[Water Environment Characteristics and Water Quality Assessment of Typical Lakes in Inner Mongolia]

Lakes on the Inner Mongolia Plateau, located in the ecologically fragile area of the northern border of China, play a very important role in regulating the regional climate and ecological environment and maintaining biodiversity. Owing to the dual influence of natural factors and human factors, the lake water environment in Inner Mongolia is facing challenges. To clarify the overall water quality of lakes in Inner Mongolia, based on the water quality data of typical lakes in Inner Mongolia in autumn 2019(October-November) and summer 2021(July-August), the temporal and spatial variation in water quality was discussed, and the influence of different indexes on lake water quality was analyzed, and the key factors affecting lake water quality were identified. The results showed as follows:① the spatiotemporal distribution of multiple physicochemical indices of typical lakes in Inner Mongolia were different in the two seasons. On the time scale, the concentration of ammonia nitrogen(NH₄⁺-N) and nitrite nitrogen(NO₂^--N) were lower in autumn than that in summer, whereas dissolved oxygen(DO) was higher in autumn than that in summer. On the spatial scale, the concentrations of total phosphorus(TP), total nitrogen(TN), chemical oxygen demand(COD), and salinity(Sal) and other indicators in the southwest lakes of Inner Mongolia were higher than those of lakes in the northeast, but the DO index showed the opposite trend. ② Dissolved total solids(TDS) was the main characteristic factor of water quality of typical lakes in Inner Mongolia. ③ The spatiotemporal distribution of lake water quality index(WQI) was significantly different. The lake water quality level decreased with the increase in TDS, and the lake water quality was better in autumn than that in summer.