互花米草入侵对滨海湿地重金属的富集迁移效应

为探究互花米草（Spartina alterniflora）入侵对滨海湿地沉积物重金属的富集迁移效应，为滨海湿地生态保护与合理利用提供依据，在山东省日照市黄家塘湾滨海湿地选取不同互花米草入侵年限的斑块，以5 cm为间隔采集0～30 cm沉积物样品和互花米草样品，分析沉积物和互花米草不同部位中重金属元素Cu、Zn、Pb和Cd的含量，并采用地累积指数法、潜在生态风险评价法、生物富集系数及转运系数等方法进行评价。结果表明：湿地沉积物重金属Cu、Zn、Pb和Cd 的含量范围为5.94～31.94 mg(kg^-1，18.59～56.87 mg(kg^-1，4.76～30.36 mg(kg^-1，0.021～0.083 mg(kg^-1，整体低于研究区域重金属环境背景值；但Cu、Pb在0～15 cm内存在轻度污染；与光滩湿地相比，互花米草入侵湿地沉积物中重金属含量增加，且随互花米草入侵年限增加，沉积物重金属含量呈增加趋势，在上层（0～15 cm）表现尤为显著；互花米草不同部位对重金属的累积存在一定差异，大致表现根>叶>茎；不同重金属在根部的富集效应表现为Cd > Zn > Cu > Pb，互花米草对重金属转运效应为Pb > Zn > Cu > Cd。相关分析表明，沉积物中重金属的累积与互花米草入侵对湿地沉积物粒度组成、有机质含量及pH的改变密切相关。不同重金属在沉积物-植物体系的迁移转运差异则主要与互花米草各部位对重金属元素的吸收差异有关。

Characteristics of heavy metal enrichment and migration affected by Spartina alterniflora invasion in coastal wetland

To study the characteristics of heavy metal enrichment and migration affected by Spartina alterniflora invasion in coastal wetland and provide a scientific basis for the ecological protection and rational utilization of the coastal wetland, three sampling sites with different invasion years of Spartina alterniflora were selected, and the heavy metal contents of Cu, Zn, Pb and Cd at 5 cm intervals in 0 - 30 cm sediments and Spartina alterniflora were analyzed and evaluated using geo-accumulation indexes, potential ecological risks evaluation methodology, bioconcentration factor and biological translocation factor. The results suggested that: the contents of Cu, Zn, Pb and Cd in sediments were 5.94-31.94 mg(kg^-1, 18.59-56.87 mg(kg^-1, 4.76-30.36 mg(kg^-1, 0.021-0.083 mg(kg^-1, respectively, lower than the environmental background values in the study region; the contents of Cu and Pb showed mild pollution in 0-15 cm sediments; the contents of heavy metals in vegetation areas were higher than those in bare flat areas, particularly in the upper level (0-15 cm). The preferential order of contents of heavy metals in different parts of Spartina alterniflora was root > leaf > stem; the preferential order of enrichment effect of heavy metals in the root was Cd > Zn > Cu > Pb; the preferential order of transport efficiency was Pb > Zn > Cu > Cd. The change of the physicochemical properties of the wetland deposits was an important reason for the accumulation of heavy metals in the sediments. The differences in migration and transport of heavy metals in the sediment-plant system were mainly related to the absorption of heavy metal elements in different parts of Spartina alterniflora.