Temporal and spatial variations of nutrients in Baiyangdian Lake, North China

Baiyangdian Lake is the largest shallow freshwater body in the North China Plain. In this study, the spatial and temporal variations of nutrients have been studied based on the monthly data of eight state monitoring stations from 2000 to 2009. The results showed that: (1) Total phosphorus and total nitrogen were major pollutants in Baiyangdian Lake. The synthesized trophic state index indicated that the lake was in eutrophic or supereutrophic state. (2) Total phosphorus concentrations were higher in summer and autumn, and total nitrogen concentrations were higher in autumn and winter for most years from 2000 to 2009. Inter-annual water quality analysis showed that Baiyangdian Lake was seriously polluted in 2006, and the water quality in 2009 was the best in recent decade. (3) The water quality in the west of the lake was worse than that in eastern section, which caused by the point source pollution. In addition, nitrogen and phosphorus from non-point source might enter the lake through domestic sewage, the wastes and animal husbandry from the villages in the lake. (4) Variations of water level were influenced by both precipitation and water recharges. Total phosphorus concentrations in the lake were negatively correlated with water levels for most years, inferring that the dilution effects of water recharges could relieve water pollution in Baiyangdian Lake. This study suggested that the integrated management of water resources should focus on both pollution source control and water recharge regulations.