洞头列岛土地利用对土壤及沉积物重金属污染的影响及其生态风险评价

The effects of land use on soil/sediment heavy metal pollution and ecological risk assessment at Dongtou Islands,Zhejiang,China

针对浙江省洞头列岛不同土地利用类型土壤及沉积物中的重金属含量进行调查,选择了五种土地利用类型,农田、森林、围涂、码头、养殖。主要评估重金属的污染现状,区域快速产业化导致的土壤及沉积物中重金属污染及生物的潜在生态风险。采用内梅罗指数法、Hakanson潜在生态危害系数法对重金属的潜在生态风险进行评价。结果表明,洞头列岛不同土地类型的土壤重金属含量均超过浙江省土壤背景值,其中,Cr、Mn、Co超标率为100%,Zn超标率为84%。多数监测点土壤重金属含量的内梅罗综合指数处于清洁水平,但养殖类型中的As、Co,围涂类型中的As、Pb,农田类型中的Pb、Cr属于尚清洁等级,围涂中的Co元素属于轻度污染等级;综合潜在生态风险指数(RI)均显著低于轻微生态危害水平,五种土地类型土壤质量的RI大小顺序为:养殖>围涂>码头>森林>农田,Pb、As是主要的重金属生态风险种类。重金属元素之间的相关性分析表明,围涂与码头土壤中重金属元素之间的相关性明显高于其他三种类型。围涂类型土壤中As与Co、Cu元素呈极显著正相关,Pb与Zn呈极显著正相关;码头类型中的Cu与Co呈极显著正相关,As、Pb与Zn呈极显著正相关。Cu与As在码头、养殖、围涂类型中的含量较高。五种土地类型中除农田和养殖用地的某些重金属来源于成土母质,其他各重金属来源主要是人为活动影响,如:交通运输、城市排污、三废排放以及汽车尾气等。因此,应该把由人类活动导致的有毒重金属的污染控制作为首要任务,制定相应的政策和法规。

The heavy metals contents in sediments/soils from different land use types were investigated at Dongtou islands, Zhejiang Province, China. The five land use types were port, aquiculture, agriculture, reclamation, and forests. It aims to assess the status of heavy metals pollution due to the regional fast-pace industrialization. The major heavy metals were chromium （Cr）, manganese （Mn）, cobalt （Co）, nickel （Ni）, copper（Cu）, zinic （Zn）, arsenic （As）, and lead （Pb）. The Nemerow index （N/） and Hakanson potential ecological risk index （R/） were adopted to assess the heavy metal pollution status and the risks to biota, respectively. The results indicated that the heavy metal contents in each land use types were higher than the provincial base values （BV）, especially the Cr, Mn, and Co over-passed BV 100% and Zn over-passed BV 84%. The Nemerow index also indicated that most of the heavy metals under investigation were no threats and at safe level, but the As and Co in aquiculture, As and Pb in reclamation, and Pb and Cr in agriculture were in the warning level, while the Co in reclamation was in light pollution status. The RI was significantly lower than the light risk level to biota; the R! values were aquiculture 〉 reclamation 〉 port 〉 forests 〉agriculture. Among all the heavy metals, Pb and As were highly toxic to environments, which had great threats to biota. In addition, the correlation analysis indicated that the reclamation soils and port sediments had much higher correlation than others. In reclamation soils, As positively correlated with Co and Cu, while Pb positively correlated with Zn. In port sediments, Cu and Co were positively correlated, while the As, Pb and Zn were positively correlated. The Cu and As contents were much higher in port sediments, aquiculture sediments, and reclamation soils. This research clearly indicated that the heavy metals of agriculture and aquiculture were originated from their parent materials, while other land use types might be introduced by anthropogenic activities, such as transportation, sewage discharge from the cities, waste disposals, and car tail gas. Thus, pollution control of human-induced toxic heavy metals in practice should be put on first priority in formulating local, provincial and/or federal level policies and regulations.