In-situ biofilm detection in field settings using multichannel seismic

Abstract

Biofilm aids a variety of geoengineering applications but a general lack of in-situ detection and monitoring methods severely limits its field usage. In this pioneering study, we show that in-situ field detection of biofilm may be possible through multichannel surface seismic. Our study was conducted at a landfill site in Norman, Oklahoma, where an ongoing interaction of a leachate plume with a fluctuating water table has created optimal conditions for biofilm growth. We acquired multichannel seismic data along a 130 m long profile and inverted the ground roll and refractions respectively for S-wave (VS) and P-wave (VP) velocity structures of the shallow (0–5 m) subsurface. We find that within ~1.2 m–~3.0 m depth, which is the water table fluctuation zone (WTFZ), VS increases by ~50% over the background but without any appreciable changes in the VP. Environmental scanning electron microscopy of soil samples from various depths along a core shows the presence of biofilm exclusively within the WTFZ. A VS-only increase due to biofilm growth is consistent with laboratory studies of similar nature and can be realized through a mechanistic model where biofilm is simultaneously present in two morphologies: grain-cementing and pore-filling. Our findings open doors to detecting biofilm in a variety of settings such as hyporheic zones and contaminant plume fringe and for a range of purposes from soil remediation to carbon sequestration to detecting life in other planets.