Ecological Indicators (Oct 2022)
Quantitative analysis of self-purification capacity of non-point source pollutants in watersheds based on SWAT model
Abstract
It is of great value to reveal the self-purification capacity of surface-sourced nutrients in the watershed and its change pattern, which is important to enrich the study of self-purification capacity of rivers and provide scientific basis for river water environment management. Based on the SWAT model and different self-purification capacity expression indicators, the self-purification capacity of non-point source pollutant nutrients and its change pattern in each river section of the Yiluo River basin from 2018 to 2021 were analyzed, and the physical significance of each indicator, its influence factor and its use range were systematically discussed. The results show that the self-purification of TN and TP in the Yiluo River exceeds 50% of the self-purification of the whole water system, but the self-purification rate is smaller than that of the Yiluo and Luo Rivers; the self-purification of TN and TP is the largest during the abundant water period and the smallest during the dry water period. The self-purification capacity expressed by the indicators of self-purification amount RL and area self-purification amount RA increases with the increase of hydrological variables such as flow (including water depth and velocity), river morphological parameters such as river width and length, and pollutant load; The self-cleaning ability expressed by the self-cleaning coefficient Kx/Kt, self-cleaning length SL, self-cleaning rate Re and load weight self-cleaning rate RLw is opposite; The self-purification rate Vf of the river only increases with the increase of water temperature. From the perspective of differences in application, the two indicators of self-purification speed Vf and area self-purification amount RA should be used for spatial comparison; The other six indicators should be used for the comparison of the same river at different times, of which the self-purification length SL can be used to reflect the influence of hydrological conditions on the self-purification process because of its sensitivity to changes in hydrological conditions.
