We explored catchment processes that control stream nutrient concentrations at an upland forest in northeastern Vermont, USA, where inputs of nitrogen via atmospheric deposition are among the highest in the nation and affect ecosystem functioning. We traced sources of water, nitrate, and dissolved organic matter (DOM) using stream water samples collected at high frequency during spring snowmelt. Hydrochemistry, isotopic tracers, and end‐member mixing analyses suggested the timing, sources, and source areas from which water and nutrients entered the stream. Although stream‐dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) both originated from leaching of soluble organic matter, flushing responses between these two DOM components varied because of dynamic shifts of hydrological flow paths and sources that supply the highest concentrations of DOC and DON. High concentrations of stream water nitrate originated from atmospheric sources as well as nitrified sources from catchment soils. We detected nitrification in surficial soils during late snowmelt which affected the nitrate supply that was available to be transported to streams. However, isotopic tracers showed that the majority of nitrate in upslope surficial soil waters after the onset of snowmelt originated from atmospheric sources. A fraction of the atmospheric nitrogen was directly delivered to the stream, and this finding highlights the importance of quick flow pathways during snowmelt events. These findings indicate that interactions among sources, transformations, and hydrologic transport processes must be deciphered to understand why concentrations vary over time and over space as well as to elucidate the direct effects of human activities on nutrient dynamics in upland forest streams.
","language":"English","publisher":"American Geophysical Union","doi":"10.1029/2008WR006983","usgsCitation":"Sebestyen, S.D., Boyer, E.W., Shanley, J.B., Kendall, C., Doctor, D.H., Aiken, G.R., and Ohte, N., 2008, Sources, transformations, and hydrological processes that control stream nitrate and dissolved organic matter concentrations during snowmelt in an upland forest: Water Resources Research, v. 44, no. 12, W12410; 14 p., https://doi.org/10.1029/2008WR006983.","productDescription":"W12410; 14 p.","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":241388,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"44","issue":"12","noUsgsAuthors":false,"publicationDate":"2008-12-10","publicationStatus":"PW","scienceBaseUri":"505b93abe4b08c986b31a610","contributors":{"authors":[{"text":"Sebestyen, Stephen D.","contributorId":195126,"corporation":false,"usgs":false,"family":"Sebestyen","given":"Stephen","email":"","middleInitial":"D.","affiliations":[],"preferred":false,"id":437443,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Boyer, Elizabeth W.","contributorId":44659,"corporation":false,"usgs":false,"family":"Boyer","given":"Elizabeth","email":"","middleInitial":"W.","affiliations":[{"id":7260,"text":"Pennsylvania State University","active":true,"usgs":false}],"preferred":false,"id":437447,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Shanley, James B. 0000-0002-4234-3437 jshanley@usgs.gov","orcid":"https://orcid.org/0000-0002-4234-3437","contributorId":1953,"corporation":false,"usgs":true,"family":"Shanley","given":"James","email":"jshanley@usgs.gov","middleInitial":"B.","affiliations":[{"id":466,"text":"New England Water Science Center","active":true,"usgs":true},{"id":405,"text":"NH/VT office of New England Water Science Center","active":true,"usgs":true}],"preferred":true,"id":437446,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Kendall, Carol 0000-0002-0247-3405 ckendall@usgs.gov","orcid":"https://orcid.org/0000-0002-0247-3405","contributorId":1462,"corporation":false,"usgs":true,"family":"Kendall","given":"Carol","email":"ckendall@usgs.gov","affiliations":[{"id":438,"text":"National Research Program - Western Branch","active":true,"usgs":true}],"preferred":true,"id":437445,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Doctor, Daniel H. 0000-0002-8338-9722 dhdoctor@usgs.gov","orcid":"https://orcid.org/0000-0002-8338-9722","contributorId":2037,"corporation":false,"usgs":true,"family":"Doctor","given":"Daniel","email":"dhdoctor@usgs.gov","middleInitial":"H.","affiliations":[{"id":243,"text":"Eastern Geology and Paleoclimate Science Center","active":true,"usgs":true},{"id":40020,"text":"Florence Bascom Geoscience Center","active":true,"usgs":true}],"preferred":true,"id":437448,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Aiken, George R. 0000-0001-8454-0984 graiken@usgs.gov","orcid":"https://orcid.org/0000-0001-8454-0984","contributorId":1322,"corporation":false,"usgs":true,"family":"Aiken","given":"George","email":"graiken@usgs.gov","middleInitial":"R.","affiliations":[{"id":191,"text":"Colorado Water Science Center","active":true,"usgs":true},{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":true,"id":437442,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Ohte, Nobuhito","contributorId":73363,"corporation":false,"usgs":false,"family":"Ohte","given":"Nobuhito","email":"","affiliations":[],"preferred":false,"id":437444,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70032207,"text":"70032207 - 2008 - Wetlands as principal zones of methylmercury production in southern Louisiana and the Gulf of Mexico region","interactions":[],"lastModifiedDate":"2018-10-17T08:14:29","indexId":"70032207","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1555,"text":"Environmental Pollution","active":true,"publicationSubtype":{"id":10}},"title":"Wetlands as principal zones of methylmercury production in southern Louisiana and the Gulf of Mexico region","docAbstract":"It is widely recognized that wetlands, especially those rich in organic matter and receiving appreciable atmospheric mercury (Hg) inputs, are important sites of methylmercury (MeHg) production. Extensive wetlands in the southeastern United States have many ecosystem attributes ideal for promoting high MeHg production rates; however, relatively few mercury cycling studies have been conducted in these environments. We conducted a landscape scale study examining Hg cycling in coastal Louisiana (USA) including four field trips conducted between August 2003 and May 2005. Sites were chosen to represent different ecosystem types, including: a large shallow eutrophic estuarine lake (Lake Pontchartrain), three rivers draining into the lake, a cypress-tupelo dominated freshwater swamp, and six emergent marshes ranging from a freshwater marsh dominated by Panicum hemitomon to a Spartina alterniflora dominated salt marsh close to the Gulf of Mexico. We measured MeHg and total Hg (THg) concentrations, and ancillary chemical characteristics, in whole and filtered surface water, and filtered porewater.
Overall, MeHg concentrations were greatest in surface water of freshwater wetlands and lowest in the profundal (non-vegetated) regions of the lake and river mainstems. Concentrations of THg and MeHg in filtered surface water were positively correlated with the highly reactive, aromatic (hydrophobic organic acid) fraction of dissolved organic carbon (DOC). These results suggest that DOC plays an important role in promoting the mobility, transport and bioavailability of inorganic Hg in these environments. Further, elevated porewater concentrations in marine and brackish wetlands suggest coastal wetlands along the Gulf Coast are key sites for MeHg production and may be a principal source of MeHg to foodwebs in the Gulf of Mexico.
Examining the relationships among MeHg, THg, and DOC across these multiple landscape types is a first step in evaluating possible links between key zones for Hg(II)-methylation and the bioaccumulation of mercury in the biota inhabiting the Gulf of Mexico region
","language":"English","publisher":"Elsevier","doi":"10.1016/j.envpol.2007.12.017","issn":"02697491","usgsCitation":"Hall, B., Aiken, G., Krabbenhoft, D., Marvin-DiPasquale, M., and Swarzenski, C., 2008, Wetlands as principal zones of methylmercury production in southern Louisiana and the Gulf of Mexico region: Environmental Pollution, v. 154, no. 1, p. 124-134, https://doi.org/10.1016/j.envpol.2007.12.017.","productDescription":"11 p.","startPage":"124","endPage":"134","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":242802,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":215035,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/j.envpol.2007.12.017"}],"volume":"154","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bd028e4b08c986b32ecd6","contributors":{"authors":[{"text":"Hall, B.D.","contributorId":42408,"corporation":false,"usgs":true,"family":"Hall","given":"B.D.","email":"","affiliations":[],"preferred":false,"id":435035,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Aiken, G. R. 0000-0001-8454-0984","orcid":"https://orcid.org/0000-0001-8454-0984","contributorId":14452,"corporation":false,"usgs":true,"family":"Aiken","given":"G. R.","affiliations":[],"preferred":false,"id":435033,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Krabbenhoft, D. P. 0000-0003-1964-5020","orcid":"https://orcid.org/0000-0003-1964-5020","contributorId":90765,"corporation":false,"usgs":true,"family":"Krabbenhoft","given":"D. P.","affiliations":[],"preferred":false,"id":435037,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Marvin-DiPasquale, M.","contributorId":28367,"corporation":false,"usgs":true,"family":"Marvin-DiPasquale","given":"M.","affiliations":[],"preferred":false,"id":435034,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Swarzenski, C.M.","contributorId":74856,"corporation":false,"usgs":true,"family":"Swarzenski","given":"C.M.","email":"","affiliations":[],"preferred":false,"id":435036,"contributorType":{"id":1,"text":"Authors"},"rank":5}]}} ,{"id":70032200,"text":"70032200 - 2008 - Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region","interactions":[],"lastModifiedDate":"2018-10-22T08:06:22","indexId":"70032200","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":835,"text":"Applied Geochemistry","active":true,"publicationSubtype":{"id":10}},"title":"Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region","docAbstract":"Mercury contained in buried landfill waste may be released via upward emission to the atmosphere or downward leaching to groundwater. Data from the US Geological Survey’s Amargosa Desert Research Site (ADRS) in arid southwestern Nevada reveal another potential pathway of Hg release: long-distance (102 m) lateral migration of elemental Hg (Hg0) through the unsaturated zone. Gas collected from multiple depths from two instrumented boreholes that sample the entire 110-m unsaturated zone thickness and are located 100 and 160 m away from the closest waste burial trench exhibit gaseous Hg concentrations of up to 33 and 11 ng m−3, respectively. The vertical distribution of gaseous Hg in the borehole closest to the disposal site shows distinct subsurface peaks in concentration at depths of 1.5 and 24 m that cannot be explained by radial diffusive transport through a heterogeneous layered unsaturated zone. The inability of current models to explain gaseous Hg distribution at the ADRS highlights the need to advance the understanding of gas-phase contaminant transport in unsaturated zones to attain a comprehensive model of landfill Hg release.
","language":"English","publisher":"Elsevier","doi":"10.1016/j.apgeochem.2007.12.014","usgsCitation":"Walvoord, M.A., Andraski, B.J., Krabbenhoft, D., and Striegl, R.G., 2008, Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region: Applied Geochemistry, v. 23, no. 3, p. 572-583, https://doi.org/10.1016/j.apgeochem.2007.12.014.","productDescription":"12 p.","startPage":"572","endPage":"583","costCenters":[{"id":465,"text":"Nevada Water Science Center","active":true,"usgs":true},{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":242702,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"23","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bb74fe4b08c986b3271af","contributors":{"authors":[{"text":"Walvoord, Michelle Ann 0000-0003-4269-8366 walvoord@usgs.gov","orcid":"https://orcid.org/0000-0003-4269-8366","contributorId":147211,"corporation":false,"usgs":true,"family":"Walvoord","given":"Michelle","email":"walvoord@usgs.gov","middleInitial":"Ann","affiliations":[{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":true,"id":435009,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Andraski, Brian J. 0000-0002-2086-0417 andraski@usgs.gov","orcid":"https://orcid.org/0000-0002-2086-0417","contributorId":168800,"corporation":false,"usgs":true,"family":"Andraski","given":"Brian","email":"andraski@usgs.gov","middleInitial":"J.","affiliations":[{"id":438,"text":"National Research Program - Western Branch","active":true,"usgs":true},{"id":38175,"text":"Toxics Substances Hydrology Program","active":true,"usgs":true},{"id":465,"text":"Nevada Water Science Center","active":true,"usgs":true}],"preferred":false,"id":435007,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Krabbenhoft, D. P. 0000-0003-1964-5020","orcid":"https://orcid.org/0000-0003-1964-5020","contributorId":90765,"corporation":false,"usgs":true,"family":"Krabbenhoft","given":"D. P.","affiliations":[],"preferred":false,"id":435008,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Striegl, Robert G. 0000-0002-8251-4659 rstriegl@usgs.gov","orcid":"https://orcid.org/0000-0002-8251-4659","contributorId":1630,"corporation":false,"usgs":true,"family":"Striegl","given":"Robert","email":"rstriegl@usgs.gov","middleInitial":"G.","affiliations":[{"id":200,"text":"Coop Res Unit Seattle","active":true,"usgs":true},{"id":36183,"text":"Hydro-Ecological Interactions Branch","active":true,"usgs":true},{"id":37277,"text":"WMA - Earth System Processes Division","active":true,"usgs":true},{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":false,"id":435006,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70032197,"text":"70032197 - 2008 - Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec, Canada","interactions":[],"lastModifiedDate":"2012-03-12T17:21:28","indexId":"70032197","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1923,"text":"Hydrogeology Journal","active":true,"publicationSubtype":{"id":10}},"title":"Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec, Canada","docAbstract":"A hydrogeological study was conducted in Potsdam sandstones on the international border between Canada (Quebec) and the USA (New York). Two sandstone formations, arkose and conglomerate (base) and well-cemented quartz arenite (upper), underlie the study area and form the major regional aquifer unit. Glacial till, littoral sand and gravel, and marine silt and clay discontinuously overlie the aquifer. In both sandstone formations, sub-horizontal bedding planes are ubiquitous and display significant hydraulic conductivities that are orders of magnitude more permeable than the intact rock matrix. Aquifer tests demonstrate that the two formations have similar bulk hydrologic properties, with average hydraulic conductivities ranging from 2 ?? 10-5 to 4 ?? 10-5 m/s. However, due to their different lithologic and structural characteristics, these two sandstones impose rather different controls on groundwater flow patterns in the study area. Flow is sustained through two types of fracture networks: sub-horizontal, laterally extensive fractures in the basal sandstone, where hydraulic connectivity is very good horizontally but very poor vertically and each of the water-bearing bedding planes can be considered as a separate planar two-dimensional aquifer unit; and the more fractured and vertically jointed system found in the upper sandstone that promotes a more dispersed, three-dimensional movement of groundwater. ?? Springer-Verlag 2007.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Hydrogeology Journal","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1007/s10040-007-0267-9","issn":"14312174","usgsCitation":"Nastev, M., Morin, R., Godin, R., and Rouleau, A., 2008, Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec, Canada: Hydrogeology Journal, v. 16, no. 2, p. 373-388, https://doi.org/10.1007/s10040-007-0267-9.","startPage":"373","endPage":"388","numberOfPages":"16","costCenters":[],"links":[{"id":214884,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1007/s10040-007-0267-9"},{"id":242640,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"16","issue":"2","noUsgsAuthors":false,"publicationDate":"2008-01-10","publicationStatus":"PW","scienceBaseUri":"505a000ee4b0c8380cd4f572","contributors":{"authors":[{"text":"Nastev, Miroslav","contributorId":10621,"corporation":false,"usgs":true,"family":"Nastev","given":"Miroslav","email":"","affiliations":[],"preferred":false,"id":434994,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Morin, R.","contributorId":6210,"corporation":false,"usgs":true,"family":"Morin","given":"R.","affiliations":[],"preferred":false,"id":434993,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Godin, Rejean","contributorId":19780,"corporation":false,"usgs":true,"family":"Godin","given":"Rejean","email":"","affiliations":[],"preferred":false,"id":434995,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Rouleau, Alain","contributorId":84165,"corporation":false,"usgs":true,"family":"Rouleau","given":"Alain","email":"","affiliations":[],"preferred":false,"id":434996,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70032155,"text":"70032155 - 2008 - National, holistic, watershed-scale approach to understand the sources, transport, and fate of agricultural chemicals","interactions":[],"lastModifiedDate":"2016-05-25T16:24:53","indexId":"70032155","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2262,"text":"Journal of Environmental Quality","active":true,"publicationSubtype":{"id":10}},"title":"National, holistic, watershed-scale approach to understand the sources, transport, and fate of agricultural chemicals","docAbstract":"This paper is an introduction to the following series of papers that report on in-depth investigations that have been conducted at five agricultural study areas across the United States in order to gain insights into how environmental processes and agricultural practices interact to determine the transport and fate of agricultural chemicals in the environment. These are the first study areas in an ongoing national study. The study areas were selected, based on the combination of cropping patterns and hydrologic setting, as representative of nationally important agricultural settings to form a basis for extrapolation to unstudied areas. The holistic, watershed-scale study design that involves multiple environmental compartments and that employs both field observations and simulation modeling is presented. This paper introduces the overall study design and presents an overview of the hydrology of the five study areas. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.
","language":"English","publisher":"ACSESS","doi":"10.2134/jeq2007.0226","issn":"00472425","usgsCitation":"Capel, P., McCarthy, K.A., and Barbash, J., 2008, National, holistic, watershed-scale approach to understand the sources, transport, and fate of agricultural chemicals: Journal of Environmental Quality, v. 37, no. 3, p. 983-993, https://doi.org/10.2134/jeq2007.0226.","productDescription":"11 p.","startPage":"983","endPage":"993","onlineOnly":"N","additionalOnlineFiles":"N","costCenters":[{"id":622,"text":"Washington Water Science Center","active":true,"usgs":true}],"links":[{"id":242504,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":214754,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.2134/jeq2007.0226"}],"volume":"37","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a6295e4b0c8380cd71fcf","contributors":{"authors":[{"text":"Capel, P. D. 0000-0003-1620-5185","orcid":"https://orcid.org/0000-0003-1620-5185","contributorId":95498,"corporation":false,"usgs":true,"family":"Capel","given":"P. D.","affiliations":[],"preferred":false,"id":434764,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"McCarthy, K. A.","contributorId":107309,"corporation":false,"usgs":true,"family":"McCarthy","given":"K.","email":"","middleInitial":"A.","affiliations":[],"preferred":false,"id":434765,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Barbash, J.E.","contributorId":62783,"corporation":false,"usgs":true,"family":"Barbash","given":"J.E.","email":"","affiliations":[],"preferred":false,"id":434763,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70032104,"text":"70032104 - 2008 - Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration","interactions":[],"lastModifiedDate":"2019-07-23T08:13:18","indexId":"70032104","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1837,"text":"Global Change Biology","active":true,"publicationSubtype":{"id":10}},"title":"Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration","docAbstract":"This study was conducted at three locations in a bottomland hardwood forest with a distinct elevation and hydrological gradient: ridge (high, dry), transition, and swamp (low, wet). At each location, concentrations of soil greenhouse gases (N2O, CH4, and CO2), their fluxes to the atmosphere, and soil redox potential (Eh) were measured bimonthly, while the water table was monitored every day. Results show that soil Eh was significantly (P < 0.001) correlated with water table: a negative correlation at the ridge and transition locations, but a positive correlation at the permanently flooded swamp location. Both soil gas profile analysis and surface gas flux measurements indicated that the ridge and transition locations could be a sink of atmospheric CH4, especially in warm seasons, but generally functioned as a minor source of CH4 in cool seasons. The swamp location was a major source of CH4, and the emission rate was higher in the warm seasons (mean 28 and median 23 mg m−2 h−1) than in the cool seasons (both mean and median 13 mg m−2 h−1). Average CO2 emission rate was 251, 380 and 52 mg m−2 h−1 for the ridge, transition and swamp location, respectively. At each location, higher CO2emission rates were also found in the warm seasons. The lowest CO2 emission rate was found at the swamp location, where soil C content was the highest, due to less microbial biomass, less CO2 production in such an anaerobic environment, and greater difficulty of CO2 diffusion to the atmosphere. Cumulative global warming potential emission from these three greenhouse gases was in an order of swamp > transition > ridge location. The ratio CO2/CH4 production in soil is a critical factor for evaluating the overall benefit of soil C sequestration, which can be greatly offset by CH4 production and emission.
","language":"English","publisher":"Wiley","doi":"10.1111/j.1365-2486.2008.01545.x","issn":"13541013","usgsCitation":"Yu, K., Faulkner, S., and Baldwin, M., 2008, Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration: Global Change Biology, v. 14, no. 4, p. 798-812, https://doi.org/10.1111/j.1365-2486.2008.01545.x.","productDescription":"15 p.","startPage":"798","endPage":"812","numberOfPages":"15","costCenters":[{"id":17705,"text":"Wetland and Aquatic Research Center","active":true,"usgs":true}],"links":[{"id":242766,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":215002,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1111/j.1365-2486.2008.01545.x"}],"volume":"14","issue":"4","noUsgsAuthors":false,"publicationDate":"2008-01-20","publicationStatus":"PW","scienceBaseUri":"505a05eae4b0c8380cd51012","contributors":{"authors":[{"text":"Yu, K.","contributorId":23756,"corporation":false,"usgs":true,"family":"Yu","given":"K.","email":"","affiliations":[],"preferred":false,"id":434566,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Faulkner, S.P.","contributorId":55190,"corporation":false,"usgs":true,"family":"Faulkner","given":"S.P.","email":"","affiliations":[],"preferred":false,"id":434567,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Baldwin, M.J. 0000-0002-7865-6590 baldwinm@usgs.gov","orcid":"https://orcid.org/0000-0002-7865-6590","contributorId":146154,"corporation":false,"usgs":true,"family":"Baldwin","given":"M.J.","email":"baldwinm@usgs.gov","affiliations":[{"id":455,"text":"National Wetlands Research Center","active":true,"usgs":true},{"id":17705,"text":"Wetland and Aquatic Research Center","active":true,"usgs":true}],"preferred":true,"id":766523,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70032038,"text":"70032038 - 2008 - Evaluation of statistical treatments of left-censored environmental data using coincident uncensored data sets: I. Summary statistics","interactions":[],"lastModifiedDate":"2018-10-22T08:43:02","indexId":"70032038","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1565,"text":"Environmental Science & Technology","onlineIssn":"1520-5851","printIssn":"0013-936X","active":true,"publicationSubtype":{"id":10}},"title":"Evaluation of statistical treatments of left-censored environmental data using coincident uncensored data sets: I. Summary statistics","docAbstract":"The main classes of statistical treatment of below-detection limit (left-censored) environmental data for the determination of basic statistics that have been used in the literature are substitution methods, maximum likelihood, regression on order statistics (ROS), and nonparametric techniques. These treatments, along with using all instrument-generated data (even those below detection), were evaluated by examining data sets in which the true values of the censored data were known. It was found that for data sets with less than 70% censored data, the best technique overall for determination of summary statistics was the nonparametric Kaplan-Meier technique. ROS and the two substitution methods of assigning one-half the detection limit value to censored data or assigning a random number between zero and the detection limit to censored data were adequate alternatives. The use of these two substitution methods, however, requires a thorough understanding of how the laboratory censored the data. The technique of employing all instrument-generated data - including numbers below the detection limit - was found to be less adequate than the above techniques. At high degrees of censoring (greater than 70% censored data), no technique provided good estimates of summary statistics. Maximum likelihood techniques were found to be far inferior to all other treatments except substituting zero or the detection limit value to censored data.","language":"English","publisher":"ACS","doi":"10.1021/es071301c","issn":"0013936X","usgsCitation":"Antweiler, R.C., and Taylor, H.E., 2008, Evaluation of statistical treatments of left-censored environmental data using coincident uncensored data sets: I. Summary statistics: Environmental Science & Technology, v. 42, no. 10, p. 3732-3738, https://doi.org/10.1021/es071301c.","productDescription":"7 p.","startPage":"3732","endPage":"3738","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":242762,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":214998,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1021/es071301c"}],"volume":"42","issue":"10","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a0cc6e4b0c8380cd52cbe","contributors":{"authors":[{"text":"Antweiler, Ronald C. 0000-0001-5652-6034 antweil@usgs.gov","orcid":"https://orcid.org/0000-0001-5652-6034","contributorId":1481,"corporation":false,"usgs":true,"family":"Antweiler","given":"Ronald","email":"antweil@usgs.gov","middleInitial":"C.","affiliations":[{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":true,"id":434265,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Taylor, Howard E. hetaylor@usgs.gov","contributorId":1551,"corporation":false,"usgs":true,"family":"Taylor","given":"Howard","email":"hetaylor@usgs.gov","middleInitial":"E.","affiliations":[{"id":5044,"text":"National Research Program - Central Branch","active":true,"usgs":true}],"preferred":true,"id":434264,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70032035,"text":"70032035 - 2008 - Anthropogenic influences on the input and biogeochemical cycling of nutrients and mercury in Great Salt Lake, Utah, USA","interactions":[],"lastModifiedDate":"2012-03-12T17:21:27","indexId":"70032035","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":835,"text":"Applied Geochemistry","active":true,"publicationSubtype":{"id":10}},"title":"Anthropogenic influences on the input and biogeochemical cycling of nutrients and mercury in Great Salt Lake, Utah, USA","docAbstract":"Despite the ecological and economic importance of Great Salt Lake (GSL), little is known about the input and biogeochemical cycling of nutrients and trace elements in the lake. In response to increasing public concern regarding anthropogenic inputs to the GSL ecosystem, the US Geological Survey (USGS) and US Fish and Wildlife Service (USFWS) initiated coordinated studies to quantify and evaluate the significance of nutrient and Hg inputs into GSL. A 6??? decrease in ??15N observed in brine shrimp (Artemia franciscana) samples collected from GSL during summer time periods is likely due to the consumption of cyanobacteria produced in freshwater bays entering the lake. Supporting data collected from the outflow of Farmington Bay indicates decreasing trends in ??15N in particulate organic matter (POM) during the mid-summer time period, reflective of increasing proportions of cyanobacteria in algae exported to GSL on a seasonal basis. The C:N molar ratio of POM in outflow from Farmington Bay decreases during the summer period, supportive of the increased activity of N fixation indicated by decreasing ??15N in brine shrimp and POM. Although N fixation is only taking place in the relatively freshwater inflows to GSL, data indicate that influx of fresh water influences large areas of the lake. Separation of GSL into two distinct hydrologic and geochemical systems from the construction of a railroad causeway in the late 1950s has created a persistent and widespread anoxic layer in the southern part of GSL. This anoxic layer, referred to as the deep brine layer (DBL), has high rates of SO42 - reduction, likely increasing the Hg methylation capacity. High concentrations of methyl mercury (CH3Hg) (median concentration = 24 ng/L) were observed in the DBL with a significant proportion (31-60%) of total Hg in the CH3Hg form. Hydroacoustic and sediment-trap evidence indicate that turbulence introduced by internal waves generated during sustained wind events can temporarily mix the elevated CH3Hg concentrations in the DBL with the more biologically active upper brine layer (UBL). Brine shrimp collected during the summer/fall time periods contained elevated Hg concentrations (median concentration = 0.34 mg/kg, dry weight (dw)) relative to samples collected during the spring (median concentration < 0.2 mg/kg, dw). Higher Hg in brine shrimp during the summer and fall may reflect the higher proportion of adult brine shrimp during this time period, resulting in an increased time for bioaccumulation of Hg. Eared grebes (Podiceps nigricollis) consume brine shrimp from GSL during the fall molting period. Median Hg concentrations in eared grebe livers increased by almost three times during the 3-5 month fall molting period. Selected duck species utilizing GSL have consistently exceeded the US Environmental Protection Agency (USEPA) screening level for Hg (0.3 mg/kg Hg wet weight), resulting in the issuance of warnings against unlimited human consumption of breast muscle tissue.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Applied Geochemistry","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1016/j.apgeochem.2008.03.002","issn":"08832927","usgsCitation":"Naftz, D., Angeroth, C., Kenney, T., Waddell, B., Darnall, N., Silva, S., Perschon, C., and Whitehead, J., 2008, Anthropogenic influences on the input and biogeochemical cycling of nutrients and mercury in Great Salt Lake, Utah, USA: Applied Geochemistry, v. 23, no. 6, p. 1731-1744, https://doi.org/10.1016/j.apgeochem.2008.03.002.","startPage":"1731","endPage":"1744","numberOfPages":"14","costCenters":[],"links":[{"id":242726,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":214964,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/j.apgeochem.2008.03.002"}],"volume":"23","issue":"6","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059ec5ae4b0c8380cd49204","contributors":{"authors":[{"text":"Naftz, D.","contributorId":37158,"corporation":false,"usgs":true,"family":"Naftz","given":"D.","affiliations":[],"preferred":false,"id":434249,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Angeroth, C.","contributorId":53607,"corporation":false,"usgs":true,"family":"Angeroth","given":"C.","email":"","affiliations":[],"preferred":false,"id":434251,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Kenney, T.","contributorId":93281,"corporation":false,"usgs":true,"family":"Kenney","given":"T.","email":"","affiliations":[],"preferred":false,"id":434255,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Waddell, B.","contributorId":17007,"corporation":false,"usgs":true,"family":"Waddell","given":"B.","email":"","affiliations":[],"preferred":false,"id":434248,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Darnall, N.","contributorId":86551,"corporation":false,"usgs":true,"family":"Darnall","given":"N.","affiliations":[],"preferred":false,"id":434254,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Silva, S.","contributorId":68518,"corporation":false,"usgs":true,"family":"Silva","given":"S.","affiliations":[],"preferred":false,"id":434253,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Perschon, C.","contributorId":52403,"corporation":false,"usgs":true,"family":"Perschon","given":"C.","email":"","affiliations":[],"preferred":false,"id":434250,"contributorType":{"id":1,"text":"Authors"},"rank":7},{"text":"Whitehead, J.","contributorId":54409,"corporation":false,"usgs":true,"family":"Whitehead","given":"J.","affiliations":[],"preferred":false,"id":434252,"contributorType":{"id":1,"text":"Authors"},"rank":8}]}} ,{"id":70032016,"text":"70032016 - 2008 - Analysis of chlorothalonil and three degradates in sediment and soil","interactions":[],"lastModifiedDate":"2018-10-22T08:11:06","indexId":"70032016","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2149,"text":"Journal of Agricultural and Food Chemistry","active":true,"publicationSubtype":{"id":10}},"title":"Analysis of chlorothalonil and three degradates in sediment and soil","docAbstract":"A method has been developed for the simultaneous extraction of chlorothalonil and three of its degradates (4-hydroxy-2,5,6-trichloroisophthalonitrile, 1-carbamoyl-3-cyano-4-hydroxy-2,5,6-trichlorobenzene, and 1,3-dicarbamoyl-2,4,5,6-tetrachlorobenzene) from soils and sediments; the compounds were extracted using sonication with acetone and isolation of the parent compound and matrix interferences from the degradates by solid phase extraction (SPE). The chlorothalonil fraction underwent further coextracted matrix interference removal with Florisil. The degradates were derivatized with N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) and chlorotrimethylsilane (TMCS). All compounds were analyzed by gas chromatography–mass spectrometry (GC-MS). Recoveries on a spiked (20 and 200 µg kg−1) sediment ranged from 80% to 91% with calculated limits of detection of 1−5 µg kg−1 dry weight sediment. An additional 20 sediment samples were collected in watersheds from the Southeastern United States where chlorothalonil is used widely on peanuts and other crops. None of the target compounds were detected. Laboratory fortified recoveries of chlorothalonil and its degradates in these environmental sediment samples ranged from 75% to 89%.
","language":"English","publisher":"ACS","doi":"10.1021/jf703695s","issn":"00218561","usgsCitation":"Hladik, M., and Kuivila, K., 2008, Analysis of chlorothalonil and three degradates in sediment and soil: Journal of Agricultural and Food Chemistry, v. 56, no. 7, p. 2310-2314, https://doi.org/10.1021/jf703695s.","productDescription":"5 p.","startPage":"2310","endPage":"2314","costCenters":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true},{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":242427,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":214681,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1021/jf703695s"}],"volume":"56","issue":"7","noUsgsAuthors":false,"publicationDate":"2008-03-13","publicationStatus":"PW","scienceBaseUri":"5059eb0de4b0c8380cd48ba3","contributors":{"authors":[{"text":"Hladik, M.L. 0000-0002-0891-2712","orcid":"https://orcid.org/0000-0002-0891-2712","contributorId":51111,"corporation":false,"usgs":true,"family":"Hladik","given":"M.L.","affiliations":[],"preferred":false,"id":434149,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Kuivila, K.M.","contributorId":34529,"corporation":false,"usgs":true,"family":"Kuivila","given":"K.M.","email":"","affiliations":[],"preferred":false,"id":434148,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70031972,"text":"70031972 - 2008 - Redox processes and water quality of selected principal aquifer systems","interactions":[],"lastModifiedDate":"2018-10-22T08:21:14","indexId":"70031972","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1861,"text":"Ground Water","active":true,"publicationSubtype":{"id":10}},"title":"Redox processes and water quality of selected principal aquifer systems","docAbstract":"Reduction/oxidation (redox) conditions in 15 principal aquifer (PA) systems of the United States, and their impact on several water quality issues, were assessed from a large data base collected by the National Water-Quality Assessment Program of the USGS. The logic of these assessments was based on the observed ecological succession of electron acceptors such as dissolved oxygen, nitrate, and sulfate and threshold concentrations of these substrates needed to support active microbial metabolism. Similarly, the utilization of solid-phase electron acceptors such as Mn(IV) and Fe(III) is indicated by the production of dissolved manganese and iron. An internally consistent set of threshold concentration criteria was developed and applied to a large data set of 1692 water samples from the PAs to assess ambient redox conditions. The indicated redox conditions then were related to the occurrence of selected natural (arsenic) and anthropogenic (nitrate and volatile organic compounds) contaminants in ground water. For the natural and anthropogenic contaminants assessed in this study, considering redox conditions as defined by this framework of redox indicator species and threshold concentrations explained many water quality trends observed at a regional scale. An important finding of this study was that samples indicating mixed redox processes provide information on redox heterogeneity that is useful for assessing common water quality issues. Given the interpretive power of the redox framework and given that it is relatively inexpensive and easy to measure the chemical parameters included in the framework, those parameters should be included in routine water quality monitoring programs whenever possible.","language":"English","publisher":"NGWA","doi":"10.1111/j.1745-6584.2007.00385.x","issn":"0017467X","usgsCitation":"McMahon, P., and Chapelle, F.H., 2008, Redox processes and water quality of selected principal aquifer systems: Ground Water, v. 46, no. 2, p. 259-271, https://doi.org/10.1111/j.1745-6584.2007.00385.x.","productDescription":"13 p.","startPage":"259","endPage":"271","costCenters":[{"id":191,"text":"Colorado Water Science Center","active":true,"usgs":true},{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":242790,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":215024,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1111/j.1745-6584.2007.00385.x"}],"volume":"46","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"50e4a3c0e4b0e8fec6cdb965","contributors":{"authors":[{"text":"McMahon, P.B. 0000-0001-7452-2379","orcid":"https://orcid.org/0000-0001-7452-2379","contributorId":10762,"corporation":false,"usgs":true,"family":"McMahon","given":"P.B.","affiliations":[],"preferred":false,"id":433952,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Chapelle, F. H.","contributorId":101697,"corporation":false,"usgs":true,"family":"Chapelle","given":"F.","email":"","middleInitial":"H.","affiliations":[],"preferred":false,"id":433953,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70031953,"text":"70031953 - 2008 - Application of multiple isotopic and geochemical tracers for investigation of recharge, salinization, and residence time of water in the Souss-Massa aquifer, southwest of Morocco","interactions":[],"lastModifiedDate":"2012-03-12T17:21:27","indexId":"70031953","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2342,"text":"Journal of Hydrology","active":true,"publicationSubtype":{"id":10}},"title":"Application of multiple isotopic and geochemical tracers for investigation of recharge, salinization, and residence time of water in the Souss-Massa aquifer, southwest of Morocco","docAbstract":"Groundwater and surface water in Souss-Massa basin in the west-southern part of Morocco is characterized by a large variation in salinity, up to levels of 37 g L-1. The high salinity coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies as well as future exploitation. A combined hydrogeologic and isotopic investigation using several chemical and isotopic tracers such as Br/Cl, ??18O, ??2H, 3H, 87Sr/86Sr, ??11B, and 14C was carried out in order to determine the sources of water recharge to the aquifer, the origin of salinity, and the residence time of water. Stable isotope, 3H and 14C data indicate that the high Atlas mountains in the northern margin of the Souss-Massa basin with high rainfall and low ??18O and ??2H values (-6 to -8??? and -36 to -50???) is currently constitute the major source of recharge to the Souss-Massa shallow aquifer, particularly along the eastern part of the basin. Localized stable isotope enrichments offset meteoric isotopic signature and are associated with high nitrate concentrations, which infer water recycling via water agricultural return flows. The 3H and 14C data suggest that the residence time of water in the western part of the basin is in the order of several thousands of years; hence old water is mined, particularly in the coastal areas. The multiple isotope analyses and chemical tracing of groundwater from the basin reveal that seawater intrusion is just one of multiple salinity sources that affect the quality of groundwater in the Souss-Massa aquifer. We differentiate between modern seawater intrusion, salinization by remnants of seawater entrapped in the middle Souss plains, recharge of nitrate-rich agricultural return flow, and dissolution of evaporate rocks (gypsum and halite minerals) along the outcrops of the high Atlas mountains. The data generated in this study provide the framework for a comprehensive management plan in which water exploitation should shift toward the eastern part of the basin where current recharge occurs with young and high quality groundwater. In contrast, we argued that the heavily exploited aquifer along the coastal areas is more vulnerable given the relatively longer residence time of the water and salinization processes in this part of the aquifer. ?? 2008 Elsevier B.V. All rights reserved.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Journal of Hydrology","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1016/j.jhydrol.2008.01.022","issn":"00221694","usgsCitation":"Bouchaou, L., Michelot, J., Vengosh, A., Hsissou, Y., Qurtobi, M., Gaye, C., Bullen, T., and Zuppi, G., 2008, Application of multiple isotopic and geochemical tracers for investigation of recharge, salinization, and residence time of water in the Souss-Massa aquifer, southwest of Morocco: Journal of Hydrology, v. 352, no. 3-4, p. 267-287, https://doi.org/10.1016/j.jhydrol.2008.01.022.","startPage":"267","endPage":"287","numberOfPages":"21","costCenters":[],"links":[{"id":214775,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/j.jhydrol.2008.01.022"},{"id":242525,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"352","issue":"3-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059eca8e4b0c8380cd493fa","contributors":{"authors":[{"text":"Bouchaou, L.","contributorId":51556,"corporation":false,"usgs":true,"family":"Bouchaou","given":"L.","affiliations":[],"preferred":false,"id":433862,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Michelot, J.L.","contributorId":58483,"corporation":false,"usgs":true,"family":"Michelot","given":"J.L.","affiliations":[],"preferred":false,"id":433864,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Vengosh, A.","contributorId":88925,"corporation":false,"usgs":true,"family":"Vengosh","given":"A.","affiliations":[],"preferred":false,"id":433868,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Hsissou, Y.","contributorId":22596,"corporation":false,"usgs":true,"family":"Hsissou","given":"Y.","email":"","affiliations":[],"preferred":false,"id":433861,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Qurtobi, M.","contributorId":78957,"corporation":false,"usgs":true,"family":"Qurtobi","given":"M.","email":"","affiliations":[],"preferred":false,"id":433866,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Gaye, C.B.","contributorId":56017,"corporation":false,"usgs":true,"family":"Gaye","given":"C.B.","email":"","affiliations":[],"preferred":false,"id":433863,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Bullen, T.D.","contributorId":79911,"corporation":false,"usgs":true,"family":"Bullen","given":"T.D.","email":"","affiliations":[],"preferred":false,"id":433867,"contributorType":{"id":1,"text":"Authors"},"rank":7},{"text":"Zuppi, G.M.","contributorId":66079,"corporation":false,"usgs":true,"family":"Zuppi","given":"G.M.","email":"","affiliations":[],"preferred":false,"id":433865,"contributorType":{"id":1,"text":"Authors"},"rank":8}]}} ,{"id":70031905,"text":"70031905 - 2008 - Biomarkers of mercury exposure at a mercury recycling facility in Ukraine","interactions":[],"lastModifiedDate":"2018-10-17T10:00:42","indexId":"70031905","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2404,"text":"Journal of Occupational and Environmental Hygiene","active":true,"publicationSubtype":{"id":10}},"title":"Biomarkers of mercury exposure at a mercury recycling facility in Ukraine","docAbstract":"This study evaluates biomarkers of occupational mercury exposure among workers at a mercury recycling operation in Gorlovka, Ukraine. The 29 study participants were divided into three occupational categories for analysis: (1) those who worked in the mercury recycling operation (Group A, n = 8), (2) those who worked at the facility but not in the yard where the recycling was done (Group B, n = 14), and (3) those who did not work at the facility (Group C, n = 7). Urine, blood, hair, and nail samples were collected from the participants, and a questionnaire was administered to obtain data on age, gender, occupational history, smoking, alcohol consumption, fish consumption, tattoos, dental amalgams, home heating system, education, source of drinking water, and family employment in the former mercury mine/smelter located on the site of the recycling facility. Each factor was tested in a univariate regression with total mercury in urine, blood, hair, and nails. Median biomarker concentrations were 4.04 μg/g-Cr (urine), 2.58 μg/L (blood), 3.95 μg/g (hair), and 1.16 μg/g (nails). Occupational category was significantly correlated (p < 0.001) with both blood and urinary mercury concentrations but not with hair or nail mercury. Four individuals had urinary mercury concentrations in a range previously found to be associated with subtle neurological and subjective symptoms (e.g., fatigue, loss of appetite, irritability), and one worker had a urinary mercury concentration in a range associated with a high probability of neurological effects and proteinuria. Comparison of results by occupational category found that workers directly involved with the recycling operation had the highest blood and urinary mercury levels. Those who worked at the facility but were not directly involved with the recycling operation had higher levels than those who did not work at the facility.
An in situ method of estimating the effective diffusion coefficient for a chemical constituent that diffuses into the primary porosity of a rock is developed by abruptly changing the concentration of the dissolved constituent in a borehole in contact with the rock matrix and monitoring the time-varying concentration. The experiment was conducted in a borehole completed in mudstone on the campus of the University of the Free State in Bloemfontein, South Africa. Numerous tracer tests were conducted at this site, which left a residual concentration of sodium chloride in boreholes that diffused into the rock matrix over a period of years. Fresh water was introduced into a borehole in contact with the mudstone, and the time-varying increase of chloride was observed by monitoring the electrical conductivity (EC) at various depths in the borehole. Estimates of the effective diffusion coefficient were obtained by interpreting measurements of EC over 34 d. The effective diffusion coefficient at a depth of 36 m was approximately 7.8×10−6 m2/d, but was sensitive to the assumed matrix porosity. The formation factor and mass flux for the mudstone were also estimated from the experiment.
","language":"English","publisher":"Springer","doi":"10.1007/s10040-007-0255-0","issn":"14312174","usgsCitation":"Gebrekristos, R., Shapiro, A., and Usher, B., 2008, In situ estimation of the effective chemical diffusion coefficient of a rock matrix in a fractured aquifer: Hydrogeology Journal, v. 16, no. 4, p. 629-639, https://doi.org/10.1007/s10040-007-0255-0.","productDescription":"11 p.","startPage":"629","endPage":"639","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":242521,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"South Africa","city":"Bloemfontein","geographicExtents":"{\n \"type\": \"FeatureCollection\",\n \"features\": [\n {\n \"type\": \"Feature\",\n \"properties\": {},\n \"geometry\": {\n \"type\": \"Polygon\",\n \"coordinates\": [\n [\n [\n 26.03759765625,\n -29.288794393648296\n ],\n [\n 26.42486572265625,\n -29.288794393648296\n ],\n [\n 26.42486572265625,\n -28.969700808694157\n ],\n [\n 26.03759765625,\n -28.969700808694157\n ],\n [\n 26.03759765625,\n -29.288794393648296\n ]\n ]\n ]\n }\n }\n ]\n}","volume":"16","issue":"4","noUsgsAuthors":false,"publicationDate":"2008-01-15","publicationStatus":"PW","scienceBaseUri":"505a399fe4b0c8380cd619a7","contributors":{"authors":[{"text":"Gebrekristos, R.A.","contributorId":25830,"corporation":false,"usgs":true,"family":"Gebrekristos","given":"R.A.","email":"","affiliations":[],"preferred":false,"id":433593,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Shapiro, A.M. 0000-0002-6425-9607","orcid":"https://orcid.org/0000-0002-6425-9607","contributorId":88384,"corporation":false,"usgs":true,"family":"Shapiro","given":"A.M.","affiliations":[],"preferred":true,"id":433595,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Usher, B.H.","contributorId":81763,"corporation":false,"usgs":true,"family":"Usher","given":"B.H.","email":"","affiliations":[],"preferred":false,"id":433594,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70031815,"text":"70031815 - 2008 - Characterization and cycling of atmospheric mercury along the central US Gulf Coast","interactions":[],"lastModifiedDate":"2018-10-22T08:05:28","indexId":"70031815","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":835,"text":"Applied Geochemistry","active":true,"publicationSubtype":{"id":10}},"title":"Characterization and cycling of atmospheric mercury along the central US Gulf Coast","docAbstract":"Concentrations of atmospheric Hg species, elemental Hg (Hg∘), reactive gaseous Hg (RGM), and fine particulate Hg (Hg-PM2.5) were measured at a coastal site near Weeks Bay, Alabama from April to August, 2005 and January to May, 2006. Mean concentrations of the species were 1.6 ± 0.3 ng m−3, 4.0 ± 7.5 pg m−3 and 2.7 ± 3.4 pg m−3, respectively. A strong diel pattern was observed for RGM (midday maximum concentrations were up to 92.7 pg m−3), but not for Hg∘ or Hg-PM2.5. Elevated RGM concentrations (>25 pg m−3) in April and May of 2005 correlated with elevated average daytime O3 concentrations (>55 ppbv) and high light intensity (>500 W m−2). These conditions generally corresponded with mixed continental-Gulf and exclusively continental air mass trajectories. Generally lower, but still elevated, RGM peaks observed in August, 2005 and January–March, 2006 correlated significantly (p < 0.05) with peaks in SO2 concentration and corresponded to periods of high light intensity and lower average daytime O3 concentrations. During these times air masses were dominated by trajectories that originated over the continent. Elevated RGM concentrations likely resulted from photochemical oxidation of Hg∘ by atmospheric oxidants. This process may have been enhanced in and by the near-shore environment relative to inland sites. The marine boundary layer itself was not found to be a significant source of RGM.
Size segregation determination, using a limited dataset from two different methods, suggested that a significant fraction of particulate Hg was bound to coarse particles (>2.5 μm). A potential source of the large fraction of coarse particulate Hg in the study area is sequestration of RGM within sea salt aerosols. The presence of rapidly depositing RGM and coarse particulate Hg may be important sources of Hg input along the Gulf Coast. However, the impact of these species on deposition rates is yet to be determined.
Analysis of earthworms offers potential for assessing the transfer of organic anthropogenic waste indicators (AWIs) derived from land-applied biosolid or manure to biota. Earthworms and soil samples were collected from three Midwest agricultural fields to measure the presence and potential for transfer of 77 AWIs from land-applied biosolids and livestock manure to earthworms. The sites consisted of a soybean field with no amendments of human or livestock waste (Site 1), a soybean field amended with biosolids from a municipal wastewater treatment plant (Site 2), and a cornfield amended with swine manure (Site 3). The biosolid applied to Site 2 contained a diverse composition of 28 AWIs, reflecting the presence of human-use compounds. The swine manure contained 12 AWIs, and was dominated by biogenic sterols. Soil and earthworm samples were collected in the spring (about 30 days after soil amendment) and fall (140−155 days after soil amendment) at all field sites. Soils from Site 1 contained 21 AWIs and soil from Sites 2 and 3 contained 19 AWIs. The AWI profiles at Sites 2 and 3 generally reflected the relative composition of AWIs present in waste material applied. There were 20 AWIs detected in earthworms from Site 1 (three compounds exceeding concentrations of 1000 µg/kg), 25 AWIs in earthworms from Site 2 (seven compounds exceeding concentrations of 1000 µg/kg), and 21 AWIs in earthworms from Site 3 (five compounds exceeding concentrations of 1000 µg/kg). A number of compounds that were present in the earthworm tissue were at concentrations less than reporting levels in the corresponding soil samples. The AWIs detected in earthworm tissue from the three field sites included pharmaceuticals, synthetic fragrances, detergent metabolites, polycyclic aromatic hydrocarbons (PAHs), biogenic sterols, disinfectants, and pesticides, reflecting a wide range of physicochemical properties. For those contaminants detected in earthworm tissue and soil, bioaccumulation factors (BAF) ranged from 0.05 (galaxolide) to 27 (triclosan). This study documents that when AWIs are present in source materials that are land applied, such as biosolids and swine manure, AWIs can be transferred to earthworms.
Atmospheric mercury (Hg) is delivered to ecosystems via rain, snow, cloud/fog, and dry deposition. The importance of snow, especially snow that has passed through the forest canopy (throughfall), in delivering Hg to terrestrial ecosystems has received little attention in the literature. The snowpack is a dynamic system that links atmospheric deposition and ecosystem cycling through deposition and emission of deposited Hg. To examine the magnitude of Hg delivery via snowfall, and to illuminate processes affecting Hg flux to catchments during winter (cold season), Hg in snow in no-canopy areas and under forest canopies measured with four collection methods were compared: (1) Hg in wet precipitation as measured by the Mercury Deposition Network (MDN) for the site in Acadia National Park, Maine, USA, (2) event throughfall (collected after snowfall cessation for accumulations of >8 cm), (3) season-long throughfall collected using the same apparatus for event sampling but deployed for the entire cold season, and (4) snowpack sampling. Estimates (mean ± SE) of Hg deposition using these methods during the 91-day cold season in 2004–2005 at conifer sites showed that season-long throughfall Hg flux (1.80 μg/m2) < snowpack Hg (2.38 ± 0.68 μg/m2) < event throughfall flux (5.63 ± 0.38 μg/m2). Mercury deposition at the MDN site (0.91 μg/m2) was similar to that measured at other no-canopy sites in the area using the other methods, but was 3.4 times less than was measured under conifer canopies using the event sampling regime. This indicates that snow accumulated under the forest canopy received Hg from the overstory or exhibited less re-emission of Hg deposited in snow relative to open areas. The soil surface of field-scale plots were sprayed with a natural rain water sample that contained an Hg tracer (202Hg) just prior to the first snowfall to explore whether some snowpack Hg might be explained from soil emissions. The appearance of the 202Hg tracer in the snowpack (0–64% of the total Hg mass in the snowpack) suggests that movement of Hg from the soil into the snowpack is possible. However, as with any tracer study the 202Hg tracer may not precisely represent the reactivity and mobility of natural Hg in soils.
The surface renewal method was used to estimate evapotranspiration (ET) for a restored marsh on Twitchell Island in the Sacramento–San Joaquin Delta, California, USA. ET estimates for the marsh, together with reference ET measurements from a nearby climate station, were used to determine crop coefficients over a 3‐year period during the growing season. The mean ET rate for the study period was 6 mm day−1, which is high compared with other marshes with similar vegetation. High ET rates at the marsh may be due to the windy, semi‐arid Mediterranean climate of the region, and the permanently flooded nature of the marsh, which results in very low surface resistance of the vegetation. Crop coefficient (Kc) values for the marsh ranged from 0·73 to 1·18. The mean Kc value over the entire study period was 0·95. The daily Kc values for any given month varied from year to year, and the standard deviation of daily Kc values varied between months. Although several climate variables were undoubtedly responsible for this variation, our analysis revealed that wind direction and the temperature of standing water in the wetland were of particular importance in determining ET rates and Kc values.
","language":"English","publisher":"Wiley","doi":"10.1002/hyp.6650","issn":"08856087","usgsCitation":"Drexler, J., Anderson, F.E., and Snyder, R.L., 2008, Evapotranspiration rates and crop coefficients for a restored marsh in the Sacramento-San Joaquin Delta, California, USA: Hydrological Processes, v. 22, no. 6, p. 725-735, https://doi.org/10.1002/hyp.6650.","productDescription":"11 p.","startPage":"725","endPage":"735","numberOfPages":"11","costCenters":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true}],"links":[{"id":239909,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":212422,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1002/hyp.6650"}],"volume":"22","issue":"6","noUsgsAuthors":false,"publicationDate":"2007-05-23","publicationStatus":"PW","scienceBaseUri":"505a0d20e4b0c8380cd52e21","contributors":{"authors":[{"text":"Drexler, Judith Z. 0000-0002-0127-3866 jdrexler@usgs.gov","orcid":"https://orcid.org/0000-0002-0127-3866","contributorId":1659,"corporation":false,"usgs":true,"family":"Drexler","given":"Judith Z.","email":"jdrexler@usgs.gov","affiliations":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true}],"preferred":false,"id":432861,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Anderson, Frank E. 0000-0002-1418-4678 fanders@usgs.gov","orcid":"https://orcid.org/0000-0002-1418-4678","contributorId":2605,"corporation":false,"usgs":true,"family":"Anderson","given":"Frank","email":"fanders@usgs.gov","middleInitial":"E.","affiliations":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true}],"preferred":true,"id":432863,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Snyder, Richard L.","contributorId":167497,"corporation":false,"usgs":false,"family":"Snyder","given":"Richard","email":"","middleInitial":"L.","affiliations":[{"id":24726,"text":"Department of Land, Air and Water Resources","active":true,"usgs":false}],"preferred":false,"id":432862,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70030644,"text":"70030644 - 2008 - The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed","interactions":[],"lastModifiedDate":"2017-01-17T11:36:50","indexId":"70030644","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1759,"text":"Geochimica et Cosmochimica Acta","active":true,"publicationSubtype":{"id":10}},"title":"The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed","docAbstract":"Willow Slough, a seasonally irrigated agricultural watershed in the Sacramento River valley, California, was sampled weekly in 2006 in order to investigate seasonal concentrations and compositions of dissolved organic carbon (DOC). Average DOC concentrations nearly doubled from winter baseflow (2.75 mg L-1) to summer irrigation (5.14 mg L-1), while a concomitant increase in carbon-normalized vanillyl phenols (0.11 mg 100 mg OC-1 increasing to 0.31 mg 100 mg OC-1, on average) indicates that this additional carbon is likely vascular plant-derived. A strong linear relationship between lignin concentration and total suspended sediments (r2 = 0.79) demonstrates that agricultural management practices that mobilize sediments will likely have a direct and significant impact on DOC composition. The original source of vascular plant-derived DOC to Willow Slough appears to be the same throughout the year as evidenced by similar syringyl to vanillyl and cinnamyl to vanillyl ratios. However, differing diagenetic pathways during winter baseflow as compared to the rest of the year are evident in acid to aldehyde ratios of both vanillyl and syringyl phenols. The chromophoric dissolved organic matter (CDOM) absorption coefficient at 350 nm showed a strong correlation with lignin concentration (r2 = 0.83). Other CDOM measurements related to aromaticity and molecular weight also showed correlations with carbon-normalized yields (e.g. specific UV absorbance at 254 nm (r2 = 0.57) and spectral slope (r2 = 0.54)). Our overall findings suggest that irrigated agricultural watersheds like Willow Slough can potentially have a significant impact on mainstem DOC concentration and composition when scaled to the entire watershed of the main tributary. ?? 2008 Elsevier Ltd.","language":"English","publisher":"Elsevier","doi":"10.1016/j.gca.2008.07.031","issn":"00167","usgsCitation":"Hernes, P., Spencer, R., Dyda, R., Pellerin, B., Bachand, P., and Bergamaschi, B., 2008, The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed: Geochimica et Cosmochimica Acta, v. 72, no. 21, p. 5266-5277, https://doi.org/10.1016/j.gca.2008.07.031.","productDescription":"12 p.","startPage":"5266","endPage":"5277","numberOfPages":"12","costCenters":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true}],"links":[{"id":239497,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":212079,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/j.gca.2008.07.031"}],"volume":"72","issue":"21","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505baf77e4b08c986b3247fa","contributors":{"authors":[{"text":"Hernes, P.J.","contributorId":89651,"corporation":false,"usgs":true,"family":"Hernes","given":"P.J.","affiliations":[],"preferred":false,"id":428013,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Spencer, R.G.M.","contributorId":60361,"corporation":false,"usgs":true,"family":"Spencer","given":"R.G.M.","email":"","affiliations":[],"preferred":false,"id":428011,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Dyda, R.Y.","contributorId":59630,"corporation":false,"usgs":true,"family":"Dyda","given":"R.Y.","email":"","affiliations":[],"preferred":false,"id":428010,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Pellerin, B.A.","contributorId":81233,"corporation":false,"usgs":true,"family":"Pellerin","given":"B.A.","email":"","affiliations":[],"preferred":false,"id":428012,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Bachand, P.A.M.","contributorId":9857,"corporation":false,"usgs":true,"family":"Bachand","given":"P.A.M.","email":"","affiliations":[],"preferred":false,"id":428008,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Bergamaschi, B.A. 0000-0002-9610-5581","orcid":"https://orcid.org/0000-0002-9610-5581","contributorId":22401,"corporation":false,"usgs":true,"family":"Bergamaschi","given":"B.A.","affiliations":[],"preferred":false,"id":428009,"contributorType":{"id":1,"text":"Authors"},"rank":6}]}} ,{"id":70033669,"text":"70033669 - 2008 - Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties","interactions":[],"lastModifiedDate":"2018-10-22T09:32:20","indexId":"70033669","displayToPublicDate":"2008-01-01T00:00:00","publicationYear":"2008","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1565,"text":"Environmental Science & Technology","onlineIssn":"1520-5851","printIssn":"0013-936X","active":true,"publicationSubtype":{"id":10}},"title":"Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties","docAbstract":"Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolates were characterized as terrestrial, microbial, or intermediate humic substances or transphilic acids. All anion exchange experiments were conducted using a magnetic ion exchange (MIEX) resin. The charge density of the DOM isolates, determined by direct potentiometric titration, was fundamental to quantifying the stoichiometry of the anion exchange mechanism. The results clearly show that all DOM isolates were removed by anion exchange; however, differences among the DOM isolates did influence their removal by MIEX resin. In particular, MIEX resin had the greatest affinity for DOM with high charge density and the least affinity for DOM with low charge density and low aromaticity. This work illustrates that the chemical characteristics of DOM and solution conditions must be considered when evaluating anion exchange treatment for the removal of DOM.
Compliance with U.S. air quality regulatory standards for atmospheric fine particulate matter (PM2.5) is based on meeting average 24 hour (35 μ m−3) and yearly (15 μg m−3) mass‐per‐unit‐volume limits, regardless of PM2.5 composition. Whereas this presents a workable regulatory framework, information on particle composition is needed to assess the fate and transport of PM2.5 and determine potential environmental/human health impacts. To address these important non‐regulatory issues an integrated approach is generally used that includes (1) field sampling of atmospheric particulate matter on filter media, using a size‐limiting cyclone, or with no particle‐size limitation; and (2) chemical extraction of exposed filters and analysis of separate particulate‐bound fractions for total mercury, trace elements and organic constituents, utilising different USGS laboratories optimised for quantitative analysis of these substances. This combination of sampling and analysis allowed for a more detailed interpretation of PM2.5 sources and potential effects, compared to measurements of PM2.5 abundance alone. Results obtained using this combined approach are presented for a 2006 air sampling campaign in Shenandoah National Park (Virginia, USA) to assess sources of atmospheric contaminants and their potential impact on air quality in the Park. PM2.5 was collected at two sampling sites (Big Meadows and Pinnacles) separated by 13.6 km. At both sites, element concentrations in PM25 were low, consistent with remote or rural locations. However, element/Zr crustal abundance enrichment factors greater than 10, indicating anthropogenic input, were found for Hg, Se, S, Sb, Cd, Pb, Mo, Zn and Cu, listed in decreasing order of enrichment. Principal component analysis showed that four element associations accounted for 84% of the PM2.5 trace element variation; these associations are interpreted to represent: (1) crustal sources (Al, REE); (2) coal combustion (Se, Sb), (3) metal production and/or mobile sources (Mo, Cd, Pb, Cu, Zn) and (4) a transient marine source (Sr, Mg). Concentrations of Hg in PM2.5 at background levels in the single pg m−3 were shown by collection and analysis of PM2.5 on filters and by an automated speciation analyser set up at the Big Meadows air quality site. The speciation unit revealed periodic elevation of reactive gaseous mercury (RGM) that co‐occurred with peaks in SO2, indicating an anthropogenic source. GC/MS total ion current chromatograms for the two sites were quite similar indicating that organic signatures were regional in extent and/or that the same compounds were present locally at each site. Calculated carbon preference index values for n‐alkanes indicated that plant waxes rather than anthropogenic sources, were the dominant alkane source. Polycyclic aromatic hydrocarbons (PAHs) were detected, with a predominance of non‐alkylated, and higher molecular weight PAHs in this fraction, suggestive of a combustion source (fossil fuel or forest fires).