设施菜地土壤镉钝化剂筛选及应用效果研究

针对设施农田土壤重金属污染与农产品累积风险日趋严重的问题,以设施农田镉污染土壤(0.4~0.8 mg·kg-1)为研究对象,在室内钝化剂筛选实验的基础上,通过田间效果验证,重点探究炭基、磷基、硅酸盐、黏土矿物等钝化材料施加浓度和磷基-炭基钝化材料复合配施对土壤镉修复效果及对植物生长的影响。结果表明:施加生物质炭、羟基磷灰石、蒙脱石等钝化剂可明显降低土壤有效态镉含量,其中羟基磷灰石+生物质炭配施效果最好,土壤有效态镉含量降低46.52%~58.11%。与对照相比,施加钝化剂均能抑制油菜对镉的吸收和根部向地上可食部分转移,使油菜地上部镉的含量较CK降低3.9%~51.2%,全部低于《食品安全国家标准》(GB 2762—2016)食品中污染物限量。考虑生产成本、材料来源等因素,推荐羟基磷灰石(225 kg·hm-2)与0.6%生物炭复合添加配施为优选钝化剂组合。田间效果分析也表明,土壤EC与土壤有效态镉含量呈显著正相关,进一步证明污染设施菜地中施加钝化剂降低土壤镉的生物有效性,是实现设施菜地安全生产的可行措施。

Screening of amendments for the remediation of cadmium-polluted protected agriculture soil

Soil is an important carrier of the natural environment and agricultural production upon which mankind depends. In April 2014, a survey bulletin of soil pollution in China reported that the exceeding standard rate of Cd reached 7.0%, ranking first in the list of inorganic pollutants. Cd is one of the most toxic heavy metal elements, and has a strong chemical activity in the soil and long-lasting toxicity. So in view of the increasing seriousness of heavy metal pollution and risks of agricultural product accumulation in farmland, the effect of different application ratios of carbon-based, phosphorus-based, silicate, clay mineral and other materials, and combined phosphorus-carbon-based passivation materials in repairing cadmium polluted soil and plant growth were studied. The results showed that the application of biochar, hydroxyapatite, montmorillonite, and other materials can significantly reduce the bioavailable cadmium content in soil. Among these materials, hydroxyapatite and biochar significantly decreased the bioavailable cadmium content in soil, which decreased by 46.52%~58.11%. Compared to the control, the application of all passivating materials inhibited the accumulation of cadmium in plants and transfer from the roots to the edible parts. Compared to the control treatment, the Cd content in the ground parts of rapeseed was reduced by 3.9%~51.2%, which is lower than that of the GB 2762-2016 National Food Safety Standard. Therefore straw biochar, hydroxyapatite, montmorillonite, and other materials could effectively reduce the bioavailability of Cd. Considering the production cost and material source, it is recommended that hydroxyapatite(225 kg·hm^-2) compounded with 0.6% biochar be used as a combination of preferred materials. Additionally, there was a significant positive correlation between the electrical conductivity(EC) and available Cd content in soil. It was also identified that the application of passivating materials could be a feasible method of decreasing the bioavailability of cadmium in heavy metal-contaminated soil for ensuring safe production in vegetable fields.