In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 5 ( 2022-03-09), p. 3149-3167
Abstract:
Abstract. A comprehensive field campaign, with measurements of HONO and related
parameters, was conducted in summer 2018 at the foot (150 m a.s.l.) and the
summit (1534 m a.s.l.) of Mt. Tai (Shandong province, China). At the summit
station, high HONO mixing ratios were observed (mean ± 1σ: 133 ± 106 pptv, maximum: 880 pptv), with a diurnal noontime peak (mean ± 1σ: 133 ± 72 pptv at 12:30 local time). Constraints on
the kinetics of aerosol-derived HONO sources (NO2 uptake on the aerosol
surface and particulate nitrate photolysis) were performed and discussed,
which enables a better understanding of the interaction of HONO and
aerosols, especially in the polluted North China Plain. Various
evidence of air mass transport from the ground to the summit level was
provided. Furthermore, daytime HONO formation from different paths and its
role in radical production were quantified and discussed. We found that the homogeneous reaction NO + OH could only explain 8.0 %
of the daytime HONO formation, resulting in strong unknown sources
(Pun). Campaigned-averaged Pun was about 290 ± 280 pptv h−1, with a maximum of about 1800 pptv h−1. Aerosol-derived HONO
formation mechanisms were not the major sources of Pun at the summit
station. Their contributions to daytime HONO formation varied from
negligible to moderate (similar to NO + OH), depending on the
chemical kinetic parameters used. Coupled with sensitivity tests on the
kinetic parameters used, the NO2 uptake on the aerosol surface and
particulate nitrate photolysis contributed 1.5 %–19 % and 0.6 %–9.6 %
of the observed Pun, respectively. Based on synchronous measurements at
the foot and the summit station, an amount of field evidence was proposed to
support the finding that the remaining majority (70 %–98 %) of Pun was dominated
by the rapid vertical transport from the ground to the summit level and
heterogeneous formation on the mountain surfaces during transport. HONO photolysis at the summit level initialized daytime photochemistry and
still represented an essential OH source in the daytime, with a contribution
of about one-quarter of O3. We provided evidence that ground-derived
HONO played a significant role in the oxidizing capacity of the upper
boundary layer through the enhanced vertical air mass exchange driven by
mountain winds. The follow-up impacts should be considered in regional
chemistry transport models.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-22-3149-2022
DOI:
10.5194/acp-22-3149-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
