A novel method of identifying estuary high-nutrient zones for water quality management

Linlin Wang; Xiaoyu Lei; Guo Yuehua; Yang Zhou; Jing-Cheng Han; Yuefei Huang; Bing Li; Xian-Zhong Mao; Zhaozhao Tang

doi:10.1016/j.scitotenv.2023.169578

A novel method of identifying estuary high-nutrient zones for water quality management

Sci Total Environ. 2024 Feb 20:912:169578. doi: 10.1016/j.scitotenv.2023.169578. Epub 2023 Dec 27.

Authors

Linlin Wang¹, Xiaoyu Lei², Guo Yuehua³, Yang Zhou⁴, Jing-Cheng Han⁵, Yuefei Huang⁶, Bing Li², Xian-Zhong Mao², Zhaozhao Tang⁴

Affiliations

¹ Water Science and Environmental Engineering Research Center, College of Chemical and Environmental Engineering, Shenzhen University, Shenzhen 518060, China; State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China.
² Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
³ CCCC First Navigation Bureau Ecological Engineering Co., Ltd., Shenzhen 518107, China.
⁴ Water Science and Environmental Engineering Research Center, College of Chemical and Environmental Engineering, Shenzhen University, Shenzhen 518060, China.
⁵ Water Science and Environmental Engineering Research Center, College of Chemical and Environmental Engineering, Shenzhen University, Shenzhen 518060, China. Electronic address: hanjc@szu.edu.cn.
⁶ State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China; Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China; State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining 810016, China.

PMID: 38154631
DOI: 10.1016/j.scitotenv.2023.169578

Abstract

Coastal shallow waters are highly vulnerable to pollution, often leading to the development of intricate eutrophication zones. However, accurately determining these areas poses a significant challenge due to the complex interplay of estuarine hydrodynamics and nutrient transformation. To address such issue, a novel method was proposed to identify high-nutrient zones through calculating the continuous zonation of released tracers when their instantaneous concentrations declined to 1/e of their initial values. The method was well tested using idealized estuary models with varying shape parameters, water depths and river discharges. The results consistently revealed that the boundaries of high-nutrient zones fell within the mixed zone, characterized by salinity levels of 10- 20 psu. In Shenzhen Bay, a typical shallow bay, distinct differences were observed in the concentrations of dissolved inorganic nitrogen (DIN) and PO₄^3-. Both the 20 psu isohaline and the proposed method effectively identified the partition boundary of high DIN and PO₄^3- in 2001-2010, but only the newly proposed method demonstrated accuracy in delineating the actual high-nutrient zone during the continuous nutrient reduction period from 2010 to 2020. This study provides a practical and feasible approach that can serve as an auxiliary decision-making tool for managing estuarine water environments, and it has potential to facilitate the implementation of timely and effective measures for pollution control.

Keywords: Estuary; Numerical model; Nutrient distribution; Zonation.