添加Delftia sp.B9对土壤Cd形态分布及水稻吸收积累Cd的影响

Effects of inoculation with the cadmium-resistant bacterium Delftia sp.B9 on soil Cd stabilization and reduction of Cd bioaccumulation in rice

为探究耐镉细菌Delftia sp.B9(菌株B9)对土壤镉(Cd)形态、水稻吸收Cd及土壤微生物群落结构的影响,本研究通过盆栽种植试验,在中度Cd污染土壤中施加不同添加量的菌株B9,并将最佳添加量应用在田间试验中验证菌株B9对土壤Cd的钝化作用及降低稻米Cd含量的效果。结果表明:盆栽试验中,与对照(CK)相比,菌株B9不同添加量均可显著提高土壤pH值,DTPA提取有效态Cd含量显著降低4.72%~15.65%,糙米Cd含量显著降低22.87%~59.90%。其中,菌株B9添加量为1.28 g·盆^(-1)(T2)时,土壤Cd的钝化效果及降低稻米Cd效果最好。与CK相比,T2处理可显著促进土壤弱酸可溶态Cd向可还原态、可氧化态及残渣态Cd转化。同时,T2处理显著提高了土壤微生物可操作分类单元(OTU)数,土壤微生物群落多样性及丰富度指数(ACE、Chao1、Shannon)均显著增加,菌株B9所属变形菌门(Proteobacteria)相对丰度显著增加。小区(株洲)早晚稻及大区(浏阳)中稻试验中,菌株B9添加量为12.50 g·m^(-2)时,稻米中Cd含量较对照组降低28.38%~91.43%。研究表明,添加菌株B9可降低土壤Cd潜在风险,降低中度Cd污染土壤中水稻吸收积累Cd的量,使稻米Cd含量符合国家食品卫生标准。

Bioremediation of Cd-polluted soil using metal-resistant bacteria has received increasing attention.In the present study,pot experiments were conducted to investigate the changes in soil Cd speciations,rice grain Cd accumulation,and soil microbial community structure after different Delftia sp.B9 biomass inoculations in the soil.Additionally,the optimum additive amounts of B9 were applied in the field experiments to verify the reductions of Cd in rice grain.The results showed that all different treatments with B9 biomass inoculations significantly increased soil pH and decreased the content of bioavailable Cd(extracted by DTPA)by 4.72%-15.65%.In comparison with CK,treatments with B9 addition decreased the Cd concentration in grains by 22.87%-59.90%;all grain Cd levels in the pot trials were within the acceptable range for food security in China(0.2 mg·kg^(-1)).T2(B9 application:1.28 g·pot-1)was the most effective remediation treatment that enhanced soil Cd fractionations into more stable forms and significantly reduced Cd accumulation in rice grains.The treatment T2 significantly increased the operational taxonomic units(OTUs)and microbial community richness and diversity indexes(ACE,Chao1,and Shannon).The relative abundance of Proteobacteria(B9 is a member of this phylum)increased significantly.The application rate of B9 was 12.50 g·m^(-2),which significantly reduced the Cd accumulation by 28.38%-91.43%for rice grains in field conditions.Studies have shown that the application of B9 reduces the potential environmental risks posed by Cd in soils and improves food safety.