Experimental and simulation studies on the attenuation coefficients of organic pollutants in “Han River and Three Tributaries” basin, China

Abstract In order to study the attenuation mechanism and spatial and temporal evolution of organic pollutants in “Han River and Three Tributaries” basin, laboratory experiments were conducted, and a novel COD attenuation coefficient model was proposed. The main environmental factors affecting COD attenuation were identified. On this basis, the attenuation term of the one-dimensional water quality model is modified, and the spatial and temporal distribution characteristics of COD in Hanbei River are simulated and analyzed using the modified water quality model. The results show that: (1) the attenuation process of COD in Hanbei River is basically in accordance with the first-order reaction kinetics, and biodegradation accounts for a large proportion of the whole attenuation process. Within a certain range, the increase of flow velocity, water temperature and sand content promoted COD attenuation, and the effect of sediment particle size on COD attenuation in Hanbei River was not obvious; (2) based on the experimental results, a model for calculating the attenuation coefficient of pollutants is derived. A time varying attenuation coefficient can be calculated, which can realistically reflect the attenuation process and the distribution pattern along the river under the changing environment; (3) Model simulations determined that the COD attenuation coefficient of Hanbei River ranged from 0.03 to 0.19. The research results of this paper provide a scientific and theoretical method to accurately determine the attenuation coefficient of pollutants. It also provides scientific support for determining the ecological water demand of typical rivers and lakes similar to “Han River and Three Tributaries” and the scale of water diversion for Interconnected River System Network.