| 长江口沉积物-水界面砷的迁移转化机制与微生物调控分析 |
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| 引用本文： | 张玉婷,段丽琴,宋金明,张乃星,尹美玲,李学刚,袁华茂.长江口沉积物-水界面砷的迁移转化机制与微生物调控分析[J].地学前缘,2022,29(4):144-155. |
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| 作者姓名： | 张玉婷 段丽琴 宋金明 张乃星 尹美玲 李学刚 袁华茂 |
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| 作者单位： | 1.中国科学院 海洋研究所 中国科学院海洋生态与环境科学重点实验室, 山东 青岛 2660712.中国科学院大学, 北京 1000493.青岛海洋科学与技术国家实验室 海洋生态与环境科学功能实验室, 山东 青岛 2662374.中国科学院 海洋大科学研究中心, 山东 青岛 2660715.国家海洋局北海预报中心, 山东 青岛 266033 |
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| 基金项目： | 国家自然科学基金项目(41976037);山东省自然科学基金资助项目(ZR2020YQ28);国家自然科学基金项目(41806133);烟台“双百计划”资助项目 |
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| 摘 要： | 为探析长江口沉积物-水界面砷的迁移转化机制,本文分析了2019年夏季长江口4个站位上覆水和间隙水中总As浓度及形态的剖面变化特征,耦合氧化还原敏感元素(Fe、Mn和S)的剖面变化剖析了沉积物-水界面砷循环的Fe-Mn-S控制机制,同时结合砷相关功能基因探讨了沉积物-水界面砷迁移转化的微生物调控过程,估算了沉积物-水界面总As的扩散通量。结果表明,除A7-4站位外,长江口其他3个站位间隙水总As以As3+为主要存在形态,且总As浓度均在上覆水中为最低值(0.748~1.57 μg·L-1),而在间隙水中随着深度增加而逐渐增加并在6~9 cm深度达到峰值(7.14~26.9 μg·L-1)。间隙水总As及As3+浓度的剖面变化趋势与溶解态Fe2+、Mn2+相似,其均在中间层出现高值,说明沉积物Fe/Mn还原带砷的释放可能是随固相Fe(Ⅲ)或Mn(Ⅳ)的还原而转移到间隙水中的。氧化层和Fe/Mn还原带过渡区间隙水砷浓度与砷异化还原菌功能基因arrA和arsC丰度存在对应关系(除A1-3站外),说明砷异化还原菌将溶解As5+或固相As5+还原为溶解As3+可能是该过渡层砷迁移转化的另一重要过程。硫酸盐还原带的间隙水总As和As3+浓度降低,但由于间隙水的低S2-浓度不利于砷硫化物生成,因此深层间隙水砷可能与铁硫矿物结合而被移除。底层环境氧化还原条件是影响沉积物-水界面砷迁移转化的重要因素,随底层水DO浓度的降低,砷迁移转化更倾向于微生物还原控制。长江口沉积物-水界面总As的扩散通量为1.18×10-7~2.07×10-7 μmol·cm-2·s-1,均表现为沉积物间隙水中总As向上覆水释放,即沉积物是研究区域水体总As的来源之一。
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| 关 键 词： | 砷(As) 迁移转化 砷功能基因 界面扩散通量 沉积物-水界面 长江口 |
| 收稿时间： | 2021-09-15 |
Arsenic migration and transformation mechanism and microbial regulation at the sediment-water interface of the Changjiang estuary |
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| ZHANG Yuting,DUAN Liqin,SONG Jinming,ZHANG Naixing,YIN Meiling,LI Xuegang,YUAN Huamao.Arsenic migration and transformation mechanism and microbial regulation at the sediment-water interface of the Changjiang estuary[J].Earth Science Frontiers,2022,29(4):144-155. |
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| Authors: | ZHANG Yuting DUAN Liqin SONG Jinming ZHANG Naixing YIN Meiling LI Xuegang YUAN Huamao |
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| Abstract: | In order to understand the arsenic (As) migration and transformation processes at the sediment-water interface (SWI) of the Changjiang estuary, the vertical profiles of the total As concentrations and speciation and redox-sensitive element (Fe, Mn and S) concentrations in the overlaying water and porewater at four sampling sites in the Changjiang estuary in summer 2019 were analyzed. The Fe-Mn-S controlling mechanism was investigated. Combined with As-related functional genes, the microbial regulation process of As cycling at the SWI was discussed. The diffusion fluxes of total As at the SWI were also estimated. It was found that As3+ was the main species of dissolved arsenic at three sites except site A7-4. At all sites, the overlying water had the lowest As concentrations (0.748-1.57 μg·L-1); whilst As concentrations in porewater increased gradually with depth and peaked (7.14-26.9 μg·L-1) at 6-9 cm depths. The vertical profiles of total As and As3+ concentrations in porewater were similar to that of dissolved Fe2+ and Mn2+, with high concentrations in the middle layers due likely to the release of solid-phase As by Fe(Ⅲ) and Mn(Ⅳ) reduction in the Fe/Mn reduction zone. The coupling relationships between porewater As concentration and abundances of arrA and arsC genes at the transition zone between oxic layer and Fe/Mn reduction layer (except for site A1-3) suggested that the reduction of dissolved As5+ or solid As5+ to dissolved As3+, by arsenic dissimilatory reducing bacteria was another important process of As migration and transformation. The combination of decreasing total As and As3+ concentrations and low S2- concentrations in porewater in the sulfate reduction zone indicated that the removal of porewater As was probably due to As complexation with iron sulfide minerals rather than formation of As sulfides. The ambient redox potential in the bottom layer of the estuary was an important factor affecting As migration and transformation at the SWI, as, with decreasing DO concentrations, the processes were more incline to microbial reduction control. The diffusion fluxes of total As at the SWI of the Changjiang estuary were (1.18-2.07)×10-7 μmol·cm-2·s-1, all attributable apparently to As release from porewater into the overlying water, suggesting sediment might be one of the sources of total As in the Changjiang estuary study area. |
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| Keywords: | arsenic migration and transformation arsenic functional genes diffusive flux the sediment-water interface the Changjiang estuary |
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