Spatial distribution and temporal variations of atmospheric sulfur deposition in Northern China: insights into the potential acidification risks
Other literature type
Pan, Y. P.
Wang, Y. S.
Tang, G. Q.
Atmospheric sulfur (S) deposition via precipitation, particles and gases was
investigated at ten sites in Northern China. Measurements were performed
continuously between December 2007 and November 2010. The total S deposition
flux in the target area ranged from 35.0 to 100.7 kg S ha<sup>−1</sup> yr<sup>−1</sup>,
noticeably higher than the values documented in Europe, North America, and
East Asia. The ten-site, 3-yr average total S deposition was
64.8 kg S ha<sup>−1</sup> yr<sup>−1</sup>, with 68% attributed to dry deposition (mainly
SO<sub>2</sub>) and the rest to wet deposition. Consequently, the spatial
distribution of the total flux was consistent to that of dry
deposition, that is, higher values were observed at industrial and urban sites
than at agricultural and rural sites. However, the seasonal variation in the
total S deposition was not obvious across the entire year because of
opposite seasonal trends in wet and dry deposition. It was found that the
wet deposition, without significant spatial and interannual differences,
was influenced by the volume of precipitation, the air-column concentrations
of S compounds and in-cloud scavenging. Similar to the wet deposition, the
dry-deposited sulfate was also less dependent on the surface concentration.
Nevertheless, the regional differences in SO<sub>2</sub> dry deposition were
mostly explained by the ambient concentration, which is closely
associated with local emissions. As expected, the spatial pattern of
total S deposition resembled that of the emission inventory, indicating the
dramatic anthropogenic imprints on the regional S budget. Although at most
of the study sites the "acid equivalents" deposition of S was comparable
to that of nitrogen (N), the importance of S in the acidification risks was more
pronounced at the industrial sites. The ten-site, 3-yr mean total "acid
equivalents" deposition of S and N was estimated to be 8.4 (range:
4.2–11.6) keq ha<sup>−1</sup> yr<sup>−1</sup>, which exceeds the critical loads for
natural ecosystems in Northern China. Taking these findings and our previous
studies together, a multi-pollutant perspective and joint mitigation
strategies to abate SO<sub>2</sub> and NH<sub>3</sub> simultaneously in the target area
are recommended to protect natural ecosystems from excess acid deposition.