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Bioavailability and ecological risk assessment of heavy metals in sediments of marine aquaculture in Zhelin Bay

基金项目：国家自然科学基金项目（No.21777150，21307120）；广州市民生科技专项（No.201803030042）；广东省化学危害应急检测技术重点实验室开放基金（No.KF2018001）

刘爽
1. 兰州理工大学石油化工学院, 兰州 730050;2. 广东省测试分析研究所, 广东省化学危害应急检测技术重点实验室, 广东省水环境污染在线监测工程技术研究中心, 广州 510070

摘要：采集柘林湾海水养殖区8个位点表层沉积物样品，考察了沉积物样品中重金属含量、生物有效性和形态分布，并分别利用基于总量的Hakanson指数法和基于形态的风险评价指数（RAC）评价了沉积物中重金属的生态危害风险.结果表明，柘林湾海水养殖区大部分位点沉积物中重金属含量符合海洋沉积物质量Ⅰ类标准限值，少数位点Zn和Pb含量超过Ⅰ类限值但低于Ⅱ类限值.沉积物中重金属的薄膜扩散梯度技术（DGT）测定浓度（C_DGT）与间隙水中的浓度（C_IW）对重金属生物可利用性评估状况基本一致，Zn、Ni和Pb生物可利用性较高.沉积物中Cr、Ni、Zn和Cu以残渣态为主，Cd和Pb以弱酸提取态为主.柘林湾沉积物中重金属总体存在轻度到中度生态危害风险，Cd和Pb生态危害风险较高.沉积物中Cr、Ni、Zn、Cu和Cd的C_DGT与其弱酸提取态含量明显正相关，重金属弱酸提取态能较好反映其生物可利用性.

Abstract：The content, bioavailability and fractionation of six heavy metals were investigated in eight maricultural surface sediments from Zhelin Bay. The ecological risk of heavy metals was evaluated by Hakanson index method based on the total metal content and risk assessment code (RAC) based on metal speciation, respectively. The results showed that the concentration of heavy metals in most sites were below the Class Ⅰ marine sediment quality limit, while the concentration of Zn and Pb in a few sites exceeded the Class Ⅰ, but not exceeded the Class Ⅱ. The concentration of bioavailable heavy metals in sediments (C_DGT) measured by the diffusive gradients in thin films technique (DGT) were generally consistent with that in pore water, among which Zn, Ni and Pb were highly bioavailable. Cr, Ni, Zn and Cu in sediments were primarily present in the residual fraction, while Cd and Pb were mainly present in acid-extractable fraction. Conclusively, in Zhelin bay, heavy metals showed slight to moderate ecological risk, among which Cd and Pb showed higher ecological risk compared to other metals. The concentration of bioavailable Cr、Ni、Zn、Cu and Cd (C_DGT) were positively correlated with their acid-extractable fraction in sediments, showing that heavy metals obtained from acid-extractable fraction in sediments can indicate their bioavailability very well.