珠江三角洲典型站点大气金属元素的湿沉降特征、来源及生态风险评价

Characteristics,sources and ecological risk assessment of metal elements in atmospheric wet deposition at typical stations in the Pearl River Delta

为研究珠江三角洲地区典型区域大气金属元素的湿沉降特征,于2016年9月—2019年8月在鼎湖山自然保护区(DHS)森林站点及广州地球化学研究所(GIG)城市站点收集降水样品,用ICP-MS测定了18种微量金属元素浓度(Ca、Na、Al、Mg、K、Fe、Zn、Ba、Cu、Mn、Sr、Ni、Cr、Pb、V、As、Co、Cd),并对采样点金属元素的时空变化特征、湿沉降通量变化、来源及潜在生态风险的评价进行了深入探讨.结果表明:位于珠江三角洲的森林站点和城市站点降水中金属元素浓度均是旱季明显高于雨季.Ca是DHS和GIG两个站点浓度最高的元素,浓度平均值分别为1685.40μg·L^(-1)和1102.87μg·L^(-1),Cd是浓度最低的元素,平均值分别为0.38μg·L^(-1)和0.20μg·L^(-1).湿沉降通量雨季高于旱季,同时,森林站点和城市站点降水中金属元素的浓度空间差异性较大;森林站点和城市站点降水中的大部分元素存在中等程度富集,森林站点高富集元素有Ca、Na、Fe、Cu和Cd,城市站点高富集元素为Ca、Na、Fe和Cu.基于PMF模型判断了湿沉降金属元素的来源,结果表明:森林站点降雨中金属元素的源主要有海洋源、扬尘源、工业源、交通源及煤和生物质燃烧源,城市站点降雨中金属元素的源主要有海洋源、扬尘源、金属加工、交通源和燃煤源;两站点的Cd被归为潜在生态风险极强的元素.

To investigate the characteristics of wet deposition of atmospheric metal elements in the Pearl River Delta region,precipitation samples were collected from September 2016 to August 2019 at the Dinghushan(DHS forest station)and Guangzhou Institute of Geochemistry(GIG suburban station).The concentrations of 18 trace metal elements(Ca,Na,Al,Mg,K,Fe,Zn,Ba,Cu,Mn,Sr,Ni,Cr,Pb,V,As,Co,Cd)were determined using ICP-MS.Additionally,the temporal and spatial variation characteristics,wet deposition flux,sources,and the potential ecological risk assessment of trace metal elements were discussed in detail.Results showed that the concentrations of metal elements in precipitation at both the DHS forest station and GIG suburban station in the Pearl River Delta region were higher in the dry season than in the rainy season.Ca had the highest concentration at both the DHS forest station and GIG suburban station,with average concentrations of 1685.40μg·L^(-1) and 1102.87μg·L^(-1),respectively.On the contrary,Cd had the lowest concentration,with average concentrations of 0.38μg·L^(-1) and 0.20μg·L^(-1),respectively.Moreover,the wet deposition flux was higher in the rainy season than in the dry season.Meanwhile,it was found that the concentration of metal elements in the DHS forest station and GIG suburban station had significant spatial variations.Most of the elements in precipitation at both sites were moderately enriched.Ca,Na,Fe,Cu,and Cd were highly enriched in DHS forest station,and Ca,Na,Fe,and Cu were highly enriched in GIG suburban station.Furthermore,the PMF model indicated that the major sources of metal elements in precipitation at the DHS forest station were marine sources,dust sources,industrial sources,traffic sources,coal combustion,and biomass burning at the DHS station.And the major sources of metal elements in precipitation at the GIG suburban station included marine sources,dust sources,metal processing,traffic sources,and coal combustion.Cd at both stations was classified as an element with a high potential ecological risk.