模拟降水对碱性盐化土壤中镉的淋滤及形态变化的影响

采用人工模拟方式,试验研究了不同pH值的降水对碱性盐化土壤中镉的连续淋滤效果,分析了淋洗后土壤中镉的形态变化特征。结果表明,在不同pH值降水对土壤中镉的淋滤过程中,12h内基本上达到高峰,12h后镉的淋滤量较低,随着时间的延续镉的淋洗量基本保持不变;降水有利于土壤中的镉释放,且pH值越低,镉的释放量越高。土壤盐化对降水淋洗镉的效果有一定影响,氯化物的存在,有利于镉的淋滤,淋滤量增加值在18%～94%之间,随着淋洗液pH值的增加,镉的淋滤量增加幅度减少;与对照组土壤样品相比,淋洗液pH降低利于增大硫酸盐型盐化土壤中镉的淋滤量,当pH值为中性时,镉的淋滤量减少;苏打型盐化土壤镉的淋洗效果与硫酸盐型土壤相似。模拟降水淋洗后,土壤中镉的形态发生明显变化,与淋洗前相比,土壤中镉的可交换态、碳酸盐结合态、有机结合态的质量分数降低,随着淋洗液酸性的增加,降低幅度增大;镉的铁锰氧化态相对质量分数在淋洗后有所增加。

Simulated rainfall leaching cadmium and cadmium fraction changes in soils

Alkaline salinity soils wes selected as the sample for simulated acid rain leaching experiment to investigate the release and fraction changes of cadmium.The results showed that leached cadmium content reached a peak within 12 hours.The leached cadmium content was lower after 12 hours and the leaching content changes little.Rainfall was favor of cadmium activation,and more cadmium contents was leached from soil wich the pH value of the leachate decresases.Soil salinity had influence on cadmium leaching effect.The presence of chloride in soils was beneficial to the leaching of cadmium and the leached cadmium content increased 18%-94%.Te amount of leached cadmium reduced with the pH value of the leachate increase.If there was sulfate in soils,leached cadmium content increased when the pH values of the leachate were lower than 7,and when the pH value of the leachate was 7,leached cadmium content was lower than the no-salinization soils.Soda type soils had similar effect with the sulfate soils.After leached,the cadmium fraction in soils changed,and the cadmium exchangeable,carbonate,organic phase content decreased while cadmium iron and manganese oxidation state increased.