Exopolysaccharide control of methane oxidation in landfill cover soil

The study objective was to examine whether a relationship exists between th e accumulation of exopolymeric substances (EPS) in landfill cover soil and the gradual decline in biotic methane oxidation observed in laboratory soil columns sparged with synthetic landfill gas. A mathematical model that com bined multicomponent gas diffusion along the vertical axis of the columns w ith biotic methane oxidation was used to predict vertical gas gradients in the columns. An initial trial assumed methane oxidizers were embedded in a thin base layer of biofilm coating the soil, and the model predictions fit experimental data from soil columns early in their operating period. A seco nd trial modeled the same system with a thick EPS layer coating the base bi ofilm and limiting diffusion of gases into and out of the cells. Prediction s from the latter trials fit experimental data from soil columns later in t heir operating period when lower methane consumption rates were observed. T he model results suggest that EPS accumulation may regulate methane oxidati on rates in landfill covers.