不同生长时期桑树对矿区土壤中重金属的富集行为

Enrichment Behavior of Heavy Metals in Mining Soil by Mulberry Trees at Different Growth Stages

为了研究桑树对矿区重金属污染土壤中重金属的富集行为,选取矿区被重金属污染的土壤和桑树品种“湘7920”为研究材料,进行了为期一年的盆栽实验,分别测定了不同生长时期桑树根、茎、叶中的重金属镉(Cd)、砷(As)的含量。结果表明:在Cd和As重度污染土壤环境中,桑树的生长不受影响;在桑树的生长过程中各个部位对Cd和As的富集能力不一致,桑根中富集的As倾向于往桑叶转移,桑叶对As的转移系数大于茎且桑叶中As最高浓度可达5.8 mg·kg^(-1);桑根对Cd的富集系数大于1,Cd在桑树根部的最大浓度为9.5 mg·kg^(-1);在桑树的不同生长时期As和Cd在桑根富集含量的百分比最高分别达到70%和83%,因此桑树不是As和Cd的超富集植物;但是桑叶对这两种金属的富集百分比随着植株生长而增加,在桑树生长后期分别达到42%和21%。因此,对于矿区的重金属污染治理,桑树具有高存活、可富集的优良特性,结合桑叶的用途,利用桑树作为矿区污染土壤中替代性种植植物,有可能成为我国矿区重金属污染土壤安全高效利用的一种新模式。

In order to study the enrichment behavior of mulberry trees in heavy metal contaminated soil in mining areas,a one-year pot experiment was conducted using heavy metal contaminated soil and mulberry variety "Xiang 7920" as research materials.The contents of heavy metals cadmium(Cd) and arsenic(As) in mulberry roots,stems,and leaves at different growth stages were measured.The results showed that in the heavily polluted soil environment with Cd and As,the growth of mulberry trees was not affected;During the growth process of mulberry trees,the enrichment ability of Cd and As in various parts is inconsistent.As enriched in mulberry roots tends to transfer to mulberry leaves,and the transfer coefficient of As in mulberry leaves is greater than that in stems.The highest concentration of As in mulberry leaves can reach 5.8 mg·kg^(-1);The enrichment coefficient of Cd in mulberry roots is greater than 1,and the maximum concentration of Cd in mulberry roots is 9.5 mg·kg^(-1);At different growth stages of mulberry trees,the highest percentages of As and Cd enrichment in mulberry roots reached70% and 83%,respectively.Therefore,mulberry trees are not super enriched plants for As and Cd;However,the enrichment percentage of these two metals in mulberry leaves increases with plant growth,reaching 42% and 21% respectively in the later stage of mulberry tree growth.Therefore,for the treatment of heavy metal pollution in mining areas,mulberry trees have excellent characteristics of high survival and enrichment.Combined with the use of mulberry leaves,using mulberry trees as alternative planting plants in contaminated soil in mining areas may become a new model for safe and efficient utilization of heavy metal contaminated soil in mining areas in China.