In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 19, No. 3 ( 2019-02-13), p. 1971-1983
Abstract:
Abstract. Gaseous sulfuric acid (H2SO4) is known as one of
the key precursors for atmospheric new particle formation (NPF) processes,
but its measurement remains challenging. Therefore, a proxy method that is
able to derive gaseous sulfuric acid concentrations from parameters that can
be measured relatively easily and accurately is highly desirable for the
atmospheric chemistry community. Although such methods are available for
clean atmospheric environments, a proxy that works well in a polluted
atmosphere, such as that found in Chinese megacities, is yet to be developed.
In this study, the gaseous sulfuric acid concentration was measured in
February–March 2018, in urban Beijing using a nitrate based – long
time-of-flight chemical ionization mass spectrometer (LToF-CIMS). A number of
atmospheric parameters were recorded concurrently including the ultraviolet
radiation B (UVB) intensity, the concentrations of O3,
NOx (sum of NO and NO2), SO2, and HONO,
and aerosol particle number size distributions. A proxy for atmospheric
daytime gaseous sulfuric acid concentration was derived via a statistical
analysis method using the UVB intensity, [SO2], the condensation
sink (CS), [O3], and [HONO] (or [NOx]) as the
predictor variables, where square brackets denote the concentrations of the corresponding species.
In this proxy method, we considered the formation of gaseous sulfuric acid from reactions
of SO2 and OH radicals during the daytime, and the loss of gaseous
sulfuric acid due to its condensation onto the preexisting particles. In
addition, we explored the formation of OH radicals from the conventional
gas-phase photochemistry using O3 as a proxy and from the
photolysis of HONO using HONO (and subsequently NOx) as a
proxy. Our results showed that the UVB intensity and [SO2] are
dominant factors in the production of gaseous sulfuric acid, and that the
simplest proxy could be constructed with the UVB intensity and
[SO2] alone. When the OH radical production from both homogenously
and heterogeneously formed precursors were considered, the relative errors
were reduced by up to 20 %.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-19-1971-2019
DOI:
10.5194/acp-19-1971-2019-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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