天然火成岩对不同污染程度土壤镉生物有效性的影响

Effects of natural igneous rocks on bioavailability of cadmium in soils with different pollution levels

为明确天然火成岩(SRC)对重金属镉(Cd)污染土壤的钝化效果,采用大田试验和盆栽试验相结合的方法,通过在超过农用地污染风险筛选值土壤(CG和LQ)和风险管控值土壤(JH)中添加SRC,研究其对土壤有效Cd、Cd形态分布以及水稻各部位Cd含量的影响。结果表明,SRC明显改变CG和LQ土壤有效Cd、pH、Cd形态分布和水稻不同部位Cd含量,而对JH土壤影响不大。添加SRC后,CG和LQ土壤pH提高了约0.2,显著降低了CG和LQ土壤CaCl2-Cd (0.01 mol/L CaCl2提取)含量,降幅在27.3%~38.9%。Cd形态分析表明,SRC能够使CG和LQ土壤植物易吸收态Cd向植物难吸收态Cd转变,酸容态Cd含量分别降低了6%~14%,铁锰氧化态Cd和有机结合态Cd分别增加了8%~9%。大田条件下,SRC显著抑制水稻根系、秸秆和子粒种对Cd的吸收,降幅分别达到53.7%、69.8%和54.6%。SRC通过提高土壤pH以及所含矿物对Cd的吸附来降低土壤中Cd的生物有效性,抑制水稻对Cd的吸收。

In order to determine the passivation effect of natural Spanish river carbonatite(SRC) on heavy metal cadmium(Cd) contaminated soils, field and pot experiments were used to study the distribution of available Cd, Cd forms and Cd of different rice parts by adding SRC in soils exceeding the risk screening values(CG and LQ) and risk control values(JH). The results showed that SRC significantly changed soil available Cd, pH, Cd forms and Cd content in different parts of rice in CG and LQ soils, but had little effect on JH soil. When SRC was added, soil pH of CG and LQ increased by about 0.2,significantly reduced the contents of CaCl2-Cd(0.01 mol/L CaCl2 extraction) in CG and LQ soils, and the reduction ranged from 27.3% to 38.9%. Forms analysis of Cd showed that SRC could change Cd from easily absorbed Cd by plants to hardly absorbed Cd in CG and LQ soil change. The content of acidic Cd decreased by 6%~14% and the content of iron-manganese oxidized Cd and organic bound Cd increased by 8%~9%, respectively. Under field conditions, SRC significantly inhibited Cd uptake by rice roots, straws and grains, with decreases of 53.7%, 69.8% and 54.6%, respectively. SRC can reduce the bioavailability of Cd in soils by increasing soil pH and adsorbing Cd by minerals, and inhibit the absorption of Cd by rice.