Seasonal hydrological variation impacts nitrogen speciation and enhances bioavailability in plateau lake sediments

Huaji Liu; Feixuan Cai; Zhongqing Huang; Chen Wang; Xueying Li; Xinze Wang; Jian Shen

doi:10.1016/j.watres.2024.122990

Seasonal hydrological variation impacts nitrogen speciation and enhances bioavailability in plateau lake sediments

Water Res. 2024 Dec 16:271:122990. doi: 10.1016/j.watres.2024.122990. Online ahead of print.

Authors

Huaji Liu¹, Feixuan Cai¹, Zhongqing Huang¹, Chen Wang¹, Xueying Li², Xinze Wang³, Jian Shen⁴

Affiliations

¹ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China; National Observation and Research Station of Erhai Lake Ecosystem in Yunnan, Dali, 671000, PR China; Shanghai Jiao Tong University Yunnan Dali Research Institute, Dali, 671000, PR China.
² National Observation and Research Station of Erhai Lake Ecosystem in Yunnan, Dali, 671000, PR China; Shanghai Jiao Tong University Yunnan Dali Research Institute, Dali, 671000, PR China.
³ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China; National Observation and Research Station of Erhai Lake Ecosystem in Yunnan, Dali, 671000, PR China; Shanghai Jiao Tong University Yunnan Dali Research Institute, Dali, 671000, PR China. Electronic address: xinzewang@sjtu.edu.cn.
⁴ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China; National Observation and Research Station of Erhai Lake Ecosystem in Yunnan, Dali, 671000, PR China; Shanghai Jiao Tong University Yunnan Dali Research Institute, Dali, 671000, PR China. Electronic address: sjlnts@sjtu.edu.cn.

PMID: 39700607
DOI: 10.1016/j.watres.2024.122990

Abstract

Global warming has intensified the distinction between dry and wet seasons in monsoonal climates. The synergistic effect of high temperatures and rainfall during the wet season promotes the release of endogenous nitrogen (N) and eutrophication within lake ecosystems. However, the seasonal variations in sediments N speciation and bioavailability, and their intrinsic connection to release potential, remain unclear. This study employed sequential extraction method and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) to characterize extractable N (Ex-N) in Erhai Lake sediments during dry and wet seasons. The results indicated that ion-exchangeable organic form N (IEF-ON) serves as a substrate for microbial mineralization, with the highest proportion of protein-like substances (26.2%). The influx of N-containing polysaccharides and poly-N glycoproteins during the wet season further increased its bioavailability. Algal-derived N exists as the weak acid-extractable organic form N (WAEF-ON), which has the highest lipid proportion (11.7%) and the lowest double bond equivalent (DBE) values. Overall, elevated water temperatures and N input during the wet season accelerate both the mineralization rate of organic N (ON) and the content of labile N components. This potentially triggers a "priming effect" that could further activate the refractory N components in the sediments. Additionally, the wet season reduces sediment pH and redox potential, making WAEF-ON and strong alkali-extractable form N (SAEF-N) more labile and susceptible to release. This study reveals the adverse effects of seasonal variations on N sequestration in lake sediments, complicating the control of endogenous pollution release under the backdrop of climate change.

Keywords: Extractable organic nitrogen; FT-ICR MS; Lake sediment; Nitrogen speciation; Seasonal variation.