Abstract:

The problem of cadmium pollution in cultivated land in China is serious, and the heavy metal passivation technology has attracted more and more attention. The key of this technology is the passivation performance of passivator. In order to seek high-efficiency passivator for cadmium contaminated soil, a new composite modified rice husk biochar material was prepared by phosphorylation-calcium salt composite modification for the remediation of cadmium contaminated soil. In this study, SEM-EDS and FTIR were used to characterize the apparent morphology and functional groups of the materials. Pot experiment was used to study the passivation effect of the materials on cadmium contaminated soil and the accumulation of cadmium in Chinese cabbage. The results showed that there were a large number of phosphates and -OH on the surface of composite phosphorylated rice husk biochar (TFQ), and a large amount of cadmium was adsorbed on the surface of TFQ. Compared with blank control, rice husk biochar (DT) and phosphorylated rice husk biochar (DTY), TFQ had the best passivation effect on soil cadmium. In the TFQ treatment, the distribution law of soil cadmium forms is as follows: iron manganese oxide bound state > residue state ≈ exchangeable state > organic bound state > carbonate bound state. Compared with the blank control, exchangeable cadmium in soil after the TFQ treatment changed significantly into an iron manganese oxide bound state. Compared with the blank control, about 94% of soil cadmium existed in an iron manganese oxide bound state, and the proportion of residue state was higher than that of other treatments, accounting for about 2.3%, and significantly enhanced the chemical stability of cadmium in soil. TFQ significantly increased soil pH, electrical conductivity and soil cation exchange capacity. At the same time, TFQ promoted the growth of Chinese cabbage and significantly reduced the content of cadmium in Chinese cabbage leaves. In conclusion, TFQ has a good effect on enhancing the stability of cadmium passivation in soil and reducing the cadmium content in Chinese cabbage leaves.

Key words: composite phosphorylated modified rice husk biochar, cadmium, passivation, Chinese cabbage, soil improvement

摘要：

中国耕地镉污染问题严峻,重金属钝化技术日益受到广泛关注,该技术的关键在于所施用钝化剂的钝化性能。为寻求高效镉污染土壤钝化剂,以稻壳生物炭为基体,采用磷酸化-钙盐复合改性手段制备新型复合稻壳生物炭材料用于镉污染土壤的钝化修复。采用SEM-EDS、FTIR表征材料形貌和表面功能基团,采用盆栽试验研究材料对镉污染土壤的钝化效果及小白菜镉积累的影响。结果表明,复合磷酸化稻壳生物炭（TFQ）材料表面存在大量磷酸根和-OH,大量镉吸附于TFQ材料表面上。与空白对照、稻壳生物炭（DT）和磷酸化稻壳生物炭（DTY）处理相比,TFQ对土壤镉的钝化效果最佳,TFQ处理中土壤镉形态分布规律为铁锰氧化物结合态>残渣态≈可交换态>有机结合态>碳酸盐结合态。与空白对照相比,TFQ处理后土壤中可交换态镉大幅向铁锰氧化物结合态转变,约94%土壤镉以铁锰氧化物结合态存在,残渣态比例较其他处理提高,约占2.3%,明显增强了土壤镉化学稳定性。TFQ显著提高了土壤pH值、电导率和土壤阳离子交换量,促进了小白菜生长,并显著降低小白菜叶片中镉含量。综上所述,TFQ对增强土壤镉稳定性和降低小白菜叶片镉含量具有良好效果。

关键词: 复合磷酸化稻壳生物炭, 镉, 钝化, 小白菜, 土壤改良