Contaminant Mass Distribution of a Mixed Organic Contaminant Plume Down-Gradient of an Aged DNAPL Source Zone in Sedimentary Rock




Buckley, Andrew Keith

Journal Title

Journal ISSN

Volume Title


University of Guelph


Releases of mixed organic solvent DNAPL occurred before 1970 at an industrial site. The DNAPL migrated through glacial sediments and shallow bedrock, accumulated between 45 and 55 m bgs in a fractured sandstone, and is a persistent source for a large groundwater plume. Here, the contaminant mass variability is characterized using five cored holes along a 238 m long transect orthogonal to groundwater flow and immediately downgradient of the source. Average sample frequency was 4.7 samples per metre. Results show distinct and sometimes unpredictable spatial variability of concentration and composition. One core was located 13 m from a hole cored and sampled in a similar manner 10.5 years earlier. Comparison of results shows an 85% reduction in total VOC mass, attributed mostly to groundwater flushing above the known DNAPL accumulation with evidence for some microbial degradation. These data are foundational to future mass flux estimates and source zone longevity calculations.



Contaminant Hydrogeology, Fractured Sedimentary Rock, Transect, Contaminated Groundwater, Discrete Fracture Network (DFN) Approach, Mixed Organic Solvent DNAPL Source Zone