The Analyses Of Variation Characteristics And Chemical Compositions Of Precipitation In Jingmen City In Recent Decade

Using the precipitation monitoring data of urban area and petrochemical industry area of Jingmen city in the period of2001-2010, this study analyzed the changes of the atmospheric precipitation, pH value and conductivity, and studied in depth about the chemical components in the precipitation and the variations and correlations, and analyzed the precipitation pollution according to the urban ambient air quality. The results are as follows:1) The annual rainfall of Jingmen city in recent decade is793.27mm, and precipitation mainly happened during May and August. The annual precipitation changed greatly, and basically appeared a trend of periodical fluctuation. The pH value and the electrical conductivity of precipitation in urban area of Jingmen city is stable and acid rain do not happen. The average pH value of annual precipitation in petrochemical industry area is lower than that in urban area, and the average annual electrical conductivity is higher. The acid rain is found to happen in this area, but its pollution was not serious. The pH value had an upward trend in urban and petrochemical areas. The electrical conductivity had an upward trend in urban area, while the electrical conductivity of the petrochemical area had a downward trend.2) The cation concentrations of precipitation in Jingmen city from high to low were Ca2+NH4+、Na+、Mg2+、K+、H+, the anion concentrations were SO42-、Cl-、NO3-、F-, and the ion concentrations appeared an upward trend overall.3) The ion concentration varied with the seasons yearly. But in general, the lowest ion concentration was summer, and then followed by autumn, while the ion concentration was relatively higher in spring and winter.4) The concentration of SO42-、NO3-appeared an upward trend, indicating an increase of acid pollution of precipitation.The ratio of SO42-/NO3-decreased, and it ranged in0.5～3in2009and2010, indicating that the precipitation pollution type of Jingmen city has transformed into sulfuric acid and nitric acid pollution from sulfuric acid pollution.5) Most of the ions in the precipitation have correlation, but the changes were very complex. It indicated a variety of sources of the precipitation ions, and they were affected by many factors. 6) Each ion concentration of the urban area Jingmen growed year by year, while the major ion concentrations of the petrochemical area appeared a downward trend yearly. The ion concentration in the petrochemical area showed the same seasonal trend as that of the urban area, but the ion concentration was basically higher than that of urban area.7) The main air pollutants in Jingmen city is respirable particulate matter (total suspended particles), and the pollution load of sulfur dioxide and nitrogen dioxide are at low level. It indicated the industrial pollution has been basically under control, while the construction pollutants have significant effects on the air quality, aggreviating the precipitation pollution.