Abstract
Concentration of linear alkylbenzenesulfonates (LAS) in the Lake Teganuma estuary indicated a seasonal variation and a downstream decrease. The downstream decrease in the studied section varied seasonally, and the average was nearly 60 % during 1987-1988. As to explain the decrease, we investigated biodegradation of LAS in water, diffusive exchange of dissolved phase LAS through the sediment/water interface, and settling of adsorbed phase LAS. The biodegradation rate constant (between 0.06 and 3.33d-1) in water and the diffusive flux rate (between -0.157 and 0.022mg·m-2·h-1) from water to sediment were obtained from field observations and experiments. Based on these information, a mathematical model was applied to simulate the downstream decrease of LAS in water. With this model, nearly 10 % of the total LAS from the river was found to be transported to sediment both in summer and winter. The settling flux of LAS in the lake estuary was ten times greater than the diffusive flux. The sessling flux was ten times smaller than the disappearing flux by biodegradation in summer but was the same level in winter.
