Burst of hydroxyl radicals in sediments derived by flooding/drought transformation process in Lake Poyang, China

Oxygenation of the reduced species has been regarded as the major source for hydroxyl radical (HO center dot) generation in aquatic environments. Yet, the O-2-induced formation of HO center dot in lake sediments during the flooding/drought transformation process remained largely unexplored. In this study, two types of sediments from Wucheng (WC) and Nanji (NJ) area in Lake Poyang, China, were collected, respectively, with the burst of HO center dot derived by flooding/drought transformation process exploring via the incubation experiments. Results showed that no obvious HO center dot can be detected for the two sediments during the flooding period, while the oancentrations of HO center dot increased rapidly for the flooding/drought transformation process due to the enhanced dissolved oxygen contents. The highest concentrations of HO center dot in the surface sediment were 2.45 = 0.19 mu mol kg(-1) for WC sediment and 0.69 +/- 0.25 mu mol kg(-1) for NJ sediment, showing higher burst potential of HO center dot for the former. The contents of Fe(II) in the surface sediments for WC area (589.3 +/- 3729 mg k g(-1)) were about two times higher than those for NJ area (308.4 +/- 94.01 mg kg(-1)) during the flooding period. Oxygenation of the surface Fe( II) contributed significantly to the burst of HO center dot in the flooding/drought transformation process. Moreover, the higher percentage of humic-like substances in WC sediment indicated that the dissolved humic fraction exhibited also important role in the HO center dot formation due to electrons transfer under redox conditions.This study highlighted the importance of reactive reduced species in manipulating the burst of HO center dot in lake sediment, which is essential for understanding the geochemical cycling of several major and trace elements as well as the behavior and fate of the contaminants in aquatic ecosystems. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study explored the burst of hydroxyl radicals in lake sediments during the flooding/drought transformation process, finding that the concentrations of HO center dot rapidly increased due to enhanced dissolved oxygen contents and surface Fe(II) oxidation. The higher percentage of humic-like substances in sediment indicated an important role in HO center dot formation through electron transfer under redox conditions. These findings contribute to our understanding of geochemical cycling of elements and fate of contaminants in aquatic ecosystems.