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| Titel |
Assessing the trends and effects of environmental parameters on the behaviour of mercury in the lower atmosphere over cropped land over four seasons |
| VerfasserIn |
A. P. Baya, B. Heyst |
| 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 ; 10, no. 17 ; Nr. 10, no. 17 (2010-09-15), S.8617-8628 |
| Datensatznummer |
250008772
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| Publikation (Nr.) |
 copernicus.org/acp-10-8617-2010.pdf |
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| Zusammenfassung |
Mercury is released to the atmosphere from natural and anthropogenic
sources. Due to its persistence in the atmosphere, mercury is subject to
long range transport and is thus a pollutant of global concern. Mercury
emitted to the atmosphere enters terrestrial and aquatic ecosystems which
act as sinks but also as sources of previously emitted and deposited mercury
when the accumulated mercury is emitted back to the atmosphere. Studying the
factors and processes that influence the behaviour of mercury from
terrestrial sources is thus important for a better understanding of the role
of natural ecosystems in the mercury cycling and emission budget.
A study was conducted over ten months (November 2006 to August 2007) at Elora,
Ontario, Canada to measure gaseous elemental mercury (GEM), reactive gaseous
mercury (RGM) and particulate bound mercury (HgP) as well as GEM fluxes
over different ground cover spanning the four seasons typical of a temperate
climate zone. GEM concentrations were measured using a mercury vapour
analyzer (Tekran 2537A) while RGM and HgP were measured with the Tekran
1130/1135 speciation unit coupled to another mercury vapour analyzer. A
micrometeorological approach was used for GEM flux determination using a
continuous two-level sampling system for GEM concentration gradient
measurement above the soil surface and crop canopy. The turbulent transfer
coefficients were derived from meteorological parameters measured on site.
A net GEM volatilization (6.31 ± 33.98 ng mM−2 hr−1, study
average) to the atmosphere was observed. Average GEM concentrations and GEM
fluxes showed significant seasonal differences and distinct diurnal patterns
while no trends were observed for HgP or RGM. Highest GEM
concentrations, recorded in late spring and fall, were due to meteorological
changes such as increases in net radiation and air temperature in spring and
lower atmospheric mixing height in fall. Highest GEM fluxes (18.1 ng m−2 hr−1,
monthly average) were recorded in late spring but also during
specific events in winter and fall. The main factors influencing the GEM
flux were soil moisture content, soil temperature, precipitation events and
ground cover. These trends indicate that the soil surface could be a
significant mercury source in spring and summer seasons but also under
specific meteorological conditions during the winter and fall. |
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