藻菌生物膜胞外聚合物与铅锌尾矿重金属的络合配位作用

矿产资源开采冶炼产生大量尾矿渣，其中富含的可溶性重金属引发的生态环境问题日益突显.铅锌矿是我国重要的矿产资源，尾矿露天堆放使得其富含的可溶性重金属淋溶迁移，对矿区周边地表环境造成严重污染.为探明自然水体环境中的藻菌生物膜与重金属的作用机理，采用三维荧光光谱技术研究干旱区天然湖泊中的藻菌生物膜EPS（胞外聚合物）与铅锌尾矿渣中5种重金属离子的络合配位作用.结果表明:①从藻菌生物膜EPS荧光光谱图中可检测出两个荧光峰，均来源于芳香类蛋白酪氨酸物质；②铅锌尾矿淋滤液中的重金属元素主要包括Pb、Co、Ni、Zn和Cd，且这5种金属离子均能有效淬灭EPS的荧光强度；③荧光淬灭滴定试验得出，Pb2+与EPS的络合能力最强，最大络合常数为4.523 1，最大结合位点数为1.177 5；Cd2+与EPS的络合能力最弱，最大络合常数为1.957 1，最大结合位点数为0.684 8；Co2+、Ni2+和Zn2+与EPS的络合能力相似.研究显示，藻菌生物膜EPS中含有的荧光基团与重金属离子的作用强度与金属离子的类型相关，二者的络合配位作用可能会影响重金属在水环境中的化学形态、迁移、生物有效性和生态毒性. 

The Complexation of Extracellular Polymeric Substances from Alga-Bacteria Biofilm with Heavy Metal Contained in Lead-Zinc Mine Tailings

The extraction and smelting of mineral resources produces a lot of tailings, and the ecological environment problems caused by the soluble heavy metals contained in tailings are becoming more and more prominent. Lead-zinc deposit is an important mineral resource in China and the leaching and migration of soluble heavy metal ions contained in Pb-Zn mine tailings which are in open yared has caused serious heavy metal pollution to surrounding surface environment. In order to explore the mechanism of biofilm and heavy metals in natural aquatic environment, three-dimensional excitation emission matrix fluorescence spectroscopy was used to study the complexation of extracellular polymeric substances (EPS) produced by alga-bacteria biofilm grow in the natural lake wetland with five metal ions contained in Pb-Zn mine tailings. The results are as follows:(1) Two fluorescence peaks were identified in the 3D-EEM of EPS and were referred to as aromatic protein tyrosine. (2) The main soluble heavy metal ions contained in leachate of lead-zinc tailings includes Pb²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Cd²⁺, and the five ions can effectively quench the fluorescence intensity of EPS. (3) It was found that fluorescence quenching that Pb²⁺ had strongest complex ability to EPS with the maximum binding constant and binding site as 4.52 and 1.18, respectively. The complexation of Cd²⁺ with EPS was the weakest, with the binding constant and binding site as 1.96 and 0.68, respectively. Co²⁺, Ni²⁺ and Zn²⁺ had their similar binding ability to EPS. The results suggest that the interaction strength of fluorophore in EPS from biofilm with heavy metals is related to metal ion type and their effects may significantly affect the chemical forms, mobility, bioavailability and ecotoxicity of heavy metals in the aquatic environment.