忻州市环境空气PM_(10)和TSP中水溶性阴离子特征分析

Characterization of water-soluble anions in PM_(10) and TSP in Xinzhou City

利用中流量采样器收集忻州市采暖季和非采暖季4个监测点位的PM10和TSP样品,通过离子色谱法测定SO2-4、NO-3和Cl-的质量浓度,并以此3种水溶性阴离子的时空分布、相关性参数和特征比值来探讨其在环境空气中的污染特征和来源.结果表明,采暖季PM10和TSP中3种水溶性阴离子的总质量浓度分别为14.24μg·m-3和21.97μg·m-3,明显高于非采暖季（分别为8.56μg·m-3和11.84μg·m-3）.采暖季和非采暖季3种水溶性阴离子总质量在PM10中所占比例分别为15.70%和13.19%,在TSP中所占比例分别为12.16%和8.84%,离子主要富集在PM10中.采暖季4个采样点位3种阴离子的质量浓度均高于非采暖季,采样点位DC的阴离子质量浓度高于其它点位,时空差异明显.采暖季NO-3与SO2-4相关性显著,说明二者形成过程的控制因子相同;非采暖季Cl-与SO2-4、NO-3的相关性显著,说明三者具有共同来源.NO-3/SO2-4比值在0.31~1.41之内,相对较高,暗示机动车尾气对空气颗粒物的影响突出,但均值都小于1,表明空气污染来源仍以燃煤等固定源排放为主.总体而言,忻州市水溶性阴离子的污染属于机动车尾气和燃煤的复合型污染.

To investigate the characteristics and sources of water-soluble ions in the atmospheric particulates in Xinzhou,PM10and TSP samples were collected by the medium volume sampler at four sampling sites during heating period and non-heating period. Concentrations of the major water-soluble anions（ SO2-4,NO-3and Cl-） were analyzed using ion chromatography. Temporal and spatial distributions,correlation parameters and NO-3/SO42-ratios were investigated in detail. It was found that the total three anions concentrations of PM10and TSP were 14. 24 μg·m-3and 21. 97 μg·m-3,respectively,during heating period,which were significantly higher than the concentrations during non-heating period,8. 56 μg·m-3and 11. 84 μg·m-3respectively.The concentration of total water-soluble anions accounted for 15. 70% and 13. 19% of PM10and 12. 16% and 8. 84% of TSP during heating period and non-heating period,respectively,which indicated that the anions were mainly concentrated in PM10. Average concentrations of three water-soluble anions at four sampling sites during heating period were higher than those during non-heating period,and the concentration of total water-soluble anions at DC site was the highest. The temporal and spatial distributions of anions concentrations were obviously different. The correlation between NO-3and SO2-4was significantly positive during heating period,indicating their formation process in the ambient air might be subject to the same control factors; the correlations between Cl-and NO-3,SO2-4were also good,indicating they mainly came from the same source. The NO-3/SO2-4ratio was in the range of0. 31 ~ 1. 41. The relatively high value indicated that mobile source became more and more predominant. The average values of NO-3/SO2-4ratios were all below 1,which indicated that the stationary emissions（ coal combustion） were dominant sources of airborne pollutants in the urban atmosphere. Coal combustion and vehicle exhaust were the main sources of water-soluble ions in Xinzhou City.