Spatial–Temporal Distribution of Phosphorus Fractions and Their Relationship in Water–Sediment Phases in the Tuojiang River, China

Dandan Liu,Yue Zhang,Qi Qiao,Zhibo Lu,Xueying Li,Lu Bai,Jingyang Liu

doi:10.3390/w14010027

Abstract

Understanding the distribution and transportation of phosphorus is vital for the sustainable development of aquatic environmental protection and ecological security. The spatial–temporal distribution of phosphorus fractions in water–sediment phases in river systems and their relationships remain unclear in Southwest China. In this study, the spatial and temporal distribution of phosphorus fractions in water–sediment phases in the Tuojiang River, a primary tributary of the Yangtze River which plays important roles in the economy and ecology of the region, and the relationships among the different phosphorus fractions were analyzed. These fractions were soluble reactive phosphorus (SRP), dissolved organic phosphorus (DOP), and total particulate phosphorus (PP) fractions in water, and exchangeable phosphorus (Ex-P), organic phosphorus (Or-P), phosphorus bound by Fe oxides (Fe-P), authigenic phosphorus (Ca-P), detrital phosphorus (De-P), and refractory phosphorus (Res-P) fractions in sediment. The SPR and Fe-P were the dominant phosphorus fractions in the water and sediment, respectively. The TP content was greater in the lower reaches than in the middle and upper reaches. The average abundances of most phosphorus fractions in water–sediment phases showed significant seasonal variations. The Fe-P, Org-P, and TP in sediments were released to the water interface, resulting in the increase of phosphorus in the overlying water. Redundancy analysis (RDA) indicated that the physicochemical properties of water and sediment have a certain influence on the spatial–temporal distribution of the phosphorus fractions. Principal component analysis (PCA) revealed that the main phosphorus source was anthropogenic activities. These results provide primary data regarding phosphorus fractions and contribute to understanding phosphorus cycling and controlling phosphorus pollution in the Tuojiang River.

Highlights

IntroductionPhosphorus is an essential nutrient element for biological growth, and excessive phosphorus is a crucial factor causing eutrophication in aquatic systems [1,2]
total phosphorus (TP)-W was positively correlated with dissolved organic phosphorus (DOP) in the dry season (Figure 5b). These findings indicated that the TP-W was affected by all phosphorus fractions of water in the dry season; the influence of DOP on TP-W was not obvious in the wet season
The spatial–temporal distribution of phosphorus fractions in water and sediments along the Tuojiang River were analyzed in the present study

Summary

Introduction

Phosphorus is an essential nutrient element for biological growth, and excessive phosphorus is a crucial factor causing eutrophication in aquatic systems [1,2]. Phosphorus bioavailability is related to the concentration of total phosphorus (TP), and to the phosphorus fraction [3] as soluble reactive phosphorus (SRP), dissolved organic phosphorus (DOP), and total particulate phosphorus (PP) in aqueous environments, and exists as six phosphorus fractions (exchangeable phosphorus (Ex-P), organic phosphorus (Or-P), phosphorus bound by Fe oxides (Fe-P), authigenic phosphorus (Ca-P), detrital phosphorus (De-P), and refractory phosphorus (Res-P)) in sediment. Each fraction has unique bioavailability, chemical reactivity, and environmental fate, which can play different roles in regulating water quality and the biogeochemical cycling of other bioactive elements in aquatic environments [4,5]. Understanding the distribution of phosphorus fractions is important in evaluating water quality and managing phosphorus pollution in aquatic environments [1]

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