Insights into characteristics, sources, and evolution of submicron aerosols during harvest seasons in the Yangtze River delta region, China
Atmospheric submicron particulate matter (PM<sub>1</sub>) is one of the most significant pollution components in China. Despite its current popularity in the studies of aerosol chemistry, the characteristics, sources and evolution of atmospheric PM<sub>1</sub> species are sti...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/15/1331/2015/acp-15-1331-2015.pdf |
| Summary: | Atmospheric submicron particulate matter (PM<sub>1</sub>) is one of the most
significant pollution components in China. Despite its current popularity in
the studies of aerosol chemistry, the characteristics, sources and evolution
of atmospheric PM<sub>1</sub> species are still poorly understood in China,
particularly for the two harvest seasons, namely, the summer wheat harvest
and autumn rice harvest. An Aerodyne Aerosol Chemical Speciation Monitor
(ACSM) was deployed for online monitoring of PM<sub>1</sub> components during
summer and autumn harvest seasons in urban Nanjing, in the Yangtze River
delta (YRD) region of China. PM<sub>1</sub> components were shown to be dominated
by organic aerosol (OA, 39 and 41%) and nitrate (23 and 20%)
during the harvest seasons (the summer and autumn harvest). Positive matrix
factorization (PMF) analysis of the ACSM OA mass spectra resolved four OA
factors: hydrocarbon-like mixed with cooking-related OA (HOA + COA), fresh
biomass-burning OA (BBOA), oxidized biomass-burning-influenced OA (OOA-BB),
and highly oxidized OA (OOA); in particular the oxidized BBOA contributes
~80% of the total BBOA loadings. Both fresh and oxidized
BBOA exhibited apparent diurnal cycles with peak concentration at night,
when the high ambient relative humidity and low temperature facilitated the
partitioning of semi-volatile organic species into the particle phase. The
fresh BBOA concentrations for the harvests are estimated as BBOA = 15.1 × (<i>m/z</i> 60–0.26% × OA),
where <i>m/z</i> (mass-to-charge ratio) 60 is a marker for
levoglucosan-like species. The (BBOA + OOA-BB)/ΔCO, (ΔCO
is the CO minus background CO), decreases as a function of <i>f</i><sub>44</sub> (fraction of <i>m/z</i> 44 in OA signal), which might indicate that BBOA was oxidized
to less volatile OOA, e.g., more aged and low volatility OOA (LV-OOA) during
the aging process. Analysis of air mass back trajectories indicates that the
high BB pollutant concentrations are linked to the air masses from the
western (summer harvest) and southern (autumn harvest) areas. |
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| ISSN: | 1680-7316 1680-7324 |