Determination of Sediment Oxygen Demand in the Ziya River Watershed, China: Based on Laboratory Core Incubation and Microelectrode Measurements.

Nan Rong,Baoqing Shan,Chao Wang

doi:10.3390/ijerph13020232

Abstract

A study coupling sedimentcore incubation and microelectrode measurementwas performed to explore the sediment oxygen demand (SOD) at 16 stations in the Ziya River Watershed, a severely polluted and anoxic river system in the north of China. Total oxygen flux values in the range 0.19–1.41 g/(m2·d) with an average of 0.62 g/(m2·d) were obtained by core incubations, and diffusive oxygen flux values in the range 0.15–1.38 g/(m2·d) with an average of 0.51 g/(m2·d) were determined by microelectrodes. Total oxygen flux obviously correlated with diffusive oxygen flux (R2 = 0.842). The microelectrode method produced smaller results than the incubation method in 15 of 16 sites, and the diffusive oxygen flux was smaller than the total oxygen flux. Although the two sets of SOD values had significant difference accepted by the two methods via the Wilcoxon signed-rank test (p < 0.05), the microelectrode method was shown to produce results that were similar to those from the core incubation method. The microelectrode method, therefore, could be used as an alternative method for traditional core incubation method, or as a method to verify SOD rates measured by other methods. We consider that high potential sediment oxygen demand would occur in the Ziya River Watershed when the dissolved oxygen (DO) recovered in the overlying water.

Highlights

Dissolved oxygen (DO) is one of the most important indicators of water and ecosystem quality in rivers, channels, reservoirs, and lakes
dissolved oxygen (DO) in the overlying water declined to 2 mg/L in 24 h for most cores, the someexception cores thatoftook h tomore decline below level
The findings of this study suggest that there is some calibration relation between the laboratory incubation method and microelectrode method for Sediment oxygen demand (SOD) measurement in this research region

Summary

Introduction

Dissolved oxygen (DO) is one of the most important indicators of water and ecosystem quality in rivers, channels, reservoirs, and lakes. The variability of DO in rivers is caused by the influence of either sources or sinks of oxygen. Sediment oxygen demand (SOD) is a major oxygen sink, in addition to respiration by aquatic plants and the oxidation of organic materials and other reduced matters in the water column. SOD has been defined as the rate of oxygen consumption, biologically or chemically, on or in the sediment at the bottom of a water body [3]. SOD encompasses both the respiration rates of benthic communities and the chemical oxidation of reduced substances in the sediment [4]. It is essential to estimate the oxygen demand exerted by sediments

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