Influence of biomass burning plumes on HONO chemistry in eastern China
Nitrous acid (HONO) plays a key role in atmospheric chemistry by influencing the budget of hydroxyl radical (OH). In this study, a two-month measurement of HONO and related quantities were analyzed during a biomass burning season in 2012 at a suburban site in the western Yangtze River delta, eastern...
Main Authors: | , , , , , , , , , , , , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2015-02-01
|
Series: | Atmospheric Chemistry and Physics |
Online Access: | http://www.atmos-chem-phys.net/15/1147/2015/acp-15-1147-2015.pdf |
Summary: | Nitrous acid (HONO) plays a key role in atmospheric
chemistry by influencing the budget of hydroxyl radical (OH). In this
study, a two-month measurement of HONO and related quantities were analyzed
during a biomass burning season in 2012 at a suburban site in the western
Yangtze River delta, eastern China. An overall high HONO concentration with
the mean value of 0.76 ppbv (0.01 ppbv to 5.95 ppbv) was observed. During
biomass burning (BB) periods, both HONO concentration and HONO/NO<sub>2</sub>
ratio were enhanced significantly (more than a factor of 2, <i>p</i> < 0.01)
compared with non-biomass burning (non-BB) periods. A correlation analysis
showed that the HONO in BB plumes was more correlated with nitrogen dioxide
(NO<sub>2</sub>) than that with potassium (a tracer of BB). Estimation by the
method of potassium tracing suggests a maximum contribution of
17 ± 12% from BB emission to the observed HONO concentrations, and the other
over 80% of the observed nighttime HONO concentrations during BB periods
were secondarily produced by the heterogeneous conversion of NO<sub>2</sub>. The
NO<sub>2</sub>-to-HONO conversion rate (<i>C</i><sub>HONO</sub>) in BB plumes was almost twice
as that in non-BB plumes (0.0062 hr<sup>−1</sup> vs. 0.0032 hr<sup>−1</sup>). Given that the
residence time of the BB air masses was lower than that of non-BB air
masses, these results suggest BB aerosols have higher NO<sub>2</sub> conversion
potentials to form HONO than non-BB aerosols. A further analysis based on
comparing the surface area at similar particle mass levels and HONO/NO<sub>2</sub> ratios at
similar surface area levels suggested larger specific surface
areas and higher NO<sub>2</sub> conversion efficiencies of BB aerosols. A mixed
plume of BB and anthropogenic fossil fuel (FF) emissions was observed on 10
June with even higher HONO concentrations and HONO/NO<sub>2</sub> ratios. The
strong HONO production potential (high HONO/NO<sub>2</sub> to PM<sub>2.5</sub> ratio)
was accompanied with a high sulfate concentration in this plume, suggesting
a promotion of mixed aerosols to the HONO formation. In summary, our study
suggests an important role of BB in atmospheric chemistry by affecting the
HONO budget. This can be especially important in eastern China, where
agricultural burning plumes are inevitably mixed with urban and industrial
pollution. |
---|---|
ISSN: | 1680-7316 1680-7324 |