苏州地区黑碳气溶胶分布特征及来源分析

Characteristics and sources of black carbon aerosols in Suzhou

基于苏州地区2018—2021年黑碳(black carbon,BC)质量浓度观测数据,结合黑碳仪模型、浓度权重轨迹分析法(concentration weighted trajectory,CWT),对苏州地区BC分布特征和来源进行了分析。结果表明,2018—2021年苏州BC平均质量浓度为1.81μg/m^(3)且呈逐年下降的趋势,与2018年相比,2021年BC年平均质量浓度下降了43.6%。同时,苏州本地源以化石燃料(fossil fuel,简记为“ff”)燃烧为主,75.5%的BC由化石燃料燃烧产生。在BC质量浓度逐年降低的同时,BCff占比也呈逐年下降的趋势。在季节变化上,BC质量浓度冬季最高,夏季最低,BC和BCff日变化均呈双峰型分布。与气温、降水量相比,相对湿度对BC质量浓度影响较小;当BC质量浓度小于6μg/m^(3)时,BC质量浓度随风速增加而减小;同时,BC质量浓度在各风向上的分布差异并不明显。潜在源分析显示,四季BC的潜在源区多集中在西南方向,浙江、安徽、江西等3个省份对苏州BC影响相对更多。

Based on continuous observations of black carbon(BC)mass concentration between 2018 and 2021 in Suzhou,and using the Aethalometer model and concentration weighted trajectory(CWT)analysis,this study investigates the distribution characteristics and potential source apportionment of BC in Suzhou.The results show that the mean BC mass concentration in Suzhou is 1.81μg/m^(3),and it presents a decreasing trend between 2018 and 2021.Compared to that in 2018,the annual mean mass concentration in 2021 decreases by 43.6%.The analysis indicates that the combustion of fossil fuels(ff)is the largest BC source in Suzhou,75.5%of BC is derived from BCff,and the proportion decreases year by year with the decrease of BC mass concentration.Moreover,the maximum and minimum BC mass concentration are shown in winter and summer,respectively,and both the diurnal variations of BC mass concentrations and BCffpresent a bimodal distribution.Compared to temperature and precipitation,relative humidity has less influence on BC mass concentrations;when BC mass concentration is smaller than 6μg/m^(3),it decreases as the wind speed increases;meanwhile,the distribution of BC mass concentration in different wind directions does not differ greatly.The source apportionment analysis suggests that the potential source areas of BC are mostly concentrated in the southwest direction,and Zhejiang,Anhui,and Jiangxi provinces have larger influence on BC in Suzhou.