A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science

Thesis (M.Sc.) - Asian Institute of Technology

Diffusional fluxes ranging from 14-30 mg NH4/m2-d and 0.1-0.5 mg P04/m2-d were computed for Laguna Lake sediments. Laboratory and in situ experimental results ~ielded rates of release in the order of 5-8 mg TIN/m2-d and 0.5-0.8 mg DIP/m -d. On the other hand, nutrient budget calculations for TIN during the 1973-1977 period showed slightly lower values, 4-5 mg TIN/m2-d, which are believed to be overestimates since the larger component would be accounted for by internal recycling of N in the water column. DIP budget calculations revealed P uptake by the sediments instead of release over the four-year period at rates of 0.8-1.0 mg DIP/m2-d. Based on these, Laguna Lake sediments would not be major sources of nutrients and, as in the case of phosphorus, could even serve as a nutrient sink. The transport of N across the sediment-water.interface was not as predo- minantly controlled by the concentration gradient between the two phases, as was P flux. This indicates that the mechanism for P release involves mainly equilibrium-controlled chemical_processes, which are less prevalent in N sedi- ments enhanced TIN release while DIP release was inhibited under aerobic condi- tions.