In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 12 ( 2020-06-30), p. 7531-7552
Abstract:
Abstract. Isoprene-derived secondary organic aerosol (iSOA) is a significant
contributor to organic carbon (OC) in some forested regions, such as
tropical rainforests and the Southeastern US. However, its contribution to
organic aerosol in urban areas that have high levels of anthropogenic
pollutants is poorly understood. In this study, we examined the formation of
anthropogenically influenced iSOA during summer in Beijing, China. Local
isoprene emissions and high levels of anthropogenic pollutants, in
particular NOx and particulate SO42-, led to the formation of
iSOA under both high- and low-NO oxidation conditions, with significant
heterogeneous transformations of isoprene-derived oxidation products to
particulate organosulfates (OSs) and nitrooxy-organosulfates (NOSs).
Ultra-high-performance liquid chromatography coupled to high-resolution mass
spectrometry was combined with a rapid automated data processing technique
to quantify 31 proposed iSOA tracers in offline PM2.5 filter
extracts. The co-elution of the inorganic ions in the extracts caused matrix
effects that impacted two authentic standards differently. The average
concentration of iSOA OSs and NOSs was 82.5 ng m−3, which was around 3 times
higher than the observed concentrations of their oxygenated precursors
(2-methyltetrols and 2-methylglyceric acid). OS formation was dependant on
both photochemistry and the sulfate available for reactive uptake, as shown by a
strong correlation with the product of ozone (O3) and particulate
sulfate (SO42-). A greater proportion of high-NO OS products were
observed in Beijing compared with previous studies in less polluted
environments. The iSOA-derived OSs and NOSs represented 0.62 %
of the oxidized organic aerosol measured by aerosol mass spectrometry on average, but
this increased to ∼3 % on certain days. These results
indicate for the first time that iSOA formation in urban Beijing is strongly
controlled by anthropogenic emissions and results in extensive conversion to
OS products from heterogenous reactions.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-20-7531-2020
DOI:
10.5194/acp-20-7531-2020-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
