竹炭促进沙柳镉转运和积累的生理生态机制

利用生物炭等土壤改良剂结合速生树种开展辅助植物修复，对于促成金属矿区及重污染土壤的植被建成、提升修复效果，具有较大潜力。目前，对生物炭与树木在重金属重污染土壤的相互作用缺乏认识。本项目在前期基础上，从柳树根际过程和生理响应2个角度，研究竹质生物炭（竹炭）促进重污染土壤中柳树Cd转运和积累的作用机制：定量分析根际土壤Cd形态和根系构型及根系分泌物响应，解析竹炭促进Cd的土壤-根系界面传输过程；利用108Cd示踪和X射线荧光光谱等技术，揭示柳树体内Cd的转运途径及竹炭对Cd分布的影响；通过光合作用和蒸腾速率、木质部和韧皮部有机酸及Cd形态分析，揭示竹炭对Cd转运驱动力及形态的影响，最终阐明竹炭促进重污染土壤柳树Cd转运和积累的作用机制。该研究对于了解生物炭-树木-土壤重金属的交互作用机制具有科学意义，对于推动生物炭辅助树木修复重金属重污染土壤具有实践价值。

Biochar amendment helps to establish vegetation and improve phytoremediation efficiency using fast-growing woody plant like Salix via immobilization metals, decrease metal toxicity and improve soil quality of severely polluted soils. However, the study and understanding on the interactions mechanisms among biochar-willow-metals system in severely polluted soil are rarely. Our previous results suggested that biochar amendment significantly enhanced root-shoot translocation and accumulation of cadmium by Salix psammophila grown in soil severely polluted by cadmium and zinc. Therefore, this proposal focuses on the interaction mechanisms of biochar amendment on cadmium translocation and accumulation in S. psammophila grown in severely polluted soil, via the investigation of the bioavailability of cadmium in rhizosphere soil, and the physiological responses, and cadmium form and space distribution in plant tissues. The cadmium availability in rhizosphere soil, root architecture and root exudates response will be analyzed to elucidated the soil-root interface of cadmium as affected by biochar amendment. 108Cd stable element tracer and X-ray fluorescence spectrum will be applied to obtain the direct evidence of translocation pathway and spatial distribution of cadmium in S. psammophila. The relationship between the photosynthesis rate and transpiration rate, and the organic ligands and cadmium in saps of xylem and phloem in S. psammophila will be evidenced and analyzed. These results will clarify the mechanisms in molecular level on enhanced root-shoot translocation and accumulation of cadmium in S. psammophila by biochar amendment in severely polluted soil. The results will shed light on the interactions mechanism of heavy metals in biochar-woody plants-soil system in severely polluted soils. It will also provide guideline on the application biochar on assisted phytoremediation using fasting growing trees in vegetation restoration and phytoremediaton to severely polluted soil.