华北某市大气PM2.5中金属污染来源解析及生态风险评价

  目的  了解华北某市主城区大气细颗粒物(fine particulate matter, PM_2.5)中金属的来源及其浓度的季节性差异，并评价金属的污染程度和生态危害程度。  方法  采集2017年3月―2018年2月的大气PM_2.5样品，使用电感耦合等离子体质谱仪对大气PM_2.5中金属元素进行测定，采用富集因子法和主成分分析法解析元素来源，采用地累积指数法和潜在生态风险指数法评估元素污染状况。  结果  该市大气PM_2.5中金属元素浓度具有季节性差异，表现出冬季高于春夏秋季的特征。富集因子法分析结果表明，四季中锑、硒、镉属于极强富集金属，主要受人为活动影响；铬、镍、铍属于无富集金属，来源自然源。主成分分析结果显示，大气PM_2.5中金属污染源主要有交通和工业生产复合污染源、燃烧活动源、燃烧和自然复合污染源。污染程度评价显示，四季中铬、镍、铍可认为无污染；砷、锑、硒、镉、铊、汞、铅的污染程度在中度及以上，但季节变化特征不一致。生态危害评价结果表明，砷、铬、镍、铊、汞、铅属于轻微危害，镉元素属于极强危害；综合危害程度属于很强危害。  结论  该市主城区大气PM_2.5中金属污染主要来源交通、工业生产、燃烧等人为活动；部分元素的污染程度以冬季最为严重，且具有潜在生态危害。因此，冬季应加强对PM_2.5的治理及防护。

Metals source analysis and ecological risk evaluation of atmospheric PM2.5 in a city of North China

  Objective  To investigate the seasonal differences and sources of metal in PM_2.5 in the main urban area of a city in North China, and to evaluate the degree of pollution and ecological harm.  Methods  Atmospheric PM_2.5 samples were collected from March 2017 to February 2018. The content of metal elements were detected by inductively coupled plasma mass spectrometry (ICP-MS). The source of metals was analyzed by the enrichment factor and principal component analysis (PCA). Pollution degree was evaluated by the geo-accumulation index and the potential ecological risk index.  Results  The seasonal differences of concentration of metal elements in PM_2.5 showed that it was higher in winter than that in another seasons. The results of enrichment factor analysis showed that Sb, Se and Cd were highly enriched in four seasons, so they were mainly affected by human activities, and Cr, Ni, Be were non-enrichment which mainly from nature. The results of PCA showed that metals in PM_2.5 were mainly from traffic and industrial composite pollution sources, combustion activity sources, and burning and natural composite pollution sources. The results of pollution degree showed that Cr, Ni and Be could be considered as pollution-free in four seasons, and As, Sb, Se, Cd, Tl, Hg and Pb were in a moderate or higher pollution levels but there was no uniform seasonal variation. The results of potential ecological risk assessment showed that As, Cr, Ni, Tl, Hg, Pb were in slight level, and Cd was stronger than others, but the comprehensive potential ecological risk of elements was extremely strong.  Conclusions  The pollution of metal in PM_2.5 mainly from traffic, industrial production and burning, etc. The pollution degree was highest in winter and had potential ecological harm. Therefore, we should pay more attention to the control and protection of PM_2.5 in winter.