es5b02690_si_001.pdf (167.31 kB)
In Situ Detection of Subsurface Biofilm Using Low-Field NMR: A Field Study
journal contribution
posted on 2015-09-15, 00:00 authored by Catherine
M. Kirkland, Maria P. Herrling, Randy Hiebert, Andrew T. Bender, Elliot Grunewald, David
O. Walsh, Sarah L. CoddSubsurface
biofilms are central to bioremediation of chemical contaminants
in soil and groundwater whereby micro-organisms degrade or sequester
environmental pollutants like nitrate, hydrocarbons, chlorinated solvents
and heavy metals. Current methods to monitor subsurface biofilm growth
in situ are indirect. Previous laboratory research conducted at MSU
has indicated that low-field nuclear magnetic resonance (NMR) is sensitive
to biofilm growth in porous media, where biofilm contributes a polymer
gel-like phase and enhances T2 relaxation.
Here we show that a small diameter NMR well logging tool can detect
biofilm accumulation in the subsurface using the change in T2 relaxation behavior over time. T2 relaxation distributions were measured over an 18 day
experimental period by two NMR probes, operating at approximately
275 kHz and 400 kHz, installed in 10.2 cm wells in an engineered field
testing site. The mean log T2 relaxation
times were reduced by 62% and 43%, respectively, while biofilm was
cultivated in the soil surrounding each well. Biofilm growth was confirmed
by bleaching and flushing the wells and observing the NMR signal’s
return to baseline. This result provides a direct and noninvasive
method to spatiotemporally monitor biofilm accumulation in the subsurface.