钙质钝化材料对四川盆地6种主要旱作土壤Cd的钝化效应

为针对性、定量化地利用钝化处理实现不同类型Cd污染土壤的安全利用,以四川盆地6种主要旱作土壤为研究对象,采用室内培养试验和土培试验探讨了6个剂量水平下,钙质钝化材料对土壤pH、CEC、有效Cd含量、Cd形态、小白菜生物量和Cd含量的影响。结果表明:(1)钙质钝化材料可提升6种土壤的pH和CEC,土壤CEC随用量的增加而持续增加,而土壤pH在提升至微碱性水平后,不再随用量的增加而增加;(2)6种土壤有效Cd含量随钝化材料用量的增加先显著降低,后趋于平稳,用量＞2.5%后均无显著变化。该添加量下,有效Cd含量降幅为典型黄壤(63.32%)＞酸性紫色土(46.65%)＞漂洗黄壤(38.51%)＞中性紫色土(34.97%)＞石灰性紫色土(18.03%)＞灰潮土(16.60%);土壤中可交换态Cd主要向碳酸盐结合态、铁锰氧化物结合态和残渣态形态转化;(3)除石灰性紫色土外,钙质钝化材料可显著提升其余5种污染土壤中小白菜的生物量并显著降低其可食部位Cd含量。用量为2.5%时,典型黄壤、漂洗黄壤和酸性紫色土中小白菜Cd含量降幅高达84.28%,79.90%,69.87%,显著优于中性紫色土、灰潮土和石灰性紫色土(5%用量时降幅仅为40.27%,31.13%,17.98%)。该研究揭示钙质钝化材料对6种Cd污染旱作土壤的剂量-效应差异,并在典型黄壤、漂洗黄壤和酸性紫色土中钝化效率较优,为不同土壤条件下钙质钝化材料的合理使用提供科学依据。

The Immobilizing Effects of Calcareous Amendment on Cd in Six Main Dry Soils in Sichuan Basin

In order to realize the safe utilization of different types of Cd-contaminated soil by amendment treatment, the effects of calcium amendment material on soil pH, CEC, available Cd content, Cd fraction, biomass and Cd content of Chinese cabbage under different dosage levels were studied by laboratory culture and soil culture experiments. The results showed that: (1) The pH and CEC of the six soils were increased by calcium amendment material, and the CEC of the soil continued to increase with the increase of the amount of calcium amendment material, while the pH of the soil did not increase with the increase of the amount of calcium amendment material. (2) With the increase of amendment material dosage, the content of available Cd in the six soils decreased significantly at first and then stabilized, and there was no significant change when the amount of amendment material was greater than 2.5%. Under this addition level, the decrease of effective Cd content was as follows: typical yellow soil (63.32%) > acid purple soil (46.65%) > rinsed yellow soil (38.51%) > neutral purple soil (34.97%) > calcareous purple soil (18.03%) > lime-aquic soil (16.60%). The exchangeable Cd in soil mainly changed to carbonate binding state, Fe-Mn oxide binding state and residue state. (3) Except calcareous purple soil, calcareous amendment material significantly increased the biomass of Chinese cabbage in the other five contaminated soils and significantly decreased the content of Cd in the edible parts. When the dosage was 2.5%, the Cd content of Chinese cabbage in typical yellow soil, rinsed yellow soil and acid purple soil decreased by 84.28%, 79.90% and 69.87%, which was significantly better than that in neutral purple soil, lime-aquic soil and callitic purple soil (the decrease was only 40.27%, 31.13% and 17.98% when the dosage was 5%). This study revealed the dose-effect difference of calcium amendment material on six kinds of Cd polluted upland soils, and the immobilizing efficiency was better in typical yellow soil, rinsed yellow soil and acid purple soil, which provided a scientific basis for rational use of calcium amendment material under different soil conditions.