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George Aiken is a senior researcher with the National Research Program of the U. S. Geological Survey. He received a M.S. degree in chemistry from the University of Colorado and a Ph.D. in applied chemistry from the Colorado School of Mines. Since joining the U.S. Geological Survey in 1976, Aiken has devoted his career to studying the chemistry of dissolved organic matter in natural waters. Presently, his research group is focused on the roles played by dissolved organic matter (DOM) in the biogeochemistry of mercury and other metals, effects of hydrology and climate change on DOM in high-latitude and temperate systems, and development of improved methods for studying DOM composition and reactivity.
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Dittman, JA, Shanley JB, Driscoll, CT, Aiken, GA, Chalmers, AT, Towse JE, and Selvendiran, P., 2010, Mercury dynamics in relation to DOC concentration and quality during high flow events in three northeastern USA streams, Water Resources Research, v.46, W07522, doi:10.1029/2009WR008351.
Spencer, R.G.M., Aiken, G.R., Dyda, R.Y., Butler, K.D. Bergamschi, B.A., and Hernes, P.J., 2010, Comparison of XAD with other dissolved lignin isolation techniques and a compilation of analytical improvements for the analysis of lignin in aquatic settings, Organic Geochemistry, 41, pp. 445-453.
Metge, D.W., Harvey, R.W., Aiken, G.R., Anders, R., Lincoln, G., and Jasperse, J., 2010, Influence of organic carbon loading, sediment associated metal oxide content and sediment grain size distributions upon Cryptosporidium parvum removal during riverbank filtration operations, Sonoma County, CA, Water Research, 44, pp. 1126-1137.
Harvey, R.W., Metge, D.W., Barber, L.B., and Aiken, G.R., 2010, Effects of altered groundwater chemistry upon the pH-dependency and magnitude of bacterial attachment during transport within an organically contaminated sandy aquifer, Water Research, 44, pp. 1062-1071.
O’Donnell, J.A., Aiken, G.R., Kane, E.S. and Jones, J.B., 2010, Source water controls on DOC character and origin in streams of the Yukon River Basin, Alaska, J Geophys Res, Vol 155, doi:10.1029/2009JG001153
Stets, E.G., Striegl, R.G., and Aiken, G.R., 2010, Dissolved organic carbon export and internal cycling in small headwaters lakes, Global Biogeochem Cycles, 24, GB4008, doi:10.1029/2010GB003815
Larsen, L.G., Aiken, G.R.,
Murphy, K.R., Butler, K.D., Spencer, R.G.M., Stedmon, C.A., Boehme, J.R., and Aiken, G.R., 2010, Measurement of dissolved organic matter fluorescence in aquatic environments: An interlaboratory comparison. Environmental Science and Technology, vol. 44, 9405-9412.
Orem, W., Gilmour, C., Axelrad, D., Krabbenhoft, D., Scheidt, D., Kalla, P., McCormick, P., Gabriel, M., and Aiken, G., 2011, Sulfur in the South Florida ecosystem: Distribution, sources, biogeochemistry, impacts, and management for restoration. Critical Reviews in Environmental Science and Technology, vol 41(6), 249-288.
Aiken, G.R., Gilmour, C.C., Krabbenhoft, D.P., and Orem, W., 2011, Dissolved organic matter in the Florida Everglades: Implications for ecosystem restoration. Critical Reviews in Environmental Science and Technology, vol 41(6), 217-248.
Deonarine, Lau, Aiken, Ryan and Hsu-Kim 2011 Effects of humic substances on precipitation and aggregation of zinc sulfide nanoparticles, Environmental Science and Technology, vol 45, pp 3217-3223, doi,org/10.1021/es1029798
Pellerin, B.A., Bergamaschi, B.A., Murdoch, P.S., Downing, B.D., Saraceno, John Franco, Aiken, G.R., and Striegl, R.G., 2011, The Aquatic Real-Time Monitoring Network: In-situ Optical Sensors for Monitoring the Nation’s Water Quality, USGS Factsheet 2011-3061.
Aiken , G.R., Hsu-Kim, H., and Ryan, J.N., 2011, Influence of dissolved organic matter on the environmental fate of metals, nanoparticles, and colloids, Environmental Science and Technology, vol 45, pp. 3196-3201, doi,org/10.1021/es103992s
Aiken, G., Hsu-Kim, H., Ryan, J., and Alvarez, P., 2011, Guest Comment: Nanoscale metal-organic matter intereactions, Environmental Science and Technology, vol 45, pp. 3194-3195, doi,org/10.1021/es2007148.
Metge , D.W., Harvey, R/.W., Aiken, G.R., Anderrs, R., Lincoln, G., Jasperse, J., and Hill, M.C., 2011, Effects of sediment associated extractable metals, degree of sediment grain sorting, and dissolved organic carbon upon Cryptosporidium parvum removal and transport within riverbank filtration sediments, Sonoma County, California, Environmental Science and Technology, vol 45, pp. 5587-5595, doi,org/10.1021/es200544p.
Nagy K., Manceau, A., Gasper, J.D., Ryan, J.N., and Aiken, G.R., 2011, Metallothionein-like multiclusters of mercury(II) and sulfur in peat. Environmental Science and Technology, vol 45, pp –7298-7306, doi,org/10.1021/es201025v.
Gerbig, C.A., Ryan, J.N., and Aiken, G.R., 2011, The effects of dissolved organic matter on mercury biogeochemistry. In Environmental Chemistry and Toxicology of Mercury (Guangliang Liu, Yong Cai, and Nelson O’Driscoll (eds.), John Wiley and Sons, Inc., pp. 259-292.
Schuster, PF, Striegl, RG, Aiken, GR, Krabbenhoft, DP, DeWild, JF, Butler, K, Kamark, B, and Dornblaser, M, 2011, Mercury Export from the Yukon River Basin and Potential Response to a Changing Climate, Environmental Science and Technology, vol. 45, 9262-9267, doi: 10.1021/es202068b.
Gerbig , CA, Kim, CS, Stegemeier, JP, Ryan, JN, and Aiken, GR, 2011, Formation of nanocolloidal metacinnabar in mercury-DOM-sulfide systems, Environmental Science and Technology, vol 45, 9180-9187, doi.org/10.1021/es201837h.
Pellerin, B.A., Saraceno, John Franco, Shanley, J.B., Sebestyn, S.D., Aiken, G.R., Wollheim, W.M., Bergamaschi, B.A., 2012, Taking the pulse of snowmelt: in-situ sensors reveal seasonal, event and diurnal patterns of nitrate and dissolved organic matter variability in an upland forest stream, Biogeochemistry, DOI 10.1007/s10533-011-9589-8
Stubbins, A, Hood, E, Raymond, PA, Aiken, GR, Sleighter, RL, Hernes, PJ, Butman, D, Hatcher, PG, Striegl, RG, Schuster, P, Abdulla, HAN, Vermilyea, AW, Scott, DT, and Spencer RGM, 2012, Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers, Nature Geosciences, doi:10.1038/NGEO1403.
Barnes, RT, Smith, RL, Aiken, GR, 2012 , Linkages between denitrification and organic matter quality, Boulder Creek Watershed, CO, Journal of Geophysical Research, vol 117, G01014, doi:10.1029/2011JG001749.
Graham, AM, Aiken, GR and Gilmour, CC, 2012, Dissolved organic matter enhances microbial mercury methylation under sulfidic conditions, Environmental Science and Technology, vol 46, 2715-2723.
Burns, D.A., Riva-Murray, K., Bradley, P.M., Aiken, G.R., and Brigham, M.E., 2012, Landscape controls on total and methyl Hg in the upper Hudson River basin, New York, USA, Journal of Geophysical Research, Biogeosciences, vol. 117, G01034, doi:10.1029/2011J001812
Spencer, RGM, Hernes, PJ, Aufdenkampe, AK, Baker, A, Gulliver, P, Stubbins, A, Aiken, GR, Dyda, RY, Butler, KD, Mwamba, VL, Mangangu, AM, Wabakanghanzi JN, and Six, J, 2011, An initial investigation into the organic matter biogeochemistry of the Congo River and estuary, Geochimica et Cosmochimica Acta, vol 84, 614-627.
Bergamaschi, BA, Krabbenhoft, DP, Aiken, GR, Patino, E, Rumbold, DG, and Orem, WH, 2012, Tidal flux of dissolved organic carbon, total mercury, and methylmercury from a mangrove marsh, Environmental Science and Technology, vol. 46, pp. 1371-1378.
Cawley, K.M., Butler, K.D., Aiken, G.R., Larsen, L., Huntington, T.G., and McKnight, D.M., in press, Identifying fluorescent pulp mill effluent in the Gulf of Maine and its watershed, Marine Pollution Bulletin, vol. 64, pp. 1678-1687, http://dx.doi.org/10.1016/j.marpolbul.2012.05.040
Spencer, R.G M., Butler, K.D., and Aiken, G.R., 2012, ,Dissolved Organic Carbon and Chromophoric Dissolved Organic Matter Properties of Rivers in the U.S.A., Journal of Geophysical Research – Biogeosciences, Vol 117, G03001, doi:10.1029/2011JG001928
Wickland, K.P., Aiken, G.R., Butler, K., Dornblaser, M.M., Spencer, R., and Striegl, R.G., 2012, Biodegradability of Dissolved Organic Carbon in the Yukon River and its Tributaries - Seasonality and Importance of Inorganic Nitrogen, Global Biogeochemical Cycles, doi:10.1029/2012GB004342
Craven, A.M., Aiken, G.R., and Ryan, J.N., 2012, Importance of the copper to dissolved organic matter ratio on the binding of copper by dissolved organic matter and implications for the biotic ligand model, Environmental Science and Technology, doi.org/10.1021/es301015p
My Science Topics
My USGS Science Strategy AreasUnderstanding Ecosystems & Predicting Ecosystems Change
Climate Variability & Change
Chemistry of Dissolved Organic matter
The overall objective of this project is to determine the role of chemical processes associated with dissolved organic matter (DOM) on the transport and reactivity of both naturally occurring and anthropogenic compounds. Defining the roles of DOM in environmental and geochemical processes is critical to understanding the nature and quality of the Nation’s water resources, and is important for future management of these resources. In recent year’s my research has focused on the influences of DOM on the biogeochemistry of Hg and other metals, the effects of hydrology and climate change on DOM in the nation’s rivers, including northern systems, such as the Yukon River, the influences of terrestrially derived DOM on satellite based assessments of water quality in the Gulf of Maine, and, the development of improved methods for studying DOM composition and reactivity.
DOM Interactions with Hg and other metals: Our research has demonstrated the importance of DOM interactions on the fate and transport of mercury and other metals through strong complexation, colloid stabilization and/or redox reactions. While the main focus has been on Hg, recently we have also been studying the effects of DOM on Cu and Zn chemistry. Overall, our efforts have resulted in a number of significant publications in the last 3 years (11 journal articles; 1 book chapter). Results are important for modeling the geochemistry and bioavailability of Hg and other metals in aquatic systems and are of interest to water resources managers in South Florida, California, and elsewhere. Presently, DOC-Hg studies continue at the NAWQA-Hg study sites, Florida Everglades (PES), Lake Pontchartrain (LEAG), Yukon River Basin and San Joachin- Sacramento River Delta. Recently we demonstrated the importance of DOM in controlling geochemistry and the bioavailability of HgS for methylation at environmentally relevant concentrations.
Sources/fate of DOC in aquatic systems: Research on DOC in various field settings (e.g NASQAN rivers, Yukon and arctic rivers, SHAEP, Penobscot, others) is providing information on factors controlling the composition and concentration of DOC in aquatic systems. Six papers and one book chapter have been published since 2010. Relevant information is sought by resource managers to assist in design of water resource management strategies (e.g. CALFED, Everglades restoration. I was a participant in the development of the USGS-NRP Contribution to DOI’s Deepwater Horizon Oil Spill Long Term Science Plan entitled Conceptual Model Framework for a Long-Term Science Plan Response to the Deepwater Horizon Oil Spill (Windham-Myers-lead) and contributed analyses to overall USGS sampling effort in response to the spill organized under the auspices of Branch of Water Quality.
Analytical Methods: Analytical methods developed in my laboratory for analysis of the composition and determinations of reactivity of DOC are being adopted by scientific community interested in DOC related issues. In addition, we have made progress utilizing organic matter optical properties in the development of tools for in-situ DOC measurements to determine water sources, to monitor changes in concentrations and nature of DOC. Six papers have been published since 2010 related to the applications of optical properties as proxies for DOM, concentration and composition. I was involved with the design of the Climate Effects Network of in-situ sensors on sentinel rivers deployed FY11. A factsheet describing this network was published in 2011.
Drinking Water: Research on the influences of DOM on the transport of pathogens in the subsurface is of growing interest for drinking water utilities. In collaboration with Ron Harvey and Dave Metge, we have been addressing fundamental questions related to these processes in Florida and California. Three papers have been published since 2010.
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