An innovative application of stable isotopes (δ 2 H and δ 18 O) 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 (δ18 O and δ2 H) of the water molecule at an industrial site where electrochemistry plant occurs impacting the groundwater quality. High ClO3 and ClO4 contents and 2 H 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 2 H enrichment (+425‰) in solutions. In the absence of hydrothermal water input containing H2 S, we demonstrate that the relationship between δ18 O and δ2 H 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.