Influence of anthropogenic nitrogen inputs and legacy nitrogen change on riverine nitrogen export in areas with high agricultural activity

Jie Liu; Wenquan Gu; Yawen Liu; Wenhui Li; Dongguo Shao

doi:10.1016/j.jenvman.2023.117833

Influence of anthropogenic nitrogen inputs and legacy nitrogen change on riverine nitrogen export in areas with high agricultural activity

J Environ Manage. 2023 Jul 15:338:117833. doi: 10.1016/j.jenvman.2023.117833. Epub 2023 Mar 31.

Authors

Jie Liu¹, Wenquan Gu², Yawen Liu¹, Wenhui Li¹, Dongguo Shao³

Affiliations

¹ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China.
² State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China. Electronic address: gwquan@whu.edu.cn.
³ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China. Electronic address: dgshao@whu.edu.cn.

PMID: 37004483
DOI: 10.1016/j.jenvman.2023.117833

Abstract

Increased riverine nitrogen (N) concentrations due to human activities is one of the leading causes of water quality decline, worldwide. Therefore, quantitative information about the N exported from watershed to the river (TN exports) is essential for defining N pollution control practices. This paper evaluated the changes in net anthropogenic N inputs (NANI) and the N stored in land ecosystems (legacy N) in the Jianghan Plain (JHP) from 1990 to 2019 and their impacts on TN exports. Moreover, an empirical model was developed to estimate TN exports, trace its source, and predict its future variations in 2020-2035 under different scenarios. According to the results, NANI exhibited a rise-decrease-rise-decrease M-shaped trend, with N fertilizer application being the dominant driver for NANI change. In terms of the NANI components, non-point-source was the primary N input form (96%). Noteworthy is that the correlation between NANI and TN exports became weaker over time, and large differences in changing trends were observed after 2014. A likely cause for this abnormal trend was that the accumulation of N surplus in soil led to N saturation in agricultural areas. Legacy N was also an important source of TN exports. However, the contribution of legacy N has rarely been considered when defining N pollution control strategies. An empirical model, incorporating legacy N, agricultural irrigation water use, and cropland area ratio, was developed. Based on this model, legacy N contributed a large proportion (15-31%). Furthermore, the results of future predictions indicated that legacy N had a larger impact on future TN exports changes compared to other factors, and increased irrigation water would increase rather than decrease TN exports. Therefore, an integrated N management strategy considering the impact of NANI, legacy N, and irrigation water use is crucial to control N pollution in areas with intensive agriculture.

Keywords: Export coefficient model; Legacy nitrogen; Nitrogen buffering capacity; Water pollution management; Water quality modeling.

MeSH terms

Agriculture
China
Ecosystem
Environmental Monitoring
Humans
Nitrogen* / analysis
Phosphorus / analysis
Rivers
Water Pollutants, Chemical* / analysis
Water Quality

Substances

Nitrogen
Water Pollutants, Chemical
Phosphorus