上海市浦东城区二次气溶胶生成的估算

利用2010年5～10月不同日最高O3小时浓度(O3,max)下PM10浓度变化评估不同O3浓度水平下二次气溶胶生成量.CO作为一次颗粒物的标志物,O3作为光化学反应水平的指示物种.结果表明不同光化学水平条件下,PM10中一次与二次气溶胶浓度及比例存在较大差异.随着光化学水平的增加,PM10中一次气溶胶排放浓度增长不大(0.036～0.044 mg.m-3),二次气溶胶的生成量却呈数倍增长(0.018～0.055 mg.m-3);二次与一次气溶胶浓度的比例也从49.8%增加到124.5%.O3,max出现的时间也随着光化学水平的增强由13:00推迟到14:00,二次气溶胶生成的主要时段也从11:00～20:00增加到09:00～20:00;此外,PM2.5中主要组分SO24-、NO3-、OC等比例随着光化学水平(即O3,max浓度)的不同而存在一定差异,当O3,max<0.10 mg.m-3时,PM2.5主要由12.0%有机碳(OC)、18.7%硫酸盐、13.1%硝酸盐和4.5%元素碳(EC)组成,而O3,max>0.20mg.m-3时,PM2.5主要由20.0%有机碳(OC)、22.9%硫酸盐、23.1%硝酸盐和4.7%元素碳(EC)组成.说明SO24-、NO3-、OC受光化学水平影响较大.

Secondary Aerosol Formation Through Photochemical Reactions Estimated by Using Air Quality Monitoring Data in the Downtown of Pudong, Shanghai

Analyses of diurnal patterns of PM₁₀ in the downtown of Pudong, Shanghai have been performed in this study at different daily ozone maximum concentrations (O_3,max) from May to October, 2010. In order to evaluate secondary aerosol formation at different ozone levels, CO was used as a tracer for primary aerosol, and O_3,max was used as an index for photochemical activity. Results show that along with increasing of O₃ concentration, the concentration of primary and secondary aerosol was increased respectively from 0.036 to 0.044 mg·m^-3 and from 0.018 to 0.055 mg·m^-3. The ratio of secondary to primary aerosol was increased from 49.8% to 124.5%. Furthermore, along with the increase of O_3,max the forming time of O_3,max and secondary aerosol was changed respectively from 13:00 to 14:00 and from 11:00-20:00 to 09:00-20:00. At the same time, the chemical composition of PM_2.5 was different at different photochemical levels. PM_2.5 was composed of 12.0% organic carbon (OC), 18.7% sulfate (SO₄^2-), 13.1% nitrate (NO₃^-) and 4.5% element carbon (EC) when O_3,max was <0.10 mg·m^-3 and PM_2.5 was composed of 20.0% organic carbon (OC), 22.9% sulfate, 23.1% nitrate and 4.7% element carbon (EC) with O_3,max>0.20 mg·m^-3. These results approved that the photochemical reactivity promoted the production of SO₄^2-, NO₃^- and OC.