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The impact of air pollutants on rainwater chemistry during “urban‐induced heavy rainfall” in downtown Tokyo, Japan
Author(s) -
Uchiyama Ryunosuke,
Okochi Hiroshi,
Katsumi Naoya,
Ogata Hiroko
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2017jd026803
Subject(s) - rainwater harvesting , environmental science , pollutant , environmental chemistry , ozone , air pollution , air pollutants , deposition (geology) , scavenging , atmospheric sciences , meteorology , chemistry , geography , geology , biochemistry , antioxidant , paleontology , organic chemistry , sediment , biology , ecology
In order to clarify the impact of air pollution on the formation of sudden and locally distributed heavy rain in urban areas (hereafter UHR = urban‐induced heavy rain), we analyzed inorganic ions in rainwater samples collected on an event basis over 5 years from October 2012 to December 2016 in Shinjuku, Tokyo. Hourly rainfall amounts and wet deposition fluxes of acidic components (the sum of H + , NH 4 + , NO 3 − , and nonsea‐salt SO 4 2− ) in UHR were 13.1 and 17.8 times larger than those in normal rainfall, respectively, indicating that large amount of air pollutants were scavenged and deposited by UHR with large amounts of rainfall. The level of air pollutants, such as NO 2 , SO 2 , and potential ozone, in the ambient air increased just before the formation of UHR and decreased sharply at the end of the UHR event. These results indicate that NO 2 , which was formed secondarily by oxidants, was further oxidized by HO radicals and formed HNO 3 just before the formation of UHR, which was subsequently scavenged by UHR.