Influence of sedimentation on nitrogen and phosphorus in the Three Gorges Reservoir

Abstract

ABSTRACT Most studies on nitrogen (N), phosphorus (P), and sedimentation in the Three Gorges Reservoir (TGR) have been mainly focused on the sedimentation distribution after impoundment of the TGR in 2003 and the adsorption and desorption effects of sediments on N and P. The present study investigated the correlation between sediment concentration and N and P, as well as the influence of the spatiotemporal distribution of sedimentation on N and P in the TGR. Based on on-site measurements and data collection, the main results concluded are as follows. The sediment concentration and total phosphorus (TP), total nitrogen (TN), and ammonia nitrogen (AN) are linearly correlated in turbid samples (TS) of the TGR; however, the correlations of the sediment with TN and AN are not as obvious as that of the sediment with TP. Since the impoundment, there has been a considerable decrease of TP and AN in the waters near the Three Gorges Dam (TGD) with the deposition of sediments; TP and TN have remained stable after normal operations of the TGR began. On the contrary, the TP and AN in the input section did not decrease with the impoundment. From the end to the head of the TGR, the TP and AN have gradually reduced, and the closer we approach the TGD, the lower the TP and AN; however, the decreasing trend of TP is much more significant than that of AN. Consequently, it has been verified that sedimentation was the main reason for the spatiotemporal distribution of N and P in the TGR. The results may lay the foundation for water environmental protection and management of the TGR.