An innovative application of stable isotopes (δ²H and δ¹⁸O) for tracing pollutant plumes in groundwater

The identification of the sources of contaminants present in groundwater at industrial sites is primordial to address environmental and industrial issues. However, available tools are often inadequate or expensive. Here, we present the data of stable isotopes (δ¹⁸O and δ²H) of the water molecule at an industrial site where electrochemistry plant occurs impacting the groundwater quality. High ClO₃ and ClO₄ contents and ²H enrichment have been measured in groundwater. Recharge of aquifer relates to infiltration of rainwater and by subsurface inflow. On-site, industrial products are generated by electrolysis. We show that the electrolysis process leads to a large ²H enrichment (+ 425‰) in solutions. In the absence of hydrothermal water input containing H₂S, we demonstrate that the relationship between δ¹⁸O and δ²H can be easily used in a way to trace the origin of the ClO₃ and ClO₄ in groundwater. Isotopes evidenced first a leakage from end-product storage tanks or during the production process itself. Then, an accumulation and release of ClO₃ and ClO₄ from soil is demonstrated. Our study successfully shows that stable isotopes are a powerful and low cost tool for tracing pollutant plumes in an industrial context using electrolysis process. - Highlights: • Available tools to trace the origin of pollutants at industrial sites are inadequate. • Data of stable isotopes of H₂O in groundwater at an industrial site are shown. • High ClO₃ and ClO₄ contents and ²H enrichment are found in groundwater. • The electrolysis process leads to a large ²H enrichment (+ 425‰) in solutions. • Isotopes enable to identify pollutants released from storage tanks or soil.