Modelling spatial oscillations in soil borehole bacteria

•A simple mathematical model.•Spatial oscillations in groundwater contaminants.•Microbial competition between fermenters and respiring heterotrophs plays the key role.•Self-sustained temporal oscillations plus spatial diffusion can give travelling waves.

Spatial oscillations in groundwater contaminant concentrations can be successfully explained by consideration of a competitive microbial community in conditions of poor nutrient supply, in which the effects of spatial diffusion of the nutrient sources are included. In previous work we showed that the microbial competition itself allowed oscillations to occur, and, in common with other reaction-diffusion systems, the addition of spatial diffusion transforms these temporal oscillations into travelling waves, sometimes chaotic. We therefore suggest that irregular chemical profiles sometimes found in contaminant plume borehole profiles may be a consequence of this competition.