2011年春季沙尘天气影响下上海大气颗粒物及其化学组分的变化特征

Characteristics of Particulate Matters and Its Chemical Compositions During the Dust Episodes in Shanghai in Spring,2011

于2011年4月28日~5月18日对上海大气中颗粒物的质量浓度及细粒子中的化学组分进行了连续观测,获得了上海受春季沙尘天气影响下大气颗粒物质量浓度和主要化学组分特征.结果表明,沙尘天气中PM10和PM2.5的质量浓度显著高于非沙尘天,最高日均浓度分别达到787.2μg·m-3和139.5μg·m-3,PM2.5/PM10的均值为(32.9±14.6)%(15.6%~85.1%);总水溶性无机离子(TWSⅡ)占PM2.5的质量分数为(27.2±19.2)%(4.8%~80.8%),二次组分SNA(SO2-4、NO-3、NH+4)占TWSⅡ的(76.9±13.9)%(41.9%~94.2%),TWSⅡ和SNA对PM2.5的贡献均小于非沙尘天,而Ca2+的含量比却有明显上升.非沙尘天测得的OC/EC值高于强沙尘天,但低于弱沙尘天.此外分析还得到,沙尘中的高矿尘粒子具有酸性缓冲作用,使得沙尘天颗粒的碱性强于沙尘发生前.非沙尘天SO2-4、NO-3主要以NH4HSO4、(NH4)2SO4和NH4NO3的形式存在,沙尘天还会与其他矿物离子结合.

A continuous air quality observation was conducted in the urban area of Shanghai from April 28 to May 18 in 2011. The mass concentration of particle matters and main chemical compositions of fine particle were measured and analyzed. The mass concentrations of PM10and PM2. 5during the dust episode were much higher than those in non-dust episode,with the maximum daily mass concentrations of PM10and PM2. 5reaching 787. 2 μg·m- 3and 139. 5 μg·m- 3,respectively. The average PM2. 5/ PM10ratio was( 32. 9 ±14. 6) %( 15. 6%-85. 1%). The total water soluble inorganic ions( TWSⅡ) contributed( 27. 2 ±19. 2) %( 4. 8%-80. 8%) of total PM2. 5,and the secondary water soluble ions( SNA),including SO2-4,NO-3and NH+ 4,were( 76. 9 ± 13. 9) %( 41. 9%-94. 2%) in TWSⅡ. The concentrations of TWSⅡ and SNA in PM2. 5during dust days became lower than those in non-dust days while the trend of the ratio of Ca2 +to PM2. 5increased. The mean OC / EC value in non-dust days was higher than that in the heavy dust pollution episode,but lower than that in weak dust days. In addition,mineral-rich particle in dust period had an acid-buffer effect, making particle alkaline in dust days stronger. In non-dust days,SO2-4and NO-3mainly existed in the form of NH4HSO4,( NH4)2SO4 and NH4NO3,and combined with other mineral ions during dust days.