光照、硫化和浓度效应对水环境中胞外聚合物与银离子相互作用的影响机制  

Combined effect of UV light,sulfidation and concentration on the interaction of EPS and silver ions in aquatic environment

作　　者：沈毅 陈芳敏 杨悦锁 杨新瑶 SHEN Yi;CHEN Fangmin;YANG Yuesuo;YANG Xinyao(Ministry of Education Key Lab for Eco-restoration of Regional Contaminated Environment, School of Enviironment. Shenyang University, Shenyang, 110044,China;Department of Civil and Environmental Engineering, Michigan State University East Lansing, MI, 48824, USA;Liaoning Key Lab of Urban IPM and Eco-seeurity, School of Life Science and Engineering, Shenyang University, Shenyang, 110044, China)

机构地区：[1]沈阳大学环境学院区域污染环境生态修复教育部重点实验室,沈阳110044 [2]密歇根州立大学土木与环境工程系,美国东兰欣市密歇根州48824 [3]沈阳大学生命科学与工程学院辽宁省城市有害生物治理与生态安全重点实验,沈阳110044

出　　处：《环境化学》2018年第6期1186-1196,共11页Environmental Chemistry

基　　金：国家自然科学基金(41471409,41672248); 辽宁省创新团队项目(LT2015017)资助

摘　　要：本文研究了紫外光照、银离子浓度和硫化反应对水环境中胞外聚合物(EPS:用海藻酸钠模拟)与银离子交互作用的影响.紫外-可见吸收光谱结果显示,在无硫有紫外光照的条件下,EPS先把银离子转化为零价纳米银,纳米银继而聚凝生成银沉淀.银离子的初始浓度会影响生成的纳米银的稳定性,失稳速度依次为初始浓度4 mmol·L^(-1)>8 mmol·L^(-1)>2 mmol·L^(-1)>1 mmol·L^(-1).高分辨透射电子显微镜(HRTEM)图表明,在有硫有紫外光照条件下,硫化反应和EPS共同作用使银离子生成硫化银和零价银两种纳米颗粒.初始银离子浓度较低(2 mmol·L^(-1)和4 mmol·L^(-1))时硫化反应有助于纳米银保持较好的稳定性;而初始银离子浓度较高(8 mmol·L^(-1))时,硫化反应会降低纳米银的稳定性.在无硫无紫外光照的条件下,EPS未能使银离子转化为纳米银,说明遮光条件会抑制EPS对银离子的还原效率.而在有硫条件下,即使遮光,银离子也会在硫离子和EPS的交互作用下转化为纳米银和纳米硫化银(除了银离子浓度为1 mmol·L^(-1)的样品).这表明硫化过程即使在黑暗环境中也能使银离子转化为纳米银.细菌可以通过胞外聚合物与银离子的相互作用,来抵御银对细胞的生态毒性.在黑暗的地下水环境中,EPS的还原能力弱于有光照的地表水(湖泊河流)环境,细菌更容易受到银的抑制;但地下水中若存在硫化物,硫化反应可以协助细菌的胞外聚合物将银离子转化为颗粒态甚至使其沉淀,从而增强EPS对细菌的保护效果.This work studied the role of UV light,silver ions concentration and sulfidation on the interaction between extracellular polymeric substance（EPS：modeled with alginate） and silver ions in water phase.UV-vis absorption spectra showed that in the presence of UV light,EPS transformed silver ions to AgNPs initially which then aggregated and precipitated.The aggregation rate of theresulting AgNPs was influenced by the initial concentration of silver ions and followed the order of 4 mmol·L^-1〉8 mmol·L^-1〉2 mmol·L^-1〉1 mmol·L^-1.High resolution transmission electron microscope（HRTEM） analysis showed that in the presence of both UV light and sulfide ion,EPS and sulfide ions transformed silver ions to both AgNPs and Ag2 S NPs.Besides,sulfidation reaction increased the stability of AgNPs at low Ag＋concentration（2—4 mmol·L^-1） while it reduced the stability of AgNPs at high Ag＋concentration（8 mmol·L^-1）.When both UV light and sulfide ions were absent,EPS failed to reduce silver ions to form AgNPs.However,in the presence of sulfide ions,even without UV light,the interaction of sulfide ions and EPS with silver ions yielded both AgNPs and Ag2S NPs（except for the sample with 1 mmol·L^-1 Ag＋）,which suggested that sulfidation process may lead to reduction of silver ions to form AgNPs even in the dark.These findings imply that bacteria could defend against the negative impact of silver ions via interaction of EPS with Ag＋.In dark groundwater,EPS has lower reducing efficiency than in illuminated surface water（i.e.lakes and rivers）,and bacteria are more vulnerable to the eco-toxicity of Ag＋.Nonetheless,the presence of sulfide could assist EPS to transform Ag＋to particles and precipitates,which substantially improves the protective role of EPS.These findings could enhanceour understanding on the behavior,fate,and antibacterial effect of AgNPs in both surface water and groundwater environment.

关 键 词：硫化 紫外光照 胞外聚合物 银离子转化 

分 类 号：X523[环境科学与工程—环境工程]