Exploring 222Rn as a tool for tracing groundwater inflows from eskers and moraines into slope peatlands of the Amos region of Quebec, Canada

Publication date: November 2016
Source:Journal of Environmental Radioactivity, Volume 164
Author(s): Laureline Berthot, Daniele L. Pinti, Marie Larocque, Sylvain Gagné, Miryane Ferlatte, Vincent Cloutier
Peatlands can play an important role in the hydrological dynamics of a watershed. However, interactions between groundwater and peat water remain poorly understood. Here, we present results of an exploratory study destined to test radon (²²²Rn) as a potential tracer of groundwater inflows from fluvioglacial landform aquifers to slope peatlands in the Amos region of Quebec, Canada. ²²²Rn occurs in groundwater but is expected to be absent from peat water because of its rapid degassing to the atmosphere. Any ²²²Rn activity detected in peat water should therefore derive from groundwater inflow. ²²²Rn activity was measured in groundwater from municipal, domestic wells and newly drilled and instrumented piezometers from the Saint-Mathieu-Berry and Barraute eskers (n = 9), from the Harricana Moraine (n = 4), and from the fractured bedrock (n = 3). Forty measurements of ²²²Rn activity were made from piezometers installed in five slope peatlands, along six transects oriented perpendicular to the fluvioglacial deposits. The relationship between ²²²Rn and total dissolved solids (TDS) measured in water from the mineral deposits underlying the peat layer suggests that ²²²Rn is introduced by lateral inflow from eskers and moraine together with salinity. This input is then diluted by peat water, depleted in both TDS and ²²²Rn. The fact that a relationship between TDS and ²²²Rn is visible calls for a continuous inflow of groundwater from lateral eskers/moraines, being ²²²Rn rapidly removed from the system by radioactive decay. Although more research is required to improve the sampling and tracing techniques, this work shows the potential of ²²²Rn tracer to identify groundwater inflow areas from granular aquifers found in eskers and moraines to slope peatlands.



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