In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 2 ( 2020-01-23), p. 865-880
Abstract:
Abstract. The hygroscopicity of organic aerosol (OA) is important for investigation
of its climatic and environmental impacts. However, the hygroscopicity
parameter κOA remains poorly characterized, especially in the
relatively polluted environment on the North China Plain (NCP). Here we
conducted simultaneous wintertime measurements of bulk aerosol chemical
compositions of PM2.5 and PM1 and bulk aerosol hygroscopicity of
PM10 and PM1 on the NCP using a capture-vaporizer time-of-flight
aerosol chemical speciation monitor (CV-ToF-ACSM) and a humidified
nephelometer system which measures the aerosol light-scattering enhancement
factor f(RH). A method for calculating κOA based on f(RH) and bulk aerosol chemical-composition measurements was developed. We found that κOA varied
in a wide range with significant diurnal variations. The derived κOA ranged from almost 0.0 to 0.25, with an average (±1σ)
of 0.08 (±0.06) for the entire study. The derived κOA was
highly correlated with f44 (fraction of m∕z 44 in OA measured by
CV-ToF-ACSM), an indicator of the oxidation degree of OA (R=0.79), and the
relationship can be parameterized as κOA=1.04×f44-0.02 (κOA=0.3×O:C-0.02, based on the relationship
between the f44 and O∕C ratio for CV-ToF-ACSM). On average, κOA
reached the minimum (0.02) in the morning near 07:30 local time (LT) and then increased
rapidly, reaching the peak value of 0.16 near 14:30 LT. The diurnal variations
in κOA were highly and positively correlated with those of mass
fractions of oxygenated OA (R=0.95), indicating that photochemical
processing played a dominant role in the increase in κOA in
winter on the NCP. Results in this study demonstrate the potential wide
applications of a humidified nephelometer system together with aerosol
composition measurements for investigating the hygroscopicity of OA in
various environments and highlight that the parameterization of κOA as a function of OA aging processes needs to be considered in
chemical transport models for better evaluating the impacts of OA on cloud
formation, atmospheric chemistry, and radiative forcing.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-20-865-2020
DOI:
10.5194/acp-20-865-2020-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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