Iron bound phosphorus predominates the contribution of phosphorus to lake system from terrigenous source: The evidence from the small watershed scale

Hezhong Yuan; Haixiang Wang; Yiwei Cai; Hongbin Yin; Qingfei Zeng; Enfeng Liu; Qiang Li; Yu Wang

doi:10.1016/j.watres.2023.120661

Iron bound phosphorus predominates the contribution of phosphorus to lake system from terrigenous source: The evidence from the small watershed scale

Water Res. 2023 Oct 15:245:120661. doi: 10.1016/j.watres.2023.120661. Epub 2023 Sep 22.

Authors

Hezhong Yuan¹, Haixiang Wang², Yiwei Cai², Hongbin Yin³, Qingfei Zeng³, Enfeng Liu⁴, Qiang Li⁵, Yu Wang⁶

Affiliations

¹ Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China. Electronic address: yuanhezhong@nuist.edu.cn.
² Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China.
³ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
⁴ College of Geography and Environment, Shandong Normal University, Ji'nan 250359, China.
⁵ Department of Natural Sciences, University of Houston-Downtown, Houston 77002, United States.
⁶ Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: wangyu@issas.ac.cn.

PMID: 37769418
DOI: 10.1016/j.watres.2023.120661

Abstract

The reduction of exogenous emissions of phosphorus (P) is a crucial measure for resolving eutrophication in lakes. However, the input of terrigenous materials still potentially contributes to an increase of P load in lake systems. In this study, we examined the phosphate oxygen isotope (δ¹⁸O_P) of various P fractions in soils and sediments in a small lake watershed, namely, Shijiuhu watershed. The high-resolution in-situ diffusive gradients in thin films (DGT) technology was also used to survey the dynamic processes of P diffusion from sediment particles to the water. The results demonstrated that lighter δ¹⁸O_P values (16.2-19.5‰) for individual P fractions in lake sediments were detected compared to other land-use patterns, indicating the cumulative biological P recycling on anaerobic condition. Fe bound P (Fe-P) overall had heavier δ¹⁸O_P values (17.3-24.8‰) than some of Ca bound P (Ca-P) and equilibrium values, suggesting that Fe-P conserved the parental isotope signatures from terrigenous source and could act as the ideal tracer for the lake sediments. The mixing effect of terrigenous detrital input and biological mineralization made the source identification uncertain by using Ca-P, which had a wider range of δ¹⁸O_P values (13.0-26.6‰). Additionally, significantly positive correlation (r = 0.551-0.913, p<0.05) between soluble reactive P (SRP) and Fe²⁺ in interstitial water obtained using DGT measurement revealed the conspicuous release and desorption of solid Fe-P toward the water. High diffusion fluxes from the sediments toward the overlying water further demonstrated that the desorption of Fe-P in the soil-originated sediments toward the solution conspicuously facilitated the accumulation of SRP in lake water. The first-time application of δ¹⁸O_P isotope combined with in-situ DGT techniques certified that it's feasible for the contribution confirmation from terrigenous to lacustrine environments, and presented the direct evidence for management strategy making about P control and eutrophication restoration at the catchment scale of lakes.

Keywords: DGT; Fe-P; Lake sediment; Soil; Terrigenous source; Watershed scale; δ(18)O(P).