天津市采暖季PM2.5组分消光特性及来源分析

为了解天津市采暖季细颗粒物组分对能见度的影响、明确消光组分来源,对天津市2017年采暖季大气PM_2.5样品进行了为期一月的连续采集,并测定水溶性离子、有机碳和元素碳的含量,通过修正IMPROVE方程研究了细颗粒物消光特性,并采用主成分分析—多元线性回归模型(PCA-MLR)对其来源进行解析,同时应用潜在源贡献因子(PSCF)和浓度权重轨迹(CWT)明确PM_2.5质量浓度的潜在污染源区域。结果表明,OC、EC以及SNA(NO3^?、NH₄⁺、SO₄^2?)的生成和积累对于能见度的下降具有重要影响,且能见度随SOR和NOR二次转化程度的升高而下降;2017年天津市采暖季日均消光系数为(294.56±262.89)Mm^?1,其中OM(34.86%)、硝酸盐(22.84%)、硫酸盐(11.59%)和EC(11.54%)为主要消光组分,硝酸盐和硫酸盐的增加对于能见度的下降起主要影响作用;根据PCA分析结果可知,天津市采暖季PM_2.5中的碳组分和水溶性离子主要来源于燃煤、生物质燃烧(68%),受扬尘(22%)和海盐(8%)的影响较小;区域传输分析结果表明天津市采暖季PM_2.5污染源潜在区域主要分布在河北中西部、河南北部、山西北部和内蒙古中部、西部。

Extinction Characteristics and Source analysis of PM2.5Components in Tianjin Heating Season

In order to study the influence of fine particulate matter on visibility and to determine the source of extinction components,PM_2.5samples were collected continuously for one month in the heating season in Tianjin in 2017,and the contents of water-soluble ions,organic carbon and elemental carbon were measured.The extinction characteristics of fine particles were studied by modifying the IMPROVE equation,and the sources of fine particles were identified by using the the principal component analysis-multivariate linear regression model(PCA-MLR)approach.At the same time,the potential source contribution function(PSCF)and concentrationweighted trajectory(CWT)method were applied to analyze the potential pollution source areas affecting the PM_2.5mass concentration.The results show that the formation and accumulation of OC,EC and SNA(NO3^?、NH₄⁺、SO₄^2?)have an important impact on the decline of atmospheric visibility,and the visibility decreases with the increase of the secondary conversion degree of SOR and NOR.The daily average extinction coefficient of Tianjin heating season in 2017 is(294.56±262.89)Mm?1,of which OM(34.86%),nitrate(22.84%),sulfate(11.59%)and EC(11.54%)were the main extinction components.The increase of nitrate and sulfate plays a major role in the decrease of visibility.According to the PCA analysis,the carbonaceous components and water-soluble ions in PM_2.5are mainly from coal combustion and biomass burning(68%),and are less affected by dust(22%)and sea salt(8%)during the heating season in Tianjin.The results of regional transmission analysis show that the potential areas of PM_2.5pollution sources are mainly located in the central and western Hebei,the northern Henan,the northwestern Shanxi,the central and western Inner Mongolia.