OH reactivity at a rural site (Wangdu) in the North China Plain: contributions from OH reactants and experimental OH budget
In 2014, a large, comprehensive field campaign was conducted in the densely populated North China Plain. The measurement site was located in a botanic garden close to the small town Wangdu, without major industry but influenced by regional transportation of air pollution. The loss rate coefficient o...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-01-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/645/2017/acp-17-645-2017.pdf |
| Summary: | In 2014, a large, comprehensive field campaign was conducted in
the densely populated North China Plain. The measurement site was
located in a botanic garden close to the small town Wangdu, without major industry but influenced by regional transportation
of air pollution. The loss rate coefficient of atmospheric
hydroxyl radicals (OH) was quantified by direct
measurements of the OH reactivity. Values ranged between 10
and 20 s<sup>−1</sup> for most of the daytime. Highest values were
reached in the late night with maximum values of around
40 s<sup>−1</sup>. OH reactants mainly originated from
anthropogenic activities as indicated (1) by a good correlation
between measured OH reactivity and carbon monoxide (linear
correlation coefficient <i>R</i><sup>2</sup> = 0.33) and (2) by a high
contribution of nitrogen oxide species to the OH reactivity
(up to 30 % in the morning). Total OH reactivity was
measured by a laser flash photolysis–laser-induced fluorescence
instrument (LP-LIF). Measured values can be explained well by
measured trace gas concentrations including organic compounds,
oxygenated organic compounds, CO and nitrogen oxides. Significant,
unexplained OH reactivity was only observed during nights,
when biomass burning of agricultural waste occurred on surrounding
fields. OH reactivity measurements also allow investigating
the chemical OH budget. During this campaign, the OH
destruction rate calculated from measured OH reactivity and
measured OH concentration was balanced by the sum of
OH production from ozone and nitrous acid photolysis and
OH regeneration from hydroperoxy radicals within the
uncertainty of measurements. However, a tendency for higher
OH destruction compared to OH production at lower
concentrations of nitric oxide is also observed, consistent with
previous findings in field campaigns in China. |
|---|---|
| ISSN: | 1680-7316 1680-7324 |