Abstract
Abstract. Ammonia in the atmosphere is essential for the formation
of fine particles that impact air quality and climate. Despite extensive
prior research to disentangle the relationship between ammonia and haze
pollution, the role of ammonia in haze formation in high ammonia-emitting regions is still not well understood. Aiming to better understand secondary
inorganic aerosol (sulfate, nitrate, ammonium – SNA) formation mechanisms under high-ammonia conditions,
1-year hourly measurement of water-soluble inorganic species (gas and
particle) was conducted at a rural supersite in Shanghai. Exceedingly high
levels of agricultural ammonia, constantly around 30 µg m−3, were
observed. We find that gas-particle partitioning of ammonia (ε(NH4+)), as opposed to ammonia concentrations, plays a critical
role in SNA formation during the haze period. From an assessment of the effects of
various parameters, including temperature (T), aerosol water content (AWC),
aerosol pH, and activity coefficient, it seems that AWC plays predominant
regulating roles for ε(NH4+). We propose a
self-amplifying feedback mechanism associated with ε(NH4+) for the formation of SNA, which is consistent with diurnal
variations in ε(NH4+), AWC, and SNA. Our results
imply that a reduction in ammonia emissions alone may not reduce SNA
effectively, at least at rural agricultural sites in China.
Funder
Natural Science Foundation of Shanghai
China Postdoctoral Science Foundation
Cited by
30 articles.
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