The effect of a biofilm on solute diffusion in low-permeability rock.

摘要

In fractured rock environments, the diffusive process by which mass is transferred between the fracture and the intact rock, known as matrix diffusion, strongly influences the persistence of groundwater contamination. Biofilms are microbiological systems that develop when microorganisms colonize solid surfaces, and their presence in fractured rock may significantly affect the mobility of contaminants in the fracture network. The objective of this preliminary study is to explore the influence imparted by the presence of a biofilm on matrix diffusion. A composite semi-analytical model that describes solute transport by diffusion from a cylindrical reservoir into a layered medium of finite diameter is developed. The model is intended for the simulation of radial diffusion experiments. The boundary value problem is solved using the Laplace transform method and Crout's method of LU Decomposition, and numerically inverted from the Laplace domain with the De Hoog algorithm. Radial diffusion experiments were conducted using fully saturated rock core samples with central reservoirs. Biofilms were developed in half of the diffusion cells. (Abstract shortened by UMI.)