| Popis: |
In this study, we aimed to clarify the temporal and spatial variation and main influencing factors of water quality in Hanfeng Lake, which is the largest lake in the Three Gorges Reservoir(TGR) region of China. A total of 14 sampling sites were studied across different regions, including the inflow, main lake body, and outlet areas of the Hanfeng Lake basin. Water samples were collected at each sampling site at the end of each month in 2015 and water quality parameters were analyzed. Multiple statistical techniques were used to identify spatial and temporal variations in water quality. The water quality of Hanfeng Lake could be clustered into four spatial regions, including the incoming water area of Nan River(Region 1), the incoming water area of East River(Region 2), the upper reaches of Hanfeng Lake (Region 3), and the middle and lower reaches of Hanfeng Lake(Region 4). Variations in water quality could also be grouped into two distinct periods:Storage period(from January to February and September to December) and drainage period(from March to August). Trophic state analysis indicated that water quality in the regulating dam(HF5) and below the regulating dam(XJ1), both of which belonged to Region 4, exhibited moderate eutrophication; Sites in other regions showed slight eutrophication. The eutrophication level was lowest in January and December and highest in October, reaching moderate eutrophication levels; other months showed mild eutrophication levels. The concentrations of total nitrogen(TN), ammonium nitrogen(NH4+-N), nitrate nitrogen(NO3--N), total phosphorus(TP), soluble phosphorus(DP), orthophosphate(PO43--P), and permanganate index(CODMn) showed downward trends from upstream to downstream in the Hanfeng Lake basin. Principal component analysis results implied that soil and water losses contributed most to the deterioration of water quality in the Hanfeng Lake and the regulation of water levels related to the TGR also significantly affected the water quality. |
