Taiyuan Precipitation Chemical Characteristics And Origin Analysis

Recent years, the focus source of pollution in Taiyuan has basically beeneffectively controlled, but the water quality of urban precipitation is still notoptimistic, indicating that non-point source pollution could not be ignored. Withthe development of urban construction and amount increasing of motor vehiclesin Taiyuan city, the concentration of air pollutant is still increasing. The waterquality of the urban environment posed a huge treat. As wet deposition ofpollutants in the air is the main removal process, it has important implicationsfor the understanding and study of atmospheric pollution component. Analyzingthe composition and sources of major pollutants in precipitation will be helpfulin urban air pollution monitoring and pollution source analysis. More effectivemeasure could be found to control pollution.In this paper, Precipitation samples were collected at an urban site inTaiyuan, a heavy coal combustion city in north China during April2011toNovember2013and were then analyzed to determine the pH and concentrationsof water-soluble inorganic ions (F-, Cl-, NO-3, SO2-+4, Na+, K+, NH+4, Ca2andMg2+) in precipitation. The results showed that the volume-weighted mean pH ofprecipitation in2011was4.94, SO2--4(403.9μeq·L-1), NO3(125.0μeq·L-1),Ca2+(347μeq·L-1) and NH4（+170.3μeq·L-1）were major ions, accounting for89%of the total ion concentration. The SO2--4/NO3ratio was3.2, lower than that ofShanxi province in1984(14.89). The volume-weighted mean pH and EC ofprecipitation in2012were5.27and98.8μs·cm-1during the samplingtime.SO2-14(471.8μeq·L-), NO-+3(93.6μeq·L-1), Ca2(477.4μeq·L-1) and NH+4（133.4μeq·L-1） were major ions, accounting for85%of the total ionconcentration. The SO2--4/NO3ratio was4.38, lower than that of Shanxi provincein1984(14.79).SO2-4remains the dominant acidic ion in term of concentration.However, NO-3has become very important to the acidity of rain water.The results showed that the wet depositions were estimated to be1.93t·km-2·a-1for sulfur;1.54t·km-2·a-1for nitrogen, of which1.28t·km-2·a-1was reduced nitrogen and0.26t·km-2·a-1was oxidized nitrogen; and5.87t·km-2·a-1for Ca2+.Ion correlation analysis, principal component analysis and theenrichment coefficient analysis revealed that anthropogenic source was thedominant source of chemical composition of rainwater in Taiyuan, especiallycoal combustion. The back trajectory analysis demonstrated that the airpollutants were came from the local plants (Thermal power plant, steel plant)and the coking plants in the southern of Taiyuan Basin...