九龙江口红树林表层沉积物重金属赋存形态及污染评价

采用改进的BCR四步提取法分析了九龙江口红树林表层沉积物中16种重金属元素的赋存形态特征，运用次生相与原生相分布比值法（RSP）、风险评价编码法（RAC）和改进的潜在生态风险指数法（MRI）评价了重金属的污染水平和生态风险.BCR提取结果表明，Cd （52.55%）和Mn （47.71%）以弱酸溶态为主要存在形态，Pb、Y和Cu以可还原和可氧化态为主要存在形态，Ba、Tl、V、Th、Cr、As、U、Hg、Ni、Zn和Co主要以残渣态存在.RSP评价结果表明，沉积物受到Cd和Mn的重度污染，受到Pb的中度污染；Cu、Y和Co表现为轻度污染，Zn、Hg、As、U、Ni、Cr、Th、V、Ba和Tl表现为无污染；RAC评价结果表明，Cd和Mn具有极高风险，Co和Zn有中度风险，Ni、Cu、Hg和Y有轻度风险，其余元素（U、As、Pb、Cr、V、Tl、Ba和Th）无风险；MRI评价结果表明，研究区沉积物重金属综合潜在生态风险表现为严重风险，Hg和Cd是主要贡献因子，Hg有严重的潜在生态危害，Cd有较重的潜在生态危害，Tl有中等潜在生态危害，其余元素为低潜在生态危害.

Speciation and Pollution Assessment of Heavy Metals in Mangrove Surface Sediments in Jiulong River Estuary

The speciation of heavy metals was analyzed using modified BCR four-step extraction methods to analyze the pollution of heavy metals in surface sediments collected from the mangrove wetland in Jiulong River Estuary. Subsequently, the pollution degree and the ecological risk of heavy metals were evaluated by using the ratio of secondary phase to primary phase (RSP), risk assessment code (RAC), and modified potential ecological risk index (MRI) assessment methods. The results of BCR four-step extraction showed that Cd (52.55%) and Mn (47.71%) mainly existed in weak-acid extractable fractions. Pb, Y, and Cu mainly existed in reducible and oxidizable fractions. Ba, Tl, V, Th, Cr, As, U, Hg, Ni, Zn, and Co mainly existed in residue fractions. The results of RSP showed that the sediments were heavily polluted by Cd and Mn and moderately polluted by Pb. Cu, Y, and Co were slightly polluted, whereas Zn, Hg, As, U, Ni, Cr, Th, V, Ba, and Tl were not polluted. The results of RAC showed that Cd and Mn were high risk, whereas Co and Zn were moderate risk. Ni, Cu, Hg, and Y were slight risk, and the other elements (U, As, Pb, Cr, V, Tl, Ba, and Th) presented no risk. The MRI results showed that the comprehensive potential ecological risk of heavy metals was serious in the surface sediments, whereas Hg and Cd were the main contribution factors. Hg was a serious potential hazard, followed by Cd. Tl was a medium potential hazard, and the other elements were low potential hazards. These results demonstrated that the mangroves were polluted by heavy metals in Jiulong River Estuary, and effective strategies should be employed to remediate the mangrove sediment in the future.