Acid Deposition Responsing Of Meteorological Elements And Air Mass Trajectories In Liaozhong Station

41 precipitation samples were collected from Feb 2007 to Jan 2008,The indexes for 41 collected samples were measured,including pH value , electrieal conductivity,the major water-soluble anion and cation (K⁺,Na⁺,NH₄⁺,Ca²⁺,Mg²⁺,F^-,Cl^-,NO₃^-,SO₄^2-)and the meteorological factors were also observed,including rainfall , wind direction wind speed pressure, relative humidity,temperature, visibility.The ion characteristics,relationship between the indexes and their sources were analyzed. Innovation of this text is it conbines one linear analyse , EOF and stepwise regression together to identify the greatest impact on the pH value of the meteorological factors. The air masses of Precipitation were simulated by Hybrid Single-Particle Lagrangian Integrated Trajeetories model and classified.Finally the analysis on the different air masses of precipitation from different directions and routes impacted on the ionic composition of wet deposition was condueted.The results showed that the wet deposition at the Liaozhong site was acidic with the range and a volume-weighted average pH value of 3.4⁷.34 and 4.63,respectively, and the frequency of acid wet deposition(PH<5.6)was70.7percent,Strong acid precipitation (pH<4.5)account for36.6 pecrent.The range of sum ions concentration was82.11³236.88μeq/L with a volume-weighted average of 658.14μeq/L and the different of the maximum and theminimum concentrationwas 39.42 times.SO₄^2-,NO₃^-were the major anions,accounting for 82 percent of total anions,with a volume-weighted average of 162.77μeq/L and 56.62μeq/L.NH₄⁺,Ca²⁺ were the major cations,accounting for 55 percent of total cations,with a volume-weighted average of 126.99μeq/L and 84.15μeq/L.The average concentration ratio between SO₄^2-and NO₃^- was 2.87, less than 3,which suggested that the acid rain of Liaozhong Site belonged to mixed type and the contribution of SO₄^2- to precipitation acidity decreased significantly, while the contribution of NO₃^-significantly increased. The ion concentrations of Liaozhong Site was minimum in summer with total ionic concentration of 494.63μeq/L.The Scouring effect of precipitation led to the low ion concentration in summer, with ionic concentration of 494.63μeq/L;While higher concentrations generally appeared in the winter,with ionic concentration of 2630.77μeq/L. Spring and autumn period belong to stable period,with ion concentrations 712.40μeq/L,1137.40μeq/L. .The correlation coefficients of SO₄^2-, NO₃^- and NH₄⁺, Ca²⁺ were significantly high,revealing their cooccurrence in precipitation mostly as (NH₄)₂SO₄, (NH₄)HSO₄, NH₄NO₃,CaSO₄, and Ca(NO₃)₂。The relation between pHvalue and acid rain precursors showed that was mainly influenced by external pollutants from long-distance transmission. In the meteorological factors, Atmospheric pressure,relative humidity, precipitation , temperature and pH value were for for the anti-correlation; visiblility,wind speed and pH value were the positive correlation; The relevance of the larger factor was relative humidity and the Correlation coefficient was-0.37;followed by the visibility,air temperature, precipitation and wind speed, and the Correlation coefficient were 0.275,-0.216,-0.212,0.218respectively. Regression analyse shows : the meteorological factor that exerts largest influence on pH was relative humidity(Regression coefficient=-0.371),secondly it wasvisibility(Regression coefficient=0.265).Precipitation air masses were classified as three sorts based on back-trajectory. Precipitation air masses from Europe continent,Mongolia,north and Northwest of China brought wet deposition with characteristies of high ions concentration,high pH,presented alkaline sometimes,precipitation air masses originating from Southeast Asia and South China were influenced by pollution sources from the south regions of China,so they brought wet deposition with charaeteristics of a little higher ion concentration,stronger acidity.Precipitation air masses from southeast of Japan and South Korea passing through the marine had lower ion concentration and near neutral. In short, acid precipitation occurred frequentlly,and sum ionconcentration of wet deposition was very high and its range was wide.