Seasonal and Spatial Distribution and Pollution Assessment of Nitrogen and Phosphorus in Sediments from One of the World’s Largest Tidal Reservoirs
Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
Shanghai National Engineering Research Center of Urban Water Resources Co., Ltd., Shanghai 200082, China
State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China
Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
Author to whom correspondence should be addressed.
Academic Editor: Luís Filipe Sanches Fernandes
Water 2021, 13(4), 395; https://doi.org/10.3390/w13040395
Received: 20 December 2020 / Revised: 27 January 2021 / Accepted: 30 January 2021 / Published: 3 February 2021
(This article belongs to the Section Water Erosion and Sediment Transport)
Endogenous nutrients released from sediments are a potential hazardous source in aquatic ecosystems, especially reservoirs. Here, we investigated seasonal and spatial variations of different species of nitrogen and phosphorus and evaluated the pollution levels of nutrients in sediments from one of the world’s largest tidal reservoirs. The results indicate that most of the total nitrogen and phosphorus were accumulated in sediments from the reservoir downstream, which were enhanced by runoff and precipitation during seasonal alteration. Total nitrogen was increased to 2471.17 mg/kg during the saltwater intrusion period. Nitrate and ammonium were the major nitrogen fractions in flood and dry seasons, respectively, while the highest level of phosphorus, especially inorganic phosphorus, was found in summer. The sediment was slightly to moderately contaminated by nitrogen but not phosphorus, especially downstream in winter, according to the applied indices. Multivariate statistical analyses reveal that nutrient input in flood seasons was more complex than that in dry seasons, which possibly originated from upstream agricultural and domestic sewage.