改性生物炭对农田土壤铬形态分布和酶活性的影响

为研究改性牛粪生物炭对土壤铬形态分布和酶活性的影响,以HNO₃改性牛粪生物炭、FeCl₃改性牛粪生物炭和原始牛粪生物炭为研究对象,研究3种改性生物炭对农田土壤铬形态分布、土壤理化特性和酶活性的影响。结果显示:HNO₃改性牛粪生物炭和FeCl₃改性牛粪生物炭相比于原始牛粪生物炭,比表面积、总孔容、微孔比表面积分别提升了2.86 m²·g^-1、0.004 cm³·g^-1、0.01 m²·g^-1和11.09 m²·g^-1、0.013 cm³·g^-1、2.20 m²·g^-1,但平均孔径分别下降了1.28 nm和3.86 nm。与未改性生物炭相比,改性生物炭官能团种类没有变化,但羟基(—OH)、羧基(—COOH)和羰基(C=O)均得到强化。Cr(Ⅵ)吸附试验中,3种生物炭均表现出良好的吸附效果,尤其是FeCl₃改性牛粪生物炭的吸附效果最优,最大吸附量达到15.90 mg·g^-1。土壤培养试验结束时(60 d),添加生物炭的土壤酸可溶态、可还原态和可氧化态铬含量分别比未添加生物炭土壤降低0.97%~2.15%、0.28%~0.94%、4.70%~9.40%。而在添加改性生物炭的土壤中残渣态铬含量(42.3%~45.2%)显著高于添加未改性生物炭的土壤(38.6%)和对照土壤(32.8%)。相关性分析结果表明,生物炭主要通过提高土壤pH、阳离子交换量和有机质含量,促进土壤中的酸可溶态铬向残渣态转化,其中FeCl₃改性牛粪生物炭的促进效果最优。生物炭的添加降低了土壤中铬的毒害作用,同时提升了土壤中脲酶、蔗糖酶和脱氢酶的活性,其中改性生物炭对土壤酶的促进效果优于原始生物炭。研究结果证明改性生物炭可以作为一种低成本、环保的吸附剂来有效修复Cr(Ⅵ)污染土壤。

Effects of modified biochar on Cr speciation and enzyme activity in farmland soil

In order to study the effects of the modified cow dung biochar on Cr speciation and enzyme activity in soil,we investigated the effects of HNO₃-modified biochar,FeCl₃-modified biochar,and unmodified cow manure biochar on Cr morphology and distribution,soil physicochemical properties,and enzyme activities.The results showed that external surface area,total pore volume,and micropore surface area of HNO₃-modified biochar were 2.86 m²·g^-1,0.004 cm³·g^-1,and 0.01 m²·g^-1 and those of FeCl₃-modified biochar were 11.09 m²·g^-1,0.013 cm³·g^-1,and 2.20 m²·g^-1 higher than those of unmodified biochar,respectively.However,the average pore size decreased by 1.28 nm and 3.86 nm for HNO₃-modified biochar and FeCl₃-modified biochar,respectively.Modified biochars had similar types of functional groups,with an increased abundance of hydroxyl(-OH),carboxyl(-COOH),and carbonyl(C=O).Batch sorption experiments revealed that all biochars had remarkable sorption performance;the highest Cr(Ⅵ)reduction was observed with FeCl₃-modified biochar application(up to 15.90 mg·g^-1).After a soil incubation test(60 d),the acid soluble,reducible,and oxidizable fractions of Cr(Ⅵ)in soil amended with added biochar were approximately 0.97%~2.15%,0.28%~0.94%and 4.70%~9.40%,respectively,lower than the values for the controlled study.The residue fraction(approximately 42.3%~45.2%)of Cr(Ⅵ)was significantly(P<0.05)higher in soil amended with modified biochar than in soil amended with unmodified biochar(38.6%)and not amended with biochar(32.8%).Correlation analysis results show that biochar remarkably changed soil physiochemical properties by increasing soil pH,organic matter,and cation exchange capacity and promoted the conversion of Cr(Ⅵ)from an acid soluble state to a residue state in soil;these are the greatest effects of FeCl₃-modified biochar.The added biochar in soil caused a significant increase in the levels of urease,sucrase,and dehydrogenase in soil and reduced the toxicity of Cr(Ⅵ).Furthermore,soil enzyme activity with modified biochar was significantly higher than that of the controlled study and that with unmodified biochar.Our findings prove that modified biochar can be used as a low-cost and environment-friendly adsorbent to effectively remediate soils contaminated with Cr(Ⅵ).