炭基微生物菌剂对红壤性水稻土-水稻系统中Cd行为的影响

Effects of Biochar-Based Microbial Agent on the Behavior of Cd in Red Paddy Soil-Rice System

为探讨炭基微生物菌剂使土壤Cd生物活性降低和水稻对Cd吸收减少的可能性,采用盆栽试验,以单施NPK化肥为对照(CF),对比分析了石灰、牡蛎壳粉和炭基微生物菌剂对Cd污染红壤性水稻土土壤化学性质、土壤Cd形态分布和水稻Cd吸收迁移的影响。结果表明,添加石灰和牡蛎壳粉均可显著提高土壤pH值(增加0.31~0.86个单位),添加炭基微生物菌剂能提高土壤总有机碳(TOC)含量,较CF增幅为10.04%(P<0.05)。添加石灰、牡蛎壳粉和炭基微生物菌剂均对生物有效Cd(DTPA有效态、酸可提取态)含量有显著的降低作用。与对照相比,添加石灰、牡蛎壳粉和炭基微生物菌剂处理的DTPA有效态Cd含量分别显著降低了24.97%、19.52%和17.13%(P<0.05),同时促进土壤Cd从酸可提取态向残渣态转化。此外,添加炭基微生物菌剂对水稻成熟期的根系、茎叶和籽粒的干物质积累均具有较明显的促进作用。与对照相比,石灰和炭基微生物菌剂处理后糙米Cd含量分别降低了42.83%和54.57%(P<0.05),糙米对土壤Cd的生物富集系数(BCF)降低了41.57%和53.93%(P<0.05)。相关分析结果显示,土壤DTPA有效态Cd含量与pH值呈显著负相关,水稻植株(糙米、茎叶、根系)Cd含量与酸可提取态和可还原态Cd含量呈显著正相关(P<0.05)。线性预测方程证明糙米中Cd积累直接来自根系和秸秆的转移,而且土壤中酸可提取态Cd是糙米中Cd积累的最佳预测因子。综上,石灰、炭基微生物菌剂对Cd污染红壤性水稻土都表现出很好的修复效果,从降镉和协同提升土壤质量的角度来看,炭基微生物菌剂可作为一种比较理想的镉污染稻田土壤修复改良剂。本研究结果为南方红壤性稻田Cd污染治理提供了新思路。

A pot experiment was conducted with rice cultivated in Cd-contaminated red paddy soils to investigate the potential of biochar-based microbial agents in mitigating soil Cd bioactivity and its subsequent uptake by rice plants.Taking single application of NPK fertilizer as control,the research focused on comparing the effects of lime,oyster shell powder,and biochar-based microbial agents on soil chemical characteristics,Cd forms in soil,and rice Cd uptake and migration in rice.The results demonstrated that the addition of lime and oyster shell powder considerably increased soil pH by 0.31 to 0.86 units.Moreover,the addition of a biochar-based microbial agents had the potential to increase total organic carbon content(TOC,increased by 10.04%,P<0.05).The amount of bioavailable Cd,including DTPA-extractable Cd and acid-extractable Cd,was significantly decreased by the addition of lime,oyster shell powder,and biochar-based microbial agents.A marked decrease in DTPA-extractable Cd by 24.97%,19.52%,and 17.13%(P<0.05),respectively,were observed when compared with the control group.Additionally,these treatments promoted the conversion of soil Cd from an acid-extractable form to a residual form.Addition of the biochar-based microbial agents significantly impacted the dry matter accumulation in various parts of rice plants at the mature stage.Cd concentration in brown rice was also significantly reduced by 42.83%and 54.57%(P<0.05),respectively,after treatment with lime and the biochar-based microbial agents.These treatments further resulted in a decrease in the bioconcentration factor(BCF)of brown rice for soil Cd by 41.57%and 53.93%(P<0.05),respectively.The Cd content in rice tissues(brown rice,straw,and root)and the Cd content in acid-extractable and reducible forms showed a significant positive association,while DTPA-extractable Cd and soil pH showed a significant negative correlation(P<0.05).The constructed linear prediction equation showed that Cd accumulation in brown rice was directly transferred from roots and straw,with acid-extractable Cd in soil being the optimal predictor of Cd accumulation in brown rice.In summary,both lime and biochar-based microbial agents were effective in remediating Cd-contaminated red paddy soils.However,biochar-based microbial agents were identified as the superior remediation method,due to their ability to reduce Cd levels and improve soil quality in Cd-contaminated paddy fields.This study offers a novel approach to reducing Cd pollution in red paddy fields in southern China.