviour. We link these nutrient responses with their dominant sources and flow pathways in the catchment. Nitrate from agriculture (with the peak loading in 1983) is stored in the unsaturated zone of the Penrith Sandstone, which can reach up to 70 m depth. Thus nitrate legacy is related to a hydrologic time lag with long travel times in the unsaturated zone. Phosphorus is mainly sorbed to soil particles, therefore it is mobilised rapidly during rainfall events (biogeochemical legacy). The phosphorus stream response will however depend on how well connected is the stream to the catchment sources (driven by soil moisture distribution) and biogeochemical activity (driven by temperature), leading to both chemostatic and non-chemostatic responses, alternating on a storm-to-storm and seasonal basis. Our results also show that transient within-channel storage is playing an important role in delivery of phosphorus, providing an additional time lag component. These results show, that consistent agricultural legacy in the catchment (high historical loads of nutrients) has different effects on nutrients stream responses, depending on their dominant sources and pathways. Both types of time lags, biogeochemical for phosphorus and hydrologic for nitrate, need to be taken into account when designing and evaluating the effectiveness of the agri-environmental mitigation measures.

Low transient storage and uptake efficiencies in seven agricultural streams: implications for nutrient demand

USGS Publications Warehouse

Sheibley, Rich W.; Duff, John H.; Tesoriero, Anthony J.

2014-01-01

We used mass load budgets, transient storage modeling, and nutrient spiraling metrics to characterize nitrate (NO3−), ammonium (NH4+), and inorganic phosphorus (SRP) demand in seven agricultural streams across the United States and to identify in-stream services that may control these conditions. Retention of one or all nutrients was observed in all but one stream, but demand for all nutrients was low relative to the mass in transport. Transient storage metrics (As/A, Fmed200, Tstr, and qs) correlated with NO3− retention but not NH4+ or SRP retention, suggesting in-stream services associated with transient storage and stream water residence time could influence reach-scale NO3− demand. However, because the fraction of median reach-scale travel time due to transient storage (Fmed200) was ≤1.2% across the sites, only a relatively small demand for NO3− could be generated by transient storage. In contrast, net uptake of nutrients from the water column calculated from nutrient spiraling metrics were not significant at any site because uptake lengths calculated from background nutrient concentrations were statistically insignificant and therefore much longer than the study reaches. These results suggest that low transient storage coupled with high surface water NO3− inputs have resulted in uptake efficiencies that are not sufficient to offset groundwater inputs of N. Nutrient retention has been linked to physical and hydrogeologic elements that drive flow through transient storage areas where residence time and biotic contact are maximized; however, our findings indicate that similar mechanisms are unable to generate a significant nutrient demand in these streams relative to the loads.

RFI flagging implications for short-duration transients

NASA Astrophysics Data System (ADS)

Cendes, Y.; Prasad, P.; Rowlinson, A.; Wijers, R. A. M. J.; Swinbank, J. D.; Law, C. J.; van der Horst, A. J.; Carbone, D.; Broderick, J. W.; Staley, T. D.; Stewart, A. J.; Huizinga, F.; Molenaar, G.; Alexov, A.; Bell, M. E.; Coenen, T.; Corbel, S.; Eislöffel, J.; Fender, R.; Grießmeier, J.-M.; Jonker, P.; Kramer, M.; Kuniyoshi, M.; Pietka, M.; Stappers, B.; Wise, M.; Zarka, P.

2018-04-01

With their wide fields of view and often relatively long coverage of any position in the sky in imaging survey mode, modern radio telescopes provide a data stream that is naturally suited to searching for rare transients. However, Radio Frequency Interference (RFI) can show up in the data stream in similar ways to such transients, and thus the normal pre-treatment of filtering RFI (flagging) may also remove astrophysical transients from the data stream before imaging. In this paper we investigate how standard flagging affects the detectability of such transients by examining the case of transient detection in an observing mode used for Low Frequency Array (LOFAR; van Haarlem et al., 2013) surveys. We quantify the fluence range of transients that would be detected, and the reduction of their SNR due to partial flagging. We find that transients with a duration close to the integration sampling time, as well as bright transients with durations on the order of tens of seconds, are completely flagged. For longer transients on the order of several tens of seconds to minutes, the flagging effects are not as severe, although part of the signal is lost. For these transients, we present a modified flagging strategy which mitigates the effect of flagging on transient signals. We also present a script which uses the differences between the two strategies, and known differences between transient RFI and astrophysical transients, to notify the observer when a potential transient is in the data stream.

Weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the McMurdo Dry Valleys

USGS Publications Warehouse

Gooseff, Michael N.; McKnight, Diane M.; Lyons, W. Berry; Blum, Alex E.

2002-01-01

In the McMurdo Dry Valleys, Antarctica, dilute glacial meltwater flows down well‐established streambeds to closed basin lakes during the austral summer. During the 6–12 week flow season, a hyporheic zone develops in the saturated sediment adjacent to the streams. Longer Dry Valley streams have higher concentrations of major ions than shorter streams. The longitudinal increases in Si and K suggest that primary weathering contributes to the downstream solute increase. The hypothesis that weathering reactions in the hyporheic zone control stream chemistry was tested by modeling the downstream increase in solute concentration in von Guerard Stream in Taylor Valley. The average rates of solute supplied from these sources over the 5.2 km length of the stream were 6.1 × 10−9 mol Si L−1 m−1 and 3.7 × 10−9 mol K L−1 m−1, yielding annual dissolved Si loads of 0.02–1.30 mol Si m−2 of watershed land surface. Silicate minerals in streambed sediment were analyzed to determine the representative surface area of minerals in the hyporheic zone subject to primary weathering. Two strategies were evaluated to compute sediment surface area normalized weathering rates. The first applies a best linear fit to synoptic data in order to calculate a constant downstream solute concentration gradient, dC/dx (constant weathering rate contribution, CRC method); the second uses a transient storage model to simulate dC/dx, representing both hyporheic exchange and chemical weathering (hydrologic exchange, HE method). Geometric surface area normalized dissolution rates of the silicate minerals in the stream ranged from 0.6 × 10−12 mol Si m−2 s−1 to 4.5 × 10−12 mol Si m−2 s−1 and 0.4 × 10−12 mol K m−2 s−1to 1.9 × 10−12 mol K m−2 s−1. These values are an order of magnitude lower than geometric surface area normalized weathering rates determined in laboratory studies and are an order of magnitude greater than geometric surface area normalized weathering rates determined in a warmer, wetter setting in temperate basins, despite the cold temperatures, lack of precipitation and lack of organic material. These results suggest that the continuous saturation and rapid flushing of the sediment due to hyporheic exchange facilitates weathering in Dry Valley streams.

Process for Nitrogen Oxide Waste Conversion to Fertilizer

NASA Technical Reports Server (NTRS)

Lueck, Dale E. (Inventor); Parrish, Clyde F. (Inventor)

2003-01-01

The present invention describes a process for converting vapor streams from sources containing at least one nitrogen-containing oxidizing agent therein to a liquid fertilizer composition comprising the steps of: a) directing a vapor stream containing at least one nitrogen-containing oxidizing agent to a first contact zone; b) contacting said vapor stream with water to form nitrogen oxide(s) from said at least one nitrogen-containing oxidizing agent; c) directing said acid(s) as a second stream to a second contact zone; d) exposing said second stream to hydrogen peroxide which is present within said second contact zone in a relative amount of at least 0.1% by weight of said second stream within said second contact zone to convert at least some of any nitrogen oxide species or ions other than in the nitrate form present within said second stream to nitrate ion; e) sampling said stream within said second contact zone to determine the relative amount of hydrogen peroxide within said second contact zone; f) adding hydrogen peroxide to said second contact zone when a level of hydrogen peroxide less than 0.1 % by weight in said second stream is determined by said sampling; g) adding a solution comprising potassium hydroxide to said second stream to maintain a pH between 6.0 and 11.0 within said second stream within said second contact zone to form a solution of potassium nitrate; and h) removing said solution of potassium nitrate from said second contact zone.

Process and Equipment for Nitrogen Oxide Waste Conversion to Fertilizer

NASA Technical Reports Server (NTRS)

Lueck, Dale E. (Inventor); Parrish, Clyde F. (Inventor)

2000-01-01

The present invention describes a process for converting vapor streams from sources containing at least one nitrogen-containing oxidizing agent therein to a liquid fertilizer composition comprising the steps of: (1) directing a vapor stream containing at least nitrogen-containing oxidizing agent to a first contact zone; (2) contacting said vapor stream with water to form nitrogen oxide(s) from said at least one nitrogen- containing oxidizing agent; (3) directing said acid(s) as a second stream to a second contact zone; (4) exposing said second stream to hydrogen peroxide which is present within said second contact zone in a relative amount of at least 0.1% by weight of said second stream within said second contact zone to convert at least some of any nitrogen oxide species or ions other than in the nitrite form present within said second stream to nitrate ion; (5) sampling said stream within said second contact zone to determine the relative amount of hydrogen peroxide within said second contact zone; (6) adding hydrogen peroxide to said second contact zone when a level on hydrogen peroxide less than 0.1% by weight in said second stream is determined by said sampling; (7) adding a solution comprising potassium hydroxide to said second stream to maintain a pH between 6.0 and 11.0 within said second stream within said second contact zone to form a solution of potassium nitrate; and (8) removing sais solution of potassium nitrate from said second contact zone.

AN INTERREGIONAL COMPARISON OF CHANNEL STRUCTURE, TRANSIENT STORAGE AND NUTRIENT UPTAKE IN STREAMS DRAINING MANAGED AND OLD GROWTH WATERSHEDS

EPA Science Inventory

We compared stream channel structure (width, depth, substrate composition) and riparian canopy with transient storage and nutrient uptake in 32 streams draining old-growth and managed watersheds in the Appalachian Mountains (North Carolina), Ouachita Mountains (Arkansas), Cascade...

The role of the hyporheic zone across stream networks

Treesearch

Steven M. Wondzell

2011-01-01

Many hyporheic papers state that the hyporheic zone is a critical component of stream ecosystems, and many of these papers focus on the biogeochemical effects of the hyporheic zone on stream solute loads. However, efforts to show such relationships have proven elusive, prompting several questions: Are the effects of the hyporheic zone on stream ecosystems so highly...

Variations in surface water-ground water interactions along a headwater mountain stream : comparisons between transient storage and water balance analyses

USGS Publications Warehouse

Ward, Adam S.; Payn, Robert A.; Gooseff, Michael N.; McGlynn, Brian L.; Bencala, Kenneth E.; Kelleher, Christa A.; Wondzell, Steven M.; Wagener, Thorsten

2013-01-01

The accumulation of discharge along a stream valley is frequently assumed to be the primary control on solute transport processes. Relationships of both increasing and decreasing transient storage, and decreased gross losses of stream water have been reported with increasing discharge; however, we have yet to validate these relationships with extensive field study. We conducted transient storage and mass recovery analyses of artificial tracer studies completed for 28 contiguous 100 m reaches along a stream valley, repeated under four base-flow conditions. We calculated net and gross gains and losses, temporal moments of tracer breakthrough curves, and best fit transient storage model parameters (with uncertainty estimates) for 106 individual tracer injections. Results supported predictions that gross loss of channel water would decrease with increased discharge. However, results showed no clear relationship between discharge and transient storage, and further analysis of solute tracer methods demonstrated that the lack of this relation may be explained by uncertainty and equifinality in the transient storage model framework. Furthermore, comparison of water balance and transient storage approaches reveals complications in clear interpretation of either method due to changes in advective transport time, which sets a the temporal boundary separating transient storage and channel water balance. We have little ability to parse this limitation of solute tracer methods from the physical processes we seek to study. We suggest the combined analysis of both transient storage and channel water balance more completely characterizes transport of solutes in stream networks than can be inferred from either method alone.

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.

Rotary adsorbers for continuous bulk separations

DOEpatents

Baker, Frederick S [Oak Ridge, TN

2011-11-08

A rotary adsorber for continuous bulk separations is disclosed. The rotary adsorber includes an adsorption zone in fluid communication with an influent adsorption fluid stream, and a desorption zone in fluid communication with a desorption fluid stream. The fluid streams may be gas streams or liquid streams. The rotary adsorber includes one or more adsorption blocks including adsorbent structure(s). The adsorbent structure adsorbs the target species that is to be separated from the influent fluid stream. The apparatus includes a rotary wheel for moving each adsorption block through the adsorption zone and the desorption zone. A desorption circuit passes an electrical current through the adsorbent structure in the desorption zone to desorb the species from the adsorbent structure. The adsorbent structure may include porous activated carbon fibers aligned with their longitudinal axis essentially parallel to the flow direction of the desorption fluid stream. The adsorbent structure may be an inherently electrically-conductive honeycomb structure.

Using Isotopic Age of Water as a Constraint on Model Identification at a Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Duffy, C.; Thomas, E.; Bhatt, G.; George, H.; Boyer, E. W.; Sullivan, P. L.

2016-12-01

This paper presents an ecohydrologic model constrained by comprehensive space and time observations of water and stable isotopes of oxygen and hydrogen for an upland catchment, the Susquehanna/Shale Hills Critical Zone Observatory (SSH_CZO). The paper first develops the theoretical basis for simulation of flow, isotope ratios and "age" as water moves through the canopy, to the unsaturated and saturated zones and finally to an intermittent stream. The model formulation demonstrates that the residence time and age of environmental tracers can be directly simulated without knowledge of the form of the underlying residence time distribution function and without the addition of any new physical parameters. The model is used to explore the observed rapid attenuation of event and seasonal isotopic ratios in precipitation over the depth of the soil zone and the impact of decreasing hydraulic conductivity with depth on the dynamics of streamflow and stream isotope ratios. The results suggest the importance of mobile macropore flow on recharge to groundwater during the non-growing cold-wet season. The soil matrix is also recharged during this season with a cold-season isotope signature. During the growing-dry season, root uptake and evaporation from the soil matrix along with a declining water table provides the main source of water for plants and determines the growing season signature. Flow path changes during storm events and transient overland flow is inferred by comparing the frequency distribution of groundwater and stream isotope histories with model results. Model uncertainty is evaluated for conditions of matrix-macropore partitioning and heterogeneous variations in conductivity with depth. The paper concludes by comparing the fully dynamical model with the simplified mixing model form in dynamic equilibrium. The comparison illustrates the importance of system memory on the time scales for flow and mixing processes and the limitations of the dynamic equilibrium assumption on estimated age and residence time.

Variations in surface water-ground water interactions along a headwater mountain stream: comparisons between transient storage and water balance analyses

Treesearch

Adam S. Ward; Robert A. Payn; Michael N. Gooseff; Brian L. McGlynn; Kenneth E. Bencala; Christa A. Kellecher; Steven M. Wondzell; Thorsten Wagener

2013-01-01

The accumulation of discharge along a stream valley is frequently assumed to be the primary control on solute transport processes. Relationships of both increasing and decreasing transient storage, and decreased gross losses of stream water have been reported with increasing discharge; however, we have yet to validate these relationships with extensive field study. We...

Eulerian-Lagrangian numerical scheme for simulating advection, dispersion, and transient storage in streams and a comparison of numerical methods

USGS Publications Warehouse

Cox, T.J.; Runkel, R.L.

2008-01-01

Past applications of one-dimensional advection, dispersion, and transient storage zone models have almost exclusively relied on a central differencing, Eulerian numerical approximation to the nonconservative form of the fundamental equation. However, there are scenarios where this approach generates unacceptable error. A new numerical scheme for this type of modeling is presented here that is based on tracking Lagrangian control volumes across a fixed (Eulerian) grid. Numerical tests are used to provide a direct comparison of the new scheme versus nonconservative Eulerian numerical methods, in terms of both accuracy and mass conservation. Key characteristics of systems for which the Lagrangian scheme performs better than the Eulerian scheme include: nonuniform flow fields, steep gradient plume fronts, and pulse and steady point source loadings in advection-dominated systems. A new analytical derivation is presented that provides insight into the loss of mass conservation in the nonconservative Eulerian scheme. This derivation shows that loss of mass conservation in the vicinity of spatial flow changes is directly proportional to the lateral inflow rate and the change in stream concentration due to the inflow. While the nonconservative Eulerian scheme has clearly worked well for past published applications, it is important for users to be aware of the scheme's limitations. ?? 2008 ASCE.

Method for heating nongaseous carbonaceous material

DOEpatents

Lumpkin, Jr., Robert E.

1978-01-01

Nongaseous carbonaceous material is heated by a method comprising introducing tangentially a first stream containing a nongaseous carbonaceous material and carbon monoxide into a reaction zone; simultaneously and separately introducing a second stream containing oxygen into the reaction zone such that the oxygen enters the reaction zone away from the wall thereof and reacts with the first stream thereby producing a gaseous product and heating the nongaseous carbonaceous material; forming an outer spiralling vortex within the reaction zone to cause substantial separation of gases, including the gaseous product, from the nongaseous carbonaceous material; removing a third stream from the reaction zone containing the gaseous product which is substantially free of the nongaseous carbonaceous material before a major portion of the gaseous product can react with the nongaseous carbonaceous material; and removing a fourth stream containing the nongaseous carbonaceous material from the reaction zone.

Multi-scale streambed topographic and discharge effects on hyporheic at the stream network scale in confined streams

Treesearch

Alessandra Marzadri; Daniele Tonina; James A. McKean; Matthew G. Tiedemann; Rohan M. Benjankar

2014-01-01

The hyporheic zone is the volume of the streambed sediment mostly saturated with stream water. It is the transitional zone between stream and shallow-ground waters and an important ecotone for benthic species, including macro-invertebrates, microorganisms, and some fish species that dwell in the hyporheic zone for parts of their lives. Most hyporheic analyses are...

Impact of transient stream flow on water exchange and reactions in the hyporheic zone of an in-stream gravel bar

NASA Astrophysics Data System (ADS)

Trauth, Nico; Schmidt, Christian; Fleckenstein, Jan H.

2015-04-01

Groundwater-surface water exchange is an important process that can facilitate the degradation of critical substances like nitrogen-species and contaminants, supporting a healthy status of the aquatic ecosystem. In our study, we simulate water exchange, solute transport and reactions within a natural in-stream gravel bar using a coupled surface and subsurface numerical model. Stream water flow is simulated by computational fluid dynamics software that provides hydraulic head distributions at the streambed, which are used as an upper boundary condition for a groundwater model. In the groundwater model water exchange, solute transport, aerobic respiration and denitrification in the subsurface are simulated. Ambient groundwater flow is introduced by lateral upstream and downstream hydraulic head boundaries that generate neutral, losing or gaining stream conditions. Stream water transports dissolved oxygen, organic carbon (as the dominant electron donor) and nitrate into the subsurface, whereas an additional nitrate source exists in the ambient groundwater. Scenarios of stream flow events varying in duration and stream stage are simulated and compared with steady state scenarios with respect to water fluxes, residence times and the solute turn-over rates. Results show, that water exchange and solute turn-over rates highly depend on the interplay between event characteristics and ambient groundwater levels. For scenarios, where the stream flow event shifts the hydraulic system to a net-neutral hydraulic gradient between the average stream stage and the ambient groundwater level (minimal exchange between ground- and surface water), solute consumption is higher, compared to the steady losing or gaining case. In contrast, events that induce strong losing conditions lead to a lower potential of solute consumption.

Systems and methods for reactive distillation with recirculation of light components

DOEpatents

Stickney, Michael J [Nassau Bay, TX; Jones, Jr., Edward M.

2011-07-26

Systems and methods for producing gas-to-liquids products using reactive distillation are provided. The method for producing gas-to-liquids products can include reacting a feedstock in a column having a distillation zone and a reaction zone to provide a bottoms stream and an overhead stream. A first portion of the overhead stream can be recycled to the column at the top of the reaction zone and second portion of the overhead stream can be recycled to the column at the bottom of the reaction zone.

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.

Method for generating hydrogen for fuel cells

DOEpatents

Ahmed, Shabbir; Lee, Sheldon H. D.; Carter, John David; Krumpelt, Michael

2004-03-30

A method of producing a H.sub.2 rich gas stream includes supplying an O.sub.2 rich gas, steam, and fuel to an inner reforming zone of a fuel processor that includes a partial oxidation catalyst and a steam reforming catalyst or a combined partial oxidation and stream reforming catalyst. The method also includes contacting the O.sub.2 rich gas, steam, and fuel with the partial oxidation catalyst and the steam reforming catalyst or the combined partial oxidation and stream reforming catalyst in the inner reforming zone to generate a hot reformate stream. The method still further includes cooling the hot reformate stream in a cooling zone to produce a cooled reformate stream. Additionally, the method includes removing sulfur-containing compounds from the cooled reformate stream by contacting the cooled reformate stream with a sulfur removal agent. The method still further includes contacting the cooled reformate stream with a catalyst that converts water and carbon monoxide to carbon dioxide and H.sub.2 in a water-gas-shift zone to produce a final reformate stream in the fuel processor.

Fuel processor and method for generating hydrogen for fuel cells

DOEpatents

Ahmed, Shabbir [Naperville, IL; Lee, Sheldon H. D. [Willowbrook, IL; Carter, John David [Bolingbrook, IL; Krumpelt, Michael [Naperville, IL; Myers, Deborah J [Lisle, IL

2009-07-21

A method of producing a H.sub.2 rich gas stream includes supplying an O.sub.2 rich gas, steam, and fuel to an inner reforming zone of a fuel processor that includes a partial oxidation catalyst and a steam reforming catalyst or a combined partial oxidation and stream reforming catalyst. The method also includes contacting the O.sub.2 rich gas, steam, and fuel with the partial oxidation catalyst and the steam reforming catalyst or the combined partial oxidation and stream reforming catalyst in the inner reforming zone to generate a hot reformate stream. The method still further includes cooling the hot reformate stream in a cooling zone to produce a cooled reformate stream. Additionally, the method includes removing sulfur-containing compounds from the cooled reformate stream by contacting the cooled reformate stream with a sulfur removal agent. The method still further includes contacting the cooled reformate stream with a catalyst that converts water and carbon monoxide to carbon dioxide and H.sub.2 in a water-gas-shift zone to produce a final reformate stream in the fuel processor.

Characterizing multiple timescales of stream and storage zone interaction that affect solute fate and transport in streams

USGS Publications Warehouse

Choi, Jungyill; Harvey, Judson W.; Conklin, Martha H.

2000-01-01

The fate of contaminants in streams and rivers is affected by exchange and biogeochemical transformation in slowly moving or stagnant flow zones that interact with rapid flow in the main channel. In a typical stream, there are multiple types of slowly moving flow zones in which exchange and transformation occur, such as stagnant or recirculating surface water as well as subsurface hyporheic zones. However, most investigators use transport models with just a single storage zone in their modeling studies, which assumes that the effects of multiple storage zones can be lumped together. Our study addressed the following question: Can a single‐storage zone model reliably characterize the effects of physical retention and biogeochemical reactions in multiple storage zones? We extended an existing stream transport model with a single storage zone to include a second storage zone. With the extended model we generated 500 data sets representing transport of nonreactive and reactive solutes in stream systems that have two different types of storage zones with variable hydrologic conditions. The one storage zone model was tested by optimizing the lumped storage parameters to achieve a best fit for each of the generated data sets. Multiple storage processes were categorized as possessing I, additive; II, competitive; or III, dominant storage zone characteristics. The classification was based on the goodness of fit of generated data sets, the degree of similarity in mean retention time of the two storage zones, and the relative distributions of exchange flux and storage capacity between the two storage zones. For most cases (>90%) the one storage zone model described either the effect of the sum of multiple storage processes (category I) or the dominant storage process (category III). Failure of the one storage zone model occurred mainly for category II, that is, when one of the storage zones had a much longer mean retention time (ts ratio > 5.0) and when the dominance of storage capacity and exchange flux occurred in different storage zones. We also used the one storage zone model to estimate a “single” lumped rate constant representing the net removal of a solute by biogeochemical reactions in multiple storage zones. For most cases the lumped rate constant that was optimized by one storage zone modeling estimated the flux‐weighted rate constant for multiple storage zones. Our results explain how the relative hydrologic properties of multiple storage zones (retention time, storage capacity, exchange flux, and biogeochemical reaction rate constant) affect the reliability of lumped parameters determined by a one storage zone transport model. We conclude that stream transport models with a single storage compartment will in most cases reliably characterize the dominant physical processes of solute retention and biogeochemical reactions in streams with multiple storage zones.

Changes In Tree Species In Riparian Zones Of Urban Streams May Have Effects On Restoration And Storm Water Control Efforts

EPA Science Inventory

A riparian zone is the land and vegetation within and directly adjacent to surface water ecosystems, such as lakes and streams. The vegetation in riparian zones provides ecosystem services (such as reducing flooding and bank erosion and reducing levels of pollutants in streams) ...

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.

NUTRIENT UPTAKE LENGTH, CHANNEL STRUCTURE, AND TRANSIENT STORAGE IN STREAMS DRAINING HARVESTED AND OLD GROWTH WATERSHEDS

EPA Science Inventory

Channel structure and transient storage were correlated with nutrient uptake length in streams draining old-growth and harvested watersheds in the Cascade Mountains of Oregon, and the redwood forests of northwestern California. Channel width and riparian canopy were measured at 1...

CHARACTERIZING STORM HYDROGRAPH RISE AND FALL DYNAMICS AND THEIR RELATIONSHIP WITH STREAM STAGE DATA

EPA Science Inventory

Stormflow transients (i.e., hydrograph rise and fall dynamics) have been shown to impact stream biota through impacts on habitat quality and availability. However, little is known about how climate variability and temporal resolution of transient data may color the putative relat...

Long-term monitoring of stream bank stability under different vegetation cover

NASA Astrophysics Data System (ADS)

Krzeminska, Dominika; Skaalsveen, Kamilla; Kerkhof, Tjibbe

2017-04-01

Vegetated buffer zones are common environmental measures in many countries, including Norway. The presence of riparian vegetation on stream banks not only provides ecological benefits but also influence bank slope stability, through several complex interactions between riparian vegetation and hydro - mechanical processes. The hydrological processes associated with slope stability are complex and yet difficult to quantify, especially because their transient effects (e.g. changes throughout the vegetation life cycle). Additionally, there is very limited amount of field scale research focusing on investigation of coupled hydrological and mechanical influence of vegetation on stream bank behavior, accounting for both seasonal time scale and different vegetation type, and none dedicated to marine clay soils (typically soil for Norway). In order to fill this gap we established continues, long term hydrogeological monitoring o selected cross - section within stream bank, covered with different types of vegetation, typical for Norwegian agriculture areas (grass, shrubs, and trees). The monitoring involves methods such as spatial and temporal monitoring of soil moisture conditions, ground water level and fluctuation of water level in the stream. Herein we will present first 10 months of monitoring data: observed hydrological trends and differences between three cross - sections. Moreover, we will present first modelling exercises that aims to estimate stream banks stability with accounting on presence of different vegetation types using BSTEM and HYDRUS models. With this presentation, we would like to stimulate the discussion and get feedback that could help us to improve both, our experimental set up and analysis approach.

Method for reacting nongaseous material with a gaseous reactant

DOEpatents

Lumpkin, Robert E.; Duraiswamy, Kandaswamy

1979-03-27

This invention relates to a new and novel method and apparatus for reacting nongaseous material with a gaseous reactant comprising introducing a first stream containing a nongaseous material into a reaction zone; simultaneously introducing a second stream containing a gaseous reactant into the reaction zone such that the gaseous reactant immediately contacts and reacts with the first stream thereby producing a gaseous product; forming a spiralling vortex within the reaction zone to cause substantial separation of gases, including the gaseous product, from the nongaseous material; forming and removing a third stream from the reaction zone containing the gaseous product which is substantially free of the nongaseous material before a major portion of the gaseous product can react with the nongaseous material; and forming and removing a fourth stream containing the nongaseous material from the reaction zone.

Experimental transient turbine blade temperatures in a research engine for gas stream temperatures cycling between 1067 and 1567 k

NASA Technical Reports Server (NTRS)

Gauntner, D. J.; Yeh, F. C.

1975-01-01

Experimental transient turbine blade temperatures were obtained from tests conducted on air-cooled blades in a research turbojet engine, cycling between cruise and idle conditions. Transient data were recorded by a high speed data acquisition system. Temperatures at the same phase of each transient cycle were repeatable between cycles to within 3.9 K (7 F). Turbine inlet pressures were repeatable between cycles to within 0.32 N/sq cm (0.47 psia). The tests were conducted at a gas stream temperature of 1567 K (2360 F) at cruise, and 1067 K (1460 F) at idle conditions. The corresponding gas stream pressures were about 26.2 and 22.4 N/sq cm (38 and 32.5 psia) respectively. The nominal coolant inlet temperature was about 811 K (1000 F).

Ash Tree Leaf Litter (Fraxinus excelsior L.) Breakdown in Two Different Biotopes and Streams

NASA Astrophysics Data System (ADS)

Fleituch, Tadeusz; Leichtfried, Maria

2004-11-01

Coarse (0.5 mm) and fine (0.1 mm) mesh size bag methodology was used for comparing the breakdown of ash tree leaves (Fraxinus excelsior L.) in two biotopes (dry - terrestrial and wet - overflown stream zones) in two low order streams (the Oberer Seebach (OSB), Lower Austria and the Brzezowka stream (BRZ), Beskidy Mountains, southern Poland). In total, 96 bags were exposed in autumn 2000. Ash-free dry mass (AFDM) ranged in dry zones of both streams from 94-62% (OSB) and 85-53% (BRZ) respectively. The decomposition process was faster in wet zones: 96-33% (OSB) and 56-11% (B) during the study period. Significant differences in ash breakdown and its chemical content between studied streams were found. Total organic carbon (TOC) and total nitrogen content (TN) of AFDM of litter showed increased differences with experiment duration between zones and between two bag types for both streams. The strongest increase of TOC and TN content (100% on average initial content) for bag types, zones, and streams was observed in the first two weeks of the experiment. These results confirm the importance of chemical compounds for microbiological processes (biofilms) in different ecosystem biotopes. (

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.

Tracer-based characterization of hyporheic exchange and benthic biolayers in streams

NASA Astrophysics Data System (ADS)

Knapp, Julia L. A.; González-Pinzón, Ricardo; Drummond, Jennifer D.; Larsen, Laurel G.; Cirpka, Olaf A.; Harvey, Judson W.

2017-02-01

Shallow benthic biolayers at the top of the streambed are believed to be places of enhanced biogeochemical turnover within the hyporheic zone. They can be investigated by reactive stream tracer tests with tracer recordings in the streambed and in the stream channel. Common in-stream measurements of such reactive tracers cannot localize where the processing primarily takes place, whereas isolated vertical depth profiles of solutes within the hyporheic zone are usually not representative of the entire stream. We present results of a tracer test where we injected the conservative tracer bromide together with the reactive tracer resazurin into a third-order stream and combined the recording of in-stream breakthrough curves with multidepth sampling of the hyporheic zone at several locations. The transformation of resazurin was used as an indicator of metabolism, and high-reactivity zones were identified from depth profiles. The results from our subsurface analysis indicate that the potential for tracer transformation (i.e., the reaction rate constant) varied with depth in the hyporheic zone. This highlights the importance of the benthic biolayer, which we found to be on average 2 cm thick in this study, ranging from one third to one half of the full depth of the hyporheic zone. The reach-scale approach integrated the effects of processes along the reach length, isolating hyporheic processes relevant for whole-stream chemistry and estimating effective reaction rates.

Tracer-based characterization of hyporheic exchange and benthic biolayers in streams

USGS Publications Warehouse

Knapp, Julia L.A.; González-Pinzón, Ricardo; Drummond, Jennifer D.; Larsen, Laurel G.; Cirpka, Olaf A.; Harvey, Judson W.

2017-01-01

Shallow benthic biolayers at the top of the streambed are believed to be places of enhanced biogeochemical turnover within the hyporheic zone. They can be investigated by reactive stream tracer tests with tracer recordings in the streambed and in the stream channel. Common in-stream measurements of such reactive tracers cannot localize where the processing primarily takes place, whereas isolated vertical depth profiles of solutes within the hyporheic zone are usually not representative of the entire stream. We present results of a tracer test where we injected the conservative tracer bromide together with the reactive tracer resazurin into a third-order stream and combined the recording of in-stream breakthrough curves with multidepth sampling of the hyporheic zone at several locations. The transformation of resazurin was used as an indicator of metabolism, and high-reactivity zones were identified from depth profiles. The results from our subsurface analysis indicate that the potential for tracer transformation (i.e., the reaction rate constant) varied with depth in the hyporheic zone. This highlights the importance of the benthic biolayer, which we found to be on average 2 cm thick in this study, ranging from one third to one half of the full depth of the hyporheic zone. The reach-scale approach integrated the effects of processes along the reach length, isolating hyporheic processes relevant for whole-stream chemistry and estimating effective reaction rates.

Method for enhancing selectivity and recovery in the fractional flotation of particles in a flotation column

DOEpatents

Klunder, Edgar B [Bethel Park, PA

2011-08-09

The method relates to particle separation from a feed stream. The feed stream is injected directly into the froth zone of a vertical flotation column in the presence of a counter-current reflux stream. A froth breaker generates a reflux stream and a concentrate stream, and the reflux stream is injected into the froth zone to mix with the interstitial liquid between bubbles in the froth zone. Counter-current flow between the plurality of bubbles and the interstitial liquid facilitates the attachment of higher hydrophobicity particles to bubble surfaces as lower hydrophobicity particles detach. The height of the feed stream injection and the reflux ratio may be varied in order to optimize the concentrate or tailing stream recoveries desired based on existing operating conditions.

AN INTERREGIONAL COMPARISON OF CHANNEL STRUCTURE WITH TRANSIENT STORAGE IN STREAMS DRAINING HARVESTED AND OLD-GROWTH WATERSHEDS

EPA Science Inventory

We compared measures of channel structure and riparian canopy with estimates of transient storage in 32 streams draining old-growth and harvested watersheds in the Southern Appalachian Mountains of North Carolina (n=4), the Ouachita Mountains of Arkansas (n=5), the Cascade Mounta...

[Research advances in macroinvertebrate ecology of the stream hyporheic zone].

PubMed

Zhang, Yue-Wei; Yuan, Xing-Zhong; Liu, Hong; Ren, Hai-Qing

2014-11-01

The stream hyporheic zone is an ecotone of surface water-ground water interactions, which is rich in biodiversity, and is an important component of stream ecosystem. The macroinvertebrates, which are at the top of food webs in the hyporheic zone to directly influence the matter and energy dynamics of the hyporheic zone, and are potential indicators of river ecological health to adjust the function of environment purification and ecological buffer. The macroinvertebrates in the hyporheic zone are divided into three categories: stygoxenes, stygophiles and stygobites. The key factors which influenced macroinvertebrates distribution in the hyporheic zone are physical size of interstitial spaces, interstitial current velocity, dissolved oxygen (DO), water temperature, available organic matter, hydraulic conductivity and hydraulic retention time. A suitable sampling method should be used for diverse research purposes in the special ecological interface. In the future, some necessary researches should focus on the life-history and life history strategy of the macroinvertebrates in the hyporheic zone, the quantitative analysis on the matter and energy dynamics in the ecological system of stream, the assessment systems of river ecological health based on the macroinvertebrates of the stream hyporheic zone, and the ecological significance of the hyporheic zone as a refuge for distribution and evolution of the macroinvertebrates.

Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification

USGS Publications Warehouse

Mulholland, P.J.; Hall, R.O.; Sobota, D.J.; Dodds, W.K.; Findlay, S.E.G.; Grimm, N. B.; Hamilton, S.K.; McDowell, W.H.; O'Brien, J. M.; Tank, J.L.; Ashkenas, L.R.; Cooper, L.W.; Dahm, Clifford N.; Gregory, S.V.; Johnson, S.L.; Meyer, J.L.; Peterson, B.J.; Poole, G.C.; Valett, H.M.; Webster, J.R.; Arango, C.P.; Beaulieu, J.J.; Bernot, M.J.; Burgin, A.J.; Crenshaw, C.L.; Helton, A.M.; Johnson, L.T.; Niederlehner, B.R.; Potter, J.D.; Sheibley, R.W.; Thomasn, S.M.

2009-01-01

We measured denitrification rates using a field 15N-NO- 3 tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (SWden) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N2 production rates far exceeded N2O production rates in all streams. The fraction of total NO-3 removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NHz 4 concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling SWden were specific discharge (discharge / width) and NO-3 concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (Uden) and NO- 3 concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although Uden increased with increasing NO- 3 concentration, the efficiency of NO-3 removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO-3 load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO-3 concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO-3 concentration. ?? 2009.

VOEventNet: An Open Source of Transient Alerts for Astronomers.

NASA Astrophysics Data System (ADS)

Drake, Andrew J.; Williams, R.; Graham, M. J.; Mahabal, A.; Djorgovski, S. G.; White, R. R.; Vestrand, W. T.; Bloom, J.

2007-12-01

Event based astronomy is acquiring an increasingly important role in astronomy as large time-domain surveys such as Palomar Transient Factory (PTF), Pan-STARRs, SkyMapper and Allan Telescope Array (ATA) surveys come online. These surveys are expected to discover thousands of transients each year ranging from near earth asteroids to distant SNe. Although the primary instruments for of these surveys are in place, in order to fully utilize these event discovery streams, automated alerting and follow-up is a necessity. For the past two years the VOEventNet network has been globally distributing information about transient astronomical events using the VOEvent format, a Virtual Observatory standard. Events messages are openly distributed so that follow-up can utilize the most appropriate resources available in order to characterize the nature of the transients. Since its inception VOEventNet has broadcast more than 3500 SDSSSS Supernova candidates, 3300 GRB alert and follow-up notices from GCN, 700 OGLE microlensing event candidates, and 4300 newly discovered asteroid and optical transient candidates from the Palomar Quest survey. Additional transient event streams are expected this season including optical transients from the Catalina Sky Survey. VOEventNet astronomical transient events streams are available to all astronomers via traditional HTML tables, RSS news-feeds, real-time publication (via Jabber and TCP), and Google Sky mashups. VOEventNet currently carries out optical transient event follow-up with the Palomar 60 and 200in (Caltech), Faulkes Telescopes North and South (LCOGTN), RAPTOR (LANL), and PARITEL (UCB; CfA).

Use of once-through treat gas to remove the heat of reaction in solvent hydrogenation processes

DOEpatents

Nizamoff, Alan J.

1980-01-01

In a coal liquefaction process wherein feed coal is contacted with molecular hydrogen and a hydrogen-donor solvent in a liquefaction zone to form coal liquids and vapors and coal liquids in the solvent boiling range are thereafter hydrogenated to produce recycle solvent and liquid products, the improvement which comprises separating the effluent from the liquefaction zone into a hot vapor stream and a liquid stream; cooling the entire hot vapor stream sufficiently to condense vaporized liquid hydrocarbons; separating condensed liquid hydrocarbons from the cooled vapor; fractionating the liquid stream to produce coal liquids in the solvent boiling range; dividing the cooled vapor into at least two streams; passing the cooling vapors from one of the streams, the coal liquids in the solvent boiling range, and makeup hydrogen to a solvent hydrogenation zone, catalytically hydrogenating the coal liquids in the solvent boiling range and quenching the hydrogenation zone with cooled vapors from the other cooled vapor stream.

Simulation of climate-change effects on streamflow, lake water budgets, and stream temperature using GSFLOW and SNTEMP, Trout Lake Watershed, Wisconsin

USGS Publications Warehouse

Hunt, Randall J.; Walker, John F.; Selbig, William R.; Westenbroek, Stephen M.; Regan, R. Steve

2013-01-01

Although groundwater and surface water are considered a single resource, historically hydrologic simulations have not accounted for feedback loops between the groundwater system and other hydrologic processes. These feedbacks include timing and rates of evapotranspiration, surface runoff, soil-zone flow, and interactions with the groundwater system. Simulations that iteratively couple the surface-water and groundwater systems, however, are characterized by long run times and calibration challenges. In this study, calibrated, uncoupled transient surface-water and steady-state groundwater models were used to construct one coupled transient groundwater/surface-water model for the Trout Lake Watershed in north-central Wisconsin, USA. The computer code GSFLOW (Ground-water/Surface-water FLOW) was used to simulate the coupled hydrologic system; a surface-water model represented hydrologic processes in the atmosphere, at land surface, and within the soil-zone, and a groundwater-flow model represented the unsaturated zone, saturated zone, stream, and lake budgets. The coupled GSFLOW model was calibrated by using heads, streamflows, lake levels, actual evapotranspiration rates, solar radiation, and snowpack measurements collected during water years 1998–2007; calibration was performed by using advanced features present in the PEST parameter estimation software suite. Simulated streamflows from the calibrated GSFLOW model and other basin characteristics were used as input to the one-dimensional SNTEMP (Stream-Network TEMPerature) model to simulate daily stream temperature in selected tributaries in the watershed. The temperature model was calibrated to high-resolution stream temperature time-series data measured in 2002. The calibrated GSFLOW and SNTEMP models were then used to simulate effects of potential climate change for the period extending to the year 2100. An ensemble of climate models and emission scenarios was evaluated. Downscaled climate drivers for the period 2010–2100 showed increases in maximum and minimum temperature over the scenario period. Scenarios of future precipitation did not show a monotonic trend like temperature. Uncertainty in the climate drivers increased over time for both temperature and precipitation. Separate calibration of the uncoupled groundwater and surface-water models did not provide a representative initial parameter set for coupled model calibration. A sequentially linked calibration, in which the uncoupled models were linked by means of utility software, provided a starting parameter set suitable for coupled model calibration. Even with sequentially linked calibration, however, transmissivity of the lower part of the aquifer required further adjustment during coupled model calibration to attain reasonable parameter values for evaporation rates off a small seepage lake (a lake with no appreciable surface-water outlets) with a long history of study. The resulting coupled model was well calibrated to most types of observed time-series data used for calibration. Daily stream temperatures measured during 2002 were successfully simulated with SNTEMP; the model fit was acceptable for a range of groundwater inflow rates into the streams. Forecasts of potential climate change scenarios showed growing season length increasing by weeks, and both potential and actual evapotranspiration rates increasing appreciably, in response to increasing air temperature. Simulated actual evapotranspiration rates increased less than simulated potential evapotranspiration rates as a result of water limitation in the root zone during the summer high-evapotranspiration period. The hydrologic-system response to climate change was characterized by a reduction in the importance of the snow-melt pulse and an increase in the importance of fall and winter groundwater recharge. The less dynamic hydrologic regime is likely to result in drier soil conditions in rainfed wetlands and uplands, in contrast to less drying in groundwater-fed systems. Seepage lakes showed larger forecast stage declines related to climate change than did drainage lakes (lakes with outlet streams). Seepage lakes higher in the watershed (nearer to groundwater divides) had less groundwater inflow and thus had larger forecast declines in lake stage; however, ground-water inflow to seepage lakes in general tended to increase as a fraction of the lake budgets with lake-stage decline because inward hydraulic gradients increased. Drainage lakes were characterized by less simulated stage decline as reductions in outlet streamflow of set losses to other water flows. Net groundwater inflow tended to decrease in drainage lakes over the scenario period. Simulated stream temperatures increased appreciably with climate change. The estimated increase in annual average temperature ranged from approximately 1 to 2 degrees Celsius by 2100 in the stream characterized by a high groundwater inflow rate and 2 to 3 degrees Celsius in the stream with a lower rate. The climate drivers used for the climate-change scenarios had appreciable variation between the General Circulation Model and emission scenario selected; this uncertainty was reflected in hydrologic flow and temperature model results. Thus, as with all forecasts of this type, the results are best considered to approximate potential outcomes of climate change.

The role of remediation, natural alkalinity sources and physical stream parameters in stream recovery.

PubMed

Kruse, Natalie A; DeRose, Lisa; Korenowsky, Rebekah; Bowman, Jennifer R; Lopez, Dina; Johnson, Kelly; Rankin, Edward

2013-10-15

Acid mine drainage (AMD) negatively impacts not only stream chemistry, but also aquatic biology. The ultimate goal of AMD treatment is restoration of the biological community, but that goal is rarely explicit in treatment system design. Hewett Fork in Raccoon Creek Watershed, Ohio, has been impacted by historic coal mining and has been treated with a calcium oxide doser in the headwaters of the watershed since 2004. All of the acidic inputs are isolated to a 1.5 km stretch of stream in the headwaters of the Hewett Fork watershed. The macroinvertebrate and fish communities have begun to recover and it is possible to distinguish three zones downstream of the doser: an impaired zone, a transition zone and a recovered zone. Alkalinity from both the doser and natural sources and physical stream parameters play a role in stream restoration. In Hewett Fork, natural alkaline additions downstream are higher than those from the doser. Both, alkaline additions and stream velocity drive sediment and metal deposition. Metal deposition occurs in several patterns; aluminum tends to deposit in regions of low stream velocity, while iron tends to deposit once sufficient alkalinity is added to the system downstream of mining inputs. The majority of metal deposition occurs upstream of the recovered zone. Both the physical stream parameters and natural alkalinity sources influence biological recovery in treated AMD streams and should be considered in remediation plans. Copyright © 2013 Elsevier Ltd. All rights reserved.

Pasture size effects on the ability of off-stream water or restricted stream access to alter the spatial/temporal distribution of grazing beef cows.

PubMed

Bisinger, J J; Russell, J R; Morrical, D G; Isenhart, T M

2014-08-01

For 2 grazing seasons, effects of pasture size, stream access, and off-stream water on cow distribution relative to a stream were evaluated in six 12.1-ha cool-season grass pastures. Two pasture sizes (small [4.0 ha] and large [12.1 ha]) with 3 management treatments (unrestricted stream access without off-stream water [U], unrestricted stream access with off-stream water [UW], and stream access restricted to a stabilized stream crossing [R]) were alternated between pasture sizes every 2 wk for 5 consecutive 4-wk intervals in each grazing season. Small and large pastures were stocked with 5 and 15 August-calving cows from mid May through mid October. At 10-min intervals, cow location was determined with Global Positioning System collars fitted on 2 to 3 cows in each pasture and identified when observed in the stream (0-10 m from the stream) or riparian (0-33 m from the stream) zones and ambient temperature was recorded with on-site weather stations. Over all intervals, cows were observed more (P ≤ 0.01) frequently in the stream and riparian zones of small than large pastures regardless of management treatment. Cows in R pastures had 24 and 8% less (P < 0.01) observations in the stream and riparian zones than U or UW pastures regardless of pasture size. Off-stream water had little effect on the presence of cows in or near pasture streams regardless of pasture size. In 2011, the probability of cow presence in the stream and riparian zones increased at greater (P < 0.04) rates as ambient temperature increased in U and UW pastures than in 2010. As ambient temperature increased, the probability of cow presence in the stream and riparian zones increased at greater (P < 0.01) rates in small than large pastures. Across pasture sizes, the probability of cow presence in the stream and riparian zone increased less (P < 0.01) with increasing ambient temperatures in R than U and UW pastures. Rates of increase in the probability of cow presence in shade (within 10 m of tree drip lines) in the total pasture with increasing temperatures did not differ between treatments. However, probability of cow presence in riparian shade increased at greater (P < 0.01) rates in small than large pastures. Pasture size was a major factor affecting congregation of cows in or near pasture streams with unrestricted access.

Transient Go: A Mobile App for Transient Astronomy Outreach

NASA Astrophysics Data System (ADS)

Crichton, D.; Mahabal, A.; Djorgovski, S. G.; Drake, A.; Early, J.; Ivezic, Z.; Jacoby, S.; Kanbur, S.

2016-12-01

Augmented Reality (AR) is set to revolutionize human interaction with the real world as demonstrated by the phenomenal success of `Pokemon Go'. That very technology can be used to rekindle the interest in science at the school level. We are in the process of developing a prototype app based on sky maps that will use AR to introduce different classes of astronomical transients to students as they are discovered i.e. in real-time. This will involve transient streams from surveys such as the Catalina Real-time Transient Survey (CRTS) today and the Large Synoptic Survey Telescope (LSST) in the near future. The transient streams will be combined with archival and latest image cut-outs and other auxiliary data as well as historical and statistical perspectives on each of the transient types being served. Such an app could easily be adapted to work with various NASA missions and NSF projects to enrich the student experience.

Modeling the Impact of Stream Discharge Events on Riparian Solute Dynamics.

PubMed

Mahmood, Muhammad Nasir; Schmidt, Christian; Fleckenstein, Jan H; Trauth, Nico

2018-03-22

The biogeochemical composition of stream water and the surrounding riparian water is mainly defined by the exchange of water and solutes between the stream and the riparian zone. Short-term fluctuations in near stream hydraulic head gradients (e.g., during stream flow events) can significantly influence the extent and rate of exchange processes. In this study, we simulate exchanges between streams and their riparian zone driven by stream stage fluctuations during single stream discharge events of varying peak height and duration. Simulated results show that strong stream flow events can trigger solute mobilization in riparian soils and subsequent export to the stream. The timing and amount of solute export is linked to the shape of the discharge event. Higher peaks and increased durations significantly enhance solute export, however, peak height is found to be the dominant control for overall mass export. Mobilized solutes are transported to the stream in two stages (1) by return flow of stream water that was stored in the riparian zone during the event and (2) by vertical movement to the groundwater under gravity drainage from the unsaturated parts of the riparian zone, which lasts for significantly longer time (> 400 days) resulting in long tailing of bank outflows and solute mass outfluxes. We conclude that strong stream discharge events can mobilize and transport solutes from near stream riparian soils into the stream. The impact of short-term stream discharge variations on solute exchange may last for long times after the flow event. © 2018, National Ground Water Association.

Geomorphic controls on hyporheic exchange flow in mountain streams.

Treesearch

T. Kasahara; S.M. Wondzell

2003-01-01

Hyporheic exchange flows were simulated using MODFLOW and MODPATH to estimate relative effects of channel morphologic features on the extent of the hyporheic zone, on hyporheic exchange flow, and on the residence time of stream water in the hyporheic zone. Four stream reaches were compared in order to examine the influence of stream size and channel constraint. Within...

Acute toxicity of an acid mine drainage mixing zone to juvenile bluegill and largemouth bass

USGS Publications Warehouse

Henry, T.B.; Irwin, E.R.; Grizzle, J.M.; Wildhaber, M.L.; Brumbaugh, W.G.

1999-01-01

The toxicity of an acid mixing zone produced at the confluence of a stream that was contaminated by acid mine drainage (AMD) and a pH-neutral stream was investigated in toxicity tests with juvenile bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides. Fish mortalities in instream cages located in the mixing zone, below the mixing zone, and upstream in both tributaries were compared to determine relative toxicity at each site. In all tests and for both species, significantly higher mortality was observed in the mixing zone than at any other location, including the acid stream, which had lower pH (2.9-4.3). The mixing zone was defined chemically by rapid precipitation of dissolved aluminum and iron, which arrived from the low-pH stream, and by the presence of white precipitates, which were attached to the substratum and which extended below the confluence. Possible seasonal changes in mixing zone toxicity were investigated by conducting field tests with bluegill in June, July, and August 1996 and in January 1997 and by conducting field tests with largemouth bass in April and May 1997. Toxicity was not significantly different at the extremes of temperature, pH, and metal concentration that occurred in June and July, as compared with January. Toxicity was significantly lower in August; however, elevated stream discharge during the August test may have disturbed mixing zone characteristics. High toxicity in AMD mixing zones may lower the survival of fishes in streams, reduce available habitat, and impede movements of migratory fish.

Method 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

A method for converting hydrocarbon fuel into hydrogen gas and carbon dioxide within a reformer 10 is disclosed. According to the method, a stream including an oxygen-containing gas is directed adjacent to a first vessel 18 and the oxygen-containing gas is heated. A stream including unburned fuel is introduced into the oxygen-containing gas stream to form a mixture including oxygen-containing gas and fuel. The mixture of oxygen-containing gas and unburned fuel is directed tangentially into a partial oxidation reaction zone 24 within the first vessel 18. The mixture of oxygen-containing gas and fuel is further directed through the partial oxidation reaction zone 24 to produce a heated reformate stream including hydrogen gas and carbon monoxide. Steam may also be mixed with the oxygen-containing gas and fuel, and the reformate stream from the partial oxidation reaction zone 24 directed into a steam reforming zone 26. High- and low-temperature shift reaction zones 64,76 may be employed for further fuel processing.

Hydrology and Nitrogen Biogeochemistry in the Hyporheic Zone of a Geomorphically Degraded Urban Stream

EPA Science Inventory

Few studies have investigated the relationship between hydrology and nitrogen biogeochemistry in hyporheic zones of degraded urban streams despite significant national efforts to restore such streams. We examined relationships between hydrology and biogeochemistry in Minebank Ru...

Evaluation of the fate and transport of chlorinated ethenes in a complex groundwater system discharging to a stream in Wonju, Korea

NASA Astrophysics Data System (ADS)

Lee, Seong-Sun; Kaown, Dugin; Lee, Kang-Kun

2015-11-01

Chlorinated ethenes such as trichloroethylene (TCE) are common and persistent groundwater contaminants. If contaminated groundwater discharges to a stream, then stream water pollution near the contamination site also becomes a problem. In this respect, the fate and transport of chlorinated ethenes around a stream in an industrial complex were evaluated using the concentration of each component, and hydrogeochemical, microbial, and compound-specific carbon isotope data. Temporal and spatial monitoring reveal that a TCE plume originating from main and local source zones continues to be discharged to a stream. Groundwater geochemical data indicate that aerobic conditions prevail in the upgradient area of the studied aquifer, whereas conditions become anaerobic in the downgradient. The TCE molar fraction is high at the main and local source zones, ranging from 87.4 to 99.2% of the total volatile organic compounds (VOCs). An increasing trend in the molar fraction of cis-1, 2-Dichloroethene (cis-DCE) and vinyl chloride (VC) was observed in the downgradient zone of the study area. The enriched δ13C values of TCE and depleted values of cis-DCE in the stream zone, compared to those of the source zone, also suggest biodegradation of VOCs. Microbial community structures in monitoring wells adjacent to the stream zone in the downgradient area were analyzed using 16S rRNA gene-based pyrosequencing to identify the microorganisms responsible for biodegradation. This was attributed to the high relative abundance of dechlorinating bacteria in monitoring wells under anaerobic conditions farthest from the stream in the downgradient area. The multilateral approaches adopted in this study, combining hydrogeochemical and biomolecular methods with compound-specific analyses, indicate that contaminants around the stream were naturally attenuated by active anaerobic biotransformation processes.

Denitrification in Agriculturally Impacted Streams: Seasonal Changes in Structure and Function of the Bacterial Community

PubMed Central

Manis, Erin; Royer, Todd V.; Johnson, Laura T.; Leff, Laura G.

2014-01-01

Denitrifiers remove fixed nitrogen from aquatic environments and hydrologic conditions are one potential driver of denitrification rate and denitrifier community composition. In this study, two agriculturally impacted streams in the Sugar Creek watershed in Indiana, USA with different hydrologic regimes were examined; one stream is seasonally ephemeral because of its source (tile drainage), whereas the other stream has permanent flow. Additionally, a simulated flooding experiment was performed on the riparian benches of the ephemeral stream during a dry period. Denitrification activity was assayed using the chloramphenicol amended acetylene block method and bacterial communities were examined based on quantitative PCR and terminal restriction length polymorphisms of the nitrous oxide reductase (nosZ) and 16S rRNA genes. In the stream channel, hydrology had a substantial impact on denitrification rates, likely by significantly lowering water potential in sediments. Clear patterns in denitrification rates were observed among pre-drying, dry, and post-drying dates; however, a less clear scenario was apparent when analyzing bacterial community structure suggesting that denitrifier community structure and denitrification rate were not strongly coupled. This implies that the nature of the response to short-term hydrologic changes was physiological rather than increases in abundance of denitrifiers or changes in composition of the denitrifier community. Flooding of riparian bench soils had a short-term, transient effect on denitrification rate. Our results imply that brief flooding of riparian zones is unlikely to contribute substantially to removal of nitrate (NO3 -) and that seasonal drying of stream channels has a negative impact on NO3 - removal, particularly because of the time lag required for denitrification to rebound. This time lag is presumably attributable to the time required for the denitrifiers to respond physiologically rather than a change in abundance or community composition. PMID:25171209

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.

Dicamptodon tenebrosus larvae within hyporheic zones of intermittent streams in California

Treesearch

David Feral; Michael A. Camann; Hartwell H. Welsh Jr.

2005-01-01

Lotic ecosystems are increasingly viewed as having three interactive spatial compartments, i.e., channel sediments, the hyporheic zone, and flood plains or riparian areas (Cummins et al. 1983; Ward 1989). The hyporheic zone is the sub-benthic habitat of interstitial spaces between substrate particles in the stream bed, and is the transition zone between surface flow...

Identifying spatial variability of groundwater discharge in a wetland stream using a distributed temperature sensor

USGS Publications Warehouse

Lowry, Christopher S.; Walker, John F.; Hunt, Randall J.; Anderson, Mary P.

2007-01-01

Discrete zones of groundwater discharge in a stream within a peat‐dominated wetland were identified on the basis of variations in streambed temperature using a distributed temperature sensor (DTS). The DTS gives measurements of the spatial (±1 m) and temporal (15 min) variation of streambed temperature over a much larger reach of stream (>800 m) than previous methods. Isolated temperature anomalies observed along the stream correspond to focused groundwater discharge zones likely caused by soil pipes within the peat. The DTS also recorded variations in the number of temperature anomalies, where higher numbers correlated well with a gaining reach identified by stream gauging. Focused zones of groundwater discharge showed essentially no change in position over successive measurement periods. Results suggest DTS measurements will complement other techniques (e.g., seepage meters and stream gauging) and help further improve our understanding of groundwater–surface water dynamics in wetland streams.

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.

High rates of organic carbon processing in the hyporheic zone of intermittent streams.

PubMed

Burrows, Ryan M; Rutlidge, Helen; Bond, Nick R; Eberhard, Stefan M; Auhl, Alexandra; Andersen, Martin S; Valdez, Dominic G; Kennard, Mark J

2017-10-16

Organic carbon cycling is a fundamental process that underpins energy transfer through the biosphere. However, little is known about the rates of particulate organic carbon processing in the hyporheic zone of intermittent streams, which is often the only wetted environment remaining when surface flows cease. We used leaf litter and cotton decomposition assays, as well as rates of microbial respiration, to quantify rates of organic carbon processing in surface and hyporheic environments of intermittent and perennial streams under a range of substrate saturation conditions. Leaf litter processing was 48% greater, and cotton processing 124% greater, in the hyporheic zone compared to surface environments when calculated over multiple substrate saturation conditions. Processing was also greater in more saturated surface environments (i.e. pools). Further, rates of microbial respiration on incubated substrates in the hyporheic zone were similar to, or greater than, rates in surface environments. Our results highlight that intermittent streams are important locations for particulate organic carbon processing and that the hyporheic zone sustains this fundamental process even without surface flow. Not accounting for carbon processing in the hyporheic zone of intermittent streams may lead to an underestimation of its local ecological significance and collective contribution to landscape carbon processes.

Influence of riparian seepage zones on nitrate variability in two agricultural headwater streams

USDA-ARS?s Scientific Manuscript database

Riparian seepage zones are one of the primary pathways of groundwater transport to headwater streams. While seeps have been recognized for their contributions to streamflow, there is little information on how seeps affect stream water quality. The objective of this study was to examine the influence...

Impacts of different rainfall patterns on hyporheic zone under transient conditions

NASA Astrophysics Data System (ADS)

Liu, Suning; Chui, Ting Fong May

2018-06-01

The hyporheic zone (HZ) plays an important role in stream ecology. Previous studies have mainly focused on the factors influencing the HZ in the steady state. However, the exchange between surface water and groundwater in the HZ can become transient during a storm. This study investigates the impacts of different rainfall patterns (varying in intensity and duration) on the HZ under transient conditions. A two-dimensional numerical model of a 10-m long and 2-m deep domain is developed, in which the streambed consists of a series of dunes. Brinkman-Darcy and Navier-Stokes equations are respectively solved for groundwater and surface water, and velocity and pressure are coupled at the interface (i.e., the streambed surface). To compare the results under different transient conditions, this study proposes two indicators, i.e., the influential time (IT, the time required for the HZ to return to its initial state once it starts to change) and the influential depth (ID, the maximum increment in the HZ depth). To detect the extent to which the HZ undergoes significant spatial changes, moving split-window and inflection point tests are conducted. The results indicate that rainfall intensity (RI) and rainfall duration (RD) both display logarithmic relationships with the IT and ID with high coefficients of determination, but only between certain lower and upper thresholds of the RI and RD. Moreover, the distributions of the IT and ID as a function of the RI and RD are mapped using the surface spline and kriging interpolation methods to facilitate future prediction of the IT and ID. In addition, it is observed that the IT has a linear negative correlation with the groundwater response while the ID is not affected by different groundwater responses. All of the derived relationships can be used to predict the impacts of a future rainfall event on the HZ.

Nitrate retention in riparian ground water at natural and elevated nitrate levels in North Central Minnesota

USGS Publications Warehouse

Duff, J.H.; Jackman, A.P.; Triska, F.J.; Sheibley, R.W.; Avanzino, R.J.

2007-01-01

The relationship between local ground water flows and NO3- transport to the channel was examined in three well transects from a natural, wooded riparian zone adjacent to the Shingobee River, MN. The hillslope ground water originated as recharge from intermittently grazed pasture up slope of the site. In the hillslope transect perpendicular to the stream, ground water NO3- concentrations decreased from ???3 mg N L-1 beneath the ridge (80 m from the channel) to 0.01 to 1.0 mg N L-1 at wells 1 to 3 m from the channel. The Cl- concentrations and NO3/Cl ratios decreased toward the channel indicating NO3- dilution and biotic retention. In the bankside well transect parallel to the stream, two distinct ground water environments were observed: an alluvial environment upstream of a relict beaver dam influenced by stream water and a hillslope environment downstream of the relict beaver dam. Nitrate was elevated to levels representative of agricultural runoff in a third well transect looted ???5 m from the stream to assess the effectiveness of the riparian zone as a NO3- sink. Subsurface NO3- injections revealed transport of up to 15 mg N L-1 was nearly conservative in the alluvial riparian environment. Addition of glucose stimulated dissolved oxygen uptake and promoted NO3- retention under both background and elevated NO 3- levels in summer and winter. Disappearance of added NO3- was followed by transient NO2- formation and, in the presence of C2H2, by N2O formation, demonstrating potential denitrification. Under current land use, most NO3- associated with local ground water is biotically retained or diluted before reaching the channel. However, elevating NO 3- levels through agricultural cultivation would likely result in increased NO3- transport to the channel. ?? ASA, CSSA, SSSA.

Incompletely Mixed Surface Transient Storage Zones at River Restoration Structures: Modeling Implications

NASA Astrophysics Data System (ADS)

Endreny, T. A.; Robinson, J.

2012-12-01

River restoration structures, also known as river steering deflectors, are designed to reduce bank shear stress by generating wake zones between the bank and the constricted conveyance region. There is interest in characterizing the surface transient storage (STS) and associated biogeochemical processing in the STS zones around these structures to quantify the ecosystem benefits of river restoration. This research explored how the hydraulics around river restoration structures prohibits application of transient storage models designed for homogenous, completely mixed STS zones. We used slug and constant rate injections of a conservative tracer in a 3rd order river in Onondaga County, NY over the course of five experiments at varying flow regimes. Recovered breakthrough curves spanned a transect including the main channel and wake zone at a j-hook restoration structure. We noted divergent patterns of peak solute concentration and times within the wake zone regardless of transect location within the structure. Analysis reveals an inhomogeneous STS zone which is frequently still loading tracer after the main channel has peaked. The breakthrough curve loading patterns at the restoration structure violated the assumptions of simplified "random walk" 2 zone transient storage models which seek to identify representative STS zones and zone locations. Use of structure-scale Weiner filter based multi-rate mass transfer models to characterize STS zones residence times are similarly dependent on a representative zone location. Each 2 zone model assumes 1 zone is a completely mixed STS zone and the other a completely mixed main channel. Our research reveals limits to simple application of the recently developed 2 zone models, and raises important questions about the measurement scale necessary to identify critical STS properties at restoration sites. An explanation for the incompletely mixed STS zone may be the distinct hydraulics at restoration sites, including a constrained high velocity conveyance region closely abutting a wake zone that receives periodic disruption from the upstream structure shearing vortices.igure 1. River restoration j-hook with blue dye revealing main channel and edge of wake zone with multiple surface transient storage zones.

Removal of Woody Riparian Vegetation Substantially Altered a Stream Ecosystem in an Otherwise Undisturbed Grassland Watershed

DOE PAGES

Larson, Danelle M.; Dodds, Walter K.; Veach, Allison M.

2018-04-23

Riparian zones are key interfaces between stream and terrestrial ecosystems. Yet, we know of no whole-watershed experiments that cut only woody vegetation in the riparian zone in an otherwise intact watershed to isolate the role of riparian zones on stream ecology. We removed all of the woody riparian vegetation (from 10- and 30-m-wide buffers in headwaters and main channels, respectively) for 5 km of stream in a single watershed while leaving the remainder of the grassland watershed un-impacted. We assessed water chemistry changes 3 years before and 3 years after riparian wood removal and in two neighboring control watersheds withmore » a before–after, control-impact design and analysis. Riparian woody removal caused 10–100-fold increases in mean stream water nitrate concentrations and pulses of high nitrate for 3 years thereafter. Other nutrients and total suspended solids increased 2–25 times for the 3 years of post-removal. In-stream rates of gross primary production, ecosystem respiration, and net ecosystem production had large treatment effect sizes but also high variance among samples. Past studies of whole-watershed deforestations showed similar water quality responses to our riparian deforestation. Riparian zones of grassland streams are sensitive to disturbance and likely impart relatively greater influence on stream structure and function than the upslope of the watershed. Finally, our results further emphasize the role of riparian zones in biogeochemically linking aquatic and terrestrial habitats.« less

Removal of Woody Riparian Vegetation Substantially Altered a Stream Ecosystem in an Otherwise Undisturbed Grassland Watershed

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

Larson, Danelle M.; Dodds, Walter K.; Veach, Allison M.

Riparian zones are key interfaces between stream and terrestrial ecosystems. Yet, we know of no whole-watershed experiments that cut only woody vegetation in the riparian zone in an otherwise intact watershed to isolate the role of riparian zones on stream ecology. We removed all of the woody riparian vegetation (from 10- and 30-m-wide buffers in headwaters and main channels, respectively) for 5 km of stream in a single watershed while leaving the remainder of the grassland watershed un-impacted. We assessed water chemistry changes 3 years before and 3 years after riparian wood removal and in two neighboring control watersheds withmore » a before–after, control-impact design and analysis. Riparian woody removal caused 10–100-fold increases in mean stream water nitrate concentrations and pulses of high nitrate for 3 years thereafter. Other nutrients and total suspended solids increased 2–25 times for the 3 years of post-removal. In-stream rates of gross primary production, ecosystem respiration, and net ecosystem production had large treatment effect sizes but also high variance among samples. Past studies of whole-watershed deforestations showed similar water quality responses to our riparian deforestation. Riparian zones of grassland streams are sensitive to disturbance and likely impart relatively greater influence on stream structure and function than the upslope of the watershed. Finally, our results further emphasize the role of riparian zones in biogeochemically linking aquatic and terrestrial habitats.« less

Hyporheic zone denitrification: controls on effective reaction depth and contribution to whole-stream mass balance

USGS Publications Warehouse

Harvey, Judson W.; Böhlke, John Karl; Voytek, Mary A.; Scott, Durelle; Tobias, Craig R.

2013-01-01

Stream denitrification is thought to be enhanced by hyporheic transport but there is little direct evidence from the field. To demonstrate at a field site, we injected 15NO3−, Br (conservative tracer), and SF6 (gas exchange tracer) and compared measured whole-stream denitrification with in situ hyporheic denitrification in shallow and deeper flow paths of contrasting geomorphic units. Hyporheic denitrification accounted for between 1 and 200% of whole-stream denitrification. The reaction rate constant was positively related to hyporheic exchange rate (greater substrate delivery), concentrations of substrates DOC and nitrate, microbial denitrifier abundance (nirS), and measures of granular surface area and presence of anoxic microzones. The dimensionless product of the reaction rate constant and hyporheic residence time, λhzτhz define a Damköhler number, Daden-hz that was optimal in the subset of hyporheic flow paths where Daden-hz ≈ 1. Optimal conditions exclude inefficient deep pathways transport where substrates are used up and also exclude inefficient shallow pathways that require repeated hyporheic entries and exits to complete the reaction. The whole-stream reaction significance, Rs (dimensionless), was quantified by multiplying Daden-hz by the proportion of stream discharge passing through the hyporheic zone. Together these two dimensionless metrics, one flow-path scale and the other reach-scale, quantify the whole-stream significance of hyporheic denitrification. One consequence is that the effective zone of significant denitrification often differs from the full depth of the hyporheic zone, which is one reason why whole-stream denitrification rates have not previously been explained based on total hyporheic-zone metrics such as hyporheic-zone size or residence time.

Influence of Gully Erosion Control on Amphibian and Reptile Communities within Riparian Zones of Channelized Streams

USDA-ARS?s Scientific Manuscript database

Riparian zones of streams in northwestern Mississippi have been impacted by agriculture, channelization, channel incision, and gully erosion. Riparian gully formation has resulted in the fragmentation of remnant riparian zones within agricultural watersheds. One widely used conservation practice for...

Mercury and methylmercury dynamics in the hyporheic zone of an Oregon stream

USGS Publications Warehouse

Hinkle, Stephen R.; Bencala, Kenneth E.; Wentz, Dennis A.; Krabbenhoft, David P.

2014-01-01

The role of the hyporheic zone in mercury (Hg) cycling has received limited attention despite the biogeochemically active nature of this zone and, thus, its potential to influence Hg behavior in streams. An assessment of Hg geochemistry in the hyporheic zone of a coarse-grained island in the Coast Fork Willamette River in Oregon, USA, illustrates the spatially dynamic nature of this region of the stream channel for Hg mobilization and attenuation. Hyporheic flow through the island was evident from the water-table geometry and supported by hyporheic-zone chemistry distinct from that of the bounding groundwater system. Redox-indicator species changed abruptly along a transect through the hyporheic zone, indicating a biogeochemically reactive stream/hyporheic-zone continuum. Dissolved organic carbon (DOC), total Hg, and methylmercury (MeHg) concentrations increased in the upgradient portion of the hyporheic zone and decreased in the downgradient region. Total Hg (collected in 2002 and 2003) and MeHg (collected in 2003) were correlated with DOC in hyporheic-zone samples: r2=0.63 (total Hg-DOC, 2002), 0.73 (total Hg-DOC, 2003), and 0.94 (MeHg-DOC, 2003). Weaker Hg/DOC association in late summer 2002 than in early summer 2003 may reflect seasonal differences in DOC reactivity. Observed correlations between DOC and both total Hg and MeHg reflect the importance of DOC for Hg mobilization, transport, and fate in this hyporheic zone. Correlations with DOC provide a framework for conceptualizing and quantifying Hg and MeHg dynamics in this region of the stream channel, and provide a refined conceptual model of the role hyporheic zones may play in aquatic ecosystems.

Water quality modeling based on landscape analysis: Importance of riparian hydrology

Treesearch

Thomas Grabs

2010-01-01

Several studies in high-latitude catchments have demonstrated the importance of near-stream riparian zones as hydrogeochemical hotspots with a substantial influence on stream chemistry. An adequate representation of the spatial variability of riparian-zone processes and characteristics is the key for modeling spatiotemporal variations of stream-water quality. This...

COMPARTMENTAL MODEL OF NITRATE RETENTION IN STREAMS

EPA Science Inventory

A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first order reaction terms to represent nitrate uptake in the free stream, and denitrifica...

KCa3.1 Modulates Neuroblast Migration Along the Rostral Migratory Stream (RMS) In Vivo

PubMed Central

Turner, Kathryn L.; Sontheimer, Harald

2014-01-01

From the subventricular zone (SVZ), neuronal precursor cells (NPCs), called neuroblasts, migrate through the rostral migratory stream (RMS) to become interneurons in the olfactory bulb (OB). Ion channels regulate neuronal migration during development, yet their role in migration through the adult RMS is unknown. To address this question, we utilized Nestin-CreERT2/R26R-YFP mice to fluorescently label neuroblasts in the adult. Patch-clamp recordings from neuroblasts reveal K+ currents that are sensitive to intracellular Ca2+ levels and blocked by clotrimazole and TRAM-34, inhibitors of intermediate conductance Ca2+-activated K+ (KCa3.1) channels. Immunolabeling and electrophysiology show KCa3.1 expression restricted to neuroblasts in the SVZ and RMS, but absent in OB neurons. Time-lapse confocal microscopy in situ showed inhibiting KCa3.1 prolonged the stationary phase of neuroblasts' saltatory migration, reducing migration speed by over 50%. Both migration and KCa3.1 currents could also be inhibited by blocking Ca2+ influx via transient receptor potential (TRP) channels, which, together with positive immunostaining for transient receptor potential canonical 1 (TRPC1), suggest that TRP channels are an important Ca2+ source modulating KCa3.1 activity. Finally, injecting TRAM-34 into Nestin-CreERT2/R26R-YFP mice significantly reduced the number of neuroblasts that reached the OB, suggesting an important role for KCa3.1 in vivo. These studies describe a previously unrecognized protein in migration of adult NPCs. PMID:23585521

Functional Process Zones Characterizing Aquatic Insect Communities in Streams of the Brazilian Cerrado.

PubMed

Godoy, B S; Simião-Ferreira, J; Lodi, S; Oliveira, L G

2016-04-01

Stream ecology studies see to understand ecological dynamics in lotic systems. The characterization of streams into Functional Process Zones (FPZ) has been currently debated in stream ecology because aquatic communities respond to functional processes of river segments. Therefore, we tested if different functional process zones have different number of genera and trophic structure using the aquatic insect community of Neotropical streams. We also assessed whether using physical and chemical variables may complement the approach of using FPZ to model communities of aquatic insects in Cerrado streams. This study was conducted in 101 streams or rivers from the central region of the state of Goiás, Brazil. We grouped the streams into six FPZ associated to size of the river system, presence of riparian forest, and riverbed heterogeneity. We used Bayesian models to compare number of genera and relative frequency of the feeding groups between FPZs. Streams classified in different FPZs had a different number of genera, and the largest and best preserved rivers had an average of four additional genera. Trophic structure exhibited low variability among FPZs, with little difference both in the number of genera and in abundance. Using functional process zones in Cerrado streams yielded good results for Ephemeroptera, Plecoptera, and Trichoptera communities. Thus, species distribution and community structure in the river basin account for functional processes and not necessarily for the position of the community along a longitudinal dimension of the lotic system.

Evaluation of the fate and transport of chlorinated ethenes in a complex groundwater system discharging to a stream in Wonju, Korea.

PubMed

Lee, Seong-Sun; Kaown, Dugin; Lee, Kang-Kun

2015-11-01

Chlorinated ethenes such as trichloroethylene (TCE) are common and persistent groundwater contaminants. If contaminated groundwater discharges to a stream, then stream water pollution near the contamination site also becomes a problem. In this respect, the fate and transport of chlorinated ethenes around a stream in an industrial complex were evaluated using the concentration of each component, and hydrogeochemical, microbial, and compound-specific carbon isotope data. Temporal and spatial monitoring reveal that a TCE plume originating from main and local source zones continues to be discharged to a stream. Groundwater geochemical data indicate that aerobic conditions prevail in the upgradient area of the studied aquifer, whereas conditions become anaerobic in the downgradient. The TCE molar fraction is high at the main and local source zones, ranging from 87.4 to 99.2% of the total volatile organic compounds (VOCs). An increasing trend in the molar fraction of cis-1, 2-Dichloroethene (cis-DCE) and vinyl chloride (VC) was observed in the downgradient zone of the study area. The enriched δ(13)C values of TCE and depleted values of cis-DCE in the stream zone, compared to those of the source zone, also suggest biodegradation of VOCs. Microbial community structures in monitoring wells adjacent to the stream zone in the downgradient area were analyzed using 16S rRNA gene-based pyrosequencing to identify the microorganisms responsible for biodegradation. This was attributed to the high relative abundance of dechlorinating bacteria in monitoring wells under anaerobic conditions farthest from the stream in the downgradient area. The multilateral approaches adopted in this study, combining hydrogeochemical and biomolecular methods with compound-specific analyses, indicate that contaminants around the stream were naturally attenuated by active anaerobic biotransformation processes. Copyright © 2015 Elsevier B.V. All rights reserved.

Simple measures of channel habitat complexity predict transient hydraulic storage in streams

EPA Science Inventory

Stream thalweg depth profiles (along path of greatest channel depth) and woody debris tallies have recently become components of routine field procedures for quantifying physical habitat in national stream monitoring efforts. Mean residual depth, standard deviation of thalweg dep...

Influence of gully erosion control on amphibian and reptile communities within riparian zones of channelized streams

USDA-ARS?s Scientific Manuscript database

Riparian zones of streams in northern Mississippi have been impacted by agriculture, channelization, channel incision, and gully erosion. Gully erosion is the most severe form of erosion and has resulted in the fragmentation of remnant riparian zones within agricultural watersheds. One widely used c...

Calculating terrain indices along streams: A new method for separating stream sides

Treesearch

T. J. Grabs; K. G. Jencso; B. L. McGlynn; J. Seibert

2010-01-01

There is increasing interest in assessing riparian zones and their hydrological and biogeochemical buffering capacity with indices derived from hydrologic landscape analysis of digital elevation data. Upslope contributing area is a common surrogate for lateral water flows and can be used to assess the variability of local water inflows to riparian zones and streams....

Method of extracting iodine from liquid mixtures of iodine, water and hydrogen iodide

DOEpatents

Mysels, Karol J.

1979-01-01

The components of a liquid mixture consisting essentially of HI, water and at least about 50 w/o iodine are separated in a countercurrent extraction zone by treating with phosphoric acid containing at least about 90 w/o H.sub.3 PO.sub.4. The bottom stream from the extraction zone is substantially completely molten iodine, and the overhead stream contains water, HI, H.sub.3 PO.sub.4 and a small fraction of the amount of original iodine. When the water and HI are present in near-azeotropic proportions, there is particular advantage in feeding the overhead stream to an extractive distillation zone wherein it is treated with additional concentrated phosphoric acid to create an anhydrous HI vapor stream and bottoms which contain at least about 85 w/o H.sub.3 PO.sub.4. Concentration of these bottoms provides phosphoric acid infeed for both the countercurrent extraction zone and for the extractive distillation zone.

How does rapidly changing discharge during storm events affect transient storage and channel water balance in a headwater mountain stream?

Treesearch

Adam S. Ward; Michael N. Gooseff; Thomas J. Voltz; Michael Fitzgerald; Kamini Singha; Jay P. Zarnetske

2013-01-01

Measurements of transient storage in coupled surface-water and groundwater systems are widely made during base flow periods and rarely made during storm flow periods. We completed 24 sets of slug injections in three contiguous study reaches during a 1.25 year return interval storm event (discharge ranging from 21.5 to 434 L s1 ) in a net gaining headwater stream within...

Reactive solute transport in acidic streams

USGS Publications Warehouse

Broshears, R.E.

1996-01-01

Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

Comparing Models and Methods for the Delineation of Stream Baseflow Contribution Areas

NASA Astrophysics Data System (ADS)

Chow, R.; Frind, M.; Frind, E. O.; Jones, J. P.; Sousa, M.; Rudolph, D. L.; Nowak, W.

2016-12-01

This study addresses the delineation of areas that contribute baseflow to a stream reach, also known as stream capture zones. Such areas can be delineated using standard well capture zone delineation methods, with three important differences: (1) natural gradients are smaller compared to those produced by supply wells and are therefore subject to greater numerical errors, (2) stream discharge varies seasonally, and (3) stream discharge varies spatially. This study focuses on model-related uncertainties due to parameter non-uniqueness, discretization schemes, and particle tracking algorithms. The methodology is applied to the Alder Creek watershed in southwestern Ontario. Four different model codes are compared: HydroGeoSphere, WATFLOW, MODFLOW, and FEFLOW. In addition, two delineation methods are compared: reverse particle tracking and reverse transport, where the latter considers local-scale parameter uncertainty by using a macrodispersion term to produce a capture probability plume. The results from this study indicate that different models can calibrate acceptably well to the same data and produce very similar distributions of hydraulic head, but can produce different capture zones. The stream capture zone is found to be highly sensitive to the particle tracking algorithm. It was also found that particle tracking by itself, if applied to complex systems such as the Alder Creek watershed, would require considerable subjective judgement in the delineation of stream capture zones. Reverse transport is an alternate approach that provides probability intervals for the baseflow contribution areas. In situations where the two approaches agree, the confidence in the delineation is reinforced.

Riparian zone hydrology and biogeochemistry as a function of stream evolution stage in glaciated landscapes of the US Northeast

NASA Astrophysics Data System (ADS)

Rook, S. P.; Vidon, P.; Walter, M. T.

2011-12-01

The management of riparian buffer strips is often regarded as one of the most economical and sustainable methods of managing non-point source pollution and water quality. However, current riparian management often follows a 'one size fits all' design, which fails to recognize the complexity of the many biogeochemical processes that regulate pollutant transformation and retention in these systems. This study addresses two critical gaps in knowledge: (1) How carbon, nitrogen, phosphorous, and iron cycles interact with one another (rather than individually). (2) How stream channel geometry and evolution regulate these nutrient cycles and greenhouse gas (GHG) dynamics in the near stream zone. This project specifically explores the hydrological and biogeochemical functioning of riparian zones across a gradient of stream meander evolution stages, with the primary goal of understanding and predicting potential interactions between nutrient dynamics in these systems. Key research questions include: (1) How does stream meander curvature affect riparian zone hydrology? (2) How does stream meander curvature influence riparian zone biogeochemistry? (3) What relationships exist among N, P, Fe, and GHG dynamics? We instrumented three riparian sites near Ithaca, NY, with a dense network of wells, piezometers, and static chambers. These sites represent three riparian zones along three evolution stages of stream meanders: an inner meander, a straight stream section, and an outer bend of the stream with an oxbow lake formation. In spring through fall 2011, water samples and gas samples were collected at a tri-weekly bases at each of the three sites. Water samples were analyzed for oxidation-reduction potential, dissolved oxygen, temperature, FeII/FeIII, nutrients (NO3-, NH4+, PO43-) and dissolved organic carbon (DOC). GHG fluxes at the soil-atmosphere interface were measured for N2O, CO2, and CH4 gases. We predict that stream curvature will significantly affect groundwater flow direction in the riparian zones. Owing to more prolonged saturation, we expect that the oxbow setting will exhibit anoxic conditions, and associated biogeochemistry. Finally, we hypothesize clear relationships among N, P, Fe, and GHG dynamics. In areas of significant denitrification, we expect to see an increase in Fe reduction, PO43- release, N2O emission, and CH4 emission, and a decrease in CO2 emission. Quantifying these interactions will enhance our ability to model riparian biogeochemical processes, promote water quality, and comprehend to what extent the promotion of riparian zones for nitrate removal is done at the expense of air quality (with respect to GHG emissions) and/or water quality (with respect to P).

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.

Experimental design for estimating parameters of rate-limited mass transfer: Analysis of stream tracer studies

USGS Publications Warehouse

Wagner, Brian J.; Harvey, Judson W.

1997-01-01

Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow moving. We present a methodology for (1) evaluating and comparing alternative stream tracer experiment designs and (2) identifying those combinations of stream transport properties that pose limitations to parameter estimation and therefore a challenge to tracer test design. The methodology uses the concept of global parameter uncertainty analysis, which couples solute transport simulation with parameter uncertainty analysis in a Monte Carlo framework. Two general conclusions resulted from this work. First, the solute injection and sampling strategy has an important effect on the reliability of transport parameter estimates. We found that constant injection with sampling through concentration rise, plateau, and fall provided considerably more reliable parameter estimates than a pulse injection across the spectrum of transport scenarios likely encountered in high-gradient streams. Second, for a given tracer test design, the uncertainties in mass transfer and storage-zone parameter estimates are strongly dependent on the experimental Damkohler number, DaI, which is a dimensionless combination of the rates of exchange between the stream and storage zones, the stream-water velocity, and the stream reach length of the experiment. Parameter uncertainties are lowest at DaI values on the order of 1.0. When DaI values are much less than 1.0 (owing to high velocity, long exchange timescale, and/or short reach length), parameter uncertainties are high because only a small amount of tracer interacts with storage zones in the reach. For the opposite conditions (DaI ≫ 1.0), solute exchange rates are fast relative to stream-water velocity and all solute is exchanged with the storage zone over the experimental reach. As DaI increases, tracer dispersion caused by hyporheic exchange eventually reaches an equilibrium condition and storage-zone exchange parameters become essentially nonidentifiable.

Gill lesions and death of bluegill in an acid mine drainage mixing zone

USGS Publications Warehouse

Henry, T.B.; Irwin, E.R.; Grizzle, J.M.; Brumbaugh, W.G.; Wildhaber, M.L.

2001-01-01

The toxicity of an acid mine drainage (AMD) mixing zone was investigated by placing bluegill (Lepomis macrochirus) at the confluence of a stream contaminated by AMD and a stream having neutral pH. A mixing channel receiving water from both streams was assembled in the field, during July and October 1996, to determine the toxicity of freshly mixed and aged water (2.9–7.5 min). The AMD stream had elevated concentrations of Al and Fe, which precipitated upon mixing, and of Mn, which did not precipitate in the mixing zone. Fish exposed to freshly mixed water had higher mortality than fish exposed to water after aging. Precipitating Al, but not Fe, accumulated on the gills of bluegill, and accumulation was more rapid early during the mixing process than after aging. Fish exposed for 3.5 h to freshly mixed water had hypertrophy and hyperplasia of gill filament and lamellar epithelial cells. Similar lesions were observed after 6.0 h in fish exposed to water aged after mixing. Results demonstrated that Al was the predominant metal accumulating on the gills of fish in this AMD mixing zone, and that mixing zones can be more toxic than AMD streams in equilibrium.

Effects of urban stream burial on nitrogen uptake and ...

EPA Pesticide Factsheets

Urbanization has resulted in extensive burial and channelization of headwater streams, yet little is known about impacts on stream ecosystem functions critical for reducing downstream nitrogen pollution. To characterize the biogeochemical impact of stream burial, we measured NO3- uptake, using 15N-NO3- isotope tracer releases, and whole stream metabolism, during four seasons in three paired buried and open streams reaches within the Baltimore Ecosystem Study Long-term Ecological Research Network. Stream burial increased NO3- uptake lengths, by a factor of 7.5 (p < 0.01) and decreased nitrate uptake velocity and areal nitrate uptake rate by factors of 8.2 (p = 0.01) and 9.6 (p < 0.001), respectively. Stream burial decreased gross primary productivity by a factor of 9.2 (p < 0.05) and decreased ecosystem respiration by a factor of 4.2 (p = 0.06). From statistical analysis of Excitation Emissions Matrices (EEMs), buried streams were also found to have significantly less labile dissolved organic matter. Furthermore, buried streams had significantly lower transient storage and water temperatures. Overall, differences in NO3- uptake and metabolism were primarily explained by decreased transient storage and light availability in buried streams. We estimate that stream burial increases daily watershed nitrate export by as much as 500% due to decreased in-stream retention and may considerably decrease carbon export via decreased primary production. These results

Methods and apparatuses for cutting, abrading, and drilling

DOEpatents

Bingham, Dennis N.; Swainston, Richard C.; Palmer, Gary L.; Ferguson, Russell L.

2001-01-01

Methods and apparatuses for treating a surface of a work piece are described. In one implementation, a laser delivery subsystem is configured to direct a laser beam toward a treatment zone on a work surface. A cryogenic material delivery subsystem is operably coupled with the laser delivery subsystem and is configured to direct a stream comprising cryogenic material toward the treatment zone. Both the laser beam and stream cooperate to treat material of the work surface within the treatment zone. In one aspect, a nozzle assembly provides the laser beam and stream of cryogenic material along a common flow axis. In another aspect, the laser beam and stream are provided along different axes.

Radial variations of large-scale magnetohydrodynamic fluctuations in the solar wind

NASA Technical Reports Server (NTRS)

Burlaga, L. F.; Goldstein, M. L.

1983-01-01

Two time periods are studied for which comprehensive data coverage is available at both 1 AU using IMP-8 and ISEE-3 and beyond using Voyager 1. One of these periods is characterized by the predominance of corotating stream interactions. Relatively small scale transient flows characterize the second period. The evolution of these flows with heliocentric distance is studied using power spectral techniques. The evolution of the transient dominated period is consistent with the hypothesis of turbulent evolution including an inverse cascade of large scales. The evolution of the corotating period is consistent with the entrainment of slow streams by faster streams in a deterministic model.

Stream and riparian management for freshwater turtles.

PubMed

Bodie, J R

2001-08-01

The regulation and management of stream ecosystems worldwide have led to irreversible loss of wildlife species. Due to recent scrutiny of water policy and dam feasibility, there is an urgent need for fundamental research on the biotic integrity of streams and riparian zones. Although riverine turtles rely on stream and riparian zones to complete their life cycle, are vital producers and consumers, and are declining worldwide, they have received relatively little attention. I review the literature on the impacts of contemporary stream management on freshwater turtles. Specifically, I summarize and discuss 10 distinct practices that produce five potential biological repercussions. I then focus on the often-overlooked use of riparian zones by freshwater turtles, calculate a biologically determined riparian width, and offer recommendations for ecosystem management. Migration data were summarized on 10 species from eight US states and four countries. A riparian zone encompassing the majority of freshwater turtle migrations would need to span 150 m from the stream edge. Freshwater turtles primarily chose high, open sandy habitats to nest. Nests in North America contained eggs and hatchlings during April through September and often through the winter. In addition, freshwater turtles utilized diverse riparian habitats for feeding, nesting, and overwintering. Additional documentation of stream and riparian habitat use by turtles is needed.

Method for production of magnesium

DOEpatents

Diaz, Alexander F.; Howard, Jack B.; Modestino, Anthony J.; Peters, William A.

1998-01-01

A continuous process for the production of elemental magnesium is described. Magnesium is made from magnesium oxide and a light hydrocarbon gas. In the process, a feed stream of the magnesium oxide and gas is continuously fed into a reaction zone. There the magnesium oxide and gas are reacted at a temperature of about 1400.degree. C. or greater in the reaction zone to provide a continuous product stream of reaction products, which include elemental magnesium. The product stream is continuously quenched after leaving the reaction zone, and the elemental magnesium is separated from other reaction products.

Method for production of magnesium

DOEpatents

Diaz, A.F.; Howard, J.B.; Modestino, A.J.; Peters, W.A.

1998-07-21

A continuous process for the production of elemental magnesium is described. Magnesium is made from magnesium oxide and a light hydrocarbon gas. In the process, a feed stream of the magnesium oxide and gas is continuously fed into a reaction zone. There the magnesium oxide and gas are reacted at a temperature of about 1400 C or greater in the reaction zone to provide a continuous product stream of reaction products, which include elemental magnesium. The product stream is continuously quenched after leaving the reaction zone, and the elemental magnesium is separated from other reaction products. 12 figs.

Streamflow losses along the Balcones Fault Zone, Nueces River basin, Texas

USGS Publications Warehouse

Land, L.F.; Boning, C.W.; Harmsen, Lynn; Reeves, R.D.

1983-01-01

Statistical evaluations of historical daily flow records for the streams that have gaging stations upstream and downstream from the recharge zone provided mathematical relationships that expressed downstream flow in terms of other significant parameters. For each stream, flow entering the recharge zone is most significant in defining downstream flow; for some streams, antecedent flows at the upstream site and ground-water levels are also significantly related to downstream flow. The analyses also determined the discharges required upstream from the recharge zone to sustain flow downstream from that zone. These discharges ranged from 355 cubic feet per second for the combined Frio and Dry Frio Rivers to 33 cubic feet per second for the Nueces River. The entire flows of lesser magnitude are generally lost to recharge to the aquifer.

Macroinvertebrate assemblage recovery following a catastrophic flood and debris flows in an Appalachian mountain stream

USGS Publications Warehouse

Snyder, C.D.; Johnson, Z.B.

2006-01-01

In June 1995, heavy rains caused severe flooding and massive debris flows on the Staunton River, a 3rd-order stream in the Blue Ridge Mountains (Virginia, USA). Scouring caused the loss of the riparian zone and repositioned the stream channel of the lower 2.1 km of the stream. Between 1998 and 2001, we conducted seasonal macroinvertebrate surveys at sites on the Staunton River and on White Oak Canyon Run, a reference stream of similar size and geology that was relatively unaffected by the flood. Our study was designed to determine the extent to which flood-induced changes to the stream channel and riparian habitats caused long-term changes to macroinvertebrate community structure and composition. Sites within the impacted zone of the Staunton River supported diverse stable benthic macroinvertebrate assemblages 3 y after the flood despite dramatic and persistent changes in environmental factors known to be important controls on stream ecosystem function. However, significant differences in total macroinvertebrate density and trophic structure could be attributed to the flood. In autumn, densities of most feeding guilds, including shredders, were higher at impacted-zone sites than at all other sites, suggesting higher overall productivity in the impacted zone. Higher shredder density in the impacted zone was surprising in light of expected decreases in leaf-litter inputs because of removal of riparian forests. In contrast, in spring, we observed density differences in only one feeding guild, scrapers, which showed higher densities at impacted-zone sites than at all other sites. This result conformed to a priori expectations that reduced shading in the impacted zone would lead to increased light and higher instream primary production. We attribute the seasonal differences in trophic structure to the effects of increased temperatures on food quality and to the relationship between the timing of our sampling and the emergence patterns of important taxa. ?? 2006 by The North American Benthological Society.

Activities and Ecological Role of Adult Aquatic Insects in the Riparian Zone of Streams

Treesearch

John K. Jackson; Vincent H. Resh

1989-01-01

Most adult aquatic insects that emerge from streams live briefly in the nearby riparian zone. Adult activities, such as mating, dispersal, and feeding, influence their distribution in the terrestrial habitat. A study at Big Sulphur Creek, California, has shown that both numbers and biomass of adult aquatic insects are greatest in the near-stream vegetation; however,...

Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects

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

Ye, Sheng; Covino, Timothy P.; Sivapalan, Murugesu

In this paper, we use a dynamic network flow model, coupled with a transient storage zone biogeochemical model, to simulate dissolved nutrient removal processes at the channel network scale. We have explored several scenarios in respect of the combination of rainfall variability, and the biological and geomorphic characteristics of the catchment, to understand the dominant controls on removal and delivery of dissolved nutrients (e.g., nitrate). These model-based theoretical analyses suggested that while nutrient removal efficiency is lower during flood events compared to during baseflow periods, flood events contribute significantly to bulk nutrient removal, whereas bulk removal during baseflow periods ismore » less. This is due to the fact that nutrient supply is larger during flood events; this trend is even stronger in large rivers. However, the efficiency of removal during both periods decreases in larger rivers, however, due to (i) increasing flow velocities and thus decreasing residence time, and (ii) increasing flow depth, and thus decreasing nutrient uptake rates. Besides nutrient removal processes can be divided into two parts: in the main channel and in the hyporheic transient storage zone. When assessing their relative contributions the size of the transient storage zone is a dominant control, followed by uptake rates in the main channel and in the transient storage zone. Increasing size of the transient storage zone with downstream distance affects the relative contributions to nutrient removal of the water column and the transient storage zone, which also impacts the way nutrient removal rates scale with increasing size of rivers. Intra-annual hydrologic variability has a significant impact on removal rates at all scales: the more variable the streamflow is, compared to mean discharge, the less nutrient is removed in the channel network. A scale-independent first order uptake coefficient, ke, estimated from model simulations, is highly dependent on the relative size of the transient storage zone and how it changes in the downstream direction, as well as the nature of hydrologic variability.« less

Machine-learning-based Brokers for Real-time Classification of the LSST Alert Stream

NASA Astrophysics Data System (ADS)

Narayan, Gautham; Zaidi, Tayeb; Soraisam, Monika D.; Wang, Zhe; Lochner, Michelle; Matheson, Thomas; Saha, Abhijit; Yang, Shuo; Zhao, Zhenge; Kececioglu, John; Scheidegger, Carlos; Snodgrass, Richard T.; Axelrod, Tim; Jenness, Tim; Maier, Robert S.; Ridgway, Stephen T.; Seaman, Robert L.; Evans, Eric Michael; Singh, Navdeep; Taylor, Clark; Toeniskoetter, Jackson; Welch, Eric; Zhu, Songzhe; The ANTARES Collaboration

2018-05-01

The unprecedented volume and rate of transient events that will be discovered by the Large Synoptic Survey Telescope (LSST) demand that the astronomical community update its follow-up paradigm. Alert-brokers—automated software system to sift through, characterize, annotate, and prioritize events for follow-up—will be critical tools for managing alert streams in the LSST era. The Arizona-NOAO Temporal Analysis and Response to Events System (ANTARES) is one such broker. In this work, we develop a machine learning pipeline to characterize and classify variable and transient sources only using the available multiband optical photometry. We describe three illustrative stages of the pipeline, serving the three goals of early, intermediate, and retrospective classification of alerts. The first takes the form of variable versus transient categorization, the second a multiclass typing of the combined variable and transient data set, and the third a purity-driven subtyping of a transient class. Although several similar algorithms have proven themselves in simulations, we validate their performance on real observations for the first time. We quantitatively evaluate our pipeline on sparse, unevenly sampled, heteroskedastic data from various existing observational campaigns, and demonstrate very competitive classification performance. We describe our progress toward adapting the pipeline developed in this work into a real-time broker working on live alert streams from time-domain surveys.

Hydrogenation apparatus

DOEpatents

Friedman, Joseph [Encino, CA; Oberg, Carl L [Canoga Park, CA; Russell, Larry H [Agoura, CA

1981-01-01

Hydrogenation reaction apparatus comprising a housing having walls which define a reaction zone and conduits for introducing streams of hydrogen and oxygen into the reaction zone, the oxygen being introduced into a central portion of the hydrogen stream to maintain a boundary layer of hydrogen along the walls of the reaction zone. A portion of the hydrogen and all of the oxygen react to produce a heated gas stream having a temperature within the range of from 1100.degree. to 1900.degree. C., while the boundary layer of hydrogen maintains the wall temperature at a substantially lower temperature. The heated gas stream is introduced into a hydrogenation reaction zone and provides the source of heat and hydrogen for a hydrogenation reaction. There also is provided means for quenching the products of the hydrogenation reaction. The present invention is particularly suitable for the hydrogenation of low-value solid carbonaceous materials to provide high yields of more valuable liquid and gaseous products.

Hydrogenation apparatus

DOEpatents

Friedman, J.; Oberg, C. L.; Russell, L. H.

1981-06-23

Hydrogenation reaction apparatus is described comprising a housing having walls which define a reaction zone and conduits for introducing streams of hydrogen and oxygen into the reaction zone, the oxygen being introduced into a central portion of the hydrogen stream to maintain a boundary layer of hydrogen along the walls of the reaction zone. A portion of the hydrogen and all of the oxygen react to produce a heated gas stream having a temperature within the range of from 1,100 to 1,900 C, while the boundary layer of hydrogen maintains the wall temperature at a substantially lower temperature. The heated gas stream is introduced into a hydrogenation reaction zone and provides the source of heat and hydrogen for a hydrogenation reaction. There also is provided means for quenching the products of the hydrogenation reaction. The present invention is particularly suitable for the hydrogenation of low-value solid carbonaceous materials to provide high yields of more valuable liquid and gaseous products. 2 figs.

Effects of pasture management and off-stream water on temporal/spatial distribution of cattle and stream bank characteristics in cool-season grass pastures.

PubMed

Schwarte, K A; Russell, J R; Morrical, D G

2011-10-01

A 2-yr grazing experiment was conducted to assess the effects of grazing management on cattle distribution and pasture and stream bank characteristics. Six 12.1-ha cool-season grass pastures in central Iowa were allotted to 1 of 3 treatments: continuous stocking with unrestricted stream access (CSU), continuous stocking with stream access restricted to 4.9-m-wide stabilized crossings (CSR), or rotational stocking with stream access restricted to a riparian paddock (RP). Pastures were stocked with 15 fall-calving Angus cows (Bos taurus L.) from mid-May to mid-October for 153 d in 2008 and 2009. A global positioning system (GPS) collar recording cow position every 10 min was placed on at least 1 cow per pasture for 2 wk of each month from May through September. Off-stream water was provided to cattle in CSU and CSR treatments during the second of the 2 wk when GPS collars were on the cattle. A black globe temperature relative humidity index (BGTHI) was measured at 10-min intervals to match the time of the GPS measurements. Each month of the grazing season, forage characteristics (sward height, forage mass, and CP, IVDMD, and P concentrations) and bare and fecal-covered ground were measured. Stream bank erosion susceptibility was visually scored in May, August, and October (pre-, mid-, and post-stocking). Cattle in RP and CSR treatments spent less time (P < 0.10) within the stream zone (0 to 3 m from stream center) in June and August and in the streamside zone (0 to 33 m from stream zone) in May through August and May through September, respectively, than cattle in CSU pastures. However, off-stream water had no effect on cattle distribution. Compared with the CSU treatment, the CSR treatment reduced the probability (P < 0.10) that cattle were within the riparian zone (0 to 36 m from stream center) at BGTHI of 50 to 100. Bare ground was greater (P < 0.10) in pastures with the CSU than CSR and RP treatments in the stream and streamside zones in September and October and in July and September. Streams in pastures with the CSU treatment had less stable banks (P < 0.10) mid- and post-stocking than RP or CSR treatments. Results show that time spent by cattle near pasture streams can be reduced by RP or CSR treatments, thereby decreasing risks of sediment and nutrient loading of pasture streams even during periods of increased BGTHI.

Delineating baseflow contribution areas for streams - A model and methods comparison

NASA Astrophysics Data System (ADS)

Chow, Reynold; Frind, Michael E.; Frind, Emil O.; Jones, Jon P.; Sousa, Marcelo R.; Rudolph, David L.; Molson, John W.; Nowak, Wolfgang

2016-12-01

This study addresses the delineation of areas that contribute baseflow to a stream reach, also known as stream capture zones. Such areas can be delineated using standard well capture zone delineation methods, with three important differences: (1) natural gradients are smaller compared to those produced by supply wells and are therefore subject to greater numerical errors, (2) stream discharge varies seasonally, and (3) stream discharge varies spatially. This study focuses on model-related uncertainties due to model characteristics, discretization schemes, delineation methods, and particle tracking algorithms. The methodology is applied to the Alder Creek watershed in southwestern Ontario. Four different model codes are compared: HydroGeoSphere, WATFLOW, MODFLOW, and FEFLOW. In addition, two delineation methods are compared: reverse particle tracking and reverse transport, where the latter considers local-scale parameter uncertainty by using a macrodispersion term to produce a capture probability plume. The results from this study indicate that different models can calibrate acceptably well to the same data and produce very similar distributions of hydraulic head, but can produce different capture zones. The stream capture zone is found to be highly sensitive to the particle tracking algorithm. It was also found that particle tracking by itself, if applied to complex systems such as the Alder Creek watershed, would require considerable subjective judgement in the delineation of stream capture zones. Reverse transport is an alternative and more reliable approach that provides probability intervals for the baseflow contribution areas, taking uncertainty into account. The two approaches can be used together to enhance the confidence in the final outcome.

A perspective on stream-catchment connections

USGS Publications Warehouse

Bencala, Kenneth E.

1993-01-01

Ecological study of the hyporheic zone is leading to recognition of a need for additional hydrologic understanding. Some of this understanding can be obtained by viewing the hyporheic zone as a succession of isolated boxes adjacent to the stream. Further understanding, particularly relevant to catchment-scale ecology, may come from studies focussed on the fluid mechanics of the flow-path connections between streams and their catchments.

Flat Branch monitoring project: stream water temperature and sediment responses to forest cutting in the riparian zone

Treesearch

Barton D. Clinton; James M. Vose; Dick L. Fowler

2010-01-01

Stream water protection during timber-harvesting activities is of primary interest to forest managers. In this study, we examine the potential impacts of riparian zone tree cutting on water temperature and total suspended solids. We monitored stream water temperature and total suspended solids before and after timber harvesting along a second-order tributary of the...

Hyporheic zone influences on concentration-discharge relationships in a headwater sandstone stream

NASA Astrophysics Data System (ADS)

Hoagland, Beth; Russo, Tess A.; Gu, Xin; Hill, Lillian; Kaye, Jason; Forsythe, Brandon; Brantley, Susan L.

2017-06-01

Complex subsurface flow dynamics impact the storage, routing, and transport of water and solutes to streams in headwater catchments. Many of these hydrogeologic processes are indirectly reflected in observations of stream chemistry responses to rain events, also known as concentration-discharge (CQ) relations. Identifying the relative importance of subsurface flows to stream CQ relationships is often challenging in headwater environments due to spatial and temporal variability. Therefore, this study combines a diverse set of methods, including tracer injection tests, cation exchange experiments, geochemical analyses, and numerical modeling, to map groundwater-surface water interactions along a first-order, sandstone stream (Garner Run) in the Appalachian Mountains of central Pennsylvania. The primary flow paths to the stream include preferential flow through the unsaturated zone ("interflow"), flow discharging from a spring, and groundwater discharge. Garner Run stream inherits geochemical signatures from geochemical reactions occurring along each of these flow paths. In addition to end-member mixing effects on CQ, we find that the exchange of solutes, nutrients, and water between the hyporheic zone and the main stream channel is a relevant control on the chemistry of Garner Run. CQ relationships for Garner Run were compared to prior results from a nearby headwater catchment overlying shale bedrock (Shale Hills). At the sandstone site, solutes associated with organo-mineral associations in the hyporheic zone influence CQ, while CQ trends in the shale catchment are affected by preferential flow through hillslope swales. The difference in CQ trends document how the lithology and catchment hydrology control CQ relationships.

Soil Microbial Community Contribution to Small Headwater Stream Metabolism.

NASA Astrophysics Data System (ADS)

Clapcott, J. E.; Gooderham, J. P.; Barmuta, L. A.; Davies, P. E.

2005-05-01

The temporal dynamics of sediment respiration were examined in seven small headwater streams in forested catchments in 2004. A strong seasonal response was observed with higher respiration rates in depositional zones than in gravel runs. The data were also examined in the context of proportional habitat distributions that highlighted the importance of high flow events in shaping whole stream metabolic budgets. This study specifically examines the question of terrestrial soil respiration contribution to whole stream metabolism by the controlled inundation of terrestrial soils. The experiment included six experimentally inundated terrestrial zones, six terrestrial controls, and six in-stream depositional zones. Sediment bacterial respiration was measured using 14C leucine incorporation and cotton strip bioassays were also employed to provide an indicative measure of sediment microbial activity. Despite high variability and exhibiting significantly lower bacterial activity than in-stream sediments, modelling using flow data and habitat mapping illustrated the important contribution of terrestrial soil respiration to the whole stream metabolic budgets of small headwater streams. In addition, microbial community composition examined using phospholipid fatty acid analysis clearly differentiated between terrestrial and aquatic communities. Freshly inundated terrestrial communities remained similar to un-inundated controls after 28 days.

Spatial and temporal variation of denitrification in the riparian zone during the hydrological year

NASA Astrophysics Data System (ADS)

Trauth, Nico; Musolff, Andreas; Knöller, Kay; Fleckenstein, Jan H.

2017-04-01

In the riparian zone, where stream water mixes with groundwater, biogeochemical reactions and solute transformations occur which may enhance the self-cleaning mechanisms of aquatic ecosystems. The water exchange and solute transport through the riparian zone is controlled by hydraulic gradients between stream and groundwater and thus varies seasonally and during stream discharge events. In this study, we focus on transport, mixing and the distribution of nitrate in the riparian zone of a gravelly alluvial aquifer with the aim to quantify its denitrification potential during the hydrological year. For this purpose, 25 groundwater wells were drilled along a 2 km stream section of the Selke river, a third-order stream in Germany. From the stream and the wells, water samples were taken 4-weekly over a period of 2 years. Water samples were analyzed to field parameters, major ions, dissolved organic carbon, and N-O isotopes. Results show a strong influence of the stream on the adjacent groundwater, which varies both in time and space. In general, we can distinguish between two endmembers: a) the stream water with low chloride (<30 mg/L) and nitrate (<10 mg/L) concentrations and b) the groundwater in 100m distance to the stream with high chloride (>70 mg/L) and nitrate (>50 mg/L) concentrations. Based on conservatively transported chloride, the mixing of the endmembers can be determined in the riparian zone. Deviations in nitrate concentrations from this mixing model may indicate nitrate degradation by e.g. denitrification. By combining this chloride-nitrate-ratio method with dissolved oxygen data and the isotopic signature of the nitrate molecule, we are able to determine the timing and the location of high denitrification patterns in the riparian aquifer. Highest variability of denitrification occurs over the year in terms of seasonality (temperature-driven) and is temporally fueled by additional organic carbon supply during discharge events.

Primary weathering rates, water transit times and concentration-discharge relations: A theoretical analysis for the critical zone

NASA Astrophysics Data System (ADS)

Ameli, Ali; Erlandsson, Martin; Beven, Keith; Creed, Irena; McDonnell, Jeffrey; Bishop, Kevin

2017-04-01

The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flowpath dynamics drive the spatio-temporal pattern of geochemical evolution and resulting streamflow concentration-discharge (C-Q) relation, but these flowpaths are complex and difficult to map quantitatively. Here, we couple a new integrated flow and particle tracking transport model with a general reversible Transition-State-Theory style dissolution rate-law to explore theoretically how C-Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (Ks) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration to intrinsic weathering rate, vertical heterogeneity in Ks enhances the gradient of weathering-derived solute concentration in the critical zone and strengthens the inverse stream C-Q relation. As the ratio of equilibrium concentration to intrinsic weathering rate decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C-Q relation approaches chemostatic behaviour, regardless of the degree of vertical heterogeneity in Ks. These findings suggest that the transport-controlled mechanisms in the hillslope can lead to chemostatic C-Q relations in the stream while the hillslope surface reaction-controlled mechanisms are associated with an inverse stream C-Q relation. In addition, as the ratio of equilibrium concentration to intrinsic weathering rate decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time)

Primary weathering rates, water transit times, and concentration-discharge relations: A theoretical analysis for the critical zone

NASA Astrophysics Data System (ADS)

Ameli, Ali A.; Beven, Keith; Erlandsson, Martin; Creed, Irena F.; McDonnell, Jeffrey J.; Bishop, Kevin

2017-01-01

The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flow path dynamics drive the spatiotemporal pattern of geochemical evolution and resulting streamflow concentration-discharge (C-Q) relation, but these flow paths are complex and difficult to map quantitatively. Here we couple a new integrated flow and particle tracking transport model with a general reversible Transition State Theory style dissolution rate law to explore theoretically how C-Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (Ks) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration (Ceq) to intrinsic weathering rate (Rmax), vertical heterogeneity in Ks enhances the gradient of weathering-derived solute concentration in the critical zone and strengthens the inverse stream C-Q relation. As CeqRmax decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C-Q relation approaches chemostatic behavior, regardless of the degree of vertical heterogeneity in Ks. These findings suggest that the transport-controlled mechanisms in the hillslope can lead to chemostatic C-Q relations in the stream while the hillslope surface reaction-controlled mechanisms are associated with an inverse stream C-Q relation. In addition, as CeqRmax decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).

Final report of fuel dynamics Test E7

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

Doerner, R.C.; Murphy, W.F.; Stanford, G.S.

1977-04-01

Test data from an in-pile failure experiment of high-power LMFBR-type fuel pins in a simulated $3/s transient-overpower (TOP) accident are reported and analyzed. Major conclusions are that (1) a series of cladding ruptures during the 100-ms period preceding fuel release injected small bursts of fission gas into the flow stream; (2) gas release influenced subsequent cladding melting and fuel release (there were no measurable FCI's (fuel-coolant interactions), and all fuel motion observed by the hodoscope was very slow); (3) the predominant postfailure fuel motion appears to be radial swelling that left a spongy fuel crust on the holder wall; (4)more » less than 4 to 6 percent of the fuel moved axially out of the original fuel zone, and most of this froze within a 10-cm region above the original top of the fuel zone to form the outlet blockage. An inlet blockage approximately 1 cm long was formed and consisted of large interconnected void regions. Both blockages began just beyond the ends of the fuel pellets.« less

Climate variability and vadose zone controls on damping of transient recharge

USGS Publications Warehouse

Corona, Claudia R.; Gurdak, Jason J.; Dickinson, Jesse; Ferré, T.P.A.; Maurer, Edwin P.

2018-01-01

Increasing demand on groundwater resources motivates understanding of the controls on recharge dynamics so model predictions under current and future climate may improve. Here we address questions about the nonlinear behavior of flux variability in the vadose zone that may explain previously reported teleconnections between global-scale climate variability and fluctuations in groundwater levels. We use hundreds of HYDRUS-1D simulations in a sensitivity analysis approach to evaluate the damping depth of transient recharge over a range of periodic boundary conditions and vadose zone geometries and hydraulic parameters that are representative of aquifer systems of the conterminous United States (U.S). Although the models were parameterized based on U.S. aquifers, findings from this study are applicable elsewhere that have mean recharge rates between 3.65 and 730 mm yr–1. We find that mean infiltration flux, period of time varying infiltration, and hydraulic conductivity are statistically significant predictors of damping depth. The resulting framework explains why some periodic infiltration fluxes associated with climate variability dampen with depth in the vadose zone, resulting in steady-state recharge, while other periodic surface fluxes do not dampen with depth, resulting in transient recharge. We find that transient recharge in response to the climate variability patterns could be detected at the depths of water levels in most U.S. aquifers. Our findings indicate that the damping behavior of transient infiltration fluxes is linear across soil layers for a range of texture combinations. The implications are that relatively simple, homogeneous models of the vadose zone may provide reasonable estimates of the damping depth of climate-varying transient recharge in some complex, layered vadose zone profiles.

The rate and extent of deforestation in watersheds of the southwestern Amazon basin.

PubMed

Biggs, Trent W; Dunne, Thomas; Roberts, Dar A; Matricardi, E

2008-01-01

The rate and extent of deforestation determine the timing and magnitude of disturbance to both terrestrial and aquatic ecosystems. Rapid change can lead to transient impacts to hydrology and biogeochemistry, while complete and permanent conversion to other land uses can lead to chronic changes. A large population of watershed boundaries (N=4788) and a time series of Landsat TM imagery (1975-1999) in the southwestern Amazon Basin showed that even small watersheds (2.5-15 km2) were deforested relatively slowly over 7-21 years. Less than 1% of all small watersheds were more than 50% cleared in a single year, and clearing rates averaged 5.6%/yr during active clearing. A large proportion (26%) of the small watersheds had a cumulative deforestation extent of more than 75%. The cumulative deforestation extent was highly spatially autocorrelated up to a 100-150 km lag due to the geometry of the agricultural zone and road network, so watersheds as large as approximately 40000 km2 were more than 50% deforested by 1999. The rate of deforestation had minimal spatial autocorrelation beyond a lag of approximately 30 km, and the mean rate decreased rapidly with increasing area. Approximately 85% of the cleared area remained in pasture, so deforestation in watersheds of Rondônia was a relatively slow, permanent, and complete transition to pasture, rather than a rapid, transient, and partial cutting with regrowth. Given the observed landcover transitions, the regional stream biogeochemical response is likely to resemble the chronic changes observed in streams draining established pastures, rather than a temporary pulse from slash-and-burn.

Using FIA and GIS Data to Estimate Areas and Volumes of Potential Stream Management Zones and Road Beautifying Buffers

Treesearch

Michael Zasada; Chris J. Cieszewski; Roger C. Lowe; Jarek Zawadzki; Mike Clutter; Jacek P. Siry

2005-01-01

Georgia Stream Management Zones (SMZ) are voluntary and have an unknown extent and impact. We use FIA data, Landsat TM imagery, and GAP and other GIS data to estimate the acreages and volumes of these buffers. We use stream data classified into trout, perennial, and intermittent, combined with DEM files containing elevation values, to assess buffers with widths...

Leaf-associated fungal diversity in acidified streams: insights from combining traditional and molecular approaches.

PubMed

Clivot, Hugues; Cornut, Julien; Chauvet, Eric; Elger, Arnaud; Poupin, Pascal; Guérold, François; Pagnout, Christophe

2014-07-01

We combined microscopic and molecular methods to investigate fungal assemblages on alder leaf litter exposed in the benthic and hyporheic zones of five streams across a gradient of increasing acidification for 4 weeks. The results showed that acidification and elevated Al concentrations strongly depressed sporulating aquatic hyphomycetes diversity in both zones of streams, while fungal diversity assessed by denaturing gradient gel electrophoresis (DGGE) appeared unaffected. Clone library analyses revealed that fungal communities on leaves were dominated by members of Ascomycetes and to a lesser extent by Basidiomycetes and Chytridiomycetes. An important contribution of terrestrial fungi was observed in both zones of the most acidified stream and in the hyporheic zone of the reference circumneutral stream. The highest leaf breakdown rate was observed in the circumneutral stream and occurred in the presence of both the highest diversity of sporulating aquatic hyphomycetes and the highest contribution to clone libraries of sequences affiliated with aquatic hyphomycetes. Both methods underline the major role played by aquatic hyphomycetes in leaf decomposition process. Our findings also bring out new highlights on the identity of leaf-associated fungal communities and their responses to anthropogenic alteration of running water ecosystems. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

FGOALS-s2 simulation of upper-level jet streams over East Asia: Mean state bias and synoptic-scale transient eddy activity

NASA Astrophysics Data System (ADS)

Song, Fengfei; Zhou, Tianjun

2013-05-01

Upper-level jet streams over East Asia simulated by the LASG/IAP coupled climate system model FGOALS-s2 were assessed, and the mean state bias explained in terms of synoptic-scale transient eddy activity (STEA). The results showed that the spatial distribution of the seasonal mean jet stream was reproduced well by the model, except that following a weaker meridional temperature gradient (MTG), the intensity of the jet stream was weaker than in National Centers for Environment Prediction (NCEP)/Department of Energy Atmospheric Model Inter-comparison Project II reanalysis data (NCEP2). Based on daily mean data, the jet core number was counted to identify the geographical border between the East Asian Subtropical Jet (EASJ) and the East Asian Polar-front Jet (EAPJ). The border is located over the Tibetan Plateau according to NCEP2 data, but was not evident in FGOALS-s2 simulations. The seasonal cycles of the jet streams were found to be reasonably reproduced, except that they shifted northward relative to reanalysis data in boreal summer owing to the northward shift of negative MTGs. To identify the reasons for mean state bias, the dynamical and thermal forcings of STEA on mean flow were examined with a focus on boreal winter. The dynamical and thermal forcings were estimated by extended Eliassen-Palm flux ( E) and transient heat flux, respectively. The results showed that the failure to reproduce the tripolar-pattern of the divergence of E over the jet regions led to an unsuccessful separation of the EASJ and EAPJ, while dynamical forcing contributed less to the weaker EASJ. In contrast, the weaker transient heat flux partly explained the weaker EASJ over the ocean.

Role of monitoring in stream restoration

EPA Science Inventory

Hydrology and dissolved organic carbon availability dictate nitrate dynamics in urban streams. So to improve N uptake, restore streams to: • Slow down stream flow • Add organic carbon • Reconnect floodplain hydrology and riparian zones

International Critical Zone Science: Opportunities to Build a Global Understanding of Land-Water Linkages

NASA Astrophysics Data System (ADS)

McDowell, W. H.

2015-12-01

Critical Zone science examines the structure and properties of the thin veneer that links surface properties to deep geology, at time scales of seconds to millennia. One of the fundamental premises of the US Critical Zone Observatories program is that CZOs should include some measurements made in common at all sites, as these common measurements will enable us to make stronger inferences about how the structure and function of the critical zone interact to drive key processes such as soil formation, stream flow generation, and nutrient export. Recent advances in real-time sensors provide new opportunities to address some fundamental questions about how hillslope soils and streams are linked. Data from the Luquillo Critical Zone Observatory in Puerto Rico, for example, document a previously undescribed transition, or flipping, of stream and soil biogeochemistry in a tropical rain forest. Under typical conditions, soil moisture is high and soil oxygen content is often low, especially at depth. Streams, in contrast, are typically near oxygen saturation. Under severe drought, however, oxygen increases dramatically in soil air and declines to values that are well below saturation in streams. This flipping in redox conditions suggests that despite the strong hydrologic connection between hillslope and stream, gas dynamics and potentially solute dynamics are decoupled along the flow path. The international CZO community has the opportunity to develop a suite of sensor arrays to document soil air, groundwater chemistry, and stream water chemistry. Progress towards realizing the potential of these international networks to develop coherent sensor programs will be addressed based on the current status of sensor deployments in CZO networks in the US, China, and Europe.

Delineating baseflow contribution areas for streams - A model and methods comparison.

PubMed

Chow, Reynold; Frind, Michael E; Frind, Emil O; Jones, Jon P; Sousa, Marcelo R; Rudolph, David L; Molson, John W; Nowak, Wolfgang

2016-12-01

This study addresses the delineation of areas that contribute baseflow to a stream reach, also known as stream capture zones. Such areas can be delineated using standard well capture zone delineation methods, with three important differences: (1) natural gradients are smaller compared to those produced by supply wells and are therefore subject to greater numerical errors, (2) stream discharge varies seasonally, and (3) stream discharge varies spatially. This study focuses on model-related uncertainties due to model characteristics, discretization schemes, delineation methods, and particle tracking algorithms. The methodology is applied to the Alder Creek watershed in southwestern Ontario. Four different model codes are compared: HydroGeoSphere, WATFLOW, MODFLOW, and FEFLOW. In addition, two delineation methods are compared: reverse particle tracking and reverse transport, where the latter considers local-scale parameter uncertainty by using a macrodispersion term to produce a capture probability plume. The results from this study indicate that different models can calibrate acceptably well to the same data and produce very similar distributions of hydraulic head, but can produce different capture zones. The stream capture zone is found to be highly sensitive to the particle tracking algorithm. It was also found that particle tracking by itself, if applied to complex systems such as the Alder Creek watershed, would require considerable subjective judgement in the delineation of stream capture zones. Reverse transport is an alternative and more reliable approach that provides probability intervals for the baseflow contribution areas, taking uncertainty into account. The two approaches can be used together to enhance the confidence in the final outcome. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Green Infrastructure Benefits for Communities Managing Nitrate in their Drinking Water Sources

EPA Science Inventory

Nitrate in water moving through the “biologically active soil zone” of riparian zones, wetlands and streams may undergo denitrification. Therefore GI techniques such as conservation and restoration of riparian zones, wetlands and streams (daylighting) have the potential to remov...

Solar energetic particle events in different types of solar wind

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

Kahler, S. W.; Vourlidas, A., E-mail: stephen.kahler@kirtland.af.mil

2014-08-10

We examine statistically some properties of 96 20 MeV gradual solar energetic proton (SEP) events as a function of three different types of solar wind (SW) as classified by Richardson and Cane. Gradual SEP (E > 10 MeV) events are produced in shocks driven by fast (V ≳ 900 km s{sup –1}) and wide (W > 60°) coronal mass ejections (CMEs). We find no differences among the transient, fast, and slow SW streams for SEP 20 MeV proton event timescales. It has recently been found that the peak intensities Ip of these SEP events scale with the ∼2 MeV protonmore » background intensities, which may be a proxy for the near-Sun shock seed particles. Both the intensities Ip and their 2 MeV backgrounds are significantly enhanced in transient SW compared to those of fast and slow SW streams, and the values of Ip normalized to the 2 MeV backgrounds only weakly correlate with CME V for all SW types. This result implies that forecasts of SEP events could be improved by monitoring both the Sun and the local SW stream properties and that the well known power-law size distributions of Ip may differ between transient and long-lived SW streams. We interpret an observed correlation between CME V and the 2 MeV background for SEP events in transient SW as a manifestation of enhanced solar activity.« less

Hydrologic connectivity between landscapes and streams: Transferring reach‐ and plot‐scale understanding to the catchment scale

USGS Publications Warehouse

Jencso, Kelsey G.; McGlynn, Brian L.; Gooseff, Michael N.; Wondzell, Steven M.; Bencala, Kenneth E.; Marshall, Lucy A.

2009-01-01

The relationship between catchment structure and runoff characteristics is poorly understood. In steep headwater catchments with shallow soils the accumulation of hillslope area (upslope accumulated area (UAA)) is a hypothesized first‐order control on the distribution of soil water and groundwater. Hillslope‐riparian water table connectivity represents the linkage between the dominant catchment landscape elements (hillslopes and riparian zones) and the channel network. Hydrologic connectivity between hillslope‐riparian‐stream (HRS) landscape elements is heterogeneous in space and often temporally transient. We sought to test the relationship between UAA and the existence and longevity of HRS shallow groundwater connectivity. We quantified water table connectivity based on 84 recording wells distributed across 24 HRS transects within the Tenderfoot Creek Experimental Forest (U.S. Forest Service), northern Rocky Mountains, Montana. Correlations were observed between the longevity of HRS water table connectivity and the size of each transect's UAA (r2 = 0.91). We applied this relationship to the entire stream network to quantify landscape‐scale connectivity through time and ascertain its relationship to catchment‐scale runoff dynamics. We found that the shape of the estimated annual landscape connectivity duration curve was highly related to the catchment flow duration curve (r2 = 0.95). This research suggests internal catchment landscape structure (topography and topology) as a first‐order control on runoff source area and whole catchment response characteristics.

Time-Scales of Storm Flow Response in the Stream and Hyporheic Zone of a Small, Steep Forested Catchment - Contrasting the Potential Contributions from the Hillslope, Riparian-Hyporheic Zones, and the Stream Channel

NASA Astrophysics Data System (ADS)

Wondzell, S. M.; Corson-rikert, H.; Haggerty, R.

2016-12-01

Storm-flow responses of small catchments are widely studied to identify water sources and mechanisms routing water through catchments. These studies typically observe rapid responses to rainfall with peak concentrations of many chemical constituents occurring on rising leg of the hydrograph. To explain this, some conceptual models suggest that stream water early in storm periods is dominated by riparian water sources with hillslope water sources dominating later in the storm. We examined changes in both stream and hyporheic water chemistry during a small, autumn storm in a forested mountain catchment to test this conceptual model. Our study site was located in WS01 at the H.J. Andrews Experimental Forest, in Oregon, USA. The watershed has a narrow valley floor, always less than 15 m wide and occasionally interrupted by narrow, constrained bedrock sections. The valley floor has a longitudinal gradient of approximately 14%. Hyporheic water tends to flow parallel the valley axis and flow paths change little with changes in stream discharge, even during storm events. A well network is located in a 30-m reach near the bottom of the watershed. We sampled the stream, 9 hyporheic wells, and a hillslope well for DOC, DIC, Cl-, and NO3- during the storm. As expected, concentrations of DOC and NO3- increased rapidly on the rising leg of the hydrograph in both the stream and the hyporheic wells. However, the stream always had higher concentrations of DOC, and lower concentrations of NO3-, than did either the hillslope well or the hyporheic wells. These data suggest that the riparian/hyporheic zone is not a likely source of water influencing stream water chemistry on the rising leg of the hydrograph. These data agree with median travel time estimates of water flowing along hyporheic flow paths - it takes many 10s of hours for water to move from the riparian/hyporheic zone to the stream - a time scale that is far too slow to explain the rapid changes observed on the rising leg of the hydrograph. These data suggest that much of the early storm responses in stream chemistry may be generated by in-channel processes, or processes occurring in the shallow streambed with very short hyporheic residence times; the influence of the riparian zone, most of the hyporheic zone, or hillslopes must occur much later in the storm event.

Aquifer response to stream-stage and recharge variations. II. Convolution method and applications

USGS Publications Warehouse

Barlow, P.M.; DeSimone, L.A.; Moench, A.F.

2000-01-01

In this second of two papers, analytical step-response functions, developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined, leaky, or water-table aquifer, are used in the convolution integral to calculate aquifer heads, streambank seepage rates, and bank storage that occur in response to streamstage fluctuations and basinwide recharge or evapotranspiration. Two computer programs developed on the basis of these step-response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream-aquifer systems in the northeastern and central United States. These applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties, recharge rates, streambank seepage rates, and bank storage. Analysis of the water-table aquifer adjacent to the Blackstone River in Massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer (negligible specific yield). This finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe, where sediment pores are saturated by tension, extends to land surface. Under this condition, the aquifer's response is determined by elastic storage only. Estimates of horizontal and vertical hydraulic conductivity, specific yield, specific storage, and recharge for a water-table aquifer adjacent to the Cedar River in eastern Iowa, determined by the use of analytical methods, are in close agreement with those estimated by use of a more complex, multilayer numerical model of the aquifer. Streambank leakance of the semipervious streambank materials also was estimated for the site. The streambank-leakance parameter may be considered to be a general (or lumped) parameter that accounts not only for the resistance of flow at the river-aquifer boundary, but also for the effects of partial penetration of the river and other near-stream flow phenomena not included in the theoretical development of the step-response functions.Analytical step-response functions, developed for several cases of transient hydraulic interaction between a fully penetrating stream and a confined, leaky, or water-table aquifer, are used in the convolution integral to calculate aquifer heads, streambank seepage rates, and bank storage that occur in response to stream-stage fluctuations and basinwide recharge or evapotranspiration. Two computer programs developed on the basis of these step-response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream-aquifer systems. These applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank seepage rates and bank storage.

Temperature Response of a Small Mountain Stream to Thunderstorm Cloud-Cover: Application of DTS Fiber-Optic Temperature Sensing

NASA Astrophysics Data System (ADS)

Thayer, D.; Klatt, A. L.; Miller, S. N.; Ohara, N.

2014-12-01

From a hydrologic point of view, the critical zone in alpine areas contains the first interaction of living systems with water which will flow to streams and rivers that sustain lowland biomes and human civilization. A key to understanding critical zone functions is understanding the flow of energy, and we can measure temperature as a way of looking at energy transfer between related systems. In this study we installed a Distributed Temperature Sensor (DTS) and fiber-optic cable in a zero-order stream at 9,000 ft in the Medicine Bow National Forest in southern Wyoming. We measured the temperature of the stream for 17 days from June 29 to July 16; the first 12 days were mostly sunny with occasional afternoon storms, and the last 5 experienced powerful, long-lasting storms for much of the day. The DTS measurements show a seasonal warming trend of both minimum and maximum stream temperature for the first 12 days, followed by a distinct cooling trend for the five days that experienced heavy storm activity. To gain insights into the timing and mechanisms of energy flow through the critical zone systems, we analyzed the timing of stream temperature change relative to solar short-wave radiation, and compared the stream temperature temporal response to the temporal response of soil temperature adjacent to the stream. Since convective thunderstorms are a dominant summer weather pattern in sub-alpine regions in the Rocky Mountains, this study gives us further insight into interactions of critical zone processes and weather in mountain ecosystems.

The influence of stream thermal regimes and preferential flow paths on hyporheic exchange in a glacial meltwater stream

USGS Publications Warehouse

Cozzetto, Karen D.; Bencala, Kenneth E.; Gooseff, Michael N.; McKnight, Diane M.

2013-01-01

Given projected increases in stream temperatures attributable to global change, improved understanding of relationships between stream temperatures and hyporheic exchange would be useful. We conducted two conservative tracer injection experiments in a glacial meltwater stream, to evaluate the effects of hyporheic thermal gradients on exchange processes, including preferential flow paths (PFPs). The experiments were conducted on the same day, the first (a stream injection) during a cool, morning period and the second (dual stream and hyporheic injections) during a warm, afternoon period. In the morning, the hyporheic zone was thermally uniform at 4°C, whereas by the afternoon the upper 10 cm had warmed to 6–12°C and exhibited greater temperature heterogeneity. Solute transport modeling showed that hyporheic cross-sectional areas (As) at two downstream sites were two and seven times lower during the warm experiment. Exchange metrics indicated that the hyporheic zone had less influence on downstream solute transport during the warm, afternoon experiment. Calculated hyporheic depths were less than 5 cm, contrasting with tracer detection at 10 and 25 cm depths. The hyporheic tracer arrival at one downstream site was rapid, comparable to the in-stream tracer arrival, providing evidence for PFPs. We thus propose a conceptual view of the hyporheic zone in this reach as being dominated by discrete PFPs weaving through hydraulically isolated areas. One explanation for the simultaneous increase in temperature heterogeneity and As decrease in a warmer hyporheic zone may be a flow path preferentiality feedback mechanism resulting from a combination of temperature-related viscosity decreases and streambed heterogeneity.

Transient technique for measuring heat transfer coefficients on stator airfoils in a jet engine environment

NASA Astrophysics Data System (ADS)

Gladden, H. J.; Proctor, M. P.

A transient technique was used to measure heat transfer coefficients on stator airfoils in a high-temperature annular cascade at real engine conditions. The transient response of thin film thermocouples on the airfoil surface to step changes in the gas stream temperature was used to determine these coefficients. In addition, gardon gages and paired thermocouples were also utilized to measure heat flux on the airfoil pressure surface at steady state conditions. The tests were conducted at exit gas stream Reynolds numbers of one-half to 1.9 million based on true chord. The results from the transient technique show good comparison with the steady-state results in both trend and magnitude. In addition, comparison is made with the STAN5 boundary layer code and shows good comparison with the trends. However, the magnitude of the experimental data is consistently higher than the analysis.

Transient technique for measuring heat transfer coefficients on stator airfoils in a jet engine environment

NASA Technical Reports Server (NTRS)

Gladden, H. J.; Proctor, M. P.

1985-01-01

A transient technique was used to measure heat transfer coefficients on stator airfoils in a high-temperature annular cascade at real engine conditions. The transient response of thin film thermocouples on the airfoil surface to step changes in the gas stream temperature was used to determine these coefficients. In addition, gardon gages and paired thermocouples were also utilized to measure heat flux on the airfoil pressure surface at steady state conditions. The tests were conducted at exit gas stream Reynolds numbers of one-half to 1.9 million based on true chord. The results from the transient technique show good comparison with the steady-state results in both trend and magnitude. In addition, comparison is made with the STAN5 boundary layer code and shows good comparison with the trends. However, the magnitude of the experimental data is consistently higher than the analysis.

Chemical vapor deposition of epitaxial silicon

DOEpatents

Berkman, Samuel

1984-01-01

A single chamber continuous chemical vapor deposition (CVD) reactor is described for depositing continuously on flat substrates, for example, epitaxial layers of semiconductor materials. The single chamber reactor is formed into three separate zones by baffles or tubes carrying chemical source material and a carrier gas in one gas stream and hydrogen gas in the other stream without interaction while the wafers are heated to deposition temperature. Diffusion of the two gas streams on heated wafers effects the epitaxial deposition in the intermediate zone and the wafers are cooled in the final zone by coolant gases. A CVD reactor for batch processing is also described embodying the deposition principles of the continuous reactor.

Trapping and exclusion zones in complex streaming patterns around a large assembly of microfluidic bubbles under ultrasound

NASA Astrophysics Data System (ADS)

Combriat, Thomas; Mekki-Berrada, Flore; Thibault, Pierre; Marmottant, Philippe

2018-01-01

Pulsating bubbles have proved to be a versatile tool for trapping and sorting particles. In this article, we investigate the different streaming patterns that can be obtained with a group of bubbles in a confined geometry under ultrasound. In the presence of an external flow strong enough to oppose the streaming velocities but not drag the trapped bubbles, we observe either the appearance of exclusion zones near the bubbles or asymmetric streaming patterns that we interpret as the superposition of a two-dimensional (2D) streaming function and of a potential flow. When studying a lattice of several bubbles, we show that the streaming pattern can be accurately predicted by superimposing the contributions of every pair of bubbles present in the lattice, thus allowing one to predict the sizes and the shapes of exclusion zones created by a group of bubbles under acoustic excitation. We suggest that such systems could be used to enhance mixing at a small scale or to catch and release chemical species initially trapped in vortices created around bubble pairs.

Scaling of transient storage parameter estimates with increasing reach length in a mountain headwater stream

Treesearch

M. Briggs; M. N. Gooseff; B. McGlynn

2006-01-01

We performed two conservative tracer injections in a mountain stream in order to access the relationship between storage parameters on the short subreach scale to the longer reach which they comprise.

The ZTF Bright Transient Survey

NASA Astrophysics Data System (ADS)

Fremling, C.; Sharma, Y.; Kulkarni, S. R.; Miller, A. A.; Taggart, K.; Perley, D. A.; Gooba, A.

2018-06-01

As a supplement to the Zwicky Transient Facility (ZTF; ATel #11266) public alerts (ATel #11685) we plan to report (following ATel #11615) bright probable supernovae identified in the raw alert stream from the ZTF Northern Sky Survey ("Celestial Cinematography"; see Bellm & Kulkarni, 2017, Nature Astronomy 1, 71) to the Transient Name Server (https://wis-tns.weizmann.ac.il) on a daily basis; the ZTF Bright Transient Survey (BTS; see Kulkarni et al., 2018; arXiv:1710.04223).

Viscosity changes of riparian water controls diurnal fluctuations of stream-flow and DOC concentration

NASA Astrophysics Data System (ADS)

Schwab, Michael; Klaus, Julian; Pfister, Laurent; Weiler, Markus

2015-04-01

Diurnal fluctuations in stream-flow are commonly explained as being triggered by the daily evapotranspiration cycle in the riparian zone, leading to stream flow minima in the afternoon. While this trigger effect must necessarily be constrained by the extent of the growing season of vegetation, we here show evidence of daily stream flow maxima in the afternoon in a small headwater stream during the dormant season. We hypothesize that the afternoon maxima in stream flow are induced by viscosity changes of riparian water that is caused by diurnal temperature variations of the near surface groundwater in the riparian zone. The patterns were observed in the Weierbach headwater catchment in Luxembourg. The catchment is covering an area of 0.45 km2, is entirely covered by forest and is dominated by a schistous substratum. DOC concentration at the outlet of the catchment was measured with the field deployable UV-Vis spectrometer spectro::lyser (scan Messtechnik GmbH) with a high frequency of 15 minutes over several months. Discharge was measured with an ISCO 4120 Flow Logger. During the growing season, stream flow shows a frequently observed diurnal pattern with discharge minima in the afternoon. During the dormant season, a long dry period with daily air temperature amplitudes of around 10 ° C occurred in March and April 2014, with discharge maxima in the afternoon. The daily air temperature amplitude led to diurnal variations in the water temperature of the upper 10 cm of the riparian zone. Higher riparian water temperatures cause a decrease in water viscosity and according to the Hagen-Poiseuille equation, the volumetric flow rate is inversely proportional to viscosity. Based on the Hagen-Poiseuille equation and the viscosity changes of water, we calculated higher flow rates of near surface groundwater through the riparian zone into the stream in the afternoon which explains the stream flow maxima in the afternoon. With the start of the growing season, the viscosity induced diurnal effect is overlain by the stronger influence of evapotranspiration. Diurnal DOC fluctuations show daily maxima in the afternoon. While daily variations in DOC concentrations are often explained by faster in-stream biogeochemical processes during daylight, we here propose that the viscosity effect in the riparian zone could explain the afternoon peaks in DOC concentrations. Our records show that daily water temperature variations and therefore viscosity changes only occur in the near surface parts of the riparian zone, where the DOC concentrations are higher than in deeper parts of the riparian zone. We calculated, that the viscosity induced higher flow rates from the near surface parts of the riparian zone can explain the DOC concentration maxima in the afternoon. As the viscosity effect does not disappear during the growing season but is just smaller than the evapotranspiration effect, the DOC concentration pattern is not changing between the dormant and growing seasons. The different controls of diurnal fluctuations of stream-flow and water quality concentrations need to be carefully considered in order to better understand the different patterns in catchment hydrology.

Temporal Hyporheic Zone Response to Water Table Fluctuations.

PubMed

Malzone, Jonathan M; Anseeuw, Sierra K; Lowry, Christopher S; Allen-King, Richelle

2016-03-01

Expansion and contraction of the hyporheic zone due to temporal hydrologic changes between stream and riparian aquifer influence the biogeochemical cycling capacity of streams. Theoretical studies have quantified the control of groundwater discharge on the depth of the hyporheic zone; however, observations of temporal groundwater controls are limited. In this study, we develop the concept of groundwater-dominated differential hyporheic zone expansion to explain the temporal control of groundwater discharge on the hyporheic zone in a third-order stream reach flowing through glacially derived terrain typical of the Great Lakes region. We define groundwater-dominated differential expansion of the hyporheic zone as: differing rates and magnitudes of hyporheic zone expansion in response to seasonal vs. storm-related water table fluctuation. Specific conductance and vertical hydraulic gradient measurements were used to map changes in the hyporheic zone during seasonal water table decline and storm events. Planar and riffle beds were monitored in order to distinguish the cause of increasing hyporheic zone depth. Planar bed seasonal expansion of the hyporheic zone was of a greater magnitude and longer in duration (weeks to months) than storm event expansion (hours to days). In contrast, the hyporheic zone beneath the riffle bed exhibited minimal expansion in response to seasonal groundwater decline compared to storm related expansion. Results indicated that fluctuation in the riparian water table controlled seasonal expansion of the hyporheic zone along the planar bed. This groundwater induced hyporheic zone expansion could increase the potential for biogeochemical cycling and natural attenuation. © 2015, National Ground Water Association.

Machine Learning-based Transient Brokers for Real-time Classification of the LSST Alert Stream

NASA Astrophysics Data System (ADS)

Narayan, Gautham; Zaidi, Tayeb; Soraisam, Monika; ANTARES Collaboration

2018-01-01

The number of transient events discovered by wide-field time-domain surveys already far outstrips the combined followup resources of the astronomical community. This number will only increase as we progress towards the commissioning of the Large Synoptic Survey Telescope (LSST), breaking the community's current followup paradigm. Transient brokers - software to sift through, characterize, annotate and prioritize events for followup - will be a critical tool for managing alert streams in the LSST era. Developing the algorithms that underlie the brokers, and obtaining simulated LSST-like datasets prior to LSST commissioning, to train and test these algorithms are formidable, though not insurmountable challenges. The Arizona-NOAO Temporal Analysis and Response to Events System (ANTARES) is a joint project of the National Optical Astronomy Observatory and the Department of Computer Science at the University of Arizona. We have been developing completely automated methods to characterize and classify variable and transient events from their multiband optical photometry. We describe the hierarchical ensemble machine learning algorithm we are developing, and test its performance on sparse, unevenly sampled, heteroskedastic data from various existing observational campaigns, as well as our progress towards incorporating these into a real-time event broker working on live alert streams from time-domain surveys.

Bright ZTF transients

NASA Astrophysics Data System (ADS)

Fremling, C.; Kulkarni, S. R.; Taggart, K.; Perley, D.

2018-05-01

As a part of ongoing commissioning of the Zwicky Transient Facility (ZTF; ATel #11266) Alert Infrastructure, here we report bright probable supernovae identified in the raw alert stream resulting from the public ZTF Northern Sky Survey ("Celestial Cinematagrophy"; see Bellm & Kulkarni, Nature Astronomy 1, 71, 2017).

Evaluating the reliability of the stream tracer approach to characterize stream-subsurface water exchange

USGS Publications Warehouse

Harvey, Judson W.; Wagner, Brian J.; Bencala, Kenneth E.

1996-01-01

Stream water was locally recharged into shallow groundwater flow paths that returned to the stream (hyporheic exchange) in St. Kevin Gulch, a Rocky Mountain stream in Colorado contaminated by acid mine drainage. Two approaches were used to characterize hyporheic exchange: sub-reach-scale measurement of hydraulic heads and hydraulic conductivity to compute streambed fluxes (hydrometric approach) and reachscale modeling of in-stream solute tracer injections to determine characteristic length and timescales of exchange with storage zones (stream tracer approach). Subsurface data were the standard of comparison used to evaluate the reliability of the stream tracer approach to characterize hyporheic exchange. The reach-averaged hyporheic exchange flux (1.5 mL s−1 m−1), determined by hydrometric methods, was largest when stream base flow was low (10 L s−1); hyporheic exchange persisted when base flow was 10-fold higher, decreasing by approximately 30%. Reliability of the stream tracer approach to detect hyporheic exchange was assessed using first-order uncertainty analysis that considered model parameter sensitivity. The stream tracer approach did not reliably characterize hyporheic exchange at high base flow: the model was apparently more sensitive to exchange with surface water storage zones than with the hyporheic zone. At low base flow the stream tracer approach reliably characterized exchange between the stream and gravel streambed (timescale of hours) but was relatively insensitive to slower exchange with deeper alluvium (timescale of tens of hours) that was detected by subsurface measurements. The stream tracer approach was therefore not equally sensitive to all timescales of hyporheic exchange. We conclude that while the stream tracer approach is an efficient means to characterize surface-subsurface exchange, future studies will need to more routinely consider decreasing sensitivities of tracer methods at higher base flow and a potential bias toward characterizing only a fast component of hyporheic exchange. Stream tracer models with multiple rate constants to consider both fast exchange with streambed gravel and slower exchange with deeper alluvium appear to be warranted.

Streamside Management Zones Affect Movement of Silvicultural Nitrogen and Phosphorus Fertilizers to Piedmont Streams

Treesearch

Joseph M. Secoges; Wallace M. Aust; John R. Seiler; C. Andrew Dolloff; William A. Lakel

2013-01-01

Forestry best management practices (BMP) recommendations for streamside management zones (SMZs) are based on limited data regarding SMZ width, partial harvests, and nutrient movements after forest fertilization. Agricultural fertilization is commonly linked to increased stream nutrients. However, less is known about effectiveness of SMZ options for controlling nutrient...

Tracking tracer breakthrough in the hyporheic zone using time‐lapse DC resistivity, Crabby Creek, Pennsylvania

USGS Publications Warehouse

Nyquist, Jonathan E.; Toran, Laura; Fang, Allison C.; Ryan, Robert J.; Rosenberry, Donald O.

2010-01-01

Characterization of the hyporheic zone is of critical importance for understanding stream ecology, contaminant transport, and groundwater‐surface water interaction. A salt water tracer test was used to probe the hyporheic zone of a recently re‐engineered portion of Crabby Creek, a stream located near Philadelphia, PA. The tracer solution was tracked through a 13.5 meter segment of the stream using both a network of 25 wells sampled every 5–15 minutes and time‐lapse electrical resistivity tomographs collected every 11 minutes for six hours, with additional tomographs collected every 100 minutes for an additional 16 hours. The comparison of tracer monitoring methods is of keen interest because tracer tests are one of the few techniques available for characterizing this dynamic zone, and logistically it is far easier to collect resistivity tomographs than to install and monitor a dense network of wells. Our results show that resistivity monitoring captured the essential shape of the breakthrough curve and may indicate portions of the stream where the tracer lingered in the hyporheic zone. Time‐lapse resistivity measurements, however, represent time averages over the period required to collect a tomographic data set, and spatial averages over a volume larger than captured by a well sample. Smoothing by the resistivity data inversion algorithm further blurs the resulting tomograph; consequently resistivity monitoring underestimates the degree of fine‐scale heterogeneity in the hyporheic zone.

Role of surface and subsurface processes in scaling N2O emissions along riverine networks

PubMed Central

Marzadri, Alessandra; Dee, Martha M.; Tonina, Daniele; Bellin, Alberto; Tank, Jennifer L.

2017-01-01

Riverine environments, such as streams and rivers, have been reported as sources of the potent greenhouse gas nitrous oxide (N2O) to the atmosphere mainly via microbially mediated denitrification. Our limited understanding of the relative roles of the near-surface streambed sediment (hyporheic zone), benthic, and water column zones in controlling N2O production precludes predictions of N2O emissions along riverine networks. Here, we analyze N2O emissions from streams and rivers worldwide of different sizes, morphology, land cover, biomes, and climatic conditions. We show that the primary source of N2O emissions varies with stream and river size and shifts from the hyporheic–benthic zone in headwater streams to the benthic–water column zone in rivers. This analysis reveals that N2O production is bounded between two N2O emission potentials: the upper N2O emission potential results from production within the benthic–hyporheic zone, and the lower N2O emission potential reflects the production within the benthic–water column zone. By understanding the scaling nature of N2O production along riverine networks, our framework facilitates predictions of riverine N2O emissions globally using widely accessible chemical and hydromorphological datasets and thus, quantifies the effect of human activity and natural processes on N2O production. PMID:28400514

Destiny of earthward streaming plasma in the plasmasheet boundary layer

NASA Technical Reports Server (NTRS)

Green, J. L.; Horwitz, J. L.

1986-01-01

The dynamics of the earth's magnetotail have been investigated, and it has become clear that the plasmasheet boundary layer field lines map into the Region I Field-Aligned Currents (FAC) of the auroral zone. It is pointed out that the role of earthward streaming ions in the plasmasheet boundary layer may be of fundamental importance in the understanding of magnetotail dynamics, auroral zone physics, and especially for ionospheric-magnetospheric interactions. The present paper has the objective to evaluate propagation characteristics for the earthward streaming ions observed in the plasmasheet boundary layer. An investigation is conducted of the propagation characteristics of protons in the plasmasheet boundary layer using independent single particle dynamics, and conclusions are discussed. The density of earthward streaming ions found in the plasmasheet boundary layer should include the ring current as well as the auroral zone precipitaiton and inner plasmasheet regions of the magnetosphere.

Effects of unsteady free stream velocity and free stream turbulence on stagnation point heat transfer

NASA Technical Reports Server (NTRS)

Gorla, R. S. R.

1984-01-01

The combined effects of transient free stream velocity and free stream turbulence on heat transfer at a stagnation point over a cylinder situated in a crossflow are studied. An eddy diffusivity model was formulated and the governing momentum and energy equations are integrated by means of the steepest descent method. The numerical results for the wall shear stress and heat transfer rate are correlated by a turbulence parameter. The wall friction and heat transfer rate increase with increasing free stream turbulence intensity.

Stream Community Structure: An Analysis of Riparian Forest Buffer Restoration in the Chesapeake Bay Watershed

NASA Astrophysics Data System (ADS)

Orzetti, L. L.; Jones, R. C.

2005-05-01

Forested riparian buffer zones have been proposed as an important aid in curtailing upland sources of pollution before they reach stream surface waters, and enhancing habitat for stream organisms. Our objective was to test the efficacy of restored forest riparian buffers along streams in the Chesapeake Bay watershed by examining the stream macrobenthic community structure. To test our hypothesis, we collected riffle benthic and water samples, and performed habitat evaluations at 30 stream sites in the mid-Atlantic Piedmont, ranging in buffer age from 0 to greater than 50 years of age. Results showed that habitat, water quality, and benthic macroinvertebrate metrics improved with age of restored buffer. Habitat scores were driven mostly by instream substrate availability and width and age of riparian buffer zones. Water quality parameters varied within buffer age groups depending age of surrounding forest vegetation. Benthic invertebrate taxa richness, % EPT, % Plecoptera, % Ephemeroptera, and the FBI all improved with age of buffer zone. Instream habitat quality was the greatest driver of benthic macroinvertebrate community diversity and health, and appeared to plateau within 10-15 years of restoration with noticeable improvements occurring within 5-10 years post restoration.

Method and system for the removal of oxides of nitrogen and sulfur from combustion processes

DOEpatents

Walsh, John V.

1987-12-15

A process for removing oxide contaminants from combustion gas, and employing a solid electrolyte reactor, includes: (a) flowing the combustion gas into a zone containing a solid electrolyte and applying a voltage and at elevated temperature to thereby separate oxygen via the solid electrolyte, (b) removing oxygen from that zone in a first stream and removing hot effluent gas from that zone in a second stream, the effluent gas containing contaminant, (c) and pre-heating the combustion gas flowing to that zone by passing it in heat exchange relation with the hot effluent gas.

Physical Habitat and Energy Inputs Determine Freshwater Invertebrate Communities in Reference and Cranberry Farm Impacted Northeastern Coastal Zone Streams

NASA Astrophysics Data System (ADS)

Lander, D. M. P.; McCanty, S. T.; Dimino, T. F.; Christian, A. D.

2016-02-01

The River Continuum Concept (RCC) predicts stream biological communities based on dominant physical structures and energy inputs into streams and predicts how these features and corresponding communities change along the stream continuum. Verifying RCC expectations is important for creating valid points of comparison during stream ecosystem evaluation. These reference expectations are critical for restoration projects, such as the restoration of decommissioned cranberry bogs. Our research compares the physical habitat and freshwater invertebrate functional feeding groups (FWIFFG) of reference, active cranberry farming, and cranberry farm passive restoration sites in Northeastern Coastal Zone streams of Massachusetts to the specific RCC FWIFFG predictions. We characterized stream physical habitat using a semi-quantitative habitat characterization protocol and sampled freshwater invertebrates using the U.S. EPA standard 20-jab multi-habitat protocol. We expected that stream habitat would be most homogeneous at active farming stations, intermediate at restoration stations, and most heterogeneous at reference stations. Furthermore, we expected reference stream FWIFFG would be accurately predicted by the RCC and distributions at restoration and active sites would vary significantly. Habitat data was analyzed using a principle component analysis and results confirmed our predictions showing more homogeneous habitat for the active and reference stations, while showing a more heterogeneous habitat at the reference stations. The FWIFFG chi-squared analysis showed significant deviation from our specific RCC FWIFFG predictions. Because published FWIFFG distributions did not match our empirical values for a least disturbed Northeastern Coastal Zone headwater stream, using our data as a community structure template for current and future restoration projects is not recommend without further considerations.

Utilizing Controlled Vibrations in a Microgravity Environment to Understand and Promote Microstructural Homogeneity During Floating-Zone Crystal Growth

NASA Technical Reports Server (NTRS)

Anilkumar, A. V.; Bhowmick, J.; Grugel, R. N.

2001-01-01

Our previous experiments with NaNO3 float-zones revealed that steady thermocapillary flow can be balanced/offset by the controlled surface streaming flow induced by end-wall vibration. In the current experiments we are examining the effects of streaming flow on steadying/stabilizing nonsteady thermocapillary flow in such zones. To this effect we have set up a controlled NaNO3 half-zone experiment, where the processing parameters, like zone dimensions and temperature gradients, can be easily varied to generate nonsteady thermocapillary flows. In the present paper we present preliminary results of our investigations into stabilizing such flows by employing endwall vibration.

Utilizing Controlled Vibrations in a Microgravity Environment to Understand and Promote Microstructural Homogeneity During Float-Zone Crystal Growth

NASA Technical Reports Server (NTRS)

Anilkumar, A. V.; Bhowmick, J.; Grugel, R. N.a

2000-01-01

Our previous experiments with NaNO3 float-zones revealed that steady thermocapillary flow can be balanced/offset by the controlled surface streaming flow induced by end-wall vibration. In the current experiments we are examining the effects of streaming flow on steadying/stabilizing nonsteady thermocapillary flow in such zones. To this effect we have set up a controlled NaNO3 half-zone experiment, where the processing parameters, like zone dimensions and temperature gradients, can be easily varied to generate nonsteady thermocapillary flows. In the present paper we present preliminary results of our investigations into stabilizing such flows by employing end-wall vibration.

Pulverized coal burner

DOEpatents

Sivy, J.L.; Rodgers, L.W.; Koslosy, J.V.; LaRue, A.D.; Kaufman, K.C.; Sarv, H.

1998-11-03

A burner is described having lower emissions and lower unburned fuel losses by implementing a transition zone in a low NO{sub x} burner. The improved burner includes a pulverized fuel transport nozzle surrounded by the transition zone which shields the central oxygen-lean fuel devolatilization zone from the swirling secondary combustion air. The transition zone acts as a buffer between the primary and the secondary air streams to improve the control of near-burner mixing and flame stability by providing limited recirculation regions between primary and secondary air streams. These limited recirculation regions transport evolved NO{sub x} back towards the oxygen-lean fuel pyrolysis zone for reduction to molecular nitrogen. Alternate embodiments include natural gas and fuel oil firing. 8 figs.

Pulverized coal burner

DOEpatents

Sivy, Jennifer L.; Rodgers, Larry W.; Koslosy, John V.; LaRue, Albert D.; Kaufman, Keith C.; Sarv, Hamid

1998-01-01

A burner having lower emissions and lower unburned fuel losses by implementing a transition zone in a low NO.sub.x burner. The improved burner includes a pulverized fuel transport nozzle surrounded by the transition zone which shields the central oxygen-lean fuel devolatilization zone from the swirling secondary combustion air. The transition zone acts as a buffer between the primary and the secondary air streams to improve the control of near-burner mixing and flame stability by providing limited recirculation regions between primary and secondary air streams. These limited recirculation regions transport evolved NO.sub.x back towards the oxygen-lean fuel pyrolysis zone for reduction to molecular nitrogen. Alternate embodiments include natural gas and fuel oil firing.

Legacy Nitrate Impacts on Groundwater and Streams

NASA Astrophysics Data System (ADS)

Tesoriero, A. J.; Juckem, P. F.; Miller, M. P.

2017-12-01

Decades of recharge of high-nitrate groundwater have created a legacy—a mass of high-nitrate groundwater—that has implications for future nitrate concentrations in groundwater and in streams. In the United States, inorganic nitrogen fertilizer applications to the land surface have increased ten-fold since 1950, resulting in sharp increases in nitrate concentrations in recharging groundwater, which pose a risk to deeper groundwater and streams. This study assesses the factors that control time lags and eventual concentrations of legacy nitrate in groundwater and streams. Results from the USGS National Water-Quality Assessment Project are presented which elucidate nitrate trends in recharging groundwater, delineate redox zones and assess groundwater and stream vulnerability to legacy nitrate sources on a regional scale. This study evaluated trends and transformations of agricultural chemicals based on groundwater age and water chemistry data along flow paths from recharge areas to streams at 20 study sites across the United States. Median nitrate recharge concentrations in these agricultural areas have increased markedly over the last 50 years, from 4 to 7.5 mg N/L. The effect that nitrate accumulation in shallow aquifers will have on drinking water quality and stream ecosystems is dependent on the redox zones encountered along flow paths and on the age distribution of nitrate discharging to supply wells and streams. Delineating redox zones on a regional scale is complicated by the spatial variability of reaction rates. To overcome this limitation, we applied logistic regression and machine learning techniques to predict the probability of a specific redox condition in groundwater in the Chesapeake Bay watershed and the Fox-Wolf-Peshtigo study area in Wisconsin. By relating redox-active constituent concentrations in groundwater samples to indicators of residence time and/or electron donor availability, we were able to delineate redox zones on a regional scale - an important indicator of groundwater vulnerability and the vulnerability of streams to legacy nitrate sources.

The stream subsurface: nitrogen cycling and the cleansing function of hyporheic zones

Treesearch

Rhonda Mazza; Steve Wondzell; Jay Zarnetske

2014-01-01

Nitrogen is an element essential to plant growth and ecosystem productivity. Excess nitrogen, however, is a common water pollutant. It can lead to algal blooms that deplete the water's dissolved oxygen, creating "dead zones" devoid of fish and aquatic insects.Previous research showed that the subsurface area of a stream, known as the hyporheic...

Dynamics of nitrate production and removal as a function of residence time in the hyporheic zone

Treesearch

Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

2011-01-01

Biogeochemical reactions associated with stream nitrogen cycling, such as nitrification and denitrification, can be strongly controlled by water and solute residence times in the hyporheic zone (HZ). We used a whole-stream steady state 15N-Iabeled nitrate and conservative tracer addition to investigate the spatial and temporal physiochemical...

Sediment trapping by streamside management zones of various widths after forest harvest and site preparation

Treesearch

William Lakel; Wallace Aust; M. Aust; Chad Bolding; C. Dolloff; Patrick Keyser; Robert Feldt

2010-01-01

Recommended widths for streamside management zones (SMZs) for sediment protection vary. The objectives of this study were to compare the effects of SMZ widths and thinning levels on sediment moving through SMZs. Four SMZ treatments were installed within 16 harvested watersheds where intermittent streams graded into small perennial streams. Sites were clearcut,...

Response of herbaceous plant community diversity and composition to overstorey harvest within riparian management zones in Northern Hardwoods

Treesearch

Eric K. Zenner; Michelle A. Martin; Brian J. Palik; Jerilynn E. Peck; Charles R. Blinn

2013-01-01

Partial timber harvest within riparian management zones (RMZs) may permit active management of riparian forests while protecting stream ecosystems, but impacts on herbaceous communities are poorly understood. We compared herbaceous plant community abundance, diversity and composition in RMZs along small streams in northern Minnesota, USA, among four treatments before...

Scrubbing of contaminants from contaminated air streams with aerogel materials with optional photocatalytic destruction

DOEpatents

Attia, Yosry A.

2000-01-01

Disclosed is a method for separating a vaporous or gaseous contaminant from an air stream contaminated therewith. This method includes the steps of: (a) passing said contaminated air into a contact zone in which is disposed an aerogel material capable of selecting adsorbing said contaminant from air and therein contacting said contaminated air with an aerogel material; and (b) withdrawing from said zone, air depleted of said contaminant. For present purposes, "contaminant" means a material not naturally occurring in ambient air and/or a material naturally occurring in air but present at a concentration above that found in ambient air. Thus, the present invention scrubs (or treats) air for the purpose of returning it to its ambient composition. Also disclosed herein is a process for the photocatalytic destruction of contaminants from an air stream wherein the contaminated air stream is passed into a control cell or contact zone in which is disposed a photocatalytic aerogel and exposing said aerogel to ultraviolet (UV) radiation for photocatalytically destroying the adsorbed contaminant, and withdrawing from said cell an exhaust air stream depleted in said contaminant.

Baseline Characterization of Forested Headwater Stream Hydrology and Water Chemistry in Southwest Georgia

Treesearch

David G. Jones; William B. Summer; Masato Miwa; C. Rhett Jackson

2004-01-01

Stream hydrology and water quality in headwater streams are important components of ecosystem health. The Dry Creek Long-Term Watershed Study is designed to evaluate the effects of upland forestry operations and stream management zone (SMZ) thinning on stream hydrology, water quality, benthic macroinvertebrates, and other biologicindicators. The study also tests the...

Repeating Earthquake and Nonvolcanic Tremor Observations of Aseismic Deep Fault Transients in Central California.

NASA Astrophysics Data System (ADS)

Nadeau, R. M.; Traer, M.; Guilhem, A.

2005-12-01

Seismic indicators of fault zone deformation can complement geodetic measurements by providing information on aseismic transient deformation: 1) from deep within the fault zone, 2) on a regional scale, 3) with intermediate temporal resolution (weeks to months) and 4) that spans over 2 decades (1984 to early 2005), including pre- GPS and INSAR coverage. Along the San Andreas Fault (SAF) in central California, two types of seismic indicators are proving to be particularly useful for providing information on deep fault zone deformation. The first, characteristically repeating microearthquakes, provide long-term coverage (decades) on the evolution of aseismic fault slip rates at seismogenic depths along a large (~175 km) stretch of the SAF between the rupture zones of the ~M8 1906 San Francisco and 1857 Fort Tejon earthquakes. In Cascadia and Japan the second type of seismic indicator, nonvolcanic tremors, have shown a remarkable correlation between their activity rates and GPS and tiltmeter measurements of transient deformation in the deep (sub-seismogenic) fault zone. This correlation suggests that tremor rate changes and deep transient deformation are intimately related and that deformation associated with the tremor activity may be stressing the seismogenic zone in both areas. Along the SAF, nonvolcanic tremors have only recently been discovered (i.e., in the Parkfield-Cholame area), and knowledge of their full spatial extent is still relatively limited. Nonetheless the observed temporal correlation between earthquake and tremor activity in this area is consistent with a model in which sub-seismogenic deformation and seismogenic zone stress changes are closely related. We present observations of deep aseismic transient deformation associated with the 28 September 2004, M6 Parkfield earthquake from both repeating earthquake and nonvolcanic tremor data. Also presented are updated deep fault slip rate estimates from prepeating quakes in the San Juan Bautista area with an assessment of their significance to previously reported quasi-periodic slip rate pulses and small to moderate magnitude (> M3.5) earthquake occurrence in the area.

Decoupling of stream and vegetation solutes during the late stages of weathering: insights from elemental and Mg isotope trends at the Luquillo Critical Zone Observatory, Puerto Rico

NASA Astrophysics Data System (ADS)

Chapela Lara, M.; Schuessler, J. A.; Buss, H. L.; McDowell, W. H.

2017-12-01

During the evolution of the critical zone, the predominant source of nutrients to the vegetation changes from bedrock weathering to atmospheric inputs and biological recycling. In parallel, the architecture of the critical zone changes with time, promoting a change in water flow regime from near-surface porous flow during early weathering stages to more complex flow regimes modulated by clay-rich regolith during the late stages of weathering. As a consequence of these two concurrent processes, we can expect the predominant sources and pathways of solutes to the streams to also change during critical zone evolution. If this is true, we would observe a decoupling between the solutes used by the vegetation and those that determine the composition of the streams during the late stages of weathering, represented by geomorphically stable tropical settings. To test these hypotheses, we are analyzing the elemental and Mg isotopic composition of regolith and streams at the humid tropical Luquillo Critical Zone Observatory. We aim to trace the relative contributions of the surficial, biologically mediated pathways and the deeper, weathering controlled nutrient pathways. We also investigate the role of lithology on the solute decoupling between the vegetation and the stream, by examining two similar headwater catchments draining two different bedrocks (andesitic volcaniclastic and granitic). Our preliminary elemental and Mg isotope results are consistent with atmospheric inputs in the upper 2 m of regolith in both lithologies and with bedrock weathering at depth. During a short storm event ( 6 h), a headwater stream draining volcaniclastic bedrock showed a large variation in Mg and δ26Mg, correlated with total suspended solids, while another similar headwater granitic stream showed a much narrower variation. A larger stream draining volcaniclastic bedrock showed changes in Mg concentration in response to rain during the same storm event, but did not change in δ26Mg, suggesting the surficial-deep decoupling of solutes we observe in regolith profiles and headwater catchments might be overwhelmed by storage effects at increasing water residence times.

Landslide-induced iron mobilisation shapes benthic accumulation of nutrients, trace metals and REE fractionation in an oligotrophic alpine stream

NASA Astrophysics Data System (ADS)

Johnston, Scott G.; Rose, Andrew L.; Burton, Edward D.; Webster-Brown, Jenny

2015-01-01

Large alpine landslides that entrain substantial organic material below the water table and create suspended floodplains may have long-term consequences for the mobilisation of redox sensitive elements, such as Fe, into streamwaters. In turn, the cycling of iron in aquatic systems can influence the fate of nutrients, alter primary productivity, enhance accumulation of trace metals and induce fractionation of rare earth elements (REE). In this study we examine a reach of a pristine oligotrophic alpine stream bracketing a 30 year-old landslide and explore the consequences of landslide-induced Fe mobilisation for aqueous geochemistry and the composition of benthic stream cobble biofilm. Elevated Fe2+ and Mn in landslide zone stream waters reflect inputs of circumneutral groundwater from the landslide debris-zone floodplain. Geochemical characteristics are consistent with reductive dissolution being a primary mechanism of Fe2+ and Mn mobilisation. Stream cobble biofilm in the landslide zone is significantly (P < 0.01) enriched in poorly crystalline Fe(III) (∼10-400 times background) and Mn (∼15-150 times background) (1 M HCl extractable; Fe(III)Ab). While the landslide zone accounts for less than ∼9% of the total stream length, we estimate it is responsible for approximately 60-80% of the stream's benthic biofilm load of poorly crystalline Fe(III) and Mn. Biofilm Fe(III) precipitates are comprised mainly of ferrihydrite, lepidocrocite and an organic-Fe species, while precipitate samples collected proximal to hyporheic seeps contain abundant sheath structures characteristic of the neutrophilic Fe(II)-oxidising bacteria Leptothrix spp. Stream-cobble Fe(III)-rich biofilm is accumulating PO43- (∼3-30 times background) and behaving as a preferential substrate for photosynthetic periphyton, with benthic PO43-, chlorophyll a, organic carbonHCl and total N all significantly positively correlated with Fe(III)Ab and significantly elevated within the landslide zone (P < 0.01). P K-edge XANES indicates P is associated with both ferric and Ca-phosphate minerals, while SEM-EDX elemental mapping of Fe(III) precipitates reveal strong spatial associations between P, Ca and Fe. Cobble Fe(III)-rich biofilm is also sorbing and accumulating multiple trace metals and REE. Within the landslide zone there are significant (P < 0.01) enrichments (up to ∼10-100 times background) for most trace metals examined here and metals display significant positive linear correlations with Fe(III)Ab on a log transformed basis. Stream cobble biofilm also exhibits distinct REE fractionation along the flow path, with light REE (La, Ce, Nd, Pr) preferentially partitioning to the Fe(III) and Mn-rich biofilm within the landslide zone. Accumulation of PO43- and trace metals in this relatively environmentally labile form may have implications for their bioavailability and downstream transport, but further research is required to assess possible ecological consequences. This study demonstrates the potential for large alpine landslides to encourage reach-scale circumneutral Fe mobilisation in adjacent streams, thereby shaping multiple aspects of benthic stream geochemistry for many years after the landslide event itself.

An alternative regionalization scheme for defining nutrient criteria for rivers and streams

USGS Publications Warehouse

Robertson, Dale M.; Saad, David A.; Wieben, Ann M.

2001-01-01

The environmental nutrient zone approach can be applied to specific states or nutrient ecoregions and used to develop criteria as a function of stream type. This approach can also be applied on the basis of environmental characteristics of the watershed alone rather than the general environmental characteristics from the region in which the site is located. The environmental nutrient zone approach will enable states to refine the basic nutrient criteria established by the USEPA by developing attainable criteria given the environmental characteristics where the streams are located.

Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance

USGS Publications Warehouse

Harvey, Judson W.; Fuller, Christopher C.

1998-01-01

We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport of trace metals. The basin-scale role of the hyporheic zone is difficult to quantify because stream-tracer studies do not always reliably characterize the cumulative effects of the hyporheic zone. This study determined cumulative effects of hyporheic reactions in Pinal Creek basin by characterizing manganese uptake at several spatial scales (stream-reach scale, hyporheic-flow-path scale, and sediment-grain scale). At the stream-reach scale a one-dimensional stream-transport model (including storage zones to represent hyporheic flow paths) was used to determine a reach-averaged time constant for manganese uptake in hyporheic zones, 1/λs, of 1.3 hours, which was somewhat faster but still similar to manganese uptake time constants that were measured directly in centimeter-scale hyporheic flow paths (1/λh= 2.6 hours), and in laboratory batch experiments using streambed sediment (1/λ = 2.7 hours). The modeled depths of subsurface storage zones (ds = 4–17 cm) and modeled residence times of water in storage zones (ts = 3–12 min) were both consistent with direct measurements in hyporheic flow paths (dh = 0–15 cm, th = 1–25 min). There was also good agreement between reach-scale modeling and direct measurements of the percentage removal of dissolved manganese in hyporheic flow paths (fs = 8.9%, andfh = 9.3%rpar;. Manganese uptake experiments in the laboratory using sediment from Pinal Creek demonstrated (through comparison of poisoned and unpoisoned treatments) that the manganese removal process was enhanced by microbially mediated oxidation. The cumulative effect of hyporheic exchange in Pinal Creek basin was to remove approximately 20% of the dissolved manganese flowing out of the drainage basin. Our results illustrate that the cumulative significance of reactive uptake in the hyporheic zone depends on the balance between chemical reaction rates, hyporheic porewater residence time, and turnover of streamflow through hyporheic flow paths. The similarity between the hyporheic reaction timescale (1/λs ≈ 1.3 hours), and the hyporheic porewater residence timescale (ts ≈ 8 min) ensured that there was adequate time for the reaction to progress. Furthermore, it was the similarity between the turnover length for stream water flow through hyporheic flow paths (Ls = stream velocity/storage-zone exchange coefficient ≈ 1.3 km) and the length of Pinal Creek (L ≈ 7 km), which ensured that all stream water passed through hyporheic flow paths several times. As a means to generalize our findings to other sites where similar types of hydrologic and chemical information are available, we suggest a cumulative significance index for hyporheic reactions, Rs = λstsL/Ls (dimensionless); higher values indicate a greater potential for hyporheic reactions to influence geochemical mass balance. Our experience in Pinal Creek basin suggests that values of Rs > 0.2 characterize systems where hyporheic reactions are likely to influence geochemical mass balance at the drainage-basin scale.

AN INTERREGIONAL COMPARISON OF CHANNEL STRUCTURE, TRANSIENT STORAGE, AND RIPARIAN COVER WITH COMMUNITY METABOLISM IN STREAMS DRAINING EARLY- AND MID-SUCCESSIONAL WATERSHEDS

EPA Science Inventory

The goal of this research was to evaluate stream ecosystem function in response to different forest harvest intensities and time since harvest. Research was conducted in North Carolina, Arkansas, Oregon, and California.

Design of Remediation Actions for Nutrient Mitigation in the Hyporheic Zone

NASA Astrophysics Data System (ADS)

Morén, I.; Wörman, A.; Riml, J.

2017-11-01

Although hyporheic exchange has been shown to be of great importance for the overall water quality of streams, it is rarely considered quantitatively in stream remediation projects. A main driver of hyporheic exchange is the hydraulic head fluctuation along the streambed, which can be enhanced by modifications of the streambed topography. Here we present an analytical 2-D spectral subsurface flow model to estimate the hyporheic exchange associated with streambed topographies over a wide range of spatial scales; a model that was validated using tracer-test-results and measurements of hydraulic conductivity. Specifically, engineered steps in the stream were shown to induce a larger hyporheic exchange velocity and shorter hyporheic residence times compared to the observed topography in Tullstorps Brook, Sweden. Hyporheic properties were used to parameterize a longitudinal transport model that accounted for reactions in terms of first-order decay and instantaneous adsorption. Theoretical analyses of the mitigation effect for nitrate due to denitrification in the hyporheic zone show that there is a Damköhler number of the hyporheic zone, associated with several different stream geomorphologies, that optimizes nitrate mass removal on stream reach scale. This optimum can be limited by the available hydraulic head gradient given by the slope of the stream and the geological constraints of the streambed. The model illustrates the complex interactions between design strategies for nutrient mitigation, hyporheic flow patterns, and stream biogeochemistry and highlights the importance to diagnose a stream prior remediation, specifically to evaluate if remediation targets are transport or reaction controlled.

Hyporheic Passive Flux Meters Reveal Inverse Vertical Zonation and High Seasonality of Nitrogen Processing in an Anthropogenically Modified Stream (Holtemme, Germany)

NASA Astrophysics Data System (ADS)

Kunz, Julia Vanessa; Annable, Michael D.; Rao, Suresh; Rode, Michael; Borchardt, Dietrich

2017-12-01

Transformation and retention of nitrogen and other biologically reactive solutes in the hyporheic zones of running water contribute to an essential ecosystem service. However, the synoptic impact of intense agricultural or urban land-uses, elevated nutrient loading, flow alterations, riparian clear-cutting, and channelization on the source-sink behavior of solutes in hyporheic zones remains largely uncharacterized and unquantified. Therefore, we studied nutrient dynamics in a hydromorphologically and chemically modified stream reach using a new monitoring approach allowing the simultaneous measurement of nutrient and water flux through a screened area in the subsurface of rivers (hyporheic passive flux meter, HPFM). With HPFMs we directly assessed time-integrated lateral hyporheic nitrate fluxes during early spring and midsummer covering different temperature and discharge regimes. Contrary to our expectations, higher stream discharge coincided with substantially lower hyporheic exchange rates. While in streams featuring a natural morphology, bed form induced exchange commonly increases with surface flow, the influence of groundwater level was dominant in this reach. Furthermore, in contrast to less impacted environments, where progressive substrate depletion with depths reduces metabolic rates in the subsurface, we identified not the upper, but the intermediate layer of the hyporheic zone as hot spot of nutrient turnover. Overall, the hyporheic zone at the study site functioned partly as nitrate source, partly as a sink. Neither of the commonly used determinants redox state and residence time could explain this source or sink function. Our results give clear evidence to carefully transfer the knowledge of hyporheic zone processes from "natural" systems to anthropologically modified streams.

Hydrogeology of a Danish Riparian Lowland: the Importance of Groundwater Upwelling on Nitrate Removal

NASA Astrophysics Data System (ADS)

Steiness, M.; van't Veen, S. G. W.; Jessen, S.; Engesgaard, P. K.

2016-12-01

Riparian zones are critical interfaces between streams and uplands with many of the characteristics for being key areas for nitrate removal. The hydrogeology is a controlling factor for the source, flow paths, magnitude of groundwater discharge to the stream, nitrate loading, and therefore the occurrence of "hot spots" with increased denitrification. A riparian lowland was investigated through field studies (geophysics, hydrogeology), water quality assessment, and flow and reactive transport modelling. One of the objectives was to understand the role of the landscape and hydrogeology on diffusive versus focused groundwater discharge and also nitrate removal. The investigated riparian zone is characterized by diffusive flow of groundwater to the stream from the northern bank (from a maize field) and groundwater upwelling in several places with overland flow to the stream from south (wetland area). Nitrate is effectively removed by pyrite oxidation (as shown by the reactive transport model high sulphate concentrations) on the northern side, whereas the groundwater-fed springs carry up to 74 mg/L nitrate. Groundwater flow modeling shows that upwelling may account for almost 25 % of the flow to the stream. Two other riparian zones were subsequently included and, on the catchment scale, the occurrence of diffusive and focused discharge is found to be common suggesting that riparian zones in this area are only partly effective in removing nitrate.

Effectiveness of streamside management zones on water quality: pretreatment measurements

Treesearch

J.L. Boggs; G. Sun; S.G. McNulty; W. Swartley; E. Treasure

2008-01-01

The objective of this paired watershed study is to quantify the effects of upland forest harvesting and Streamside Management Zones (SMZs) on stream water quantity and quality in North Carolina. Four watersheds ranging from 12 to 28 hectares (i.e., two on Hill Forest and two on Umstead Research Farm) with perennial stream channels were gauged for flow monitoring and...

Assessment of streamside management zones for conserving benthic macroinvertebrate communities following timber harvest in eastern Kentucky headwater catchments

Treesearch

Joshua Adkins; Christopher Barton; Scott Grubbs; Jeffrey Stringer; Randy Kolka

2016-01-01

Headwater streams generally comprise the majority of stream area in a watershed and can have a strong influence on downstream food webs. Our objective was to determine the effect of altering streamside management zone (SMZ) configurations on headwater aquatic insect communities. Timber harvests were implemented within six watersheds in eastern Kentucky. The SMZ...

The transition from riparian to upland forest plant communities on headwater streams in the southern Sierra Nevada, California, United States

Treesearch

Christopher R. Dolanc; Carolyn T. Hunsaker

2017-01-01

Abstract. Fixed-width buffer zones on rivers and streams are designed to protect the diverse riparian community and its important function in the ecosystem. However, recent data suggest that riparian areas of some western forests have become more fire prone because of restrictions on fuel reduction treatments within buffer zones....

Silvicultural management within streamside management zones of intermittent streams: effects on decomposition, productivity, nutrient cycling, and channel vegetation

Treesearch

R. Governo; B. G. Lockaby; Robert B. Rummer; C. Colson

2004-01-01

The purpose of this watershed study on three intermittent streams was to evaluate responses of riparian processes to three streamside management zone (SMZ) treatments; no harvest, clearcut, and partial hawest (50% basal area removal). Riparian response variables measured included litter$all, leaf litter decomposition, understory vegetation, soil temperature and water...

Watershed scale assessment of the impact of forested riparian zones on stream water quality

Treesearch

J. A. Webber; K. W. J. Williard; M. R. Whiles; M. L. Stone; J. J. Zaczek; D. K. Davie

2003-01-01

Federal and state land management agencies have been promoting forest and grass riparian zones to combat non-point source nutrient and sediment pollution of our nations' waters. The majority of research examining the effectiveness of riparian buffers at reducing nutrient and sediment inputs to streams has been conducted at the field scale. This study took a...

Effects of riparian buffer width on wood loading in headwater streams after repeated forest thinning

Treesearch

Julia I. Burton; Deanna H. Olson; Klaus J. Puettmann

2016-01-01

Forested riparian buffer zones are used in conjunction with upland forest management, in part, to provide for the recruitment for large wood to streams. Small headwater streams account for the majority of stream networks in many forested regions. Yet, our understanding of how riparian buffer width influences wood dynamics in headwater streams is relatively less...

Songbird use of floodplain and upland forests along the Upper Mississippi River corridor during spring migration

USGS Publications Warehouse

Kirsch, Eileen M.; Heglund, Patricia J.; Gray, Brian R.; Mckann, Patrick

2013-01-01

The Upper Mississippi River is thought to provide important stopover habitat for migrating landbirds because of its north-south orientation and floodplain forests. The river flows through the Driftless Area of southwestern Wisconsin and southeastern Minnesota where forests are plentiful, yet forests of the floodplain and Driftless Area uplands differ greatly in landscape setting, tree species composition, and topography. We compared landbird assemblages in these upland and floodplain forests over three springs, 2005–2007, using line-transect surveys at randomly selected areas in and within 16 km of the floodplain. We found more species of both transient and locally breeding migrants per survey in floodplain than in upland forest. Detections of transient neotropical migrants did not differ statistically by habitat. Detections of locally breeding neotropical and temperate-zone migrants and transient temperate-zone migrants were greater in floodplain than in upland forest. Between floodplain and upland forest, assemblages of locally breeding species, including neotropical and temperate-zone migrants (of which some individuals were in transit), differed substantially, but assemblages of transients (including both neotropical and temperate-zone migrants) did not differ as much. Only two species of transient migrants had clear affinities for floodplain forest, and none had an affinity for upland forest, whereas most locally breeding migrants had an affinity for either upland or floodplain forest. Within each spring, however, detections of transient neotropical migrants shifted from being greater in floodplain to greater in upland forests. This intraseasonal shift may be related to the phenology of certain tree species.

Transport of a conservative and "smart" tracers' in a first-order creek: role of transient storage type

USDA-ARS?s Scientific Manuscript database

Quantification of microbial fate and transport in streams has become one of most important topics in studying biogeochemical properties and behavior of stream ecosystems. Using "smart" tracer such as resazurin (Raz) allows assessment of sediment-water interactions and associated biological activity ...

Exploring lag times between monthly atmospheric deposition and stream chemistry in Appalachian Forest using cross-correlation

USDA-ARS?s Scientific Manuscript database

Although long-term reductions in surface water nitrogen and sulfate concentrations have been widely observed in response to reductions in atmospheric deposition, documenting and inter-relating transient variations in deposition and stream time series has proven problematical due to low signal-to-noi...

Metathesis process for preparing an alpha, omega-functionalized olefin

DOEpatents

Burdett, Kenneth A.; Mokhtarzadeh, Morteza; Timmers, Francis J.

2010-10-12

A cross-metathesis process for preparing an .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, and an .alpha.-olefin having three or more carbon atoms, such as 1-decene. The process involves contacting in a first reaction zone an .alpha.-functionalized internal olefin, such as methyl oleate, and an .alpha.-olefinic monomer having three or more carbon atoms, such as 1-decene, with a first metathesis catalyst to prepare an effluent stream containing the .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, an unfunctionalized internal olefin, such as 9-octadecene, unconverted reactant olefins, and optionally, an .alpha.,.omega.-difunctionalized internal olefinic dimer, such as dimethyl 9-octadecen-1,18-dioate; separating said effluent streams; then contacting in a second reaction zone the unfunctionalized internal olefin with ethylene in the presence of a second metathesis catalyst to obtain a second product effluent containing the .alpha.-olefinic monomer having three or more carbon atoms; and cycling a portion of the .alpha.-olefinic monomer stream(s) to the first zone.

On the nonlinear forced response of the North Atlantic atmosphere to meridional shifts of the Gulf Stream path

NASA Astrophysics Data System (ADS)

Seo, H.; Kwon, Y. O.; Joyce, T. M.; Ummenhofer, C.

2016-12-01

This study examines the North Atlantic atmospheric circulation response to the meridional shift of Gulf Stream path using a large-ensemble, high-resolution, and hemispheric-scale WRF simulations. The model is forced with wintertime SST anomalies derived from a wide range of Gulf Stream shift scenarios. The key result of the model experiments, supported in part by an independent analysis of a reanalysis data set, is that the large-scale, quasi-steady North Atlantic circulation response is unambiguously nonlinear about the sign and amplitude of chosen SST anomalies. This nonlinear response prevails over the weak linear response and resembles the negative North Atlantic Oscillation, the leading intrinsic mode of variability in the model and the observations. Further analysis of the associated dynamics reveals that the nonlinear responses are accompanied by the anomalous southward shift of the North Atlantic eddy-driven jet stream, which is reinforced nearly equally by the high-frequency transient eddy feedback and the low-frequency high-latitude wave breaking events. The result highlights the importance of the intrinsically nonlinear transient eddy dynamics and eddy-mean flow interactions in generating the nonlinear forced response to the meridional shift in the Gulf Stream.

Integrated assessment of sources, chemical stressors and stream quality along a groundwater fed stream system

NASA Astrophysics Data System (ADS)

Løgstrup Bjerg, Poul; Sonne, Anne T.; Rønde, Vinni; McKnight, Ursula S.

2016-04-01

Streams are impacted by significant contamination at the catchment scale, as they are often locations of multiple chemical stressor inputs. The European Water Framework Directive requires EU member states to ensure good chemical and ecological status of surface water bodies by 2027. This requires monitoring of stream water quality, comparison with environmental quality standards (EQS) and assessment of ecological status. However, the achievement of good status of stream water also requires a strong focus on contaminant sources, pathways and links to stream water impacts, so source management and remedial measures can be implemented. Fate and impacts of different contaminant groups are governed by different processes and are dependent on the origin (geogenic, anthropogenic), source type (point or diffuse) and pathway of the contaminant. To address this issue, we identified contaminant sources and chemical stressors on a groundwater-fed stream to quantify the contaminant discharges, link the chemical impact and stream water quality and assess the main chemical risk drivers in the stream system potentially driving ecological impact. The study was conducted in the 8 m wide Grindsted stream (Denmark) along a 16 km stream stretch that is potentially impacted by two contaminated sites (Grindsted Factory site, Grindsted Landfill), fish farms, waste water discharges, and diffuse sources from agriculture and urban areas. Water samples from the stream and the hyporheic zone as well as bed sediment samples were collected during three campaigns in 2012 and 2014. Data for xenobiotic organic groundwater contaminants, pesticides, heavy metals, general water chemistry, physical conditions and stream flow were collected. The measured chemical concentrations were converted to toxic units (TU) based on the 48h acute toxicity tests with D. magna. The results show a substantial impact of the Grindsted Factory site at a specific stretch of the stream. The groundwater plume caused elevated concentrations of chlorinated ethenes, benzene and site specific pharmaceuticals in both the hyporheic zone and the stream water. Observed stream water vinyl chloride concentrations (up to 6 μg/L) are far above the Danish EQS (0.05 μg/L) for several km downstream of the discharge area. For heavy metals, comparison with EQS in stream water, the hyporheic zone and streambed showed concentrations around or above the threshold values for barium, copper, lead, nickel and zinc. The calculated TU was generally similar along the stream, but for arsenic and nickel higher values were observed where the groundwater plume discharges into the stream. Also, log TU sum values for organic contaminants were elevated in both the hyporheic zone and stream. Thus, the overall chemical stress in the main discharge area is much higher than upstream, while it gradually decreases downstream. In conclusion, this work clearly shows that groundwater contaminant plumes can impact stream water quality significantly in discharge areas, and extend far downstream. A surprisingly high impact of heavy metals with diffuse and/or biogenic origin on stream quality was identified. This work highlights the importance of a holistic assessment of stream water quality to identify and quantify the main contaminant sources and resulting chemical stream stressors leading to potential ecological impacts.

Sources of Geomagnetic Activity during Nearly Three Solar Cycles (1972-2000)

NASA Technical Reports Server (NTRS)

Richardson, I. G.; Cane, H. V.; Cliver, E. W.; White, Nicholas E. (Technical Monitor)

2002-01-01

We examine the contributions of the principal solar wind components (corotating highspeed streams, slow solar wind, and transient structures, i.e., interplanetary coronal mass ejections (CMEs), shocks, and postshock flows) to averages of the aa geomagnetic index and the interplanetary magnetic field (IMF) strength in 1972-2000 during nearly three solar cycles. A prime motivation is to understand the influence of solar cycle variations in solar wind structure on long-term (e.g., approximately annual) averages of these parameters. We show that high-speed streams account for approximately two-thirds of long-term aa averages at solar minimum, while at solar maximum, structures associated with transients make the largest contribution (approx. 50%), though contributions from streams and slow solar wind continue to be present. Similarly, high-speed streams are the principal contributor (approx. 55%) to solar minimum averages of the IMF, while transient-related structures are the leading contributor (approx. 40%) at solar maximum. These differences between solar maximum and minimum reflect the changing structure of the near-ecliptic solar wind during the solar cycle. For minimum periods, the Earth is embedded in high-speed streams approx. 55% of the time versus approx. 35% for slow solar wind and approx. 10% for CME-associated structures, while at solar maximum, typical percentages are as follows: high-speed streams approx. 35%, slow solar wind approx. 30%, and CME-associated approx. 35%. These compositions show little cycle-to-cycle variation, at least for the interval considered in this paper. Despite the change in the occurrences of different types of solar wind over the solar cycle (and less significant changes from cycle to cycle), overall, variations in the averages of the aa index and IMF closely follow those in corotating streams. Considering solar cycle averages, we show that high-speed streams account for approx. 44%, approx. 48%, and approx. 40% of the solar wind composition, aa, and the IMF strength, respectively, with corresponding figures of approx. 22%, approx. 32%, and approx. 25% for CME-related structures, and approx. 33%, approx. 19%, and approx. 33% for slow solar wind.

MODELING STREAM-AQUIFIER INTERACTIONS WITH LINEAR RESPONSE FUNCTIONS

EPA Science Inventory

The problem of stream-aquifer interactions is pertinent to conjunctive-use management of water resources and riparian zone hydrology. Closed form solutions are derived for stream-aquifer interactions in rates and volumes expressed as convolution integrals of impulse response and ...

The Effect of Beaver Activity on the Ammonium Uptake and Water Residence Time Characteristics of a Third-Order Stream Reach

NASA Astrophysics Data System (ADS)

Briggs, M.; Gooseff, M. N.; Wollheim, W. M.; Peterson, B. J.; Morkeski, K.

2009-12-01

Increasing beaver populations within low gradient basins in the northeastern United States are fundamentally changing the way water and dissolved nutrients are exported through these stream networks to the coast. Beaver dams can increase water residence time and contact with organic material, promote anoxic conditions and enhance both surface and hyporheic transient storage; all of these may have an impact on biogeochemical reactivity and nutrient retention. To quantitatively assess some of these effects we co-injected NaCl and NH4+ into the same 3rd-order stream reach in Massachusetts, USA under pre- and post-dam conditions. These experiments were done at similar discharge rates to isolate the impacts of a large natural beaver dam (7 m X 1.3 m) on the low-gradient (0.002) system where variable discharge also imparts a strong control on residence time. During the post-dam experiment there was an estimated 2300 m3 of water impounded behind the structure, which influenced more than 300 m of the 650 m stream reach. Our results showed that median transport time through the reach increased by 160% after dam construction. Additionally the tracer tailing time normalized to the corresponding median transport time increased from 1.08 to 1.51, indicating a pronounced tailing of the tracer signal in the post-dam condition. Data collected within the beaver pond just upstream of the dam indicated poor mixing and the presence of preferential flow paths through the generally stagnant zone. The uptake length (Sw) for NH4+ was 1250 m under the pre-dam condition, and may have changed for the post-dam reach in part because of the observed changes in residence time. As beaver population growth continues within these basins the consequences may be a smoothing of the outlet hydrograph and increased nutrient and organic matter removal and storage along the stream network.

Simulating spontaneous aseismic and seismic slip events on evolving faults

NASA Astrophysics Data System (ADS)

Herrendörfer, Robert; van Dinther, Ylona; Pranger, Casper; Gerya, Taras

2017-04-01

Plate motion along tectonic boundaries is accommodated by different slip modes: steady creep, seismic slip and slow slip transients. Due to mainly indirect observations and difficulties to scale results from laboratory experiments to nature, it remains enigmatic which fault conditions favour certain slip modes. Therefore, we are developing a numerical modelling approach that is capable of simulating different slip modes together with the long-term fault evolution in a large-scale tectonic setting. We extend the 2D, continuum mechanics-based, visco-elasto-plastic thermo-mechanical model that was designed to simulate slip transients in large-scale geodynamic simulations (van Dinther et al., JGR, 2013). We improve the numerical approach to accurately treat the non-linear problem of plasticity (see also EGU 2017 abstract by Pranger et al.). To resolve a wide slip rate spectrum on evolving faults, we develop an invariant reformulation of the conventional rate-and-state dependent friction (RSF) and adapt the time step (Lapusta et al., JGR, 2000). A crucial part of this development is a conceptual ductile fault zone model that relates slip rates along discrete planes to the effective macroscopic plastic strain rates in the continuum. We test our implementation first in a simple 2D setup with a single fault zone that has a predefined initial thickness. Results show that deformation localizes in case of steady creep and for very slow slip transients to a bell-shaped strain rate profile across the fault zone, which suggests that a length scale across the fault zone may exist. This continuum length scale would overcome the common mesh-dependency in plasticity simulations and question the conventional treatment of aseismic slip on infinitely thin fault zones. We test the introduction of a diffusion term (similar to the damage description in Lyakhovsky et al., JMPS, 2011) into the state evolution equation and its effect on (de-)localization during faster slip events. We compare the slip spectrum in our simulations to conventional RSF simulations (Liu and Rice, JGR, 2007). We further demonstrate the capability of simulating the evolution of a fault zone and simultaneous occurrence of slip transients. From small random initial distributions of the state variable in an otherwise homogeneous medium, deformation localizes and forms curved zones of reduced states. These spontaneously formed fault zones host slip transients, which in turn contribute to the growth of the fault zone.

Effects of beach morphology and waves on onshore larval transport

NASA Astrophysics Data System (ADS)

Fujimura, A.; Reniers, A.; Paris, C. B.; Shanks, A.; MacMahan, J.; Morgan, S.

2015-12-01

Larvae of intertidal species grow offshore, and migrate back to the shore when they are ready to settle on their adult substrates. In order to reach the habitat, they must cross the surf zone, which is characterized as a semi-permeable barrier. This is accomplished through physical forcing (i.e., waves and current) as well as their own behavior. Two possible scenarios of onshore larval transport are proposed: Negatively buoyant larvae stay in the bottom boundary layer because of turbulence-dependent sinking behavior, and are carried toward the shore by streaming of the bottom boundary layer; positively buoyant larvae move to the shore during onshore wind events, and sink to the bottom once they encounter high turbulence (i.e., surf zone edge), where they are carried by the bottom current toward the shore (Fujimura et al. 2014). Our biophysical Lagrangian particle tracking model helps to explain how beach morphology and wave conditions affect larval distribution patterns and abundance. Model results and field observations show that larval abundance in the surf zone is higher at mildly sloped, rip-channeled beaches than at steep pocket beaches. Beach attributes are broken up to examine which and how beach configuration factors affect larval abundance. Modeling with alongshore uniform beaches with variable slopes reveal that larval populations in the surf zone are negatively correlated with beach steepness. Alongshore variability enhances onshore larval transport because of increased cross-shore water exchange by rip currents. Wave groups produce transient rip currents and enhance cross-shore exchange. Effects of other wave components, such as wave height and breaking wave rollers are also considered.

Electron heating within interaction zones of simple high-speed solar wind streams

NASA Technical Reports Server (NTRS)

Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gosling, J. T.; Lemons, D. S.

1978-01-01

In the present paper, electron heating within the high-speed portions of three simple stream-stream interaction zones is studied to further our understanding of the physics of heat flux regulation in interplanetary space. To this end, the thermal signals present in the compressions at the leading edges of the simple high-speed streams are analyzed, showing that the data are inconsistent with the Spitzer conductivity. Instead, a polynomial law is found to apply. Its implication concerning the mechanism of interplanetary heat conduction is discussed, and the results of applying this conductivity law to high-speed flows inside of 1 AU are studied. A self-consistent model of the radial evolution of electrons in the high-speed solar wind is proposed.

Hydrology and Hyporheic Nitrogen Biogeochemistry in a Geomorphically Degraded Urban Stream

EPA Science Inventory

Few studies have investigated the relationship between hydrology and nitrogen biogeochemistry in hyporheic zones of degraded urban streams despite significant national efforts to restore such streams in attempts to improve the nutrient uptake functions in these ecosystems. We ex...

Effect of deforestation on stream water chemistry in the Skrzyczne massif (the Beskid Śląski Mountains in southern Poland).

PubMed

Kosmowska, Amanda; Żelazny, Mirosław; Małek, Stanisław; Siwek, Joanna Paulina; Jelonkiewicz, Łukasz

2016-10-15

The purpose of the study was to identify the factors affecting stream water chemistry in the small mountain catchments deforested to varying degrees, from 98.7 to 14.1%, due to long-term acid deposition. Water samples were collected monthly in 2013 and 2014 from 17 streams flowing across three distinct elevation zones in the Skrzyczne massif (Poland): Upper, Middle and Lower Forest Zone. Chemical and physical analyses, including the pH, electrical conductivity (EC), total mineral content (Mt), water temperature, and the concentrations of Ca(2+), Mg(2+), Na(+), K(+), HCO3(-), SO4(2-), Cl(-), and NO3(-), were conducted. Based on Principal Component Analysis (PCA), the most important factor affecting water chemistry was human impact associated with changes in pH, SO4(2-) concentration, and the concentration of most of the main ions. The substantial acidity of the studied environment contributed to the exclusion of natural factors, associated with changes in discharge, from the list of major factors revealed by PCA. All of the streams were characterized by very low EC, Mt, and low concentrations of the main ions such as Ca(2+) and HCO3(-). This is the effect of continuous leaching of solutes from the soils by acidic precipitation. The lowest parameter values were measured for the streams situated in the Upper Forest Zone, which is associated with greater acid deposition at the higher elevations. In the streams located in the Upper Forest Zone, a higher percentage of SO4(2-) occurred than in the streams situated in the Middle and Lower Forest Zones. However, the largest share of SO4(2-) was measured in the most deforested catchment. The saturation of the studied deforested catchment with sulfur compounds is reflected by a positive correlation between SO4(2-) and discharge. Hence, a forest acts as a natural buffer that limits the level of acidity in the natural environment caused by acidic atmospheric deposition. Copyright © 2016 Elsevier B.V. All rights reserved.

Riparian zone flowpath dynamics during snowmelt in a small headwater catchment

NASA Astrophysics Data System (ADS)

McGlynn, B. L.; McDonnell, J. J.; Shanley, J. B.; Kendall, C.

1999-09-01

The hydrology of the near-stream riparian zone in upland humid catchments is poorly understood. We examined the spatial and temporal aspects of riparian flowpaths during snowmelt in a headwater catchment within the Sleepers River catchment in northern Vermont. A transect of 15 piezometers was sampled for Ca, Si, DOC, other major cations, and δ18O. Daily piezometric head values reflected variations in the stream hydrograph induced by melt and rainfall. The riparian zone exhibited strong upward discharge gradients. An impeding layer was identified between the till and surficial organic soil. Water solute concentrations increased toward the stream throughout the melt. Ca concentrations increased with depth and DOC concentrations decreased with depth. The concentrations of Ca in all piezometers were lower during active snowmelt than during post-melt low flow. Ca data suggest snowmelt infiltration to depth; however, only upslope piezometers exhibited snowmelt infiltration and consequent low δ18O values,(while δ18O values varied less than 0.5‰ in the deep riparian piezometers throughout the study period. Ca and δ18O values in upslope piezometers during low streamflow were comparable to Ca and δ18O in riparian piezometers during high streamflow. The upland water Ca and δ18O may explain the deep riparian Ca dilution and consistent δ18O composition. The temporal pattern in Ca and δ18O indicate that upland water moves to the stream via a lateral displacement mechanism that is enhanced by the presence of distinct soil/textural layers. Snowmelt thus initiates the flux of pre-melt, low Ca upland water to depth in the riparian zone, but itself does not appear at depth in the riparian zone during spring melt. This is despite the coincident response of upland groundwater and stream discharge.

DEVELOPMENT OF WATERSHED MANAGEMENT AND DECISION SUPPORT TOOLS FOR THE CANAAN VALLEY INSTITUTE (CVI) RIPARIAN ZONE AND STREAM RESTORATION

EPA Science Inventory

The USEPA Mid-Atlantic Highlands Streams Assessment (MAHA) report concluded that over 31% of stream miles in the Mid-Atlantic Highlands were in poor condition, and only 17% stream miles could be considered to be in good condition, based on their fish populations. Insect populatio...

A Comparison of Vegetation Within and Outside Riparian Areas Bordering Ephemeral Streams in the Ouachita Mountains

Treesearch

David K. Radabaugh; Hal O. Liechty; James M. Guldin

2004-01-01

Abstract - Ephemeral streams frequently occur in shortleaf pine (Pinus echinata Mill.) hardwood stands that grow on the upper and mid-slopes of the Ouachita Mountains in Arkansas. Stream management zones are established around these ephemeral streams in the Ouachita National Forest to minimize impacts of adjacent forest management...

Zone separator for multiple zone vessels

DOEpatents

Jones, John B.

1983-02-01

A solids-gas contact vessel, having two vertically disposed distinct reaction zones, includes a dynamic seal passing solids from an upper to a lower zone and maintaining a gas seal against the transfer of the separate treating gases from one zone to the other, and including a stream of sealing fluid at the seal.

Biogeochemistry and Hydrology in Streams Impacted by Legacy Sediments and Urbanization: Implications for Stream Restoration

EPA Science Inventory

The groundwater–surface water interface, consisting of shallow groundwater adjacent to stream channels, is a hot spot for nitrogen removal processes, a storage zone for other solutes, and a target for restoration activities. Characterizing groundwater-surface water interac...

Nitrogen dynamics at the groundwater-surface water interface of a degraded urban stream (journal)

EPA Science Inventory

Urbanization degrades stream ecosystems by altering hydrology and nutrient dynamics, yet relatively little effort has been devoted to understanding biogeochemistry of urban streams at the ground water-surface water interface. This zone may be especially important for nitrogen re...

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

Relative Linkages of Stream Dissolved Oxygen with the Climatic, Hydrological, and Biogeochemical Drivers across the East Coast of U.S.A.

NASA Astrophysics Data System (ADS)

Abdul-Aziz, O. I.; Ahmed, S.

2017-12-01

Dissolved oxygen (DO) is a key indicator of stream water quality and ecosystem health. However, the temporal dynamics of stream DO is controlled by a multitude of interacting environmental drivers. The relative linkages of stream DO with the relevant environmental drivers were determined in this study across the U.S. East Coast by employing a systematic data analytics approach. The study analyzed temporal data for 51 water quality monitoring stations from USGS NWIS and EPA STORET databases. Principal component analysis and factor analysis, along with Pearson's correlation analysis, were applied to identify the interrelationships and unravel latent patterns among DO and the environmental drivers. Power law based partial least squares regression models with a bootstarp Monte-Carlo procedure (1000 iterations) were developed to reliably estimate the environmental linkages of DO by resolving multicollinearity. Based on the similarity of dominant drivers, the streams were categorized into three distinct environmental regimes. Stream DO in the northern part of temperate zone (e.g., northeast coast) had the strongest linkage with water temperature; suggesting an environmental regime with dominant climatic control. However, stream DO in the tropical zones (e.g., southeast Florida) was mostly driven by pH; indicating an environmental regime likely controlled by redox chemistry. Further, a transitional regime was found between the temperate and tropical zones, where stream DO was controlled by both water temperature and pH. The results suggested a strong effect of the climatic gradient (temperate to tropical) on stream DO along the East Coast. The identified environmental regimes and the regime-specific relative linkages provided new information on the dominant controls of coastal stream water quality dynamics. The findings would guide the planning and management of coastal stream water quality and ecosystem health across the U.S. East Coast and around the world.

realfast: Real-time, Commensal Fast Transient Surveys with the Very Large Array

NASA Astrophysics Data System (ADS)

Law, C. J.; Bower, G. C.; Burke-Spolaor, S.; Butler, B. J.; Demorest, P.; Halle, A.; Khudikyan, S.; Lazio, T. J. W.; Pokorny, M.; Robnett, J.; Rupen, M. P.

2018-05-01

Radio interferometers have the ability to precisely localize and better characterize the properties of sources. This ability is having a powerful impact on the study of fast radio transients, where a few milliseconds of data is enough to pinpoint a source at cosmological distances. However, recording interferometric data at millisecond cadence produces a terabyte-per-hour data stream that strains networks, computing systems, and archives. This challenge mirrors that of other domains of science, where the science scope is limited by the computational architecture as much as the physical processes at play. Here, we present a solution to this problem in the context of radio transients: realfast, a commensal, fast transient search system at the Jansky Very Large Array. realfast uses a novel architecture to distribute fast-sampled interferometric data to a 32-node, 64-GPU cluster for real-time imaging and transient detection. By detecting transients in situ, we can trigger the recording of data for those rare, brief instants when the event occurs and reduce the recorded data volume by a factor of 1000. This makes it possible to commensally search a data stream that would otherwise be impossible to record. This system will search for millisecond transients in more than 1000 hr of data per year, potentially localizing several Fast Radio Bursts, pulsars, and other sources of impulsive radio emission. We describe the science scope for realfast, the system design, expected outcomes, and ways in which real-time analysis can help in other fields of astrophysics.

A software tool to assess uncertainty in transient-storage model parameters using Monte Carlo simulations

USGS Publications Warehouse

Ward, Adam S.; Kelleher, Christa A.; Mason, Seth J. K.; Wagener, Thorsten; McIntyre, Neil; McGlynn, Brian L.; Runkel, Robert L.; Payn, Robert A.

2017-01-01

Researchers and practitioners alike often need to understand and characterize how water and solutes move through a stream in terms of the relative importance of in-stream and near-stream storage and transport processes. In-channel and subsurface storage processes are highly variable in space and time and difficult to measure. Storage estimates are commonly obtained using transient-storage models (TSMs) of the experimentally obtained solute-tracer test data. The TSM equations represent key transport and storage processes with a suite of numerical parameters. Parameter values are estimated via inverse modeling, in which parameter values are iteratively changed until model simulations closely match observed solute-tracer data. Several investigators have shown that TSM parameter estimates can be highly uncertain. When this is the case, parameter values cannot be used reliably to interpret stream-reach functioning. However, authors of most TSM studies do not evaluate or report parameter certainty. Here, we present a software tool linked to the One-dimensional Transport with Inflow and Storage (OTIS) model that enables researchers to conduct uncertainty analyses via Monte-Carlo parameter sampling and to visualize uncertainty and sensitivity results. We demonstrate application of our tool to 2 case studies and compare our results to output obtained from more traditional implementation of the OTIS model. We conclude by suggesting best practices for transient-storage modeling and recommend that future applications of TSMs include assessments of parameter certainty to support comparisons and more reliable interpretations of transport processes.

Rethinking hyporheic flow and transient storage to advance understanding of stream-catchment connections

USGS Publications Warehouse

Bencala, K.E.; Gooseff, M.N.; Kimball, B.A.

2011-01-01

Although surface water and groundwater are increasingly referred to as one resource, there remain environmental and ecosystem needs to study the 10 m to 1 km reach scale as one hydrologic system. Streams gain and lose water over a range of spatial and temporal scales. Large spatial scales (kilometers) have traditionally been recognized and studied as river-aquifer connections. Over the last 25 years hyporheic exchange flows (1-10 m) have been studied extensively. Often a transient storage model has been used to quantify the physical solute transport setting in which biogeochemical processes occur. At the longer 10 m to 1 km scale of stream reaches it is now clear that streams which gain water overall can coincidentally lose water to the subsurface. At this scale, the amounts of water transferred are not necessarily significant but the exchanges can, however, influence solute transport. The interpretation of seemingly straightforward questions about water, contaminant, and nutrient fluxes into and along a stream can be confounded by flow losses which are too small to be apparent in stream gauging and along flow paths too long to be detected in tracer experiments. We suggest basic hydrologic approaches, e.g., measurement of flow along the channel, surface and subsurface solute sampling, and routine measurements of the water table that, in our opinion, can be used to extend simple exchange concepts from the hyporheic exchange scale to a scale of stream-catchment connection. Copyright 2011 by the American Geophysical Union.

Dry creek long-term watershed study: assessment of immediate response of aquatic macroinvertebrates to watershed level harvesting and thinning of streamside management zones

Treesearch

M.W. Griswold; R.T. Winn; T.L. Crisman; W.R. White

2006-01-01

Streamside Management Zones (SMZs) are meant to protect riparian habitat and the stream ecosystem. Benthic macroinvertebrates are recognized bioindicators of water quality in streams, typically occupying multiple trophic levels in these systems and providing food for vertebrates. Thus, it is important to understand the effects of harvest within and adjacent to the SMZ...

Effect of forest harvesting best management practices on coarse woody debris distribution in stream and riparian zones in three Appalachian watersheds

Treesearch

J. M. McClure; R. K. Kolka; A. White

2004-01-01

The distribution of coarse woody debris (CWD) was analyzed in three Appalachian watersheds in eastern Kentucky, eighteen years after harvest. The three watersheds included an unharvested control (Control), a second watershed with best management practices (BMPs) applied that included a 15.2 m unharvested zone near the stream (BMP watershed), and a third watershed that...

Catalytic distillation process

DOEpatents

Smith, Jr., Lawrence A.

1982-01-01

A method for conducting chemical reactions and fractionation of the reaction mixture comprising feeding reactants to a distillation column reactor into a feed zone and concurrently contacting the reactants with a fixed bed catalytic packing to concurrently carry out the reaction and fractionate the reaction mixture. For example, a method for preparing methyl tertiary butyl ether in high purity from a mixed feed stream of isobutene and normal butene comprising feeding the mixed feed stream to a distillation column reactor into a feed zone at the lower end of a distillation reaction zone, and methanol into the upper end of said distillation reaction zone, which is packed with a properly supported cationic ion exchange resin, contacting the C.sub.4 feed and methanol with the catalytic distillation packing to react methanol and isobutene, and concurrently fractionating the ether from the column below the catalytic zone and removing normal butene overhead above the catalytic zone.

Catalytic distillation process

DOEpatents

Smith, L.A. Jr.

1982-06-22

A method is described for conducting chemical reactions and fractionation of the reaction mixture comprising feeding reactants to a distillation column reactor into a feed zone and concurrently contacting the reactants with a fixed bed catalytic packing to concurrently carry out the reaction and fractionate the reaction mixture. For example, a method for preparing methyl tertiary butyl ether in high purity from a mixed feed stream of isobutene and normal butene comprising feeding the mixed feed stream to a distillation column reactor into a feed zone at the lower end of a distillation reaction zone, and methanol into the upper end of said distillation reaction zone, which is packed with a properly supported cationic ion exchange resin, contacting the C[sub 4] feed and methanol with the catalytic distillation packing to react methanol and isobutene, and concurrently fractionating the ether from the column below the catalytic zone and removing normal butene overhead above the catalytic zone.

Spatial occupancy patterns and activity of arid rangeland cattle grazing small riparian pastures.

PubMed

Larson, Larry; Johnson, Douglas E; Wilson, Marie; Wilson, Kerry; Louhaichi, Mounir; Williams, John

2017-03-01

The spatial occupancy patterns and activity of cattle grazing three riparian pastures was investigated in northeastern Oregon using Global Positioning System (GPS) collars logging at 1-sec intervals. Cattle consistently selected plant communities as grazing areas that had forage in sufficient volume to meet their requirements and favored communities as resting areas that were dry and open. Cattle were stationary for more than 50% of the time in each pasture and consistently rested between dark and 04:00 hours. Interaction with stream channels was found to be 1-2% of total occupancy time and occurred on less than 10% of channel length. Cattle were indifferent or avoided channel areas relative to their area and, when in this zone, they spent most of their time moving not resting. Cattle did not prefer the stream bank zone and spent only 2% of their time in that zone. When occupied, the stream bank zone was used as a travel corridor to gain access to water or cross the channel to access other pasture areas. These results are in contrast with the general belief that cattle are a primary occupant of the stream bank/channel area; additional research is needed to define factors influencing cattle occupancy. © 2016 Japanese Society of Animal Science.

Guidelines for collecting and processing samples of stream bed sediment for analysis of trace elements and organic contaminants for the National Water-Quality Assessment Program

USGS Publications Warehouse

Shelton, Larry R.; Capel, Paul D.

1994-01-01

A major component of the U.S. Geological Survey's National Water-Quality Assessment program is to assess the occurrence and distribution of trace elements and organic contaminants in streams. The first phase of the strategy for the assessment is to analyze samples of bed sediments from depositional zones. Fine-grained particles deposited in these zones are natural accumulators of trace elements and hydrophobic organic compounds. For the information to be comparable among studies in many different parts of the Nation, strategies for selecting stream sites and depositional zones are critical. Fine-grained surficial sediments are obtained from several depositional zones within a stream reach and composited to yield a sample representing average conditions. Sample collection and processing must be done consistently and by procedures specifically designed to separate the fine material into fractions that yield uncontaminated samples for trace-level analytes in the laboratory. Special coring samplers and other instruments made of Teflon are used for collection. Samples are processed through a 2.0-millimeter stainless-steel mesh sieve for organic contaminate analysis and a 63-micrometer nylon-cloth sieve for trace-element analysis. Quality assurance is maintained by strict collection and processing procedures, duplicate samplings, and a rigid cleaning procedure.

Two-stage fixed-bed gasifier with selectable middle gas off-take point

DOEpatents

Strickland, Larry D.; Bissett, Larry A.

1992-01-01

A two-stage fixed bed coal gasifier wherein an annular region is in registry with a gasification zone underlying a devolatilization zone for extracting a side stream of high temperature substantially tar-free gas from the gasifier. A vertically displaceable skirt means is positioned within the gasifier to define the lower portion of the annular region so that vertical displacement of the skirt means positions the inlet into the annular region in a selected location within or in close proximity to the gasification zone for providing a positive control over the composition of the side stream gas.

Where does boreal stream DOC come from? - Quantifying the contribution from different landscape compartments using stable C isotope ratios.

NASA Astrophysics Data System (ADS)

Brink Bylund, J.; Bastviken, D.; Morth, C.; Laudon, H.; Giesler, R.; Buffam, I.

2007-12-01

Stable carbon isotope (δ13C) ratios are frequently used as a source tracer of e.g. organic matter (OM) produced in terrestrial versus aquatic environments. To our knowledge there has been no previous attempt to quantify the relative contribution of dissolved organic carbon (DOC) from various landscape compartments in catchments of different sizes. Here, we test to what extent δ13C values can be used also to quantify the relative contribution of DOC from wetlands/riparian zones along streams, and off stream forest habitats, respectively. We present data on spatial and temporal variability of DOC concentrations and δ13C-DOC values, during the year of 2005 in Krycklan catchment, a boreal stream network in northern Sweden. Ten stream sites, ranging from order 1 to 4, were monitored in sub catchments with different wetland coverage. Spatial variation of DOC concentration showed a weak but statistically significant relationship with wetland area, with higher concentration with increasing percent of wetland in the drainage area. During base flow the difference in δ13C-DOC values was significantly different between forest (-27.5‰) and wetland (-28.1‰). This spatial pattern disappears during spring peak flow when higher discharge flushing upper soil layer and the riparian zone on DOC in the catchments. A simple mixing model using DOC and δ13C-DOC showed that stream water DOC could be describe as a mixture of DOC coming from forest (deep) groundwater and wetland/riparian zone water. The result indicates that during spring peak flow almost all stream DOC (84-100%) is derived from wetlands and riparian zones. The wetland/riparian water dominates the stream DOC flux at all hydrological events, except for two sites, one forest dominated and one mixed catchment, where the forest groundwater dominated the DOC transport during base flow. Although the total wetland area in Krycklan catchment only represent 8.3%, it contributed, together with riparian zones, to as much as 83% of the yearly DOC transport. This study shows that there is a great potential in using stable carbon isotopes to quantify the relative contribution of DOC from various landscape compartments in catchments. Quantitative patterns are crucial for several reasons. It is for example necessary in predicting the response to global warming which will result in a changed hydrology and shifts in the relative area of the landscape compartments in boreal environments. KEY WORDS carbon isotopes; dissolved organic carbon; streams; boreal; landscape compartments; wetland; groundwater

Small mammal habitat use within restored riparian habitats adjacent to channelized streams in Mississippi

USDA-ARS?s Scientific Manuscript database

Riparian zones of channelized agricultural streams in northwestern Mississippi typically consist of narrow vegetative corridors low in habitat diversity and lacking riparian wetlands. Land clearing practices and stream channelization has led to the development of gully erosion and further fragmenta...

The importance of wood in headwater streams of the Oregon Coast Range

USGS Publications Warehouse

May, Christine; Gresswell, Robert E.; Erickson, Janet L.

2004-01-01

Although headwater streams comprise the majority of stream length in mountainous regions, little is known about their form and function in comparison to higher-order rivers. A better understanding of the role of headwater streams in routing water, wood, and sediment is needed to clarify the physical and biological connections among uplands, riparian zones, and downstream reaches.

Defining perennial, intermittent and ephemeral channels in eastern Kentucky: application to forestry best management practices

Treesearch

J. R. Svec; R. K. Kolka; J. W. Stringer

2003-01-01

In Kentucky stream classification is used to determine which forestry best management practice (BMP) to apply in riparian zones. Kentucky defines stream classes as follows (Stringer and others 1998): a) perennial streams that hold water throughout the year, b) intermittent streams that hold water during wet portions of the year, and c) ephemeral channels that hold...

Automated Detection and Modeling of Slow Slip: Case Study of the Cascadia Subduction Zone

NASA Astrophysics Data System (ADS)

Crowell, B. W.; Bock, Y.; Liu, Z.

2012-12-01

The discovery of transient slow slip events over the past decade has changed our understanding of tectonic hazards and the earthquake cycle. Proper geodetic characterization of transient deformation is necessary for studies of regional interseismic, coseismic and postseismic tectonics, and miscalculations can affect our understanding of the regional stress field. We utilize two different methods to create a complete record of slow slip from continuous GPS stations in the Cascadia subduction zone between 1996 and 2012: spatiotemporal principal component analysis (PCA) and the relative strength index (RSI). The PCA is performed on 100 day windows of nearby stations to locate signals that exist across many stations in the network by looking at the ratio of the first two eigenvalues. The RSI is a financial momentum oscillator that looks for changes in individual time series with respect to previous epochs to locate rapid changes, indicative of transient deformation. Using both methods, we create a complete history of slow slip across the Cascadia subduction zone, fully characterizing the timing, progression, and magnitude of events. We inject the results from the automated transient detection into a time-dependent slip inversion and apply a Kalman filter based network inversion method to image the spatiotemporal variation of slip transients along the Cascadia margin.

Rapid Software-Based Design and Optical Transient Liquid Molding of Microparticles.

PubMed

Wu, Chueh-Yu; Owsley, Keegan; Di Carlo, Dino

2015-12-22

Microparticles with complex 3D shape and composition are produced using a novel fabrication method, optical transient liquid molding, in which a 2D light pattern exposes a photopolymer precursor stream shaped along the flow axis by software-aided inertial flow engineering. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Time dependent emission line profiles in the radially streaming particle model of Seyfert galaxy nuclei and quasi-stellar objects

NASA Technical Reports Server (NTRS)

Hubbard, R.

1974-01-01

The radially-streaming particle model for broad quasar and Seyfert galaxy emission features is modified to include sources of time dependence. The results are suggestive of reported observations of multiple components, variability, and transient features in the wings of Seyfert and quasi-stellar emission lines.

Nitrogen transport and transformations in a coastal plain watershed: Influence of geomorphology on flow paths and residence times

USGS Publications Warehouse

Tesoriero, Anthony J.; Spruill, Timothy B.; Mew, H.E.; Farrell, Kathleen M.; Harden, Stephen L.

2005-01-01

Nitrogen transport and groundwater-surface water interactions were examined in a coastal plain watershed in the southeastern United States. Groundwater age dates, calculated using chlorofluorocarbon and tritium concentrations, along with concentrations of nitrogen species and other redox-active constituents, were used to evaluate the fate and transport of nitrate. Nitrate is stable only in recently recharged (<10 years) water found in the upper few meters of saturated thickness in the upland portion of a surficial aquifer. Groundwater with a residence time between 10 and 30 years typically has low nitrate and elevated excess N2 concentrations, indications that denitrification has reduced nitrate concentrations. Groundwater older than 30 years also has low nitrate concentrations but contains little or no excess N2, suggesting that this water did not contain elevated concentrations of nitrate along its flow path. Nitrate transport to streams varies between first- and third-order streams. Hydrologic, lithologic, and chemical data suggest that the surficial aquifer is the dominant source of flow and nitrate to a first-order stream. Iron-reducing conditions occur in groundwater samples from the bed and banks of the first-order stream, suggesting that direct groundwater discharge is denitrified prior to entering the stream. However, nitrogen from the surficial aquifer is transported directly to the stream via a tile drain that bypasses these reduced zones. In the alluvial valley of a third-order stream the erosion of a confining layer creates a much thicker unconfined alluvial aquifer with larger zones of nitrate stability. Age dating and chemical information (SiO 2, Na/K ratios) suggest that water in the alluvial aquifer is derived from short flow paths through the riparian zone and/or from adjacent streams during high-discharge periods. Copyright 2005 by the American Geophysical Union.

Auxiliary reactor for a hydrocarbon reforming system

DOEpatents

Clawson, Lawrence G.; Dorson, Matthew H.; Mitchell, William L.; Nowicki, Brian J.; Bentley, Jeffrey M.; Davis, Robert; Rumsey, Jennifer W.

2006-01-17

An auxiliary reactor for use with a reformer reactor having at least one reaction zone, and including a burner for burning fuel and creating a heated auxiliary reactor gas stream, and heat exchanger for transferring heat from auxiliary reactor gas stream and heat transfer medium, preferably two-phase water, to reformer reaction zone. Auxiliary reactor may include first cylindrical wall defining a chamber for burning fuel and creating a heated auxiliary reactor gas stream, the chamber having an inlet end, an outlet end, a second cylindrical wall surrounding first wall and a second annular chamber there between. The reactor being configured so heated auxiliary reactor gas flows out the outlet end and into and through second annular chamber and conduit which is disposed in second annular chamber, the conduit adapted to carry heat transfer medium and being connectable to reformer reaction zone for additional heat exchange.

Transients which are born on the way from the Sun to Earth

NASA Astrophysics Data System (ADS)

Yermolaev, Yuri; Nikolaeva, Nadezhda; Lodkina, Irina; Yermolaev, Michael

2016-07-01

As well known only disturbed types of solar wind (SW) streams can contain the IMF component perpendicular to the ecliptic plane (in particular the southward IMF component) and be geoeffective. Such disturbed types are the following SW streams: interplanetary manifestation of coronal mass ejection (ICME) including magnetic cloud (MC) and Ejecta, Sheath - compression region before ICME and corotating interaction region (CIR) - compression region before high-speed stream (HSS) of solar wind. Role of solar transients, CME and ICME, in generation of geomagnetic disturbances and space weather prediction is intensively studied by many researchers. However transients Sheath and CIR which are born on the way from the Sun to Earth due to corresponding high speed piston (fast ICME for Sheath and HSS from coronal hole for CIR), are investigated less intensively, and their contribution to geoefficiency are underestimated. For example, on 19 December, 1980 the southward component of IMF Bz increased up to 30 nT and the compressed region Sheath before MC induced the strong magnetic storm with Dst ~ -250 nT. We present and discuss statistical data on Sheath and CIR geoeffectiveness. The work was supported by the Russian Foundation for Basic Research, project 16-02-00125 and by Program of Presidium of the Russian Academy of Sciences.

Exchanges across land-water-scape boundaries in urban systems: strategies for reducing nitrate pollution.

PubMed

Cadenasso, M L; Pickett, S T A; Groffman, P M; Band, L E; Brush, G S; Galvin, M F; Grove, J M; Hagar, G; Marshall, V; McGrath, B P; O'Neil-Dunne, J P M; Stack, W P; Troy, A R

2008-01-01

Conservation in urban areas typically focuses on biodiversity and large green spaces. However, opportunities exist throughout urban areas to enhance ecological functions. An important function of urban landscapes is retaining nitrogen thereby reducing nitrate pollution to streams and coastal waters. Control of nonpoint nitrate pollution in urban areas was originally based on the documented importance of riparian zones in agricultural and forested ecosystems. The watershed and boundary frameworks have been used to guide stream research and a riparian conservation strategy to reduce nitrate pollution in urban streams. But is stream restoration and riparian-zone conservation enough? Data from the Baltimore Ecosystem Study and other urban stream research indicate that urban riparian zones do not necessarily prevent nitrate from entering, nor remove nitrate from, streams. Based on this insight, policy makers in Baltimore extended the conservation strategy throughout larger watersheds, attempting to restore functions that no longer took place in riparian boundaries. Two urban revitalization projects are presented as examples aimed at reducing nitrate pollution to stormwater, streams, and the Chesapeake Bay. An adaptive cycle of ecological urban design synthesizes the insights from the watershed and boundary frameworks, from new data, and from the conservation concerns of agencies and local communities. This urban example of conservation based on ameliorating nitrate water pollution extends the initial watershed-boundary approach along three dimensions: 1) from riparian to urban land-water-scapes; 2) from discrete engineering solutions to ecological design approaches; and 3) from structural solutions to inclusion of individual, household, and institutional behavior.

Hyporheic invertebrate assemblages at reach scale in a Neotropical stream in Brazil.

PubMed

Mugnai, R; Messana, G; Di Lorenzo, T

2015-11-01

In the Neotropical Region, information concerning hyporheic communities is virtually non-existent. We carried out a sampling survey in the hyporheic zone of the Tijuca River, in the Tijuca National Park, located in the urban area of the city of Rio de Janeiro. Biological samples from the hyporheic zone were collected in three different stream reaches, in June 2012. The main objectives were: 1) to describe the structure of invertebrate assemblages in the hyporheic zone of a neotropical stream; 2) to apply a reach-scale approach in order to investigate spatial patterns of the hyporheic assemblages in relation to hydrology, depth and microhabitat typology. A total of 1460 individuals were collected and identified in 31 taxa belonging to Nematoda, Annelida, Crustacea, Hydrachnidia and Insecta. The class Insecta dominated the upper layer of the hyporheic zone. Copepods were the most abundant taxon among crustaceans and occurred mostly in the upwelling areas of the reaches. The results of this study represent one of the few contributions so far about hyporheic invertebrate assemblages of the Neotropical Region.

Preliminary study of the effects of headwater riparian reserves with upslope thinning on stream habitats and amphibians in western Oregon.

Treesearch

D.H. Olson; C. Rugger

2007-01-01

We conducted a preliminary examination of the responses of stream amphibians and instream habitat conditions to alternative riparian buffer zones with forest thinning upslope. Pre- and posttreatment surveys were carried out on 68 headwater stream reaches (including 23 unthinned reference reaches) at 11 sites in western Oregon. Streams were in managed conifer stands 40...

Pasture BMP effectiveness using an HRU-based subarea approach in SWAT.

PubMed

Sheshukov, Aleksey Y; Douglas-Mankin, Kyle R; Sinnathamby, Sumathy; Daggupati, Prasad

2016-01-15

Many conservation programs have been established to motivate producers to adopt best management practices (BMP) to minimize pasture runoff and nutrient loads, but a process is needed to assess BMP effectiveness to help target implementation efforts. A study was conducted to develop and demonstrate a method to evaluate water-quality impacts and the effectiveness of two widely used BMPs on a livestock pasture: off-stream watering site and stream fencing. The Soil and Water Assessment Tool (SWAT) model was built for the Pottawatomie Creek Watershed in eastern Kansas, independently calibrated at the watershed outlet for streamflow and at a pasture site for nutrients and sediment runoff, and also employed to simulate pollutant loads in a synthetic pasture. The pasture was divided into several subareas including stream, riparian zone, and two grazing zones. Five scenarios applied to both a synthetic pasture and a whole watershed were simulated to assess various combinations of widely used pasture BMPs: (1) baseline conditions with an open stream access, (2) an off-stream watering site installed in individual subareas in the pasture, and (3) stream or riparian zone fencing with an off-stream watering site. Results indicated that pollutant loads increase with increasing stocking rates whereas off-stream watering site and/or stream fencing reduce time cattle spend in the stream and nutrient loads. These two BMPs lowered organic P and N loads by more than 59% and nitrate loads by 19%, but TSS and sediment-attached P loads remained practically unchanged. An effectiveness index (EI) quantified impacts from the various combinations of off-stream watering sites and fencing in all scenarios. Stream bank contribution to pollutant loads was not accounted in the methodology due to limitations of the SWAT model, but can be incorporated in the approach if an amount of bank soil loss is known for various stocking rates. The proposed methodology provides an adaptable framework for pasture BMP assessment and was utilized to represent a consistent, defensible process to quantify the effectiveness of BMP proposals in a BMP auction in eastern Kansas. Copyright © 2015 Elsevier Ltd. All rights reserved.

InSAR coherence study of unusual rain events in the Atacama Desert

NASA Astrophysics Data System (ADS)

Jordan, T. E.; Scott, C. P.; Lohman, R.

2017-12-01

The Atacama Desert (AD) occupies much of Chile at latitudes 18-27°S. The surficial materials vary, dependent on proximity to the ocean, slope, position within a surface water drainage system, mean annual rainfall, human land disturbance, and the local history of climate changes. Three major divisions of soil composition include: near coastal zone of silicate mineral soils, mostly devoid of plants; central hyperarid zone dominated by gypsum, devoid of plants; eastern zone of silicate-based soils, very sparse plants. The AD in March 2015 experienced the largest rain event of modern history, and again in June 2017 almost as much rain fell within the study area (24.2-25.7°S, coast to Andes Mountains). Those natural experiments set the stage for InSAR remote sensing of surface changes in a 24,000 square kilometer area. We used interferometric coherence of radar to measure the similarity in the reflective ground properties at the time of two SAR acquisitions, and a time series of European Space Agency's Sentinel-1A data sets acquired between January 2015 and August 2017. Date pairs lacking an intervening rain event reveal extensive regions of high coherence, and in those areas we focus on the temporal evolution of coherence across dates of, and following dates of, the major rains. Permanent change of the surface is most extensive in the eastern and western sectors, yet the degree of permanent change was small except in valley bottoms. In the sector with gypsum soil small degrees of permanent change occurred over 30% of the surface including in narrow (1-3 km) elongate (10-60 km) stripes that cross-cut topography, likely revealing rain bands. The spatial pattern of transient change in coherence differs. Over half the gypsum-dominated zone displays a transient change signal, whose spatial pattern corresponds to geomorphological forms; older landforms display greater transient coherence changes. In the silicate-dominated eastern region the transient signals are smaller. In both zones the transient change in coherence recovered to the pre-rain conditions over several months. Analysis to date indicates that the transient signal in the driest AD reflects an interaction of water with the CaSO4 mineral structure, whereas in the eastern zone it more likely reflects liquid water retention.

Engineered Hyporheic Zones as Novel Water Quality Best Management Practice: Flow and Contaminant Attenuation in Constructed Stream Experiments

NASA Astrophysics Data System (ADS)

Herzog, S.; McCray, J. E.; Higgins, C. P.

2015-12-01

The hyporheic zone is a hotspot for biogeochemical processing that can attenuate a variety of nonpoint source contaminants in streamwater. However, hyporheic zones in urban and agricultural streams are often degraded and poorly connected with surface water. In order to increase hyporheic exchange and improve water quality, we introduced engineered streambeds as a stormwater and restoration best management practice. Modifications to streambed hydraulic conductivity and reactivity are termed Biohydrochemical Enhancement structures for Streamwater Treatment (BEST). BEST are subsurface modules that utilize low- and high-permeability sediments to drive efficient hyporheic exchange, and reactive geomedia to increase reaction rates within the hyporheic zone. This work presents the first physical performance data of BEST modules at the pilot scale. BEST modules were installed in a constructed stream facility at the Colorado School of Mines in Golden, CO. This facility features two 15m artificial streams, which included an all sand control condition alongside the BEST test condition. Streams were continuously operated at a discharge of 1 L/s using recycled water. Time-lapse electrical resistivity surveys demonstrated that BEST modules provided substantially greater hyporheic exchange than the control condition. Water quality samples at the hyporheic and reach scales also revealed greater attenuation of nitrogen, coliforms, and select metals and trace organics by BEST modules relative to the control condition. These experimental results were also compared to previous numerical model simulations to evaluate model accuracy. Together, these results show that BEST may be an effective best management practice for improving streamwater quality in urban and agricultural settings.

Explosion-assisted preparation of dispersed gold-bearing different-grade ore for selective mining

NASA Astrophysics Data System (ADS)

Trubachev, AI; Zykov, NV

2017-02-01

It is found that there are transient zones (between quality and off-quality ore areas) with the respective content of useful component in an ore body, and a variant of explosive treatment of such zones before the selective mining is put forward. Practicability of two processing technologies is evaluated: processing of high-grade and low-grade ore from the transient zones and heap leaching of metals from the low-grade and impoverished ore. Open mining technology is conventional truck-and-shovel scheme, with distributed ore flows to processing plant and (or) to heap leaching, which generally enhances the mine efficiency.

Estimation of river pollution index in a tidal stream using kriging analysis.

PubMed

Chen, Yen-Chang; Yeh, Hui-Chung; Wei, Chiang

2012-08-29

Tidal streams are complex watercourses that represent a transitional zone between riverine and marine systems; they occur where fresh and marine waters converge. Because tidal circulation processes cause substantial turbulence in these highly dynamic zones, tidal streams are the most productive of water bodies. Their rich biological diversity, combined with the convenience of land and water transports, provide sites for concentrated populations that evolve into large cities. Domestic wastewater is generally discharged directly into tidal streams in Taiwan, necessitating regular evaluation of the water quality of these streams. Given the complex flow dynamics of tidal streams, only a few models can effectively evaluate and identify pollution levels. This study evaluates the river pollution index (RPI) in tidal streams by using kriging analysis. This is a geostatistical method for interpolating random spatial variation to estimate linear grid points in two or three dimensions. A kriging-based method is developed to evaluate RPI in tidal streams, which is typically considered as 1D in hydraulic engineering. The proposed method efficiently evaluates RPI in tidal streams with the minimum amount of water quality data. Data of the Tanshui River downstream reach available from an estuarine area validate the accuracy and reliability of the proposed method. Results of this study demonstrate that this simple yet reliable method can effectively estimate RPI in tidal streams.

Explaining leptokurtic movement distributions: intrapopulation variation in boldness and exploration.

PubMed

Fraser, D F; Gilliam, J F; Daley, M J; Le, A N; Skalski, G T

2001-08-01

Leptokurtic distributions of movement distances observed in field-release studies, in which some individuals move long distances while most remain at or near their release point, are a common feature of mobile animals. However, because leptokurtosis is predicted to be transient in homogeneous populations, persistent leptokurtosis suggests a population heterogeneity. We found evidence for a heterogeneity that may generate persistent leptokurtosis. We tested individuals of the Trinidad killifish Rivulus hartii for boldness in a tank test and released them back into their native stream. Boldness in the tank test predicted distance moved in the field releases, even after effects of size and sex were removed. Further, data from a 19-mo mark-recapture study showed that individual growth correlated positively with movement in a predator-threatened river zone where the Rivulus population is spatially fragmented and dispersal is likely to be a hazardous activity. In contrast, no such correlation existed in a predator-absent zone where the population is unfragmented. These results show that a behavioral trait, not discernible from body size or sex, contributes to dispersal and that a component of fitness of surviving "dispersers" is elevated above that of "stayers," a fundamental assumption or prediction of many models of the evolution of dispersal through hazardous habitat.

Streamflow losses in the Black Hills of western South Dakota

USGS Publications Warehouse

Hortness, Jon E.; Driscoll, Daniel G.

1998-01-01

Losses occur in numerous streams that cross outcrops of various sedimentary rocks that are exposed around the periphery of the Black Hills of South Dakota. These streamflow losses are recognized as an important source of local recharge to regional bedrock aquifers. Most streams lose all of their flow up to some threshold rate. Streamflow is maintained through a loss zone when the threshold is exceeded. Streamflow records for 86 measurement sites are used to determine bedrock loss thresholds for 24 area streams, which have individual loss thresholds that range from negligible (no loss) to as much as 50 cubic feet per second. In addition, insights are provided regarding springflow that occurs in the immediate vicinity of selected loss zones. Most losses occur to outcrops of the Madison Limestone and Minnelusa Formation. Losses to the Deadwood Formation probably are minimal. Losses to the Minnekahta Limestone generally are small; however, they are difficult to quantify because of potential losses to extensive alluvial deposits that commonly are located near Minnekahta outcrops. Loss thresholds for each stream are shown to be relatively constant, without measurable effects from streamflow rates or duration of flow through the loss zones. Calculated losses for measurements made during high-flow conditions generally have larger variability than calculated losses for low-flow conditions; however, consistent relations between losses and streamflow have not been identified. Some of this variability results from the inability to account for tributary inflows and changes in storage. Calculated losses are shown to decrease, in some cases, during periods of extended flow through loss zones. Decreased 'net' losses, however, generally can be attributed to springflow (ground-water discharge) within a loss zone, which may occur during prolonged periods of wet climatic conditions. Losses to unsaturated alluvial deposits located adjacent to the stream channels are found to have significant effects on determination of bedrock losses. Large losses occur in filling initial storage in unsaturated alluvial deposits downstream from loss zones, when bedrock loss thresholds are first exceeded. Losses to alluvial deposits in the range of tens of cubic feet per second and alluvial storage capacities in the range of hundreds of acre-feet are documented. Significant changes in loss thresholds for Grace Coolidge Creek, Spring Creek, and Whitewood Creek are documented. Introduction of large quantities of fine-grained sediments into these stream channels may have affected loss thresholds for various periods of time.

A New Dimensionless Number for Redox Conditions within the Hyporheic Zone: Morphological and Biogeochemical Controls

NASA Astrophysics Data System (ADS)

Marzadri, A.; Tonina, D.; Bellin, A.

2012-12-01

We introduce a new Damköhler number, Da, to quantify the biogeochemical status of the hyporheic zone and to upscale local hyporheic processes to reach scale. Da is defined as the ratio between the median hyporheic residence time, τup,50, which is a representative time scale of the hyporheic flow, and a representative time scale of biogeochemical reactions, which we define as the time τlim needed to consume dissolved oxygen to a prescribed threshold concentration below which reducing reactions are activated: Da = τup,50/τlim. This approach accounts for streambed topography and surface hydraulics via the hyporheic residence time and biogeochemical reaction via the time limit τlim. Da can readily evaluate the redox status of the hyporheic zone. Values of Da larger than 1 indicate prevailing anaerobic conditions, whereas values smaller than 1 prevailing aerobic conditions. This new Damköhler number can quantify the efficiency of hyporheic zone in transforming dissolved inorganic nitrogen species such as ammonium and nitrate, whose transformation depends on the redox condition of the hyporheic zone. We define a particular value of Da, Das, that indicates when the hyporheic zone is a source or a sink of nitrate. This index depends only on the relative abundance of ammonium and nitrate. The approach can be applied to any hyporheic zone of which the median hyporheic residence time is known. Application to streams with pool-riffle morphology shows that Da increases passing from small to large streams implying that the fraction of the hyporheic zone in anaerobic conditions increases with stream size.

An Offshore Geophysical Network in the Pacific Northwest for Earthquake and Tsunami Early Warning and Hazard Research

NASA Astrophysics Data System (ADS)

Wilcock, W. S. D.; Schmidt, D. A.; Vidale, J. E.; Harrington, M.; Bodin, P.; Cram, G.; Delaney, J. R.; Gonzalez, F. I.; Kelley, D. S.; LeVeque, R. J.; Manalang, D.; McGuire, C.; Roland, E. C.; Tilley, J.; Vogl, C. J.; Stoermer, M.

2016-12-01

The Cascadia subduction zone hosts catastrophic earthquakes every few hundred years. On land, there are extensive geophysical networks available to monitor the subduction zone, but since the locked portion of the plate boundary lies mostly offshore, these networks are ideally complemented by seafloor observations. Such considerations helped motivate the development of scientific cabled observatories that cross the subduction zone at two sites off Vancouver Island and one off central Oregon, but these have a limited spatial footprint along the strike of the subduction zone. The Pacific Northwest Seismic Network is leading a collaborative effort to implement an earthquake early warning system in the Washington and Oregon using data streams from land networks as well as the few existing offshore instruments. For subduction zone earthquakes that initiate offshore, this system will provide a warning. However, the availability of real time offshore instrumentation along the entire subduction zone would improve its reliability and accuracy, add up to 15 s to the warning time, and ensure an early warning for coastal communities near the epicenter. Furthermore, real-time networks of seafloor pressure sensors above the subduction zone would enable monitoring and contribute to accurate predictions of the incoming tsunami. There is also strong scientific motivation for offshore monitoring. We lack a complete knowledge of the plate convergence rate and direction. Measurements of steady deformation and observations of transient processes such as fluid pulsing, microseismic cycles, tremor and slow-slip are necessary for assessing the dimensions of the locked zone and its along-strike segmentation. Long-term monitoring will also provide baseline observations that can be used to detect and evaluate changes in the subduction environment. There are significant engineering challenges to be solved to ensure the system is sufficiently reliable and maintainable. It must provide continuous monitoring over its operational life in the harsh ocean environment and at least parts of the system must continue to operate following a megathrust event. These requirements for robustness must be balanced with the desire for a flexible design that can accommodate new scientific instrumentation over the life of the project.

Denitrification in sediments from the hyporheic zone adjacent to a small forested stream

USGS Publications Warehouse

Duff, J.H.; Triska, F.J.

1990-01-01

Denitrifying potentials increased with increasing distance from the stream channel. Dissolved oxygen was 100% of the concentration expected in equilibrium with the atmosphere in water obtained from monitoring wells immediately adjacent to the stream but was as low as 7% of the expected value in water 11.4 m inland. Both nitrate and dissolved organic carbon decreased over summer in wells at the base of the alder-forested slope. A 48-h injection of nitrate-amended stream water into hyporheic water 8.4 m inland stimulated nitrous oxide production in the presence of acetylene. Nitrous oxide was generated as nitrate and acetylene were co-transported to a well 13 m down-gradient. Acetylene-block experiments coupled with the chemistry data suggest that denitrification can modify the chemistry of water during passage through the hyporheic zone. -from Authors

The influence of stream bed geomorphology on chemical species within the hyporheic zone over time and space

NASA Astrophysics Data System (ADS)

Quick, A. M.; Reeder, W. J.; Farrell, T. B.; Benner, S. G.; Tonina, D.; Feris, K. P.

2017-12-01

The hyporheic zone is well established as an important zone of biogeochemical activity in streams and rivers. Multiple large scale flume experiments were carried out to mimic bedform-controlled hyporheic zones in small streams. The laboratory setting allowed for geochemical measurement resolution and replicates that would not be possible in a natural setting. Two flume experiments that consisted of three small streams with variable sizes of bedform dunes were carried out in which chemical species were measured in the surface water and along hyporheic flow lines in the subsurface. The species measured included dissolved oxygen, pH, alkalinity, major cations (Na+, Mg2+, Ca2+, K+, Si4+, Al3+), anions (NO3-, NO2-, SO42-, PO43-, Cl-), and many trace elements (As, Sr, Co, Ni, Cu, Zn, Pb, U, V). Observed spatial and temporal trends reflect microbiological processes, changing redox conditions, and chemical weathering. In general, microbial respiration causes DO to decrease with residence time, leading to aerobic and anaerobic zones that influence redox-sensitive species and pH gradients that influence mineral solubility. Most other species concentrations, including those of major cations and trace elements, increase with residence time and generally decrease over time elapsed during the experiment. The different dune morphologies dictate flow velocities in the hyporheic zone; for most species, steeper dunes with higher velocities had lower concentrations at the end of the experiment, indicating the role of dune shape in the weathering rates of minerals in hyporheic sediment and the concentrations of dissolved species entering the surface water over time. Many of the observed trends can be applied, at least qualitatively, to understanding how these species will behave in natural settings. This insight will contribute to the understanding of many of the applications of the hyporheic zone (e.g. bioremediation, habitat, greenhouse gas emissions, etc.).

SOIL ALUMINUM DISTRIBUTION IN THE NEAR-STREAM ZONE AT THE BEAR BROOK WATERSHED IN MAINE

EPA Science Inventory

Near-stream and upslope soil chemical properties were analyzed to infer linkages between soil and surface water chemistry at the Bear Brook Watershed in Maine [BBWM]. Organic and mineral soil samples were collected along six 20 m transects perpendicular to the stream and one 200 ...

Linking nitrogen management, seep chemistry, and stream water quality in two agricultural headwater watersheds

USDA-ARS?s Scientific Manuscript database

Riparian seepage zones in headwater agricultural watersheds represent important sources of nitrate-nitrogen (NO3-N) to surface waters, often connecting N-rich groundwater systems to streams. In this study, we examined how NO3-N concentrations in seep and stream water were affected by NO3-N processin...

Hyporheic exchange and fulvic acid redox reactions in an alpine stream/wetland ecosystem, Colorado front range

USGS Publications Warehouse

Miller, Matthew P.; McKnight, Diane M.; Cory, R.M.; Williams, Mark W.; Runkel, Robert L.

2006-01-01

The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (?? ??? 10-3 s -1). Parallel factor analysis of fluorescence spectra was used to quantify the redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (?? = 6.5 ?? 10-3 s -1) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (?? = 1.2 ?? 10-3 s-1) and production of nitrate (?? = -1.0 ?? 10-3 s-1) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale. ?? 2006 American Chemical Society.

Hillslope-riparian-stream connectivity and flow directions at the Panola Mountain Research Watershed

NASA Astrophysics Data System (ADS)

van Meerveld, Ilja; Seibert, Jan; Peters, Jake

2015-04-01

The question how water travels from rainfall to the stream network has engaged hydrologists for decades as it determines the streamflow response to rainfall and stream water quality. In order to obtain a better understanding of water's journey from the hillslope to the stream, and in particular the effects of rainfall amount, bedrock topography and variations in soil depth on hillslope subsurface flow pathways and hillslope-riparian zone-stream connectivity, we analyzed data from 26 groundwater wells in a hillslope-riparian study area in the Panola Mountain Research Watershed, Georgia, USA. The water levels in the riparian zone were sustained throughout the wet winter period, while the wells on the hillslope showed very peaky and short-lived responses. Perched groundwater on the hillslope either developed across almost the entire hillslope or not at all, suggesting that either the majority of the hillslope became connected to the stream or that no connection was established. There were clear differences in the timing of the groundwater responses, with water levels near the stream and on the upper hillslope rising earlier than on the lower hillslope and midslope. The midslope with deep soils played a critical role in the establishment of hillslope-stream connectivity. A sharp increase in water level was measured at the lower hillslope wells and in some riparian wells when connectivity between the hillslope and the riparian zone was established. Sustained streamflow (more than 0.5 mm/h for more than 12 h) occurred only when the hillslope was connected to the stream. The groundwater flow directions were highly variable across the midslope with deep soils: the flow directions followed the local bedrock topography when perched groundwater levels were low and the surface topography when groundwater levels were higher. The flow directions could even point in the general upslope direction but followed the local bedrock topography. This suggests that first the bedrock hollow filled but that once water levels were higher and saturation was more widespread, the flow directions followed the surface topography and were downslope. This competing influence of the surface and bedrock topography was not observed in the riparian zone, where the flow directions were either downslope or changed from a combined downslope and downstream direction towards a more downslope direction during events.

Joule heating induced stream broadening in free-flow zone electrophoresis.

PubMed

Dutta, Debashis

2018-03-01

The use of an electric field in free-flow zone electrophoresis (FFZE) automatically leads to Joule heating yielding a higher temperature at the center of the separation chamber relative to that around the channel walls. For small amounts of heat generated, this thermal effect introduces a variation in the equilibrium position of the analyte molecules due to the dependence of liquid viscosity and analyte diffusivity on temperature leading to a modification in the position of the analyte stream as well as the zone width. In this article, an analytic theory is presented to quantitate such effects of Joule heating on FFZE assays in the limit of small temperature differentials across the channel gap yielding a closed form expression for the stream position and zone variance under equilibrium conditions. A method-of-moments approach is employed to develop this analytic theory, which is further validated with numerical solutions of the governing equations. Interestingly, the noted analyses predict that Joule heating can drift the location of the analyte stream either way of its equilibrium position realized in the absence of any temperature rise in the system, and also tends to reduce zone dispersion. The extent of these modifications, however, is governed by the electric field induced temperature rise and three Péclet numbers evaluated based on the axial pressure-driven flow, transverse electroosmotic and electrophoretic solute velocities in the separation chamber. Monte Carlo simulations of the FFZE system further establish a time and a length scale over which the results from the analytic theory are valid. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Three-dimensional steady-state simulation of flow in the sand-and-gravel aquifer, southern Escambia County, Florida

USGS Publications Warehouse

Trapp, Henry; Geiger, L.H.

1986-01-01

The sand-and-gravel aquifer is the only freshwater aquifer in southern Escambia County, Florida and is the source of public water supply for the area, including the City of Pensacola. The aquifer was simulated by a two-layer, digital model to provide hydrologic information for water resource planning. The lower layer represents the main-producing zone; the upper layer represents all of the aquifer above the main-producing zone including an unconfined zone and discontinuous perched, confined , and confining zones. The model was designed for steady-state simulation and predicts the response of the aquifer (changes in water levels) to groundwater pumping where steady-state conditions have been reached. Input to the model includes matrices representing constant-head nodes, starting head, transmissivity of layer 1, leakance between layers 1 and 2, lateral hydraulic conductivity of layer 2, and altitude of the base layer 2. The sources of water to the model are from recharge by infiltrated precipitation (estimated from base runoff), inflow across boundaries, and induced recharge from river leakance in periods of prolonged groundwater pumping. Model output includes final head and drawdown for each layer and total values for discharge and recharge in the model area. The model was calibrated for 1972 pumping and tested by simulating pumpages during 1939-40, 1958, and 1977. Sensitivity analyses showed water levels in both layers were most sensitive to changes in the recharge matrix and least sensitive to river leakage. Suggestions for further development of the model include subdivision and expansion of the grid, assignment of storage coefficients for transient simulations, more intensive study of the stream-aquifer relations, and consideration of the effects of infiltration basins on recharge. (Author 's abstract)

HYDES: A generalized hybrid computer program for studying turbojet or turbofan engine dynamics

NASA Technical Reports Server (NTRS)

Szuch, J. R.

1974-01-01

This report describes HYDES, a hybrid computer program capable of simulating one-spool turbojet, two-spool turbojet, or two-spool turbofan engine dynamics. HYDES is also capable of simulating two- or three-stream turbofans with or without mixing of the exhaust streams. The program is intended to reduce the time required for implementing dynamic engine simulations. HYDES was developed for running on the Lewis Research Center's Electronic Associates (EAI) 690 Hybrid Computing System and satisfies the 16384-word core-size and hybrid-interface limits of that machine. The program could be modified for running on other computing systems. The use of HYDES to simulate a single-spool turbojet and a two-spool, two-stream turbofan engine is demonstrated. The form of the required input data is shown and samples of output listings (teletype) and transient plots (x-y plotter) are provided. HYDES is shown to be capable of performing both steady-state design and off-design analyses and transient analyses.

CONTINUOUS PRECIPITATION METHOD FOR CONVERSION OF URANYL NITRATE TO URANIUM HEXAFLUORIDE

DOEpatents

Reinhart, G.M.; Collopy, T.J.

1962-11-13

A continuous precipitation process is given for converting a uranyl nitrate solution to uranium tetrafluoride. A stream of the uranyl nitrate solution and a stream of an aqueous ammonium hydroxide solution are continuously introduced into an agitated reaction zone maintained at a pH of 5.0 to 6.5. Flow rates are adjusted to provide a mean residence time of the resulting slurry in the reaction zone of at least 30 minutes. After a startup period of two hours the precipitate is recovered from the effluent stream by filtration and is converted to uranium tetrafluoride by reduction to uranium dioxide with hydrogen and reaction of the uranium dioxide with anhydrous hydrogen fluoride. (AEC)

Experimental investigation of acoustic streaming in a cylindrical wave guide up to high streaming Reynolds numbers.

PubMed

Reyt, Ida; Bailliet, Hélène; Valière, Jean-Christophe

2014-01-01

Measurements of streaming velocity are performed by means of Laser Doppler Velocimetry and Particle Image Velociimetry in an experimental apparatus consisting of a cylindrical waveguide having one loudspeaker at each end for high intensity sound levels. The case of high nonlinear Reynolds number ReNL is particularly investigated. The variation of axial streaming velocity with respect to the axial and to the transverse coordinates are compared to available Rayleigh streaming theory. As expected, the measured streaming velocity agrees well with the Rayleigh streaming theory for small ReNL but deviates significantly from such predictions for high ReNL. When the nonlinear Reynolds number is increased, the outer centerline axial streaming velocity gets distorted towards the acoustic velocity nodes until counter-rotating additional vortices are generated near the acoustic velocity antinodes. This kind of behavior is followed by outer streaming cells only and measurements in the near wall region show that inner streaming vortices are less affected by this substantial evolution of fast streaming pattern. Measurements of the transient evolution of streaming velocity provide an additional insight into the evolution of fast streaming.

Interplanetary flow systems associated with cosmic ray modulation in 1977-1980

NASA Technical Reports Server (NTRS)

Burlaga, L. F.; Mcdonald, F. B.; Ness, N. F.; Schwenn, R.; Lazarus, A. J.; Mariani, F.

1984-01-01

The hydromagnetic flow configurations associated with the cosmic ray modulation in 1977-1980 were determined using solar wind plasma and magnetic field data from Voyager 1 and 2 and Helios 1. The modulation was related to two types of large-scale systems of flows: one containing a number of transients such as shocks and postshock flows, the other consisting primarily of a series of quasi-stationary flows following interaction regions containing a stream interface and often bounded by a forward-reverse shock pair. Each of three major episodes of cosmic ray modulation was associated with the passage of a system of transient flows. Plateaus in the cosmic ray intensity-time profile were associated with the passage of systems of corotating streams.

Combustion chamber and thermal vapor stream producing apparatus and method

DOEpatents

Sperry, John S.; Krajicek, Richard W.; Cradeur, Robert R.

1978-01-01

A new and improved method and apparatus for burning a hydrocarbon fuel for producing a high pressure thermal vapor stream comprising steam and combustion gases for injecting into a subterranean formation for the recovery of liquefiable minerals therefrom, wherein a high pressure combustion chamber having multiple refractory lined combustion zones of varying diameters is provided for burning a hydrocarbon fuel and pressurized air in predetermined ratios injected into the chamber for producing hot combustion gases essentially free of oxidizing components and solid carbonaceous particles. The combustion zones are formed by zones of increasing diameters up a final zone of decreasing diameter to provide expansion zones which cause turbulence through controlled thorough mixing of the air and fuel to facilitate complete combustion. The high pressure air and fuel is injected into the first of the multiple zones where ignition occurs with a portion of the air injected at or near the point of ignition to further provide turbulence and more complete combustion.

The Effect of Carbon Dioxide (CO 2) Ice Cloud Condensation on the Habitable Zone

NASA Astrophysics Data System (ADS)

Lincowski, Andrew; Meadows, Victoria; Robinson, Tyler D.; Crisp, David

2016-10-01

The currently accepted outer limit of the habitable zone (OHZ) is defined by the "maximum greenhouse" limit, where Rayleigh scattering from additional CO2 gas overwhelms greenhouse warming. However, this long-standing definition neglects the radiative effects of CO2 clouds (Kopparapu, 2013); this omission was justified based on studies using the two-stream approximation, which found CO2 clouds to be highly likely to produce a net warming. However, recent comparisons of the radiative effect of CO2 clouds using both a two-stream and multi-stream radiative transfer model (Kitzmann et al, 2013; Kitzmann, 2016) found that the warming effect was reduced when the more sophisticated multi-stream models were used. In many cases CO2 clouds caused a cooling effect, meaning that their impact on climate could not be neglected when calculating the outer edge of the habitable zone. To better understand the impact of CO2 ice clouds on the OHZ, we have integrated CO2 cloud condensation into a versatile 1-D climate model for terrestrial planets (Robinson et al, 2012) that uses the validated multi-stream SMART radiative transfer code (Meadows & Crisp, 1996; Crisp, 1997) with a simple microphysical model. We present preliminary results on the habitable zone with self-consistent CO2 clouds for a range of atmospheric masses, compositions and host star spectra, and the subsequent effect on surface temperature. In particular, we evaluate the habitable zone for TRAPPIST-1d (Gillon et al, 2016) with a variety of atmospheric compositions and masses. We present reflectance and transit spectra of these cold terrestrial planets. We identify any consequences for the OHZ in general and TRAPPIST-1d in particular. This more comprehensive treatment of the OHZ could impact our understanding of the distribution of habitable planets in the universe, and provide better constraints for statistical target selection techniques, such as the habitability index (Barnes et al, 2015), for missions like JWST, WFIRST-AFTA and the LUVOIR mission concept.

Earthquake-driven fluid flow rates inferred from borehole temperature measurements within the Japan Trench plate boundary fault zone

NASA Astrophysics Data System (ADS)

Fulton, P. M.; Brodsky, E. E.

2016-12-01

Using borehole sub-seafloor temperature measurements, we have recently identified signatures suggestive of earthquake-driven fluid pulses within the Japan Trench plate boundary fault zone during a major aftershock sequence. Here we use numerical models to show that these signatures are consistent with time-varying fluid flow rates out of permeable zones within the formation into the borehole annulus. In addition, we also identify an apparent time-varying sensitivity of whether suspected fluid pulses occur in response to earthquakes of a given magnitude and distance. The results suggest a damage and healing process and therefore provides a mechanism to allow for a disproportionate amount of heat and chemical transport in the short time frame after an earthquake. Our observations come from an observatory installed across the main plate boundary fault as part of IODP's Japan Trench Fast Drilling Project (JFAST) following the March 2011 Mw 9.0 Tohoku-oki earthquake. It operated from July 2012 - April 2013 during which a Mw 7.3 earthquake and numerous aftershocks occurred. High-resolution temperature time series data reveal spatially correlated transients in response to earthquakes with distinct patterns interpreted to reflect advection by transient pulses of fluid flow from permeable zones into the borehole annulus. Typical transients involve perturbations over 12 m with increases of 10 mK that build over 0.1 days at shallower depths and decreases at deeper depths. They are consistently centered around 792.5 m below seafloor (mbsf) where a secondary fault and permeable zone have been independently identified within the damage zone above the main plate boundary fault at 820 mbsf . Model simulations suggest transient flow rates of up to 10-3m/s from the formation that quickly decrease. Comparison of characteristics of earthquakes identified in nearby ocean bottom pressure measurements suggest there is not a clear relationship between fluid pulses and static strain. There does appear to be a time-varying sensitivity likely from dynamic stresses suggestive of a damage process followed by healing over 1 month time. The transient redistribution of fluid pressures and fluid flow within fault zones inferred here is a potential mechanism for earthquake triggering and episodic heat and chemical transport.

Solute transport in streams of varying morphology inferred from a high resolution network of potentiometric wireless chloride sensors

NASA Astrophysics Data System (ADS)

Klaus, Julian; Smettem, Keith; Pfister, Laurent; Harris, Nick

2017-04-01

There is ongoing interest in understanding and quantifying the travel times and dispersion of solutes moving through stream environments, including the hyporheic zone and/or in-channel dead zones where retention affects biogeochemical cycling processes that are critical to stream ecosystem functioning. Modelling these transport and retention processes requires acquisition of tracer data from injection experiments where the concentrations are recorded downstream. Such experiments are often time consuming and costly, which may be the reason many modelling studies of chemical transport have tended to rely on relatively few well documented field case studies. This leads to the need of fast and cheap distributed sensor arrays that respond instantly and record chemical transport at points of interest on timescales of seconds at various locations in the stream environment. To tackle this challenge we present data from several tracer experiments carried out in the Attert river catchment in Luxembourg employing low-cost (in the order of a euro per sensor) potentiometric chloride sensors in a distributed array. We injected NaCl under various baseflow conditions in streams of different morphologies and observed solute transport at various distances and locations. This data is used to benchmark the sensors to data obtained from more expensive electrical conductivity meters. Furthermore, the data allowed spatial resolution of hydrodynamic mixing processes and identification of chemical 'dead zones' in the study reaches.

Quantification of mass loading to Strawberry Creek near the Gilt Edge mine, Lawrence County, South Dakota, June 2003

USGS Publications Warehouse

Kimball, Briant A.; Runkel, Robert L.; Walton-Day, Katherine; Williamson, Joyce E.

2006-01-01

Although remedial actions have taken place at the Gilt Edge mine in the Black Hills of South Dakota, questions remain about a possible hydrologic connection along shear zones between some of the pit lakes at the mine site and Strawberry Creek. Spatially detailed chemical sampling of stream and inflow sites occurred during low-flow conditions in June 2003 as part of a mass-loading study by the U.S. Geological Survey to investigate the possible connection of shear zones to the stream. Stream discharge was calculated by tracer dilution; discharge increased by 25.3 liters per second along the study reach, with 9.73 liters per second coming from three tributaries and the remaining increase coming from small springs and dispersed, subsurface inflow. Chemical differences among inflow samples were distinguished by cluster analysis and indicated that inflows ranged from those unaffected by interaction with mine wastes to those that could have been affected by drainage from pit lakes. Mass loading to the stream from several inflows resulted in distinct chemical changes in stream water along the study reach. Mass loading of the mine-related metals, including cadmium, copper, nickel, and zinc, principally occurred from the discharge from the Gilt Edge mine, and those metals were substantially attenuated downstream. Secondary loadings of metals occurred in the vicinity of the Oro Fino shaft and from two more inflows about 200 m downstream from there. These are both locations where shear zones intersect the stream and may indicate loading associatedwith these zones. Loading downstream from the Oro Fino shaft had a unique chemical character, high in base-metal concentrations, that could indicate an association with water in the pit lakes. The loading from these downstream sources, however, is small in comparison to that from the initial mine discharge and does not appear to have a substantial impact on Strawberry Creek.

BEST Engineered Hyporheic Zones: Enhanced Hyporheic Exchange and Resazurin and Nitrate Cycling in Constructed Stream Experiments

NASA Astrophysics Data System (ADS)

Herzog, S.; McCray, J. E.; Higgins, C. P.

2016-12-01

The hyporheic zone is a hotspot for biogeochemical processing that can attenuate a variety of nonpoint source contaminants in streamwater. However, hyporheic zones in urban and agricultural streams are often degraded and poorly connected with surface water. To increase hyporheic exchange and improve water quality, we introduced engineered streambeds as a stormwater and restoration best management practice. Modifications to streambed hydraulic conductivity and reactivity are termed Biohydrochemical Enhancements for Streamwater Treatment (BEST). BEST are subsurface modules that utilize low-permeability sediments to drive efficient hyporheic exchange, and reactive geomedia to increase reaction rates within the hyporheic zone. This research utilized two artificial stream flumes at the Colorado School of Mines in Golden, CO. Each lined stream flume was 15m long, 0.3m wide, had 0.3m sediment depth, and was continuously dosed with recycled water at 0.25 L/s. One flume served as an all-sand control condition, the other featured BEST modules at 1m spacing with a mixture of 70/30 sand/woodchips (v/v). NaCl breakthrough curves were monitored and analyzed using STAMMT-L, a mobile-immobile exchange model, which showed greater hyporheic exchange and residence times in the BEST stream relative to the control. This result is even more apparent when the calibrated models are used to simulate longer stream reaches. Water quality samples at the reach scale also revealed greater attenuation of nitrate and transformation of the indicator compound resazurin into resorufin. Together these compounds demonstrate that BEST can attenuate contaminants that degrade under anaerobic and aerobic conditions, respectively. These experimental results were also compared to previous numerical simulations to evaluate model accuracy, and show reasonable agreement. Altogether, these results show that BEST may be an effective novel best management practice for improving streamwater quality in urban and agricultural settings.

An analytic description of electrodynamic dispersion in free-flow zone electrophoresis.

PubMed

Dutta, Debashis

2015-07-24

The present work analyzes the electrodynamic dispersion of sample streams in a free-flow zone electrophoresis (FFZE) chamber resulting due to partial or complete blockage of electroosmotic flow (EOF) across the channel width by the sidewalls of the conduit. This blockage of EOF has been assumed to generate a pressure-driven backflow in the transverse direction for maintaining flow balance in the system. A parallel-plate based FFZE device with the analyte stream located far away from the channel side regions has been considered to simplify the current analysis. Applying a method-of-moments formulation, an analytic expression was derived for the variance of the sample zone at steady state as a function of its position in the separation chamber under these conditions. It has been shown that the increase in stream broadening due to the electrodynamic dispersion phenomenon is additive to the contributions from molecular diffusion and sample injection, and simply modifies the coefficient for the hydrodynamic dispersion term for a fixed lateral migration distance of the sample stream. Moreover, this dispersion mechanism can dominate the overall spatial variance of analyte zones when a significant fraction of the EOF is blocked by the channel sidewalls. The analysis also shows that analyte streams do not undergo any hydrodynamic broadening due to unwanted pressure-driven cross-flows in an FFZE chamber in the absence of a transverse electric field. The noted results have been validated using Monte Carlo simulations which further demonstrate that while the sample concentration profile at the channel outlet approaches a Gaussian distribution only in FFZE chambers substantially longer than the product of the axial pressure-driven velocity and the characteristic diffusion time in the system, the spatial variance of the exiting analyte stream is well described by the Taylor-Aris dispersion limit even in analysis ducts much shorter than this length scale. Copyright © 2015 Elsevier B.V. All rights reserved.

Fault zone hydrogeologic properties and processes revealed by borehole temperature monitoring

NASA Astrophysics Data System (ADS)

Fulton, P. M.; Brodsky, E. E.

2015-12-01

High-resolution borehole temperature monitoring can provide valuable insight into the hydrogeologic structure of fault zones and transient processes that affect fault zone stability. Here we report on results from a subseafloor temperature observatory within the Japan Trench plate boundary fault. In our efforts to interpret this unusual dataset, we have developed several new methods for probing hydrogeologic properties and processes. We illustrate how spatial variations in the thermal recovery of the borehole after drilling and other spectral characteristics provide a measure of the subsurface permeability architecture. More permeable zones allow for greater infiltration of cool drilling fluids, are more greatly thermally disturbed, and take longer to recover. The results from the JFAST (Japan Trench Fast Drilling Project) observatory are consistent with geophysical logs, core data, and other hydrologic observations and suggest a permeable damage zone consisting of steeply dipping faults and fractures overlays a low-permeability clay-rich plate boundary fault. Using high-resolution time series data, we have also developed methods to map out when and where fluid advection occurs in the subsurface over time. In the JFAST data, these techniques reveal dozens of transient earthquake-driven fluid pulses that are spatially correlated and consistently located around inferred permeable areas of the fault damage zone. These observations are suspected to reflect transient fluid flow driven by pore pressure changes in response to dynamic and/or static stresses associated with nearby earthquakes. This newly recognized hydrologic phenomenon has implications for understanding subduction zone heat and chemical transport as well as the redistribution of pore fluid pressure which influences fault stability and can trigger other earthquakes.

Tracer-dilution experiments and solute-transport simulations for a mountain stream, Saint Kevin Gulch, Colorado. Water resources investigation

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

Broshears, R.E.; Bencala, K.E.; Kimball, B.A.

In 1986, the U.S. Geological Survey began an investigation to characterize within-stream hydrologic, chemical, and biological processes that influence the distribution and transport of hazardous constituents in the headwaters of the Arkansas River. The report describes the results of tracer-dilution experiments and associated solute-transport simulations for a 1804-meter stretch of Saint Kevin Gulch, a stream affected by acid mine drainage in Lake County, Colorado. The report describes transient changes in tracer (lithium chloride) concentration at six instream sites.

Riparian control of stream-water chemistry: Implications for hydrochemical basin models

USGS Publications Warehouse

Hooper, R.P.; Aulenbach, Brent T.; Burns, Douglas A.; McDonnell, J.; Freer, J.; Kendall, C.; Beven, K.

1998-01-01

End-member mixing analysis has been used to determine the hydrological structure for basin hydrochemical models at several catchments. Implicit in this use is the assumption that controlling end members have been identified, and that these end members represent distinct landscape locations. At the Panola Mountain Research Watershed, the choice of controlling end members was supported when a large change in the calcium and sulphate concentration of one of the end members was reflected in the stream water. More extensive sampling of groundwater and soil water indicated, however, that the geographic extent of the contributing end members was limited to the riparian zone. Hillslope solutions were chemically distinct from the riparian solutions and did not appear to make a large contribution to streamflow. The dominant control of the riparian zone on stream-water chemistry suggests that hydrological flow paths cannot be inferred from stream-water chemical dynamics.

The feasibility of imaging subglacial hydrology beneath ice streams with ground-based electromagnetics

NASA Astrophysics Data System (ADS)

Siegfried, M. R.; Key, K.

2017-12-01

Subglacial hydrologic systems in Antarctica and Greenland play a fundamental role in ice-sheet dynamics, yet critical aspects of these systems remain poorly understood due to a lack of observations. Ground-based electromagnetic (EM) geophysical methods are established for mapping groundwater in many environments, but have never been applied to imaging lakes beneath ice sheets. Here we study the feasibility of passive and active source EM imaging for quantifying the nature of subglacial water systems beneath ice streams, with an emphasis on the interfaces between ice and basal meltwater, as well as deeper groundwater in the underlying sediments. Specifically, we look at the passive magnetotelluric method and active-source EM methods that use a large loop transmitter and receivers that measure either frequency-domain or transient soundings. We describe a suite of model studies that exam the data sensitivity as a function of ice thickness, water conductivity and hydrologic system geometry for models representative of a subglacial lake and a grounding zone estuary. We show that EM data are directly sensitive to groundwater and can image its lateral and depth extent. By combining the conductivity obtained from EM data with ice thickness and geological structure from conventional geophysical techniques such as ground-penetrating radar and active seismic techniques, EM data have the potential to provide new insights on the interaction between ice, rock, and water at critical ice-sheet boundaries.

Modeling E. coli Release And Transport In A Creek During Artificial High-Flow Events

NASA Astrophysics Data System (ADS)

Yakirevich, A.; Pachepsky, Y. A.; Gish, T. J.; Cho, K.; Shelton, D. R.; Kuznetsov, M. Y.

2012-12-01

In-stream fate and transport of E. coli, is a leading indicator of microbial contamination of natural waters, and so needs to be understood to eventually minimize surface water contamination by microbial organisms. The objective of this work was to simulate E. coli release and transport from soil sediment in a creek bed both during and after high water flow events. The artificial high-water flow events were created by releasing 60-80 m3 of city water on a tarp-covered stream bank at a rate of 60 L/s in four equal allotments in July of 2008, 2009 and 2010. The small first-order creek used in this study is part of the Beaver Dam Creek Tributary and is located at the USDA Optimizing Production inputs for Economic and Environmental Enhancement (OPE3) research site, in Beltsville, Maryland. In 2009 and 2010 a conservative tracer difluorobenzoic acid (DFBA) was added to the released water. Specifically, water flow rates, E. coli and DFBA concentrations as well as water turbidity were monitored with automated samplers at the ends of the three in-stream weirs reaching a total length of 630 m. Sediment particle size distributions and the streambed E. coli concentrations were measured along a creek before and after experiment. The observed DFBA breakthrough curves (BTCs) exhibited long tails after the water pulse and tracer peaks indicating that transient storage might be an important element of the in-stream transport process. Turbidity and E. coli BTCs also exhibited long tails indicative of transient storage and low rates of settling caused by re-entrainment. Typically, turbidity peaked prior to E. coli and returned to lower base-line levels more rapidly. A one-dimensional model was applied to simulate water flow, E. coli and DFBA transport during these experiments. The Saint-Venant equations were used to calculate water depth and discharge while a stream solute transport model accounted for advection-dispersion, lateral inflow/outflow, exchange with the transient storage, and resuspension of bacteria by shear stress from stream bottom sediments. Reach-specific model parameters were estimated by using observed time series of flow rates and concentrations at three weir stations. Transient storage and dispersion parameters were obtained with DFBA BTCs, then critical shear stress and resuspension rate were assessed by fitting computed E. coli BTCs to observations. To obtain a good model fit for E. coli, we generally had to make the transient storage for E. coli larger than for DFBA. Comparison of simulated and measured E. coli concentrations indicated that significant resuspension of E. coli continued when water flow returned to the base level after the water pulse passed and bottom shear stress was small. The hypothetical mechanism of this extended release could be the enhanced boundary layer (water-streambed) exchange due to changes in biofilm properties by erosion and sloughing detachment.

Calibration of a transient transport model to tritium data in streams and simulation of groundwater ages in the western Lake Taupo catchment, New Zealand

NASA Astrophysics Data System (ADS)

Gusyev, M. A.; Toews, M.; Morgenstern, U.; Stewart, M.; White, P.; Daughney, C.; Hadfield, J.

2013-03-01

Here we present a general approach of calibrating transient transport models to tritium concentrations in river waters developed for the MT3DMS/MODFLOW model of the western Lake Taupo catchment, New Zealand. Tritium has a known pulse-shaped input to groundwater systems due to the bomb tritium in the early 1960s and, with its radioactive half-life of 12.32 yr, allows for the determination of the groundwater age. In the transport model, the tritium input (measured in rainfall) passes through the groundwater system, and the simulated tritium concentrations are matched to the measured tritium concentrations in the river and stream outlets for the Waihaha, Whanganui, Whareroa, Kuratau and Omori catchments from 2000-2007. For the Kuratau River, tritium was also measured between 1960 and 1970, which allowed us to fine-tune the transport model for the simulated bomb-peak tritium concentrations. In order to incorporate small surface water features in detail, an 80 m uniform grid cell size was selected in the steady-state MODFLOW model for the model area of 1072 km2. The groundwater flow model was first calibrated to groundwater levels and stream baseflow observations. Then, the transient tritium transport MT3DMS model was matched to the measured tritium concentrations in streams and rivers, which are the natural discharge of the groundwater system. The tritium concentrations in the rivers and streams correspond to the residence time of the water in the groundwater system (groundwater age) and mixing of water with different age. The transport model output showed a good agreement with the measured tritium values. Finally, the tritium-calibrated MT3DMS model is applied to simulate groundwater ages, which are used to obtain groundwater age distributions with mean residence times (MRTs) in streams and rivers for the five catchments. The effect of regional and local hydrogeology on the simulated groundwater ages is investigated by demonstrating groundwater ages at five model cross-sections to better understand MRTs simulated with tritium-calibrated MT3DMS and lumped parameter models.

Hg isotopes reveal in-stream processing and legacy inputs in East Fork Poplar Creek, Oak Ridge, Tennessee, USA

DOE PAGES

Demers, Jason D.; Blum, Joel D.; Brooks, Scott C.; ...

2018-03-01

In this paper, natural abundance stable Hg isotope measurements were used to place new constraints on sources, transport, and transformations of Hg along the flow path of East Fork Poplar Creek (EFPC), a point-source contaminated headwater stream in Oak Ridge, Tennessee. Particulate-bound Hg in the water column of EFPC within the Y-12 National Security Complex, was isotopically similar to average metallic Hg(0) used in industry, having a mean δ 202Hg value of -0.42 ± 0.09‰ (1SD) and near-zero Δ 199Hg. On average, particulate fraction δ 202Hg values increased downstream by 0.53‰, while Δ 199Hg decreased by -0.10‰, converging with themore » Hg isotopic composition of the fine fraction of streambed sediment along the 26 km flow path. The dissolved fraction behaved differently. Although initial Δ 199Hg values of the dissolved fraction were also near-zero, these values increased transiently along the flow path. Initial δ 202Hg values of the dissolved fraction were more variable than in the particulate fraction, ranging from -0.44 to 0.18‰ among three seasonal sampling campaigns, but converged to an average δ 202Hg value of 0.01 ± 0.10‰ (1SD) downstream. Dissolved Hg in the hyporheic and riparian pore water had higher and lower δ 202Hg values, respectively, compared to dissolved Hg in stream water. Finally, variations in Hg isotopic composition of the dissolved and suspended fractions along the flow path suggest that: (1) physical processes such as dilution and sedimentation do not fully explain decreases in total mercury concentrations along the flow path; (2) in-stream processes include photochemical reduction, but microbial reduction is likely more dominant; and (3) additional sources of dissolved mercury inputs to EFPC at baseflow during this study predominantly arise from the hyporheic zone.« less

Hg isotopes reveal in-stream processing and legacy inputs in East Fork Poplar Creek, Oak Ridge, Tennessee, USA

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

Demers, Jason D.; Blum, Joel D.; Brooks, Scott C.

In this paper, natural abundance stable Hg isotope measurements were used to place new constraints on sources, transport, and transformations of Hg along the flow path of East Fork Poplar Creek (EFPC), a point-source contaminated headwater stream in Oak Ridge, Tennessee. Particulate-bound Hg in the water column of EFPC within the Y-12 National Security Complex, was isotopically similar to average metallic Hg(0) used in industry, having a mean δ 202Hg value of -0.42 ± 0.09‰ (1SD) and near-zero Δ 199Hg. On average, particulate fraction δ 202Hg values increased downstream by 0.53‰, while Δ 199Hg decreased by -0.10‰, converging with themore » Hg isotopic composition of the fine fraction of streambed sediment along the 26 km flow path. The dissolved fraction behaved differently. Although initial Δ 199Hg values of the dissolved fraction were also near-zero, these values increased transiently along the flow path. Initial δ 202Hg values of the dissolved fraction were more variable than in the particulate fraction, ranging from -0.44 to 0.18‰ among three seasonal sampling campaigns, but converged to an average δ 202Hg value of 0.01 ± 0.10‰ (1SD) downstream. Dissolved Hg in the hyporheic and riparian pore water had higher and lower δ 202Hg values, respectively, compared to dissolved Hg in stream water. Finally, variations in Hg isotopic composition of the dissolved and suspended fractions along the flow path suggest that: (1) physical processes such as dilution and sedimentation do not fully explain decreases in total mercury concentrations along the flow path; (2) in-stream processes include photochemical reduction, but microbial reduction is likely more dominant; and (3) additional sources of dissolved mercury inputs to EFPC at baseflow during this study predominantly arise from the hyporheic zone.« less

Brook trout use of thermal refugia and foraging habitat influenced by brown trout

USGS Publications Warehouse

Hitt, Nathaniel P.; Snook, Erin; Massie, Danielle L.

2017-01-01

The distribution of native brook trout (Salvelinus fontinalis) in eastern North America is often limited by temperature and introduced brown trout (Salmo trutta), the relative importance of which is poorly understood but critical for conservation and restoration planning. We evaluated effects of brown trout on brook trout behavior and habitat use in experimental streams across increasing temperatures (14–23 °C) with simulated groundwater upwelling zones providing thermal refugia (6–9 °C below ambient temperatures). Allopatric and sympatric trout populations increased their use of upwelling zones as ambient temperatures increased, demonstrating the importance of groundwater as thermal refugia in warming streams. Allopatric brook trout showed greater movement rates and more even spatial distributions within streams than sympatric brook trout, suggesting interference competition by brown trout for access to forage habitats located outside thermal refugia. Our results indicate that removal of introduced brown trout may facilitate native brook trout expansion and population viability in downstream reaches depending in part on the spatial configuration of groundwater upwelling zones.

Reactivation of a cryptobiotic stream ecosystem in the McMurdo Dry Valleys, Antarctica: A long-term geomorphological experiment

USGS Publications Warehouse

McKnight, Diane M.; Tate, C.M.; Andrews, E.D.; Niyogi, D.K.; Cozzetto, K.; Welch, K.; Lyons, W.B.; Capone, D.G.

2007-01-01

The McMurdo Dry Valleys of Antarctica contain many glacial meltwater streams that flow for 6 to 12??weeks during the austral summer and link the glaciers to the lakes on the valley floors. Dry valley streams gain solutes longitudinally through weathering reactions and microbial processes occurring in the hyporheic zone. Some streams have thriving cyanobacterial mats. In streams with regular summer flow, the mats are freeze-dried through the winter and begin photosynthesizing with the onset of flow. To evaluate the longer term persistence of cyanobacterial mats, we diverted flow to an abandoned channel, which had not received substantial flow for approximately two decades. Monitoring of specific conductance showed that for the first 3??years after the diversion, the solute concentrations were greater in the reactivated channel than in most other dry valley streams. We observed that cyanobacterial mats became abundant in the reactivated channel within a week, indicating that the mats had been preserved in a cryptobiotic state in the channel. Over the next several years, these mats had high rates of productivity and nitrogen fixation compared to mats from other streams. Experiments in which mats from the reactivated channel and another stream were incubated in water from both of the streams indicated that the greater solute concentrations in the reactivated channel stimulated net primary productivity of mats from both streams. These stream-scale experimental results indicate that the cryptobiotic preservation of cyanobacterial mats in abandoned channels in the dry valleys allows for rapid response of these stream ecosystems to climatic and geomorphological change, similar to other arid zone stream ecosystems. ?? 2006 Elsevier B.V. All rights reserved.

Discharge of New Subglacial Lake on Whillians Ice Stream: Implication for Ice Stream Flow Dynamics.

NASA Astrophysics Data System (ADS)

Sergienko, O. V.; Fricker, H. A.; Bindschadler, R. A.; Vornberger, P. L.; Macayeal, D. R.

2006-12-01

One of the surprise discoveries made possible by the ICESat laser altimeter mission of 2004-2006 is the presence of a large subglacial lake below the grounding zone of Whillians Ice Stream (dubbed here `Lake Helen' after the discoverer, Helen Fricker). What is even more surprising is the fact that this lake discharged a substantial portion of its volume during the ICESat mission, and changes in lake volume and surface elevation of the ice stream are documented in exquisite detail [Fricker et al., in press]. The presence and apparent dynamism of large subglacial lakes in the grounding zone of a major ice stream raises questions about their effects on ice-stream dynamics. Being liquid and movable, water modifies basal friction spatially and temporally. Melting due to shear heating and geothermal flux reduces basal traction, making the ice stream move fast. However, when water collects in a depression to form a lake, it potentially deprives the surrounding bed of lubricating water, and additionally makes the ice surface flat, thereby locally decreasing the ice stream driving stress. We study the effect of formation and discharge of a subglacial lake at the mouth of and ice stream using a two dimensional, vertically integrated, ice-stream model. The model is forced by the basal friction, ice thickness and surface elevation. The basal friction is obtained by inversion of the ice surface velocity, ice thickness and surface elevation come from observations. To simulate the lake formation we introduce zero basal friction and "inflate" the basal elevation of the ice stream at the site of the lake. Sensitivity studies of the response of the surrounding ice stream and ice shelf flow are performed to delineate the influence of near-grounding-line subglacial water storage for ice streams in general.

Time-domain electromagnetic tests in the Wadi Bidah District, Kingdom of Saudi Arabia

USGS Publications Warehouse

Flanigan, Vincent J.; Sadek, Hamdy; Smith, Bruce; Tippens, C.L.

1983-01-01

A time-domain electromagnetic (TDEM) method was tested in two areas of mineralization in Precambrian rocks in the Wadi Bidah district, Kingdom of Saudi Arabia. Transient-decay voltages in profile mode were measured across the Sha'ab at Tare and Rabathan prospects by use of three transmitterreceiver loop configurations. At the Sha'ab at Tare prospect all of the loop configurations indicated the mineralized zone. Analysis of the coincident loop data at Sha'ab at Tare reveals that gossanous and altered rock of i0 ohm-m resistivity extends to a depth of 35 m, where there is an unweathered, dry mineralized zone of about 1 ohm-m resistivity. The model further suggests that the rocks at a depth of 55 m and below the water table are even less resistive (0. 1 ohm-m). The TDEM method successfully discriminated conductors within from those below the weathered zone at the Rabathan prospect. Conductors below the weathered zone are identified by a lack of transient response in the early part of the transient decay curve, followed by an increasing response in the middle to late parts of the transient decay curve. Results of these limited tests suggest the potential value of integrating TDEM with other geophysical tools in the Kingdom. Recommendations are made to expand these tests into a more comprehensive program that will evaluate the TDEM potential in various geologic environments that are host to mineral deposits of diverse origin.

Escape tectonics and the extrusion of Alaska: Past, present, and future

USGS Publications Warehouse

Redfield, T.F.; Scholl, D. W.; Fitzgerald, P.G.; Beck, M.E.

2007-01-01

The North Pacific Rim is a tectonically active plate boundary zone parts of which may be characterized as a laterally moving orogenic stream. Crustal blocks are transported along large-magnitude strike-slip faults in western Canada and central Alaska toward the Aleutian-Bering Sea subduction zones. Throughout much of the Cenozoic, at and west of its Alaskan nexus, the North Pacific Rim orogenic Stream (NPRS) has undergone tectonic escape. During transport, relatively rigid blocks acquired paleomagnetic rotations and fault-juxtaposed boundaries while flowing differentially through the system, from their original point of accretion and entrainment toward the free face defined by the Aleutian-Bering Sea subduction zones. Built upon classical terrane tectonics, the NPRS model provides a new framework with which to view the mobilistic nature of the western North American plate boundary zone. ?? 2007 The Geological Society of America.

Encoding model of temporal processing in human visual cortex.

PubMed

Stigliani, Anthony; Jeska, Brianna; Grill-Spector, Kalanit

2017-12-19

How is temporal information processed in human visual cortex? Visual input is relayed to V1 through segregated transient and sustained channels in the retina and lateral geniculate nucleus (LGN). However, there is intense debate as to how sustained and transient temporal channels contribute to visual processing beyond V1. The prevailing view associates transient processing predominately with motion-sensitive regions and sustained processing with ventral stream regions, while the opposing view suggests that both temporal channels contribute to neural processing beyond V1. Using fMRI, we measured cortical responses to time-varying stimuli and then implemented a two temporal channel-encoding model to evaluate the contributions of each channel. Different from the general linear model of fMRI that predicts responses directly from the stimulus, the encoding approach first models neural responses to the stimulus from which fMRI responses are derived. This encoding approach not only predicts cortical responses to time-varying stimuli from milliseconds to seconds but also, reveals differential contributions of temporal channels across visual cortex. Consistent with the prevailing view, motion-sensitive regions and adjacent lateral occipitotemporal regions are dominated by transient responses. However, ventral occipitotemporal regions are driven by both sustained and transient channels, with transient responses exceeding the sustained. These findings propose a rethinking of temporal processing in the ventral stream and suggest that transient processing may contribute to rapid extraction of the content of the visual input. Importantly, our encoding approach has vast implications, because it can be applied with fMRI to decipher neural computations in millisecond resolution in any part of the brain. Copyright © 2017 the Author(s). Published by PNAS.

Predicting changes in hydrologic retention in an evolving semi-arid alluvial stream

USGS Publications Warehouse

Harvey, J.W.; Conklin, M.H.; Koelsch, R.S.

2003-01-01

Hydrologic retention of solutes in hyporheic zones or other slowly moving waters of natural channels is thought to be a significant control on biogeochemical cycling and ecology of streams. To learn more about factors affecting hydrologic retention, we repeated stream-tracer injections for 5 years in a semi-arid alluvial stream (Pinal Creek, Ariz.) during a period when streamflow was decreasing, channel width increasing, and coverage of aquatic macrophytes expanding. Average stream velocity at Pinal Creek decreased from 0.8 to 0.2 m/s, average stream depth decreased from 0.09 to 0.04 m, and average channel width expanded from 3 to 13 m. Modeling of tracer experiments indicated that the hydrologic retention factor (Rh), a measure of the average time that solute spends in storage per unit length of downstream transport, increased from 0.02 to 8 s/m. At the same time the ratio of cross-sectional area of storage zones to main channel cross-sectional area (As/A) increased from 0.2 to 0.8 m2/m2, and average water residence time in storage zones (ts) increased from 5 to 24 min. Compared with published data from four other streams in the US, Pinal Creek experienced the greatest change in hydrologic retention for a given change in streamflow. The other streams differed from Pinal Creek in that they experienced a change in streamflow between tracer experiments without substantial geomorphic or vegetative adjustments. As a result, a regression of hydrologic retention on streamflow developed for the other streams underpredicted the measured increases in hydrologic retention at Pinal Creek. The increase in hydrologic retention at Pinal Creek was more accurately predicted when measurements of the Darcy-Weisbach friction factor were used (either alone or in addition to streamflow) as a predictor variable. We conclude that relatively simple measurements of channel friction are useful for predicting the response of hydrologic retention in streams to major adjustments in channel morphology as well as changes in streamflow. Published by Elsevier Ltd.

Behavioural changes in three species of freshwater macroinvertebrates exposed to the pyrethroid lambda-cyhalothrin: laboratory and stream microcosm studies.

PubMed

Nørum, Ulrik; Friberg, Nikolai; Jensen, Maria R; Pedersen, Jakob M; Bjerregaard, Poul

2010-07-15

Pesticides are transported from crop fields to adjacent streams via surface run-off, drains, groundwater, wind drift and atmospheric deposition and give rise to transient pulse contamination. Although the concentrations observed, typically <10 microg L(-1), cannot be expected to be acutely lethal, effects in streams at the population and ecosystem level have been reported. One of the most conspicuous phenomena associated with these transient pesticide pulses is drift, where large numbers of freshwater invertebrates are carried along by the current and disappear from the contaminated stretch of the stream. The aim of the present study was to evaluate the feasibility of linking laboratory studies of the sublethal effects of pulse exposure to the pyrethroid lambda-cyhalothrin on the locomotory behaviour of stream invertebrates with effects on drift behaviour under more environmentally realistic conditions in stream microcosms. In the laboratory as well as in the microcosms, the order of sensitivities of the three species tested was (with Leuctra nigra being the most sensitive): L. nigra>Gammarus pulex>Heptagenia sulphurea. The LOECs determined for L. nigra (1 ng L(-1)), G. pulex (10 ng L(-1)) and H. sulphurea (100 ng L(-1)) are all within expected environmental concentrations. For the species of invertebrates investigated, it was possible to extrapolate directly from pyrethroid-induced behavioural changes observed in the laboratory to drift under more realistic conditions in stream microcosms. Consequently, the fast and cost-effective video tracking methodology may be applied for screening for potential effects of a wider range of pesticides and other stressors on the locomotory behaviour of freshwater invertebrates. The results indicate that such behavioural changes may be predictive of effects at the ecosystem level. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Flume experiments elucidate relationships between stream morphology, hyporheic residence time, and nitrous oxide production

NASA Astrophysics Data System (ADS)

Quick, Annika; Farrell, Tiffany B.; Reeder, William Jeffrey; Feris, Kevin P.; Tonina, Daniele; Benner, Shawn G.

2015-04-01

The hyporheic zone is a potentially important producer of nitrous oxide, a powerful greenhouse gas. The location and magnitude of nitrous oxide generation within the hyporheic zone involves complex interactions between multiple nitrogen species, redox conditions, microbial communities, and hydraulics. To better understand nitrous oxide generation and emissions from streams, we conducted large-scale flume experiments in which we monitored pore waters along hyporheic flow paths within stream dune structures. Measurements of dissolved oxygen, ammonia, nitrate, nitrite, and dissolved nitrous oxide showed distinct spatial relationships reflecting redox changes along flow paths. Using residence times along a flow path, clear trends in oxygen conditions and nitrogen species were observed. Three dune sizes were modeled, resulting in a range of residence times, carbon reactivity levels and respiration rates. We found that the magnitude and location of nitrous oxide production in the hyporheic zone is related to nitrate loading, dune morphology, and residence time. Specifically, increasing exogenous nitrate levels in surface water to approximately 3 mg/L resulted in an increase in dissolved N2O concentrations greater than 500% (up to 10 µg/L N-N2O) in distinct zones of specific residence times. We also found, however, that dissolved N2O concentrations decreased to background levels further along the flow path due to either reduction of nitrous oxide to dinitrogen gas or degassing. The decrease in measurable N2O along a flow path strongly suggests an important relationship between dune morphology, residence time, and nitrous oxide emissions from within stream sediments. Relating streambed morphology and loading of nitrogen species allows for prediction of nitrous oxide production in the hyporheic zone of natural systems.

Vadose zone controls on damping of climate-induced transient recharge fluxes in U.S. agroecosystems

NASA Astrophysics Data System (ADS)

Gurdak, Jason

2017-04-01

Understanding the physical processes in the vadose zone that link climate variability with transient recharge fluxes has particular relevance for the sustainability of groundwater-supported irrigated agriculture and other groundwater-dependent ecosystems. Natural climate variability on interannual to multidecadal timescales has well-documented influence on precipitation, evapotranspiration, soil moisture, infiltration flux, and can augment or diminish human stresses on water resources. Here the behavior and damping depth of climate-induced transient water flux in the vadose zone is explored. The damping depth is the depth in the vadose zone that the flux variation damps to 5% of the land surface variation. Steady-state recharge occurs when the damping depth is above the water table, and transient recharge occurs when the damping depth is below the water table. Findings are presented from major agroecosystems of the United States (U.S.), including the High Plains, Central Valley, California Coastal Basin, and Mississippi Embayment aquifer systems. Singular spectrum analysis (SSA) is used to identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6-12 mo cycle), Pacific/North American oscillation (PNA) (<1-4 yr cycle), El Niño/Southern Oscillation (ENSO) (2-7 yr cycle), North Atlantic Oscillation (NAO) (3-6 yr cycle), Pacific Decadal Oscillation (PDO) (15-30 yr cycle), and Atlantic Multidecadal Oscillation (AMO) (50-70 yr cycle). SSA results indicate that nearly all of the quasi-periodic signals in the precipitation and groundwater levels have a statistically significant lag correlation (95% confidence interval) with the AO, PNA, ENSO, NAO, PDO, and AMO indices. Results from HYDRUS-1D simulations indicate that transient water flux through the vadose zone are controlled by highly nonlinear interactions between mean infiltration flux and infiltration period related to the modes of climate variability and the local soil textures, layering, and depth to the water table. Simulation results for homogeneous profiles generally show that shorter-period climate oscillations, smaller mean fluxes, and finer-grained soil textures generally produce damping depths closer to land surface. Simulation results for layered soil textures indicate more complex responses in the damping depth, including the finding that finer-textured layers in a coarser soil profile generally result in damping depths closer to land surface, while coarser-textured layers in coarser soil profile result in damping depths deeper in the vadose zone. Findings from this study improve understanding of how vadose zone properties influences transient recharge flux and damp climate variability signals in groundwater systems, and have important implications for sustainable management of groundwater resources and coupled agroecosystems under future climate variability and change.

Transport and transformation of soil-derived CO2, CH4 and DOC sustain CO2 supersaturation in small boreal streams.

PubMed

Rasilo, Terhi; Hutchins, Ryan H S; Ruiz-González, Clara; Del Giorgio, Paul A

2017-02-01

Streams are typically supersaturated in carbon dioxide (CO 2 ) and methane (CH 4 ), and are recognized as important components of regional carbon (C) emissions in northern landscapes. Whereas there is consensus that in most of the systems the CO 2 emitted by streams represents C fixed in the terrestrial ecosystem, the pathways delivering this C to streams are still not well understood. We assessed the contribution of direct soil CO 2 injection versus the oxidation of soil-derived dissolved organic C (DOC) and CH 4 in supporting CO 2 supersaturation in boreal streams in Québec. We measured the concentrations of CO 2 , CH 4 and DOC in 43 streams and adjacent soil waters during summer base-flow period. A mass balance approach revealed that all three pathways are significant, and that the mineralization of soil-derived DOC and CH 4 accounted for most of the estimated stream CO 2 emissions (average 75% and 10%, respectively), and that these estimated contributions did not change significantly between the studied low order (≤3) streams. Whereas some of these transformations take place in the channel proper, our results suggest that they mainly occur in the hyporheic zones of the streams. Our results further show that stream CH 4 emissions can be fully explained by soil CH 4 inputs. This study confirms that these boreal streams, and in particular their hyporheic zones, are extremely active processors of soil derived DOC and CH 4 , not just vents for soil produced CO 2 . Copyright © 2016 Elsevier B.V. All rights reserved.

Meet EPA Ecologist Paul Mayer, Ph.D.

EPA Pesticide Factsheets

EPA ecologist Paul Mayer, Ph.D. works in EPA's Groundwater and Ecosystem Restoration division where he studies riparian zones (the area along rivers and streams where the habitats are influenced by both the land and water) and stream restoration

RoboTAP: Target priorities for robotic microlensing observations

NASA Astrophysics Data System (ADS)

Hundertmark, M.; Street, R. A.; Tsapras, Y.; Bachelet, E.; Dominik, M.; Horne, K.; Bozza, V.; Bramich, D. M.; Cassan, A.; D'Ago, G.; Figuera Jaimes, R.; Kains, N.; Ranc, C.; Schmidt, R. W.; Snodgrass, C.; Wambsganss, J.; Steele, I. A.; Mao, S.; Ment, K.; Menzies, J.; Li, Z.; Cross, S.; Maoz, D.; Shvartzvald, Y.

2018-01-01

Context. The ability to automatically select scientifically-important transient events from an alert stream of many such events, and to conduct follow-up observations in response, will become increasingly important in astronomy. With wide-angle time domain surveys pushing to fainter limiting magnitudes, the capability to follow-up on transient alerts far exceeds our follow-up telescope resources, and effective target prioritization becomes essential. The RoboNet-II microlensing program is a pathfinder project, which has developed an automated target selection process (RoboTAP) for gravitational microlensing events, which are observed in real time using the Las Cumbres Observatory telescope network. Aims: Follow-up telescopes typically have a much smaller field of view compared to surveys, therefore the most promising microlensing events must be automatically selected at any given time from an annual sample exceeding 2000 events. The main challenge is to select between events with a high planet detection sensitivity, with the aim of detecting many planets and characterizing planetary anomalies. Methods: Our target selection algorithm is a hybrid system based on estimates of the planet detection zones around a microlens. It follows automatic anomaly alerts and respects the expected survey coverage of specific events. Results: We introduce the RoboTAP algorithm, whose purpose is to select and prioritize microlensing events with high sensitivity to planetary companions. In this work, we determine the planet sensitivity of the RoboNet follow-up program and provide a working example of how a broker can be designed for a real-life transient science program conducting follow-up observations in response to alerts; we explore the issues that will confront similar programs being developed for the Large Synoptic Survey Telescope (LSST) and other time domain surveys.

Transport and concentration controls for chloride, strontium, potassium and lead in Uvas Creek, a small cobble-bed stream in Santa Clara County, California, U.S.A. 2. Mathematical modeling

USGS Publications Warehouse

Jackman, A.P.; Walters, R.A.; Kennedy, V.C.

1984-01-01

Three models describing solute transport of conservative ion species and another describing transport of species which adsorb linearly and reversibly on bed sediments are developed and tested. The conservative models are based on three different conceptual models of the transient storage of solute in the bed. One model assumes the bed to be a well-mixed zone with flux of solute into the bed proportional to the difference between stream concentration and bed concentration. The second model assumes solute in the bed is transported by a vertical diffusion process described by Fick's law. The third model assumes that convection occurs in a selected portion of the bed while the mechanism of the first model functions everywhere. The model for adsorbing species assumes that the bed consists of particles of uniform size with the rate of uptake controlled by an intraparticle diffusion process. All models are tested using data collected before, during and after a 24-hr. pulse injection of chloride, strontium, potassium and lead ions into Uvas Creek near Morgan Hill, California, U.S.A. All three conservative models accurately predict chloride ion concentrations in the stream. The model employing the diffusion mechanism for bed transport predicts better than the others. The adsorption model predicts both strontium and potassium ion concentrations well during the injection of the pulse but somewhat overestimates the observed concentrations after the injection ceases. The overestimation may be due to the convection of solute deep into the bed where it is retained longer than the 3-week post-injection observation period. The model, when calibrated for strontium, predicts potassium equally well when the adsorption equilibrium constant for strontium is replaced by that for potassium. ?? 1984.

Novel Insights Linking Ecological Health to Biogeochemical Hotspots across the Groundwater-Surface Water Interface in Mixed Land Use Stream Systems

NASA Astrophysics Data System (ADS)

McKnight, U. S.; Sonne, A. T.; Rasmussen, J. J.; Rønde, V.; Traunspurger, W.; Höss, S.; Bjerg, P. L.

2017-12-01

Increasing modifications in land use and water management have resulted in multiple stressors impacting freshwater ecosystems globally. Chemicals with the potential to impact aquatic habitats are still often evaluated individually for their adverse effects on ecosystem health. This may lead to critical underestimations of the combined impact caused by interactions occurring between stressors not typically evaluated together, e.g. xenobiotic groundwater pollutants and trace metals. To address this issue, we identified sources and levels of chemical stressors along a 16-km groundwater-fed stream corridor (Grindsted, Denmark), representative for a mixed land use stream system. Potential pollution sources included two contaminated sites (factory, landfill), aquaculture, wastewater/industrial discharges, and diffuse sources from agriculture and urban areas. Ecological status was determined by monitoring meiobenthic and macrobenthic invertebrate communities.The stream was substantially impaired by both geogenic and anthropogenic sources of metals throughout the investigated corridor, with concentrations close to or above threshold values for barium, copper, lead, nickel and zinc in the stream water, hyporheic zone and streambed sediment. The groundwater plume from the factory site caused elevated concentrations of chlorinated ethenes, benzene and pharmaceuticals in both the hyporheic zone and stream, persisting for several km downstream. Impaired ecological conditions, represented by a lower abundance of meiobenthic individuals, were found in zones where the groundwater plume discharges to the stream. The effect was only pronounced in areas characterized by high xenobiotic organic concentrations and elevated dissolved iron and arsenic levels - linked to the dissolution of iron hydroxides caused by the degradation of xenobiotic compounds in the plume. The results thus provide ecological evidence for the interaction of organic and inorganic chemical stressors, which may provide a missing link enabling the reconnection of chemical and ecological findings. This study highlights the importance of stream-aquifer interfaces for ecosystem functioning in terms of biological habitat, and that multiple stressor systems need to be tackled from a holistic perspective.

Aquifer response to stream-stage and recharge variations. II. Convolution method and applications

NASA Astrophysics Data System (ADS)

Barlow, P. M.; DeSimone, L. A.; Moench, A. F.

2000-05-01

In this second of two papers, analytical step-response functions, developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined, leaky, or water-table aquifer, are used in the convolution integral to calculate aquifer heads, streambank seepage rates, and bank storage that occur in response to stream-stage fluctuations and basinwide recharge or evapotranspiration. Two computer programs developed on the basis of these step-response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream-aquifer systems in the northeastern and central United States. These applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties, recharge rates, streambank seepage rates, and bank storage. Analysis of the water-table aquifer adjacent to the Blackstone River in Massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer (negligible specific yield). This finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe, where sediment pores are saturated by tension, extends to land surface. Under this condition, the aquifer's response is determined by elastic storage only. Estimates of horizontal and vertical hydraulic conductivity, specific yield, specific storage, and recharge for a water-table aquifer adjacent to the Cedar River in eastern Iowa, determined by the use of analytical methods, are in close agreement with those estimated by use of a more complex, multilayer numerical model of the aquifer. Streambank leakance of the semipervious streambank materials also was estimated for the site. The streambank-leakance parameter may be considered to be a general (or lumped) parameter that accounts not only for the resistance of flow at the river-aquifer boundary, but also for the effects of partial penetration of the river and other near-stream flow phenomena not included in the theoretical development of the step-response functions.

Techniques of fisheries management: water quality assessment with stream insects

Treesearch

A. Dennis Lemly

2000-01-01

Nutrient enrichment of streams is a long-standing problem that continues to have substantial local and regional consequences. For example, water quality of streams in the southern Appalachian Mountains of the U.S. can be seriously degraded by organic nutrients leached from animal wastes if cattle or other livestock are allowed to graze in the riparian zone. Local...

Hillslope hydrologic connectivity controls riparian groundwater turnover: Implications of catchment structure for riparian buffering and stream water sources

Treesearch

Kelsey G. Jencso; Brian L. McGlynn; Michael N. Gooseff; Kenneth E. Bencala; Steven M. Wondzell

2010-01-01

Hydrologic connectivity between catchment upland and near stream areas is essential for the transmission of water, solutes, and nutrients to streams. However, our current understanding of the role of riparian zones in mediating landscape hydrologic connectivity and the catchment scale export of water and solutes is limited. We tested the relationship between the...

Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico

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

Buss, Heather; Brantley, S. L.; Scatena, Fred

2013-01-01

Recent work has suggested that weathering processes occurring in the subsurface produce the majority of silicate weathering products discharged to the world s oceans, thereby exerting a primary control on global temperature via the well-known positive feedback between silicate weathering and CO2. In addition, chemical and physical weathering processes deep within the critical zone create aquifers and control groundwater chemistry, watershed geometry and regolith formation rates. Despite this, most weathering studies are restricted to the shallow critical zone (e.g., soils, outcrops). Here we investigate the chemical weathering, fracturing and geomorphology of the deep critical zone in the Bisley watershed inmore » the Luquillo Critical Zone Observatory, Puerto Rico, from two boreholes drilled to 37.2 and 27.0 m depth, from which continuous core samples were taken. Corestones exposed aboveground were also sampled. Weathered rinds developed on exposed corestones and along fracture surfaces on subsurface rocks slough off of exposed corestones once rinds attain a thickness up to ~1 cm, preventing the corestones from rounding due to diffusion limitation. Such corestones at the land surface are assumed to be what remains after exhumation of similar, fractured bedrock pieces that were observed in the drilled cores between thick layers of regolith. Some of these subsurface corestones are massive and others are highly fractured, whereas aboveground corestones are generally massive with little to no apparent fracturing. Subsurface corestones are larger and less fractured in the borehole drilled on a road where it crosses a ridge compared to the borehole drilled where the road crosses the stream channel. Both borehole profiles indicate that the weathering zone extends to well below the stream channel in this upland catchment; hence weathering depth is not controlled by the stream level within the catchment and not all of the water in the watershed is discharged to the stream.« less

Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico

USGS Publications Warehouse

Buss, Heather L.; Brantley, Susan L.; Scatena, Fred; Bazilevskaya, Katya; Blum, Alex E.; Schulz, Marjorie S.; Jiménez, Rafael; White, Arthur F.; Rother, G.; Cole, D.

2013-01-01

Recent work has suggested that weathering processes occurring in the subsurface produce the majority of silicate weathering products discharged to the world's oceans, thereby exerting a primary control on global temperature via the well-known positive feedback between silicate weathering and CO2. In addition, chemical and physical weathering processes deep within the critical zone create aquifers and control groundwater chemistry, watershed geometry and regolith formation rates. Despite this, most weathering studies are restricted to the shallow critical zone (e.g. soils, outcrops). Here we investigate the chemical weathering, fracturing and geomorphology of the deep critical zone in the Bisley watershed in the Luquillo Critical Zone Observatory, Puerto Rico, from two boreholes drilled to 37.2 and 27.0 m depth, from which continuous core samples were taken. Corestones exposed aboveground were also sampled. Weathered rinds developed on exposed corestones and along fracture surfaces on subsurface rocks slough off of exposed corestones once rinds attain a thickness up to ~1 cm, preventing the corestones from rounding due to diffusion limitation. Such corestones at the land surface are assumed to be what remains after exhumation of similar, fractured bedrock pieces that were observed in the drilled cores between thick layers of regolith. Some of these subsurface corestones are massive and others are highly fractured, whereas aboveground corestones are generally massive with little to no apparent fracturing. Subsurface corestones are larger and less fractured in the borehole drilled on a road where it crosses a ridge compared with the borehole drilled where the road crosses the stream channel. Both borehole profiles indicate that the weathering zone extends to well below the stream channel in this upland catchment; hence weathering depth is not controlled by the stream level within the catchment and not all of the water in the watershed is discharged to the stream

Reducing equifinality using isotopes in a process-based stream nitrogen model highlights the flux of algal nitrogen from agricultural streams

NASA Astrophysics Data System (ADS)

Ford, William I.; Fox, James F.; Pollock, Erik

2017-08-01

The fate of bioavailable nitrogen species transported through agricultural landscapes remains highly uncertain given complexities of measuring fluxes impacting the fluvial N cycle. We present and test a new numerical model named Technology for Removable Annual Nitrogen in Streams For Ecosystem Restoration (TRANSFER), which aims to reduce model uncertainty due to erroneous parameterization, i.e., equifinality, in stream nitrogen cycle assessment and quantify the significance of transient and permanent removal pathways. TRANSFER couples nitrogen elemental and stable isotope mass-balance equations with existing hydrologic, hydraulic, sediment transport, algal biomass, and sediment organic matter mass-balance subroutines and a robust GLUE-like uncertainty analysis. We test the model in an agriculturally impacted, third-order stream reach located in the Bluegrass Region of Central Kentucky. Results of the multiobjective model evaluation for the model application highlight the ability of sediment nitrogen fingerprints including elemental concentrations and stable N isotope signatures to reduce equifinality of the stream N model. Advancements in the numerical simulations allow for illumination of the significance of algal sloughing fluxes for the first time in relation to denitrification. Broadly, model estimates suggest that denitrification is slightly greater than algal N sloughing (10.7% and 6.3% of dissolved N load on average), highlighting the potential for overestimation of denitrification by 37%. We highlight the significance of the transient N pool given the potential for the N store to be regenerated to the water column in downstream reaches, leading to harmful and nuisance algal bloom development.

A methodology for delineating planning-level channel migration zones.

DOT National Transportation Integrated Search

2014-07-01

The Washington State administrative codes that implement the Shoreline Management Act (SMA) require communities to identify the general location of channel migration zones (CMZs), and regulate development within these areas on shoreline streams. Shor...

Transient cnoidal waves explain the formation and geometry of fault damage zones

NASA Astrophysics Data System (ADS)

Veveakis, Manolis; Schrank, Christoph

2017-04-01

The spatial footprint of a brittle fault is usually dominated by a wide area of deformation bands and fractures surrounding a narrow, highly deformed fault core. This diffuse damage zone relates to the deformation history of a fault, including its seismicity, and has a significant impact on flow and mechanical properties of faulted rock. Here, we propose a new mechanical model for damage-zone formation. It builds on a novel mathematical theory postulating fundamental material instabilities in solids with internal mass transfer associated with volumetric deformation due to elastoviscoplastic p-waves termed cnoidal waves. We show that transient cnoidal waves triggered by fault slip events can explain the characteristic distribution and extent of deformation bands and fractures within natural fault damage zones. Our model suggests that an overpressure wave propagating away from the slipping fault and the material properties of the host rock control damage-zone geometry. Hence, cnoidal-wave theory may open a new chapter for predicting seismicity, material and geometrical properties as well as the location of brittle faults.

Holding onto the Green Zone: A Youth Program for the Study and Stewardship of Community Riparian Areas. Action Guide

ERIC Educational Resources Information Center

US Department of the Interior, 2008

2008-01-01

Scientists call the land along the edges of a river, stream, or lake a riparian zone. In this guide, riparian zone will be called the Green Zone. Riparian zones make up only a small part of land in the United States. But they are very important. They protect water quality and quantity, supply food and shelter for fish and wildlife, and provide…

Freeze core sampling to validate time-lapse resistivity monitoring of the hyporheic zone.

PubMed

Toran, Laura; Hughes, Brian; Nyquist, Jonathan; Ryan, Robert

2013-01-01

A freeze core sampler was used to characterize hyporheic zone storage during a stream tracer test. The pore water from the frozen core showed tracer lingered in the hyporheic zone after the tracer had returned to background concentration in collocated well samples. These results confirmed evidence of lingering subsurface tracer seen in time-lapse electrical resistivity tomographs. The pore water exhibited brine exclusion (ion concentrations in ice lower than source water) in a sediment matrix, despite the fast freezing time. Although freeze core sampling provided qualitative evidence of lingering tracer, it proved difficult to quantify tracer concentration because the amount of brine exclusion during freezing could not be accurately determined. Nonetheless, the additional evidence for lingering tracer supports using time-lapse resistivity to detect regions of low fluid mobility within the hyporheic zone that can act as chemically reactive zones of importance in stream health. © 2012, The Author(s). GroundWater © 2012, National Ground Water Association.

On the feeding zone of planetesimal formation by the streaming instability

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

Yang, Chao-Chin; Johansen, Anders, E-mail: ccyang@astro.lu.se, E-mail: anders@astro.lu.se

2014-09-10

The streaming instability is a promising mechanism to overcome the barriers in direct dust growth and lead to the formation of planetesimals. Most previous studies of the streaming instability, however, were focused on a local region of a protoplanetary disk with a limited simulation domain such that only one filamentary concentration of solids has been observed. The characteristic separation between filaments is therefore not known. To address this, we conduct the largest-scale simulations of the streaming instability to date, with computational domains up to 1.6 gas scale heights both horizontally and vertically. The large dynamical range allows the effect ofmore » vertical gas stratification to become prominent. We observe more frequent merging and splitting of filaments in simulation boxes of high vertical extent. We find multiple filamentary concentrations of solids with an average separation of about 0.2 local gas scale heights, much higher than the most unstable wavelength from linear stability analysis. This measures the characteristic separation of planetesimal forming events driven by the streaming instability and thus the initial feeding zone of planetesimals.« less

The Zwicky Transient Facility Public Alert Stream

NASA Astrophysics Data System (ADS)

Masci, F.; Kulkarni, S. R.; Graham, M.; Prince, T.; Helou, G.

2018-06-01

The Zwicky Transient Facility (ZTF; ATel #11266) announces the start of public alerts. These alerts will originate from the ZTF public surveys (Bellm & Kulkarni 2017; Nature Astronomy 1, 71) as described at www.ztf.caltech.edu/page/msip Alerts are generated by the ZTF Science Data System housed at IPAC-Caltech (www.ipac.caltech.edu) using a realtime image-subtraction pipeline (Masci et al. 2018; www.ztf.caltech.edu/page/technical).

Influence of land use on hyporheos in catchment of the Jarama River (central Spain)

NASA Astrophysics Data System (ADS)

Iepure, S.; Martínez-Hernández, V.; Herrera, S.; de Bustamante, I.; Rasines, R.

2012-04-01

The Water Framework Directive (2000) requires integrated assessment of water bodies based on water resources but also the evaluation of land-use catchment effect on chemical and ecological conditions of aquatic ecosystems. The hyporheic zone (HZ) supporting obligate subterranean species are particularly vulnerable in river ecosystems when environmental stress occurs at surface and require management strategies to protect both the stream catchment and the aquifer that feed the stream channel. The influence of catchment land-use in the Jarama basin (central Spain) on river geomorphology and hyporheic zone granulometry, chemical and biological variables inferred from crustacean community biodiversity (species richness, taxonomic distinctness) and ecology was assessed. The study was conducted in four streams from the Madrid metropolitan area under distinct local land-use and water resource protection: i) a preserved forested natural sites where critical river ecosystem processes were unaltered or less altered by human activities, and ii) different degree of anthropogenic impact sites from agriculture, urban industrial and mining activities. The river bed permeability reduction and the increase of low sediment size input associated with changes in geomorphology of the stream channels are greatly affected by land-use changes in the Jarama watershed. Water chemical parameters linked to land-use increase from the natural stream to the urban industrial and agricultural dominated catchment. Principal coordinate analysis (PCO) and multidimensional scaling (MDS) clearly discriminate the pristine sites from forested areas by those under anthropogenic stressors. In streams draining forested areas, groundwater discharge and regular exchange between groundwater and surface water occur due to relatively high permeability of the sediments. Consequently, forested land-use produce sites of high water quality and crustacean richness (both groundwater dwellers and surface-benthos species), as indicate the expected diversity pattern after the simulation procedure for taxonomic distinctness. Crustacean diversity (Shannon index) was greatest in less extensive agricultural land-use sites where riparian zone is slightly developed, while intensive agricultural activities cause a decline of water quality and therefore of crustacean richness. Intensively urban industrial land-use yield highly contaminated hyporheic water with heavy metals and VOC (i.e. toluene, benzene). Complementarily, the streams geomorphology and low rates of water flow favour the deposition of fine sediments that clog the interstices, generate a reverse dynamic of river channel and induce a reduction of groundwater discharge. In results, the hyporheic is unsuitable for hyporheos that are missing or harbour reduced populations of exclusively surface-water taxa. There are sites of intermediate biodiversity including hypogeans, located in natural regional parks thriving well-established riparian zone and relatively good water quality. The differences among sites in the Jarama basin indicate the impact that changes in land-use have upon the hyporheic ecology as shown the pattern of crustacean community distribution, diversity and ecological structure. We suggest that in rehabilitation processes of streams sectors require the understanding and recognition of the potential roles of the hyporheic zone and its biota in the whole stream ecosystem.

Hydrologic flow paths control dissolved organic carbon fluxes and metabolism in an Alpine stream hyporheic zone

NASA Astrophysics Data System (ADS)

Battin, Tom J.

1999-10-01

The objective of the present paper was to link reach-scale streambed reactive uptake of dissolved organic carbon (DOC) and dissolved oxygen (DO) to subsurface flow paths in an alpine stream (Oberer Seebach (OSB)). The topography adjacent to the stream channel largely determined flow paths, with shallow hillslope groundwater flowing beneath the stream and entering the alluvial groundwater at the opposite bank. As computed from hydrometric data, OSB consistently lost stream water to groundwater with fluxes out of the stream averaging 943 ± 47 and 664 ± 45 L m-2 h-1 at low (Q < 600 L s-1) and high (Q > 600 L s-1) flow, respectively. Hydrometric segregation of streambed fluxes and physicochemical mixing analysis indicated that stream water was the major input component to the streambed with average contributions of 70-80% to the hyporheic zone (i.e., the subsurface zone where shallow groundwater and stream water mix). Surface water was also the major source of DOC with 0.512 ± 0.043 mg C m-2 h-1 to the streambed. The DOC flux from shallow riparian groundwater was lower (0.309 ± 0.071 mg C m-2 h-1) and peaked in autumn with 1.011 mg C m-2 h-1. I computed the relative proportion of downstream discharge through the streambed as the ratio of the downstream length (Ssw) a stream water parcel travels before entering the streambed to the downstream length (Shyp) a streambed water parcel travels before returning to the stream water. The relative streambed DOC retention efficiency, calculated as (input-output)/input of interstitial DOC, correlated with the proportion (Ssw/Shyp) of downstream discharge (r2 = 0.76, p = 0.006). Also, did the streambed metabolism (calculated as DO uptake from mass balance) decrease with low subsurface downstream routing, whereas elevated downstream discharge through the streambed stimulated DO uptake (r2 = 0.69, p = 0.019)? Despite the very short DOC turnover times (˜0.05 days, calculated as mean standing stock/annual input) within the streambed, the latter constitutes a net sink of DOC (˜14 mg C m-2 h-1). Along with high standing stocks of sediment associated particulate organic carbon, these results suggest microbial biofilms as the major retention and storage site of DOC in an alpine stream where large hydrologic exchange controls DOC fluxes.

Documentation of the Streamflow-Routing (SFR2) Package to Include Unsaturated Flow Beneath Streams - A Modification to SFR1

USGS Publications Warehouse

Niswonger, Richard G.; Prudic, David E.

2005-01-01

Many streams in the United States, especially those in semiarid regions, have reaches that are hydraulically disconnected from underlying aquifers. Ground-water withdrawals have decreased water levels in valley aquifers beneath streams, increasing the occurrence of disconnected streams and aquifers. The U.S. Geological Survey modular ground-water model (MODFLOW-2000) can be used to model these interactions using the Streamflow-Routing (SFR1) Package. However, the approach does not consider unsaturated flow between streams and aquifers and may not give realistic results in areas with significantly deep unsaturated zones. This documentation describes a method for extending the capabilities of MODFLOW-2000 by incorporating the ability to simulate unsaturated flow beneath streams. A kinematic-wave approximation to Richards' equation was solved by the method of characteristics to simulate unsaturated flow beneath streams in SFR1. This new package, called SFR2, includes all the capabilities of SFR1 and is designed to be used with MODFLOW-2000. Unlike SFR1, seepage loss from the stream may be restricted by the hydraulic conductivity of the unsaturated zone. Unsaturated flow is simulated independently of saturated flow within each model cell corresponding to a stream reach whenever the water table (head in MODFLOW) is below the elevation of the streambed. The relation between unsaturated hydraulic conductivity and water content is defined by the Brooks-Corey function. Unsaturated flow variables specified in SFR2 include saturated and initial water contents; saturated vertical hydraulic conductivity; and the Brooks-Corey exponent. These variables are defined independently for each stream reach. Unsaturated flow in SFR2 was compared to the U.S. Geological Survey's Variably Saturated Two-Dimensional Flow and Transport (VS2DT) Model for two test simulations. For both test simulations, results of the two models were in good agreement with respect to the magnitude and downward progression of a wetting front through an unsaturated column. A third hypothetical simulation is presented that includes interaction between a stream and aquifer separated by an unsaturated zone. This simulation is included to demonstrate the utility of unsaturated flow in SFR2 with MODFLOW-2000. This report includes a description of the data input requirements for simulating unsaturated flow in SFR2.

Restoring hydrological and biogeochemical ecosystem services in streams: how can science inform practice?

NASA Astrophysics Data System (ADS)

Lautz, L.; Gordon, R.; Daniluk, T.; Zimmer, M. A.; Endreny, T. A.; McGrath, K.

2014-12-01

Society is increasingly recognizing the value of stream ecosystem functions, as evidenced by the enormous economic investment being made in stream restoration across the United States. Stream restoration projects have a variety of goals, including improvement in water quality and in-stream habitat. Popular approaches to restoration (such as Natural Channel Design, or NCD) aim to move degraded streams along a trajectory toward a dynamic ecological endpoint that represents natural conditions. Project designs primarily focus on channel form and function, but stream-groundwater exchanges of water and solutes are not typically a design consideration, although a primary component of fully functioning stream ecosystems. Here, we synthesize results from field investigations of the impact of NCD stream restoration on stream-groundwater exchanges by (1) comparing restored sites to reference reaches, which serve as the basis for the restoration design, (2) characterizing multiple restored sites to determine universal characteristics of streams restored by NCD, and (3) monitoring a stream pre- and post- restoration. NCD restoration creates hot spots of rapid hyporheic exchange upstream of channel spanning structures, with water fluxes across the bed interface up to an order of magnitude higher than at pre-restoration or reference reaches. Elevated flux rates result in short hyporheic residence times, which are not sufficiently long to generate net changes in nutrient concentrations. Hot spots of biogeochemical transformations are instead located around secondary bedforms, such as pool-riffle sequences, where gross water exchange rates are more moderate. Reference reaches show greater evidence of groundwater discharge to the hyporheic zone relative to restored reaches, although observations before and after restoration suggest NCD can modify the spatial extent of groundwater discharge zones. Gross water exchange across the streambed interface along restored reaches is a small percentage of stream discharge, suggesting the primary impact of restoration on stream-groundwater exchange is promoting biochemical heterogeneity in the subsurface, rather than longitudinal net changes in stream solute concentrations. Results inform future design to achieve restoration goals.

Application of a 3D Model to Assess the Thermo-Hydrological Effects of Climate Warming in a Discontinuous Permafrost Zone, Umiujaq, Northern Quebec, Canada

NASA Astrophysics Data System (ADS)

Parhizkar, M.; Therrien, R.; Molson, J. W. H.; Lemieux, J. M.; Fortier, R.; Talbot Poulin, M. C.; Therrien, P.; Ouellet, M.

2016-12-01

The rate of permafrost degradation in northern Quebec, Canada, has increased over the last two decades due to climate warming, which is expected to significantly modify the hydrogeologic and thermal regimes. Groundwater accessibility is also expected to increase and could become a significant source of drinking water for northern communities. In this project, an integrated surface water / groundwater flow model, HydroGeoSphere, is being applied to a 2 km2catchment in northern Quebec to assess the effect of future climate change on thermo-hydrological conditions as well as on changes in groundwater availability for northern communities. The catchment is located in a discontinuous but widespread permafrost zone near Umiujaq (northern Quebec, Canada) where the subsurface consists of a 10-30 m-thick coarse-grained glaciofluvial layer forming a good aquifer beneath a permafrost-rich silty marine unit. A conceptual thermo-hydrological model of the catchment has been built from field data collected over 5 years, including hydraulic heads, stream flow rates, subsurface geology, as well as ground temperatures and thermal fluxes around two 10-20 m-thick permafrost mounds. The integrated 3D numerical model includes variably-saturated groundwater flow with transient recharge, as well as advective-conductive heat transport driven by transient air temperatures (varying from about -40 to +30 ºC) and a geothermal heat flux of 60 mW/m2. The model is calibrated to observed heads and temperatures by coupling PEST with HydroGeoSphere, allowing changes in hydraulic and thermal conductivities. Preliminary results are consistent with the available observed data, however non-uniqueness remains an important issue. The simulations are providing useful predictions of the permafrost thaw rate and associated changes to the hydrogeological flow system, including increased aquifer recharge following permafrost thaw.

Initial Results from Lunar Electromagnetic Sounding with ARTEMIS

NASA Astrophysics Data System (ADS)

Fuqua, H.; Fatemi, S.; Poppe, A. R.; Delory, G. T.; Grimm, R. E.; De Pater, I.

2016-12-01

Electromagnetic Sounding constrains conducting layers of the lunar interior by observing variations in the Interplanetary Magnetic Field. Here, we focus our analysis on the time domain transfer function method locating transient events observed by two magnetometers near the Moon. We analyze ARTEMIS and Apollo magnetometer data. This analysis assumes the induced field responds undisturbed in a vacuum. In actuality, the dynamic plasma environment interacts with the induced field. Our models indicate distortion but not confinement occurs in the nightside wake cavity. Moreover, within the deep wake, near-vacuum region, distortion of the induced dipole fields due to the interaction with the wake is minimal depending on the magnitude of the induced field, the geometry of the upstream fields, and the upstream plasma parameters such as particle densities, solar wind velocity, and temperatures. Our results indicate the assumption of a vacuum dipolar response is reasonable within this minimally disturbed zone. We then interpret the ATEMIS magnetic field signal through a geophysical forward model capturing the induced response based on prescribed electrical conductivity models. We demonstrate our forward model passes benchmarking analyses and solves the magnetic induction response for any input signal as well as any 2 or 3 dimensional conductivity profile. We locate data windows according to the following criteria: (1) probe locations such that the wake probe is within 500km altitude within the wake cavity and minimally disturbed zone, and the second probe is in the free streaming solar wind; (2) a transient event consisting of an abrupt change in the magnetic field occurs enabling the observation of induction; (3) cross correlation analysis reveals the magnetic field signals are well correlated between the two probes and distances observed. Here we present initial ARTEMIS results providing further insight into the lunar interior structure. This method and modeling results are applicable to any airless body with a conducting interior, interacting directly with the solar wind in the absence of a parent body magnetic field as well as any two point magnetometer constellation.

Emergent Archetype Hydrological-Biogeochemical Response Patterns in Heterogeneous Catchments

NASA Astrophysics Data System (ADS)

Jawitz, J. W.; Gall, H. E.; Rao, P.

2013-12-01

What can spatiotemporally integrated patterns observed in stream hydrologic and biogeochemical signals generated in response to transient hydro-climatic and anthropogenic forcing tell us about the interactions between spatially heterogeneous soil-mediated hydrological and biogeochemical processes? We seek to understand how the spatial structure of solute sources coupled with hydrologic responses affect observed concentration-discharge (C-Q) patterns. These patterns are expressions of the spatiotemporal structure of solute loads exported from managed catchments, and their likely ecological consequences manifested in receiving water bodies (e.g., wetlands, rivers, lakes, and coastal waters). We investigated the following broad questions: (1) How does the correlation between flow-generating areas and biogeochemical source areas across a catchment evolve under stochastic hydro-climatic forcing? (2) What are the feasible hydrologic and biogeochemical responses that lead to the emergence of the observed archetype C-Q patterns? and; (3) What implications do these coupled dynamics have for catchment monitoring and implementation of management practices? We categorize the observed temporal signals into three archetypical C-Q patterns: dilution; accretion, and constant concentration. We introduce a parsimonious stochastic model of heterogeneous catchments, which act as hydrologic and biogeochemical filters, to examine the relationship between spatial heterogeneity and temporal history of solute export signals. The core concept of the modeling framework is considering the types and degree of spatial correlation between solute source zones and flow generating zones, and activation of different portions of the catchments during rainfall events. Our overarching hypothesis is that each of the archetype C-Q patterns can be generated by explicitly linking landscape-scale hydrologic responses and spatial distributions of solute source properties within a catchment. The model simulations reproduce the three major C-Q patterns observed in published data, offering valuable insight into coupled catchment processes. The findings have important implications for effective catchment management for water quality improvement, and stream monitoring strategies.

Pore Pressure Evolution in Shallow Subduction Earthquake Sequences and Effects on Aseismic Slip Transients -- Numerical Modeling With Rate and State Friction

NASA Astrophysics Data System (ADS)

Liu, Y.; Rice, J. R.

2005-12-01

In 3D modeling of long tectonic loading and earthquake sequences on a shallow subduction fault [Liu and Rice, 2005], with depth-variable rate and state friction properties, we found that aseismic transient slip episodes emerge spontaneously with only a simplified representation of effects of metamorphic fluid release. That involved assumption of a constant in time but uniformly low effective normal stress in the downdip region. As suggested by observations in several major subduction zones [Obara, 2002; Rogers and Dragert, 2003; Kodaira et al, 2004], the presence of fluids, possibly released from dehydration reactions beneath the seismogenic zone, and their pressurization within the fault zone may play an important role in causing aseismic transients and associated non-volcanic tremors. To investigate the effects of fluids in the subduction zone, particularly on the generation of aseismic transients and their various features, we develop a more complete physical description of the pore pressure evolution (specifically, pore pressure increase due to supply from dehydration reactions and shear heating, decrease due to transport and dilatancy during slip), and incorporate that into the rate and state based 3D modeling. We first incorporated two important factors, dilatancy and shear heating, following Segall and Rice [1995, 2004] and Taylor [1998]. In the 2D simulations (slip varies with depth only), a dilatancy-stabilizing effect is seen which slows down the seismic rupture front and can prevent rapid slip from extending all the way to the trench, similarly to Taylor [1998]. Shear heating increases the pore pressure, and results in faster coseismic rupture propagation and larger final slips. In the 3D simulations, dilatancy also stabilizes the along-strike rupture propagation of both seismic and aseismic slips. That is, aseismic slip transients migrate along the strike faster with a shorter Tp (the characteristic time for pore pressure in the fault core to re-equilibrate with that of its surroundings). This is consistent with our previous simulations, which show that the aseismic transients migrate along the strike at a higher speed under a lower, constant in time, effective normal stress. As a combination of the two factors, we show the pore pressure evolution with drops (due to dilatancy during slip) and then rises (due to shear heating) on the fault over multiple time scales. We next plan to formulate, and merge with the slip-rupture analysis, fuller fluid release models based on phase equilibria and models of transport in which the average fault-parallel permeability is a decreasing function of the effective normal stress. The thrust fault zone, at seismogenic depths and slightly downdip, is represented in a conceptually similar manner to the well-studied major continental faults, assuming the fault core materials have a lower permeability than the neighboring damaged zone. Heat diffusion in the fault core and damaged zone will also be considered in the modeling. The simulation results may help to improve our understanding of the processes of the aseismic transients observed within a transform plate boundary along the SAF near Cholame, California [Nadeau and Dolenc, 2005].

Dry creek long-term watershed study: effects of timber harvest on hydrology and sediment export in headwater streams in Southwest Georgia

Treesearch

W.B. Summer; C. Rhett Jackson; D. Jones; M. Miwa

2006-01-01

Properly established streamside management zones (SMZs) reduce potential impacts of timber harvesting on stream hydro-period and sediment fluxes. Effects of upland silvicultural practices on stream hydrology and effects of partial harvesting within SMZs on water quality are not well documented. The objectives of this study are to determine the effects of these forest...

Strong seepage of shallow groundwater shifts the timing of the annual thermal signals in stream water

NASA Astrophysics Data System (ADS)

Briggs, M. A.; Johnson, Z. C.; Snyder, C.; Hitt, N. P.; White, E. A.; Lane, J. W., Jr.; Nelms, D. L.

2016-12-01

Conventional wisdom indicates that while short-term (e.g. diurnal) thermal variance in streams may be attenuated by groundwater seepage, annual temperature swings will essentially track the local air temperature signal. However, the temperature of shallow (less than 5 m depth) groundwater from seepage zones may not be constant and near the local mean air temperature, but instead will fluctuate seasonally, and show a pronounced phase lag from the annual air signal. The degree of phase lag will be dependent on the rate of vertical fluid and heat exchange through shallow aquifer sediments. Gaining headwater streams might be expected to adopt similar phase lags to local seepage zones. We explore these dynamics through 9 mountain watersheds in Shenandoah National Park, VA, USA that harbor critical habitat for cold-water brook trout (Salvelinus fontinalis). Daily paired air and stream water temperature records were collected for up to 5 years at several stream locations along each watershed. Sinusoids fit to multiple-year data from more than 100 total locations indicate an average phase shift from air to surface water of approximately 10 d; this may primarily be due to strong conductive exchange with the rocky alluvial aquifer in generally incised and shaded channels. A subset of these transects (n=4) showed phase-lags greater than 20 d, coinciding with locations of particularly pronounced diurnal variance attenuation, indicating strong groundwater influence. Shallow bedrock, evaluated throughout the watersheds with passive seismic methods, restricts downward infiltration of precipitation in the mountain bedrock aquifers. Numerical 1D vertical aquifer models indicate similar phase lags in shallow groundwater at the bedrock contact to that observed in stream seepage zones. Therefore, contrary to conventional wisdom, shaded mountain streams with strong groundwater influence may adopt the annual thermal signature of the adjacent aquifer, shifting the stream thermal maxima timing from that predicted by air temperature. This research illustrates the utility of long-term paired air/stream thermal records, which further refine the evaluation of apparent groundwater influence to aquatic habitat.

Personalized professional content recommendation

DOEpatents

Xu, Songhua

2015-10-27

A personalized content recommendation system includes a client interface configured to automatically monitor a user's information data stream transmitted on the Internet. A hybrid contextual behavioral and collaborative personal interest inference engine resident to a non-transient media generates automatic predictions about the interests of individual users of the system. A database server retains the user's personal interest profile based on a plurality of monitored information. The system also includes a server programmed to filter items in an incoming information stream with the personal interest profile and is further programmed to identify only those items of the incoming information stream that substantially match the personal interest profile.

Flow line sampler

DOEpatents

Nicholls, Colin I.

1992-07-14

An on-line product sampling apparatus and method for measuring product samples from a product stream (12) in a flow line (14) having a sampling aperture (11), includes a sampling tube (18) for containing product samples removed from flow line (14). A piston (22) removes product samples from the product stream (12) through the sampling aperture (11) and returns samples to product stream (12). A sensor (20) communicates with sample tube (18), and senses physical properties of samples while the samples are within sample tube (18). In one embodiment, sensor (20) comprises a hydrogen transient nuclear magnetic resonance sensor for measuring physical properties of hydrogen molecules.

Nonvolcanic Deep Tremors in the Transform Plate Bounding San Andreas Fault Zone

NASA Astrophysics Data System (ADS)

Nadeau, R. M.; Dolenc, D.

2004-12-01

Recently, deep ( ˜ 20 to 40 km) nonvolcanic tremor activity has been observed on convergent plate boundaries in Japan and in the Cascadia region of North America (Obara, 2002; Rodgers and Dragert, 2003; Szeliga et al., 2004). Because of the abundance of available fluids from subduction processes in these convergent zones, fluids are believed to play an important role in the generation of the tremor activity. The transient rates of tremor activity in these regions are also observed to correlate either with the occurrence of larger earthquakes (Obara, 2002) or with geodetically determined transient creep events that release large amounts of strain energy deep beneath the locked Cascadia megathrust (M.M. Miller et al., 2002; Rodgers and Dragert, 2003; Szeliga et al., 2004). These associations suggest that nonvolcanic tremor activity may participate in a fundamental mode of deep moment release and in the triggering of large subduction zone events (Rodgers and Dragert, 2003). We report the discovery of deep ( ˜ 20 to 45 km) nonvolcanic tremor activity on the transform plate bounding San Andreas Fault (SAF) in central California where, in contrast to subduction zones, long-term deformation directions are horizontal and fluid availability from subduction zone processes is absent. The source region of the SAF tremors lies beneath the epicentral region of the great 1857 magnitude (M) ˜ 8, Fort Tejon earthquake whose rupture zone is currently locked (Sieh, 1978). Activity rate transients of the tremors occurring since early 2001 also correlate with seismicity rate variations above the tremor source region.

Analysis of groundwater flow and stream depletion in L-shaped fluvial aquifers

NASA Astrophysics Data System (ADS)

Lin, Chao-Chih; Chang, Ya-Chi; Yeh, Hund-Der

2018-04-01

Understanding the head distribution in aquifers is crucial for the evaluation of groundwater resources. This article develops a model for describing flow induced by pumping in an L-shaped fluvial aquifer bounded by impermeable bedrocks and two nearly fully penetrating streams. A similar scenario for numerical studies was reported in Kihm et al. (2007). The water level of the streams is assumed to be linearly varying with distance. The aquifer is divided into two subregions and the continuity conditions of the hydraulic head and flux are imposed at the interface of the subregions. The steady-state solution describing the head distribution for the model without pumping is first developed by the method of separation of variables. The transient solution for the head distribution induced by pumping is then derived based on the steady-state solution as initial condition and the methods of finite Fourier transform and Laplace transform. Moreover, the solution for stream depletion rate (SDR) from each of the two streams is also developed based on the head solution and Darcy's law. Both head and SDR solutions in the real time domain are obtained by a numerical inversion scheme called the Stehfest algorithm. The software MODFLOW is chosen to compare with the proposed head solution for the L-shaped aquifer. The steady-state and transient head distributions within the L-shaped aquifer predicted by the present solution are compared with the numerical simulations and measurement data presented in Kihm et al. (2007).

Recent (2008-10) water quality in the Barton Springs segment of the Edwards aquifer and its contributing zone, central Texas, with emphasis on factors affecting nutrients and bacteria

USGS Publications Warehouse

Mahler, Barbara J.; Musgrove, MaryLynn; Sample, Thomas L.; Wong, Corinne I.

2011-01-01

The Barton Springs zone, which comprises the Barton Springs segment of the Edwards aquifer and the watersheds to the west that contribute to its recharge, is in south-central Texas, an area with rapid growth in population and increasing amounts of land area affected by development. During November 2008-March 2010, an investigation of factors affecting the fate and transport of nutrients and bacteria in the Barton Springs zone was conducted by the U.S. Geological Survey (USGS), in cooperation with the Texas Commission on Environmental Quality. The primary objectives of the study were to characterize occurrence of nutrients and bacteria in the Barton Springs zone under a range of flow conditions; to improve understanding of the interaction between surface-water quality and groundwater quality; and to evaluate how factors such as streamflow variability and dilution affect the fate and transport of nutrients and bacteria in the Barton Springs zone. The USGS collected and analyzed water samples from five streams (Barton, Williamson, Slaughter, Bear, and Onion Creeks), two groundwater wells (Marbridge and Buda), and the main orifice of Barton Springs in Austin, Texas. During the period of the study, during which the hydrologic conditions transitioned from exceptional drought to wetter than normal, water samples were collected routinely (every 3 to 4 weeks) from the streams, wells, and spring and, in response to storms, from the streams and spring. All samples were analyzed for major ions, nutrients, the bacterium Escherichia coli, and suspended sediment. During the dry period, the geochemistry of groundwater at the two wells and at Barton Springs was dominated by flow from the aquifer matrix and was relatively similar and unchanging at the three sites. At the onset of the wet period, when the streams began to flow, the geochemistry of groundwater samples from the Marbridge well and Barton Springs changed rapidly, and concentrations of most major ions and nutrients and densities of Escherichia coli became more similar to those of samples from the streams relative to concentrations and densities during the dry period. Geochemical modeling indicated that the proportion of Barton Springs discharge composed of stream recharge increased from about 0-8 percent during the dry period to about 80 percent during the wet period. The transition from exceptional drought to wetter-than-normal conditions resulted in a number of marked changes that highlight factors affecting the fate and transport of nutrients and bacteria and the strong influence of stream recharge on water quality in the Barton Springs segment of the Edwards aquifer and had a pronounced effect on the fate of nitrogen species. Organic nitrogen loaded to and stored in soils during the dry period was nitrified to nitrate when the soils were rewetted, resulting in elevated concentrations of nitrate plus nitrite in streams as these constituents were progressively leached during continued wet weather. Estimated mean monthly loads of organic nitrogen and nitrate plus nitrite in stream recharge and Barton Springs discharge, which were relatively low and constant during the dry period, increased during the wet period. Loads of organic nitrogen, on average, were about six times greater in stream recharge than in Barton Springs discharge, indicating that organic nitrogen likely was being converted to nitrate within the aquifer. Loads of total nitrogen (organic nitrogen plus ammonia and nitrate plus nitrite) in stream recharge (162 kilograms per day) and in Barton Springs discharge (157 kilograms per day) for the period of the investigation were not significantly different. Dilution was not an important factor affecting concentrations of nitrate plus nitrite in the streams or in Barton Springs during the period of this investigation: Concentrations of nitrate plus nitrite did not decrease in streams with increasing stream discharge, and nitrate plus nitrite concentrations measured at Barton

A field comparison of multiple techniques to quantify groundwater - surface-water interactions

USGS Publications Warehouse

González-Pinzón, Ricardo; Ward, Adam S; Hatch, Christine E; Wlostowski, Adam N; Singha, Kamini; Gooseff, Michael N.; Haggerty, Roy; Harvey, Judson; Cirpka, Olaf A; Brock, James T

2015-01-01

Groundwater–surface-water (GW-SW) interactions in streams are difficult to quantify because of heterogeneity in hydraulic and reactive processes across a range of spatial and temporal scales. The challenge of quantifying these interactions has led to the development of several techniques, from centimeter-scale probes to whole-system tracers, including chemical, thermal, and electrical methods. We co-applied conservative and smart reactive solute-tracer tests, measurement of hydraulic heads, distributed temperature sensing, vertical profiles of solute tracer and temperature in the stream bed, and electrical resistivity imaging in a 450-m reach of a 3rd-order stream. GW-SW interactions were not spatially expansive, but were high in flux through a shallow hyporheic zone surrounding the reach. NaCl and resazurin tracers suggested different surface–subsurface exchange patterns in the upper ⅔ and lower ⅓ of the reach. Subsurface sampling of tracers and vertical thermal profiles quantified relatively high fluxes through a 10- to 20-cm deep hyporheic zone with chemical reactivity of the resazurin tracer indicated at 3-, 6-, and 9-cm sampling depths. Monitoring of hydraulic gradients along transects with MINIPOINT streambed samplers starting ∼40 m from the stream indicated that groundwater discharge prevented development of a larger hyporheic zone, which progressively decreased from the stream thalweg toward the banks. Distributed temperature sensing did not detect extensive inflow of ground water to the stream, and electrical resistivity imaging showed limited large-scale hyporheic exchange. We recommend choosing technique(s) based on: 1) clear definition of the questions to be addressed (physical, biological, or chemical processes), 2) explicit identification of the spatial and temporal scales to be covered and those required to provide an appropriate context for interpretation, and 3) maximizing generation of mechanistic understanding and reducing costs of implementing multiple techniques through collaborative research.

Zone heating for fluidized bed silane pyrolysis

NASA Technical Reports Server (NTRS)

Iya, Sridhar K. (Inventor)

1987-01-01

An improved heated fluidized bed reactor and method for the production of high purity polycrystalline silicon by silane pyrolysis wherein silicon seed particles are heated in an upper heating zone of the reactor and admixed with particles in a lower reaction zone, in which zone a silane-containing gas stream, having passed through a lower cooled gas distribution zone not conducive to silane pyrolysis, contacts the heated seed particles whereon the silane is heterogeneously reduced to silicon.

Hyperosmotically induced volume change and calcium signaling in intervertebral disk cells: the role of the actin cytoskeleton.

PubMed

Pritchard, Scott; Erickson, Geoffrey R; Guilak, Farshid

2002-11-01

Loading of the spine alters the osmotic environment in the intervertebral disk (IVD) as interstitial water is expressed from the tissue. Cells from the three zones of the IVD, the anulus fibrosus (AF), transition zone (TZ), and nucleus pulposus (NP), respond to osmotic stress with altered biosynthesis through a pathway that may involve calcium (Ca(2+)) as a second messenger. We examined the hypothesis that IVD cells respond to hyperosmotic stress by increasing the concentration of intracellular calcium ([Ca(2+)](i)) through a mechanism involving F-actin. In response to hyperosmotic stress, control cells from all zones decreased in volume and cells from the AF and TZ exhibited [Ca(2+)](i) transients, while cells from the NP did not. Extracellular Ca(2+) was necessary to initiate [Ca(2+)](i) transients. Stabilization of F-actin with phalloidin prevented the Ca(2+) response in AF and TZ cells and decreased the rate of volume change in cells from all zones, coupled with an increase in the elastic moduli and apparent viscosity. Conversely, actin breakdown with cytochalasin D facilitated Ca(2+) signaling while decreasing the elastic moduli and apparent viscosity for NP cells. These results suggest that hyperosmotic stress induces volume change in IVD cells and may initiate [Ca(2+)](i) transients through an actin-dependent mechanism.

Supply-demand mismatch transients in susceptible peri-infarct hot zones explain the origins of spreading injury depolarizations.

PubMed

von Bornstädt, Daniel; Houben, Thijs; Seidel, Jessica L; Zheng, Yi; Dilekoz, Ergin; Qin, Tao; Sandow, Nora; Kura, Sreekanth; Eikermann-Haerter, Katharina; Endres, Matthias; Boas, David A; Moskowitz, Michael A; Lo, Eng H; Dreier, Jens P; Woitzik, Johannes; Sakadžić, Sava; Ayata, Cenk

2015-03-04

Peri-infarct depolarizations (PIDs) are seemingly spontaneous spreading depression-like waves that negatively impact tissue outcome in both experimental and human stroke. Factors triggering PIDs are unknown. Here, we show that somatosensory activation of peri-infarct cortex triggers PIDs when the activated cortex is within a critical range of ischemia. We show that the mechanism involves increased oxygen utilization within the activated cortex, worsening the supply-demand mismatch. We support the concept by clinical data showing that mismatch predisposes stroke patients to PIDs as well. Conversely, transient worsening of mismatch by episodic hypoxemia or hypotension also reproducibly triggers PIDs. Therefore, PIDs are triggered upon supply-demand mismatch transients in metastable peri-infarct hot zones due to increased demand or reduced supply. Based on the data, we propose that minimizing sensory stimulation and hypoxic or hypotensive transients in stroke and brain injury would reduce PID incidence and their adverse impact on outcome. Copyright © 2015 Elsevier Inc. All rights reserved.

Supply-demand mismatch transients in susceptible peri-infarct hot zones explain the origin of spreading injury depolarizations

PubMed Central

von Bornstädt, Daniel; Houben, Thijs; Seidel, Jessica; Zheng, Yi; Dilekoz, Ergin; Qin, Tao; Sandow, Nora; Kura, Sreekanth; Eikermann-Haerter, Katharina; Endres, Matthias; Boas, David A.; Moskowitz, Michael A.; Lo, Eng H.; Dreier, Jens P.; Woitzik, Johannes; Sakadžić, Sava; Ayata, Cenk

2015-01-01

SUMMARY Peri-infarct depolarizations (PIDs) are seemingly spontaneous spreading depression-like waves that negatively impact tissue outcome in both experimental and human stroke. Factors triggering PIDs are unknown. Here, we show that somatosensory activation of peri-infarct cortex triggers PIDs when the activated cortex is within a critical range of ischemia. We show that the mechanism involves increased oxygen utilization within the activated cortex, worsening the supply-demand mismatch. We support the concept by clinical data showing that mismatch predisposes to PIDs in human stroke as well. Conversely, transient worsening of mismatch by episodic hypoxemia or hypotension also reproducibly triggers PIDs. Therefore, PIDs are triggered upon supply-demand mismatch transients in metastable peri-infarct hot zones due to increased demand or reduced supply. Based on the data, we propose that minimizing sensory stimulation and hypoxic or hypotensive transients in stroke and brain injury would reduce PID incidence and their adverse impact on outcome. PMID:25741731

Does tree harvesting in riparian areas increase stream sedimentation and turbidity - world-wide experience relative to Australia.

NASA Astrophysics Data System (ADS)

Neary, D.; Smethurst, P.; Petrone, K.

2009-04-01

A typical improved-pasture property in the high-rainfall zone of Australia contains 0.5-2.0 km of waterways per 100 ha. Nationwide, some 25-30 million ha of improved pasture contains about 100,000 km of streams, of which about 75% are currently un-buffered and contributing to soil and water degradation. Farmers and natural resource managers are considering ways to enhance environmental outcomes at farm and catchment scales using stream-side buffers of trees and other perennial vegetation. Benefits of buffers include improved water quality, biodiversity, carbon sequestration and aesthetics. Lack of sound information and funding for establishing and managing buffer zones is hindering wide-scale adoption of this practice. Stream-side areas of farms are generally highly productive (wet and nutrient-rich) and contain a high biodiversity, but they are also high-risk zones for soil and water values and stock safety. Development of options based on a balance between environmental and economic outcomes would potentially promote wider adoption. Australian codes of forest practice currently discourage or prevent harvesting of trees in streamside buffers. These codes were developed exclusively for large-scale native forests and industrial-scale plantations, and were applicable to farm forestry as now required. In countries including USA and Germany trees in stream-side buffers are harvested using Best Management Practices. Trees may grow at a faster rate in riparian zones and provide a commercial return, but the impacts of tree establishment and harvesting on water yield and quality must be evaluated. However, there have been few designed experiments investigating this problem. Australia has recently initiated studies to explore the use of high-value timber species and associated vegetation in riparian zones to improve water quality, particularly suspended sediment. Preliminary information from the Yan Yan Gurt Catchment in Victoria indicate that forested riparian strips can retain 98% of the sediment entrained in runoff from agricultural sections of the catchment. This paper examines the science background from North American and European experiences relative to Australia, with particular emphasis on sediment relationships after tree harvesting using Best Management Practices.

Agricultural Intensification in the Amazon: Tracking Nitrogen Fertilizer from Soy-Maize Double Cropping to Streams

NASA Astrophysics Data System (ADS)

Cabrera, V. D.; Jankowski, K.; Neill, C.; Macedo, M.; Deegan, L.; Brando, P. M.; Nascimento, S.; Nascimento, E.; Rocha, S.; Coe, M. T.; Nunes, D.

2015-12-01

Globalization and the increasing demand for food create pressure to both expand and intensify agriculture. These changes have potentially large consequences for the solute concentrations and functioning of streams. In the Brazilian Amazon, crop agriculture expanded greatly during the last 20 years. More recently, farmers have intensified production on existing cropland by double cropping of soy and maize during the same year. Maize, a novel crop for the region, requires much higher applications of nitrogen (N) fertilizer than soybeans. To determine whether this novel land use and associated N addition influenced N concentrations in groundwater and stream water, we measured N concentrations in groundwater wells and streams from small headwater watersheds across three land uses (soy-maize, soy, and tropical forest) in the Upper Xingu Basin, a region of rapid cropland intensification in the southern Amazon. Each watershed contained six groundwater wells arranged in a transect reaching cropland field edge on either side of the stream. Total inorganic N concentrations were higher in wells adjacent to fields where double cropping occurred, while stream concentrations did not differ overall among land uses. This suggests the riparian zones are critical in the removal of N, but as the intensification of agriculture continues the ability of the riparian zone to prevent N from traveling to streams is unknown. Their protection is critical to the functioning of tropical watersheds.

Coronal disturbances and their terrestrial effects /Tutorial Lecture/

NASA Technical Reports Server (NTRS)

Rust, D. M.

1983-01-01

An assessment is undertaken of recent approaches to the prediction of the interplanetary consequences of coronal disturbances, with attention to the relationships of shocks and energetic particles to coronal transients, of proton events to gamma-ray and microwave bursts, of geomagnetic storms to filament eruptions, and of solar wind increases to the flare site magnetic field direction. A discussion is given concerning the novel phenomenon of transient coronal holes, which appear astride the long decay enhancements of 2-50 A X-ray emission following H-alpha filament eruptions. These voids in the corona are similar to long-lived coronal holes, which are the sources of high speed solar wind streams. The transient coronal holes may also be associated with transient solar wind speed increases.

Do Riparian Buffers Protect Stream Invertebrate Communities in South American Atlantic Forest Agricultural Areas?

PubMed

Hunt, L; Marrochi, N; Bonetto, C; Liess, M; Buss, D F; Vieira da Silva, C; Chiu, M-C; Resh, V H

2017-12-01

We investigated the influence and relative importance of insecticides and other agricultural stressors in determining variability in invertebrate communities in small streams in intensive soy-production regions of Brazil and Paraguay. In Paraguay we sampled 17 sites on tributaries of the Pirapó River in the state of Itapúa and in Brazil we sampled 18 sites on tributaries of the San Francisco River in the state of Paraná. The riparian buffer zones generally contained native Atlantic forest remnants and/or introduced tree species at various stages of growth. In Brazil the stream buffer width was negatively correlated with sediment insecticide concentrations and buffer width was found to have moderate importance in mitigating effects on some sensitive taxa such as mayflies. However, in both regions insecticides had low relative importance in explaining variability in invertebrate communities, while various habitat parameters were more important. In Brazil, the percent coverage of soft depositional sediment in streams was the most important agriculture-related explanatory variable, and the overall stream-habitat score was the most important variable in Paraguay streams. Paraguay and Brazil both have laws requiring forested riparian buffers. The ample forested riparian buffer zones typical of streams in these regions are likely to have mitigated the effects of pesticides on stream invertebrate communities. This study provides evidence that riparian buffer regulations in the Atlantic Forest region are protecting stream ecosystems from pesticides and other agricultural stressors. Further studies are needed to determine the minimum buffer widths necessary to achieve optimal protection.

Product-to-parent reversion processes: Stream-hyporheic spiraling increases ecosystem exposure and environmental persistence

NASA Astrophysics Data System (ADS)

Ward, A. S.; Cwiertny, D. M.; Kolodziej, E. P.

2014-12-01

The product-to-parent reversion of metabolites of trenbolone acetate (TBA), a steroidal growth promoter used widely in beef cattle production, was recently observed to occur in environmental waters. The rapid forward reaction is by direct photolysis (i.e., photohydration), with the much slower reversion reaction occurring via dehydration in the dark. The objective of this study is to quantify the potential effect of this newly discovered reversible process on TBA metabolite concentrations and total bioactivity exposure in fluvial systems. Here, we demonstrate increased persistence of TBA metabolites in the stream and hyporheic zone due to the reversion process, increasing chronic and acute exposure to these endocrine-active compounds along a stream. The perpetually dark hyporheic zone is a key location for reversion in the system, ultimately providing a source of the parent compound to the stream and increasing mean in-stream concentration of 17α-trenbolone (17α-TBOH) by 40% of the input concentration under representative fluvial conditions. As such, regulatory frameworks for compounds undergoing product-to-parent reversion will require new approaches for assessing total exposure to bioactive compounds. Further, we demonstrate generalized cases for prediction of exposure for species with product-to-parent reversion in stream-hyporheic systems.

Dynamic Grouping of Hippocampal Neural Activity During Cognitive Control of Two Spatial Frames

PubMed Central

Kelemen, Eduard; Fenton, André A.

2010-01-01

Cognitive control is the ability to coordinate multiple streams of information to prevent confusion and select appropriate behavioral responses, especially when presented with competing alternatives. Despite its theoretical and clinical significance, the neural mechanisms of cognitive control are poorly understood. Using a two-frame place avoidance task and partial hippocampal inactivation, we confirmed that intact hippocampal function is necessary for coordinating two streams of spatial information. Rats were placed on a continuously rotating arena and trained to organize their behavior according to two concurrently relevant spatial frames: one stationary, the other rotating. We then studied how information about locations in these two spatial frames is organized in the action potential discharge of ensembles of hippocampal cells. Both streams of information were represented in neuronal discharge—place cell activity was organized according to both spatial frames, but almost all cells preferentially represented locations in one of the two spatial frames. At any given time, most coactive cells tended to represent locations in the same spatial frame, reducing the risk of interference between the two information streams. An ensemble's preference to represent locations in one or the other spatial frame alternated within a session, but at each moment, location in the more behaviorally relevant spatial frame was more likely to be represented. This discharge organized into transient groups of coactive neurons that fired together within 25 ms to represent locations in the same spatial frame. These findings show that dynamic grouping, the transient coactivation of neural subpopulations that represent the same stream of information, can coordinate representations of concurrent information streams and avoid confusion, demonstrating neural-ensemble correlates of cognitive control in hippocampus. PMID:20585373

Gulf Coast Deep Water Port Facilities Study. Appendix C. Eastern Gulf Hydrobiological Zones.

DTIC Science & Technology

1973-04-01

MARINE 5IOTA C-22 1. Benthic Plants C-22 2. Plankton C;23 3. Benthic Invertebrates C-27 4. Fish C-33 5. Marine Mammals C-35 6. Marine Birds C-37 7. Rare...56 B. RESIDENT AND TRANSIENT MARINE BIOTA C-56 1. Plankton C-56 2. Benthic Invertebrates C-62 3. Fish C-62 4. Marine Mammals C-684 Artur D Little Inc...TRANSIENT MARINE BIOTA C-78 l.-Plankton C-78 .-2. Benthic Invertebrates C8 3. F ish C-81 4. Marine Mammals C-85 V. ZONAL ANALYSIS C-87 A. ZONE V

Instream Large Wood: Dentrification Hotspots With Low N2O Production

EPA Science Inventory

The maintenance and restoration of forested riparian cover is important for watershed nitrogen (N) cycling. Forested riparian zones provide woody debris to streams that may stimulate in-stream denitrification and nitrous oxide (N2O) production. We examined the effects of woody an...

Biodiversity management approaches for stream-riparian areas: perspectives for Pacific Northwest headwater forests, microclimates, and amphibians.

Treesearch

D.H. Olson; P.D. Anderson; C.A. Frissell; H.H. Welsh; D.F. Bradford

2007-01-01

New science insights are redefining stream riparian zones, particularly relative to headwaters, microclimate conditions, and fauna such as amphibians. We synthesize data on these topics, and propose management approaches to target sensitive biota at reach to landscape scales.

Woody Debris: Denitrification Hotspots and N2O Production in Fluvial Systems

EPA Science Inventory

The maintenance and restoration of forested riparian cover is important for watershed nitrogen (N) cycling. Forested riparian zones provide woody debris to streams that may stimulate in-stream denitrification and control nitrous oxide (N2O) production. We examined the effects of ...

Influence of multi-scale hydrologic controls on river network connectivity and riparian function

EPA Science Inventory

The ecological functions of rivers and streams and their associated riparian zones are strongly influenced by surface and subsurface hydrologic routing of water within river basins and river networks. Hydrologic attributes of the riparian area for a given stream reach are typica...

Assessing the chemical contamination dynamics in a mixed land use stream system.

PubMed

Sonne, Anne Th; McKnight, Ursula S; Rønde, Vinni; Bjerg, Poul L

2017-11-15

Traditionally, the monitoring of streams for chemical and ecological status has been limited to surface water concentrations, where the dominant focus has been on general water quality and the risk for eutrophication. Mixed land use stream systems, comprising urban areas and agricultural production, are challenging to assess with multiple chemical stressors impacting stream corridors. New approaches are urgently needed for identifying relevant sources, pathways and potential impacts for implementation of suitable source management and remedial measures. We developed a method for risk assessing chemical stressors in these systems and applied the approach to a 16-km groundwater-fed stream corridor (Grindsted, Denmark). Three methods were combined: (i) in-stream contaminant mass discharge for source quantification, (ii) Toxic Units and (iii) environmental standards. An evaluation of the chemical quality of all three stream compartments - stream water, hyporheic zone, streambed sediment - made it possible to link chemical stressors to their respective sources and obtain new knowledge about source composition and origin. Moreover, toxic unit estimation and comparison to environmental standards revealed the stream water quality was substantially impaired by both geogenic and diffuse anthropogenic sources of metals along the entire corridor, while the streambed was less impacted. Quantification of the contaminant mass discharge originating from a former pharmaceutical factory revealed that several 100 kgs of chlorinated ethenes and pharmaceutical compounds discharge into the stream every year. The strongly reduced redox conditions in the plume result in high concentrations of dissolved iron and additionally release arsenic, generating the complex contaminant mixture found in the narrow discharge zone. The fingerprint of the plume was observed in the stream several km downgradient, while nutrients, inorganics and pesticides played a minor role for the stream health. The results emphasize that future investigations should include multiple compounds and stream compartments, and highlight the need for holistic approaches when risk assessing these dynamic systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experiments on Suppression of Thermocapillary Oscillations in Sodium Nitrate Floating Half-Zones by High-frequency End-wall Vibrations

NASA Technical Reports Server (NTRS)

Anilkumar, A.; Grugel, R. N.; Bhowmick, J.; Wang, T.

2004-01-01

Experiments to suppress thermocapillary oscillations using high-frequency vibrations were carried out in sodium nitrate floating half-zones. Such a half-zone is formed by melting one end of a vertically held sodium nitrate crystal rod in contact with a hot surface at the top. Thermocapillary convection occurs in the melt because of the temperature gradient at the free surface of the melt. In the experiments, when thermocapillary oscillations occurred, the bottom end of the crystal rod was vibrated at a high frequency to generate a streaming flow in a direction opposite to that of the thermocapillary convection. It is observed that, by generating a sufficiently strong streaming flow, the thermocapillary flow can be offset enough such that the associated thermocapillary oscillations can be quenched.

Impact of debris dams on hyporheic interaction along a semi-arid stream

NASA Astrophysics Data System (ADS)

Lautz, Laura K.; Siegel, Donald I.; Bauer, Robert L.

2006-01-01

Hyporheic exchange increases the potential for solute retention in streams by slowing downstream transport and increasing solute contact with the substrate. Hyporheic exchange may be a major mechanism to remove nutrients in semi-arid watersheds, where livestock have damaged stream riparian zones and contributed nutrients to stream channels. Debris dams, such as beaver dams and anthropogenic log dams, may increase hyporheic interactions by slowing stream water velocity, increasing flow complexity and diverting water to the subsurface.Here, we report the results of chloride tracer injection experiments done to evaluate hyporheic interaction along a 320 m reach of Red Canyon Creek, a second order stream in the semi-arid Wind River Range of Wyoming. The study site is part of a rangeland watershed managed by The Nature Conservancy of Wyoming, and used as a hydrologic field site by the University of Missouri Branson Geologic Field Station. The creek reach we investigated has debris dams and tight meanders that hypothetically should enhance hyporheic interaction. Breakthrough curves of chloride measured during the field experiment were modelled with OTIS-P, a one-dimensional, surface-water, solute-transport model from which we extracted the storage exchange rate and cross-sectional area of the storage zone As for hyporheic exchange. Along gaining reaches of the stream reach, short-term hyporheic interactions associated with debris dams were comparable to those associated with severe meanders. In contrast, along the non-gaining reach, stream water was diverted to the subsurface by debris dams and captured by large-scale near-stream flow paths. Overall, hyporheic exchange rates along Red Canyon Creek during snowmelt recession equal or exceed exchange rates observed during baseflow at other streams.

Tissue plasminogen activator (tPA) as a reporter gene in transient gene expression.

PubMed

Cheng, S M; Lee, S G; Kalyan, N K; McCloud, S; Levner, M; Hung, P P

1987-01-01

Using the gene coding for tissue plasminogen activator (tPA) as a reporter gene, a transient gene expression system has been established. Vectors containing the full-length cDNA of tPA with its signal sequences were introduced into mammalian recipient cells by a modified gene transfer procedure. Thirty hours after transfection, the secreted tPA was found in serum-free medium and measured by a fibrin-agarose plate assay (FAPA). In this assay, tPA converts plasminogen into plasmin which then degrades high-Mr fibrin to produce cleared zones. The sizes of these zones correspond to quantities of tPA. The combination of transient tPA expression system and the FAPA provides a quick, sensitive, quantitative and non-destructive method to examine the strength of eukaryotic regulatory elements in tissue-culture cells.

Controlled temperature expansion in oxygen production by molten alkali metal salts

DOEpatents

Erickson, Donald C.

1985-06-04

A continuous process is set forth for the production of oxygen from an oxygen containing gas stream, such as air, by contacting a feed gas stream with a molten solution of an oxygen acceptor to oxidize the acceptor and cyclically regenerating the oxidized acceptor by releasing oxygen from the acceptor wherein the oxygen-depleted gas stream from the contact zone is treated sequentially to temperature reduction by heat exchange against the feed stream so as to condense out entrained oxygen acceptor for recycle to the process, combustion of the gas stream with fuel to elevate its temperature and expansion of the combusted high temperature gas stream in a turbine to recover power.

Controlled temperature expansion in oxygen production by molten alkali metal salts

DOEpatents

Erickson, D.C.

1985-06-04

A continuous process is set forth for the production of oxygen from an oxygen containing gas stream, such as air, by contacting a feed gas stream with a molten solution of an oxygen acceptor to oxidize the acceptor and cyclically regenerating the oxidized acceptor by releasing oxygen from the acceptor wherein the oxygen-depleted gas stream from the contact zone is treated sequentially to temperature reduction by heat exchange against the feed stream so as to condense out entrained oxygen acceptor for recycle to the process, combustion of the gas stream with fuel to elevate its temperature and expansion of the combusted high temperature gas stream in a turbine to recover power. 1 fig.

Method for removing undesired particles from gas streams

DOEpatents

Durham, M.D.; Schlager, R.J.; Ebner, T.G.; Stewart, R.M.; Hyatt, D.E.; Bustard, C.J.; Sjostrom, S.

1998-11-10

The present invention discloses a process for removing undesired particles from a gas stream including the steps of contacting a composition containing an adhesive with the gas stream; collecting the undesired particles and adhesive on a collection surface to form an aggregate comprising the adhesive and undesired particles on the collection surface; and removing the agglomerate from the collection zone. The composition may then be atomized and injected into the gas stream. The composition may include a liquid that vaporizes in the gas stream. After the liquid vaporizes, adhesive particles are entrained in the gas stream. The process may be applied to electrostatic precipitators and filtration systems to improve undesired particle collection efficiency. 11 figs.

Method and apparatus for decreased undesired particle emissions in gas streams

DOEpatents

Durham, M.D.; Schlager, R.J.; Ebner, T.G.; Stewart, R.M.; Bustard, C.J.

1999-04-13

The present invention discloses a process for removing undesired particles from a gas stream including the steps of contacting a composition containing an adhesive with the gas stream; collecting the undesired particles and adhesive on a collection surface to form an aggregate comprising the adhesive and undesired particles on the collection surface; and removing the agglomerate from the collection zone. The composition may then be atomized and injected into the gas stream. The composition may include a liquid that vaporizes in the gas stream. After the liquid vaporizes, adhesive particles are entrained in the gas stream. The process may be applied to electrostatic precipitators and filtration systems to improve undesired particle collection efficiency. 5 figs.

Method and apparatus for decreased undesired particle emissions in gas streams

DOEpatents

Durham, Michael Dean; Schlager, Richard John; Ebner, Timothy George; Stewart, Robin Michele; Bustard, Cynthia Jean

1999-01-01

The present invention discloses a process for removing undesired particles from a gas stream including the steps of contacting a composition containing an adhesive with the gas stream; collecting the undesired particles and adhesive on a collection surface to form an aggregate comprising the adhesive and undesired particles on the collection surface; and removing the agglomerate from the collection zone. The composition may then be atomized and injected into the gas stream. The composition may include a liquid that vaporizes in the gas stream. After the liquid vaporizes, adhesive particles are entrained in the gas stream. The process may be applied to electrostatic precipitators and filtration systems to improve undesired particle collection efficiency.

Method for removing undesired particles from gas streams

DOEpatents

Durham, Michael Dean; Schlager, Richard John; Ebner, Timothy George; Stewart, Robin Michele; Hyatt, David E.; Bustard, Cynthia Jean; Sjostrom, Sharon

1998-01-01

The present invention discloses a process for removing undesired particles from a gas stream including the steps of contacting a composition containing an adhesive with the gas stream; collecting the undesired particles and adhesive on a collection surface to form an aggregate comprising the adhesive and undesired particles on the collection surface; and removing the agglomerate from the collection zone. The composition may then be atomized and injected into the gas stream. The composition may include a liquid that vaporizes in the gas stream. After the liquid vaporizes, adhesive particles are entrained in the gas stream. The process may be applied to electrostatic precipitators and filtration systems to improve undesired particle collection efficiency.

Reactor for fluidized bed silane decomposition

NASA Technical Reports Server (NTRS)

Iya, Sridhar K. (Inventor)

1989-01-01

An improved heated fluidized bed reactor and method for the production of high purity polycrystalline silicon by silane pyrolysis wherein silicon seed particles are heated in an upper heating zone of the reactor and admixed with particles in a lower zone, in which zone a silane-containing gas stream, having passed through a lower cooled gas distribution zone not conducive to silane pyrolysis, contacts the heated seed particles whereon the silane is heterogeneously reduced to silicon.

Release of E.coli D21g with transients in water content

USDA-ARS?s Scientific Manuscript database

Transients in water content are well known to mobilize microorganisms that are retained in the vadose zone. However, there is no consensus on the relative importance of drainage and imbibition events on microorganism release. To overcome this limitation, we have systematically studied the release o...

Examining the role of dissolved organic nitrogen in stream ecosystems across biomes and Critical Zone gradients

NASA Astrophysics Data System (ADS)

Wymore, A.; Rodriguez-Cardona, B.; Coble, A. A.; Potter, J.; Lopez Lloreda, C.; Perez Rivera, K.; De Jesus Roman, A.; Bernal, S.; Martí Roca, E.; Kram, P.; Hruska, J.; Prokishkin, A. S.; McDowell, W. H.

2016-12-01

Watershed nitrogen exports are often dominated by dissolved organic nitrogen (DON); yet, little is known about the role ambient DON plays in ecosystems. As an organic nutrient, DON may serve as either an energy source or as a nutrient source. One hypothesized control on DON is nitrate (NO3-) availability. Here we examine the interaction of NO3- and DON in streams across temperate forests, tropical rainforests, and Mediterranean and taiga biomes. Experimental streams also drain contrasting Critical Zones which provide gradients of vegetation, soil type and lithology (e.g. volcaniclastic, granitic, ultramafic, Siberian Traps Flood Basalt) in which to explore how the architecture of the Critical Zone affects microbial biogeochemical reactions. Streams ranged in background dissolved organic carbon (DOC) concentration (1-50 mg C/L) and DOC: NO3- ratios (10-2000). We performed a series of ecosystem-scale NO3- additions in multiple streams within each environment and measured the change in DON concentration. Results demonstrate that there is considerable temporal and spatial variation across systems with DON both increasing and decreasing in response to NO3- addition. Ecologically this suggests that DON can serve as both a nutrient source and an energy source to aquatic microbial communities. In contrast, DOC concentrations rarely changed in response to NO3- additions suggesting that the N-rich fraction of the ambient dissolved organic matter pool is more bioreactive than the C-rich fraction. Contrasting responses of the DON and DOC pools indicate different mechanisms controlling their respective cycling. It is likely that DON plays a larger role in ecosystems than previously recognized.

Geochemical evolution of the Critical Zone across variable time scales informs concentration-discharge relationships: Jemez River Basin Critical Zone Observatory

NASA Astrophysics Data System (ADS)

McIntosh, Jennifer C.; Schaumberg, Courtney; Perdrial, Julia; Harpold, Adrian; Vázquez-Ortega, Angélica; Rasmussen, Craig; Vinson, David; Zapata-Rios, Xavier; Brooks, Paul D.; Meixner, Thomas; Pelletier, Jon; Derry, Louis; Chorover, Jon

2017-05-01

This study investigates the influence of water, carbon, and energy fluxes on solute production and transport through the Jemez Critical Zone (CZ) and impacts on C-Q relationships over variable spatial and temporal scales. Chemical depletion-enrichment profiles of soils, combined with regolith thickness and groundwater data indicate the importance to stream hydrochemistry of incongruent dissolution of silicate minerals during deep bedrock weathering, which is primarily limited by water fluxes, in this highly fractured, young volcanic terrain. Under high flow conditions (e.g., spring snowmelt), wetting of soil and regolith surfaces and presence of organic acids promote mineral dissolution and provide a constant supply of base cations, Si, and DIC to soil water and groundwater. Mixing of waters from different hydrochemical reservoirs in the near stream environment during "wet" periods leads to the chemostatic behavior of DIC, base cations, and Si in stream flow. Metals transported by organic matter complexation (i.e., Ge, Al) and/or colloids (i.e., Al) during periods of soil saturation and lateral connectivity to the stream display a positive relationship with Q. Variable Si-Q relationships, under all but the highest flow conditions, can be explained by nonconservative transport and precipitation of clay minerals, which influences long versus short-term Si weathering fluxes. By combining measurements of the CZ obtained across different spatial and temporal scales, we were able to constrain weathering processes in different hydrological reservoirs that may be flushed to the stream during hydrologic events, thereby informing C-Q relationships.

Which key properties controls the preferential transport in the vadose zone under transient hydrological conditions

NASA Astrophysics Data System (ADS)

Groh, J.; Vanderborght, J.; Puetz, T.; Gerke, H. H.; Rupp, H.; Wollschlaeger, U.; Stumpp, C.; Priesack, E.; Vereecken, H.

2015-12-01

Understanding water flow and solute transport in the unsaturated zone is of great importance for an appropriate land use management strategy. The quantification and prediction of water and solute fluxes through the vadose zone can help to improve management practices in order to limit potential risk on our fresh water resources. Water related solute transport and residence time is strongly affected by preferential flow paths in the soil. Water flow in soils depends on soil properties and site factors (climate or experiment conditions, land use) and are therefore important factors to understand preferential solute transport in the unsaturated zone. However our understanding and knowledge of which on-site properties or conditions define and enhance preferential flow and transport is still poor and mostly limited onto laboratory experimental conditions (small column length and steady state boundary conditions). Within the TERENO SOILCan lysimeter network, which was designed to study the effects of climate change on soil functions, a bromide tracer was applied on 62 lysimeter at eight different test sites between Dec. 2013 and Jan. 2014. The TERENO SOILCan infrastructure offers the unique possibility to study the occurrence of preferential flow and transport of various soil types under different natural transient hydrological conditions and land use (crop, bare and grassland) at eight TERENO SOILCan observatories. Working with lysimeter replicates at each observatory allows defining the spatial variability of preferential transport and flow. Additionally lysimeters in the network were transferred within and between observatories in order to subject them to different rainfall and temperature regimes and enable us to relate the soil type susceptibility of preferential flow and transport not only to site specific physical and land use properties, but also to different transient boundary conditions. Comparison and statistical analysis between preferential flow indicators 5% arrival time and potential key soil properties, site factors and boundary conditions will be presented in order to identify key properties which control the preferential transport in the vadose zone under transient hydrological conditions.

Assessing the ecological benefits and opportunity costs of alternative stream management zone widths for eastern hardwoods

Treesearch

Chris B. LeDoux; Ethel Wilkerson

2008-01-01

Leaving buffer zones adjacent to waterways can effectively reduce the water quality concerns associated with timber harvesting. However, riparian areas are also some of the most productive sites and can yield high quality wood. The amount of unharvested timber left in SMZs (Streamside Management Zones) can represent a substantial opportunity cost to landowners. In this...

Assessing the ecological benefits and opportunity costs of alternative stream management zone widths

Treesearch

Chris B. LeDoux; Ethel Wilkerson

2008-01-01

Leaving buffer zones adjacent to waterways can effectively reduce the water quality concerns associated with timber harvesting. However, riparian areas are also some of the most productive sites and can yield high quality wood. The amount of unharvested timber left in SMZs (Streamside Management Zones) can represent a substantial opportunity cost to landowners. In this...

Ecological functions of riparian zones in Oregon hydrological landscapes

EPA Science Inventory

The ecological functions of streams and associated riparian zones are strongly influenced by the hydrological attributes of watersheds and landscapes in which they occur. Oregon hydrologic landscape regions (HLRs) have been defined based on four types of GIS data: 1) climate, 2) ...

Transient bow shock around a cylinder in a supersonic dusty plasma

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

Meyer, John K.; Merlino, Robert L.

2013-07-15

Visual observations of the formation of a bow shock in the transient supersonic flow of a dusty plasma incident on a biased cylinder are presented. The bow shock formed when the advancing front of a streaming dust cloud was reflected by the obstacle. After its formation, the density jump of the bow shock increased as it moved upstream of the obstacle. A physical picture for the formation of the electrohydrodynamic bow shock is discussed.

Dynamic river networks as the context for evaluating riparian influence on river basin solute export

EPA Science Inventory

Many studies have examined the influence of riparian areas on nitrogen as water drains from hillslopes and through riparian zones at the stream reach scale. Most of these studies have been conducted along relatively small streams. However, water quality concerns typically deal wi...

The Effects of Spatial Resolution on Impervious Cover Classifications in Watersheds and Riparian Zones in Vermont

EPA Science Inventory

Impervious cover (roads, rooftops, etc.) is a known stressor on stream biota and habitat and is often used as an indicator for assessing the effects of urbanization on stream health. Understanding how spatial data resolution impacts estimates of impervious cover is important for ...

Nutrient sampling slam: high resolution surface-water sampling in streams reveals patterns in groundwater chemistry and flow paths

EPA Science Inventory

The groundwater–surface water interface (GSWI), consisting of shallow groundwater adjacent to stream channels, is a hot spot for nitrogen removal processes, a storage zone for other solutes, and a target for restoration activities. Characterizing groundwater-surface water intera...

NITRATE REMOVAL EFFECTIVENESS OF A RIPARIAN BUFFER ALONG A SMALL AGRICULTURAL STREAM IN WESTERN OREGON

EPA Science Inventory

We established two study sites with similar soils and hydrology but contrasting riparian vegetation along Lake Creek, an intermittent stream that drains perennial ryegrass fields in the Willamette Valley of western Oregon. One site had a non-cultivated riparian zone with a plant...

Ground-Water Occurrence and Contribution to Streamflow, Northeast Maui, Hawaii

USGS Publications Warehouse

Gingerich, Stephen B.

1999-01-01

The study area lies on the northern flank of the East Maui Volcano (Haleakala) and covers about 129 square miles between the drainage basins of Maliko Gulch to the west and Makapipi Stream to the east. About 989 million gallons per day of rainfall and 176 million gallons per day of fog drip reaches the study area and about 529 million gallons per day enters the ground-water system as recharge. Average annual ground-water withdrawal from wells totals only about 3 million gallons per day; proposed (as of 1998) additional withdrawals total about 18 million gallons per day. Additionally, tunnels and ditches of an extensive irrigation network directly intercept at least 10 million gallons per day of ground water. The total amount of average annual streamflow in gaged stream subbasins upstream of 1,300 feet altitude is about 255 million gallons per day and the total amount of average annual base flow is about 62 million gallons per day. Six major surface-water diversion systems in the study area have diverted an average of 163 million gallons per day of streamflow (including nearly all base flow of diverted streams) for irrigation and domestic supply in central Maui during 1925-97. Fresh ground water is found in two main forms. West of Keanae Valley, ground-water flow appears to be dominated by a variably saturated system. A saturated zone in the uppermost rock unit, the Kula Volcanics, is separated from a freshwater lens near sea level by an unsaturated zone in the underlying Honomanu Basalt. East of Keanae Valley, the ground-water system appears to be fully saturated above sea level to altitudes greater than 2,000 feet. The total average annual streamflow of gaged streams west of Keanae Valley is about 140 million gallons per day at 1,200 feet to 1,300 feet altitude. It is not possible to estimate the total average annual streamflow at the coast. All of the base flow measured in the study area west of Keanae Valley represents ground-water discharge from the high-elevation saturated zone. Total average daily ground-water discharge from the high-elevation saturated zone upstream of 1,200 feet altitude is greater than 38 million gallons per day, all of which is eventually removed from the streams by surface-water diversion systems. Perennial streamflow has been measured at altitudes greater than 3,000 feet in several of the streams. Discharge from the high-elevation saturated zone is persistent even during periods of little rainfall. The total average annual streamflow of the gaged streams east of Keanae Valley is about 109 million gallons per day at about 1,300 feet altitude. It is not possible to estimate the total average annual streamflow at the coast nor at higher altitudes. All of the base flow measured east of Keanae Valley represents ground-water discharge from the vertically extensive freshwater-lens system. Total average daily ground-water discharge to gaged streams upstream of 1,200 feet altitude is about 27 million gallons per day. About 19 million gallons per day of ground water discharges through the Kula and Hana Volcanics between about 500 feet and 1,300 feet altitude in the gaged stream sub-basins. About 13 million gallons per day of this discharge is in Hanawi Stream. The total ground-water discharge above 500 feet altitude in this part of the study area is greater than 56 million gallons per day.

Oxygen Carbon Dynamics within the Hyporheic Zone of a Headwater Stream

NASA Astrophysics Data System (ADS)

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

2016-12-01

Streams and rivers influence global carbon fluxes; on an aerial basis, they have disproportionately high export rates compared to land. Various mechanisms exist for the movement of terrestrially derived carbon to the stream network including transport of organic and inorganic carbon with groundwater and hillslope runoff. A secondary process that has received little attention is carbon dynamics of hyporheic flow along flow paths that pass beneath the vegetated riparian zone. Through use of high frequency monitoring of dissolved inorganic carbon and dissolved oxygen we find that the riparian zone is a net source of carbon throughout the year. Increases in DIC relative stream water are generally more than double decreases in O2 on a molar basis. Metabolic quotients of C to O2 are close to 1.0, therefore respiration of dissolved or particulate organic carbon along flow paths would result in an equal magnitude increase in inorganic carbon to decrease in O2. Diffusion from the high CO2 soil atmosphere into hyporheic water has been considered, however 2-D reactive transport modeling using PFLOTRAN indicates that soil diffusion processes are unlikely to produce observed increases in carbon and that alternative transport mechanisms including root respiration or diel water level fluctuations are necessary for mass balance. Results of the analysis will feed into a comprehensive distributed model of the system that explores carbon dynamics at the reach scale.

Variation of organic matter quantity and quality in streams at Critical Zone Observatory watersheds

USGS Publications Warehouse

Miller, Matthew P.; Boyer, Elizabeth W.; McKnight, Diane M.; Brown, Michael G.; Gabor, Rachel S.; Hunsaker, Carolyn T.; Iavorivska , Lidiia; Inamdar, Shreeram; Kaplan, Louis A.; Johnson, Dale W.; Lin, Henry; McDowell, William H.; Perdrial, Julia N.

2016-01-01

The quantity and chemical composition of dissolved organic matter (DOM) in surface waters influence ecosystem processes and anthropogenic use of freshwater. However, despite the importance of understanding spatial and temporal patterns in DOM, measures of DOM quality are not routinely included as part of large-scale ecosystem monitoring programs and variations in analytical procedures can introduce artifacts. In this study, we used consistent sampling and analytical methods to meet the objective of defining variability in DOM quantity and quality and other measures of water quality in streamflow issuing from small forested watersheds located within five Critical Zone Observatory sites representing contrasting environmental conditions. Results show distinct separations among sites as a function of water quality constituents. Relationships among rates of atmospheric deposition, water quality conditions, and stream DOM quantity and quality are consistent with the notion that areas with relatively high rates of atmospheric nitrogen and sulfur deposition and high concentrations of divalent cations result in selective transport of DOM derived from microbial sources, including in-stream microbial phototrophs. We suggest that the critical zone as a whole strongly influences the origin, composition, and fate of DOM in streams. This study highlights the value of consistent DOM characterization methods included as part of long-term monitoring programs for improving our understanding of interactions among ecosystem processes as controls on DOM biogeochemistry.

Liquid additives for particulate emissions control

DOEpatents

Durham, Michael Dean; Schlager, Richard John; Ebner, Timothy George; Stewart, Robin Michele; Hyatt, David E.; Bustard, Cynthia Jean; Sjostrom, Sharon

1999-01-01

The present invention discloses a process for removing undesired particles from a gas stream including the steps of contacting a composition containing an adhesive with the gas stream; collecting the undesired particles and adhesive on a collection surface to form an aggregate comprising the adhesive and undesired particles on the collection surface; and removing the agglomerate from the collection zone. The composition may then be atomized and injected into the gas stream. The composition may include a liquid that vaporizes in the gas stream. After the liquid vaporizes, adhesive particles are entrained in the gas stream. The process may be applied to electrostatic precipitators and filtration systems to improve undesired particle collection efficiency.

Denitrification in the recharge area and discharge area of a transient agricultural nitrate plume in a glacial outwash sand aquifer, Minnesota

USGS Publications Warehouse

Böhlke, J.K.; Wanty, R.; Tuttle, M.; Delin, G.; Landon, Matthew K.

2002-01-01

Recharge rates of nitrate (NO3−) to groundwater beneath agricultural land commonly are greater than discharge rates of NO3− in nearby streams, but local controls of NO3−distribution in the subsurface generally are poorly known. Groundwater dating (CFC, 3H) was combined with chemical (ions and gases) and stable isotope (N, S, and C) analyses to resolve the effects of land use changes, flow patterns, and water‐aquifer reactions on the distributions of O2, NO3−, SO4=, and other constituents in a two‐dimensional vertical section leading from upland cultivated fields to a riparian wetland and stream in a glacial outwash sand aquifer near Princeton, Minnesota. Within this section a “plume” of oxic NO3−‐rich groundwater was present at shallow depths beneath the fields and part of the wetland but terminated before reaching the stream or the wetland surface. Groundwater dating and hydraulic measurements indicate travel times in the local flow system of 0 to >40 years, with stratified recharge beneath the fields, downward diversion of the shallow NO3−‐bearing plume by semiconfining organic‐rich valley‐filling sediments under the wetland and upward discharge across the valley and stream bottom. The concentrations and δ15N values of NO3− and N2 indicate that the NO3− plume section was bounded in three directions by a curvilinear zone of active denitrification that limited its progress; however, when recalculated to remove the effects of denitrification, the data also indicate changes in both the concentrations and δ15N values of NO3− that was recharged in the past. Isotope data and mass balance calculations indicate that FeS2 and other ferrous Fe phases were the major electron donors for denitrification in at least two settings: (1) within the glacial‐fluvial aquifer sediments beneath the recharge and discharge areas and (2) along the bottom of the valley‐filling sediments in the discharge area. Combined results indicate that the shape and progress of the oxic NO3− plume termination were controlled by a combination of (1) historical and spatial variations in land use practices, (2) contrast in groundwater flow patterns between the agricultural recharge area and riparian wetland discharge area, and (3) distribution and abundance of electron donors in both the sand aquifer and valley‐filling sediments. The data are consistent with slow migration of redox zones through the aquifer in response to recharging oxic groundwater during Holocene time, then an order‐of‐magnitude increase in the flux of electron acceptors as a result of agricultural NO3− contamination in the late twentieth century, to which the redox zone configuration still may be adjusting. The importance of denitrification for NO3− movement through formerly glaciated terrains should depend on the source areas and depositional environments of the glacial sediments, as well as geomorphology and recent stream‐valley sediment history.

Transient human auditory cortex activation during volitional attention shifting

PubMed Central

Uhlig, Christian Harm; Gutschalk, Alexander

2017-01-01

While strong activation of auditory cortex is generally found for exogenous orienting of attention, endogenous, intra-modal shifting of auditory attention has not yet been demonstrated to evoke transient activation of the auditory cortex. Here, we used fMRI to test if endogenous shifting of attention is also associated with transient activation of the auditory cortex. In contrast to previous studies, attention shifts were completely self-initiated and not cued by transient auditory or visual stimuli. Stimuli were two dichotic, continuous streams of tones, whose perceptual grouping was not ambiguous. Participants were instructed to continuously focus on one of the streams and switch between the two after a while, indicating the time and direction of each attentional shift by pressing one of two response buttons. The BOLD response around the time of the button presses revealed robust activation of the auditory cortex, along with activation of a distributed task network. To test if the transient auditory cortex activation was specifically related to auditory orienting, a self-paced motor task was added, where participants were instructed to ignore the auditory stimulation while they pressed the response buttons in alternation and at a similar pace. Results showed that attentional orienting produced stronger activity in auditory cortex, but auditory cortex activation was also observed for button presses without focused attention to the auditory stimulus. The response related to attention shifting was stronger contralateral to the side where attention was shifted to. Contralateral-dominant activation was also observed in dorsal parietal cortex areas, confirming previous observations for auditory attention shifting in studies that used auditory cues. PMID:28273110

Groundwater contaminants in the deep benthic zone of urban streams in Canada (Invited)

NASA Astrophysics Data System (ADS)

Roy, J. W.; Bickerton, G.

2010-12-01

There is little information available on the potential threat that groundwater containing land-based contaminants poses to aquatic ecosystems in urban environments. In this study, a rapid screening approach was applied at the stream reach-scale for eight urban streams (reaches from 100 to < 1000 m). The objective was to determine what types of groundwater contaminants could be detected in the deeper benthic zone of these streams, if any, to start to address questions of whether such contaminants are a concern and which types are the most problematic. The benthic community may be especially at risk since it may experience higher contaminant concentrations than the stream itself due to fewer losses from sorption, degradation and volatilization processes. For each stream, groundwater samples from below the stream bed (typically 25-75 cm) were collected using a drive-point mini-profiler at intervals of 10-15 m along the stream and were subsequently analysed for general chemistry and a wide range of common and emerging urban contaminants. For a few test streams with known contamination, the area of contamination was identified with this technique. In addition, previously unknown contaminants or areas of contamination were identified at all nine streams. Identified contaminants included benzene and other petroleum hydrocarbons, fuel oxygenates (e.g. MTBE), perchlorate, pesticides, artificial sweeteners, and various chlorinated solvent compounds. In addition, elevated levels of nitrate, phosphate, some heavy metals, including cadmium and arsenic, and elevated chloride (likely indicating road salt) were detected. Most streams had many different types of contaminants, often overlapping over small stretches, and together often covering substantial portions of the monitored reach. The findings provide support for this screening approach for delineating areas of potential ecological concern and identifying possible sources of groundwater contamination, for urban settings. They also suggest that the presence of multiple groundwater contaminants may be a more common threat to the benthic community of urban streams than currently perceived.

Detection of postseismic fault-zone collapse following the Landers earthquake

USGS Publications Warehouse

Massonnet, D.; Thatcher, W.; Vadon, H.

1996-01-01

Stress changes caused by fault movement in an earthquake induce transient aseismic crustal movements in the earthquake source region that continue for months to decades following large events. These motions reflect aseismic adjustments of the fault zone and/or bulk deformation of the surroundings in response to applied stresses, and supply information regarding the inelastic behaviour of the Earth's crust. These processes are imperfectly understood because it is difficult to infer what occurs at depth using only surface measurements, which are in general poorly sampled. Here we push satellite radar interferometry to near its typical artefact level, to obtain a map of the postseismic deformation field in the three years following the 28 June 1992 Landers, California earthquake. From the map, we deduce two distinct types of deformation: afterslip at depth on the fault that ruptured in the earthquake, and shortening normal to the fault zone. The latter movement may reflect the closure of dilatant cracks and fluid expulsion from a transiently over-pressured fault zone.

The partitioning of copper among selected phases of geologic media of two porphyry copper districts, Puerto Rico

USGS Publications Warehouse

Learned, R.E.; Chao, T.T.; Sanzolone, R.F.

1981-01-01

In experiments designed to determine the manner in which copper is partitioned among selected phases that constitute geologic media, we have applied the five-step sequential extraction procedure of Chao and Theobald to the analysis of drill core, soils, and stream sediments of the Rio Vivi and Rio Tanama porphyry copper districts of Puerto Rico. The extraction procedure affords a convenient means of determining the trace-metal content of the following fractions: (1) Mn oxides and "reactive" Fe oxides; (2) "amorphous" Fe oxides; (3) "crystalline" Fe oxides; (4) sulfides and magnetite; and (5) silicates. An additional extraction between steps (1) and (2) was performed to determine organic-related copper in stream sediments. The experimental results indicate that apportionment of copper among phases constituting geologic media is a function of geochemical environment. Distinctive partitioning patterns were derived from the analysis of drill core from each of three geochemical zones: (a) the supergene zone of oxidation; (b) the supergene zone of enrichment; and (c) the hypogene zone; and similarly, from the analysis of; (d) soils on a weakly leached capping; (e) soils on a strongly leached capping; and (f) active stream sediment. The experimental results also show that geochemical contrasts (anomaly-to-background ratios) vary widely among the five fractions of each sampling medium investigated, and that at least one fraction of each medium provides substantially stronger contrast than does the bulk medium. Fraction (1) provides optimal contrast for stream sediments of the district; fraction (2) provides optimal contrast for soils on a weakly leached capping; fraction (3) provides optimal contrast for soils on a strongly leached capping. Selective extraction procedures appear to have important applications to the orientation and interpretive stages of geochemical exploration. Further investigation and testing of a similar nature are recommended. ?? 1981.

LINKING STORMFLOW HYDROLOGY AND BIOTA IN SUBURBAN STREAMS

EPA Science Inventory

Suburban land development has been found to alter the hydrology of landscapes, changing streamflow transient behavior, which may contribute to the typical negative impacts of development on aquatic ecosystems. The linkages between residential development, hydrologic response, and...

40 CFR 63.1257 - Test methods and compliance procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... the design minimum and average flame zone temperatures and combustion zone residence time; and shall... establish the design exhaust vent stream organic compound concentration level, adsorption cycle time, number... regeneration cycle, design carbon bed temperature after regeneration, design carbon bed regeneration time, and...

40 CFR 63.1257 - Test methods and compliance procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... the design minimum and average flame zone temperatures and combustion zone residence time; and shall... establish the design exhaust vent stream organic compound concentration level, adsorption cycle time, number... regeneration cycle, design carbon bed temperature after regeneration, design carbon bed regeneration time, and...

Ecohydrological and subsurface controls on drought-induced contraction and disconnection of stream networks

NASA Astrophysics Data System (ADS)

Godsey, S.; Kirchner, J. W.; Whiting, J. A.

2016-12-01

Temporary headwater streams - both intermittent and ephemeral waterways - supply water to approximately 1/3 of the US population, and 60% of streams used for drinking water are temporary. Stream ecologists increasingly recognize that a gradient of processes across the drying continuum affect ecosystems at dynamic terrestrial-aquatic interfaces. Understanding the hydrological controls across that gradient of drying may improve management of these sensitive systems. One possible control on surface flows includes transpiration losses from either the riparian zone or the entire watershed. We mapped several stream networks under extreme low flow conditions brought on by severe drought in central Idaho and California in 2015. Compared to previous low-flow stream length estimates, the active drainage network had generally decreased by a very small amount across these sites, perhaps because stored water buffered the precipitation decrease, or because flowing channel heads are fixed by focused groundwater flow emerging at springs. We also examined the apparent sources of water for both riparian and hillslope trees using isotopic techniques. During drought conditions, we hypothesized that riparian trees - but not those far from flowing streams - would be sustained by streamflow recharging riparian aquifers, and thus would transpire water that was isotopically similar to streamflow because little soil water would remain available below the wilting point and stream water would be sustain those trees. We found a more complex pattern, but in most places stream water and water transpired by trees were isotopically distinct regardless of flow intermittency or tree location. We also found that hillslope trees outside of the riparian zone appeared to be using different waters from those used by riparian trees. Finally, we explore subsurface controls on network extent, showing that bedrock characteristics can influence network stability and contraction patterns.

Spatial variation in basic chemistry of streams draining a volcanic landscape on Costa Rica's Caribbean slope

USGS Publications Warehouse

Pringle, C.M.; Triska, F.J.; Browder, G.

1990-01-01

Spatial variability in selected chemical, physical and biological parameters was examined in waters draining relatively pristine tropical forests spanning elevations from 35 to 2600 meters above sea level in a volcanic landscape on Costa Rica's Caribbean slope. Waters were sampled within three different vegetative life zones and two transition zones. Water temperatures ranged from 24-25 ??C in streams draining lower elevations (35-250 m) in tropical wet forest, to 10 ??C in a crater lake at 2600 m in montane forest. Ambient phosphorus levels (60-300 ??g SRP L-1; 66-405 ??g TP L-1) were high at sites within six pristine drainages at elevations between 35-350 m, while other undisturbed streams within and above this range in elevation were low (typically <30.0 ??g SRP L-1). High ambient phosphorus levels within a given stream were not diagnostic of riparian swamp forest. Phosphorus levels (but not nitrate) were highly correlated with conductivity, Cl, Na, Ca, Mg and SO4. Results indicate two major stream types: 1) phosphorus-poor streams characterized by low levels of dissolved solids reflecting local weathering processes; and 2) phosphorus-rich streams characterized by relatively high Cl, SO4, Na, Mg, Ca and other dissolved solids, reflecting dissolution of basaltic rock at distant sources and/or input of volcanic brines. Phosphorus-poor streams were located within the entire elevation range, while phosphorus-rich streams were predominately located at the terminus of Pleistocene lava flows at low elevations. Results indicate that deep groundwater inputs, rich in phosphorus and other dissolved solids, surface from basaltic aquifers at breaks in landform along faults and/or where the foothills of the central mountain range merge with the coastal plain. ?? 1990 Kluwer Academic Publishers.

Effects of geomorphology, habitat, and spatial location on fish assemblages in a watershed in Ohio, USA.

PubMed

D'Ambrosio, Jessica L; Williams, Lance R; Witter, Jonathan D; Ward, Andy

2009-01-01

In this paper, we evaluate relationships between in-stream habitat, water chemistry, spatial distribution within a predominantly agricultural Midwestern watershed and geomorphic features and fish assemblage attributes and abundances. Our specific objectives were to: (1) identify and quantify key environmental variables at reach and system wide (watershed) scales; and (2) evaluate the relative influence of those environmental factors in structuring and explaining fish assemblage attributes at reach scales to help prioritize stream monitoring efforts and better incorporate all factors that influence aquatic biology in watershed management programs. The original combined data set consisted of 31 variables measured at 32 sites, which was reduced to 9 variables through correlation and linear regression analysis: stream order, percent wooded riparian zone, drainage area, in-stream cover quality, substrate quality, gradient, cross-sectional area, width of the flood prone area, and average substrate size. Canonical correspondence analysis (CCA) and variance partitioning were used to relate environmental variables to fish species abundance and assemblage attributes. Fish assemblages and abundances were explained best by stream size, gradient, substrate size and quality, and percent wooded riparian zone. Further data are needed to investigate why water chemistry variables had insignificant relationships with IBI scores. Results suggest that more quantifiable variables and consideration of spatial location of a stream reach within a watershed system should be standard data incorporated into stream monitoring programs to identify impairments that, while biologically limiting, are not fully captured or elucidated using current bioassessment methods.

Drivers and Spatio-Temporal Extent of Hyporheic Patch Variation: Implications for Sampling

PubMed Central

Braun, Alexander; Auerswald, Karl; Geist, Juergen

2012-01-01

The hyporheic zone in stream ecosystems is a heterogeneous key habitat for species across many taxa. Consequently, it attracts high attention among freshwater scientists, but generally applicable guidelines on sampling strategies are lacking. Thus, the objective of this study was to develop and validate such sampling guidelines. Applying geostatistical analysis, we quantified the spatio-temporal variability of parameters, which characterize the physico-chemical substratum conditions in the hyporheic zone. We investigated eight stream reaches in six small streams that are typical for the majority of temperate areas. Data was collected on two occasions in six stream reaches (development data), and once in two additional reaches, after one year (validation data). In this study, the term spatial variability refers to patch contrast (patch to patch variance) and patch size (spatial extent of a patch). Patch contrast of hyporheic parameters (specific conductance, pH and dissolved oxygen) increased with macrophyte cover (r2 = 0.95, p<0.001), while patch size of hyporheic parameters decreased from 6 to 2 m with increasing sinuosity of the stream course (r2 = 0.91, p<0.001), irrespective of the time of year. Since the spatial variability of hyporheic parameters varied between stream reaches, our results suggest that sampling design should be adapted to suit specific stream reaches. The distance between sampling sites should be inversely related to the sinuosity, while the number of samples should be related to macrophyte cover. PMID:22860053

Calcium signaling in liver.

PubMed

Gaspers, Lawrence D; Thomas, Andrew P

2005-01-01

In hepatocytes, hormones linked to the formation of the second messenger inositol 1,4,5-trisphosphate (InsP3) evoke transient increases or spikes in cytosolic free calcium ([Ca2+]i), that increase in frequency with the agonist concentration. These oscillatory Ca2+ signals are thought to transmit the information encoded in the extracellular stimulus to down-stream Ca2+-sensitive metabolic processes. We have utilized both confocal and wide field fluorescence microscopy techniques to study the InsP3-dependent signaling pathway at the cellular and subcellular levels in the intact perfused liver. Typically InsP3-dependent [Ca2+]i spikes manifest as Ca2+ waves that propagate throughout the entire cytoplasm and nucleus, and in the intact liver these [Ca2+]i increases are conveyed through gap junctions to encompass entire lobular units. The translobular movement of Ca2+ provides a means to coordinate the function of metabolic zones of the lobule and thus, liver function. In this article, we describe the characteristics of agonist-evoked [Ca2+]i signals in the liver and discuss possible mechanisms to explain the propagation of intercellular Ca2+ waves in the intact organ.

Simultaneous treatment of SO2 containing stack gases and waste water

NASA Technical Reports Server (NTRS)

Poradek, J. C.; Collins, D. D. (Inventor)

1978-01-01

A process for simultaneously removing sulfur dioxide from stack gases and the like and purifying waste water such as derived from domestic sewage is described. A portion of the gas stream and a portion of the waste water, the latter containing dissolved iron and having an acidic pH, are contacted in a closed loop gas-liquid scrubbing zone to effect absorption of the sulfur dioxide into the waste water. A second portion of the gas stream and a second portion of the waste water are controlled in an open loop gas-liquid scrubbing zone. The second portion of the waste water contains a lesser amount of iron than the first portion of the waste water. Contacting in the openloop scrubbing zone is sufficient to acidify the waste water which is then treated to remove solids originally present.

Buffer strip design for protecting water quality and fish habitat

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

Belt, G.H.; O'Laughlin, J.

1994-04-01

Buffer strips are protective areas adjacent to streams or lakes. Among other functions, they protect water quality and fish habitat. A typical buffer strip is found in western Oregon, where they are called Riparian Management Areas (RMAs). The authors use the term buffer strip to include functional descriptions such as filter, stabilization, or leave strips, and administrative designations such as Idaho's Stream Protection Zone (SPZ), Washington's Riparian Management Zone (RMZ), and the USDA Forest Service's Streamside Management Zone (SMZ). They address water quality and fishery protective functions of buffer strips on forestlands, pointing out improvements in buffer strip design possiblemore » through research or administrative changes. Buffer strip design requirements found in some western Forest Practices Act (FPA) regulations are also compared and related to findings in the scientific literature.« less

Boron isotopes at the catchment scale, a new potential tool to infer critical zone processes.

NASA Astrophysics Data System (ADS)

Gaillardet, J.; Noireaux, J.; Braun, J. J.; Riotte, J.; Louvat, P.; Bouchez, J.; Lemarchand, D.; Muddu, S.; Mohan Kumar, M.; Candaudap, F.

2017-12-01

Boron is a mid-mass element that has two isotopes, 10B and 11B. These isotopes are largely fractioned by a number of chemical, biological and physical processes. Boron as a great affinity for clays and is useful for life, making it a double tracer of critical zone processes. This study focuses on the Mule Hole Critical Zone Observatory in South India. This is part of the French Research Infrastructure OZCAR and has benefited from the fruitful Indo-French collaboration (Indo-French Cell for Water Sciences) for more that 15 years. Boron and its isotopes were measured in the different compartment of the CZ in Mule Hole, vegetation, atmosphere, throughfall, soil, soil water, river water and compared to the behavior of other elements. The well constrained hydrology in Mule Hole allowed us to calculate the main fluxes affecting boron in the Critical Zone and came to the first order conclusion that the recycling of boron by vegetation is by far the most important flux within the system, reaching 15-20 times the catchment outlet flux. From an isotopic point of view, the total range of variation is measured between -3 ‰ and 77‰, with a bedrock value at 10‰ in classical delta unit, making boron a well suited tracer for constraining CZ processes. The flux of boron most enriched in heavy boron is the throughfall, showing the importance of biological processes in controlling the boron isotopic composition of the stream. Boron in soils in depleted in the heavy isotope but is enriched in boron compared to the bedrock, a surprising situation that we interpret as the legacy of a previous stage of transient weathering. These results indicate a strong decoupling between the behaviors of boron at the surface of the CZ and at depth.

Modeling the release of E. coli D21g with transients in water content

USDA-ARS?s Scientific Manuscript database

Transients in water content are well known to mobilize colloids that are retained in the vadose zone. However, there is no consensus on the proper model formulation to simulate colloid release during drainage and imbibition. We present a model that relates colloid release to changes in the air-water...

A new offshore transport mechanism for shoreline-released tracer induced by transient rip currents and stratification

NASA Astrophysics Data System (ADS)

Kumar, Nirnimesh; Feddersen, Falk

2017-03-01

Offshore transport from the shoreline across the inner shelf of early-stage larvae and pathogens is poorly understood yet is critical for understanding larval fate and dilution of polluted shoreline water. With a novel coupling of a transient rip current (TRC) generating surf zone model and an ocean circulation model, we show that transient rip currents ejected onto a stratified inner shelf induce a new, previously unconsidered offshore transport pathway. For incident waves and stratification typical for Southern California in the fall, this mechanism subducts surf zone-origin tracers and transports them at least 800 m offshore at 1.2 km/d analogous to subduction at ocean fronts. This mechanism requires both TRCs and stratification. As TRCs are ubiquitous and the inner shelf is often stratified, this mechanism may have an important role in exporting early-stage larvae, pathogens, or other tracers onto the shelf.

RhoE deficiency alters postnatal subventricular zone development and the number of calbindin-expressing neurons in the olfactory bulb of mouse.

PubMed

Ballester-Lurbe, Begoña; González-Granero, Susana; Mocholí, Enric; Poch, Enric; García-Manzanares, María; Dierssen, Mara; Pérez-Roger, Ignacio; García-Verdugo, José M; Guasch, Rosa M; Terrado, José

2015-11-01

The subventricular zone represents an important reservoir of progenitor cells in the adult brain. Cells from the subventricular zone migrate along the rostral migratory stream and reach the olfactory bulb, where they originate different types of interneurons. In this work, we have analyzed the role of the small GTPase RhoE/Rnd3 in subventricular zone cell development using mice-lacking RhoE expression. Our results show that RhoE null mice display a remarkable postnatal broadening of the subventricular zone and caudal rostral migratory stream. This broadening was caused by an increase in progenitor proliferation, observed in the second postnatal week but not before, and by an altered migration of the cells, which appeared in disorganized cell arrangements that impaired the appropriate contact between cells in the rostral migratory stream. In addition, the thickness of the granule cell layer in the olfactory bulb was reduced, although the density of granule cells did not differ between wild-type and RhoE null mice. Finally, the lack of RhoE expression affected the olfactory glomeruli inducing a severe reduction of calbindin-expressing interneurons in the periglomerular layer. This was already evident in the newborns and even more pronounced 15 days later when RhoE null mice displayed 89% less cells than control mice. Our results indicate that RhoE has pleiotropic functions on subventricular cells because of its role in proliferation and tangential migration, affecting mainly the development of calbindin-expressing cells in the olfactory bulb.

Rare complication characterized by late-onset transient neurological symptoms without hyperperfusion after carotid artery stenting: A report of three cases

PubMed Central

Nakahara, Ichiro; Ohta, Tsuyoshi; Matsumoto, Shoji; Ishibashi, Ryota; Gomi, Masanori; Miyata, Haruka; Nishi, Hidehisa; Watanabe, Sadayoshi

2015-01-01

We experienced a rare complication after carotid artery stenting (CAS) characterized by transient neurological symptoms with no evidence of distal emboli or hyperperfusion. Using neuroimaging, we investigated the pathogenesis of the complication that occurred after CAS in three patients who developed neurological symptoms over a period of ten hours after CAS and improved within two days. None of the three patients showed signs of fresh infarctions on diffusion-weighted imaging or hyperperfusion on single-photon emission computed tomography. However, high signal intensity was observed in the leptomeningeal zone of the cerebral hemisphere on the stent side in all three patients and in the leptomeningeal zone of the contralateral anterior cerebral artery territory in one patient. These areas were assessed using fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging without gadolinium administration. The high signal intensity in the leptomeningeal zone disappeared as the symptoms improved. Based on the transient nature of the neurological disorders and the normalization of FLAIR imaging findings in these patients, the pathogenesis of this complication might have been vasogenic edema due to vasoparalysis of the local vessels caused by the hemodynamic changes occurring after CAS. PMID:25934779

Episodic tremor and slip explained by fluid-enhanced microfracturing and sealing

NASA Astrophysics Data System (ADS)

Bernaudin, M.; Gueydan, F.

2017-12-01

A combination of non-volcanic tremor and transient slow slip events behaviors is commonly observed at plate interface, between locked/seismogenic zone at low depths and stable/ductile creep zone at larger depths. This association defines Episodic Tremor and Slip, systematically highlighted by over-pressurized fluids and near failure shear stress conditions. Here we propose a new mechanical approach that provides for the first time a mechanical and field-based explanation of the observed association between non-volcanic tremor and slow slip events. In contrast with more classical rate-and-state models, this physical model uses a ductile rheology with grain size sensitivity, fluid-driven microfracturing and sealing (e.g. grain size reduction and grain growth) and related pore fluid pressure fluctuations. We reproduce slow slip events by transient ductile strain localization as a result of fluid-enhanced microfracturing and sealing. Moreover, occurrence of macrofracturing during transient strain localization and local increase in pore fluid pressure well simulate non-volcanic tremor. Our model provides therefore a field-based explanation of episodic tremor and slip and moreover predicts the depth and temperature ranges of their occurrence in subduction zones. It implies furthermore that non-volcanic tremor and slow slip events are physically related.

Evaluating hillslope and riparian contributions to dissolved nitrogen (N) export from a boreal forest catchment

NASA Astrophysics Data System (ADS)

Blackburn, M.; Ledesma, José L. J.; Näsholm, Torgny; Laudon, Hjalmar; Sponseller, Ryan A.

2017-02-01

Catchment science has long held that the chemistry of small streams reflects the landscapes they drain. However, understanding the contribution of different landscape units to stream chemistry remains a challenge which frequently limits our understanding of export dynamics. For limiting nutrients such as nitrogen (N), an implicit assumption is that the most spatially extensive landscape units (e.g., uplands) act as the primary sources to surface waters, while near-stream zones function more often as sinks. These assumptions, based largely on studies in high-gradient systems or in regions with elevated inputs of anthropogenic N, may not apply to low-gradient, nutrient-poor, and peat-rich catchments characteristic of many northern ecosystems. We quantified patterns of N mobilization along a hillslope transect in a northern boreal catchment to assess the extent to which organic matter-rich riparian soils regulate the flux of N to streams. Contrary to the prevailing view of riparian functioning, we found that near-stream, organic soils supported concentrations and fluxes of ammonium (NH4+) and dissolved organic nitrogen that were much higher than the contributing upslope forest soils. These results suggest that stream N chemistry is connected to N mobilization and mineralization within the riparian zone rather than the wider landscape. Results further suggest that water table fluctuation in near-surface riparian soils may promote elevated rates of net N mineralization in these landscapes.

Water quality in riparian boreal forest: a multi-method approach to scale biogeochemical drivers from groundwater hotspots to catchment outlets.

NASA Astrophysics Data System (ADS)

Ploum, Stefan; Kuglerová, Lenka; Leach, Jason; Laudon, Hjalmar

2017-04-01

Stream chemistry in boreal regions is for a large degree defined by the riparian zone. Within the riparian zone, groundwater hotspots represent a very small area, but likely play a major role in controlling stream water quality. Hotspots have shown to be unique in their plant species richness, soil texture and biogeochemistry. Also in terms of stream metabolism, hotspots show different responses, either due to local biotic or abiotic conditions. Readily available hydrological mapping tools, combined with biogeochemical data (stream temperature and stable water isotopes) show that there is great potential in predicting groundwater hotspots using terrain-based approaches. However, the role of individual hotspots varies in time. Presumably their hydrological regime is highly dependent on landscape properties of the upstream area. To improve the predictability of hotspots in space and time, a mechanistic understanding is needed. We achieve this by a combined approach including a damming experiment, high resolution optic fiber stream temperature measurements (DTS), a dense groundwater well network, stream and groundwater trace element analysis, frost monitoring and infrared (IR) imagery. This field-based strategy sheds light on the underlying drivers of groundwater hotspots and links them to landscape characteristics. This allows to move away from highly monitored reaches, and evaluate the relation between upland landscape features and the temporal variability of groundwater exfiltration rates on a catchment scale.

Corridors of migrating neurons in the human brain and their decline during infancy.

PubMed

Sanai, Nader; Nguyen, Thuhien; Ihrie, Rebecca A; Mirzadeh, Zaman; Tsai, Hui-Hsin; Wong, Michael; Gupta, Nalin; Berger, Mitchel S; Huang, Eric; Garcia-Verdugo, Jose-Manuel; Rowitch, David H; Alvarez-Buylla, Arturo

2011-09-28

The subventricular zone of many adult non-human mammals generates large numbers of new neurons destined for the olfactory bulb. Along the walls of the lateral ventricles, immature neuronal progeny migrate in tangentially oriented chains that coalesce into a rostral migratory stream (RMS) connecting the subventricular zone to the olfactory bulb. The adult human subventricular zone, in contrast, contains a hypocellular gap layer separating the ependymal lining from a periventricular ribbon of astrocytes. Some of these subventricular zone astrocytes can function as neural stem cells in vitro, but their function in vivo remains controversial. An initial report found few subventricular zone proliferating cells and rare migrating immature neurons in the RMS of adult humans. In contrast, a subsequent study indicated robust proliferation and migration in the human subventricular zone and RMS. Here we find that the infant human subventricular zone and RMS contain an extensive corridor of migrating immature neurons before 18 months of age but, contrary to previous reports, this germinal activity subsides in older children and is nearly extinct by adulthood. Surprisingly, during this limited window of neurogenesis, not all new neurons in the human subventricular zone are destined for the olfactory bulb--we describe a major migratory pathway that targets the prefrontal cortex in humans. Together, these findings reveal robust streams of tangentially migrating immature neurons in human early postnatal subventricular zone and cortex. These pathways represent potential targets of neurological injuries affecting neonates.

Stream inflow and predation risk affect littoral habitat selection by benthic fish

Treesearch

Karl M. Polivka; Lisa M. Friedli; Elizabeth C. Green

2013-01-01

We examined small, fishless headwater streams to determine whether transport of macroinvertebrates into the littoral zone of an oligotrophic lake augmented food availability for Cottus asper, an abundant predatory fish in our study system. We sampled fish and macroinvertebrates during the recruitment and growth season of 2 years, either monthly (2004...

Impact of stream geomorphology on greenhouse gas concentration in a New York mountain stream

Treesearch

Philippe Vidon; Satish Serchan

2016-01-01

As increased greenhouse gas concentrations (GHG: N2O, CO2, CH4) in our atmosphere remain a major concern, better quantifying GHG fluxes from natural systems is essential. In this study, we investigate GHG concentrations in saturated riparian sediments (dry, wet, mucky), streambed hyporheic zone...

Appendix C: GLEES Macroinvertebrates

Treesearch

B. C. Kondratieff

1994-01-01

This Appendix identifies macroinvertebrate species found in streams and lakes at GLEES during a preliminary qualitative survey conducted in the summer of 1988 by Dr. Boris Kondratieff. The littoral zones of each lake and each stream were sampled by hand-picking and with a triangle net. Insect voucher specimens are maintained in the Gillette Entomological Museum at...

THE HYDRAULIC CHARACTERISTICS AND GEOCHEMISTRY OF HYPORHEIC AND PARAFLUVIAL ZONES IN ARCTIC TUNDRA STREAMS, NORTH SLOPE, ALASKA

EPA Science Inventory

Sodium bromide and Rhodamine WT were used as conservative tracers to examine the hydrologic characteristics of seven tundra streams in Arctic Alaska, during the summers of 1994-1996. Continuous tracer additions were conducted in seven rivers ranging from 1st to 5th order with sam...

78 FR 45871 - National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-30

... components: Hydrogeologic study; Surface water sampling study; Stream biological study; Air quality survey... components: Biological survey; Biota survey; Surface water and sediment characterization; Groundwater... impacted groundwater in three water bearing zones at the Site; the unconsolidated materials zone, the upper...

40 CFR 61.356 - Recordkeeping requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... also establish the design minimum and average temperature in the combustion zone and the combustion... temperatures, combustion zone residence time, and description of method and location where the vent stream is... control device are not operated as designed including all periods and the duration when: (i) Any valve car...

Style and Rate of Late Pleistocene - Holocene Deformation of the Poukawa Fault Zone, Central Hawke's Bay, New Zealand

NASA Astrophysics Data System (ADS)

Basili, R.; Langridge, R. M.; Villamor, P.; Rieser, U.

2008-12-01

The Poukawa Fault Zone is one component of a complex system of contractional faulting in eastern North Island, New Zealand. It is located within the actively uplifting Hikurangi Margin where the Australian plate meets the Pacific plate at a convergence rate of over 40 mm/yr. The most destructive earthquake in New Zealand history, the 1931 Hawke's Bay earthquake of M 7.8, occurred just off the northern termination of the Poukawa Fault Zone. To the south and probably within the Poukawa Fault Zone, another strong earthquake struck near Waipukurau in 1863. We have characterized the contemporary style of faulting along the zone on the basis of an integrated analysis of a broad spectrum of data, including exploratory trenching; geomorphic data aided by 1m resolution digital orthophotos, a LIDAR-derived Terrain Model, and GPS-RTK surveys; stratigraphic and paleoseismic analysis; radiocarbon and OSL dating and tephra correlation. We have also made a detailed reconstruction of the terrace sequences formed where the Kaikora Stream crosses at a high angle to the Poukawa Fault Zone. These data show that the Poukawa Fault Zone is a contractional fault system formed by a series of NE-SW strands with style varying, from west to east, from high-angle east-dipping reverse to low-angle west-dipping thrusting. The geometry of the system suggests that these faults may merge at shallow depth into a single large structure capable of generating strong earthquakes similar to those that occurred in the past on nearby sections. All these faults variously displace the top of the Ohakean aggradation surface (12-15 ka) thereby generating scarps of several meters. The Kaikora Stream terrace sequences also testify to a series of uplift events associated with the late-Holocene growth of two of the eastern thrust faults. Two reaches of Kaikora Stream show evidence of uplifted and abandoned inset Holocene stream terraces found in association with a surface-rupture trace and an active fold. The four terraces in each case correspond in number with paeloearthquake events recognized in trenches nearby (Kelsey et al. 1998). Based on these relations the recurrence interval of surface faulting and folding is c. 3000-3700 yr. The abandonment of a low inset terrace capped by peat and Waimihia Tephra (c. 3400 yr BP) is consistent with this average recurrence. Based on the deformation of the dated Ohakean surface across the entire Poukawa Fault Zone, its reverse slip rate is c. 1-2 mm/yr.

From soil water to surface water - how the riparian zone controls element transport from a boreal forest to a stream

NASA Astrophysics Data System (ADS)

Lidman, Fredrik; Boily, Åsa; Laudon, Hjalmar; Köhler, Stephan J.

2017-06-01

Boreal headwaters are often lined by strips of highly organic soils, which are the last terrestrial environment to leave an imprint on discharging groundwater before it enters a stream. Because these riparian soils are so different from the Podzol soils that dominate much of the boreal landscape, they are known to have a major impact on the biogeochemistry of important elements such as C, N, P and Fe and the transfer of these elements from terrestrial to aquatic ecosystems. For most elements, however, the role of the riparian zone has remained unclear, although it should be expected that the mobility of many elements is affected by changes in, for example, pH, redox potential and concentration of organic carbon as they are transported through the riparian zone. Therefore, soil water and groundwater was sampled at different depths along a 22 m hillslope transect in the Krycklan catchment in northern Sweden using soil lysimeters and analysed for a large number of major and trace elements (Al, As, B, Ba, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, La, Li, Mg, Mn, Na, Ni, Pb, Rb, Se, Si, Sr, Th, Ti, U, V, Zn, Zr) and other parameters such as sulfate and total organic carbon (TOC). The results showed that the concentrations of most investigated elements increased substantially (up to 60 times) as the water flowed from the uphill mineral soils and into the riparian zone, largely as a result of higher TOC concentrations. The stream water concentrations of these elements were typically somewhat lower than in the riparian zone, but still considerably higher than in the uphill mineral soils, which suggests that riparian soils have a decisive impact on the water quality of boreal streams. The degree of enrichment in the riparian zone for different elements could be linked to the affinity for organic matter, indicating that the pattern with strongly elevated concentrations in riparian soils is typical for organophilic substances. One likely explanation is that the solubility of many organophilic elements increases as a result of the higher concentrations of TOC in the riparian zone. Elements with low or modest affinity for organic matter (e.g. Na, Cl, K, Mg and Ca) occurred in similar or lower concentrations in the riparian zone. Despite the elevated concentrations of many elements in riparian soil water and groundwater, no increase in the concentrations in biota could be observed (bilberry leaves and spruce shoots).

Biological function in the twilight zone of sequence conservation.

PubMed

Ponting, Chris P

2017-08-16

Strong DNA conservation among divergent species is an indicator of enduring functionality. With weaker sequence conservation we enter a vast 'twilight zone' in which sequence subject to transient or lower constraint cannot be distinguished easily from neutrally evolving, non-functional sequence. Twilight zone functional sequence is illuminated instead by principles of selective constraint and positive selection using genomic data acquired from within a species' population. Application of these principles reveals that despite being biochemically active, most twilight zone sequence is not functional.

Effects of acid mine drainage on the stream ecosystem of the east fork of the Obey River, Tennessee

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

Nichols, L.E.; Bulow, F.L.

1973-01-01

The stream ecosystem of the east fork of the Obey River, Tennessee was studied from January through December 1970. Emphasis centered on water quality, macroinvertebrates, fish and aquatic flora affected by acid mine drainage. Two control stations were established within the study area, one located below the zone of pollution. A reservoir station was established to detect any neutralization occurring within Dale Hollow Reservoir below the confluence of the east fork and west fork. An area approximately 40 miles in length was found to be severely degraded by acid mine drainage. Limited macroinvertebrate populations existed within this region. Chironomus andmore » Sialis were the predominate benthic indicator organisms present in the polluted zone. Euglena mutabilis was the most abundant representative organism of the aquatic flora. This organism was found to be characteristic of acid mine pollution. Fish were recovered above and below, but not within, the zone of pollution. Fish recovered were characteristic of the type of habitat in which they were collected, being either typical stream or reservoir fish. A fish kill occurred in the east fork embayment of Dale Hollow on August 15, 1970 from acid mine drainage discharged upstream.« less

Heat tracer methods

USGS Publications Warehouse

Healy, Richard W.; Scanlon, Bridget R.

2010-01-01

The flow of heat in the subsurface is closely linked to the movement of water (Ingebritsen et al., 2006). As such, heat has been used as a tracer in groundwater studies for more than 100 years (Anderson, 2005). As with chemical and isotopic tracers (Chapter 7), spatial or temporal trends in surface and subsurface temperatures can be used to infer rates of water movement. Temperature can be measured accurately, economically, at high frequencies, and without the need to obtain water samples, facts that make heat an attractive tracer. Temperature measurements made over space and time can be used to infer rates of recharge from a stream or other surface water body (Lapham, 1989; Stonestrom and Constantz, 2003); measurements can also be used to estimate rates of steady drainage through depth intervals within thick unsaturated zones (Constantz et al., 2003; Shan and Bodvarsson, 2004). Several thorough reviews of heat as a tracer in hydrologic studies have recently been published (Constantz et al., 2003; Stonestrom and Constantz, 2003; Anderson, 2005; Blasch et al., 2007; Constantz et al., 2008). This chapter summarizes heat-tracer approaches that have been used to estimate recharge.Some clarification in terminology is presented here to avoid confusion in descriptions of the various approaches that follow. Diffuse recharge is that which occurs more or less uniformly across large areas in response to precipitation, infiltration, and drainage through the unsaturated zone. Estimates of diffuse recharge determined using measured temperatures in the unsaturated zone are referred to as potential recharge because it is possible that not all of the water moving through the unsaturated zone will recharge the aquifer; some may be lost to the atmosphere by evaporation or plant transpiration. Estimated fluxes across confining units in the saturated zone are referred to as interaquifer flow (Chapter 1). Focused recharge is that which occurs directly from a point or line source, such as a stream, on land surface. Focused recharge may vary widely in space and time. If the water table intersects a stream channel, estimates of stream loss are called actual recharge, or just recharge. If the water table lies below the stream channel, estimates are referred to as potential recharge. For simplicity, all vertical water fluxes are referred to as drainage throughout this chapter. Whether the estimated quantity represents actual or potential recharge or drainage depends on the circumstances of each individual study.

Understanding of changes in river flow using recently collected field and observational data from Russian Arctic

NASA Astrophysics Data System (ADS)

Shiklomanov, A. I.; Tokarev, I. V.; Davydov, S. P.; Davydova, A.; Streletskiy, D. A.

2017-12-01

There is substantial evidence supporting increasing river runoff in the Eurasian pan-Arctic, but the causes of these changes are not well understood. To determine the contributions of various water sources to river runoff generation in small streams and large rivers located in the continuous permafrost zone, an extensive field campaign was carried out near the town of Cherskii, Russia. Measurements of hydrometeorological characteristics, as well as stable isotope composition and hydrochemistry of precipitation, river flow and ground ice, were obtained during the 2013-2016 period. When combined with older data (2005-2009), the isotopic composition of atmospheric precipitation showed a general trend towards heavier winter precipitation, attributed mainly to observed increases in winter air temperature. Samples of water and ground ice from several boreholes showed that isotopic compositions of water from the active layer, transient layer and permafrost are significantly different. Thus, stable isotopes can be used to assess contributions of different soil layers to stream flow generation. Increases in streamflow of small test watersheds were observed during dry periods in August-September. These increases were associated with considerable stable isotope depletion in streamflow samples, which is likely caused by thawing of the transient- and possibly upper permafrost layers. The absence of correlation between water and air temperature during these periods (R2 = 0.22 in August-September and R2 = 0.8 in June-July) also suggests an increasing contribution of thawing ground ice to the streamflow. To quantitatively assess the contribution of various water sources to the river runoff of Kolyma River, we used stable isotope data along with a physically based hydrological model developed at the University of New Hampshire. Preliminary results suggest that thawing permafrost increased August-September discharge in Kolyma near Cherskii by 8% in 2013, 11% in 2014 and 4% in 2015, even though none of these years was extremely warm or wet. We estimate that 5cm of permafrost thaw (with 30% ice content) over the entire Kolyma basin can contribute about 10 km3/year (or 10%) to annual discharge and significantly change the water regime during low-flow periods (fall-winter).

Lateral, vertical, and longitudinal connectivity of runoff source areas drive stream hydro-biogeochemical signals across a low relief drainage network

NASA Astrophysics Data System (ADS)

Zimmer, M. A.; McGlynn, B. L.

2017-12-01

Our understanding of the balance between longitudinal, lateral, and vertical expansion and contraction of reactive flowpaths and source areas in headwater catchments is limited. To address this, we utilized an ephemeral-to-perennial stream network in the Piedmont region of North Carolina, USA to gain new understanding about critical zone mechanisms that drive runoff generation and biogeochemical signals in both groundwater and stream water. Here, we used chemical and hydrometric data collected from zero through second order catchments to characterize spatial and temporal runoff and overland, shallow soil, and deep subsurface flow across characteristic landscape positions. Our results showed that the active stream network was driven by two superimposed runoff generation regimes that produced distinct hydro-biogeochemical signals at the catchment outlet. The baseflow runoff generation regime expanded and contracted the stream network seasonally through the rise and fall of the seasonal water table. Superimposed on this, event-activated source area contributions were driven by surficial and shallow subsurface flowpaths. The subsurface critical zone stratigraphy in this landscape coupled with the precipitation regime activated these shallow flowpaths frequently. This drove an increase in dissolved organic carbon (DOC) concentrations with increases in runoff across catchment scales. DOC-runoff relationship variability and spread was driven by the balance between runoff regimes as well as a seasonal depletion of DOC from shallow subsurface flowpath activation and annual replenishment from litterfall. From this, we suggest that the hydro-biogeochemical signals at larger catchment outlets can be driven by a balance of longitudinal, lateral, and vertical source area contributions, critical zone structure, and complex hydrological processes.

Liquid additives for particulate emissions control

DOEpatents

Durham, M.D.; Schlager, R.J.; Ebner, T.G.; Stewart, R.M.; Hyatt, D.E.; Bustard, C.J.; Sjostrom, S.

1999-01-05

The present invention discloses a process for removing undesired particles from a gas stream including the steps of contacting a composition containing an adhesive with the gas stream; collecting the undesired particles and adhesive on a collection surface to form an aggregate comprising the adhesive and undesired particles on the collection surface; and removing the agglomerate from the collection zone. The composition may then be atomized and injected into the gas stream. The composition may include a liquid that vaporizes in the gas stream. After the liquid vaporizes, adhesive particles are entrained in the gas stream. The process may be applied to electrostatic precipitators and filtration systems to improve undesired particle collection efficiency. 11 figs.

Evaluation of ground-water flow and solute transport in the Lompoc area, Santa Barbara County, California

USGS Publications Warehouse

Bright, Daniel J.; Nash, David B.; Martin, Peter

1997-01-01

Ground-water quality in the Lompoc area, especially in the Lompoc plain, is only marginally acceptable for most uses. Demand for ground water has increased for municipal use since the late 1950's and has continued to be high for irrigation on the Lompoc plain, the principal agricultural area in the Santa Ynez River basin. As use has increased, the quality of ground water has deteriorated in some areas of the Lompoc plain. The dissolved-solids concentration in the main zone of the upper aquifer beneath most of the central and western plains has increased from less than 1,000 milligrams per liter in the 1940's to greater than 2,000 milligrams per liter in the 1960's. Dissolved- solids concentration have remained relatively constant since the 1960's. A three-dimensional finite-difference model was used to simulate ground-water flow in the Lompoc area and a two-dimensional finite-element model was used to simulate solute transport to gain a better understanding of the ground-water system and to evaluate the effects of proposed management plans for the ground-water basin. The aquifer system was simulated in the flow model as four horizontal layers. In the area of the Lompoc plain, the layers represent the shallow, middle, and main zones of the upper aquifer, and the lower aquifer. For the Lompoc upland and Lompoc terrace, the four layers represent the lower aquifer. The solute transport model was used to simulate dissolved-solids transport in the main zone of the upper aquifer beneath the Lompoc plain. The flow and solute-transport models were calibrated to transient conditions for 1941-88. A steady-state simulation was made to provide initial conditions for the transient-state simulation by using long-term average (1941-88) recharge rates. Model- simulated hydraulic heads generally were within 5 feet of measured heads in the main zone for transient conditions. Model-simulated dissolved- solids concentrations for the main zone generally differed less than 200milligrams per liter from concentrations in 1988. During 1941-88 about 1,096,000 acre-feet of water was pumped from the aquifer system. Average pumpage for this period (22,830 acre-feet per year) exceeded pumpage for the steady-state simulation by 16,590 acre-feet per year. The results of the transient simulation indicate that about 60 percent of this increase in pumpage was contributed by increased recharge, 28 percent by decreased natural discharge from the system (primarily discharge to the Santa Ynez River and transpiration), and 13 percent was withdrawn from storage. Total simulated downward leakage from the middle zone to the main zone in the central plain and upward leakage from the consolidated rocks to the main zone significantly increased in response to increased pumpage, which increased from about 6,240 to 30,870 acre-feet per year from 1941 to 1988. Average dissolved-solid concentration in the middle zone in 1987-88 ranged from 2,000 to 3,000 milligrams per liter beneath the northeastern plain and the dissolved-solids concentration of two samples from the consolidated rocks beneath the western plain averaged 4,300 milligrams per liter. Because the dissolved-solids concentration for the middle zone and the consolidated rocks is higher than the simulated steady-state dissolved-solids concentration of the main zone, the increase in the leakage from these two sources resulted in increased dissolved-solids concentration in the main zone during the transient period. The model results indicate that the main source of increased dissolved- solids concentration in the northeastern and central plains was downward leakage from the middle zone; whereas, upward leakage from the consolidated rocks was the main source of the increased dissolved-solids concentrations in the northwestern and western plains. The models were used to estimate changes in hydraulic head and in dissolved-solids concentration resulting from three proposed management alternatives: (1) average recharge

Groundwater flow path dynamics and nitrogen transport potential in the riparian zone of an agricultural headwater catchment

USDA-ARS?s Scientific Manuscript database

Stream riparian zones are often thought of as areas that provide natural remediation for groundwater contaminants, especially agricultural nitrogen (N). While denitrification and vegetative uptake tend to be efficient N removal processes in slow moving shallow groundwater, these mechanisms decrease ...

Small Mammal Communities Of Streamside Zones in the Ouachita Mountains

Treesearch

Philip A. Tappe; Ronald E. Thill; M. Anthony Melchiors; T. Bently Wigley; David G. Peitz

2004-01-01

Natural forest stands along perennial and intermittent streams, commonly called streamside zones (SZs), frequently are retained for wildlife habitat enhancement and watershed protection when adjacent stands are harvested. However, little is known regarding wildlife habitat relationships within SZs, especially as they relate to SZ widths and influences of habitat...

Early history of subplate and interstitial neurons: from Theodor Meynert (1867) to the discovery of the subplate zone (1974)

PubMed Central

Judaš, Miloš; Sedmak, Goran; Pletikos, Mihovil

2010-01-01

In this historical review, we trace the early history of research on the fetal subplate zone, subplate neurons and interstitial neurons in the white matter of the adult nervous system. We arrive at several general conclusions. First, a century of research clearly testifies that interstitial neurons, subplate neurons and the subplate zone were first observed and variously described in the human brain – or, in more general terms, in large brains of gyrencephalic mammals, characterized by an abundant white matter and slow and protracted prenatal and postnatal development. Secondly, the subplate zone cannot be meaningfully defined using a single criterion – be it a specific population of cells, fibres or a specific molecular or genetic marker. The subplate zone is a highly dynamic architectonic compartment and its size and cellular composition do not remain constant during development. Thirdly, it is important to make a clear distinction between the subplate zone and the subplate (and interstitial) neurons. The transient existence of the subplate zone (as a specific architectonic compartment of the fetal telencephalic wall) should not be equated with the putative transient existence of subplate neurons. It is clear that in rodents, and to an even greater extent in humans and monkeys, a significant number of subplate cells survive and remain functional throughout life. PMID:20979585

Hyporheic flow and transport processes: mechanisms, models, and biogeochemical implications

USGS Publications Warehouse

Boano, Fulvio; Harvey, Judson W.; Marion, Andrea; Packman, Aaron I.; Revelli, Roberto; Ridolfi, Luca; Anders, Wörman

2014-01-01

Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed."

Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications

NASA Astrophysics Data System (ADS)

Boano, F.; Harvey, J. W.; Marion, A.; Packman, A. I.; Revelli, R.; Ridolfi, L.; Wörman, A.

2014-12-01

Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed.

Residence-time framework for modeling multicomponent reactive transport in stream hyporheic zones

NASA Astrophysics Data System (ADS)

Painter, S. L.; Coon, E. T.; Brooks, S. C.

2017-12-01

Process-based models for transport and transformation of nutrients and contaminants in streams require tractable representations of solute exchange between the stream channel and biogeochemically active hyporheic zones. Residence-time based formulations provide an alternative to detailed three-dimensional simulations and have had good success in representing hyporheic exchange of non-reacting solutes. We extend the residence-time formulation for hyporheic transport to accommodate general multicomponent reactive transport. To that end, the integro-differential form of previous residence time models is replaced by an equivalent formulation based on a one-dimensional advection dispersion equation along the channel coupled at each channel location to a one-dimensional transport model in Lagrangian travel-time form. With the channel discretized for numerical solution, the associated Lagrangian model becomes a subgrid model representing an ensemble of streamlines that are diverted into the hyporheic zone before returning to the channel. In contrast to the previous integro-differential forms of the residence-time based models, the hyporheic flowpaths have semi-explicit spatial representation (parameterized by travel time), thus allowing coupling to general biogeochemical models. The approach has been implemented as a stream-corridor subgrid model in the open-source integrated surface/subsurface modeling software ATS. We use bedform-driven flow coupled to a biogeochemical model with explicit microbial biomass dynamics as an example to show that the subgrid representation is able to represent redox zonation in sediments and resulting effects on metal biogeochemical dynamics in a tractable manner that can be scaled to reach scales.

Role of the microtubule cytoskeleton in gravisensing Chara rhizoids.

PubMed

Braun, M; Sievers, A

1994-04-01

The arrangement of the microtubule cytoskeleton in tip-growing and gravisensing Chara rhizoids has been documented by immunofluorescence microscopy. Predominantly axially oriented undulating bundles of cortical microtubules were found in the basal zone of the rhizoids and colocalized with the microfilament bundles underlying the cytoplasmic streaming. Microtubules penetrate the subapical zone, forming a three-dimensional network that envelops the nucleus and organelles. Microtubules are present up to 5 to 10 microns basal from the apical cytoplasmic region containing the statoliths. No microtubules were found in the apical zone of the rhizoid which is the site of tip growth and gravitropism. Depolymerization of microtubules by application of oryzalin does not affect cytoplasmic streaming and gravitropic growth until the relatively stationary and polarly organized apical and subapical cytoplasm is converted into streaming cytoplasm. When the statoliths and the apical cytoplasm are included in the cytoplasmic streaming, tip growth and gravitropism are stopped. Oryzalin-induced disruption of the microtubule cytoskeleton also results in a rearrangement of the dense network of apical and subapical microfilaments into thicker bundles, whereas disruption of the microfilament cytoskeleton by cytochalasin D had no effect on the organization of the microtubule cytoskeleton. It is, therefore, concluded that the arrangement of microtubules is essential for the polar cytoplasmic zonation and the functionally polar organization of the actin cytoskeleton which is responsible for the motile processes in rhizoids. Microtubules are not involved in the primary events of gravitropism in Chara rhizoids.

Effect of emergent aquatic insects on bat foraging in a riparian forest.

PubMed

Fukui, Dai; Murakami, Masashi; Nakano, Shigeru; Aoi, Toshiki

2006-11-01

1. Riparian zones serve several ecological functions for bats. They provide a source of prey and likely provide favourable structural habitats and shelter from predators. Many studies have shown that bats use the space above streams, ponds or riparian vegetation as feeding habitat. These studies, however, have never distinguished between the effects of habitat structure and prey availability on the foraging activities of bats. Such effects can only be distinguished by an experimental approach. We predicted that bat activity along a stream is influenced by the number of emerged aquatic insects. 2. We evaluated the response of terrestrial consumers, insectivorous bats, to changes in the abundance of emergent aquatic insects by conducting a manipulative field experiment. In a deciduous riparian forest in Japan, aquatic insect flux from the stream to the riparian zone was controlled with an insect-proof cover over a 1.2 km stream reach. 3. We estimated the abundance of emergent aquatic and flying terrestrial arthropods near the treatment and control reaches using Malaise traps. The foraging activity of bats was evaluated in both treatment and control reaches using ultrasonic detectors. 4. The insect-proof cover effectively reduced the flux of emergent aquatic insects to the riparian zone adjacent to the treatment reach. Adjacent to the control reach, adult aquatic insect biomass was highest in spring, and then decreased gradually. Terrestrial insect biomass increased gradually during the summer at both treatment and control reaches. 5. Foraging activity of bats was correlated with insect abundance. In spring, foraging activity of bats at the control reach was significantly greater than at the treatment reach, and increased at both sites with increasing terrestrial insect abundance. 6. Our result suggests that the flux of aquatic insects emerging from streams is one of the most important factors affecting the distribution of riparian-foraging bats. As is the case with other riparian consumers, resource subsidies from streams can directly enhance the performance or population density of riparian-dependent bats. To conserve and manage bat populations, it is important to protect not only forest ecosystems, but also adjacent aquatic systems such as streams.

Engineering hyporheic zones to target nitrification versus denitrification: performance data from constructed stream flumes

NASA Astrophysics Data System (ADS)

Herzog, S.; Portmann, A. C.; Halpin, B. N.; Higgins, C.; McCray, J. E.

2017-12-01

Nonpoint source nitrogen pollution from agricultural and urban runoff is one of the leading causes of impairment to US rivers and streams. The hyporheic zone (HZ) offers a natural biogeochemical hotspot for the attenuation of nitrogen within streams, thereby complementing efforts to prevent aquatic nitrogen pollution in the first place. However, HZ in urban and agricultural streams are often degraded by scouring and colmation, which limit their potential to improve stream water quality at the reach scale. A recent effort to mitigate nitrogen pollution in the Chesapeake Bay region provides denitrification credits for hyporheic restoration projects. Unfortunately, many of the featured hyporheic zone best management practices (BMP) (e.g., weirs, cross-vanes) tend to create only localized, aerobic hyporheic flows that are not optimal for the anaerobic denitrification reaction. In short, practitioners lack an adaptable BMP that can both 1) increase hyporheic exchange, and 2) tailor HZ residence times to match reactions of interest. Here we present new performance data for an HZ engineering technique called Biohydrochemical Enhancements for Streamwater Treatment (BEST). BEST are subsurface modules that utilize low-permeability sediments to drive efficient hyporheic exchange and control residence times, along with reactive geomedia to increase reaction rates within HZ sediments. This research utilized two artificial stream flumes: One flume served as an all-sand control condition, the other featured BEST modules at 1m spacing with a mixture of 70/30 sand/woodchips (v/v). Two different BEST media were tested: a coarse sand module with K 0.5 cm/s, and a fine sand module with K 0.15 cm/s. The flume with coarse sand BEST modules created aerobic HZ conditions and demonstrated rapid nitrification of ammonia at rates significantly higher than the control. However, denitrification was much slower and not significantly different between the two streams. In contrast, the fine sand module promoted anaerobic conditions and increased denitrification rates significantly compared to the all-sand control, but at the expense of nitrification. These results highlight the need to tailor HZ designs to provide appropriate conditions for reactions of interest, and demonstrate the applicability of BEST for this purpose.

Transient removal of alkaline zones after excitation of Chara cells is associated with inactivation of high conductance in the plasmalemma

PubMed Central

2009-01-01

The action potential (AP) of excitable plant cells is a multifunctional physiological signal. Its generation in characean algae suppresses the pH banding for 15–30 min and enhances the heterogeneity of spatial distribution of photosynthetic activity. This suppression is largely due to the cessation of H+ influx (OH− efflux) in the alkaline cell regions. Measurements of local pH and membrane conductance in individual space-clamped alkaline zones (small cell areas bathed in an isolated pool of external medium) showed that the AP generation is followed by the transient disappearance of alkaline zone in parallel with a large decrease in membrane conductance. These changes, specific to alkaline zones, were only observed under continuous illumination following a relaxation period of at least 15 min after previous excitation. The excitation of dark-adapted cells produced no conductance changes in the post-excitation period. The results indicate that the origin of alkaline zones in characean cells is not due to operation of electroneutral H+/HCO3− symport or OH−/HCO3− antiport. It is concluded that the membrane excitation is associated with inactivation of plasmalemma high conductance in the alkaline cell regions. PMID:19820298

Operational Draft Regional Guidebook for the Functional Assessment of High-gradient Ephemeral and Intermittent Headwater Streams in Western West Virginia and Eastern Kentucky

DTIC Science & Technology

2010-07-01

VCCANOPY applies to the habitat function only. Channel canopy cover affects the temperature, nutrient cycling, and habitat of riparian and stream...altering amphibian habitat. Changes in canopy cover and composition affect the quality of stream inputs from the riparian zone (Wipfli et al. 2007) and the...systems (Mulholland 1992). Riparian plant communities provide habitat and are affected by canopy shading, with shade-tolerant species germinating

Field-scale observations of a transient geobattery resulting from natural attenuation of a crude oil spill

USGS Publications Warehouse

Heenan, Jeffrey; Ntarlagiannis, Dimitris; Slater, Lee; Beaver, Carol; Rossbach, S.; Revil, A.; Atekwana, E.A.; Bekins, Barbara A.

2017-01-01

We present evidence of a geobattery associated with microbial degradation of a mature crude oil spill. Self-potential measurements were collected using a vertical array of nonpolarizing electrodes, starting at the land surface and passing through the smear zone where seasonal water table fluctuations have resulted in the coating of hydrocarbons on the aquifer solids. These passive electrical potential measurements exhibit a dipolar pattern associated with a current source. The anodic and cathodic reactions of this natural battery occur below and above the smear zone, respectively. The smear zone is characterized by high magnetic susceptibility values associated with the precipitation of semiconductive magnetic iron phase minerals as a by-product of biodegradation, facilitating electron transfer between the anode and the cathode. This geobattery response appears to have a transient nature, changing on a monthly scale, probably resulting from chemical and physical changes in subsurface conditions such as water table fluctuations.

Subliminal Speech Perception and Auditory Streaming

ERIC Educational Resources Information Center

Dupoux, Emmanuel; de Gardelle, Vincent; Kouider, Sid

2008-01-01

Current theories of consciousness assume a qualitative dissociation between conscious and unconscious processing: while subliminal stimuli only elicit a transient activity, supraliminal stimuli have long-lasting influences. Nevertheless, the existence of this qualitative distinction remains controversial, as past studies confounded awareness and…

Technical Note: Approximate solution of transient drawdown for constant-flux pumping at a partially penetrating well in a radial two-zone confined aquifer

NASA Astrophysics Data System (ADS)

Huang, C.-S.; Yang, S.-Y.; Yeh, H.-D.

2015-06-01

An aquifer consisting of a skin zone and a formation zone is considered as a two-zone aquifer. Existing solutions for the problem of constant-flux pumping in a two-zone confined aquifer involve laborious calculation. This study develops a new approximate solution for the problem based on a mathematical model describing steady-state radial and vertical flows in a two-zone aquifer. Hydraulic parameters in these two zones can be different but are assumed homogeneous in each zone. A partially penetrating well may be treated as the Neumann condition with a known flux along the screened part and zero flux along the unscreened part. The aquifer domain is finite with an outer circle boundary treated as the Dirichlet condition. The steady-state drawdown solution of the model is derived by the finite Fourier cosine transform. Then, an approximate transient solution is developed by replacing the radius of the aquifer domain in the steady-state solution with an analytical expression for a dimensionless time-dependent radius of influence. The approximate solution is capable of predicting good temporal drawdown distributions over the whole pumping period except at the early stage. A quantitative criterion for the validity of neglecting the vertical flow due to a partially penetrating well is also provided. Conventional models considering radial flow without the vertical component for the constant-flux pumping have good accuracy if satisfying the criterion.

Temporal windows in visual processing: "prestimulus brain state" and "poststimulus phase reset" segregate visual transients on different temporal scales.

PubMed

Wutz, Andreas; Weisz, Nathan; Braun, Christoph; Melcher, David

2014-01-22

Dynamic vision requires both stability of the current perceptual representation and sensitivity to the accumulation of sensory evidence over time. Here we study the electrophysiological signatures of this intricate balance between temporal segregation and integration in vision. Within a forward masking paradigm with short and long stimulus onset asynchronies (SOA), we manipulated the temporal overlap of the visual persistence of two successive transients. Human observers enumerated the items presented in the second target display as a measure of the informational capacity read-out from this partly temporally integrated visual percept. We observed higher β-power immediately before mask display onset in incorrect trials, in which enumeration failed due to stronger integration of mask and target visual information. This effect was timescale specific, distinguishing between segregation and integration of visual transients that were distant in time (long SOA). Conversely, for short SOA trials, mask onset evoked a stronger visual response when mask and targets were correctly segregated in time. Examination of the target-related response profile revealed the importance of an evoked α-phase reset for the segregation of those rapid visual transients. Investigating this precise mapping of the temporal relationships of visual signals onto electrophysiological responses highlights how the stream of visual information is carved up into discrete temporal windows that mediate between segregated and integrated percepts. Fragmenting the stream of visual information provides a means to stabilize perceptual events within one instant in time.

Coupling GIS and multivariate approaches to reference site selection for wadeable stream monitoring.

PubMed

Collier, Kevin J; Haigh, Andy; Kelly, Johlene

2007-04-01

Geographic Information System (GIS) was used to identify potential reference sites for wadeable stream monitoring, and multivariate analyses were applied to test whether invertebrate communities reflected a priori spatial and stream type classifications. We identified potential reference sites in segments with unmodified vegetation cover adjacent to the stream and in >85% of the upstream catchment. We then used various landcover, amenity and environmental impact databases to eliminate sites that had potential anthropogenic influences upstream and that fell into a range of access classes. Each site identified by this process was coded by four dominant stream classes and seven zones, and 119 candidate sites were randomly selected for follow-up assessment. This process yielded 16 sites conforming to reference site criteria using a conditional-probabilistic design, and these were augmented by an additional 14 existing or special interest reference sites. Non-metric multidimensional scaling (NMS) analysis of percent abundance invertebrate data indicated significant differences in community composition among some of the zones and stream classes identified a priori providing qualified support for this framework in reference site selection. NMS analysis of a range standardised condition and diversity metrics derived from the invertebrate data indicated a core set of 26 closely related sites, and four outliers that were considered atypical of reference site conditions and subsequently dropped from the network. Use of GIS linked to stream typology, available spatial databases and aerial photography greatly enhanced the objectivity and efficiency of reference site selection. The multi-metric ordination approach reduced variability among stream types and bias associated with non-random site selection, and provided an effective way to identify representative reference sites.

Dynamic Change of Water Quality in Hyporheic Zone at Water Curtain Cultivation Area, Cheongju, Korea

NASA Astrophysics Data System (ADS)

Moon, S. H.; Kim, Y.

2015-12-01

There has been recently growing numbers of facilities for water curtain cultivation of strawberry and lettuce in Korea. These areas are nearly all located in the fluvial deposits near streams which can replenish water resources into exhausted groundwater aquifers during peak season. The purpose of this study is on groundwater chemistry and the change in physical and chemical properties due to stream-groundwater exchange or mixing in the representative agricultural area among the Jurassic granitic terrain of Korea. In the study area, groundwater level continuously decreased from November through March due to intensive use of groundwater, which forced stream water into aquifer. After March, groundwater level was gradually recovered to the original state. To evaluate the extent and its variations of stream water mixing into aquifer, field parameters including T, pH, EC and DO values, concentrations of major ions and oxygen and hydrogen stable isotopic ratios were used. Field measurements and water sample collections were performed several times from 2012 to 2015 mainly during peak time of groundwater use. To compare the temporal variations and areal differences, 21 wells from four cross sections perpendicular to stream line were used. While water temperature, EC values and concentrations of Ca, Mg, Si, HCO3 showed roughly gradual increase from stream line to 150 m distance, pH and DO values showed reverse phenomenon. This can be used to evaluate the extent and limit of stream water introduction into aquifer. However, individual wells showed yearly variations in those parameters and this dynamic and unstable feature indicates that mixing intensity of stream water over groundwater in this hyporheic zone varied year by year according to amounts of groundwater use and decrease of groundwater level.

Riparian zones attenuate nitrogen loss following bark beetle-induced lodgepole pine mortality

NASA Astrophysics Data System (ADS)

Biederman, Joel A.; Meixner, Thomas; Harpold, Adrian A.; Reed, David E.; Gutmann, Ethan D.; Gaun, Janelle A.; Brooks, Paul D.

2016-03-01

A North American bark beetle infestation has killed billions of trees, increasing soil nitrogen and raising concern for N loss impacts on downstream ecosystems and water resources. There is surprisingly little evidence of stream N response in large basins, which may result from surviving vegetation uptake, gaseous loss, or dilution by streamflow from unimpacted stands. Observations are lacking along hydrologic flow paths connecting soils with streams, challenging our ability to determine where and how attenuation occurs. Here we quantified biogeochemical concentrations and fluxes at a lodgepole pine-dominated site where bark beetle infestation killed 50-60% of trees. We used nested observations along hydrologic flow paths connecting hillslope soils to streams of up to third order. We found soil water NO3 concentrations increased 100-fold compared to prior research at this and nearby southeast Wyoming sites. Nitrogen was lost below the major rooting zone to hillslope groundwater, where dissolved organic nitrogen (DON) increased by 3-10 times (mean 1.65 mg L-1) and NO3-N increased more than 100-fold (3.68 mg L-1) compared to preinfestation concentrations. Most of this N was removed as hillslope groundwater drained through riparian soils, and NO3 remained low in streams. DON entering the stream decreased 50% within 5 km downstream, to concentrations typical of unimpacted subalpine streams (~0.3 mg L-1). Although beetle outbreak caused hillslope N losses similar to other disturbances, up to 5.5 kg ha-1y-1, riparian and in-stream removal limited headwater catchment export to <1 kg ha-1y-1. These observations suggest riparian removal was the dominant mechanism preventing hillslope N loss from impacting streams.

Quantifying the fate of agricultural nitrogen in an unconfined aquifer: Stream-based observations at three measurement scales

NASA Astrophysics Data System (ADS)

Gilmore, Troy E.; Genereux, David P.; Solomon, D. Kip; Solder, John E.; Kimball, Briant A.; Mitasova, Helena; Birgand, François

2016-03-01

We compared three stream-based sampling methods to study the fate of nitrate in groundwater in a coastal plain watershed: point measurements beneath the streambed, seepage blankets (novel seepage-meter design), and reach mass-balance. The methods gave similar mean groundwater seepage rates into the stream (0.3-0.6 m/d) during two 3-4 day field campaigns despite an order of magnitude difference in stream discharge between the campaigns. At low flow, estimates of flow-weighted mean nitrate concentrations in groundwater discharge ([NO3-]FWM) and nitrate flux from groundwater to the stream decreased with increasing degree of channel influence and measurement scale, i.e., [NO3-]FWM was 654, 561, and 451 µM for point, blanket, and reach mass-balance sampling, respectively. At high flow the trend was reversed, likely because reach mass-balance captured inputs from shallow transient high-nitrate flow paths while point and blanket measurements did not. Point sampling may be better suited to estimating aquifer discharge of nitrate, while reach mass-balance reflects full nitrate inputs into the channel (which at high flow may be more than aquifer discharge due to transient flow paths, and at low flow may be less than aquifer discharge due to channel-based nitrate removal). Modeling dissolved N2 from streambed samples suggested (1) about half of groundwater nitrate was denitrified prior to discharge from the aquifer, and (2) both extent of denitrification and initial nitrate concentration in groundwater (700-1300 µM) were related to land use, suggesting these forms of streambed sampling for groundwater can reveal watershed spatial relations relevant to nitrate contamination and fate in the aquifer.

A Preliminary Study of Streamside Air Temperatures Within the Coast Redwood Zone 2001 to 2003

Treesearch

Tracie Nelson; Richard Macedo; Bradley E. Valentine

2007-01-01

Timber harvest practices must address potential impacts to aquatic and riparian habitats. Stream shading and cool water temperature regimes are important to protect stream-dwelling organisms. We are examining riparian temperature regimes within the coastal redwood area of Mendocino County. Summer temperature gradients are being characterized along fifteen transects set...

Downhole material injector for lost circulation control

DOEpatents

Glowka, D.A.

1991-01-01

This invention is comprised of an apparatus and method for simultaneously and separately emplacing two streams of different materials through a drillstring in a borehole to a downhole location for lost circulation control. The two streams are mixed outside the drillstring at the desired downhole location and harden only after mixing for control of a lost circulation zone.

Downhole material injector for lost circulation control

DOEpatents

Glowka, D.A.

1994-09-06

Apparatus and method are disclosed for simultaneously and separately emplacing two streams of different materials through a drill string in a borehole to a downhole location for lost circulation control. The two streams are mixed outside the drill string at the desired downhole location and harden only after mixing for control of a lost circulation zone. 6 figs.

Streamside policies for headwater channels: an example considering debris flows in the Oregon coastal province.

Treesearch

K.M. Burnett; D.J. Miller

2007-01-01

Headwater streams differ in susceptibility to debris flows and thus in importance as wood and sediment sources for larger rivers. Identifying and appropriately managing the most susceptible headwater streams is of interest. We developed and illustrated a method to delineate alternative aquatic conservation emphasis zones (ACEZs) considering probabilities for traversal...

NPS pollution related to forest management activities in southern states

Treesearch

Johnny M. Grace

2004-01-01

Road systems on the nation’s public lands are vital links; providing access to perform management prescriptions, fire management, and recreation opportunities. Sediment movement downslope of forest road systems is a concern because these sediments have the potential to reach stream systems. Filter strips and stream side management zones (SMZs) are recommended and...

Efficacy of buffer zones in disconnecting roads and streams in the coastal plain

Treesearch

J.M. III Grace; E. Davis

2010-01-01

Established forest BMPs rely heavily on the forest floor to disconnect upslope activities from stream systems. Optimizing the buffer length required to negate the storm runoff contribution of upslope activities has been a point of interest for soil scientist, hydrologist, and conservation professionals for the last century. Minimum buffer lengths have been recommended...

Fire severity in intermittent stream drainages, Western Cascade Range, Oregon.

Treesearch

Jennifer E. Tollefson; Frederick J. Swanson; John H. Cissel

2004-01-01

We quantified fire severity patterns within intermittent stream drainages in a recently burned area of the central western Cascades, Oregon. Aerial photographs were used to estimate post fire live canopy cover within streamside and upland zones on the southeast and southwest-facing slopes of 33 watersheds. Live canopy cover did not differ significantly between...

Transient flow conditions in probabilistic wellhead protection: importance and ways to manage spatial and temporal uncertainty in capture zone delineation

NASA Astrophysics Data System (ADS)

Enzenhoefer, R.; Rodriguez-Pretelin, A.; Nowak, W.

2012-12-01

"From an engineering standpoint, the quantification of uncertainty is extremely important not only because it allows estimating risk but mostly because it allows taking optimal decisions in an uncertain framework" (Renard, 2007). The most common way to account for uncertainty in the field of subsurface hydrology and wellhead protection is to randomize spatial parameters, e.g. the log-hydraulic conductivity or porosity. This enables water managers to take robust decisions in delineating wellhead protection zones with rationally chosen safety margins in the spirit of probabilistic risk management. Probabilistic wellhead protection zones are commonly based on steady-state flow fields. However, several past studies showed that transient flow conditions may substantially influence the shape and extent of catchments. Therefore, we believe they should be accounted for in the probabilistic assessment and in the delineation process. The aim of our work is to show the significance of flow transients and to investigate the interplay between spatial uncertainty and flow transients in wellhead protection zone delineation. To this end, we advance our concept of probabilistic capture zone delineation (Enzenhoefer et al., 2012) that works with capture probabilities and other probabilistic criteria for delineation. The extended framework is able to evaluate the time fraction that any point on a map falls within a capture zone. In short, we separate capture probabilities into spatial/statistical and time-related frequencies. This will provide water managers additional information on how to manage a well catchment in the light of possible hazard conditions close to the capture boundary under uncertain and time-variable flow conditions. In order to save computational costs, we take advantage of super-positioned flow components with time-variable coefficients. We assume an instantaneous development of steady-state flow conditions after each temporal change in driving forces, following an idea by Festger and Walter, 2002. These quasi steady-state flow fields are cast into a geostatistical Monte Carlo framework to admit and evaluate the influence of parameter uncertainty on the delineation process. Furthermore, this framework enables conditioning on observed data with any conditioning scheme, such as rejection sampling, Ensemble Kalman Filters, etc. To further reduce the computational load, we use the reverse formulation of advective-dispersive transport. We simulate the reverse transport by particle tracking random walk in order to avoid numerical dispersion to account for well arrival times.

Detection of postseismic fault-zone collapse following the Landers earthquake

NASA Astrophysics Data System (ADS)

Massonnet, Didier; Thatcher, Wayne; Vadon, Hélèna

1996-08-01

STRESS changes caused by fault movement in an earthquake induce transient aseismic crustal movements in the earthquake source region that continue for months to decades following large events1-4. These motions reflect aseismic adjustments of the fault zone and/or bulk deformation of the surroundings in response to applied stresses2,5-7, and supply information regarding the inelastic behaviour of the Earth's crust. These processes are imperfectly understood because it is difficult to infer what occurs at depth using only surface measurements2, which are in general poorly sampled. Here we push satellite radar interferometry to near its typical artefact level, to obtain a map of the postseismic deformation field in the three years following the 28 June 1992 Landers, California earthquake. From the map, we deduce two distinct types of deformation: afterslip at depth on the fault that ruptured in the earthquake, and shortening normal to the fault zone. The latter movement may reflect the closure of dilatant cracks and fluid expulsion from a transiently over-pressured fault zone6-8.

LINKING STORMFLOW HYDROLOGY AND BIOTIC ASSESSMENTS IN SUBURBAN STREAMS

EPA Science Inventory

Suburban land development has been found to alter the hydrology of landscapes, changing streamflow transient behavior (i.e., "flashiness" of storm runoff response), which may contribute to some of the commonly observed and typically negative impacts of development on aquatic ecos...

Hydroecological Connections: Hyporheic Zone Weathering of Silicate Minerals Controls Diatom Biodiversity in Microbial Mats in Glacial Meltwater Streams of the McMurdo Dry Valleys, Antarctica

NASA Astrophysics Data System (ADS)

McKnight, D. M.; Dyson, I.; Esposito, R. M.; Gooseff, M. N.; Lyons, W. B.; Welch, K. A.

2015-12-01

The McMurdo Dry Valleys of Antarctica is comprised of alpine and terminal glaciers, large expanses of patterned ground, and ice-covered lakes in the valley floors, which are linked by glacial meltwater streams that flow during the austral summer. As part of the McMurdo Dry Valleys Long-Term Ecological research project, we have observed stream ecosystem response to a sustained 18 year cool period with low flows, which has been recently interrupted by three "flood events" during sunny, warm summers. Many of these streams contain thriving microbial mats comprised of cyanobacteria and endemic diatoms, the most diverse group of eukaryotic organisms in the valleys. Of the 45 diatom taxa, some common taxa are heavily silicified, Hantzschia amphioxys f. muelleri, while others are only lightly silicified. By comparing diatom communities in streams which flow every summer with those in streams that only flow during flood events, we found that hydrologic flow regime acts as a strong environmental filter on diatom community composition. Following the first flood event in 2001/02, mat biomass was two-fold lower due to scouring and recovered over several years, with lesser declines following the subsequent floods. In the longer streams, the diatom community composition remained stable through the flood events, whereas in two of the shorter streams, Green and Bowles Creeks, the diatom community shifted after the first flood event to a greater abundance of lightly silicified taxa. Water quality monitoring and reactive transport modeling have shown that rapid weathering of silicate minerals in the hyporheic zone accounts for the downstream increases in Si concentration which are observed in the longer streams. One mechanism driving this greater abundance of lightly silicified diatoms in shorter streams could be the greater dilution of the Si supply from hyporheic weathering in shorter streams under high flows. Given that the stream diatom community is well preserved in the 40,000-year sediment record from the receiving lake, greater understanding of hydrologic and biogeochemical controls on diatom community composition provides insight into the evolution of the lakes and geologic history of the region.

Applying electrical resistivity tomography and biological methods to assess the surface-groundwater interaction in two Mediterranean rivers (central Spain)

NASA Astrophysics Data System (ADS)

Iepure, Sanda; Gómez Ortiz, David; Lillo Ramos, Javier; Rasines Ladero, Ruben; Persoiu, Aurel

2014-05-01

Delineation of the extent of hyporheic zone (HZ) in river ecosystems is problematic due to the scarcity of spatial information about the structure of riverbed sediments and the magnitude and extent of stream interactions with the parafluvial and riparian zones. The several existing methods vary in both quality and quantity of information and imply the use of hydrogeological and biological methods. In the last decades, various non-invasive geophysical techniques were developed to characterise the streambed architecture and also to provide detailed spatial information on its vertical and horizontal continuity. All classes of techniques have their strengths and limitations; therefore, in order to assess their potential in delineating the lateral and vertical spatial extents of alluvial sediments, we have combined the near-surface images obtained by electrical resistivity tomography (ERT) with biological assessment of invertebrates in two Mediterranean lowland rivers from central Spain. We performed in situ imaging of the thickness and continuity of alluvial sediments under the riverbed and parafluvial zone during base-flow conditions (summer 2013 and winter 2014) at two different sites with distinct lithology along the Tajuña and Henares Rivers. ERT was performed by installing the electrodes (1 m spacing) on a 47 m long transect normal to the river channel using a Wener-Schlumberger array, across both the riparian zones and the river bed. Invertebrates were collected in the streambed from a depth of 20-40 cm, using the Bou-Rouch method, and from boreholes drilled to a depth of 1.5 m in the riparian zone. The ERT images obtained at site 1 (medium and coarse sand dominated lithology) shows resistivity values ranging from ~20 to 80 ohm•m for the in-stream sediments, indicating a permeable zone up to ~ 0.5 m thick and extending laterally for ca. 5 m from the channel. These sediments contribute to active surface/hyporheic water exchanges and to low water retention in stream sediments, as also indicated by the similar physico-chemical parameters in thw two zones, and the composition of hyporheic biota, dominated exclusively by surface-dwellers (e.g. Cladocera, Chironomidae, Cyclopoida (Microcyclops rubellus), Ostracoda (Pryonocypris zenkeri). A low resistivity (< 70 ohm•m) permeable zone located at 2.3 m depth bellow the streambed and unconnected with the river channel was also detected and associated with a shallow floodplain aquifer. In contrast, the resistivity image at site 2 (fine and very fine sand dominated lithology) shows a low permeability zone in the upper ~ 0.5 m of the profile, with resistivity values ranging from ~45 to 80 ohm•m, indicating a reduced HZ extension in both vertical and lateral dimensions. Here, both water retention and interaction between water and sediments are higher than at site 1 and consequently the water chemistry is distinct from that of the river channel (lower conductivity, temperature and dissolved oxygen in hyporheic waters). These features of the sedimentary layers create suitable habitats conditions in HZ for the development of a mixture of both epigean (e.g., Ostracoda (Darwinula stevensoni)) and hypogean stygobites dwellers (e.g., Cyclopoida (Acanthocyclops n. sp)). Furthermore, a low resistivity (< 30 ohm•m) high permeability zone was detected 2 m from the riverbed, at a depth of ca. 3 meters, being associated either to a suspended aquifer supplied with water from the terraces, or to water accumulation within tree roots, that might be temporary connected with the stream-hyporheic system. The two examples show that non-invasive ERT images and biological assessment provides complementary and valuable information about the characterisation of the sub-channel architecture and its potential connection with the parafluvial and riparian zones. Our results provide initial templates for high-resolution in situ studies with broad and integrated methods to identify the boundaries between hyporheic and parafluvial zones and the time-scale fluctuations in response to water exchanges with the surface stream.

Method for removing acid gases from a gaseous stream

DOEpatents

Gorin, Everett; Zielke, Clyde W.

1981-01-01

In a process for hydrocracking a heavy aromatic polynuclear carbonaceous feedstock containing reactive alkaline constituents to produce liquid hydrocarbon fuels boiling below about 475.degree. C. at atmospheric pressure by contacting the feedstock with hydrogen in the presence of a molten metal halide catalyst, thereafter separating a gaseous stream containing hydrogen, at least a portion of the hydrocarbon fuels and acid gases from the molten metal halide and regenerating the molten metal halide, thereby producing a purified molten metal halide stream for recycle to the hydrocracking zone, an improvement comprising; contacting the gaseous acid gas, hydrogen and hydrocarbon fuels-containing stream with the feedstock containing reactive alkaline constituents to remove acid gases from the acid gas containing stream. Optionally at least a portion of the hydrocarbon fuels are separated from gaseous stream containing hydrogen, hydrocarbon fuels and acid gases prior to contacting the gaseous stream with the feedstock.

Avian Communities of Streamside Zones in The Ouachita Mountains of Arkansas

Treesearch

Ronald E. Thill; Philip A. Tappe; M. Anthony Melchiors; T. Bently Wigley

2004-01-01

Linear strips of forest along intermittent and perennial streams, commonly called streamside zones (SZs), are frequently retained for watershed protection and wildlife habitat enhancement in southern pine forests when adjacent stands are harvested. However, little is known regarding wildlife communities associated with SZs, particularly in relation to varying SZ widths...

40 CFR 63.1365 - Test methods and initial compliance procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... temperature of 760 °C, the design evaluation must document that these conditions exist. (ii) For a combustion... autoignition temperature of the organic HAP, must consider the vent stream flow rate, and must establish the design minimum and average temperature in the combustion zone and the combustion zone residence time. (B...

40 CFR 63.1365 - Test methods and initial compliance procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... temperature of 760 °C, the design evaluation must document that these conditions exist. (ii) For a combustion... autoignition temperature of the organic HAP, must consider the vent stream flow rate, and must establish the design minimum and average temperature in the combustion zone and the combustion zone residence time. (B...

40 CFR 63.1365 - Test methods and initial compliance procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... temperature of 760 °C, the design evaluation must document that these conditions exist. (ii) For a combustion... autoignition temperature of the organic HAP, must consider the vent stream flow rate, and must establish the design minimum and average temperature in the combustion zone and the combustion zone residence time. (B...

40 CFR 63.1365 - Test methods and initial compliance procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... temperature of 760 °C, the design evaluation must document that these conditions exist. (ii) For a combustion... autoignition temperature of the organic HAP, must consider the vent stream flow rate, and must establish the design minimum and average temperature in the combustion zone and the combustion zone residence time. (B...

Patents - Harold Clayton Urey

Science.gov Websites

) US 2,947,472 CENTRIFUGE APPARATUS - Urey, H. C.; Skarstrom, C; Cohen, K; August 2, 1960 (to U. S Commission) This patent is concerned with a heavy water enriched uranium power reactor capable of producing reactor where the stream from both reaction zone and absorber zone is separated from the liquid and solid

Residual timber values within Piedmont streamside management zones of different widths and harvest levels

Treesearch

William A. Lakel; Wallace Aust; C. Andrew Dolloff; Patrick D. Keyser

2015-01-01

Forested streamside management zones (SMZs) provide numerous societal benefits including protection of water quality and enhancement of in-stream and riparian habitats. However, values of residual timber in SMZs are often ignored, yet maintenance of unnecessarily wide SMZs can potentially reduce merchantable timber. Therefore, forestland owners, managers, and logging...

Structure and composition of streamside management zones following reproduction cutting in shortleaf pine stands

Treesearch

Hal O. Liechty; James M. Guldin

2009-01-01

Streamside management zones (SMZs) in the Ouachita Mountains of Arkansas and Oklahoma are frequently established along headwater ephemeral and intermittent streams to protect water quality, provide wildlife habitat, and increase landscape diversity. To better understand the function of these riparian forest corridors, we characterized the tree density and composition,...

Coarse Particulate Organic Matter: Storage, Transport, and Retention

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

Tiegs, Scott; Lamberti, Gary A.; Entrekin, Sally A.

2017-08-01

Coarse particulate organic matter, or CPOM, is a basal energy and nutrient resource in many stream ecosystems and is provided by inputs from the riparian zone, incoming tributaries, and to a lesser extent from in-stream production. The ability of a stream to retain CPOM or slow its transport is critical to its consumption and assimilation by stream biota. In this chapter, we describe basic exercises to measure (1) the amount of CPOM in the streambed and (2) the retention of CPOM from standardized particle releases. We further describe advanced exercises that (1) experimentally enhance the retentiveness of a stream reachmore » and (2) measure organic carbon transport and turnover (i.e., spiraling) in the channel.« less

Coarse Particulate Organic Matter: Storage, Transport, and Retention

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

Tiegs, Scott; Lamberti, Gary A.; Entrekin, Sally A.

Coarse particulate organic matter, or CPOM, is a basal energy and nutrient resource in many stream ecosystems and is provided by inputs from the riparian zone, incoming tributaries, and to a lesser extent from in-stream production. The ability of a stream to retain CPOM or slow its transport is critical to its consumption and assimilation by stream biota. In this chapter, we describe basic exercises to measure (1) the amount of CPOM in the streambed and (2) the retention of CPOM from standardized particle releases. We further describe advanced exercises that (1) experimentally enhance the retentiveness of a stream reachmore » and (2) measure organic carbon transport and turnover (i.e., spiraling) in the channel.« less

The role of water exchange between a stream channel and its hyporheic zone in nitrogen cycling at the terrestrial-aquatic interface

USGS Publications Warehouse

Triska, F.J.; Duff, J.H.; Avanzino, R.J.

1993-01-01

The subsurface riparian zone was examined as an ecotone with two interfaces. Inland is a terrestrial boundary, where transport of water and dissolved solutes is toward the channel and controlled by watershed hydrology. Streamside is an aquatic boundary, where exchange of surface water and dissolved solutes is bi-directional and flux is strongly influenced by channel hydraulics. Streamside, bi-directional exchange of water was qualitatively defined using biologically conservative tracers in a third order stream. In several experiments, penetration of surface water extended 18 m inland. Travel time of water from the channel to bankside sediments was highly variable. Subsurface chemical gradients were indirectly related to the travel time. Sites with long travel times tended to be low in nitrate and DO (dissolved oxygen) but high in ammonium and DOC (dissolved organic carbon). Sites with short travel times tended to be high in nitrate and DO but low in ammonium and DOC. Ammonium concentration of interstitial water also was influenced by sorption-desorption processes that involved clay minerals in hyporheic sediments. Denitrification potential in subsurface sediments increased with distance from the channel, and was limited by nitrate at inland sites and by DO in the channel sediments. Conversely, nitrification potential decreased with distance from the channel, and was limited by DO at inland sites and by ammonium at channel locations. Advection of water and dissolved oxygen away from the channel resulted in an oxidized subsurface habitat equivalent to that previously defined as the hyporheic zone. The hyporheic zone is viewed as stream habitat because of its high proportion of surface water and the occurrence of channel organisms. Beyond the channel's hydrologic exchange zone, interstitial water is often chemically reduced. Interstitial water that has not previously entered the channel, groundwater, is viewed as a terrestrial component of the riparian ecotone. Thus, surface water habitats may extend under riparian vegetation, and terrestrial groundwater habitats may be found beneath the stream channel. ?? 1993 Kluwer Academic Publishers.

GCN/TAN: A Status Report

NASA Astrophysics Data System (ADS)

Barthelmy, Scott

2015-04-01

The Gamma-ray Coordinates Network / Transient Astronomy Network (GCN/TAN) is your one-stop shopping place for all transient astronomy. It collects nearly all the astrophysical transients from the missions (space-based and ground-based), puts them into a standard format, and distributes them to whomever wishes to receive them. This is all done autonomously (completely autonomous within GCN/TAN, and almost always autonomously within the producer end of operations). This automation means minimal time delays (<0.1 sec within GCN for socket-based distribution methods, and up to 30 sec for email-based which is dependant on the internet email protocol and the number of hops (both of which are out of the control of GCN/TAN). A status report on the current set of sources of transient information, plus recently-added and soon-to-be-added source will be given. Also, a standing request for GCN/TAN to incorporate your transient data stream; plus instruction for customers to receive GCN/TAAN Notice and Circular information.

Interpreting signals from astrophysical transient experiments.

PubMed

O'Brien, Paul T; Smartt, Stephen J

2013-06-13

Time-domain astronomy has come of age with astronomers now able to monitor the sky at high cadence, both across the electromagnetic spectrum and using neutrinos and gravitational waves. The advent of new observing facilities permits new science, but the ever-increasing throughput of facilities demands efficient communication of coincident detections and better subsequent coordination among the scientific community so as to turn detections into scientific discoveries. To discuss the revolution occurring in our ability to monitor the Universe and the challenges it brings, on 25-26 April 2012, a group of scientists from observational and theoretical teams studying transients met with representatives of the major international transient observing facilities at the Kavli Royal Society International Centre, UK. This immediately followed the Royal Society Discussion Meeting 'New windows on transients across the Universe' held in London. Here, we present a summary of the Kavli meeting at which the participants discussed the science goals common to the transient astronomy community and analysed how to better meet the challenges ahead as ever more powerful observational facilities come on stream.

Transient river response, captured by channel steepness and its concavity

NASA Astrophysics Data System (ADS)

Vanacker, Veerle; von Blanckenburg, Friedhelm; Govers, Gerard; Molina, Armando; Campforts, Benjamin; Kubik, Peter W.

2015-01-01

Mountain rivers draining tropical regions are known to be great conveyor belts carrying efficiently more than half of the global sediment flux to the oceans. Many tropical mountain areas are located in tectonically active belts where the hillslope and stream channel morphology are rapidly evolving in response to changes in base level. Here, we report basin-wide denudation rates for an east-west transect through the tropical Andes. Hillslope and channel morphology vary systematically from east to west, reflecting the transition from high relief, strongly dissected topography in the escarpment zones into relatively low relief topography in the inter-Andean valley. The spatial pattern of differential denudation rates reflects the transient adjustment of the landscape to rapid river incision following tectonic uplift and river diversion. In the inter-Andean valley, upstream of the wave of incision, slopes and river channels display a relatively smooth, concave-up morphology and denudation rates (time scale of 104-105 a) are consistently low (3 to 200 mm/ka). In contrast, slopes and river channels of rejuvenated basins draining the eastern cordillera are steep to very steep; and the studied drainage basins show a wide range of denudation rate values (60 to 400 mm/ka) that increase systematically with increasing basin mean slope gradient, channel steepness, and channel convexity. Drainage basins that are characterised by strong convexities in their river longitudinal profiles systematically have higher denudation rates. As such, this is one of the first studies that provides field-based evidence of a correlation between channel concavity and basin mean denudation rates, consistent with process-based fluvial incision models.

Hydrological and Geochemical Influences on the Dissolved Silica Concentrations in Natural Water in a Steep Headwater Catchment

NASA Astrophysics Data System (ADS)

Asano, Y.; Uchida, T.; Ohte, N.

2002-12-01

Dissolved silica has been used as a useful indicator of a chemical weathering in many geochemical studies in natural environment. Previous hydrological studies indicated that various hydrological processes affect the dissolution and precipitation of silica in hillslope and transport of this silica to stream; however, information is still limited to link this knowledge to understand geochemical processes. The observations of dissolved silica concentration in groundwater, spring and stream water was conducted at the unchannelled hillslope in the Tanakami Mountains of central Japan; (1) to clarify the effects of preferential flowpaths including lateral and vertical flow in soil layer and flow through bedrock fracture in the variation of dissolved silica concentration in runoff and groundwater, and (2) to isolate the effects of mixing of water from geochemically diverse water sources on the dissolved silica concentration. The mean dissolved silica concentrations in soil water at 40 cm depth and transient groundwater formed in upslope area were relatively constant independent of the variation in the new water ratio. The mean dissolved silica concentrations were similar regardless of the sampling depth in soil although the mean residence times of water increase with depth. These results indicated that dissolved silica concentrations in soil water and transient groundwater were defined almost independent of contact time of water with minerals. While the mean dissolved silica concentration in perennial groundwater, which was recharged by infiltrating water through soil and water emerging from bedrock in a area near to spring, was more than twice that of transient groundwater and the variation was relatively large. The mean dissolved silica concentration increased significantly at downslope from perennial groundwater, spring to the stream and the spring and stream concentrations also showed large variation. The dissolved silica concentrations of those perennial groundwater, the spring and the stream was controlled by the mixing of water from soil and bedrock. Our results demonstrated that in most areas of this headwater catchment, the preferential flowpaths give only small effect on dissolved silica concentrations. While in a small area (less than 10% of the longitudinal axis of the hollow near the spring), the dissolved silica concentration were controlled by the mixing of water from geochemically diverse water sources.

Stream dynamics between 1 AU and 2 AU: A detailed comparison of observations and theory

NASA Technical Reports Server (NTRS)

Burlaga, L. F.; Pizzo, V.; Lazarus, A.; Gazis, P. R.

1984-01-01

A radial alignment of three solar wind stream structures observed by IMP-7 and -8 (at 1.0 AU) and Voyager 1 and 2 (in the range 1.4 to 1.8 AU) in late 1977 is presented. It is demonstrated that several important aspects of the observed dynamical evolution can be both qualitatively and quantitatively described with a single-fluid 2-D MHD numerical model of quasi-steady corotating flow, including accurate prediction of: (1) the formation of a corotating shock pair at 1.75 AU in the case of a simple, quasi-steady stream; (2) the coalescence of the thermodynamic and magnetic structures associated with the compression regions of two neighboring, interacting, corotating streams; and (3) the dynamical destruction of a small (i.e., low velocity-amplitude, short spatial-scale) stream by its overtaking of a slower moving, high-density region associated with a preceding transient flow. The evolution of these flow systems is discussed in terms of the concepts of filtering and entrainment.

Morphology and sedimentation in Caribbean montane streams" examples from Jamaica and Puerto Rico

Treesearch

R. Ahmad; F.N. Scatena; A Gupta

1993-01-01

This paper presents a summary description of the morphology, sedimentation, and behaviour of the montane streams of eastern Jamaica and eastern Puerto Rico. The area is located within a 200 km wide seismically active zone of Neogene left-lateral strike-slip deformation which defines the plate boundary between the Caribbean and North American Plates. Tropical storms,...

A temporal stable isotopic (d18O, dD, d-excess) comparison in glacier meltwater streams, Taylor Valley, Antarctica

USDA-ARS?s Scientific Manuscript database

In this paper, we describe the importance of hyporheic dynamics within Andersen Creek and Von Guerard Stream, Taylor Valley, Antarctica, from the 2010-11 melt season using natural tracers. Water collection started at flow onset and continued, with weekly hyporheic zone sampling. The water d18O and d...

Soil and water characteristics in restored canebrake and forest riparian zones

Treesearch

Danielle M. Andrews; Christopher D. Barton; Randy Kolka; Charles C. Rhoades; Adam J. Dattilo

2011-01-01

The degradation of streams has been widespread in the United States. In Kentucky, for instance, almost all of its large streams have been impounded or channelized. A restoration project was initiated in a channelized section of Wilson Creek (Nelson Co., Kentucky) to return its predisturbance meandering configuration. A goal of the project was to restore the native...

Chapter 2: Stream and riparian habitat analysis and monitoring with a high-resolution terrestrial-aquatic LiDAR

Treesearch

Jim McKean; Dan Isaak; Wayne Wright

2009-01-01

Management of aquatic habitat in streams requires description of conditions and processes both inside the channels and in the adjacent riparian zones. Biological and physical processes in these environments operate over a range of spatial scales from microhabitat to whole river networks. Limitations of previous survey technologies have focused management and research...

Subsurface transport of orthophosphate in five agricultural watersheds, USA

USGS Publications Warehouse

Domagalski, Joseph L.; Johnson, Henry M.

2011-01-01

Concentrations of dissolved orthophosphate (ortho P) in the unsaturated zone, groundwater, tile drains, and groundwater/stream water interfaces were assessed in five agricultural watersheds to determine the potential for subsurface transport. Concentrations of iron oxides were measured in the aquifer material and adsorption of ortho P on oxide surfaces was assessed by geochemical modeling. Attenuation of ortho P in these aquifers was attributed primarily to sorption onto iron oxides, and in one location onto clay minerals. Only one location showed a clear indication of phosphorus transport to a stream from groundwater discharge, although groundwater did contribute to the stream load elsewhere. Subsurface ortho P movement at a site in California resulted in a plume down gradient from orchards, which was attenuated by a 200 m thick riparian zone with natural vegetation. Iron oxides had an effect on phosphorus movement and concentrations at all locations, and groundwater chemistry, especially pH, exerted a major control on the amount of phosphorus adsorbed. Groundwater pH at a site in Maryland was below 5 and that resulted in complete sequestration of phosphorus and no movement toward the stream. Geochemical modeling indicated that as the surfaces approached saturation, groundwater concentrations of ortho P rise rapidly.

Role of streams in myxobacteria aggregate formation

NASA Astrophysics Data System (ADS)

Kiskowski, Maria A.; Jiang, Yi; Alber, Mark S.

2004-10-01

Cell contact, movement and directionality are important factors in biological development (morphogenesis), and myxobacteria are a model system for studying cell-cell interaction and cell organization preceding differentiation. When starved, thousands of myxobacteria cells align, stream and form aggregates which later develop into round, non-motile spores. Canonically, cell aggregation has been attributed to attractive chemotaxis, a long range interaction, but there is growing evidence that myxobacteria organization depends on contact-mediated cell-cell communication. We present a discrete stochastic model based on contact-mediated signaling that suggests an explanation for the initialization of early aggregates, aggregation dynamics and final aggregate distribution. Our model qualitatively reproduces the unique structures of myxobacteria aggregates and detailed stages which occur during myxobacteria aggregation: first, aggregates initialize in random positions and cells join aggregates by random walk; second, cells redistribute by moving within transient streams connecting aggregates. Streams play a critical role in final aggregate size distribution by redistributing cells among fewer, larger aggregates. The mechanism by which streams redistribute cells depends on aggregate sizes and is enhanced by noise. Our model predicts that with increased internal noise, more streams would form and streams would last longer. Simulation results suggest a series of new experiments.

Estimating the timing and location of shallow rainfall-induced landslides using a model for transient, unsaturated infiltration

USGS Publications Warehouse

Baum, Rex L.; Godt, Jonathan W.; Savage, William Z.

2010-01-01

Shallow rainfall-induced landslides commonly occur under conditions of transient infiltration into initially unsaturated soils. In an effort to predict the timing and location of such landslides, we developed a model of the infiltration process using a two-layer system that consists of an unsaturated zone above a saturated zone and implemented this model in a geographic information system (GIS) framework. The model links analytical solutions for transient, unsaturated, vertical infiltration above the water table to pressure-diffusion solutions for pressure changes below the water table. The solutions are coupled through a transient water table that rises as water accumulates at the base of the unsaturated zone. This scheme, though limited to simplified soil-water characteristics and moist initial conditions, greatly improves computational efficiency over numerical models in spatially distributed modeling applications. Pore pressures computed by these coupled models are subsequently used in one-dimensional slope-stability computations to estimate the timing and locations of slope failures. Applied over a digital landscape near Seattle, Washington, for an hourly rainfall history known to trigger shallow landslides, the model computes a factor of safety for each grid cell at any time during a rainstorm. The unsaturated layer attenuates and delays the rainfall-induced pore-pressure response of the model at depth, consistent with observations at an instrumented hillside near Edmonds, Washington. This attenuation results in realistic estimates of timing for the onset of slope instability (7 h earlier than observed landslides, on average). By considering the spatial distribution of physical properties, the model predicts the primary source areas of landslides.

Numerical investigation of transient behaviour of the recuperative heat exchanger in a MR J-T cryocooler using different heat transfer correlations

NASA Astrophysics Data System (ADS)

Damle, R. M.; Ardhapurkar, P. M.; Atrey, M. D.

2016-12-01

In J-T cryocoolers operating with mixed refrigerants (nitrogen-hydrocarbons), the recuperative heat exchange takes place under two-phase conditions. Simultaneous boiling of the low pressure stream and condensation of the high pressure stream results in higher heat transfer coefficients. The mixture composition, operating conditions and the heat exchanger design are crucial for obtaining the required cryogenic temperature. In this work, a one-dimensional transient algorithm is developed for the simulation of the two-phase heat transfer in the recuperative heat exchanger of a mixed refrigerant J-T cryocooler. Modified correlation is used for flow boiling of the high pressure fluid while different condensation correlations are employed with and without the correction for the low pressure fluid. Simulations are carried out for different mixture compositions and numerical predictions are compared with the experimental data. The overall heat transfer is predicted reasonably well and the qualitative trends of the temperature profiles are also captured by the developed numerical model.

Transient electrokinetic transport in a finite length microchannel: currents, capacitance, and an electrical analogy.

PubMed

Mansouri, Ali; Bhattacharjee, Subir; Kostiuk, Larry W

2007-11-08

Numerical simulations with the fluid mechanics based on the unsteady Navier-Stokes equations and the Poisson-Nernst-Planck formulation of electrostatics and ion transport were used to explore the transient transport of charge through a finite length cylindrical microchannel that is driven by a pressure difference. The evolution of the transcapillary potential from a no-flow equilibrium to the steady-state-steady-flow streaming potential was analyzed by following the convection, migration, and net currents. Observations of the unsteady characteristics of the streaming current, electrical resistance, and capacitance led to an electrical analogy. This electrical analogy was made from a current source (to represent convection current), which was placed in parallel with a capacitor (to allow the accumulation of charge) and a resistor (to permit a migration current). A parametric study involving a range of geometries, fluid mechanics, electrostatics, and mass transfer states allowed predictive submodels for the current source, capacitor, and resistor to be developed based on a dimensional analysis.

The Astrophysical Multimessenger Observatory Network (AMON)

NASA Technical Reports Server (NTRS)

Smith. M. W. E.; Fox, D. B.; Cowen, D. F.; Meszaros, P.; Tesic, G.; Fixelle, J.; Bartos, I.; Sommers, P.; Ashtekar, Abhay; Babu, G. Jogesh;

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

Yan, Rui; Praggastis, Brenda L.; Smith, William P.

While streaming data have become increasingly more popular in business and research communities, semantic models and processing software for streaming data have not kept pace. Traditional semantic solutions have not addressed transient data streams. Semantic web languages (e.g., RDF, OWL) have typically addressed static data settings and linked data approaches have predominantly addressed static or growing data repositories. Streaming data settings have some fundamental differences; in particular, data are consumed on the fly and data may expire. Stream reasoning, a combination of stream processing and semantic reasoning, has emerged with the vision of providing "smart" processing of streaming data. C-SPARQLmore » is a prominent stream reasoning system that handles semantic (RDF) data streams. Many stream reasoning systems including C-SPARQL use a sliding window and use data arrival time to evict data. For data streams that include expiration times, a simple arrival time scheme is inadequate if the window size does not match the expiration period. In this paper, we propose a cache-enabled, order-aware, ontology-based stream reasoning framework. This framework consumes RDF streams with expiration timestamps assigned by the streaming source. Our framework utilizes both arrival and expiration timestamps in its cache eviction policies. In addition, we introduce the notion of "semantic importance" which aims to address the relevance of data to the expected reasoning, thus enabling the eviction algorithms to be more context- and reasoning-aware when choosing what data to maintain for question answering. We evaluate this framework by implementing three different prototypes and utilizing five metrics. The trade-offs of deploying the proposed framework are also discussed.« less

Technical Note: Approximate solution of transient drawdown for constant-flux pumping at a partially penetrating well in a radial two-zone confined aquifer

NASA Astrophysics Data System (ADS)

Huang, C.-S.; Yang, S.-Y.; Yeh, H.-D.

2015-03-01

An aquifer consisting of a skin zone and a formation zone is considered as a two-zone aquifer. Existing solutions for the problem of constant-flux pumping (CFP) in a two-zone confined aquifer involve laborious calculation. This study develops a new approximate solution for the problem based on a mathematical model including two steady-state flow equations with different hydraulic parameters for the skin and formation zones. A partially penetrating well may be treated as the Neumann condition with a known flux along the screened part and zero flux along the unscreened part. The aquifer domain is finite with an outer circle boundary treated as the Dirichlet condition. The steady-state drawdown solution of the model is derived by the finite Fourier cosine transform. Then, an approximate transient solution is developed by replacing the radius of the boundary in the steady-state solution with an analytical expression for a dimensionless time-dependent radius of influence. The approximate solution is capable of predicting good temporal drawdown distributions over the whole pumping period except at the early stage. A quantitative criterion for the validity of neglecting the vertical flow component due to a partially penetrating well is also provided. Conventional models considering radial flow without the vertical component for the CFP have good accuracy if satisfying the criterion.

Waste Load Allocation for Conservative Substances to Protect Aquatic Organisms

NASA Astrophysics Data System (ADS)

Hutcheson, M. R.

1992-01-01

A waste load allocation process is developed to determine the maximum effluent concentration of a conservative substance that will not harm fish and wildlife propagation. If this concentration is not exceeded in the effluent, the acute toxicity criterion will not be violated in the receiving stream, and the chronic criterion will not be exceeded in the zone of passage, defined in many state water quality standards to allow the movement of aquatic organisms past a discharge. Considerable simplification of the concentration equation, which is the heart of any waste load allocation, is achieved because it is based on the concentration in the receiving stream when the concentration gradient on the zone of passage boundary is zero. Consequently, the expression obtained for effluent concentration is independent of source location or stream morphology. Only five independent variables, which are routinely available to regulatory agencies, are required to perform this allocation. It aids in developing permit limits which are protective without being unduly restrictive or requiring large expenditures of money and manpower on field investigations.

Aufeis accumulations in stream bottoms in arctic and subarctic environments as a possible indicator of geologic structure: Chapter F in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

USGS Publications Warehouse

Wanty, Richard B.; Wang, Bronwen; Vohden, Jim; Day, Warren C.; Gough, Larry P.; Gough, Larry P.; Day, Warren C.

2007-01-01

The thickest (>3 meters) and most extensive aufeis (100’s of meters to kilometers along valleys) coincided with locations of laterally extensive (>5 kilometers) mapped high-angle brittle fault zones, suggesting that the fault zones are hydraulically conductive. Additional evidence of water flow is provided by observed changes in stream-water chemistry in reaches in which aufeis forms, despite a lack of surface tributaries. Minor or no aufeis was observed in many other drainage valleys where no laterally extensive structures have been mapped, implying that aufeis formation results from more than a topographic effect or discharge from bank storage. Thus, the presence of thick, laterally extensive aufeis in highgradient streams may be a useful aid to geologic structural mapping in arctic and subarctic climates.

Headwater Influences on Downstream Water Quality

PubMed Central

Oakes, Robert M.

2007-01-01

We investigated the influence of riparian and whole watershed land use as a function of stream size on surface water chemistry and assessed regional variation in these relationships. Sixty-eight watersheds in four level III U.S. EPA ecoregions in eastern Kansas were selected as study sites. Riparian land cover and watershed land use were quantified for the entire watershed, and by Strahler order. Multiple regression analyses using riparian land cover classifications as independent variables explained among-site variation in water chemistry parameters, particularly total nitrogen (41%), nitrate (61%), and total phosphorus (63%) concentrations. Whole watershed land use explained slightly less variance, but riparian and whole watershed land use were so tightly correlated that it was difficult to separate their effects. Water chemistry parameters sampled in downstream reaches were most closely correlated with riparian land cover adjacent to the smallest (first-order) streams of watersheds or land use in the entire watershed, with riparian zones immediately upstream of sampling sites offering less explanatory power as stream size increased. Interestingly, headwater effects were evident even at times when these small streams were unlikely to be flowing. Relationships were similar among ecoregions, indicating that land use characteristics were most responsible for water quality variation among watersheds. These findings suggest that nonpoint pollution control strategies should consider the influence of small upland streams and protection of downstream riparian zones alone is not sufficient to protect water quality. PMID:17999108

Diel fluctuations of viscosity-driven riparian inflow affect streamflow DOC concentration

NASA Astrophysics Data System (ADS)

Schwab, Michael P.; Klaus, Julian; Pfister, Laurent; Weiler, Markus

2018-04-01

Diel fluctuations of stream water DOC concentrations are generally explained by a complex interplay of different instream processes. We measured the light absorption spectrum of water and DOC concentrations in situ and with high frequency by means of a UV-Vis spectrometer during 18 months at the outlet of a forested headwater catchment in Luxembourg (0.45 km2). We generally observed diel DOC fluctuations with a maximum in the afternoon during days that were not affected by rainfall-runoff events. We identified an increased inflow of terrestrial DOC to the stream in the afternoon, causing the DOC maxima in the stream. The terrestrial origin of the DOC was derived from the SUVA-254 (specific UV absorbance at 254 nm) index, which is a good indicator for the aromaticity of DOC. In the studied catchment, the most likely process that can explain the diel DOC input variations towards the stream is the so-called viscosity effect. The water temperature in the upper parts of the saturated riparian zone is increasing during the day, leading to a lower viscosity and therefore a higher hydraulic conductivity. Consequently, more water from areas that are rich in terrestrial DOC passes through the saturated riparian zone and contributes to streamflow in the afternoon. We believe that not only diel instream processes, but also viscosity-driven diel fluctuations of terrestrial DOC input should be considered to explain diel DOC patterns in streams.

Spatial and temporal variability of macroinvertebrates in spawning and non-spawning habitats during a salmon run in Southeast Alaska.

PubMed

Campbell, Emily Y; Merritt, Richard W; Cummins, Kenneth W; Benbow, M Eric

2012-01-01

Spawning salmon create patches of disturbance through redd digging which can reduce macroinvertebrate abundance and biomass in spawning habitat. We asked whether displaced invertebrates use non-spawning habitats as refugia in streams. Our study explored how the spatial and temporal distribution of macroinvertebrates changed during a pink salmon (Oncorhynchus gorbuscha) spawning run and compared macroinvertebrates in spawning (riffle) and non-spawning (refugia) habitats in an Alaskan stream. Potential refugia included: pools, stream margins and the hyporheic zone, and we also sampled invertebrate drift. We predicted that macroinvertebrates would decline in riffles and increase in drift and refugia habitats during salmon spawning. We observed a reduction in the density, biomass and taxonomic richness of macroinvertebrates in riffles during spawning. There was no change in pool and margin invertebrate communities, except insect biomass declined in pools during the spawning period. Macroinvertebrate density was greater in the hyporheic zone and macroinvertebrate density and richness increased in the drift during spawning. We observed significant invertebrate declines within spawning habitat; however in non-spawning habitat, there were less pronounced changes in invertebrate density and richness. The results observed may be due to spawning-related disturbances, insect phenology, or other variables. We propose that certain in-stream habitats could be important for the persistence of macroinvertebrates during salmon spawning in a Southeast Alaskan stream.

Spatial and Temporal Variability of Macroinvertebrates in Spawning and Non-Spawning Habitats during a Salmon Run in Southeast Alaska

PubMed Central

Campbell, Emily Y.; Merritt, Richard W.; Cummins, Kenneth W.; Benbow, M. Eric

2012-01-01

Spawning salmon create patches of disturbance through redd digging which can reduce macroinvertebrate abundance and biomass in spawning habitat. We asked whether displaced invertebrates use non-spawning habitats as refugia in streams. Our study explored how the spatial and temporal distribution of macroinvertebrates changed during a pink salmon (Oncorhynchus gorbuscha) spawning run and compared macroinvertebrates in spawning (riffle) and non-spawning (refugia) habitats in an Alaskan stream. Potential refugia included: pools, stream margins and the hyporheic zone, and we also sampled invertebrate drift. We predicted that macroinvertebrates would decline in riffles and increase in drift and refugia habitats during salmon spawning. We observed a reduction in the density, biomass and taxonomic richness of macroinvertebrates in riffles during spawning. There was no change in pool and margin invertebrate communities, except insect biomass declined in pools during the spawning period. Macroinvertebrate density was greater in the hyporheic zone and macroinvertebrate density and richness increased in the drift during spawning. We observed significant invertebrate declines within spawning habitat; however in non-spawning habitat, there were less pronounced changes in invertebrate density and richness. The results observed may be due to spawning-related disturbances, insect phenology, or other variables. We propose that certain in-stream habitats could be important for the persistence of macroinvertebrates during salmon spawning in a Southeast Alaskan stream. PMID:22745724

Product-to-parent reversion increases ecosystem exposure to and environmental persistence of 17α-trenbolone

NASA Astrophysics Data System (ADS)

Ward, Adam; Cwiertny, David; Kolodziej, Edward; Brehm, Colleen

2016-04-01

The product-to-parent reversion of metabolites of trenbolone acetate (TBA), a steroidal growth promoter used widely in beef cattle production, was recently observed to occur in environmental waters. The rapid forward reaction is by direct photolysis (i.e., photohydration), with the much slower reversion reaction occurring via dehydration in the dark. The objective of this study is to quantify the potential effect of this newly discovered reversible process on TBA metabolite concentrations and total bioactivity exposure in fluvial systems. Here, we demonstrate increased persistence of TBA metabolites in the stream and hyporheic zone due to the reversion process, increasing chronic and acute exposure to these endocrine-active compounds along a stream. The perpetually dark hyporheic zone is a key location for reversion in the system, ultimately providing a source of the parent compound to the stream and increasing mean in-stream concentration of 17α-trenbolone (17α-TBOH) by 40% of the input concentration under representative fluvial conditions. We demonstrate generalized cases for prediction of exposure for species with product-to-parent reversion in stream-hyporheic systems. Recognizing this risk, regulatory frameworks for compounds undergoing product-to-parent reversion will require new approaches for assessing total exposure to bioactive compounds. We discuss the role of regulating "joint" or "mixture" bioactivity as an emerging paradigm for more meaningful management of micropollutants.

Dissolved oxygen concentration profiles in the hyporheic zone through the use of a high density fiber optic measurement network

NASA Astrophysics Data System (ADS)

Reeder, W. J.; Quick, A. M.; Farrell, T. B.; Benner, S. G.; Feris, K. P.; Tonina, D.

2013-12-01

The hyporheic zone (HZ) is a potentially important source of the potent greenhouse gas, nitrous oxide (N2O); stream processes may account for up to 10% of global anthropogenic N2O emissions. However, mechanistic understanding and predictive quantification of this gas flux is hampered by complex temporally and spatially variable interactions between flow dynamics and biogeochemical processes. Reactive inorganic nitrogen (Nr) is typically present at low concentrations in natural stream waters, but many rural and urban streams suffer from an excess of Nr, typically in the form of ammonium (NH4+) and nitrate (NO3-). These reactive species are either assimilated by living biomass or transformed by microbial processes. The two primary microbial transformations of Nr are nitrification (NH4+ to NO3-) and denitrification (NO3- to N2). Denitrification, which occurs almost exclusively in the anoxic zone of the HZ, permanently removes between 30-70% of all Nr entering streams, other mechanisms may retain nitrogen. The mass transport of reactive species (i.e. O2, NO3- and N2O) by hyporheic flow strongly influences reaction rates, residence times, and subsequent N2O flux. By extension, stream flow and channel morphology presumably control, and may be effective predictors of, N2O generation rates. By recreating the stream processes in the University of Idaho flume, we are able to control the bed morphology, fluxes and residence times through the HZ and concentrations of Nr from exogenous (stream water) and endogenous (organic material in the streambed) sources. For the present experiment, the flume was divided into three streams, each with different morphologies (3, 6 and 9cm dunes) and all using the same source water. Stream water for this first experimental phase had no significant loading of Nr. As such, all reaction products were the result of endogenous sources of Nr. To measure dissolved oxygen (DO) concentrations we deployed 120 channels of a novel, fiber-optic optode system which was coupled with an advanced optical multiplexer that allowed us to cycle continuously through all 120 channels. Using this approach, we were able to accurately map the evolution and extent of the anoxic regions within the HZ and demonstrate that bed morphology exhibits significant control over residence times and the spatial temporal evolution of the anoxic region. In addition to the DO measurements, we deployed 240 Rhizon water samplers to extract pore water, which we used to measure Nr and N2O concentrations, and an ion Clark-type electrode sensor to measure N2O concentrations at the streambed surface (results discussed separately). Integrating these various results will allow us to refine the existing models for N2O emissions from urban and rural streams.

Free-radicals aided combustion with scramjet applications

NASA Technical Reports Server (NTRS)

Yang, Yongsheng; Kumar, Ramohalli

1992-01-01

Theoretical and experimental investigations aimed at altering 'nature-prescribed' combustion rates in hydrogen/hydrocarbon reactions with (enriched) air are presented. The intent is to anchor flame zones in supersonic streams, and to ensure proper and controllable complete combustion in scramjets. The diagnostics are nonintrusive through IR thermograms and acoustic emissions in the control and free-radicals altered flame zones.

Overstory and regeneration dynamics in riparian management zones of northern Minnesota forested watersheds

Treesearch

Brian. Palik; Michelle. Martin; Erik. Zenner; Charles. Blinn; Randall. Kolka

2012-01-01

We quantified tree regeneration under different riparian management zone (RMZ) treatments along first-order streams in Minnesota, USA. A primary objective for long-term management of RMZs in the study region is to maintain some tree cover and promote establishment of later successional tree species and conifers. We also compared regeneration response to contrasting...

40 CFR 63.1257 - Test methods and compliance procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

...)(2), or 63.1256(h)(2)(i)(C) with a minimum residence time of 0.5 seconds and a minimum temperature of... temperature of the organic HAP, must consider the vent stream flow rate, and must establish the design minimum and average temperature in the combustion zone and the combustion zone residence time. (B) For a...

40 CFR 63.1257 - Test methods and compliance procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

...)(2), or 63.1256(h)(2)(i)(C) with a minimum residence time of 0.5 seconds and a minimum temperature of... temperature of the organic HAP, must consider the vent stream flow rate, and must establish the design minimum and average temperature in the combustion zone and the combustion zone residence time. (B) For a...

40 CFR 63.1257 - Test methods and compliance procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

...)(2), or 63.1256(h)(2)(i)(C) with a minimum residence time of 0.5 seconds and a minimum temperature of... temperature of the organic HAP, must consider the vent stream flow rate, and must establish the design minimum and average temperature in the combustion zone and the combustion zone residence time. (B) For a...

Ecological Exposure Research: Water

EPA Pesticide Factsheets

Overview of ecological exposure water research, including invasive species, Functional Process Zones (FPZs), biomarkers, pharmaceuticals in water, headwater streams, DNA barcoding, wetland ecosystem services, and sediment remediation.

Beaver Colony Density Trends on the Chequamegon-Nicolet National Forest, 1987 – 2013

PubMed Central

Ribic, Christine A.; Donner, Deahn M.; Beck, Albert J.; Reinecke, Sue; Eklund, Dan

2017-01-01

The North American beaver (Castor canadensis) is a managed species in the United States. In northern Wisconsin, as part of the state-wide beaver management program, the Chequamegon-Nicolet National Forest removes beavers from targeted trout streams on U.S. Forest Service lands. However, the success of this management program has not been evaluated. Targeted removals comprise only 3% of the annual beaver harvest, a level of effort that may not affect the beaver population. We used colony location data along Forest streams from 1987–2013 (Nicolet, northeast Wisconsin) and 1997–2013 (Chequamegon, northwest Wisconsin) to assess trends in beaver colony density on targeted trout streams compared to non-targeted streams. On the Chequamegon, colony density on non-targeted trout and non-trout streams did not change over time, while colony density on targeted trout streams declined and then stabilized. On the Nicolet, beaver colony density decreased on both non-targeted streams and targeted trout streams. However, colony density on targeted trout streams declined faster. The impact of targeted trapping was similar across the two sides of the Forest (60% reduction relative to non-targeted trout streams). Exploratory analyses of weather influences found that very dry conditions and severe winters were associated with transient reductions in beaver colony density on non-targeted streams on both sides of the Forest. Our findings may help land management agencies weigh more finely calibrated beaver control measures against continued large-scale removal programs. PMID:28081271

Beaver Colony Density Trends on the Chequamegon-Nicolet National Forest, 1987 - 2013.

PubMed

Ribic, Christine A; Donner, Deahn M; Beck, Albert J; Rugg, David J; Reinecke, Sue; Eklund, Dan

2017-01-01

The North American beaver (Castor canadensis) is a managed species in the United States. In northern Wisconsin, as part of the state-wide beaver management program, the Chequamegon-Nicolet National Forest removes beavers from targeted trout streams on U.S. Forest Service lands. However, the success of this management program has not been evaluated. Targeted removals comprise only 3% of the annual beaver harvest, a level of effort that may not affect the beaver population. We used colony location data along Forest streams from 1987-2013 (Nicolet, northeast Wisconsin) and 1997-2013 (Chequamegon, northwest Wisconsin) to assess trends in beaver colony density on targeted trout streams compared to non-targeted streams. On the Chequamegon, colony density on non-targeted trout and non-trout streams did not change over time, while colony density on targeted trout streams declined and then stabilized. On the Nicolet, beaver colony density decreased on both non-targeted streams and targeted trout streams. However, colony density on targeted trout streams declined faster. The impact of targeted trapping was similar across the two sides of the Forest (60% reduction relative to non-targeted trout streams). Exploratory analyses of weather influences found that very dry conditions and severe winters were associated with transient reductions in beaver colony density on non-targeted streams on both sides of the Forest. Our findings may help land management agencies weigh more finely calibrated beaver control measures against continued large-scale removal programs.

Beaver colony density trends on the Chequamegon-Nicolet National Forest, 1987 – 2013

USGS Publications Warehouse

Ribic, Christine; Donner, Deahn M.; Beck, Albert J.; Rugg, David J.; Reinecke, Sue; Eklund, Dan

2017-01-01

The North American beaver (Castor canadensis) is a managed species in the United States. In northern Wisconsin, as part of the state-wide beaver management program, the Chequamegon-Nicolet National Forest removes beavers from targeted trout streams on U.S. Forest Service lands. However, the success of this management program has not been evaluated. Targeted removals comprise only 3% of the annual beaver harvest, a level of effort that may not affect the beaver population. We used colony location data along Forest streams from 1987–2013 (Nicolet, northeast Wisconsin) and 1997–2013 (Chequamegon, northwest Wisconsin) to assess trends in beaver colony density on targeted trout streams compared to non-targeted streams. On the Chequamegon, colony density on non-targeted trout and non-trout streams did not change over time, while colony density on targeted trout streams declined and then stabilized. On the Nicolet, beaver colony density decreased on both non-targeted streams and targeted trout streams. However, colony density on targeted trout streams declined faster. The impact of targeted trapping was similar across the two sides of the Forest (60% reduction relative to non-targeted trout streams). Exploratory analyses of weather influences found that very dry conditions and severe winters were associated with transient reductions in beaver colony density on non-targeted streams on both sides of the Forest. Our findings may help land management agencies weigh more finely calibrated beaver control measures against continued large-scale removal programs.

An analytical solution for predicting the transient seepage from a subsurface drainage system

NASA Astrophysics Data System (ADS)

Xin, Pei; Dan, Han-Cheng; Zhou, Tingzhang; Lu, Chunhui; Kong, Jun; Li, Ling

2016-05-01

Subsurface drainage systems have been widely used to deal with soil salinization and waterlogging problems around the world. In this paper, a mathematical model was introduced to quantify the transient behavior of the groundwater table and the seepage from a subsurface drainage system. Based on the assumption of a hydrostatic pressure distribution, the model considered the pore-water flow in both the phreatic and vadose soil zones. An approximate analytical solution for the model was derived to quantify the drainage of soils which were initially water-saturated. The analytical solution was validated against laboratory experiments and a 2-D Richards equation-based model, and found to predict well the transient water seepage from the subsurface drainage system. A saturated flow-based model was also tested and found to over-predict the time required for drainage and the total water seepage by nearly one order of magnitude, in comparison with the experimental results and the present analytical solution. During drainage, a vadose zone with a significant water storage capacity developed above the phreatic surface. A considerable amount of water still remained in the vadose zone at the steady state with the water table situated at the drain bottom. Sensitivity analyses demonstrated that effects of the vadose zone were intensified with an increased thickness of capillary fringe, capillary rise and/or burying depth of drains, in terms of the required drainage time and total water seepage. The analytical solution provides guidance for assessing the capillary effects on the effectiveness and efficiency of subsurface drainage systems for combating soil salinization and waterlogging problems.

The Stream Depletion Model Paradox and a First Solution

NASA Astrophysics Data System (ADS)

Malama, B.

2017-12-01

Hitherto, stream depletion models available in the hydrogeology literature use the xed head Dirichletboundary condition at the stream, and as such do not account for groundwater pumping induced streamdrawdown. They simply treat stream depletion as the decrease in stream discharge due capture by pumping,the groundwater that would discharge to the stream without pumping. We refer to this model predictedstream depletion without stream drawdown as the depletion paradox. It is intuitively clear, however, thatadverse impacts of long-term groundwater abstraction in the neighborhood of a stream include streamdrawdown, which has led to many a dry streambed in the American west and other arid regions. Streamdrawdown is especially acute for low stream ows. A mathematical model that allows for transient streamdrawdown is proposed by introducing the concept of stream storage. The model simply extends the constanthead model at the stream by including a mass-balance condition. The model is developed for a fullypenetrating stream and groundwater abstraction in a conned aquifer. The dependence of model predictedstream depletion and drawdown on stream storage, streambed conductance, aquifer anisotropy, and radialdistance to the pumping well is evaluated. The model is shown to reduce to that of Hantush in the limitas stream storage becomes innitely large, and to the Theis solution with a no- ow boundary at the streamlocation when stream storage gets vanishingly small. The results suggest that using xed stream stage modelsleads to an underestimation the late-time aquifer drawdwon response to pumping in the neighborhood of astream because it correspond to innite stream storage. This is especially critical for management of surfacewater and groundwater resources in systems subjected to prolonged groundwater abstraction and measurablestream drawdown. The model also shows a maximum stream depletion rate, beyond which stream ow to thewell diminishes and eventually vanishes. This suggests that models with xed stream stage overestimate theavailable groundwater supply from streams to pumping wells because of the inherent assumption of innitestream storage. This has implications for sustainable management of groundwater resources near streams.

The volume of fine sediment in pools: An index of sediment supply in gravel-bed streams

Treesearch

Thomas E. Lisle; Sue Hilton

1992-01-01

Abstract - During waning flood flows in gravel-bed streams, fine-grained bedload sediment (sand and fine gravel) is commonly winnowed from zones of high shear stress, such as riffles, and deposited in pools, where it mantles an underlying coarse layer. As sediment load increases, more fine sediment becomes availabe to fill pools. The volume of fine sediment in pools...

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.

Use of standardized visual assessments of riparian and stream condition to manage riparian bird habitat in eastern Oregon.

PubMed

Cooke, Hilary A; Zack, Steve

2009-07-01

The importance of riparian vegetation to support stream function and provide riparian bird habitat in semiarid landscapes suggests that standardized assessment tools that include vegetation criteria to evaluate stream health could also be used to assess habitat conditions for riparian-dependent birds. We first evaluated the ability of two visual assessments of woody vegetation in the riparian zone (corridor width and height) to describe variation in the obligate riparian bird ensemble along 19 streams in eastern Oregon. Overall species richness and the abundances of three species all correlated significantly with both, but width was more important than height. We then examined the utility of the riparian zone criteria in three standardized and commonly used rapid visual riparian assessment protocols--the USDI BLM Proper Functioning Condition (PFC) assessment, the USDA NRCS Stream Visual Assessment Protocol (SVAP), and the U.S. EPA Habitat Assessment Field Data Sheet (HAFDS)--to assess potential riparian bird habitat. Based on the degree of correlation of bird species richness with assessment ratings, we found that PFC does not assess obligate riparian bird habitat condition, SVAP provides a coarse estimate, and HAFDS provides the best assessment. We recommend quantitative measures of woody vegetation for all assessments and that all protocols incorporate woody vegetation height. Given that rapid assessments may be the only source of information for thousands of kilometers of streams in the western United States, incorporating simple vegetation measurements is a critical step in evaluating the status of riparian bird habitat and provides a tool for tracking changes in vegetation condition resulting from management decisions.

Should the Clean Water Act Follow Stream Water Underground? Managing Beyond the Stream Banks

NASA Astrophysics Data System (ADS)

Taptich, M. N.; Gooseff, M. N.

2010-12-01

The Clean Water Act was designed to protect the integrity of surface waters of the United States. Originally limited to solely waters that were traditionally navigable, the jurisdictional bounds of the Clean Water Act have been expanded to include many other ‘waters of the United States,’ some of which are in fact unnavigable. This expansion of the definition of ‘navigable waters’ has brought many litigative challenges to the true jurisdictional limits of the Act. The recent Supreme Court opinions in Rapanos v. United States (2006) and the subsequent interpretation by lower federal courts have set the precedent for a new approach to jurisdictional determinations, where considerations of function and effect act as gatekeepers for inclusion under the CWA. Justice Kennedy’s significant nexus standard from Rapanos (2006) limits jurisdictional coverage under the Clean Water Act to ‘waters that have a significant nexus with traditional navigable waters.’ Thus, establishing a ‘significant nexus’ between a water body in question and traditionally navigable waters satisfies the requisites needed for inclusion within the scope of the Clean Water Act. By and large there has been a lack of consideration for the near subsurface components of streams when discussing the application of the significant nexus standard. We propose that hyporheic zones, a volume of alluvial aquifer that hosts the exchange of stream water, should be covered under the Clean Water Act, since these zones are intimately connected with their adjoining surface waters and facilitate many processes that are key to supporting healthy stream ecosystems and good water quality. Given the opinions rendered in Rapanos (2006) and the guidance offered by the EPA and Corps following the decision, we demonstrate that the hyporheic zone fulfills each of the functional and ecological example factors used to establish a significant nexus. The implications of this argument include the conversion of our conceptual image of a stream to move beyond the channel banks and bed and to recognize that streams are only one part of a larger hydrologic and ecological system. Under this paradigm of thought, future considerations for establishing water quality standards could include activities preformed and enjoyed just beyond a stream’s ordinary high water mark.

The dark side of the hyporheic zone: Depth profiles of nitrogen and its processing in stream sediments

USGS Publications Warehouse

Stelzer, R.S.; Bartsch, L.A.; Richardson, W.B.; Strauss, E.A.

2011-01-01

1.Although it is well known that sediments can be hot spots for nitrogen transformation in streams, many previous studies have confined measurements of denitrification and nitrate retention to shallow sediments (<5cm deep). We determined the extent of nitrate processing in deeper sediments of a sand plains stream (Emmons Creek) by measuring denitrification in core sections to a depth of 25cm and by assessing vertical nitrate profiles, with peepers and piezometers, to a depth of 70cm. 2.Denitrification rates of sediment slurries based on acetylene block were higher in shallower core sections. However, core sections deeper than 5cm accounted for 68% of the mean depth-integrated denitrification rate. 3.Vertical hydraulic gradient and vertical profiles of pore water chloride concentration suggested that deep ground water upwelled through shallow sediments before discharging to the stream channel. The results of a two-source mixing model based on chloride concentrations suggested that the hyporheic zone was very shallow (<5cm) in Emmons Creek. 4.Vertical profiles showed that nitrate concentration in shallow ground water was about 10-60% of the nitrate concentration of deep ground water. The mean nitrate concentrations of deep and shallow ground water were 2.17 and 0.73mgNO3-NL-1, respectively. 5.Deep ground water tended to be oxic (6.9mgO2L-1) but approached anoxia (0.8mgO2L-1) after passing through shallow, organic carbon-rich sediments, which suggests that the decline in the nitrate concentrations of upwelling ground water was because of denitrification. 6.Collectively, our results suggest that there is substantial nitrate removal occurring in deep sediments, below the hyporheic zone, in Emmons Creek. Our findings suggest that not accounting for nitrate removal in deep sediments could lead to underestimates of nitrogen processing in streams and catchments. ?? 2011 Blackwell Publishing Ltd.

Glacially-megalineated limestone terrain of Anticosti Island, Gulf of St. Lawrence, Canada; onset zone of the Laurentian Channel Ice Stream

NASA Astrophysics Data System (ADS)

Eyles, Nick; Putkinen, Niko

2014-03-01

Anticosti is a large elongate island (240 km long, 60 km wide) in eastern Canada within the northern part of a deep water trough (Gulf of St. Lawrence) that terminates at the Atlantic continental shelf edge. The island's Pleistocene glaciological significance is that its long axis lay transverse to ice from the Quebec and Labrador sectors of the Laurentide Ice Sheet moving south from the relatively high-standing Canadian Shield. Recent glaciological reconstructions place a fast-flowing ice stream along the axis of the Gulf of St. Lawrence but supporting geologic evidence in terms of recognizing its hard-bedded onset zone and downstream streamlined soft bed is limited. Anticosti Island consists of gently southward-dipping limestone plains composed of Ordovician and Silurian limestones (Vaureal, Becscie and Jupiter formations) with north-facing escarpments transverse to regional ice flow. Glacial deposits are largely absent and limestone plains in the higher central plateau of the island retain a relict apparently ‘preglacial’ drainage system consisting of deeply-incised dendritic bedrock valleys. In contrast, the bedrock geomorphology of the lower lying western and eastern limestone plains of the island is strikingly different having been extensively modified by glacial erosion. Escarpments are glacially megalineated with a distinct ‘zig-zag’ planform reflecting northward-projecting bullet-shaped ‘noses’ (identified as rock drumlins) up to 2 km wide at their base and 4 km in length with rare megagrooved upper surfaces. Drumlins are separated by southward-closing, funnel-shaped ‘through valleys’ where former dendritic valleys have been extensively altered by the streaming of basal ice through gaps in the escarpments. Glacially-megalineated bedrock terrain such as on the western and eastern flanks of Anticosti Island is elsewhere associated with the hard-bedded onset zones of fast flowing ice streams and provides important ground truth for the postulated Laurentian Channel Ice Stream (LCIS) within the Gulf of St. Lawrence sector of the Laurentide Ice Sheet.

Estimating Locations of Perennial Streams in Idaho Using a Generalized Least-Squares Regression Model of 7-Day, 2-Year Low Flows

USGS Publications Warehouse

Wood, Molly S.; Rea, Alan; Skinner, Kenneth D.; Hortness, Jon E.

2009-01-01

Many State and Federal agencies use information regarding the locations of streams having intermittent or perennial flow when making management and regulatory decisions. For example, the application of some Idaho water quality standards depends on whether streams are intermittent. Idaho Administrative Code defines an intermittent stream as one having a 7-day, 2-year low flow (7Q2) less than 0.1 ft3/s. However, there is a general recognition that the cartographic representation of perennial/intermittent status of streams on U.S. Geological Survey (USGS) topographic maps is not as accurate or consistent as desirable from one map to another, which makes broad management and regulatory assessments difficult and inconsistent. To help resolve this problem, the USGS has developed a methodology for predicting the locations of perennial streams based on regional generalized least-squares (GLS) regression equations for Idaho streams for the 7Q2 low-flow statistic. Using these regression equations, the 7Q2 streamflow may be estimated for naturally flowing streams in most areas in Idaho. The use of these equations in conjunction with a geographic information system (GIS) technique known as weighted flow accumulation allows for an automated and continuous estimation of 7Q2 streamflow at all points along stream reaches. The USGS has developed a GIS-based map of the locations of streams in Idaho with perennial flow based on a 7Q2 of 0.1 ft3/s and a transition zone of plus or minus 1 standard error. Idaho State cooperators plan to use this information to make regulatory and water-quality management decisions. Originally, 7Q2 equations were developed for eight regions of similar hydrologic characteristics in the study area, using long-term data from 234 streamflow-gaging stations. Equations in five of the regions were revised based on spatial patterns observed in the initial perennial streams map and unrealistic behavior of the equations in extrapolation. The standard errors of prediction for the final equations ranged from a minimum of +75.0 to -42.9 percent in the central part of the study area to a maximum of +277 to -73.5 percent in the southern part of the study area. The equations are applicable only to unregulated, naturally-flowing streams and may produce unreliable results outside the range of explanatory variables used for equation development. Extrapolation outside the range of available data was necessary, however, to predict perennial flow initiation points and transition zones along stream reaches. The map of perennial streams was evaluated by comparing predicted stream classifications with four independent datasets, including field observations by other government agencies. Overall, 81 percent of the comparison data points agreed with the USGS perennial streams model. Regions with the highest number of disagreements had a high percentage of mountainous and forested area with potential mountain front recharge zones, and regions with the highest agreements had a high percentage of low gradient, low elevation area. As a whole, the USGS model predicted a higher number of perennial streams than predictions made with the independent datasets. Some disagreements were due to poor site location coordinates, timing of the comparison site visits during unusually wet or dry years, discrepancies in classification criteria, and variable ground water contributions to flow in some areas. The Idaho Department of Environmental Quality Beneficial Use Reconnaissance Program (BURP) dataset is considered the most representative dataset for comparison because it covered a range of climate conditions and the number of sites visited were consistent from year to year during the study period. Eighty-five percent of BURP comparison data points agreed with the USGS perennial streams model. Although site-specific flow data may be needed to correctly classify streams in some areas, this information rarely is available and is not always practical to o

Vadose Zone as a Potential Carbon Source: a Look at Seasonal Spikes in Hyporheic Zone pCO2

NASA Astrophysics Data System (ADS)

Brandes, J.

2016-12-01

Connections between soils, terrestrial streams and the atmosphere are not yet thoroughly understood as contributing factors to the global carbon budget. We collected data from an undisturbed soil column adjacent to a small stream in a forested watershed in the H. J. Andrews Experimental Forest in the Western Cascades of Oregon in the United States. Our data includes: CO2 (ppm); temperature (oC); depth below water table (m); and soil moisture (cm3/cm3) and spans approximately one year. We are analyzing the data using the gradient method and have observed distinct seasonal patterns which may support previous research describing temporal processes. We can expect to see changing soil moisture characteristics which may promote either vertical CO2 diffusion out of the surface or vertical/lateral advection into subsurface flow. We hypothesize that there is flushing of soil CO2 into the hyporheic zone during precipitation events following soil CO2 buildup.

Simulated effects of groundwater withdrawals from aquifers in Ocean County and vicinity, New Jersey

USGS Publications Warehouse

Cauller, Stephen J.; Voronin, Lois M.; Chepiga, Mary M.

2016-10-21

Rapid population growth since the 1930s in Ocean County and vicinity, New Jersey, has placed increasing demands upon the area’s freshwater resources. To examine effects of groundwater withdrawals, a three-dimensional groundwater-flow model was developed to simulate the groundwater-flow systems of five area aquifers: the unconfined Kirkwood-Cohansey aquifer system and Vincentown aquifer, and three confined aquifers— the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, and the Piney Point aquifer. The influence of withdrawals is evaluated by using transient groundwater-flow model simulations that incorporate three withdrawal schemes. These are (1) no-withdrawal conditions; (2) 2000–03 withdrawal conditions, using reported monthly withdrawals at all production wells from January 2000 through December 2003; and (3) maximum-allocation withdrawal conditions using the maximum withdrawal allowed by New Jersey Department of Environmental Protection permits at each well. Particle tracking analysis, using results from model simulations, delineated particle flow paths from production wells to the point of recharge, and estimated particle travel times.Compared with no-withdrawal conditions, 2000–03 withdrawal conditions reduced the amount of groundwater flow out of the Kirkwood-Cohansey aquifer system into streams, increased the net flow of water into other layers, reduced net flow into or out of storage, and reduced flow from the Kirkwood-Cohansey aquifer system to constant head cells.Freshwater discharging to the Barnegat Bay-Little Egg Harbor estuary from streams and groundwater is essential to maintaining the ecology of the bay. Examination of selected stress periods indicates that simulated base flow in streams flowing into the Barnegat Bay-Little Egg Harbor estuary is reduced by as much as 49 cubic feet per second for 2000 to 2003 withdrawal conditions when compared with no-withdrawal conditions.In the three confined aquifers, water levels during periods of low recharge and high withdrawals, and high recharge and low withdrawals, were examined to determine seasonal effects on the confined flow systems. The simulated potentiometric surface of the Rio Grande water-bearing zone and the Atlantic City 800-foot sand during selected stress periods indicates substantial declines from no-withdrawal conditions to 2000–03 conditions as a result of groundwater withdrawals. Cones of depression in Toms River Township, Seaside Heights and Seaside Park Boroughs, and Barnegat Light Borough developed in the potentiometric surface of the Piney Point aquifer in response to withdrawals.Maximum-allocation withdrawals decreased flow out of the Kirkwood-Cohansey aquifer system to constant head cells, increased flow out of the aquifer system to adjacent and lower layers, and reduced groundwater discharge to streams when compared with 2000–03 withdrawal conditions. Increases in withdrawals from the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, and the Piney Point aquifer result in an increase in simulated net groundwater flow into these aquifers. Base-flow reduction from 2000–03 conditions to maximum-allocation conditions of 25 to 29 cubic feet per second in all streams draining to the Barnegat Bay-Little Egg Harbor also is indicated. Potentiometric surfaces of the Rio Grande water-bearing zone, Atlantic City 800-foot sand, and the Piney Point aquifer during two stress periods of simulated maximum-allocation withdrawal conditions indicated the expansion of several cones of depression developed during 2000–03 withdrawals.Simulation of average 2000–03 withdrawal conditions indicated the extent to which the groundwater-flow system is susceptible to potential saltwater intrusion into near-shore wells. Travel time from recharge to discharge location ranged from 11 to approximately 50,700 years in near-shore Kirkwood-Cohansey aquifer system wells. Those in Seaside Heights Borough, in Island Beach State Park (Berkeley Township), and in Ship Bottom Borough have particle travel times from 140 to 12,000 years and flow paths that originated under Barnegat Bay or the Atlantic Ocean from the simulation of average maximum-allocation withdrawal conditions.Travel time along flow paths to wells screened in the Rio Grande water-bearing zone and the Atlantic City 800-foot sand from recharge to discharge point ranged from nearly 530 years to greater than 3.73 million years from the simulation of average 2000–03 withdrawal conditions. Particle tracking indicated that most wells screened in these aquifers derived a large part of their recharge from the Oswego River Basin, with a small portion of flow originating either beneath Barnegat Bay or to the east beneath the Atlantic Ocean. Travel time along flow paths that start beneath either Barnegat Bay or the Atlantic Ocean ranged from 2,300 to approximately 134,000 years from the simulation of average maximum-allocation withdrawal conditions."

Subsurface drainage processes and management impacts

Treesearch

Elizabeth T. Keppeler; David Brown

1998-01-01

Storm-induced streamflow in forested upland watersheds is linked to rainfall by transient, variably saturated flow through several different flow paths. In the absence of exposed bedrock, shallow flow-restrictive layers, or compacted soil surfaces, virtually all of the infiltrated rainfall reaches the stream as subsurface flow. Subsurface runoff can occur within...

Sequence of slow slip events and low frequency earthquakes in the shallow part of the Nankai Trough seismogenic zone observed by seafloor observation network.

NASA Astrophysics Data System (ADS)

Araki, E.; Saffer, D. M.; Kopf, A.; To, A.; Ide, S.; Nakano, M.; Kimura, T.; Machida, Y.

2016-12-01

Seismic behavior of the thrust zone in trench side of the seismically coupled plate interface in the Nankai Trough is poorly understood because shore based seismic and geodetic observation does not have enough sensitivity to detect slow activity in the area. In these years, we constructed dense seafloor observation network in combination with pore-fluid pressure, strain, and seismic sensing in IODP deep boreholes (C0002G and C0010A) and 20+ seafloor broadband seismometers cabled to the observation network called DONET for long-term continuous observation in the To-Nankai area of the Nankai Trough, south of Japan. Analysis of the seismic records from DONET seafloor seismometer and pore-fluid pressure records from the boreholes in the period from Jan. 2011 to Apr. 2016 revealed the activities of the slow slip events (SSE), low frequency tremor (LFT), and very low frequency earthquakes (VLFE) in the observation network, detecting seven sequence of pore-fluid pressure transients in these boreholes representing SSEs and many LFT and VLFEs from seismic records. Some of the SSE sequence accompanies active LFT swarms in the regions offshore of the locked seismogenic zone. Some of the pressure transient initiate precedent to the LFT swarms, as well as some does not accompany obvious LFT activity, as if the SSE occurs "silently", suggesting LFT does not express SSE but LFT seems activated by the SSE. This is also supported by change of SSE pressure transient rate in accordance with LFT activity, observed in sequences in Mar. 2011, Oct. 2015, and April 2016. In the Oct. 2015 sequence, observed pressure transient in two boreholes indicates the slip propagates updip in the shallow subduction zone. In many sequences including this sequence, we ientify that the LFT swarm tends to migrate updip direction. The pressure transient in Apr. 2016 also followed this tendency, initiating from co-seismic compression by Apr. 1 earthquake occurred downdip side of the boreholes, followed by further compression due to the after slip, and slow release of the pressure suggesting SSE along with very active LFT and VLFE activities migrating offshore direction in the following two weeks period. The SSE seemed further activated by teleseismic events Kumamoto earthquake in Apr. 17.

Stream-related preferences of inputs to the superior colliculus from areas of dorsal and ventral streams of mouse visual cortex.

PubMed

Wang, Quanxin; Burkhalter, Andreas

2013-01-23

Previous studies of intracortical connections in mouse visual cortex have revealed two subnetworks that resemble the dorsal and ventral streams in primates. Although calcium imaging studies have shown that many areas of the ventral stream have high spatial acuity whereas areas of the dorsal stream are highly sensitive for transient visual stimuli, there are some functional inconsistencies that challenge a simple grouping into "what/perception" and "where/action" streams known in primates. The superior colliculus (SC) is a major center for processing of multimodal sensory information and the motor control of orienting the eyes, head, and body. Visual processing is performed in superficial layers, whereas premotor activity is generated in deep layers of the SC. Because the SC is known to receive input from visual cortex, we asked whether the projections from 10 visual areas of the dorsal and ventral streams terminate in differential depth profiles within the SC. We found that inputs from primary visual cortex are by far the strongest. Projections from the ventral stream were substantially weaker, whereas the sparsest input originated from areas of the dorsal stream. Importantly, we found that ventral stream inputs terminated in superficial layers, whereas dorsal stream inputs tended to be patchy and either projected equally to superficial and deep layers or strongly preferred deep layers. The results suggest that the anatomically defined ventral and dorsal streams contain areas that belong to distinct functional systems, specialized for the processing of visual information and visually guided action, respectively.

Experimental saltwater intrusion in coastal aquifers using automated image analysis: Applications to homogeneous aquifers

NASA Astrophysics Data System (ADS)

Robinson, G.; Ahmed, Ashraf A.; Hamill, G. A.

2016-07-01

This paper presents the applications of a novel methodology to quantify saltwater intrusion parameters in laboratory-scale experiments. The methodology uses an automated image analysis procedure, minimising manual inputs and the subsequent systematic errors that can be introduced. This allowed the quantification of the width of the mixing zone which is difficult to measure in experimental methods that are based on visual observations. Glass beads of different grain sizes were tested for both steady-state and transient conditions. The transient results showed good correlation between experimental and numerical intrusion rates. The experimental intrusion rates revealed that the saltwater wedge reached a steady state condition sooner while receding than advancing. The hydrodynamics of the experimental mixing zone exhibited similar traits; a greater increase in the width of the mixing zone was observed in the receding saltwater wedge, which indicates faster fluid velocities and higher dispersion. The angle of intrusion analysis revealed the formation of a volume of diluted saltwater at the toe position when the saltwater wedge is prompted to recede. In addition, results of different physical repeats of the experiment produced an average coefficient of variation less than 0.18 of the measured toe length and width of the mixing zone.

Efficient dispersal and substrate acquisition traits in a marine invasive species via transient chimerism and colony mobility

PubMed Central

Fidler, Andrew E.; Bacq-Labreuil, Aurelie; Rachmilovitz, Elad

2018-01-01

Over the past three decades the colonial ascidian Didemnum vexillum has been expanding its global range, significantly impacting marine habitats and aquaculture facilities. What biological features make D. vexillum so highly invasive? Here, we show that juxtaposed allogeneic D. vexillum colony fragments (‘ramets’) may, initially, form chimeric entities. Subsequently, zooids of the differing genotypes within such chimeras coordinately retreat away from fusion zones. A few days following such post-fusion retreat movements there is further ramet fission and the formation of zooid-depauperate tunic zones. Using polymorphic microsatellite loci to distinguish between genotypes, we found that they were sectorial at the fusion zones and the subsequent ramet movements resulted in further spatial separation of the paired-genotypes indicating that the fusion events observed did not lead to formation of long-term, stable chimeras. Thus, movements of D. vexillum colony ramets from initial fusion zones lead to progressive segregation of genotypes probably minimizing potential somatic/germ-cell competition/parasitism. We speculate that relatively fast (≤10 mm/day) movement of D. vexillum colonies on substrates along with frequent, and perhaps unrestrained, transient allogeneic fusions play significant roles in this species’ striking invasiveness and capacity to colonize new substrates.

Transient Interaction Between Reduction and Slagging Reactions of Wustite in Simulated Cohesive Zone of Blast Furnace

NASA Astrophysics Data System (ADS)

Ma, Kaihui; Xu, Jian; Deng, Junyi; Wang, Dongdong; Xu, Yang; Liao, Zhehan; Sun, Chengfeng; Zhang, Shengfu; Wen, Liangying

2018-06-01

The blast furnace cohesive zone plays an important role in the gas flow distribution and heat-transfer efficiency. Previous work mainly employed temperature-based indices to evaluate and predict the shape and thickness of the cohesive zone, whereas the internal reactions and related effects on the softening and melting properties of a complex burden are ignored. In this study, an innovative index, namely, shrinkage rate (SR), is first proposed to directly estimate the shrinkage behavior of wustite (FeO)-packed bed inside a simulated cohesive zone. The index is applied as the temperature increases to elucidate the transient interaction between reduction and slagging reactions. Results show that the thermally induced slagging reaction causes the packed bed to shrink at lower temperature, and the SR doubles when compounds with low melting temperature are generated by adding a reasonable concentration of CaO or SiO2. The reduction reaction becomes the driving force during the shrinkage of the packed bed between 1173 K and 1273 K when CO is introduced in the mixture gas. Then, the dominating factors for further shrinkage include slagging, reduction, or both factors. These factors vary with respect to the added compounds or temperature.