Abstract

  Temporary water reservoirs built on peat soils may exhibit water quality impairment from elevated dissolved organic carbon (DOC) build-up. Microbiological decay of the organic carbon in the bed, with subsequent DOC release, produces "tea" colored water which may require treatment prior to use. The objective of this study was to conduct experiments for developing a quantitative rate expression for DOC release from the peat sediment source. A series of experiments were designed to obtain data on the release process of three peat soils with 0.65, 10 and 19% carbon respectively. Parallel DOC release experiments with and without sodium azide treatment of the soils was used to distinguish between the residual DOC diffusive release from porewater and that produced within the bed by microbial processes. The DOC rates delivered to the water column increased while the inorganic carbon (IC) rates decreased as percent carbon in the sediment bed increased. At each of the three %C levels tested the DOC production rate was a constant. DOC production by the 10 and 19%C sediment is an anaerobic process that is terminated by sodium azide addition. For the low %C sediment IC production appeared to be an abiotic process. A coupled reaction-diffusion model with a constant DOC rate equation was consistent with the experimental data collected. A constant rate of production consolidates all the data and supports a consistent %C functionality. Based on the data and the model it appears that a small "diffusive release" pulse of DOC appears in the reservoir water initially following flooding. This is then followed by a much larger quantity causing concentration to increase linearly with time. A predictive algorithm based on the model is offered as a means of estimating the DOC concentration versus time build-up in the reservoir water column.