Armstrong, David E.

Gorski, P.R., D.E. Armstrong, J.P. Hurley, and M.M. Shafer. 2006. Speciation of aqueous methylmercury influences uptake by a freshwater alga (Selenastrum Capricornutum). Environ. Toxicol. Chem. 25: 534-540.

Chadwick, S.P., C.L. Babiarz, J.P. Hurley, and D.E. Armstrong. 2005. Influences of iron, manganese, and dissolved organic carbon on the hypolimnetic cycling of amended mercury. Sci. Tot. Environ. (Article In Press).

Stoor, R.W., J.P. Hurley, C.L. Babiarz, and D.E. Armstrong. 2005. Subsurface sources of methyl mercury to Lake Superior from a wetland-forested watershed. Sci. Tot. Environ. (Article In Press)

Tang, D., M.M. Shafer, D.A. Karner, and D.E. Armstrong. 2005. Response of non-protein thiols to copper stress and extracellular release of glutathione in the Diatom Thalassiosira weissflogii. Limnol. Oceanogr. 50:516-525.

Tang, D., M.M. Shafer, D.A. Karner, J.T. Overdier, and D.E. Armstrong. 2004. Factors affecting the presence of dissolved glutathione in estuarine waters. Environ. Sci. Technol. 38:4247-4253.

Shafer, M.M., S.R. Hoffmann, J.T. Overdier, and D.E. Armstrong. 2004. Physical and kinetic speciation of copper and zinc in three geochemically contrasting marine estuaries. Environ. Sci. Technol. 38:3810-3819

Gorski, P.R., L.B. Cleckner, H.P. Hurley, M.E. Sierszen, and D.E. Armstrong. 2003. Factors affecting enhanced mercury bioaccumulation in inland lakes of Isle Royale National Park, USA. Sci. Total Environ. 304:327-348.

Poister, D. and D.E. Armstrong. 2003. Seasonal sedimentation trends in a mesotrophic lake: Influence of diatoms and implications for phosphorus dynamics. Biogeochem. 65:1-13.

Tang, D., M.M. Shafer, K. Vang, D.A. Karner, and D.E. Armstrong. 2003. Determination of dissolved thiols using solid-phase extraction and liquid chromatographic determination of fluorescently derivatized thiolic compounds. J. Chromatog. A, 998:31-40.

Wood, C.M., T. W. La Point, D.E. Armstrong, et al. 2002. Biological Effects of Silver, Chaper 2. IN Andren, AW, Bober TW, editors; Silver in the Environment: Transport, Fate, And Effects. Pensacola, FL, USA: Society of Environmental Toxicology and Chemistry (SETAC). P 192.

Herrin, R.T., A.W. Andren, and D.E. Armstrong. 2001. Determination of silver speciation in natural waters I: Laboratory tests of Chelex-100 chelating resin as a competing ligand. Environ. Sci. Technol. 35:1953-1958

Herrin, R.T., A.W. Andren, M.M. Shafer, and D.E. Armstrong. 2001. Determination of silver speciation in natural waters II. Binding strength of silver ligands in surface waters. Environ. Sci. Technol. 35:1959-1966.

Babiarz, C.L., J.P. Hurley, S.R. Hoffmann, A.W. Andren, M.M. Shafer, and D.E. Armstrong. 2001. Partitioning of mercury to the colloidal phase in freshwaters. Environ. Sci. Technol. 35:4773-4782.

Zelewski, L.M., G. Benoit, and D.E. Armstrong. 2001. Mercury dynamics in Tivoli South Bay, a freshwater tidal mudflat wetland in the Hudson River. Biogeochem. 52:93-112.

Zelewski, L.M., D.P. Krabbenhoft, and D.E. Armstrong. 2001. Trace metal concentration in shallow groundwater. Groundwater 39:485-491

Baron, M.G., R.T. Herrin, and D.E. Armstrong. 2000. The measurement of silver in road salt by electrothermal atomic absorption spectrometry. Analyst 125:123-126.

Hoffmann, S.R., M.M. Shafer, C.L. Babiarz, and D.E. Armstrong. 2000. A critical evaluation of tangential-flow ultrafiltration for trace metal studies in fresh water systems: I. Organic carbon. Environ. Sci. Techol. 34:3420-3427.

Babiarz, C.L., S.R. Hoffmann, M.M. Shafer, J.P. Hurley, A.W. Andren, and D.E. Armstrong. 2000. A critical evaluation of tangential-flow ultrafiltration for trace metal studies in fresh water systems: 2.Total mercury and methylmercury. Environ. Sci. Technol. 34:3428-3434.

Selected Awards, Honors and Societies

American Chemical Society
American Society of Limnology & Oceanography
International Association for Great Lakes Research

Summary

My research program, involving colleagues and graduate students, is concerned with three main areas of aquatic chemistry: biogeochemical processes governing phosphorus, and other natural elements in lakes and watersheds; the sources, transport, and fate of organic chemicals in lakes; and trace metal chemistry, speciation, and bioavailability in aquatic systems.

One current project focuses on the chemistry and bioavailability of phosphorus in stream sediments, where we are exploring the role of stream sediments in the storage, transport and transformations of phosphorus during movement from an agricultural watershed, through a stream, and then into a lake. Natural radionuclides (⁷Be and ²¹⁰Pb) are used to characterize stream sediment dynamics. We are also exploring the biogeochemical processes regulating the internal loading of phosphorus in lakes.

Our research on metals is concerned with the chemical speciation of trace metals (Cu, Cd, Hg, others) in freshwaters and the relationships between speciation and metal bioavailability and toxicity to phytoplankton. We measure and model metal speciation, including association with ligands that are contained within the complex mixture we call natural organic matter using voltammetry and other techniques. Metal speciation is incorporated into a framework known as the Biotic Ligand Model which couples competition between the organism and aqueous metal-binding ligands. We are also investigating where strong metal-binding ligands are formed by making measurements along hydrologic flow paths (watershed uplands to groundwater to stream). Mercury is of special concern because the species that bioaccumulates in foodwebs (methyl mercury) is formed in the environment. Our research involves understanding the environmental factors and biogeochemical processes governing the transport, methylation, and bioavailability of mercury in lakes and watersheds.

Our research involves field investigations in lakes, streams, and watersheds as well as laboratory experiments. We exploit contrasting biogeochemical environments in order to identify key factors and processes. Quantitative assessments of chemical concentrations, speciation, and fluxes are emphasized.

Copyright 2010 The Board of Regents of the University of Wisconsin System
Date last modified: 19-Aug-2011
Content by: armstron@engr.wisc.edu
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