深圳湾近岸海域表层沉积物中重金属污染评价

Assessment on heavy metals pollution in coastal surface sediments of Shenzhen Bay

通过对深圳湾表层沉积物中的Zn、Cr、Cd、Ni、Pb、Cu等6种元素的重金属分析可知,所测样品指标的平均值已全部超过广东海岸带沉积物背景值。利用地累积指数法对6种重金属的评价结果为Cd>Zn>Pb>Cu>Cr>Ni,其中以Cd污染最为严重,以偏中污染和中度污染为主,部分区域出现偏重污染。参照《海洋沉积物质量》(GB18668-2002),Zn的平均值超过背景值的6倍,已属于超Ⅱ类沉积物。Cr为超Ι类,Cd为近Ⅲ类,其均值已超过背景值的9倍;Pb属于Ι类沉积物。Cu的均值显示其已属于超Ⅱ类沉积物。结合粒度分析,其在空间分布上,重金属有沉积物中的富集程度与粒径大小密切相关,其在粒径较大的深圳湾河口区污染程度最小。而在时间尺度上,在近20多年中与背景值相比,重金属在沉积物中的增加则与经济发展密切相关。

The measurements of heavy metals concentrations in the surface sediments in Shenzhen Bay show that the average of each metal, Zn, Cr, Cd, Ni, Pb, Cu is exceeded the background value in the coastal sediments of Guangdong Province. The results of geo-aecumulation index assessment show that the polluted grade is Cd 〉 Zn 〉 Pb 〉 Cu 〉 Cr 〉 Ni. Cd concentration is much high in some area with little heavy pollution calling on more attention. The average concentration of Zn is more 6 times as large as the background value which belongs to Ⅱsediments, Cd is near Ⅲ grade, Pb is Ⅰgrade and Cu is Ⅱgrade. The concentration of heavy metals shows the positive relationship with the sand size of sediments based on the spatial distribution. Comparing with each background value, the concentrations of heavy metals have the close relationship with the economic develooment.