膨润土对不同类型农田土壤重金属形态及生物有效性的影响

通过盆栽试验,研究了膨润土对3种类型农田土壤中土壤理化性质、Cd、As、V和Cr的形态、小白菜(Brassica chinensis L.)生长、重金属吸收及根际微生物群落的影响.结果表明,添加膨润土降低了3种土壤中可交换态Cd比例,降幅依次为黄壤(Gy,19. 44%)黄褐土(Sy,13. 85%)潮土(Bf,5. 03%),小白菜地上部Cd对应降幅为Gy(34. 81%) Bf(23. 91%) Sy(11. 11%);与各自对照相比,Bf和Sy中可交换态As比例降低,降幅分别为4. 53%和25. 16%,Gy中可交换态As比例升高了0. 57%;可交换态Cr比例均升高,增幅依次为Sy(31. 30%) Gy(2. 91%) Bf(0. 58%); As、V和Cr残渣态均升高(Sy中Cr除外),小白菜对其吸收也不同程度地降低.膨润土有助于3种土壤中小白菜的生长,Bf中小白菜生物量、根表面积、根尖数分别增大了147. 55%、80. 71%和124. 31%.此外,膨润土降低了3种类型土壤中速效氮、速效磷和有机质的含量,增大了速效钾含量和根际微生物群落多样性.因此,认为膨润土均适用于这3种土壤的修复改良.

Effects of Bentonite on Chemical Forms and Bioavailability of Heavy Metals in Different Types of Farmland Soils

A pot experiment was conducted to evaluate the effects of bentonite on the physicochemical properties of soil; chemical forms of Cd, As, V, and Cr; pakchoi (Brassica chinensis L.) growth; metal uptake; and rhizosphere microbial community in three different types of farmland soils. The results showed that bentonite decreased the exchangeable Cd in the sequence of Yellow earths (Gy, 19.44%) > Yellow-cinnamon soils (Sy, 13.85%) > Fluvo-aquic soils (Bf, 5.03%), and the content of Cd in shoots of pakchoi declined in the sequence of Gy (34.81%) > Bf (23.91%) > Sy (11.11%), compared with the controls. Compared with the controls, the exchangeable As in Bf and Sy decreased by 4.53% and 25.16%, respectively, while the exchangeable As in Gy increased by 0.57%. The exchangeable Cr was increased in the sequence of Sy (31.30%) > Gy (2.91%) > Bf (0.58%). The residual As, V, and Cr increased (except for Cr in Sy), and their uptake was also reduced in different degrees. The addition of bentonite significantly promoted the growth of pakchoi in the three soil types, especially in Bf. pakchoi biomass, root surface area, and number of root tips increased by 147.55%, 80.71%, and 124.31%, respectively, in Bf, compared with the control. In addition, bentonite reduced the content of available nitrogen, phosphorus, and organic matter; increased the content of available potassium; and increased the diversity of rhizosphere microbial community in all three soils. Therefore, bentonite could be highly recommended as a safe stabilizer in these three types of soil.