Long-term trend of chemical constituents in precipitation in Tokyo metropolitan area, Japan, from 1990 to 2002.
Long-term trend of chemical constituents in precipitation in Tokyo metropolitan area, Japan, from 1990 to 2002.
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DOI：
10.1016/j.scitotenv.2004.07.024
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发表时间：
2005-03
期刊：
影响因子：
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通讯作者：
T. Okuda;Tamami Iwase;Hideko Ueda;Y. Suda;Shigeru Tanaka;Y. Dokiya;K. Fushimi;M. Hosoe
中科院分区：
文献类型：
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作者：
T. Okuda;Tamami Iwase;Hideko Ueda;Y. Suda;Shigeru Tanaka;Y. Dokiya;K. Fushimi;M. Hosoe
为了了解酸雨的实际状况和机理，必须在大范围内连续和定期地了解降水的pH值及其化学成分。本研究利用日本东京都市区的酸雨观测网，对大范围的酸雨进行了调查，并分析了每个降水样品的主要化学成分。从1990年6月到2002年5月，在东京都区的几个采样点连续收集了12年的降水，并测量了其pH值和化学成分浓度。平均pH值范围为4.23至4.62，清楚地表明整个东京都市区的降水酸化。时间趋势模型被用来描述化学成分浓度的时间变化，包括年变化率，季节变化和降水的影响。用最小二乘法对过去12年的季节和年度趋势进行了检验。非海盐（NSS）-Ca 2+显示在早春的最大值，季节性可能引起的空气中的黄色灰尘从亚洲的富钙颗粒。nss-SO 42 −的年下降趋势可能与东京都市圈大气SO2气体浓度最近的下降趋势相对应。NO3−、NH 4+和nss-Ca 2+的年变化趋势显示出很大的站点间差异。内陆郊区NO3−、NH 4+和nss-Ca 2+浓度的增加可能是由于其本地来源的增加，如车辆交通和城市垃圾焚烧。H+的年变化率在各站点均为略负或几乎为零，因此自1990年以来，东京都降水酸化没有变得更严重。
In order to understand the actual status and mechanism of acid rain, it is important to know the pH of precipitation and its chemical constituents on a continuous and regular basis over a wide area. This study examines acid rain over a wide area using an observational network in the Tokyo metropolitan area of Japan, and analyzes the major chemical constituents of every precipitation sample. Precipitation was collected continuously for a period of 12 years from June 1990 to May 2002 at several sampling sites in the Tokyo metropolitan area, and its pH and chemical constituent concentrations were measured. The average pH ranged from 4.23 to 4.62, clearly indicating acidification of precipitation over the entire Tokyo metropolitan area. A time-trend model was applied to describe temporal variations of chemical constituent concentrations, including annual change rate, seasonal variation, and precipitation effects. Seasonal and annual trends for the past 12 years were examined with the model, using the least squares method. Nonsea salt (nss)-Ca2+shows a maximum value in early spring, a seasonality probably caused by calcium-rich particles in airborne yellow dust from Asia. Slightly decreasing annual trends of nss-SO42−may correspond to the recent decreasing trend of atmospheric SO2gas concentrations in the Tokyo metropolitan area. The annual trends of NO3−, NH4+, and nss-Ca2+show a large site-to-site difference. The increasing NO3−, NH4+, and nss-Ca2+concentrations at inland suburban sites may be caused by increases in their local sources such as vehicle traffic and municipal waste incineration. The annual change rate of H+is slightly negative or almost zero at every site, so the acidification of precipitation has not become worse since 1990 over the Tokyo metropolitan area.