3 research outputs found
Appendix A. Quality control metrics for mercury and nitrogen analyses.
Quality control metrics for mercury and nitrogen analyses
Isotopic Characterization of Mercury Downstream of Historic Industrial Contamination in the South River, Virginia
Historic point source mercury (Hg)
contamination from industrial processes on the South River (Waynesboro,
Virginia) ended decades ago, but elevated Hg concentrations persist
in the river system. In an effort to better understand Hg sources,
mobility, and transport in the South River, we analyzed total Hg (THg)
concentrations and Hg stable isotope compositions of streambed sediments,
stream bank soils, suspended particles, and filtered surface waters.
Samples were collected along a longitudinal transect of the South
River, starting upstream of the historic Hg contamination point-source
and extending downstream to the confluence with the South Fork Shenandoah
River. Analysis of the THg concentration and Hg isotopic composition
of these environmental samples indicates that the regional background
Hg source is isotopically distinct in both Δ<sup>199</sup>Hg
and δ<sup>202</sup>Hg from Hg derived from the original source
of contamination, allowing the tracing of contamination-sourced Hg
throughout the study reach. Three distinct end-members are required
to explain the Hg isotopic and concentration variation observed in
the South River. A consistent negative offset in δ<sup>202</sup>Hg values (∼0.28‰) was observed between Hg in the suspended
particulate and dissolved phases, and this fractionation provides
insight into the processes governing partitioning and transport of
Hg in this contaminated river system
Investigation of Local Mercury Deposition from a Coal-Fired Power Plant Using Mercury Isotopes
Coal combustion accounts for approximately two-thirds of global anthropogenic mercury (Hg) emissions. Enhanced deposition of Hg can occur close to coal-fired utility boilers (CFUBs), but it is difficult to link specific point sources with local deposition. Measurement of Hg stable isotope ratios in precipitation holds promise as a tool to assist in the identification of local Hg deposition related to anthropogenic emissions. We collected daily event precipitation samples in close proximity to a large CFUB in Crystal River, Florida. Precipitation samples collected in Crystal River were isotopically distinct and displayed large negative δ<sup>202</sup>Hg values (mean = −2.56‰, 1 SD = 1.10‰, <i>n</i> = 28). In contrast, precipitation samples collected at other sites in FL that were not greatly impacted by local coal combustion were characterized by δ<sup>202</sup>Hg values close to 0‰ (mean = 0.07‰, 1 SD = 0.17‰, <i>n</i> = 13). These results indicate that, depending on factors such as powdered coal isotopic composition and efficiency of Hg removal from flue gas, Hg deposited near CFUBs can be isotopically distinct. As this tool is further refined through future studies, Hg stable isotopes may eventually be used to quantify local deposition of Hg emitted by large CFUBs