Sources and behavior of perchlorate in a shallow Chalk aquifer under military (World War I) and agricultural influences

Abstract

Perchlorate (ClO4ö) has been detected at concentrations of concern for human health on a large scale in groundwater used for drinking water supplies in NE France. Two sources are suspected: a military source related to World War I (WWI) and an agricultural source related to past use of Chilean nitrate fertilizers. The sources and behavior of ClO4ö have been studied in groundwater and rivers near the Reims city, by monitoring monthly the major ions and ClO4- concentrations for two years (2017–2019), and by measuring the isotopic composition of ClO4ö and NO3ö in water samples. ClO4ö was detected throughout the study area with high concentrations (> 4 μg⋅L-1) detected mainly downgradient of the Champagne Mounts, where large quantities of ammunition were used, stored and destroyed during and after WWI. A WWI military origin of ClO4- is inferred from isotopic analysis and groundwater ages. Different tendencies of ClO4- variation are observed and interpreted by a combination of ClO4- concentrations, aquifer functioning and historical investigations, revealing major sources of ClO4- (e.g., unexploded ordnance, ammunition destruction sites) and its transfer mechanisms in the aquifer. Finally, we show that concentrations of ClO4ö in groundwater seems unlikely to decrease in the short- to medium-term.