Abstract:

To determine the contribution of ammonia nitrogen release from the surface sediments of reservoirs, the total nitrogen and ammonia nitrogen contents in surface sediments ($<$10 cm), overlying water, and interstitial water in typical areas of a reservoir were analyzed via on-site sampling of a reservoir in East China combined with an ammonia nitrogen release test, which revealed the temporal and spatial distribution characteristics of nitrogen in the reservoir sediments. The results showed that the ammonia nitrogen and total nitrogen contents in the reservoir showed clear seasonal changes, and the total nitrogen concentration in the surface sediment was higher than that in the summer. The total nitrogen concentration in the surface sediment was higher than that in the overlying water, and the ammonia nitrogen diffusion flux in the sediment was 0.18$\sim$0.53 mg/(m$^{2}\cdot $d), which was one order of magnitude lower than that of a heavily polluted reservoir. During the thermodynamic distribution of ammonia nitrogen in the sediment-interstitial water-overlying water, the surface sediment had an adsorption effect on ammonia nitrogen, which could buffer the sudden ammonia nitrogen pollution problem to a certain extent; however, the strong disturbance of the water flow could also promote the diffusion of ammonia nitrogen in the sediment to the water body in a short time.

Key words: sediment, overlying water, interstitial water, nitrogen conversion, adsorption, desorption