Using Natural Tracers to Track the Groundwater Flow in a Mining Area

Natural tracers, including 222Rn, 226Ra, δ18O, and δ2H are frequently used in hydrological studies to determine the origin, dynamics and mixing of waters. In order to assess the seasonal variation of groundwater flow in Rosia Montana mining area, water samples have been collected from ten points for nine months, on a monthly basis. The 222Rn and 226Ra concentrations reflect a low level of radioactivity in the area, the values being below the national and international thresholds for drinking water. Significant differences in the trends of the isotopic composition have been noticed, both for the mining affected and non-affected sampling sites, suggesting different pathways, residence times and geochemical processes that may occur. A Local Meteoric Water Line needs to be built in order to compare the measured isotopic ratios. The groundwater recharge in the system of galleries comes from atmospheric precipitations, being submitted to a longer or shorter path, and very likely, to different degrees of interaction with the rock. The performed preliminary investigations have revealed the good potential to a more complete image on the underground water circulation and related processes by using a combination of isotopic and classic chemical analyses.