基于210Po/210Pb活度比的大气颗粒物滞留时间研究

摘要

In this study,airborne particles (TSP and PM2.5) were collected in Shenzhen during the period from September 2015 to March 2016,and analyzed for 210Pb and 210Po.The residence time of aerosols (RTA) was calculated based on 210Po/210Pb ratios and the influencing factors were discussed.The results indicate that the RTA of TSP and PM2.5 in Shenzhen is within the range of 4.5-32.2 d (with an average of 14.7 d) and 11.1-23.6 d (with an average of 16.1 d),respectively.The RTA varies with aerosol particle size and meteorological conditions.Precipitation plays an important role in reducing RTA of coarse particles.Higher RTA was observed under inversion weather conditions.The apparent residence time derived from 210Po/210Pb ratios is a consequence of both residence time and transit time of aerosols.%2015年9月至2016年3月,研究分析了深圳市大气气溶胶中(TSP、PM2.5) 210Pb和210Po的放射性比活度,并依据210po/ 210pb的活度比,计算了两种不同粒径范围的大气颗粒物滞留时间(RTA),探讨了大气RTA的影响因素.结果表明,深圳市大气TSP滞留时间为4.5～32.2 d,平均14.7 d;PM2.5的滞留时间为11.1～23.6 d,平均16.1 d.大气颗粒物滞留时间与粒径大小和气象条件密切相关,降雨可有效降低粗颗粒大气滞留时间,而逆温静风条件则可使大气RTA显著增加.通过气溶胶中210Po/210Pb的活度比计算获得的表观大气滞留时间是大气颗粒物滞留时间与气溶胶迁移传输时间共同作用的结果.