Abstract
Abstract. 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−1 yr−1, 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−1 yr−1, with 68% attributed to dry deposition (mainly SO2) 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 SO2 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−1 yr−1, 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 SO2 and NH3 simultaneously in the target area are recommended to protect natural ecosystems from excess acid deposition.
Highlights
Acid deposition, originating largely from man-made emissions of three gaseous pollutants, namely, sulfur dioxide (SO2), nitrogen oxides (NOx) and ammonia (NH3), is a global environmental issue because of its transboundary effects on the biogeochemical cycles (Rodhe et al, 2002; Flechard et al, 2011)
A particular concern involves acid deposition that exceeds the critical loads of an ecological system, which might cause long-term harmful effects with several deleterious consequences, such as the eutrophication of coastal waters and acidification of lakes, streams and soils, which reduce species diversity (Reuss et al, 1987; Sickles et al, 2009; Yang et al, 2012b)
The 10-site average concentrations of SO2 observed in the present study (27.5 μg S m−3) were 3 times that of the reported values at one regional background Global Atmosphere Watch station (
Summary
Acid deposition, originating largely from man-made emissions of three gaseous pollutants, namely, sulfur dioxide (SO2), nitrogen oxides (NOx) and ammonia (NH3), is a global environmental issue because of its transboundary effects on the biogeochemical cycles (Rodhe et al, 2002; Flechard et al, 2011). With acid deposition posing a serious environmental hazard, decision makers need to determine emission control strategies for effective mitigation and the extent of emissions reduction that would promote ecosystem recovery from acid deposition (Driscoll et al, 2001). To address these concerns, it is essential to gain a quantitative knowledge of acid deposition through. Pan et al.: Wet and dry deposition of sulfur in Northern China monitoring various acidic species such as SO2, NOx and NH3 as well as particulate and aqueous forms such as sulfate (SO24−), nitrate (NO−3 ) and ammonium (NH+4 )
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