 |
| Titel |
Seasonal and diurnal variations of Hg° over New England |
| VerfasserIn |
H. Mao, R. W. Talbot, J. M. Sigler, B. C. Sive, J. D. Hegarty |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 5 ; Nr. 8, no. 5 (2008-03-11), S.1403-1421 |
| Datensatznummer |
250005802
|
| Publikation (Nr.) |
 copernicus.org/acp-8-1403-2008.pdf |
|
|
|
|
|
| Zusammenfassung |
| Factors influencing diurnal to interannual variability in
Hg° over New England were investigated using multi-year measurements
conducted by AIRMAP at the Thompson Farm (TF) coastal site, an inland
elevated site at Pac Monadnock (PM), and two month measurements on Appledore
Island (AI) in the Gulf of Maine. Mixing ratios of Hg° at TF showed
distinct seasonality with maxima in March and minima in October. Hg° at
AI tracked the trend at TF but with higher minima, while at PM the diurnal
and annual cycles were dampened. In winter, Hg° was correlated most
strongly with CO and NOy, indicative of anthropogenic emissions as
their primary source. Our analysis indicates that Hg° had a regional
background level of ~160 fmol/mol in winter, a dry deposition velocity
of ~0.20 cm s−1 with a ~16 day lifetime in the coastal
boundary layer in summer. The influence of oceanic emissions on ambient
Hg° levels was identified using the Hg°-CHBr3 correlation at
both TF and AI. Moreover, the lower Hg° levels and steeper decreasing
warm season trend at TF (0.5–0.6 fmol/mol d−1) compared to PM
(0.2–0.3 fmol/mol d−1) likely reflected the impact of marine halogen
chemistry. Large interannual variability in warm season Hg° levels in
2004 versus 2005/2006 may be due to the role of precipitation patterns in
influencing surface evasion of Hg°. In contrast, changes in wintertime
maximum levels of Hg° were small compared to drastic reductions in CO,
CO2, NOy, and SO2 from 2004/2005 to 2006/2007. These trends
could be explained by a homogeneous distribution of Hg° over North
American in winter due to its long lifetime and/or rapid removal of reactive
mercury from anthropogenic sources. We caution that during warmer winters,
the Hg°-CO slope possibly reflects Hg° loss relative to changes in
CO more than their emission ratio. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|