Impact of extreme rainfall on non-point source nitrogen loss in coastal basins of Laizhou Bay, China

Meng Jiang; Hui Peng; Shengkang Liang; Shuo Wang; Latif Kalin; Enis Baltaci; Yang Liu

doi:10.1016/j.scitotenv.2023.163427

Impact of extreme rainfall on non-point source nitrogen loss in coastal basins of Laizhou Bay, China

Sci Total Environ. 2023 Jul 10:881:163427. doi: 10.1016/j.scitotenv.2023.163427. Epub 2023 Apr 12.

Authors

Meng Jiang¹, Hui Peng², Shengkang Liang³, Shuo Wang¹, Latif Kalin⁴, Enis Baltaci⁵, Yang Liu⁶

Affiliations

¹ Key Laboratory of Marine Environment Science and Ecology, Ministry of Education and College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
² Key Laboratory of Marine Environment Science and Ecology, Ministry of Education and College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China. Electronic address: pengh@ouc.edu.cn.
³ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean of China, Qingdao 266100, China. Electronic address: liangsk@ouc.edu.cn.
⁴ College of Forestry, Wildlife and Environment, Auburn University, 36849 Auburn, AL, USA. Electronic address: kalinla@auburn.edu.
⁵ Parsons Corporation, Atlanta, GA, USA.
⁶ Laboratory of Fisheries Oceanography, Fishery College, Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266100, China. Electronic address: yangliu315@ouc.edu.cn.

PMID: 37059154
DOI: 10.1016/j.scitotenv.2023.163427

Abstract

Extreme rainfalls often lead to large amounts of nitrogen (N) loss from river basins. However, the composition and spatial variation of N loss caused by extreme events and the effects of control measures are not well understood. To shed light into this question, the Soil and Water Assessment Tool (SWAT) was used to evaluate the spatiotemporal characteristics of organic and inorganic nitrogen (ON and IN) losses in the coastal basins of Laizhou Bay during typhoons Rumbia and Lekima. The effects of best management practices on controlling N loss were also explored during such extreme rainfall events. Results showed that extreme rainfall promoted transport of ON more than IN. The mass of ON and IN transported by the two typhoons exceeded 57 % and 39 % of the average annual N flux, respectively, and the loads were positively correlated with streamflow. During the two typhoons, the loss of ON was mainly concentrated in areas with steep slopes (θ > 15°) and natural vegetation (forests, grasslands, and shrublands). The IN loss was higher in areas with a 5-10° slope. Furthermore, subsurface flow was the main IN transport mechanism in areas with steep slope (θ > 5°). Simulations showed that implementation of filter strips in areas with slopes exceeding 10° can reduce N loss, with much greater reductions in ON (>36 %) than IN (>0.3 %). This study provides important insights into N loss during extreme events and the key role filter strips can play in trapping them before they reach downstream waterbodies.

Keywords: Extreme rainfall; LULC; Nitrogen; Non-point source; Slope.