Occurrence characteristics and transport fluxes of nitrogen and phosphorus at sediment-water interface of Panjiakou Reservoir in spring

The sediments from Panjiakou Reservoir were selected as the research object. The overall status of nutrient pollution and the release characteristics of internal loading of the reservoir were analyzed. The vertical distribution characteristics and spatial differences of nutrient were analysed by obtaining interstitial water in sediments via high-resolution interstitial water samplers (HR-Peeper). The transport fluxes of nutrient at the sediment-water interface were obtained by static release test of intact sediment cores, and the internal loading characteristics of Panjiakou Reservoir were analysed. The release risk of nutrient in the sediments was relatively high, and the TN and TP content was 3701.59~8221.28 mg/kg and 756.28~1696.15 mg/kg, respectively. According to the C/N ratio, the main cause of eutrophication in Panjiakou Reservoir was the residual feed and fish manure from cage culture before 2017. The static release results of the intact sediment cores showed that the exchange fluxes of NH4+-N, NO3--N, NO2--N and SRP were 23.71~156.80, -7.37 ~ -161.78, 1.64 ~ 33.4, and 0.56 ~ 2.86mg/(m2•d), respectively, and the internal loading of Panjiakou Reservoir was relatively high. The results are related to the high contents of organic matter, nitrogen and phosphorus, oxygen consumption by biological decomposition and gradually increasing water temperature in spring, which leads to the accelerated release of nutrient into the overlying water column. The internal loading of Panjiakou Reservoir can accelerate the process of eutrophication, and measures should be taken to control the internal loading of Panjiakou Reservoir. © 2021, Editorial Board of China Environmental Science. All right reserved.