The Impact of Sediment–Water Ratio and Hydraulic Residence Time on the Release of Inorganic Nitrogen from Sediments in the Pearl River Delta

Author:

Gong Zerui1,Wang Yanling1,Hu Heping2,Chen Pengfei1ORCID,Lu Yao1,Wang Lei1,Huang Shaobin1

Affiliation:

1. School of Environment and Energy, South China University of Technology, Guangzhou 510006, China

2. China Water Resources Pearl River Planning Surveying & Designing Co., Ltd., Guangzhou 510610, China

Abstract

Black-odorous water bodies in the Pearl River Delta have been treated. However, the re-release of nitrogen (N)-containing compounds in sediment can cause a relapse of black-odorous water bodies. Sediment–water ratio (SWR) and hydraulic residence time (HRT) influence pollutant release. Therefore, how to control SWR and HRT during the treatment process has become an urgent problem. This study focuses on the dynamic release of endogenous inorganic N from sediments into overlying water in a river channel of Dongguan City, Guangdong Province. Physicochemical parameters (dissolved inorganic nitrogen (DIN), NH4+-N, NO3−-N, NO2−-N, dissolved oxygen (DO), pH, oxidation-reduction potential (ORP), chemical oxygen demand (COD), Fe and total phosphorus (TP)) of overlying water were monitored under different SWRs (0.71, 0.38, and 0.16) and HRTs (13 days and 6.5 days), and the nitrogen release flux under different conditions was compared. Finally, the correlation and influence pathways among environmental factors were analyzed. The results showed that SWR significantly affected DO, pH, ORP, and sediment N release fluxes while prolonging HRT-promoted denitrification. DIN → NO2−-N → DO pathway had a total effect of 19.6%, and DIN may promote low DO concentration via NO2− oxidation. Maintaining reasonable SWR and HRT can reduce the release of inorganic N from sediment into the overlying water. This study provides a theoretical basis for controlling black-odorous water bodies.

Funder

National Natural Science Foundation of China

Science and Technology Innovation Program from Water Resources of Guangdong Province

Publisher

MDPI AG

Subject

Water Science and Technology,Aquatic Science,Geography, Planning and Development,Biochemistry

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