HR: 0800h
AN: A11C-0611    [Abstracts]
TI: Seasonal and Diurnal Variation in Reactive Gaseous Mercury (RGM) in New England
AU: * Sigler, J M
EM: jsigler@gust.sr.unh.edu
AF: University of New Hampshire, Climate Change Research Center, Institute for the study of Earth, Oceans and Space (EOS), Morse Hall, 39 College Rd., Durham, NH 03857, United States
AU: Mao, H
EM: hmao@gust.sr.unh.edu
AF: University of New Hampshire, Climate Change Research Center, Institute for the study of Earth, Oceans and Space (EOS), Morse Hall, 39 College Rd., Durham, NH 03857, United States
AU: Talbot, R
EM: robert.talbot@unh.edu
AF: University of New Hampshire, Climate Change Research Center, Institute for the study of Earth, Oceans and Space (EOS), Morse Hall, 39 College Rd., Durham, NH 03857, United States
AB: Elemental (Hg°) and reactive gaseous mercury (RGM) were measured continuously at two sites in New Hampshire throughout 2007. Additionally, these species were monitored at an oceanic site (Appledore Island, Gulf of Maine) during the summer of 2007. At Thompson Farm, a rural site located 25 km inland, RGM mixing ratios ranged from 0-22 ppq with a mean of 0.5 ppq. Distinct diurnal variation in RGM was observed, with highest concentrations in the mid-afternoon, several hours after the daily peak in Hg°, and diminishing to near zero at night, suggesting photochemical production of RGM during the daytime and depletion at night. Strong summertime correlation of RGM with Hg° and ozone (O₃), especially at night, suggests fast deposition or RGM. Seasonal variation in RGM was also observed, with highest concentrations in spring and lowest in summer. RGM was well-correlated with sulfur dioxide (SO₂), suggesting influence from combustion sources at local to regional scales. At Pac Monadnock, a high-elevation site located l85 km inland, RGM was significantly lower than at TF throughout the year (Hg° was lower in all seasons except for summer), with a mean mixing ratio of ~0.16 ppqv. Mean RGM mixing ratios were close to or below the detection limit in spring and summer, and little diurnal variation was observed. This site is situated far from combustion sources and therefore shows a more regional signal that is largely devoid of RGM. During summer of 2007, RGM at Appledore Island was significantly higher than at the other two sites, ranging from 0-50 ppqv with a mean of ~10 ppqv, and representing approximately 6% of TGM. This and the elevated Hg° concentrations at the site (156 ppqv in summer, compared to 143 and 146 ppqv at Thompson Farm and Pac Monadnock, respectively) may suggest a strong oceanic source of Hg°, and significant production of RGM in the presence of halogen species. Additionally, enhanced RGM was observed at TF during summertime under easterly and southeasterly flow, possibly suggesting oceanic impact on Hg chemistry at TF.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting