Anthropogenic Impacts on a Bedrock Aquifer at the Village Scale

Abstract

This study focuses on assessing groundwater potability in a highly complex and heterogeneous fractured bedrock aquifer having variable overburden cover. Eight monitoring wells were installed in a privately serviced lakeside village, and groundwater was routinely sampled over a 2-year timeframe for concentration analysis of nitrate, fecal indicator bacteria, stable isotopes, and a total of 41 pharmaceutical compounds. While pollutant concentrations remained low throughout the study, the presence of fecal indicator bacteria and pharmaceuticals was noted at least once (but not always consistently) in most sampling intervals. An interpretation based on the integration of chemical, bacterial, and site characterization datasets suggests that: (1) the fracture network is complex and heterogeneous with limited vertical connectivity; (2) existing pathways are sufficient for the quick and widespread migration of surface contaminants to depth; (3) anthropogenic contaminants from both septic systems and agriculture are likely sourced in the surrounding uplands where overburden is thin; and (4) fecal contamination, as observed over the long term, is ubiquitous at the village scale. Groundwater quality is continually changing in this hydrogeologic environment and the determination of potability on the larger scale is not likely to be adequately captured with infrequent domestic well sampling (i.e., voluntary annual sampling by homeowners).

The potential of major ion chemistry to assess groundwater vulnerability of a regional aquifer in southern Quebec (Canada)

“…However, index methods raise criticism because they often fail to predict the occurrence of contaminants in groundwater (Mehnert et al 2005;Stigter et al 2008). One reason could be because indexed aquifer vulnerability methods do not take into account groundwater flow dynamics, which may control the lateral migration of contaminants from the land surface to the aquifer (Kozuskanich 2014). The scientific literature holds many examples of modification and adaptation of index methods intended to increase their reliability in specific contexts or to increase their efficiency to correlate with contaminant occurrence (Bojórquez-Tapia et al 2009;Zhou 2012;Chen 2013).…”

Septic System Impacts on Source Water: Two Novel Field Tracer Experiments in Fractured Sedimentary Bedrock

“…Regardless of the causes of these malfunctions, failing septic systems pose serious health risks for Indigenous communities in Canada, and are particularly troubling for Indigenous communities located above fractured bedrock aquifers, where septic system malfunctions can lead to the rapid and widespread migration of contaminants in groundwater without much attenuation [14]. Even when no malfunctions are visible, septic systems pose a threat in these vulnerable aquifer settings where groundwater flow rates are rapid [25,26].…”

Impacts of a Rural Subdivision on Groundwater Quality: Results of Long‐Term Monitoring

“…Long‐term studies of the impacts of subdivisions on groundwater quality are few. Kozuskanich et al () conducted a 2‐year study of groundwater quality in a small village in Ontario (Canada) where residents rely on domestic wells for water supply and wastewater disposal is through septic systems. They repeatedly found fecal bacterial and pharmaceutical compounds in groundwater from eight monitoring wells in a fractured bedrock aquifer.…”