An integrated approach combining soil profile, records and tree ring analysis to identify the origin of environmental contamination in a former uranium mine (Rophin, France)

A combined DGT - DET approach for an in situ investigation of uranium resupply from large soil profiles in a wetland impacted by former mining activities

“…The history, geology and hydrogeology of the Rophin tailings storage site have been described elsewhere (Martin et al 2020, Roux et al 2020. As a brief background, the U ore of Rophin, mainly parsonsite (Pb2(UO2)(PO4)2, 2H2O,UVI), was mined from 1949 to using an ore washing plant process and associated settling ponds that continued to operate until 1957 with pitchblende (UO2, UIV) from the 'Bois-Noirs' mine.…”

“…According to Martin et al (2020), these mining residues were released into the Rophin watershed, thus impacting the wetland under investigation.…”

“…This layer exhibits a low U concentration of around 50 mg.kg -1 , which is in accordance with the local geological background. This layer is considered as the soil reference prior to the period of mining operations and discharge of residues at the Rophin site (Martin et al 2020, Roux et al 2020. Just above the O-layer, the presence of gravels (64 to cm) should be noted, thus suggesting the existence of a former creek channeling mine discharge.…”

“…Understanding the fate of radionuclides in the vicinity of former uranium (U) mines is of great importance given both the potential enhancement of environmental dose rates and the transfer of radionuclides into ecosystems. Uranium concentrations may locally exceed natural background levels in the vicinity of former U mining sites (Fuller et al 2020, Chautard et al 2020, Lottermoser and Ashley 2005, Martin et al 2020, particularly in natural and artificial wetlands such as peats and flooded soils (Stetten et al 2018, Wang et al 2014, Wang et al 2013, Schöner et al 2009. All information on the geochemical speciation and dynamics of U in soils for the purpose of regulating U transfer into other environmental compartment is therefore of major interest.…”

“…In this study, a combination of DET and DGT probes was simultaneously deployed in situ within a particularly interesting wetland featuring an anthropogenic anomaly (Martin et al 2020, Roux et al 2020. The main objective of this work is to determine the lability of U according to soil characteristics as well as the origin of the contamination.…”