Temporal And Spatial Distribution Of Precipitation And Classification Of Air Mass Path That Affect Precipitation's Ph In Liaoning Province

Based on the precipitation observational data of 45 stations in Liaoning Province in 2007,this study investigated temporal and spatial distribution of Liaoning'acid rain, analyzed chemical characteristics of precipitation in the main acid rain area (Dalian and Dandong City)and other representative stations, combined backward trajectory and synoptic system , analyzed the impact of air masses'origination on precipitation's pH. The results indicated that :â‘ In 2007,Liaoning acid rain areas were mainly distributed in the southeast region, Dalian and Dandong City, the frequency of heavy rain were higher. Shenyang, Fushun, Tieling, Huludao,Jinzhou City also appeared the phenomenon of acid rain; the lowest pH of all the stations occurred at, 6,7,8,10,11 months, mainly in the summer.â‘¡The relationship between acid rain and nearly floor gaseous pollution concentration was not significant,the relationship between precipitation's pH and degree of air pollution and impact of human activities was not significant, acid rain more affected by external transport.â‘¢The main acid rain areas, Dalian and Dandong City both were SO₄^2- dominant acid rain . In the chemical composition of precipitation,the primary anion were Sulfate, the primary cation were calcium ion,In Dalian City,the proportion of cation was Ca²⁺>NH₄⁺>Na⁺>Mg²⁺>K+,anion was SO₄^2->Cl->NO₃^->F^-.In DanDong City,the proportion of cation was Ca²⁺>Mg²⁺>Na⁺>NH₄⁺>K+,anion was SO₄^2->NO₃^->Cl->F^-. Compared with the Dandong City, Dalian more influenced by the ocean component.â‘£When the ratio of(∑anionic /∑cationic )was higher,the precipitation was not necessarily acidic,there may be other anions'and cations'interference.The balance of anion and cation was relatively poor in Environmental Protection Bureau of Yingkou City and monitoring station of Fuxin City.⑤The correlation between measured precipitation ions were higher in Dalian City,but lower in Dandong City, explained the ion source of Dandong City was more complex.The result of correlation analysis between precipitation ions of Dalian City showed that, sulfate and nitrate had a common source, ammonia mainly in the form of (NH₄)₂SO₄,NH₄HSO₄ and NH₄NO₃ in the atmosphere. Calcium and magnesium had a common source, both mainly from the soil.â‘¥According to the backward trajectory analysis in the 1500 metres height, the frequency of south-southwest air mass was larger in the main acid rain station (in Dalian Heishijiao and monitoring station of Dandong City),the precipitation pH of south-southwest air mass was relatively low in other stations, explained the pollution sources of North China had a great impact to the precipitation's pH of LiaoNing Province. The maximum value of total ion concentration of precipitation appeared in Northeast and North-Northwest air mass. the neutralization capacity of Northeast air mass was stronger, the south-southwest air mass was weaker, mainly due to the concentration of Calcium and magnesium was higher in North air mass than in South air mass, but there was a greater difference between different precipitation in the same category air mass.⑦Selected typical precipitation days in Dalian Heishijiao and monitoring station of DanDong City, researched the corresponding weather situation on 850hpa, The results indicated that: the precipitation's pH of south-southwest air mass was lower, but affected by cyclone and anticyclone, individual samples affected by North air mass, the acid of precipitation was weaker. Besides North air mass, the typical precipitation sample was affected by pollution sources of North China and industrial sources of southeast(Seoul and Busan), the total ion concentration of precipitation was high and the pH was low. The precipitation of south-southeast air mass was cleaning, the total ion concentration of precipitation was lower and the pH was highest, but individual samples affected by flow field , the total ion concentration of precipitation was high and the pH was low. When study area was located center of cyclone, circumambient pollution sources affected precipitation , the total ion concentration of precipitation was high.