Sediment Oxygen Uptake: Kinetic Model Expressions and Their Relations to Sediment Quality

Abstract

        The oxygen uptake processes of suspended sediments (OUS) have been studied under laboratory conditions using an electrolytic BOD. The progressive exertion of OUS of given sediments generally increased with a tendency to taper off with time. Cumulative OUS curve showed a sharp initial increase of oxygen uptake, followed by relatively stable oxygen uptake rates that lasted until the fifth day of incubation. The expression of the curve was proposed to be accomplished by three distinct processes. The first; (A), a basic oxygen uptake phase in which organisms present in the sediments consumed oxygen biochemically with nearly constant rate. Mathematical equation, L_m = λt, was proposed to explain its characteristic. The second; (B), the immediate chemical oxygen uptake phase in which end-products of anaerobic decomposition such as hydrogen sulfides reacted chemically with molecular oxygen in the suspended sediment solution and first-order kinetic model was proposed as L_{c =} L_c∞  {1-exp[Ø(t-t_o)]}. The third; (C), the bacterial oxygen uptake phase in which specific labile organic matters were attached in significant amounts and bacterial respiration took place biochemically. Sigmoid characteristic of bacterial growth curve was fitted by the kinetic model L_{b =} L_b∞exp{(-K/ξ) exp[-ξ (t-t_o)]}. The approximated basic “λ” parameter showed significant relation to the levels of total organic carbon and total organic nitrogen of the sediments. The parameter “L_c∞” in the chemical oxidation phase reflected the quantity of sediment tatal sulfides, whereas “Ø” indicated the reaction rate that alternated as the change in sediment depths. The  parameter “L_b∞”of the bacterial respiration phase apparently related to sediment organic properties, and the parameters “K” and “ξ” illustrated the shape expression  of OUS during bacterial respiration phase and depended upon the depths of the deposits.