The researchers studied phosphorus levels in the sediment of Shanzi Reservoir in different seasons. They found that the sediments had high phosphorus content, with more in summer. Inorganic phosphorus was the main form present, mostly bound to iron and organic matter. Dissolved phosphorus was released from the sediment more in summer than winter, affecting water quality. Summer rainstorms could disrupt water temperature layers, leading to more phosphorus release. In winter, phosphorus moved to the surface water layer, impacting water quality differently.