干旱区研究

干旱区研究 ›› 2018, Vol. 35 ›› Issue (1): 243-248.doi: 10.13866/j.azr.2018.01.30

• 生态与环境 • 上一篇    

新疆奎屯排碱渠生物膜胞外聚合物与As(Ⅲ)的络合作用

林青华1,2, 张道勇1,3   

  1. 1.中国科学院地球化学研究所, 环境地球化学国家重点实验室, 贵州 贵阳 550081;
    2.中国科学院大学, 北京 100049;
    3.浙江工业大学环境学院, 浙江 杭州 310014
  • 收稿日期:2017-04-01 修回日期:2017-05-26 出版日期:2018-01-15 发布日期:2025-11-16
  • 作者简介:林青华(1991-),女,硕士研究生,研究方向为污染环境的生物处理技术. E-mail:1551544845@qq.com
  • 基金资助:
    新疆维吾尔自治区重点实验室开放课题(2015KL025);国家自然科学基金项目(U1403181)资助

Complexation of As (Ⅲ) with Extracellular Polymeric Substance from Biofilm in the Salt-discharging Channel in Kuytun,Xinjiang

LIN Qing-hua1,2, ZHANG Dao-yong1,3   

  1. 1. State Key Laboratory of Environmental Geochemistry,Chinese Academy of Sciences,Guiyang 550002,Guizhou,China;
    2. University of Chinese Academy of Sciences,Beijing 100049,China;
    3. College of Environment,Zhejiang University of Technology,Hangzhou 310014,Zhejiang,China
  • Received:2017-04-01 Revised:2017-05-26 Published:2018-01-15 Online:2025-11-16

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摘要： 新疆奎屯地区是地质背景高砷区,排碱渠水体砷(As)污染严重,排碱渠中普遍发育的生物膜胞外聚合物(EPS)与As之间的络合会影响砷的迁移扩散,进而影响到砷的生物毒性和生态风险。目前,排碱渠中普遍发育的生物膜EPS对水中As的迁移转化及行为归宿的影响还完全不清楚。本文结合荧光猝灭滴定技术和等温微量热滴定技术研究了该地区普遍发育的藻生物膜EPS与As(Ⅲ)之间的相互作用。荧光猝灭实验表明:排碱渠生物膜EPS有3个荧光峰:峰 A属于含芳环基团的蛋白质Ⅱ; 峰 B 属于溶解性的微生物类蛋白质;峰C属于类腐殖酸。峰A和峰B统称为类蛋白质物质,其中峰B被确定为类色氨酸物质。类蛋白物质与As(Ⅲ)具有较强的结合作用,而类腐殖酸物质与As(Ⅲ)几乎没有结合能力。EPS与As(Ⅲ)荧光淬灭作用属于静态淬灭和动态碰撞淬灭,同时存在的复合淬灭机制。EPS中含芳环基团的蛋白质Ⅱ和类色氨酸物质与As(Ⅲ)的结合常数lgKb分别为3.82和2.22,说明As(Ⅲ) 与前者的结合强度比后者大一个数量级,前者与As(Ⅲ)形成络合物的稳定性稍微大于后者。As(Ⅲ)可以与含芳环基团的蛋白质Ⅱ的多类位点结合,且在多类结合位点之间存在拮抗竞争作用,而类色氨酸物质中只有一类位点参与As的络合。等温微量热滴定实验结果经过Independent 模型拟合,求得了EPS和As(Ⅲ)络合反应的热动力学参数:ΔH、ΔG、ΔS。负的焓变ΔH和负的吉布斯自由能ΔG证明EPS与As(Ⅲ)间的络合反应是一个自发进行的放热反应。随着络合反应进行,反应体系的无序度增加,反应为熵驱动。排碱渠生物膜EPS中的类蛋白质在As(Ⅲ)的迁移转化及其生态风险中起着重要作用,而EPS中的类腐殖酸物质不会对As(Ⅲ)的环境行为产生显著影响。

关键词: 排碱渠, 砷污染, 生物膜, 胞外聚合物, 荧光猝灭, 等温量热滴定, 奎屯, 新疆

Abstract: There is a heavy arsenic pollution in the salt-discharging channel due to the geological background in Kuytun,Xinjiang. The complexation between extracellular polymeric substance of the algal biofilm and As (Ⅲ) influences the transportation and diffusion of arsenic and further affects the biological toxicity and the ecological risk of arsenic.At present,the effects of the widespread biofilm on the transport and fate of arsenic in channel are completely unknown.In this study,the interaction of extracellular polymeric substance of the algal biofilm and As (Ⅲ) was investigated by fluorescence quenching test and isothermal titration calorimetry.The results of fluorescence quenching test showed that the fluorescent components of extracellular polymeric substance were composed of three fluorescence peaks: Peak A belonged to aromatic protein Ⅱ,Peak B belonged to soluble microbial by-product-like,and Peak C belonged to humic acid-like.Peak A and B were collectively referred to protein-like substance,and peak B was further intended to be tryptophan-like substance.There was a strong complexation between the protein-like substance and As (Ⅲ),while the interaction between As (Ⅲ) and the humic-like substance was ignorable.Both static quenching and dynamic collision were involved in fluorescence quenching of extracellular polymeric substance by As (Ⅲ).The binding constant,lgKb,for interaction of As (Ⅲ) with the aromatic protein-like substance and tryptophan-like substance were 3.82 and 2.22 respectively,indicating the binding affinity of As (Ⅲ) to the former is one order of magnitude greater than the latter.Multiple sites were involved in competition for binding As (Ⅲ) in the aromatic protein-like substance,and only one class of binding sites were taken part in tryptophan-like substance for their complexation with As (Ⅲ).The data obtained from isothermal titration calorimetry test were fitted by independent model,and the thermal dynamic parameters ΔH,ΔG and ΔS of complexation reaction were acquired.Negative enthalpy change ΔH and negative Gibbs free energy ΔG proved that the complexation between extracellular polymeric substance and the As (Ⅲ) is a spontaneous exothermic reaction.The degree of disorder in the complexing reaction increases,and the reaction is driven by entropy.The protein-like substance in the biofilm in salt-discharging channel may have significant effects on environmental fate and risk of arsenic,while the role of humic acid-like substance in extracellular polymeric substance is ignorable.

Key words: salt-discharging channel, arsenic pollution, biofilm, EPS, fluorescence quenching, isothermal titration calorimetry, Kuytun, Xinjiang