2 research outputs found
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
Atmospheric Mercury Temporal Trends in the Northeastern United States from 1992 to 2014: Are Measured Concentrations Responding to Decreasing Regional Emissions?
Long-term
atmospheric mercury measurements at Underhill, VT (VT99),
and Huntington Forest, NY (NY20), from 1992 to 2014 and 2005 to 2014,
respectively, were used to determine concentration trends using Mann–Kendall’s
tau test with Sen’s slope estimator. These data, measured generally
downwind of large Hg sources in the Midwestern United States, provide
the longest record of ambient Hg concentrations available in the United
States. At VT99, concentrations of gaseous element mercury (GEM),
gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) declined
at rates of −1.8, −3.2, and −6.7%/year, respectively.
At NY20, GEM and GOM concentrations declined at rates of −1.6
and −7.8%/year, respectively; however, PBM concentrations increased
at a rate of 2.0%/year, which is likely related to winter wood burning.
A trajectory ensemble analysis using the potential source contribution
function indicates the source locations associated with high mercury
concentrations changed from Toronto–Buffalo and Pennsylvania
areas to east coast urban centers. The declining GEM concentrations
in the northeastern United States are positively correlated with decreasing
SO<sub>2</sub> emissions in the upwind area. Overall, the results
indicate that decreased mercury concentrations measured during the
past decade are consistent with decreased Hg emissions from regional
point sources and that increasing global emissions have not overwhelmed
those decreases