Wen Xin, Yang Xu, Wang Tantan, Li Zihao, Ma Chi, Chen Wenhao, He Yubo, Zhang Chang
College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China.
College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China.
Chemosphere. 2023 Jun;327:138437. doi: 10.1016/j.chemosphere.2023.138437. Epub 2023 Mar 22.
The photochemical behavior of dissolved organic matter (DOM) in surface water and its effect on Hg(II) photoreduction has been extensively studied, but the contribution of DOM in paddy water to Hg(II) photoreduction is largely unknown. Herein, the effect of DOM from biochar (BC), rice straw (RS), and chicken manure (CM) on Hg(II) photoreduction were examined. The comparable reduction efficiency of Hg(II) suggested that DOM-like fraction (62.3-63.7%) contributes more than suspended particulate matter-like fraction (17.7-23.4%) and bacteria-like fraction (13.0-20.0%) in paddy water. Under irradiation, the typical DOM significantly promoted Hg(II) photoreduction, and the reduction efficiency of BC (65.5 ± 2.1%) was higher than that of CM (48.3 ± 2.6%) and RS (32.8 ± 2.4%) in 6 h. The quenching and kinetics experiments showed that superoxide anion (O) was the main reactive species for Hg(II) photoreduction. Fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry revealed that DOM with a higher degree of lignin/carboxy-rich acyclic molecules, condensed aromatics structures, and phenolic compounds could promote the formation of O. These findings highlight the importance of DOM in Hg(II) photoreduction and provide new ideas for regulating Hg cycling and bioavailability in paddy environments.
地表水溶解有机物（DOM）的光化学行为及其对Hg（II）光还原的影响已得到广泛研究，但稻田水中DOM对Hg（II）光还原的贡献在很大程度上尚不清楚。在此，研究了生物炭（BC）、稻草（RS）和鸡粪（CM）中的DOM对Hg（II）光还原的影响。Hg（II）的可比还原效率表明，稻田水中类DOM组分（62.3 - 63.7%）的贡献大于类悬浮颗粒物组分（17.7 - 23.4%）和类细菌组分（13.0 - 20.0%）。在光照下，典型的DOM显著促进了Hg（II）的光还原，6小时内BC的还原效率（65.5 ± 2.1%）高于CM（48.3 ± 2.6%）和RS（32.8 ± 2.4%）。猝灭和动力学实验表明，超氧阴离子（O）是Hg（II）光还原的主要反应物种。荧光光谱和傅里叶变换离子回旋共振质谱表明，具有较高木质素/富含羧基的无环分子、缩合芳烃结构和酚类化合物的DOM可以促进O的形成。这些发现突出了DOM在Hg（II）光还原中的重要性，并为调节稻田环境中汞的循环和生物有效性提供了新思路。
