东寨港红树林湿地沉积物-植物体系重金属的分布与富集特征

Distribution and Enrichment of Heavy Metals in Mangrove Wetland Sediments and Plants from Dongzhai Harbor

【目的】通过对红树林湿地沉积物-植物系统中重金属的迁移和富集行为进行研究,对于控制潮间带区域重金属污染具有重要意义。【方法】测定海南东寨港红树林湿地沉积物中重金属元素含量、有效态含量及7种红树植物各部位中重金属元素含量,分析了重金属元素在沉积物和7种红树植物不同部位的分布特征及其富集和迁移能力,并对红树植物体内重金属元素主要来源进行初步探讨。【结果】沉积物中重金属Cr、Cu、As、Cd、Zn全量均值明显高于海南水系沉积物背景值,只有Pb全量略低于背景值;重金属Cr、Cu、As、Cd、超背景值采样点率高达100%;红树植物所吸收的Cr、Ni、As和Pb主要分布在根部和茎部,其原因是由于重金属元素Cr、Ni、As和Pb在沉积物中无生物活性;7种红树植物对重金属元素均未出现富集现象(除桐花树对As具有较强的富集能力);研究区红树植物对As元素的迁移能力均较弱,与王鹏等研究的结果类似,其余植物对重金属的迁移系数均小于1,主要原因是红树植物本身具有对重金属的耐性,通过自身耐性机理对重金属离子吸收的阻止和控制,另外也与生存环境相关;红树植物中重金属Ni、Zn和Cd的富集主要来源于沉积物,而Cr、Cu、As和Pb来源于沉积物的可能性很小。【结论】研究表明强烈的人类活动已使得研究区沉积物Cr、Cu、As、Cd、Zn出现了明显的累积。不同重金属元素在同一红树植物体内的含量不同,同一种重金属元素在不同红树植物体中的含量也存在差异。表明在相同环境的不同植物类型,由于其自身的结构和生理特征,对不同重金属元素的累积能力存在一定差异。

【Objective】This paper aimed to study the migration and enrichment of heavy metals in the sediment plant system of mangrove wetlands,which had an important significance for controlling heavy metal pollution in intertidal zone.【Method】The distribution,enrichment and migration characteristics of heavy metals in mangrove wetland sediments and the seven types of plants were studied by means of determining the contents of heavy metals in sediments and in different parts of each mangrove plant in mangrove wetland of Dongzhai harbor.The main sources of heavy metals in the mangroves were discussed.【Result】The total contents of heavy metals Cr,Cu,As,Cd,Zn were significantly higher than that of the background value of stream sediments in Hainan,and only Pb amount was slightly lower;The sampling rates of heavy metal Cr,Cu,As,Cd and ultra-background value were up to 100%;The Cr,Ni,As and Pb absorbed by mangrove plants were mainly distributed in the roots and stems,and the reason was that the heavy metals Cr,Ni,As and Pb were not biologically active in sediments;No enrichment of heavy metal elements was found in all the seven species of mangrove plants(except Aegiceras corniculatum to As had a strong enrichment ability);The migratory ability of mangrove plants to As was weak in the study area,the transfer coefficient of heavy metal to other plants was less 1,and the main reason was that the mangrove plants themselves had heavy metal tolerance,which the mechanism of self-resistance of heavy metal ions prevented absorption and control and also related to the living environment.The main sources of heavy metals Ni,Zn and Cd in the mangroves mainly comes from sediments,while Cr,Cu,As and Pb were less likely to be derived from sediments.【Conclusion】The strong anthropogenic activities resulted in the significant accumulation of these heavy metals in sediments of the study area;The contents of different heavy metal elements in the same mangrove plant were different,and the contents of the same heavy metal element in different mangrove plants were also different,indicating that different plant types in the same environment had different contents due to their own structural and physiological characteristics.There were some differences in the accumulative ability of heavy metal elements.