Dr. Hammerschmidt's research is focused on developing a quantitative understanding of the biological, chemical, and physical mechanisms and processes that affect the transport, transformation, and fate of mercury and other trace metals in watersheds, coastal and pelagic marine systems, and the atmosphere.
Postdoctoral scholar, Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, 2005-2007
Ph.D., Oceanography (chemical), University of Connecticut, 2005
M.S., Biology, University of Wisconsin-La Crosse, 1999
B.S., Biology/Aquatic Sciences, University of Wisconsin-La Crosse, 1997
Diploma, Fairmont (Minnesota) High School, 1993
- EES 4240/6240 Oceanography, 3 credit hrs
- EES 4010/6010 Quality Assurance of Environmental Analysis, 0.5 credit hrs
- EES 4590/6590 Aquatic Geochemistry, 3 credit hrs [Odd Years]
- EES 4510/6510 Effective Scientific Communication, 3 credit hrs [Even Years]
- EES 4010/6010 Limnology, 3 credit hrs
On-going projects include the following:
Experiments Measuring Bioavailability in Oxic and Spiked Sediments (EMBOSS). Collaborative project with David Costello (Kent State) and Allen Burton (University of Michigan), and supported by the metals industry. 2012−2015.
The established models of metal bioavailability in sediments (e.g., SEM-AVS/fOC) are sufficient for predicting non-toxic conditions in anoxic sediments yet there is a great deal of uncertainty in whether or not organisms respond negatively to metal above non-toxic thresholds. Some of the uncertainty has been hypothesized to be due to Fe and Mn oxides that can bind metals in excess of sulfides and further reduce bioavailability. Additionally, bioassays used to derive sediment criteria often utilize metal spiked sediments, which, as has been demonstrated in soils, may be more toxic than field-contaminated sediments. These experiments are comparing identical metal (Cu, Ni, Zn) concentrations in spiked and field-contaminated soils in an experimental flume through time to study: (1) the toxicity of spiked and field-contaminated sediments at the same concentration, (2) the role of Fe and Mn oxides in reducing bioavailability, (3) the time and conditions under which aged spiked sediments approach the geochemistry and toxicity of field-contaminated sediments.
GEOTRACES Arctic Section: Mercury Speciation and Cycling in the Arctic Ocean. Collaborative project with Carl Lamborg (University of California Santa Cruz), and supported by NSF-Ocean Sciences. 2015−2017.
GEOTRACES is an international, multi-year coordinated effort to examine the biogeochemistry of trace elements and isotopes (TEIs) in all of the major ocean basins and a few notable marginal seas. The GEOTRACES program provides a unique opportunity for the world-wide community of chemical oceanographers studying TEIs to work in a collective and coordinated fashion to more easily and comprehensively cover ocean regions of interest and produce the broadest possible set of information to facilitate hypothesis testing. This opportunity is especially true of the Arctic Ocean in the next few years because multiple countries will be mounting oceanographic campaigns in different sectors of the basin but also with planned “cross-over” stations that will be occupied by at least two groups on different cruises for purposes of intercalibration.
We are participating in the U.S. GEOTRACES cruise to the Arctic Ocean with the goal of constructing a high-resolution vertical and horizontal section of total mercury (Hg), monomethylmercury (MMHg), dimethylmercury (DMHg), and elemental Hg (Hg0) in seawater of this important ocean region. In addition to filtered water samples, we are analyzing suspended particles and sediment for total Hg and MMHg, dissolved and particulate thiols, snow and ice for Hg and Br, and searching for microbial genes related to Hg cycling. This work will contribute much needed information to answer questions related to the extent and rate of change of Hg loadings to this sensitive ecosystem.
Benthic Phosphorus Fluxes in the Lower Great Miami River Watershed, southwest Ohio. Collaborative project with Mike Ekberg (Miami Conservancy District), and supported by regional POTWs. 2015−2016.
All organisms require nutrients to sustain life and growth. Nitrogen (N) and phosphorus (P) are primary nutrients for algal and macrophyte production and are essential to the functioning of healthy aquatic ecosystems. However, overabundance of nutrients, and particularly P in most freshwater systems, can exert negative ecosystem effects, including alteration of trophic dynamics by increasing algal and macrophyte production, increasing turbidity (through algal production), decreasing concentrations of dissolved oxygen (DO), and increasing the magnitude of diel fluctuations of DO and pH. These symptoms of eutrophication shift species composition away from those typical of high-quality warmwater streams towards less desirable species compositions of degraded warmwater streams.
Human activities over the last century have increased the total mass of N and P introduced into aquatic ecosystems. This increase is due to municipal and industrial wastewater discharges, fertilizer use, and atmospheric inputs. Despite improvements in water quality due to better treatment of wastewater discharges, an overabundance of nutrients still exists in the Great Miami River Watershed. Algal blooms on the Great Miami River were observed by the Ohio Environmental Protection Agency 1995 and again in 2011. Nutrient enrichment is listed by OEPA as one of the most pervasive causes of impairment in the Upper Great Miami River Watershed in a recent study of biological and water quality.
Recent evaluations of nutrient loading in the Great Miami River Watershed suggest that nonpoint sources contribute most of the annual P load carried by the river. Often a significant amount of the annual nutrient load can be attributed to just a few large runoff events that typically occur between late winter and early summer. Thus, management programs directed at preventing export of nutrients downstream should focus primarily on preventing nutrients from being exported from agricultural land and entering streams and aquifers. However, most evaluations of biological community productivity and diversity (e.g., Index of Biological Integrity, Invertebrate Community Index, Modified Index of Well Being) in the Great Miami River and its tributaries are conducted during summer and early fall when low-flow conditions prevail and significant runoff events carrying large nutrient loads from nonpoint sources are not occurring. These evaluations show a decline in biological community performance in the Lower Great Miami River, downstream of Dayton. Results from these evaluations also show strong evidence of excess nutrients. For example, the evaluations documented elevated concentrations soluble forms of P in the water column as well as increased periphyton biomass and large diel swings of DO concentrations. Regulators of municipal wastewater treatment plants have concluded that point sources of nutrients are the primary driver of trophic dynamics during low-flow conditions in summer and fall. Therefore, degradation in biological communities due to nutrient enrichment can best be ameliorated by lowering permit nutrient concentrations in effluent. But, is this conclusion correct?
We are investigating whether benthic remobilization is a significant source of P to the Lower Great Miami River during low-flow conditions in summer and early fall. The objective of this study is to quantify fluxes of P from riverbed sediments at eight representative locations along the mainstem of the Lower Great Miami River between Dayton and Hamilton, Ohio.
Mercury Biogeochemistry on the Continental Shelf and Slope. Collaborative study with Bill Fitzgerald (University of Connecticut), and supported by NSF-Ocean Sciences.
Methylmercury is the form of mercury (Hg) that bioaccumulates and biomagnifies in marine food webs, especially piscivorous fish, and represents the primary human health concern related to mercury in the environment. Most fish consumed by humans are of marine origin, and the coastal zone, including biologically productive upwelling regions, is the major source of marine fish productivity. Unfortunately, little is known about the sources and cycling of methylmercury in marine systems, especially the important continental shelf regions. Benthic Hg methylation on the continental shelf and slope is a potentially significant contributor of methylmercury to the marine environment, including biota and the open ocean. Thus, and given the limited information and knowledge regarding Hg distributions and biogeochemistry in shelf sediments and waters, we are conducting a three-year investigation that is focused on processes and reactions affecting the cycling of methylmercury in sediments and waters over a broad region of the shelf and slope of the northwestern Atlantic Ocean. This study includes sampling of multiple environmental matrixes for analysis of Hg and mercury species (methylmercury, dimethylmercury, elemental Hg): water, suspended particles, sediment, sediment pore fluids, and zooplankton. This descriptive component is complemented by mechanistic studies that are examining 1) factors affecting the sediment-water exchange of methylmercury, 2) the identity of microorganisms that produce and demethylate methylmercury in sediments, 3) bioaccumulation of methylmercury in planktonic food webs, 4) geochemical factors affecting net production of methylmercury in sediments, and 5) photochemical reactions that demethylate mercury and result in it being less available for uptake by organisms. These measurements and experiments are focused around three 11-day oceanographic cruises (one each in 2008, 2009, and 2010) in the northwest Atlantic Ocean that have provided a platform for student research and involvement. On the 2009 cruise, for example, nine of the 13 science party members were students.
GEOTRACES Pacific Section: Mercury Speciation Along a Zonal Section in the Eastern Tropical South Pacific Ocean. Collaborative study with Carl Lamborg (University of California Santa Cruz), and supported by NSF-Ocean Sciences.
We are measuring Hg speciation in the eastern tropical South Pacific (ETSP) Ocean in order to construct a high-resolution, full-depth, zonal section of Hg species across this important ocean basin for which almost no Hg data currently exist. Indeed, only one major cruise has examined distributions of Hg species in parts of the South Pacific and at depths shallower than 1000 m. The ETSP is a truly ideal region within which to investigate the sources and cycling of Hg species in the ocean. The cruise track (below) allows us to explore multiple oceanographic features that we hypothesize will have a dramatic influence on the inputs and cycling of Hg in the ocean. The interesting features of the cruise track include:
1) A narrow continental margin from which we hypothesize to observe substantial export of Hg, monomethylmercury (CH3Hg+), and dimethylmercury ((CH3)2Hg);
2) An expansive and suboxic (< 10 µM) oxygen minimum zone (OMZ) within which we expect to find, quite possibly, some of the highest levels of methylated Hg in the ocean;
3) A large gradient in the nitrogen cycling tracer, N*, which indicates that the Peru upwelling is a location of significant denitrification. Our work in the North Atlantic and our colleagues’ observations in the North Pacific and Indian Oceans suggests that denitrification may be an important modulator of Hg methylation;
4) A submarine hydrothermal plume from the East Pacific Rise (EPR), near 15 °S, that we suspect is a significant input of Hg species into the deep Pacific Ocean, as we observed at the Mid-Atlantic Ridge during the U.S. GEOTRACES North Atlantic section; and
5) A large gradient in biological productivity, ranging from oligotrophic water near Tahiti to the very productive eastern boundary current upwelling system off the coast of Peru. We hypothesize that this gradient in productivity and respiration will result in dramatic differences in vertical Hg distributions and its bioavailability and transformation to elemental Hg (Hg0), CH3Hg+, and (CH3)2Hg.
Other ongoing student projects:
- Lead in Dayton tap water
- Mercury in south Florida sharks
- Mercury mobilization from soil as a result of land use changes
- Environmental factors affecting concentrations of methylmercury in fish of the Laurentian Great Lakes region
- Temporal variation of mercury in effluent from municipal wastewater treatment plants in southwest Ohio
- Methylmercury bioaccumulation in mesopelagic organisms of the northern Gulf of Mexico
Dr. Hammerschmidt is currently advising research of multiple students (expected year of graduation):
- Emily L. Holliday, M.S. student (2020)
- Paul J. Fleischman, M.S. student (2020)
- Ashley N. Livingston, M.S. student (2020)
- Baylee S. Stark, M.S. student (2019)
- Lindsay D. Starr, Ph.D. student (2021)
- Caitlin Erbacher, B.S. student (2021)
- Grace Whitney, B.S. student (2021)
Student Theses and Dissertations
- Lisa M. Romas, M.S., 2010. Functional identification of microorganisms that transform mercury in marine sediments. (Now, employed at NJ DEP)
- Melissa D. Tabatchnick, M.S., 2010. Mercury speciation in temperate tree foliage. (Now, student in physical therapy school in RI)
- Avani P. Naik, M.S., 2010. Trace metal fluxes in southwest Ohio watersheds. (Now, environmental consultant in PA)
- Katlin L. Bowman, B.S., 2010. Decomposition of methylmercury in seawater. (Now, postdoc at Univ. California Santa Cruz)
- Robbie L. Weller, B.S., 2011. Methylmercury in zooplankton on the continental margin of the northwest Atlantic Ocean. (Now, veterinarian in OH)
- Matthew J. Konkler, M.S., 2011. Methylmercury in mosquitoes: Impact of a large coal-fired power station in central Ohio. (Now, research assistant at Oregon State Univ.)
- Astrea Taylor, M.S., 2012. Fluxes of phosphorus to Grand Lake St. Mary’s. (Now, at Ohio EPA)
- Jaclyn E. Klaus, B.S., 2012. Functional identification of mercury transforming microorganisms in freshwater sediments. (Now, Michigan DNR)
- Deepthi Nalluri, B.S., 2013. Methylmercury in dried shark fins and shark fin soup from American restaurants. (Currently, M.D. student at Boonshoft School of Medicine)
- Daniel L. Marsh, M.S., 2013. Trace metals in sediments on the continental margin of the northwest Atlantic Ocean. (Now, Corp. account manager for ChemTreat)
- Kelsey M. Danner, M.S., 2013. Copper and nickel partitioning with nanoscale goethite. (Now, Ph.D. student at Ohio State)
- Rebecca L. Gamby, M.S., 2014. Effect of deforestation and cultivation on mercury in soil. (Now, high school science teacher in OH)
- Jaclyn E. Klaus, M.S., 2014. Net methylmercury production in two contrasting stream sediments and association accumulation and toxicity to periphyton. (now, nursing student)
- Sarah E. Harvey, M.S., 2014. Stability of methylmercury in water. (Now, at Ohio EPA)
- Katlin Bowman, Ph.D., 2014. Mercury distributions and cycling in the North Atlantic and eastern tropical South Pacific Oceans. (Postdoc at UC Santa Cruz)
- Heather B. Perusini, M.S., 2016. Temporal variation of mercury in effluent from two municipal wastewater treatment plants in southwest Ohio.
- Katelynn L. Alcorn, B.S., 2016. Methylmercury accumulation in meso- and bathypelagic fish of the northern Gulf of Mexico. (Now, M.D. student at Boonshoft School of Medicine)
- Kelly M. Muterspaw, B.S., 2017. Methylmercury accumulation in meso- and bathypelagic fish of the northern Gulf of Mexico. (Now, M.D. student at Boonshoft School of Medicine)
- Rachel A. Walker, M.S., 2017. Methylmercury accumulation in spotted salamanders of southern Ohio. (Now, at Volvo paint division, Blacksburg, VA)
- Dane C. Boring, M.S., 2017. Effect of land use on mercury in topsoils. (Now, Kansas Department of Health & Environment)
- Kortney R. Mullen, M.S., 2017. Benthic phosphorus fluxes in the Lower Great Miami River. (Now, Suez Water Technologies)
- Kayla M. Haman, M.S., 2018. Lead in tap water from the City of Dayton, Ohio (Now, Civil & Environmental Consultants, Inc., OH)
- Alison M. Agather, Ph.D., 2018. Distribution of mercury species in the western Arctic Ocean (Now, program coordinator NOAA Weather Program Office)
- Baylee Stark, M.S., 2019. Lead in tap water of public school near Dayton, Ohio (Now, Ohio EPA Air)
Hammerschmidt's WSU student coauthors are in bold text:
80. Perusini, H. B., C. R. Hammerschmidt (2020) Temporal variation of mercury in effluent from two municipal wastewater treatment plants in southwest Ohio. Environmental Toxicology & Chemistry. https://doi.org/10.1002/etc.4692
79. Bowman, K. L., E. R. Collins, A. M. Agather, C. H. Lamborg, C. R. Hammerschmidt, D. Kaul, C. Dupont, C. Christensen, D. G. Elias (2020) Distribution of mercury-cycling genes in the Arctic and Equatorial Pacific Oceans and their relationship to mercury speciation. Limnology & Oceanography 65, S310-S320.
78. Nogaro, G., A. J. Burgin, A.Taylor, C. R. Hammerschmidt (2019) Alum treatment did not improve water quality in hypereutrophic Grand Lake St. Mary's, Ohio. In Internal Phosphorus Loading in Lakes: Causes, Case Studies, and Management (A. D. Steinman, B. M. Spears, eds.).
77. Costello, D. M., A. M. Harrison, C. R. Hammerschmidt, R. M. Mendonca, G. A. Burton, Jr. (2019) Hitting reset on sediment toxicity: sediment homogenization alters the toxicity of metal-amended sediments. Environmental Toxicology & Chemistry 38, 1995-2007.
76. Agather, A. M., K. L. Bowman, C. H. Lamborh, C. R. Hammerschmidt (2019) Distribution of mercury species in the Western Arctic Ocean (U.S. GEOTRACES GN01). Marine Chemistry 216, 103686.
75. Schlitzer, R. et al. (2018) The GEOTRACES Intermediate Data Product 2017. Chemical Geology 493, 210-223.
74. Fitzgerald, W. F., D. R. Engstrom, C. R. Hammerschmidt, C H. Lamborg, P. H. Balcom, A. S. Lima-Braun, M. H. Bothner, C. M. Reddy (2018) Global and local sources of mercury deposition in coastal New England reconstructed from a multiproxy, high-resolution, estuarine sediment record. Environmental Science & Technlogy 52, 7614–7620.
73. Slone, L. A., M. J. McCarthy, J. A. Myers, C. R. Hammerschmidt, S. E. Newell (2018) River sedimment nitrogen removal and recycling within an agricultural Midwestern USA watershed. Freshwater Science 37, 1–12.
72. Blum, P. W., A. E. Hershey, M. T.-K. Tsui, C. R. Hammerschmidt, A. M. Agather (2017) Methylmercury and methane production potentials in North Carolina Piedmont stream sediments. Biogeochemistry 137, 181–195.
71. Matulik, A. G., D. W. Kersetter, N Hammerschlag, T. Divoll, C. R. Hammerschmidt, D. C. Evers (2017) Bioaccumulation and biomagnification of mercury and methylmercury in four sympatric coastal sharks in a protected subtropical lagoon. Marine Pollution Bulletin 116, 357–364.
70. Mason, R. P., C. R. Hammerschmidt, C. H. Lamborg, K. L. Bowman, G. J. Swarr, R. U. Shelley (2017) The air-sea exchange of mercury in the low latitude Pacific and Atlantic Oceans. Deep-Sea Research I 122, 17–28.
69. Lamborg, C. H., C. R. Hammerschmidt, K. L. Bowman (2016) An examination of the role of particles in oceanic mercury cycling. Philosophical Transactions of the Royal Society A doi: 10.1098/rsta.2015.0297.
68. Bowman, K. L., C. R. Hammerschmidt, C. H. Lamborg, G. J. Swarr, A. M. Agather (2016) Distribution of mercury species across a zonal section of the eastern tropical South Pacific Ocean (U.S. GEOTRACES GP16). Marine Chemistry 186, 156-166.
67. Swarr, G. J., T. Kading, C. H. Lamborg, C. R. Hammerschmidt, K. L. Bowman (2016) Dissolved low-molecular weight thiol concentrations from the U.S. GEOTRACES North Atlantic Ocean zonal transect. Deep-Sea Research I 116, 77-87.
66. Costello, D. M., C. R. Hammerschmidt, G. A. Burton (2016) Nickel partitioning and toxicity in sediment during aging: Variation in toxicity related to stability of metal partitioning. Environmental Science & Technology 50, 11337-11345.
65. Gustin, M. S., D. C. Evers, M. S. Bank, C. R. Hammerschmidt, A. Pierce, N. Basu, J. Blum, P. Bustamante, C. Chen, C. T. Driscoll, M. Horvat, D. Jaffe, J. Pacyna, N. Pirrone, M. Selin. (2016) Importance of integration and implementation of emerging and future research into the Minamata Convention. Environmental Science & Technology 50, 2767–2770.
64. Fetters, K. J., D. M. Costello, C. R. Hammerschmidt, G. A. Burton (2016) Toxicological effects of short-term resuspension of metal contaminated freshwater and marine sediments. Environmental Toxicology and Chemistry 35, 676-686.
63. Klaus, J. E., C. R. Hammerschmidt, D. M. Costello, G. A. Burton Jr. (2016) Net methylmercury production in two contrasting stream sediments and associated accumulation and toxicity to periphyton. Environmental Toxicology & Chemistry 35, 1759-1765.
62. Custer, K. W., C. R. Hammerschmidt, G. A. Burton, (2016) Nickel toxicity to benthic organisms: The role of dissolved organic carbon, suspended solids, and route of exposure. Environmental Pollution 208, 309–317.
61. Buck, C. S., C. R. Hammerschmidt, K. L. Bowman, G. A. Gill, W. M. Landing (2015) Flux of total and methyl mercury to the northern Gulf of Mexico from U.S. estuaries. Environmental Science & Technology 49, 13992–13999.
60. Gamby, R. L., C. R. Hammerschmidt, D. M. Costello, C. H. Lamborg, J. R. Runkle (2015) Deforestation and cultivation mobilize mercury from topsoil. Science of the Total Environment 532, 467–473.
59. Costello, D. M., C. R. Hammerschmidt, G. A. Burton (2015) Copper sediment toxicity and partitioning during oxidation in a flow-through flume. Environmental Science & Technology 49, 6926–6933.
58. Walters, D. M., D. F. Raikow, C. R. Hammerschmidt, M. G. Mehling, A. Kovatch, J. T. Oris (2015) Primary productivity reduces methylmercury bioaccumulation and trophic transfer in experimental stream food webs. Environmental Science & Technology 49, 7762–7769.
57. Danner, K. M., C. R. Hammerschmidt, D. M. Costello, G. A. Burton (2015) Copper and nickel partitioning with nanoscale goethite under variable aquatic conditions. Environmental Toxicology & Chemistry 34, 1705–1710.
55. Hammerschmidt, C. R., M. S. Gustin, J. Bennett. (2014) Mercury biogeochemical cycling and processes: implications for human and ecosystem health. Science of the Total Environment 496, 635.
54. Nalluri, D., Z. Baumann, D. L. Abercrombie, D. D. Chapman, C. R. Hammerschmidt, N. S. Fisher (2014) Methylmercury in dried shark fins and shark fin soup from American restaurants. Science of the Total Environment 469, 644–648.
53. Lamborg, C. H., C. R. Hammerschmidt, K. L. Bowman, G. S. Swarr, K. M. Munson, D. C. Ohnemus, P. J. Lam, L-E. Heimbürger, M. J. A. Rijkenberg, M. A. Saito (2014) A global ocean inventory of anthropogenic mercury based on water column measurements. Nature 512, 65–68.
52. Fitzgerald, W. F., C. R. Hammerschmidt, D. R. Engstrom, P. H. Balcom, C. H. Lamborg, C.-M. Tseng (2014) Mercury in the Alaskan Arctic. In Alaska’s Changing Arctic: Ecological Consequences for Tundra, Streams and Lakes, J. E. Hobbie and G. W. Kling (Eds.), Oxford University Press, New York. pp. 287–302.
51. Lamborg, C. H., K. L. Bowman, C. R. Hammerschmidt, C. C. Gilmour, K. Munson, N. Selin, C.-M. Tseng (2014) Mercury in the anthropocene ocean. Oceanography 27, 76–87.
50. Barst, B. D., C. R. Hammerschmidt, M. M. Chumchal, D. C. G. Muir, J. D. Smith, A. P. Roberts, T. R. Rainwater, P. E. Drevnick (2013) Determination of mercury speciation in fish tissue with a direct mercury analyzer. Environmental Toxicology & Chemistry 32, 1237–1241.
49. Blank, N., A. G. Hudson, P. Vonlanthen, A. Hudson, O. Seehausen, C. R. Hammerschmidt, D. B. Senn (2013) Speciation leads to divergent methylmercury accumulation in sympatric whitefish in Swiss lakes. Aquatic Sciences 75, 261–273.
48. Hammerschmidt, C. R., M. Finiguerra, R. L. Weller, W. F. Fitzgerald (2013) Methylmercury accumulation in plankton on the continental margin of the northwest Atlantic Ocean. Environmental Science & Technology 47, 3671–3677.
47. Nogaro, G., A. J. Burgin, V. Schoepfer, M. J. Konkler, K. L. Bowman, C. R. Hammerschmidt (2013) Aluminum sulfate (alum) application interactions with coupled metal and nutrient cycling in a hypereutrophic lake ecosystem. Environmental Pollution 176, 267–274.
46. Nogaro, G., C. R. Hammerschmidt (2013) Influence of macrofauna on microbial production of methylmercury in sediments on the New England continental shelf. Hydrobiologia 701, 289–299.
45. Driscoll, C. T., C. Y. Chen, C. R. Hammerschmidt, R. P. Mason, C. C. Gilmour, E. M. Sunderland, B. K. Greenfield, K. L. Buckman, C. H. Lamborg (2012) Nutrient supply and mercury dynamics in coastal ecosystems: a conceptual model. Environmental Research 119, 118–131.
44. Mason, R. P., A. L. Choi, W. F. Fitzgerald, C. R. Hammerschmidt, C. H. Lamborg, E. M. Sunderland (2012) Mercury biogeochemical cycling in the ocean and policy implications. Environmental Research 119, 101–117.
43. Costello, D. M., G. A. Burton, C. R. Hammerschmidt, W. K. Taulbee (2012) Evaluating the performance of passive sampling devices (DGTs) for predicting nickel sediment toxicity. Environmental Science & Technology 46, 10239–10246.
42. Depew, D. C., N. Basu, N. M. Burgess, L. M. Campbell, E. W. Devlin, P. E. Drevnick, C. R. Hammerschmidt, C. A. Murphy, M. B. Sandheinrich, J. G. Wiener (2012) Toxicity of dietary methylmercury to fish: derivation of ecologically meaningful threshold concentrations. Environmental Toxicology & Chemistry 31, 1536–1547.
41. Konkler, M. J., C. R. Hammerschmidt (2012) Methylmercury in mosquitoes: Impact of a large coal-fired power plant in central Ohio. Environmental Toxicology & Chemistry 31, 1657–1661.
40. Hammerschmidt, C. R., K. L. Bowman (2012) Vertical methylmercury distribution in the subtropical North Pacific. Marine Chemistry 132–133, 77–82. http://www.sciencedirect.com/science/article/pii/S0304420312000242
39. Lamborg, C. H., C. R. Hammerschmidt, G. A. Gill, R. P. Mason , S. Guchuki (2012) An intercomparison of methods and protocol development for Hg speciation in open ocean seawater suitable for use on GEOTRACES cruises. Limnology & Oceanography: Methods 10, 90–100.
38. Tabatchnick, M. D., G. Nogaro, C. R. Hammerschmidt (2012) Potential sources of methylmercury in tree foliage. Environmental Pollution 160, 82–87.
37. Hammerschmidt, C. R. (2011) Mercury and carbon dioxide emissions: uncoupling a toxic relationship. Environmental Toxicology & Chemistry 30, 2640−2646.
36. Hammerschmidt, C. R., K. L. Bowman, M. D. Tabatchnick, C. H. Lamborg (2011) Storage bottle material and cleaning for determination of total mercury in seawater. Limnology & Oceanography: Methods 9, 426–431.
35. Naik, A. P., C. R. Hammerschmidt (2011) Mercury and trace metal partitioning and fluxes in suburban southwest Ohio watersheds. Water Research 45, 5151–5160.
34. Costello, D. M., G. A. Burton, Jr., C. R. Hammerschmidt, E. Rogevich, C. Schlekat (2011) Nickel phase partitioning and toxicity in field-deployed sediments. Environmental Science & Technology 45, 5798–5805.
33. Brumbaugh, W. G., C. R. Hammerschmidt, L. Zanella, E. Rogevich, G. Salata, R. Bolek (2011) Inter-laboratory comparison of measurements of acid-volatile sulfide and simultaneously extracted nickel in spiked sediments. Environmental Toxicology & Chemistry 30,1306–1309.
32. Bowman, K. L., C. R. Hammerschmidt (2011) Extraction of monomethylmercury from seawater for low-femtomolar determination. Limnology & Oceanography: Methods 9, 121–128.
31. Bowling, A. M., C. R. Hammerschmidt, J. T. Oris (2011) Necrophagy by a benthic omnivore influences biomagnification of methylmercury in fish. Aquatic Toxicology 102, 134–141.
30. Hammerschmidt, C. R., W. F. Fitzgerald (2010) Iron-mediated photochemical decomposition of methylmercury in an arctic Alaskan lake. Environmental Science & Technology 44, 6138–6143.
29. Cloran, C. E., G. A. Burton, Jr., C. R. Hammerschmidt, K. W. Taulbee, K. Custer, K. L. Bowman (2010) Effects of suspended solids and dissolved organic carbon on nickel toxicity. Environmental Toxicology & Chemistry 29, 1781–1787.
28. Hammerschmidt, C. R., G. A. Burton, Jr. (2010) Measurements of acid volatile sulfide and simultaneously extracted metals are irreproducible among laboratories. Environmental Toxicology & Chemistry 29, 1453–1456.
27. Evers, D.C., R.P. Mason, N.C. Kamman, C.Y. Chen, A.L. Bogomolni, D.L. Taylor, C.R. Hammerschmidt, S.H. Jones, N.M. Burgess, K. Munney, K.C. Parsons (2008) Integrated mercury monitoring program for temperate estuarine and marine ecosystems on the North American Atlantic coast. EcoHealth 5, 426–441.
26. Lamborg, C. H., O. Yigiterhan, W. F. Fitzgerald, P. H. Balcom, C. R. Hammerschmidt, J. Murray (2008) Vertical distribution of mercury species at two sites in the western Black Sea. Marine Chemistry 111, 77–89.
25. Hammerschmidt, C. R., W. F. Fitzgerald (2008) Methylmercury in arctic Alaskan mosquitoes: Implications for impact of atmospheric mercury depletion events. Environmental Chemistry 5, 127−130.
24. Drevnick, P. E., A. P. Roberts, R. R. Otter, C. R. Hammerschmidt, R. Klaper, J. T. Oris. (2008) Mercury toxicity in livers of northern pike (Esox lucius) from Isle Royale, USA. Comparative Biochemistry and Physiology-Part C 147, 331-338.
23. Rolfhus, K. R., M. B. Sandheinrich, J. G. Wiener, S. W. Bailey, K. A. Thoreson, C. R. Hammerschmidt (2008) Analysis of fin clips as a non-lethal method for monitoring mercury in fish. Environmental Science & Technology 42, 871−877.
22. Balcom, P. H., C. R. Hammerschmidt, W. F. Fitzgerald, C. H. Lamborg, J. S. O’Connor (2008) Seasonal distributions and cycling of mercury and methylmercury in the waters of New York/New Jersey Harbor Estuary. Marine Chemistry 109, 1−17.
21. Hammerschmidt, C. R., W. F. Fitzgerald (2008) Sediment-water exchange of methylmercury determined from shipboard benthic flux chambers. Marine Chemistry 109, 86−97.
20. Hammerschmidt, C. R., W. F. Fitzgerald, P. H. Balcom, P. T. Visscher (2008) Organic matter and sulfide inhibit methylmercury production in sediments of New York/New Jersey Harbor. Marine Chemistry 109, 165−182.
18. Fitzgerald, W. F., C. H. Lamborg, C. R. Hammerschmidt (2007) Marine biogeochemical cycling of mercury. Chemical Reviews 107, 641-662.
17. Hammerschmidt, C. R., W. F. Fitzgerald (2006) Methylmercury in freshwater fish linked to atmospheric mercury deposition. Environmental Science & Technology 40, 7764–7770.
16. Hammerschmidt, C. R., W. F. Fitzgerald (2006) Bioaccumulation and trophic transfer of methylmercury in Long Island Sound. Archives of Environmental Contamination & Toxicology 51, 416-424.
15. Lamborg, C. H., K. L. Von Damm, W. F. Fitzgerald, C. R. Hammerschmidt, R. Zierenberg (2006) Mercury and monomethylmercury in fluids from Sea Cliff submarine hydrothermal field, Gorda Ridge. Geophysical Research Letters 33, L17606.
14. Hammerschmidt, C. R., W. F. Fitzgerald, C. H. Lamborg, P. H. Balcom, C.-M. Tseng (2006) Biogeochemical cycling of methylmercury in lakes and tundra watersheds of arctic Alaska. Environmental Science & Technology 40, 1204-1211.
13. Hammerschmidt, C. R., W. F. Fitzgerald (2006) Photodecomposition of methylmercury in an arctic Alaskan lake. Environmental Science & Technology 40, 1212-1216.
12. Hammerschmidt, C. R., W. F. Fitzgerald (2006) Methylmercury cycling in sediments on the continental shelf of southern New England. Geochimica et Cosmochimica Acta 70, 918-930.
11. Hammerschmidt, C. R., M. B. Sandheinrich (2005) Maternal diet during oogenesis is the major source of methylmercury in fish embryos. Environmental Science & Technology 39, . 3580-3584.
10. Hammerschmidt, C. R., W. F. Fitzgerald (2005) Methylmercury in mosquitoes related to atmospheric mercury deposition and contamination. Environmental Science & Technology 39, 3034-3039.
9. Fitzgerald, W. F., D. R. Engstrom, C. H. Lamborg, C.-M. Tseng, P. H. Balcom, C. R. Hammerschmidt (2005) Modern and historic atmospheric mercury fluxes in northern Alaska: Global sources and arctic depletion. Environmental Science & Technology 39, 557-568.
8. Tseng, C.-M., C. R. Hammerschmidt, W. F. Fitzgerald (2004) Determination of methylmercury in environmental matrixes by on-line flow injection and atomic fluorescence spectrometry. Analytical Chemistry 76, 7131-7136.
7. Hammerschmidt, C. R., W. F. Fitzgerald, C. H. Lamborg, P. H. Balcom, P. T. Visscher (2004) Biogeochemistry of methylmercury in sediments of Long Island Sound. Marine Chemistry 90, 31-52.
6. Balcom, P. H., W. F. Fitzgerald, G. M. Vandal, C. H. Lamborg, C. S. Langer, K. R. Rolfhus, C. R. Hammerschmidt (2004) Mercury sources and cycling in the Connecticut River and Long Island Sound. Marine Chemistry 90, 53-74.
5. Hammerschmidt, C. R., W. F. Fitzgerald (2004) Geochemical controls on the production and distribution of methylmercury in near-shore marine sediments. Environmental Science & Technology 38, 1487-1495.
4. Lamborg, C. H., C.-M. Tseng, W. F. Fitzgerald, P. H. Balcom, C. R. Hammerschmidt (2003) Determination of the mercury complexation characteristics of dissolved organic matter in natural waters with “reducible Hg” titrations. Environmental Science & Technology 37, 3316-3322.
3. Hammerschmidt, C. R., M. B. Sandheinrich, J. G. Wiener, R. G. Rada (2002) Effects of dietary methylmercury on reproduction of fathead minnows. Environmental Science & Technology 36, 877-883.
2. Hammerschmidt, C. R., W. F. Fitzgerald (2001) Formation of artifact methylmercury during extraction from a sediment reference material. Analytical Chemistry 73, 5930-5936.
1. Hammerschmidt, C. R., J. G. Wiener, B. E. Frazier, R. G. Rada (1999) Methylmercury content of eggs in yellow perch related to maternal exposure in four Wisconsin lakes. Environmental Science & Technology 33, 999-1003.