利用大型土柱自然淋溶条件下研究土壤重金属的迁移及形态转化

Migration and Transformation of Heavy Metals in Soils by Lysimeter Study with Field Condition

为研究不同重金属在土壤中的迁移和形态转化,通过分层填装土柱,在土柱0~5 cm深度范围内添加Pb、Ag、Bi、In、Sb和Sn等重金属污染土壤,并在自然条件下淋溶4 a,分析各重金属在红壤、潮土、黑土和砂土中的迁移速率及其形态组成.结果表明：1在〉30 cm深度范围内,红壤、潮土和黑土中各重金属质量分数与其相应本底值相比变化不大;与试验前土壤相比,砂土整个剖面中6种重金属质量分数均较高.26种重金属在4种土壤中的残留率表现为砂土〈潮土〈黑土〈红壤;对于0~10 cm土壤中Pb的残留率,在潮土中大于Ag和Sb,在黑土中大于Ag,在红壤中大于In,在砂土中则大于Sn.3模拟试验后残留在土柱中的重金属主要分布在土壤表层（0~30 cm）,而深层（〉30 cm）较少;6种重金属在红壤、潮土、黑土和砂土中的残留率平均值分别为98.0%、65.1%、65.9%和56.5%.4与添加污染土壤之前相比,试验后土壤中残渣态等稳定形态重金属质量分数较低,其中Pb、In和Sb均以碳酸盐结合态和有机金属络合态为主,Ag和Sn分别以有机金属络合态、双氧水可提取有机结合态和有机金属络合态、无定形铁锰氧化物结合态为主,而Bi则以碳酸盐结合态和双氧水可提取有机结合态为主.结果显示,红壤中Pb的迁移风险较低,潮土和黑土中Ag、Sb的迁移风险较高,而砂土中Sn和Sb的迁移风险需要格外关注.

The migration and chemical transformation of Pb, Ag, Bi, In, Sb and Sn in four soils were investigated using lysimeter experiments. The polluted soils were added to the soil surface and were exposed to the natural environment to ensure that they were at or close to field capacity for four years. The results showed that： 1 ） Compared with the background values, the six heavy metals did not increase significantly in deep soil layers （ 〉 30 cm） in Primosol, lsohumosol and Ferrosol after four years. The heavy metals were significantly increased in all the soil layers in Sand soil （0-135 cm）. 2） The rates of the heavy metals retained in the lysimeters were inthe following order： Sand soil 〈 Primosol 〈 Isohumosol 〈 Ferrosol. 3 ） Pb retained in surface soil （0-10 cm） was greater compared to Ag and Sb for the Primosol, Ag for Isohumosol, In for Ferrosol and Sn for Sand soil. Proportions of 98.0% , 65.1% , 65.9% and 56.5% of the added heavy metals remained in the lysimeters with the Ferrosol, Primosol, Isohumosol and Sand soil, respectively. 4） The immobility fractions of the heavy metals wereat low levels after leaching compared with background values. Pb, In and Sb in the soils after leaching were mainly associated with both carbonate-bound and metal-organic complex-bound, while Ag and Sn in the soils were mainly associated with metal-organic complex- bound, H2O2 extractable organic-bound and amorphous metal oxide-bound. Bi was mainly associated with carbonate-bound and H2O2 extractable organic-bound. Pb had greater migration risk than the other heavy metals in the Ferrosol, while the Ag and Sb had greater migration risk in the Primosol and Isohumosol. Sn and Sb were of much concern in the Sand soil.