In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 7 ( 2022-04-05), p. 4339-4353
Abstract:
Abstract. Peroxyacetyl nitrate (PAN) acting as a typical indicator of photochemical
pollution can redistribute NOx and modulate O3 production. Coupled with
the observation-based model (OBM) and a generalized additive model (GAM),
the intensive observation campaigns were conducted to reveal the pollution
characteristics of PAN and its impact on O3, the contributions of
influencing factors to PAN formation were also quantified in this paper. The
F values of GAM results reflecting the importance of the influencing factors
showed that ultraviolet radiation (UV; F value = 60.64), Ox
(Ox = NO2 + O3, 57.65), and air temperature (T, 17.55) were the
main contributors in the PAN pollution in spring, while the significant
effects of Ox (58.45), total VOCs (TVOCs, 21.63), and T (20.46) were found in
autumn. The PAN formation rate in autumn was 1.58 times higher than that in
spring, relating to the intense photochemical reaction and meteorological
conditions. Model simulations revealed that acetaldehyde oxidation
(46 %±4 %) contributed to the dominant formation pathway of PA (hence
PAN), followed by methylglyoxal oxidation (28 %±3 %) and radical
cycling (19 %±3 %). The PAN formation was highly VOC sensitive, as
surplus NOx (compared with VOCs abundance) prevented NOx from being the
limiting factor photochemical formation of secondary pollution. At our site,
PAN promoted and inhibited O3 formation under high and low ROx levels,
respectively. The PAN promoting O3 formation mainly occurred during the
periods of 11:00–16:00 (local time) when the favourable meteorological
conditions (high UV and T) stimulated the photochemical reactions to offer
ROx radicals, which accounted for 17 % of the whole monitoring periods in
spring and 31 % in autumn. The analysis of PAN formation mechanism and its
positive or negative effect on ozone provided scientific insights into
photochemical pollution mechanisms under various pollution scenarios in
coastal areas.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-22-4339-2022
DOI:
10.5194/acp-22-4339-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
