钙肥配施生物质炭-铁锰复合材料对酸化水稻土中镉砷的钝化

Passivation of Cadmium and Arsenic in Acidified Paddy Soil by Calcium Fertilizer with Biochar-ferromanganese Composites

大气氮、硫沉降的加剧和肥料的不合理施用,导致土壤酸化问题愈发严重;在重金属污染土壤中,酸化不仅会严重影响地力,还会使常规钝化修复材料(如生物质炭)的有效性和持续性受到影响.施用钙肥或可改善土壤酸化,同时缓解生物质炭材料在土壤中的老化,提高其对复合污染土壤的修复能力,然而其影响机制尚不明确.基于此,选取铁锰氧化物(FM)与山核桃蒲生物质炭(BC)制备生物质炭-铁锰复合材料(BFM),并对其进行模拟酸化,通过表征及水溶液吸附试验,探究酸化后材料理化性质及其吸附性能的变化;而后开展正交试验,探究酸化条件下BFM与钙肥配施对土壤pH和Cd、As有效性的影响并得到最佳配施方案.结果表明,BFM中BC和FM的最佳比例为7∶3(质量比),对Cd(Ⅱ)和As(Ⅲ)的去除率分别高达94.58%和97.14%,吸附容量为120.74 mg·g^(-1)和129.29 mg·g^(-1)(固液比1∶500).酸化处理后BFM表面孔隙结构减少,官能团种类和数量变化,导致材料对水溶液中Cd(Ⅱ)和As(Ⅲ)的去除率分别下降73.97%~92.84%和73.56%~93.61%.钙肥与BFM配施能显著提高土壤pH,提升幅度为3.06%~37.84%;对pH的提升效果随培养时间和酸化程度的增加而下降.与空白对照相比,配施使土壤有效态Cd含量显著降低了22.67%~97.78%;土壤有效态As含量总体较为稳定.对正交试验结果进行效应曲线分析可得,在酸化程度较弱(pH=5.6)的情况下,以2%添加量配合2%的硅钙肥和2%的钙镁磷肥共同施用对土壤Cd具有较好的钝化效果;在酸化程度较强(pH=4.0)的情况下,以2%添加量配合2%的硅钙肥共同施用对土壤As具有较好的钝化效果.综上所述,模拟酸化会影响BFM的吸附性能,钙肥与之配施后能够提高土壤pH,改善土壤酸化,同时缓解BFM在酸化土壤中的老化并改善其对重金属污染土壤的修复能力.

Due to the aggravation of atmospheric nitrogen and sulfur deposition and the unreasonable application of fertilizer,soil acidification is becoming increasingly serious.In heavy metal-contaminated soils,acidification not only seriously affects fertility but also the effectiveness and sustainability of conventional passivation remediation materials such as biochar.The application of calcium fertilizer may improve soil acidification,alleviate the aging of biochar materials in soil,and improve its remediation ability to composite polluted soil.However,the mechanism of its effect is still unclear.Based on this,this study selected iron-manganese oxide(FM)and hickory cattails biochar(BC)to prepare biocharferromanganese composites(BFM)and conducted simulated acidification on it.Through characterization and an aqueous adsorption test,the changes in physicochemical properties and adsorption properties of the material after acidification were explored.Then,orthogonal tests were carried out to explore the effects of the combination of BFM and calcium fertilizer on soil pH and the availability of Cd and As under acidification conditions and to obtain the best combination scheme.The results showed that the optimal ratio of BC and FM in BFM was 7∶3(quality ratio),the removal rates of Cd(Ⅱ)and As(Ⅲ)were as high as 94.58%and 97.14%,respectively,and the adsorption capacities were 120.74 mg·g^(-1) and 129.29 mg·g^(-1)(solid-liquid ratio 1∶500).After acidification treatment,the pore structure of BFM surface decreased,and the types and quantities of functional groups changed,resulting in the removal rates of Cd(Ⅱ)and As(Ⅲ)in aqueous solution decreasing by 73.97%-92.84%and 73.56%-93.61%,respectively.The combined application of calcium fertilizer and BFM could significantly increase soil pH,with an increase range of 3.06%-37.84%.The effect of increasing pH decreased with the increase in culture time and acidification degree.Compared with that in the blank control,the content of available Cd in soil was significantly reduced by 22.67%-97.78%.The content of available As in soil was generally stable.According to the effect curve analysis of the orthogonal test results,under the condition of weak acidification degree(pH=5.6),the application of 2%supplemental amount with 2%silica-calcium fertilizer and 2%calcium-magnesium phosphate fertilizer had a good passivation effect on soil Cd.Under the condition of strong acidification degree(pH=4.0),the application of 2%supplemental amount and 2%silica-calcium fertilizer had a good passivation effect on soil As.In summary,simulated acidification will affect the adsorption performance of BFM,and calcium fertilizer combined with it can increase soil pH,improve soil acidification,alleviate the aging of BFM in acidified soil,and improve its repair ability to heavy metal-polluted soil.