School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, 136 Jinshui East Road, Zhengzhou 450046, China.
Shanghai Municipal Engineering Group, Shanghai Municipal Engineering Design Institute, 901 North Zhongshan Road, Shanghai 200092, China.
Int J Environ Res Public Health. 2021 Jun 6;18(11):6138. doi: 10.3390/ijerph18116138.
In recent years, problems such as water quality deterioration, saltwater invasion, and low oxygen have appeared in estuaries all over the world. The Minjiang River in Fujian, as a typical tidal estuary area, is facing these thorny problems. In this paper, the effects of topography and hydrologic evolution on the water age and water quality of the lower reaches of the Minjiang River were simulated by building a hydrodynamic and water quality model. The results show that: (1) It was found that the riverbed incision of the lower reaches of the Minjiang River led to the overall decline of river water level, the increase of river volume, and the increase of downstream water age, which eventually led to the decrease of dissolved oxygen (DO) and the deterioration of water quality in the downstream from Shuikou to Baiyantan. However, the decline of topography led to the increase of tidal volume in the estuary, the enhancement of the dilution effect of oxygen-rich water bodies in the open sea, and the increase of DO in the lower reaches of Baiyantan. (2) Under no tidal action, the concentration of pollutants in the water of the North Channel increased, the DO decreased, and the DO decreased from Baiyantan to the offshore water. After the enhancement of tidal action, the dilution of oxygen-enriched water from the offshore water increased, and the DO increased. (3) The hydrological and water quality characteristics of the upper part of the lower reaches of the Minjiang River were mainly controlled by topography, runoff, and pollutant discharge, which were more affected by the tidal current transport operation and pollutant discharge near the open sea. In recent decades, the deterioration of water quality and the aggravation of saltwater intrusion in the Minjiang River were closely related to the serious topographic downcutting. The results provide a scientific basis for revealing the deterioration of estuary water quality and long-term management of the estuary.
近年来，世界各地的河口都出现了水质恶化、海水入侵和低氧等问题。福建闽江作为一个典型的潮汐河口地区，也面临着这些棘手的问题。本文通过建立水动力和水质模型，模拟了地形和水文演化对闽江河口下游水龄和水质的影响。结果表明：（1）闽江河口下游河床下切导致河水位整体下降、河流量增加、下游水龄增加，最终导致下游自水口至白岩潭段溶解氧（DO）下降、水质恶化。但地形下降导致河口潮量增加，开阔海域富氧水体的稀释效应增强，白岩潭下游 DO 增加。（2）无潮流作用时，北港水中污染物浓度增加，DO 下降，DO 自白岩潭至近海逐渐下降。潮流增强后，来自近海的富氧水稀释作用增强，DO 增加。（3）闽江河口下游上段的水文水质特征主要受地形、径流量和污染物排放控制，受近岸潮流输运作业和污染物排放影响较大。近几十年来，闽江水质恶化和海水入侵加剧与严重的地形下切密切相关。研究结果为揭示河口水质恶化和河口长期管理提供了科学依据。
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