生物炭对土壤-植物体系中铅镉迁移累积的影响

为探讨不同特性生物炭对土壤-植物体系中典型重金属铅（Pb）和镉（Cd）迁移累积的影响，分别选择花生壳、水稻壳、小麦秸秆、椰壳及生物燃气副产物5种材料制备的生物炭及不同粒径椰壳生物炭作为土壤调理剂，进行多茬蔬菜盆栽试验，研究各茬蔬菜可食用部位生物量及Pb和Cd累积量，土壤理化性质及土壤有效态Pb和Cd含量变化规律。结果显示，生物炭的施加均可不同程度提升土壤pH、土壤有机碳含量及阳离子交换量（CEC）。除小麦秸秆生物炭外，其余4种生物炭均可显著降低土壤有效态Pb和Cd及蔬菜可食用部位Pb和Cd累积量，并对蔬菜有明显促生长效果。生物炭粒径越小对土壤有效态Pb和Cd含量的降低、蔬菜生长的促进及蔬菜Pb和Cd累积量的降低作用越显著。蔬菜生长与土壤pH、有机碳含量及CEC水平均呈显著正相关关系，而蔬菜Pb和Cd累积量及土壤有效态Pb和Cd含量则与土壤pH、有机碳及CEC含量呈显著负相关关系。连续3茬蔬菜轮作后，80~120目椰壳生物炭、花生壳生物炭、水稻壳生物炭及生物燃气副产物生物炭仍对Pb和Cd复合污染酸性土壤具有明显的修复效果。结果表明，生物炭可通过改变土壤pH、CEC、有机碳等基本理化性质，对土壤重金属产生钝化作用，显著促进蔬菜的生长并可消减蔬菜对土壤重金属元素的累积效应。

Effects of biochar on the migration and accumulation of lead and cadmium in soil-plant systems

The aim of the present study was to examine the effects of different biochar treatments on the migration and accumulation of heavy metals(lead and cadmium)in soil-plant systems. Pot experiments were conducted based on biochar treatments comprising peanut shells, rice husks, wheat straw, coconut husks, or biogas waste products of varying particle sizes. Then, the biomass and accumulation of lead and cadmium in edible plant parts, the variation in soil physical and chemical properties, and the available lead and cadmium contents in the soil were determined. The results showed that biochar application could improve soil pH, soil organic carbon content, and cation exchange capacity(CEC)to varying degrees. With the exception of wheat straw biochar, the other four biochar treatments significantly reduced the accumulation of available lead and cadmium in the soil and edible plant parts and had obvious growth-promoting effects on vegetables. The smaller the biochar particle size, the more significant the decrease in soil available lead and cadmium contents, the more obvious the promotion of vegetable growth, and the greater the decrease in vegetable lead and cadmium accumulation. Vegetable growth was significantly positively correlated with soil pH, organic carbon content, and CEC, whereas vegetable lead and cadmium accumulation and soil available lead and cadmium contents were significantly negatively correlated with soil pH, organic carbon content, and CEC. After three successive crops of vegetables, coconut husk biochar of 80~120 meshes, peanut shell biochar, rice husk biochar, and biogas waste biochar still showed obvious beneficial effects on acid soils polluted with lead and cadmium. The above results show that most biochar treatments significantly promoted vegetable growth, reduced soil heavy metals contents, and mitigated the cumulative effects of soil heavy metals on vegetables by improving soil physicochemical properties such as soil pH value, CEC, and organic carbon content.