Occurrence Characteristics of Nitrogen and Phosphorus at Sediment-Water Interface in the Xiangxi Bay and Phosphorus Release Risk
To investigate the dynamic distribution of nutrient salts in the tributaries of the Three Gorges Reservoir Area,a survey was conducted from June 2016 to June 2022 to examine the temporal and spatial distribution of total nitrogen(TN)and total phos-phorus(TP)in the sediment,interstitial water and overlying water of the Xiangxi Bay in the Three Gorges Reservoir Area,and the risk of phosphorus release was also analyzed.The results showed that during the complete flooding-drying cycle(June 2016 to March 2017)the total TN and TP contents in spring and summer were higher than those in autumn and winter,and the TP con-tents of sediments in the upper and middle reaches were higher than those in the lower reaches;the TN and TP contents decreased with increasing depth.There were significant differences in the TN and TP mean contents between overlying water and interstitial water(TN:2.32 and 11.41 mg/L,TP:0.19 and 0.45 mg/L,respectively).The annual variations(2016-06,2019-06 and 2022-06)indicated that there were no significant annual changes in TN and TP contents in the sediment.The TN contents in over-lying water showed an apparent decreasing trend over time.The annual variation trend of TP contents in the overlying water of the upstream sampling site(S1)was consistent with that in the sediment,decreasing year by year.The range of TP release fluxes from sediments was 0.024～0.140 mg·m-2·d-1,demonstrating that phosphorus in sediments might act as a"source"and pose a risk of release into water bodies.
the Three Gorges Reservoir Areathe Xiangxi Baysedimentnitrogenphosphorusrelease flux
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