Abstract:

Taking Futian Mangrove National Nature Reserve as the study area, sediments cores (0–50 cm) were sampled among three kinds of habitat, including fish pond, Avicennia marina forest and mudflat. The spatial distribution features of physicochemical properties and heavy metals in sediment cores were analyzed. The potential ecological risk index of heavy metals was calculated and analyzed. Analysis of physicochemical properties revealed that pH value followed the order: mudflat>Avicennia marina forest>fish pond; electrical conductivity, salinity, and total organic carbon (TOC) followed the order: Avicennia marina forest>mudflat>fish pond. The metal concentrations in sediments decreased in the following order: Zn (103.45–214.14 μg/g), Cu (70.92–133.50 μg/g), Pb (54.90–84.65 μg/g), Cd (6.57–7.25 μg/g). The concentrations of Zn, Cu and Pb followed the order: Avicennia marina forest>mudflat>fish pond and the concentrations of Cd followed the order: Avicennia marina forest≈mudflat>fish pond. The lowest level was located at fish pond (P<0.05). The concentrations of Zn and Cu were extremely different (P<0.05) among different vertical depths. Only the concentration of Cu was significantly affected by the interaction effect of sites and depths (P<0.05). Bivariate correlations results indicated that TOC had a significantly positive correlation with Pb in the fish pond (P<0.05), and the correlation of different kinds of heavy metals were complicated in Avicennia marina forest and mudflat. Different kinds of heavy metals had a significantly positive correlation in the fish pond (P<0.05), indicating that the source of 4 species of heavy metals might be same. In addition, the average contents of Cd, Cu, Zn, and Pb in all sediments of the Futian Mangrove Nature Reserve exceeded the first class of criteria GB 18668-2002．The single potential ecological risk of heavy metals followed the order: Cd>Cu>Pb>Zn and Avicennia marina forest>mudflat>fish pond. The integrated potential ecological risks at sampling sites reached high risk level completely, mainly due to Cd contamination, followed by Cu.

Key words: Shenzhen Bay, fish pond, mangrove, sediment, heavy metal, ecological risk

摘要：

在深圳湾红树林的鱼塘、白骨壤林和光滩3种生境中采集沉积物样柱, 分析沉积物的理化性质和重金属(Cd, Cu, Zn 和 Pb)含量及其空间分布特征, 并用Hakanson潜在生态风险指数法评价其生态风险。结果表明, 3 种生境的沉积物在整个沉积深度(0~50 cm)范围内, pH从高到低依次为光滩>白骨壤林>鱼塘; 盐度、电导率和总有机碳(TOC)的高低顺序均为白骨壤林>光滩>鱼塘。整体上重金属的含量分别为Zn 103.45~214.14 μg/g, Cu 70.92~133.50 μg/g, Pb 54.90~84.65 μg/g, Cd 6.57~7.25 μg/g。3种生境沉积物中的4 种重金属含量分布存在极显著差异(P<0.001), Zn, Cu和Pb在3种生境中的含量高低顺序均为白骨壤林>光滩>鱼塘, Cd含量为白骨壤林≈光滩>鱼塘。其中, 鱼塘沉积物的重金属含量最低(P<0.05); Zn和Cu含量随深度变化差异显著(P<0.05), 仅Cu含量随样地和深度变化表现出显著的交互效应(P<0.05)。相关性分析结果表明, TOC在鱼塘重金属Pb积累中起一定的作用(P<0.05), 鱼塘沉积物中4种重金属污染物具有一定的同源性。潜在生态风险评价结果显示, 各重金属潜在生态风险(Eⁱ_r)程度从高到低依次为Cd>Cu>Pb>Zn。各重金属元素的潜在生态风险指数从高到低均为白骨壤林>光滩>鱼塘。综合潜在生态风险指数(RI)显示, 3种生境沉积物的重金属污染达到高潜在生态风险级别, 主要来自Cd污染, Cu污染次之。

关键词: 深圳湾, 鱼塘, 红树林, 沉积物, 重金属, 生态风险