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Chemical Composition of Fog Water at Four Sites in Taiwan

Category: Interaction between Air and Precipitation Chemistry

Volume: 16 | Issue: 3 | Pages: 618-631
DOI: 10.4209/aaqr.2015.03.0154
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Stefan Simon 1, Otto Klemm1, Tarek El-Madany1, Joschka Walk1, Katharina Amelung1, Po-Hsiung Lin2, Shih-Chieh Chang3, Neng-Huei Lin4, Guenter Engling5,6, Shih-Chieh Hsu7, Tsong-Huei Wey8, Ya-Nan Wang9, Yu-Chi Lee10

  • 1 Climatology Working Group, Institute of Landscape Ecology, University of Münster, (null), Germany
  • 2 Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan
  • 3 Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien, Taiwan
  • 4 Department of Atmospheric Sciences, National Central University, Chung-Li, Taiwan
  • 5 Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan
  • 6 Division of Atmospheric Sciences, Desert Research Institute, Reno, NV, USA
  • 7 Trace Element Laboratory, Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan
  • 8 The Experimental Forest, National Taiwan University, Jhu-Shan, Nantou, Taiwan
  • 9 School of Forest and Resource Conservation, National Taiwan University, Taipei, Taiwan
  • 10 Central Weather Bureau, Taipei, Taiwan

Highlights

Chemical composition of fog water was clearly dominated by H+, NH4+, NO3 and SO42–.
pHs ranged from 2.27 to 5.95.
Sulfur dioxide emissions and nitrogen oxide emissions were the main precursors of fog acidity.
Ammonium ions were the main neutralizer.
Analysis of backward trajectories showed pollution from Mainland China at all sites.


Abstract

This study characterizes and compares the chemical composition of fog water at four sites in Taiwan. Fog was sampled with identical active fog collectors (modified Caltech design) using identical sampling strategies at all four sites. While the sites varied largely in terms of altitude above mean sea level (asl), type of fog, and the potential sources of constituents in fog water, the chemical composition of fog water was in all cases clearly dominated by H+, NH4+, NO3 and SO42–, making up more than 85% of the total ion concentrations. The pH ranged from 2.27 to 5.95.    Sulfur dioxide emissions from coal combustion in Mainland China and Taiwan as well as nitrogen oxide emissions from urbanized central-west Taiwan and the greater Taipei region were the main precursors of fog acidity. Ammonia, originating from agriculture emissions, was the main neutralizer. The Kinmen site (48 m asl), situated on an island close to Mainland China, exhibited the lowest pH and the highest sulfate concentrations. At the Xitou site on the western slopes of the Taiwan Central Mountain Range (1150 m asl), ammonium from agriculture dominated and lead to relatively high pH. At the same time, the nitrate/sulfate ratio was highest at this site (> 1 in equivalent units), resulting from relatively large contributions from street traffic. The ion concentrations at the Chilan site (1650 m asl) and the Lulin high mountain site (2862 m asl) were much lower than those at Xitou and Kinmen. While the ion concentrations at Chilan were considerably lower than at Lulin, the ion loadings, which is the amount of dissolved ions per volume of air, were similar at Chilan and Lulin.

Keywords

Cloud Fog chemistry Fog collection Taiwan Air pollution


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