Synchronicity Between the Rates of Reaeration and Pollutants Degradation During Self-Purification in a Large River

The pollutants after were discharged into the water can gradually degrade through the self-purification. The oxygen consumption and pollutant degradation rates characterize the self-purification of small and medium-sized streams, while the dynamics of the two characteristics for large rivers has not been reported yet. The in-situ investigation for 297 sites in the 1700 km stream of the Yangtze River was conducted. The oxygen consumption rate was 0.003d^- 1, and the degradation rate of organic pollutants was greater than that of inorganics. The degradation of anion surfactant was the fastest, while the degradation of TN was the slowest, with rates of 0.043 and 0.001 d^- 1, respectively. The oxygen consumption rate was negatively correlated with the degradation rate of COD, anion surfactant, and TP, indicating the synchronicity between reaeration and degradation during the self-purification. This study highlighted the role of synchronicity in modelling of water quality and estimation of environmental capacity for large rivers.