海南小海表层沉积环境及重金属污染综合评价

Comprehensive evaluation of the environment and the heavy metals pollution in the surface sediments of Xiaohai,Hainan Province

利用2008年在海南小海采集的30个表层沉积物样品,对其进行了TP、TN、TOC、石油类和Hg、Cd、Cu、Pb、Zn、Cr、As重金属元素含量的测定,并采用综合污染指数法和潜在生态危害指数法对该区重金属的污染程度进行了评价,结果显示:(1)研究区表层沉积物中TP含量呈中部高沿岸带低的特征,这可能是由于沿岸带初级生产力高于小海中部,所消耗的磷营养盐较多的缘故;TOC和TN的含量则表现为与TP含量分布相反的特征,即沿岸带高而中部低,这可能是由于沿岸带人为活动对小海沿岸碳、氮元素含量的影响较大的缘故。Hg、Cd、Cu、Pb、Zn、Cr和As 7种重金属元素均表现出在小海中部附近海域和北坡镇沿岸带出现高值,而在小海北边入口处和梅开-英豪沿岸带出现低值的分布特征,这可能与在北坡镇附近的工业区排水时向该海域输入了含有这些重金属元素的污染物所致,而其它区域则受工业排污影响较小,也可能与入海口的潮汐水动力的稀释作用有关。(2)研究区综合污染指数(ISQJ)、潜在生态危害污染指数(ERI)的最大值分别为2.283和240.0,平均值也较高,分别达1.494和151.0,各重金属元素的潜在生态危害系数(Eri)大小顺序为:Hg>Cd>Pb>As>Cu>Cr>Zn,反映出研究区将达到中等污染程度的现状,而某些海域的污染程度已达到重污染水平,研究区受Hg和Cd元素污染较为严重。由此可见,小海的沉积环境已受到较为严重的破坏,未来该海域应该重视重金属Hg和Cd元素的污染治理,以避免小海沉积环境的进一步恶化。

Thirty surface sediment samples （XH01, XH02, XH05 - XH32）were collected in Xiaohai of Wanning, Hainan Province in 2008. The contents of total organic carbon（TOC）, total nitrogen（TN）, total phosphorus（TP）, oil and heavy metals（Hg, Cu, Pb, Zn, Cd, Cr and As） in the surface sediments were analyzed. The Integrated Pollution Index and Potential Ecological Risk Index were used to assess the extent of heavy metals pollution. The results show that the high contents of TN and TOC mainly distribute along the bay-shore, and the lower values are mainly located in the central of bay. The high contents of TP and heavy metals mainly distribute at the north of Beipo and the estuary of Xiaohai, however, the lower values mainly distribute along the Meikai Yinghao at the eastern bay and Beipo-Zhoujiazhuang at western bay. The spatial distributions of these chemical elements show that their distributions are controlled by human activities and natural factors. The level of heavy metals pollution and the potential ecological risk in the study area were evaluated by using the Integrated Pollution Index and Lar Hakanson＇s Potential Ecological Risk Index respectively. Maximum value of Comprehensive Pollution Index （ISQJ）, Potential Ecological Risk Index（ERI ） were 2. 283,240.0, which indicated that the degree of pollution in some areas has reached the level of heavy pollution. The average of ISQJ ,ERI were 1. 494,151.0,which indicated that heavy metals pollution in the study area is slight to moderate, and the potential ecological risk level is also belongs to lower to moderate level. The Potential Ecological Risk Index（ERr） of the heavy metals in the surface sediments of Xiaohai is in the order of Hg〉Cd〉Pb〉As〉Cu〉Cr〉Zn. It revealed Hg and Cd were serious pollution in the environment of Xiaohai. More attention should be paid to heavy metals pollution in order to prevent further deterioration of ecological environment of Xiaohai.