| Based on the research status and achievements of acid rain at home and abroad,this paper makes detailed statistical analysis for the atmospheric precipitation monitoring data from 2007 to 2015 in Kaihua County, especially the precipitation pH value and precipitation ion during the period of 5 years of 2010-2014. Finnaly,combined with natural environmental conditions（topography, weather and climate,etc.） and social environment（ambient air quality, the development of social economy,etc.）, the precipitation event and cause of the acid rain in Kaihua County is analyzed and investigated. Some preventive measures to reduce them also are proposed. The research results include:（1） During 2007-2012, the annual average pH of precipitation in Kaihua County was in the range of 4.22-4.74, which is less than the definition value of acid rain（pH=5.6）. The precipitation of acid rain occurred until 2013. From 2007 to 2012, the average pH of precipitation was in a strong acid rain range, which was between4.0-4.49. From the beginning of 2009, the average annual pH of precipitation was in a rising stage. The corresponding frequency of acid rain also decreased from 100% to98.1% in 2015. It shows that the environmental quality has been improved in recent years, but the situation is still grim.（2） Acid rain deposition is greatly influenced by the season in Kaihua Country.Climatic factors is one of the main causes of acid rain deposition in Kaihua County.The acid rain deposition is easy to happen in dry climate without wind such as in winter. The reason should be that some harmful gases in the air is unable to disperse.The acid rain deposition is less in rainy season such as in summer.（3） The main cause of acid rain deposition is sulfur dioxide（SO2） and nitrogen（NOx） gas in air. After a series of chemical reactions, they are converted to sulfate ions(SO42-) and nitrate ions（NO3-）, respectively. According to the proportion of the two kinds of ion concentration in acid rain, the acid rain deposition can be divided into sulphuric, nitric and mixed acid type. The acid rain deposition in Kaihua County belongs to the mixed acid rain.（4） The effects of four kinds of main ions, sulfate ion(SO42-), nitrate ion（NO3-）,ammonium ion（NH4+） and calcium(Ca2+) was analyzed by the gray correlation theory.It was found that the influence of these four kinds of ions on pH value of precipitationwas NH4+> Ca2+> SO42->NO3-.（5） According to the environmental quality bulletin and the data during2007-2015 of Kaihua County, we found that the content of SO2 and NOx in air is relatively low, which is around 0.03mg/L. But acid rain frequency is very high in Kaihua County. So the surrounding area is one of the main causes of pollution.Combined with climate factors, acid rain deposition in Kaihua County is more outstanding. |
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