Investigation of chloroform plumes in a porous media

A sand box model was used in the laboratory to study the development and stability of the contaminant plume with respect to space and time. Steady, uniform flow velocities were established in a saturated, homogeneous, isotropic porous media by adjusting the heads in the upstream and downstream chambers. Chloroform was introduced as an instantaneous point source as well as a continuous point source. Samples were collected from a dense network of ports along and perpendicular to the direction of flow at regular time intervals, and their concentrations were determined using the Gas Chromatograph (GC) technique. The stability of the contaminant plume was studied while varying the concentration of the contaminant as well as the Darcy velocities. In the initial studies the development of the chloroform plume and the attenuation effect was observed. The results of this study showed that the stability of the chloroform plume depended both on the concentration as well as Darcy velocities. Computed values of the longitudinal and transverse dispersion coefficients for the chloroform ranged from 0.39 to 0.70 cm²/sec and 0.15×10³ to 0.21×10³ cm²/sec respectively. Also, the longitudinal and transverse dispersivity of the porous media was determined to be 0.195 cm and 0.0039 cm respectively, indicating the importance of advection in the transport process. There were significant changes in the dispersion coefficients to the variation in groundwater velocities than to the variation of chloroform concentrations.