Distribution Characteristics and Spatial Differences of Phosphorus in the Main Stream of the Urban River Stretches of the Middle and Lower Reaches of the Yangtze River

Lei Dong,Xianqiang Tang,Zhuo Huang,Li Lin,Liangyuan Zhao,Rui Li,Min Wu

doi:10.3390/w12030910

Lei Dong, Xianqiang Tang + Show 5 more

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https://doi.org/10.3390/w12030910

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Journal: Water	Publication Date: Mar 23, 2020
Citations: 8	License type: CC BY 4.0

Affiliation: Changjiang Water Resources Commission

Abstract

Excessive phosphorus is the main problem of water pollution in the main stream of the Yangtze River, while it is not clear about the distribution characteristics and spatial differences of phosphorus in the urban river stretches of the middle and lower reaches of the Yangtze River. In this study, a field survey in June 2014 revealed that the average particulate phosphorus (PP) concentration ranged from 0.195 mg/L to 0.105 mg/L from Wuhan (WH) in the middle reaches of the Yangtze River to Shanghai (SH, 1081 km from WH) in the lower reaches of the Yangtze River, and the average PP-to-the total phosphorus (TP) ratio decreased from 85.71% in WH to 45.65% in SH, while the average soluble reactive phosphate (SRP) concentration ranged from 0.033 to 0.125 mg/L, and the average SRP-to-total dissolved phosphorus (TDP) ratio increased from 60.73% in WH to 88.28% in SH. In general, PP was still an important form of TP in the middle and lower reaches of the Yangtze River. The concentrations of PP and SRP at different sampling locations and water depths in the same monitoring section showed differences, which might be related to the transportation and sedimentation of suspended sediment (SS) and differences in the location of urban sewage outlets. Historical data showed that the concentration and particle size of the SS decreased over time, while the discharge of wastewater also increased over time in the Yangtze River Basin. The measured results showed that there was a significant positive correlation between SS and PP. As a result, the concentration of SRP might increase in the middle and lower reaches of the Yangtze River. If the SRP concentration is not properly controlled, the degree of eutrophication of water body could significantly increase in the Yangtze River estuary, the riparian zone of the urban river stretches, the tributary slow-flow section, and the corresponding lakes connected with the Yangtze River.

Highlights

With changing natural conditions and economic and social development in the Yangtze RiverBasin, the hydrological characteristics and the pollutants caused by human activities have changed; altering the concentrations of major pollutants
The contribution rates of chemical oxygen demand (COD) and ammonia nitrogen from point sources accounted for 54.2% and 55.9% of contribution, respectively, indicating that COD and ammonia nitrogen mainly came from point source pollution, which is closely related to the large-scale discharge of industrial and domestic wastewater
Along the main stream of the urban river stretches from the middle to lower reaches of the Yangtze River, the average turbidity level observably increased from 30.88 nephelometric turbidity units (NTU) in Wuhan (WH) to 64.40 NTU in Nanjing (NJ) and decreased to 51.28 NTU in Shanghai (SH), which increased by 66.1% overall

Summary

Introduction

With changing natural conditions and economic and social development in the Yangtze RiverBasin, the hydrological characteristics and the pollutants caused by human activities have changed; altering the concentrations of major pollutants. With changing natural conditions and economic and social development in the Yangtze River. The contribution rates of COD and ammonia nitrogen from point sources accounted for 54.2% and 55.9% of contribution, respectively, indicating that COD and ammonia nitrogen mainly came from point source pollution, which is closely related to the large-scale discharge of industrial and domestic wastewater. The contribution rates of TN and TP from point sources were only 21.4% and 24.5%, respectively, indicating that nitrogen and phosphorus were mainly from nonpoint source pollution [1]. In the past ten years, under the guidance of the water pollution prevention and control policy aimed at reducing COD and ammonia nitrogen in the aquatic environment, the treatment effect of ammonia nitrogen and COD was remarkable in the Yangtze River. The eutrophication of rivers due to hydrodynamic reasons are generally less severe than those of relatively static water bodies, such as lakes and reservoirs, but the accumulation of nutrients increases the risk of eutrophication of rivers

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