Nutrients releasing from fish feed and Potamogeton Crispus L. residuals

Abstract

The releasing experiments of Nitrogen, Phosphorus and Organic matter from the residual fish feed and Potamogeton Crispus L residuals. were carried out in Nansi Lakes. The results showed that the amount of Nutrients released by the little particles is much more than the big ones. The release of Nitrogen from the 3 kind of residual fish feed were rapid at the first stage, reached the peak value of 6.6 mg/l,3.7 mg/l,2.5 mg/l, respectively, then be stable and finally increased again; The release of Phosphorus from the 3 kind of residual fish feed were increased flatly,and finally reached the maximum value of 4.4 mg/l,6.3 mg/l,5.3 mg/l, respectively; while the release of COD was rapid at the first stage, reached the maximum value of 123.5 mg/l,83.7 mg/l,71.4 mg/l, respectively and finally reached an equilibrium value. The DO content in the water column decreased during the whole release process, and finally reached the minimum value of 0.14 mg/l,0.25 mg/l,0.19 mg/l, respectively. The release rate of Nitrogen, Phosphorus and COD from the decaying Potamogeton Crispus L. residual sgradually increased till to the 8th day with a peak value of 7.43 mg/l,12.57 mg/l,0.67 mg/l,1.18 mg/l,97.56 mg/l,229.05 mg/l, respectively., and then decreased, and then decreased till to 14th day.