基于总量和形态的表层沉积物重金属污染及来源——以马鞍列岛海域为例

为了解马鞍列岛海域沉积物特征及重金属污染状况，于2017年6月采集了该海域表层沉积物样品，并对表层沉积物pH值、氧化还原电位（Eh）、粒度（D_3，2]）等地球化学指标进行了同步原位调查，采用改进后的沉积物重金属形态分析的连续提取法（European Community Bureau of Reference （BCR））分析了7种重金属（Cr、As、Ni、Zn、Pb、Cu、Cd）各形态含量，并结合富集因子系数（EF）、地累积指数法（I_geo）等方法初步探索了马鞍列岛海域沉积物中重金属的污染特征及其来源.结果显示，马鞍列岛海域沉积物呈中性-弱碱性，属还原环境；近岛礁区以粉砾和粘粒为主，而远岛礁区以砂砾和粉砾为主；7种重金属总量均满足我国海洋沉积物质量I类标准；Cr、As、Ni以原生相为主，而Zn、Pb、Cu、Cd均以次生相为主；Cd以可交换态及碳酸盐结合态（F1）以及有机物及硫化物结合态（F3）为主要赋存形态，Zn、Pb、Cu以铁锰氧化物结合态（F2）为主要赋存形态，而Cr、As、Ni以残渣态为主要赋存形态；以Fe作为参比，7种重金属的富集程度顺序为Cd > Cu > Ni > Zn > Pb > Cr > As；通过空间污染状况分析发现，Cu、Cd在受人为活动影响较大的近岛礁区存在富集污染现象，其他重金属则主要表现为天然来源，除Ni外，Cu、Pb、Cd、As、Cr、Zn含量均呈近岛礁区>远岛礁区的空间分布特征.总体上，马鞍列岛国家级特别海洋保护区沉积物重金属污染程度较低，生态环境保护与底质修复效果较好.

Contamination level and source determination of heavy metals in surface sediments from the Ma'an Archipelago based on the total content and speciation analysis

In order to understand the pollution characteristics of seven heavy metals in the surface sediments from the Ma'an Archipelago, several sediment samples were collected in June 2017 and their geochemical parameters such as pH, oxidation-reduction potential (Eh), and grain size (D_3,2]) were simultaneously recorded. The modified method of BCR was used to determine the total content and speciation of the seven heavy metals (Cr, As, Ni, Zn, Pb, Cu, Cd). Among them, Cr, As and Ni were mainly existed in the occurrence form of primary phase, Zn, Pb, Cu and Cd were detected in the occurrence form of secondary phases; Also, the pollution characteristics and sources of the heavy metals in the sediments were primarily explored by using the enrichment factor coefficient (EF) and geoaccumulation index (I_geo). The results showed that the sediments of the Ma'an Archipelago were neutral-weakly alkaline, belonged to the reducing environment. The clay particles were mainly found in the adjacent reef area of island, and the gravel particles were mainly distributed in the further region from the island. The entire pollution level of seven heavy metals satisfied the Class I Standards of Marine Sediment Quality. The Cd was mainly composed of the exchangeable and carbonate fractions (F1), organic matter and sulfide fractions (F3). And the Zn, Pb and Cu were mainly presented in the iron-manganese oxide states (F2), while Cr, As, and Ni were found in the residual state. Refer to Fe, the order of the enrichment degree of the seven heavy metals was Cd > Cu > Ni > Zn > Pb > Cr > As. The results of spatial analysis showed that the Cu, Cd mainly existed in the reef area closed to the island, proving their anthropogenic sources, while other heavy metals were mainly released from natural sources. Moreover, except Ni, higher contents of Cu, Pb, Cd, As, Cr, and Zn were found near the island. In general, the total amount of heavy metals in sediments from the National Special Marine Protected Area of Ma'an Archipelago were relatively low, and the effects of ecological protection and restoration of local sediment maintained well.