In recent years, due to unsustainable production methods and the demands of daily life, the water quality of the Yangtze River has deteriorated. In response to Yangtze River protection policy, and to protect and restore the ecological environment of the river, a two-dimensional model of the Jiangsu section was established to study the water environmental capacity (WEC) of 90 water environment functional zones. The WEC of the river in each city was calculated based on the results of the water environment functional zones. The results indicated that the total WECs of the study area for chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), and total phosphorus (TP) were 251,198 t/year, 24,751 t/year, and 3251 t/year, respectively. Among the eight cities studied, Nanjing accounted for the largest proportion (25%) of pollutants discharged into the Yangtze River; Suzhou (11%) and Zhenjiang (12%) followed, and Wuxi contributed the least (0.4%). The results may help the government to control the discharge of pollutants by enterprises and sewage treatment plants, which would improve the water environment and effectively maintain the water ecological function. This research on the WEC of the Yangtze River may serve as a basis for pollution control and water quality management, and exemplifies WEC calculations of the world’s largest rivers.

中文翻译：

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基于污染区控制的长江江苏段水环境功能区水环境容量计算

近年来，由于不可持续的生产方法和日常生活的需求，长江的水质恶化。为了响应长江保护政策，保护和恢复河流的生态环境，建立了江苏断面的二维模型，研究了90个水环境功能区的水环境容量。根据水环境功能区的结果，计算每个城市的河流的WEC。结果表明，研究区域的化学需氧量（COD），氨氮（NH ₃-N）和总磷（TP）分别为251,198吨/年，24,751吨/年和3251吨/年。在所研究的八个城市中，南京排入长江的污染物占最大比例（25％）。苏州（11％）和镇江（12％）紧随其后，无锡贡献最小（0.4％）。结果可帮助政府控制企业和污水处理厂的污染物排放，从而改善水环境，有效维持水的生态功能。对长江水电的这项研究可以作为污染控制和水质管理的基础，并举例说明世界上最大河流的水电计算。