Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada.
Univ. Toulon, Aix Marseille Univ., CNRS/INSU, IRD, MIO UM 110, Mediterranean Institute of Oceanography, La Garde, France.
Sci Total Environ. 2020 May 10;716:137118. doi: 10.1016/j.scitotenv.2020.137118. Epub 2020 Feb 4.
The presence of arsenic in irrigation and drinking waters is a threat to worldwide human health. Dissolved organic matter (DOM) is a ubiquitous and photoreactive sorbent of arsenic, capable of both suppressing and enhancing its mobility. Microbes can control the mobilization of mineral-bound arsenic, through redox processes thought to occur intracellularly. The role that DOM plays on the bioavailability of arsenic to microbes is often invoked but remains untested experimentally. Here, using a whole-cell biosensor, we tested the role of DOM on As(III) and As(V) bioavailability. Using cation amendments, we explored the nature of As-DOM interactions. We found As bioavailability to be dependent on [As]/[DOM] ratio and on the strength of As binding to DOM which varied as a function of time. We further tested the role of DOM on As(III) photooxidation and showed that As(III) photooxidation rate is limited by the strength of its interactions with DOM and sensitive to ionic competitive desorption. Our study demonstrates the dynamic control that photoreactive DOM poses on the bioavailability and reactivity of As in the environment and highlights the kinetic controls that DOM can possibly exert on As toxicity at various levels in foodwebs.
砷在灌溉和饮用水中的存在对全球人类健康构成威胁。溶解有机质（DOM）是一种普遍存在且具有光反应性的砷吸附剂，既能抑制又能增强砷的迁移性。微生物可以通过被认为在细胞内发生的氧化还原过程来控制矿物结合态砷的迁移。DOM 对微生物砷生物利用度的作用经常被提及，但尚未通过实验进行测试。在这里，我们使用全细胞生物传感器测试了 DOM 对 As(III)和 As(V)生物利用度的作用。通过阳离子添加剂，我们探索了 As-DOM 相互作用的性质。我们发现 As 的生物利用度取决于 [As]/[DOM] 比值和 As 与 DOM 结合的强度，而这两个因素随时间变化。我们进一步测试了 DOM 对 As(III)光氧化的作用，并表明 As(III)光氧化速率受到其与 DOM 相互作用强度的限制，且对离子竞争解吸敏感。我们的研究表明，光反应性 DOM 对环境中 As 的生物利用度和反应性具有动态控制作用，并强调了 DOM 可能在食物网的各个层面上对 As 毒性产生的动力学控制作用。
