Mercury Cycling in Stream Ecosystems. 1. Water Column Chemistry and Transport

Abstract

We studied total mercury (THg) and methylmercury (MeHg) in eight streams, located in Oregon, Wisconsin, and Florida, that span large ranges in climate, landscape characteristics, atmospheric Hg deposition, and water chemistry. While atmospheric deposition was the source of Hg at each site, basin characteristics appeared to mediate this source by providing controls on methylation and fluvial THg and MeHg transport. Instantaneous concentrations of filtered total mercury (FTHg) and filtered methylmercury (FMeHg) exhibited strong positive correlations with both dissolved organic carbon (DOC) concentrations and streamflow for most streams, whereas mean FTHg and FMeHg concentrations were correlated with wetland density of the basins. For all streams combined, whole water concentrations (sum of filtered and particulate forms) of THg and MeHg correlated strongly with DOC and suspended sediment concentrations in the water column.

Mercury Cycling in Stream Ecosystems. 3. Trophic Dynamics and Methylmercury Bioaccumulation

“…Invertebrate composites were freeze-dried, pulverized, and analyzed for MeHg by the USGS Wisconsin Mercury Research Laboratory, Middleton, Wisconsin (15). Hg in fish tissue is predominantly MeHg [>95% (24)], so tissue samples from individual fish were freeze-dried, pulverized, and Tables S1 and S2.…”

Specific ultra-violet absorbance as an indicator of mercury sources in an Adirondack River basin

“…The strong association of Hg and organic matter in surface waters has long been recognized (Lindberg and Harriss 1974;Mierle and Ingram 1991), and numerous studies of Hg in streams and lakes of mid-and northern latitudes of the northern hemisphere have generally shown strong correlations between dissolved Hg concentrations and dissolved organic carbon (DOC) concentrations, and between particulate Hg concentrations and particulate organic carbon concentrations (POC) (Grigal 2002;Yin and Balogh 2002;Dennis et al 2005;Brigham et al 2009;Riscassi and Scanlon 2011). The association of Hg with organic matter is sufficiently strong in many surface waters, that measures such as DOC or absorbance at 254 nm (UV 254 ) have been suggested as surrogates for Hg concentrations, because Hg analyses are expensive and may be unstable in automated water samplers (Dittman et al 2009).…”

“…For example, Hg and DOC concentrations are weakly related in the Everglades where a diversity of organic matter sources and complex biogeochemical processes are observed . Similarly, in surface waters strongly influenced by urban land use, diverse sources of Hg and DOC such as waste water treatment facilities often preclude a simple linear relation between dissolved Hg and DOC concentrations (Brigham et al 2009). …”

Analysis of potential mercury policies: The impact of stream basin characteristics on susceptible populations

“…For small to medium streams, canopy cover limits primary productivity driving the process of bloom dilution in the opposite direction: limited primary production results in less biomass and more concentrated Hg at the base of the food web (Hill and Larsen 2005;Allan and Castillo 2007). Wetlands result in increased bioaccumulation by enhancing redox conditions that favor methylation of IHg (Balogh et al 2004;Brigham et al 2009). …”