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Title: Effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events

In this study, the effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events was investigated by analysis of comprehensive measurements of aerosol composition and concentrations [e.g., particular matters (PM2.5), nitrate (NO3), sulfate (SO4), ammonium (NH4)], gas-phase precursors [e.g., nitrogen oxides (NOx), sulfur dioxide (SO2), and ozone (O3)], and relevant meteorological parameters [e.g., visibility and relative humidity (RH)]. The measurements were conducted in Beijing, China from Sep. 07, 2012 to Jan. 16, 2013. The results show that the conversion ratios of N from NOx to nitrate (Nratio) and S from SO2 to sulfate (Sratio) both significantly increased in haze events, suggesting enhanced conversions from NOx and SO2 to their corresponding particle phases in the late haze period. Further analysis shows that Nratio and Sratio increased with increasing RH, with Nratio and Sratio being only 0.04 and 0.03, respectively, when RH < 40%, and increasing up to 0.16 and 0.12 when RH reached 60–80%, respectively. The enhanced conversion ratios of N and S in the late haze period is likely due to heterogeneous aqueous reactions, because solar radiation and thus the photochemical capacity are reduced by the increases in aerosols and RH. This point was furthermore » affirmed by the relationships of Nratio and Sratio to O3: the conversion ratios increase with decreasing O3 concentration when O3 concentration is lower than <15 ppb but increased with increasing O3 when O3 concentration is higher than 15 ppb. The results suggest that heterogeneous aqueous reactions likely changed aerosols and their precursors during the haze events: in the beginning of haze events, the precursor gases accumulated quickly due to high emission and low reaction rate; the occurrence of heterogeneous aqueous reactions in the late haze period, together with the accumulated high concentrations of precursor gases such as SO2 and NOx, accelerated the formation of secondary inorganic aerosols, and led to rapid increase of the PM2.5 concentration.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [3] ;  [1]
  1. Beijing Key Lab. of Cloud, Beijing (China); Institute of Urban Meteorology, Beijing (China)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Beijing Key Lab. of Cloud, Beijing (China)
Publication Date:
OSTI Identifier:
1228838
Report Number(s):
BNL--108476-2015-JA
Journal ID: ISSN 1352-2310; R&D Project: 2015-BNL-EE631EECA-Budg; KP1703020
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Atmospheric Environment
Additional Journal Information:
Journal Volume: 122; Journal Issue: C; Journal ID: ISSN 1352-2310
Publisher:
Elsevier
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES Beijing hazes; heterogeneous aqueous reactions; inorganic aerosol; particles size