The Research On Chemical Characteristics And Influence Sources Of The Acidy Precipitation In Dalian

With the development of economy and the acceleration of urbanization process, Dalian has now become one of major acid rain areas in Liaoning province and it is an urgent need to further study on pollution status and source of acid rain. In this paper, the acidity characteristics, chemical characteristics and sources were analyzed on the basis of the monitoring data of atmospheric precipitation using correlational analysis method, enrichment factor method and backward trajectory simulation, and the main countermeasures of controlling acid rain were provided. The main conclusions were shown as follows:(1) The acid rain in dalian2011was a strong acid rain pollution with the frequency of45.1%, the precipitation pH value distribution range of3.82to7.74and the annual average pH value of4.95. The highest frequency of acid rain was69.6%in Lushun, and the lowest was32.3%in HeiShiJiao. Acid rain mainly occurred in5～12month, especially was concentrated in summer and fall, and larger rainfall might be one of the important condition resulting in acid rain.(2)The order of annual average concentration of water-solubility inorganic ion from high to low was:SO42->Ca2+>NH4+>Cl->NO3->Na+>K+>Mg2+>H+>F-. SO42-,Cl-and NO3-were the major constituents of anion, which reached96.7%, while human activities, NH4+and Na+were the major constituents of cationic and reached77.9%. The results of correlation analysis indicated that the correlation coefficients of SO42-and NO3-, Ca2+and SO42-, Mg2+and SO42-, Na+and SO42-, Na+and Mg2+, Na+and Ca2+,NO3-and Mg2+, NO3-and NH4+are all above0.85and they have the similar sources or formation pathways.(3) The contribution of marine source, soil source and artificial source to the total ionic concentration in precipitation were17.65%、9.03%and70.67%, respectively.SO42-was affected by marine source, soil source and artificial source with3.71%,1.52%and94.77%. NO3-was fullly caused by human activities. The contribution of marine source to Cl-was65.78%, and the contribution of artificial source could not be ignored, which was33.74%. Ca2+and K+came from land and combined action from the earth’s crust source artificial sources. The contribution of37.71%Mg2+came from oceans, and62.29%was from the soil.(4) The results from backward trajectory simulation of precipitation air in dalian region (represented by HeiShiJiao) showed that precipitation is mainly affected by the southern air masses (southeast, south, southwest), accounting for about77.4%of the total precipitation events. The acidity of southwest air precipitation was highest, while the acid rain frequency of north-northwest of air precipitation was minimum.This studies would have an important guiding function on policymaking to control acid rain in dalian control and also provide a new reference to lay down environmental protection policy.