Quantitative assessment of background pollutants using a modified method in data-poor regions

Evaluation of water environmental capacity in a northern river-reservoir continuum using environmental fluid dynamics code

The hydrodynamics, water temperature, and water quality model for the Dan River and Renzhuang Reservoir continuum were developed using field monitoring data and the Environmental Fluid Dynamics Code (EFDC). An in-situ water discharge experiment enabled the calculation of water propagation time using a simulated flood progression method and the hydrodynamics module of EFDC. Based on these model results, degradation coefficients for chemical oxygen demand, biochemical oxygen demand, nitrogen (N), phosphorus (P), fluoride, arsenic were determined, revealing significantly higher values when the wetland barrage was opening. According to field monitoring and EFDC model outputs, the water environment capacity (WEC) of total nitrogen (TN) in Dan River was even negative, with the WEC of TN and total phosphorus (TP) in Renzhuang Reservoir being very low at 147 kg/d and 1490 kg/d, respective. Furthermore, the water environment carrying capacity (WECC) was found to be extremely low (~0.2 %) and limited by TN and TP. The results demonstrated that the spatiotemporal variations of water quality presented by the EFDC model facilitate an intuitive and comprehensive observation of water quality compliance rates over time and space, providing valuable references for decision-makers. The WEC and WECC of the study area underscored the urgency of N and P coordination control.

Response of surface water quality characteristics to socio-economic factors in Eastern-Central China

Following the implementation of the strictest water resource management system in China, it has become increasingly important to understand and improve the surface water quality and the rate at which water function zones reach the water quality standard. Based on the monthly monitoring data from 450 monitoring sites at the provincial borders of 27 provinces in China in 2019, the overall surface water quality at provincial boundaries in China was evaluated. The Canadian Council of Ministers of the Environment-water quality index (CCME-WQI) showed that the provincial boundary water quality exceeded the fair level, and F1 was the most influential factor. Then, 27 factors that directly or indirectly affect the surface water quality were identified, and the indirect influencing factors were integrated into the ecological environmental quality index and human activities quantitative index. Finally, the 27 factors were integrated into six factors, and the relationship between these indicators and CCME-WQI as well as the concentration of influencing elements with respect to regulatory standard limits were analyzed. The proportion of building land was the most significant factor affecting the quality of the aquatic environment in provincial boundaries. In addition, the economic development level, proportion of farmland, and degree of social development were identified as significant influencing factors. The six factors have different degrees of impact on the concentrations of major elements with respect to standard limits. This study basically explores water resource management and offers significant reference and guidelines for the improvement of the quality of surface water at provincial boundaries in China.