Controlling internal nitrogen and phosphorus loading using Ca-poor soil capping in shallow eutrophic lakes: Long-term effects and mechanisms

Chuanzhe Sun; Jicheng Zhong; Gang Pan; Robert J G Mortimer; Juhua Yu; Shuailong Wen; Lei Zhang; Hongbin Yin; Chengxin Fan

doi:10.1016/j.watres.2023.119797

Controlling internal nitrogen and phosphorus loading using Ca-poor soil capping in shallow eutrophic lakes: Long-term effects and mechanisms

Water Res. 2023 Apr 15:233:119797. doi: 10.1016/j.watres.2023.119797. Epub 2023 Feb 26.

Authors

Chuanzhe Sun¹, Jicheng Zhong², Gang Pan³, Robert J G Mortimer⁴, Juhua Yu⁵, Shuailong Wen¹, Lei Zhang⁶, Hongbin Yin⁶, Chengxin Fan⁶

Affiliations

¹ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
² State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China. Electronic address: jczhong@niglas.ac.cn.
³ School of Humanities, York St John University, Lord Mayor's Walk, York, YO31 7EX, UK; School of Chemical and Environmental Sciences, Guangdong Ocean University, Zhanjiang 524088, China.
⁴ School of Humanities, York St John University, Lord Mayor's Walk, York, YO31 7EX, UK.
⁵ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China; Institute of Soil and Fertilizer, Fujian Academy of Agricultural Sciences, Fuzhou, 350013, PR China.
⁶ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China.

PMID: 36870105
DOI: 10.1016/j.watres.2023.119797

Abstract

Clean soil is a potential capping material for controlling internal nutrient loading and helping the recovery of macrophytes in eutrophic lakes, but the long-term effects and underlying mechanisms of clean soil capping under in-situ conditions remain poorly understood. In this study, a three-year field capping enclosure experiment combining intact sediment core incubation, in-situ porewater sampling, isotherm adsorption experiments and analysis of sediment nitrogen (N) and phosphorus (P) fractions was conducted to assess the long-term performance of clean soil capping on internal loading in Lake Taihu. Our results indicate that clean soil has excellent P adsorption and retention capacity as an ecologically safe capping material and can effectively mitigate NH₄⁺-N and SRP (soluble reactive P) fluxes at the sediment-water interface (SWI) and porewater SRP concentration for one year after capping. The mean NH₄⁺-N and SRP fluxes of capping sediment were 34.86 mg m^-2 h^-1 and -1.58 mg m^-2 h^-1, compared 82.99 mg m^-2 h^-1 and 6.29 mg m^-2 h^-1 for control sediment. Clean soil controls internal NH₄⁺-N release through cation (mainly Al³⁺) exchange mechanisms, while for SRP, clean soil can not only react with SRP due to its high Al and Fe content, but also stimulate the migration of active Ca²⁺ to the capping layer, thus precipitating as Ca-bound P (Ca-P). Clean soil capping also contributed to the restoration of macrophytes during the growing season. However, the effect of controlling internal nutrient loading only lasted for one year under in-situ conditions, after which the sediment properties returned to pre-capping conditions. Our results highlight that clean Ca-poor soil is a promising capping material and further research is needed to extend the longevity of this geoengineering technology.

Keywords: Ca-poor clean soil; Capping; Eutrophication; Internal nutrient loading; Sediment-water interface; Shallow lakes.

MeSH terms

China
Eutrophication
Geologic Sediments
Lakes
Nitrogen / analysis
Phosphorus / analysis
Soil*
Water Pollutants, Chemical* / analysis

Substances

Soil
Phosphorus
Nitrogen
Water Pollutants, Chemical