嘉兴市冬季一次污染过程PM_(2.5)组分特征及来源分析

Analysis on the Composition Characteristics and Sources of PM_(2.5) During a Winter Pollution Process in Jiaxing in Winter

为了研究嘉兴市城区大气污染过程的颗粒物化学组分特征,利用Minimum R-squared (MRS)方法、轨迹聚类和浓度权重轨迹法(CWT)对2020年12月9~14日一次污染过程中不同污染阶段的气象要素、PM化学组分特征和污染潜在源区进行分析,结果表明本次污染过程主要受弱偏北气流下的本地积累及上游污染输送影响.在污染阶段风速和能见度低,二次无机盐(NO_(3)^(-)、SO_(4)^(2-)和NH_(4)^(+)之和,SNA)浓度上升明显,为PM主要组分,且二次生成明显.监测期间均受机动车尾气排放和燃煤共同影响。污染消散阶段,受冷空气影响,风速增大,能见度转好。本地积累阶段、本地叠加上游输送阶段和消散阶段SOC在OC中占比呈上升趋势,且在传输过程中老化程度较高。结合CWT结果和轨迹聚类结果,本次PM污染潜在源区为安徽和江苏北部交界处、淮安、扬州、苏锡常等沿线地区。了解PM污染特征及来源,可为相关部门提供防治对策理论依据。

In order to study the chemical composition characteristics of particulate matter in the process of air pollution in Jiaxing city,the Minimum R—squared(MRS)method,trajectory clustering and concentration weighted trajectory(CWT)method were used to analyze the meteorological elements,PM_(2.5) chemical components and potential pollution sources of different pollution stages in a pollution process from December 9 to 14,2020.The results showed that the pollution process is mainly affected by local accumulation under weak northerly air flow and upstream pollution transport.In the pollution stage,the wind speed and visibility are low,and the concentration of secondary inorganic salts(NO_(3)^(-),SO_(4)^(2-)and NH_(4)^(+),SNA)increases significantly,which is the main component of PM_(2.5),and the secondary generation is obvious.The monitoring period is affected by vehicle exhaust emission and coal combustion.In the stage of pollution dissipation,under the influence of cold air,the wind speed increases and the visibility improves.The proportion of SOC in OC in local accumulation stage,local superimposed upstream transport stage and dissipation stage showed an upward trend,and the aerosol had a high degree of aging in the process of transport.Combined with the results of CWT and trajectory clustering,the potential sources of PM_(2.5) pollution are along the junction of Anhui and northern Jiangsu,Huai’an,Yangzhou and Suzhou.Understanding the characteristics and sources of PM_(2.5) pollution,can provide theoretical basis for relevant departments to carry out prevention and control countermeasures.