Significant geographic gradients in particulate sulfate over Japan determined from multiple-site measurements and a chemical transport model: Impacts of transboundary pollution from the Asian continent |
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| Authors: | Masahide Aikawa Toshimasa Ohara Takatoshi Hiraki Okihiro Oishi Akihiro Tsuji Makiko Yamagami Kentaro Murano Hitoshi Mukai |
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| Institution: | 1. Department of Marine Environment and Engineering, National Sun Yat-sen University, Taiwan;2. Kuroshio Research Group, Asia-pacific Ocean Research Center, National Sun Yat-sen University, Taiwan;3. Department of Public Health, College of Health Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan;4. Research Center of Environmental Medicine, College of Health Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan;1. School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, China;2. State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing 100084, China;3. Joint Institute for Regional Earth System Science and Engineering, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA;4. College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100022, China;5. SKL-ESPC and BIC-ESAT, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China |
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| Abstract: | We found a significant geographic gradient (longitudinal and latitudinal) in the sulfate (SO42?) concentrations measured at multiple sites over the East Asian Pacific Rim region. Furthermore, the observed gradient was well reproduced by a regional chemical transport model. The observed and modeled SO42? concentrations were higher at the sites closer to the Asian continent. The concentrations of SO42? from China as calculated by the model also showed the fundamental features of the longitudinal/latitudinal gradient. The proportional contribution of Chinese SO42? to the total in Japan throughout the year was above 50–70% in the control case, using data for Chinese sulfur dioxide (SO2) emission from the Regional Emission Inventory in Asia (40–60% in the low Chinese emissions case, using Chinese SO2 emissions data from the State Environmental Protection Administration of China), with a winter maximum of approximately 65–80%, although the actual concentrations of SO42? from China were highest in summer. The multiple-site measurements and the model analysis strongly suggest that the SO42? concentrations in Japan were influenced by the outflow from the Asian continent, and this influence was greatest in the areas closer to the Asian continent. In contrast, we found no longitudinal/latitudinal gradient in SO2 concentrations; instead SO2 concentrations were significantly correlated with local SO2 emissions. Our results show that large amounts of particulate sulfate are transported over long distances from the East Asian Pacific Rim region, and consequently the SO42? concentrations in Japan are controlled by the transboundary outflow from the Asian continent. |
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