Improvement of water quality has frequently been delayed due to high recycling rates of nutrients across the sediment-water interface in a reservoir. Diffusive fluxes and annual loads of ammonia nitrogen (NH4+-N) and phosphate (PO43--P) in sediments from Guanting Reservoir (GTR) were estimated according to their vertical distribution. The average contents of NH4+-N and PO43--P in surface pore water were higher by factors of 6.9 - 11.7 and 1.3 - 6.4 than those in overlying water, respectively. The ranges of fluxes were 1.59 - 13.0 (mg m2 d-1) for NH4+-N, and 0.002 - 0.196 (mg m2 d-1) for PO43--P. The annual load contributions from sediments of GTR were 659 t a-1 for NH4+-N and 4.83 t a-1 for PO43--P. Notably, the upstream of GTR accounted for 50.7% annual loads for NH4+-N, while the downstream contributed 71.2% loads to PO43--P. This study will better inform future environmental management for the reservoir.
Keywords: Diffusive flux; Guanting Reservoir (GTR); Pore water; Sediment–water interface.