Spatial Heterogeneity and Vertical Distribution of Nitrogen Forms in Sediments of Qilu Lake

Wei Li; Tianxiang Li; Mingyan Liu; Yaping Liu; Lixin Jiao; Miao Zhang; Bo Yao; Jingyi Yan; Jianxun Wu; Xin Wen; Dengling Jiang

doi:10.54691/2q44p450

Authors

Wei Li North China University of Science and Technology, Tangshan 063210, China;State Key Laboratory of Environmental Criteria and Risk Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Tianxiang Li State Key Laboratory of Environmental Criteria and Risk Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Mingyan Liu State Key Laboratory of Environmental Criteria and Risk Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China;Xinjiang Tianhe Environmental Technology Consulting Co., Ltd., Urumqi 830092, China
Yaping Liu State Key Laboratory of Environmental Criteria and Risk Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Lixin Jiao State Key Laboratory of Environmental Criteria and Risk Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Miao Zhang Kunming Research Academy of Ecological and Environmental Sciences, Kunming 650032, China
Bo Yao Kunming Research Academy of Ecological and Environmental Sciences, Kunming 650032, China
Jingyi Yan Kunming Research Academy of Ecological and Environmental Sciences, Kunming 650032, China
Jianxun Wu Kunming Research Academy of Ecological and Environmental Sciences, Kunming 650032, China
Xin Wen Kunming Research Academy of Ecological and Environmental Sciences, Kunming 650032, China
Dengling Jiang North China University of Science and Technology, Tangshan 063210, China

DOI:

https://doi.org/10.54691/2q44p450

Keywords:

Qilu Lake; Sediment; Nitrogen Forms; Vertical Distribution.

Abstract

To reveal the spatial heterogeneity and vertical distribution characteristics of nitrogen forms in the sediments of Qilu Lake, overlying water and surface sediment samples were collected from 15 sampling sites in June 2023, and sediment core samples were additionally collected from seven representative sites. The occurrence characteristics, release contributions, and interrelationships of various nitrogen fractions in overlying water, surface sediments, and sediment cores were systematically analyzed. The results showed that inorganic nitrogen dominated the nitrogen pool in the overlying water of Qilu Lake, with relatively low NH₄⁺-N concentrations and comparatively higher NO₃^--N concentrations. Site Q9 exhibited the most pronounced nitrogen enrichment. DIN was the predominant component of DTN. In surface sediments, TN, PMON, SN, and various forms of EN and PMN all exhibited marked spatial heterogeneity, and the high-value zones of different nitrogen pools did not completely overlap, indicating that various nitrogen fractions possess distinct distribution patterns within the lake basin. The release contributions of nitrogen forms in sediment cores differed significantly among lake zones, with the western zone showing the most pronounced inter-site variability. Vertical profiles of sediment cores revealed that NH₄⁺-N concentrations were relatively high in shallow layers at most sites, whereas site Q9 exhibited a distinct increasing trend with depth. NO₃^--N concentrations fluctuated considerably among sites. PMN generally decreased from shallow to deep layers. TN remained relatively stable with depth at most sites, with only site Q15 showing notable vertical variation. Correlation analysis indicated that, among the labile nitrogen fractions in surface sediments, NH₄⁺-N in EN exhibited the strongest correlations with overlying water NH₄⁺-N, DIN, and DTN, while other labile nitrogen fractions showed relatively weaker correlations with inorganic nitrogen in overlying water. These findings demonstrate that nitrogen fractions in the sediments of Qilu Lake exhibit significant heterogeneity in both spatial and vertical dimensions, and that there exists a strong coupling relationship between the surface labile nitrogen pool and inorganic nitrogen in the overlying water, which can provide a scientific basis for the identification and management of internal nitrogen pollution in the lake.

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