Science.gov

Sample records for acid deposition rates

  1. Acid Deposition

    EPA Science Inventory

    This indicator presents acid deposition trends in the contiguous U.S. from 1989 to 2007. Data are broken down by wet and dry deposition and deposition of nitrogen and sulfur compounds. Acid deposition is particularly damaging to lakes, streams, and forests and the plants and a...

  2. Fundamental Study on Temperature Dependence of Deposition Rate of Silicic Acid - 13270

    SciTech Connect

    Shinmura, Hayata; Niibori, Yuichi; Mimura, Hitoshi

    2013-07-01

    The dynamic behavior of the silicic acid is one of the key factors to estimate the condition of the repository system after the backfill. This study experimentally examined the temperature dependence of dynamic behavior of supersaturated silicic acid in the co-presence of solid phase, considering Na ions around the repository, and evaluated the deposition rate constant, k, of silicic acid by using the first-order reaction equation considering the specific surface area. The values of k were in the range of 1.0x10{sup -11} to 1.0x10{sup -9} m/s in the temperature range of 288 K to 323 K. The deposition rate became larger with increments of temperature under the Na ion free condition. Besides, in the case of Na ions 0.6 M, colloidal silicic acid decreased dramatically at a certain time. This means that the diameter of the colloidal silicic acid became larger than the pore size of filter (0.45 μm) due to bridging of colloidal silicic acid. Furthermore, this study estimated the range of altering area and the aperture of flow-path in various value of k corresponding to temperature by using advection-dispersion model. The concentration in the flow-path became lower with increments of temperature, and when the value of k is larger than 1.0x10{sup -11} m/s, the deposition range of supersaturated silicic acid was estimated to be less than 20 m around the repository. In addition, the deposition of supersaturated silicic acid led the decrement of flow-path aperture, which was remarkable under the condition of relatively high temperature. Such a clogging in flow paths is expected as a retardation effect of radionuclides. (authors)

  3. Soil calcium status and the response of stream chemistry to changing acidic deposition rates

    USGS Publications Warehouse

    Lawrence, G.B.; David, M.B.; Lovett, Gary M.; Murdoch, Peter S.; Burns, Douglas A.; Stoddard, J.L.; Baldigo, Barry P.; Porter, J.H.; Thompson, A.W.

    1999-01-01

    Despite a decreasing trend in acidic deposition rates over the past two to three decades, acidified surface waters in the northeastern United States have shown minimal changes. Depletion of soil Ca pools has been suggested as a cause, although changes in soil Ca pools have not been directly related to long-term records of stream chemistry. To investigate this problem, a comprehensive watershed study was conducted in the Neversink River Basin, in the Catskill Mountains of New York, during 1991-1996. Spatial variations of atmospheric deposition, soil chemistry, and stream chemistry were evaluated over an elevation range of 817-1234 m to determine whether these factors exhibited elevational patterns. An increase in atmospheric deposition of SO4 with increasing elevation corresponded with upslope decreases of exchangeable soil base concentrations and acid-neutralizing capacity of stream water. Exchangeable base concentrations in homogeneous soil incubated within the soil profile for one year also decreased with increasing elevation. An elevational gradient in precipitation was not observed, and effects of a temperature gradient on soil properties were not detected. Laboratory leaching experiments with soils from this watershed showed that (1) concentrations of Ca in leachate increased as the concentrations of acid anions in added solution increased, and (2) the slope of this relationship was positively correlated with base saturation. Field and laboratory soil analyses are consistent with the interpretation that decreasing trends in acid-neutralizing capacity in stream water in the Neversink Basin, dating back to 1984, are the result of decreases in soil base saturation caused by acidic deposition.

  4. Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

    NASA Astrophysics Data System (ADS)

    Provine, J.; Schindler, Peter; Kim, Yongmin; Walch, Steve P.; Kim, Hyo Jin; Kim, Ki-Hyun; Prinz, Fritz B.

    2016-06-01

    The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiNx), particularly for use a low k dielectric spacer. One of the key material properties needed for SiNx films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiNx and evaluate the film's WER in 100:1 dilutions of HF in H2O. The remote plasma capability available in PEALD, enabled controlling the density of the SiNx film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiNx of 6.1 Å/min, which is similar to WER of SiNx from LPCVD reactions at 850 °C.

  5. DRY DEPOSITION MODULE FOR REGIONAL ACID DEPOSITION

    EPA Science Inventory

    Methods to compute surface dry deposition velocities for sulfur dioxide, sulfate, ozone, NO plus NO2, and nitric acid vapor over much of the North American continent have been developed for use with atmospheric numerical models of long-range transport and deposition. The resultin...

  6. SOIL REACTION AND ACIDIC DEPOSITION

    EPA Science Inventory

    This chapter discusses the major chemical processes by which acidic deposition interacts with soils. he focus is on forest soils, as the effects of acidic deposition on soils used for production of food and fiber are generally small compared to effects of agricultural practices s...

  7. ACID DEPOSITION AND FOREST DECLINE

    EPA Science Inventory

    The location, topography and other characteristics of the high-elevation forests of eastern North America cause them to be receptors of high levels of acid deposition and airborn trace metals. No other major forested areas in the U.S. are subjected to such intensely acid cloud mo...

  8. (Acidic deposition and the environment)

    SciTech Connect

    Garten, C.T.; Lindberg, S.E.; Van Miegroet, H.

    1990-10-24

    The travelers presented several papers at the Fourth International Conference on Acidic Deposition. These covered the following topics: atmospheric chemistry and deposition of airborne nitrogen compounds, soil solution chemistry in high-elevation spruce forests, and forest throughfall measurements for estimating total sulfur deposition to ecosystems. In addition, S. E. Lindberg was invited to organize and chair a conference session on Throughfall and Stemflow Experiments, and to present an invited lecture on Atmospheric Deposition and Canopy Interactions of Metals and Nitrogen in Forest Ecosystems: The Influence of Global Change'' at the 110th Anniversary Celebration of the Free University of Amsterdam.

  9. Plasma-Enhanced Atomic Layer Deposition of SiN-AlN Composites for Ultra Low Wet Etch Rates in Hydrofluoric Acid.

    PubMed

    Kim, Yongmin; Provine, J; Walch, Stephen P; Park, Joonsuk; Phuthong, Witchukorn; Dadlani, Anup L; Kim, Hyo-Jin; Schindler, Peter; Kim, Kihyun; Prinz, Fritz B

    2016-07-13

    The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposited (ALD) of hydrofluoric acid (HF) etch resistant and electrically insulating films for sidewall spacer processing. Silicon nitride (SiN) has been the prototypical material for this need and extensive work has been conducted into realizing sufficiently lower wet etch rates (WERs) as well as leakage currents to meet industry needs. In this work, we report on the development of plasma-enhanced atomic layer deposition (PEALD) composites of SiN and AlN to minimize WER and leakage current density. In particular, the role of aluminum and the optimum amount of Al contained in the composite structures have been explored. Films with near zero WER in dilute HF and leakage currents density similar to pure PEALD SiN films could be simultaneously realized through composites which incorporate ≥13 at. % Al, with a maximum thermal budget of 350 °C. PMID:27295338

  10. (International conference on acidic deposition)

    SciTech Connect

    McLaughlin, S.B. Jr.

    1990-10-05

    The traveler took the opportunity to participate in a mini-sabbatical at the Institute of Terrestrial Ecology (ITE) in Edinburgh, Scotland, as a part of planned travel to Glasgow, Scotland, to attend the International Conference on Acidic Precipitation. The purpose of the sabbatical was to provide quality time for study and interchange of ideas with scientists at ITE working on physiological effects of acidic deposition and to allocate significant time for writing and synthesizing of results of physiological studies from the National Forest Response Program's Spruce/Fir Research Cooperative. The study focused on the very significant cytological and physiological effects of calcium deficiency in trees, a response that appears to be amplified in spruce by acidic deposition.

  11. Calcium phosphate deposition rate, structure and osteoconductivity on electrospun poly(l-lactic acid) matrix using electrodeposition or simulated body fluid incubation

    PubMed Central

    He, Chuanglong; Jin, Xiaobing; Ma, Peter X.

    2013-01-01

    Mineralized nanofibrous scaffolds have been proposed as promising scaffolds for bone regeneration due to their ability to mimic both nanoscale architecture and chemical composition of natural bone extracellular matrix (ECM). In this study, a novel electrodeposition method was compared with an extensively explored simulated body fluid (SBF) incubation method in terms of the deposition rate, chemical composition, and morphology of calcium phosphate formed on electrospun fibrous thin matrices with a fiber diameter in the range from about 200 nm to about 1400 nm prepared using 6, 8, 10 and 12 wt% poly(l-lactic acid) (PLLA) solutions in a mixture of dichloromethane and acetone (2:1 in volume). The effects of the surface modification using the two mineralization techniques on osteoblastic cell (MC3T3-E1) proliferation and differentiation were also examined. It was found that electrodeposition was two to three orders of magnitude faster than the SBF method in mineralizing the fibrous matrices, reducing the mineralization time from about two weeks to an hour to achieve the same amounts of mineralization. The mineralization rate also varied with the fiber diameter but in opposite directions between the two mineralization methods. As a general trend, the increase of fiber diameter resulted in a faster mineralization rate for the electrodeposition method but a slower mineralization rate for the SBF incubation method. Using the electrodeposition method, one can control the chemical composition and morphology of the calcium phosphate by varying the electric deposition potential and electrolyte temperature to tune the mixture of dicalcium phosphate dihydrate (DCPD) and hydroxy apatite (HAp). Using the SBF method, one can only obtain a low crystallinity HAp. The mineralized electrospun PLLA fibrous matrices from either method similarly facilitate the proliferation and osteogenic differentiation of preosteoblastic MC3T3-E1 cells as compared to neat PLLA matrices. Therefore, the

  12. Acid deposition in east Asia

    SciTech Connect

    Phadnis, M.J.; Carmichael, G.R.; Ichikawa, Y.

    1996-12-31

    A comparison between transport models was done to study the acid deposition in east Asia. The two models in question were different in the way the treated the pollutant species and the way simulation was carried out. A single-layer, trajectory model with simple (developed by the Central Research Institute of Electric Power Industry (CRIEPI), Japan) was compared with a multi-layered, eulerian type model (Sulfur Transport Eulerian Model - II [STEM-II]) treating the chemical processes in detail. The acidic species used in the simulation were sulfur dioxide and sulfate. The comparison was done for two episodes: each a month long in winter (February) and summer (August) of 1989. The predicted results from STEM-II were compared with the predicted results from the CRIEPI model as well as the observed data at twenty-one stations in Japan. The predicted values from STEM-II were similar to the ones from the CRIEPI results and the observed values in regards to the transport features. The average monthly values of SO{sub 2} in air, sulfate in air and sulfate in precipitation were in good agreement. Sensitivity studies were carried out under different scenarios of emissions, dry depositions velocities and mixing heights. The predicted values in these sensitivity studies showed a strong dependence on the mixing heights. The predicted wet deposition of sulfur for the two months is 0.7 gS/m2.mon, while the observed deposition is around 1.1 gS/m2.mon. It was also observed that the wet deposition on the Japan sea side of the islands is more than those on the Pacific side and the Okhotsk sea, mainly because of the continental outflow of pollutant air masses from mainland China and Korea. The effects of emissions from Russia and volcanoes were also evaluated.

  13. Emerging acid deposition research and monitoring issues

    SciTech Connect

    Birnbaum, R.

    1997-12-31

    The research baselines established for acid rain in the 1980s position scientists and policy makers to evaluate the environmental effectiveness of the acid rain control program and to test the variety of scientific hypotheses made regarding the chemical, transport and biological processes involved in acidic deposition. Several new research questions have evolved. How effective are the emissions reductions? What is the residual risk? How have ecological recovery rates been affected and what other environmental factors influence recovery? What are the critical requirements to measure ecological change including the extent and rate while also capturing the extent and severity of emerging ecological stressors (such as watershed nitrogen saturation)? These and other questions are currently being synthesized within and outside of EPA to develop a long-term strategy to provide guidance to emerging research and monitoring issues.

  14. ADVANCES IN CONTROL TECHNOLOGY FOR ACID DEPOSITION

    EPA Science Inventory

    Causes and effects of acid deposition are the subject of widespread discussion both in the U.S. and Europe. Two major concerns are the acidification of lakes and streams, and forest damage. The proposed mechanism for acidification of lakes and streams is the deposition of acidic ...

  15. ACIDIC DEPOSITION AND CISTERN DRINKING WATER SUPPLIES

    EPA Science Inventory

    The Water quality charecteristics, including the trace element Cd, cu, Pb, and Zn, in rainwater cistern supplies representing an area receiving acidic deposition were compared to cistern water chemistry in a control area that does not receive a significant input of acidic deposit...

  16. Mesoscale acid deposition modeling studies

    NASA Technical Reports Server (NTRS)

    Kaplan, Michael L.; Proctor, F. H.; Zack, John W.; Karyampudi, V. Mohan; Price, P. E.; Bousquet, M. D.; Coats, G. D.

    1989-01-01

    The work performed in support of the EPA/DOE MADS (Mesoscale Acid Deposition) Project included the development of meteorological data bases for the initialization of chemistry models, the testing and implementation of new planetary boundary layer parameterization schemes in the MASS model, the simulation of transport and precipitation for MADS case studies employing the MASS model, and the use of the TASS model in the simulation of cloud statistics and the complex transport of conservative tracers within simulated cumuloform clouds. The work performed in support of the NASA/FAA Wind Shear Program included the use of the TASS model in the simulation of the dynamical processes within convective cloud systems, the analyses of the sensitivity of microburst intensity and general characteristics as a function of the atmospheric environment within which they are formed, comparisons of TASS model microburst simulation results to observed data sets, and the generation of simulated wind shear data bases for use by the aviation meteorological community in the evaluation of flight hazards caused by microbursts.

  17. Effects of acid deposition on agricultural production

    SciTech Connect

    Moskowitz, P.D.; Medeiros, W.H.; Oden, N.L.; Thode, H.C. Jr.; Coveney, E.A.; Jacobson, J.S.; Rosenthal, R.E.; Evans, L.S.; Lewin, K.F.; Allen, F.L.

    1985-09-01

    A preliminary assessment, both qualitative and quantitative, was carried out on the effects of acid deposition on agriculture. An inventory was made of US crops exposed to different acid deposition levels in 1982. Most crops (valued at more than $50 billion) were exposed to annual average acid deposition levels greater than pH 4.6, but crops worth more than $220 billion were exposed to even lower pH levels. Published results of experiments on crop response to acid deposition have not identified any single crop as being consistently sensitive, and suggest that present levels of acidic precipitation in the US are not significantly affecting growth and yield of crops. Because relatively few experiments appropriate to a quantitative acid deposition assessment have been conducted, the quantitative section is necessarily based on a restricted data set. Corn, potatoes, and soybeans have been studied in experimental environments which simulate agronomic conditions and which have adequate statistical power for yield estimates; only some varieties of soybeans have demonstrated statistically significant sensitivity to acid deposition.

  18. ACIDIC DEPOSITION PHENOMENON AND ITS EFFECTS: CRITICAL ASSESSMENT DOCUMENT

    EPA Science Inventory

    The Acidic Deposition Phenomenon and Its Effects: Critical Assessment Document (CAD) is a summary, integration, and interpretation of the current scientific understanding of acidic deposition. It is firmly based upon The Acidic Deposition Phenomenon and Its Effects: Critical Asse...

  19. ATMOSPHERIC ACID DEPOSITION DAMAGE TO PAINTS

    EPA Science Inventory

    Available data from laboratory and field studies of damage to paints by erosion have been analyzed to develop an atmospheric acid deposition damage function for exterior house paints containing calcium carbonate or silicate extenders. Regression analysis coefficients associated w...

  20. Florida acid deposition study - an overview

    SciTech Connect

    Henderson, C.D.; Hendrickson, E.R.

    1983-01-01

    Comprehensive literature searches were performed in the areas of source attribution and long-range transport and ecological and material effects. The literature searches were designed to determine the impacts of acid deposition that are specific to Florida. In January 1982 the results of Phase I programs were issued. These reports were: (1) Monitoring Program Phase I Summary Report; (2) Source Attribution Phase I Summary Report; and (3) A Literature Review of the Ecological and Materials Effects of Acid Deposition.

  1. Deposition rates of oxidized iron on Mars

    NASA Technical Reports Server (NTRS)

    Burns, R. G.

    1993-01-01

    The reddened oxidized surface of Mars is indicative of temporal interactions between the Martian atmosphere and its surface. During the evolution of the Martian regolith, primary ferromagnesian silicate and sulfide minerals in basaltic rocks apparently have been oxidized to secondary ferric-bearing assemblages. To evaluate how and when such oxidized deposits were formed on Mars, information about the mechanisms and rates of chemical weathering of Fe(2+)-bearing minerals has been determined. In this paper, mechanisms and rates of deposition of ferric oxide phases on the Martian surface are discussed.

  2. High rate vacuum deposited silicon layers

    NASA Astrophysics Data System (ADS)

    Kipperman, A. H. M.; van Zolingen, R. J. C.

    1982-08-01

    Silicon layers were deposited in vacuum at high rates (up to 50 microns/min) on aluminum-, silicon oxide-, and silicon nitride-coated stainless steel, pyrex, and silicon substrates. The morphological, crystallographic, and electrical properties of the layers were studied in as-grown and annealed conditions. Layers as-grown on aluminum-coated substrates had unsatisfactory electrical properties and too high an aluminum concentration to be acceptable for solar cells. Thermal annealing of layers on SiO2- and on Si3N4-coated substrates markedly improved their crystallographic and electrical properties. In all cases, silicon layers deposited at about 550 C showed a columnar structure which, after prolonged etching, was found to be composed of fibrils of about 0.3 microns in diameter extending over the entire thickness of the layer. It is suggested that further tests should be carried out at a substrate temperature of about 800 C maintaining the high deposition rates.

  3. Acidic deposition and soil processes

    SciTech Connect

    Newton, R.M.; April, R.H.

    1985-08-01

    The results of the Integrated Lake-Watershed Acidification Study (ILWAS) show that the sensitivity of a watershed to surface water acidification is determined by the flow paths of water through the terrestrial system. If the water infiltrates through the soils into the groundwater system, acid neutralization occurs through weathering reactions involving minerals in the soils and till. Runoff and shallow interflow result in acid surface waters. Flow paths are determined in the ILWAS watersheds by the thickness of the glacial till. Complete neutralization can occur even in areas underlain by sensitive bedrock if the flow path through the mineral horizons is long enough. This appears to hold even in areas outside of the Adirondacks. 11 references, 5 figures.

  4. RESULTS FROM THE MOUNTAIN ACID DEPOSITION PROGRAM

    EPA Science Inventory

    The Mountain Acid Deposition Program (MADPro) was initiated in 1993 as part of the research necessary to support the objectives of the Clean Air Status and Trends Network (CASTNet), which was created to address the. requirements of the Clean Air Act Amendments (CAAA). The main ob...

  5. Acid deposition control benefits as problematic

    SciTech Connect

    Crocker, T.D.

    1985-01-01

    The author argues that the government's mistaken beliefs downgrade the benefits of acid deposition control, and may misdirect research of the effects of acid rain upon natural and human systems. It can be argued as to whether or not the factors (generally existing prices and yield changes from current standing stocks of environmental goods) upon which the $5 billion estimate for control was built have a major or minor influence upon the true economic consequences of acid deposition. As the application of Bayes' rule demonstrates, any lessening in arbitrariness of numerical assignments to the factors could lead to a major revision in the estimate. Assessment stories probably contribute to the paralysis of political will even though their truth value is small.

  6. CASTNet mountain acid deposition monitoring program

    SciTech Connect

    Bowser, J.J.; Anderson, J.B.; Edgerton, E.S.; Mohnen, V.; Baumgardener, R.

    1994-12-31

    Concern over the influence of air pollution on forest decline has led the USEPA to establish the Mountain Acid Deposition Monitoring Program (MADMP) to quantify total deposition at high altitudes, i.e., above cloud base. Clouds can be a major source of atmospheric deposition to sensitive, mountain ecosystems. This program is a part of the Clean Air Status and Trends Network (CASTNet), a national assessment of the effects of the 1990 Clean Air Act. The objectives of MADMP are to estimate total deposition, measure cloud chemistry, and characterize spacial and temporal trends at four selected high altitude sites in the Eastern US. Four MADMP sites have been established for the 1994 field season: Clingman`s Dome, Great Smoky Mountain Nat. Park, TN; Slide Mountain, Catskill State Park, NY; Whiteface Mountain, Adirondack State Park, NY; and Whitetop Mountain, Mt. Rogers Nat`l Recreational Area, VA. An automated cloud collection system will be utilized in combination with continuous measurements of cloud liquid water content in order to estimate cloudwater deposition. Other relevant data will include continuous meteorological measurements, ozone and sulfur dioxide concentrations, wet deposition from rainfall analysis, and dry deposition from filter pack analysis. Quality assurance and quality control measures will be employed to maximize accuracy and precision.

  7. Acidic deposition and surface water chemistry

    NASA Astrophysics Data System (ADS)

    Church, M. R.

    A pair of back-to-back (morning and afternoon) hydrology sessions, held December 10, 1987, at the AGU Fall Meeting in San Francisco, Calif., covered “Predicting the Effects of Acidic Deposition on Surface Water Chemistry.” The combined sessions included four invited papers, 12 contributed papers, and a panel discussion at its conclusion. The gathering dealt with questions on a variety of aspects of modeling the effects of acidic deposition on surface water chemistry.Contributed papers included discussions on the representation of processes in models as well as limiting assumptions in model application (V. S. Tripathi et al., Oak Ridge National Laboratory, Oak Ridge, Tenn., and E. C. Krug, Illinois State Water Survey, Champaign), along with problems in estimating depositional inputs to catchments and thus inputs to be used in the simulation of catchment response (M. M. Reddy et al., U.S. Geological Survey, Lakewood, Colo.; and E. A. McBean, University of Waterloo, Waterloo, Canada). L. A. Baker et al. (University of Minnesota, Minneapolis) dealt with the problem of modeling seepage lake systems, an exceedingly important portion of the aquatic resources in Florida and parts of the upper U.S. Midwest. J. A. Hau and Y. Eckstein (Kent State University, Kent, Ohio) considered equilibrium modeling of two northern Ohio watersheds that receive very different loads of acidic deposition but are highly similar in other respects.

  8. Acid deposition in Maryland: Implications of the results of the National Acid Precipitation Assessment Program

    SciTech Connect

    DeMuro, J.; Bowmann, M.; Ross, J.; Blundell, C.; Price, R.

    1991-07-01

    Acid deposition, commonly referred to as 'acid rain,' is a major global environmental concern. Acid deposition has reportedly resulted in damage to aquatic, terrestrial, and physical resources and has potentially adverse effects on human health. A component of the Maryland acid deposition program is the preparation of an annual report that summarizes yearly activities and costs of ongoing acid deposition research and monitoring programs.

  9. (Acidic deposition: Its nature and impacts)

    SciTech Connect

    Cook, R.B.; Turner, R.S. ); Ryan, P.F. )

    1990-10-18

    The travelers presented papers on various aspects of modeling performed as part of the US National Acidic Precipitation Assessment Program (NAPAP) at the Fourth International Conference on Acidic Deposition: Its Nature and Impacts. The meeting was sponsored by the Royal Society of Edinburgh and was attended by over 800 scientists, primarily from Europe and North America. The conference focused on nine aspects of the nature and impacts of atmospheric pollutants, including ozone: chemistry of atmospheric pollutants; processes controlling the deposition of pollutants; effects of pollutants on soils; physiology of plant responses to pollutants; effects of pollutants in agricultural and natural or seminatural ecosystems; atmospheric pollutants and forests; effects of pollutants on the chemistry of freshwater streams and lakes; effects of pollutants on freshwater plants and animals; and effects of pollutants, indoors and outdoors, on materials and buildings.

  10. Acidic Depositions: Effects on Wildlife and Habitats

    USGS Publications Warehouse

    1993-01-01

    The phenomenon of 'acid rain' is not new; it was recognized in the mid-1800s in industrialized Europe. In the 1960s a synthesis of information about acidification began in Europe, along with predictions of ecological effects. In the U.S. studies of acidification began in the 1920s. By the late 1970s research efforts in the U.S. and Canada were better coordinated and in 1980 a 10-year research program was undertaken through the National Acid Precipitation Assessment Plan (NAPAP) to determine the causes and consequences of acidic depositions. Much of the bedrock in the northeastern U.S. and Canada contains total alkalinity of 20 kg/ha/yr of wet sulphate depositions and are vulnerable to acidifying processes. Acidic depositions contribute directly to acidifying processes of soil and soil water. Soils must have sufficient acid-neutralizing capacity or acidity of soil will increase. Natural soil-forming processes that lead to acidification can be accelerated by acidic depositions. Long-term effects of acidification are predicted, which will reduce soil productivity mainly through reduced availability of nutrients and mobilization of toxic metals. Severe effects may lead to major alteration of soil chemistry, soil biota, and even loss of vegetation. Several species of earthworms and several other taxa of soil-inhabiting invertebrates, which are important food of many vertebrate wildlife species, are affected by low pH in soil. Loss of canopy in declining sugar maples results in loss of insects fed on by certain neotropical migrant bird species. No definitive studies categorically link atmospheric acidic depositions with direct or indirect effects on wild mammals. Researchers have concentrated on vegetative and aquatic effects. Circumstantial evidence suggests that effects are probable for certain species of aquatic-dependent mammals (water shrew, mink, and otter) and that these species are at risk from the loss of foods or contamination of these foods by metals

  11. Estimates of cloud water deposition at Mountain Acid Deposition Program sites in the Appalachian Mountains.

    PubMed

    Baumgardner, Ralph E; Isil, Selma S; Lavery, Thomas F; Rogers, Christopher M; Mohnen, Volker A

    2003-03-01

    Cloud water deposition was estimated at three high-elevation sites in the Appalachian Mountains of the eastern United States (Whiteface Mountain, NY; Whitetop Mountain, VA; and Clingman's Dome, TN) from 1994 through 1999 as part of the Mountain Acid Deposition Program (MADPro). This paper provides a summary of cloud water chemistry, cloud liquid water content, cloud frequency, estimates of cloud water deposition of sulfur and nitrogen species, and estimates of total deposition of sulfur and nitrogen at these sites. Other cloud studies in the Appalachians and their comparison to MADPro are also summarized. Whiteface Mountain exhibited the lowest mean and median concentrations of sulfur and nitrogen ions in cloud water, while Clingman's Dome exhibited the highest mean and median concentrations. This geographic gradient is partly an effect of the different meteorological conditions experienced at northern versus southern sites in addition to the difference in pollution content of air masses reaching the sites. All sites measured seasonal cloud water deposition rates of SO4(2-) greater than 50 kg/ha and NO3(-) rates of greater than 25 kg/ha. These high-elevation sites experienced additional deposition loading of SO4(2-) and NO3(-) on the order of 6-20 times greater compared with lower elevation Clean Air Status and Trends Network (CASTNet) sites. Approximately 80-90% of this extra loading is from cloud deposition. PMID:12661689

  12. Ancillary effects of selected acid deposition control policies

    SciTech Connect

    Moe, R.J.; Lyke, A.J.; Nesse, R.J.

    1986-08-01

    NAPAP is examining a number of potential ways to reduce the precursors (sulfur dioxide and nitrogen oxides) to acid deposition. However, the policies to reduce acid deposition will have other physical, biological and economic effects unrelated to acid deposition. For example, control policies that reduce sulfur dioxide emissions may also increase visibility. The effects of an acid deposition policy that are unrelated to acid deposition are referred to as ''ancillary'' effects. This reserch identifies and characterizes the principle physical and economic ancillary effects associated with acid deposition control and mitigation policies. In this study the ancillary benefits associated with four specific acid deposition policy options were investigated. The four policy options investigated are: (1) flue gas desulfurization, (2) coal blending or switching, (3) reductions in automobile emissions of NO/sub x/, and (4) lake liming. Potential ancillary benefits of each option were identified and characterized. Particular attention was paid to the literature on economic valuation of potential ancillary effects.

  13. Deposition of salicylic acid into hamster sebaceous.

    PubMed

    Motwani, M R; Rhein, L D; Zatz, J L

    2004-01-01

    In an earlier paper, we identified vehicles that are miscible with sebum, using differential scanning calorimetry (DSC). In this paper, the potential of these vehicles to deliver salicylic acid (SA) into the sebum-filled follicles of hamster ears is examined. The main objective of this study is to correlate the melting transitions of a model sebum with the follicular delivery of SA, using two different types of vehicles (fatty and polar). Generally, the fatty vehicles show higher deposition than the polar vehicles. Follicular delivery of salicylic acid correlates well with its solubility in the respective vehicles. This extent of deposition also shows a relationship with the effect of the vehicle on thermal behavior of the model sebum. The nature of the relationship depends on the vehicle (polar or fatty) tested. We conclude that DSC could be used to identify appropriate vehicles for drugs whose follicular delivery depends on solubility. The results also suggest that delivery into the sebaceous glands occurs by two different mechanisms, depending upon the polarity of the vehicle and the physicochemical properties of the drug. The results of these experiments are further extended to investigate follicular delivery of SA from two different types of oil-in-water emulsion formulations. From these studies we conclude that either increasing the volume of the oil phase or changing the emulsion to a water-in-oil emulsion would increase follicular deposition. Our research highlights the role of sebum, its compatibility with drug molecules, and vehicle selection in the transport of drugs into the follicles. The overall results of these experiments provide a reasonable understanding of the mechanisms underlying the transport of drugs to, and subsequently through, the sebaceous follicle. PMID:15645108

  14. Acid deposition and air quality related values in north central Colorado wilderness areas. Final report

    SciTech Connect

    Hidy, G.M.

    1995-05-01

    Terrestrial and aquatic ecosystem response to atmospheric acid, sulfur, and nitrate deposition has been studied only in a very limited way in Colorado wilderness areas. However, the observed deposition rates in north central Colorado remain low relative to affected areas in the eastern United States and well within a range where no adverse ecological effects are expected. This report presents a survey of scientific information describing acid deposition and air quality related values, which may have implications for utility plant operations.

  15. STATUS OF RESEARCH TO DEVELOP ACIDIC DRY DEPOSITION MONITORING CAPABILITY

    EPA Science Inventory

    Dry deposition is thought to be as important as wet deposition in acidifying ecosystems. However, at present acidic dry deposition of relevant particles and gases cannot be monitored directly in a quantitative manner. The U.S. EPA Workshop on Dry Deposition (Report No. EPA-600/9-...

  16. Mathematical modeling of acid deposition due to radiation fog

    SciTech Connect

    Pandis, S.N.; Seinfeld, J.H. )

    1989-09-20

    A Lagrangian model has been developed to study acidic deposition due to radiation fog. The model couples submodels describing the development and dissipation of radiation fog, the gas-phase chemistry and transfer, and the aqueous-phase chemistry. The model is applied to a radiation fog episode in Bakersfield in the San Joaquin Valley of California over the period January 4--5 1985. Model predictions for temperature profile, fog development, liquid water content, gas-phase concentrations of SO{sub 2}, HNO{sub 3}, and NH{sub 3}, {ital p}H, aqueous-phase concentrations of OS{sup 2{minus}}{sub 4}, NH{sup +}{sub 4}, and NO{sup {minus}}{sub 3}, and finally deposition rates of the above ions are compared with the observed values. The deposition rates of the major ions are predicted to increase significantly during the fog episode, the most notable being the increase of sulfate deposition. Pathways for sulfate production that are of secondary importance in a cloud environment may become signficant in a fog. Expressing the mean droplet settling velocity as a function of liquid water content is found to be quite influential in the model's predictions. {copyright} American Geophysical Union 1989

  17. High-deposition-rate ceramics synthesis

    SciTech Connect

    Allendorf, M.D.; Osterheld, T.H.; Outka, D.A.

    1995-05-01

    Parallel experimental and computational investigations are conducted in this project to develop validated numerical models of ceramic synthesis processes. Experiments are conducted in the High-Temperature Materials Synthesis Laboratory in Sandia`s Combustion Research Facility. A high-temperature flow reactor that can accommodate small preforms (1-3 cm diameter) generates conditions under which deposition can be observed, with flexibility to vary both deposition temperature (up to 1500 K) and pressure (as low as 10 torr). Both mass spectrometric and laser diagnostic probes are available to provide measurements of gas-phase compositions. Experiments using surface analytical techniques are also applied to characterize important processes occuring on the deposit surface. Computational tools developed through extensive research in the combustion field are employed to simulate the chemically reacting flows present in typical industrial reactors. These include the CHEMKIN and Surface-CHEMKIN suites of codes, which permit facile development of complex reaction mechanisms and vastly simplify the implementation of multi-component transport and thermodynamics. Quantum chemistry codes are also used to estimate thermodynamic and kinetic data for species and reactions for which this information is unavailable.

  18. A Calculation of Spatial Range of Colloidal Silicic Acid Deposited Downstream from the Alkali Front

    NASA Astrophysics Data System (ADS)

    Niibori, Yuichi; Iijima, Kazuki; Tamura, Naoyuki; Mimura, Hitoshi

    A high alkali domain spreads out due to the use of cement materials for the construction of the repository of radioactive wastes. Sudden change of pH at this alkali front produces colloidal silicic acid (polymeric silicic acid) in addition to the deposition of supersaturated monomeric silicic acid onto the fracture surface of flow-pathway. The colloidal silicic acid also deposits with relatively small rate-constant in the co-presence of solid phase. Once the flow-path surface is covered with the amorphous silica, the surface seriously degrades the sorption behavior of radionuclides (RNs). Therefore, so far, the authors have examined the deposition rates of supersaturated silicic acid. This study summarized the deposition rate-constants defined by the first-order reaction equation under various conditions of co-presence of amorphous silica powder. Then, using the smallest rate-constant (1.0×10-12 m/s in the co-presence of calcium ions of 1 mM) and a simulation code, COLFRAC-MRL, the spatial range of colloidal silicic acid deposited downstream from the alkali front was estimated. The results suggested the clogging caused by the deposition of colloidal silicic acid in flow-path. The altered spatial range in the flow-path was limited to around 30 m in fracture and to several centimeters in rock matrix.

  19. Acid deposition: Atmospheric processes in Eastern North America

    SciTech Connect

    Not Available

    1983-01-01

    This report examines scientific evidence on the relationship between emissions of acid-forming pollutants and damage to sensitive ecosystems from acid rain and other forms of acid deposition. The report's conclusions represent the most authoritative statement yet that reductions in emissions of these pollutants will result in proportional reductions in acid rain.

  20. Acid deposition and the acidification of soils and waters

    SciTech Connect

    Reuss, J.O.; Johnson, D.W.

    1985-01-01

    A conceptual model of acid deposition is presented consistent with established physicochemical principles and the bulk of available information. The authors seek to provide insight into probable long-term effects of acid deposition; a testable hypotheses; plus design and interpretation of the research. (PSB)

  1. Intermittency in dust deposition rates around the world

    NASA Astrophysics Data System (ADS)

    Fraser, N.; Schumer, R.

    2011-12-01

    Deposition rates for intermittent processes tend to depend on temporal measurement interval. This age interval bias can be used as a tool in evaluating the intermittency of dust deposition. Dust deposition is an intermittent process controlled by dust creation (erosion) and transport (dry winds). During glacial periods it is more likely that cold, dry winds will transport dust regionally and sometimes globally than during the warmer, wetter interglacial periods As deposition rates are estimated in loess cores over longer and longer time spans, it is more likely that large non-depositional or erosional periods may be incorporated into the average rate. Since loess cores are sampled by depth and material profile, the reported analysis rarely have equally space time intervals which causes age interval bias. 57 loess core profiles from Central Asia, New Zealand, North and South America, and Europe show the presence of power-law distributed hiatuses within the dust deposition record. Regional and global analysis of these 57 loess cores showed that dust deposition rates are equally affected by age interval bias no matter the scale. It is difficult to infer changes in dust deposition rates over time without equally spaced age intervals.

  2. The influence of a small amount of maleic acid on crystal deposition phenomena of methacrylic acid in melt crystallization

    NASA Astrophysics Data System (ADS)

    Hino, Tomomichi; Kato, Shinpei; Takiyama, Hiroshi

    2013-06-01

    Crystal deposition phenomena were investigated in the suspension melt crystallization of an organic acid. Methacrylic acid was used as the target substance, a certain amount of methanol was used as the solvent, and the effect of a small amount of maleic acid by-produced in methacrylic acid synthesis was focused on. Batch crystallizations were carried out on a laboratory scale using various concentrations of maleic acid. In the presence of maleic acid, a certain deviation from equilibrium of the pure binary system was observed in the final composition of mother liquor. Moreover, nevertheless the final temperature in the crystallizer was same, the amount of crystal deposition in the presence of maleic acid was smaller than in the absence of maleic acid. It was suggested that the final amount of crystal deposition decreased in the presence of maleic acid. Additionally, it was observed that the obtained crystal size was smaller in the presence of maleic acid. Hence, a simplified kinetic analysis of crystal deposition rates was carried out to make the effect of maleic acid clear. Consequently, it was suggested that the cause of the above-mentioned phenomena was the existence of the maleic acid concentration dependent pseudo-liquidus line.

  3. ROCKY MOUNTAIN ACID DEPOSITION MODEL ASSESSMENT: EVALUATION OF MESOSCALE ACID DEPOSITION MODELS FOR USE IN COMPLEX TERRAIN

    EPA Science Inventory

    The report includes an evaluation of candidate meteorological models and acid deposition models. The hybrid acid deposition/air quality modeling system for the Rocky Mountains makes use of a mesoscale meteorological model, which includes a new diagnostic wind model, as a driver f...

  4. Acid deposition in aquatic ecosystems: Setting limits empirically

    NASA Astrophysics Data System (ADS)

    Newcombe, Charles P.

    1985-07-01

    The problem of acid deposition and its harmful effects on aquatic ecosystems has created a new branch of science that is called upon to provide the knowledge on which legislative controls can be based. However, because of the nature of existing legislation, which requires evidence of cause and effect between industrial emissions and pollution, and because of science's inability to provide this information over the short term, considerable controversy has arisen about whether sufficient information exists to warrant control measures at this time. Among those who advocate controls, there is genuine divergence of opinion about how stringent the controls must be to achieve any desired level of protection. The controversy has led to an impasse between the scientific and political participants, which is reflected in the slow pace of progress toward an effective management strategy. Resolution of the impasse, at least in the short term, may demand that science and politics rely on empirical models rather than explanatory ones. The empirical model, which is the major proposal in this article, integrates all of the major variables and many of the minor ones, and constructs a three-dimensionally curved surface capable of representing the status of any waterbody subjected to the effects of acid deposition. When suitably calibrated—a process involving the integration of knowledge and data from aquatic biology, geochemistry, meteorology, and limnology—it can be used to depict limits to the rate of acid deposition required for any level of environmental protection. Because it can generate a pictorial display of the effects of management decisions and legislative controls, the model might serve as a basis for enhancing the quality of communication among all the scientific and political participants and help to resolve many of their controversies.

  5. ROCKY MOUNTAIN ACID DEPOSITION MODEL ASSESSMENT: ACID RAIN MOUNTAIN MESOSCALE MODEL (ARM3)

    EPA Science Inventory

    The Acid Rain Mountain Mesoscale Model (ARM3) is a mesoscale acid deposition/air quality model that was developed for calculating incremental acid deposition (sulfur and nitrogen species) and pollutant concentration impacts in complex terrain. The model was set up for operation w...

  6. Deposition Rates and Characterization of Arabian Mineral Dust

    NASA Astrophysics Data System (ADS)

    Puthan Purakkal, J.; Stenchikov, G. L.; Engelbrecht, J. P.

    2015-12-01

    Airborne mineral dust directly and indirectly impacts on global climate, continental and marine biochemistry, human and animal health, agriculture, equipment, and visibility. Annual global dust emissions are poorly known with estimates differing by a factor of at least two. Local dust emission and deposition rates are even less quantified. Dust deposition rate is a key parameter, which helps to constrain the modeled dust budget of the atmosphere. However, dust deposition remains poorly known, due to the limited number of reliable measurements. Simulations and satellite observations suggest that coastal dusts contribute substantially to the total deposition flux into the Red Sea. Starting December 2014, deposition samplers, both the "frisbee" type, and passive samplers for individual particle scanning electron microscopy were deployed at King Abdullah University of Science and Technology (KAUST), along the Red Sea in Saudi Arabia. Sampling periods of one month were adopted. The deposition rates range from 3 g m-2 month-1 for fair weather conditions to 23 g m-2 month-1 for high dust events. The X-ray diffraction (XRD) analyses of deposited dust samples show mineralogical compositions different from any of the parent soils, the former consisting mainly of gypsum, calcite, and smaller amounts of albite, montmorillonite, chlorite, quartz and biotite. The deposited dust samples on the other hand contain more gypsum and less quartz than the previously collected soil samples. This presentation discusses the results from XRD, chemical analysis and SEM-based individual particle analysis of the soils and the deposited dust samples. The monthly dust accumulation rates and their seasonal and spatial variability are compared with the regional model predictions. Data from this study provide an observational basis for validating the regional dust mass balance along the Arabian Red Sea coastal plain.

  7. Glow discharge deposition at high rates using disilane

    SciTech Connect

    Rajeswaran, G.; Corderman, R.R.; Kampas, F.J.; Vanier, P.E.

    1985-01-01

    The research program reported makes use of the fact that amorphous silicon films can be grown faster from disilane in a glow discharge than from the traditional silane. The goal is to find a method to grow films at a high rate and with sufficiently high quality to be used in an efficient solar cell. It must also be demonstrated that the appropriate device structure can be successfully fabricated under conditions which give high deposition rates. High quality intrinsic films have been deposited at 20 A/s. Efficiency of 5.6% on steel substrates and 5.3% on glass substrates were achieved using disilane i-layers deposited at 15 A/s in a basic structure, without wide-gap doped layers or light trapping. Wide gap p-layers were deposited using disilane. Results were compared with those obtained at Vactronic using high power discharges of silane-hydrogen mixtures. (LEW)

  8. Amino acid geochemistry of fossil bones from the Rancho La Brea asphalt deposit, California

    USGS Publications Warehouse

    McMenamin, M.A.S.; Blunt, D.J.; Kvenvolden, K.A.; Miller, S.E.; Marcus, L.F.; Pardi, R.R.

    1982-01-01

    Low aspartic acid d:l ratios and modern collagenlike concentration values indicate that amino acids in bones from the Rancho La Brea asphalt deposit, Los Angeles, California are better preserved than amino acids in bones of equivalent age that have not been preserved in asphalt. Amino acids were recovered from 10 Rancho La Brea bone samples which range in age from less than 200 to greater than 36,000 yr. The calibrated rates of aspartic acid racemization range from 2.1 to 5.0 ?? 10-6yr-1. Although this wide range of rate constants decreases the level of confidence for age estimates, use of the larger rate constant of 5.0 ?? 10-6yr-1 provides minimum age estimates which fit the known stratigraphic and chronologic records of the Rancho La Brea deposits. ?? 1982.

  9. ESTIMATES OF CLOUD WATER DEPOSITION AT MOUNTAIN DEPOSITION AT MOUNTAIN ACID DEPOSITION PROGRAM SITES IN THE APPALACHIAN MOUNTAINS

    EPA Science Inventory

    Cloud water deposition was estimated at three high elevation sites in the Appalachian Mountains of the eastern United States (Whiteface Mountain, NY, Whitetop Mountain, VA, and Clingrnan's Dome, TN) from 1994 through 1999 as part of the Mountain Acid Deposition Program (MADPro). ...

  10. Factors affecting response of surface waters to acidic deposition

    SciTech Connect

    Turner, R.S.; Johnson, D.W.; Elwood, J.W.; Van Winkle, W.; Clapp, R.B.; Reuss, J.O.

    1986-04-01

    Knowledge of watershed hydrology and of the biogeochemical reactions and elemental pools and fluxes occurring in watersheds can be used to classify the response of watersheds and surface waters to acidic deposition. A conceptual mosel is presented for classifying watersheds into those for which (1) surface water chemistry will change rapidly with deposition quality (direct response) (2) surface water chemistry will change only slowly over time (delayed response), and (3) surface water chemistry will not change significantly, even with continued acidic deposition (capacity-protected). Techniques and data available for classification of all watersheds in a region into these categories are discussed.

  11. Deposition Rate and Size Distribution of Volcanic Ash

    NASA Astrophysics Data System (ADS)

    Hikida, M.

    2006-12-01

    Sakurajima Volcano has been in violent activity since 1955 and erupting large amount of volcanic ash and stones from the crater. Volcanic fallouts have caused damages to the agricaltural products in the area and denuded the mountainside of vegitation. Deposited ash and stones on the mountainside has also caused hazardrous debris flows in the rivers. Therefore, it is necessary to know the deposition rate of the fallouts in prediction of debris flow. Due to the violent volcanic activity, however, it is prohibited to enter within two kilometers of the crater, making it impossible to measure the depth of deposited fallouts in the area. Theoretical study on deposition rate of volcanic fallouts should be needed to estimate the amount of fallouts in the upstream area. At first, motion of a particle erupted from the crater into the air was computed to examine its trajectory. From the simulation of the trajectory, a particle was assumed to fall at its terminal veloctity, and theoretical equation which give the deposition rate of volcanic ash and the distribution of deposited ash were obtained. In the derivation of these equations, the probability density functions of eruption column height, the terminal velocity of the erupted particles and the wind velocity were introduced. The computed values of amount of deposited ash show good agreement with the data taken from 93 collection points around Sakurajima Volcano. The annual amount of erupted volcanic ash was estimated to be about thirteen millions tons. The sample of deposited fallouts were taken to analize the size distribution. The data was also used to check the applicability of the theory presented.

  12. EMISSION INVENTORY APPLICATIONS TO REGIONAL ACID DEPOSITION MODELING

    EPA Science Inventory

    A comprehensive Regional Acid Deposition Model (RADM) is being developed and a simpler fast-turn-around 'engineering' model(s) (EM) is being designed by the National Center for Atmospheric Research as part of the National Acid Precipitation Assessment Program (NAPAP). This paper ...

  13. ANTHROPOGENIC EMISSIONS INVOLVED IN ACIDIC DEPOSITION PROCESSES

    EPA Science Inventory

    The paper describes the methodology that was used to develop the 1985 National Acid Precipitation Assessment Program (NAPAP) Emissions Inventory, including quality control procedures. and summarizes the inventory contents. evelopment of the 1985 inventory required detailed invest...

  14. ACID PRECIPITATION IN NORTH AMERICA: 1984 ANNUAL DATA SUMMARY FROM ACID DEPOSITION SYSTEM DATA BASE

    EPA Science Inventory

    The report gives a summary of 1984 wet deposition precipitation chemistry data collected in North America and available in the Acid Deposition System (ADS) data base. North American wet deposition monitoring networks with data in ADS are NADP/NTN, CANSAP, APN, UAPSP, MAP3S/PCN, W...

  15. ACID PRECIPITATION IN NORTH AMERICA: 1983 ANNUAL DATA SUMMARY FROM ACID DEPOSITION SYSTEM DATA BASE

    EPA Science Inventory

    The report gives a summary of 1983 wet deposition precipitation chemistry data collected in North America and available in the Acid Deposition System (ADS) data base. North American wet deposition monitoring networks with data in ADS are NADP/NTN, CANSAP, APN, UAPSP, MAP3S/PCN, W...

  16. Magnetic thin film deposition with pulsed magnetron sputtering: deposition rate and film thickness distribution

    NASA Astrophysics Data System (ADS)

    Ozimek, M.; Wilczyński, W.; Szubzda, B.

    2016-02-01

    The goal of conducted study was an experimental determining the relations between technological parameters of magnetron sputtering process on deposition rate (R) and thickness uniformity of magnetic thin films. Planar Ni79Fei6Mo5 target with a diameter of 100 mm was sputtered in argon (Ar) atmosphere. Deposition rate was measured in a function of gas pressure, target power and target-substrate distance. The highest value of R≈280 nmmin-1. The obtained results in deposition rate of magnetic film were compared to deposition rate of cooper (Cu), aluminum (Al), titanium (Ti) and titanium oxide (TiOx) and the deposition rate of Ni-Fe alloy were higher that Al and Ti. The film thickness distribution was measured for radial distance from the target centre ranging up to 60 mm and target-substrate distance ranging form 70 to 115 mm. Among others it was stated that for the larger value of target-substrate distance the larger uniform of film thickness are obtained.

  17. Experimental study of porosity reduction in high deposition-rate Laser Material Deposition

    NASA Astrophysics Data System (ADS)

    Zhong, Chongliang; Gasser, Andres; Schopphoven, Thomas; Poprawe, Reinhart

    2015-12-01

    For several years, the interest in Additive Manufacturing (AM) is continuously expanding, owing to the paradigm shift that new production processes, such as Laser Material Deposition (LMD), provide over conventional manufacturing technologies. With LMD, three-dimensional, complex components out of a wide range of materials can be manufactured consecutively layer-by-layer. Despite the technological advantages of the LMD process, currently achieved deposition-rates of approx. 0.5 kg/h for Inconel 718 (IN 718) remain a major concern in regards to processing times and economic feasibility. Moreover, processing conditions need to be chosen carefully or else material defects can be systematically formed either at the interface separating two adjacent clad layers, at the bonding zone or within the bulk of the layer. In this respect, the effects of powder humidity, laser power, nominal powder particle size, powder morphology and shielding gas flow rate on the porosity in laser deposited single tracks at an increased deposition-rate of approx. 2 kg/h was investigated through experiments. Based on experimental results, several approaches of reducing porosity in high deposition-rate LMD are proposed in this paper.

  18. A mechanistic study of phosphinocarboxylic acid for boiler deposit control

    SciTech Connect

    Chang, K.Y.; Patel, S.

    1995-11-01

    A laboratory study has been carried out to identify the key properties of phosphinocarboxylic acid polymers to control boiler water deposits. These multifunctional properties are its ability to: transport iron, disperse boiler water sludge that contains iron oxide, silica and calcium phosphate and dissolution of deposits. The thermal and hydrolytic stability of the phosphinocarboxylic acid polymers was investigated in autoclave studies up to 1,500 psig. The post-autoclave samples were analyzed by Nuclear Magnetic Resonance Spectroscopy and Aqueous Gel Permeation Chromatography to ascertain the polymer integrity. In addition performance tests were carried out for pre- and post-autoclave polymer samples. The performance testing clearly shows that phosphinocarboxylic acid polymers are effective in maintaining deposit control in a boiler due to their inherent thermal stability.

  19. A new look at liming as an approach to accelerate recovery from acidic deposition effects.

    PubMed

    Lawrence, Gregory B; Burns, Douglas A; Riva-Murray, Karen

    2016-08-15

    Acidic deposition caused by fossil fuel combustion has degraded aquatic and terrestrial ecosystems in North America for over four decades. The only management option other than emissions reductions for combating the effects of acidic deposition has been the application of lime to neutralize acidity after it has been deposited on the landscape. For this reason, liming has been a part of acid rain science from the beginning. However, continued declines in acidic deposition have led to partial recovery of surface water chemistry, and the start of soil recovery. Liming is therefore no longer needed to prevent further damage, so the question becomes whether liming would be useful for accelerating recovery of systems where improvement has lagged. As more is learned about recovering ecosystems, it has become clear that recovery rates vary with watershed characteristics and among ecosystem components. Lakes appear to show the strongest recovery, but recovery in streams is sluggish and recovery of soils appears to be in the early stages. The method in which lime is applied is therefore critical in achieving the goal of accelerated recovery. Application of lime to a watershed provides the advantage of increasing Ca availability and reducing or preventing mobilization of toxic Al, an outcome that is beneficial to both terrestrial and aquatic ecosystems. However, the goal should not be complete neutralization of soil acidity, which is naturally produced. Liming of naturally acidic areas such as wetlands should also be avoided to prevent damage to indigenous species that rely on an acidic environment. PMID:27092419

  20. A new look at liming as an approach to accelerate recovery from acidic deposition effects

    USGS Publications Warehouse

    Lawrence, Gregory B.; Burns, Douglas A.; Murray, Karen

    2016-01-01

    Acidic deposition caused by fossil fuel combustion has degraded aquatic and terrestrial ecosystems in North America for over four decades. The only management option other than emissions reductions for combating the effects of acidic deposition has been the application of lime to neutralize acidity after it has been deposited on the landscape. For this reason, liming has been a part of acid rain science from the beginning. However, continued declines in acidic deposition have led to partial recovery of surface water chemistry, and the start of soil recovery. Liming is therefore no longer needed to prevent further damage, so the question becomes whether liming would be useful for accelerating recovery of systems where improvement has lagged. As more is learned about recovering ecosystems, it has become clear that recovery rates vary with watershed characteristics and among ecosystem components. Lakes appear to show the strongest recovery, but recovery in streams is sluggish and recovery of soils appears to be in the early stages. The method in which lime is applied is therefore critical in achieving the goal of accelerated recovery. Application of lime to a watershed provides the advantage of increasing Ca availability and reducing or preventing mobilization of toxic Al, an outcome that is beneficial to both terrestrial and aquatic ecosystems. However, the goal should not be complete neutralization of soil acidity, which is naturally produced. Liming of naturally acidic areas such as wetlands should also be avoided to prevent damage to indigenous species that rely on an acidic environment.

  1. Changes in soil pH across England and Wales in response to decreased acid deposition

    NASA Astrophysics Data System (ADS)

    Kirk, G. J. D.; Bellamy, P. H.

    2009-04-01

    In our recent analysis of data from the National Soil Inventory of England and Wales, we found widespread changes in soil pH across both countries between the two samplings of the Inventory. In general, soil pH increased - i.e. soils became less acid - under all land uses. The Inventory was first sampled in 1978-83 on a 5-km grid over the whole area. This yielded about 6,000 sites of which 5,662 could be sampled for soil. Roughly 40% of the sites were re-sampled at intervals from 12 to 25 years after the original sampling - in 1994/96 for agricultural land and in 2002/03 for non-agricultural. Exactly the same sampling and analytical protocols were used in the two samplings. In arable soils, the increase in pH was right across the range, whereas in grassland soils the main increase was at the acid end of the scale (pH < 5.5) with a small increase above pH 7. Some part of the change is likely to have been due to changes in land management. This includes better targeting of agricultural lime on acid soils; changes in nitrogen fertilizer use; deeper ploughing bringing up more calcareous subsoil on soils on calcareous materials; and so forth. However a major driver appears to have been decreased acid deposition to land. The total amounts of nitrogen compounds deposited were relatively unchanged over the survey period, but the amounts of acidifying sulphur compounds decreased by approximately 50%. We constructed a linear regression model to assess the relation between the rate of change in pH (normalised to an annual basis) and the rate of change in acid deposition, as modified by soil properties (pH, clay content, organic matter content), rainfall and past acid deposition. We used data on rainfall and acid deposition over the survey period on the same 5-km grid as the NSI data. We fitted the model separately for each land use category. The results for arable land showed a significant effect of the change in rate of acid deposition, though a significant part of the

  2. Modelling airborne concentration and deposition rate of maize pollen

    NASA Astrophysics Data System (ADS)

    Jarosz, Nathalie; Loubet, Benjamin; Huber, Laurent

    2004-10-01

    The introduction of genetically modified (GM) crops has reinforced the need to quantify gene flow from crop to crop. This requires predictive tools which take into account meteorological conditions, canopy structure as well as pollen aerodynamic characteristics. A Lagrangian Stochastic (LS) model, called SMOP-2D (Stochastic Mechanistic model for Pollen dispersion and deposition in 2 Dimensions), is presented. It simulates wind dispersion of pollen by calculating individual pollen trajectories from their emission to their deposition. SMOP-2D was validated using two field experiments where airborne concentration and deposition rate of pollen were measured within and downwind from different sized maize (Zea mays) plots together with micrometeorological measurements. SMOP-2D correctly simulated the shapes of the concentration profiles but generally underestimated the deposition rates in the first 10 m downwind from the source. Potential explanations of this discrepancy are discussed. Incorrect parameterisation of turbulence in the transition from the crop to the surroundings is probably the most likely reason. This demonstrates that LS models for particle transfer need to be coupled with air-flow models under complex terrain conditions.

  3. Phenolic acids as bioindicators of fly ash deposit revegetation.

    PubMed

    Djurdjević, L; Mitrović, M; Pavlović, P; Gajić, G; Kostić, O

    2006-05-01

    The floristic composition, the abundance, and the cover of pioneer plant species of spontaneously formed plant communities and the content of total phenolics and phenolic acids, as humus constituents, of an ash deposit after 7 years of recultivation were studied. The restoration of both the soil and the vegetation on the ash deposits of the "Nikola Tesla-A" thermoelectric power plant in Obrenovac (Serbia) is an extremely slow process. Unfavorable physical and chemical characteristics, the toxicity of fly ash, and extreme microclimatic conditions prevented the development of compact plant cover. The abundance and cover of plants increased from the central part of the deposit towards its edges (ranging from 1-80%). Festuca rubra L., Crepis setosa Hall., Erigeron canadensis L., Cirsium arvense (L.) Scop., Calamagrostis epigeios (L.) Roth., and Tamarix gallica L. were the most abundant species, thus giving the highest cover. Humus generated during the decomposition process of plant remains represents a completely new product absent in the ash as the starting material. The amount of total phenolics and phenolic acids (38.07-185.16 microg/g of total phenolics and 4.12-27.28 microg/g of phenolic acids) in fly ash increased from the center of the deposit towards its edges in correlation with the increase in plant abundance and cover. Ash samples contained high amounts of ferulic, vanillic, and p-coumaric acid, while the content of both p-hydroxybenzoic and syringic acid was relatively low. The presence of phenolic acids indicates the ongoing process of humus formation in the ash, in which the most abundant pioneer plants of spontaneously formed plant communities play the main role. Phenolic compounds can serve as reliable bioindicators in an assessment of the success of the recultivation process of thermoelectric power plants' ash deposits. PMID:16418890

  4. Influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel films

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Anderoglu, O.; Misra, A.; Wang, H.

    2007-04-01

    The authors have studied the influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel thin films. Transmission electron microscopy shows that the volume fraction of twinned grains increases with increasing deposition rate, whereas the average columnar grain size and twin spacing stay approximately unchanged. These experimental results agree qualitatively with their analytical model that predicts deposition rate dependent formation of growth twins. The film hardness increases monotonically with increasing volume fraction of twinned grains.

  5. Influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel films

    SciTech Connect

    Zhang, X.; Anderoglu, O.; Misra, A.; Wang, H.

    2007-04-09

    The authors have studied the influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel thin films. Transmission electron microscopy shows that the volume fraction of twinned grains increases with increasing deposition rate, whereas the average columnar grain size and twin spacing stay approximately unchanged. These experimental results agree qualitatively with their analytical model that predicts deposition rate dependent formation of growth twins. The film hardness increases monotonically with increasing volume fraction of twinned grains.

  6. Phenolic acids as bioindicators of fly ash deposit revegetation

    SciTech Connect

    L. Djurdjevic; M. Mitrovic; P. Pavlovic; G. Gajic; O. Kostic

    2006-05-15

    The floristic composition, the abundance, and the cover of pioneer plant species of spontaneously formed plant communities and the content of total phenolics and phenolic acids, as humus constituents, of an ash deposit after 7 years of recultivation were studied. The restoration of both the soil and the vegetation on the ash deposits of the 'Nikola Tesla-A' thermoelectric power plant in Obrenovac (Serbia) is an extremely slow process. Unfavorable physical and chemical characteristics, the toxicity of fly ash, and extreme microclimatic conditions prevented the development of compact plant cover. The abundance and cover of plants increased from the central part of the deposit towards its edges. Festuca rubra L., Crepis setosa Hall., Erigeron canadensis L., Cirsium arvense (L.) Scop., Calamagrostis epigeios (L.) Roth., and Tamarix gallica L. were the most abundant species, thus giving the highest cover. Humus generated during the decomposition process of plant remains represents a completely new product absent in the ash as the starting material. The amount of total phenolics and phenolic acids in fly ash increased from the center of the deposit towards its edges in correlation with the increase in plant abundance and cover. The presence of phenolic acids indicates the ongoing process of humus formation in the ash, in which the most abundant pioneer plants of spontaneously formed plant communities play the main role. Phenolic compounds can serve as reliable bioindicators in an assessment of the success of the recultivation process of thermoelectric power plants' ash deposits.

  7. Biosynthetic growth hormone increases the collagen deposition rate in rat aorta and heart.

    PubMed

    Brüel, A; Oxlund, H

    1995-02-01

    Disorders of the cardiovascular system often are associated with alterations in the metabolism of the collagens of these tissues. A method for in vivo determination of collagen deposition rate in small tissue samples is delineated and used for assessment of the effect of biosynthetic growth hormone (GH) injections on the collagen deposition rate in rat aorta and cardiac musculature. Rats were injected with GH, and the controls with saline, twice daily for 7 days. The in vivo collagen deposition rate was measured by injecting iv a large dose of [3H]-proline with a flooding dose of "cold" proline, followed by determination of the production of [3H]-hydroxyproline during a 4-h labelling period. Extractable collagens that were not bound in the tissue and therefore do not contribute mechanical strength to it were removed from the samples. 3H-Labelled- and "cold" amino acids were assessed by reversed-phase HPLC combined with simultaneous flow scintillation detection on the same sample. In the control group the deposition per hour was 0.13 +/- 0.02% (mean +/- SEM) in aortic intima media and 0.72 +/- 0.09% in cardiac left ventricular musculature. Growth hormone induced a threefold increase (p < 0.001 and p < 0.01, respectively) in the collagen deposition rate: 0.45 +/- 0.06% in aortic intima media and 2.43 +/- 0.45% in cardiac left ventricular musculature. The method described enables a rapid and sensitive determination of collagen deposition per hour in small tissue samples from experimental animals. The collagen deposition rate of cardiac musculature is fivefold higher compared with that of aortic intima media.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7858738

  8. PARAMETRIC METHODOLOGIES OF CLOUD VERTICAL TRANSPORT FOR ACID DEPOSITION MODELS

    EPA Science Inventory

    A CUmulus VENTing (CUVENT) cloud module has been developed that calculates the vertical flux of mass from the boundary layer to the cloud layer by an ensemble of nonprecipitating subgrid-scale air mass clouds. This model will be integrated into the Regional Acid Deposition Model ...

  9. POLLUTANT SAMPLER FOR MEASUREMENTS OF ATMOSPHERIC ACIDIC DRY DEPOSITION

    EPA Science Inventory

    An acidic pollutant sampler for dry deposition monitoring has been designed and evaluated in laboratory and field studies. The system, which is modular and simple to operate, samples gaseous HNO3, NH3, SO2 and NO2 and particulate SO4(-2), NO3(1-) and NH4(1+) and is made of Teflon...

  10. Global impacts of sulfate deposition from acid rain on methane emissions from natural wetlands.

    NASA Astrophysics Data System (ADS)

    Gauci, V.

    2003-04-01

    Natural wetlands form the largest methane (CH_4) source to the atmosphere. A collection of recent field and laboratory studies point to an anthropogenic control on CH_4 emissions from these systems: acid rain sulfate (SO_42-) deposition. These studies ranging from the UK, USA, Canada, Sweden and Czech Republic demonstrate that low rates of SO_42- deposition, within the range commonly experienced in acid rain impacted regions, can suppress CH_4 emissions by as much as 40% and that the response of CH_4 emissions to increasing rates of SO_42- deposition closely mirrors changes in sulfate reduction rates with SO_42- deposition. This indicates that the suppression in CH_4 flux is the result of acid rain stimulating a competitive exclusion of methanogenesis by sulfate reducing bacteria, resulting in reduced methane production. These findings were extrapolated to the global scale by combining modelled, spatially explicit data sets of CH_4 emission from wetlands across the globe with modelled S deposition. Results indicate that this interaction may be important at the global scale, suppressing CH_4 emissions from wetlands in 2030 by as much as 20--28Tg, and, in the process, offsetting predicted climate induced growth in the wetland CH_4 source.

  11. Emissions involved in acidic deposition processes: Methodology and results

    SciTech Connect

    Placet, M.

    1990-01-01

    Data on the emissions involved in atmospheric acid-base chemistry are crucial to the assessment of acidic deposition and its effects. Sulfur dioxide (SO{sub 2}), nitrogen oxides (NO{sub x}), and volatile organic compounds (VOCs) are the primary chemical compounds involved in acidic deposition processes. In addition, other emission species -- e.g., ammonia, alkaline dust particles, hydrogen chloride, and hydrogen fluoride -- are involved in atmospheric acid-base chemistry, either by contributing acidic constituents or by neutralizing acidic species. Several emissions data bases have been developed under the auspices of the National Acid Precipitation Program (NAPAP). In addition to those developed by NAPAP, emissions data bases and emissions trends estimates also have been developed by organizations such as the Electric Power Research Institute (EPRI) and the U.S. Environmental Protection Agency (EPA). This paper briefly describes and compares the methods used in developing these emissions data bases and presents an overview of their emissions estimates. A more detailed discussion of these topics can be found in the State-of-Science Report on emissions recently released by NAPAP and in the references cited in that report. 14 refs., 4 figs., 1 tab.

  12. Anthropogenic Oxidation of Seafloor Massive Sulfide (SMS) deposits: Implications for Localized Seafloor Acid Generation

    NASA Astrophysics Data System (ADS)

    Bilenker, L.; Romano, G. Y.; Mckibben, M. A.

    2011-12-01

    A rapid increase in the price of transition metals in recent years has piqued interest in deep sea in situ mining of seafloor massive sulfide (SMS) deposits. There are important unanswered questions about the potential environmental effects of seafloor mining, particularly localized sulfuric acid generation. Currently there is a paucity of data on the oxidation kinetics of sulfide minerals in seawater. Seafloor massive sulfides oxidize rapidly via irreversible, acid-producing reactions. The oxidation kinetics of these minerals need to be quantified to estimate the significance of acid production. Laboratory experiments have been performed to evaluate the effects of pH, temperature, oxidant concentration, and mineral surface area on the rate of oxidation of chalcopyrite (CuFeS2) and pyrrhotite (Fe1-xS) in seawater. Temperature controlled circulation baths, Teflon reaction vessels, synthetic seawater, and pure, hand sorted natural sulfide mineral crystals are used in experiments. Both batch and flow-through reactor methods are employed. Reaction products are analyzed using ICP-MS. The rate law is expressed as follows: R = k (MO2,aq)a(MH+)b where R is the specific mineral oxidation rate (moles/m2/sec), k is the rate constant (a function of temperature), and a and b are reaction orders for molar aqueous species' concentrations (M). The initial rate method is used to determine the reaction order of each variable. Chalcopyrite and pyrrhotite are being studied because as the slowest- and fastest-oxidizing of the common sulfide minerals found in SMS deposits, they bound the range of rates seen in seafloor settings and can be used to place lower and upper limits on abiotic rates of metal release and sulfuric acid production. Experiments to date indicate an oxidation rate of pyrrhotite several times faster than that of chalcopyrite. The rate laws, when incorporated into reactive-transport computer codes, will enable the prediction of localized anthropogenic sulfuric acid

  13. Electrophoretic deposition of tannic acid-polypyrrolidone films and composites.

    PubMed

    Luo, Dan; Zhang, Tianshi; Zhitomirsky, Igor

    2016-05-01

    Thin films of polyvinylpyrrolidone (PVP)-tannic acid (TA) complexes were prepared by a conceptually new strategy, based on electrophoretic deposition (EPD). Proof of concept investigations involved the analysis of the deposition yield, FTIR and UV-vis spectroscopy of the deposited material, and electron microscopy studies. The analysis of the deposition mechanism indicated that the limitations of the EPD in the deposition of small phenolic molecules, such as TA, and electrically neutral polymers, similar to PVP, containing hydrogen-accepting carbonyl groups, can be avoided. The remarkable adsorption properties of TA and film forming properties of the PVP-TA complexes allowed for the EPD of materials of different types, such as huntite mineral platelets and hydrotalcite clay particles, TiO2 and MnO2 oxide nanoparticles, multiwalled carbon nanotubes, TiN and Pd nanoparticles. Moreover, PVP-TA complexes were used for the co-deposition of different materials and formation of composite films. In another approach, TA was used as a capping agent for the hydrothermal synthesis of ZnO nanorods, which were then deposited by EPD using PVP-TA complexes. The fundamental adsorption and interaction mechanisms of TA involved chelation of metal atoms on particle surfaces with galloyl groups, π-π interactions and hydrogen bonding. The films prepared by EPD can be used for various applications, utilizing functional properties of TA, PVP, inorganic and organic materials of different types and their composites. PMID:26878711

  14. Nitric Acid-Sea Salt Reactions: Implications for Nitrogen Deposition to Water Surfaces.

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Sørensen, L. L.

    2000-05-01

    Many previous studies have indicated the importance of nitric acid (HNO3) reactions on sea salt particles for flux divergence of HNO3 in the marine surface layer. The potential importance of this reaction in determining the spatial and temporal patterns of nitrogen dry deposition to marine ecosystems is investigated using models of sea spray generation and particle- and gas-phase dry deposition. Under horizontally homogeneous conditions with near-neutral stability and for wind speeds between 3.5 and 10 m s1, transfer of HNO3 to the particle phase to form sodium nitrate may decrease the deposition velocity of nitrogen by over 50%, leading to greater horizontal transport prior to deposition to the sea surface. Conversely, for wind speeds above 10 m s1, transfer of nitrogen to the particle phase would increase the deposition rate and hence decrease horizontal transport prior to surface removal.

  15. MOUNTAIN ACID DEPOSITION PROGRAM (MADPRO): CLOUD DEPOSITION TO THE APPALACHIAN MOUNTAINS, 1994 THROUGH 1999

    EPA Science Inventory

    The mountain Acid Deposition Program (MADPro) was initiated in 1993 as part of the research necessary to support the objectives of the Clean Air Status and Trends Network (CASTNet), which was created to address the requirements of the Clean Air Act Amendments (CAAA). The two ma...

  16. Dry deposition and heavy acid loading in the vicinity of Masaya Volcano, a major sulfur and chlorine source in Nicaragua.

    PubMed

    Delmelle, P; Stix, J; Bourque, C P; Baxter, P J; Garcia-Alvarez, J; Barquero, J

    2001-04-01

    Certain volcanoes constitute the world's largest sources of SO2, HCl, and HF emissions and contribute significantly to regional acid deposition. However, the impact of volcanic acid emissions to nearby ecosystems remain poorly documented. In this paper, the spatial pattern of acid dry depositions was monitored within 44 km of Masaya Volcano, Nicaragua, with a network of sulfation plates. Measured SO2 deposition rates were <2-791 mg m(-2) day(-1). The plates also collected the dry deposition of HCI at rates of <1-297 mg m(-2) day(-1). A similar deposition velocity Vd (gas transfer) of 1.6 +/- 0.8 cm/s was calculated for SO2 and HCl above the plate surfaces. Quantities of SO2 and HCI deposited daily within the area surveyed amounted to 1.5 x 10(8) g and 5.7 x 10(7) g, respectively, which correspond to about 10% of the total SO2 and HCl released by the volcano. These depositions may generate an equivalent hydrogen flux ranging from <1 to 30 mg m(-2) day(-1). Our results demonstrate that volcano emissions can dramatically affect acid deposition downwind and in turn cause extreme acid loading of the local ecosystems. This study opens exciting prospects for investigating the sensivity of volcanic ash soils to acid inputs. PMID:11348058

  17. Role of acid rain in atmospheric deposition. Final report

    SciTech Connect

    Winchester, J.W.

    1990-12-31

    A study was conducted to assess the potential importance of atmospheric nitrate deposition for a north Florida estuary. A comparison, based on statistical analysis of fluxes of ten dissolved constituents of rain water and river water, has been carried out for the watershed of the Apalachicola River, utilizing weekly rain water chemical data from the National Acid Deposition Program (NADP) for five sites within the watershed area, monitored from 1978-84 until late 1989, and less frequent river water chemical data from the U.S. Geological Survey for one site at Chattahoochee, Florida, monitored from 1965 until late 1989. Similar statistical analysis was performed on monitoring data for the Sopchoppy and Ochlockonee Rivers of north Florida. Atmospheric deposition to the watershed appears to be sufficient to account for essentially all the dissolved nitrate and ammonium and total organic nitrogen flow in the three rivers. However, after deposition most of the nitrate may be transformed to other chemical forms during the flow of the rivers toward their estuaries. In an additional statistical analysis of rain water monitoring data from the eight state southeastern USA region, it was found that both meteorological conditions and transport from pollution sources appear to control deposition fluxes of nitrate and sulfate acid air pollutants.

  18. Analysis of the rate of wildcat drilling and deposit discovery

    USGS Publications Warehouse

    Drew, L.J.

    1975-01-01

    The rate at which petroleum deposits were discovered during a 16-yr period (1957-72) was examined in relation to changes in a suite of economic and physical variables. The study area encompasses 11,000 mi2 and is located on the eastern flank of the Powder River Basin. A two-stage multiple-regression model was used as a basis for this analysis. The variables employed in this model were: (1) the yearly wildcat drilling rate, (2) a measure of the extent of the physical exhaustion of the resource base of the region, (3) a proxy for the discovery expectation of the exploration operators active in the region, (4) an exploration price/cost ratio, and (5) the expected depths of the exploration targets sought. The rate at which wildcat wells were drilled was strongly correlated with the discovery expectation of the exploration operators. Small additional variations in the wildcat drilling rate were explained by the price/cost ratio and target-depth variables. The number of deposits discovered each year was highly dependent on the wildcat drilling rate, but the aggregate quantity of petroleum discovered each year was independent of the wildcat drilling rate. The independence between these last two variables is a consequence of the cyclical behavior of the exploration play mechanism. Although the discovery success ratio declined sharply during the initial phases of the two exploration plays which developed in the study area, a learning effect occurred whereby the discovery success ratio improved steadily with the passage of time during both exploration plays. ?? 1975 Plenum Publishing Corporation.

  19. Application of thermal spray coatings using high deposition rate equipment

    SciTech Connect

    Novak, H.L.

    1995-12-01

    Reusable launch vehicles located by the ocean are subject to harsh seacoast environments before launch and immersion after splashdown at sea and towback to the refurbishment facility. High strength aluminum and non-corrosion resistant steel alloys are prone to general corrosion and pitting due to galvanic couples and protective coating damage. Additional protection of structural materials with thermally sprayed pure aluminum coatings was evaluated for plasma, arc spray and high velocity oxy-fuel (HVOF) processes. Comparisons are made for corrosion rates of various coated aluminum alloy and steel substrates when exposed to ASTM B-117 neutral salt fog testing and also to beach exposure tests performed at Kennedy Space Center, Florida. Recent development work involved the use of high deposition rate thermal arc-spray equipment. The use of an inverter power supply reduced powdering and enhanced operator visibility. Deposition rates of 45.36--68.04 kilograms/hour are obtainable using 4.76--6.35 millimeter diameter wire electrodes.

  20. Simulated seasonal variations in wet acid depositions over East Asia.

    PubMed

    Ge, Cui; Zhang, Meigen; Zhu, Lingyun; Han, Xiao; Wang, Jun

    2011-11-01

    The air quality modeling system Regional Atmospheric Modeling System-Community Multi-scale Air Quality (RAMS-CMAQ) was applied to analyze temporospatial variations in wet acid deposition over East Asia in 2005, and model results obtained on a monthly basis were evaluated against extensive observations, including precipitation amounts at 704 stations and SO4(2-), NO3-, and NH4+ concentrations in the atmosphere and rainwater at 18 EANET (the Acid Deposition Monitoring Network in East Asia) stations. The comparison shows that the modeling system can reasonably reproduce seasonal precipitation patterns, especially the extensive area of dry conditions in northeast China and north China and the major precipitation zones. For ambient concentrations and wet depositions, the simulated results are in reasonable agreement (within a factor of 2) with observations in most cases, and the major observed features are mostly well reproduced. The analysis of modeled wet deposition distributions indicates that East Asia experiences noticeable variations in its wet deposition patterns throughout the year. In winter, southern China and the coastal areas of the Japan Sea report higher S04(2-) and NO3- wet depositions. In spring, elevated SO4(2-) and NO3-wet depositions are found in northeastern China, southern China, and around the Yangtze River. In summer, a remarkable rise in precipitation in northeastern China, the valleys of the Huaihe and Yangtze rivers, Korea, and Japan leads to a noticeable increase in SO4(2-) and NO3- wet depositions, whereas in autumn, higher SO4(2-) and NO3-wet depositions are found around Sichuan Province. Meanwhile, due to the high emission of SO2, high wet depositions of SO4(2-) are found throughout the entire year in the area surrounding Sichuan Province. There is a tendency toward decreasing NO3- concentrations in rainwater from China through Korea to Japan in both observed and simulated results, which is a consequence of the influence of the continental

  1. High growth rate homoepitaxial diamond film deposition at high temperatures by microwave plasma-assisted chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Vohra, Yogesh K. (Inventor); McCauley, Thomas S. (Inventor)

    1997-01-01

    The deposition of high quality diamond films at high linear growth rates and substrate temperatures for microwave-plasma chemical vapor deposition is disclosed. The linear growth rate achieved for this process is generally greater than 50 .mu.m/hr for high quality films, as compared to rates of less than 5 .mu.m/hr generally reported for MPCVD processes.

  2. The effect of deposition rate on the intrinsic stress in copper and silver thin films

    NASA Astrophysics Data System (ADS)

    Del Vecchio, A. L.; Spaepen, F.

    2007-03-01

    The effect of changing the deposition rate on the development of stress in evaporated copper and silver thin films deposited on oxidized silicon was examined. In situ stress measurements were made during deposition in ultrahigh vacuum using a scanning laser curvature system. In some experiments, the deposition rate was alternated without interruption of deposition. For copper thin films, a change in deposition rate has no effect on the development of the tensile stress, while the magnitude of the postcoalescence compressive stress decreases with increasing deposition rate. In silver films, the film thickness at the tensile maximum increases slightly with increasing deposition rate, while the magnitude of the postcoalescence compressive stress again decreases with increasing deposition rate. Analysis of the heat flow during deposition shows that the radiative heating and condensation contribute roughly equally to the temperature rise of the sample.

  3. Suppression of rice methane emission by sulfate deposition in simulated acid rain

    NASA Astrophysics Data System (ADS)

    Gauci, Vincent; Dise, Nancy B.; Howell, Graham; Jenkins, Meaghan E.

    2008-09-01

    Sulfate in acid rain is known to suppress methane (CH4) emissions from natural freshwater wetlands. Here we examine the possibility that CH4 emissions from rice agriculture may be similarly affected by acid rain, a major and increasing pollution problem in Asia. Our findings suggest that acid rain rates of SO42- deposition may help to reduce CH4 emissions from rice agriculture. Emissions from rice plants treated with simulated acid rain at levels of SO42- consistent with the range of deposition in Asia were reduced by 24% during the grain filling and ripening stage of the rice season which accounts for 50% of the overall CH4 that is normally emitted in a rice season. A single application of SO42- at a comparable level reduced CH4 emission by 43%. We hypothesize that the reduction in CH4 emission may be due to a combination of effects. The first mechanism is that the low rates of SO42- may be sufficient to boost yields of rice and, in so doing, may cause a reduction in root exudates to the rhizosphere, a key substrate source for methanogenesis. Decreasing a major substrate source for methanogens is also likely to intensify competition with sulfate-reducing microorganisms for whom prior SO42- limitation had been lifted by the simulated acid rain S deposition.

  4. Precipitation-chemistry measurements from the California Acid Deposition Monitoring Program, 1985-1990

    USGS Publications Warehouse

    Blanchard, Charles L.; Tonnessen, Kathy A.

    1993-01-01

    The configuration of the California Acid Deposition Monitoring Program (CADMP) precipitation network is described and quality assurance results summarized. Comparison of CADMP and the National Acid Deposition Program/National Trends Network (NADP/NTN) data at four parallel sites indicated that mean depth-weighted differences were less than 3 μeq ℓ−1 for all ions, being statistically significant for ammonium, sulfate and hydrogen ion. These apparently small differences were 15–30% of the mean concentrations of ammonium, sulfate and hydrogen ion. Mean depth-weighted concentrations and mass deposition rates for the period 1985–1990 are summarized; the latter were highest either where concentrations or precipitation depths were relatively high.

  5. Electrophoretic deposition and electrochemical behavior of novel graphene oxide-hyaluronic acid-hydroxyapatite nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Li, Ming; Liu, Qian; Jia, Zhaojun; Xu, Xuchen; Shi, Yuying; Cheng, Yan; Zheng, Yufeng; Xi, Tingfei; Wei, Shicheng

    2013-11-01

    Novel ternary graphene oxide-hyaluronic acid-hydroxyapatite (GO-HY-HA) nanocomposite coatings were prepared on Ti substrate using anodic electrophoretic deposition (EPD). Hyaluronic acid was employed as charging additive and dispersion agent during EPD. The kinetics and mechanism of the deposition, and the microstructure of the coated samples were investigated using scanning electron microscopy, X-ray diffraction, Raman spectrum, thermo-gravimetric analysis, and microscopic Fourier transform infrared analysis. The results showed that the addition of GO sheets into the HY-HA suspensions could increase the deposition rate and inhibit cracks creation and propagation in the coatings. The corrosion resistant of the resulting samples were evaluated using potentiodynamic polarization method in simulated body fluid, and the GO-HY-HA coatings could effectively improve the anti-corrosion property of the Ti substrate.

  6. ACIDIC DEPOSITION IN THE NORTHEASTERN U.S.: SOURCES AND INPUTS, ECOSYSTEM EFFECTS, AND MANAGEMENT STRATEGIES

    EPA Science Inventory

    Acidic deposition results from the emissions of air pollutants. Effects of acidic deposition in the northeastern US include the acidification of soil and water, causing stresses to terrestrial and aquatic biota.

  7. High-rate deposition of hydrogenated amorphous silicon films and devices

    SciTech Connect

    Luft, W.

    1987-04-01

    This report summarizes the status of high-rate deposition technologies associated with amorphous silicon thin films for photovoltaic applications. The report lists (1) deposition rates for a-Si:H films according to source and method and (2) efficiencies and other parameters of a-Si:H solar cells. Two main deposition source materials, silane and disilane, are discussed, as well as effects of boron doping. The effects of various deposition parameters on film characteristics and on deposition rate are presented, as well as the effects of annealing on high-deposition-rate films. Light-induced effects are also discussed. Finally, progress and problems in this field of study are summarized.

  8. Acid Deposition From Stratospheric Geoengineering With Sulfate Aerosols

    NASA Astrophysics Data System (ADS)

    Kravitz, B.; Robock, A.; Oman, L.; Stenchikov, G.

    2008-12-01

    We used a general circulation model of the Earth's climate to conduct geoengineering experiments involving stratospheric injection of sulfur dioxide [Robock et al., 2008] and analyzed the resulting deposition of sulfate. When sulfur is injected into the tropical or Arctic stratosphere, the main additional surface deposition occurs in midlatitude bands, because of strong cross-tropopause flux in the jet stream regions, and there are some larger local increases, specifically in Northern Canada and the Western Pacific Ocean. We used critical load studies to determine the effects of this increase in acid deposition on terrestrial ecosystems. For annual injection of 5 Tg of SO2 into the tropical stratosphere or 3 Tg of SO2 into the Arctic stratosphere, the additional surface sulfate deposition is not enough to negatively impact most ecosystems. Robock, Alan, Luke Oman, and Georgiy Stenchikov (2008), Regional climate responses to geoengineering with tropical and Arctic SO2 injections. J. Geophys. Res., 113, D16101, doi:10.1029/2008JD010050.

  9. Mitigation of acid deposition: Liming of surface waters. Final report

    SciTech Connect

    Bartoshesky, J.; Price, R.; DeMuro, J.

    1989-05-01

    In recent years acid deposition has become a serious concern internationally. Scientific literature has documented the acidification of numerous lakes and streams in North America and Scandinavia resulting in the depletion or total loss of fisheries and other aquatic biota. Liming represents the only common corrective practice aimed specifically at remediating an affected acid receptor. This report reviews a range of liming technologies and liming materials, as well as the effect of surface-water liming on water quality and aquatic biota. As background to the liming discussion, the hydrologic cycle and the factors that make surface waters sensitive to acid deposition are also discussed. Finally, a brief review of some of the liming projects that have been conducted, or are currently in operation is presented, giving special emphasis to mitigation efforts in Maryland. Liming has been effectively used to counteract surface-water acidification in parts of Scandinavia, Canada, and the U.S. To date, liming has generally been shown to improve physical and chemical conditions and enhance the biological recovery of aquatic ecosystems affected by acidification.

  10. Polyglycolic acid microneedles modified with inkjet-deposited antifungal coatings.

    PubMed

    Boehm, Ryan D; Daniels, Justin; Stafslien, Shane; Nasir, Adnan; Lefebvre, Joe; Narayan, Roger J

    2015-01-01

    In this study, the authors examined use of piezoelectric inkjet printing to apply an antifungal agent, voriconazole, to the surfaces of biodegradable polyglycolic acid microneedles. Polyglycolic acid microneedles with sharp tips (average tip radius = 25 ± 3 μm) were prepared using a combination of injection molding and drawing lithography. The elastic modulus (9.9 ± 0.3 GPa) and hardness (588.2 ± 33.8 MPa) values of the polyglycolic acid material were determined using nanoindentation and were found to be suitable for use in transdermal drug delivery devices. Voriconazole was deposited onto the polyglycolic acid microneedles by means of piezoelectric inkjet printing. It should be noted that voriconazole has poor solubility in water; however, it is readily soluble in many organic solvents. Optical imaging, scanning electron microscopy, energy dispersive x-ray spectrometry, and Fourier transform infrared spectroscopy were utilized to examine the microneedle geometries and inkjet-deposited surface coatings. Furthermore, an in vitro agar plating study was performed on the unmodified, vehicle-modified, and voriconazole-modified microneedles. Unlike the unmodified and vehicle-modified microneedles, the voriconazole-modified microneedles showed antifungal activity against Candida albicans. The unmodified, vehicle-modified, and voriconazole-modified microneedles did not show activity against Escherichia coli, Pseudomonas aeruginosa, or Staphylococcus aureus. The results indicate that piezoelectric inkjet printing may be useful for loading transdermal drug delivery devices such as polyglycolic acid microneedles with antifungal pharmacologic agents and other pharmacologic agents with poor solubility in aqueous solutions. PMID:25732934

  11. Aeolian dust deposition rates in Northern French forests and inputs to their biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Lequy, Émeline; Legout, Arnaud; Conil, Sébastien; Turpault, Marie-Pierre

    2013-12-01

    This study describes the Aeolian dust deposition (ADD) in 4 sites of Northern France. Between December 2009 and March 2012, we sampled (i) Aeolian dust every four weeks, and (ii) 6 episodes of forecasted high atmospheric dust load mainly from the Saharan desert, the largest source of Aeolian dust in the world. These samples were treated with oxygen peroxide to remove organic matter so as to only compare the mineral fraction of the samples in the 4 sampling sites and to analyze their mineralogy. The solid samples contained the hardly soluble part of Aeolian dust (H-ADD). Its deposition was of 1.9 ± 0.3 g m-2 year-1 with a seasonal pattern of high deposition from spring to early autumn and a low deposition in winter. H-ADD deposition during the forecasted episodes of high atmospheric load did not systematically exceed the deposition rate during the rest of the sampling period. This indicates that such episodes little contributed to the annual H-ADD rate. The mineralogy revealed a heterogeneous set of minerals dominated by silicates with a common basis of major types (quartz, feldspars, mica, chlorite, kaolinite and interlayered clay minerals in every sample) with randomly trace minerals (Fe-oxides, sulfates, amphibole, talc, gibbsite and carbonates). The chemistry of H-ADD led to a dominant input of Si (up to 4.4 kg ha-1 year-1), while the nutrients inputs of Ca, K, Mg and P from ADD and the atmospheric organics (APD) in openfield were together of 1.5 ± 0.5 kg ha-1 year-1 with a high contribution of soluble minerals and organic matter of ca. 40% for Mg and K, and of ca. 80% for Ca and P. Nutrient inputs from APD are especially an interesting source of P for forests developed on acidic soils.

  12. A 120-year record of the spatial and temporal distribution of gravestone decay and acid deposition

    NASA Astrophysics Data System (ADS)

    Mooers, Howard D.; Cota-Guertin, Avery R.; Regal, Ronald R.; Sames, Anthony R.; Dekan, Amanda J.; Henkels, Linnea M.

    2016-02-01

    This investigation examines the spatial and temporal variability of marble gravestone decay throughout West Midlands County and adjacent portions of Warwickshire, Staffordshire, and Worcestershire. Gravestone decay has been used effectively as a quantitative measure of acid deposition. Numerous techniques have been used to assess gravestone decay and each is subject to different sources of error. To minimize error we focus only on marble gravestones that use the flush lead lettering technique. Decay of the marble leaves the lead lettering raised above the surface, and the distance can be measured with the use of a digital micrometer. Gravestone decay can be used to quantify the spatial and temporal distribution of acid deposition. Our gravestone decay database consists of 1417 individual measurements on 591 tombstones in 33 cemeteries and covers the period from 1860 to 2010. Sites range from industrial and residential areas to rural settings. These data allow us to establish the natural background rates of decay, the effects of urban/residential expansion, and the efficacy of environmental regulations. Decay rates vary from a minimum of 0.2 mm/century in remote rural areas to nearly 3.0 mm/century in the Birmingham City Center. The data are corrected for environmental variables, converted to acid deposition rates, and plotted at 10-year intervals from 1890 to 2010.

  13. Modeling the contribution of soil fauna to litter decomposition influenced by acidic deposition

    SciTech Connect

    Cai, B.; Loucks, O.L; Kuperman, R. Argonne National Lab., IL )

    1993-06-01

    The effect of acidic deposition on soil pH and therefore on soil invertebrates and litter decomposition is being investigated in oak-hickory forests across a three-state, midwest, pollution gradient. The role of soil invertebrates has been assessed previously through the use of feeding, assimilation and respiratory rates. These energetic parameters depend strongly on the form of the allometric equations which have been improved here by incorporating uncertainties in body and population size. Results show that changes in reproduction and turnover dynamics of soil invertebrates (particularly of earthworms) due to acid-induced changes in soil pH explains observed patterns in litter depth.

  14. Calcite crystal growth rate inhibition by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, M.M.; Hoch, A.R.

    2001-01-01

    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  15. Distribution and effects of acidic deposition on wildlife and ecosystems

    USGS Publications Warehouse

    Stromborg, K.L.; Longcore, J.R.

    1987-01-01

    Acidic deposition occurs over most of the United States and the deposition patterns and theoretical vulnerabilities of aquatic ecosystems to chemical changes can be delineated, but few data exist on concomitant biological effects. Hypothetical direct effects are limited primarily to toxicity of various heavy metals mobilized at reduced pH. Results of studies in Scandinavia suggest that aluminum interferes with avian reproduction near acidified lakes. Some amphibian populations located on acid-vulnerable substrates may be adversely affected by reduced pH in the vernal pools used for egg laying and larval growth. Indirect effects on populations are difficult to detect because few historical data exist for wildlife populations and trophic relationships in vulnerable areas. Current research in the U.S.A. focuses on measuring habitat characteristics, food availability, and avian use of vulnerable wetland habitats. Results of Scandinavian studies suggest that some species of waterfowl may prefer acidified, I fish-free habitats because invertebrates essential for meeting nutritional requirements are more easily obtained in the absence of competition from fish. However, avian species dependent on fish would be absent from these habitats. Alteration of either the vegetative structure or primary productivity of wetlands might indirectly affect avian populations by causing decreased invertebrate productivity and consequent food limitations for birds.

  16. Acidity, nutrients, and minerals in atmospheric precipitation over Florida: deposition patterns, mechanisms and ecological effects

    SciTech Connect

    Brezonik, P.L.; Hendry, C.D. Jr.; Edgerton, E.S.; Schulze, R.L.; Crisman, T.L.

    1983-06-01

    A monitoring network of 21 bulk and 4 wet/dry collectors located throughout Florida measured spatial and temporal trends during a one-year period from May 1978 to April 1979. The project summary notes that statewide deposition rates of nitrogen and phosphorus were below the loading rates associated with eutrophication, although nutrient concentrations were higher during the summer. Overall, pH appears to have relatively small effects (in the range 4.7-6.8) on community structure in soft-water Florida lakes. More dramatic effects could occur under more acidic conditions in the future. 4 references, 5 figures, 1 table.

  17. Responses of 20 lake-watersheds in the Adirondack region of New York to historical and potential future acidic deposition.

    PubMed

    Zhou, Qingtao; Driscoll, Charles T; Sullivan, Timothy J

    2015-04-01

    Critical loads (CLs) and dynamic critical loads (DCLs) are important tools to guide the protection of ecosystems from air pollution. In order to quantify decreases in acidic deposition necessary to protect sensitive aquatic species, we calculated CLs and DCLs of sulfate (SO4(2-))+nitrate (NO3-) for 20 lake-watersheds from the Adirondack region of New York using the dynamic model, PnET-BGC. We evaluated lake water chemistry and fish and total zooplankton species richness in response to historical acidic deposition and under future deposition scenarios. The model performed well in simulating measured chemistry of Adirondack lakes. Current deposition of SO4(2-)+NO3-, calcium (Ca2+) weathering rate and lake acid neutralizing capacity (ANC) in 1850 were related to the extent of historical acidification (1850-2008). Changes in lake Al3+ concentrations since the onset of acidic deposition were also related to Ca2+ weathering rate and ANC in 1850. Lake ANC and fish and total zooplankton species richness were projected to increase under hypothetical decreases in future deposition. However, model projections suggest that lake ecosystems will not achieve complete chemical and biological recovery in the future. PMID:25544337

  18. COMPREHENSIVE EXPERIMENTAL DESIGN PLAN TO RELATE POLLUTANT SOURCES TO ACIDIC DEPOSITION

    EPA Science Inventory

    Because verifiable numerical models that incorporate all processes determining the dispersion, transformations, and deposition of emitted pollutants associated with acidic deposition from the atmosphere are only now under development, it was deemed worthwhile to determine whether...

  19. USING THE REGIONAL ACID DEPOSITION MODEL TO DETERMINE THE NITROGEN DEPOSITION AIRSHED OF THE CHESAPEAKE BAY WATERSHED

    EPA Science Inventory

    The Regional Acid Deposition Model, RADM, an advanced Eulerian model, is used to develop an estimate of the primary airshed of nitrogen oxide (NOx) emissions that is contributing nitrogen deposition to the Chesapeake Bay watershed. rief description of RADM together with a summary...

  20. Oxygen isotope fractionation in travertine-depositing pools at Baishuitai, Yunnan, SW China: Effects of deposition rates

    NASA Astrophysics Data System (ADS)

    Sun, Hailong; Liu, Zaihua; Yan, Hao

    2014-05-01

    Travertine δ18O values can be used to reconstruct paleo-temperatures if the oxygen isotope fractionation factors between travertine and water are accurately understood. For this purpose, the δ18O values of pool travertine and its parent water, and the deposition rates of the calcite were investigated at Baishuitai (Yunnan, SW China) over the course of the full hydrological year, April 23 2006-April 25 2007. The results show that the travertine-water isotope fractionation factors are close to the commonly accepted equilibrium line of Kim and O'Neil (1997). This differs from the results obtained by Yan et al. (2012) who found that the oxygen isotope fractionation factors in the travertine-depositing pools were close to the line suggested as equilibrium relationship by Coplen (2007). The average calcite deposition rate (2.30 mg cm-2 d-1) in the present study is six times larger than that (0.38 mg cm-2 d-1) in Yan et al. (2012). If slower calcite precipitation leads to equilibrium oxygen isotopic fractionation, then the results of this study support the results of Coplen (2007) that indicate that the equilibrium fractionation factor may be greater than the commonly accepted one derived by Kim and O'Neil (1997). The relationship between oxygen isotope fractionation factor and calcite deposition rate in our study also agrees with the results of Dietzel et al. (2009) who found that the kinetic-isotope effect favors preferential incorporation of 16O in solid calcite as the calcite deposition rate increases. There was a threshold for calcite precipitation rate control on oxygen isotopic equilibrium. In our case of travertine-depositing pools, when the calcite deposition rate was lower than 0.38 mg cm-2 d-1, oxygen isotopic equilibrium between calcite and water was attained. Therefore, calcite deposition rate is a potentially important consideration when using δ18O in natural carbonates as a proxy for terrestrial and ocean temperature.

  1. ACID PRECIPITATION IN NORTH AMERICA: 1985 ANNUAL AND SEASONAL DATA SUMMARIES FROM ACID DEPOSITION SYSTEM DATA BASE

    EPA Science Inventory

    The report gives a summary of 1985 wet deposition precipitation chemistry data collected in North America and available in the Acid Deposition System (ADS) data base. North American wet deposition monitoring networks with data in ADS are NADP/NTN, CANSAP, APN, UAPSP, MAP3S/PCN, W...

  2. Cloud acidity and acidic deposition in the lower troposphere and ozone depletion in the Antarctic stratosphere: Modeling and data analysis regarding the role of atmospheric aerosol

    SciTech Connect

    Lin, Nenghuei.

    1991-01-01

    This study focused on the role of atmospheric aerosols in determining the cloud acidity and acidic deposition in the lower troposphere and the ozone depletion in the Antarctic stratosphere. For the former, a cloud chemistry model is developed to study the in-cloud chemistry and acidity in cloud droplets. The cloud chemistry model includes the absorption of trace gases, the oxidation of aqueous phase SO{sub 2}, and the scavenging of atmospheric aerosols. A new scheme is developed to differentiate the acidity and chemical composition distributing in individual cloud droplets. The above cloud chemistry model is incorporated into a two-layer flow model in order to investigate the effects of mountain waves on the cloud acidity. Using the three-year database acquired at Mt. Mitchell site, the in-cloud chemistry and acidic deposition through dry, wet and cloud deposition pathways are investigated. The in-cloud scavenging of submicron aerosols such as sulfates and nitrates is parameterized as a function of cloud deposition rate. The deposition fluxes of sulfur (S) compounds are found primarily contributed by cloud capture mechanism followed by incident precipitation and dry deposition. A comparison of deposition estimates at Mt. Mitchell with those at other sites shows that the sulfate deposition at sites exceeding 1,200 m MSL in elevation in Bavaria (Germany) and eastern USA is almost identical within error limits. The features of the Antarctic stratospheric aerosols during the ozone depletion episode of October 1987 are investigated based on the SAGE 2 (Stratospheric Aerosol and Gas Experiment 2) data. The study focuses on (1) inferring the aerosol size spectrum using a modified randomized minimization-search-technique (RMST), and (2) investigating the vertical, zonal and columnar averages of aerosol properties, together with the ozone concentration.

  3. RAINS-ASIA: An assessment model for acid deposition in Asia

    SciTech Connect

    Downing, R.J.; Ramankutty, R.; Shah, J.J.

    1997-08-31

    Asia`s rapid economic growth has fueled a growing appetite for commercial energy, which is satisfied by fossil fuels that emit pollutants. These pollutants are oxidized and transported into the atmosphere, creating acidic depositions known as acid rain that can damage foliage, soils, and surface waters. At current energy consumption growth rates, by the year 2000 sulfur dioxide emissions from Asia will surpass the emissions of North America and Europe combined. RAINS-ASIA is an assessment tool developed by the World Bank, the Asian Development Bank, and donors to study the implications of alternative energy development strategies for air pollution and acid rain and to help identify cost-effective abatement methods. This report provides an overview of the model and some results of analyses that have been conducted as part of the RAINS-ASIA program.

  4. High-rate deposition of hydrogenated amorphous silicon films and devices

    SciTech Connect

    Luft, W.

    1988-12-01

    In high-rate deposition of a-Si:H films, the effect of deposition parameters on material properties are examined when silane and disilane are the feed gases. The emphasis is on RF glow discharge, but other deposition methods are also covered. The problems of gas-phase polymerization and power formation at high rates have been overcome by modified reactor designs. Deposition rates of 1-3 nm/s are adequate for economically fabricating the intrinsic layer. Laboratory-size a-Si:H cells with greater than 10% efficiency have been achieved with both silane and disilane at rates in the 1- to 2-nm/s range.

  5. The allelopathic effects of invasive plant Solidago canadensis on seed germination and growth of Lactuca sativa enhanced by different types of acid deposition.

    PubMed

    Wang, Congyan; Xiao, Hongguang; Zhao, Lulu; Liu, Jun; Wang, Lei; Zhang, Fei; Shi, Yanchun; Du, Daolin

    2016-04-01

    Invasive species can exhibit allelopathic effects on native species. Meanwhile, the types of acid deposition are gradually changing. Thus, the allelopathic effects of invasive species on seed germination and growth of native species may be altered or even enhanced under conditions with diversified acid deposition. This study aims to assess the allelopathic effects (using leaves extracts) of invasive plant Solidago canadensis on seed germination and growth of native species Lactuca sativa treated with five types of acid deposition with different SO4(2-) to NO3(-) ratios (1:0, sulfuric acid; 5:1, sulfuric-rich acid; 1:1, mixed acid; 1:5, nitric-rich acid; 0:1, nitric acid). Solidago canadensis leaf extracts exhibited significantly allelopathic effects on germination index, vigor index, and germination rate index of L. sativa. High concentration of S. canadensis leaf extracts also similarly exhibited significantly allelopathic effects on root length of L. sativa. This may be due to that S. canadensis could release allelochemicals and then trigger allelopathic effects on seed germination and growth of L. sativa. Acid deposition exhibited significantly negative effects on seedling biomass, root length, seedling height, germination index, vigor index, and germination rate index of L. sativa. This may be ascribed to the decreased soil pH values mediated by acid deposition which could produce toxic effects on seedling growth. Sulfuric acid deposition triggered more toxic effects on seedling biomass and vigor index of L. sativa than nitric acid deposition. This may be attributing to the difference in exchange capacity with hydroxyl groups (OH(-)) between SO4(2-) and NO3(-) as well as the fertilizing effects mediated by nitric deposition. All types of acid deposition significantly enhanced the allelopathic effects of S. canadensis on root length, germination index, vigor index, and germination rate index of L. sativa. This may be due to the negatively synergistic effects of

  6. Key Factors Influencing Rates of Heterotrophic Sulfate Reduction in Hydrothermal Massive Sulfide Deposits

    NASA Astrophysics Data System (ADS)

    Frank, K. L.; Rogers, K. L.; Rogers, D.; Johnston, D. T.; Girguis, P. R.

    2015-12-01

    Hydrothermal vents are thermally and geochemically dynamic habitats, and the organisms therein are subject to steep fluctuations in temperature and chemistry. To date, the influence of these environmental dynamics on microbial sulfate reduction has not been well constrained. Here, via multivariate experiments, we evaluate the effects of key environmental variables (temperature, pH, H2S, SO42-, DOC) on sulfate reduction rates and metabolic energy yields in a hydrothermal flange recovered from the Grotto vent in the Main Endeavor Field, Juan de Fuca ridge. Sulfate reduction was measured in batch reactions across a range of physico-chemical conditions. Temperature and pH were the strongest stimuli and maximum sulfate reduction rates were observed at 50°C and pH 6, suggesting that the in situ community of sulfate reducing organisms at Grotto may be most active in a slightly acidic and moderate thermal/chemical regime. At pH 4, sulfate reduction rates increased with sulfide concentrations most likely due to the mitigation of metal toxicity. While substrate concentrations also influenced sulfate reduction rates, energy-rich conditions muted the effect of metabolic energetics on sulfate reduction rates. We posit that variability in sulfate reduction rates reflect the response of the active microbial consortia to environmental constraints on in situ microbial physiology, toxicity, and the type and extent of energy limitation. These experiments help to constrain models of the spatial contribution of heterotrophic sulfate within the complex gradients inherent to hydrothermal deposits.

  7. Experimental verification of vapor deposition rate theory in high velocity burner rigs

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Santoro, Gilbert J.

    1985-01-01

    The main objective has been the experimental verification of the corrosive vapor deposition theory in high-temperature, high-velocity environments. Towards this end a Mach 0.3 burner-rig appartus was built to measure deposition rates from salt-seeded (mostly Na salts) combustion gases on the internally cooled cylindrical collector. Deposition experiments are underway.

  8. Do the paleolimnological reconstructions reflect the influence of acid deposition?

    SciTech Connect

    Smirnov, D.Y.

    1996-12-31

    The using possibility of paleolimnological analyses was considered with the documentation aim of acid-forming substances distant transfer on territory of Northern Fennoscandia. The Holocene and ancient interglacial lakes pH-and alkalinity trends, reconstructed by means of bottom sediments diatomic analyses, were studied. It has been made evident that the tendency to sharp changes of these data is revealed on final stages of interglacial periods. At that time the high amplitude of climatic changes with low periodicity is resulting in catastrophic changes of landscapes in the frames of water-catchments bodies. During the last millennium the climatic situation in the Northern Fennoscandia was changing repeatedly (Medieval Warm Epoch, Little Ice Age, the rise in temperature in 20-40`s of XXth century). In the Little Ice Age (XVI-XIX centuries) the decrease of average annual temperature and intensification of winds velocity have caused a rapid retreat of latitudinal and high-altitude forest boundaries, accompanied by sharp reconstruction of tundra-,forest-tundra-and northern taiga landscapes. These processes have accelerated due to the enforcement of economic activity which caused the destruction of vegetation cover (salt-working, and ship-building since the XIXth century, pasture of reindeer herds since the end of XIXth century). Acidifying of ground and surface waters in the current century could be caused by the increased entry of organic acids, as a result of plant residues decomposition. The decomposition process was activated in the end of XIXth - beginning of XXth century in connection with the rise of temperature and increase of precipitation. Thus, the trends in pH and alkalinity changes in this region can not be used as indicators of acid-forming substances atmospheric deposition increase.

  9. Photosynthetic and growth responses of Schima superba seedlings to sulfuric and nitric acid depositions.

    PubMed

    Yao, Fang-Fang; Ding, Hui-Ming; Feng, Li-Li; Chen, Jing-Jing; Yang, Song-Yu; Wang, Xi-Hua

    2016-05-01

    A continuing rise in acid deposition can cause forest degradation. In China, acid deposition has converted gradually from sulfuric acid deposition (SAD) to nitric acid deposition (NAD). However, the differing responses of photosynthesis and growth to depositions of sulfuric vs. nitric acid have not been well studied. In this study, 1-year-old seedlings of Schima superba, a dominant species in subtropical forests, were treated with two types of acid deposition SO4 (2-)/NO3 (-) ratios (8:1 and 0.7:1) with two applications (foliar spraying and soil drenching) at two pH levels (pH 3.5 and pH 2.5) over a period of 18 months. The results showed that the intensity, acid deposition type, and spraying method had significant effects on the physiological characteristics and growth performance of seedlings. Acid deposition at pH 2.5 via foliar application reduced photosynthesis and growth of S. superba, especially in the first year. Unlike SAD, NAD with high acidity potentially alleviated the negative effects of acidity on physiological properties and growth, probably due to a fertilization effect that improved foliar nitrogen and chlorophyll contents. Our results suggest that trees were damaged mainly by direct acid stress in the short term, whereas in the long term, soil acidification was also likely to be a major risk to forest ecosystems. Our data suggest that the shift in acid deposition type may complicate the ongoing challenge of anthropogenic acid deposition to ecosystem stability. PMID:26797956

  10. Relationships between soil properties and community structure of soil macroinvertebrates in oak-history forests along an acidic deposition gradient

    SciTech Connect

    Kuperman, R.G.

    1996-02-01

    Soil macroinvertebrate communities were studied in ecologically analogous oak-hickory forests across a three-state atmospheric pollution gradient in Illinois, Indiana, and Ohio. The goal was to investigate changes in the community structure of soil fauna in study sites receiving different amounts of acidic deposition for several decades and the possible relationships between these changes and physico-chemical properties of soil. The study revealed significant differences in the numbers of soil animals among the three study sites. The sharply differentiated pattern of soil macroinvertebrate fauna seems closely linked to soil chemistry. Significant correlations of the abundance of soil macroinvertebrates with soil parameters suggest that their populations could have been affected by acidic deposition in the region. Abundance of total soil macroinvertebrates decreased with the increased cumulative loading of acidic deposition. Among the groups most sensitive to deposition were: earthworms gastropods, dipteran larvae, termites, and predatory beetles. The results of the study support the hypothesis that chronic long-term acidic deposition could aversely affect the soil decomposer community which could cause lower organic matter turnover rates leading to an increase in soil organic matter content in high deposition sites.

  11. Deposition kinetics and characterization of stable ionomers from hexamethyldisiloxane and methacrylic acid by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Urstöger, Georg; Resel, Roland; Koller, Georg; Coclite, Anna Maria

    2016-04-01

    A novel ionomer of hexamethyldisiloxane and methacrylic acid was synthesized by plasma enhanced chemical vapor deposition (PECVD). The PECVD process, being solventless, allows mixing of monomers with very different solubilities, and for polymers formed at high deposition rates and with high structural stability (due to the high number of cross-links and covalent bonding to the substrate) to be obtained. A kinetic study over a large set of parameters was run with the aim of determining the optimal conditions for high stability and proton conductivity of the polymer layer. Copolymers with good stability over 6 months' time in air and water were obtained, as demonstrated by ellipsometry, X-Ray reflectivity, and FT-IR spectroscopy. Stable coatings showed also proton conductivity as high as 1.1 ± 0.1 mS cm-1. Chemical analysis showed that due to the high molecular weight of the chosen precursors, it was possible to keep the plasma energy-input-per-mass low. This allowed limited precursor fragmentation and the functional groups of both monomers to be retained during the plasma polymerization.

  12. 19 CFR 351.107 - Cash deposit rates for nonproducing exporters; rates in antidumping proceedings involving a...

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE ANTIDUMPING AND COUNTERVAILING DUTIES... Producers X, Y, and Z. In such a situation, the Secretary may establish cash deposit rates for Exporter...

  13. 19 CFR 351.107 - Cash deposit rates for nonproducing exporters; rates in antidumping proceedings involving a...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE ANTIDUMPING AND COUNTERVAILING DUTIES... Producers X, Y, and Z. In such a situation, the Secretary may establish cash deposit rates for Exporter...

  14. 19 CFR 351.107 - Cash deposit rates for nonproducing exporters; rates in antidumping proceedings involving a...

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE ANTIDUMPING AND COUNTERVAILING DUTIES... Producers X, Y, and Z. In such a situation, the Secretary may establish cash deposit rates for Exporter...

  15. Experimental verification of corrosive vapor deposition rate theory in high velocity burner rigs

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Santoro, G. J.

    1986-01-01

    The ability to predict deposition rates is required to facilitate modelling of high temperature corrosion by fused salt condensates in turbine engines. A corrosive salt vapor deposition theory based on multicomponent chemically frozen boundary layers (CFBL) has been successfully verified by high velocity burner rig experiments. The experiments involved internally air-impingement cooled, both rotating full and stationary segmented cylindrical collectors located in the crossflow of sodium-seeded combustion gases. Excellent agreement is found between the CFBL theory an the experimental measurements for both the absolute amounts of Na2SO4 deposition rates and the behavior of deposition rate with respect to collector temperature, mass flowrate (velocity) and Na concentration.

  16. Characterization of thin-film deposition in a pulsed acrylic acid polymerizing discharge

    SciTech Connect

    Voronin, Sergey A.; Bradley, James W.; Fotea, Catalin; Zelzer, Mischa; Alexander, Morgan R.

    2007-07-15

    In this study, thin-film deposition in a pulsed rf polymerizing discharge (13.56 MHz) struck in acrylic acid has been investigated by mass spectrometry, x-ray photoelectron spectroscopy, and quartz crystal microbalance techniques. The experiment was conducted at a fixed acrylic acid pressure of 1.3 Pa and 'on' pulse duration of 0.1 ms, whereas the 'off' time was varied between 0 and 20 ms. The rf input power in the 'on' time and gas flow rate were varied between 10 and 50 W and 1.5 and 4.8 sccm (sccm denotes cubic centimeter per minute at STP), respectively. These changes of the discharge conditions resulted in large-scale progressive variations in film and gas-phase plasma composition. In particular, the -COOH functionality of the monomer was increasingly retained in the plasma-generated thin films as the duty cycle was lowered (i.e., with lowered time-averaged powers). The monomer retention reached its maximum value of 66% for 'off' times exceeding 5 ms, when the discharge was operating in the power-deficient regime. The results show that the film deposition rate is a strong function of the monomer flow rate, whereas -COOH retention is correlated to the amount of unfragmented monomer in the plasma, controlled by the applied power.

  17. Pulsed and continuous wave acrylic acid radio frequency plasma deposits: plasma and surface chemistry.

    PubMed

    Voronin, Sergey A; Zelzer, Mischa; Fotea, Catalin; Alexander, Morgan R; Bradley, James W

    2007-04-01

    Plasma polymers have been formed from acrylic acid using a pulsed power source. An on-pulse duration of 100 micros was used with a range of discharge off-times between 0 (continuous wave) and 20,000 micros. X-ray photoelectron spectroscopy (XPS) has been used in combination with trifluoroethanol (TFE) derivatization to quantify the surface concentration of the carboxylic acid functionality in the deposit. Retention of this functionality from the monomer varied from 2% to 65%. When input power was expressed as the time-averaged energy per monomer molecule, E(mean), the deposit chemistry achieved could be described using a single relationship for all deposition conditions. Deposition rates were monitored using a quartz crystal microbalance, which revealed a range from 20 to 200 microg m(-2) s(-1), and these fell as COOH functional retention increased. The flow rate was found to be the major determinant of the deposition rate, rather than being uniquely defined by E(mean), connected to the rate at which fresh monomer enters the system in the monomer deficient regime. The neutral species were collected in a time-averaged manner. As the energy delivered per molecule in the system (E(mean)) decreased, the amount of intact monomer increased, with the average neutral mass approaching 72 amu as E(mean) tends to zero. No neutral oligomeric species were detected. Langmuir probes have been used to determine the temporal evolution of the density and temperature of the electrons in the plasma and the plasma potential adjacent to the depositing film. It has been found that even 500 micros into the afterglow period that ionic densities are still significant, 5-10% of the on-time density, and that ion accelerating sheath potentials fall from 40 V in the on-time to a few volts in the off-time. We have made the first detailed, time- and energy-resolved mass spectrometry measurements in depositing acrylic acid plasma. These have allowed us to identify and quantify the positive ion

  18. Application of a Depositional Facies Model to an Acid Mine Drainage Site▿ †

    PubMed Central

    Brown, Juliana F.; Jones, Daniel S.; Mills, Daniel B.; Macalady, Jennifer L.; Burgos, William D.

    2011-01-01

    Lower Red Eyes is an acid mine drainage site in Pennsylvania where low-pH Fe(II) oxidation has created a large, terraced iron mound downstream of an anoxic, acidic, metal-rich spring. Aqueous chemistry, mineral precipitates, microbial communities, and laboratory-based Fe(II) oxidation rates for this site were analyzed in the context of a depositional facies model. Depositional facies were defined as pools, terraces, or microterracettes based on cm-scale sediment morphology, irrespective of the distance downstream from the spring. The sediments were composed entirely of Fe precipitates and cemented organic matter. The Fe precipitates were identified as schwertmannite at all locations, regardless of facies. Microbial composition was studied with fluorescence in situ hybridization (FISH) and transitioned from a microaerophilic, Euglena-dominated community at the spring, to a Betaproteobacteria (primarily Ferrovum spp.)-dominated community at the upstream end of the iron mound, to a Gammaproteobacteria (primarily Acidithiobacillus)-dominated community at the downstream end of the iron mound. Microbial community structure was more strongly correlated with pH and geochemical conditions than depositional facies. Intact pieces of terrace and pool sediments from upstream and downstream locations were used in flowthrough laboratory reactors to measure the rate and extent of low-pH Fe(II) oxidation. No change in Fe(II) concentration was observed with 60Co-irradiated sediments or with no-sediment controls, indicating that abiotic Fe(II) oxidation was negligible. Upstream sediments attained lower effluent Fe(II) concentrations compared to downstream sediments, regardless of depositional facies. PMID:21097582

  19. U.S. EPA WORKSHOP TO DEVELOP A SIMPLE MODEL FOR ACID DEPOSITION

    EPA Science Inventory

    The Acid Deposition Planning Staff in the Office of Acid Deposition/EPA requested that the Atmospheric Sciences Research Laboratory undertake the development of a low-computational-demanding model suitable for educational use in understanding the linear or non-linear nature of th...

  20. Method to control deposition rate instabilities—High power impulse magnetron sputtering deposition of TiO{sub 2}

    SciTech Connect

    Kossoy, Anna E-mail: anna.kossoy@gmail.com; Magnusson, Rögnvaldur L.; Tryggvason, Tryggvi K.; Leosson, Kristjan; Olafsson, Sveinn

    2015-03-15

    The authors describe how changes in shutter state (open/closed) affect sputter plasma conditions and stability of the deposition rate of Ti and TiO{sub 2} films. The films were grown by high power impulse magnetron sputtering in pure Ar and in Ar/O{sub 2} mixture from a metallic Ti target. The shutter state was found to have an effect on the pulse waveform for both pure Ar and reactive sputtering of Ti also affecting stability of TiO{sub 2} deposition rate. When the shutter opened, the shape of pulse current changed from rectangular to peak-plateau and pulse energy decreased. The authors attribute it to the change in plasma impedance and gas rarefaction originating in geometry change in front of the magnetron. TiO{sub 2} deposition rate was initially found to be high, 1.45 Å/s, and then dropped by ∼40% during the first 5 min, while for Ti the change was less obvious. Instability of deposition rate poses significant challenge for growing multilayer heterostructures. In this work, the authors suggest a way to overcome this by monitoring the integrated average energy involved in the deposition process. It is possible to calibrate and control the film thickness by monitoring the integrated pulse energy and end growth when desired integrated pulse energy level has been reached.

  1. ESTIMATION OF CARBOXYLIC ACID ESTER HYDROLYSIS RATE CONSTANTS

    EPA Science Inventory

    SPARC chemical reactivity models were extended to calculate hydrolysis rate constants for carboxylic acid esters from molecular structure. The energy differences between the initial state and the transition state for a molecule of interest are factored into internal and external...

  2. Heart Rate Response and Lactic Acid Concentration in Squash Players.

    ERIC Educational Resources Information Center

    Beaudin, Paula; And Others

    1978-01-01

    It was concluded that playing squash is an activity that results in heart rate responses of sufficient intensity to elicit aerobic training effects without producing high lactic acid concentration in the blood. (MM)

  3. PROTOTYPE CONCENTRATION MONITOR FOR ESTIMATING ACIDIC DRY DEPOSITION

    EPA Science Inventory

    Dry deposition contributes significantly to the acidification of the ecosystem. However, difficulties in measuring dry deposition of reactive gases and fine particles make routine direct monitoring impractical. An alternate approach is to use the 'concentration monitoring' method...

  4. Debris-flow deposits and watershed erosion rates near southern Death Valley, CA, United States

    USGS Publications Warehouse

    Schmidt, K.M.; Menges, C.M.

    2003-01-01

    Debris flows from the steep, granitic hillslopes of the Kingston Range, CA are commensurate in age with nearby fluvial deposits. Quaternary chronostratigraphic differentiation of debris-flow deposits is based upon time-dependent characteristics such as relative boulder strength, derived from Schmidt Hammer measurements, degree of surface desert varnish, pedogenesis, and vertical separation. Rock strength is highest for Holocene-aged boulders and decreases for Pleistocene-aged boulders weathering to grus. Volumes of age-stratified debris-flow deposits, constrained by deposit thickness above bedrock, GPS surveys, and geologic mapping, are greatest for Pleistocene deposits. Shallow landslide susceptibility, derived from a topographically based GIS model, in conjunction with deposit volumes produces watershed-scale erosion rates of ???2-47 mm ka-1, with time-averaged Holocene rates exceeding Pleistocene rates. ?? 2003 Millpress.

  5. Effects of gas flow rate on deposition rate and number of Si clusters incorporated into a-Si:H films

    NASA Astrophysics Data System (ADS)

    Toko, Susumu; Torigoe, Yoshihiro; Keya, Kimitaka; Seo, Hyunwoong; Itagaki, Naho; Koga, Kazunori; Shiratani, Masaharu

    2016-01-01

    The suppression of cluster incorporation into a-Si:H films is the key to better film stability, because incorporated clusters contribute to the formation of SiH2 bonds and hence lead to light-induced degradation of the films. To deposit stable a-Si:H solar cells at a high deposition rate (DR), we studied the effects of the gas flow rate on DR and the number of Si clusters incorporated into a-Si:H films with discharge power as a parameter, using a multihollow discharge-plasma chemical vapor deposition method. We succeeded in depositing high-quality a-Si:H films with the incorporation of few clusters at DR of 0.1 nm/s. We also found that, under a low gas flow rate and a high discharge power, high-density clusters exist in plasma and hence DR is reduced as a result of radical loss to the clusters.

  6. Sensitivity of stream basins in Shenandoah National Park to acid deposition

    USGS Publications Warehouse

    Lynch, D.D.; Dise, N.B.

    1985-01-01

    Six synoptic surveys of 56 streams that drain the Shenandoah National Park, Virginia, were conducted in cooperation with the University of Virginia to evaluate sensitivity of dilute headwater streams to acid deposition and to determine the degree of acidification of drainage basins. Flow-weighted alkalinity concentration of most streams is below 200 microequivalents per liter, which is considered the threshold of sensitivity. Streams draining resistant siliceous bedrocks have an extreme sensitivity (alkalinity below 20 microequivalents/L); those draining granite and granodiorite have a high degree of sensitivity (20 to 100 microequivalents/L); and streams draining metamorphosed volcanics have moderate to marginal sensitivity (100 to 200 microequivalents/L). A comparison of current stream water chemistry to that predicted by a model based on carbonic acid weathering reactions suggests that all basins in the Park shows signs of acidification by atmospheric deposition. Acidification is defined as a neutralization of stream water alkalinity and/or an increase in the base cation weathering rate. Acidification averages 50 microequivalents/L, which is fairly evenly distributed in the Park. However, the effects of acidification are most strongly felt in extremely sensitive basins, such as those underlain by the Antietam Formation, which have stream water pH values averaging 4.99 and a mineral acidity of 7 microequivalents/L. (USGS)

  7. High rate chemical vapor deposition of carbon films using fluorinated gases

    DOEpatents

    Stafford, Byron L.; Tracy, C. Edwin; Benson, David K.; Nelson, Arthur J.

    1993-01-01

    A high rate, low-temperature deposition of amorphous carbon films is produced by PE-CVD in the presence of a fluorinated or other halide gas. The deposition can be performed at less than 100.degree. C., including ambient room temperature, with a radio frequency plasma assisted chemical vapor deposition process. With less than 6.5 atomic percent fluorine incorporated into the amorphous carbon film, the characteristics of the carbon film, including index of refraction, mass density, optical clarity, and chemical resistance are within fifteen percent (15%) of those characteristics for pure amorphous carbon films, but the deposition rates are high.

  8. High power pulsed magnetron sputtering: A method to increase deposition rate

    SciTech Connect

    Raman, Priya McLain, Jake; Ruzic, David N; Shchelkanov, Ivan A.

    2015-05-15

    High power pulsed magnetron sputtering (HPPMS) is a state-of-the-art physical vapor deposition technique with several industrial applications. One of the main disadvantages of this process is its low deposition rate. In this work, the authors report a new magnetic field configuration, which produces deposition rates twice that of conventional magnetron's dipole magnetic field configuration. Three different magnet pack configurations are discussed in this paper, and an optimized magnet pack configuration for HPPMS that leads to a higher deposition rate and nearly full-face target erosion is presented. The discussed magnetic field produced by a specially designed magnet assembly is of the same size as the conventional magnet assembly and requires no external fields. Comparison of deposition rates with different power supplies and the electron trapping efficiency in complex magnetic field arrangements are discussed.

  9. Effects of acid deposition on terrestrial ecosystems and their rehabilitation strategies in China.

    PubMed

    Feng, Zong-wei; Miao, Hong; Zhang, Fu-zhu; Huang, Yi-zong

    2002-04-01

    South China has become the third largest region associated with acid deposition following Europe and North America, the area subject to damage by acid deposition increased from 1.75 million km2 in 1985 to 2.8 million km2 in 1993. Acid deposition has caused serious damage to ecosystem. Combined pollution of acid rain and SO2 showed the obvious multiple effects on crops. Vegetable was more sensitive to acid deposition than foodstuff crops. Annual economic loss of crops due to acid deposition damage in eleven provinces of south China was 4.26 billion RMB Yuan. Acid deposition caused serious damage to forest. Annual economic loss of wood volume was about 1.8 billion RMB Yuan and forest ecological benefit loss 16.2 billion in eleven provinces of south China. Acid deposition in south China was typical "sulfuric acid type". According to the thoughts of sustainable development, some strategies were brought forward as follows: (1) enhancing environmental management, specifying acid-controlling region, controlling and abating the total emission amount of SO2; (2) selecting practical energy technologies of clean coal, for example, cleansing and selecting coal, sulfur-fixed-type industrial briqutting, abating sulfur from waste gas and so on; (3) developing other energy sources to replace coal, including water electricity, atomic energy and the new energy such as solar energy, wind energy and so on; (4) in acid deposition region of south China, selecting acid-resistant type of crop and tree to decrease agricultural losses, planting more green fertilizer crops, using organic fertilizers and liming, in order to improve buffer capacities of soil. PMID:12046292

  10. 19 CFR 351.107 - Cash deposit rates for nonproducing exporters; rates in antidumping proceedings involving a...

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 3 2012-04-01 2012-04-01 false Cash deposit rates for nonproducing exporters; rates in antidumping proceedings involving a nonmarket economy country. 351.107 Section 351.107 Customs Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE ANTIDUMPING AND COUNTERVAILING DUTIES Scope and Definitions § 351.107 Cash...

  11. 19 CFR 351.107 - Cash deposit rates for nonproducing exporters; rates in antidumping proceedings involving a...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...; rates in antidumping proceedings involving a nonmarket economy country. 351.107 Section 351.107 Customs... proceedings involving a nonmarket economy country. (a) Introduction. This section deals with the establishment... involving imports from a nonmarket economy country. (b) Cash deposit rates for nonproducing...

  12. ACID PRECIPITATION IN NORTH AMERICA: 1987 ANNUAL AND SEASONAL DATA SUMMARIES FROM ACID DEPOSITION SYSTEM DATA BASE

    EPA Science Inventory

    This report summarizes the 1987 wet deposition precipitation chemistry data collected in North America and available in the Acid Deposition System (ADS) data base. nterpretative statistical analyses are not a focus of this report; however, users of the report will learn about maj...

  13. ACID PRECIPITATION IN NORTH AMERICA: 1980, 1981 AND 1982 ANNUAL DATA SUMMARIES FROM ACID DEPOSITION SYSTEM DATA BASE

    EPA Science Inventory

    The Acid Deposition System (ADS) data base for North American wet deposition data is used to provide an overview of the major North American monitoring networks: NADP, CANSAP, APN, MAP3S/PCN, EPRI/SURE, UAPSP and APIOS daily and cumulative. Individual site annual statistical summ...

  14. Key Factors Influencing Rates of Heterotrophic Sulfate Reduction in Active Seafloor Hydrothermal Massive Sulfide Deposits

    PubMed Central

    Frank, Kiana L.; Rogers, Karyn L.; Rogers, Daniel R.; Johnston, David T.; Girguis, Peter R.

    2015-01-01

    Hydrothermal vents are thermally and geochemically dynamic habitats, and the organisms therein are subject to steep gradients in temperature and chemistry. To date, the influence of these environmental dynamics on microbial sulfate reduction has not been well constrained. Here, via multivariate experiments, we evaluate the effects of key environmental variables (temperature, pH, H2S, SO42−, DOC) on sulfate reduction rates and metabolic energy yields in material recovered from a hydrothermal flange from the Grotto edifice in the Main Endeavor Field, Juan de Fuca Ridge. Sulfate reduction was measured in batch reactions across a range of physico-chemical conditions. Temperature and pH were the strongest stimuli, and maximum sulfate reduction rates were observed at 50°C and pH 6, suggesting that the in situ community of sulfate-reducing organisms in Grotto flanges may be most active in a slightly acidic and moderate thermal/chemical regime. At pH 4, sulfate reduction rates increased with sulfide concentrations most likely due to the mitigation of metal toxicity. While substrate concentrations also influenced sulfate reduction rates, energy-rich conditions muted the effect of metabolic energetics on sulfate reduction rates. We posit that variability in sulfate reduction rates reflect the response of the active microbial consortia to environmental constraints on in situ microbial physiology, toxicity, and the type and extent of energy limitation. These experiments help to constrain models of the spatial contribution of heterotrophic sulfate reduction within the complex gradients inherent to seafloor hydrothermal deposits. PMID:26733984

  15. Key Factors Influencing Rates of Heterotrophic Sulfate Reduction in Active Seafloor Hydrothermal Massive Sulfide Deposits.

    PubMed

    Frank, Kiana L; Rogers, Karyn L; Rogers, Daniel R; Johnston, David T; Girguis, Peter R

    2015-01-01

    Hydrothermal vents are thermally and geochemically dynamic habitats, and the organisms therein are subject to steep gradients in temperature and chemistry. To date, the influence of these environmental dynamics on microbial sulfate reduction has not been well constrained. Here, via multivariate experiments, we evaluate the effects of key environmental variables (temperature, pH, H2S, [Formula: see text], DOC) on sulfate reduction rates and metabolic energy yields in material recovered from a hydrothermal flange from the Grotto edifice in the Main Endeavor Field, Juan de Fuca Ridge. Sulfate reduction was measured in batch reactions across a range of physico-chemical conditions. Temperature and pH were the strongest stimuli, and maximum sulfate reduction rates were observed at 50°C and pH 6, suggesting that the in situ community of sulfate-reducing organisms in Grotto flanges may be most active in a slightly acidic and moderate thermal/chemical regime. At pH 4, sulfate reduction rates increased with sulfide concentrations most likely due to the mitigation of metal toxicity. While substrate concentrations also influenced sulfate reduction rates, energy-rich conditions muted the effect of metabolic energetics on sulfate reduction rates. We posit that variability in sulfate reduction rates reflect the response of the active microbial consortia to environmental constraints on in situ microbial physiology, toxicity, and the type and extent of energy limitation. These experiments help to constrain models of the spatial contribution of heterotrophic sulfate reduction within the complex gradients inherent to seafloor hydrothermal deposits. PMID:26733984

  16. Effects of some components of acid-mine drainage and acid deposition on the spermatozoa of longear sunfish, Lepomis megalotis

    SciTech Connect

    Pearson, B.J.

    1983-01-01

    The effects of low pH and the metals aluminum, zinc, and cadmium, components of acid-mine effluents and acid deposition, on spermatozoa of longear sunfish, Lepomis megalotis, were investigated. Sperm were exposed to solutions of 400 ppm aluminum chloride, 50 ppm zinc chloride, 2 ppm cadmium chloride, separately and in combination, at pH values of 6.9, 4.8, and 3.8. Sperm were additionally exposed to test solutions in which the metal salt concentration was reduced by one-half and observed for changes in motility and in the ability to exclude stain. All test solutions at a low pH were deleterious, the greatest damage occurring in solutions of a combination of all 3 metal chlorides and of aluminum chloride separately. Motility tests showed that both full and reduced metal concentrations had significant effects on motility. Staining tests were supportive of motility test results and indicated that in most cases shorter exposure times did not significantly improve survival rates. It was generally found that a decrease in pH increased the effects of each metal separately and when combined. Aluminum, zinc, and cadmium chlorides appeared to act antagonistically when tested in combination. It was concluded that the components of acid waters which were tested have deleterious effects on longer spermatozoa, reducing their viability and thereby reducing reproductive success of the species.

  17. Effects of Yb 3+ on the corrosion resistance and deposition rate of electroless Ni-P deposits

    NASA Astrophysics Data System (ADS)

    Yan, M.; Ying, H. G.; Ma, T. Y.; Luo, W.

    2008-12-01

    Ni-P alloy coatings were deposited with the addition of Yb 3+ in the electroless plating solution. The effects of Yb 3+ concentration on the corrosion resistance and deposition rate of electroless Ni-P coatings were investigated. The results showed that the addition of Yb 3+ could significantly improve the corrosion resistance of the coatings. When increasing Yb 3+ up to 0.20 g L -1, the corrosion potential Ecorr of the electroless Ni-P coating in 3.5% NaCl solution increased from -0.381 to -0.08 V, and the corrosion current density Icorr decreased from 7.36 to 0.62 μA cm -2. At 0.20 g L -1 Yb 3+, the coating could be as long as 960 h free of corrosion in the neutral salt spray. In addition, the deposition rate can also be accelerated by Yb 3+ addition. The mechanisms of Yb 3+ influencing on the corrosion resistance and deposition rate of electroless Ni-P coatings were discussed.

  18. Growth characteristics of Ti-based fumaric acid hybrid thin films by molecular layer deposition.

    PubMed

    Cao, Yan-Qiang; Zhu, Lin; Li, Xin; Cao, Zheng-Yi; Wu, Di; Li, Ai-Dong

    2015-09-01

    Ti-based fumaric acid hybrid thin films were successfully prepared using inorganic TiCl4 and organic fumaric acid as precursors by molecular layer deposition (MLD). The effect of deposition temperature from 180 °C to 350 °C on the growth rate, composition, chemical state, and topology of hybrid films has been investigated systematically by means of a series of analytical tools such as spectroscopic ellipsometry, atomic force microscopy (AFM), high resolution X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The MLD process of the Ti-fumaric acid shows self-limiting surface reaction with a reasonable growth rate of ∼0.93 Å per cycle and small surface roughness of ∼0.59 nm in root-mean-square value at 200 °C. A temperature-dependent growth characteristic has been observed in the hybrid films. On increasing the temperature from 180 °C to 300 °C, the growth rate decreases from 1.10 to 0.49 Å per cycle and the XPS composition of the film's C : O : Ti ratio changes from 8.35 : 7.49 : 1.00 to 4.66 : 4.80 : 1.00. FTIR spectra indicate that the hybrid films show bridging bonding mode at a low deposition temperature of 200 °C and bridging/bidentate mixed bonding mode at elevated deposition temperatures of 250 and 300 °C. The higher C and O amounts deviating from the ideal composition may be ascribed to increased organic incorporation into the hybrid films at lower deposition temperature and temperature-dependent density of reactive sites (-OH). The composition of hybrid films grown at 350 °C shows a dramatic decrease in C and O elemental composition (C : O : Ti = 1.97 : 2.76 : 1.00) due to the thermal decomposition of the fumaric acid precursor. The produced by-product H2O changes the structure of the hybrid films, resulting in the formation of more Ti-O bonds at high temperatures. The stability of the hybrid films against chemical and thermal treatment, and long-term storage by

  19. A simplified method for assessing particle deposition rate in aircraft cabins

    NASA Astrophysics Data System (ADS)

    You, Ruoyu; Zhao, Bin

    2013-03-01

    Particle deposition in aircraft cabins is important for the exposure of passengers to particulate matter, as well as the airborne infectious diseases. In this study, a simplified method is proposed for initial and quick assessment of particle deposition rate in aircraft cabins. The method included: collecting the inclined angle, area, characteristic length, and freestream air velocity for each surface in a cabin; estimating the friction velocity based on the characteristic length and freestream air velocity; modeling the particle deposition velocity using the empirical equation we developed previously; and then calculating the particle deposition rate. The particle deposition rates for the fully-occupied, half-occupied, 1/4-occupied and empty first-class cabin of the MD-82 commercial airliner were estimated. The results show that the occupancy did not significantly influence the particle deposition rate of the cabin. Furthermore, the simplified human model can be used in the assessment with acceptable accuracy. Finally, the comparison results show that the particle deposition rate of aircraft cabins and indoor environments are quite similar.

  20. High deposition rate preparation of amorphous silicon solar cells by rf glow discharge decomposition of disilane

    SciTech Connect

    Kenne, J.; Ohashi, Y.; Matsushita, T.; Konagai, M.; Takahashi, K.

    1984-01-15

    The optical and electrical properties of hydrogenated amorphous silicon films produced by rf glow discharge decomposition of disilane diluted in helium (Si/sub 2/H/sub 6//He = 1/9) have been studied while systematically varying the film deposition rate. The properties and composition of the films were monitored by measuring the optical band gap, IR vibrational spectrum, dark conductivity, and the photoconductivity as a function of the deposition rate. The photoluminescence of the high deposition rate films gave a peak at 1.33 eV. These films, whose properties are rather similar to those of the conventional a-Si:H films prepared from monosilane, have been used to fabricate nip-type a-Si:H solar cells. At a deposition rate of 11 A/sec, a conversion efficiency of 6.86% was obtained. This high efficiency shows that disilane is applicable for mass production fabrication of a-Si:H solar cells.

  1. The emerging role of NO{sub x} in acid deposition

    SciTech Connect

    Price, D.A.; Birnbaum, R.E.

    1997-12-31

    The oxides of nitrogen (NO{sub x}) have long been recognized as a principal precursor to acid deposition. Until recently, however, scientific knowledge about the nature and extent of NO{sub x}`s contribution to acidity in the atmosphere and to acid deposition damages on earth has been nascent; the National Acid Precipitation Assessment Program (NAPAP) and related research during the 1980s focused primarily on the linkage between sulfur dioxide (SO{sub 2}) emissions with acid deposition. This paper summarizes an integrative assessment on the science of NO{sub x} and acid deposition and the multiple environmental benefits associated with decreases in NO{sub x} emissions from coal-fired power plants. The Acid Rain Program performed this staff assessment to support the Phase II Acid Rain NO{sub x} Emission Reduction Rule, proposed on January 19, 1996 (61 FR 1442), and the Office of Air and Radiation (OAR) Integrated NO{sub x} Strategy. Model projections from EPA`s Acid Deposition Standard Feasibility Study (October 1995) provided the initial indication of the important role of NO{sub x} in the future chronic acidification of certain sensitive watershed ecosystems. Corroborative findings from the Bear Brook Watershed Manipulation Experiment and other recent field studies are discussed. This paper also presents an overview discussion of the current state-of-knowledge with respect to NO{sub x}`s role in the acidification of forests, soils, and vegetation as well as acidic-related damage to materials and structures. Basic terms and processes such as {open_quotes}atmospheric nitrogen deposition,{close_quotes} {open_quotes}nitrogen saturation,{close_quotes} {open_quotes}chronic vs. episodic acidification,{close_quotes} and {open_quotes}direct vs. soil-mediated acidification effects{close_quotes} are defined in context so as to facilitate understanding of the emerging role of NO{sub x} in acid deposition.

  2. Vacuolar deposition of ascorbate-derived oxalic acid in barley

    SciTech Connect

    Wagner, G.J.

    1981-03-01

    L-(1-/sup 14/C)Ascorbic acid was supplied to detached barley seedlings to determine the subcellular location of oxalic acid, one of its metabolic products. Intact vacuoles isolated from protoplasts of labeled leaves contained (/sup 14/C)oxalic acid which accounted for about 70% of the intraprotoplast soluble oxalic acid. Tracer-labeled oxalate accounted for 36 and 72% of the /sup 14/C associated with leaf vacuoles of seedlings labeled for 22 and 96 hours, respectively.

  3. Geochemical investigations of selected Eastern United States watersheds affected by acid deposition.

    USGS Publications Warehouse

    Bricker, O.P.

    1986-01-01

    The effects of acid deposition on surface waters in eastern USA watersheds of similar size, physiography, climate and land-use are related to the composition of the underlying bedrock. Watersheds developed on greenstone, calcareous shale, sandstone, granite and schist differ in their ability to neutralize acid rain; consequently, stream acidity is similar to that of precipitation. Watersheds developed on granite and schist are intermediate in their capacity to neutralize acid deposition. Bedrock composition appears to be the major property controlling surface-water chemistry in these systems; hydrological flowpaths and the nature of surficial materials and vegetation also influence chemical responses to acid deposition in watersheds. 453This and the following 10 abstracts are for papers forming a thematic set on geochemical aspects of acid rain. -P.Br.

  4. Influence of solution deposition rate on properties of V2O5 thin films deposited by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Abd-Alghafour, N. M.; Ahmed, Naser M.; Hassan, Zai; Mohammad, Sabah M.

    2016-07-01

    Vanadium oxide (V2O5) thin films were deposited on glass substrates by using a cost-efficient spray pyrolysis technique. The films were grown at 350° through thermal decomposition of VCl3 in deionized water with different solution spray rates. The high resolution X-ray diffraction results revealed the formation of nanocrystalline films having orthorhombic structures with preferential orientation along (101) direction. The spray rate influenced the surface morphology and crystallite size of the films. The crystallite size was found to increase whereas the micro-strain was decreased by increasing the spray deposition rates. The increase in crystallite size and decrease in the macrostrain resulted in an improvement in the films' crystallinity. The UV-Visible spectroscopy analysis indicated that the average transmittance of all films lies in the range 75-80 %. The band gap of V2O5 film was decreased from 2.65 to 2.46 eV with increase of the spray deposition rate from 5 ml/min to 10 ml/min. first, second, and third level headings (first level heading).

  5. The solubility of aluminum in acidic forest soils: Long-term changes due to acid deposition

    NASA Astrophysics Data System (ADS)

    Mulder, Jan; Stein, Alfred

    1994-01-01

    Despite the ecological and pedogenic importance of Al, its solubility control in acidic forest soils is poorly understood. Here we discuss the solubility of Al and its development with time in three acid brown forest soils in The Netherlands, which are under extreme acidification from atmospheric deposition. All soil solutions (to a 60 cm depth) were undersaturated with respect to synthetic gibbsite (Al(OH) 3; log K = 9.12 at 8°C), with the highest degree of undersaturation occurring in the surface soil. In about one third of the individual soil layers a significant positive correlation existed between the activity of Al 3+ and H +, but this relationship was far less than cubic. Kinetically constrained dissolution of Al is unlikely to explain the disequilibrium with respect to gibbsite, because undersaturation was highest through summer when water residence times were longest and temperatures greatest. Time series analysis of six year data sets for several soil layers revealed a significant annual decline in soil solution pH and Al solubility (defined as log Al + 3 pH) despite a constant concentration of strong acid anions. The annual decline of both pH and Al solubility was greatest in the surface soil and was positively correlated with the relative depletion of reactive organically bound soil Al. The results support our earlier hypothesis that in strongly acidified forest soils complexation by solid phase organics controls the solubility of Al even in mineral soil layers, relatively low in organic C. The data lend no support to the current widespread and often uncritical use of gibbsite as a model for the Al solubility in highly acidic forest soils (pH < 4.5) of the temperate zone.

  6. Acidic Deposition along the Appalachian Trail Corridor and its Effects on Acid-Sensitive Terrestrial and Aquatic Resources

    NASA Astrophysics Data System (ADS)

    Lawrence, G. B.; Sullivan, T. J.; Burns, D. A.; Bailey, S. W.; Cosby, B. J., Jr.; Dovciak, M.; Ewing, H. A.; McDonnell, T. C.; Riemann, R.; Quant, J.; Rice, K. C.; Siemion, J.; Weathers, K. C.

    2015-12-01

    The Appalachian National Scenic Trail (AT) spans 3,500 km from Georgia to Maine. Over its length, the trail passes through a corridor with wide variations in climate, bedrock type, soils, and stream water quality. These factors create a diverse range of ecosystems. The health of these ecosystems is a cause for concern because the AT passes through the heavily populated eastern U.S. with its many sources of sulfur (S) and nitrogen (N) emissions that produce acidic deposition. To address concerns about the health of the AT, a study was designed to evaluate the condition and sensitivity of the AT corridor with respect to acidic deposition. Collections of stream water (265 sites), soil (60 sites), tree cores (15 sites) and atmospheric deposition samples (4 sites) were made along with understory and overstory vegetation measurements (30 sites) over the full trail length within a 40 km-wide corridor. Existing data on atmospheric deposition, geology, vegetation, stream chemistry, and soil chemistry were also used in the analysis. Mean acid-neutralizing capacity (ANC) was lowest in the streams in the North section, intermediate in the Central section and highest the South section, despite the South having the highest acid rain levels. At least 40% of the study streams exhibited pH and/or Ali measurements that indicated potential harm to biota. Approximately 70% of the soil sites had values of base saturation under 20%, the threshold below which acidic deposition can mobilize inorganic aluminum (Ali), the form harmful to terrestrial and aquatic life. Compositional similarity of understory and canopy species was positively correlated with acidic deposition, suggesting that during past decades, species poorly adapted to acidic deposition were replaced with tolerant species. Target loads modeling indicated that exceedance of sulfur target loads to achieve stream ANC = 50 μeq/L by the year 2100occurred throughout the trail corridor.

  7. DEPOSITION OF SULFATE ACID AEROSOLS IN THE DEVELOPING HUMAN LUNG

    EPA Science Inventory

    Computations of aerosol deposition as affected by (i) aerosol hygroscopicity, (ii) human age, and (iii) respiratory intensity are accomplished using a validated mathematical model. he interactive effects are very complicated but systematic. ew general observations can be made; ra...

  8. Student Knowledge of Scientific and Natural Resource Concepts Concerning Acidic Deposition.

    ERIC Educational Resources Information Center

    Brody, Michael; And Others

    1989-01-01

    Assessed is the level of scientific and natural resource knowledge possessed by fourth-, eighth- and eleventh-grade students. Misconceptions are noted. Discussed are implications for teaching about acidic deposition. (CW)

  9. LABORATORY AND FIELD EVALUATIONS OF EXTRANSENSITIVE SULFUR DIXOIDE AND NITROGEN DIOXIDE ANALYZERS FOR ACID DEPOSITION MONITORING

    EPA Science Inventory

    Studies of environmental acid deposition require monitoring of very low levels of several atmospheric pollutants. arious passive and active samplers have been used to collect integrated atmospheric samples for such studies. ontinuous analyzers offer an advantage because of their ...

  10. The Selection of the Spray Deposition Rate during the Spray Rolling Process

    SciTech Connect

    Yaojun Lin; Kevin M. McHugh; Yizhang Zhou; Enrique J. Lavernia

    2004-11-01

    This article presents a detailed theoretical analysis of the selection of the maximum and minimum spray deposition rates under steady-state conditions during the spray-rolling process. The following predictions are made on the basis of the preceding theoretical analysis. First, the key factor that may control the minimum spray deposition rate is either the removal of porosity or the removal of prior droplet boundaries. With an increase in initial liquid fraction at the deposit/roll interfaces, the mechanism changes from the former to the latter. Second, the mechanism that controls the maximum spray deposition rate is related to either the drag-in angle or the distance between the nozzle and the deposited material’s surface. With an increase in roll diameter or a decrease in distance between the nozzle and the roll-axis plane, the controlling mechanism is changed from the former to the latter. Third, both the calculated maximum and minimum spray deposition rates markedly increase with an increase in roll diameter and roll rotational frequency. In addition, the present theoretical analysis suggests that spray rolling can be optimized to manufacture strips with a high production rate.

  11. Solar Flux Deposition And Heating Rates In Jupiter's Atmosphere

    NASA Astrophysics Data System (ADS)

    Perez-Hoyos, Santiago; Sánchez-Lavega, A.

    2009-09-01

    We discuss here the solar downward net flux in the 0.25 - 2.5 µm range in the atmosphere of Jupiter and the associated heating rates under a number of vertical cloud structure scenarios focusing in the effect of clouds and hazes. Our numerical model is based in the doubling-adding technique to solve the radiative transfer equation and it includes gas absorption by CH4, NH3 and H2, in addition to Rayleigh scattering by a mixture of H2 plus He. Four paradigmatic Jovian regions have been considered (hot-spots, belts, zones and Polar Regions). The hot-spots are the most transparent regions with downward net fluxes of 2.5±0.5 Wm-2 at the 6 bar level. The maximum solar heating is 0.04±0.01 K/day and occurs above 1 bar. Belts and zones characterization result in a maximum net downward flux of 0.5 Wm-2 at 2 bar and 0.015 Wm-2 at 6 bar. Heating is concentrated in the stratospheric and tropospheric hazes. Finally, Polar Regions are also explored and the results point to a considerable stratospheric heating of 0.04±0.02 K/day. In all, these calculations suggest that the role of the direct solar forcing in the Jovian atmospheric dynamics is limited to the upper 1 - 2 bar of the atmosphere except in the hot-spot areas. Acknowledgments: This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07.

  12. Degradation rates of glycerol polyesters at acidic and basic conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polyesters prepared from glycerol with mixtures of adipic and citric acids were evaluated in the laboratory to estimate degradation rates over a range of pH conditions. These renewable polymers provide a market for glycerol that is generated during biodiesel production. The polyesters were prepared...

  13. Reactive Iron deposition and ground water inflow control neutralization processes in acidic mine lakes

    NASA Astrophysics Data System (ADS)

    Blodau, C.

    2002-12-01

    The controls on the internal neutralization of highly acidified waters by iron sulphide accumulation are yet poorly understood. To elucidate the influence of ground water inflow on neutralization processes, inventories of solid phase iron and sulphur, pore water profiles and rates of ferrous iron and sulphate production and consumption were analyzed in different areas of an acidic mine lake. Ground water inflow had previously been determined by ground water modelling and chamber measurements (Knoll et al., 1999). The investigated sediments adjacent to mine tailings, which were subject to the inflow of groundwater (10-30 L d-1 m-2), were richer in dissolved ferrous iron iron (30 vs. 5 mmol L-1) and sulphate (30 vs. 10 mmol L-1) and showed higher pH values (6 vs. 4) than the sediments in areas of the lake not being influenced by groundwater inflow. Sediments adjacent to the mine tailings also showed higher rates of sulphate reduction and iron sulphide accumulation (Fig. 1). From these data it is suggested that neutralization processes in iron rich, acidic mine lakes neutralization processes primarily occur in areas influenced by the inflow of acid mine groundwater. These waters usually have considerably higher pH values than the surface waters in the lakes due to buffering processes in the tailings. The seepage of this water through the sediment might thus lead to higher pH values and thus to a higher thermodynamic competitiveness of sulfate reduction vs. iron reduction (Blodau and Peiffer 2002). This causes increased neutralization rates. These findings have consequences for remediation measures in highly acidic lakes. In areas influenced by the inflow of mine drainage increases in carbon availability, for example by the deposition of particulate organic matter, should enhance iron sulphide formation rates, whereas in other areas increases in carbon availability would only result in enhanced rates of iron reduction without a lasting gain in alkalinity. Blodau, C

  14. High rate, large area laser-assisted chemical vapor deposition of nickel from nickel carbonyl

    NASA Astrophysics Data System (ADS)

    Paserin, Vlad

    High-power diode lasers (HPDL) are being increasingly used in industrial applications. Deposition of nickel from nickel carbonyl (Ni(CO)4 ) precursor by laser-induced chemical vapor deposition (CVD) was studied with emphasis on achieving high deposition rates. An HPDL system was used to provide a novel energy source facilitating a simple and compact design of the energy delivery system. Nickel deposits on complex, 3-dimensional polyurethane foam substrates were prepared and characterized. The resulting "nickel foam" represents a novel material of high porosity (>95% by volume) finding uses, among others, in the production of rechargeable battery and fuel cell electrodes and as a specialty high-temperature filtration medium. Deposition rates up to ˜19 mum/min were achieved by optimizing the gas precursor flow pattern and energy delivery to the substrate surface using a 480W diode laser. Factors affecting the transition from purely heterogeneous decomposition to a combined hetero- and homogeneous decomposition of nickel carbonyl were studied. High quality, uniform 3-D deposits produced at a rate more than ten times higher than in commercial processes were obtained by careful balance of mass transport (gas flow) and energy delivery (laser power). Cross-flow of the gases through the porous substrate was found to be essential in facilitating mass transport and for obtaining uniform deposits at high rates. When controlling the process in a transient regime (near the onset of homogenous decomposition), unique morphology features formed as part of the deposits, including textured surface with pyramid-shape crystallites, spherical and non-spherical particles and filaments. Operating the laser in a pulsed mode produced smooth, nano-crystalline deposits with sub-100 nm grains. The effect of H2S, a commonly used additive in nickel carbonyl CVD, was studied using both polyurethane and nickel foam substrates. H2S was shown to improve the substrate coverage and deposit

  15. Gas phase versus surface contributions to photolytic laser chemical vapor deposition rates

    NASA Astrophysics Data System (ADS)

    Braichotte, D.; van den Bergh, H.

    1988-04-01

    The rate of cw photolytic laser chemical vapor deposition (LCVD) of platinum is measured for λ≈350 nm as a function of the light intensity and the metalorganic vapor pressure. The growth of the metal films is studied in situ and in real time by monitoring their optical transmission. At low intensities the transmitted light decreases monotonically with time, and the LCVD process is photolytic with its rate limiting step in the surface adlayer. At higher intensities we observe two distinct time domains: Relatively slow initial photolytic deposition with its rate limiting step in the gas phase, which is followed by much faster pyrolytic LCVD. An improved method for distinguishing between adlayer and gas-phase limiting processes is demonstrated. These observations are confirmed by studying the photolytic deposition rates while varying the thickness of the adlayer.

  16. Dissolution rates of carbonated hydroxyapatite in hydrochloric acid.

    PubMed

    Hankermeyer, Christine R; Ohashi, Kevin L; Delaney, David C; Ross, John; Constantz, Brent R

    2002-02-01

    Osteoclasts have been shown to dissolve efficiently and effectively the mineral phase of bone by locally controlling the environment surrounding the cell. Although this mineral phase has been identified and well characterized as carbonated hydroxyapatite, there is little understanding of the factors that affect the dissolution properties of this mineral phase. Mimicking the mechanism by which osteoclasts dissolve the mineral phase of bone may provide insight into methods for the decalcification of atherosclerotic mineral deposits in the vascular system. Accordingly, a detailed characterization of the effects of various chemical and mechanical parameters on the dissolution of carbonated hydroxyapatite mineral was investigated in this study. Increases in the mineral dissolution rate (2-10 times) were associated with increases in dissolving solution [H+], osmolality, temperature, and flow rate. Mineral dissolution rate increases (5-8 times) were associated with greater surface area of the mineral and mechanical agitation of the dissolving solution. PMID:11771694

  17. PROJECTION OF RESPONSE OF TREES AND FORESTS TO ACIDIC DEPOSITION AND ASSOCIATED POLLUTANTS

    EPA Science Inventory

    In 1986 the National, Acid Precipitation Assessment Program (NAPAP) established the Forest Response Program (FRP) to assess the effects of acidic deposition and associated pollutants on forests. Modeling studies were developed in parallel with both field studies on the pattern an...

  18. Dietary conjugated linoleic acids increase intramuscular fat deposition and decrease subcutaneous fat deposition in Yellow Breed × Simmental cattle.

    PubMed

    Zhang, Haibo; Dong, Xianwen; Wang, Zhisheng; Zhou, Aiming; Peng, Quanhui; Zou, Huawei; Xue, Bai; Wang, Lizhi

    2016-04-01

    This study was conducted to estimate the effect of dietary conjugated linoleic acids (CLA) on intramuscular and subcutaneous fat deposition in Yellow Breed × Simmental cattle. The experiment was conducted for 60 days. The results showed that the average backfat thickness, (testicles + kidney + pelvic) fat percentage and subcutaneous fat percentage in dietary CLA were significantly lower than in the control group, while intramuscular the fat percentage was significantly higher. Compared to the control group, the Longissimus muscle enzyme activities of lipoprotein lipase (LPL), fatty acid synthase (FAS) and acetyl-coenzyme A carboxylase (ACC) in dietary CLA and the subcutaneous fat enzyme activities of LPL, hormone-sensitive lipase (HSL) and carnitine palmitoyltransferase-1 (CPT-1) were significantly increased. Similarly, compared to the control group, the Longissimus muscle sterol regulatory element binding protein 1 (SREBP-1), FAS, stearoyl-coenzyme A desaturase (SCD), ACC, peroxisome proliferator-activated receptor γ (PPARγ), heart fatty-acid binding protein (H-FABP) and LPL gene expression in dietary CLA were significant increased, as were the subcutaneous fat of PPARγ, H-FABP, LPL, CPT-1 and HSL in dietary CLA. These results indicated that dietary CLA increases IMF deposition mainly by the up-regulation of lipogenic gene expression, while decreasing subcutaneous fat deposition mainly by the up-regulation of lipolytic gene expression. PMID:26582037

  19. Inclusion of Floc Growth in a Simple River Mouth Plume Model and Its Effect on Deposition Rate and Deposit Pattern

    NASA Astrophysics Data System (ADS)

    Strom, K.

    2014-12-01

    Rivers are the primary conduits for delivery of sediments and organic matter to the sea. This is visually evident when sediment-laden rivers enter coastal waters, producing sediment plumes. The sediment and organic material from such plumes may deposit and be preserved in estuarine and deltaic zones, or may be carried and mixed by ocean currents to deposit elsewhere on the shelf. Both of these outcomes are governed in large part by depositional mechanics that are dependent, at least in part, on the settling velocity of the sediment. This is especially true in modeling, where the settling velocity has been noted to be the primary controlling parameter for accurate prediction of depositional patters from river plumes. Settling velocity is largely controlled by grain size, shape, and density, which for mud can be quite dynamic due to the process of flocculation. Flocculation yields mud aggregates of variable size and density that may be dependent on the turbulent energy and salt levels under which they were formed. Since turbulent energy and salinity both change in river mouth jet/plumes, the dynamic flocculation process may exert significant control on the eventual distribution of sediment in these zones. In this study, two different approaches to floc modeling are integrated into a steady-state river mouth plume integral model. The two floc models are (1) a version of the Winterwerp (1998) model, and (2) a condition-dependent equilibrium floc size model similar to what is typically used in large-scale 2 and 3D hydraulic and sediment transport simulations. Inclusion of these two models into the buoyant river-mouth plume equations allows for the settling velocity of the mud to be functionally tied to the turbulent shear rate and suspended sediment concentration. The concentration and deposition rates are then compared through the plume both without and with the inclusion of the two different floc treatments. The role that entrainment of ambient fluid plays in the

  20. Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates

    DOEpatents

    Mahan, Archie Harvin; Molenbroek, Edith C.; Gallagher, Alan C.; Nelson, Brent P.; Iwaniczko, Eugene; Xu, Yueqin

    2002-01-01

    A method of fabricating device quality, thin-film a-Si:H for use as semiconductor material in photovoltaic and other devices, comprising in any order; positioning a substrate in a vacuum chamber adjacent a plurality of heatable filaments with a spacing distance L between the substrate and the filaments; heating the filaments to a temperature that is high enough to obtain complete decomposition of silicohydride molecules that impinge said filaments into Si and H atomic species; providing a flow of silicohydride gas, or a mixture of silicohydride gas containing Si and H, in said vacuum chamber while maintaining a pressure P of said gas in said chamber, which, in combination with said spacing distance L, provides a P.times.L product in a range of 10-300 mT-cm to ensure that most of the Si atomic species react with silicohydride molecules in the gas before reaching the substrate, to thereby grow a a-Si:H film at a rate of at least 50 .ANG./sec.; and maintaining the substrate at a temperature that balances out-diffusion of H from the growing a-Si:H film with time needed for radical species containing Si and H to migrate to preferred bonding sites.

  1. Prediction of Chemical Vapor Deposition Rates on Monofilaments and Its Implications for Fiber Properties

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Kuczmarski, M.; Veitch, L. C.

    1992-01-01

    Deposition rates are predicted in a cylindrical upflow reactor designed for chemical vapor deposition (CVD) on monofilaments. Deposition of silicon from silane in a hydrogen carrier gas is chosen as a relevant example. The effects of gas and surface chemistry are studied in a two-dimensional axisymmetric flow field for this chemically well-studied system. Model predictions are compared to experimental CVD rate measurements. The differences in some physical and chemical phenomena between such small diameter (about 150 microns) fiber substrates and other typical CVD substrates are highlighted. The influence of the Soret mass transport mechanism is determined to be extraordinarily significant. The difficulties associated with the accurate measurement and control of the fiber temperature are discussed. Model prediction sensitivities are investigated with respect to fiber temperatures, fiber radii, Soret transport, and chemical kinetic parameters. The implications of the predicted instantaneous rates are discussed relative to the desired fiber properties for both the batch and the continuous processes.

  2. Study on deposition rate and laser energy efficiency of Laser-Induction Hybrid Cladding

    NASA Astrophysics Data System (ADS)

    Wang, DengZhi; Hu, QianWu; Zheng, YinLan; Xie, Yong; Zeng, XiaoYan

    2016-03-01

    Laser-Induction Hybrid Cladding (LIHC) was introduced to prepare metal silicide based composite coatings, and influence of different factors such as laser type, laser power, laser scan speed and induction preheating temperature on the coating deposition rate and laser energy efficiency was studied systematically. Compared with conventional CO2 laser cladding, fiber laser-induction hybrid cladding improves the coating deposition rate and laser energy efficiency by 3.7 times. When a fiber laser with laser power of 4 kW was combined with an induction preheating temperature of 850 °C, the maximum coating deposition rate and maximum laser energy efficiency reaches 71 g/min and 64% respectively.

  3. DEPOSITION TANK CORROSION TESTING FOR ENHANCED CHEMICAL CLEANING POST OXALIC ACID DESTRUCTION

    SciTech Connect

    Mickalonis, J.

    2011-08-29

    An Enhanced Chemical Cleaning (ECC) process is being developed to aid in the high level waste tank closure at the Savannah River Site. The ECC process uses an advanced oxidation process (AOP) to destroy the oxalic acid that is used to remove residual sludge from a waste tank prior to closure. The AOP process treats the dissolved sludge with ozone to decompose the oxalic acid through reactions with hydroxyl radicals. The effluent from this oxalic acid decomposition is to be sent to a Type III waste tank and may be corrosive to these tanks. As part of the hazardous simulant testing that was conducted at the ECC vendor location, corrosion testing was conducted to determine the general corrosion rate for the deposition tank and to assess the susceptibility to localized corrosion, especially pitting. Both of these factors impact the calculation of hydrogen gas generation and the structural integrity of the tanks, which are considered safety class functions. The testing consisted of immersion and electrochemical testing of A537 carbon steel, the material of construction of Type III tanks, and 304L stainless steel, the material of construction for transfer piping. Tests were conducted in solutions removed from the destruction loop of the prototype ECC set up. Hazardous simulants, which were manufactured at SRNL, were used as representative sludges for F-area and H-area waste tanks. Oxalic acid concentrations of 1 and 2.5% were used to dissolve the sludge as a feed to the ECC process. Test solutions included the uninhibited effluent, as well as the effluent treated for corrosion control. The corrosion control options included mixing with an inhibited supernate and the addition of hydroxide. Evaporation of the uninhibited effluent was also tested since it may have a positive impact on reducing corrosion. All corrosion testing was conducted at 50 C. The uninhibited effluent was found to increase the corrosion rate by an order of magnitude from less than 1 mil per year (mpy

  4. Does livestock grazing affect sediment deposition and accretion rates in salt marshes?

    NASA Astrophysics Data System (ADS)

    Nolte, Stefanie; Müller, Frauke; Schuerch, Mark; Wanner, Antonia; Esselink, Peter; Bakker, Jan P.; Jensen, Kai

    2013-12-01

    Accretion rates, defined as the vertical growth of salt marshes measured in mm per year, may be influenced by grazing livestock in two ways: directly, by increasing soil compaction through trampling, and indirectly, by reducing aboveground biomass and thus decreasing sediment deposition rates measured in g/m² per year. Although accretion rates and the resulting surface elevation change largely determine the resilience of salt marshes to sea-level rise (SLR), the effect of livestock grazing on accretion rates has been little studied. Therefore, this study aimed to investigate the effect of livestock grazing on salt-marsh accretion rates. We hypothesise that accretion will be lower in grazed compared to ungrazed salt marshes. In four study sites along the mainland coast of the Wadden Sea (in the south-eastern North Sea), accretion rates, sediment deposition rates, and soil compaction of grazed and ungrazed marshes were analysed using the 137Cs radionuclide dating method. Accretion rates were on average 11.6 mm yr-1 during recent decades and thus higher than current and projected rates of SLR. Neither accretion nor sediment deposition rates were significantly different between grazing treatments. Meanwhile, soil compaction was clearly affected by grazing with significantly higher dry bulk density on grazed compared to ungrazed parts. Based on these results, we conclude that other factors influence whether grazing has an effect on accretion and sediment deposition rates and that the effect of grazing on marsh growth does not follow a direct causal chain. It may have a great importance when interacting with other biotic and abiotic processes on the marsh.

  5. Acidic deposition in the northeastern United States: Sources and inputs, ecosystem effects, and management strategies

    USGS Publications Warehouse

    Driscoll, C.T.; Lawrence, G.B.; Bulger, A.J.; Butler, T.J.; Cronan, C.S.; Eagar, C.; Lambert, K.F.; Likens, G.E.; Stoddard, J.L.; Weathers, K.C.

    2001-01-01

    North America and Europe are in the midst of a large-scale experiment. Sulfuric and nitric acids have acidified soils, lakes, and streams, thereby stressing or killing terrestrial and aquatic biota. It is therefore critical to measure and to understand the recovery of complex ecosystems in response to decreases in acidic deposition. Fortunately, the NADP, CASTNet, and AIRMoN-dry networks are in place to measure anticipated improvements in air quality and in atmospheric deposition. Unfortunately, networks to measure changes in water quality are sparse, and networks to monitor soil, vegetation, and fish responses are even more limited. There is an acute need to assess the response of these resources to decreases in acid loading. It would be particularly valuable to assess the recovery of aquatic biota - which respond directly to acid stress - to changes in surface water chemistry (Gunn and Mills 1998). We used long-term research from the HBEF and other sites across the northeastern United States to synthesize data on the effects of acidic deposition and to assess ecosystem responses to reductions in emissions. On the basis of existing data, it is clear that in the northeastern United States ??? reductions of SO2 emissions since 1970 have resulted in statistically significant decreases in SO42- in wet and bulk deposition and in surface waters ??? emissions of NOX and concentrations of NO3- in wet and bulk deposition and in surface waters have shown no increase or decrease since the 1980s ??? estimates of NH3 emissions are uncertain, although atmospheric deposition of NH4+ remains important for forest management and stream NO3- loss ??? acidic deposition has accelerated the leaching of base cations from soils, thus delaying the recovery of ANC in lakes and streams from decreased emissions of SO2 (at the HBEF the available soil Ca pool appears to have declined 50% over the past 50 years) ???sulfur and N from atmospheric deposition have accumulated in forest soils across

  6. Si deposition rates in a two-dimensional CVD (chemical vapor deposition) reactor and comparisons with model calculations

    SciTech Connect

    Breiland, W.G.; Coltrin, M.E.

    1989-10-01

    Deposition rates are presented for silicon from silane in a helium carrier gas using a tubular CVD reactor with a two-dimensional flow geometry. Measured surface-temperature profiles, inlet gas velocities, total pressures, and silane/helium concentrations are reported, providing exact boundary conditions that can be used in a two-dimensional numerical CVD model. Comparisons are made between this data and two variations of a model by Coltrin, Kee, and Miller in which different empirical expressions for the silane and disilane reactive sticking coefficient are used.

  7. Epitaxial growth of Ge-Sb-Te films on KCl by high deposition rate pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Thelander, E.; Gerlach, J. W.; Ross, U.; Frost, F.; Rauschenbach, B.

    2014-06-01

    Pulsed laser deposition was employed to deposit epitaxial Ge2Sb2Te5-layers (GST) on (100) oriented KCl-substrates. XRD-measurements show a process temperature window for epitaxial growth of the cubic phase between 200 and 300 °C. Below 250 °C (111) oriented GST dominates the growth process and above 250 °C the (100) orientation is the dominating one. Pole figure measurements confirm these results and additionally reveal that the (111) orientation consists of 4 domains with 90° azimuthal separation with an initial 15° rotation with the substrate lattice, i.e., [2-1-1]GST || [100]KCl. The (100) orientation grows cube-on-cube with KCl. A systematic variation of the deposition rate showed that it is possible to obtain epitaxial films in the range between 2.5 and 250 nm/min with no significant deterioration of crystal quality. A smooth topography of (111) oriented films was found, whereas the (100) dominated films in general show higher surface roughness as evidenced from atomic force microscopy investigations.

  8. SPODOSOL VARIABILITY AND ASSESSMENT OF RESPONSE TO ACIDIC DEPOSITION

    EPA Science Inventory

    Variability in forest soils makes it difficult to observe short-term changes in chemical properties under field conditions. uried soil-bag technique was developed to examine the chemical response of a Maine forest soil to loadings of strong acids (HNO3 and H2SO4). cids were added...

  9. EFFECTS OF ACID DEPOSITION ON PAINTED WOOD SUBSTRATES

    EPA Science Inventory

    This report describes the progress that has been made within the Coatings Effect Research Program that EPA conducts for Task Group VII within the National Acid Precipitation Assessment Program (NAPAP). The major objective of this phase of the research program is to identify early...

  10. Post-depositional migration and preservation of methanesulfonic acid (MSA) in polar ice cores

    NASA Astrophysics Data System (ADS)

    Osman, M.; Marchal, O.; Guo, W.; Das, S. B.; Evans, M. J.

    2015-12-01

    Methanesulfonic acid (MSA; CH3SO3-) in ice cores is a unique, high-resolution proxy of regional sea ice behavior, marine primary productivity, and synoptic climatology. Significant uncertainties remain, however, in both our understanding of the production and transfer of MSA to the ice sheet, as well as its preservation over time, compromising the paleoclimatological utility of the proxy. Here we apply a numerical modeling approach to quantitatively investigate the post-depositional processes affecting MSA migration and preservation within the firn and ice column, building on recent observational and theoretical studies. Our model allows us to evaluate the timing and magnitude of the vertical movement of MSA in response to varying influences, including the competing effects of 1) concentration gradients of sea-salts typically deposited asynchronously to MSA, 2) snow accumulation and densification rates, and 3) in situ temperature gradients. We first test the model against a recently collected ice core from a high accumulation site in coastal West Antarctica, where monthly-resolved MSA records show an abrupt shift from a summer-to-winter maximum in MSA at ~23m depth (ρ ≈ 650 kg/m3), near the firn-ice transition. We find our model to be a robust predictor of the observed migrational features in this record, capturing both (i) the abrupt shift in summer-to-winter maximal concentrations of MSA (steady state ≈ 3.2 yrs), and (ii) the depression of the seasonal amplitude at depth. Further, our modeling results suggest post-depositional effects can lead to substantial interannual alteration of the MSA signal, contrary to previous assumptions that MSA migration is confined within annual layers at high accumulation sites. Using a broad range of polar MSA records and their associated, site-specific environmental conditions, we will evaluate the fidelity of subannual to interannual variability of MSA records and systematically determine the factors conducive to its

  11. First year sugar maple (Acer saccharum, Marsh. ) seedling nutrition, vesicular-arbuscular mycorrhizal colonization, physiology, and growth along an acidic deposition gradient in Michigan

    SciTech Connect

    McLaughlin, J.W.

    1992-01-01

    A field study was conducted to evaluate the use of foliar amino acid and root reducing sugar accumulations to separate acidic deposition from natural (i.e., soil phosphorus, mycorrhizae, and temperature) ecosystem stressors on first-year sugar maple seedling growth in three Michigan forests. Seedling growth was greatest at the sites exposed to highest levels of acidic deposition. However, sites receiving greatest acidic deposition rates also had high available soil phosphorus contents. No significant differences occurred, suggesting increased nitrogen loadings were not reflected in seedling tissue nitrogen. Seedling root or foliar calcium, magnesium, or potassium also were not significantly different, suggesting those elements were not growth limiting. Significant differences, however, occurred for seedling arginine and glutamine concentrations in foliage and reducing sugar concentrations in roots and were negatively correlated with seedling tissue phosphorus concentrations, suggesting phosphorus was limiting seedling growth at the low acidic deposition site. Vesicular-arbuscular mycorrhizal colonization of seedling roots was greater at the low acidic deposition site and positively correlated with seedling amino acid and reducing sugar accumulation but negatively correlated with sucrose concentrations in seedling roots, indicating that the fungal partner may have stimulated sucrose degradation to reducing sugars. Both air and soil temperatures were positively correlated with total sugar and sucrose concentrations in seedling roots. High levels of arginine, glutamine, and reducing sugars were negatively correlated with seedling growth indicating that seedlings at the low acidic deposition site were more stressed than seedlings at the sites receiving higher levels of pollutant loads. The results suggest differences in foliar arginine and glutamine and root reducing sugars in the forests in this study are likely due to natural rather than acidic deposition stress.

  12. The deposition of conjugated linoleic acids in eggs of laying hens fed diets varying in fat level and fatty acid profile.

    PubMed

    Raes, Katleen; Huyghebaert, Gerard; De Smet, Stefaan; Nollet, Lode; Arnouts, Sven; Demeyer, Daniel

    2002-02-01

    The objective of this study was to investigate the incorporation of conjugated linoleic acid (CLA) into eggs and its effect on the fatty acid metabolism when layers are fed diets with different fat sources and fat levels. Layers were fed either a low fat diet (LF) or one of three high fat diets based on soybean oil (SB), animal fat (AF) or flaxseed oil (FSO). CLA was added at a concentration of 1 g/100 g feed from two different CLA premixes with a different CLA profile. For the trial, 144 laying hens were allocated to 12 treatments (4 basal fat sources x 3 CLA treatments) with 3 replicates of 4 hens each. No significant differences were observed in feed intake, egg weight, feed conversion or laying rate between chickens fed control and CLA-supplemented diets. Differences in yolk fat, cholesterol or yolk color were not clearly related to the dietary CLA. However, the supplementation of CLA to the diets had clear effects on the fatty acid composition, i.e., a decrease in monounsaturated fatty acids (MUFA) and an increase in saturated fatty acids (SFA) was observed, whereas the polyunsaturated fatty acids (PUFA) content were essentially unaffected. The results suggest that CLA may influence the activity of the desaturases to a different extent in the synthesis of (n-6) and (n-3) long-chain fatty acids. These effects of CLA depend on the level of (n-6) and (n-3) fatty acids available in the feed. The apparent deposition rate (%) is clearly higher for the c9, t11 isomer than for the t10, c12 isomer. Adding CLA to layers diets rich in (n-3) fatty acids produces eggs that could promote the health of the consumer in terms of a higher intake of (n-3) fatty acids and CLA. PMID:11823576

  13. Disilane as a growth rate catalyst of plasma deposited microcrystalline silicon thin films

    NASA Astrophysics Data System (ADS)

    Dimitrakellis, P.; Kalampounias, A. G.; Spiliopoulos, N.; Amanatides, E.; Mataras, D.; Lahootun, V.; Coeuret, F.; Madec, A.

    2016-07-01

    The effect of small disilane addition on the gas phase properties of silane-hydrogen plasmas and the microcrystalline silicon thin films growth is presented. The investigation was conducted in the high pressure regime and for constant power dissipation in the discharge with the support of plasma diagnostics, thin film studies and calculations of discharge microscopic parameters and gas dissociation rates. The experimental data and the calculations show a strong effect of disilane on the electrical properties of the discharge in the pressure window from 2 to 3 Torr that is followed by significant raise of the electron number density and the drop of the sheaths electric field intensity. Deposition rate measurements show an important four to six times increase even for disilane mole fractions as low as 0.3 %. The deposition rate enhancement was followed by a drop of the material crystalline volume fraction but films with crystallinity above 40 % were deposited with different combinations of total gas pressure, disilane and silane molar ratios. The enhancement was partly explained by the increase of the electron impact dissociation rate of silane which rises by 40% even for 0.1% disilane mole fraction. The calculations of the gas usage, the dissociation and the deposition efficiencies show that the beneficial effect on the growth rate is not just the result of the increase of Si-containing molecules density but significant changes on the species participating to the deposition and the mechanism of the film growth are caused by the disilane addition. The enhanced participation of the highly sticking to the surface radical such as disilylene, which is the main product of disilane dissociation, was considered as the most probable reason for the significant raise of the deposition efficiency. The catalytic effect of such type of radical on the surface reactivity of species with lower sticking probability is further discussed, while it is also used to explain the restricted

  14. Reduction Rates for Higher Americium Oxidation States in Nitric Acid

    SciTech Connect

    Grimes, Travis Shane; Mincher, Bruce Jay; Schmitt, Nicholas C

    2015-09-30

    The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show that the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.

  15. A New Technique for the Automatic Monitoring of Erosion and Deposition Rates

    NASA Astrophysics Data System (ADS)

    Lawler, D. M.

    1991-08-01

    The rates and processes of erosion and deposition of soils and sediments are subjects of widespread and increasing concern in the Earth and environmental sciences. Process inference from field studies, however, has been hampered by a lack of information on the precise magnitude, frequency and timing of erosional and depositional activity, because no automatic monitoring technique has hitherto been available. I describe here an automatic Photo-Electronic Erosion Pin (PEEP) system which, apparently for the first time, allows quasi-continuous time series of erosion and deposition data to be collected. Example results from a river bank site show how the PEEP system helps to define the true temporal distribution of geomorphological change, quantify the erosional impact of individual forcing events, and discriminate between competing hypotheses of process control in erosional and depositional contexts. The system should thus allow more effective testing of erosion models of high temporal resolution and facilitate a more rigorous linking of catchment sediment output to supply dynamics.

  16. Growth of and mineral deposition in young rats fed saturated and unsaturated fatty acids

    SciTech Connect

    Magee, A.; D'Souza, D. John Hopkins Univ., Baltimore, MD )

    1991-03-15

    Male weanling rats were used in 4 week experiments to study effects of saturated and unsaturated fatty acids on growth and mineral deposition in several organs (bone, kidneys, liver, spleen, testes). Minerals evaluated were calcium, copper, iron, magnesium, manganese, phosphorus, and zinc, and levels of these minerals in tests diets were appropriate for growing rats. Two levels of dietary fat were used, and fatty acids included in the study were butyric/capronic, palmitic/stearic, oleic, and linoleic/linolenic acids. Decreased weight gains were observed in rats fed saturated fatty acids or 10% fat, while increases in weight gains were associated with increases in polyunsaturated/saturated (P/S) ratios. Copper, iron, or zinc levels tended to be higher in organs of rats fed saturated fatty acids. P/S ratios had no effect on copper or zinc deposition, but decreases in liver iron and increases in spleen iron were observed in rats fed the higher P/S ratios. Manganese levels were generally unaffected by fatty acid types, fat level, or P/S ratio, although liver manganese levels were higher in rats fed unsaturated fatty acids. Dietary fatty acids, fat level, or P/S ratios had no apparent effects on calcium, magnesium, phosphorus, or zinc deposition in femurs and tibias of rats.

  17. Environmental factors affecting the low temperature isomerization of homohopanes in acidic peat deposits, central China

    NASA Astrophysics Data System (ADS)

    Huang, Xianyu; Meyers, Philip A.; Xue, Jiantao; Gong, Linfeng; Wang, Xinxin; Xie, Shucheng

    2015-04-01

    Progressively more evidence reveals the abundant occurrence of the C31 homohopane with a 17α, 21β-configuration (C31 αβ) in immature peats. This compound is commonly considered to be an indicator of thermal maturity in petroleum source rocks, but in peats it has also been interpreted to reflect the oxidation and subsequent decarboxylation reactions of bacteriohopanepolyols with microbially mediated epimerization at C-17 that is catalyzed by the acidic peat conditions. To learn more about the environmental factors that affect the low-temperature isomerization of homohopanes, we investigated the distribution patterns of homohopanes in a well-studied peat core from the Dajiuhu peatland, central China, together with data from modern surface peat samples from Dajiuhu and three other locations. From comparison with paleotemperature and paleohydrologic records in the peat core, we hypothesize that the ratio of C31 αβ hopane relative to the ββ isomer (C31 αβ/ββ) is mainly influenced on a centennial to millennial timescale by ambient temperature with a secondary effect from redox conditions that are defined by peatland water levels. The surface peat samples revealed that relatively high C31 αβ/ββ values occurred under pH < 6. These results suggest that pH is indeed an important factor in the low-temperature isomerization of C31 homohopanes, although the magnitude of the pH effect may be less than those of ambient temperature and redox conditions. In both surface peat and peat horizons from the Dajiuhu peatland, the amount of the C31 αβ compound with R configuration relative to that with S configuration (C31 R/S) varied closely with C31 αβ/ββ, suggesting that the epimerization at both C-17 and C-22 may happen synchronously and at similar rates. This study reveals that the isomerization of homohopanes has the potential to reflect paleoenvironmental changes in acidic peat deposits. In addition, acidic peat samples investigated in this and previous studies

  18. Effects of long-term grazing on sediment deposition and salt-marsh accretion rates

    NASA Astrophysics Data System (ADS)

    Elschot, Kelly; Bouma, Tjeerd J.; Temmerman, Stijn; Bakker, Jan P.

    2013-11-01

    Many studies have attempted to predict whether coastal marshes will be able to keep up with future acceleration of sea-level rise by estimating marsh accretion rates. However, there are few studies focussing on the long-term effects of herbivores on vegetation structure and subsequent effects on marsh accretion. Deposition of fine-grained, mineral sediment during tidal inundations, together with organic matter accumulation from the local vegetation, positively affects accretion rates of marsh surfaces. Tall vegetation can enhance sediment deposition by reducing current flow and wave action. Herbivores shorten vegetation height and this could potentially reduce sediment deposition. This study estimated the effects of herbivores on 1) vegetation height, 2) sediment deposition and 3) resulting marsh accretion after long-term (at least 16 years) herbivore exclusion of both small (i.e. hare and goose) and large grazers (i.e. cattle) for marshes of different ages. Our results firstly showed that both small and large herbivores can have a major impact on vegetation height. Secondly, grazing processes did not affect sediment deposition. Finally, trampling by large grazers affected marsh accretion rates by compacting the soil. In many European marshes, grazing is used as a tool in nature management as well as for agricultural purposes. Thus, we propose that soil compaction by large grazers should be taken in account when estimating the ability of coastal systems to cope with an accelerating sea-level rise.

  19. Chronic hyperuricemia, uric acid deposit and cardiovascular risk.

    PubMed

    Grassi, Davide; Ferri, Livia; Desideri, Giovambattista; Di Giosia, Paolo; Cheli, Paola; Del Pinto, Rita; Properzi, Giuliana; Ferri, Claudio

    2013-01-01

    Hyperuricemia is commonly associated with traditional risk factors such as dysglicemia, dyslipidemia, central obesity and abnormal blood pressure, i.e. the metabolic syndrome. Concordantly, recent studies have revived the controversy over the role of circulating uric acid, hyperuricemia, and gout as an independent prognostic factor for cardiovascular morbidity and mortality. In this regard, different studies also evaluated the possible role of xanthine inhibitors in inducing blood pressure reduction, increment in flow-mediated dilation, and improved cardiovascular prognosis in various patient settings. The vast majority of these studies have been conducted with either allopurinol or its active metabolite oxypurinol, i.e. two purine-like non-selective inhibitors of xanthine oxidase. More recently, the role of uric acid as a risk factor for cardiovascular disease and the possible protective role exerted by reduction of hyperuricemia to normal level have been evaluated by the use of febuxostat, a selective, non purine-like xanthine oxidase inhibitor. In this review, we will report current evidence on hyperuricemia in cardiovascular disease. The value of uric acid as a biomarker and as a potential therapeutic target for tailored old and novel "cardiometabolic" treatments will be also discussed. PMID:23173592

  20. Chronic Hyperuricemia, Uric Acid Deposit and Cardiovascular Risk

    PubMed Central

    Grassi, Davide; Ferri, Livia; Desideri, Giovambattista; Giosia, Paolo Di; Cheli, Paola; Pinto, Rita Del; Properzi, Giuliana; Ferri, Claudio

    2013-01-01

    Hyperuricemia is commonly associated with traditional risk factors such as dysglicemia, dyslipidemia, central obesity and abnormal blood pressure, i.e. the metabolic syndrome. Concordantly, recent studies have revived the controversy over the role of circulating uric acid, hyperuricemia, and gout as an independent prognostic factor for cardiovascular morbidity and mortality. In this regard, different studies also evaluated the possible role of xanthine inhibitors in inducing blood pressure reduction, increment in flow-mediated dilation, and improved cardiovascular prognosis in various patient settings. The vast majority of these studies have been conducted with either allopurinol or its active metabolite oxypurinol, i.e. two purine-like non-selective inhibitors of xanthine oxidase. More recently, the role of uric acid as a risk factor for cardiovascular disease and the possible protective role exerted by reduction of hyperuricemia to normal level have been evaluated by the use of febuxostat, a selective, non purine-like xanthine oxidase inhibitor. In this review, we will report current evidence on hyperuricemia in cardiovascular disease. The value of uric acid as a biomarker and as a potential therapeutic target for tailored old and novel “cardiometabolic” treatments will be also discussed. PMID:23173592

  1. Elastic and Anelastic Behavior of TBCs Sprayed at High-Deposition Rates

    NASA Astrophysics Data System (ADS)

    Valarezo, A.; Dwivedi, G.; Sampath, S.; Musalek, R.; Matejicek, J.

    2015-01-01

    Coatings sprayed at high-deposition rates often result in stiff, dense, and highly stressed coatings. The high deposition temperature at which the coatings are formed is responsible for these characteristics. In this paper, TBCs were sprayed at high-deposition rates, increasing the tensile quenching stresses beyond the threshold of crack opening during spraying. Dense structures were observed within a pass, in the presence of micro and macro defects specifically horizontal cracks within interpasses and vertical segmentation cracks. Mechanical properties, mainly the elastic and anelastic behavior of TBCs were significantly affected by the strain accommodation and friction occurring within intersplats and interpass interfaces. The strain tolerance obtained in as-sprayed conditions decreased as the microstructure and defects sintered during high-temperature heat cycles. The non-linearity degree decreased while the elastic modulus of the various coatings increased to a maximum value.

  2. Effects of acidic deposition on paint: A chamber study

    SciTech Connect

    Spence, J.W.; Lemmons, T.J.; Hou, Y.; Schadt, R.J.; Fornes, R.E.

    1993-08-01

    Exterior acrylic latex and alkyd architectural coatings were exposed to different conditions in a chamber exposure system involving simulated sunlight, dew, and photochemical smog-containing sulfur dioxide (SO2). A simulated sunlight exposure of the coating films in the presence of clean air was also incorporated into the experimental design. Changes in surface features after 1,370 hours of exposure were characterized by scanning electron microscope (SEM) and energy dispersive analysis of x-rays (EDAX). Gaseous species that deposited to the films were determined by ion chromatography of the dew collections. Color-change measurements of the exposed films were recorded as Delta E values. Latex and alkyd films that were formulated with calcium carbonate (CACO3) as an extender pigment were found to undergo the most change in surface features, composition, and color.

  3. TEST METHODS TO CHARACTERIZE PARTICULATE MATTER EMISSIONS AND DEPOSITION RATES IN A RESEARCH HOUSE

    EPA Science Inventory

    The paper discusses test methods to characterize particulate matter (PM) emissions and deposition rates in a research house. In a room in the research house, specially configured for PM source testing, a high-efficiency particulate air (HEPA)-filtered air supply system, used for...

  4. Dry acid deposition on leaves of Ligustrum and a new surrogate leaf

    SciTech Connect

    Ondo, J.L.; John, W.; Wall, S.M.

    1984-01-01

    The dry deposition of acidic particles and gases on plants depends on micrometeorology in the canopy and on the surface structure of the leaves. The authors chose two methods to collect and analyze this deposition: washing sulfate and nitrate deposits from the leaves of two species of Ligustrum, an ornamental shrub, and using a surrogate leaf which would absorb acidic gases through pores into a reservoir. The plants are kept in 5-gallon pots in order to be transportable. The leaves are washed, then exposed for a given length of time. Then the leaves are harvested and extracted in distilled water. This extract is analyzed by ion chromatography for sulfate and nitrate. The surrogate leaf is constructed with a nuclepore filter membrane simulating the stomatal openings of a leaf. There is a moist filter in the interior leading to a reservoir. Sulfur dioxide and other acidic gases diffuse through the nuclepore pores and are absorbed in the moist filter. After exposure the exterior surfaces are washed to extract any dry particulate, and the interior filter is analyzed for dissolved acidic gases. The ''leaf'' is small enough to be placed in the canopy in field studies. This surrogate leaf has also been used as a passive monitor in indoor air pollution studies. The surrogate leaves and the ligustrum have been exposed side by side at sites in Berkeley and in the Los Angeles air basin. A comparison has been made between the deposition on natural leaves and the deposition on the artificial leaves.

  5. Electrophoretic deposition of hyaluronic acid and composite films for biomedical applications

    NASA Astrophysics Data System (ADS)

    Ma, R.; Li, Y.; Zhitomirsky, I.

    2010-06-01

    Hyaluronic acid (HYH) is a natural biopolymer, which has tremendous potential for various biomedical applications. Electrophoretic deposition (EPD) methods have been developed for the fabrication of HYH films and composites. New methods for the immobilization of drugs and proteins have been utilized for the fabrication of organic composites. Electrophoretic deposition enabled the fabrication of organic-inorganic composites containing bioceramics and bioglass in the HYH matrix. It was shown that the deposition yield, microstructure, and composition of the films can be controlled. Potential applications of EPD for the surface modification of biomedical implants and fabrication of biosensors are highlighted.

  6. Descriptive risk assessment of the effects of acidic deposition on Rocky Mountain amphibians

    USGS Publications Warehouse

    Corn, Paul Stephen; Vertucci, Frank A.

    1992-01-01

    We evaluated the risk of habitat acidification to the six species of amphibians that occur in the mountains of Colorado and Wyoming. Our evaluation included extrinsic environmental factors (habitat sensitivity and amount of acidic atmospheric deposition) and species-specific intrinsic factors (sensitivity to acid conditions, habitat preferences, and timing of breeding). Only one of 57 surveyed localities had both acid neutralizing capacity μeq/L and sulfate deposition >10 kg/ha/yr, extrinsic conditions with a possible risk of acidification. Amphibian breeding habitats in the Rocky Mountains do not appear to be sufficiently acidic to kill amphibian embryos. Some species breed in high-elevation vernal pools during snowmelt, and an acidic pulse during snowmelt may pose a risk to embryos of these species. However, the acidic pulse, if present, probably occurs before open water appears and before breeding begins. Although inherent variability of amphibian population size may make detection of declines from anthropogenic effects difficult, acidic deposition is unlikely to have caused the observed declines of Bufo boreas and Rana pipiens in Colorado and Wyoming. Amphibians in the Rocky Mountains are not likely to be at risk with acidification inputs at present levels.

  7. The effects of acid deposition on sulfate reduction and methane production in peatlands

    NASA Technical Reports Server (NTRS)

    Murray, Georgia L.; Hines, Mark E.; Bayley, Suzanne E.

    1992-01-01

    Peatlands, as fens and bods, make up a large percentage of northern latitude terrestrial environments. They are organic rich and support an active community of anaerobic bacteria, such as methanogenic and sulfate-reducing bacteria. The end products of these microbial activities, methane and hydrogen sulfide, are important components in the global biogeochemical cycles of carbon and sulfur. Since these two bacterial groups compete for nutritional substrates, increases in sulfate deposition due to acid rain potentially can disrupt the balance between these processes leading to a decrease in methane production and emission. This is significant because methane is a potent greenhouse gas that effects the global heat balance. A section of Mire 239 in the Experimental Lakes Area, in Northwestern Ontario, was artificially acidified and rates of sulfate reduction and methane production were measured with depth. Preliminary results suggested that methane production was not affected immediately after acidification. However, concentrations of dissolved methane decreased and dissolved sulfide increased greatly after acidification and both took several days to recover. The exact mechanism for the decrease in methane was not determined. Analyses are under way which will be used to determine rates of sulfate reduction. These results will be available by Spring and will be discussed.

  8. Influence of Perfluorooctanoic Acid on the Transport and Deposition Behaviors of Bacteria in Quartz Sand.

    PubMed

    Wu, Dan; Tong, Meiping; Kim, Hyunjung

    2016-03-01

    The significance of perfluorooctanoic acid (PFOA) on the transport and deposition behaviors of bacteria (Gram-negative Escherichia coli and Gram-positive Bacillus subtilis) in quartz sand is examined in both NaCl and CaCl2 solutions at pH 5.6 by comparing both breakthrough curves and retained profiles with PFOA in solutions versus those without PFOA. All test conditions are found to be highly unfavorable for cell deposition regardless of the presence of PFOA; however, 7%-46% cell deposition is observed depending on the conditions. The cell deposition may be attributed to micro- or nanoscale roughness and/or to chemical heterogeneity of the sand surface. The results show that, under all examined conditions, PFOA in suspensions increases cell transport and decreases cell deposition in porous media regardless of cell type, presence or absence of extracellular polymeric substances, ionic strength, and ion valence. We find that the additional repulsion between bacteria and quartz sand caused by both acid-base interaction and steric repulsion as well as the competition for deposition sites on quartz sand surfaces by PFOA are responsible for the enhanced transport and decreased deposition of bacteria with PFOA in solutions. PMID:26866280

  9. Projection of response of trees and forests to acidic deposition and associated pollutants

    SciTech Connect

    Kiester, A.R.; Ford, E.D.; Avery, A.; Gay, C.; Droessler, T.

    1990-09-01

    In 1986 the National Acid Precipitation Assessment Program (NAPAP) established the Forest Response Program (FRP) to assess the effects of acidic deposition and associated pollutants on forests. Modeling studies were developed in parallel with both field studies on the pattern and trends of forest condition and physiological studies of seedlings, saplings, and branches of mature trees. The goals of the modeling effort were to simulate the dynamics of the processes by which acidic deposition and ozone affect tree physiological processes and therefore lead to changes in growth. Results from models of the physiological function of leaves, branches, roots, xylem, and canopies are presented here. These models illustrate three aspects of the dynamics of these processes. First, growth and the effects of pollutants are stochastic processes; that is, they vary randomly over time. The models help to account for the large amount of variability seen in normal field conditions. Second, some physiological processes can compensate for the effects of acidic deposition or ozone. Third, pollutants may have more than one effect on tree growth, and these effects may be synergistic. The potential nonlinearities and the variabilities demonstrated by these models lead to the conclusions that forest health effects may be developing that are not yet apparent; and for regulation of acidic deposition and associated pollutants to have a detectable effect, regulatory changes will probably have to be of substantial magnitude.

  10. Characteristics of ultrafine particle sources and deposition rates in primary school classrooms

    NASA Astrophysics Data System (ADS)

    Laiman, Rusdin; He, Congrong; Mazaheri, Mandana; Clifford, Samuel; Salimi, Farhad; Crilley, Leigh R.; Megat Mokhtar, Megat Azman; Morawska, Lidia

    2014-09-01

    The aim of this work was to investigate changes in particle number concentration (PNC) within naturally ventilated primary school classrooms arising from local sources either within or adjacent to the classrooms. We quantify the rate at which ultrafine particles were emitted either from printing, grilling, heating or cleaning activities and the rate at which the particles were removed by both deposition and air exchange processes. At each of 25 schools in Brisbane, Australia, two weeks of measurements of PNC and CO2 were taken both outdoors and in the two classrooms. Bayesian regression modelling was employed in order to estimate the relevant rates and analyse the relationship between air exchange rate (AER), particle infiltration and the deposition rates of particle generated from indoor activities in the classrooms. During schooling hours, grilling events at the school tuckshop as well as heating and printing in the classrooms led to indoor PNCs being elevated by a factor of more than four, with emission rates of (2.51 ± 0.25) × 1011 p min-1, (8.99 ± 6.70) × 1011 p min-1 and (5.17 ± 2.00) × 1011 p min-1, respectively. During non-school hours, cleaning events elevated indoor PNC by a factor of above five, with an average emission rate of (2.09 ± 6.30) × 1011 p min-1. Particles were removed by both air exchange and deposition; chiefly by ventilation when AER > 0.7 h-1 and by deposition when AER < 0.7 h-1.

  11. Long-term recovery of lakes in the Adirondack region of New York to decreases in acidic deposition

    NASA Astrophysics Data System (ADS)

    Waller, Kristin; Driscoll, Charles; Lynch, Jason; Newcomb, Dani; Roy, Karen

    2012-01-01

    After years of adverse impacts to the acid-sensitive ecosystems of the eastern United States, the Acid Rain Program and Nitrogen Budget Program were developed to control sulfur dioxide (SO 2) and nitrogen oxide (NO x) emissions through market-based cap and trade systems. We used data from the National Atmospheric Deposition Program's National Trends Network (NTN) and the U.S. EPA Temporally Integrated Monitoring of Ecosystems (TIME) program to evaluate the response of lake-watersheds in the Adirondack region of New York to changes in emissions of sulfur dioxide and nitrogen oxides resulting from the Acid Rain Program and the Nitrogen Budget Program. TIME is a long-term monitoring program designed to sample statistically selected subpopulations of lakes and streams across the eastern U.S. to quantify regional trends in surface water chemistry due to changes in atmospheric deposition. Decreases in wet sulfate deposition for the TIME lake-watersheds from 1991 to 2007 (-1.04 meq m -2-yr) generally corresponded with decreases in estimated lake sulfate flux (-1.46 ± 0.72 meq m -2-yr), suggesting declines in lake sulfate were largely driven by decreases in atmospheric deposition. Decreases in lake sulfate and to a lesser extent nitrate have generally coincided with increases in acid neutralizing capacity (ANC) resulting in shifts in lakes among ANC sensitivity classes. The percentage of acidic Adirondack lakes (ANC <0 μeq L -1) decreased from 15.5% (284 lakes) to 8.3% (152 lakes) since the implementation of the Acid Rain Program and the Nitrogen Budget Program. Two measures of ANC were considered in our analysis: ANC determined directly by Gran plot analysis (ANC G) and ANC calculated by major ion chemistry (ANC calc = CB - CA). While these two metrics should theoretically show similar responses, ANC calc (+2.03 μeq L -1-yr) increased at more than twice the rate as ANC G (+0.76 μeq L -1-yr). This discrepancy has important implications for assessments of lake recovery

  12. A numerical and experimental analysis of reactor performance and deposition rates for CVD on monofilaments

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Kuczmarski, M.; Veitch, L.; Tsui, P.; Chait, A.

    1990-01-01

    The computational fluid dynamics (CFD) code FLUENT is adopted to simulate a cylindrical upflow reactor designed for chemical vapor deposition (CVD) on monofilaments. Equilibrium temperature profiles along the fiber and quartz reactor wall are experimentally measured and used as boundary conditions in numerical simulations. Two-dimensional axisymmetric flow and temperature fields are calculated for hydrogen and argon; the effect of free convection is assessed. The gas and surface chemistry is included for predicting silicon deposition from silane. The model predictions are compared with experimentally measured silicon CVD rates. Inferences are made for optimum conditions to obtain uniformity.

  13. Optimization of deposition rate in HiPIMS by controlling the peak target current

    NASA Astrophysics Data System (ADS)

    Tiron, V.; Velicu, I.-L.; Vasilovici, O.; Popa, G.

    2015-12-01

    High power impulse magnetron sputtering (HiPIMS) is a very attractive ionized physical vapour deposition technique which has been of great interest over the last decade. Thanks to the high ionization degree of the sputtered material (typically  >50%), this technique is used mainly for enhancing and tailoring coating properties. However, the lower deposition rate compared to the conventional direct-current (dc) magnetron sputtering process still represents a major drawback of HiPIMS. In this contribution, a study of the ability to control the peak target current in HiPIMS discharge through certain experimental parameters and, thus, to overcome the deposition rate limitation is presented. The HiPIMS was operated with ultra-short pulse durations (<20 μs) and two different operation modes have been used: single-pulse mode and multi-pulse mode, respectively. The peak target current was controlled by changing the target voltage, pulse duration, magnetic field, and target erosion depth. For a certain favorable combination of experimental parameters, it was found that the deposition rate value can be increased by a factor of up to 3.5, reaching values only 20% lower than those found in dc.

  14. An overview of a 5-year research program on acid deposition in China

    NASA Astrophysics Data System (ADS)

    Wang, T.; He, K.; Xu, X.; Zhang, P.; Bai, Y.; Wang, Z.; Zhang, X.; Duan, L.; Li, W.; Chai, F.

    2011-12-01

    Despite concerted research and regulative control of sulfur dioxide in China, acid rain remained a serious environmental issue, due to a sharp increase in the combustion of fossil fuel in the 2000s. In 2005, the Ministry of Science and Technology of China funded a five-year comprehensive research program on acid deposition. This talk will give an overview of the activities and the key findings from this study, covering emission, atmospheric processes, and deposition, effects on soil and stream waters, and impact on typical trees/plants in China. The main results include (1) China still experiences acidic rainfalls in southern and eastern regions, although the situation has stabilized after 2006 due to stringent control of SO2 by the Chinese Government; (2) Sulfate is the dominant acidic compound, but the contribution of nitrate has increased; (3) cloud-water composition in eastern China is strongly influenced by anthropogenic emissions; (4) the persistent fall of acid rain in the 30 years has lead to acidification of some streams/rivers and soils in southern China; (5) the studied plants have shown varying response to acid rain; (6) some new insights have been obtained on atmospheric chemistry, atmospheric transport, soil chemistry, and ecological impacts, some of which will be discussed in this talk. Compared to the situation in North America and Europe, China's acid deposition is still serious, and continued control of sulfur and nitrogen emission is required. There is an urgent need to establish a long-term observation network/program to monitor the impact of acid deposition on soil, streams/rivers/lakes, and forests.

  15. Deposition Rates of High Power Impulse Magnetron Sputtering: Physics and Economics

    SciTech Connect

    Anders, Andre

    2009-11-22

    Deposition by high power impulse magnetron sputtering (HIPIMS) is considered by some as the new paradigm of advanced sputtering technology, yet this is met with skepticism by others for the reported lower deposition rates, if compared to rates of more conventional sputtering of equal average power. In this contribution, the underlying physical reasons for the rate changes are discussed, including (i) ion return to the target and self-sputtering, (ii) the less-than-linear increase of the sputtering yield with increasing ion energy, (iii) yield changes due to the shift of species responsible for sputtering, (iv) changes to due to greater film density, limited sticking, and self-sputtering on the substrate, (v) noticeable power losses in the switch module, (vi) changes of the magnetic balance and particle confinement of the magnetron due to self-fields at high current, and (vii) superposition of sputtering and sublimation/evaporation for selected materials. The situation is even more complicated for reactive systems where the target surface chemistry is a function of the reactive gas partial pressure and discharge conditions. While most of these factors imply a reduction of the normalized deposition rate, increased rates have been reported for certain conditions using hot targets and less poisoned targets. Finally, some points of economics and HIPIMS benefits considered.

  16. Attenuation effects on the kerma rates in air after cesium depositions on grasslands.

    PubMed

    Jacob, P; Meckbach, R; Paretzke, H G; Likhtarev, I; Los, I; Kovgan, L; Komarikov, I

    1994-01-01

    Since the reactor accident of Chernobyl, cesium depth profiles and nuclide-specific kerma rates in air have been determined for various grassland sites in south Bavaria and in Ukraine. The sites are described by soil characteristics, annual precipitation, distance from release point, mode of deposition, and activity per unit area. The effects of surface roughness and migration of cesium into the soil on the kerma rate in air over grasslands was determined by two methods. The kerma rates in air obtained by the evaluations of in situ gamma-ray spectrometry results and of measured activity distributions in the soil showed only negligible differences for the observation period of 6 years after deposition. For the sites in Ukraine the kerma rate in air per activity per unit area was found to be systematically 40% higher than in Bavaria. The results from Bavaria on the attenuation of the kerma rate and a data set, including experiences from the weapons test fallout, are analytically approximated as a function of time up to 25 years after deposition. PMID:7809371

  17. Deposition rates of high power impulse magnetron sputtering: Physics and economics

    SciTech Connect

    Anders, Andre

    2010-07-15

    Deposition by high power impulse magnetron sputtering (HIPIMS) is considered by some as the new paradigm of advanced sputtering technology, yet this is met with skepticism by others for the reported lower deposition rates, if compared to rates of more conventional sputtering of equal average power. In this contribution, the underlying physical reasons for the rate changes are discussed, including (i) ion return to the target and self-sputtering, (ii) the less-than-linear increase in the sputtering yield with increasing ion energy, (iii) yield changes due to the shift of species responsible for sputtering, (iv) changes due to greater film density, limited sticking, and self-sputtering on the substrate, (v) noticeable power losses in the switch module, (vi) changes in the magnetic balance and particle confinement of the magnetron due to self-fields at high current, and (vii) superposition of sputtering and sublimation/evaporation for selected materials. The situation is even more complicated for reactive systems where the target surface chemistry is a function of the reactive gas partial pressure and discharge conditions. While most of these factors imply a reduction in the normalized deposition rate, increased rates have been reported for certain conditions using hot targets and less poisoned targets. Finally, some points of economics and HIPIMS benefits are considered.

  18. Calcite precipitation rates in the field: Measurement and prediction for a travertine-depositing stream

    SciTech Connect

    Herman, J.S.; Lorah, M.M. )

    1988-10-01

    Rates of calcite precipitation from a travertine-depositing stream were determined from changes in stream composition between consecutive sampling points and were compared with rates predicted from a laboratory-derived rate law. The agreement in rates was generally within an order of magnitude and routinely within a factor of 3. Least agreement between measured and predicted rates was obtained for sections of flowpath where relatively little change in bulk chemical composition occurred, which were the sections with the greatest mass transfer calculation error, and for the stream segment including a waterfall, which was the section with the greatest error in estimated surface area. Reaction rate obtained from the mass of calcite precipitated onto seed crystals placed in the stream significantly underestimated the mass transfer rate. For the travertine-depositing stream of Warm River Cave and Falling Spring Creek, Virginia, the coupling of equilibrium speciation models with mass balance calculations and simple field measurements allowed successful field-based quantification of reaction rates.

  19. Integrated assessment of acid deposition impacts using reduced-form modeling. Final report

    SciTech Connect

    Sinha, R.; Small, M.J.

    1996-05-01

    Emissions of sulfates and other acidic pollutants from anthropogenic sources result in the deposition of these acidic pollutants on the earth`s surface, downwind of the source. These pollutants reach surface waters, including streams and lakes, and acidify them, resulting in a change in the chemical composition of the surface water. Sometimes the water chemistry is sufficiently altered so that the lake can no longer support aquatic life. This document traces the efforts by many researchers to understand and quantify the effect of acid deposition on the water chemistry of populations of lakes, in particular the improvements to the MAGIC (Model of Acidification of Groundwater in Catchments) modeling effort, and describes its reduced-form representation in a decision and uncertainty analysis tool. Previous reduced-form approximations to the MAGIC model are discussed in detail, and their drawbacks are highlighted. An improved reduced-form model for acid neutralizing capacity is presented, which incorporates long-term depletion of the watershed acid neutralization fraction. In addition, improved fish biota models are incorporated in the integrated assessment model, which includes reduced-form models for other physical and chemical processes of acid deposition, as well as the resulting socio-economic and health related effects. The new reduced-form lake chemistry and fish biota models are applied to the Adirondacks region of New York.

  20. Feather-like Structured YSZ Coatings at Fast Rates by Plasma Spray Physical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Shinozawa, A.; Eguchi, K.; Kambara, M.; Yoshida, T.

    2010-01-01

    A variety of yttria-stabilized zirconia (YSZ) coatings have been attained by plasma spray physical vapor deposition (PS-PVD) with fine YSZ powders at high power. The coating structures were found to change significantly with the powder feeding rates but less with the substrate temperature and the rate of the substrate rotation, and a porous feather like structure was attained at 500 Torr (666.6 millibar) and a rate of >200 μm/min. Such a coating produces porosity reaching >50%, thermal conductivity as small as 0.5 W/mK and lower infra-red transmittance compared to the sprayed splat coating with identical thickness.

  1. Quaternary downcutting rates from cave-deposited river sediment and Holocene erosion rates from river sand in the Central Pyrenees

    NASA Astrophysics Data System (ADS)

    Vernant, Philippe; Genti, Manon; Chéry, Jean; Cazes, Gaël; Braucher, Régis

    2016-04-01

    We use 26Al and 10Be to infer the time of cave-deposited river sediment emplacement in the Central Pyrenees and the Cevennes. Using these ages, we derive mid-term downcutting rates (1-4.106 a). We also use the cosmogenic radionuclides 10Be concentration in quartz extracted from river sand to estimate short-term (102-105 a) erosion rates. Along the N-S profile across the central Pyrenees, we do not see any significant change in erosion rates during the Quaternary. On the other hand, the erosion rates are highly correlated with the local elevation. They vary roughly from 50 m/Myr in the foreland up to 800 m/Myr in the axial part of the mountain range. The mechanisms responsible for the Pyrenees moderate, but frequent, seismicity have yet to be determined. Based on numerical modeling and our erosion rates, we propose that this seismicity could be explained by the isostatic rebound associated to the erosion of the range. To evaluate the likeliness of this hypothesis, we aim at comparing the Pyrenees and the Cevennes to check if the rates are significantly different between these mountain ranges with very different seismic behavior.

  2. High-rate laser metal deposition of Inconel 718 component using low heat-input approach

    NASA Astrophysics Data System (ADS)

    Kong, C. Y.; Scudamore, R. J.; Allen, J.

    Currently many aircraft and aero engine components are machined from billets or oversize forgings. This involves significant cost, material wastage, lead-times and environmental impacts. Methods to add complex features to another component or net-shape surface would offer a substantial cost benefit. Laser Metal Deposition (LMD), currently being applied to the repair of worn or damaged aero engine components, was attempted in this work as an alternative process route, to build features onto a base component, because of its low heat input capability. In this work, low heat input and high-rate deposition was developed to deposit Inconel 718 powder onto thin plates. Using the optimised process parameters, a number of demonstrator components were successfully fabricated.

  3. High-k (k=30) amorphous hafnium oxide films from high rate room temperature deposition

    SciTech Connect

    Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Milne, William I.; Flewitt, Andrew J.; Dutson, James D.; Wakeham, Steve J.; Thwaites, Mike J.

    2011-06-20

    Amorphous hafnium oxide (HfO{sub x}) is deposited by sputtering while achieving a very high k{approx}30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfO{sub x} (cubic k{approx}30). The films also possess a high electrical resistivity of 10{sup 14} {Omega} cm, a breakdown strength of 3 MV cm{sup -1}, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate ({approx}25 nm min{sup -1}) makes these high-k amorphous HfO{sub x} films highly advantageous for plastic electronics and high throughput manufacturing.

  4. Enhanced acid rain and atmospheric deposition of nitrogen, sulfur and heavy metals in Northern China

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Wang, Y.

    2013-12-01

    Atmospheric deposition is known to be important mechanism reducing air pollution. In response to the growing concern on the potential effects of the deposited material entering terrestrial and aquatic environments as well as their subsequent health effects, since 2007 we have established a 10-site monitoring network in Northern China, where particularly susceptible to severe air pollution. Wet and dry deposition was collected using an automatic wet-dry sampler. The presentation will focus on the new results of atmospheric deposition flux for a number of chemical species, such as nutrients (e.g. nitrogen and phosphorus), acidic matters (e.g. sulfur and proton), heavy metals and Polycyclic Aromatic Hydrocarbons, etc. This is to our knowledge the first detailed element budget study in the atmosphere across Northern China. We find that: (1) Over the 3 year period, 26% of precipitation events in the target area were more acid than pH 5.60 and these acidic events occurred in summer and autumn. The annual volume-weighted mean (VWM) pH value of precipitation was lower than 5.60 at most sites, which indicated the acidification of precipitation was not optimistic. The primary ions in precipitation were NH4+, Ca2+, SO42- and NO3-, with 10-sites-average concentrations of 221, 216, 216 and 80 μeq L-1, respectively. The ratio of SO42- to NO3- was 2.7; suggesting SO42- was the dominant acid component. (2) The deposited particles were neutral in general and the pH value increased from rural area to industrial and coastal sites. It is not surprising to note that the annual VWM pH value of precipitation was higher than 5.60 at three urban sites (Beijing and Tianjin mega cities) and one coastal site near the Bohai Bay, considering the fact that high buffer capacity of alkaline component, gas NH3 and mineral aerosols, at these sites compared to other places. (3) The 10-sites annual total deposition amounts for sulfur and nitrogen compounds were 60 and 65 kg N/S ha-1 yr-1

  5. Preparation of waxes and humic acids from brown coal from the Sergeevskoe deposit

    SciTech Connect

    L.P. Noskova; A.V. Rokhin; A.P. Sorokin

    2007-06-15

    The comparative extraction of coal with organic solvents was performed. Humic acids were separated from solid residues. The yields, particle-size distributions, and chemical compositions of the resulting products were analyzed. It was demonstrated that brown-coal wax and humic fertilizers can potentially be obtained using coal from the Sergeevskoe deposit.

  6. EFFECT OF SOIL PROCESSES ON THE ACIDIFICATION OF WATER BY ACID DEPOSITION

    EPA Science Inventory

    The mechanism whereby acid deposition can cause acidification of surface waters via equilibrium processes in soil solution was investigated using chemical equilibrium models. These models show that for soils with low to moderately low exchangeable bases the soil solution pH is on...

  7. Do Uric Acid Deposits in Zooxanthellae Function as Eye-Spots?

    PubMed Central

    Yamashita, Hiroshi; Kobiyama, Atsushi; Koike, Kazuhiko

    2009-01-01

    The symbiosis between zooxanthellae (dinoflagellate genus Symbiodinium) and corals is a fundamental basis of tropical marine ecosystems. However the physiological interactions of the hosts and symbionts are poorly understood. Recently, intracellular crystalline deposits in Symbiodinium were revealed to be uric acid functioning for nutrient storage. This is the first exploration of these enigmatic crystalline materials that had previously been misidentified as oxalic acid, providing new insights into the nutritional strategies of Symbiodinium in oligotrophic tropical waters. However, we believe these deposits also function as eye-spots on the basis of light and electron microscopic observations of motile cells of cultured Symbiodinium. The cells possessed crystalline deposit clusters in rows with each row 100–150 nm thick corresponding to 1/4 the wavelength of light and making them suitable for maximum wave interference and reflection of light. Crystalline clusters in cells observed with a light microscope strongly refracted and polarized light, and reflected or absorbed short wavelength light. The facts that purines, including uric acid, have been identified as the main constituents of light reflectors in many organisms, and that the photoreceptor protein, opsin, was detected in our Symbiodinium strain, support the idea that uric acid deposits in Symbiodinium motile cells may function as a component of an eye-spot. PMID:19609449

  8. DISCOVERING THE CAUSES, CONSEQUENCES, AND IMPLICATIONS OF ACID RAIN AND ATMOSPHERIC DEPOSITION

    EPA Science Inventory

    Much has been learned in recent years about air pollution, acid precipitation and atmospheric deposition and their effects on public welfare. There are still unanswered questions about certain aspects of these problems and possible strategies for their solution. Public concern ab...

  9. FIELD COMPARISON OF METHODS FOR THE MEASUREMENT OF CONTRIBUTORS TO ACIDIC DRY DEPOSITION

    EPA Science Inventory

    A field study was conducted to compare methods for sampling and analysis of atmospheric constituents that are important contributors to acidic dry deposition. hree multicomponent samplers were used: the Canadian filter pack (FP), the annular denuder system (ADS), and the transiti...

  10. EFFECTS OF ACIDIC DEPOSITION ON NORTH AMERICAN LAKES: PALAEOLIMNOLOGICAL EVIDENCE FORM DIATOMS AND CHRYSOPHYTES

    EPA Science Inventory

    Analysis of sediment diatom and chrysophyte assemblages is the best technique currently available for inferring past lakewater pH trends, and use of the approach for assessing the ecological effects of acidic deposition is increasing rapidly. s of August 1989, sediment core infer...

  11. ACIDIFICATION AND RECOVERY OF A SPODOSOL BS HORIZON FROM ACIDIC DEPOSITION

    EPA Science Inventory

    A laboratory study was conducted to examine acidification and recovery of a Spodosol Bs horizon from acidic deposition in the Bear Brook Watershed (BBW) in central Maine. echanical vacuum extractor was used to draw solutions through a soil column at three treatments containing 40...

  12. Response of DOC in acid-sensitive Maine lakes to decreasing sulfur deposition (1993 - 2009)

    EPA Science Inventory

    In response to the Clean Air Act Amendments of 1990, sulfur deposition has decreased across the northeastern United States. As a result, sulfate concentrations in lakes and streams have also decreased and many surface waters have become less acidic. Over the same time period, th...

  13. EVALUATING CHANGES IN FOREST CONDITION POTENTIALLY RELATED TO ACIDIC DEPOSITION: AN EXAMPLE USING RED SPRUCE

    EPA Science Inventory

    As a result of concern about forest decline in Europe and the USA, research has been conducted to investigate changes in forest condition that might be associated with acidic deposition and related pollutants (principally ozone). ymptoms of tree decline observed in the field typi...

  14. ANALYTICAL TECHNIQUES FOR MEASURING THE EFFECTS OF ACID DEPOSITION ON COATINGS ON WOOD

    EPA Science Inventory

    Preliminary experiments have been carried out to characterize the potential deleterious effects of acidic deposition on three representative paints: an oil alkyd paint and two acrylic latex formulations. The base polymer latex common to both latex paints was also studied individu...

  15. Rapid growth rates of syndepositional marine aragonite cements in steep marginal slope deposits, Bahamas and Belize

    SciTech Connect

    Grammer, G.M.; Ginsburg, R.N.; Swart, P.K.; McNeill, D.F. . Div. of Marine Geology); Jull, A.J.T. . NSF Accelerator Facility); Prezbindowski, D.R. )

    1993-09-01

    Growth rates of marine botryoidal aragonite cements from steep (35-45[degree]) marginal slope deposits in the Bahamas and Belize have been determined by accelerator mass spectrometer radiocarbon dating of samples taken at the base and top of individual botryoids. The pore-filling cements, which range from approximately 11,000-13,000 years old, grew at average rates of 8-10mm/100 yr with maximum rates > 25mm/100 yr. Radiocarbon dating of coexisting skeletal components indicates that cementation was syndepositional. Microsampling transects across individual botryoids for stable-isotope analyses show little variation in [delta][sup 31]C and [delta][sup 18]O, supporting the conclusion that cementation was extremely rapid. Although the cements show a progressive depletion in isotopic composition of approximately 1[per thousand]([delta][sup 13]C) and 2[per thousand]([delta][sup 18]O) from 13 ka to 11 ka, the average variation ([delta][sub 1]) within individual pore-filling cements, ranging in size 2 mm to 32 mm (bottom to top), was 0.11[per thousand]([delta][sup 13]C) and 0.14[per thousand]([delta][sup 18]O). Results of this study provide the first quantitative data on growth rates of marine carbonate cements in a marginal slope environment. The data indicate that marginal slope deposits may lithify within several tens of years and suggest that geologically instantaneous cementation may be critical in stabilizing steep carbonate slope deposits at or above angles of repose.

  16. Chemical recovery of surface waters across the northeastern united states from reduced inputs of acidic deposition: 1984-2001.

    PubMed

    Warby, Richard A F; Johnson, Chris E; Driscoll, Charles T

    2005-09-01

    Changes in lake water chemistry between 1984 and 2001 at 130 stratified random sites across the northeastern United States were studied to evaluate the population-level effects of decreases in acidic deposition. Surface-water S04(2-) concentrations decreased across the region at a median rate of -1.53 microequiv L(-1) year(-1). Calcium concentrations also decreased, with a median rate of -1.73 microequiv L(-1) year(-1). This decrease in Ca2+ retarded the recovery of surface water acid neutralizing capacity (Gran ANC), which increased at a median rate of 0.66 microequiv L(-1) year(-1). There were small increases in pH in all subregions except central New England and Maine, where the changes were not statistically significant. Median NO3- trends were not significant except in the Adirondacks, where NO3- concentrations increased at a rate of 0.53 microequiv L(-1) year(-1). A regionwide decrease in the concentration of total Al, especially in ponds with low ANC values (ANC < 25 microequiv L(-1)), was observed in the Adirondack subregion. These changes in Al were consistent with the general pattern of increasing pH and ANC. Despite the general pattern of chemical recovery, many ponds remain chronically acidic or are susceptible to episodic acidification. The continued chemical and biological recovery at sites in the northeastern United States will depend on further controls on S and N emissions. PMID:16190211

  17. Amino-acid racemizarion in Quaternary shell deposits at Willapa Bay, Washington

    USGS Publications Warehouse

    Kvenvolden, K.A.; Blunt, D.J.; Clifton, H.E.

    1979-01-01

    Extents of racemization ( d l ratios) of amino acids in fossil Saxidomus giganteus (Deshayes) and Ostrea lurida Carpenter were measured on shell deposits exposed at 21 sites on the east side of Willapa Bay, Washington. Amino acids from Saxidomus show less variability in d Spl ratios and, therefore, are of greater use in correlation and age estimation than are amino acids from Ostrea. Shells of two different ages, about 120,000 ?? 40,000 yr old and about 190,000 ?? 40,000 yr old, are present. These ages correspond to Stages 5 and 7 of the marine isotope record defined by Shackleton and Opdyke in 1973 and hence the shell deposits likely formed during two different high stands of sea level. The stratigraphic record at Willapa Bay is consistent with this interpretation. ?? 1979.

  18. SPECTRAL REFLECTANCE METHOD TO MEASURE ACID DEPOSITION EFFECTS ON BUILDING STONE.

    USGS Publications Warehouse

    Kingston, Marguerite J.; Ager, Cathy M.

    1985-01-01

    As part of the National Acid Precipitation Assessment Program (NAPAP), the U. S. Geological Survey is cooperating with other agencies to test the effects of acid deposition on building stone. A 10-year test-site study has been organized for the purpose of correlating possible stone deterioration with environmental factors. In Summer 1984, slabs of building stone, 3 by 2 by 2 inches, were exposed to the atmosphere at four test sites where the pH of precipitation and other meteorological variables are continuously monitored. This paper examines the development of one experimental technique used in this study - the application of diffuse spectral reflectance methods for laboratory and in situ measurement of those properties of stone which may be affected by acid deposition.

  19. High performance hydrogenated amorphous silicon solar cells made at a high deposition rate by glow discharge of disilane

    SciTech Connect

    Ohashi, Y.; Kenne, J.; Konagai, M.; Takahashi, K.

    1983-06-15

    The deposition rate, electronic and optical properties of hydrogenated amorphous silicon films prepared from rf glow discharge decomposition of disilane (Si/sub 2/H/sub 6/) diluted in helium have been measured. These films show excellent electrical and optical properties and, most importantly, a high deposition rate coupled with satisfactory solar cell application was realized for the first time. At a deposition rate of 11 A/s, 5.47% and 6.5% conversion efficiencies were obtained with a first trial of n-i-p type solar cells deposited on SnO/sub 2//ITO glass and metal substrates, respectively.

  20. Effects of Folic Acid on Secretases Involved in Aβ Deposition in APP/PS1 Mice.

    PubMed

    Tian, Tian; Bai, Dong; Li, Wen; Huang, Guo-Wei; Liu, Huan

    2016-01-01

    Alzheimer's disease (AD) is the most common type of dementia. Amyloid-β protein (Aβ) is identified as the core protein of neuritic plaques. Aβ is generated by the sequential cleavage of the amyloid precursor protein (APP) via the APP cleaving enzyme (α-secretase, or β-secretase) and γ-secretase. Previous studies indicated that folate deficiency elevated Aβ deposition in APP/PS1 mice, and this rise was prevented by folic acid. In the present study, we aimed to investigate whether folic acid could influence the generation of Aβ by regulating α-, β-, and γ-secretase. Herein, we demonstrated that folic acid reduced the deposition of Aβ42 in APP/PS1 mice brain by decreasing the mRNA and protein expressions of β-secretase [beta-site APP-cleaving enzyme 1 (BACE1)] and γ-secretase complex catalytic component-presenilin 1 (PS1)-in APP/PS1 mice brain. Meanwhile, folic acid increased the levels of ADAM9 and ADAM10, which are important α-secretases in ADAM (a disintegrin and metalloprotease) family. However, folic acid has no impact on the protein expression of nicastrin (Nct), another component of γ-secretase complex. Moreover, folic acid regulated the expression of miR-126-3p and miR-339-5p, which target ADAM9 and BACE1, respectively. Taken together, the effect of folic acid on Aβ deposition may relate to making APP metabolism through non-amyloidogenic pathway by decreasing β-secretase and increasing α-secretase. MicroRNA (miRNA) may involve in the regulation mechanism of folic acid on secretase expression. PMID:27618097

  1. Acid deposition: atmospheric processes in eastern North America, a review of current scientific understanding

    SciTech Connect

    Not Available

    1983-01-01

    There is no observational evidence of a strong nonlinearity in the relationship between annual average total emissions and total deposition of sulfur in eastern North America. The finding is supported by theoretical calculations using the best available laboratory measurements of photochemical rate parameters. Currently available models of long-range atmospheric transport and transformation are not sufficiently developed to assess relationships between emissions from specific sources and deposition at specific receptor sites with high reliability.

  2. High emission rate of sulfuric acid from Bezymianny volcano, Kamchatka

    NASA Astrophysics Data System (ADS)

    Zelenski, Michael; Taran, Yuri; Galle, Bo

    2015-09-01

    High concentrations of primary sulfuric acid (H2SO4) in fumarolic gases and high emission rate of sulfuric acid aerosol in the plume were measured at Bezymianny volcano, an active dome-growing andesitic volcano in central Kamchatka. Using direct sampling, filter pack sampling, and differential optical absorption spectroscopy measurements, we estimated an average emission of H2SO4 at 243 ± 75 t/d in addition to an average SO2 emission of 212 ± 65 t/d. The fumarolic gases of Bezymianny correspond to arc gases released by several magma bodies at different stages of degassing and contain 25-92% of entrained air. H2SO4 accounts for 6-87 mol% of the total sulfur content, 42.8 mol% on average, and SO2 is the rest. The high H2SO4 in Bezymianny fumaroles can be explained by catalytic oxidation of SO2 inside the volcanic dome. Because sulfate aerosol is impossible to measure remotely, the total sulfur content in a plume containing significant H2SO4 may be seriously underestimated.

  3. Contemporaneous deposition of phyllosilicates and sulfates: Using Australian acidic saline lake deposits to describe geochemical variability on Mars

    USGS Publications Warehouse

    Baldridge, A.M.; Hook, S.J.; Crowley, J.K.; Marion, G.M.; Kargel, J.S.; Michalski, J.L.; Thomson, B.J.; de Souza, Filho C.R.; Bridges, N.T.; Brown, A.J.

    2009-01-01

    Studies of the origin of the Martian sulfate and phyllosilicate deposits have led to the hypothesis that there was a marked, global-scale change in the Mars environment from circum-neutral pH aqueous alteration in the Noachian to an acidic evaporitic system in the late Noachian to Hesperian. However, terrestrial studies suggest that two different geochemical systems need not be invoked to explain such geochemical variation.Western Australian acidic playa lakes have large pH differences separated vertically and laterally by only a few tens of meters, demonstrating how highly variable chemistries can coexist over short distances in natural environments. We suggest diverse and variable Martian aqueous environments where the coetaneous formation of phyllosilicates and sulfates at the Australian sites are analogs for regions where phyllosilicates and sulfates coexist on Mars. In these systems, Fe and alkali earth phyllosilicates represent deep facies associated with upwelling neutral to alkaline groundwater, whereas aluminous phyllosilicates and sulfates represent near-surface evaporitic facies formed from more acidic brines. Copyright 2009 by the American Geophysical Union.

  4. High Anatase Rate Titanium Dioxide Coating Deposition by Low Power Microwave Plasma Spray

    NASA Astrophysics Data System (ADS)

    Redza, Ahmad; Kondo, Toshiki; Yasui, Toshiaki; Fukumoto, Masahiro

    2016-02-01

    Titanium dioxide is a promising photocatalyst material because of the magnificent properties of this material where it is able to remove the air pollution substance and the deodorizing function. Generally, the deposition method of a titanium dioxide coating is carried out by an organic system binder but the powerful photocatalytic reaction will degrades the binder. Therefore, thermal spray is considered to be the alternative method but this method will induce crystallization transformation of titanium dioxide from anatase phase with high photocatalytic activity to rutile phase with low photocatalyst which caused by high heat input. Since our microwave plasma spraying device is operable at low power comparing with conventional high power plasma spray, the reduce effect of the heat input onto the particles at the time of spraying can be achieved and coating deposition with high rate of anatase phase is expected. Therefore, in this research, the coating deposition by controlling the heat input into the spray particle which can be resulted in high rate of anatase phase with high photocatalytic activity was conducted. By controlled condition, coating with optimum anatase rate of 83% is able to be fabricated by this method.

  5. Silicon nucleation and film evolution on silicon dioxide using disilane: Rapid thermal chemical vapor deposition of very smooth silicon at high deposition rates

    SciTech Connect

    Violette, K.E.; Oeztuerk, M.C.; Christensen, K.N.; Maher, D.M.

    1996-02-01

    An investigation of Si{sub 2}H{sub 6} and H{sub 2} for rapid thermal chemical vapor deposition (RTCVD) of silicon on SiO{sub 2} has been performed at temperatures ranging from 590 to 900 C and pressures ranging from 0.1 to 1.5 Torr. Deposition at 590 C yields amorphous silicon films with the corresponding ultrasmooth surface with a deposition rate of 68 nm/min. Cross-sectional transmission electron microscopy of a sample deposited at 625 C and 1 Torr reveals a bilayer structure which is amorphous at the growth surface and crystallized at the oxide interface. Higher temperatures yield polycrystalline films where the surface roughness depends strongly on both deposition pressure and temperature. Silane-based amorphous silicon deposition in conventional systems yields the expected ultrasmooth surfaces, but at greatly reduced deposition rates unsuitable for single-wafer processing. However, disilane, over the process window considered here, yields growth rates high enough to be appropriate for single-wafer manufacturing, thus providing a viable means for deposition of very smooth silicon films on SiO{sub 2} in a single-wafer environment.

  6. Controls on suppression of methane flux from a peat bog subjected to simulated acid rain sulfate deposition

    NASA Astrophysics Data System (ADS)

    Gauci, Vincent; Dise, Nancy; Fowler, David

    2002-01-01

    The effect of acid rain SO42- deposition on peatland CH4 emissions was examined by manipulating SO42- inputs to a pristine raised peat bog in northern Scotland. Weekly pulses of dissolved Na2SO4 were applied to the bog over two years in doses of 25, 50, and 100 kg S ha-1 yr-1, reflecting the range of pollutant S deposition loads experienced in acid rain-impacted regions of the world. CH4 fluxes were measured at regular intervals using a static chamber/gas chromatographic flame ionization detector method. Total emissions of CH4 were reduced by between 21 and 42% relative to controls, although no significant differences were observed between treatments. Estimated total annual fluxes during the second year of the experiment were 16.6 g m-2 from the controls and (in order of increasing SO42- dose size) 10.7, 13.2, and 9.8 g m-2 from the three SO42- treatments, respectively. The relative extent of CH4 flux suppression varied with changes in both peat temperature and peat water table with the largest suppression during cool periods and episodes of falling water table. Our findings suggest that low doses of SO42- at deposition rates commonly experienced in areas impacted by acid rain, may significantly affect CH4 emissions from wetlands in affected areas. We propose that SO42- from acid rain can stimulate sulfate-reducing bacteria into a population capable of outcompeting methanogens for substrates. We further propose that this microbially mediated interaction may have a significant current and future effect on the contribution of northern peatlands to the global methane budget.

  7. Computer Program for the Calculation of Multicomponent Convective Diffusion Deposition Rates from Chemically Frozen Boundary Layer Theory

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Chen, B. K.; Rosner, D. E.

    1984-01-01

    The computer program based on multicomponent chemically frozen boundary layer (CFBL) theory for calculating vapor and/or small particle deposition rates is documented. A specific application to perimter-averaged Na2SO4 deposition rate calculations on a cylindrical collector is demonstrated. The manual includes a typical program input and output for users.

  8. High Acetic Acid Production Rate Obtained by Microbial Electrosynthesis from Carbon Dioxide.

    PubMed

    Jourdin, Ludovic; Grieger, Timothy; Monetti, Juliette; Flexer, Victoria; Freguia, Stefano; Lu, Yang; Chen, Jun; Romano, Mark; Wallace, Gordon G; Keller, Jurg

    2015-11-17

    High product specificity and production rate are regarded as key success parameters for large-scale applicability of a (bio)chemical reaction technology. Here, we report a significant performance enhancement in acetate formation from CO2, reaching comparable productivity levels as in industrial fermentation processes (volumetric production rate and product yield). A biocathode current density of -102 ± 1 A m(-2) and an acetic acid production rate of 685 ± 30 (g m(-2) day(-1)) have been achieved in this study. High recoveries of 94 ± 2% of the CO2 supplied as the sole carbon source and 100 ± 4% of electrons into the final product (acetic acid) were achieved after development of a mature biofilm, reaching an elevated product titer of up to 11 g L(-1). This high product specificity is remarkable for mixed microbial cultures, which would make the product downstream processing easier and the technology more attractive. This performance enhancement was enabled through the combination of a well-acclimatized and enriched microbial culture (very fast start-up after culture transfer), coupled with the use of a newly synthesized electrode material, EPD-3D. The throwing power of the electrophoretic deposition technique, a method suitable for large-scale production, was harnessed to form multiwalled carbon nanotube coatings onto reticulated vitreous carbon to generate a hierarchical porous structure. PMID:26484732

  9. Acid dew and the role of chemistry in the dry deposition of reactive gases to wetted surfaces

    NASA Technical Reports Server (NTRS)

    Chameides, William L.

    1987-01-01

    A formalism is developed to describe the dry deposition of soluble reactive gases to wetted surfaces in terms of the relevant meteorological conditions, the surface roughness, the total amount of liquid water present on the surface, the rate of accumulation of this water, and the species' solubility and reactivity in the surface water. This formulation is then incorporated into a model designed to simulate the generation of acidic dew from the deposition of HNO3, SO2, S(IV) oxidants, H2O2, and O3. Similar to the observations of dew in the continental U.S., the model generates a dewdrop pH of about 4 by the end of the night; the pH can rapidly fall to toxic levels due to rapid evaporation after sunrise. Relatively low deposition velocities are predicted for the SO2 and O3 because of their lower solubilities and hence larger surface resistances than those of the other oxidants. Because the chemical lifetime of the SO2 in the dew is influenced by the atmospheric levels of H2O2, O3, and SO2, the SO2 deposition velocity is a strong function of these species' atmospheric abundances.

  10. Use of stream chemistry for monitoring acidic deposition effects in the Adirondack region of New York

    USGS Publications Warehouse

    Lawrence, G.B.; Momen, B.; Roy, K.M.

    2004-01-01

    Acid-neutralizing capacity (ANC) and pH were measured weekly from October 1991 through September 2001 in three streams in the western Adirondack Mountain region of New York to identify trends in stream chemistry that might be related to changes in acidic deposition. A decreasing trend in atmospheric deposition of SO42- was observed within the region over the 10-yr period, although most of the decrease occurred between 1991 and 1995. Both ANC and pH were inversely related to flow in all streams; therefore, a trend analysis was conducted on (i) the measured values of ANC and pH and (ii) the residuals of the concentration-discharge relations. In Buck Creek, ANC increased significantly (p 0.10). In Bald Mountain Brook, ANC and residuals of ANC increased significantly (p < 0.01), although the trend was diatonic-a distinct decrease from 1991 to 1996 was followed by a distinct increase from 1996 to 2001. In Fly Pond outlet, ANC and residuals of ANC increased over the study period (p < 0.01), although the trend of the residuals resulted largely from an abrupt increase in 1997. In general, the trends observed in the three streams are similar to results presented for Adirondack lakes in a previous study, and are consistent with the declining trend in atmospheric deposition for this region, although the observed trends in ANC and pH in streams could not be directly attributed to the trends in acidic deposition.

  11. The Tracking and Analysis Framework (TAF): A tool for the integrated assessment of acid deposition

    SciTech Connect

    Bloyd, C.N.; Henrion, M.; Marnicio, R.J.

    1995-06-01

    A major challenge that has faced policy makers concerned with acid deposition is obtaining an integrated view of the underlying science related to acid deposition. In response to this challenge, the US Department of Energy is sponsoring the development of an integrated Tracking and Analysis Framework (TAF) which links together the key acid deposition components of emissions, air transport, atmospheric deposition, and aquatic effects in a single modeling structure. The goal of TAF is to integrate credible models of the scientific and technical issues into an assessment framework that can directly address key policy issues, and in doing so act as a bridge between science and policy. Key objectives of TAF are to support coordination and communication among scientific researchers; to support communications with policy makers, and to provide rapid response for analyzing newly emerging policy issues; and to provide guidance for prioritizing research programs. This paper briefly describes how TAF was formulated to meet those objectives and the underlying principals which form the basis for its development.

  12. Nitrogen mineralization rates of the acidic, xeric soils of the New Jersey Pinelands: field rates

    SciTech Connect

    Poovarodom, S.; Tate, R.L. III; Bloom, R.A.

    1988-04-01

    Using the buried-bag procedure, the authors quantified nitrogen mineralization rates in the xeric, acidic Lakehurst, and Atsion sands of the New Jersey Pine Barrens. Average annual nitrogen yields in the upper 15 cm for the Lakehurst and the Atsion sands were 38.4 and 53.0 kg N/ha, corresponding to 4.5 and 2.5% of the total nitrogen, respectively. Net nitrogen mineralization in both soils exhibited distinct seasonal patterns with maxima in summer and minimum rates in the winter. Nitrification accounted for only 5% of the total N mineralized in both soils. This is consistent with the finding of low populations of autotrophic nitrifiers in these soils.

  13. Quantification of hydrochloric acid and particulate deposition resulting from space shuttle launches at John F. Kennedy space center, Florida, USA

    NASA Astrophysics Data System (ADS)

    Dreschel, Thomas W.; Hall, Carlton R.

    1990-07-01

    Observations of damage to vegetation, acute reductions in surface water pH, and kills of small fish prompted the Biomedical Operations and Research Office at the John F. Kennedy Space Center to initiate intensive environmental evaluations of possible acute and long-term chronic impacts that may be produced by repeated launches of the space shuttle. An important step in this evaluation was the identification of deposition patterns and the quantification of ecosystem loading rates of exhaust constituents from the solid rocket motors (SRMs) in the area of the launch pad. These constituents are primarily aluminum oxide (Al2O3) and hydrochloric acid (HCl). During three launches of the space transportation system (STS-11, 13, and 14) up to 100 bulk deposition collectors, 83 mm in diameter containing 100 ml of deionized water, were deployed in a grid pattern covering 12.6 ha north of launch pad 39-A. Estimates of HCl and particulate deposition levels were made based on laboratory measurements of items entrained in the collectors. Captured particulates consisted of a variety of items including Al2O3, sand grains, sea shell fragments, paint chips, and other debris ablated from the launch pad surface by the initial thrust of the SRMs. Estimated ranges of HCl and particulate deposition in the study area were 0-127 g/m2 and 0-246 g/m2, respectively. Deposition patterns were highly influenced by wind speed and direction. These measurements indicate that, under certain meteorological conditions, up to 7.1 × 103 kg of particulates and 3.4 × 103 kg of HCl can be deposited to the near-field environment beyond the launch pad perimeter fence.

  14. Effects of acid deposition on calcium nutrition and health of Southern Appalachian spruce fir forests

    SciTech Connect

    McLaughlin, S.B.; Wullschleger, S.; Stone, A.; Wimmer, R.; Joslin, J.D.

    1995-02-01

    The role of acid deposition in the health of spruce fir forests in the Southern Appalachian Mountains has been investigated by a wide variety of experimental approaches during the past 10 years. These studies have proceeded from initial dendroecological documentation of altered growth patterns of mature trees to increasingly more focused ecophysiological research on the causes and characteristics of changes in system function associated with increased acidic deposition. Field studies across gradients in deposition and soil chemistry have been located on four mountains spanning 85 km of latitude within the Southern Appalachians. The conclusion that calcium nutrition is an important component regulating health of red spruce in the Southern Appalachians and that acid deposition significantly reduces calcium availability in several ways has emerged as a consistent result from multiple lines or research. These have included analysis of trends in wood chemistry, soil solution chemistry, foliar nutrition, gas exchange physiology, root histochemistry, and controlled laboratory and field studies in which acid deposition and/or calcium nutrition has been manipulated and growth and nutritional status of saplings or mature red spruce trees measured. This earlier research has led us to investigate the broader implications and consequences of calcium deficiency for changing resistance of spruce-fir forests to natural stresses. Current research is exploring possible relationships between altered calcium nutrition and shifts in response of Fraser fir to insect attack by the balsam wooly adelgid. In addition, changes in wood ultrastructural properties in relation to altered wood chemistry is being examined to evaluate its possible role in canopy deterioration, under wind and ice stresses typical of high elevation forests.

  15. Acid deposition sensitivity map of the Southern Appalachian Assessment area; Virginia, North Carolina, South Carolina, Tennessee, Georgia, and Alabama

    USGS Publications Warehouse

    Pepper, John D.; Grosz, Andrew E.; Kress, Thomas H.; Collins, Thomas K.; Kappesser, Gary B.; Huber, Cindy M.; Webb, James R.

    1995-01-01

    Project Summary: The following digital product represents the Acid Deposition Sensitivity of the Southern Appalachian Assessment Area. Areas having various susceptibilities to acid deposition from air pollution are designated on a three tier ranking in the region of the Southern Appalachian Assessment (SAA). The assessment is being conducted by Federal agencies that are members of the Southern Appalachian Man and Biosphere (SAMAB) Cooperative. Sensitivities to acid deposition, ranked high, medium, and low are assigned on the basis of bedrock compositions and their associated soils, and their capacities to neutralize acid precipitation.

  16. Giant uranium deposits formed from exceptionally uranium-rich acidic brines

    NASA Astrophysics Data System (ADS)

    Richard, Antonin; Rozsypal, Christophe; Mercadier, Julien; Banks, David A.; Cuney, Michel; Boiron, Marie-Christine; Cathelineau, Michel

    2012-02-01

    Giant uranium deposits were formed during the Mesoproterozoic era, 1.6-1.0 Gyr ago, in both Canada and Australia. The deposits are thought to have formed from large-scale circulation of brines at temperatures of 120-200 °C that percolated between sedimentary basins and underlying crystalline basement rocks. However, the precise conditions for transport of the uranium in these brines are poorly understood. Here we use mass spectrometry to analyse the uranium content of brines preserved in naturally occurring fluid inclusions in ore deposits from the Athabasca Basin, Canada. We measure concentrations of uranium in the range 1.0×10-6-2.8×10-3moll-1. These concentrations are three orders of magnitude above any other common crustal fluids. Experimentally, we measure the solubility of uranium as a function of NaCl content and pH, in mixtures that are analogous to ore-forming brines at 155°C. To account for the high uranium content observed in the Athabasca deposits, we find that the brines must have been acidic, with a pH between 2.5 and 4.5. Our results strongly suggest that the world's richest uranium deposits formed from highly concentrated uranium-bearing acidic brines. We conclude that these conditions are a necessary requirement for the formation of giant uranium deposits in relatively short periods of time of about 0.1-1 Myr, similar to other world-class deposits of lead-zinc and gold.

  17. A Study of Effects of Acid Deposition on Pine Forest Ecosystem in Southwestern China

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Li, F.; Lv, Z.; Song, W.; Yang, S.

    2013-12-01

    We used a long-term soil acidification model (LTSAM) and a terrestrial biogeochemical model (CENTURY) coupled to simulate the effects of acid deposition on pine forest ecosystem in southwestern China, based on indoor experiment results of aluminum toxicity to individual plant growth. The results of indoor aluminum experiments show that high aluminum concentration may restrict the plant growth and the acidic condition may aggravate it. The behavior of restriction of plant growth includes decreases of pine seedling biomass, root elongation and the sorption of soil cations (e.g. Ca2+, Mg2+, Na+ and K+). The model simulation results about soil chemistry show that, as acid deposition increases more, the pH value decreases faster, the soil aluminum ion concentration increase more rapidly, and the nutrition ions in soil solution decrease more quickly. The increased acid deposition also has negative impacts on the forest ecosystem according to the biogeochemical model simulation, for example, decreases of vegetation biomass, net primary productivity (NPP) and net CO2 uptake. Furthermore, the decrease of plant biomass will result in the decrease of the soil organic carbon content for the limited decomposition material supply.

  18. Influence of alkaline suspended particles on the chemical composition of acid deposition in Kaohsiung City, Taiwan

    SciTech Connect

    Yuan, C.S.; Lin, Z.J.; Wu, M.Y.; Liu, J.I.; Yuan, C.

    1998-12-31

    This study investigated the influence of alkaline suspended particles on the chemical composition of acid deposition both temporally and spatially in Kaohsiung metropolitan area in Taiwan. During the period of January--December, 1996, both wet and dry deposition samples were collected by automatic acid precipitation samplers at six sampling sites which covered the entire metropolitan area. Major cations (NH{sub 4}{sup +}, K{sup +}, Na{sup +}, Ca{sup +2}, and Mg{sup +2}) and anions (F{sup {minus}}, Cl{sup {minus}}, NO{sub 3}{sup {minus}}, and SO{sub 4}{sup {minus}2}) of acid deposition samples were analyzed in a central laboratory, while the pH value and conductivity of rainwater samples were measured in situ. Results from chemical analysis indicated that Ca{sup +2} was the most abundant cation in acid deposition samples. Major cations were Ca{sup +2} and NH{sub 4}{sup +}, while major anions were SO{sub 4}{sup {minus}2} and NO{sub 3}{sup {minus}}. This study also revealed that the pH value, suspended solids, Ca{sup +2}, and NH{sub 4}{sup +} of rainwater decreased with rainy time in a sequential rainwater sampling process. It was estimated that approximately 80% of suspended particles could be washed out by rain droplets in the first hour of raining process. Therefore, alkaline suspended particles in the atmosphere played an very important role on the chemical composition of acid precipitation in Kaohsiung metropolitan area in Taiwan.

  19. Method to grow pure nanocrystalline diamond films at low temperatures and high deposition rates

    DOEpatents

    Carlisle, John A.; Gruen, Dieter M.; Auciello, Orlando; Xiao, Xingcheng

    2009-07-07

    A method of depositing nanocrystalline diamond film on a substrate at a rate of not less than about 0.2 microns/hour at a substrate temperature less than about 500.degree. C. The method includes seeding the substrate surface with nanocrystalline diamond powder to an areal density of not less than about 10.sup.10sites/cm.sup.2, and contacting the seeded substrate surface with a gas of about 99% by volume of an inert gas other than helium and about 1% by volume of methane or hydrogen and one or more of acetylene, fullerene and anthracene in the presence of a microwave induced plasma while maintaining the substrate temperature less than about 500.degree. C. to deposit nanocrystalline diamond on the seeded substrate surface at a rate not less than about 0.2 microns/hour. Coatings of nanocrystalline diamond with average particle diameters of less than about 20 nanometers can be deposited with thermal budgets of 500.degree. C.-4 hours or less onto a variety of substrates such as MEMS devices.

  20. Effect of energy deposition rate on plasma expansion characteristics and nanoparticle generation by electrical explosion of conductors

    NASA Astrophysics Data System (ADS)

    Sahoo, Somanand; Saxena, Alok K.; Kaushik, Trilok C.; Gupta, Satish C.

    2015-12-01

    The process of electrical explosion of metal conductors has been used to produce nano particles under normal atmospheric conditions. The impact of average rate of energy deposition, overheat factor on size distribution of particles and expansion characteristics of plasma generated from exploding conductors have been experimentally investigated. The particle size was characterized by TEM and XRD while expansion rate was measured using streak photography.The geometric mean diameter of size distribution was found to be influenced by rate of energy deposition in the conductors. It is observed that higher the rate of energy deposition, higher will be the expansion velocity, and smaller will be the size of particles formed.

  1. Nitrogen Deposition Reduces Decomposition Rates Through Shifts in Microbial Community Composition and Function

    NASA Astrophysics Data System (ADS)

    Waldrop, M.; Zak, D.; Sinsabaugh, R.

    2002-12-01

    Atmospheric nitrogen (N) deposition may alter soil biological activity in northern hardwood forests by repressing phenol oxidase enzyme activity and altering microbial community composition, thereby slowing decomposition and increasing the export of phenolic compounds. We tested this hypothesis by adding 13C-labelled cellobiose, vanillin, and catechol to control and N fertilized soils (30 and 80 kg ha-1) collected from three forests; two dominated by Acer Saccharum and one dominated by Quercus Alba and Quercus Velutina. While N deposition increased total microbial respiration, it decreased soil oxidative enzyme activities, resulting in slower degradation rates of all compounds, and larger DOC pools. This effect was larger in the oak forest, where fungi dominate C-cycling processes. DNA and 13C-phospolipid analyses showed that N addition altered the fungal community and reduced the activity of fungal and bacterial populations in soil, potentially explaining reduced soil enzyme activities and incomplete decomposition.

  2. The effect of Be and Cr electrode deposition rate on the performance of MIS solar cells

    NASA Astrophysics Data System (ADS)

    Moharram, A. H.; Panayotatos, P.; Yeh, J. L.; Lalevic, B.

    1985-07-01

    An experimental study has been performed on MIS solar cells with Be, Cr and layered Cr-Be electrodes on single crystal Si, Wacker and Monsanto poly-Si substrates. Electrical characterization in the dark and under illumination was correlated to X-ray and Auger spectroscopy results. It was found that the electrode deposition rate directly affects the oxygen content of the electrodes for all metal-substrate configurations. This oxygen is believed to originate from the deposition ambient as well as from the SiO2 layer. In the case of cells with Cr and layered Cr-Be electrodes oxygen acts to reduce the electrode work function (thus increasing the open-circuit voltage) in direct proportion to the relative content of oxygen to chromium.

  3. Responses of streams in central Appalachian Mountain region to reduced acidic deposition--comparisons with other regions in North America and Europe.

    PubMed

    Chen, Yushun; Lin, Lian-Shin

    2009-03-15

    Data from 5 wet deposition stations and 21 streams during 1980-2006 were analyzed to investigate chemical responses of streams to reduced acidic deposition in the central Appalachian Mountain region of West Virginia, USA. Wet deposition of acidic anions (i.e., sulfate, nitrate, and chloride) and hydrogen ions decreased significantly during the studied time period. Stream sulfate showed a delayed response to the reduced acidic deposition, and showed a decrease in the 2000s (-5.54 microeq L(-1) yr(-1)) and the whole period (-0.49 microeq L(-1) yr(-1)). No significant trend of stream nitrate+nitrite and chloride was observed. Stream alkalinity increased in the 1990s (+23.33 microeq L(-1) yr(-1)) and the whole period (+7.26 microeq L(-1) yr(-1)). Stream hydrogen ions decreased in the 1990s (-0.002 microeq L(-1) yr(-1)), 2000s (-0.001 microeq L(-1) yr(-1)), and the whole period (-0.001 microeq L(-1) yr(-1)). Compared with most acidic streams and lakes in the United States and Europe, a lower decreasing rate of hydrogen ions and higher increasing rate of alkalinity were observed in the alkaline West Virginian streams in the 1990s. However, due to their initial negative or zero alkalinity values, those acidic streams showed a higher percent increase in alkalinity than that in the alkaline West Virginian streams (from 800 microeq L(-1) yr(-1) to 1200 microeq L(-1) yr(-1)). Total aluminum in the West Virginian streams decreased in the 1990s (-0.67 micromol L(-1) yr(-1)) and the whole period (-0.22 micromol L(-1) yr(-1)). The current study advanced our understanding of streams' responses to the reduced acidic deposition in the Mid-Appalachians since the passage of the 1970 and 1990 Amendments to the United States Clean Air Act (US CAAA). PMID:19073337

  4. Regional relationships between geomorphic/hydrologic parameters and surface water chemistry relative to acidic deposition

    SciTech Connect

    Rochelle, B.P.; Liff, C.I.; Campbell, W.G.; Cassell, D.L.; Church, M.R.

    1989-01-01

    The authors determined geomorphic and hydrologic parameters for 144 forested, lake watersheds in the Northeast (NE) of the United States based primarily on measurements from topographic maps. These parameters were used to test for relationships with selected surface water chemistry relevant to acidic deposition. Analyses were conducted on regional and subregional scales delineated based on soils, land use, physiography, total sulfur deposition and statistical clustering of selected geomorphic/hydrologic parameters. Significant relationships were found among the geomorphic/hydrologic parameters and the surface water chemistry for the NE. Elevation had the most significant relationship with surface water chemistry, particularly in the mountainous areas of the NE. Other factors occurring consistently as significant predictors of surface water chemistry were maximum relief, relief ratio, runoff, and estimates of basin elongation. Results suggest that elevational parameters might be surrogates for other watershed characteristics, such as soils or spatial deposition patterns.

  5. Inkjet deposition of itraconazole onto poly(glycolic acid) microneedle arrays.

    PubMed

    Boehm, Ryan D; Jaipan, Panupong; Skoog, Shelby A; Stafslien, Shane; VanderWal, Lyndsi; Narayan, Roger J

    2016-03-01

    Poly(glycolic acid) microneedle arrays were fabricated using a drawing lithography process; these arrays were modified with a drug release agent and an antifungal agent by piezoelectric inkjet printing. Coatings containing poly(methyl vinyl ether-co-maleic anhydride), a water-soluble drug release layer, and itraconazole (an antifungal agent), were applied to the microneedles by piezoelectric inkjet printing. Microscopic evaluation of the microneedles indicated that the modified microneedles contained the piezoelectric inkjet printing-deposited agents and that the surface coatings were released in porcine skin. Energy dispersive x-ray spectrometry aided in confirmation that the piezoelectric inkjet printing-deposited agents were successfully applied to the desired target areas of the microneedle surface. Fourier transform infrared spectroscopy was used to confirm the presence of the component materials in the piezoelectric inkjet printing-deposited material. Itraconazole-modified microneedle arrays incubated with agar plates containing Candida albicans cultures showed zones of growth inhibition. PMID:26869165

  6. Studies of acid deposition and its effects in two small catchments in Hunan, China

    NASA Astrophysics Data System (ADS)

    Xue, Nandong; Seip, Hans Martin; Liao, Bohan; Vogt, Rolf D.

    Acid deposition and its effects were studied by analysing the chemistry in precipitation, stream water, soil water and soils in two catchments in Hunan. One site, Linkesuo (denoted LKS), is on the outskirts of Changsha, the provincial capital of Hunan, the other (Bailutang, denoted BLT) on the outskirts of Chenzhou in southern Hunan. Volume-weighted average pH values and sulphate concentrations in wet deposition were 4.58 (BLT) and 4.90 (LKS) and 174 μmolc L-1 and 152 μmolc L-1, respectively. Wet deposition of sulphate has been estimated as 4.3 gS m-2yr-1 and 3.4 gS m-2yr-1 at BLT and LKS, respectively. Estimates of the corresponding total depositions (dry + wet) are 6.1 gS m-2yr-1 and 5.3 gS m-2yr-1. In precipitation and throughfall, sulphate was the major anion and calcium the major cation. In stream and soil water, nitrate was slightly higher than sulphate on an equivalent basis and magnesium (Mg) not much lower than calcium (Ca). Important soil properties, such as soil pH, soil organic matter (SOM) content, exchangeable acidic cations, exchangeable base cations, effective cation exchange capacity (CECe), base saturation (BS), and aluminium (Al) and iron (Fe) pools, were determined for five forest soil profiles (consisting of four horizons) in each of the two catchments. The soils in BLT are generally more acid, have lower BS and higher Al and Fe pools than the LKS soils. The Al- and Fe-pools were generally higher in the topsoils (i.e. the O and A horizons) than in deeper soils (i.e. E and B horizons) especially at the most acidic site (BLT). There are significant correlations between Fe-pools and the corresponding Al-pools in both catchments except between the amorphous Feox and Alox. Considering the long-term high deposition of sulphate, there is a risk of future ecological damage due to acidification, especially in the BLT catchment, although vegetation damage has yet to be observed in the catchments. This condition appears to be representative of a large

  7. Modeling wet deposition of acid substances over the PRD region in China

    NASA Astrophysics Data System (ADS)

    Lu, Xingcheng; Fung, Jimmy Chi Hung; Wu, Dongwei

    2015-12-01

    The Pearl River Delta (PRD) region in southern China has suffered heavily from acid rain in the last 10 years due to the anthropogenic emission of sulfur dioxide and nitrogen dioxide. Several measurement-based studies about this issue have been conducted to analyze the chemical composition of precipitation in this area. However, no detailed, high resolution numerical simulation regarding this topic has ever been done in this region. In this study, the WRF-SMOKE-CMAQ system was applied to simulate the wet deposition of acid substances (SO42- and NO3-) in the PRD region from 2009 to 2011 with a resolution of 3 km. The simulation output agreed well with the observation data. Our results showed that Guangzhou was the city most affected by acid rain in this region. The ratio of non-sea-salt sulfate to nitrate indicated that the acid rain in this region belonged to the sulfate-nitrate mixed type. The source apportionment result suggests that point source and super regional source are the ones that contribute the pollutants most in the rain water over PRD Region. The sulfate and nitrate input to some reservoirs via wet deposition was also estimated based on the model simulation. Our results suggest that further cross-city cooperation and emission reduction are needed to further curb acid rain in this region.

  8. The effects of climate change on the nitrogen cycle and acid deposition

    SciTech Connect

    Penner, J.E.; Walton, J.J. ); Graboske, B.C. )

    1990-09-01

    Increases in greenhouse gases are expected to lead to a number of changes to the atmosphere which may impact regional and global chemical cycles. With the increasing awareness of climate change and the possibility of global chemical changes to the atmosphere, it becomes important to ask whether these changes to global climate and chemical cycles might benefit or hinder control programs aimed at reducing acid deposition. In the following, we review several possible changes to climate that may be expected to impact the global cycle of reactive nitrogen. We then use our global model of the reactive nitrogen cycle to estimate the effects of several of the more important changes on the continental-scale deposition of nitric acid. 7 refs., 1 tab.

  9. Valuation of damages to recreational trout fishing in the Upper Northeast due to acidic deposition

    SciTech Connect

    Englin, J.E.; Cameron, T.A.; Mendelsohn, R.E.; Parsons, G.A.; Shankle, S.A.

    1991-04-01

    This report documents methods used to estimate economic models of changes in recreational fishing due to the acidic deposition. The analysis was conducted by Pacific Northwest Laboratory (PNL) and its subcontractors for the US Environmental Protection Agency (EPA) and the US Department of Energy (DOE) in support of the National Acidic Precipitation Assessment Program (NAPAP). The primary data needed to estimate these models were collected in the 1989 Aquatic Based Recreation Survey (ABRS), which was jointly funded by the DOE and the EPA's Office of Policy Planning and Evaluation. 11 refs., 5 figs., 15 tabs.

  10. Analysis of potential combustion source impacts on acid deposition using an independently derived inventory. Volume I

    SciTech Connect

    Not Available

    1983-12-01

    This project had three major objectives. The first objective was to develop a fossil fuel combustion source inventory (NO/sub x/, SO/sub x/, and hydrocarbon emissions) that would be relatively easy to use and update for analyzing the impact of combustion emissions on acid deposition in the eastern United States. The second objective of the project was to use the inventory data as a basis for selection of a number of areas that, by virtue of their importance in the acid rain issue, could be further studied to assess the impact of local and intraregional combustion sources. The third objective was to conduct an analysis of wet deposition monitoring data in the areas under study, along with pertinent physical characteristics, meteorological conditions, and emission patterns of these areas, to investigate probable relationships between local and intraregional combustion sources and the deposition of acidic material. The combustion source emissions inventory has been developed for the eastern United States. It characterizes all important area sources and point sources on a county-by-county basis. Its design provides flexibility and simplicity and makes it uniquely useful in overall analysis of emission patterns in the eastern United States. Three regions with basically different emission patterns have been identified and characterized. The statistical analysis of wet deposition monitoring data in conjunction with emission patterns, wind direction, and topography has produced consistent results for each study area and has demonstrated that the wet deposition in each area reflects the characteristics of the localized area around the monitoring sites (typically 50 to 150 miles). 8 references, 28 figures, 39 tables.

  11. Key factors influencing rates of heterotrophic sulfate reduction in hydrothermal massive sulfide deposits

    NASA Astrophysics Data System (ADS)

    Frank, K. L.; Rogers, D.; Girguis, P. R.

    2012-12-01

    Despite sulfate reduction's ubiquity in marine systems, relatively little is known about how environmental or ecological factors influence rates of sulfate reduction. While numerous studies have considered how sulfate reduction and methanogenesis compete for reductants in natural and human-made systems, less is known about how temperature or metabolite concentration, such as sulfate and sulfide concentrations, affects rates of sulfate reduction. Here we use a factorial experimental design to evaluate the effects of key variables on sulfate reduction kinetics in sulfide deposits recovered from hydrothermal vents in the Main Endeavor Field, Juan de Fuca ridge. Microbial sulfate reduction rates were measured by 35-S tracer techniques over a range of environmentally relevant chemical conditions (pH, H2S, SO42-, and organic carbon concentrations) and temperatures (4, 50 and 90°C). Maximum sulfate reduction rates were observed at 50°C, and sulfate reduction rates had significant positive correlations with increasing sulfide, pH and sulfate. However, sulfate reduction rates did not correlate to exogenous dissolved organic carbon, implicating exogenous hydrogen or endogenous organic matter as the reductant (or even sulfur disproportionation). This research presents an opportunity to better understand the key variables that influence the rates of microbial sulfate reduction in hydrothermal environments and provides a framework for modeling sulfate reduction in mid-ocean ridge systems.

  12. Hazards in determination and extrapolation of depositional rates of recent sediments

    SciTech Connect

    Isphording, W.C. . Dept. of Geology-Geography); Jackson, R.B. )

    1992-01-01

    Calculation of depositional rates for the past 250 years in estuarine sediments at sites in the Gulf of Mexico have been carried out by measuring changes that have taken place on bathymetric charts. Depositional rates during the past 50 to 100 years can similarly be estimated by this method and may be often confirmed by relatively abrupt changes at depth in the content of certain heavy metals in core samples. Analysis of bathymetric charts of Mobile Bay, Alabama, dating back to 1858, disclosed an essentially constant sedimentation rate of 3.9 mm/year. Apalachicola Bay, Florida, similarly, was found to have a rate of 5.4 mm/year. Though, in theory, these rates should provide reliable estimates of the influx of sediment into the estuaries, considerable caution must be used in attempting to extrapolate them to any depth in core samples. The passage of hurricanes in the Gulf of Mexico is a common event and can rapidly, and markedly, alter the bathymetry of an estuary. The passage of Hurricane Elena near Apalachicola Bay in 1985, for example, removed over 84 million tons of sediment from the bay and caused an average deepening of nearly 50 cm. The impact of Hurricane Frederick on Mobile Bay in 1979 was more dramatic. During the approximate 7 hour period when winds from this storm impacted the estuary, nearly 290 million tons of sediment was driven out of the bay and an average deepening of 46 cm was observed. With such weather events common in the Gulf Coast, it is not surprising that when radioactive age dating methods were used to obtain dates of approximately 7,500 years for organic remains in cores from Apalachicola Bay, that the depths at which the dated materials were obtained in the cores corresponded to depositional rates of only 0.4 mm/year, or one-tenth that obtained from historic bathymetric data. Because storm scour effects are a common occurrence in the Gulf, no attempt should be made to extrapolate bathymetric-derived rates to beyond the age of the charts.

  13. Ascorbic acid and rates of cognitive decline in Alzheimer's disease.

    PubMed

    Bowman, Gene L; Dodge, Hiroko; Frei, Balz; Calabrese, Carlo; Oken, Barry S; Kaye, Jeffrey A; Quinn, Joseph F

    2009-01-01

    The brain maintains high levels of ascorbic acid (AA) despite a concentration gradient favoring diffusion from brain to peripheral tissues. Dietary antioxidants, including AA, appear to modify the risk of Alzheimer's disease (AD). The objective of this study was to test the hypothesis that neurodegeneration in AD is modified by brain levels of AA. Thirty-two patients with mild to moderate AD participated in a biomarker study involving standardized clinical assessments over one year. Cerebrospinal fluid (CSF) and serum were collected at baseline for AA and albumin content. Cognitive measures were collected at baseline and one year. CSF and plasma AA failed to predict cognitive decline independently, however, CSF: plasma AA ratio did. After adding CSF Albumin Index (an established marker of blood-brain barrier integrity) to the regression models the effect of CSF: plasma AA ratio as a predictor of cognitive decline was weakened. CSF: plasma AA ratio predicts rate of decline in AD. This relationship may indicate that the CSF: plasma AA ratio is an index of AA availability to the brain or may be an artifact of a relationship between blood-brain barrier impairment and neurodegeneration. PMID:19158425

  14. Climate dependency of tree growth suppressed by acid deposition effects on soils in Northwest Russia

    USGS Publications Warehouse

    Lawrence, G.B.; Lapenis, A.G.; Berggren, D.; Aparin, B.F.; Smith, K.T.; Shortle, W.C.; Bailey, S.W.; Varlyguin, D.L.; Babikov, B.

    2005-01-01

    Increased tree growth in temperate and boreal forests has been proposed as a direct consequence of a warming climate. Acid deposition effects on nutrient availability may influence the climate dependency of tree growth, however. This study presents an analysis of archived soil samples that has enabled changes in soil chemistry to be tracked with patterns of tree growth through the 20th century. Soil samples collected in 1926, 1964, and 2001, near St. Petersburg, Russia, showed that acid deposition was likely to have decreased root-available concentrations of Ca (an essential element) and increased root-available concentrations of Al (an inhibitor of Ca uptake). These soil changes coincided with decreased diameter growth and a suppression of climate-tree growth relationships in Norway spruce. Expected increases in tree growth from climate warming may be limited by decreased soil fertility in regions of northern and eastern Europe, and eastern North America, where Ca availability has been reduced by acidic deposition. ?? 2005 American Chemical Society.

  15. Characterisation of DLC films deposited using titanium isopropoxide (TIPOT) at different flow rates.

    PubMed

    Said, R; Ali, N; Ghumman, C A A; Teodoro, O M N D; Ahmed, W

    2009-07-01

    In recent years, there has been growing interest in the search for advanced biomaterials for biomedical applications, such as human implants and surgical cutting tools. It is known that both carbon and titanium exhibit good biocompatibility and have been used as implants in the human body. It is highly desirable to deposit biocompatible thin films onto a range of components in order to impart biocompatibility and to minimise wear in implants. Diamond like carbon (DLC) is a good candidate material for achieving biocompatibility and low wear rates. In this study, thin films of diamond-like-carbon DLC were deposited onto stainless steel (316) substrates using C2H2, argon and titanium isopropoxide (TIPOT) precursors. Argon was used to generate the plasma in the plasma enhanced vapour deposition (PECVD) system. A critical coating feature governing the performance of the component during service is film thickness. The as-grown films were in the thickness range 90-100 nm and were found to be dependent on TIPOT flow rate. Atomic force microscopy (AFM) was used to characterise the surface roughness of the samples. As the flow rate of TIPOT increased the average roughness was found to increase in conjunction with the film thickness. Raman spectroscopy was used to investigate the chemical structure of amorphous carbon matrix. Surface tension values were calculated using contact angle measurements. In general, the trend of the surface tension results exhibited an opposite trend to that of the contact angle. The elemental composition of the samples was characterised using a VG ToF SIMS (IX23LS) instrument and X-ray photoelectron spectroscopy (XPS). Surprisingly, SIMS and XPS results showed that the DLC samples did not show evidence of titanium since no peaks representing to titanium appeared on the SIMS/XPS spectra. PMID:19916446

  16. CHEMICAL AND BIOLOGICAL STATUS OF LAKES AND STREAMS IN THE UPPER MIDWEST: ASSESSMENT OF ACIDIC DEPOSITION EFFECTS

    EPA Science Inventory

    Many lakes in three areas in the Upper Midwest--northeastern Minnesota, northern Wisconsin, and the Upper Peninsula of Michigan--have low acid neutralizing capacity (ANC) and may be susceptible to change by acidic deposition. These acidic lakes are precipitation-dominated, clearw...

  17. Radionuclides in the terrestrial ecosystem near a Canadian uranium mill -- Part 3: Atmospheric deposition rates (pilot test)

    SciTech Connect

    Thomas, P.A.

    2000-06-01

    Atmospheric deposition rates of uranium series radionuclides were directly measured at three sites near the operating Key Lake uranium mill in northern Saskatchewan. Sites impacted by windblown tailings and mill dusts had elevated rates of uranium deposition near the mill and elevated {sup 226}Ra deposition near the tailings compared to a control site. Rainwater collectors, dust jars, and passive vinyl collectors previously used at the Ranger Mine in Australia were pilot-tested. Adhesive vinyl surfaces (1 m{sup 2}) were oriented horizontally, vertically, and facing the ground as a means of measuring gravitational settling, wind impaction, and soil resuspension, respectively. Although the adhesive glue on the vinyls proved difficult to digest, relative differences in deposition mode were found among radionuclides and among sites. Dry deposition was a more important transport mechanism for uranium, {sup 226}Ra, and {sup 210}Pb than rainfall, while more {sup 210}Po was deposited with rainfall.

  18. Increase of the deposition rate in reactive sputtering of metal oxides using a ceramic nitride target

    SciTech Connect

    Severin, D.; Wuttig, M.; Kappertz, O.; Nyberg, T.; Berg, S.; Pflug, A.

    2009-05-01

    We present a method to eliminate hysteresis effects and to increase the deposition rate for the reactive sputtering of metal oxides. This is achieved by using a ceramic nitride target in an argon-oxygen atmosphere. Although the use of a ceramic nitride target leads to pronounced changes of the processing characteristics, incorporation of nitrogen into the growing film is very small. These observations can be theoretically predicted using an extension of Berg's model [S. Berg and T. Nyberg, Thin Solid Films 476, 215 (2005)] to two different reactive gases and a compound target.

  19. Deposition rate and etching rate due to neutral radicals and dust particles measured using QCMs together with a dust eliminating filter

    NASA Astrophysics Data System (ADS)

    Katayama, Ryu; Koga, Kazunori; Yamashita, Daisuke; Kamataki, Kunihiro; Seo, Hyunwoong; Itagaki, Naho; Shiratani, Masaharu; Ashikawa, Naoko; Tokitani, Masayuki; Masuzaki, Suguru; Nishimura, Kiyohiko; Sagara, Akio; the LHD experimental Group Team

    2015-09-01

    We have developed an in-situ method for measuring deposition rate of radicals and dust particles using quartz crystal microbalances (QCMs) together with a dust eliminating filter. The QCMs have three channels of quartz crystals. Channel 1 was used to measure total deposition rate due to radicals and dust particles. Channel 2 was covered with a dust eliminating filter. Channel 3 was covered with a stainless-steel plate. Moreover, all QCMs are covered with a grounded stainless steel mesh for suppressing influx of charged particles. The measurements were conducted in the Large Helical Device in the National Institute for Fusion Science, Japan. Although the deposition measurements during the discharges were difficult, we obtained deposition rate and etching rate by comparing the data before and after each discharge. The frequency difference for channel 1 changes from 0.1 Hz (etching) to -0.5 Hz (deposition), while those for channels 2 and 3 are within a range of +/-0.1 Hz and +/-0.05 Hz, respectively. The QCM method gives information on deposition rate and etching rate due to neutral radicals and dust particles.

  20. Dual-chamber plasma deposition of A-Si:H solar cells at high rates using disilane

    SciTech Connect

    Rajeswaran, G.; Vanier, P.E.; Corderman, R.R.; Kampas, F.J.

    1985-01-01

    The use of a separated chamber deposition system for the fabrication of a-Si:H solar cells from disilane at high deposition rates results in a substantial improvement in short circuit current compared to that obtained from a single-chamber system. The spectral responses of cells fabricated in the dual-chamber mode are compared to those made in the single-chamber mode. The results are interpreted by assuming that the rate of removal of boron contaminants from the chamber is independent of deposition rate.

  1. Corrosion and runoff rates of Cu and three Cu-alloys in marine environments with increasing chloride deposition rate.

    PubMed

    Odnevall Wallinder, Inger; Zhang, Xian; Goidanich, Sara; Le Bozec, Nathalie; Herting, Gunilla; Leygraf, Christofer

    2014-02-15

    Bare copper sheet and three commercial Cu-based alloys, Cu15Zn, Cu4Sn and Cu5Al5Zn, have been exposed to four test sites in Brest, France, with strongly varying chloride deposition rates. The corrosion rates of all four materials decrease continuously with distance from the coast, i.e. with decreasing chloride load, and in the following order: Cu4Sn>Cu sheet>Cu15Zn>Cu5Al5Zn. The patina on all materials was composed of two main layers, Cu2O as the inner layer and Cu2(OH)3Cl as the outer layer, and with a discontinuous presence of CuCl in between. Additional minor patina constituents are SnO2 (Cu4Sn), Zn5(OH)6(CO3)2 (Cu15Zn and Cu5Al5Zn) and Zn6Al2(OH)16CO3·4H2O/Zn2Al(OH)6Cl·2H2O/Zn5Cl2(OH)8·H2O and Al2O3 (Cu5Al5Zn). The observed Zn- and Zn/Al-containing corrosion products might be important factors for the lower sensitivity of Cu15Zn and Cu5Al5Zn against chloride-induced atmospheric corrosion compared with Cu sheet and Cu4Sn. Decreasing corrosion rates with exposure time were observed for all materials and chloride loads and attributed to an improved adherence with time of the outer patina to the underlying inner oxide. Flaking of the outer patina layer was mainly observed on Cu4Sn and Cu sheet and associated with the gradual transformation of CuCl to Cu2(OH)3Cl of larger volume. After three years only Cu5Al5Zn remains lustrous because of a patina compared with the other materials that appeared brownish-reddish. Significantly lower release rates of metals compared with corresponding corrosion rates were observed for all materials. Very similar release rates of copper from all four materials were observed during the fifth year of marine exposure due to an outer surface patina that with time revealed similar constituents and solubility properties. PMID:24321319

  2. Extremely high rate deposition of polymer multilayer optical thin film materials

    SciTech Connect

    Affinito, J.D.

    1993-03-01

    This paper highlights a new technique for extremely high rate deposition of optical dielectric films (vacuum deposition of polymer multilayer thin films). This is a way to produce multilayer optical filters comprised of thousands of layers of either linear or nonlinear optical materials. The technique involves the flash evaporation of an acrylic monomer onto a moving substrate; the monomer is then cured. Acrylic polymers deposited to date are very clear for wavelengths between 0.35 and 2.5 {mu}m; they have extinction coefficients of k{approx}10{sup {minus}7}. Application of electric field during cross linking can polarize (``pole``) the film to greatly enhance the nonlinear optical properties. ``Poling`` films with the polymer multilayer technique offers advantages over conventional approaches, in that the polarization should not decay over time. Battelle`s Pacific Northwest Laboratory is well suited for bringing linear and nonlinear polymer multilayer optical filter technology to manufacturing production status for batch and wide area web applications. 10 figs.

  3. Extremely high rate deposition of polymer multilayer optical thin film materials

    SciTech Connect

    Affinito, J.D.

    1993-01-01

    This paper highlights a new technique for extremely high rate deposition of optical dielectric films (vacuum deposition of polymer multilayer thin films). This is a way to produce multilayer optical filters comprised of thousands of layers of either linear or nonlinear optical materials. The technique involves the flash evaporation of an acrylic monomer onto a moving substrate; the monomer is then cured. Acrylic polymers deposited to date are very clear for wavelengths between 0.35 and 2.5 [mu]m; they have extinction coefficients of k[approx]10[sup [minus]7]. Application of electric field during cross linking can polarize (''pole'') the film to greatly enhance the nonlinear optical properties. ''Poling'' films with the polymer multilayer technique offers advantages over conventional approaches, in that the polarization should not decay over time. Battelle's Pacific Northwest Laboratory is well suited for bringing linear and nonlinear polymer multilayer optical filter technology to manufacturing production status for batch and wide area web applications. 10 figs.

  4. A comprehensive study on different modelling approaches to predict platelet deposition rates in a perfusion chamber

    PubMed Central

    Pallarès, Jordi; Senan, Oriol; Guimerà, Roger; Vernet, Anton; Aguilar-Mogas, Antoni; Vilahur, Gemma; Badimon, Lina; Sales-Pardo, Marta; Cito, Salvatore

    2015-01-01

    Thrombus formation is a multiscale phenomenon triggered by platelet deposition over a protrombotic surface (eg. a ruptured atherosclerotic plaque). Despite the medical urgency for computational tools that aid in the early diagnosis of thrombotic events, the integration of computational models of thrombus formation at different scales requires a comprehensive understanding of the role and limitation of each modelling approach. We propose three different modelling approaches to predict platelet deposition. Specifically, we consider measurements of platelet deposition under blood flow conditions in a perfusion chamber for different time periods (3, 5, 10, 20 and 30 minutes) at shear rates of 212 s−1, 1390 s−1 and 1690 s−1. Our modelling approaches are: i) a model based on the mass-transfer boundary layer theory; ii) a machine-learning approach; and iii) a phenomenological model. The results indicate that the three approaches on average have median errors of 21%, 20.7% and 14.2%, respectively. Our study demonstrates the feasibility of using an empirical data set as a proxy for a real-patient scenario in which practitioners have accumulated data on a given number of patients and want to obtain a diagnosis for a new patient about whom they only have the current observation of a certain number of variables. PMID:26391513

  5. Comparisons of Solar Wind Coupling Parameters with Auroral Energy Deposition Rates

    NASA Technical Reports Server (NTRS)

    Elsen, R.; Brittnacher, M. J.; Fillingim, M. O.; Parks, G. K.; Germany G. A.; Spann, J. F., Jr.

    1997-01-01

    Measurement of the global rate of energy deposition in the ionosphere via auroral particle precipitation is one of the primary goals of the Polar UVI program and is an important component of the ISTP program. The instantaneous rate of energy deposition for the entire month of January 1997 has been calculated by applying models to the UVI images and is presented by Fillingim et al. In this session. A number of parameters that predict the rate of coupling of solar wind energy into the magnetosphere have been proposed in the last few decades. Some of these parameters, such as the epsilon parameter of Perrault and Akasofu, depend on the instantaneous values in the solar wind. Other parameters depend on the integrated values of solar wind parameters, especially IMF Bz, e.g. applied flux which predicts the net transfer of magnetic flux to the tail. While these parameters have often been used successfully with substorm studies, their validity in terms of global energy input has not yet been ascertained, largely because data such as that supplied by the ISTP program was lacking. We have calculated these and other energy coupling parameters for January 1997 using solar wind data provided by WIND and other solar wind monitors. The rates of energy input predicted by these parameters are compared to those measured through UVI data and correlations are sought. Whether these parameters are better at providing an instantaneous rate of energy input or an average input over some time period is addressed. We also study if either type of parameter may provide better correlations if a time delay is introduced; if so, this time delay may provide a characteristic time for energy transport in the coupled solar wind-magnetosphere-ionosphere system.

  6. Experimental investigation on the energy deposition and expansion rate under the electrical explosion of aluminum wire in vacuum

    SciTech Connect

    Shi, Zongqian; Wang, Kun; Shi, Yuanjie; Wu, Jian; Han, Ruoyu

    2015-12-28

    Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ∼2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ∼18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.

  7. Experimental investigation on the energy deposition and expansion rate under the electrical explosion of aluminum wire in vacuum

    NASA Astrophysics Data System (ADS)

    Shi, Zongqian; Wang, Kun; Shi, Yuanjie; Wu, Jian; Han, Ruoyu

    2015-12-01

    Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ˜2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ˜18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.

  8. Pulsed Helium Ion Beam Induced Deposition: A Means to High Growth Rates

    SciTech Connect

    Alkemade, Paul F. A.; Miro, Hozanna; Van Veldhoven, Emile; Maas, Diederick; Smith, Daryl; Rack, P. D.

    2011-01-01

    The sub-nanometer beam of a helium ion microscope was used to study and optimize helium-ion beam induced deposition of PtC nanopillars with the (CH{sub 3}){sub 3}Pt(CPCH{sub 3}) precursor. The beam current, beam dwell time, precursor refresh time, and beam focus have been independently varied. Continuous beam exposure resulted in narrow but short pillars, while pulsed exposure resulted in thinner and higher ones. Furthermore, at short dwell times the deposition efficiency was very high, especially for a defocused beam. Efficiencies were measured up to 20 times the value for continuous exposure conditions. The interpretation of the experimental data was aided by a Monte Carlo simulation of the deposition. The results indicate that two regimes are operational in ion beam induced deposition (IBID). In the first one, the adsorbed precursor molecules originally present in the beam interaction region decompose. After the original precursor layer is consumed, further depletion is averted and growth continues by the supply of molecules via adsorption and surface diffusion. Depletion around the beam impact site can be distinguished from depletion on the flanges of the growing pillars. The Monte Carlo simulations for low precursor surface coverage reproduce measured growth rates, but predict considerably narrower pillars, especially at short dwell times. Both the experiments and the simulations show that the pillar width rapidly increases with increasing beam diameter. Optimal writing strategy, good beam focusing, and rapid beam positioning are needed for efficient and precise fabrication of extended and complex nanostructures by He-IBID.

  9. Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains

    USGS Publications Warehouse

    Nanus, L.; Williams, M.W.; Campbell, D.H.; Tonnessen, K.A.; Blett, T.; Clow, D.W.

    2009-01-01

    The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration 3000 m, with 80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.

  10. A Longitudinal Evaluation of the Rate of Flow of Freshman Applications and Freshman Tuition Deposits. SAIR Conference Paper.

    ERIC Educational Resources Information Center

    Yost, Michael

    Freshmen recruitment and admissions trends at Trinity University, a small, independent Texas university, are described. Attention is directed to the weekly rates at which freshman applications and tuition deposits were received over a 4-year time period. The patterns of the receipt of applications and deposits were consistent across years. The…

  11. Dry atmospheric deposition rates of metals along a coastal transect in southern California

    NASA Astrophysics Data System (ADS)

    Sabin, Lisa D.; Schiff, Kenneth C.

    While recent studies indicate atmospheric deposition is a significant source of metals to the Santa Monica Bay and coastal river systems of the Los Angeles area, the spatial extent of the atmospheric source along the entire southern California coast has not been measured in 30 years. This study provides measurements of dry atmospheric deposition of chromium, copper, lead, nickel and zinc at eight sites located along the coast between Santa Barbara and San Diego, and compares these data to historic measurements from the 1970s. Median dry deposition fluxes across sites ranged between 0.23 and 3.6 (chromium), 0.21 and 5.4 (nickel), 0.52 and 14 (lead), 0.89 and 29 (copper), and 4.8 and 160 (zinc) μg m -2 day -1. Differences in metal dry deposition rates observed between sites were dominated by proximity to urban areas and/or other nearby sources, with the highest metal fluxes observed near the Los Angeles Harbor (LAH) and San Diego Bay (SDB) sites. Compared with data from the 1970s, lead fluxes were typically one to two orders of magnitude lower in the present study (2006), indicating atmospheric sources of this metal have decreased over the past three decades in southern California. Chromium fluxes were also lower in 2006 compared with the 1970s, although to a lesser extent than for lead. In contrast, copper and zinc fluxes were typically within the same order of magnitude between the two time periods, with some higher measurements observed in 2006 compared with the 1970s at the LAH and SDB sites. This result indicates atmospheric sources of copper and zinc have not decreased over the past three decades in southern California, and have increased near our harbor/urban sites. Differences in sampling conditions (e.g., Santa Ana winds) and measurement techniques may also explain, in part, the differences observed in metal flux rates for these time periods. However, these limitations were most important for those metals with the smallest difference in flux rates measured

  12. Effects of themokarst on sediment deposition rates in two arctic headwater streams

    NASA Astrophysics Data System (ADS)

    Kampman, J.; Flinn, M. B.

    2010-12-01

    Recent research has revealed increased permafrost degradation and incidences of thermokarst features as products of a changing arctic climate. These features have important implications for aquatic ecosystems across the landscape, as increased frequencies of such features are expected to increase sediment load into affected streams. We examined two headwater streams impacted by thermokarst failures near Toolik Lake Field Station in Northern Alaska, USA. Samples were collected using 3” diameter PVC traps nested in the substrate which were then partitioned into four individual size classes (2mm, 1mm, >250um and <250um) and normalized for period of deployment. Each individual size fraction was collected within a reference and impacted reach at each site, dried for a 24hr period to quantify dry mass, then ashed in a muffle furnace to quantify ash-free dry mass. Rates of sedimentation were quantified as grams*m-2*d-1. Data collected in summer 2010 revealed a significant input of total sediment deposited in areas impacted by thermokarst failures relative to reference reaches which were unaffected. We observed a near doubling of total sedimentation rates in the impacted reaches compared to our reference reaches (p<0.01). There was a significant increase in the amount of organic matter delivered to the impacted sites (p<0.01). However, this increase contributes to only a small fraction (~10-15%) of the total composition of sediment delivered to impacted reaches. Inorganic deposits were insignificant within affected reaches, which we attribute to large variability within each trap, as a possible consequence of varying geomorphology between each study stream. The largest inputs of organic matter were deposited in the form of VFPOM (<250um), while inorganic deposits were variable across all class sizes. The results from our study indicate thermokarst failures have a significant impact on sedimentation rates in headwater streams. We predict this may have various ecological

  13. Versatile high rate plasma deposition and processing with very high frequency excitation

    SciTech Connect

    Heintze, M.

    1997-07-01

    The interest in plasma deposition using very high frequency (VHF) excitation arose after the preparation of a-Si:H at high growth rates was demonstrated. Subsequently the improved process flexibility and the control of material properties offered by the variation of the plasma excitation frequency was recognized. The preparation of amorphous and microcrystalline thin films in a VHF-plasma is described. The increased growth rates have been attributed to an enhancement of film precursor formation at VHF, to the decreased sheath thickness as well as to an enhancement of the surface reactivity by positive ions. Plasma diagnostic investigations show that the parameters mainly affected by the excitation frequency are the ion flux to the electrodes as well as the sheaths potentials and widths, rather than the plasma density. 55 refs., 13 figs.

  14. Chemical and biological recovery from acid deposition within the Honnedaga Lake watershed, New York, USA.

    PubMed

    Josephson, Daniel C; Robinson, Jason M; Chiotti, Justin; Jirka, Kurt J; Kraft, Clifford E

    2014-07-01

    Honnedaga Lake in the Adirondack region of New York has sustained a heritage brook trout population despite decades of atmospheric acid deposition. Detrimental impacts from acid deposition were observed from 1920 to 1960 with the sequential loss of acid-sensitive fishes, leaving only brook trout extant in the lake. Open-lake trap net catches of brook trout declined for two decades into the late 1970s, when brook trout were considered extirpated from the lake but persisted in tributary refuges. Amendments to the Clean Air Act in 1990 mandated reductions in sulfate and nitrogen oxide emissions. By 2000, brook trout had re-colonized the lake coincident with reductions in surface-water sulfate, nitrate, and inorganic monomeric aluminum. No changes have been observed in surface-water acid-neutralizing capacity (ANC) or calcium concentration. Observed increases in chlorophyll a and decreases in water clarity reflect an increase in phytoplankton abundance. The zooplankton community exhibits low species richness, with a scarcity of acid-sensitive Daphnia and dominance by acid-tolerant copepods. Trap net surveys indicate that relative abundance of adult brook trout population has significantly increased since the 1970s. Brook trout are absent in 65 % of tributaries that are chronically acidified with ANC of <0 μeq/L and toxic aluminum levels (>2 μmol/L). Given the current conditions, a slow recovery of chemistry and biota is expected in Honnedaga Lake and its tributaries. We are exploring the potential to accelerate the recovery of brook trout abundance in Honnedaga Lake through lime applications to chronically and episodically acidified tributaries. PMID:24671614

  15. Development of a state-of-the-art acid-deposition model for the South Coast Air Basin of California. Final report

    SciTech Connect

    Pandis, S.N.; Seinfeld, J.H.

    1989-03-25

    Three different aqueous-phase modules have been developed to describe the physicochemical processes associated with the aqueous-phase in the atmosphere. These modules constitute the central core of an urban-scale acid deposition model and can be incorporated into an Eulerian three dimensional grid-based system. The fog model (Module 2) has been implemented in a trajectory framework and has been employed to predict the temperature profile, fog development, liquid water content, gas and aqueous phase concentrations of pollutants, and wet deposition rates of main ionic species during the radiation fog episode in Bakersfield in the San Joaquin Valley of California over the period January 4-5, 1985.

  16. Low Phytic Acid Barley Responses to Phosphorus Rates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Low phytic acid (LPA) barley (Hordeum vulgare L.) cultivars partition phosphorus in seed tissue differently than conventional barley cultivars through a reduction in seed phytic acid (myo-inositol-1,2,3,4,5,6-hexkisphosphate) coupled with an increase in inorganic phosphorus. The response of the LPA...

  17. Interactions of aluminum with forest soils and vegetation: Implications for acid deposition

    SciTech Connect

    Maynard, A.A.

    1989-01-01

    Recent evidence suggests that an important ecological consequence of acidic deposition is increased aluminum mobilization. There is concern that increased aluminum activity may produce toxic effects in forested ecosystems. My studies were concerned with the behavior of pedogenic and added aluminum in soils derived from chemically different parent material. Soil aluminum was related to the aluminum content of the vegetation found growing in the soils. In addition, aluminum levels of forest litter was compared to levels determined 40 years ago. Field, greenhouse, and laboratory investigations were conducted in which the effects of aluminum concentration on germination and early growth was determined. Soils were then used in greenhouse and laboratory studies to establish patterns of soil and plant aluminum behavior with implications to acid deposition. Results show that the amount of aluminum extracted was related to the pH value of the extracting solution and to the chemical characteristics of the soil. Some acid rain solutions extracted measurable amounts of aluminum from selected primary minerals. Germination and early growth of Pinus radiata was controlled by levels of aluminum in the soil or in solution. Field studies indicated that most forest species were sensitive to rising levels of aluminum in the soil. In general, ferns and fern allies were less sensitive to very high levels of aluminum in the soil, continuing to grow when more advanced dicots have disappeared. Aluminum tissue levels of all species were related to the concentration of aluminum in the soil as was the reappearance of species. Aluminum levels in leaf litter have risen at least 50% in the last 40 years. These values were consistent over 3 years. The implications to acid deposition were discussed.

  18. Age determinations and growth rates of Pacific ferromanganese deposits using strontium isotopes

    USGS Publications Warehouse

    Ingram, B.L.; Hein, J.R.; Farmer, G.L.

    1990-01-01

    87Sr 86Sr ratios, trace element and REE compositions, and textural characteristics were determined for three hydrogenetic Fe-Mn crusts, one hydrothermal deposit, and two mixed hydrothermalhydrogenetic crusts from the Pacific. The Sr isotope data are compared to the Sr seawater curve for the Cenozoic to determine the ages and growth rates of the crusts. The 87Sr 86Sr in the crusts does not increase monotonically with depth as expected if the Sr were solely derived from seawater and perfectly preserved since deposition. This indicates post-depositional exchange of Sr or heterogeneous sources for the Sr originally contained in the crusts. Textures of hydrogenetic crusts generally correlate with Sr isotopic variations. The highest porosity intervals commonly exhibit the highest 87Sr 86Sr ratios, indicating exchange with younger seawater. Intervals with the lowest porosity commonly have lower 87Sr 86Sr and may preserve the original Sr isotopic ratios. Minimum ages of crust growth inception were calculated from dense, low porosity intervals. Growth of the hydrogenetic crusts began at or after 23 Ma, although their substrates are Cretaceous. Estimated average growth rates of the three hydrogenetic crusts vary between 0.9 and 2.7 mm/Ma, consistent with published rates determined by other techniques. Within the Marshall Islands crust, growth rates for individual layers varied greatly between 1.0 and 5.4 mm/Ma. For one crust, very low 87Sr 86Sr ratios occurred in detrital-rich intervals. Hydrothermal Fe-Mn oxide from the active Lau Basin back-arc spreading axis (Valu Fa Ridge) has an 87Sr 86Sr ratio with a predominantly seawater signature ( 87Sr 86Sr 0.709196), indicating a maximum age of 0.9 Ma. One crust from an off-axis seamount west of Gorda Ridge may have begun precipitating hydrogenetically at 0.5 Ma (0.709211), and had increasing hydrothermal or volcanic input in the top half of the crust, indicated by a significantly lower 87Sr 86Sr ratio (0.709052). ?? 1990.

  19. Ages and Accumulation Rates of the Martian Polar Layered Deposits Estimated from Orbital Tuning

    NASA Astrophysics Data System (ADS)

    Sori, M.; Bailey, E. A.; Perron, J.; Huybers, P. J.; Aharonson, O.; Limaye, A.

    2013-12-01

    Layers of dusty water ice in the polar caps of Mars have been hypothesized to record climate changes driven by variation of the planet's orbit and spin axis, but the time interval over which the polar layered deposits (PLDs) formed is unknown, and an orbital influence has not been conclusively demonstrated. We performed orbital tuning of reconstructed PLD stratigraphic sequences in an attempt to constrain the accumulation interval and test for the presence of an orbital signal. Our procedure uses dynamic time warping (DTW) to search for a match between two time series - the polar insolation history and brightness or topographic information in the PLDs - and then assesses the significance of potential matches using a Monte Carlo procedure. We selected 30 images of the northern PLDs from the Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor spacecraft and used Mars Orbiter Laser Altimeter profiles to transform each image into a record of image brightness as a function of vertical depth. To constrain the PLD age and accumulation rate, we tuned each image record to Martian insolation records for varying time intervals. If a particular insolation interval produced the strongest match to an image, and if the match became weaker as the image was tuned to progressively longer or shorter intervals, we chose the best-fitting interval as an estimated accumulation time for that PLD sequence, and used the depth range to estimate a corresponding PLD accumulation rate. We also tuned the insolation records to synthetic records containing no orbital influence to test whether the image matches were spurious. Of the 30 MOC images analyzed, 16 produce insolation intervals that we consider strong matches. These images yield an average deposition rate of 0.5 × 0.2 mm/yr for the northern PLDs. The images represent only a fraction of the entire stratigraphy; extrapolating that deposition rate farther back in time yields an age of ~4 Ma for the entire PLD sequence present in the

  20. An Investigation of Solid-State Amidization and Imidization Reactions in Vapor Deposited Poly (amic acid)

    SciTech Connect

    Anthamatten, M; Letts, S A; Day, K; Cook, R C; Gies, A P; Hamilton, T P; Nonidez, W K

    2004-06-28

    The condensation polymerization reaction of 4,4'-oxydianiline (ODA) with pyromellitic dianhydride (PMDA) to form poly(amic acid) and the subsequent imidization reaction to form polyimide were investigated for films prepared using vapor deposition polymerization techniques. Fourier-transform infrared spectroscopy (FT-IR), thermal analysis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of films at different temperatures indicate that additional solid-state polymerization occurs prior to imidization reactions. Experiments reveal that, upon vapor deposition, poly(amic acid) oligomers form that have a number-average molecular weight of about 1500 Daltons. Between 100 - 130 C these chains undergo additional condensation reaction to form slightly higher molecular weight oligomers. Calorimetry measurements show that this reaction is exothermic ({Delta}H {approx} -30 J/g) with an activation energy of about 120 kJ/mol. Experimental reaction enthalpies are compared to results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150 - 300 C) imidization of amide linkages occurs as an endothermic reaction ({Delta}H {approx} +120 J/g) with an activation energy of about 130 kJ/mol. Solid-state kinetics were found to depend on reaction conversion as well as the processing conditions used to deposit films.

  1. Numerical study on the deposition rate of hematite particle on polypropylene walls: role of surface roughness.

    PubMed

    Henry, Christophe; Minier, Jean-Pierre; Lefèvre, Grégory; Hurisse, Olivier

    2011-04-19

    test case. These new numerical results show that nonzero deposition rates are now obtained even in repulsive conditions, which confirms that surface roughness is a relevant aspect to introduce in general approaches to deposition. PMID:21405065

  2. Solar Energy Deposition Rates in the Mesosphere Derived from Airglow Measurements: Implications for the Ozone Model Deficit Problem

    NASA Technical Reports Server (NTRS)

    Mlynczak, Martin G.; Garcia, Rolando R.; Roble, Raymond G.; Hagan, Maura

    2000-01-01

    We derive rates of energy deposition in the mesosphere due to the absorption of solar ultraviolet radiation by ozone. The rates are derived directly from measurements of the 1.27-microns oxygen dayglow emission, independent of knowledge of the ozone abundance, the ozone absorption cross sections, and the ultraviolet solar irradiance in the ozone Hartley band. Fifty-six months of airglow data taken between 1982 and 1986 by the near-infrared spectrometer on the Solar-Mesosphere Explorer satellite are analyzed. The energy deposition rates exhibit altitude-dependent annual and semi-annual variations. We also find a positive correlation between temperatures and energy deposition rates near 90 km at low latitudes. This correlation is largely due to the semiannual oscillation in temperature and ozone and is consistent with model calculations. There is also a suggestion of possible tidal enhancement of this correlation based on recent theoretical and observational analyses. The airglow-derived rates of energy deposition are then compared with those computed by multidimensional numerical models. The observed and modeled deposition rates typically agree to within 20%. This agreement in energy deposition rates implies the same agreement exists between measured and modeled ozone volume mixing ratios in the mesosphere. Only in the upper mesosphere at midlatitudes during winter do we derive energy deposition rates (and hence ozone mixing ratios) consistently and significantly larger than the model calculations. This result is contrary to previous studies that have shown a large model deficit in the ozone abundance throughout the mesosphere. The climatology of solar energy deposition and heating presented in this paper is available to the community at the Middle Atmosphere Energy Budget Project web site at http://heat-budget.gats-inc.com.

  3. Solar energy deposition rates in the mesosphere derived from airglow measurements: Implications for the ozone model deficit problem

    NASA Astrophysics Data System (ADS)

    Mlynczak, Martin G.; Garcia, Rolando R.; Roble, Raymond G.; Hagan, Maura

    2000-07-01

    We derive rates of energy deposition in the mesosphere due to the absorption of solar ultraviolet radiation by ozone. The rates are derived directly from measurements of the 1.27-μm oxygen dayglow emission, independent of knowledge of the ozone abundance, the ozone absorption cross sections, and the ultraviolet solar irradiance in the ozone Hartley band. Fifty-six months of airglow data taken between 1982 and 1986 by the near-infrared spectrometer on the Solar-Mesosphere Explorer satellite are analyzed. The energy deposition rates exhibit altitude-dependent annual and semi-annual variations. We also find a positive correlation between temperatures and energy deposition rates near 90 km at low latitudes. This correlation is largely due to the semiannual oscillation in temperature and ozone and is consistent with model calculations. There is also a suggestion of possible tidal enhancement of this correlation based on recent theoretical and observational analyses. The airglow-derived rates of energy deposition are then compared with those computed by multidimensional numerical models. The observed and modeled deposition rates typically agree to within 20%. This agreement in energy deposition rates implies the same agreement exists between measured and modeled ozone volume mixing ratios in the mesosphere. Only in the upper mesosphere at midlatitudes during winter do we derive energy deposition rates (and hence ozone mixing ratios) consistently and significantly larger than the model calculations. This result is contrary to previous studies that have shown a large model deficit in the ozone abundance throughout the mesosphere. The climatology of solar energy deposition and heating presented in this paper is available to the community at the Middle Atmosphere Energy Budget Project web site at http://heat.budget.gats.inc.com.

  4. ACIDIC DEPOSITION AND THE CORROSION AND DETERIORATION OF MATERIALS IN THE ATMOSPHERE: A BIBLIOGRAPHY, 1880-1982

    EPA Science Inventory

    The bibliography contains more than 1300 article citations and abstracts on the effects of acidic deposition, air pollutants, and biological and meteorological factors on the corrosion and deterioration of materials in the atmosphere. The listing includes citations for the years ...

  5. Chemical recovery of surface waters across the Northeastern United States from reduced inputs of acidic deposition: 1984-2001

    SciTech Connect

    Richard A.F. Warby; Chris E. Johnson; Charles T. Driscoll

    2005-09-01

    Changes in lake water chemistry between 1984 and 2001 at 130 stratified random sites across the northeastern United States were studied to evaluate the population-level effects of decreases in acidic deposition. Surface-water SO{sub 4}{sup 2-} concentrations decreased across the region at a median rate of -1.53 {mu}equiv L{sup -1} year{sup -1}. Calcium concentrations also decreased, with a median rate of -1.73 {mu}equiv L{sup -1} year{sup -1}. This decrease in Ca{sub 2+} retarded the recovery of surface water acid neutralizing capacity (Gran ANC), which increased at a median rate of 0.66 {mu}equiv L{sup -1} year{sup -1}. There were small increases in pH in all subregions except central New England and Maine, where the changes were not statistically significant. Median NO{sub 3}{sup -} trends were not significant except in the Adirondacks, where NO{sub 3}{sup -} concentrations increased at a rate of 0.53 equiv L{sup -1} year{sup -1}. A regionwide decrease in the concentration of total Al, especially in ponds with low ANC values (ANC {lt} 25 {mu}equiv L{sup -1}), was observed in the Adirondack subregion. These changes in Al were consistent with the general pattern of increasing pH and ANC. Despite the general pattern of chemical recovery, many ponds remain chronically acidic or are susceptible to episodic acidification. The continued chemical and biological recovery at sites in the northeastern United States will depend on further controls on S and N emissions. 27 refs., 4 figs., 3 tabs.

  6. Reaction rates, depositional history and sources of indium in sediments from Appalachian and Canadian Shield lakes

    NASA Astrophysics Data System (ADS)

    Tessier, André; Gobeil, Charles; Laforte, Lucie

    2014-07-01

    Sediment cores were collected at the deepest site of twelve headwater lakes from the Province of Québec, Canada that receive contaminants only from atmospheric deposition, either directly to the lake surface or indirectly from the watershed. Several of the lakes are located within relatively short distance (<40 km) and others at more than 200 km from potential sources of contamination. The sediments were dated and analyzed for In and other elements including Fe, Mn, Al and organic C. Fe-rich authigenic material was collected on Teflon sheets inserted vertically into the sediments at the only study site whose hypolimnion remains perennially oxic. Porewater samples collected at the coring site of four of the lakes were also analyzed for In and other solutes including sulfide, sulfate, Fe, Mn, inorganic and organic C and major ions. The porewater In profiles display concentration gradients at or below the sediment-water interface. Modeling these profiles with a one-dimensional transport-reaction equation assuming steady state allows definition of depth intervals (zones) where In is either released to or removed from porewater and quantification of net In reactions rates in each zone. The position of the In consumption zones, the shape of the vertical profiles of dissolved In, sulfide and iron, as well as thermodynamic calculations of saturation states collectively suggest that In(OH)3(s) and In2S3(s) do not precipitate in the sediments and that adsorption of In onto sedimentary FeS(s) does not occur. However, similarities in the In and Fe porewater profiles, and the presence of In in the authigenic Fe-rich solids, reveal that part of the In becomes associated with authigenic Fe oxyhydroxides in the perennially oxic lake and is coupled to the Fe redox cycling. Comparison of the In/Corg and In/Fe molar ratios in the authigenic Fe-rich material and in surface sediments (0-0.5 cm) of this lake suggests that most non-lithogenic In was bound to humic substances. From the

  7. High rate reactive magnetron sputter deposition of Al-doped ZnO with unipolar pulsing and impedance control system

    SciTech Connect

    Nishi, Yasutaka; Hirohata, Kento; Tsukamoto, Naoki; Sato, Yasushi; Oka, Nobuto; Shigesato, Yuzo

    2010-07-15

    Al-doped ZnO (AZO) films were deposited on quartz glass substrates, unheated and heated to 200 deg. C, using reactive sputtering with a special feedback system of discharge impedance combined with midfrequency pulsing. A planar Zn-Al alloy target was connected to the switching unit, which was operated in a unipolar pulse mode. The oxidation of the target surface was precisely controlled by a feedback system for the entire O{sub 2} flow ratio including ''the transition region''. The deposition rate was about 10-20 times higher than that for films deposited by conventional sputtering using an oxide target. A deposition rate of AZO films of 390 nm/min with a resistivity of 3.8x10{sup -4} {Omega} cm and a transmittance in the visible region of 85% was obtained when the films were deposited on glass substrates heated to 200 deg. C with a discharge power of 4 kW.

  8. Declining acidic deposition begins reversal of forest-soil acidification in the northeastern U.S. and eastern Canada

    USGS Publications Warehouse

    Lawrence, Gregory B.; Hazlett, Paul W.; Fernandez, Ivan J.; Ouimet, Rock; Bailey, Scott W.; Shortle, Walter C.; Smith, Kevin T.; Antidormi, Michael

    2015-01-01

    Decreasing trends in acidic deposition levels over the past several decades have led to partial chemical recovery of surface waters. However, depletion of soil Ca from acidic deposition has slowed surface water recovery and led to the impairment of both aquatic and terrestrial ecosystems. Nevertheless, documentation of acidic deposition effects on soils has been limited, and little is known regarding soil responses to ongoing acidic deposition decreases. In this study, resampling of soils in eastern Canada and the northeastern U.S. was done at 27 sites exposed to reductions in wet SO42– deposition of 5.7–76%, over intervals of 8–24 y. Decreases of exchangeable Al in the O horizon and increases in pH in the O and B horizons were seen at most sites. Among all sites, reductions in SO42– deposition were positively correlated with ratios (final sampling/initial sampling) of base saturation (P < 0.01) and negatively correlated with exchangeable Al ratios (P < 0.05) in the O horizon. However, base saturation in the B horizon decreased at one-third of the sites, with no increases. These results are unique in showing that the effects of acidic deposition on North American soils have begun to reverse.

  9. Declining Acidic Deposition Begins Reversal of Forest-Soil Acidification in the Northeastern U.S. and Eastern Canada.

    PubMed

    Lawrence, Gregory B; Hazlett, Paul W; Fernandez, Ivan J; Ouimet, Rock; Bailey, Scott W; Shortle, Walter C; Smith, Kevin T; Antidormi, Michael R

    2015-11-17

    Decreasing trends in acidic deposition levels over the past several decades have led to partial chemical recovery of surface waters. However, depletion of soil Ca from acidic deposition has slowed surface water recovery and led to the impairment of both aquatic and terrestrial ecosystems. Nevertheless, documentation of acidic deposition effects on soils has been limited, and little is known regarding soil responses to ongoing acidic deposition decreases. In this study, resampling of soils in eastern Canada and the northeastern U.S. was done at 27 sites exposed to reductions in wet SO4(2-) deposition of 5.7-76%, over intervals of 8-24 y. Decreases of exchangeable Al in the O horizon and increases in pH in the O and B horizons were seen at most sites. Among all sites, reductions in SO4(2-) deposition were positively correlated with ratios (final sampling/initial sampling) of base saturation (P < 0.01) and negatively correlated with exchangeable Al ratios (P < 0.05) in the O horizon. However, base saturation in the B horizon decreased at one-third of the sites, with no increases. These results are unique in showing that the effects of acidic deposition on North American soils have begun to reverse. PMID:26495963

  10. Implications of a gradient in acid and ion deposition across the northern Great Lakes states

    SciTech Connect

    Glass, G.E.; Loucks, O.L.

    1986-01-01

    Average precipitation pH, 1979-1982, declines from west to east from 5.3 to 4.3 along a cross section of sites in Minnesota, Wisconsin, and Michigan. This answers questions about the seasonal and geographic pattern of anthropogenic acid precursor emissions and reaction products (SO/sub 4//sup 2 -/, NO/sub 3//sup -/, H/sup +/, NH/sub 2//sup +/) that increase from west to east. Except for higher concentrations of Ca/sup 2 +/ and Mg/sup 2 +/ observed at one site in the cultivated areas of southwestern Minnesota, the contribution of soil-related metal cations to the total ions in solution is small (17%) and relatively uniform across the region. Significant seasonal and geographic patterns in precipitation chemistry and deposition values are observed. Close correspondence of the sums of strong acid anions with the sums of hydrogen and ammonium ions in precipitation is observed, indicating anthropogenic sources of sulfur and nitrogen oxides. Present atmospheric inputs show close chemical correspondence when precipitation chemistry values are compared to the resulting ionic composition of weakly buffered lakes in north central Wisconsin and northern Michigan. The wet deposition of total acidity in the middle and eastern part of the region is comparable to that of impacted sites in the Adirondacks and in regions of Scandinavia. 39 references, 3 figures, 6 tables.

  11. Lacustrine responses to decreasing wet mercury deposition rates: results from a case study in northern Minnesota

    USGS Publications Warehouse

    Brigham, Mark E.; Sandheinrich, Mark B.; Gay, David A.; Maki, Ryan P.; Krabbenhoft, David P.; Wiener, James G.

    2014-01-01

    We present a case study comparing metrics of methylmercury (MeHg) contamination for four undeveloped lakes in Voyageurs National Park to wet atmospheric deposition of mercury (Hg), sulfate (SO4–2), and hydrogen ion (H+) in northern Minnesota. Annual wet Hg, SO4–2, and H+ deposition rates at two nearby precipitation monitoring sites indicate considerable decreases from 1998 to 2012 (mean decreases of 32, 48, and 66%, respectively). Consistent with decreases in the atmospheric pollutants, epilimnetic aqueous methylmercury (MeHgaq) and mercury in small yellow perch (Hgfish) decreased in two of four lakes (mean decreases of 46.5% and 34.5%, respectively, between 2001 and 2012). Counter to decreases in the atmospheric pollutants, MeHgaq increased by 85% in a third lake, whereas Hgfish increased by 80%. The fourth lake had two disturbances in its watershed during the study period (forest fire; changes in shoreline inundation due to beaver activity); this lake lacked overall trends in MeHgaq and Hgfish. The diverging responses among the study lakes exemplify the complexity of ecosystem responses to decreased loads of atmospheric pollutants.

  12. Acidic deposition, cation mobilization, and biochemical indicators of stress in healthy red spruce

    USGS Publications Warehouse

    Shortle, W.C.; Smith, K.T.; Minocha, R.; Lawrence, G.B.; David, M.B.

    1997-01-01

    Dendrochemical and biochemical markers link stress in apparently healthy red spruce trees (Picea rubens) to acidic deposition. Acidic deposition to spruce forests of the northeastern USA increased sharply during the 1960s. Previous reports related visible damage of trees at high elevations to root and soil processes. In this report, dendrochemical and foliar biochemical markers indicate perturbations in biological processes in healthy red spruce trees across the northeastern USA. Previous research on the dendrochemistry of red spruce stemwood indicated that under uniform environmental conditions, stemwood concentrations of Ca and Mg decreased with increasing radial distance from the pith. For nine forest locations, frequency analysis shows that 28 and 52% of samples of red spruce stemwood formed in the 1960s are enriched in Ca and Mg, respectively, relative to wood formed prior to and after the 1960s. This enrichment in trees throughout the northeastern USA may be interpretable as a signal of increased availability of essential cations in forest soils. Such a temporary increase in the availability of Ca and Mg could be caused by cation mobilization, a consequence of increased acidic deposition. During cation mobilization, essential Ca and Mg as well as potentially harmful Al become more available for interaction with binding sites in the soil and absorbing roots. As conditions which favor cation mobilization continue, Ca and Mg can be leached or displaced from the soil. A measure of the interaction between Ca and Al is the Al/Ca binding ratio (molar charge ratio of exchangeable Al to exchangeable Ca). As the Al/Ca binding ratio in the root zone increased from 0.3 to 1.9, the foliar concentration of the biochemical stress marker putrescine also increased from 45 to 145 nm g-1. The correlation of the putrescine concentration to the Al/Ca binding ratio (adj. r2 = 0.68, P < 0.027) suggests that foliar stress may be linked to soil chemistry.

  13. HCl in rocket exhaust clouds - Atmospheric dispersion, acid aerosol characteristics, and acid rain deposition

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Sebacher, D. I.; Bendura, R. J.; Wornom, D. E.

    1983-01-01

    Both measurements and model calculations of the temporal dispersion of peak HCl (g + aq) concentration in Titan III exhaust clouds are found to be well characterized by one-term power-law decay expressions. The respective coefficients and decay exponents, however, are found to vary widely with meteorology. The HCl (g), HCl (g + aq), dewpoint, and temperature-pressure-altitude data for Titan III exhaust clouds are consistent with accurately calculated HCl/H2O vapor-liquid compositions for a model quasi-equilibrated flat surface aqueous aerosol. Some cloud evolution characteristics are also defined. Rapid and extensive condensation of aqueous acid clearly occurs during the first three min of cloud rise. Condensation is found to be intensified by the initial entrainment of relatively moist ambient air from lower levels, that is, from levels below eventual cloud stabilization. It is pointed out that if subsequent dilution air at stabilization altitude is significantly drier, a state of maximum condensation soon occurs, followed by an aerosol evaporation phase.

  14. Evolution of radioactive dose rates in fresh sediment deposits along coastal rivers draining Fukushima contamination plume

    PubMed Central

    Evrard, Olivier; Chartin, Caroline; Onda, Yuichi; Patin, Jeremy; Lepage, Hugo; Lefèvre, Irène; Ayrault, Sophie; Ottlé, Catherine; Bonté, Philippe

    2013-01-01

    Measurement of radioactive dose rates in fine sediment that has recently deposited on channel bed-sand provides a solution to address the lack of continuous river monitoring in Fukushima Prefecture after Fukushima Dai-ichi nuclear power plant (FDNPP) accident. We show that coastal rivers of Eastern Fukushima Prefecture were rapidly supplied with sediment contaminated by radionuclides originating from inland mountain ranges, and that this contaminated material was partly exported by typhoons to the coastal plains as soon as by November 2011. This export was amplified during snowmelt and typhoons in 2012. In 2013, contamination levels measured in sediment found in the upper parts of the catchments were almost systematically lower than the ones measured in nearby soils, whereas their contamination was higher in the coastal plains. We thereby suggest that storage of contaminated sediment in reservoirs and in coastal sections of the river channels now represents the most crucial issue. PMID:24165695

  15. Auroral energy deposition rate, characteristic electron energy, and ionospheric parameters derived from Dynamics Explorer 1 images

    NASA Technical Reports Server (NTRS)

    Rees, M. H.; Lummerzheim, D.; Roble, R. G.; Winningham, J. D.; Craven, J. D.

    1988-01-01

    Auroral images obtained by the Spin Scan Auroral Imager (SAI) aboard the DE-1 satellite were used to derive auroral energy deposition rate, characteristic electron energy, and ionospheric parameters. The principles involved in the imaging technique and the physical mechanisms that underlie the relationship between the spectral images and the geophysical parameters are discussed together with the methodology for implementing such analyses. It is shown that images obtained with the SAI provide global parameters at 12-min temporal resolution; the spatial resolution is limited by the field of view of a pixel. The analysis of the 12-min images presented yielded a representation of ionospheric parameters that was better than can be obtained using empirical models based on local measurements averaged over long periods of time.

  16. On the Strain Rate Sensitivity of Abs and Abs Plus Fused Deposition Modeling Parts

    NASA Astrophysics Data System (ADS)

    Vairis, A.; Petousis, M.; Vidakis, N.; Savvakis, K.

    2016-06-01

    In this work the effect of strain rate on the tensile strength of fused deposition modeling parts built with Acrylonitrile-butadiene-styrene (ABS) and ABS plus material is presented. ASTM D638-02a specimens were built with ABS and ABS plus and they were tested on a Schenck Trebel Co. tensile test machine at three different test speeds, equal, lower, and higher to the test speed required by the ASTM D638-02a standard. The experimental tensile strength results were compared and evaluated. The fracture surfaces of selected specimens were examined with a scanning electron microscope, to determine failure mode of the filament strands. It was found that, as the test speed increases, specimens develop higher tensile strength and have higher elastic modulus. Specimens tested in the highest speed of the experiment had on average about 10% higher elastic modulus and developed on average about 11% higher tensile strength.

  17. Photoluminescence and anti-deliquesce of cesium iodide and its sodium-doped films deposited by thermal evaporation at high deposition rates

    NASA Astrophysics Data System (ADS)

    Hsu, Jin-Cherng; Chiang, Yueh-Sheng; Ma, Yu-Sheng

    2013-03-01

    Cesium iodide (CsI) and sodium iodide (NaI) are good scintillators due to their high luminescence efficiency. These alkali halides can be excited by ultra-violet or by ionizing radiation. In this study, CsI and its Na-doped films about 8 μm thick were deposited by thermal evaporation boat without heating substrates at high deposition rates of 30, 50, 70, 90, and 110 nm/sec, respectively. The as-deposited films were sequentially deposited a silicon dioxide film to protect from deliquesce. And, the films were also post-annealed in vacuum at 150, 200, 250, and 300 °C, respectively. We calculated the packing densities of the samples according to the measurements of Fourier transform infrared spectroscopy (FTIR) and observed the luminescence properties by photoluminescence (PL) system. The surfaces and cross sections of the films were investigated by scanning electron microscope (SEM). From the above measurements we can find the optimal deposition rate of 90 nm/sec and post-annealing temperature of 250 °C in vacuum for the asdeposited cesium iodide and its sodium-doped films.

  18. Thermal and trophic stability of deeper Maine lakes in granite waterhsheds implacted by acid deposition

    SciTech Connect

    Stauffer, R.E.; Wittchen, B.D. )

    1990-09-01

    Acid deposition can lead to lake and watershed acidification, increases in lake transparency, and reduction in thermal stability and hypolimnetic oxygen deficits. On the basis of lake surveys during August-September 1985, we determined to what extent the deeper (maximum depth z{sub m}{gt}17 m) Maine lakes in acid-sensitive granitic watersheds have registered changes in temperature and oxygen stratification, as compared to 1938-1942, when G.P. Cooper performed the earliest scientific surveys of the state's lakes. After correcting for small but geographically consistent interannual differences in summer hypolimnetic temperatures related to spring turnover, and weather-dependent differences in mixed layer depth, there has been no significant change in thermal stratification in these Maine lakes over approximately 43 years. On the basis of specific historical contrasts in the late summer metalimnetic, hypolimnetic, and bathylimnetic oxygen concentrations there has been no significant change in lake trophic state or transparency.

  19. A Martian analog in Kansas: Comparing Martian strata with Permian acid saline lake deposits

    NASA Astrophysics Data System (ADS)

    Benison, Kathleen C.

    2006-05-01

    An important result of the Mars Exploration Rover's (MER) mission has been the images of sedimentary structures and diagenetic features in the Burns Formation at Meridiani Planum. Bedding, cross-bedding, ripple marks, mud cracks, displacive evaporite crystal molds, and hematite concretions are contained in these Martian strata. Together, these features are evidence of past saline groundwater and ephemeral shallow surface waters on Mars. Geochemical analyses of these Martian outcrops have established the presence of sulfates, iron oxides, and jarosite, which strongly suggests that these waters were also acidic. The same assemblage of sedimentary structures and diagenetic features is found in the salt-bearing terrestrial red sandstones and shales of the middle Permian (ca. 270 Ma) Nippewalla Group of Kansas, which were deposited in and around acid saline ephemeral lakes. These striking sedimentological and mineralogical similarities make these Permian red beds and evaporites the best-known terrestrial analog for the Martian sedimentary rocks at Meridiani Planum.

  20. Assessing biogeographic patterns in the changes in soil invertebrate biodiversity due to acidic deposition

    SciTech Connect

    Sugg, P.M.; Kuperman, R.G.; Loucks, O.L. |

    1995-09-01

    We are studying the response of soil faunal communities to a gradient in acidic deposition across midwestern hardwood forests. We have documented a pattern of population decrease and species loss for soil invertebrates along the acidification gradient. We now ask the following question: When confronted with apparent diversity changes along a region-wide pollution gradient, how can one assess the possibility of natural biogeographic gradients accounting for the pattern? As a first approximation, we use published range maps from taxonomic monographs to determine the percent of the regional fauna with ranges encompassing each site. For staphylinid beetles, range data show no sign of a biogeographic gradient. Yet for soil staphylinids, a large decrease is seen in alpha diversity (as species richness) from low to high acid dose sites (from 20 species to 8). Staphylinid species turnover is greatest in the transition from low to intermediate dose sites.

  1. Acid fog deposition and the declining forest in Tanzawa mountains, Japan.

    NASA Astrophysics Data System (ADS)

    Igawa, M.; Shigihara, A.; Goto, S.; Nanzai, B.

    2010-07-01

    Since 1988, we have investigated fog chemistry in Mt. Oyama, Tanzawa mountains, Japan, and acid fog has been frequently observed there. We have observed fog on Mt. Oyama by using a night view video camera placed at the base of the mountain, by using a visibility meter at the top of the mountain, and by an active fog sampler at the mountainside. We have reported the fog frequency at the top of Mt. Oyama to be 46% measured by the video camera, but it was overestimated. The visibility measured at the top of the mountain is the most reliable index, and the top of the mountain is covered with fog for about 30%. The frequency of about 15% was added for the case of the visibility of a few km when it was measured by a night view video camera placed at the base of the mountain (8.5 km far from the top). Fog-water deposition increases with the increasing altitude to be much larger than the rain-water deposition. The factors affecting on the occult precipitation intensity were investigated by the simultaneous measurement of the rainfall intensity under a canopy, the wind speed and direction, and the visibility at the top of the mountain. Air pollution has been improved recently in Japan, but acid fog is not improved and has been affecting the leaves of the trees. In Tanzawa mountains, many fir trees and beech trees are declining, while cedar trees show no decline symptoms. We have investigated the effect of acid fog on the trees of these species by exposing simulated acid fog on the seedlings of the species. Seedlings of fir and beech are much damaged by the long term exposure of pH 3 fog, while cedar seedlings are not affected by the acid fog. By the exposure of simulated acid fog, the epicuticle wax is eroded at first, then the cross linking polycation between sugar chains of cell wall is ion-exchanged with proton and the cell wall is swollen, and the membrane calcium is desorbed from the membrane, which lowers the tolerance of the trees to the climate change. Fir and beech

  2. IMPACTS OF ACIDIC DEPOSITION: CONTEXT AND CASE STUDIES OF FOREST SOILS IN THE SOUTHEASTERN U.S.

    EPA Science Inventory

    The authors designed their assessment to include both the basic foundation needed by non-experts and the detailed information needed by experts. Their assessment includes background information on acidic deposition (Chap. 1), an in-depth discussion of the nature of soil acidity a...

  3. EFFECTS OF ACIDIC DEPOSITION ON STREAMS IN THE APPALACHIAN MOUNTAINS AND PIEDMONT REGION OF THE MID-ATLANTIC UNITED STATES

    EPA Science Inventory

    Streams in the Appalachian Mountain area of the Mid-Atlantic receive some of the largest acidic deposition loadings of any region of the United States. ompilation of survey data from the Mid-Appalachians yields a consistent picture of the acid-base status of streams. cidic stream...

  4. TREATOGENIC ACTIVITY OF TRICHOLORACETIC ACID IN THE RATE

    EPA Science Inventory

    Trichloroacetic acid (TCA) is a by-product of the chlorine disinfection of water containing natural organic material. t is detectable in finished drinking water at levels comparable to the trihalomethanes (930-160 ug/L). CA is also formed in vivo after ingestion of hypochelorite ...

  5. Influence of travel speed on spray deposition uniformity from an air-assisted variable-rate sprayer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A newly developed LiDAR-guided air-assisted variable-rate sprayer for nursery and orchard applications was tested at various travel speeds to compare its spray deposition and coverage uniformity with constant-rate applications. Spray samplers, including nylon screens and water-sensitive papers (WSP)...

  6. DIRECT MEASUREMENT TECHNIQUE FOR THE DETERMINING VENTILATION RATE IN THE DEPOSIT FEEDING CLAM, MACOMA NASUTA (BIVALVIA, TELLINACEAE)

    EPA Science Inventory

    An exposure chamber, the "clambox", was developed to measure ventilation rate, sediment processing rate, and efficiency of pollutant uptake byMacoma nasuta Conrad, a surface surface deposit-feeding clams. Clams, collected from Yaquina, Bay, Oregon, USA, were cemented into a hole ...

  7. Hatching success in salamanders and chorus frogs at two sites in Colorado, USA: Effects of acidic deposition and climate

    USGS Publications Warehouse

    Muths, E.; Campbell, D.H.; Corn, P.S.

    2003-01-01

    The snowpack in the vicinity of the Mount Zirkel Wilderness Area is among the most acidic in the western United States. We analyzed water chemistry and examined hatching success in tiger salamanders and chorus frogs at ponds there and at nearby Rabbit Ears Pass (Dumont) to determine whether acid deposition affects amphibians or their breeding habitats at these potentially sensitive locations. We found a wide range of acid neutralizing capacity among ponds within sites; the minimum pH recorded during the experiment was 5.4 at one of 12 ponds with all others at pH ??? 5.7. At Dumont, hatching success for chorus frogs was greater in ponds with low acid neutralizing capacity; however, lowest pHs were >5.8. At current levels of acid deposition, weather and pond characteristics are likely more important than acidity in influencing hatching success in amphibian larvae at these sites.

  8. Imbalance in Fatty-Acid-Chain Length of Gangliosides Triggers Alzheimer Amyloid Deposition in the Precuneus

    PubMed Central

    Oikawa, Naoto; Matsubara, Teruhiko; Fukuda, Ryoto; Yasumori, Hanaki; Hatsuta, Hiroyuki; Murayama, Shigeo; Sato, Toshinori; Suzuki, Akemi; Yanagisawa, Katsuhiko

    2015-01-01

    Amyloid deposition, a crucial event of Alzheimer’s disease (AD), emerges in distinct brain regions. A key question is what triggers the assembly of the monomeric amyloid ß-protein (Aß) into fibrils in the regions. On the basis of our previous findings that gangliosides facilitate the initiation of Aß assembly at presynaptic neuritic terminals, we investigated how lipids, including gangliosides, cholesterol and sphingomyelin, extracted from synaptic plasma membranes (SPMs) isolated from autopsy brains were involved in the Aß assembly. We focused on two regions of the cerebral cortex; precuneus and calcarine cortex, one of the most vulnerable and one of the most resistant regions to amyloid deposition, respectively. Here, we show that lipids extracted from SPMs isolated from the amyloid-bearing precuneus, but neither the amyloid-free precuneus nor the calcarine cortex, markedly accelerate the Aß assembly in vitro. Through liquid chromatography-mass spectrometry of the lipids, we identified an increase in the ratio of the level of GD1b-ganglioside containing C20:0 fatty acid to that containing C18:0 as a cause of the enhanced Aß assembly in the precuneus. Our results suggest that the local glycolipid environment play a critical role in the initiation of Alzheimer amyloid deposition. PMID:25798597

  9. Sensitivity of high-elevation streams in the Southern Blue Ridge Province to acidic deposition

    USGS Publications Warehouse

    Winger, P.V.; Lasier, P.J.; Hudy, M.; Fowler, D.; Van Den Avyle, M.J.

    1987-01-01

    The Southern Blue Ridge Province, which encompasses parts of northern Georgia, eastern Tennessee, and western North Carolina, has been predicted to be sensitive to impacts from acidic deposition, owing to the chemical composition of the bedrock geology and soils. This study confirms the predicted potential sensitivity, quantifies the level of total alkalinity and describes the chemical characteristics of 30 headwater streams of this area. Water chemistry was measured five times between April 1983 and June 1984 at first and third order reaches of each stream during baseflow conditions. Sensitivity based on total alkalinity and the Calcite Saturation Index indicates that the headwater streams of the Province are vulnerable to acidification. Total alkalinity and p11 were generally higher in third order reaches (mean, 72 ?eq/? and 6.7) than in first order reaches (64 ?eq/? and 6.4). Ionic concentrations were low, averaging 310 and 340 ?eq/? in first and third order reaches, respectively. A single sampling appears adequate for evaluating sensitivity based on total alkalinity, but large temporal variability requires multiple sampling for the detection of changes in pH and alkalinity over time. Monitoring of stream water should continue in order to detect any subtle effects of acidic deposition on these unique resource systems.

  10. The distribution of common construction materials at risk to acid deposition in the United States

    NASA Astrophysics Data System (ADS)

    Lipfert, Frederick W.; Daum, Mary L.

    Information on the geographic distribution of various types of exposed materials is required to estimate the economic costs of damage to construction materials from acid deposition. This paper focuses on the identification, evaluation and interpretation of data describing the distributions of exterior construction materials, primarily in the United States. This information could provide guidance on how data needed for future economic assessments might be acquired in the most cost-effective ways. Materials distribution surveys from 16 cities in the U.S. and Canada and five related databases from government agencies and trade organizations were examined. Data on residential buildings are more commonly available than on nonresidential buildings; little geographically resolved information on distributions of materials in infrastructure was found. Survey results generally agree with the appropriate ancillary databases, but the usefulness of the databases is often limited by their coarse spatial resolution. Information on those materials which are most sensitive to acid deposition is especially scarce. Since a comprehensive error analysis has never been performed on the data required for an economic assessment, it is not possible to specify the corresponding detailed requirements for data on the distributions of materials.

  11. Use of Soil-Streamwater Relationships to Assess Regional Patterns of Recovery from Acidic Deposition Effects

    NASA Astrophysics Data System (ADS)

    Siemion, J.; Lawrence, G. B.; Murdoch, P. S.

    2012-12-01

    Declines of acidic deposition levels by as much as 50% since 1990 have led to partial recovery of surface waters in the Northeastern United States, but continued depletion of soil calcium through this same period suggests a disconnection between soil and surface water chemistry. To investigate the role of soil-surface water interactions in recovery from acidification, the first regional survey to directly relate soil chemistry to stream chemistry during high flow was implemented in the Catskill region of New York, where acidic deposition levels are among the highest in the East. More than 40% of streams sampled in the southwestern Catskill Mountains were determined to be acidified with inorganic monomeric aluminum concentrations that exceeded a threshold that is toxic to aquatic biota and more than 80% likely to exceed this threshold during the highest flows, but less than 10% were acidified in the northwestern portion of the region. Median Oa horizon soil base saturation ranged from 50-80% across the region, but median base saturation in the upper 10cm of the B horizon was less than 20% across the region and was only 2% in the southwestern area. Therefore, aluminum is likely to be interfering with calcium uptake in the mineral horizon by trees in half the watersheds where soils were collected. These results indicate stream chemistry over the Catskill region does not reflect the calcuim depletion of the B horizon that our sampling suggests is ubiquitous throughout the region.

  12. Stretchability of Silver Films on Thin Acid-Etched Rough Polydimethylsiloxane Substrates Fabricated by Electrospray Deposition

    NASA Astrophysics Data System (ADS)

    Mehdi, S. M.; Cho, K. H.; Kang, C. N.; Choi, K. H.

    2015-07-01

    This paper investigates the fabrication of Ag films through the electrospray deposition (ESD) technique on sub-millimeter-thick acid-etched rough polydimethylsiloxane (PDMS) substrates having both low and high modulus of elasticity. The main focus of the study is on the stretchable behavior of ESD-deposited Ag nanoparticles-based thin films on these substrates when subjected to axial strains. Experimental results suggest that the as-fabricated films on thin acid-etched rough low modulus PDMS has an average stretchability of 5.6% with an average increase in the resistance that is 23 times that of the initial resistance at electrical failure (complete rupture of the films). Comparatively, the stretchability of Ag films on the high modulus PDMS was found to be 3 times higher with 4.65 times increase in the resistance at electrical failure. Also, a high positive value of the piezoresistive coefficient for these films suggests that the resistivity changes during stretching, and thus deviation from the simplified models is inevitable. Based on these results, new models are presented that quantify the changes in resistance with strain.

  13. nC60 deposition kinetics: the complex contribution of humic acid, ion concentration, and valence.

    PubMed

    McNew, Coy P; LeBoeuf, Eugene J

    2016-07-01

    The demonstrated toxicity coupled with inevitable environmental release of nC60 raise serious concerns about its environmental fate and transport, therefore it is crucial to understand how nC60 will interact with subsurface materials including attached phase soil and sediment organic matter (AP-SOM). This study investigated the attachment of nC60 onto a Harpeth humic acid (HHA) coated silica surface under various solution conditions using a quartz crystal microbalance with dissipation monitoring. The HHA coating greatly enhanced nC60 attachment at low ion concentrations while hindering attachment at high ion concentrations in the presence of both mono and divalent cations. At low ion concentrations, the HHA greatly reduced the surface potential of the silica, enhancing nC60 deposition through reduction in the electrostatic repulsion. At high ion concentrations however, the reduced surface potential became less important due to the near zero energy barrier to deposition and therefore non-DLVO forces dominated, induced by compaction of the HHA layer, and leading to hindered attachment. In this manner, observed contributions from the HHA layer were more complex than previously reported and by monitoring surface charge and calculated DLVO interaction energy alongside attachment experiments, this study advances the mechanistic understanding of the variable attachment contributions from the humic acid layer. PMID:27061365

  14. Heavy metals and acidic components in total deposited matter in Sibenik and National Park Kornati, Croatia.

    PubMed

    Cacković, Mirjana; Kalinić, Natasa; Vadjić, Vladimira; Pehnec, Gordana

    2009-01-01

    This article presents the results of 6 years (1999-2004) of monitoring acidic components (fluoride, chloride, nitrate, sulfate) and heavy metals (lead, cadmium, thallium) in total deposited matter (TDM) in the town of Sibenik and the National Park Kornati, Croatia, in order to determine their levels, spatial and temporal variations, and possible emission source. Bulk deposition samples were collected using the Bergerhoff samplers. TDM matter was determined gravimetrically. Acidic anions were analyzed using ion chromatography. Metallic components were determined by atomic absorption spectrometry. Results show that the levels of measured pollutants were relatively low compared to those reported in other investigations. Statistical analysis indicates that the measured pollutants originate from several sources such as resuspended soil, industry, road dust, traffic, and secondary aerosols as the most important. The levels of TDM show a slightly increasing trend at all sampling sites. A significant increasing trend in the levels of nitrate and sulfate in TDM could be the consequence of increasing traffic activity and urbanization. The significant increasing trend in the ratio between nitrate and sulfate in TDM indicates that the nitrate and sulfate relative contribution to acidification is increasing. The level of heavy metals in TDM was in order of lead > thallium > cadmium at all sampling sites with slightly decreasing trend. PMID:18414927

  15. Water evaporation rates across hydrophobic acid monolayers at equilibrium spreading pressure.

    PubMed

    Tsuji, Minami; Nakahara, Hiromichi; Moroi, Yoshikiyo; Shibata, Osamu

    2008-02-15

    The effect of alkanoic acid [CH(3)(CH(2))(n-2)COOH; HCn] and perfluoroalkanoic acid [CF(3)(CF(2))(n-2)COOH; FCn] monolayers on the water evaporation rate was investigated by thermogravimetry tracing the decrease in amount of water with time. The evaporation rate from the surface covered by a monolayer was measured as a function of temperature and hydrophobic chain length of the acids, where the monolayer was under an equilibrium spreading pressure. From thermal behavior of the crystallized acids, their solid states are C-type in crystalline state over the temperature range from 298.2 to 323.2 K. The dry air was flowed through a furnace tube of a thermogravimetry apparatus at the flow rate of 80 mL min(-1), where the evaporation rate becomes almost constant irrespective of the flow rate. The temperature dependence of the evaporation rate was analyzed kinetically to evaluate the activation energy and thermodynamics values for the activated complex, which demonstrated that these values were almost the same for both alkanoic acids and perfluoroalkanoic acids, although the effect of perfluoroalkanoic acids on the evaporation rate was smaller than that of corresponding hydrogenated fatty acids. The difference in the evaporation rate between FCn and HCn was examined by atomic force microscopy (AFM), Brewster angle microscopy (BAM), surface potential (DeltaV) at equilibrium spreading pressure, and Langmuir curve (pi-A isotherm), and their results were consistent and supported the difference. PMID:18048050

  16. Relationship between the electrochemical activity of Raney nickel and the rate of hydrogenation of maleic acid

    SciTech Connect

    Pervii, E.N.; Sofronkov, A.N.; Fedyshina, N.M.

    1986-02-10

    The purpose of this investigation was to determine the conditions in which a direct correlation exists between the rate of hydrogenation of maleic acid and the electrochemical activity of catalysts of hydrogen ionization. The rate of maleic acid hydrogenation in presence of Raney nickel catalyst was studied by a combination of volumetric and potentiometric methods.

  17. Supported plasma sputtering apparatus for high deposition rate over large area

    DOEpatents

    Moss, Ronald W.; McClanahan, Jr., Edwin D.; Laegreid, Nils

    1977-01-01

    A supported plasma sputtering apparatus is described having shaped electrical fields in the electron discharge region between the cathode and anode and the sputter region between the target and substrate while such regions are free of any externally applied magnetic field to provide a high deposition rate which is substantially uniform over a wide area. Plasma shaping electrodes separate from the anode and target shape the electrical fields in the electron discharge region and the sputter region to provide a high density plasma. The anode surrounds the target to cause substantially uniform sputtering over a large target area. In one embodiment the anode is in the form of an annular ring surrounding a flat target surface, such anode being provided with a ribbed upper surface which shields portions of the anode from exposure to sputtered material to maintain the electron discharge for a long stable operation. Several other embodiments accomplish the same result by using different anodes which either shield the anode from sputtered material, remove the sputtered coating on the anode by heating, or simultaneously mix sputtered metal from the auxiliary target with sputtered insulator from the main target so the resultant coating is conductive. A radio frequency potential alone or together with a D.C. potential, may be applied to the target for a greater sputtering rate.

  18. Response of DOC in Acid-Sensitive Maine Lakes to Decreasing Sulfur Deposition (1993 - 2009)

    NASA Astrophysics Data System (ADS)

    Oelsner, G. P.; Sanclements, M.; McKnight, D. M.; Stoddard, J. L.

    2010-12-01

    In response to the Clean Air Act Amendments of 1990, sulfur deposition has decreased across the northeastern United States. As a result, sulfate concentrations in lakes and streams have also decreased and many surface waters have become less acidic. Over the same time period, there has been a concurrent increase in dissolved organic carbon (DOC) concentrations in many lakes and streams which has been difficult to interpret. To assess the biogeochemical processes driving increasing DOC concentrations we analyzed archived samples from 9 acid-sensitive lakes in Maine collected between 1993 and 2009 using UV-Vis and fluorescence spectroscopy. The fluorescence index (FI) was calculated for all samples. The FI represents the ratio of the emission intensity at 450 nm to 550 nm at an excitation wavelength of 370 nm and provides information regarding the source of dissolved organic matter (DOM). This index has a value of approximately 1.9 for microbially derived fluvic acids and a value of approximately 1.4 for terrestrially (higher-plant) derived fluvic acids. All four lakes with increasing DOC trends had concomitant decreases in the FI index. Two of five lakes with no significant DOC trend also demonstrated no trend in FI values over time, while three lakes revealed a decrease in FI values. To confirm that the FI measured in whole water was primarily reflective of fulvic acids (FA), XAD-resin was used to isolate FA from a subset of samples. Analysis of the FA indicates that the FI values for the humic substances are slightly higher, yet well correlated with whole water samples. This suggests that despite prolonged storage in plastic, the FI trends are meaningful. The FI trends suggest a terrestrial source for the increasing DOC and may be driven by increased DOM production from soils experiencing decreased acid loading. Decreases in sulfate deposition can increase soil pH and soil organic matter solubility, as well as decrease the ionic strength of the soil solution, and

  19. The effect of linoleic acid on the whole body synthesis rates of polyunsaturated fatty acids from α-linolenic acid and linoleic acid in free-living rats.

    PubMed

    Domenichiello, Anthony F; Kitson, Alex P; Chen, Chuck T; Trépanier, Marc-Olivier; Stavro, P Mark; Bazinet, Richard P

    2016-04-01

    Docosahexaenoic acid (DHA) is thought to be important for brain function. The main dietary source of DHA is fish, however, DHA can also be synthesized from precursor omega-3 polyunsaturated fatty acids (n-3 PUFA), the most abundantly consumed being α-linolenic acid (ALA). The enzymes required to synthesize DHA from ALA are also used to synthesize longer chain omega-6 (n-6) PUFA from linoleic acid (LNA). The large increase in LNA consumption that has occurred over the last century has led to concern that LNA and other n-6 PUFA outcompete n-3 PUFA for enzymes involved in DHA synthesis, and therefore, decrease overall DHA synthesis. To assess this, rats were fed diets containing LNA at 53 (high LNA diet), 11 (medium LNA diet) or 1.5% (low LNA diet) of the fatty acids with ALA being constant across all diets (approximately 4% of the fatty acids). Rats were maintained on these diets from weaning for 8 weeks, at which point they were subjected to a steady-state infusion of labeled ALA and LNA to measure DHA and arachidonic acid (ARA) synthesis rates. DHA and ARA synthesis rates were generally highest in rats fed the medium and high LNA diets, while the plasma half-life of DHA was longer in rats fed the low LNA diet. Therefore, increasing dietary LNA, in rats, did not impair DHA synthesis; however, low dietary LNA led to a decrease in DHA synthesis with tissue concentrations of DHA possibly being maintained by a longer DHA half-life. PMID:27012633

  20. Bortezomib produces high hematological response rates with prolonged renal survival in monoclonal immunoglobulin deposition disease.

    PubMed

    Cohen, Camille; Royer, Bruno; Javaugue, Vincent; Szalat, Raphael; El Karoui, Khalil; Caulier, Alexis; Knebelmann, Bertrand; Jaccard, Arnaud; Chevret, Sylvie; Touchard, Guy; Fermand, Jean-Paul; Arnulf, Bertrand; Bridoux, Frank

    2015-11-01

    Monoclonal immunoglobulin deposition disease (MIDD) is a rare complication of plasma cell disorders, defined by linear Congo red-negative deposits of monoclonal light chain, heavy chain, or both along basement membranes. While renal involvement is prominent, treatment strategies, such as the impact of novel anti-myeloma agents, remain poorly defined. Here we retrospectively studied 49 patients with MIDD who received a median of 4.5 cycles of intravenous bortezomib plus dexamethasone. Of these, 25 received no additional treatment, 18 also received cyclophosphamide, while 6 also received thalidomide or lenalidomide. The hematological diagnoses identified 38 patients with monoclonal gammopathy of renal significance, 10 with symptomatic multiple myeloma, and 1 with Waldenstrom macroglobulinemia. The overall hematologic response rate, based on the difference between involved and uninvolved serum-free light chains (dFLCs), was 91%. After median follow-up of 54 months, 5 patients died and 10 had reached end-stage renal disease. Renal response was achieved in 26 patients, with a 35% increase in median eGFR and an 86% decrease in median 24-h proteinuria. Predictive factors were pre-treatment eGFR over 30 ml/min per 1.73 m(2) and post-treatment dFLC under 40 mg/l; the latter was the sole predictive factor of renal response by multivariable analysis. Thus, bortezomib-based therapy is a promising treatment strategy in MIDD, mainly when used early in the disease course. dFLC response is a favorable prognostic factor for renal survival. PMID:26176826

  1. Measurement of the rates of oxindole-3-acetic acid turnover, and indole-3-acetic acid oxidation in Zea mays seedlings

    NASA Technical Reports Server (NTRS)

    Nonhebel, H. M.; Bandurski, R. S. (Principal Investigator)

    1986-01-01

    Oxindole-3-acetic acid is the principal catabolite of indole-3-acetic acid in Zea mays seedlings. In this paper measurements of the turnover of oxindole-3-acetic acid are presented and used to calculate the rate of indole-3-acetic acid oxidation. [3H]Oxindole-3-acetic acid was applied to the endosperm of Zea mays seedlings and allowed to equilibrate for 24 h before the start of the experiment. The subsequent decrease in its specific activity was used to calculate the turnover rate. The average half-life of oxindole-3-acetic acid in the shoots was found to be 30 h while that in the kernels had an average half-life of 35h. Using previously published values of the pool sizes of oxindole-3-acetic acid in shoots and kernels from seedlings of the same age and variety, and grown under the same conditions, the rate of indole-3-acetic acid oxidation was calculated to be 1.1 pmol plant-1 h-1 in the shoots and 7.1 pmol plant-1 h-1 in the kernels.

  2. The effect of organic acids on plagioclase dissolution rates and stoichiometry

    NASA Astrophysics Data System (ADS)

    Welch, Susan A.; Ullman, William J.

    1993-06-01

    The rates of plagioclase dissolution in solutions containing organic acids are up to ten times greater than the rates determined in solutions containing inorganic acids at the same acidity. Initial rates of dissolution are poorly reproduced in replicate experiments. After a day, however, the rates of plagioclase dissolution calculated from the rates of silicon release are reproducible and constant for up to nineteen days. Steady-state rates of dissolution are highest (up to 1.3 × 10 -8 mol/m 2/sec) in acidic solutions (pH ≈ 3) and decrease (to 1 × 10 -11 mol/m 2/sec) as acidity decreases toward neutral pH. The polyfunctional acids, oxalate, citrate, succinate, pyruvate, and 2-ketoglutarate, are the most effective at promoting dissolution. Acetate and propionate are not as effective as the other organic acids but are nonetheless more effective than solutions containing only inorganic acids. The degree of ligand-promoted enhancement of dissolution rate (rate in organic-containing solution/rate in inorganic solution at the same pH) decreases as acidity increases, indicating that the ligand-promoted dissolution mechanism becomes relatively more important as the rate of proton-promoted dissolution decreases. The stoichiometry of release to solution indicates that dissolution is selective even after the rates of dissolution become constant. As in previously published studies, Na and Ca are rapidly released from the plagioclase feldspar, leaving a surface enriched in Si and/or Al. The ratio of Al/Si released to solution indicates that the stoichiometry of the residual plagioclase surface is a function of pH and the nature of the organic ligand. The ligands which remove Al in preference to Si from the dissolving mineral surface are also those which enhance overall plagioclase dissolution rates.

  3. A biogeochemical comparison of two well-buffered catchments with contrasting histories of acid deposition

    USGS Publications Warehouse

    Shanley, J.B.; Kram, P.; Hruska, J.; Bullen, T.D.

    2004-01-01

    Much of the biogeochemical cycling research in catchments in the past 25 years has been driven by acid deposition research funding. This research has focused on vulnerable base-poor systems; catchments on alkaline lithologies have received little attention. In regions of high acid loadings, however, even well-buffered catchments are susceptible to forest decline and episodes of low alkalinity in streamwater. As part of a collaboration between the Czech and U.S. Geological Surveys, we compared biogeochemical patterns in two well-studied, well-buffered catchments: Pluhuv Bor in the western Czech Republic, which has received high loading of atmospheric acidity, and Sleepers River Research Watershed in Vermont, U.S.A., where acid loading has been considerably less. Despite differences in lithology, wetness, forest type, and glacial history, the catchments displayed similar patterns of solute concentrations and flow. At both catchments, base cation and alkalinity diluted with increasing flow, whereas nitrate and dissolved organic carbon increased with increasing flow. Sulfate diluted with increasing flow at Sleepers River, while at Pluhuv Bor the sulfate-flow relation shifted from positive to negative as atmospheric sulfur (S) loadings decreased and soil S pools were depleted during the 1990s. At high flow, alkalinity decreased to near 100 ??eq L-1 at Pluhuv Bor compared to 400 ??eq L-1 at Sleepers River. Despite the large amounts of S flushed from Pluhuv Bor soils, these alkalinity declines were caused solely by dilution, which was greater at Pluhuv Bor relative to Sleepers River due to greater contributions from shallow flow paths at high flow. Although the historical high S loading at Pluhuv Bor has caused soil acidification and possible forest damage, it has had little effect on the acid/base status of streamwater in this well-buffered catchment. ?? 2004 Kluwer Academic Publishers.

  4. Chemical and biological status of lakes and streams in the upper midwest: assessment of acidic deposition effects

    USGS Publications Warehouse

    Wiener, J.G.; Eilers, J.M.

    1987-01-01

    Many lakes in three areas in the Upper Midwest - northeastern Minnesota, northern Wisconsin, and the Upper Peninsula of Michigan - have low acid neutralizing capacity (ANC) and may be susceptible to change by acidic deposition. Northcentral Wisconsin and the Upper Peninsula of Michigan together contain about 150-300 acidic lakes (ANC ≤ 0), whereas none have been found in Minnesota. These acidic lakes are precipitation-dominated, Clearwater seepage lakes having small surface area, shallow depth, and low concentrations of dissolved organic carbon. The spatial distribution of these acidic lakes parallels a west to east gradient of increasing sulfate and hydrogen ion deposition. Several of these acidic lakes exhibit chemical characteristics and biological changes consistent with those observed elsewhere in waters reported to be acidified by acidic deposition. However, an hypothesis of recent lake acidification is not supported by analyses of either historical chemical data or diatom remains in lake sediments, and natural sources of acidity and alternative ecological processes have not been conclusively eliminated as causative factors. Streams in this three-state region have high ANC and appear to be insensitive to acidic deposition. The species richness and composition of lacustrine fish communities in the region are partly related to pH and associated chemical factors. Sport fishes considered acid-sensitive and of primary concern with regard to acidification include walleye, smallmouth bass, and black crappie. The fishery in at least one lake, Morgan Lake in Wisconsin (pH 4.6), may have declined because of acidification. Given the general lack of quantitative fishery data for acidic Wisconsin and Michigan lakes, however, more general conclusions concerning impacts or the absence of impacts of acidification on the region's fishery resources are not possible.

  5. Growth and reproductive ecology of the eastern brook trout, Salvelinus fontinalis, in streams of differing vulnerability to acidic atmospheric deposition

    SciTech Connect

    Light, R.W.

    1983-01-01

    Three naturally infertile streams of differing vulnerability to acidic atmospheric deposition were studied to determine the status of their brook trout, Salvelinus fontinalis, populations and associated benthic communities. Of the three streams, Upper Three Runs was judged to be the least fertile, followed by Little Fishing Creek, with Roaring Run being the most fertile. The median weighted pH of acidic deposition impacting the watersheds was 3.8 for Upper Three Runs and 4.0 for Little Fishing Creek and Roaring Run. Brook trout from Roaring Run grew at a similar rate to those from Little Fishing Creek, with trout from Upper Three Runs showing the slowest growth. Roaring Run brook trout also had the highest relative condition of the three streams. Brook trout from Roaring Run and Little Fishing Creek generally matured one year later (age group II) than those from Upper Three Runs. Early maturity may be selected for in Upper Three Runs due to small annual increases in fecundity in higher age groups. Although the data were limited, there was a trend for brook trout from Upper Three Runs to produce fewer and larger ova. Roaring Run had higher volumes of benthos during fall and summer, and higher numbers during fall. Roaring Run and Little Fishing Creek had more, larger crayfish present, which added significantly to the volume of benthos in these streams. Qualitatively, Upper Three Runs had more shredders and fewer scrapers on a volume basis than the other two streams. On a per fish basis, the drift available to the fish in Roaring Run was always highest in volume, and highest in number during fall and spring. The brook trout from Roaring Run therefore had an advantage over those in the other two streams, by having a higher drift available per fish.

  6. Effects of acidic deposition on nutrient uptake, nutrient cycling and growth processes of vegetation in the spruce-fir ecosystem

    SciTech Connect

    McLaughlin, S.B.; Garten, C.T.; Wullschleger, S.D.

    1996-10-16

    This report summarizes progress in three years of field research designed to evaluate biological and chemical indicators of the current and future health of the Southern Appalachian spruce-fir ecosystem. The emphasis of this research has been on the identification and understanding of mechanisms through which current levels of acidic deposition are impacting ecosystem processes. The identification of these principal mechanisms and key biological indicators of change was designed to improve our capabilities to detect, monitor, and assess the effects of air quality regulations and attendant future air quality changes on ecosystem response. Individual research tasks focused on the following research areas: (1) the significance of foliar uptake of atmospheric sources of nitrogen in relationship to plant utilization of N from available soil reserves; (2) linkages between atmospheric inputs to the soil surface, solution chemistry, and decomposition in the upper organic soil horizons; (3) effects of soil solution chemistry on uptake of cations and aluminum by fine roots; and (4) the effects of varying rates of calcium supply on carbon metabolism of Fraser fir and red spruce, and the relationship between calcium levels in wood cells and integrity of wood formed in bole and branches. Each of the individual tasks was designed to focus upon a mechanism or process that we consider critical to understanding chemical and biological linkages. These linkages will be important determinants in understanding the basis of past and potential future responses of the high elevation Southern Appalachian Forest to acidic deposition and other co-occurring environmental stresses. This report contains (1) background and rationale for the research undertaken in 1992-94; (2) a summary of principal research findings; (3) publications from this research; and (4) characterization of data sets produced by this research which will be the basis of future research, analyses and/or publications.

  7. Calcium Fluoride Precipitation and Deposition From 12 mmol/L Fluoride Solutions With Different Calcium Addition Rates

    PubMed Central

    Markovic, M; Takagi, S; Chow, LC; Frukhtbeyn, S

    2009-01-01

    The effects of different Ca-addition rates on calcium fluoride (CaF2) precipitation and deposition were investigated in 12 mmol/L sodium fluoride solutions to which 0.1 mol/L calcium chloride solution was continuously added at average rates of (5, 7.5, 10, 12.5, 15 or 20) mmol L−1 min−1. The changes in ionic fluoride and calcium concentrations, as well as turbidity, were continuously recorded by F and Ca electrodes, and a fiber optic based spectrophotometer, respectively. The F− concentration decreased and turbidity increased with time indicating precipitation of CaF2. For the systems with Ca-addition rates of (5, 7.5, 10, 12.5, 15, and 20) mmol L−1 min−1, the 1 min CaF2 depositions in the model substrate (cellulose filter paper, pores 0.2 µm) expressed as mean ± SD of deposited F per substrate surface area were (3.78 ± 0.31, 11.45 ± 0.89, 9.31 ± 0.68, 8.20 ± 0.56, 6.63 ± 0.43, and 2.09 ± 0.28) µg/cm2, respectively (n = 10 for each group). The 1-min F depositions did not show positive correlation to Ca-addition rates. The lowest 1-min F deposition was obtained in the systems with the highest Ca-addition rate of 20 mmol L−1 min−1 for which CaF2 precipitation rate reached the maximum value of 0.31 mmol L−1 s−1 almost immediately after beginning of reaction (6 s). The largest 1-min F depositions were obtained from the systems with Ca addition rates of (7.5 to 12.5) mmol L−1 min−1 in which CaF2 precipitation rates continuously increased reaching the maximum values of (0.13 to 0.20) mmol L−1 s−1 after (18 to 29) s, respectively. The 1-min F depositions were greatly enhanced in comparison with the control F solutions that did not have continuous Ca-addition. This indicates that continuous Ca addition that controls the rate of CaF2 formation could be a critical factor for larger F depositions from F solutions. The efficacy of conventional F mouthrinses could be improved with addition of a substance that continuously releases Ca.

  8. Experimental and theoretical deposition rates from salt-seeded combustion gases of a Mach 0.3 burner rig

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.; Kohl, F. J.; Stearns, C. A.; Gokoglu, S. A.; Rosner, D. E.

    1984-01-01

    Deposition rates on platinum-rhodium cylindrical collectors rotating in the cross streams of the combustion gases of a salt-seeded Mach 0.3 burner rig were determined. The collectors were internally air cooled so that their surface temperatures could be widely varied while they were exposed to constant combustion gas temperatures. The deposition rates were compared with those predicted by the chemically frozen boundary layer (CFBL) computer program, which is based on multicomponent vapor transport through the boundary layer. Excellent agreement was obtained between theory and experiment for the NaCl-seeded case, but the agreement lessened as the seed was changed to synthetic sea salt, NaNO3, and K2SO4, respectively, and was particularly poor in the case of Na2SO4. However, when inertial impaction was assumed to be the deposition mechanism for the Na2SO4 case, the predicted rates agreed well with the experimental rates. The former were calculated from a mean particle diameter that was derived from the measured intial droplet size distribution of the solution spray. Critical experiments showed that liquid phase deposits were blown off the smooth surface of the platinum-rhodium collectors by the aerodynamic shear forces of the high-velocity combustion gases but that rough or porous surfaces retained their liquid deposits.

  9. ENHANCED GROWTH RATE AND SILANE UTILIZATION IN AMORPHOUS SILICON AND NANOCRYSTALLINE-SILICON SOLAR CELL DEPOSITION VIA GAS PHASE ADDITIVES

    SciTech Connect

    Ridgeway, R G; Hegedus, S S; Podraza, N J

    2012-08-31

    Air Products set out to investigate the impact of additives on the deposition rate of both CSi and Si-H films. One criterion for additives was that they could be used in conventional PECVD processing, which would require sufficient vapor pressure to deliver material to the process chamber at the required flow rates. The flow rate required would depend on the size of the substrate onto which silicon films were being deposited, potentially ranging from 200 mm diameter wafers to the 5.7 m2 glass substrates used in GEN 8.5 flat-panel display tools. In choosing higher-order silanes, both disilane and trisilane had sufficient vapor pressure to withdraw gas at the required flow rates of up to 120 sccm. This report presents results obtained from testing at Air Products electronic technology laboratories, located in Allentown, PA, which focused on developing processes on a commercial IC reactor using silane and mixtures of silane plus additives. These processes were deployed to compare deposition rates and film properties with and without additives, with a goal of maximizing the deposition rate while maintaining or improving film properties.

  10. Analysis of southeastern Canada lake-water chemistry data in relation to acidic deposition

    SciTech Connect

    Olson, R.J.; Cook, R.B.; Ross-Todd, B.M.; Beauchamp, J.J.

    1990-05-01

    Lake-water chemistry data were obtained for lakes in southeastern Canada to study relationships between atmospheric deposition and acid-base chemistry as part of the National Acid Precipitation Assessment Program State of Science and Technology reports. Quality assurance checks were made to ensure that the data used were of sufficient quality and were comparable to data from the United States. Ninety-eight percent of the 8506 sampled lakes had pH, ANC, and SO{sub 4}{sup 2 {minus}} data and were used in our analyses. Of these, we created a subset of 4017 lakes having data for more variable (Ca{sup 2+}, Mg{sup 2+}, Na{sup +}, K{sup +}, DOC, and conductivity) to analyze potential sources of lake-water acidity. The objectives of this work were to determine the geographical extent and number of potentially affected systems and to infer causes of acidification based on ion ratios. 35 refs., 28 figs., 12 tabs.

  11. Acidification and recovery of a Spodosol BS horizon from acidic deposition

    SciTech Connect

    Dahlgren, R.A.; McAvoy, D.C.; Driscoll, C.T.

    1990-01-01

    A laboratory study was conducted to examine acidification and recovery of a Spodosol Bs horizon from acidic deposition in the Bear Brook Watershed (BBW) in central Maine. A mechanical vacuum extractor was used to draw solutions through a soil column at three treatments containing 40, 100, or 160 micromol/L SO4(2-). Following 44 d of leaching, all treatments were decreased to the 40 micromol/L SO4(2-) level to examine recovery from acidification. Acidic additions were initially neutralized by release of basic cations and sulfate adsorption. Following attainment of steady state conditions for basic cations and SO4(2-) with respect to the soil adsorption complex, Al dissolution was the primary neutralization mechanism. Aqueous Al activities appeared to be regulated by equilibrium with an Al(OH)3 mineral phase. Following decreases in acid loadings, recovery was rapid resulting in retention of basic cations, reversible release of SO4(2-) and a marked reduction in the concentrations of soluble Al.

  12. Acidification and recovery of a spodosol Bs horizon from acidic deposition

    SciTech Connect

    Dahlgren, R.A.; McAvoy, D.C.; Driscoll, C.T. )

    1990-04-01

    A laboratory study was conducted to examine acidification and recovery of a Spodosol Bs horizon from acidic deposition in the Bear Brook Watershed (BBW) in central Maine. A mechanical vacuum extractor was used to draw solutions through a soil column at three treatments containing 40, 100, or 160 {mu}mol/L SO{sub 4}{sup 2{minus}}. Following 44 days of leaching, all treatments were decreased to the 40 {mu}mol/L SO{sub 4}{sup 2{minus}} level to examine recovery from acidification. Acid additions were initially neutralized by release of basic cations and sulfate adsorption. Following attainment of steady-state conditions for basic cations and SO{sub 4}{sup 2{minus}} with respect to the soil adsorption complex, Al dissolution was the primary neutralization mechanism. Aqueous Al activities appeared to be regulated by equilibrium with an Al(OH){sub 3} mineral phase. Following decreases in acid loadings, recovery was rapid resulting in retention of basic cations, reversible release of SO{sub 4}{sup 2{minus}}, and a marked reduction in the concentrations of soluble Al.

  13. Chemical vapor deposition of B-doped polycrystalline diamond films: Growth rate and incorporation efficiency of dopants

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Deneuville, A.; Fontaine, F.; Gheeraert, E.; Campargue, A.; Chenevier, M.; Rodolphe, S.

    1995-12-01

    The growth rate and the incorporation efficiency of dopants have been studied in the case of chemical vapor deposition of B-doped polycrystalline diamond films. The deposition rate is found to decrease with the addition of diborane in the gas phase. This is correlated with a modification of the plasma chemistry as observed by emission spectroscopy (decrease in the H/H2, CH/H, and C2/H ratios with the addition of diborane). The concentration of boron incorporated in the films is observed to vary with the square of the boron concentration in the gas phase.

  14. High Rate Deposition of High Quality ZnO:Al by Filtered Cathodic Arc

    SciTech Connect

    Mendelsberg, Rueben J.; Lim, S.H.N.; Milliron, D.J.; Anders, Andre

    2010-11-18

    High quality ZnO:Al (AZO) thin films were prepared on glass substrates by direct current filtered cathodic arc deposition. Substrate temperature was varied from room temperature to 425oC, and samples were grown with and without the assistance of low power oxygen plasma (75W). For each growth condition, at least 3 samples were grown to give a statistical look at the effect of the growth environment on the film properties and to explore the reproducibility of the technique. Growth rate was in the 100-400 nm/min range but was apparently random and could not be easily traced to the growth conditions explored. For optimized growth conditions, 300-600 nm AZO films had resistivities of 3-6 x 10-4 ?Omega cm, carrier concentrations in the range of 2-4 x 1020 cm3, Hall mobility as high as 55 cm2/Vs, and optical transmittance greater than 90percent. These films are also highly oriented with the c-axis perpendicular to the substrate and a surface roughness of 2-4 nm.

  15. Sediment data for computations of deposition rates in the tidal Potomac system, Maryland and Virginia

    SciTech Connect

    Glenn, J.L.; Martin, E.A.; Rice, C.A.

    1986-01-01

    Sixty-two cores ranging in length from 33 to 1,002 cm were collected from the tidal Potomac system and from selected tributaries downstream from the local head-of-tides between June 1978 and July 1981. Segments from selected depths below the sediment surface have been analyzed for a variety of constituents, including lead-210, trace metals, nutrients, and particle size. The core sites were positioned throughout the hydrologic divisions and geomorphic units of the tidal Potomac system and in water depths ranging from 1 to 30 cm. Alpha counting methods were used to determine the polonium-210 radioactivity and secular equilibrium was assumed between lead-210 and polonium-210. The alpha decay of polonium-210 provides a measure of the lead-210 radioactivity of the lead-210 produced by in-situ decay of radium-226 in the sediment column and the lead-210 from external sources. Only the unsupported lead-210 was used in computations of the deposition rate. The background level of lead-210 in tidal Potomac system sediment cores usually is based on in-situ measurements of total lead-210 at depths below which no unsupported lead-210 is believed to be present, and the lead-210 concentrations are relatively constant. 6 refs., 3 figs., 1 tab.

  16. High Growth Rate YSZ Thermal Barrier Coatings Deposited by MOCVD Demonstrate High Thermal Cycling Lifetime

    SciTech Connect

    Varanasi, Venu G; Besmann, Theodore M; Payzant, E Andrew; Pint, Bruce A; Lothian, Janet L; Anderson, Timothy J

    2011-01-01

    Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) were prepared by metalorganic chemical vapor deposition (MOCVD) using Y(OBut{sup n}){sub 3}, Zr(OBut{sup n}){sub 4} precursors and O{sub 2} carrier gas. A thermodynamic analysis guided experiments by optimizing elemental molar (n) stoichiometric ratios for the (Zr-Y-O-C-H system). This analysis showed single-phase YSZ was favored at 950 C, 1 kPa, n{sub O}/(n{sub Y} + n{sub Zr}) > 30, n{sub Y}/(n{sub Y} + n{sub Zr}) = 0.06-0.10 (fixed n{sub C}, n{sub H}). Experimental YSZ growth had multiple phases (fcc, monoclinic), had a relatively high growth rate (43 {micro}m/h, 1005 C), had an Arrhenius dependence (845-950 C, E{sub a} = 53.8 {+-} 7.9 kJ/mol), had columnar grains (SEM analysis), and had a coating through-thickness n{sub Y}/(n{sub Y} + n{sub Zr}) = 0.04 (EPMA analysis). Doubling the inlet yttrium precursor mole fraction resulted in fcc YSZ growth with a coating through-thickness n{sub Y}/(n{sub Y} + n{sub Zr}) = 0.07. Hot-insertion thermal cycling of YSZ coatings on FeCrAlY bond coats showed >1000 h lifetime, matching current standards for EB-PVD YSZ coatings.

  17. Spectral Characterization of Suspected Acid Deposition Damage in Red Spruce (picea Rubens) Stands from Vermont

    NASA Technical Reports Server (NTRS)

    Vogelmann, J. E.; Rock, B. N.

    1985-01-01

    In an attempt to demonstrate the utility of remote sensing systems to monitor sites of suspected acid rain deposition damage, intensive field activities, coupled with aircraft overflights, were centered on red spruce stands in Vermont during August and September of 1984. Remote sensing data were acquired using the Airborne Imaging Spectrometer, Thematic Mapper Simulator, Barnes Model 12 to 1000 Modular Multiband Radiometer and Spectron Engineering Spectrometer (the former two flown on the NASA C-130; the latter two on A Bell UH-1B Iroquois Helicopter). Field spectral data were acquired during the week of the August overflights using a high spectral resolution spectrometer and two broad-band radiometers. Preliminary analyses of these data indicate a number of spectral differences in vegetation between high and low damage sites. Some of these differences are subtle, and are observable only with high spectral resolution sensors; others are less subtle and are observable using broad-band sensors.

  18. Early indications of soil recovery from acidic deposition in U.S. red spruce forests

    USGS Publications Warehouse

    Lawrence, Gregory B.; Shortle, Walter C.; David, Mark B.; Smith, Kevin T.; Warby, Richard A.F.; Lapenis, Andrei G.

    2012-01-01

    Forty to fifty percent decreases in acidic deposition through the 1980s and 1990s led to partial recovery of acidified surface waters in the northeastern United States; however, the limited number of studies that have assessed soil change found increased soil acidification during this period. From existing data, it's not clear whether soils continued to worsen in the 1990s or if recovery had begun. To evaluate possible changes in soils through the 1990s, soils in six red spruce (Picea rubens Sarg.) stands in New York, Vermont, New Hampshire, and Maine, first sampled in 1992 to 1993, were resampled in 2003 to 2004. The Oa-horizon pH increased (P 42−, which decreased the mobility of Al throughout the upper soil profile. Results indicate a nascent recovery driven largely by vegetation processes.

  19. Simulation of acid mine drainage generation around Küre VMS Deposits, Northern Turkey

    NASA Astrophysics Data System (ADS)

    Demirel, Cansu; Kurt, Mehmet Ali; Çelik Balci, Nurgül

    2015-04-01

    experiments with mixed acidophiles at higher temperatures. Further depleted Fe(III) values coinciding with decreasing pH may point to precipitation of secondary phases (i.e. jarosite). This study revealed that the metals (Fe, Cu, Co and Zn) released during short term leaching of the ore (34 days) are generally caused by acid produced by dissolution reactions rather than oxidation. In the long term experiments a more complex biogeochemical reactions (oxidation and dissolution) take place in conjunction. Key words: Bioleaching, AMD, heavy metal release, environment, acidophilic bacteria, Küre copper ore deposits, volcanogenic massive sulfide deposits

  20. Sulfuric acid karst and its relationship to hydrocarbon reservoir porosity, native sulfur deposits, and the origin of Mississippi Valley-type ore deposits

    SciTech Connect

    Hill, C.A. , Albuquerque, NM )

    1993-03-01

    The Delaware Basin of southeastern New Mexico and West Texas contains hydrocarbons and native sulfur in the basin and sulfuric acid-formed caves and Mississippi Valley-type (MVT) ore deposits around the margins of the basin. Hydrocarbons reacting with sulfate evaporite rock produced hydrogen sulfide gas, which gas oxidized to native sulfur in the basin and which gas also migrated from basin to reef and accumulated there in structural and stratigraphic traps. In the reduced zone of the carbonate reef margin the H[sub 2]S combined with metal-chloride complexes to form MVTs, and in the oxidized zone later in time the H[sub 2]S formed sulfuric acid which dissolved out the famous caves of the region (e.g., Carlsbad Cavern, Lechuguilla Cave). Sulfuric acid karst can be recognized by the discontinuity, large size, and spongework nature of its cave passages, and by the presence of native sulfur, endellite, and large gypsum deposits within these caves. Sulfuric acid oilfield karst refers to cavernous porosity filled with hydrocarbons and can be produced by the mixing of waters of different H[sub 2]S content or by the oxidation of H[sub 2]S to sulfuric acid. Sulfur and carbon-oxygen isotopes have been used to establish and trace the sequence of related hydrocarbon, sulfur, MVT, and karst events in the Delaware Basin.

  1. Acidic deposition, cation mobilization, and biochemical indicators of stress in healthy red spruce

    SciTech Connect

    Shortle, W.C.; Smith, K.T.; Minocha, R.

    1997-05-01

    Dendrochemical and biochemical markers link stress in apparently healthy red spruce trees (Picea rubens) to acidic deposition. Previous reports related visible damage of trees at high elevations to root and soil processes. In this report, dendrochemical and foliar biochemical markers indicate perturbations in biological processes in healthy red spruce trees across the northeastern USA. Previous research on the dendrochemistry of red spruce stemwood indicated that under uniform environmental conditions, stemwood concentrations of Ca and Mg decreased with increasing radial distance from the pith. For nine forest locations, frequency analysis shows that 28 and 52% of samples of red spruce stemwood formed in the 1960s are enriched in Ca and Mg, respectively, relative to wood formed prior to and after the 1960s. This enrichment in trees throughout the northeastern USA may be interpretable as a signal of increased availability of essential cations in forest soils. Such a temporary increase in the availability of Ca and Mg could be caused by cation mobilization, a consequence of increased acidic deposition. During cation mobilization, essential and Ca and Mg as well as potentially harmful Al become more available for interaction with binding sites in the soil and absorbing roots. As conditions which favor cation mobilization continue, Ca and Mg can be leached or displaced from the soil. A measure of the interaction between Ca and Al is the Al/Ca binding ratio (molar charge ratio of exchangeable Al to exchangeable Ca). As the Al/Ca binding ratio in the root zone increased from 0.3 to 1.9, the foliar concentration of the biochemical stress marker putrescine also increased form 45 to 145 nm g{sup {minus}1}. The correlation of the putrescine concentration to the Al/Ca binding ratio (adj. r{sup 2} = 0.68, P <0.027) suggests that foliar stress may be linked to soil chemistry. 32 refs., 2 figs., 1 tab.

  2. Colloidal asphaltene deposition in laminar pipe flow: Flow rate and parametric effects

    NASA Astrophysics Data System (ADS)

    Hashmi, S. M.; Loewenberg, M.; Firoozabadi, A.

    2015-08-01

    Deposition from a suspended phase onto a surface can aversely affect everyday transport processes on a variety of scales, from mineral scale corrosion of household plumbing systems to asphaltene deposition in large-scale pipelines in the petroleum industry. While petroleum may be a single fluid phase under reservoir conditions, depressurization upon production often induces a phase transition in the fluid, resulting in the precipitation of asphaltene material which readily aggregates to the colloidal scale and deposits on metallic surfaces. Colloidal asphaltene deposition in wellbores and pipelines can be especially problematic for industrial purposes, where cleanup processes necessitate costly operational shutdowns. In order to better understand the parametric dependence of deposition which leads to flow blockages, we carry out lab-scale experiments under a variety of material and flow conditions. We develop a parametric scaling model to understand the fluid dynamics and transport considerations governing deposition. The lab-scale experiments are performed by injecting precipitating petroleum fluid mixtures into a small metal pipe, which results in deposition and clogging, assessed by measuring the pressure drop across the pipe. Parametric scaling arguments suggest that the clogging behavior is determined by a combination of the Peclet number, volume fraction of depositing material, and the volume of the injection itself.

  3. DETERMINATION OF PARTICLE DEPOSITION RATES FOR COOKING AND OTHER INDOOR SOURCE

    EPA Science Inventory

    Residential indoor particle concentrations are dependent on indoor sources, penetration of outdoor particles, air change with outdoors, and deposition of particles on indoor surfaces as well as other loss mechanisms. Of these factors, few data are available on deposition of pa...

  4. Recycling of metal-organic chemical vapor deposition waste of GaN based power device and LED industry by acidic leaching: Process optimization and kinetics study

    NASA Astrophysics Data System (ADS)

    Swain, Basudev; Mishra, Chinmayee; Kang, Leeseung; Park, Kyung-Soo; Lee, Chan Gi; Hong, Hyun Seon; Park, Jeung-Jin

    2015-05-01

    Recovery of metal values from GaN, a metal-organic chemical vapor deposition (MOCVD) waste of GaN based power device and LED industry is investigated by acidic leaching. Leaching kinetics of gallium rich MOCVD waste is studied and the process is optimized. The gallium rich waste MOCVD dust is characterized by XRD and ICP-AES analysis followed by aqua regia digestion. Different mineral acids are used to find out the best lixiviant for selective leaching of the gallium and indium. Concentrated HCl is relatively better lixiviant having reasonably faster kinetic and better leaching efficiency. Various leaching process parameters like effect of acidity, pulp density, temperature and concentration of catalyst on the leaching efficiency of gallium and indium are investigated. Reasonably, 4 M HCl, a pulp density of 50 g/L, 100 °C and stirring rate of 400 rpm are the effective optimum condition for quantitative leaching of gallium and indium.

  5. Effects of deposition rate on the structure and electron density of evaporated BaSi2 films

    NASA Astrophysics Data System (ADS)

    Hara, Kosuke O.; Trinh, Cham Thi; Arimoto, Keisuke; Yamanaka, Junji; Nakagawa, Kiyokazu; Kurokawa, Yasuyoshi; Suemasu, Takashi; Usami, Noritaka

    2016-07-01

    In order to control the electrical properties of an evaporated BaSi2 film, which is an emerging candidate for the absorber-layer material of earth-abundant thin-film solar cells, we have investigated the effects of deposition rate on the produced phases, microstructure, and carrier density of the thin films grown by thermal evaporation of BaSi2. X-ray diffraction results show that a high substrate temperature is necessary for BaSi2 formation at a high deposition rate, which is discussed from viewpoints of vapor composition and diffusion time. Microstructural characteristics such as grain size of 30-120 nm, oxide particle arrays present around the interface, and partial oxidation at a low substrate temperature are revealed by cross-sectional transmission electron microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy combined with an energy-dispersive X-ray spectroscopy. With increasing deposition rate, the crystalline quality of BaSi2 is found to improve, as evidenced by a decrease in full-width at half maximum of a [ Si 4 ] 4 - vibration band in Raman spectra. At the same time, electron density, which is determined by Hall measurement, decreases with deposition rate. The variation of electron density is discussed on the basis of microstructural characteristics and BaSi2 formation mechanism. The most probable reason is concluded to be composition deviation from stoichiometry.

  6. An evaluation of the regional acid deposition model surface module for ozone uptake at three sites in the San Joaquin Valley of California

    NASA Technical Reports Server (NTRS)

    Massman, W. J.; Pederson, J.; Delany, A.; Grantz, D.; Hertog, G. Den; Neumann, H. H.; Oncley, S. P.; Pearson, R., Jr.; Shaw, R. H.

    1994-01-01

    Plants and soils act as major sinks for the destruction of tropospheric ozone, especially during daylight hours when plant stomata open and are thought to provide the dominant pathway for the uptake of ozone. The present study, part of the California Ozone Deposition Experiment, compares predictions of the regional acid deposition model ozone surface conductance module with surface conductance data derived from eddy covariance measurements of ozone flux taken at a grape, a cotton, and a grassland site in the San Joaquin Valley of California during the summer of 1991. Results indicate that the model (which was developed to provide long-term large-area estimates for the eastern United States) significantly overpredicts the surface conductance at all times of the day for at least two important types of plant cover of the San Joaquin Valley and that it incorrectly partitions the ozone flux between transpiring and nontranspiring components of the surface at the third site. Consequently, the model either overpredicts or inaccurately represents the observed deposition velocities. Other results indicate that the presence of dew does not reduce the rate of ozone deposition, contradicting to model assumptions, and that model assumptions involving the dependency of stomata upon environmental temperature are unnecessary. The effects of measurement errors and biases, arising from the presence of the roughness sublayer and possible photochemical reactions, are also discussed. A simpler model for ozone surface deposition (at least for the San Joaquin Valley) is proposed and evaluated.

  7. An evaluation of the regional acid deposition model surface module for ozone uptake at three sites in the San Joaquin Valley of California

    NASA Astrophysics Data System (ADS)

    Massman, W. J.; Pederson, J.; Delany, A.; Grantz, D.; den Hartog, G.; Neumann, H. H.; Oncley, S. P.; Pearson, R.; Shaw, R. H.

    1994-04-01

    Plants and soils act as major sinks for the destruction of tropospheric ozone, especially during daylight hours when plant stomata open and are thought to provide the dominant pathway for the uptake of ozone. The present study, part of the California Ozone Deposition Experiment, compares predictions of the regional acid deposition model ozone surface conductance module with surface conductance data derived from eddy covariance measurements of ozone flux taken at a grape, a cotton, and a grassland site in the San Joaquin Valley of California during the summer of 1991. Results indicate that the model (which was developed to provide long-term large-area estimates for the eastern United States) significantly overpredicts the surface conductance at all times of the day for at least two important types of plant cover of the San Joaquin Valley and that it incorrectly partitions the ozone flux between transpiring and nontranspiring components of the surface at the third site. Consequently, the model either overpredicts or inaccurately represents the observed deposition velocities. Other results indicate that the presence of dew does not reduce the rate of ozone deposition, contradicting to model assumptions, and that model assumptions involving the dependency of stomata upon environmental temperature are unnecessary. The effects of measurement errors and biases, arising from the presence of the roughness sublayer and possible photochemical reactions, are also discussed. A simpler model for ozone surface deposition (at least for the San Joaquin Valley) is proposed and evaluated.

  8. Liquid-Phase Heat-Release Rates of the Systems Hydrazine-Nitric Acid and Unsymmetrical Dimethylhydrazine-Nitric Acid

    NASA Technical Reports Server (NTRS)

    Somogyi, Dezso; Feiler, Charles E.

    1960-01-01

    The initial rates of heat release produced by the reactions of hydrazine and unsymmetrical dimethylhydrazine with nitric acid were determined in a bomb calorimeter under conditions of forced mixing. Fuel-oxidant weight ratio and injection velocity were varied. The rate of heat release apparently depended on the interfacial area between the propellants. Above a narrow range of injection velocities representing a critical amount of interfacial area, the rates reached a maximum and were almost constant with injection velocity. The maximum rate for hydrazine was about 70 percent greater than that for unsymmetrical dimethylhydrazine. The total heat released did not vary with mixture ratio over the range studied.

  9. Patterns of acid deposition variability in the Eastern United States, 1981-84

    USGS Publications Warehouse

    Lins, H.F.; Lanfear, K.J.; Schertz, T.L.

    1987-01-01

    An increase in pH and a decrease in sulfate concentration of precipitation were recorded at National Atmospheric Deposition Program and National Trends Network (NADP/NTN) monitoring sites in the Eastern United States between 1981 and 1984. The decline in acidity, however, was not spatially or temporally uniform. The range in acidity and sulfate concentrations decreased during the four-yr period. Variations in the area of constant pH surfaces take the general form of area reductions in both the lower (pH 4.01-4.40) and upper (pH 4.91-5.40) range of values with concomitant area increases in the middle (pH 4.41-4.90) range. The pattern for sulfate is simpler, with area increases occurring in the lower (1.0-1.9 mg/L) range, decreases in the upper (2.5-4.4 mg/L) range, with approximate stability in the middle (2.0-2.4 mg/L) range of values. (Author 's abstract)

  10. Acid deposition in the Athabasca Oil Sands Region: a policy perspective.

    PubMed

    Whitfield, Colin J; Watmough, Shaun A

    2015-12-01

    Industrial emissions of sulphur (S) and nitrogen (N) to the atmosphere associated with the oil sands industry in north-eastern Alberta are of interest as they represent the largest localized source in Canada (with potential for future growth) and the region features acid-sensitive upland terrain. Existing emission management policy for the Regional Municipality of Wood Buffalo, where the industry is located, is based on a time-to-effect approach that relies on dynamic model simulations of temporal changes in chemistry and features highly protective chemical criteria. In practice, the policy is difficult to implement and it is unlikely that a scientifically defensible estimate of acidification risk can be put forward due to the limitations primarily associated with issues of scale, chemical endpoint designation (selection of chemical limit for ecosystem protection from acidification) and data availability. A more implementable approach would use a steady-state critical load (CL) assessment approach to identify at-risk areas. The CL assessment would consider areas of elevated acid deposition associated with oil sands emissions rather than targeted political jurisdictions. Dynamic models should only be (strategically) used where acidification risk is identified via CL analysis, in order to characterize the potential for acidification-induced changes that can be detrimental to sensitive biota within the lifespan of the industry. PMID:26607154

  11. 210Pb mass accumulation rates in the depositional area of the Magra River (Mediterranean Sea, Italy)

    NASA Astrophysics Data System (ADS)

    Delbono, I.; Barsanti, M.; Schirone, A.; Conte, F.; Delfanti, R.

    2016-08-01

    Nine sediment cores were collected between 2009 and 2012 in the inner continental shelf (Mediterranean Sea, Italy) mainly influenced by the Magra River, at water depths ranging from 11 to 64 m. Mass Accumulation Rates (MARs) were calculated through 210Pb analysed by Gamma spectrometry. Three different dating models (single and two-layer CF-CS, CRS) were applied to clay normalised 210Pbxs profiles and 137Cs was used to validate the 210Pb geochronology. The maximum MAR values (>2 g cm-2 yr-1) were found in the region adjacent to the Magra River mouth and outside the Gulf of La Spezia (0.9±0.1 g cm-2 yr-1 at St. 3-C6 and 4-C4). Results from 137Cs/210Pbxs ratios calculated in Surface Mixed Layers (SMLs) evidenced the coastal boundaries of the Magra River depositional area, which is very limited towards south. Differently, in the north-west sector, fine sediments are generally driven by the Ligurian Current and move towards north-west: at the deepest and most distant station from the River mouth, the MAR value is the lowest one in the study area. Few major Magra River floods occurred during the sediment core sampling period. By using the short-lived radioisotope 7Be as a tracer of river floods, a clear 7Be signature of 2009 flood is present at St. 1-SA1C. Finally, by analyzing the clay normalised 210Pbxs profiles, a decrease of its activity dating the years 1999 and 2000 is observed in four cores, corresponding to two major Magra River floods occurring in those years.

  12. Protodeboronation of Heteroaromatic, Vinyl, and Cyclopropyl Boronic Acids: pH-Rate Profiles, Autocatalysis, and Disproportionation.

    PubMed

    Cox, Paul A; Leach, Andrew G; Campbell, Andrew D; Lloyd-Jones, Guy C

    2016-07-27

    pH-rate profiles for aqueous-organic protodeboronation of 18 boronic acids, many widely viewed as unstable, have been studied by NMR and DFT. Rates were pH-dependent, and varied substantially between the boronic acids, with rate maxima that varied over 6 orders of magnitude. A mechanistic model containing five general pathways (k1-k5) has been developed, and together with input of [B]tot, KW, Ka, and KaH, the protodeboronation kinetics can be correlated as a function of pH (1-13) for all 18 species. Cyclopropyl and vinyl boronic acids undergo very slow protodeboronation, as do 3- and 4-pyridyl boronic acids (t0.5 > 1 week, pH 12, 70 °C). In contrast, 2-pyridyl and 5-thiazolyl boronic acids undergo rapid protodeboronation (t0.5 ≈ 25-50 s, pH 7, 70 °C), via fragmentation of zwitterionic intermediates. Lewis acid additives (e.g., Cu, Zn salts) can attenuate (2-pyridyl) or accelerate (5-thiazolyl and 5-pyrazolyl) fragmentation. Two additional processes compete when the boronic acid and the boronate are present in sufficient proportions (pH = pKa ± 1.6): (i) self-/autocatalysis and (ii) sequential disproportionations of boronic acid to borinic acid and borane. PMID:27355973

  13. Accretion rate of extraterrestrial matter: Iridium deposited over the last 70 million years

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    1988-01-01

    In order to quantify the accretion rate of extraterrestrial matter during the Cenozoic, Ir concentrations were measured in a continuous series of 450 samples across most of the length of piston core LL44-GPC3. LL44-GPC3 is a 25-meter-long, large-diameter piston core of abyssal clay from the central North Pacific. This core contains a nearly continuous record of sedimentation over the last 70 Ma, as this site migrated from a region near the Equator in the late Cretaceous to its present position north of Hawaii. The first-cut survey across the core is nearing completion, and all of the conclusions of the earlier study, in which was reported the concentrations of Ir, Co, and Sb across 9 meters of this core, remain unchanged. The only strongly enhanced Ir concentrations occur at the Cretaceous-Tertiary (K-T) boundary and outside the K-T boundary Ir correlates well with Co, a terrestrial element which is largely present in hydrogenous ferromanganese oxide precipitates from seawater. Concentrations of both elements appear to be inversely correlated with the sedimentation rate. Although the K-T Ir anomaly is unique in magnitude in this core, there are several small bumps in the Ir profile which may reflect smaller accretionary events. The most promising Ir enhancement was observed in a 30 cm section approximately 1 m below the K-T boundary. Preliminary data suggest deposition of an excess across this interval at a time estimate to be approximate 1 Ma before the K-T impact event, but there is insufficient evidence at present to prove that this reflects enhanced accretion of extraterrestrial matter. A detailed model is being prepared of the chemical record of sedimentation in this core using a combined database of 39 elements in approximately 450 samples across the Cenozoic. Preliminary working model indicates that the only sedimentary sources which contribute significantly to the Ir budget in this core are the hydrogenous precipitates and extraterrestrial particulates.

  14. Measurement of Fatty Acid Oxidation Rates in Animal Tissues and Cell Lines

    PubMed Central

    Huynh, Frank K.; Green, Michelle F.; Koves, Timothy R.; Hirschey, Matthew D.

    2014-01-01

    While much oncological research has focused on metabolic shifts in glucose and amino acid oxidation, recent evidence suggests that fatty acid oxidation (FAO) may also play an important role in the metabolic reprogramming of cancer cells. Here, we present a simple method for measuring FAO rates using radiolabeled palmitate, common laboratory reagents, and standard supplies. This protocol is broadly applicable for measuring FAO rates in cultured cancer cells as well as in both malignant and nontransformed animal tissues. PMID:24862277

  15. Wetlands serve as natural sources for improvement of stream ecosystem health in regions affected by acid deposition

    USGS Publications Warehouse

    Pound, Katrina L; Lawrence, Gregory B.; Passy, Sophia I.

    2013-01-01

    For over 40 years, acid deposition has been recognized as a serious international environmental problem, but efforts to restore acidified streams and biota have had limited success. The need to better understand the effects of different sources of acidity on streams has become more pressing with the recent increases in surface water organic acids, or 'brownification' associated with climate change and decreased inorganic acid deposition. Here, we carried out a large scale multi-seasonal investigation in the Adirondacks, one of the most acid-impacted regions in the United States, to assess how acid stream producers respond to local and watershed influences and whether these influences can be used in acidification remediation. We explored the pathways of wetland control on aluminum chemistry and diatom taxonomic and functional composition. We demonstrate that streams with larger watershed wetlands have higher organic content, lower concentrations of acidic anions, and lower ratios of inorganic to organic monomeric aluminum, all beneficial for diatom biodiversity and guilds producing high biomass. Although brownification has been viewed as a form of pollution, our results indicate that it may be a stimulating force for biofilm producers with potentially positive consequences for higher trophic levels. Our research also reveals that the mechanism of watershed control of local stream diatom biodiversity through wetland export of organic matter is universal in running waters, operating not only in hard streams, as previously reported, but also in acid streams. Our findings that the negative impacts of acid deposition on Adirondack stream chemistry and biota can be mitigated by wetlands have important implications for biodiversity conservation and stream ecosystem management. Future acidification research should focus on the potential for wetlands to improve stream ecosystem health in acid-impacted regions and their direct use in stream restoration, for example, through

  16. Wetlands serve as natural sources for improvement of stream ecosystem health in regions affected by acid deposition.

    PubMed

    Pound, Katrina L; Lawrence, Gregory B; Passy, Sophia I

    2013-09-01

    For over 40 years, acid deposition has been recognized as a serious international environmental problem, but efforts to restore acidified streams and biota have had limited success. The need to better understand the effects of different sources of acidity on streams has become more pressing with the recent increases in surface water organic acids, or 'brownification,' associated with climate change and decreased inorganic acid deposition. Here, we carried out a large scale multi-seasonal investigation in the Adirondacks, one of the most acid-impacted regions in the United States, to assess how acid stream producers respond to local and watershed influences and whether these influences can be used in acidification remediation. We explored the pathways of wetland control on aluminum chemistry and diatom taxonomic and functional composition. We demonstrate that streams with larger watershed wetlands have higher organic content, lower concentrations of acidic anions, and lower ratios of inorganic to organic monomeric aluminum, all beneficial for diatom biodiversity and guilds producing high biomass. Although brownification has been viewed as a form of pollution, our results indicate that it may be a stimulating force for biofilm producers with potentially positive consequences for higher trophic levels. Our research also reveals that the mechanism of watershed control of local stream diatom biodiversity through wetland export of organic matter is universal in running waters, operating not only in hard streams, as previously reported, but also in acid streams. Our findings that the negative impacts of acid deposition on Adirondack stream chemistry and biota can be mitigated by wetlands have important implications for biodiversity conservation and stream ecosystem management. Future acidification research should focus on the potential for wetlands to improve stream ecosystem health in acid-impacted regions and their direct use in stream restoration, for example, through

  17. Acidic deposition and its effects on forest productivity: a review of the present state of knowledge, research activities, and information needs

    SciTech Connect

    Pinkerton, J.E.

    1981-01-01

    The present state of knowledge with regard to acid deposition is reviewed. Sources include the literature and direct contact with persons responsible for carrying out all completed, ongoing, and planned research activities, national and international, related to acidic deposition and its effects, with emphasis on forest productivity. In addition, a list of information needs in seven areas was developed, these include: a characterization of forest soils to define their sensitivity to acidic deposition; effects on forest soil chemical and biological processes; development of improved dry deposition measurement methods; changes in precipitation composition due to forest canopies; more extensive monitoring of acidic deposition in industry owned forest lands; expansion of long-term greenhouse and controlled field experiments; and the relationship of acidic deposition and intensive forestry management practices. 85 references. (MDF)

  18. Atmospheric deposition and canopy exchange of anions and cations in two plantation forests under acid rain influence

    NASA Astrophysics Data System (ADS)

    Shen, Weijun; Ren, Huili; Darrel Jenerette, G.; Hui, Dafeng; Ren, Hai

    2013-01-01

    Acid deposition as a widely concerned environmental problem in China has been less studied in plantation forests compared to urban and secondary forests, albeit they constitute 1/3 of the total forested areas of the country. We measured the rainwater amount and chemistry outside and beneath the canopies of two widely distributed plantations (Acacia mangium and Dimocarpus longan) in the severe acid rain influenced Pearl River Delta region of southeastern China for two years. Our results showed that the frequency of acid rain was 96% on the basis of pH value <5.6. The volume-weighted mean (vwm) pH was 4.62 and higher in the dry (Oct.-Mar.) than in the wet (Apr.-Sep.) seasons. The major acidic anion was sulfate with vwm concentration of 140 μeq l-1 and annual deposition flux of 110.3 kg ha-1 yr-1. The major neutralizing cations were calcium (94.8 μeq l-1 and 28 kg ha-1 yr-1) and ammonium (41.2 μeq l-1 and 11.7 kg ha-1 yr-1). Over 95% of these major acidic anions and neutralizing cations were derived from anthropogenic and terrestrial sources as a result of industrial, agricultural and forestry activities. Plantation canopy had marked impacts on rainwater chemistry, with the measured anion and cation concentrations being significantly enriched in throughfall (TF) and stemflow (SF) rainwater by 1.4 (for NO) to 20-fold (for K+) compared to those in bulk precipitation (BP). Dry deposition generally contributed about 13-22% of the total deposition while canopy leaching mainly occurred for K+ (>88%) and NH (10-38%). The two tree species showed distinct impacts on rainfall redistribution and rainwater chemistry due to their differences in canopy architecture and leaf/bark texture, suggesting that species-specific effects should not be overlooked while assessing the acid deposition in forested areas.

  19. MAPLE-deposited PFO films: influence of the laser fluence and repetition rate on the film emission and morphology

    NASA Astrophysics Data System (ADS)

    Caricato, A. P.; Anni, M.; Cesaria, M.; Lattante, S.; Leggieri, G.; Leo, C.; Martino, M.; Perulli, A.; Resta, V.

    2015-06-01

    The Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique is emerging as an alternative route to the conventional methods for depositing organic materials, although the MAPLE-deposited films very often present high surface roughness and characteristic morphological features. Films of the blue-emitting polymer, poly(9,9-dioctylfluorene)—PFO, have been deposited by MAPLE to investigate the influence of the laser fluence and repetition rate on both their topography and emission properties. The laser fluence has been changed from 150 up to 450 mJ/cm2, while laser repetition rates of 2 and 10 Hz have been considered. The interplay/relationship between the topography and the emission properties of the MAPLE-deposited films has been studied by confocal microscopy, photoluminescence spectrometry and atomic force microscopy. It has been found that under high irradiation (fluence of 450 mJ/cm2) conditions, the sample surface is characterized by bubbles presenting the intrinsic PFO blue emission. Instead, while improvements in the film morphology can be observed for lowered fluence and laser repetition rate, green emission becomes predominant in such conditions. Such result is very interesting to better understand the MAPLE ablation mechanism, which is discussed in this study.

  20. Impact of aerosol composition and foliage characteristics on forest canopy deposition rates: A laboratory study

    NASA Astrophysics Data System (ADS)

    Hornsby, K. E.; Pryor, S. C.

    2013-12-01

    Forests are a major sink for atmospheric aerosols. Hence it has been suggested that (i) increased tree planting in urban areas might lead to a reduction in aerosol particle concentrations and thus a reduction in respiratory conditions and heart complications, and (ii) forests may be responsible for removing a disproportionately large fraction of potentially climate-relevant fine and ultra-fine aerosol particles from the atmosphere. However, larger uncertainties remain with respect to controls on uptake rates for forests. E.g. the deposition flux partitioning between foliage and non-foliage elements, the influence of particle size and composition, the role of leaf surface morphology and stomatal aperture in surface uptake. Improved understanding of the relative importance of these factors and the variability across different tree species should help determine how much of a sink naturally occurring and planted forests can provide downstream of fine particle production. In this study, a sample of trees native to southern Indiana were exposed to ultra-fine aerosol particle populations in a 1.5 m x 1.5 m x 1.5 m Teflon chamber. Stable particle size distributions (PSD) with geometric mean diameters (GMD) ranging from 40 to 80 nm were generated from sodium chloride, ammonium nitrate, ammonium sulfate and sodium sulfite solutions using a TSI model 3940 Aerosol Generation System (AGS). The aerosol stream was diluted using scrubbed and dried zero air to allow a variation of total number concentration across two orders of magnitude. PSD in the chamber are continuously measured using a TSI Scanning Mobility Particle Spectrometer (SMPS) comprising an Electrostatic Classifier (EC model 3080) attached to a Long DMA (LDMA model 3081) and a TSI model 3025A Butanol Condensation Particle Counter (CPC) operated with both the internal diffusion loss and multiple charge corrections turned on. The composition of the chamber air was also monitored for carbon dioxide (CO2) and water vapor

  1. ACID DEPOSITION STRATEGIES, THE LIMB (LIMESTONE INJECTION/MULTISTAGE BURNERS) PROGRAM AND IMPLICATIONS FOR CONTROL TECHNOLOGY REQUIREMENTS

    EPA Science Inventory

    The paper summarizes the various acid deposition bills introduced in the U.S. Congress during the past 2 years and discusses emission sources. A rapidly emerging technology called Limestone Injection/Multistage Burners (LIMB), which has the potential for simultaneous SO2 and NOx ...

  2. CHARACTERIZATION OF PAINTED SURFACES IN THE UNITED STATES FROM THE PERSPECTIVE OF POTENTIAL DAMAGE FROM ACIDIC DEPOSITION

    EPA Science Inventory

    Data on the types and applications of exterior paints used in the United States are reviewed from the perspective of potential damage by air pollution or acidic deposition. The data indicate that, of the painted structures in the U.S., the costs of painting residential buildings ...

  3. Effects of varying media, temperature, and growth rates on the intracellular concentrations of yeast amino acids.

    PubMed

    Martínez-Force, E; Benítez, T

    1995-01-01

    Variations of the yeast free amino acid pool under different culture conditions were studied in two Saccharomyces strains, the laboratory haploid strain S288C and the industrial fermentative yeast IFI256. The internal amino acid pool of both strains was measured when grown in laboratory (minimal and complete) versus semiindustrial (molasses with or without added biotin and/or diammonium phosphate) media, in fermentable (glucose, fructose, sucrose) versus respirable (glycerol) carbon sources, in different temperatures (22, 30, and 37 degrees C), pHs (2.0-4.75), and growth rates (0.018-0.24 h-1) in continuous culture, and at different phases of the growth curve in batch culture (lag, exponential, early and late stationary). Results indicated that environmental conditions, particularly the presence of amino acids in the media, enormously influenced the intracellular amino acid concentration. Higher values were detected in molasses than in laboratory media and in fermentable carbon sources (glucose, fructose, sucrose) than in glycerol. Variations in the amino acid pool along the growth curve were greater at 37 degrees C than at other temperatures; in all cases, the highest values were measured at the beginning of the exponential phase. In continuous culture and at different growth rates, intracellular free amino acid concentrations increased by 3-10-fold when the growth rate was lower than 0.05 h-1, representing 20-35% of the total (free plus protein) amino acid content and indicating that amino acid yield was a partly growth-linked parameter. PMID:7654310

  4. Support Effects on Bronsted acid site densities and alcohol dehydration turnover rates on tungsten oxide domains

    SciTech Connect

    Macht, Josef; Baertsch, Chelsey D.; May-Lozano, Marcos; Soled, Stuart L.; Wang, Yong; Iglesia, Enrique

    2005-03-01

    Initial activity and acid site density of several WAl, WSi (MCM41) and one WSn sample were determined. Trans/cis 2-butene selectivity is dependent on the support. Presumably, these differences are due to subtle differences in base strengths. 2-Butanol dehydration rates (per W-atom) reached maximum values at intermediate WOx surface densities on WAl, as reported for 2-butanol dehydration reactions on WZr. Titration results indicate that Bronsted acid sites are required for 2-butanol dehydration on WAl, WSi and WSn. UV-visible studies suggest that WAl is much more difficult to reduce than WZr. The detection of reduced centers on WAl, the number of which correlates to Bronsted acid site density and catalyst activity, as well as the temperature dependence of Bronsted acid site density indicate the in-situ formation of these active sites. We infer that this mechanism is common among all supported WOx samples described in this study. Turnover rates are a function of Bronsted acid site density only. High acid site densities lead to high turnover rates. Higher active site densities may cause stronger conjugate bases, as a higher electron density has to be stabilized, and thus weaker acidity, enabling a faster rate of product desorption. The maximum achievable active site density is dependent on the support. WZr reaches a higher active site density than WAl.

  5. Rainwater trifluoroacetic acid (TFA) in Guangzhou, South China: levels, wet deposition fluxes and source implication.

    PubMed

    Wang, Qiaoyun; Wang, Xinming; Ding, Xiang

    2014-01-15

    The origin of trifluoroacetic acid (TFA) occurring in hydrosphere has long been a controversial issue. Hydrochlorofluorocarbons and hydrofluorocarbons (HCFCs/HFCs) as replacements of chlorofluorocarbons (CFCs) are precursors of TFA in the atmosphere, their contribution to rainwater TFA is a concern as their ambient mixing ratios are continually growing. Here we present rainwater TFA monitored from April 2007 to March 2008 in urban Guangzhou, a central city in south China's highly industrialized and densely populated Pearl River Delta region. Rainwater TFA levels ranged 45.8-974 ng L(-1) with a median of 166 ng L(-1). TFA levels negatively correlated with rainfall amount, the yearly rainfall-weighted average for TFA was 152 ng L(-1). The annual TFA wet deposition flux was estimated to be 229 g km(-2) yr(-1), and the total wet deposition of TFA reached ~1.7 tyr(-1) in Guangzhou. The Two-Box model was applied to estimate attributions of HCFCs/HFCs and fluoropolymers to rainwater TFA assuming TFA generated was proportional to gross domestic product (GDP), gross industrial product (GIP) or number of private cars. The results revealed that the degradation of HCFCs/HFCs and fluoropolymers could explain 131.5-152.4 ng L(-1) rainwater TFA, quite near the observed rainfall-weighted annual mean of 152 ng L(-1), suggesting rainwater TFA in Guangzhou was predominantly originated from these anthropogenic precursors. HCFCs/HFCs accounted for 83.3-96.5% of rainwater TFA observed, while fluoropolymers' contributions were minor (~5%). HFC-134a alone could explain 55.9-90.0% of rainwater TFA, and its contribution would be greatly enhanced with its wide use in mobile air conditioning systems and rapid increase in ambient mixing ratios. PMID:24035981

  6. Influence of variable rates of neritic carbonate deposition on atmospheric carbon dioxide and pelagic sediments

    NASA Technical Reports Server (NTRS)

    Walker, J. C.; Opdyke, B. C.

    1995-01-01

    Short-term imbalances in the global cycle of shallow water calcium carbonate deposition and dissolution may be responsible for much of the observed Pleistocene change in atmospheric carbon dioxide content. However, any proposed changes in the alkalinity balance of the ocean must be reconciled with the sedimentary record of deep-sea carbonates. The possible magnitude of the effect of shallow water carbonate deposition on the dissolution of pelagic carbonate can be tested using numerical simulations of the global carbon cycle. Boundary conditions can be defined by using extant shallow water carbonate accumulation data and pelagic carbonate deposition/dissolution data. On timescales of thousands of years carbonate deposition versus dissolution is rarely out of equilibrium by more than 1.5 x 10(13) mole yr-1. Results indicate that the carbonate chemistry of the ocean is rarely at equilibrium on timescales less than 10 ka. This disequilibrium is probably due to sea level-induced changes in shallow water calcium carbonate deposition/dissolution, an interpretation that does not conflict with pelagic sedimentary data from the central Pacific.

  7. Influence of variable rates of neritic carbonate deposition on atmospheric carbon dioxide and pelagic sediments.

    PubMed

    Walker, J C; Opdyke, B C

    1995-06-01

    Short-term imbalances in the global cycle of shallow water calcium carbonate deposition and dissolution may be responsible for much of the observed Pleistocene change in atmospheric carbon dioxide content. However, any proposed changes in the alkalinity balance of the ocean must be reconciled with the sedimentary record of deep-sea carbonates. The possible magnitude of the effect of shallow water carbonate deposition on the dissolution of pelagic carbonate can be tested using numerical simulations of the global carbon cycle. Boundary conditions can be defined by using extant shallow water carbonate accumulation data and pelagic carbonate deposition/dissolution data. On timescales of thousands of years carbonate deposition versus dissolution is rarely out of equilibrium by more than 1.5 x 10(13) mole yr-1. Results indicate that the carbonate chemistry of the ocean is rarely at equilibrium on timescales less than 10 ka. This disequilibrium is probably due to sea level-induced changes in shallow water calcium carbonate deposition/dissolution, an interpretation that does not conflict with pelagic sedimentary data from the central Pacific. PMID:11540240

  8. Formation rates, stability and reactivity of sulfuric acid - amine clusters predicted by computational chemistry

    NASA Astrophysics Data System (ADS)

    Kurtén, Theo; Ortega, Ismael; Kupiainen, Oona; Olenius, Tinja; Loukonen, Ville; Reiman, Heidi; McGrath, Matthew; Vehkamäki, Hanna

    2013-04-01

    Despite the importance of atmospheric particle formation for both climate and air quality, both experiments and non-empirical models using e.g. sulfuric acid, ammonia and water as condensing vapors have so far been unable to reproduce atmospheric observations using realistic trace gas concentrations. Recent experimental and theoretical evidence has shown that this mystery is likely resolved by amines. Combining first-principles evaporation rates for sulfuric acid - dimethylamine clusters with cluster kinetic modeling, we show that even sub-ppt concentrations of amines, together with atmospherically realistic concentrations of sulfuric acid, result in formation rates close to those observed in the atmosphere. Our simulated cluster formation rates are also close to, though somewhat larger than, those measured at the CLOUD experiment in CERN for both sulfuric acid - ammonia and sulfuric acid - dimethylamine systems. A sensitivity analysis indicates that the remaining discrepancy for the sulfuric acid - amine particle formation rates is likely caused by steric hindrances to cluster formation (due to alkyl groups of the amine molecules) rather than by significant errors in the evaporation rates. First-principles molecular dynamic and reaction kinetic modeling shed further light on the microscopic physics and chemistry of sulfuric acid - amine clusters. For example, while the number and type of hydrogen bonds in the clusters typically reach their equilibrium values on a picosecond timescale, and the overall bonding patterns predicted by traditional "static" quantum chemical calculations seem to be stable, the individual atoms participating in the hydrogen bonds continuously change at atmospherically realistic temperatures. From a chemical reactivity perspective, we have also discovered a surprising phenomenon: clustering with sulfuric acid molecules slightly increases the activation energy required for the abstraction of alkyl hydrogens from amine molecules. This implies

  9. Determination of the reaction rate coefficient of sulphide mine tailings deposited under water.

    PubMed

    Awoh, Akué Sylvette; Mbonimpa, Mamert; Bussière, Bruno

    2013-10-15

    The efficiency of a water cover to limit dissolved oxygen (DO) availability to underlying acid-generating mine tailings can be assessed by calculating the DO flux at the tailings-water interface. Fick's equations, which are generally used to calculate this flux, require knowing the effective DO diffusion coefficient (Dw) and the reaction (consumption) rate coefficient (Kr) of the tailings, or the DO concentration profile. Whereas Dw can be accurately estimated, few studies have measured the parameter Kr for submerged sulphide tailings. The objective of this study was to determine Kr for underwater sulphide tailings in a laboratory experiment. Samples of sulphide mine tailings (an approximately 6 cm layer) were placed in a cell under a water cover (approximately 2 cm) maintained at constant DO concentration. Two tailings were studied: TA1 with high sulphide content (83% pyrite) and TA2 with low sulphide content (2.8% pyrite). DO concentration was measured with a microelectrode at various depths above and below the tailings-water interface at 1 mm intervals. Results indicate that steady-state condition was rapidly attained. As expected, a diffusive boundary layer (DBL) was observed in all cases. An iterative back-calculation process using the numerical code POLLUTEv6 and taking the DBL into account provided the Kr values used to match calculated and experimental concentration profiles. Kr obtained for tailings TA1 and TA2 was about 80 d(-1) and 6.5 d(-1), respectively. For comparison purposes, Kr obtained from cell tests on tailings TA1 was lower than Kr calculated from the sulphate production rate obtained from shake-flask tests. Steady-state DO flux at the water-tailings interface was then calculated with POLLUTEv6 using tailings characteristics Dw and Kr. For the tested conditions, DO flux ranged from 608 to 758 mg O2/m(2)/d for tailings TA1 and from 177 to 221 mg O2/m(2)/d for tailings TA2. The impact of placing a protective layer of inert material over

  10. Variation of Atmospheric Deposition of Acid Species and Yellow Sand Particles From 1987 to 1999 Through Modeling Studies and Observations

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Uno, I.; Zhang, M.; Akimoto, H.

    2002-05-01

    Acid deposition is of serious environmental concern in East Asia. Wet and dry deposition monitoring datasets have been collected for long enough to understand the deposition distribution and its variation in time and space in this region Field observations indicate that acid precipitation often occurs in the southern part of China, even though emissions of the precursors are stronger in the north, where such high levels of strong acids in precipitation have not been widely. The acidity of rainwater is heavily influenced and modified by natural soil dust from desert and semi-arid areas. This soil aerosol, or _gKOSA", is lifted from Asian deserts and the Loess plateau, and then carried by the prevailing wind over East Asia. A comprehensive Air Quality Prediction Modeling System (AQPMS) is used to perform year-long, quantitative simulation of rainwater pH in East Asia for 1987 and 1999, respectively with emissions of Akimoto et al.(1987) and Street et al.(2000), to discuss the variation of deposition of acid species and yellow sand particles due to the emission change in the past dozen years. Monitoring data at 17 sites of EANET (the Acid Deposition Monitoring Network in East Asia) in addition to the field observation data of SEPA(State Environmental Protection Agency) of China are used to evaluate the model, and a reasonable agreement is obtained. Emission in Sichuan province has decreased and emission in central China including Hubei province and Hunan province has increased. Model simulation shows the change of emission pattern caused the serious acid-rain-hit area moving southeastward as observed. In the west part of Sichuan province, the pH value increased, this is partly due to the success of countermeasures against acid rain in China since 1996, which reduce the emission in Sichuan area much more than expected. The variations of annual distribution of rain pH, sulfate, nitrite and yellow sand particles deposition are also discussed in detail, so do the

  11. ESTIMATION OF PHOSPHATE ESTER HYDROLYSIS RATE CONSTANTS. II. ACID AND GENERAL BASE CATALYZED HYDROLYSIS

    EPA Science Inventory

    SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to calculate acid and neutral hydrolysis rate constants of phosphate esters in water. The rate is calculated from the energy difference between the initial and transition states of a ...

  12. The effect of limestone treatments on the rate of acid generation from pyritic mine gangue.

    PubMed

    Burt, R A; Caruccio, F T

    1986-09-01

    Surface water enters the Haile Gold Mine, Lancaster County, South Carolina by means of a small stream and is ponded behind a dam and in an abandoned pit. This water is affected by acidic drainage. In spite of the large exposures of potentially acid producing pyritic rock, the flux of acid to the water is relatively low. Nevertheless, the resulting pH values of the mine water are low (around 3.5) due to negligible buffering capacity. In view of the observed low release of acidity, the potential for acid drainage abatement by limestone ameliorants appears feasible.This study investigated the effects of limestone treatment on acid generation rates of the Haile mine pyritic rocks through a series of leaching experiments. Below a critical alkalinity threshold value, solutions of dissolved limestone were found consistently to accelerate the rate of pyrite oxidation by varying degrees. The oxidation rates were further accelerated by admixing solid limestone with the pyritic rock. However, after a period of about a month, the pyrite oxidation rate of the admixed samples declined to a level lower than that of untreated pyrite. Leachates produced by the pyrite and limestone mixtures contained little if any iron. Further, in the mixtures, an alteration of the pyrite surface was apparent.The observed behaviour of the treated pyrite appears to be related to the immersion of the pyrite grains within a high alkalinity/high pH environment. The high pH increases the rate of oxidation of ferrous iron which results in a higher concentration of ferric iron at the pyrite surface. This, in turn, increases the rate of pyrite oxidation. Above a threshold alkalinity value, the precipitation of hydrous iron oxides at the pyrite surface eventually outpaces acid generation and coats the pyrite surface, retarding the rate of pyrite oxidation. PMID:24214013

  13. Spatial distribution of average charge state and deposition rate in high power impulse magnetron sputtering of copper

    SciTech Connect

    Anders, Andre; Horwat, David; Anders, Andre

    2008-05-10

    The spatial distribution of copper ions and atoms in high power impulse magnetron sputtering (HIPIMS) discharges was determined by (i) measuring the ion current to electrostatic probes and (ii) measuring the film thickness by profilometry. A set of electrostatic and collection probes were placed at different angular positions and distances from the target surface. The angular distribution of the deposition rate and the average charge state of the copper species (including ions and neutrals) were deduced.The discharge showed a distinct transition to a high current mode dominated by copper self-sputtering when the applied voltage exceeded the threshold of 535 V. For a lower voltage, the deposition rate was very low and the average charge state was found to be less than 0.4. For higher voltage (and average power), the absolute deposition rates were much higher, but they were smaller than the corresponding direct current (DC) rates if normalized to the same average power. At the high voltage level, the spatial distribution of the average charge state showed some similarities with the distribution of the magnetic field, suggesting that the generation and motion of copper ions is affected by magnetized electrons. At higher voltage, the average charge state increases with the distance from the target and locally may exceed unity, indicating the presence of significant amounts of doubly charged copper ions.

  14. Nitrogen cycling in s subarctic Alaskan watershed: the role of lichens and the potential effects of acid deposition

    SciTech Connect

    Gunther, A.J.

    1987-01-01

    It has been hypothesized that the loss of nitrogen-fixing lichens due to stress from air pollution could have adverse effects upon nitrogen availability, and thus primary productivity, in some ecosystems. There is general agreement, however, that the ecological role of these lichens has not been sufficiently well defined to determine whether they are keystone species. The objectives of this study were: (1) to examine the importance of nitrogen-fixing lichens to the nitrogen cycle in the drainage of Brooks Lake, Alaska, a nitrogen-limited nursery lake for the commercially important sockeye salmon (Oncorhychus nerka); and (2) to investigate the sensitivity of nitrogen fixation by lichens in this ecosystem to acid deposition. Biological nitrogen fixation was found to be the major source of new nitrogen to the Brooks Lake drainage. The rate of fixation is approximately 3 kg N/ha-yr, which compares to 0.3 kg N/ha-yr in precipitation and only 0.02 kg N/ha-yr in returning adult salmon. Cyanophillic lichens contribute about 0.21 kg N/ha-yr. The low levels of nitrogen in precipitation, combined with a lack of nitrogen-fixation activity in open lake waters, indicates that nitrogen in tributary streams is the major source of new nitrogen for Brooks Lake. The measurements of nitrogen inputs, along with estimates of other stocks and flows of nitrogen, were used to construct a steady-state box model of the nitrogen cycle in the drainage.

  15. Aquatic amphibians in the Sierra Nevada: Current status and potential effects of acidic deposition on populations. Final report

    SciTech Connect

    Bradford, D.F.; Gordon, M.S.

    1992-05-01

    Toxicity testing indicated that amphibians are at little risk from low pH in water acidified to a pH of 5.0 and aluminum concentrations from 39 to 80 micrograms/l. However, sublethal effects (reduced growth rate and earlier hatching) were observed for pH as high as 5.25 and the aluminum concentrations tested. The authors tested the hypothesis that acidification of habitats in the field has resulted in elimination of populationss from waters most vulnerable to acidification, i.e., low in pH or ANC, or from waters low in ionic strength a condition that increases the sensitivity of amphibians to low pH. The authors surveyed potential breeding sites for two declining and one non-declining species at high elevation within 30 randomly selected survey areas, and compared chemical parameters between sites containing a species and sites lacking the species. No significant differences were found that were consistent with the hypothesis, and water chemistry did not differ among sites inhabited by the three species. These findings imply that acidic deposition is unlikely to have been a cause of recent amphibian population declines in the Sierra Nevada.

  16. A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus

    NASA Astrophysics Data System (ADS)

    Vet, Robert; Artz, Richard S.; Carou, Silvina; Shaw, Mike; Ro, Chul-Un; Aas, Wenche; Baker, Alex; Bowersox, Van C.; Dentener, Frank; Galy-Lacaux, Corinne; Hou, Amy; Pienaar, Jacobus J.; Gillett, Robert; Forti, M. Cristina; Gromov, Sergey; Hara, Hiroshi; Khodzher, Tamara; Mahowald, Natalie M.; Nickovic, Slobodan; Rao, P. S. P.; Reid, Neville W.

    2014-08-01

    A global assessment of precipitation chemistry and deposition has been carried out under the direction of the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) Scientific Advisory Group for Precipitation Chemistry (SAG-PC). The assessment addressed three questions: (1) what do measurements and model estimates of precipitation chemistry and wet, dry and total deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity, and phosphorus show globally and regionally? (2) has the wet deposition of major ions changed since 2000 (and, where information and data are available, since 1990) and (3) what are the major gaps and uncertainties in our knowledge? To that end, regionally-representative measurements for two 3-year-averaging periods, 2000-2002 and 2005-2007, were compiled worldwide. Data from the 2000-2002 averaging period were combined with 2001 ensemble-mean modeling results from 21 global chemical transport models produced in Phase 1 of the Coordinated Model Studies Activities of the Task Force on Hemispheric Transport of Air Pollution (TF HTAP). The measurement data and modeling results were used to generate global and regional maps of major ion concentrations in precipitation and deposition. A major product of the assessment is a database of quality assured ion concentration and wet deposition data gathered from regional and national monitoring networks. The database is available for download from the World Data Centre for Precipitation Chemistry (http://wdcpc.org/)

  17. Nicotinic acid supplementation in diet favored intramuscular fat deposition and lipid metabolism in finishing steers.

    PubMed

    Yang, Zhu-Qing; Bao, Lin-Bin; Zhao, Xiang-Hui; Wang, Can-Yu; Zhou, Shan; Wen, Lu-Hua; Fu, Chuan-Bian; Gong, Jian-Ming; Qu, Ming-Ren

    2016-06-01

    Nicotinic acid (NA) acting as the precursor of NAD(+)/NADH and NADP(+)/NADPH, participates in many biochemical processes, e.g. lipid metabolism. The main purpose of this study was to investigate the effects of dietary NA on carcass traits, meat quality, blood metabolites, and fat deposition in Chinese crossbred finishing steers. Sixteen steers with the similar body weight and at the age of 24 months were randomly allocated into control group (feeding basal diet) and NA group (feeding basal diet + 1000 mg/kg NA). All experimental cattle were fed a 90% concentrate diet and 10% forage straw in a 120-day feeding experiment. The results showed that supplemental NA in diet increased longissimus area, intramuscular fat content (17.14% vs. 9.03%), marbling score (8.08 vs. 4.30), redness (a*), and chroma (C*) values of LD muscle, but reduced carcass fat content (not including imtramuscular fat), pH24 h and moisture content of LD muscle, along with no effect on backfat thickness. Besides, NA supplementation increased serum HDL-C concentration, but decreased the serum levels of LDL-C, triglyceride, non-esterified fatty acid, total cholesterol, and glycated serum protein. In addition, NA supplementation increased G6PDH and ICDH activities of LD muscle. These results suggested that NA supplementation in diet improves the carcass characteristics and beef quality, and regulates the compositions of serum metabolites. Based on the above results, NA should be used as the feed additive in cattle industry. PMID:27048556

  18. Nitric acid dry deposition to conifer forests: Niwot Ridge spruce-fir-pine study

    USGS Publications Warehouse

    Sievering, H.; Kelly, T.; McConville, G.; Seibold, C.; Turnipseed, A.

    2001-01-01

    The dry deposition velocity of nitric acid, Vd(HNO3), over a 12-m (mean height) spruce-fir forest at Niwot Ridge, Colorado was estimated during 13 daytime periods using the flux-gradient approach. Turbulence intensity at this site is high (mean u* of 0.65ms-1 with u of 2.9ms-1) and contributed to the large observed Vd(HNO3). The overriding contributor is identified to be the small aerodynamic needle width of the conifer trees. Two cases had inflated Vd(HNO3) due to height-differentiated nitric acid loss to soil-derived particle surfaces. Not considering these cases, the mean Vd(HNO3) was 7.6cms-1. The mean laminar boundary layer resistance (Rb) was found to be 7.8sm-1 (of similar magnitude to that of the aerodynamic resistance, 8.5sm-1). The data-determined Rb is bracketed by two theoretical estimates of the mean Rb, 5.9 and 8.6sm-1, that include consideration of the small canopy length scale (aerodynamic needle width), 1mm or less, at this conifer forest. However, the poor correlation of data-determined Rb values with both sets of theoretical estimates indicates that measurement error needs to be reduced and/or improved formulations of theoretical Rb values are in order. The large observed Vd(HNO3) at this conifer forest site is attributed to high turbulence intensity, and, especially, to small aerodynamic needle width. Copyright ?? 2001 Elsevier Science Ltd.

  19. Atomic/Molecular Layer Deposition of Lithium Terephthalate Thin Films as High Rate Capability Li-Ion Battery Anodes.

    PubMed

    Nisula, Mikko; Karppinen, Maarit

    2016-02-10

    We demonstrate the fabrication of high-quality electrochemically active organic lithium electrode thin films by the currently strongly emerging combined atomic/molecular layer deposition (ALD/MLD) technique using lithium terephthalate, a recently found anode material for lithium-ion battery (LIB), as a proof-of-the-concept material. Our deposition process for Li-terephthalate is shown to well comply with the basic principles of ALD-type growth including the sequential self-saturated surface reactions, a necessity when aiming at micro-LIB devices with three-dimensional architectures. The as-deposited films are found crystalline across the deposition temperature range of 200-280 °C, which is a trait highly desired for an electrode material but rather unusual for hybrid inorganic-organic thin films. Excellent rate capability is ascertained for the Li-terephthalate films with no conductive additives required. The electrode performance can be further enhanced by depositing a thin protective LiPON solid-state electrolyte layer on top of Li-terephthalate; this yields highly stable structures with capacity retention of over 97% after 200 charge/discharge cycles at 3.2 C. PMID:26812433

  20. Determination of silica deposition rates and thresholds applied towards protection of injection reservoirs

    SciTech Connect

    Geothermal Development Associates; Don Michels Associates

    1999-07-01

    This program was instituted to quantify certain aspects of silica scaling deposition processes at the Miravalles Geothermal Field, Costa Rica. The program objective was to identify the highest temperature at which silica scale will develop from partially evaporated and significantly cooled geothermal liquid under operating conditions. Integral to the study objective was the quantification of certain aspects of silica deposition processes at the Miravalles Geothermal Field, Costa Rica. There, the objective was to reduce the scaling risk associated with adding a bottoming-cycle to generate more electricity from the liquids already being produced.

  1. Effects of acidic deposition on the erosion of carbonate stone - experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

    USGS Publications Warehouse

    Baedecker, P.A.; Reddy, M.M.; Reimann, K.J.; Sciammarella, C.A.

    1992-01-01

    One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30?? to horizontal at the five NAPAP materials exposure sites range from ~15 to ~30?? ??m yr-1 for marble, and from ~25 to ~45 ??m yr -1 for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ~30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ~70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide ('clean rain'). These results are for marble and limestone slabs exposed at an angle of 30?? from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60?? or 85??. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC

  2. Acid deposition in Maryland. Summary of research and monitoring results compiled through 1991 and a discussion of the 1990 Clean Air Act Amendments. Report for 1991-1992

    SciTech Connect

    Price, R.; Mountain, D.

    1992-10-01

    This is the sixth annual report submitted under Maryland legislative requirements. The report focuses on more than a decade of acid deposition research conducted in Maryland. In addition, the report discusses Title IV - Acid Deposition Control of the 1990 Clean Air Act Amendments (CAAA) and its potential impacts on Maryland.

  3. Chemically frozen multicomponent boundary layer theory of salt and/or ash deposition rates from combustion gases

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Chen, B.-K.; Fryburg, G. C.; Kohl, F. J.

    1979-01-01

    There is increased interest in, and concern about, deposition and corrosion phenomena in combustion systems containing inorganic condensible vapors and particles (salts, ash). To meet the need for a computationally tractable deposition rate theory general enough to embrace multielement/component situations of current and future gas turbine and magnetogasdynamic interest, a multicomponent chemically 'frozen' boundary layer (CFBL) deposition theory is presented and its applicability to the special case of Na2SO4 deposition from seeded laboratory burner combustion products is demonstrated. The coupled effects of Fick (concentration) diffusion and Soret (thermal) diffusion are included, along with explicit corrections for effects of variable properties and free stream turbulence. The present formulation is sufficiently general to include the transport of particles provided they are small enough to be formally treated as heavy molecules. Quantitative criteria developed to delineate the domain of validity of CFBL-rate theory suggest considerable practical promise for the present framework, which is characterized by relatively modest demands for new input information and computer time.

  4. Photosynthesis and oxidative stress in the restinga plant species Eugenia uniflora L. exposed to simulated acid rain and iron ore dust deposition: potential use in environmental risk assessment.

    PubMed

    Neves, Natália Rust; Oliva, Marco Antonio; da Cruz Centeno, Danilo; Costa, Alan Carlos; Ribas, Rogério Ferreira; Pereira, Eduardo Gusmão

    2009-06-01

    The Brazilian sandy coastal plain named restinga is frequently subjected to particulate and gaseous emissions from iron ore factories. These gases may come into contact with atmospheric moisture and produce acid rain. The effects of the acid rain on vegetation, combined with iron excess in the soil, can lead to the disappearance of sensitive species and decrease restinga biodiversity. The effects of iron ore dust deposition and simulated acid rain on photosynthesis and on antioxidant enzymes were investigated in Eugenia uniflora, a representative shrub species of the restinga. This study aimed to determine the possible utility of this species in environmental risk assessment. After the application of iron ore dust as iron solid particulate matter (SPM(Fe)) and simulated acid rain (pH 3.1), the 18-month old plants displayed brown spots and necrosis, typical symptoms of iron toxicity and injuries caused by acid rain, respectively. The acidity of the rain intensified leaf iron accumulation, which reached phytotoxic levels, mainly in plants exposed to iron ore dust. These plants showed the lowest values for net photosynthesis, stomatal conductance, transpiration, chlorophyll a content and electron transport rate through photosystem II (PSII). Catalase and superoxide dismutase activities were decreased by simulated acid rain. Peroxidase activity and membrane injury increased following exposure to acid rain and simultaneous SPM(Fe) application. Eugenia uniflora exhibited impaired photosynthetic and antioxidative metabolism in response to combined iron and acid rain stresses. This species could become a valuable tool in environmental risk assessment in restinga areas near iron ore pelletizing factories. Non-invasive evaluations of visual injuries, photosynthesis and chlorophyll a fluorescence, as well as invasive biochemical analysis could be used as markers. PMID:19321190

  5. Influence of Substrate Temperature on Structural Properties and Deposition Rate of AlN Thin Film Deposited by Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Jin, Hao; Feng, Bin; Dong, Shurong; Zhou, Changjian; Zhou, Jian; Yang, Yi; Ren, Tianling; Luo, Jikui; Wang, Demiao

    2012-07-01

    Aluminum nitride (AlN) thin films with c-axis preferred orientation have been prepared by reactive direct-current (DC) magnetron sputtering. The degree of preferred crystal orientation, the cross-sectional structure, and the surface morphology of AlN thin films grown on Si (100) substrates at various substrate temperatures from 60°C to 520°C have been investigated by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. Results show that the substrate temperature has a significant effect on the structural properties, such as the degree of c-axis preferred orientation, the full-width at half-maximum (FWHM) of the rocking curve, the surface morphology, and the cross-sectional structure as well as the deposition rate of the AlN thin films. The optimal substrate temperature is 430°C, with corresponding root-mean-square surface roughness ( R rms) of 1.97 nm, FWHM of AlN (002) diffraction of 2.259°, and deposition rate of 20.86 nm/min. The mechanisms behind these phenomena are discussed. Finally, film bulk acoustic resonators based on AlN films were fabricated; the corresponding typical electromechanical coupling coefficient ( k {t/2}) is 5.1% with series and parallel frequencies of 2.37 GHz and 2.42 GHz, respectively.

  6. Flip-flop of oleic acid in a phospholipid membrane: rate and mechanism.

    PubMed

    Wei, Chenyu; Pohorille, Andrew

    2014-11-13

    Flip-flop of protonated oleic acid molecules dissolved at two different concentrations in membranes made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine is studied with the aid of molecular dynamics simulations at a time scale of several microseconds. Direct, single-molecule flip-flop events are observed at this time scale, and the flip-flop rate is estimated at 0.2-0.3 μs(-1). As oleic acid molecules move toward the center of the bilayer during flip-flop, they undergo gradual, correlated translational, and rotational motion. Rare, double-flipping events of two hydrogen-bonded oleic acid molecules are also observed. A two-dimensional free energy surface is obtained for the translational and rotational degree of freedom of the oleic acid molecule, and the minimum energy path on this surface is determined. A barrier to flip-flop of ~4.2 kcal/mol is found at the center of the bilayer. A two-dimensional diffusion model is found to provide a good description of the flip-flop process. The fast flip-flop rate lends support to the proposal that fatty acids permeate membranes without assistance of transport proteins. It also suggests that desorption rather than flip-flop is the rate-limiting step in fatty acid transport through membranes. The relation of flip-flop rates to the evolution of ancestral cellular systems is discussed. PMID:25319959

  7. Aqueous solution deposition kinetics of iron oxyhydroxide on sulfonic acid terminated self-assembled monolayers

    SciTech Connect

    Rieke, P.C.; Marsh, B.D.; Wood, L.L.; Tarasevich, B.J.; Liu, J.; Song, L.; Fryxell, G.E. )

    1995-01-01

    The deposition kinetics of iron oxyhydroxide on sulfonic acid terminated self-assembled monolayers were studied. The thin films of FeOOH were formed on the substrates by thermal hydrolysis of millimolar aqueous solutions of Fe(NO[sub 3])[sub 3] at a pH of approximately 2.0. The thickness of the films was measured ellipsometrically at various times. Both Fe(NO[sub 3])[sub 3] and HNO[sub 3] concentrations were independently varied to provide varying degrees of solution supersaturation. Depending on these concentrations, an induction time was observed before film growth commenced. The correlation between supersaturation and induction time was modeled using classical nucleation theory. Very good agreement was observed regardless of whether supersaturation was varied via the concentration of Fe(NO[sub 3])[sub 3] or HNO[sub 3]. From these results an interfacial free energy for nucleation of 148 mJ/m[sup 2] was calculated. The critical nucleus species was identified as a tetrameric iron species by considering the order of nucleation. 49 refs., 11 figs., 1 tab.

  8. A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus

    NASA Astrophysics Data System (ADS)

    Vet, Robert; Artz, Richard S.; Carou, Silvina

    2014-08-01

    Investigating and assessing the chemical composition of precipitation and atmospheric deposition is essential to understanding how atmospheric pollutants contribute to contemporary environmental concerns including ecosystem acidification and eutrophication, loss of biodiversity, air pollution and global climate change. Evidence of the link between atmospheric deposition and these environmental issues is well established. The state of scientific understanding of this link is that present levels of atmospheric deposition of sulfur and nitrogen adversely affect terrestrial and aquatic ecosystems, putting forest sustainability and aquatic biodiversity at risk. Nitrogen and phosphorus loadings are linked to impacts on the diversity of terrestrial and aquatic vegetation through biological cycling, and atmospheric deposition plays a major role in the emission-transport-conversion-loss cycle of chemicals in the atmosphere as well as the formation of particulate matter and ozone in the troposphere. Evidence also shows that atmospheric constituents are changing the earth's climate through direct and indirect atmospheric processes. This Special Issue, comprising a single article titled "A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus", presents a recent comprehensive review of precipitation chemistry and atmospheric deposition at global and regional scales. The information in the Special Issue, including all supporting data sets and maps, is anticipated to be of great value not only to the atmospheric deposition community but also to other science communities including those that study ecosystem impacts, human health effects, nutrient processing, climate change, global and hemispheric modeling and biogeochemical cycling. Understanding and quantifying pollutant loss from the atmosphere is, and will remain, an important component of each of these scientific fields as they

  9. Direct measurement technique for determining ventilation rate in the deposit-feeding clam Macoma nasuta (bivalvia, tellinaceae)

    SciTech Connect

    Specht, D.T.; Lee, H.

    1989-01-01

    An exposure chamber, the 'clambox', was developed to measure ventilation rate, sediment processing rate, and efficiency of pollutant uptake by Macoma nasuta, Conrad, a surface-deposit-feeding clam. Clams, collected from Yaquina Bay, Oregon, USA, were cemented into a hole in a piece of rubber dental dam so that the inhalant siphons were separated by a membrane. The dental dam was then clamped between two glass chambers. The inhalant and exhalant siphons were thus diirected into separate chambers of the device so that the amount of water or feces discharged into the exhalant camber provided direct measure ventilation rate and sediment processing rate, respectively. The short-term pattern was for ventilation to be intermittently interrupted, essentially ceasing for 12 to 120 min, followed by a short period of active ventilation and then a resumption of the normal rate.

  10. Surface Ages and Resurfacing Rates of the Polar Layered Deposits on Mars

    NASA Technical Reports Server (NTRS)

    Herkenhoff, K. E.; Plaut, J. J.

    1999-01-01

    The martian polar layered deposits (PLD) are probably the best source of information about the recent climate history of Mars, but their origin and the mechanisms of accumulation are still a mystery. The polar layers are sedimentary deposits that most planetary scientists believe are composed of water ice and varying amounts of wind-blown dust, but their composition is poorly constrained. Interpretation of the observed polar stratigraphy in terms of global climate changes is complicated by the significant difference in surface ages between the north and south PLD inferred from crater statistics. While no craters have been found in the north PLD, the surface of the south PLD appears to have been stable for many of the orbital/axial cycles that are thought to have induced global climate changes on Mars. Using medium-resolution Viking imagery, Plaut et al. found at least 15 impact craters in the southern layered deposits and concluded that their surface is 120 +/- 40 million years old. In contrast, Cutts et al. found no fresh impact craters larger than about 300 meters in summertime images of the north polar layered deposits. Additional information is contained in the original extended abstract.

  11. In situ growth rate measurements during plasma-enhanced chemical vapour deposition of vertically aligned multiwall carbon nanotube films

    NASA Astrophysics Data System (ADS)

    Jönsson, M.; Nerushev, O. A.; Campbell, E. E. B.

    2007-08-01

    In situ laser reflectivity measurements are used to monitor the growth of multiwalled carbon nanotube (MWCNT) films grown by DC plasma-enhanced chemical vapour deposition (PECVD) from an iron catalyst film deposited on a silicon wafer. In contrast to thermal CVD growth, there is no initial increase in the growth rate; instead, the initial growth rate is high (as much as 10 µm min-1) and then drops off rapidly to reach a steady level (2 µm min-1) for times beyond 1 min. We show that a limiting factor for growing thick films of multiwalled nanotubes (MWNTs) using PECVD can be the formation of an amorphous carbon layer at the top of the growing nanotubes. In situ reflectivity measurements provide a convenient technique for detecting the onset of the growth of this layer.

  12. Influence of fatty acid oxidation rate on glycerol release from cardiac myocytes

    SciTech Connect

    Larsen, T.S.; Severson, D.L.

    1986-03-05

    Quiescent cardiac myocytes are characterized by low rates of fatty acid oxidation due to the reduced energy demand compared with beating hearts. The accumulation of intracellular fatty acid metabolites may, therefore, result in feed-back inhibition of the cardiac lipase responsible for the mobilization of triacylglycerols (lipolysis). The objective of this study was to examine if interventions that increase fatty acid oxidation rates in myocytes have an effect on lipolysis. Addition of 100 ..mu..M dinitrophenol (DNP) to calcium-tolerant rat ventricular myocytes caused an increase in the rate of /sup 14/C-oleic acid oxidation from 1.11 +/- 0.06 to 2.38 +/- 0.17 nmol /sup 14/CO/sub 2//10/sup 6/ cells/min (115% stimulation; mean +/- S.D., n = 3). In parallel incubations, DNP increased the rate of lipolysis from 4.4 +/- 1.7 to 13.6 +/- 3.2 nmol glycerol/10/sup 6/ cells/30 min (215% stimulation). The addition of 1 mM barium to a modified Ringer's incubation medium produced an increase in the contractile activity of the myocytes, and increased the rates of oleic acid oxidation from 0.62 +/- 0.16 to 0.88 +/- 0.23 nmol/10/sup 6/ cells/min (42% stimulation; n = 6) and lipolysis from 13.1 +/- 6.5 to 22.2 +/- 6.4 nmol/10/sup 6/ cells/30 min (70% stimulation). These data show that stimulation of fatty acid oxidation in myocardial myocytes is accompanied by increased lipolytic rates, the latter probably due to release of feed-back inhibition of cardiac lipases by accumulated fatty acid metabolites.

  13. Effects of acidic deposition and soil acidification on sugar maple trees in the Adirondack Mountains, New York

    USGS Publications Warehouse

    Sullivan, Timothy J.; Lawrence, Gregory B.; Bailey, Scott W.; McDonnell, Todd C.; Beier, Colin M.; Weathers, K.C.; McPherson, G.T.; Bishop, Daniel A.

    2013-01-01

    We documented the effects of acidic atmospheric deposition and soil acidification on the canopy health, basal area increment, and regeneration of sugar maple (SM) trees across the Adirondack region of New York State, in the northeastern United States, where SM are plentiful but not well studied and where widespread depletion of soil calcium (Ca) has been documented. Sugar maple is a dominant canopy species in the Adirondack Mountain ecoregion, and it has a high demand for Ca. Trees in this region growing on soils with poor acid–base chemistry (low exchangeable Ca and % base saturation [BS]) that receive relatively high levels of atmospheric sulfur and nitrogen deposition exhibited a near absence of SM seedling regeneration and lower crown vigor compared with study plots with relatively high exchangeable Ca and BS and lower levels of acidic deposition. Basal area increment averaged over the 20th century was correlated (p < 0.1) with acid–base chemistry of the Oa, A, and upper B soil horizons. A lack of Adirondack SM regeneration, reduced canopy condition, and possibly decreased basal area growth over recent decades are associated with low concentrations of nutrient base cations in this region that has undergone soil Ca depletion from acidic deposition.

  14. Atmospheric pressure plasma chemical vapor deposition reactor for 100 mm wafers, optimized for minimum contamination at low gas flow rates

    NASA Astrophysics Data System (ADS)

    Anand, Venu; Nair, Aswathi R.; Shivashankar, S. A.; Mohan Rao, G.

    2015-08-01

    Gas discharge plasmas used for thinfilm deposition by plasma-enhanced chemical vapor deposition (PECVD) must be devoid of contaminants, like dust or active species which disturb the intended chemical reaction. In atmospheric pressure plasma systems employing an inert gas, the main source of such contamination is the residual air inside the system. To enable the construction of an atmospheric pressure plasma (APP) system with minimal contamination, we have carried out fluid dynamic simulation of the APP chamber into which an inert gas is injected at different mass flow rates. On the basis of the simulation results, we have designed and built a simple, scaled APP system, which is capable of holding a 100 mm substrate wafer, so that the presence of air (contamination) in the APP chamber is minimized with as low a flow rate of argon as possible. This is examined systematically by examining optical emission from the plasma as a function of inert gas flow rate. It is found that optical emission from the plasma shows the presence of atmospheric air, if the inlet argon flow rate is lowered below 300 sccm. That there is minimal contamination of the APP reactor built here, was verified by conducting an atmospheric pressure PECVD process under acetylene flow, combined with argon flow at 100 sccm and 500 sccm. The deposition of a polymer coating is confirmed by infrared spectroscopy. X-ray photoelectron spectroscopy shows that the polymer coating contains only 5% of oxygen, which is comparable to the oxygen content in polymer deposits obtained in low-pressure PECVD systems.

  15. High-rate deposition of a-SiNx:H for photovoltaic applications by the expanding thermal plasma

    NASA Astrophysics Data System (ADS)

    Kessels, W. M. M.; Hong, J.; van Assche, F. J. H.; Moschner, J. D.; Lauinger, T.; Soppe, W. J.; Weeber, A. W.; Schram, D. C.; van de Sanden, M. C. M.

    2002-09-01

    Driven by the need for improvement of the economical competitiveness of photovoltaic energy, the feasibility of high-rate (>1 nm/s) amorphous silicon nitride (a-SiNx):H deposited by the expanding thermal plasma (ETP) technique has been explored with respect to the application of the a-SiNx:H as functional antireflection coating on crystalline silicon solar cells. First, the deposition rate and the a-SiNx:H film properties, such as refractive index, Si, N, and H atomic density, and hydrogen bonding configurations, have been mapped for various operating conditions. From ellipsometry, elastic recoil detection, and infrared spectroscopy, it has been shown that deposition rates up to 20 nm/s can be reached with a fair film homogeneity and that the refractive index and the N/Si ratio can fully be tuned by the plasma composition while the hydrogen content can be controlled by the substrate temperature. Good antireflection coating performance of the a-SiNx:H has therefore been observed for monocrystalline silicon solar cells. These cells with ETP a-SiNx:H yielded only slightly lower conversion efficiencies than high-quality reference cells due to a much lower degree of surface passivation. This lack of surface passivation has also been shown in a separate study on the surface recombination velocity. Furthermore, it has been tested whether the a-SiNx:H films lead to silicon bulk passivation, which is essential for solar cells based on cheaper, defective silicon stock material such as multicrystalline silicon. It has been proven that bulk passivation of the cells is indeed induced by the high-rate ETP deposited a-SiNx:H after a high-temperature step in which the metal contacts of the cells are processed. These results make the ETP technique an interesting candidate for high-throughput processing of competitive silicon solar cells. copyright 2002 American Vacuum Society.

  16. Effects of dose, flow rate, and bile acid on diclofenac disposition in the perfused rat liver.

    PubMed

    Uraki, Misato; Kawase, Atsushi; Matsushima, Yuka; Iwaki, Masahiro

    2016-06-01

    An in situ perfused rat liver system is useful for studying the hepatic disposition of drugs and their metabolites. However, the effects of the perfusion conditions on drug disposition are unclear. We examined the effects of conditions such as flow rate (13 or 26 mL/min) and bile acid on disposition of diclofenac (DF) as a model drug and DF metabolites [diclofenac-1-O-acyl glucuronide (DF-Glu) or 4'-hydroxydiclofenac (DF-4'OH)] in the absence of albumin. DF, DF-Glu, and DF-4'OH concentrations in the perfusate and cumulative amounts of DF-Glu excreted in bile were measured using high-performance liquid chromatography methods. DF in the perfusate was rapidly eliminated as the perfusate flow rate increased. The area under the plasma concentration-time curve from 0 to 60 min (AUC0-60) for DF-Glu and DF-4'OH in a perfusate containing bile acid was lower at a flow rate of 26 and 13 mL/min, respectively. The bile flow rate at 26 mL/min with 24 μM of bile acid in the perfusate was significantly higher (ca. 3.5 times) compared with that at 13 mL/min without bile acid. Cumulative biliary DF-Glu excretion was also dramatically affected by the flow rate and addition of bile acid. This study indicated that the flow rate and bile acid in the perfused rat liver were key factors for bile flow rate and DF, DF-Glu, and DF-4'OH disposition in the absence of albumin. PMID:25656736

  17. Effects of dietary combination of n-3 and n-9 fatty acids on the deposition of linoleic and arachidonic acid in broiler chicken meats.

    PubMed

    Shin, D; Choi, S H; Go, G; Park, J H; Narciso-Gaytán, C; Morgan, C A; Smith, S B; Sánchez-Plata, M X; Ruiz-Feria, C A

    2012-04-01

    To minimize the amount of n-6 fatty acids in broiler chicken meat, 120 Cobb × Ross male broilers were divided into 6 different groups and fed a basal corn-soybean meal diet containing 5% fat from 5 different lipid sources: 1) a commercial mix of animal and vegetable oil, 2) soybean oil and olive oil (2.5% each), 3) flaxseed oil and olive oil (2.5% each), 4) flaxseed oil, eicosapentaenoic acid (C20:5; EPA; n-3), and olive oil (2.45, 0.05, and 2.5% respectively; FEO), 5) flaxseed oil, docosahexaenoic acid (C22:6; DHA; n-3), and olive oil (2.45, 0.05, and 2.5% respectively; FDO), and 6) fish oil and olive oil (2.5% each; FHO). At 6 and 9 wk, one bird per pen (4 pens per treatment) was processed, and liver, breast, and thigh samples were collected and used for fatty acid profiles or Δ6- and Δ9-desaturase mRNA gene expression levels. The deposition of linoleic acid (C18:2; n-6) or arachidonic acid (C20:4; n-6) was decreased in breast and thigh muscles of chickens fed n-3 fatty acids for 9 wk compared with chickens fed animal and vegetable oil and soybean oil and olive oil diets (P < 0.05). The addition of EPA to the diet (FEO; P > 0.05) did not reduce the deposition of linoleic acid and arachidonic acid as much as DHA (FDO; P < 0.05), and it suppressed the expression of Δ6- and Δ9-desaturase. When EPA and DHA were blended (FHO) and supplied to broiler chickens for 9 wk, EPA and DHA combination effects were observed on the deposition of LA and arachidonic acid in breast and thigh muscles. Thereby, the addition of a mixed EPA and DHA to a broiler chicken diet may be recommendable to reduce arachidonic acid accumulation in both broiler chicken breast and thigh meats, providing a functional broiler chicken meat to consumers. PMID:22399741

  18. Enhanced formic acid oxidation on polycrystalline platinum modified by spontaneous deposition of gold. Fourier transform infrared spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Cappellari, Paula S.; García, Gonzalo; Florez-Montaño, Jonathan; Barbero, Cesar A.; Pastor, Elena; Planes, Gabriel A.

    2015-11-01

    Formic acid and adsorbed carbon monoxide electrooxidation on polycrystalline Pt and Au-modified Pt surfaces were studied by cyclic voltammetry, lineal sweep voltammetry and in-situ Fourier transform infrared spectroscopy techniques. With this purpose, a polycrystalline Pt electrode was modified by spontaneous deposition of gold atoms, achieving a gold surface coverage (θ) in the range of 0 ≤ θ ≤ 0.47. Results indicate the existence of two main pathways during the formic acid oxidation reaction, i.e. dehydration and dehydrogenation routes. At higher potentials than 0.5 V the dehydrogenation pathway appears to be the operative at both Pt and Au electrodes. Meanwhile, the dehydration reaction is the main pathway for Pt at lower potentials than 0.5 V. It was found that reaction routes are easily tuned by Au deposition on the Pt sites responsible for the formic acid dehydration reaction, and hence for the catalytic formation of adsorbed carbon monoxide. Gold deposition on these Pt open sites produces an enhanced activity toward the HCOOH oxidation reaction. In general terms, the surface inhibition of the reaction by adsorbed intermediates (indirect pathway) is almost absent at gold-modified Pt electrodes, and therefore the direct pathway appears as the main route during the formic acid electrooxidation reaction.

  19. Reconstruction of 20th Century Atmospheric Deposition Rates in the Sierra Nevada (California) using Spheroidal Carbonaceous Particles

    NASA Astrophysics Data System (ADS)

    Heard, A.; Sickman, J. O.; Rose, N.

    2012-12-01

    Atmospheric nitrogen deposition is altering biogeochemical cycles and ecological processes in high-elevation aquatic ecosystems. A need for stricter standards based on measurable ecological effects has been identified as an important step towards their long-term protection. One of the challenges with identifying ecological thresholds is a lack of knowledge of background conditions (pre- industrial) and changes that may have occurred prior to extensive monitoring programs. However, this information can be obtained using paleolimnological approaches. We are investigating historic atmospheric deposition in the Sierra Nevada using spheroidal carbonaceous particles (SCPs) in lake sediments. SCPs are strong geochemical indicators of anthropogenic atmospheric deposition because they are only produced by industrial combustion of fossil fuels---there are no natural sources. We detected SCPs as early as 1870 at Moat Lake in the eastern Sierra Nevada. SCP concentrations increased over time, peaking in the mid-1980's (2,399 gDM-1) while SCP accumulation rates peaked in the early 1920's (105 no, cm-2 yr-1) (Figure 1). Lakes along the western slope of the Sierra (Pear and Emerald) show similar patterns although differences vary by site and are likely explained by watershed characteristics and proximity to emission sources. SCP concentrations at Pear and Emerald lakes peak 10-15 years earlier than Moat. A consistent decrease was observed at Pear and Moat following the peak concentrations until present. Present day concentrations are 556 gDM-1 at Moat and 473 gDM-1 at Pear. At Emerald lake SCPs also initially decreased starting in 1964, but an increasing trend is observed from 1995 through present. These data improve our understanding of historic atmospheric deposition patterns and are being used to inform additional palaeolimnological research, including diatom analyses, with the broader objective of reconstructing historic nitrogen deposition and estimating critical loads for

  20. Relative Reaction Rates of Sulfamic Acid and Hydroxylamine with Nitric Acid

    SciTech Connect

    Karraker, D.G.

    2001-03-28

    This report describes a study of comparative reaction rates where the reductant is in excess, as in the 1B bank in the Purex process. The results of this work apply to planned plant tests to partially substitute HAN for the ferrous sulfamate reductant in the Purex 1B bank.

  1. A Method for Observing Soil Re-Deposition and Soil Loss Rates in Large Field Experiments

    NASA Astrophysics Data System (ADS)

    Hsieh, Y. P.; Bugna, G. C.; Nemours, D.

    2014-12-01

    The lack of quality soil erosion field data, which is required for the verification and calibration of soil erosion models, has been one of the serious problems in the soil conservation modeling today. Observing soil erosion of a relatively large field under truly unobstructed runoff conditions has rarely been done and doccumented. Report here is the results of our observation of soil erosion in a 7.3 ha peanut-cotton cropping system in the Mears Farm of Grand Ridge, FL. We used the mesh-pad method to quantify soil loss from the field and soil re-deposition in the field over the cropping season of 2010. The main slope (1-3 %) of the field is about 210 m long. We show that the amount of soil re-deposition was 50-150 times of the soil loss from the slope. The corresponding organic matter, nitrogen, phosphorous and silt and clay contents of the lost soil, however, were 20.9%, 21%, 17.6% and 14.2%, respectively, of the total amounts re-deposited on the slope. The amounts of soil loss predicted by a SWAT model was 10-20 times greater than our observed values. Soil erosion process was quite heterogeneous, as shown by the mesh-pad method, even on a seemingly uniform cultivated field. Soil erosion models need to be verified and calibrated by extensive quality field data in order to improve their performance.

  2. Different responses of two Mosla species to potassium limitation in relation to acid rain deposition*

    PubMed Central

    Wang, Meng; Gu, Bao-jing; Ge, Ying; Liu, Zhen; Jiang, De-an; Chang, Scott X.; Chang, Jie

    2009-01-01

    The increasingly serious problem of acid rain is leading to increased potassium (K) loss from soils, and in our field investigation, we found that even congenerically relative Mosla species show different tolerance to K-deficiency. A hydroponic study was conducted on the growth of two Mosla species and their morphological, physiological and stoichiometric traits in response to limited (0.35 mmol K/L), normal (3.25 mmol K/L) and excessive (6.50 mmol K/L) K concentrations. Mosla hangchowensis is an endangered plant, whereas Mosla dianthera a widespread weed. In the case of M. hangchowensis, in comparison with normal K concentration, K-limitation induced a significant reduction in net photosynthetic rate (P n), soluble protein content, and superoxide dismutase (SOD) activity, but an increase in malondialdehyde (MDA) concentration. However, leaf mass ratio (LMR) and root mass ratio (RMR) were changed little by K-limitation. In contrast, for M. dianthera, K-limitation had little effect on P n, soluble protein content, SOD activity, and MDA concentration, but increased LMR and RMR. Critical values of N (nitrogen):K and K:P (phosphorus) ratios in the shoots indicated that limitation in acquiring K occurred under K-limited conditions for M. hangchowensis but not for M. dianthera. We found that low K content in natural habitats was a restrictive factor in the growth and distribution of M. hangchowensis, and soil K-deficiency caused by acid rain worsened the situation of M. hangchowensis, while M. dianthera could well acclimate to the increasing K-deficiency. We suggest that controlling the acid rain and applying K fertilizers may be an effective way to rescue the endangered M. hangchowensis. PMID:19650194

  3. Simulation of Fine Resist Profile Formation by Electron Beam Drawing and Development with Solubility Rate Based on Energy Deposition Distribution

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Komori, Takuya; Zhang, Yulong; Yin, You; Hosaka, Sumio

    2013-12-01

    We proposed a model for calculating the resist profile in electron beam drawing. The model predicts the solubility rate on the basis of the energy deposition distribution (EDD) for the development of latent patterns in the resist. By unifying the exposure dose D (via experiments) and EDDs (via calculations), we roughly determined solubility rates for three-dimensional EDDs, and established the proposed model. The development simulation was achieved by the sequential calculation method for solubility rates based on EDD which was calculated by Monte Carlo simulation. By determining a suitable EDD region to achieve good patterning, we obtained a sharp nanodot pattern of the resist. This simulation results are in good agreement with the experimental results obtained using a combination of 2.3 wt % tetramethylammonium hydroxide (TMAH) and 4 wt % NaCl as the developer. The model was demonstrated to be useful for predicting resist profiles with different experimental solubility rates of developers.

  4. ANEMOS: A computer code to estimate air concentrations and ground deposition rates for atmospheric nuclides emitted from multiple operating sources

    SciTech Connect

    Miller, C.W.; Sjoreen, A.L.; Begovich, C.L.; Hermann, O.W.

    1986-11-01

    This code estimates concentrations in air and ground deposition rates for Atmospheric Nuclides Emitted from Multiple Operating Sources. ANEMOS is one component of an integrated Computerized Radiological Risk Investigation System (CRRIS) developed for the US Environmental Protection Agency (EPA) for use in performing radiological assessments and in developing radiation standards. The concentrations and deposition rates calculated by ANEMOS are used in subsequent portions of the CRRIS for estimating doses and risks to man. The calculations made in ANEMOS are based on the use of a straight-line Gaussian plume atmospheric dispersion model with both dry and wet deposition parameter options. The code will accommodate a ground-level or elevated point and area source or windblown source. Adjustments may be made during the calculations for surface roughness, building wake effects, terrain height, wind speed at the height of release, the variation in plume rise as a function of downwind distance, and the in-growth and decay of daughter products in the plume as it travels downwind. ANEMOS can also accommodate multiple particle sizes and clearance classes, and it may be used to calculate the dose from a finite plume of gamma-ray-emitting radionuclides passing overhead. The output of this code is presented for 16 sectors of a circular grid. ANEMOS can calculate both the sector-average concentrations and deposition rates at a given set of downwind distances in each sector and the average of these quantities over an area within each sector bounded by two successive downwind distances. ANEMOS is designed to be used primarily for continuous, long-term radionuclide releases. This report describes the models used in the code, their computer implementation, the uncertainty associated with their use, and the use of ANEMOS in conjunction with other codes in the CRRIS. A listing of the code is included in Appendix C.

  5. Effects of substrate temperatures and deposition rates on properties of aluminum fluoride thin films in deep-ultraviolet region.

    PubMed

    Sun, Jian; Li, Xu; Zhang, Weili; Yi, Kui; Shao, Jianda

    2012-12-10

    Aluminum fluoride (AlF(3)) is a low-refractive-index material widely used in coatings for deep-ultraviolet (DUV) optical systems, especially 193 nm laser systems. Low optical loss and stability are essential for film application. In this study, AlF(3)> thin films were prepared by thermal evaporation with a resistive heating boat. The effects of substrate temperatures and deposition rates on the optical properties in vacuum and in air, composition, and microstructures were discussed respectively. In vacuum the deposition parameters directly influenced the microstructures that determined the refractive index. When the films were exposed to air, aluminum oxide (Al(2)O(3)) formed in the films with water adsorption. Thus the refractive index increased and a nonmonotonic changing trend of the refractive index with substrate temperature was observed. The Al(2)O(3) was also found to be conductive to reducing absorption loss. AlF(3) films prepared at a high substrate temperature and deposition rate could yield stable structures with large optical loss. PMID:23262545

  6. Field Metabolic Rate and PCB Adipose Tissue Deposition Efficiency in East Greenland Polar Bears Derived from Contaminant Monitoring Data

    PubMed Central

    Pavlova, Viola; Nabe-Nielsen, Jacob; Dietz, Rune; Svenning, Jens-Christian; Vorkamp, Katrin; Rigét, Frank Farsø; Sonne, Christian; Letcher, Robert J.; Grimm, Volker

    2014-01-01

    Climate change will increasingly affect the natural habitat and diet of polar bears (Ursus maritimus). Understanding the energetic needs of polar bears is therefore important. We developed a theoretical method for estimating polar bear food consumption based on using the highly recalcitrant polychlorinated biphenyl (PCB) congener, 2,2′,4,4′,55-hexaCB (CB153) in bear adipose tissue as an indicator of food intake. By comparing the CB153 tissue concentrations in wild polar bears with estimates from a purposely designed individual-based model, we identified the possible combinations of field metabolic rates (FMR) and CB153 deposition efficiencies in East Greenland polar bears. Our simulations indicate that if 30% of the CB153 consumed by polar bear individuals were deposited into their adipose tissue, the corresponding FMR would be only two times the basal metabolic rate. In contrast, if the modelled CB153 deposition efficiency were 10%, adult polar bears would require six times more energy than that needed to cover basal metabolism. This is considerably higher than what has been assumed for polar bears in previous studies though it is similar to FMRs found in other marine mammals. An implication of this result is that even relatively small reductions in future feeding opportunities could impact the survival of East Greenland polar bears. PMID:25101837

  7. Conductive ZnO:Zn Composites for High-Rate Sputtering Deposition of ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Zhou, Li Qin; Dubey, Mukul; Simões, Raul; Fan, Qi Hua; Neto, Victor

    2015-02-01

    We report an electrically conductive composite prepared by sintering ZnO and metallic Zn powders. Microstructure analysis combined with electrical conductivity studies indicated that when the proportion of metallic Zn reached a threshold (˜20 wt.%), a metal matrix was formed in accordance with percolation theory. This composite has potential as a sputtering target for deposition of high-quality ZnO. Use of the ZnO:Zn composite completely eliminates target poisoning effects in reactive sputtering of the metal, and enables deposition of thin ZnO films at rates much higher than those obtained by sputtering of pure ZnO ceramic targets. The optical transmittance of the ZnO films prepared by use of this composite is comparable with that of films produced by radio frequency sputtering of pure ZnO ceramic targets. The sputtering characteristics of the conductive ZnO:Zn composite target are reported, and possible mechanisms of the high rate of deposition are also discussed.

  8. Field metabolic rate and PCB adipose tissue deposition efficiency in East Greenland polar bears derived from contaminant monitoring data.

    PubMed

    Pavlova, Viola; Nabe-Nielsen, Jacob; Dietz, Rune; Svenning, Jens-Christian; Vorkamp, Katrin; Rigét, Frank Farsø; Sonne, Christian; Letcher, Robert J; Grimm, Volker

    2014-01-01

    Climate change will increasingly affect the natural habitat and diet of polar bears (Ursus maritimus). Understanding the energetic needs of polar bears is therefore important. We developed a theoretical method for estimating polar bear food consumption based on using the highly recalcitrant polychlorinated biphenyl (PCB) congener, 2,2',4,4',55-hexaCB (CB153) in bear adipose tissue as an indicator of food intake. By comparing the CB153 tissue concentrations in wild polar bears with estimates from a purposely designed individual-based model, we identified the possible combinations of field metabolic rates (FMR) and CB153 deposition efficiencies in East Greenland polar bears. Our simulations indicate that if 30% of the CB153 consumed by polar bear individuals were deposited into their adipose tissue, the corresponding FMR would be only two times the basal metabolic rate. In contrast, if the modelled CB153 deposition efficiency were 10%, adult polar bears would require six times more energy than that needed to cover basal metabolism. This is considerably higher than what has been assumed for polar bears in previous studies though it is similar to FMRs found in other marine mammals. An implication of this result is that even relatively small reductions in future feeding opportunities could impact the survival of East Greenland polar bears. PMID:25101837

  9. Stress assessment and spectral characterization of suspected acid deposition damage in red spruce (Picea Rubens) from Vermont

    NASA Technical Reports Server (NTRS)

    Rock, B. N.; Vogelmann, J. E.

    1985-01-01

    The effects of acid deposition on Picea rubens are studied. The Picea rubens located at Camels Hump Mt., Mt. Ascutney, and Ripton, VT were analyzed using stress level evaluations, in situ spectral data, pressure bomb analysis, and aircraft sensors. Spruce stress per circular plot and percent spruce mortality are calculated. The relation between stress levels and elevation and exposure and weather patterns is examined. It is observed that variations in the reflectance curves of the foliage and branches are related to cellular health, the type of cellular arrangement, and the degree of leaf tissue hydration; the leaf and twig specimens from high stress sites are more reflective in the red portion of the visible and less reflective in the NIR portion of the spectrum. The pressure bomb data reveal that the xylem water tension is higher in specimens from high stress sites. It is noted that remote sensing permits discrimination and mapping of suspected acid deposition damage.

  10. Comparison among model estimates of critical loads of acidic deposition using different sources and scales of input data.

    PubMed

    McDonnell, T C; Cosby, B J; Sullivan, T J; McNulty, S G; Cohen, E C

    2010-09-01

    The critical load (CL) of acidic atmospheric deposition represents the load of acidity deposited from the atmosphere to the earth's surface at which harmful acidification effects on sensitive biological receptors are thought to occur. In this study, the CL for forest soils was estimated for 27 watersheds throughout the United States using a steady-state mass balance approach based on both national and site-specific data and using different approaches for estimating base cation weathering. Results suggested that the scale and source of input data can have large effects on the calculated CL and that the most important parameter in the steady-state model used to estimate CL is base cation weathering. These results suggest that the data and approach used to estimate weathering must be robust if the calculated CL is to be useful for its intended purpose. PMID:20609503

  11. Graphene decorated microelectrodes for simultaneous detection of ascorbic, dopamine, and folic acids by means of chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Namdar, N.; Hassanpour Amiri, M.; Dehghan Nayeri, F.; Gholizadeh, A.; Mohajerzadeh, S.

    2015-09-01

    In this paper, high quality and large area graphene layers were synthesized using thermal chemical vapour deposition on copper foil substrates. We use graphene incorporated electrodes to measure simultaneously ascorbic acid, dopamine and folic acid. Cyclic voltammetry and differential pulse voltammetry methods were used to evaluate electrochemical behaviour of the grown graphene layers. The graphene-modified electrode shows large electrochemical potential difference compared to bare gold electrodes with higher current responses. Also our fabricated electrodes configuration can be used easily for microfluidic analysis.

  12. Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Pervolaraki, M.; Komninou, Ph.; Kioseoglou, J.; Athanasopoulos, G. I.; Giapintzakis, J.

    2013-08-01

    One-step growth of n-doped Si nanostructures by picosecond ultra fast pulsed laser deposition at 1064 nm is reported for the first time. The structure and morphology of the Si nanostructures were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy. Transmission electron microscopy studies revealed that the shape of the Si nanostructures depends on the ambient argon pressure. Fibrous networks, cauliflower formations and Si rectangular crystals grew when argon pressure of 300 Pa, 30 Pa and vacuum (10-3 Pa) conditions were used, respectively. In addition, the electrical resistance of the vacuum made material was investigated.

  13. Identification of research relating to the critical loads concept and its potential application to the regulation of acidic deposition

    SciTech Connect

    Bhatti, N.

    1993-12-01

    The overwhelming majority of strategies currently implemented to regulate acidic deposition have focused on source-based or emission-control techniques. In the past few years, however, the fact that such source-based. strategies may not be sufficient to prevent adverse ecological effects and may therefore need to be supplemented with other control options, such as receptor-based strategies, has become apparent. Partly in response to this insufficiency of regulatory controls, the US Congress has required the National Acid Precipitation Assessment Program to determine (1) what deposition levels are needed to prevent such ecological damage, (2) whether such safe deposition levels (i.e., critical loads) can realistically be identified, and (3) what the costs and benefits of attaining such deposition levels are. This report reviews and culls the existing research on these alternative control strategies, emphasizing the critical loads concept, to determine the advantages and limitations and the cost-benefit relationships associated with receptor-based control options. The results of this study indicate that in spite of the significant limitations associated with the critical loads concept, this strategy dominates all discussions of non-source-based control options and offers considerable advantages, including cost-effectiveness, over the more traditional source-based control methods. Summaries of 10 of the most relevant studies dealing with alternative control strategies and the costs and benefits associated with them are also presented in this report.

  14. 3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid

    PubMed Central

    Assaud, Loïc; Monyoncho, Evans; Pitzschel, Kristina; Allagui, Anis; Petit, Matthieu; Hanbücken, Margrit

    2014-01-01

    Summary Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects. PMID:24605281

  15. Thermal post-deposition treatment effects on nanocrystalline hydrogenated silicon prepared by PECVD under different hydrogen flow rates

    NASA Astrophysics Data System (ADS)

    Amor, Sana Ben; Meddeb, Hosny; Daik, Ridha; Othman, Afef Ben; Slama, Sonia Ben; Dimassi, Wissem; Ezzaouia, Hatem

    2016-01-01

    In this paper, hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited on mono-crystalline silicon substrate by plasma enhanced chemical vapor deposition (PECVD) under different hydrogen flow rates followed by a thermal treatment in an infrared furnace at different temperature ranging from 300 to 900 °C. The investigated structural, morphological and optoelectronic properties of samples were found to be strongly dependent on the annealing temperature. Raman spectroscopy revealed that nc-Si:H films contain crystalline, amorphous and mixed structures as well. We find that post-deposition thermal treatment may lead to a tendency for structural improvement and a decrease of the disorder in the film network at moderate temperature under 500 °C. As for annealing at higher temperature up to 900 °C induces the recrystallization of the film which is correlated with the grain size and volume fraction in the layer. We demonstrate that high annealing temperature can lead to a decrease of silicon-hydrogen bonds corresponding to a reduction of the amorphous matrix in the layer promoting the formation of covalent Si-Si bonds. The effusion of the hydrogen from the grown film leads to increase its density and therefore induces a decrease in the thickness of the layer. For post-deposition thermal treatment in temperature range under 700 °C, the post-deposition anneal seems to be crucial for obtaining good passivation quality as expressed by a minority carrier lifetime of 17 μs, as it allows a significant reduction in defect states at the layer/substrate interface. While for a temperature higher than 900 °C, the lifetime reduction is obtained because of hydrogen effusion phenomenon, thus a tendency for crystallization in the grown film.

  16. WRF/Chem study of dry and wet deposition of trifluoroacetic acid produced from the atmospheric degradation of a few short-lived HFCs

    NASA Astrophysics Data System (ADS)

    Kazil, J.; McKeen, S. A.; Kim, S.; Ahmadov, R.; Grell, G. A.; Talukdar, R. K.; Ravishankara, A. R.

    2011-12-01

    HFC-134a (1,1,1,2-tetrafluoroethane) is the prevalent (used in >80% passenger cars and commercial vehicles worldwide) refrigerant in automobile air conditioning units (MACs). With an atmospheric lifetime of ~14 years and a global warming potential (GWP) of 1430 on a 100-year time horizon, HFC-134a does not meet current and expected requirements for MAC refrigerants in many parts of the world. Therefore, substitutes with lower GWP are being sought. One of the simplest way to achieve lower GWP is to use chemicals with shorter atmospheric lifetimes. In this work, we investigate the dry and wet deposition and the rainwater concentration of trifluoroacetic acid (TFA) produced by the atmospheric oxidation of 2,3,3,3-tetrafluoropropene (TFP) and 1,2,3,3,3-pentafluoropropene (PFP). The WRF/Chem model was used to calculate dry and wet TFA deposition over the contiguous USA during the May-September 2006 period that would result from replacing HFC-134a in MACs with a 1:1 molar ratio mixture of 2,3,3,3-tetrafluoropropene (TFP) and 1,2,3,3,3-pentafluoropropene (PFP). The simulation is evaluated by comparing observations of precipitation and sulfate wet deposition at stations of the National Atmospheric Deposition Program (NADP). Simulated precipitation and sulfate wet deposition correlate well with the observations, but exhibit a positive bias for precipitation and a negative bias for sulfate wet deposition. Atmospheric lifetimes of TFP and PFP against oxidation by the hydroxyl radical OH, a prognostic species in WRF/Chem, are ~5 and ~4 days in the simulation, respectively. The model setup allows the attribution of dry and wet TFA deposition to individual source regions (California, Houston, Chicago, and the remaining contiguous USA in this work). TFA deposition is highest in the eastern USA because of numerous large sources and high precipitation in the region. West of the Continental Divide, TFA deposition is significantly lower, and its origin is dominated by emissions from

  17. High-rate ( similar to 50-A/s) deposition of ZnO films for amorphous silicon alloy solar-cell back-reflector application

    SciTech Connect

    Banerjee, A.; Wolf, D.; Yang, J.; Guha, S. )

    1991-08-01

    Back reflectors have been fabricated by the deposition of ZnO films on textured Ag films. High deposition rates of {similar to}50 A/s have been achieved by the dc magnetron sputtering technique. The ZnO target used has been prepared in our laboratory. Amorphous silicon alloy solar cells have been deposited on the ZnO/textured Ag back reflector. Control samples have been prepared by the deposition of identical cells on the same back reflector, but in which the ZnO films have been prepared by a low-rate {similar to}5-A/s rf sputtering process. The short-circuit current density, which has been used as the primary test parameter for evaluating the back reflectors, is slightly superior in the case of the high-rate ZnO back reflector. The high-rate deposition process is, therefore, attractive for large-volume production application.

  18. Brooktrout Lake case study: biotic recovery from acid deposition 20 years after the 1990 Clean Air Act Amendments.

    PubMed

    Sutherland, James W; Acker, Frank W; Bloomfield, Jay A; Boylen, Charles W; Charles, Donald F; Daniels, Robert A; Eichler, Lawrence W; Farrell, Jeremy L; Feranec, Robert S; Hare, Matthew P; Kanfoush, Sharon L; Preall, Richard J; Quinn, Scott O; Rowell, H Chandler; Schoch, William F; Shaw, William H; Siegfried, Clifford A; Sullivan, Timothy J; Winkler, David A; Nierzwicki-Bauer, Sandra A

    2015-03-01

    The Adirondack Mountain region is an extensive geographic area (26,305 km(2)) in upstate New York where acid deposition has negatively affected water resources for decades and caused the extirpation of local fish populations. The water quality decline and loss of an established brook trout (Salvelinus fontinalis [Mitchill]) population in Brooktrout Lake were reconstructed from historical information dating back to the late 1880s. Water quality and biotic recovery were documented in Brooktrout Lake in response to reductions of S deposition during the 1980s, 1990s, and 2000s and provided a unique scientific opportunity to re-introduce fish in 2005 and examine their critical role in the recovery of food webs affected by acid deposition. Using C and N isotope analysis of fish collagen and state hatchery feed as well as Bayesian assignment tests of microsatellite genotypes, we document in situ brook trout reproduction, which is the initial phase in the restoration of a preacidification food web structure in Brooktrout Lake. Combined with sulfur dioxide emissions reductions promulgated by the 1990 Clean Air Act Amendments, our results suggest that other acid-affected Adirondack waters could benefit from careful fish re-introduction protocols to initiate the ecosystem reconstruction of important components of food web dimensionality and functionality. PMID:25621941

  19. Evaluating the interaction of faecal pellet deposition rates and DNA degradation rates to optimize sampling design for DNA-based mark-recapture analysis of Sonoran pronghorn.

    PubMed

    Woodruff, S P; Johnson, T R; Waits, L P

    2015-07-01

    Knowledge of population demographics is important for species management but can be challenging in low-density, wide-ranging species. Population monitoring of the endangered Sonoran pronghorn (Antilocapra americana sonoriensis) is critical for assessing the success of recovery efforts, and noninvasive DNA sampling (NDS) could be more cost-effective and less intrusive than traditional methods. We evaluated faecal pellet deposition rates and faecal DNA degradation rates to maximize sampling efficiency for DNA-based mark-recapture analyses. Deposition data were collected at five watering holes using sampling intervals of 1-7 days and averaged one pellet pile per pronghorn per day. To evaluate nuclear DNA (nDNA) degradation, 20 faecal samples were exposed to local environmental conditions and sampled at eight time points from one to 124 days. Average amplification success rates for six nDNA microsatellite loci were 81% for samples on day one, 63% by day seven, 2% by day 14 and 0% by day 60. We evaluated the efficiency of different sampling intervals (1-10 days) by estimating the number of successful samples, success rate of individual identification and laboratory costs per successful sample. Cost per successful sample increased and success and efficiency declined as the sampling interval increased. Results indicate NDS of faecal pellets is a feasible method for individual identification, population estimation and demographic monitoring of Sonoran pronghorn. We recommend collecting samples <7 days old and estimate that a sampling interval of four to seven days in summer conditions (i.e., extreme heat and exposure to UV light) will achieve desired sample sizes for mark-recapture analysis while also maximizing efficiency [Corrected]. PMID:25522240

  20. Factors affecting the rate of hydrolysis of phenylboronic acid in lab-scale precipitate reactor studies

    SciTech Connect

    Bannochie, C.J.; Marek, J.C.; Eibling, R.E.; Baich, M.A.

    1992-10-01

    Removing aromatic carbon from an aqueous slurry of cesium-137 and other alkali tetraphenylborates by acid hydrolysis will be an important step in preparing high-level radioactive waste for vitrification at the Savannah River Site`s Defense Waste Processing Facility (DWPF). Kinetic data obtained in bench-scale precipitate hydrolysis reactors suggest changes in operating parameters to improve product quality in the future plant-scale radioactive operation. The rate-determining step is the removal of the fourth phenyl group, i.e. hydrolysis of phenylboronic acid. Efforts to maximize this rate have established the importance of several factors in the system, including the ratio of copper(II) catalyst to formic acid, the presence of nitrite ion, reactions of diphenylmercury, and the purge gas employed in the system.

  1. Factors affecting the rate of hydrolysis of phenylboronic acid in lab-scale precipitate reactor studies

    SciTech Connect

    Bannochie, C.J.; Marek, J.C.; Eibling, R.E.; Baich, M.A.

    1992-01-01

    Removing aromatic carbon from an aqueous slurry of cesium-137 and other alkali tetraphenylborates by acid hydrolysis will be an important step in preparing high-level radioactive waste for vitrification at the Savannah River Site's Defense Waste Processing Facility (DWPF). Kinetic data obtained in bench-scale precipitate hydrolysis reactors suggest changes in operating parameters to improve product quality in the future plant-scale radioactive operation. The rate-determining step is the removal of the fourth phenyl group, i.e. hydrolysis of phenylboronic acid. Efforts to maximize this rate have established the importance of several factors in the system, including the ratio of copper(II) catalyst to formic acid, the presence of nitrite ion, reactions of diphenylmercury, and the purge gas employed in the system.

  2. [*C]octanoic acid breath test to measure gastric emptying rate of solids.

    PubMed

    Maes, B D; Ghoos, Y F; Rutgeerts, P J; Hiele, M I; Geypens, B; Vantrappen, G

    1994-12-01

    We have developed a breath test to measure solid gastric emptying using a standardized scrambled egg test meal (250 kcal) labeled with [14C]octanoic acid or [13C]octanoic acid. In vitro incubation studies showed that octanoic acid is a reliable marker of the solid phase. The breath test was validated in 36 subjects by simultaneous radioscintigraphic and breath test measurements. Nine healthy volunteers were studied after intravenous administration of 200 mg erythromycin and peroral administration of 30 mg propantheline, respectively. Erythromycin significantly enhanced gastric emptying, while propantheline significantly reduced gastric emptying rates. We conclude that the [*C]octanoic breath test is a promising and reliable test for measuring the gastric emptying rate of solids. PMID:7995200

  3. Long term response of acid-sensitive Vermont Lakes to sulfate deposition

    EPA Science Inventory

    Atmospheric deposition of sulfur can negatively affect the health of lakes and streams, particularly in poorly buffered catchments. In response to the Clean Air Act Amendments, wet deposition of sulfate decreased more than 35% in Vermont between 1990 and 2008. However, most of ...

  4. Initial results from the Pawnee eddy correlation system for acid deposition research

    SciTech Connect

    Zeller, K.; Massman, W.; Stocker, D.; Fox, D.G.; Stellman, D.; Hazlett, D.

    1989-01-01

    The Pawnee grassland eddy correlation dry deposition project is described. Instrumentation, methods of analysis, and initial data and research findings are presented. Data from this eddy correlation system show agreement with previous observations of deposition velocities for atmospheric ozone, NO{sub 2}, and NO{sub x}; micrometeorological theory; and micrometeorological site characteristics.

  5. Factors influencing the rate of non-enzymatic activation of carboxylic and amino acids by ATP

    NASA Technical Reports Server (NTRS)

    Mullins, D. W., Jr.; Lacey, J. C., Jr.

    1981-01-01

    The nonenzymatic formation of adenylate anhydrides of carboxylic and amino acids is discussed as a necessary step in the origin of the genetic code and protein biosynthesis. Results of studies are presented which have shown the rate of activation to depend on the pKa of the carboxyl group, the pH of the medium, temperature, the divalent metal ion catalyst, salt concentration, and the nature of the amino acid. In particular, it was found that of the various amino acids investigated, phenylalanine had the greatest affinity for the adenine derivatives adenosine and ATP. Results thus indicate that selective affinities between amino acids and nucleotides were important during prebiotic chemical evolution, and may have played a major role in the origin of protein synthesis and genetic coding.

  6. Seasonal and rainfall-type variations in inorganic ions and dicarboxylic acids and acidity of wet deposition samples collected from subtropical East Asia

    NASA Astrophysics Data System (ADS)

    Tsai, Ying I.; Hsieh, Li-Ying; Kuo, Su-Ching; Chen, Chien-Lung; Wu, Pei-Ling

    2011-07-01

    Rainfall samples were collected over a period of 3 years and 8 months in subtropical East Asia. They are categorized into different rainfall types and analyzed to assess the ionic composition and its effect on the acidity of wet deposition in southern Taiwan. Only 4% of samples had a pH of <5.0, indicating that the study area is not impacted significantly by acid rain. The volume-weighted mean (VWM) pH by rainfall type was Spring Rain 5.74, Typhoon Rain 5.56, Summer Rain 5.46, Typhoon Outer Circulation (TOC) Rain 5.45, Plum Rain 5.32 and Autumn-Winter Rain 5.29. Dilution effects were important to the equivalent ionic concentration of different rainfall types. HCO 3-, SO 42- and Cl - were detected as major anions whereas NH 4+, Na + and Ca 2+ were major cations. CO 2-derived HCO 3- was the major ionic species in all but Typhoon Rain and Spring Rain, in which the major species were Na + and Cl - and Ca 2+, respectively. Excluding HCO 3-, the major species were NH 4+, Na + and Ca 2+ in Plum Rain, the secondary photochemical products SO 42-, NO 3- and NH 4+ in TOC Rain and Summer Rain, and Na + and Ca 2+ in Autumn-Winter Rain. Calculation of arithmetic means showed that dicarboxylic acids contributed between 0.25% and 0.53% of the total ionic concentration and of these, oxalic acid contributed the least (81.3% of the dicarboxylic acid) to TOC Rain and the most (96.1% of the dicarboxylic acid) to Spring Rain, suggestive of long-range transport in the latter. Differences in wet deposition composition were shown to be a result of differences in local emissions and long-range transport (hence of prevailing wind direction) during the period of rainfall and of the frequency and volume of rain that typifies each rainfall type. Principal component analysis (PCA) further revealed that traffic-related and industrial organic and inorganic pollutants, their secondary photochemical products, sea salts, and dust are important contributors to wet deposition. Moreover, the ratio of

  7. Viscous flow rates of icy topography on the north polar layered deposits of Mars

    NASA Astrophysics Data System (ADS)

    Sori, Michael M.; Byrne, Shane; Hamilton, Christopher W.; Landis, Margaret E.

    2016-01-01

    We investigate the importance of viscous flow in shaping topography at the north polar layered deposits (NPLD) of Mars by using finite element modeling to calculate the distribution of stresses and flow velocities. Present-day impact craters on the NPLD are too small and cold for viscous relaxation to have been an important mechanism in controlling their current dimensions; this effect may be ignored when analyzing crater size-frequency distributions. Scarps at the NPLD margins, where avalanches of dust and carbon dioxide frost occur, are sufficiently steep, high, and warm to experience significant viscous flow. We find flow velocities at the base of these steep scarps on the order of tens to hundreds of cm/yr, which are fast enough to significantly affect their slope over kiloyear timescales. Alternatively, the scarps could be close to steady state in which observed block falls provide a competing effect to viscous flow.

  8. National Acid Precipitation Assessment Program: Acidic deposition: An inventory of non-Federal research, monitoring, and assessment information

    SciTech Connect

    Herrick, C.N.

    1990-01-01

    The Acid Precipitation Act of 1990 (Title VII of the Energy Security Act of 1980, P.L. 96-294) established the Interagency Task Force on Acid Precipitation to develop and implement the National Acid Precipitation Assessment Program (NAPAP). The information included in the document was provided to NAPAP's Task Group Leaders and State-of-Science and State-of-Technology authors in July 1989. The early release was intended to assure that the authors would be aware of the information at an early phase in the assessment production process.

  9. Ablation of atheroma by laser energy: a comparative study of the efficacy of different temporal rates of energy deposition

    NASA Astrophysics Data System (ADS)

    Ramsay, Donald J.; Walker, Philip J.; Dadswell, Nicola G.; May, James; Piper, James A.; Wacher, Christine

    1990-06-01

    Laser angioplasty continues to attract interest as a potential method for treating atherosclerotic arterial disease. Current efforts are aimed at finding the most effective combination of laser and delivery system. High energy pulsed ultraviolet or infrared lasers demonstrate good photoablative properties but there remain practical difficulties with the optical fibre delivery. Continuous wave lasers are widely used in conjunction with "hot-tip" fibres for thermal ablation but their direct (optical) ablation efficiency is low, causing significant surrounding thermal damage in soft tissue. While considerable attention has been directed previously at the ablative effects for different laser wavelengths, little systematic study has been made of the efficacy for different temporal rates of energy deposition. We have compared the efficacy for tissue ablation in cadaveric human aorta of three different laser systems with similar wavelengths in the visible (green) but different temporal rates of energy deposition. The laser sources were the continuous wave argon ion laser (514.5 nm), the high pulse energy, frequency doubled Nd:YAG laser (532 nm) and the copper vapour laser. The copper vapour laser is a high repetition rate, high average power, pulsed laser emitting in the green (511 nm) and yellow (578 nm) which has temporal characteristics intermediate between those of the Nd:YAG laser and the argon ion laser, and has the potential to be effective both for direct optical ablation and hot-tip thermal ablation.

  10. Evaluating ammonia deposition rates for deciduous forest using measurements and modelling

    NASA Astrophysics Data System (ADS)

    Hansen, K.; Geels, C.; Hertel, O.; Skjøth, C. A.; Jensen, B.; Soerensen, L. L.; Boegh, E.

    2012-04-01

    Atmospheric ammonia (NH3) is a major contributor to soil acidification and eutrophication of natural terrestrial ecosystem leading to e.g. reduced biodiversity (Erisman et al. 2007, Environmental Pollution, Stevens et al. 2004, Science, Sutton et al. 2009, Biogeoscience). In order to assess these impacts, quantifying the magnitude of the NH3 flux in the biosphere atmosphere system is essential. Model simulations using the Danish Ammonia Modelling System (DAMOS) have recently indicated that particular forest ecosystems are exposed to critical load exceedances of N (Geels et al., not yet submitted). However, there are relatively few datasets of atmospheric NH3 fluxes available for forests which can contribute verifying model results. The atmospheric dry deposition of NH3 for the beech (Fagus sylvatica) forest, Lille Bøgeskov, in Sorø, Denmark, is investigated using the high resolution micrometeorological measuring technique, Relaxed Eddy Accumulation (REA), for 26 October - 11 November 2010. Measurements of atmospheric NH3 concentrations and fluxes are compared to local-scale model simulations using the Danish Ammonia Modelling System (DAMOS). It was found that long-term measured and modelled atmospheric mean concentrations of NH3 agreed well within the range of 0.56-0.68 µg NH3-N m-3, however, observed emission fluxes of up to app. 0.8 µg NH3-N m-2 s-1 after leaf fall were not represented by DAMOS because the model system does not consider vegetative and soil NH3 emissions from non-agricultural areas (Skjøth et al. 2011, ACPD). New atmospheric NH3 flux measurements for Lille Bøgeskov have been conducted throughout 2011 and these data are presented and discussed in relation to the 2010 data of atmospheric NH3. Future studies aim to improve the description of dry deposition of NH3 for vegetative surfaces in local-scale models whereby the NH3 vegetative emission and its contribution to the atmospheric NH3 concentration and flux is considered.

  11. High-rate deposition of MgO by reactive ac pulsed magnetron sputtering in the transition mode

    SciTech Connect

    Kupfer, H.; Kleinhempel, R.; Richter, F.; Peters, C.; Krause, U.; Kopte, T.; Cheng, Y.

    2006-01-15

    A reactive ac pulsed dual magnetron sputtering process for MgO thin-film deposition was equipped with a closed-loop control of the oxygen flow rate (F{sub O2}) using the 285 nm magnesium radiation as input. Owing to this control, most of the unstable part of the partial pressure versus flowrate curve became accessible. The process worked steadily and reproducible without arcing. A dynamic deposition rate of up to 35 nm m/min could be achieved, which was higher than in the oxide mode by about a factor of 18. Both process characteristics and film properties were investigated in this work in dependence on the oxygen flow, i.e., in dependence on the particular point within the transition region where the process is operated. The films had very low extinction coefficients (<5x10{sup -5}) and refractive indices close to the bulk value. They were nearly stoichiometric with a slight oxygen surplus (Mg/O=48/52) which was independent of the oxygen flow. X-ray diffraction revealed a prevailing (111) orientation. Provided that appropriate rf plasma etching was performed prior to deposition, no other than the (111) peak could be detected. The intensity of this peak increased with increasing F{sub O{sub 2}}, indicating an even more pronounced (111) texture. The ion-induced secondary electron emission coefficient (iSEEC) was distinctly correlated with the markedness of the (111) preferential orientation. Both refractive index and (111) preferred orientation (which determines the iSEEC) were found to be improved in comparison with the MgO growth in the fully oxide mode. Consequently, working in the transition mode is superior to the oxide mode not only with respect to the growth rate, but also to most important film properties.

  12. The effect of random precipitation times on the scavenging rate for tropospheric nitric acid

    NASA Technical Reports Server (NTRS)

    Stewart, Richard W.

    1988-01-01

    A model for the effective scavenging rate of a soluble species has been developed. The model takes into account the possibility of positive as well as negative correlations between departures from the mean of the scavenging rate and species concentration. The model is demonstrated for the case of late afternoon rainout of nitric acid occurring just prior to the nighttime cessation of its chemical production. The calculations give effective scavenging rates which are about a factor of 2 to 3 greater than those calculated using the models of Rodhe and Grandell (1972) and Giorgi and Chameides (1985).

  13. Water geochemistry of the Qiantangjiang River, East China: Chemical weathering and CO2 consumption in a basin affected by severe acid deposition

    NASA Astrophysics Data System (ADS)

    Liu, Wenjing; Shi, Chao; Xu, Zhifang; Zhao, Tong; Jiang, Hao; Liang, Chongshan; Zhang, Xuan; Zhou, Li; Yu, Chong

    2016-09-01

    The chemical composition of the Qiantangjiang River, the largest river in Zhejiang province in eastern China, was measured to understand the chemical weathering of rocks and the associated CO2 consumption and anthropogenic influences within a silicate-dominated river basin. The average total dissolved solids (TDS, 113 mg l-1) and total cation concentration (TZ+, 1357 μeq l-1) of the river waters are comparable with those of global major rivers. Ca2+ and HCO3- followed by Na2+ and SO42-, dominate the ionic composition of the river water. There are four major reservoirs (carbonates, silicates, atmospheric and anthropogenic inputs) contributing to the total dissolved load of the investigated rivers. The dissolved loads of the rivers are dominated by both carbonate and silicate weathering, which together account for about 76.3% of the total cationic load origin. The cationic chemical weathering rates of silicate and carbonate for the Qiantangjiang basin are estimated to be approximately 4.9 ton km-2 a-1 and 13.9 ton km-2 a-1, respectively. The calculated CO2 consumption rates with the assumption that all the protons involved in the weathering reaction are provided by carbonic acid are 369 × 103 mol km-2 a-1 and 273 × 103 mol km-2 a-1 by carbonate and silicate weathering, respectively. As one of the most severe impacted area by acid rain in China, H2SO4 from acid precipitation is also an important proton donor in weathering reactions. When H2SO4 is considered, the CO2 consumption rates for the river basin are estimated at 286 × 103 mol km-2 a-1 for carbonate weathering and 211 × 103 mol km-2 a-1 for silicate weathering, respectively. The results highlight that the drawdown effect of CO2 consumption by carbonate and silicate weathering can be largely overestimated if the role of sulfuric acid is ignored, especially in the area heavily impacted by acid deposition like Qiantangjiang basin. The actual CO2 consumption rates (after sulfuric acid weathering effect

  14. Effects of acid deposition on dissolution of carbonate stone during summer storms in the Adirondack Mountains, New York, 1987-89

    USGS Publications Warehouse

    Schuster, Paul F.; Reddy, Michael M.; Sherwood, S.I.

    1994-01-01

    This study is part of a long-term research program designed to identify and quantify acid rain damage to carbonate stone. Acidic deposition accelerates the dissolution of carbonate-stone monuments and building materials. Sequential sampling of runoff from carbonate-stone (marble) and glass (reference) microcatchments in the Adirondack Mountains in New York State provided a detailed record of the episodic fluctuations in rain rate and runoff chemistry during individual summer storms. Rain rate and chemical concentrations from carbonate-stone and glass runoff fluctuated three to tenfold during storms. Net calcium-ion concentrations from the carbonatestone runoff, a measure of stone dissolution, typically fluctuated twofold during these storms. High net sulfate and net calcium concentrations in the first effective runoff at the start of a storm indicated that atmospheric pollutants deposited on the stone surface during dry periods formed calcium sulfate minerals, an important process in carbonate stone dissolution. Dissolution of the carbonate stone generally increased up to twofold during coincident episodes of low rain rate (less than 5 millimeters per hour) and decreased rainfall (glass runoff) pH (less than 4.0); episodes of high rain rate (cloudbursts) were coincident with a rapid increase in rainfall pH and also a rapid decrease in the dissolution of carbonate-stone. During a storm, it seems the most important factors causing increased dissolution of carbonate stone are coincident periods of low rain rate and decreased rainfall pH. Dissolution of the carbonate stone decreased slightly as the rain rate exceeded about 5 millimeters per hour, probably in response to rapidly increasing rainfall pH during episodes of high rain rate and shorter contact time between the runoff and the stone surface. High runoff rates resulting from cloudbursts remove calcium sulfate minerals formed during dry periods prior to storms and also remove dissolution products formed in large

  15. A Demonstration of Acid Rain and Lake Acidification: Wet Deposition of Sulfur Dioxide.

    ERIC Educational Resources Information Center

    Goss, Lisa M.

    2003-01-01

    Introduces a science demonstration on the dissolution of sulfuric oxide emphasizing the concept of acid rain which is an environmental problem. Demonstrates the acidification from acid rain on two lake environments, limestone and granite. Includes safety information. (YDS)

  16. Humic substances and trace metals associated with Fe and Al oxides deposited in an acidic mountain stream

    USGS Publications Warehouse

    McKnight, Diane M.; Wershaw, R. L.; Bencala, K.E.; Zellweger, G.W.; Feder, G.L.

    1992-01-01

    Hydrous iron and aluminum oxides are deposited on the streambed in the confluence of the Snake River and Deer Creek, two streams in the Colorado Rocky Mountains. The Snake River is acidic and has high concentrations of dissolved Fe and Al. These metals precipitate at the confluence with the pristine, neutral pH, Deer Creek because of the greater pH (4.5-6.0) in the confluence. The composition of the deposited oxides changes consistently with distance downstream, with the most upstream oxide samples having the greatest Fe and organic carbon content. Fulvic acid accounts for most of the organic content of the oxides. Results indicate that streambed oxides in the confluence are not saturated with respect to their capacity to sorb dissolved humic substances from streamwater. The contents of several trace metals (Mn, Zn, Cu, Pb, Ni and Co) also decrease with distance downstream and are correlated with both the Fe and organic carbon contents. Strong metal-binding sites associated with the sorbed fulvic acid are more than sufficient to account for the trace metal content of the oxides. Complexation of trace metals by sorbed fulvic acid may explain the observed downstream decrease in trace metal content.

  17. Comparison of parameterized nitric acid rainout rates using a coupled stochastic-photochemical tropospheric model

    NASA Technical Reports Server (NTRS)

    Stewart, Richard W.; Thompson, Anne M.; Owens, Melody A.; Herwehe, Jerold A.

    1989-01-01

    A major tropospheric loss of soluble species such as nitric acid results from scavenging by water droplets. Several theoretical formulations have been advanced which relate an effective time-independent loss rate for soluble species to statistical properties of precipitation such as the wet fraction and length of a precipitation cycle. In this paper, various 'effective' loss rates that have been proposed are compared with the results of detailed time-dependent model calculations carried out over a seasonal time scale. The model is a stochastic precipitation model coupled to a tropospheric photochemical model. The results of numerous time-dependent seasonal model runs are used to derive numerical values for the nitric acid residence time for several assumed sets of preciptation statistics. These values are then compared with the results obtained by utilizing theoretical 'effective' loss rates in time-independent models.

  18. Patterns of wet deposition of acidic matter in Maryland: January-June 1984. Final report

    SciTech Connect

    Maxwell, C.; Bartoshesky, J.; Pfeffer, N.; Campbell, S.

    1987-03-03

    A data base containing precipitation-chemistry data collected by multiple monitoring programs in and around Maryland for the January through June 1984 time period was compiled. Isopleth maps were constructed showing the spatial variation in the precipitation concentrations and depositions of hydrogen ion, sulfate, nitrate, ammonium, calcium, sodium, chloride, potassium, and magnesium. For each parameter, the concentration pattern was very similar to its deposition pattern. The patterns suggest the occurrence of a ridge of high sulfate, nitrate, and hydrogen ion concentrations and depositions extending from south-central Pennsylvania, south into Maryland along the western shore of the Chesapeake Bay.

  19. Measurement and Analysis of Extracellular Acid Production to Determine Glycolytic Rate.

    PubMed

    Mookerjee, Shona A; Brand, Martin D

    2015-01-01

    Extracellular measurement of oxygen consumption and acid production is a simple and powerful way to monitor rates of respiration and glycolysis(1). Both mitochondrial (respiration) and non-mitochondrial (other redox) reactions consume oxygen, but these reactions can be easily distinguished by chemical inhibition of mitochondrial respiration. However, while mitochondrial oxygen consumption is an unambiguous and direct measurement of respiration rate(2), the same is not true for extracellular acid production and its relationship to glycolytic rate (3-6). Extracellular acid produced by cells is derived from both lactate, produced by anaerobic glycolysis, and CO2, produced in the citric acid cycle during respiration. For glycolysis, the conversion of glucose to lactate(-) + H(+) and the export of products into the assay medium is the source of glycolytic acidification. For respiration, the export of CO2, hydration to H2CO3 and dissociation to HCO3(-) + H(+) is the source of respiratory acidification. The proportions of glycolytic and respiratory acidification depend on the experimental conditions, including cell type and substrate(s) provided, and can range from nearly 100% glycolytic acidification to nearly 100% respiratory acidification (6). Here, we demonstrate the data collection and calculation methods needed to determine respiratory and glycolytic contributions to total extracellular acidification by whole cells in culture using C2C12 myoblast cells as a model. PMID:26709455

  20. Preparation and properties of high-deposition-rate a-Si:H films and solar cells using disilane: Annual subcontract report, 1 May 1987--30 April 1988

    SciTech Connect

    Bhat, P.K.; Chatham, H.; Madan, A.

    1988-06-01

    This report contains results of the first year of research on producing p-i-n amorphous silicon solar cells with the intrinsic layer deposited from higher order silanes at deposition rates of 1 nm/s or more. The research was divided into three major areas: diagnostic studies of monosilane and disilane RF discharges using optical emission spectroscopy and mass spectrometry to assist in optimizing discharge conditions and gas-phase processes; parametric studies of material properties of 1-layers prepared form disilane as a function of deposition rate and other process parameters; and parametric studies of p-i-n devices with the i-layer prepared from disilane at various deposition rates. The focus during the first year was to fabricate a p-i-n solar cell with 9/percent/ AM1.5 efficiency over an area greater than 0.08 cm/sup 2/ with the i-layer deposited at 1 nm/s or more. Material properties such as the dark and AM1.5 light conductivities, optical band gap, and conductivity activation energy showed a weak dependence on deposition rate. The performance characteristics of unoptimized p-i-n solar cells with i-layers prepared from disilane were independent of the deposition rate of the i-layer. A p-i-n device was prepared at a rate close to 1 nm/s with an AM1.5 efficiency of 9/percent/. 20 refs, 26 figs, 2 tabs.

  1. Acid deposition coverage in five North American newspapers, 1979-1982

    SciTech Connect

    Kauffeld, J.A.; Fortner, R.W.

    1987-01-01

    Daily newspapers in some areas receiving acid rain, in some areas reported to be producing acid rain, and in some areas apparently ''neutral'' in the issue were content analyzed for their coverage of acid rain between 1979 and 1982. Of the five papers, the greatest amount of coverage was in the Cleveland Plain Dealer and the Toronto Globe and Mail. Coverage of acid rain effects was greatest in the Washington Post, as was the number of items suggesting remedies for the problem. Articles from papers in areas receiving acid rain contained more indications of urgency than those from areas blamed for the problem.

  2. Dynamics of cryogen deposition relative to heat extraction rate during cryogen spray cooling

    NASA Astrophysics Data System (ADS)

    Verkruysse, Wim; Majaron, Boris; Aguilar, Guillermo; Svaasand, Lars O.; Nelson, J. Stuart

    2000-05-01

    Goal is to investigate how delivery nozzle design influences the cooling rate of cryogen spray as used in skin laser treatments. Cryogen was sprayed through nozzles that consist of metal tubes with either a narrow or wide diameter and two different lengths. Fast-flashlamp photography showed that the wide nozzles, in particular the long wide one, produced a cryogen jet (very small spray cone angle) rather than a spray (cone angles of about 15 degrees or higher) and appeared to atomize the cryogen less finely than the narrow nozzles. We measured the cooling rate by spraying some cryogen on an epoxy-block with thermocouples embedded. The heat extraction rate of the wide nozzles was higher than that of the narrow nozzles. The results suggest that finely atomized droplets produced by the narrow nozzles do not have enough kinetic energy to break through a layer of liquid cryogen accumulated on the object, which may act as a thermal barrier and, thus, slow down heat extraction. Presumably, larger droplets or non- broken jets ensure a more violent impact on this layer and therefore ensure an enhanced thermal contact. The margin of error for the heat extraction estimate is analyzed when using the epoxy-block. We introduce a complementary method for estimating heat extraction rate of cryogen sprays.

  3. Spray deposition inside tree canopies from a newly developed variable-rate air assisted sprayer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Conventional spray applications in orchards and ornamental nurseries are not target-oriented, resulting in significant waste of pesticides and contamination of the environment. To address this problem, a variable-rate air-assisted sprayer implementing laser scanning technology was developed to apply...

  4. High Elevation Lakes of the Western US: Are we Studying Systems Recovering from Excess Atmospheric Deposition of Acids and Nutrients?

    NASA Astrophysics Data System (ADS)

    Sickman, J. O.

    2011-12-01

    Instrumental records and monitoring of high elevation lakes began in most areas of the western US in the early 1980s. Much effort has been devoted to detecting changes in these aquatic ecosystems resulting from increased atmospheric deposition of acids and nutrients. However, there is growing evidence that thresholds for atmospheric pollutants were crossed much earlier in the 20th Century and that some of the subsequent hydrochemical and ecological changes observed in these lakes may be the result of recovery from earlier atmospheric forcing. We examine responses of high elevation lakes to atmospheric deposition on annual to century timescales using data from a 29-year study of Emerald Lake (Sequoia National Park) and paleolimnological analyses of other high elevation lakes incorporating diatom species analyses and geochemical proxies for fossil-fuel burning. At Emerald Lake, we have observed multiple transitions between nitrogen and phosphorus limitation of phytoplankton, the earliest of which occurred in the beginning of the 1980s and may be the result of reduction in N deposition due to the Clean Air Act. Critical loads analyses incorporating diatom species in lake sediments suggest that thresholds for N deposition were crossed in the period of 1950-1980 in the Rocky Mountains and likely much earlier, 1900-1920, in the Sierra Nevada. Diatom species composition is strongly controlled by acid neutralizing capacity (ANC) in the Sierra Nevada and we have observed a pronounced decline and recovery of ANC over the period of 1920-1980 in some Sierra Nevada lakes that coincides with the abundance of spheroidal carbonaceous particles (i.e., a diagnostic tracer of fossil fuel combustion) preserved in lake sediments; these patterns appear to be driven by increased emissions of oxidized N and S in the mid-20th Century and reductions in acid precursor levels caused by the Clean Air Act in the 1970s. Thus, when interpreting observational records from western high elevation

  5. Relationship between the Averaged Deposition Rate Coefficients for Colloids in a Single Pore and Various Pore-scale Parameters

    NASA Astrophysics Data System (ADS)

    Narayanan, S.; Mohan Kumar, M.; Hassanizadeh, S. M.; Raoof, A.

    2014-12-01

    The colloid deposition behavior observed at the Darcy scale represents an average of the processes occurring at the pore scale. Hence, a better understanding of the processes occurring at the Darcy scale can be obtained by studying colloid transport at the pore-scale and then upscaling the results. In this study, we have developed a mathematical model to simulate the transport of colloids in a cylindrical pore by considering various processes such as advection, diffusion, colloid-soil surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, the bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion; whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-solid interaction forces dominate the transport in the potential region where colloid deposition occurs and are calculated using DLVO theory. The expressions for mass transfer rate coefficients between the diffusion and potential regions have been derived for different DLVO energy profiles. These are incorporated in the pore-scale equations in the form of a boundary condition at the diffusion-potential region interface. The model results are used to obtain the colloid breakthrough curve at the end of a long pore, and then it is fitted with 1D advection-dispersion-adsorption model so as to determine the averaged attachment and detachment rate coefficients at the scale of a single pore. A sensitivity analysis of the model to six pore-scale parameters (colloid and wall surface potentials, solution ionic strength, average pore-water velocity, colloid radius, and pore radius) is carried out so as to find the relation between the averaged deposition rate coefficients at pore scale vs the pore-scale parameters. We found an hyper exponential relation between the colloid attachment

  6. Tailoring deposition and morphology of discharge products towards high-rate and long-life lithium-oxygen batteries.

    PubMed

    Xu, Ji-Jing; Wang, Zhong-Li; Xu, Dan; Zhang, Lei-Lei; Zhang, Xin-Bo

    2013-01-01

    Lithium-oxygen batteries are an attractive technology for electrical energy storage because of their exceptionally high-energy density; however, battery applications still suffer from low rate capability, poor cycle stability and a shortage of stable electrolytes. Here we report design and synthesis of a free-standing honeycomb-like palladium-modified hollow spherical carbon deposited onto carbon paper, as a cathode for a lithium-oxygen battery. The battery is capable of operation with high-rate (5,900 mAh g ⁻¹ at a current density of 1.5 A g⁻¹) and long-term (100 cycles at a current density of 300 mA g⁻¹ and a specific capacity limit of 1,000 mAh g⁻¹). These properties are explained by the tailored deposition and morphology of the discharge products as well as the alleviated electrolyte decomposition compared with the conventional carbon cathodes. The encouraging performance also offers hope to design more advanced cathode architectures for lithium-oxygen batteries. PMID:24052126

  7. Criteria for significance of simultaneous presence of both condensible vapors and aerosol particles on mass transfer (deposition) rates

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.

    1986-01-01

    The simultaneous presence of aerosol particles and condensible vapors in a saturated boundary layer which may affect deposition rates to subcooled surfaces because of vapor-particle interactions is discussed. Scavenging of condensible vapors by aerosol particles may lead to increased particle size and decreased vapor mass fraction, which alters both vapor and particle deposition rates. Particles, if sufficiently concentrated, may also coagulate. Criteria are provided to assess the significance of such phenomena when particles are already present in the mainstream and are not created inside the boundary layer via homogeneous nucleation. It is determined that there is direct proportionality with: (1) the mass concentration of both condensible vapors and aerosol particles; and (2) the square of the boundary layer thickness to particle diameter ratio (delta d sub p) square. Inverse proportionality was found for mainstream to surface temperature difference if thermophoresis dominates particle transport. It is concluded that the square of the boundary layer thickness to particle diameter ratio is the most critical factor to consider in deciding when to neglect vapor-particle interactions.

  8. Graphene hydrogels deposited in nickel foams for high-rate electrochemical capacitors.

    PubMed

    Chen, Ji; Sheng, Kaixuan; Luo, Peihui; Li, Chun; Shi, Gaoquan

    2012-08-28

    Graphene hydrogel/nickel foam composite electrodes for high-rate electrochemical capacitors are produced by reduction of an aqueous dispersion of graphene oxide in a nickel foam (upper half of figure). The micropores of the hydrogel are exposed to the electrolyte so that ions can enter and form electrochemical double-layers. The nickel framework shortens the distances of charge transfer. Therefore, the electrochemical capacitor exhibits highrate performance (see plots). PMID:22786775

  9. Sediment-deposition rates and organic compounds in bottom sediment at four sites in Lake Mead, Nevada, May 1998

    USGS Publications Warehouse

    Covay, K.J.; Beck, D.A.

    2001-01-01

    In May 1998 the U.S. Geological Survey, in cooperation with the University of Nevada, Las Vegas, investigated rates of sediment deposition and concentrations of selected synthetic organic compounds at four sites in Lake Mead. Sediment cores were extracted from two sites (one shallow and one deep) in Las Vegas Bay, from one site in the Overton Arm, and from one site near the historic confluence of the Colorado and Virgin Rivers. The sediment cores were age-dated using cesium-137 and were analyzed for the presence of organochlorine compounds (pesticides and degradation products, polychlorinated biphenyls, dioxins, and furans) and for semivolatile organic compounds (polycyclic aromatic hydrocarbons and phenols). Sediment-deposition rates after impoundment of the Colorado River by Hoover Dam were determined by measuring the accumulation of mass during three different periods: (1) from the approximate impoundment date for each site (1935-37) to the initial occurrence of cesium-137 in the atmosphere (1952); (2) from 1952 to the maximum concentration of cesium-137 in the atmosphere (1964); and (3) from 1964 to the collection date of the sample (1998). Sediment-deposition rates for the entire post-impoundment period (1935-98) averaged 1.45 (g/cm2)/yr (grams per square centimeter per year) at the Las Vegas Bay shallow site, 1.25 (g/cm2)/yr at the Las Vegas Bay deep site, 0.80 (g/cm2)/yr at the Overton Arm site, and 0.65 (g/cm2)/yr at the Colorado and Virgin Rivers confluence site. Sediment-deposition rates after impoundment of the Colorado River by Hoover Dam were determined by measuring the accumulation of mass during three different periods: (1) from the approximate impoundment date for each site (1935-37) to the initial occurrence of cesium-137 in the atmosphere (1952); (2) from 1952 to the maximum concentration of cesium-137 in the atmosphere (1964); and (3) from 1964 to the collection date of the sample (1998). Sediment-deposition rates for the entire post

  10. Impact of deposition parameters on the material quality of SPC poly-Si thin films using high-rate PECVD of a-Si:H

    NASA Astrophysics Data System (ADS)

    Kumar, Avishek; Widenborg, Per Ingemar; Dalapati, Goutam Kumar; Sandhya Subramanian, Gomathy; Aberle, Armin Gerhard

    2015-05-01

    The impact of the deposition parameters such as gas flow (sccm) and RF plasma power density (W/cm2) on the deposition rate of a-Si:H films is systematically investigated. A high deposition rate of up to 146 nm/min at 13.56 MHz is achieved for the a-Si:H films deposited with high lateral uniformity on 30 × 40 cm2 large-area glass substrates. A relationship between the SiH4 gas flow and the RF power density is established. The SiH4 gas flow to RF power density ratio of about 2.4 sccm/mW cm-2 is found to give a linear increase in the deposition rate. The influence of the deposition rate on the material quality is studied using UV-VIS-NIR spectrophotometer and Raman characterisation techniques. Poly-Si thin film with crystal quality as high as 90% of single-crystalline Si wafer is obtained from the SPC of high rate deposited a-Si:H films.

  11. Trajectory analysis of acid deposition data from the new jersey pine barrens

    NASA Astrophysics Data System (ADS)

    Budd, William W.

    This research provides an example of the application of a simple method for evaluating regional interrelationships using air parcel trajectory analysis. An assessment of trajectories associated with storms affecting McDonald's Branch watershed (39°50'N, 74°30'W) is presented. A simple classification system is used to examine regional contributions of acid precursors. The results of the work suggest that major regional sources of acid precursor emissions dominated precipitation acidity for the Pine Barrens region from 1978 to 1981. An incremental approach to acid precipitation policy is suggested.

  12. Decomposition of phenylarsonic acid by AOP processes: degradation rate constants and by-products.

    PubMed

    Jaworek, K; Czaplicka, M; Bratek, Ł

    2014-10-01

    The paper presents results of the studies photodegradation, photooxidation, and oxidation of phenylarsonic acid (PAA) in aquatic solution. The water solutions, which consist of 2.7 g dm(-3) phenylarsonic acid, were subjected to advance oxidation process (AOP) in UV, UV/H2O2, UV/O3, H2O2, and O3 systems under two pH conditions. Kinetic rate constants and half-life of phenylarsonic acid decomposition reaction are presented. The results from the study indicate that at pH 2 and 7, PAA degradation processes takes place in accordance with the pseudo first order kinetic reaction. The highest rate constants (10.45 × 10(-3) and 20.12 × 10(-3)) and degradation efficiencies at pH 2 and 7 were obtained at UV/O3 processes. In solution, after processes, benzene, phenol, acetophenone, o-hydroxybiphenyl, p-hydroxybiphenyl, benzoic acid, benzaldehyde, and biphenyl were identified. PMID:24824504

  13. Acid tolerance in amphibians

    SciTech Connect

    Pierce, B.A.

    1985-04-01

    Studies of amphibian acid tolerance provide information about the potential effects of acid deposition on amphibian communities. Amphibians as a group appear to be relatively acid tolerant, with many species suffering increased mortality only below pH 4. However, amphibians exhibit much intraspecific variation in acid tolerance, and some species are sensitive to even low levels of acidity. Furthermore, nonlethal effects, including depression of growth rates and increases in developmental abnormalities, can occur at higher pH.

  14. Visible-light active thin-film WO{sub 3} photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

    SciTech Connect

    Oka, Nobuto Murata, Akiyo; Nakamura, Shin-ichi; Jia, Junjun; Shigesato, Yuzo; Iwabuchi, Yoshinori; Kotsubo, Hidefumi

    2015-10-01

    A process based on reactive gas flow sputtering (GFS) for depositing visible-light active photocatalytic WO{sub 3} films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO{sub 3} films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH{sub 3}CHO under visible light irradiation. The decomposition time for 60 ppm of CH{sub 3}CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO{sub 3} films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH{sub 3}CHO.

  15. Visible-light active thin-film WO3 photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

    NASA Astrophysics Data System (ADS)

    Oka, Nobuto; Murata, Akiyo; Nakamura, Shin-ichi; Jia, Junjun; Iwabuchi, Yoshinori; Kotsubo, Hidefumi; Shigesato, Yuzo

    2015-10-01

    A process based on reactive gas flow sputtering (GFS) for depositing visible-light active photocatalytic WO3 films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO3 films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH3CHO under visible light irradiation. The decomposition time for 60 ppm of CH3CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO3 films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH3CHO.

  16. Swfoldrate: predicting protein folding rates from amino acid sequence with sliding window method.

    PubMed

    Cheng, Xiang; Xiao, Xuan; Wu, Zhi-cheng; Wang, Pu; Lin, Wei-zhong

    2013-01-01

    Protein folding is the process by which a protein processes from its denatured state to its specific biologically active conformation. Understanding the relationship between sequences and the folding rates of proteins remains an important challenge. Most previous methods of predicting protein folding rate require the tertiary structure of a protein as an input. In this study, the long-range and short-range contact in protein were used to derive extended version of the pseudo amino acid composition based on sliding window method. This method is capable of predicting the protein folding rates just from the amino acid sequence without the aid of any structural class information. We systematically studied the contributions of individual features to folding rate prediction. The optimal feature selection procedures are adopted by means of combining the forward feature selection and sequential backward selection method. Using the jackknife cross validation test, the method was demonstrated on the large dataset. The predictor was achieved on the basis of multitudinous physicochemical features and statistical features from protein using nonlinear support vector machine (SVM) regression model, the method obtained an excellent agreement between predicted and experimentally observed folding rates of proteins. The correlation coefficient is 0.9313 and the standard error is 2.2692. The prediction server is freely available at http://www.jci-bioinfo.cn/swfrate/input.jsp. PMID:22933332

  17. Effect of dietary fatty acids on metabolic rate and nonshivering thermogenesis in golden hamsters.

    PubMed

    Jefimow, Małgorzata; Wojciechowski, Michał S

    2014-02-01

    Hibernating rodents prior to winter tend to select food rich in polyunsaturated fatty acids (PUFA). Several studies found that such diet may positively affect their winter energy budget by enhancing torpor episodes. However, the effect of composition of dietary fatty acids (FA) on metabolism of normothermic heterotherms is poorly understood. Thus we tested whether diets different in FA composition affect metabolic rate (MR) and the capacity for nonshivering thermogenesis (NST) in normothermic golden hamsters (Mesocricetus auratus). Animals were housed in outdoor enclosures from May 2010 to April 2011 and fed a diet enriched with PUFA (i.e., standard food supplemented weekly with sunflower and flax seeds) or with saturated and monounsaturated fatty acids (SFA/MUFA, standard food supplemented with mealworms). Since diet rich in PUFA results in lower MR in hibernating animals, we predicted that PUFA-rich diet would have similar effect on MR of normothermic hamsters, that is, normothermic hamsters on the PUFA diet would have lower metabolic rate in cold and higher NST capacity than hamsters supplemented with SFA/MUFA. Indeed, in winter resting metabolic rate (RMR) below the lower critical temperature was higher and NST capacity was lower in SFA/MUFA-supplemented animals than in PUFA-supplemented ones. These results suggest that the increased capacity for NST in PUFA-supplemented hamsters enables them lower RMR below the lower critical temperature of the thermoneural zone. PMID:24151228

  18. High rate deposition of photocatalytic TiO{sub 2} films with high activity by hollow cathode gas-flow sputtering method

    SciTech Connect

    Kubo, Yoshiyuki; Iwabuchi, Yoshinori; Yoshikawa, Masato; Sato, Yasushi; Shigesato, Yuzo

    2008-07-15

    Photocatalytic TiO{sub 2} films were deposited by a hollow cathode gas-flow sputtering method using two Ti metal targets mounted parallel to each other. The Ar and O{sub 2} flow rates were 3000 and 0-50 SCCM (SCCM denotes cubic centimeter per minute at STP), respectively, and total gas pressure during the deposition was maintained at 45 Pa. The highest deposition rate for the photocatalytic TiO{sub 2} films was 162 nm/min at 30 SCCM of O{sub 2} flow. The as-deposited films and postannealed films, annealed in air at 300 deg. C for 1 h, were used to carry out photocatalytic decomposition of acetaldehyde (CH{sub 3}CHO). In particular, the postannealed films showed extremely high photocatalytic activity compared to the photocatalytic activity of films deposited by conventional reactive sputtering.

  19. Regional assessment of the response of the acid-base status of lake watersheds in the Adirondack region of New York to changes in atmospheric deposition using PnET-BGC.

    PubMed

    Chen, Limin; Driscoll, Charles T

    2005-02-01

    Understanding the response of soil and surface waters to changes in atmospheric deposition is critical for guiding future legislation on air pollution. The Adirondack region of New York experiences among the most severe ecological impacts from acidic deposition. The region is characterized by considerable variability in atmospheric deposition, surficial and bedrock geology, hydrologic flow paths, and vegetation resulting in variability in effects of acidic deposition. In this study, an integrated biogeochemical model (PnET-BGC) was applied to 37 forest lake watersheds to assess the response of soil and surface waters of the Adirondacks to changes in atmospheric deposition at a regional scale. Model-simulated surface water chemistry was validated against data from two synoptic surveys conducted in 1984 and 2001. Results indicate that the model is able to capture the observed changes in surface water chemistry during this period. The model was further used to forecast the response of soil and surface waters to three future emission control scenarios. Results indicate that under the Clean Air Act, surface water SO4(2-) concentrations will continue to decrease at a median rate of -0.38 microeq/L-yr, and surface water ANC is predicted to increase at a median rate of 0.11 microeq/L-yr. More aggressive emission reductions will accelerate the rate of recovery. Under an aggressive control scenario, which represents an additional 75% reduction in SO2 emissions beyond the implementation of the Clean Air Act, surface water SO4(2-) concentrations are predicted to decrease at a median rate of -0.88 microeq/L-yr, and surface water ANC is predicted to increase at a median rate of 0.43 microeq/L-yr. Model predictions of several biologically relevant chemical indicators are also reported. PMID:15757340

  20. A Demonstration of Acid Rain and Lake Acidification: Wet Deposition of Sulfur Dioxide

    NASA Astrophysics Data System (ADS)

    Goss, Lisa M.

    2003-01-01

    A demonstration showing acid rain and lake acidification is described. In this demonstration, SO2 gas is generated in a large graduated cylinder and then dissolved in water droplets from a simple spray bottle. The droplets carry the acid into simulated lakes, one of which includes solid CaCO3 to mimic limestone's natural buffering capacity.

  1. Dry deposition of ammonia, nitric acid, ammonium, and nitrate to alpine tundra at Niwot Ridge, Colorado

    USGS Publications Warehouse

    Rattray, G.; Sievering, H.

    2001-01-01

    Micrometeorological measurements and ambient air samples, analyzed for concentrations of NH3, HNO3, NH4+, and NO3-, were collected at an alpine tundra site on Niwot Ridge, Colorado. The measured concentrations were extremely low and ranged between 5 and 70ngNm-3. Dry deposition fluxes of these atmospheric species were calculated using the micrometeorological gradient method. The calculated mean flux for NH3 indicates a net deposition to the surface and indicates that NH3 contributed significantly to the total N deposition to the tundra during the August-September measurement period. Our pre-measurement estimate of the compensation point for NH3 in air above the tundra was 100-200ngNm-3; thus, a net emission of NH3 was expected given the low ambient concentrations of NH3 observed. Based on our results, however, the NH3 compensation point at this alpine tundra site appears to have been at or below about 20ngNm-3. Large deposition velocities (>2cms-1) were determined for nitrate and ammonium and may result from reactions with surface-derived aerosols. Copyright (C) 2001 Elsevier Science B.V.Micrometeorological measurements and ambient air samples, analyzed for concentrations of NH3, HNO3, NH4+, and NO3-, were collected at an alpine tundra site on Niwot Ridge, Colorado. The measured concentrations were extremely low and ranged between 5 and 70 ng N m-3. Dry deposition fluxes of these atmospheric species were calculated using the micrometeorological gradient method. The calculated mean flux for NH3 indicates a net deposition to the surface and indicates that NH3 contributed significantly to the total N deposition to the tundra during the August-September measurement period. Our pre-measurement estimate of the compensation point for NH3 in air above the tundra was 100-200 ng N m-3; thus, a net emission of NH3 was expected given the low ambient concentrations of NH3 observed. Based on our results, however, the NH3 compensation point at this alpine tundra site appears to

  2. Integrating yttrium iron garnet onto nongarnet substrates with faster deposition rates and high reliability

    SciTech Connect

    Sung, S.-Y.; Qi Xiaoyuan; Stadler, Bethanie J.H.

    2005-09-19

    Magneto-optical garnets (Y{sub 3}Fe{sub 5}O{sub 12} or YIG) were grown monolithically by a novel reactive radio-frequency sputtering method that used a partial pressure differential to increase sputtering rates. MgO and quartz substrates were used as they are good buffer layers and optical claddings for integration. A wide single-phase field for annealed YIG was found (26.9-43.2 at % Y), and the magnetic properties were measured. The films had refractive indices of 2.1 and out-of-plane Faraday rotations up to 0.2 deg. /{mu}m at 633 nm. The dielectric matrix was used to calculate the difference in the propagation constants of forward and backward traveling light ({delta}{beta}=1.999x10{sup -5})

  3. SAVANNAH RIVER SITE TANK CLEANING: CORROSION RATE FOR ONE VERSUS EIGHT PERCENT OXALIC ACID SOLUTION

    SciTech Connect

    Ketusky, E.; Subramanian, K.

    2011-01-20

    Until recently, the use of oxalic acid for chemically cleaning the Savannah River Site (SRS) radioactive waste tanks focused on using concentrated 4 and 8-wt% solutions. Recent testing and research on applicable dissolution mechanisms have concluded that under appropriate conditions, dilute solutions of oxalic acid (i.e., 1-wt%) may be more effective. Based on the need to maximize cleaning effectiveness, coupled with the need to minimize downstream impacts, SRS is now developing plans for using a 1-wt% oxalic acid solution. A technology gap associated with using a 1-wt% oxalic acid solution was a dearth of suitable corrosion data. Assuming oxalic acid's passivation of carbon steel was proportional to the free oxalate concentration, the general corrosion rate (CR) from a 1-wt% solution may not be bound by those from 8-wt%. Therefore, after developing the test strategy and plan, the corrosion testing was performed. Starting with the envisioned process specific baseline solvent, a 1-wt% oxalic acid solution, with sludge (limited to Purex type sludge-simulant for this initial effort) at 75 C and agitated, the corrosion rate (CR) was determined from the measured weight loss of the exposed coupon. Environmental variations tested were: (a) Inclusion of sludge in the test vessel or assuming a pure oxalic acid solution; (b) acid solution temperature maintained at 75 or 45 C; and (c) agitation of the acid solution or stagnant. Application of select electrochemical testing (EC) explored the impact of each variation on the passivation mechanisms and confirmed the CR. The 1-wt% results were then compared to those from the 8-wt%. The immersion coupons showed that the maximum time averaged CR for a 1-wt% solution with sludge was less than 25-mils/yr for all conditions. For an agitated 8-wt% solution with sludge, the maximum time averaged CR was about 30-mils/yr at 50 C, and 86-mils/yr at 75 C. Both the 1-wt% and the 8-wt% testing demonstrated that if the sludge was removed from

  4. Deposition and rainwater concentrations of trifluoroacetic acid in the United States from the use of HFO-1234yf

    NASA Astrophysics Data System (ADS)

    Kazil, J.; McKeen, S.; Kim, S.-W.; Ahmadov, R.; Grell, G. A.; Talukdar, R. K.; Ravishankara, A. R.

    2014-12-01

    Currently, HFC-134a (1,1,1,2-tetrafluoroethane) is the most common refrigerant in automobile air conditioners. This high global warming potential substance (100 year GWP of 1370) will likely be phased out and replaced with HFO-1234yf (2,3,3,3-tetrafluoropropene) that has a 100 year GWP of 4. HFO-1234yf will be oxidized to produce trifluoroacetic acid (TFA) in clouds. TFA, a mildly toxic substance with detrimental effects on some aquatic organisms at high concentrations (≥100μgL-1), would be transported by rain to the surface and enter bodies of water. We investigated the dry and wet deposition of TFA from HFO-1234yf over the contiguous USA using the Advanced Research Weather Research and Forecasting model (ARW) with interactive chemical, aerosol, and cloud processes (WRF/Chem) model. Special focus was placed on emissions from three continental USA regions with different meteorological characteristics. WRF/Chem simulated meteorology, cloud processes, gas and aqueous phase chemistry, and dry and wet deposition between May and September 2006. The model reproduced well the multimonth total sulfate wet deposition (4% bias) and its spatial variability (r = 0.86) observed by the National Atmospheric Deposition Program. HFO-1234yf emissions were obtained by assuming the number of automobile air conditioners to remain unchanged, and substituting HFO-1234yf, mole-per-mole for HFC-134a. Our estimates of current HFC-134a emissions were in agreement with field data. Average TFA rainwater concentration was 0.89μgL-1, with peak values of 7.8μgL-1, for the May-September 2006 period over the contiguous USA. TFA rainwater concentrations over the dry western USA were often significantly higher, but wet-deposited TFA amounts remained relatively low at such locations.

  5. REGIONAL AIR QUALITY AND ACID DEPOSITION MODELING AND THE ROLE FOR VISUALIZATION

    EPA Science Inventory

    The U.S Environmental Protection Agency (EPA) uses air quality and deposition models to advance the scientific understanding of basic physical and chemical processes related to air pollution, and to assess the effectiveness of alternative emissions control strategies. his paper p...

  6. Modeling of local co-deposition rates near Tore Supra gas injection sources

    NASA Astrophysics Data System (ADS)

    Loarer, Th.; Hogan, J.; Tsitrone, E.; Brosset, C.; Bucalossi, J.; Gunn, J.; Pegourie, B.

    2003-10-01

    Using the Tore Supra Composants Internes et Limiteurs (CIEL) configuration, long discharges (>4 mins), with high extracted energy (>0.7 GJ) have been demonstrated. Examination after periods of long duration operation has revealed a high level of retention of injected deuterium, a result which has important implications for tritium retention in ITER [1, 2]. The zone near the neutral gas injection port at the outboard midplane is a high redeposition area. To understand the retention mechanism, and to evaluate alternative injection methods which could reduce it, we have modeled this process with the neutral deuterium version of the 3-D Monte Carlo code, BBQ and the 1-D WDIFFUSE wall transport code. Transport of neutral atoms and molecules is calculated, to determine the expected codeposition rate stimulated by the charge exchange cascade process near the injection port. Retention is estimated from WDIFFUSE using the results of W. Jakob [3] for the increased range of energetic particles in soft films. The reduction in retained levels which could be achieved by using an alternative injection location (diagnostic port in the toroidal limiter) is predicted from the validated model. [1] E. Tsitrone et al, , EPS 2003, St Peterburg [2] Th. Loarer et al, EPS 2003, St Peterburg [3] W. Jakob, J. Thin Films, 1998

  7. Some physical effects of reaction rate on PbS thin films obtained by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Altıokka, Barış; Baykul, Mevlana Celalettin; Altıokka, Mehmet Rıza

    2013-12-01

    Thin films of polycrystalline lead sulfide (PbS) have been deposited on glass substrates at 303±1 K using chemical bath deposition (CBD). The precipitation of PbS on solid surfaces under four different reaction conditions was performed using a sodium sulfite (Na2SO3) compound as an inhibitor. The kinetics model for the reaction between Pb2+ and S2- was developed according to the amounts of Pb2+ concentrations measured by atomic absorption spectroscopy (AAS) during the precipitation of PbS. The surface morphologies of PbS thin films were studied with a Scanning Electron Microscope (SEM). It was found that the precipitation rate effects the formation of pinhole. To obtain a good quality of thin films the optimum concentration of lead nitrate (Pb(NO3)2), sodium hydroxide (NaOH), thiourea (CS(NH2)2) and Na2SO3 in the final solution was determined to be 0.0089, 0.1460, 0.510 and 0.00023 M, respectively. The film structures were characterized by X-ray diffractometer (XRD). The XRD results showed that the films formed galena cubic structures which represent the natural mineral of PbS. The crystallite sizes of the films were found to be between 23 and 37 nm.

  8. Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates with increased stability using the hot wire filament technique

    DOEpatents

    Molenbroek, Edith C.; Mahan, Archie Harvin; Gallagher, Alan C.

    2000-09-26

    A method or producing hydrogenated amorphous silicon on a substrate, comprising the steps of: positioning the substrate in a deposition chamber at a distance of about 0.5 to 3.0 cm from a heatable filament in the deposition chamber; maintaining a pressure in said deposition chamber in the range of about 10 to 100 millitorr and pressure times substrate-filament spacing in the range of about 10 to 100 millitorr-cm, heating the filament to a temperature in the range of about 1,500 to 2,000.degree. C., and heating the substrate to a surface temperature in the range of about 280 to 475.degree. C.; and flowing silicohydride gas into the deposition chamber with said heated filament, decomposing said silicohydride gas into silicon and hydrogen atomic species and allowing products of gas reactions between said atomic species and the silicohydride gas to migrate to and deposit on said substrate while adjusting and maintaining said pressure times substrate-filament spacing in said deposition chamber at a value in said 10 to 100 millitorr range to produce statistically about 3 to 50 atomic collisions between the silicon and hydrogen atomic species migrating to said substrate and undecomposed molecules of the silane or other silicohydride gas in the deposition chamber.

  9. Effect of magnetic field strength on deposition rate and energy flux in a dc magnetron sputtering system

    SciTech Connect

    Ekpe, Samuel D.; Jimenez, Francisco J.; Field, David J.; Davis, Martin J.; Dew, Steven K.

    2009-11-15

    Variations in the magnetic field strongly affect the plasma parameters in a magnetron sputtering system. This in turn affects the throughput as well as the energy flux to the substrate. The variation in the magnetic field in this study, for a dc magnetron process, is achieved by shifting the magnet assembly slightly away from the target. Measurements of the plasma parameters show that while the electron density at the substrate increases with decrease in magnetic field, the electron temperature decreases. The cooling of the electron temperature is consistent with results reported elsewhere. The deposition rate per input magnetron power is found to increase slightly with the decrease in magnetic field for the process conditions considered in this study. Results suggest that the energy flux to the substrate tends to show a general decrease with the shift in the magnet assembly.

  10. Skeletal Muscle Lipid Deposition and Insulin Resistance: Impact of Dietary Fatty Acids and Exercise

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evidence has mounted indicating that elevated intramuscular triacylglycerol levels are associated with diminished insulin sensitivity in skeletal muscle. This lipid accumulation is most likely due to enhanced fatty acid uptake into the muscle coupled with diminished mitochondrial lipid oxidation. Th...

  11. Tauroursodeoxycholic acid improves the implantation and live-birth rates of mouse embryos.

    PubMed

    Lin, Tao; Diao, Yun Fei; Kang, Jung Won; Lee, Jae Eun; Kim, Dong Kyu; Jin, Dong Il

    2015-06-01

    We previously demonstrated that tauroursodeoxycholic acid (TUDCA) improved the developmental competence of mouse embryos by attenuating endoplasmic reticulum (ER) stress-induced apoptosis during preimplantation development. Here, we present a follow-up study examining whether TUDCA enhances the implantation and live-birth rate of mouse embryos. Mouse 2-cell embryos were collected by oviduct flushing and cultured in the presence or absence of 50 μM TUDCA. After culture (52 h), blastocysts were transferred to 2.5-day pseudopregnant foster mothers. It was found that the rates of pregnancy and implantation as well as the number of live pups per surrogate mouse were significantly higher in the TUDCA-treated group compared to the control group, but there was no significant difference in the mean weights of the pups or placentae. Thus, we report for the first time that TUDCA supplementation of the embryo culture medium increased the implantation and livebirth rates of transferred mouse embryos. PMID:26051458

  12. The Effect of Slaughter Season on the Fatty Acid Profile in Four Types of Fat Deposits in Crossbred Beef Bulls

    PubMed Central

    Sobczuk-Szul, Monika; Wroński, Marek; Wielgosz-Groth, Zofia; Mochol, Magdalena; Rzemieniewski, Arkadiusz; Nogalski, Zenon; Pogorzelska-Przybyłek, Paulina; Purwin, Cezary

    2013-01-01

    The objective of this study was to determine the effect of slaughter season on the fatty acid profile in four types of fat deposits in crossbred (Polish Holstein Friesian Black-and-White×Limousine) beef bulls. The percentage share of fatty acids was determined by gas chromatography and were divided into the following categories of fatty acids: saturated (SFAs), unsaturated (UFAs), monounsaturated (MUFAs), polyunsaturated (PUFAs), desirable hypocholesterolemic (DFAs) and undesirable hypercholesterolemic (OFAs), n-3 and n-6. Perinephric fat was characterized by the highest SFA concentrations (59.89%), and subcutaneous fat had the highest MUFA content (50.63%). Intramuscular fat was marked by a high percentage share of PUFAs and the highest PUFA/SFA ratio. The slaughter season had a significant effect on the levels of C18:3, C20:4 (p≤0.01) and conjugated linoleic acid (p≤0.05). There was an interaction between the slaughter season and fat type for the content of C20:4 (p≤0.01) and C20:5 (p≤0.05). The results of this study show that beef from cattle slaughtered in the summer season has a higher nutritional value and more health-promoting properties. PMID:25049787

  13. PHOSPHATED, ACID-ETCHED IMPLANTS DECREASE MINERAL APPOSITION RATES NEAR IMPLANTS IN CANINES

    PubMed Central

    Foley, Christine Hyon; Kerns, David G.; Hallmon, William W.; Rivera-Hidalgo, Francisco; Nelson, Carl J.; Spears, Robert; Dechow, Paul C.; Opperman, Lynne A.

    2010-01-01

    Purpose: This study evaluated the effects of phosphate-coated titanium on mineral apposition rate (MAR) and new bone-to-implant contact (BIC) in canines. Materials and Methods: 2.2 mm × 4 mm electrolytically phosphated or non-phosphated titanium implants with acid-etched surfaces were placed in 48 mandibular sites in 6 foxhounds. Tetracycline and calcein dyes were administered 1 week after implant placement and 1 week before sacrifice. At twelve weeks following implant healing, animals were sacrificed. MAR and BIC were evaluated using fluorescence microscopy. Light microscopic and histological evaluation was performed on undecalcified sections. Results: Microscopic evaluation showed the presence of healthy osteoblasts lining bone surfaces near implants. Similar bone-to-implant contact was observed in phosphated and non-phosphated titanium implant sites. MAR was significantly higher near non-phosphated titanium implant surfaces than the phosphated titanium samples. No significant differences were found between dogs or implant sites. Discussion and Conclusion: Acid-etched only implants showed significantly higher mineral apposition rates compared to acid-etched, phosphate-coated implants. PMID:20369085

  14. A Comparison of Mathematical Models of Fish Mercury Concentration as a Function of Atmospheric Mercury Deposition Rate and Watershed Characteristics

    NASA Astrophysics Data System (ADS)

    Smith, R. A.; Moore, R. B.; Shanley, J. B.; Miller, E. K.; Kamman, N. C.; Nacci, D.

    2009-12-01

    Mercury (Hg) concentrations in fish and aquatic wildlife are complex functions of atmospheric Hg deposition rate, terrestrial and aquatic watershed characteristics that influence Hg methylation and export, and food chain characteristics determining Hg bioaccumulation. Because of the complexity and incomplete understanding of these processes, regional-scale models of fish tissue Hg concentration are necessarily empirical in nature, typically constructed through regression analysis of fish tissue Hg concentration data from many sampling locations on a set of potential explanatory variables. Unless the data sets are unusually long and show clear time trends, the empirical basis for model building must be based solely on spatial correlation. Predictive regional scale models are highly useful for improving understanding of the relevant biogeochemical processes, as well as for practical fish and wildlife management and human health protection. Mechanistically, the logical arrangement of explanatory variables is to multiply each of the individual Hg source terms (e.g. dry, wet, and gaseous deposition rates, and residual watershed Hg) for a given fish sampling location by source-specific terms pertaining to methylation, watershed transport, and biological uptake for that location (e.g. SO4 availability, hill slope, lake size). This mathematical form has the desirable property that predicted tissue concentration will approach zero as all individual source terms approach zero. One complication with this form, however, is that it is inconsistent with the standard linear multiple regression equation in which all terms (including those for sources and physical conditions) are additive. An important practical disadvantage of a model in which the Hg source terms are additive (rather than multiplicative) with their modifying factors is that predicted concentration is not zero when all sources are zero, making it unreliable for predicting the effects of large future reductions in

  15. Improving arachidonic acid fermentation by Mortierella alpina through multistage temperature and aeration rate control in bioreactor.

    PubMed

    Gao, Min-Jie; Wang, Cheng; Zheng, Zhi-Yong; Zhu, Li; Zhan, Xiao-Bei; Lin, Chi-Chung

    2016-05-18

    Effective production of arachidonic acid (ARA) using Mortierella alpina was conducted in a 30-L airlift bioreactor. Varying the aeration rate and temperature significantly influenced cell morphology, cell growth, and ARA production, while the optimal aeration rate and temperature for cell growth and product formation were quite different. As a result, a two-stage aeration rate control strategy was constructed based on monitoring of cell morphology and ARA production under various aeration rate control levels (0.6-1.8 vvm). Using this strategy, ARA yield reached 4.7 g/L, an increase of 38.2% compared with the control (constant aeration rate control at 1.0 vvm). Dynamic temperature-control strategy was implemented based on the fermentation performance at various temperatures (13-28°C), with ARA level in total cellular lipid increased by 37.1% comparing to a constant-temperature control (25°C). On that basis, the combinatorial fermentation strategy of two-stage aeration rate control and dynamic temperature control was applied and ARA production achieved the highest level of 5.8 g/L. PMID:26038800

  16. Insights from the metagenome of an acid salt lake: the role of biology in an extreme depositional environment.

    PubMed

    Johnson, Sarah Stewart; Chevrette, Marc Gerard; Ehlmann, Bethany L; Benison, Kathleen Counter

    2015-01-01

    The extremely acidic brine lakes of the Yilgarn Craton of Western Australia are home to some of the most biologically challenging waters on Earth. In this study, we employed metagenomic shotgun sequencing to generate a microbial profile of the depositional environment associated with the sulfur-rich sediments of one such lake. Of the 1.5 M high-quality reads generated, 0.25 M were mapped to protein features, which in turn provide new insights into the metabolic function of this community. In particular, 45 diverse genes associated with sulfur metabolism were identified, the majority of which were linked to either the conversion of sulfate to adenylylsulfate and the subsequent production of sulfide from sulfite or the oxidation of sulfide, elemental sulfur, and thiosulfate via the sulfur oxidation (Sox) system. This is the first metagenomic study of an acidic, hypersaline depositional environment, and we present evidence for a surprisingly high level of microbial diversity. Our findings also illuminate the possibility that we may be meaningfully underestimating the effects of biology on the chemistry of these sulfur-rich sediments, thereby influencing our understanding of past geobiological conditions that may have been present on Earth as well as early Mars. PMID:25923206

  17. Soil nutrient bioavailability and nutrient content of pine trees (Pinus thunbergii) in areas impacted by acid deposition in Korea.

    PubMed

    Yang, Jae E; Lee, Wi-Young; Ok, Yong Sik; Skousen, Jeffrey

    2009-10-01

    Acid deposition has caused detrimental effects on tree growth near industrial areas of the world. Preliminary work has indicated that concentrations of NO(3-), SO(4)(2-), F( - ) and Al in soil solutions were 2 to 33 times higher in industrial areas compared to non-industrial areas in Korea. This study evaluated soil nutrient bioavailability and nutrient contents of red pine (Pinus thunbergii) needles in forest soils of industrial and non-industrial areas of Korea. Results confirm that forest soils of industrial areas have been acidified mainly by deposition of sulfate, resulting in increases of Al, Fe and Mn and decreases of Ca, Mg and K concentrations in soils and soil solutions. In soils of industrial areas, the molar ratios of Ca/Al and Mg/Al in forest soils were <2, which can lead to lower levels and availability of nutrients for tree growth. The Ca/Al molar ratio of Pinus thunbergii needles on non-industrial sites was 15, while that of industrial areas was 10. Magnesium concentrations in needles of Pinus thunbergii were lower in soils of industrial areas and the high levels of acid cations such as Al and Mn in these soils may have antagonized the uptake of base cations like Mg. Continued acidification can further reduce uptake of base cations by trees. Results show that Mg deficiency and high concentrations of Al and Mn in soil solution can be limiting factors for Pinus thunbergii growth in industrial areas of Korea. PMID:18758977

  18. Insights from the Metagenome of an Acid Salt Lake: The Role of Biology in an Extreme Depositional Environment

    PubMed Central

    Johnson, Sarah Stewart; Chevrette, Marc Gerard; Ehlmann, Bethany L.; Benison, Kathleen Counter

    2015-01-01

    The extremely acidic brine lakes of the Yilgarn Craton of Western Australia are home to some of the most biologically challenging waters on Earth. In this study, we employed metagenomic shotgun sequencing to generate a microbial profile of the depositional environment associated with the sulfur-rich sediments of one such lake. Of the 1.5 M high-quality reads generated, 0.25 M were mapped to protein features, which in turn provide new insights into the metabolic function of this community. In particular, 45 diverse genes associated with sulfur metabolism were identified, the majority of which were linked to either the conversion of sulfate to adenylylsulfate and the subsequent production of sulfide from sulfite or the oxidation of sulfide, elemental sulfur, and thiosulfate via the sulfur oxidation (Sox) system. This is the first metagenomic study of an acidic, hypersaline depositional environment, and we present evidence for a surprisingly high level of microbial diversity. Our findings also illuminate the possibility that we may be meaningfully underestimating the effects of biology on the chemistry of these sulfur-rich sediments, thereby influencing our understanding of past geobiological conditions that may have been present on Earth as well as early Mars. PMID:25923206

  19. Deposition of Lignin Droplets Produced During Dilute Acid Pretreatment of Maize Stems Retards Enzymatic Hydrolysis of Cellulose

    SciTech Connect

    Selig, M. J.; Viamajala, S.; Decker, S. R.; Tucker, M. P.; Himmel, M. E.; Vinzant, T. B.

    2007-01-01

    Electron microscopy of lignocellulosic biomass following high-temperature pretreatment revealed the presence of spherical formations on the surface of the residual biomass. The hypothesis that these droplet formations are composed of lignins and possible lignin carbohydrate complexes is being explored. Experiments were conducted to better understand the formation of these lignin droplets and the possible implications they might have on the enzymatic saccharification of pretreated biomass. It was demonstrated that these droplets are produced from corn stover during pretreatment under neutral and acidic pH at and above 130C, and that they can deposit back onto the surface of residual biomass. The deposition of droplets produced under certain pretreatment conditions (acidic pH; T > 150C) and captured onto pure cellulose was shown to have a negative effect (5-20%) on the enzymatic saccharification of this substrate. It was noted that droplet density (per unit area) was greater and droplet size more variable under conditions where the greatest impact on enzymatic cellulose conversion was observed. These results indicate that this phenomenon has the potential to adversely affect the efficiency of enzymatic conversion in a lignocellulosic biorefinery.

  20. Preparation and evaluation of SiO2-deposited stearic acid-g-chitosan nanoparticles for doxorubicin delivery

    PubMed Central

    Yuan, Hong; Bao, Xin; Du, Yong-Zhong; You, Jian; Hu, Fu-Qiang

    2012-01-01

    Purpose: Both polymer micelles and mesoporous silica nanoparticles have been widely researched as vectors for small molecular insoluble drugs. To combine the advantages of copolymers and silica, studies on the preparation of copolymer-silica composites and cellular evaluation were carried out. Methods: First, a stearic acid-g-chitosan (CS-SA) copolymer was synthesized through a coupling reaction, and then silicone oxide (SiO2)-deposited doxorubicin (DOX)-loaded stearic acid-g-chitosan (CS-SA/SiO2/DOX) nanoparticles were prepared through the sol-gel reaction. Physical and chemical properties such as particle size, zeta potential, and morphologies were examined, and small-angle X-ray scattering (SAXS) analysis was employed to identify the mesoporous structures of the generated nanoparticles. Cellular uptake and cytotoxicity studies were also conducted. Results: CS-SA/SiO2/DOX nanoparticles with different amounts of SiO2 deposited were obtained, and SAXS studies showed that mesoporous structures existed in the CS-SA/SiO2/DOX nanoparticles. The mesoporous size of middle-ratio and high-ratio deposited CS-SA/SiO2/DOX nanoparticles were 4–5 nm and 8–10 nm, respectively. Based on transmission electron microscopy images of CS-SA/SiO2/DOX nanoparticles, dark rings around the nanoparticles could be observed in contrast with CS-SA/DOX micelles. Furthermore, CS-SA/SiO2/DOX nanoparticles exhibited faster release behavior in vitro than CS-SA/DOX micelles; cellular uptake research in A549 indicated that the CS-SA/SiO2/DOX nanoparticles were taken up by A549 cells more rapidly, and that CS-SA/SiO2/DOX nanoparticles entered the cell more easily when the amount of SiO2 was higher. IC50 values of CS-SA/DOX micelles, CS-SA/SiO2/DOX-4, CS-SA/SiO2/DOX-8, and CS-SA/SiO2/DOX-16 nanoparticles against A549 cells measured using the MTT assay were 1.69, 0.93, 0.32, and 0.12 μg/mL, respectively. Conclusion: SiO2-deposited stearic acid-g-chitosan organic–inorganic composites show promise

  1. A nitrilo-tri-acetic-acid/acetic acid route for the deposition of epitaxial cerium oxide films as high temperature superconductor buffer layers

    SciTech Connect

    Thuy, T.T.; Lommens, P.; Narayanan, V.; Van de Velde, N.; De Buysser, K.; Herman, G.G.; Cloet, V.; Van Driessche, I.

    2010-09-15

    A water based cerium oxide precursor solution using nitrilo-tri-acetic-acid (NTA) and acetic acid as complexing agents is described in detail. This precursor solution is used for the deposition of epitaxial CeO{sub 2} layers on Ni-5at%W substrates by dip-coating. The influence of the complexation behavior on the formation of transparent, homogeneous solutions and gels has been studied. It is found that ethylenediamine plays an important role in the gelification. The growth conditions for cerium oxide films were Ar-5% gas processing atmosphere, a solution concentration level of 0.25 M, a dwell time of 60 min at 900 {sup o}C and 5-30 min at 1050 {sup o}C. X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), pole figures and spectroscopic ellipsometry were used to characterize the CeO{sub 2} films with different thicknesses. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) was used to determine the carbon residue level in the surface of the cerium oxide film, which was found to be lower than 0.01%. Textured films with a thickness of 50 nm were obtained. - Graphical abstract: Study of the complexation and hydrolysis behavior of Ce{sup 4+} ions in the presence of nitrilo-tri-acetic acid and the subsequent development of an aqueous chemical solution deposition route suited for the processing of textured CeO{sub 2} buffer layers on Ni-W tapes.

  2. Iron deposition as acidic groundwater encounters carbonates in the alluvium of Pinal Creek, Arizona, U.S.A.

    USGS Publications Warehouse

    Lind, Carol J.; Oscarson, R.L.

    1997-01-01

    In a column experiment, acidic groundwater from Pinal Creek Arizona, a Cu mining area, was eluted through a composited alluvial sample obtained from a core that had been removed from a well downgradient of the acidic groundwater. The minerals present in typical grains and flakes in the alluvium before and after the elution were determined by X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive multichannel analyses (EDX). The concentrations of Fe, Ti, Mn, Si, Al, Na, Ca, K, Mg and S in these grains and flakes and in their microcrystalline surface coatings were measured by EDX. In addition to magnetite, hematite, and Fe-Ti oxides, Fe was most concentrated in micas (especially biotite-like flakes) and in the microcrystalline coatings. The measured elements in these microcrystalline coatings were primarily K, Fe, Al, and Si. The microcrystalline coatings on the mica flakes also contained Mg. The approximate 1:3 Mg:Si atomic ratios (ARs) of the biotite-like flakes both before and after the elution would suggest that the Fe deposited during the elution had not substituted for Mg in these flakes. As a result of the elution, assuming no loss of Si, the averaged recorded Fe:Si AR of the microcrystalline coatings increased from (0,46 to 0.58):3.00. Iron deposition on the typical grains and flakes may relate to the presence of Fe in the particle on which it is deposited or to the presence of Fe in the microcrystalline surface coatings before elution. The data here are not sufficient for a statistical evaluation, but elution caused the following trends: (1) The Fe:Si A R increased in the (K,Fe,Al,Si)-microcrystalline surface coatings; (2) For the mica flakes, there was more than a 2-fold increase in the Fe:Si AR for the microcrystalline surface coatings of the Fe-rich biotite-like flakes but no measurable increase of the Fe:Si AR for the microcrystalline surface coatings of the muscovite-like flakes that contained 3-5 times less Fe; (3) Also for the

  3. Formation of Acid Mine Drainage Water at Sb (Au) Deposit Pezinok

    NASA Astrophysics Data System (ADS)

    Rusko, Miroslav; Andráš, Peter; Kušnierová, Mária; Aschenbrenner, Štefan; Krnáč, Jozef; Dubiel, Ján

    2011-01-01

    The article presents the results of leaching experiments regarding the comparison of chemical and biological-chemical leaching of ores from the Sb-(Au-) base metal deposit Pezinok (Malé Karpaty., the Western Carpathians) under the same conditions in solution. Discussed are the differences between chemical and biological-chemical leaching activity. The extent and the kinetics of the biological-chemical leaching of the technogenous sediments from the setting-pits are significantly higher than those without bacteria.

  4. The importance of acid digestion of urine prior to spontaneous deposition of 210Po.

    PubMed

    Fellman, A; Ralston, L; Hickman, D; Ayres, L; Cohen, N; Spitz, H; Robinson, B

    1989-10-01

    Historically, radiochemical analysis of 210Po in urine has used spontaneous deposition of the nuclide directly from raw urine onto a suitable metal disc. Consequently, the urinary excretion fraction for Po in some current metabolic and dosimetric models is based on studies which inherently assume that metabolized (i.e., filtered out of the blood by the kidneys) 210Po is plated with the same efficiency as tracer 210Po which has been added to urine samples. Urine samples collected after intravenous administration of 210Po citrate to two species of nonhuman primates were divided and simultaneously analyzed via two methods: the historical procedure of plating 210Po from raw urine for one sample and a method which includes the addition of 208Po tracer and sample digestion with concentrated HNO3 prior to 210Po deposition for the other sample. A more significant amount of 210Po was consistently recovered when the urine was wet ashed then when it was not wet ashed. A temporal relationship was found to describe the change in the ratio of the deposition recoveries for the two methods. Possible mechanisms for this phenomenon and its dosimetric implications are discussed. PMID:2507478

  5. Biomimetic Deposition of Hydroxyapatite by Mixed Acid Treatment of Titanium Surfaces.

    PubMed

    Zhao, J M; Park, W U; Hwang, K H; Lee, J K; Yoon, S Y

    2015-03-01

    A simple chemical method was established for inducing bioactivity of Ti metal. In the present study, two kinds of mixed acid solutions were used to treat Ti specimens to induce Ca-P formation. Following a strong mixed acid activation process, Ca-P coatings successfully formed on the Ti surfaces in the simulated body fluid. Strong mixed acid etching was used to increase the roughness of the metal surface, because the porous and rough surfaces allow better adhesion between Ca-P coatings and substrate. Nano-scale modification of titanium surfaces can alter cellular and tissue responses, which may benefit osseointegration and dental implant therapy. Some specimens were treated with a 5 M NaOH aqueous solution, and then heat treated at 600 °C in order to form an amorphous sodium titanate layer on their surface. This treated titanium metal is believed to form a dense and uniform bone-like apatite layer on its surface in a simulated body fluid (SBF). This study proved that mixed acid treatment is not only important for surface passivation but is also another bioactive treatment for titanium surfaces, an alternative to alkali treatment. In addition, mixed acid treatment uses a lower temperature and shorter time period than alkali treatment. PMID:26413704

  6. Suppression of fat deposition in broiler chickens by (-)-hydroxycitric acid supplementation: A proteomics perspective

    PubMed Central

    Peng, Mengling; Han, Jing; Li, Longlong; Ma, Haitian

    2016-01-01

    (-)-Hydroxycitric acid (HCA) suppresses fatty acid synthesis in animals, but its biochemical mechanism in poultry is unclear. This study identified the key proteins associated with fat metabolism and elucidated the biochemical mechanism of (-)-HCA in broiler chickens. Four groups (n = 30 each) received a diet supplemented with 0, 1000, 2000 or 3000 mg/kg (-)-HCA for 4 weeks. Of the differentially expressed liver proteins, 40 and 26 were identified in the mitochondrial and cytoplasm respectively. Pyruvate dehydrogenase E1 components (PDHA1 and PDHB), dihydrolipoyl dehydrogenase (DLD), aconitase (ACO2), a-ketoglutarate dehydrogenase complex (DLST), enoyl-CoA hydratase (ECHS1) and phosphoglycerate kinase (PGK) were upregulated, while NADP-dependent malic enzyme (ME1) was downregulated. Biological network analysis showed that the identified proteins were involved in glycometabolism and lipid metabolism, whereas PDHA1, PDHB, ECHS1, and ME1 were identified in the canonical pathway by Ingenuity Pathway Analysis. The data indicated that (-)-HCA inhibited fatty acid synthesis by reducing the acetyl-CoA supply, via promotion of the tricarboxylic acid cycle (upregulation of PDHA1, PDHB, ACO2, and DLST expression) and inhibition of ME1 expression. Moreover, (-)-HCA promoted fatty acid beta-oxidation by upregulating ECHS1 expression. These results reflect a biochemically relevant mechanism of fat reduction by (-)-HCA in broiler chickens. PMID:27586962

  7. Suppression of fat deposition in broiler chickens by (-)-hydroxycitric acid supplementation: A proteomics perspective.

    PubMed

    Peng, Mengling; Han, Jing; Li, Longlong; Ma, Haitian

    2016-01-01

    (-)-Hydroxycitric acid (HCA) suppresses fatty acid synthesis in animals, but its biochemical mechanism in poultry is unclear. This study identified the key proteins associated with fat metabolism and elucidated the biochemical mechanism of (-)-HCA in broiler chickens. Four groups (n = 30 each) received a diet supplemented with 0, 1000, 2000 or 3000 mg/kg (-)-HCA for 4 weeks. Of the differentially expressed liver proteins, 40 and 26 were identified in the mitochondrial and cytoplasm respectively. Pyruvate dehydrogenase E1 components (PDHA1 and PDHB), dihydrolipoyl dehydrogenase (DLD), aconitase (ACO2), a-ketoglutarate dehydrogenase complex (DLST), enoyl-CoA hydratase (ECHS1) and phosphoglycerate kinase (PGK) were upregulated, while NADP-dependent malic enzyme (ME1) was downregulated. Biological network analysis showed that the identified proteins were involved in glycometabolism and lipid metabolism, whereas PDHA1, PDHB, ECHS1, and ME1 were identified in the canonical pathway by Ingenuity Pathway Analysis. The data indicated that (-)-HCA inhibited fatty acid synthesis by reducing the acetyl-CoA supply, via promotion of the tricarboxylic acid cycle (upregulation of PDHA1, PDHB, ACO2, and DLST expression) and inhibition of ME1 expression. Moreover, (-)-HCA promoted fatty acid beta-oxidation by upregulating ECHS1 expression. These results reflect a biochemically relevant mechanism of fat reduction by (-)-HCA in broiler chickens. PMID:27586962

  8. Intracellular pH Recovery Rates in Bivalve Hemocytes Following Exposure to Acidic Environmental Conditions

    NASA Astrophysics Data System (ADS)

    Croxton, A.; Wikfors, G. H.

    2012-12-01

    Predictions of ocean acidification effects upon carbonate shell-forming species have caused great concern for the future of shellfisheries. Nevertheless, bivalve species inhabiting an estuarine environment have evolved in these environments with fluctuating pH levels. Previous experimental studies conducted in our laboratory have demonstrated the ability of oyster hemocytes to maintain intracellular homeostasis under acidic external conditions. However, little information is known of this homeostatic mechanism in other molluscan shellfish species present in these same habitats. In the current study we propose to determine if other bivalve species of aquaculture interest also possess this intracellular regulation by applying an in vitro hemocyte pH-recovery assay, previously developed for oysters, on the northern quahog, Mercenaria mercenaria, the blue mussel, Mytilus edulis, and the softshell clam, Mya arenaria. Preliminary results from the determination of initial intracellular pH levels, the initial step in the rate recovery assay, indicated a pH range between 7.0-7.4. This range was comparable to initial values measured in oysters, and consistent with data reported in the current literature. The second step of the hemocyte pH-recovery assay involves exposing oyster hemocytes to acidic external conditions and measuring the ability of the hemocyte intracellular pH to maintain homeostasis (i.e. recovery rate). Results from the recovery rate process will be presented.

  9. Field rates for natural attenuation of arsenic in Tinto Santa Rosa acid mine drainage (SW Spain).

    PubMed

    Asta, Maria P; Ayora, Carlos; Acero, Patricia; Cama, Jordi

    2010-05-15

    Reactive transport modelling of the main processes related to the arsenic natural attenuation observed in the acid mine drainage (AMD) impacted stream of Tinto Santa Rosa (SW Spain) was performed. Despite the simplicity of the kinetic expressions used to deal with arsenic attenuation processes, the model reproduced successfully the major chemical trends observed along the acid discharge. Results indicated that the rate of ferrous iron oxidation was similar to the one obtained in earlier field studies in which microbial catalysis is reported to occur. With regard to the scaled arsenic oxidation rate, it is one order of magnitude faster than the values obtained under laboratory conditions suggesting the existence of a catalytic agent in the natural system. Schwertmannite precipitation rate, which was represented by a simple kinetic expression relying on Fe(III) and pH, was in the range calculated for other AMD impacted sites. Finally, the obtained distribution coefficients used for representing arsenic sorption onto Fe(III) precipitates were lower than those deduced from reported laboratory data. This discrepancy is attributed to a decrease in the schwertmannite arsenate sorption capacity as sulphate increases in the solution. PMID:20153577

  10. Suppression of Growth Rate of Colony-Associated Fungi by High Fructose Corn Syrup Feeding Supplement, Formic Acid, and Oxalic Acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Select colony-associated fungi (bee isolates). Absidia sp., Ascosphaera apis, Aspergillus flavus, Fusarium sp., Penicillium glabrum, Mucor sp., showed a 40% reduction in radial growth rate with formic acid, a 28% reduction with oxalic acid, and a 15% reduction with fructose and high fructose corn sy...

  11. Calcite growth-rate inhibition by fulvic acids isolated from Big Soda Lake, Nevada, USA, The Suwannee River, Georgia, USA and by polycarboxylic acids

    USGS Publications Warehouse

    Reddy, Michael M.; Leenheer, Jerry

    2011-01-01

    Calcite crystallization rates are characterized using a constant solution composition at 25°C, pH=8.5, and calcite supersaturation (Ω) of 4.5 in the absence and presence of fulvic acids isolated from Big Soda Lake, Nevada (BSLFA), and a fulvic acid from the Suwannee River, Georgia (SRFA). Rates are also measured in the presence and absence of low-molar mass, aliphatic-alicyclic polycarboxylic acids (PCA). BSLFA inhibits calcite crystal-growth rates with increasing BSLFA concentration, suggesting that BSLFA adsorbs at growth sites on the calcite crystal surface. Calcite growth morphology in the presence of BSLFA differed from growth in its absence, supporting an adsorption mechanism of calcite-growth inhibition by BSLFA. Calcite growth-rate inhibition by BSLFA is consistent with a model indicating that polycarboxylic acid molecules present in BSLFA adsorb at growth sites on the calcite crystal surface. In contrast to published results for an unfractionated SRFA, there is dramatic calcite growth inhibition (at a concentration of 1 mg/L) by a SRFA fraction eluted by pH 5 solution from XAD-8 resin, indicating that calcite growth-rate inhibition is related to specific SRFA component fractions. A cyclic PCA, 1, 2, 3, 4, 5, 6-cyclohexane hexacarboxylic acid (CHXHCA) is a strong calcite growth-rate inhibitor at concentrations less than 0.1 mg/L. Two other cyclic PCAs, 1, 1 cyclopentanedicarboxylic acid (CPDCA) and 1, 1 cyclobutanedicarboxylic acid (CBDCA) with the carboxylic acid groups attached to the same ring carbon atom, have no effect on calcite growth rates up to concentrations of 10 mg/L. Organic matter ad-sorbed from the air onto the seed crystals has no effect on the measured calcite crystal-growth rates.

  12. Streamwater acid-base chemistry and critical loads of