摘要
为研究长三角背景点夏季PM 2.5污染特征,于2018年5月30日—8月15日在上海市崇明岛对PM 2.5样品进行昼夜采集,并对其中水溶性无机离子(Cl^-、NO3^-、SO4^2-、Na^+、NH4^+、K^+、Mg^2+、Ca^2+)进行了分析.运用PSCF(潜在源贡献)方法判别污染物排放源区,并结合PCA(主成分分析)和PMF(正交矩阵因子)源解析探究PM 2.5来源.结果表明:①观测期间崇明岛ρ(PM 2.5)平均值为(33±21)μg/m^3,低于GB 3095—2012《环境空气质量标准》一级标准限值(35μg/m^3),但在部分时段存在显著超标现象,ρ(PM 2.5)最高值在120μg/m^3以上.②水溶性无机离子质量浓度平均值为(14±9.3)μg/m^3,占PM 2.5的42.4%,其中SNA(SO4^2-、NO3^-、NH4^+三者统称)为主要离子,占水溶性离子总质量浓度的85.7%.③n(NH4^+)/n(SO4^2-)(NH4^+与SO4^2-的摩尔浓度比)显示,清洁期〔ρ(PM 2.5)<15μg/m^3〕呈贫铵状态,过渡期〔15≤ρ(PM 2.5)≤35μg/m^3〕和污染期〔ρ(PM 2.5)>35μg/m^3〕均呈富铵状态;过渡期SNA主要以NH 4HSO4和NH 4NO 3形式存在,而污染期则主要以(NH 4)2SO4和NH 4NO 3形式存在.④通过对两次典型污染事件进行离子相关性分析和PSCF分析发现,E1污染事件(5月30日—6月8日)为局地生物质燃烧型污染事件,E2污染事件(7月23日—8月1日)为区域传输污染事件.源解析结果进一步表明,两次典型污染事件期间气态污染物的二次转化对PM 2.5的贡献最显著,贡献率分别为62.8%和59.8%;其次是生物质燃烧,其贡献率分别为32.5%和20.1%;E2污染事件期间海盐源对崇明岛PM 2.5贡献率较高(16.6%),远超过E1污染事件期间对PM 2.5的贡献率(2.7%).研究显示,区域输送对崇明岛PM 2.5有显著贡献,二次颗粒物累积是崇明岛PM 2.5超标的主要原因.
PM 2.5 samples were collected on a day night basis on Chongming Island,a background site of the Yangtze River Delta from May 30 th to August 15 th,2018,and measured for water-soluble ions in order to improve our understanding of the air pollution characteristics in the region.The PSCF(potential source contribution function)method was used to identify the spatial distribution of the pollutant emissions.The source contributions to PM 2.5 were quantified by using the PCA(principal component analysis)and PMF(positive matrix factorization)methods.Our results showed that:(1)The average mass concentration of PM 2.5 was(33±21)μg/m^3 during the campaign with the highest value greater than 120μg/m^3,indicating that air quality on Chongming Island was generally better than the first grade standard value(35μg/m^3)of Ambient Air Quality Standards(GB 3095-2012).(2)The concentration of water-soluble inorganic ions in PM 2.5 during the campaign was(14±9.3)μg/m^3,accounting for 42.4%of the PM 2.5 mass,and SNA was the dominant species,which accounted for 85.7%of the mass concentration of water-soluble inorganic ions.(3)A further analysis based on molar ratio of n(NH4^+)to n(SO4^2-)showed that ammonium concentration was low in the periods withρ(PM 2.5)<15μg/m^3(the clean period).It was high in the periods withρ(PM 2.5)between 15-35μg/m^3(the transition period)and higher than 35μg/m^3(the polluted period).Ammonium existed as NH 4HSO4 and NH 4NO 3 during the transition periods and as(NH 4)2SO4 and NH 4NO 3 during the polluted periods.(4)PM 2.5 loadings and chemical composition results suggested that two types of pollution events occurred during the campaign,which were characterized by local biomass burning emissions(E1,from May 30 th to June 8 th)and regional transport(E2,from July 23 rd to August 1 st),respectively.Source apportionment further revealed that secondary formation was the largest contributor in the two events,accounting for 62.8%and 59.8%of the PM 2.5 masses,respectively,followed by biomass burning emissions,which contributed separately to 32.5%and 20.1%of the PM 2.5 during E1 and E2.Sea salt was also found to be an important source during the E2 period,contributing to 16.6%of the PM 2.5 mass and much larger than that(2.7%)during the E1 period.This work determined that PM 2.5 on Chongming Island is mostly derived from regional transport and the high level of PM 2.5 at the background site during the haze periods is largely caused by the accumulation of secondary particulate matter.
作者
王心培
王格慧
谢郁宁
吴灿
薛国艳
陈玉宝
丁志健
WANG Xinpei;WANG Gehui;XIE Yuning;WU Can;XUE Guoyan;CHEN Yubao;DING Zhijian(Key Laboratory of Geographic Information Science of the Ministry of Education,School of Geographic Sciences,East China Normal University,Shanghai 200241,China;Institute of Eco-Chongming,Shanghai 200062,China)
出处
《环境科学研究》
EI
CAS
CSCD
北大核心
2020年第6期1366-1375,共10页
Research of Environmental Sciences
基金
国家自然科学基金项目(No.41773117)。
关键词
SNA
赋存形态
生物质燃烧
海盐源
来源解析
sulfate
nitrate and ammonia(SNA)
existing format
biomass burning
sea salt
source apportionment
