Differential responses of the electron transfer capacities of soil humic acid and fulvic acid to long-term wastewater irrigation

Yiman Gao; Yuan Zhang; Xiaoyuan Ge; Yi Gong; Huiru Chen; Jing Su; Beidou Xi; Wenbing Tan

doi:10.1016/j.scitotenv.2024.173114

Differential responses of the electron transfer capacities of soil humic acid and fulvic acid to long-term wastewater irrigation

Sci Total Environ. 2024 Jul 10:933:173114. doi: 10.1016/j.scitotenv.2024.173114. Epub 2024 May 11.

Authors

Yiman Gao¹, Yuan Zhang², Xiaoyuan Ge³, Yi Gong⁴, Huiru Chen⁵, Jing Su⁶, Beidou Xi¹, Wenbing Tan⁷

Affiliations

¹ State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
² Institute of Geographical Sciences, Hebei Academy of Sciences, Hebei Technology Innovation Center for Geographic Information Application, Shijiazhuang 050011, China.
³ State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; Lan Zhou Jiao Tong University, Lanzhou 730070, China.
⁴ State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; Beijing University of Chemical Technology, Beijing 100029, China.
⁵ State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; North China University of Water Resources and Electric Power, Zheng Zhou 450046, China.
⁶ State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China. Electronic address: sujing@craes.org.cn.
⁷ State Key Laboratory of Environmental Criteria and Risk Assessment, and State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China. Electronic address: wenbingtan@126.com.

PMID: 38740205
DOI: 10.1016/j.scitotenv.2024.173114

Abstract

Wastewater irrigation is used to supplement agricultural irrigation because of its benefits and freshwater resource scarcity. However, whether wastewater irrigation for many years affects the electron transfer capacity (ETC) of natural organic matter in soil remains unclear, and organic matter could influence the decomposition and mineralization of substances with redox characteristics in soil through electron transfer, ultimately affecting the soil environment. The composition of soil humic substances (HS) is highly complex, and the effects of soil humic acid (HA) and fulvic acid (FA) on ETC is poorly understood. In this study, we separately evaluated the responses of the electron-accepting capacity (EAC) and electron-donating capacity (EDC) of soil HA and FA in agricultural fields to various durations of wastewater irrigation. Results showed that the EAC of HA and FA increased significantly with increasing the duration of wastewater irrigation. When wastewater irrigation lasted for 56 years, the EAC of HA showed a higher increment (590 %) than that of FA (223 %). The EDC of soil HA and FA, conversely, decreased compared to the control, with the highest reduction of 35.6 % for HA and 65.9 % for FA. Specifically, the EDC of HA gradually decreased starting from 29 years of wastewater irrigation, whereas the decrease in the EDC of FA exhibited no clear pattern in relation to the duration of wastewater irrigation. Increased soil organic matter and total nitrogen content under long-term wastewater irrigation led to an increase in sucrase and phosphatase activities, along with an increase in EAC and a decrease in EDC of HS. This suggests that soil enzyme activities may ultimately lead to changes in ETC. The results of this research provide practical insights into the redox system in soil and its driving role in soil organic matter transformation and nutrient cycling under wastewater irrigation.

Keywords: Duration of wastewater irrigation; Soil enzyme activity; Soil humic substances; electron-accepting capacity; electron-donating capacity.