Evaluation of tropospheric SO<sub>2</sub> retrieved from MAX-DOAS measurements in Xianghe, China
Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of sulfur dioxide (SO<sub>2</sub>) have been performed at the Xianghe station (39.8° N, 117.0° E) located at ~ 50 km southeast of Beijing from March 2010 to February 2013. Tropospheric SO<sub&...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/11149/2014/acp-14-11149-2014.pdf |
| Summary: | Ground-based multi-axis differential optical absorption spectroscopy
(MAX-DOAS) measurements of sulfur dioxide (SO<sub>2</sub>) have been performed at
the Xianghe station (39.8° N, 117.0° E) located at
~ 50 km southeast of Beijing from March 2010 to February 2013.
Tropospheric SO<sub>2</sub> vertical profiles and corresponding vertical column
densities (VCDs), retrieved by applying the optimal estimation method to the
MAX-DOAS observations, have been used to study the seasonal and diurnal
cycles of SO<sub>2</sub>, in combination with correlative measurements from in situ
instruments, as well as meteorological data. A marked seasonality was
observed in both SO<sub>2</sub> VCD and surface concentration, with a maximum in
winter (February) and a minimum in summer (July). This can be explained by
the larger emissions in winter due to the domestic heating and, in case of
surface concentration, by more favorable meteorological conditions for the
accumulation of SO<sub>2</sub> close to the ground during this period. Wind speed
and direction are also found to be two key factors in controlling the level
of the SO<sub>2</sub>-related pollution at Xianghe. In the case of east or
southwest wind, the SO<sub>2</sub> concentration does not change significantly
with the wind speed, since the city of Tangshan and heavy polluting
industries are located to the east and southwest of the station,
respectively. In contrast, when wind comes from other directions, the
stronger the wind, the less SO<sub>2</sub> is observed due to a more effective
dispersion. Regarding the diurnal cycle, the SO<sub>2</sub> amount is
larger in the early morning and late evening and lower at noon, in line with
the diurnal variation of pollutant emissions and atmospheric stability. A
strong correlation with correlation coefficients between 0.6 and 0.9 is also
found between SO<sub>2</sub> and aerosols in winter, suggesting that anthropogenic
SO<sub>2</sub>, through the formation of sulfate aerosols, contributes
significantly to the total aerosol content during this season. The observed
diurnal cycles of MAX-DOAS SO<sub>2</sub> surface concentration are also in very
good agreement (correlation coefficient close to 0.9) with those from
collocated in situ data, indicating the good reliability and robustness of
our retrieval. |
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| ISSN: | 1680-7316 1680-7324 |