Distribution Characteristics of Phosphorus in the Yarlung Zangbo River Basin

Shuqing Nan,Wendian Huang,Ruidong An,Xunchi Pu,Linglei Zhang,Jia Li

doi:10.3390/w10070913

Abstract

Phosphorus is an important limiting biogenic material. The special topography and climate of the Yarlung Zangbo River Basin generate unique distribution and transport characteristics of total phosphorus (TP). A survey of TP concentration, precipitation, runoff, sediment content, suspended load discharge, and relevant data was carried out for the Yarlung Zangbo River Basin in the last ten years. In combination with the regional geography and social economies, the basic spatial-temporal characteristics of P-water-sediment were analyzed by using the correlation and time series analysis methods. Furthermore, the transport characteristics of P and the main control factors were also studied. The results show that the TP concentration in this basin displays the characteristics of interannual cyclical variation and annual phasic variation, and the peak value appears in the wet season. Among the Yarlung Zangbo River, Nyangqu River, Lhasa River, and Nyang River, the TP concentration is the highest in the Nyangqu River, exceeding 0.4 mg/L several times in the wet season. In this basin, the distribution patterns of the TP concentration are similar to those of the rainfall, runoff, suspended load discharge, and sediment concentration. The coupling property of the TP concentration is the strongest with the suspended load discharge among the meteorological and hydrological parameters. The spatial variation of dissolved P in the wet and dry seasons in 2016 responded to the distribution patterns of the population density, environmental factors, farming, and animal husbandry. This indicates that the TP in the water is mainly from non-point sources and is affected by agricultural, geographical, and ecological factors. The transport of TP is mainly controlled by the suspended load discharge due to precipitation.

Highlights

Phosphorus is one of the key elements in the primary production process of global aquatic ecosystems
In the United States, the quality level of total phosphorus (TP) is poor in 46% of the rivers [3]; in the European Union, the average annual TP concentration varies from 0.001 mg/L to 7.30 mg/L in rivers [4]; and among monitoring stations in various basins in China, the TP concentration at 15.1%
The following results have been obtained through this research: (1) In the YLZB River Basin, the fluctuation intensity of the TP concentration in a single year is larger than the interannual fluctuation intensity

Summary

Introduction

Phosphorus is one of the key elements in the primary production process of global aquatic ecosystems. The water may be eutrophicated and the original ecological structure destroyed if the concentration of total phosphorus (TP) is more than 0.2 mg/L [1,2]. In the United States, the quality level of TP is poor in 46% of the rivers [3]; in the European Union, the average annual TP concentration varies from 0.001 mg/L to 7.30 mg/L in rivers [4]; and among monitoring stations in various basins in China, the TP concentration at 15.1%. To study the migration and transformation of source elements, Europe and the United States launched the projects of Euroharp-nutret, Advances in Understanding Sources, Transport, and the Biological Effects Nutrients from Headwater Streams to Coastal Rivers, etc. The EU Water Framework Directive (WFD), the Clean Water Act (CWA), Water 2018, 10, 913; doi:10.3390/w10070913 www.mdpi.com/journal/water

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Conclusion