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

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 (Rn) as a potential tracer of groundwater inflows from fluvioglacial landform aquifers to slope peatlands in the Amos region of Quebec, Canada. Rn occurs in groundwater but is expected to be absent from peat water because of its rapid degassing to the atmosphere. Any Rn activity detected in peat water should therefore derive from groundwater inflow. Rn 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 Rn activity were made from piezometers installed in five slope peatlands, along six transects oriented perpendicular to the fluvioglacial deposits. The relationship between Rn and total dissolved solids (TDS) measured in water from the mineral deposits underlying the peat layer suggests that Rn 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 Rn. The fact that a relationship between TDS and Rn is visible calls for a continuous inflow of groundwater from lateral eskers/moraines, being Rn 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 Rn tracer to identify groundwater inflow areas from granular aquifers found in eskers and moraines to slope peatlands.