上海市夏季颗粒物污染过程数值模拟研究

利用观测资料和嵌套网格空气质量模式(Nested Air Quality Prediction Model System,NAQPMS)模拟研究了2010年7月26日—8月26日上海市及周边城市PM10、PM2.5及其无机盐组分的浓度变化趋势及时空分布特点.结果表明,NAQPMS模式较为合理的重现了上海各方位站点及其周边城市PM10、PM2.5及其硫酸盐、硝酸盐等无机化学组分的浓度水平与变化趋势,相关系数在0.7以上.研究期间造成上海颗粒物污染的主要原因是:弱气旋低压系统控制下,西南或西北气流将内陆污染物输送至上海市,当低压中心移至上海附近时带来的辐合气流使得污染进一步累积上升.长三角地区PM2.5主要无机盐组分分布特征表明,上海市及周边城市的硫酸盐、硝酸盐和铵盐的总和占PM2.5浓度的40%~60%,二次气-粒转化过程贡献明显,且以SO2向SO2-4的氧化转换为主;污染上升过程中NO-3/SO2-4比率增大,说明流动源的贡献有所增加.

Modeling study of particulate matter pollution episode on summertime in Shanghai

The Nested Air Quality Prediction Model System (NAQPMS) was used to investigate the temporal and spatial variations of PM₁₀, PM_2.5 and secondary inorganic aerosols over Yangtze River Delta (YRD) on summertime 2010. Comparison between simulated and observed aerosol showed that NAQPMS was able to capture the variation of PM₁₀ over YRD. The secondary inorganic aerosols in Shanghai were well simulated by comparing to the observation, with correlation coefficients over 0.7. In summertime, weak cyclones often appeared over YRD region, which led to accumulation of air pollutants. Northwesterly airflow induced by the weak cyclones could bring air pollutants to Shanghai, resulting in air pollution episodes. In summertime 2010, high surface PM_2.5 was mainly located in Jiangsu and Shanghai, and secondary inorganic aerosol including sulfate, nitrite and ammonium accounted for up to 40%~60%. In addition, secondary aerosol transformation, mainly SO₂ to SO₄^2-, was significant during pollution episodes. The ratio of NO₃^-/SO₄^2- elevated during polluted periods, and this was probably related to vehicle emission.