华南多金属尾矿库生物结皮对重金属的固定机制

水分及氧气是多金属尾矿砂氧化产酸致重金属释放的重要驱动因子。传统的控制思路是构建隔离层以切断水、气与尾矿砂接触的途径，但往往忽视了在水、气持续输入情况下实现重金属固定的可能性。生物结皮是受损土壤生态系统原始演替的先锋，具有对多金属尾矿库重金属污染进行原位控制的潜力。本项目针对华南地区多金属矿尾矿库处于干湿交替乃至淹水状态的特点以及生物结皮中藻类大量释放氧气的特性，通过野外调查及室内模拟，结合XPS、ICP-MS、HRTEM、微生物信息学分析等手段，研究尾矿库生物结皮的特异性形成过程及结构组分，考察研究结皮中生物、非生物组分对重金属的吸附固定的贡献，尤其是从硫氧化及Fe、Mn、Al矿质化（形成次生氧化物）过程对重金属释放、固定的竞争关系阐明生物结皮在水、气持续输入条件下对重金属原位固定的机制。研究结果对于原位控制尾矿库重金属污染具有重要参考价值，也可拓宽学界对生物结皮生态系统服务功能的认识。

Water and oxygen are the important driving factors for heavy metal release from polymetallic tailings. The traditional control idea is to construct an isolation layer to cut off the contact between water/air and tailings. However, the possibility of heavy metal immobilization under the condition of continuous water and air input is often ignored. Biocrust is the pioneer in the original succession of damaged soil ecosystem and has the potential to control the heavy metal pollution of polymetallic tailing ponds in situ. Based on the dry-wet shift and even flooding characteristic, and the strong oxygen producing ability of alga in biocrust as well, in polymetallic mine tailings in southern China, a series of field investigation and indoor simulation experiment are designed. With techniques of XPS, ICP-MS, HRTEM and microbial bioinformatics analysis, we study the specificity of the tailings biocrusts’ forming process and structure of components, investigate the contributions of biotic and abiotic components in biocrust to heavy metal adsorption and immobilization. In particular, we illustrate the in situ heavy metal immobilization by biocrust in a circumstance with continuous water and air input by evaluating the competition between sulfide oxidation resulting in heavy metal release Fe, Mn and Al mineralization resulting in heavy metal immobilization. The expected results have important reference value for in-situ control of heavy metal pollution in tailing ponds, and can also broaden the scientific understanding of the ecosystem service function of biocrust.