改性生物炭对弱碱性Cd污染土壤钝化修复效应和土壤环境质量的影响

Effect of modified biochar on immobilization remediation of weakly alkaline Cd⁃contaminated soil and environmental quality

通过大田示范试验,研究了钙基改性生物炭对弱碱性Cd污染土壤的钝化修复效应及对土壤理化性质、团聚体结构、土壤酶活性和玉米体内Cd累积特征的影响.结果表明,向弱碱性土壤中添加改性生物炭提高了土壤pH值、有效态阳离子交换量和有机质含量.与对照相比,添加钙基改性生物炭后土壤有效态Cd(DTPA-Cd)含量的降幅达到12.0%~30.2%,且Cd赋存形态由活性较高的可交换态和可还原态向更稳定的残渣态转变.改性生物炭的施加明显降低了Cd在植物体内富集的风险,玉米根、茎、叶和籽粒中Cd含量明显受到抑制,3种玉米品种籽粒中Cd含量较对照分别下降了52.65%~72.56%(郑单958)、37.54%~50.80%(蠡玉16)和23.60%~51.20%(三北218).添加改性生物炭在一定程度上改善了土壤环境质量,土壤过氧化氢酶、脲酶和碱性磷酸酶活性随着改性生物炭施加量的增加呈逐渐升高的趋势.改性生物炭处理下,5~8 mm和2~5 mm粒级团聚体所占比例增加,而≤0.25 mm粒级团聚体占比有所下降,团聚体平均几何直径(GMD)和平均质量直径(MWD)分别增加了10.35%~29.34%和13.20%~27.03%,显示土壤团聚体稳定性增加.玉米籽粒中(郑单958)Cd含量与土壤有效态Cd含量呈显著负相关关系(p<0.01).研究表明,钙基改性生物炭在钝化修复弱碱性Cd污染土壤和改善土壤环境质量方面具有一定的研究前景和可行性.

Field demonstration experiments were conducted to investigate the effects of Ca-based modified biochar on immobilization remediation of weakly alkaline Cd-contaminated soil,physiochemical properties,aggregate structure,enzyme activity and Cd accumulation in maize.The results showed that the values of pH,available cation exchange capacity and organic matter were increased after applying modified biochar to soil.Compared with the control treatments,the content of DTPA⁃Cd reduced by 12.0%to 30.2%,and the acid soluble and reducible states of Cd was converted into residual form in contaminated soil.The application of modified biochar reduced the risk of Cd enrichment in maize,and the content of Cd in root,stem,leaf and grain of maize was significantly inhibited.The concentration of Cd in the three maize grain decreased by 52.65%~72.56%(Zhengdan 958),37.54%~50.80%(Liyu 16)and 23.60%~51.20%(Sanbei 218),respectively,in contrast with CK.The addition of modified biochar could improve the soil environmental quality,and the activity of catalase,urease and alkaline phosphatase increased gradually with increasing modified biochar.The percentage of 5~8 mm and 2~5 mm particle aggregates was increased after applying modified biochar,while the ratio of particle aggregates(≤0.25 mm)was reduced,the amount of geometric mean diameter(GMD)and mean weight diameter(MWD)of soil aggregates increased by 10.35%~29.34%and 13.20%~27.03%,respectively,indicating the stability of aggregates improved.There was an extremely(p<0.01)correlation between the content of Cd in the maize grain(Zhengdan 958)and the extracted content of Cd in soil.Therefore,Ca⁃modified biochar has research prospects and feasibility in immobilization remediation of weakly alkaline Cd⁃contaminated soil and improvement of soil environmental quality.