Formation and mechanisms of hydroxyl radicals during the oxygenation of sediments in Lake Poyang, China

Haiyan Du; Yuanxin Cao; Zhe Li; Lina Li; Huacheng Xu

doi:10.1016/j.watres.2021.117442

Formation and mechanisms of hydroxyl radicals during the oxygenation of sediments in Lake Poyang, China

Water Res. 2021 Sep 1:202:117442. doi: 10.1016/j.watres.2021.117442. Epub 2021 Jul 18.

Authors

Haiyan Du¹, Yuanxin Cao², Zhe Li³, Lina Li⁴, Huacheng Xu⁵

Affiliations

¹ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
² State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China.
³ CAS Key Lab of Reservoir Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
⁴ Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai 201210, China.
⁵ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: hcxu@niglas.ac.cn.

PMID: 34304073
DOI: 10.1016/j.watres.2021.117442

Abstract

Seasonal flooding-drought transformation process of lake sediments lead to changes of dissolved oxygen and redox conditions and the resultant generation of hydroxyl radical (HO^•). To date, information on HO^• formation and its regulators in seasonal lake sediments is largely unexplored. In this study, a total of nineteen sediments were collected from Lake Poyang, China, with the formation and mechanisms of HO^• during the oxygenation process exploring via the incubation experiments, Fe K-edge X-ray adsorption spectroscopy, ultrafiltration, and fluorescent spectroscopy. Results showed that the concentrations of HO^• generated ranged from 3.75 ± 1.13 to 271.8 ± 22.81 μmol kg^-1, demonstrating high formation potential and obvious spatial heterogeneity. The yield of HO^• formed was positively correlated with the contents of Fe(II), sedimentary organic carbon, and dissolved organic carbon, showing a general contribution of these reduced substances to HO^• formation. Furthermore, application of Fe K-edge X-ray adsorption spectroscopy revealed the key species of sedimentary Fe-smectite for HO^• formation due to its high peroxidase-like activity. Besides inorganic Fe(II), the sedimentary dissolved organic matters (DOMs) represented an important regulator for HO^• formation, which contributed about 2-11% of the total HO^• generation. Moreover, the DOM-induced formation potential was found to be highly related to the molecular weight distribution that the low molecular weight- (LMW, <1 kDa) fraction exhibited higher HO^• formation potential than the bulk and high molecular weight- (HMW, 1 kDa-0.45 μm) counterparts. In addition, the omnipresent mineral Fe(II)-DOM interaction in sediment matrix exhibited another 2-6% of contribution to the total HO^• production. This study highlighted the importance of contents and species of Fe(II) and DOM in manipulating the HO^• yield, providing new insight into understanding the formation mechanisms of HO^• in the seasonal lake sediment.

Keywords: Dissolved organic matter; Fe(II); Hydroxyl radical; Lake sediment; Molecular weight fraction.

MeSH terms

Carbon / analysis
China
Geologic Sediments
Hydroxyl Radical*
Lakes*
Molecular Weight

Substances

Hydroxyl Radical
Carbon