Using radon as a groundwater tracer to study hypotelminorheic habitats

Hypotelminorheic, or shallow groundwater, habitats are important hot spots of urban biodiversity that have not been thoroughly studied. These habitats occur when groundwater discharges via small seepage springs into slight depressions in an area of low to moderate slope, known as a perched aquifer. Near Potomac Heritage Trail is a hypotelminorheic habitat that is home to the endangered invertebrate Stygobromus hayi (Hubricht & Mackin). In an effort to understand the hydrology of this critical habitat, this study explored whether radon could be used to determine residence time in the perched aquifer which could provide valuable information to preserve and protect S. hayi. The results from the study did not reveal significant correlations between radon concentration and seep discharge rate, most likely due to snowfall that disrupted the daily sample collection routine and caused a delayed influx of water from snowmelt into the perched aquifer. However, the correlation between radon and precipitation was statistically significant, suggesting it may be a useful indicator of hydrological processes in the seep. Further research spanning a longer time period and studying more sites is needed to provide greater insight towards understanding hydrological patterns in hypotelminorheic habitats.