西安市南郊春季降水化学成分特征

Chemical Composition of Spring Precipitation in Southern Suburb of Xi'an City

2010年3-4月间采集了7次西安南郊降水样品,测定电导率、pH值、主要离子浓度。结果表明,降水pH值的平均值为6.6;电导率平均为110.5μs/cm,说明降水中水溶性离子浓度高。Ca2+为含量最丰富的阳离子,平均浓度为15.3 mg/L。由于北方春季沙尘天气频繁,空气中固体颗粒较多,所以降水中Ca2+浓度较高。同时,建筑施工产生的扬尘,也会增大Ca2+浓度。SO24-、NO-3为主要的阴离子,平均浓度分别为32.5 mg/L、13.6 mg/L。2010年,SO24-/NO-3的物质量浓度比值为1.55,比2007年同期的观测数据明显降低,说明西安市氮氧化物的污染加重。比较降雨前后空气质量及前、后段降水的化学组成变化,表明大气降水能有效去除大气污染物,有效缓解大气污染。

Electrical conductivity, pH value and concentration of major ion were determined in the rainwater samples collected from the southern suburb of Xi＇ an City during the period of March to April in 2010. The results showed that the average pH value was 6.6, the mean electrical conductivity was 110.5 txs/cm, which proved that the concentration of water-soluble ion was high in rainwater. The average concentration of Ca2＋ was 15.3 rag/L, which was the principal cation in precipitation. As in spring raising dust happened frequentey in North China, there was more solid particle in the air. The raising dust which produced by construction sites could also increase the concentration of Ca2＋ ,SO^- and NO3, that were the principal anions, which average concentration were 32.5 rag/L,13.6 rag/L, respectively. The ratio of SO42-/NO3was 1.55 in 2010, decreased obviously compared with that in 2007. It showed the pollution of nitrogen oxide were more serious. The change of air quality before and after rainfall, proved rainfall could decrease air pollution, effectively.