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| Titel |
Speciated mercury at marine, coastal, and inland sites in New England – Part 1: Temporal variability |
| VerfasserIn |
H. Mao, R. Talbot |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 11 ; Nr. 12, no. 11 (2012-06-08), S.5099-5112 |
| Datensatznummer |
250011230
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| Publikation (Nr.) |
 copernicus.org/acp-12-5099-2012.pdf |
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| Zusammenfassung |
| A comprehensive analysis was conducted using long-term continuous
measurements of gaseous elemental mercury (Hg0), reactive gaseous
mercury (RGM), and particulate phase mercury (HgP) at coastal (Thompson
Farm, denoted as TF), marine (Appledore Island, denoted as AI), and elevated
inland (Pac Monadnock, denoted as PM) sites from the AIRMAP Observatories in
southern New Hampshire, USA. Decreasing trends in background Hg0 were
identified in the 7.5- and 5.5-yr records at TF and PM with decline rates
of 3.3 parts per quadrillion by volume (ppqv) yr−1 and 6.3 ppqv yr−1,
respectively. Common characteristics at these sites were the
reproducible annual cycle of Hg0 with its maximum in winter-spring and
minimum in fall, comprised of a positive trend in the warm season (spring –
early fall) and a negative one in the cool season (late fall – winter).
Year-to-year variability was observed in the warm season decline in Hg0
at TF varying from a minimum total (complete) seasonal loss of 43 ppqv in
2009 to a maximum of 92 ppqv in 2005, whereas variability remained small at
AI and PM. The coastal site TF differed from the other two sites with its
exceptionally low levels (as low as below 50 ppqv) in the nocturnal
inversion layer possibly due to dissolution in dew water. Measurements of
Hg0 at PM exhibited the smallest diurnal to annual variability among
the three environments, where peak levels rarely exceeded 250 ppqv and the
minimum was typically 100 ppqv. It should be noted that summertime diurnal
patterns at TF and AI were opposite in phase indicating strong sink(s) for
Hg0 during the day in the marine boundary layer, which was consistent
with the hypothesis of Hg0 oxidation by halogen radicals there. Mixing
ratios of RGM in the coastal and marine boundary layers reached annual
maxima in spring and minima in fall, whereas at PM levels were generally
below the limit of detection (LOD) except in spring. RGM levels at AI were
higher than at TF and PM indicating a stronger source strength in the marine
environment. Mixing ratios of HgP at AI and TF were close in magnitude
to RGM levels and were mostly below 1 ppqv. Diurnal variation in HgP
was barely discernible at TF and AI in spring and summer. Higher levels of
HgP were observed during the day, while values that were smaller, but
above the LOD, occurred at night. |
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