厦门海沧区PM_(2.5)中金属元素污染评价及来源分析

Pollution Assessment and Source Analysis of Metals in PM_(2.5) in Haicang District,Xiamen City,China

为了了解金属元素的污染特征和潜在来源,以及重金属元素的风险水平,本研究于2015年4月至2016年1月采集了厦门海沧区不同类型站点四季大气PM_(2.5)样品348份,用X射线荧光分析仪(XRF)测定了其中K、Ca、Na、Mg、Al、Zn、Cu、Fe、Ti、As、V、Mn、Ba、Co等14种金属元素的质量浓度.本研究分析了码头、生活区、工业区和背景区这4个类型站点PM_(2.5)中金属元素的时空分布特征,综合利用富集因子法和健康风险评价模型进行了金属元素的污染评价,并采用相关性分析、主成分分析和后向气团轨迹初步探讨了金属元素的来源.结果表明,采样期间厦门海沧区PM_(2.5)中14种金属元素总质量浓度在PM_(2.5)中的占比为5.4%~10.6%.金属元素总质量浓度的时空变化特征与PM_(2.5)的较为一致,均表现为春冬季浓度高于夏秋季,海润码头和新阳工业区高于海沧分局和市委党校.而夏季海润码头和海沧分局PM_(2.5)日均值超标率较高的现象,与海润码头作业以及风向有关.新阳工业区Zn的质量浓度最高,市委党校次之;海润码头V的质量浓度最高,夏季海沧分局易出现V的浓度高值;均说明污染源站点(新阳工业区和海润码头)排放的污染物对其附近站点的金属元素质量浓度产生了影响.K质量浓度冬季最高,As超标现象出现在冬季和春季,说明冬季生物质燃烧以及燃煤等燃烧排放对大气污染的影响较为严重.Cu、Zn、As、Co、Na和Mn在各站点的富集因子范围为67~8449,富集均较严重.非致癌重金属Zn、Cu、Mn风险值之和低于一般可接受的风险水平(1×10^(-6)a^(-1)),其中Mn对总风险值的贡献范围为74%~88%.综合相关性分析和主成分分析结果表明,厦门海沧区PM_(2.5)中金属元素主要来源于地面扬尘、机动车排放、燃煤和工业排放以及船舶排放,各来源分别可以解释变量的34.5%、12.5%、10.6%、7.8%.后向气团轨迹表明春、秋和冬季均受到局地气团的影响,而夏季气团运动相对较强;春冬季途经长三角内陆的气团可能导致PM_(2.5)浓度偏高.

To determine the spatial-temporal distributions and potential sources of metals in PM（2.5）and assess health risks from heavy metals,348 PM（2.5）samples were collected in the Haicang District of Xiamen,China from April 2015 to January 2016. Metals（ K,Ca,Na,Mg,Al,Zn,Cu,Fe,Ti,As,V,Mn,Ba,Co） in PM（2.5）were detected using an X-ray fluorescence analyzer（ XRF）. Pollution assessment was performed via enrichment factor calculation and health risk assessment. Potential sources were explored using Pearson＇s correlation coefficient,principal component analysis,and the HYSPLIT Trajectory Model. Results showed that the total concentration of 14 metal elements contributed to 5. 4%-10. 6% of PM（2.5）during the sampling period. The total concentration of metals was higher in spring and winter than those in summer and autumn. The concentrations were higher in the port and the industrial areas than in residential areas and background locations,in agreement with the seasonal and spatial distribution of PM（2.5）. The frequency of PM（2.5）daily concentrations exceeding the Chinese Ambient Air Quality Standards was higher in the port and residential areas in the summer due to operations at the port and the wind direction. Zn concentration was the highest in the industrial area followed by the background location. Meanwhile,the highest concentration of V was observed in the port area; V concentration in the residential area was high in the summer. These variations in Zn and V indicated that the elements emitted in the polluted areas migrated easily to residential and background areas. K concentrations were the highest in winter and As showed a higher rate of exceeding the standard in winter and spring,indicating that activities,such as biomass burning and coal combustion in the winter severely impacted air quality. The enrichment factors of Cu,Zn,As,Co,Na,and Mn varied considerably,from 67 to 8,449. The total risk level for non-carcinogenic heavy metals（ Zn,Cu,Mn） was lower than the average level of risk acceptance（ 1 × 10^-6a^-1） and Mn contributed 74%-88% of the total risk level of Zn,Cu,and Mn. The combined results of the correlation analysis and the principal component analysis revealed thatmetals in PM（2.5）were mainly came from re-suspension of ground dust,motor vehicle emissions,coal combustion,industrial emissions,and heavy oil combustion,with contributions of 34. 5%,12. 5%,10. 6%,and 7. 8% respectively. The HYSPLIT Trajectory Model showed that Xiamen was affected by the local air mass in spring,autumn,and winter,but not in summer. Moreover,the rise of PM（2.5）in spring and winter was attributed to air masses traveling through the Yangtze River Delta.