Analysis of the variation characteristics of acid acid rain and its influencing factors in Hunan Province

Abstract

Based on the measurement data of the acid rain observations from Hunan Meteorological Department from 1992 to 2012, combining with the concentrations of atmospheric pollutants, the temporal and spatial distributions of acid rain, the concentrations of pollutants, and the factors influencing acid rain were analyzed. The results show that in the last twenty years, the average pH value of precipitation was less than 5.6; the most severe zone for acid rain distributes in the Changsha-Zhuzhou-Xiangtan city group, with the average pH value below 4.5. The inter-annual variation of acid rain presents three stages: during 1992-2000, the acidity of precipitation presented oscillating reducing; during 2001–2007, the acidity of precipitation increased; during 2008-2012, the acidity of precipitation reduced continuously, and the intensity of acid rain has shifted from strong phase to moderate phase. The strong acid rain mostly appears in autumn and winter, and also in spring in central and southern Hunan, whereas the weak acid rain mainly distributes in spring in the rest regions, and also in summer. In 2009, the concentration of NO₂ is more than that of SO₂ , and the vitriolic model of acid rain has converted into the vitriolic-nitric mixed model. Acid rain in Hunan are mainly caused by the energy structure, where coal dominates and occupies 60%. Recently, the emission load of SO₂ is controlled effectively, then the acid rain pollution has been alleviated.