| Acid rain has been becoming more and more serious in China since 1990s', especially in Hunan province situated in central-south China. The history, present situations, investigative fields and harms of acid rain pollution were reviewed. Considering with the more severe acid rain pollution in urban, the status and formation factors of air pollution were analyzed, based on the natural and social conditions of Hunan province. In this thesis, the concentrations, emitted quantity, geographical distribution of SO2 in Hunan were examined and the emitted quantity and variation law in the future were also estimated and predicted. The wet precipitation chemistry and the temporal and spatial characteristics of pH value of rainwater in Hunan province were discussed. Taking Changsha city for example, the atmospheric pollution and acid rain pollution were also investigated, including the temporal and spatial variation law of major air pollutants, such as SO2, NOx(NO2), TSP, and the characteristics of the representative chemical compositions of rainwater, confined to three monitoring stations in Changsha in the period of 1990-2001. What's more, the influence of the pollutants on the formation of acid rain in Changsha was analyzed. The pH value of rainwater was predicted based on the GM (1, 1) model. It's shown from the results as follows: the type of acid rain is the typical H2SO4-type; the larger emission intensity of SO2 is distributed in industrial regions located in the central and west-south part of Hunan; the emission amount of SO2 will gradually increase as long as the effective treatment measures are not taken; SO42-, NO3- , Ca2+, NH4+ are the major chemical compositions of atmospheric precipitation in Hunan province, accounting for more than 60 % of the total ionic amount of rainwater. The distribution of lower pH value of rainwater coincides to the distribution of catchments of the four river systems of Hunan (Xiang Jiang river, Zi Jiang river, Yuan Jiang river and Li Shui river), showing that the pollutants discharged from the local industrial sources are the main causes of the severe atmosphere pollution in some regions of Hunan province. The predicted results show that the acidity of rainwater would be further acidified in the future ten years if no effective measures are adopted.Based on the monitoring data from January 2001 to June 2002, it's estimated and analyzed in Shaoshan forest on the distribution characteristics of the chemicalcompositions of the precipitation in atmosphere and the forest, the net-precipitation and the total deposition of the ions in the multiple canopies within one whole year and the atmospheric deposition, total canopy leaching, base cations leaching and the uptake of H+ and NH4+ by the canopies. It is indicated from the results that the dominant anion was SO42- both in the atmospheric precipitation and the forested rainfall, accounting for 52.87 % and 48.92 % of total anion respectively, while the dominant cation was Ca24, accounting for 37.62 % and 42.81 % of total cations respectively. The ion concentrations in the forest rainfall significantly increased, with the largest concentration increase up to 9.7 times. The chemical data of the atmospheric precipitation and the forest rainfall were analyzed by using the principal component analysis to find the possible sources of the measured chemical species. Two major components that accounted for 92.76 % in total variance were extracted in the atmospheric precipitation and three major components that accounted for 96.70 % in total variance were extracted in the forested rainfall. The net-precipitation of Ca2+ from canopy leaching and the containing Ca2+ substances in the atmosphere were positive in Canopy and Sub-canopy. For Mg2+, except the vegetation developing and growing season, the obvious leaching evidence of Mg2+ from the canopies has been proved. The significant differences occurred between the large leaching from the Canopy and the absorption by the Sub-canopy. The leaching of SO42-, NO3-, Cl- also existed in the two layers o... |
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