外来输送对舟山城区不同季节PM_(2.5)污染的影响研究

IMPACT OF TRANSPORTED PM_(2.5)POLLUTION ON URBAN ZHOUSHAN IN DIFFERENT SEASONS

为了揭示外来输送对浙江舟山城区PM_(2.5)污染的影响,在对2016年3月—2019年2月舟山城区PM_(2.5)日均质量浓度季节变化分析的基础上,利用后向轨迹聚类分析、潜在源分析函数和浓度权重轨迹分析方法,对比分析了影响舟山城区PM_(2.5)外来输送路径和潜在外来源区的季节特征。结果表明:春季和秋季以东北偏北和局地偏南路径占比最大,夏季以偏南路径占比最大,冬季以西北路径占比最大。春季西北路径和局地偏南路径分别对PM_(2.5)质量浓度平均值和最大值贡献最大,夏季西北偏北路径和偏南路径分别对PM_(2.5)质量浓度平均值和最大值贡献最大,秋季局地偏南路径对PM_(2.5)质量浓度平均值和最大值贡献最大,冬季西北路径对PM_(2.5)质量浓度平均值和最大值贡献最大。春季的潜在源区主要分布在安徽中北部到东南部、河南东部和福建北部沿海。夏季和秋季的潜在源区主要分布在安徽东南部、江苏南部和浙江西南部。冬季的潜在源区主要分布在山东西南部、江苏西北部、浙江北部、安徽东北部和河南东部。与2013—2016年数据的研究结果相比,不同季节主要输送路径的传输方向较一致,夏季和冬季仍分别主要受偏南路径和西北路径气流的影响。不同之处在于舟山夏季PM_(2.5)受西北偏北路径输送的影响增多,春季和秋季PM_(2.5)受来自浙江省内局地偏南路径输送的影响较明显。安徽、江苏、山东和浙江的部分地区仍是舟山PM_(2.5)主要的潜在源区,但浙江北部和江苏的分布范围有所减小,并有向山东西北部、浙江西南部和福建北部沿海延伸的趋势。

To understand the impact of transported PM_(2.5)pollution on urban Zhoushan,we first analyzed the seasonal variation of daily average PM_(2.5)mass concentration in urban Zhoushan from March 2016 to February 2019,and then we applied the backward trajectory cluster analysis,potential source contribution function,and concentration weighted trajectory method to analyze the seasonal characteristics of pathways and potential sources of transported PM_(2.5)pollution in urban Zhoushan.The results showed that:In spring and autumn,the transported PM_(2.5)pollution was mainly from the north-northeast pathways and partially from the southerly pathways,while in summer and winter the southerly and northwest pathways were dominant.In spring,the northwest pathways and the southerly pathways contributed the most to the PM_(2.5)average and maximum mass concentration,respectively.In summer,the average and the maximum value of PM_(2.5)mass concentration were significantly affected by the north-northwest pathways and southerly pathways,respectively.The partially southerly pathways and the northwest pathways contributed the most in autumn and in winter,respectively.Northern,central,and southeastern Anhui,eastern Henan,and the northern coast of Fujian were the main potential sources of PM_(2.5)in urban Zhoushan in spring.Southeastern Anhui,southern Jiangsu,and southwestern Zhejiang were the main potential sources in summer and autumn.Southwestern Shandong,northwestern Jiangsu,northern Zhejiang,northeastern Anhui,and eastern Henan were the main potential sources in winter.Compared with the results of the years from 2013 to 2016,the prevailing directions of transport pathways in different seasons were consistent.In summer and winter,it was still mainly affected by those from southerly pathways and northwest pathways,respectively.The differences were that in this study,PM_(2.5)in summer was increasingly affected by those from the north-northwest pathways,whereas PM_(2.5)in spring and autumn was significantly affected by those from the partially southerly pathways in Zhejiang.Areas of Anhui,Jiangsu,Shandong,and Zhejiang were still the main potential sources of PM_(2.5)in Zhoushan,with less PM_(2.5)transported from northern Zhejiang and Jiangsu,and more from northwestern Shandong,southwestern Zhejiang,and the northern coast of Fujian.