Spatio-temporal Variation in Nutrient Profiles and Exchange Fluxes at the Sediment-Water Interface in Yuqiao Reservoir, China.

Wen Wen,Wu Wu,Jiang Jiang,Zhong Zhong,Yang Yang

doi:10.3390/ijerph16173071

Abstract

Nutrients released from sediments have a significant influence on the water quality in eutrophic lakes and reservoirs. To clarify the internal nutrient load and provide reference for eutrophication control in Yuqiao Reservoir, a drinking water source reservoir in China, pore water profiles and sediment core incubation experiments were conducted. The nutrients in the water (soluble reactive P (SRP), nitrate-N (NO3−-N), nitrite-N (NO2−-N), and ammonium-N (NH4+-N)) and in the sediments (total N (TN), total P (TP) and total organic carbon (TOC)) were quantified. The results show that NH4+-N was the main component of inorganic N in the pore water. NH4+-N and SRP were higher in the pore water than in the overlying water, and the concentration gradient indicated a diffusion potential from the sediment to the overlying water. The NH4+-N, NO3−-N, and SRP fluxes showed significant differences amongst the seasons. The NH4+-N and SRP fluxes were significantly higher in the summer than in other seasons, while NO3−-N was higher in the autumn. The sediment generally acted as a source of NH4+-N and SRP and as a sink for NO3−-N and NO2−-N. The sediments release 1133.15 and 92.46 tons of N and P, respectively, to the overlying water each year.

Highlights

Eutrophication is widespread worldwide because of the coupled relationship between ever-growing human population and the concomitant increase in anthropogenic nutrient loading of aquatic ecosystems [1]
NH4 + -N was the main form of dissolved inorganic nitrogen (DIN) in the pore water (94.92%) in this study
High TN, TP, and TOC contents occurred in the sediments at Yuqiao Reservoir compared with other eutrophic lakes and reservoirs

Summary

Introduction

Eutrophication is widespread worldwide because of the coupled relationship between ever-growing human population and the concomitant increase in anthropogenic nutrient loading of aquatic ecosystems [1]. The increased nutrient (N and P) loading in overlying water promotes the growth of harmful algae and aggravates algal blooms [2,3]. These pose a threat to freshwater ecosystems and drinking water supplies because cyanobacteria synthesize toxic secondary metabolites, such as cyanotoxins [4]. Controlling the external input is one of the most effective ways to reduce the risk of algal blooms; in eutrophic lakes and reservoirs, nutrient release from sediments is an important source for the overlying water [5,6]. Controlling and reducing internal nutrient loading that is stored in the sediment is crucial for water quality. Nutrient flux at the SWI is a crucial factor affecting nutrient balance and regulating primary productivity in the water [8]

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