不同价态铬在不同水分条件下的生物有效性及其对水稻的毒性

氧化还原过程在铬的形态转化中起了重要作用,而铬形态的转化能够影响其生物有效性及毒性。通过温室土培试验研究了六价铬(Cr(Ⅵ))与三价铬(Cr(Ⅲ))在淹水与不淹水条件下在土壤溶液中的动态变化及水稻对其吸收的变化。结果表明,土壤中添加Cr(Ⅲ)时,土壤溶液中检测不出Cr;而随着土壤中添加Cr(Ⅵ)浓度的增加,土壤溶液中Cr(Ⅵ)的浓度增加,但是溶液中检测不出Cr(Ⅲ);淹水处理总体上降低了土壤溶液中Cr(Ⅵ)的浓度。而土壤添加Cr(Ⅲ)、Cr(Ⅵ)和水分处理对土壤溶液p H没有显著影响,p H在7.08.0之间变动。土壤添加Cr(Ⅵ)处理的水稻中,只有90 mg·kg-1Cr(Ⅵ)淹水处理的水稻成活,而其余处理水稻没有成活。土壤中添加Cr(Ⅲ)处理,水稻幼苗生物量随Cr(Ⅲ)浓度的增加而显著降低;除了200mg·kg-1Cr(Ⅲ)处理外,其余淹水处理的水稻幼苗生物量明显高于不淹水处理的。土壤添加Cr(Ⅲ)处理的水稻,在不淹水条件下水稻空壳率比较高,淹水条件下,随着土壤中添加Cr(Ⅲ)浓度水平的增加,水稻各部位Cr含量有增加的趋势,但增加不显著,秸秆最高Cr含量达到33.80 mg·kg-1,籽粒中Cr含量最高0.30 mg·kg-1。土壤固定Cr(Ⅲ)的能力远强于Cr(Ⅵ),添加Cr(Ⅵ)处理的土壤溶液中Cr(Ⅵ)的浓度很高,对水稻表现出较强的生长抑制。

Bioavailability and Toxicity of Cr(III) and Cr(VI) to Rice (Oryza sativa L.) as Influenced by Water Management

Redox processes play an important role in the form transformation of chromium, which can affect the bioavailability and toxicity of plants. Soil culture experiment was carried out in the greenhouse to study the effect of hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)) on the chromium dynamics in soil solution and chromium uptake by rice under flooded and aerobic conditions. The results showed that Cr was not detected in the soil solution in the Cr(III) treatment, while the concentration of Cr(VI) increased with the addition of Cr(VI) in the soil. And the Cr(VI) concentration was generally lower in the flooded treatment than under the aerobic conditions. Cr(III) was not detected in the soil solution in all treatments. pH value in the soil solution ranged from 7.0 to 8.0, which was not significantly influenced by the addition of Cr and water management. In the Cr(VI) treatment, rice seedlings survived only at the treatment of 90 mg Cr(VI) per kg soil, while in the Cr(III) treatment, the biomass of rice seedlings decreased with the increasing concentration of Cr(III). Compared with the aerobic treatment, flooded treatment increased the biomass of rice seedlings with the exception of the treatment of 200 mg Cr(III) per kg soil. Under the aerobic condition, Cr(III) addition affected the rice grain filling, Cr concentrations in all parts of rice showed increasing trend with the increase of Cr(III) addition in soil under the flooded condition. And the highest Cr contents in the straw and brown rice were 33.80 mg?kg^-1 and 0.30 mg?kg^-1, respectively. The results indicated that Cr(VI) is more toxic to rice than Cr(III) because of its high-mobility in the soil.