重金属在施污土壤中分布及被大豆植株的吸收

Distribution of heavy metals in cropland soils amended with sewage sludge and in the uptake by soybean

对施污剂量分别为10、30和60mg·hm-2的土壤,采用修正的BCR三步连续提取法分步提取并分析Pb,Cd,Cu,Zn的不同形态。利用高压密封消解技术和ICP-MS分析Pb,Cd,Cu,Zn在大豆器官中的分布及其转移、富集特征。施污土壤中重金属主要以残渣态存在,Pb,Cu,Zn元素的含量基本未超过我国土壤环境质量标准。4种重金属在弱酸性土壤中残渣态含量比例的高低依次为Cu>Zn>Cd>Pb。与土壤中稳定性强的Cu相比,在污泥农田利用时更应注重土壤中过量的Pb和Cd被植物的吸收利用。大豆植株的不同器官对4种重金属的富集能力不同,其在大豆器官中含量Pb,Cd为:茎叶>根>籽粒,相反Cu,Zn为:籽粒>根>茎叶。大豆对土壤中重金属富集系数高低顺序依次为Cd>Cu>Zn>Pb。

The modified BCR three-step sequential extraction procedure was used to predict and analyze Cu,Pb,Cd and Zn distributional patterns in the soil which were polluted at doses of 10, 30 and 60 mg. hm-2. The high-pressure airtight digestion technique and ICP-MS were used to determine the distribu- tion, translocation and accumulating of Pb, Cd, Cu and Zn in different organs of soybean. The heavy metals in polluted soil were mainly existed in the forms of residue. The amount of Pb, Cu and Zn did not exceed the Safe Controlling Standards of China. The residual fraction order of Pb, Cd, Cu and Zn in weak acid soil was followed as： Cu〉Zn〉Cd〉Pb. Compared with Cu which was more stable in soil, Pb and Cd of higher contents in soil should be given more attention, because they were easily absorbed by plants. Different organs of soybean have different accumulating capabilities on the four different metals. The relative sequence of the contents of Pb and Cd in soybean organs predicted as： stems and leaves 〉 roots 〉 seeds; in contrast, for Cu and Zn the order was： seeds 〉 roots ~ stems and leaves. The order of soybean enrichment coefficient for these metals was followed as： Cd〉Cu〉Zn〉Pb.