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| Titel |
Long-term measurements of aerosol and carbon monoxide at the ZOTTO tall tower to characterize polluted and pristine air in the Siberian taiga |
| VerfasserIn |
X. Chi, J. Winderlich, J.-C. Mayer, A. V. Panov, M. Heimann, W. Birmili, J. Heintzenberg, Y. Cheng, M. O. Andreae |
| 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 ; 13, no. 24 ; Nr. 13, no. 24 (2013-12-18), S.12271-12298 |
| Datensatznummer |
250085888
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| Publikation (Nr.) |
 copernicus.org/acp-13-12271-2013.pdf |
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| Zusammenfassung |
| Siberia is one of few continental regions in the Northern Hemisphere where
the atmosphere may sometimes approach pristine background conditions. We
present the time series of aerosol and carbon monoxide (CO) measurements
between September 2006 and December 2011 at the Zotino Tall Tower Observatory
(ZOTTO) in Central Siberia (61° N; 89° E). We investigate
the seasonal, weekly and diurnal variations of aerosol properties (including
absorption and scattering coefficients and derived parameters, such as
equivalent black carbon (BCe), Ångström exponent, single
scattering albedo, and backscattering ratio) and the CO mixing ratios.
Criteria were established to distinguish polluted from near-pristine air
masses, providing quantitative characteristics for each type. Depending on
the season, 23–36% of the sampling time at ZOTTO was found to be
representative of a clean atmosphere. The summer pristine data indicate that
primary biogenic and secondary organic aerosol formation are quite strong
particle sources in the Siberian taiga. The summer seasons 2007–2008 were
dominated by an Aitken mode around 80 nm size, whereas the summer 2009 with
prevailing easterly winds produced particles in the accumulation mode around
200 nm size. We found these differences to be mainly related to air
temperature, through its effect on the production rates of biogenic volatile
organic compounds (VOC) precursor gases. In winter, the particle size
distribution peaked at 160 nm, and the footprint of clean background air was
characteristic for aged particles from anthropogenic sources at great
distances from ZOTTO and diluted biofuel burning emissions from domestic
heating. The wintertime polluted air originates mainly from large cities
south and southwest of the site; these particles have a dominant mode around
100 nm, and the ΔBCe / ΔCO ratio of
7–11 ng m−3 ppb−1 suggests dominant contributions from coal and
biofuel burning for heating. During summer, anthropogenic emissions are the
dominant contributor to the pollution particles at ZOTTO, while only 12%
of the polluted events are classified as biomass-burning-dominated, but then
often associated with extremely high CO concentrations and aerosol absorption
coefficients. Two biomass-burning case studies revealed different ΔBCe / ΔCO ratios from different fire types, with the
agricultural fires in April~2008 yielding a very high ratio of
21 ng m−3 ppb−1. Overall, we find that anthropogenic sources
dominate the aerosol population at ZOTTO most of the time, even during
nominally clean episodes in winter, and that near-pristine conditions are
encountered only in the growing season and then only episodically. |
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