生物质炭对水稻根际土壤Cd形态转化的影响及作用机制

Cadmium contamination on farmland soil is increasingly serious in China. Rice has been found to a food crop with high capacity to accumulate Cd. As Cd has the stronger environment transfer and bio-toxicity, it is easy to affect human health through the food chain migration. Biochar has important significance in passivating the soil Cd, reducing bio-toxicity and hindering the Cd transfer to rice for ensuring rice safety. But it is not clear to the mechanism on the effectiveness of reducing Cd through biochar. This research adopts the method of molecular biology such as FISH, PCR-DGGE were used by pot and root-bag experiment, in order to further study: 1) The characteristic of conversion on cadmium contaminated paddy soil through the different types of biochar input; 2) The effect of biochar on rhizosphere microenvironment, especially the microbial diversity; 3) The influence of biochar on aggregates microenvironment and the existing forms of Cd. By these researches, it indicates the passivation effect of three special biochars on cadmium contaminated paddy soil; the effect of biochar on recovery of ecological diversity of microorganism to the Cd availability and aggregate microenvironment characteristics and functions of biochar on the passivation process of soil Cd. These researches provide scientific basis and technical support for enriching the theory of passivation and remediation of biochar on cadmium contaminated paddy soil.

我国农田土壤Cd污染问题日趋严峻，水稻籽粒因具有高镉吸收积累能力而受到广泛关注。具有较强环境迁移和生物毒性的Cd元素易通过食物链迁移富集影响人类健康。利用生物炭钝化土壤Cd形态，降低生物毒性，阻控水稻吸Cd，对保障稻米安全具有重要现实意义，但其钝化修复的作用机制尚不明确。本项目采用原状土盆栽模拟和根袋实验，运用原位荧光杂交（FISH）、变性梯度凝胶电泳(PCR-DGGE)等手段，深入研究：1）不同类型生物质炭输入下污染根际水稻土Cd赋存形态的转化特征；2）生物质炭对根际土壤微环境的影响；3）生物质炭对团聚体微域环境及Cd赋存形态的影响。明确3种特色生物质炭对Cd污染土壤的钝化效果；揭示生物质炭输入下根际土壤微生物分子生态多样性恢复对Cd生物有效性的影响；明晰生物质炭钝化土壤Cd形态过程中团聚体微域环境的特性与作用。通过上述研究为丰富生物质炭修复Cd污染水稻土理论提供重要科学依据和技术支撑。

我国农田土壤Cd污染问题日趋严峻，具有较强环境迁移和生物毒性的Cd元素易通过食物链迁移富集影响人类健康。利用生物炭钝化土壤Cd形态，降低生物毒性，阻控水稻吸Cd，对保障稻米安全具有重要现实意义。本项目采用原状土盆栽模拟和根袋实验，运用原位荧光杂交（FISH）、高通量测序等分子生物学手段，深入研究生物质炭输入下污染根际水稻土Cd赋存形态的转化特征及其作用机制。研究结果表明生物质炭输入后可改变镉在土壤中赋存比例，使土壤中可交换态镉比例降低并向残渣态转化，从而降低镉的生物有效性。Cd污染条件下，生物质炭的施用提高了土壤中碳代谢酶及氧化还原酶的活性，增强了微生物群落碳源代谢活性及功能多样性，2.5%生物质炭处理下的提高效果尤为突出；土壤微生物的碳源代谢活性及功能多样性在不同粒级团聚中呈“V”型分布，5～1mm、<0.25mm团聚中最高。<0.25mm微团聚体中微生物碳代谢功能多样性重金属Cd胁迫效应与生物质炭保护效应均最显著。生物质炭的施用恢复了Cd污染土壤的细菌基因多样性，2.5%生物质炭用量下的恢复效果显著；土壤细菌丰富度提高了6.79%～21.04%；变形菌门（Proteobacteria）、酸酐菌门（Acidobacteria）、芽单胞菌门（Gemmatimonadetes）为主的43个菌门构成红壤中细菌群落。进一步分析阐明，Cd污染和生物质炭施用均能影响细菌基因多样性。Steroidobacter、Bradyrhizobium、Anaerolinea、Chloronema为生物质炭修复Cd污染过程的关键影响菌种。该结果明确生物炭对Cd污染土壤的钝化效果；揭示生物炭输入下根际土壤微生物分子生态多样性恢复对Cd生物有效性的影响。为丰富生物炭修复Cd污染水稻土理论提供重要科学依据和技术支撑。