典型“组群式”城市夏季大气颗粒物中水溶性离子化学特征及来源

Chemical Characteristics and Sources of Water-Soluble Ions of Airborne Particles during Summer in the Typical 'Group' City

为探究典型"组群式"城市——淄博市夏季大气颗粒物中水溶性离子化学特征及来源,于2016年8月对淄博市6个城市点(桓台、张店、临淄、淄川、博山、周村)、2个郊区点(沂源、高青)及1个清洁对照点(鲁山)同步进行PM_(2.5)和PM_(10)采样,分析了大气颗粒物质量浓度及9种水溶性离子的空间分布特征,并利用主成分分析方法探讨了PM_(2.5)和PM_(10)中水溶性离子的主要来源.结果表明:(1)淄博夏季各点位(清洁对照点除外)PM_(2.5)和PM_(10)质量浓度日均值范围分别为57.2~112和77.4~163μg/m3,空间分布特征表现为城市点>郊区点>清洁对照点;各点位PM_(2.5)/PM_(10)(质量浓度之比)在0.61~0.80之间,表明淄博夏季大气颗粒物污染以PM_(2.5)为主.(2)水溶性离子在PM_(2.5)和PM_(10)中占比分别为53.3%和48.5%,其中二次无机离子分别占总离子浓度的91.4%和83.7%,表明大气颗粒物主要以二次离子为主,并且主要富集在PM_(2.5)中;PM_(2.5)中∑阴离子/∑阳离子(摩尔浓度之比)为1.07,PM_(10)中该比值为0.87,说明PM_(2.5)接近中性,而PM_(10)呈弱碱性.(3)淄博夏季各点位离子来源具有一定的空间差异性,城市点、郊区点与清洁对照点间的CD(分歧系数)均高于0.2,而城市点间CD值低于0.2,说明城市点位间的水溶性离子的化学性质较为相似.(4)主成分分析表明,淄博夏季大气PM_(2.5)中的水溶性离子可能主要来源于工业源、生物质锅炉、燃煤、二次源、道路尘及建筑尘,而PM_(10)中的离子主要来源于道路尘、建筑尘、海盐及二次源.研究显示,淄博市颗粒物污染严重,具有明显的空间分布特征,水溶性离子来源复杂,应采取分区、多源控制的污染防治对策.

To investigate the characteristics and sources of water-soluble ions of atmospheric particulate matters,PM 2.5 and PM 10 were collected simultaneously at six urban sites(i.e.,Huantai,Zhangdian,Linzi,Zichuan,Boshan and Zhoucun),two suburban sites(i.e.,Yiyuan and Gaoqing)and one background site(i.e.,Lushan)in summer(August,2016)in the typical‘group’city:Zibo City,Shandong Province,China.Mass concentrations of PM 2.5 and PM 10 and spatial distribution characteristics of nine water-soluble ions were analyzed;the sources of water-soluble ions associated with PM 2.5 and PM 10 were identified by using principal component analysis(PCA).The results showed:the daily average concentrations of PM 2.5 and PM 10 at all urban and suburban sites were 57.2-112 and 77.4-163μg m 3,respectively;the spatial distribution characteristics of particles mass concentrations was urban sites>suburban sites>background site.The value of PM 2.5 PM 10 was 0.61-0.80 in all sites,indicating PM 2.5 was the main pollutant during sampling period.Water-soluble ions accounted for 53.3%and 48.5%in the mass concentrations of PM 2.5 and PM 10,respectively.The secondary inorganic ions(i.e.,sulfate,nitrate and ammonium)were the most abundant fraction with the contribution of more than 91.4%and 83.7%to total water-soluble ions in PM 2.5 and PM 10,respectively,suggesting that the levels of secondary ions were relatively high and mainly enriched in PM 2.5.The value of∑anion∑cationic was 1.07 for PM 2.5,and 0.87 for PM 10,illustrating that PM 2.5 was in neutral while PM 10 was weakly alkaline.Coefficient of Divergence(CD)values between urban or suburban sites and background site were higher than 0.2,while among urban sites were lower than 0.2,manifesting the chemical characteristics of water-soluble ions were similar among urban sites.PCA results showed that the water-soluble ions of PM 2.5 might be from the industrial sources,biomass boiler,coal combustion,secondary reaction,road dust and construction dust,while the water-soluble ions of PM 10 may be from road dust,construction dust,sea salt and secondary reaction.In conclusion,the PM pollution was heavy during summer in Zibo City,and the concentrations and chemical components varied with sites.Different countermeasures should be taken according to the pollution characteristics of different sites.