Evidence for tritium persistence as organically bound forms in river sediments since the past nuclear weapon tests

Abstract

Tritium of artificial origin was initially introduced to the environment from the global atmospheric fallout after nuclear weapons tests. Its level was increased in rainwaters by a factor 1000 during peak emissions in 1963 within the whole northern hemisphere. Here we demonstrate that tritium from global atmospheric fallout stored in sedimentary reservoir for decades as organically bound forms in recalcitrant organic matter while tritium released by nuclear industries in rivers escape from such storages. Additionally, we highlight that organically bound tritium concentrations in riverine sediments culminate several years after peaking emission in the atmosphere due to the transit time of organic matter from soils to river systems. These results were acquired by measuring both free and bound forms of tritium in a 70 year old sedimentary archive cored in the Loire river basin (France). Such tritium storages, assumed to be formed at the global scale, as well as the decadal time lag of tritium contamination levels between atmosphere and river systems have never been demonstrated until now. Our results bring new lights on tritium persistence and dynamics within the environment and demonstrate that sedimentary reservoir constitute both tritium sinks and potential delayed sources of mobile and bioavailable tritium for freshwaters and living organisms decades after atmospheric contamination.

3He flux obtained from South Pole air and snow‐ice and its connection to interplanetary dust particles

“…Still, it is unclear why the 3 He would adhere to the oily residue. Previous work has shown that bomb tritium can be organically bound (Eyrolle et al., 2019) but whether organics would host tritium in the biologically poor South Pole environment, and whether organic molecules can retain 3 He, are open questions. Note that production of 3 He by the beta decay of tritium‐rich fallout would not affect the vast majority of the core samples, most of which were deposited before the atomic era.…”

Deciphering sources of U contamination using isotope ratio signatures in the Loire River sediments: Exploring the relevance of 233U/236U and stable Pb isotope ratios

“…It is important to note that in the case of fluvial environments, the sedimentation rate is variable over time contrary to lakes and quiet environments. Consequently, the 210 Pb xs dating method is not available in this study as previously mentioned in Grosbois et al (2012), Eyrolle et al (2019), Morereau (2020) and Copard et al (2021). Hence, these identified chronological landmarks (1963, 1969, 1980 and 1986) allow obtaining a robust age model presenting two main periods with constant sedimentation rates, the 1963 -1986 period with 2.4 ± 0.2 cm/y and the 1986 -2016 period with 1.3 ± 0.2 cm/y with uncertainties estimated to ± 2 years.…”

“…In 1969 and 1980, two nuclear accidents took place at the former Saint-Laurent-des-Eaux NPP (NUGG reactors named SLA1 and SLA2 respectively). These events led to the fusion of fuel elements and plutonium was detected in water and sediment in the Loire River (Eyrolle et al, 2019;Guignard and Catoire, 2015;IRSN, 2016;Thomas, 1982). All NUGG reactors located on the Loire watershed were definitely stopped in 1992.…”

“…Operations in both U mining sites and NPPs can lead to radionuclide releases increasing their concentration in the environment. Several studies were performed in order to retrace the historical evolution and the origin of various radionuclides transiting along the Loire River during the last century (Copard et al, 2021;Eyrolle et al, 2019). Nevertheless, the uranium and lead from nuclear activities which were transferred along the Loire River since the beginning of the nuclear age remain poorly documented.…”

Hydrogeological Behaviour and Geochemical Features of Waters in Evaporite-Bearing Low-Permeability Successions: A Case Study in Southern Sicily, Italy

“…(1) The chemical component carrying 3 H may also be the cause of increasing δ 2/1 H. This carrier could be methane formed by degradation of organic matter in an environment where tritium may reach high values, such as sediments rich in organic matter that acquired a high tritium concentration at the time of atomic weapon experiments. For instance, Eyrolle et al [98] reported high tritium concentrations in the organic portion of the sediments from the Loire River in Western France.…”