Effects of Agricultural and Forestry Biochar on Soil Heavy Metal Cr Toxicity

doi:10.11924/j.issn.1000-6850.casb2025-0185

Abstract

Abstract:

This study investigated the efficacy of agricultural and forestry biochar in mitigating chromium (Cr) toxicity in artificially contaminated soil through a 40-day passivation treatment. Biochars derived from different biomass sources and pyrolysis temperatures were applied to the contaminated soil at varying ratios for pot experiments with coriander. Soil and plant samples were collected and analyzed at 0, 7, 14 and 21 days after cultivation to assess Cr immobilization and bioavailability. The results demonstrated that rice straw biochar pyrolyzed at 200°C for 4 h exhibited the highest efficiency in reducing Cr toxicity, and the effect was the best at an 8% application rate. The acid-extractable Cr content in the soil decreased by 99.8% after 7 days, while the leaching concentration of Cr (VI) dropped from an initial 175.08 μg/g to undetectable levels. Furthermore, Cr was effectively stabilized in the soil, significantly inhibiting its accumulation in the roots, stems and leaves of coriander. These findings indicated a substantial reduction in both Cr toxicity and mobility. Risk Assessment Code (RAC) analysis confirmed that the environmental risks associated with Cr contamination were markedly reduced after 7 days of treatment with 4% and 8% rice straw biochar. The study highlighted that agricultural and forestry biochar could facilitate soil remediation by converting Cr into residual and less bioavailable forms, thereby reducing soil toxicity. Additionally, this approach supports the sustainable reutilization of agricultural and forestry biomass.

Key words: biochar, chromium, soil remediation, morphological migration, pot experiment

ZUO Xiangru, WU Xue, LU Kangle, XIA Minyi, ZHANG Jiaan, ZHANG Zifang, XIONG Qiao. Effects of Agricultural and Forestry Biochar on Soil Heavy Metal Cr Toxicity[J]. Chinese Agricultural Science Bulletin, 2025, 41(23): 90-100.

Figures/Tables 13

References 31

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组分	操作方法
弱酸可提取态(F1)	将0.5 g样品加入到20 mL的0.1 mol/L HOAc，放在恒温振荡器中25℃下连续震荡16 h
可还原态(F2)	向上一步的残渣中加入20 mL 0.5 mol/L NH₂OH·HCl，放在恒温振荡器中25℃下连续震荡16 h
可氧化态(F3)	向上一步的残渣中加入5 mL 30% H₂O₂，搅拌均匀后室温静置1 h后用水浴加热至85℃，再加入5 mL 30% H₂O₂，在恒温85℃下保持1 h，加入25 mL 1 mol/L的NH₄OAC放在恒温振荡器中25℃下连续震荡16 h
残渣态(F4)	残渣中重金属含量

组分	操作方法
弱酸可提取态(F1)	将0.5 g样品加入到20 mL的0.1 mol/L HOAc，放在恒温振荡器中25℃下连续震荡16 h
可还原态(F2)	向上一步的残渣中加入20 mL 0.5 mol/L NH₂OH·HCl，放在恒温振荡器中25℃下连续震荡16 h
可氧化态(F3)	向上一步的残渣中加入5 mL 30% H₂O₂，搅拌均匀后室温静置1 h后用水浴加热至85℃，再加入5 mL 30% H₂O₂，在恒温85℃下保持1 h，加入25 mL 1 mol/L的NH₄OAC放在恒温振荡器中25℃下连续震荡16 h
残渣态(F4)	残渣中重金属含量

活性形态所占比例	RAC风险等级
RAC<1%	无风险
1%<RAC<10%	低风险
10%<RAC<30%	中等风险
30%<RAC<50%	高等风险
RAC>50%	极高风险

活性形态所占比例	RAC风险等级
RAC<1%	无风险
1%<RAC<10%	低风险
10%<RAC<30%	中等风险
30%<RAC<50%	高等风险
RAC>50%	极高风险

处理	7 d		14 d		21 d
处理	风险值	风险等级	风险值	风险等级	风险值	风险等级
空白	27.45	中等风险	23.39	中等风险	22.17	中等风险
1%BC200	19.78	中等风险	14.75	中等风险	11.68	中等风险
2.5%BC200	13.32	中等风险	10.71	中等风险	7.53	低风险
4%BC200	9.99	低风险	7.44	低风险	7.38	低风险
8%BC200	8.08	低风险	7.80	低风险	6.25	低风险