DOI: 10.5061/dryad.dncjsxm2f
title: The nature and extent of bomb tritium remaining in deep vadose zones: A synthesis and prognosis

description: Tritium present in deep vadose zones is a useful tracer for estimating
 groundwater recharge, but its full utility is constrained by not knowing
 where and for how long the tritium tracing method remains applicable. We
 obtained 44 tritium profiles from 17 globally distributed sites with
 vadose zone thicknesses of 13−624 m and used transport models to estimate
 the number of years that tritium may still be useful. Results show that
 the method may still be usable for 26 of 44 soil profiles surveyed, mainly
 in China, Australia, USA, South Africa, and Senegal, with a remaining
 useful period of between 6 and 83 years. We also developed a statistical
 model that uses outputs from a hydrological model to predict the
 applicability of the tritium tracing method. Global implementation of the
 statistical model showed that the method remains usable at 20% of Earth’s
 land mass (excluding Antarctica and Greenland) over the next few decades.
description: The dataset – soil water tritium profiles (n = 40) – was compiled
 from the peer-reviewed literature (see Text S2 in manuscript). This was
 supplemented with 4 profiles from study sites in Changwu, Shaanxi
 Province, China. The dataset was compiled by co-authors
 Yanan Huang (huangynbox@nwafu.edu.cn) and Zhi Li (lizhibox@nwafu.edu.cn) of Northwest A&F University.
description: The dataset -- soil water tritium profiles (n = 40) -- was compiled from
 the peer-reviewed literature (see Text S2 in manuscript). This was
 supplemented with 4 profiles from study sites in Changwu, Shaanxi
 Province, China. The dataset was compiled by co-authors Yanan Huang
 () and Zhi Li
 () of Northwest A&F University. For any
 questions regarding the dataset, please send an email to Yanan Huang
 () and Zhi Li
 (). --- Filename:
 tritium_profile_all_data.csv * SiteID - refers to the assigned site
 identifier as also referenced to in tritium_sourcepapers.csv * depth (m) -
 depth of sampling in meters * 3H - tritium concentration in T.U. or
 tritium units * sampling year - year of sampling Filename:
 tritium_sourcepapers.csv * No - numeric identifier assigned to each unique
 soil tritium profile * Country - country where the sample was collected *
 SiteID - refers to the assigned site identifier as also referenced to in
 tritium_profile_all_data.csv * Source paper - Author-year of the source
 paper from where the data was retrieved * Title - title of the published
 paper Filename: GeospatialModel_20230722.csv * No - numeric identifier
 assigned to each unique soil tritium profile * Country - country where the
 sample was collected * SiteID - refers to the assigned site identifier as
 also referenced in tritium_profile_all_data.csv. This ID is unique to the
 soil profile at a given site (n = 44) * SiteUniID - refers to the unique
 site identifier for each site (n = 17) * aet_p - actual evapotranspiration
 divided by mean annual precipitation * pet_p - potential
 evapotranspiration divided by mean annual precipitation * dwt - depth to
 water table in m (vadose zone thickness) * peak_v - porewater velocity in
 m y-1 calculated using the Lorentzian growth peak model (Equation S9) *
 cxtfit_v - porewater velocity in m y-1 estimated from CXTFIT-STANMOD *
 cxtfit_D - dispersion coefficient in m2 y-1 estimated from CXTFIT-STANMOD
 * cxtfit_R2 - CXTFIT model R-squared * Applicability tau - the number of
 years, before or after the year 2022, that the tritium method may still be
 applicable. The threshold of peak concentration here is set at 0.3 TU
 Filename: parameters.csv * No - numeric identifier assigned to each unique
 soil tritium profile * Country - country where the sample was collected *
 SiteID - refers to the assigned site identifier as also referenced in
 tritium_profile_all_data.csv. This ID is unique to the soil profile at a
 given site (n = 44) * year - time elapsed in years between 1963 and
 sampling year * Input_V -porewater velocity in m y-1 * Input_D -
 dispersion coefficient in m2 y-1 * Input_MU - decay constant of tritium
 times time elapsed in years * Input_MASS - tritium input concentration in
 T.U. or tritium units * Initial conc. -tritium initial concentration
 Filename: soil_type_land_use.csv * No - numeric identifier assigned to
 each unique soil tritium profile * Location - site name and country *
 SiteID - refers to the assigned site identifier as also referenced in
 tritium_profile_all_data.csv. This ID is unique to the soil profile at a
 given site (n = 44) * Land use - land use type from the literature where
 explicitly mentioned * Soil type - based on HWSD (Harmonized World Soil
 Database) * Sand - % sand * Silt - % silt * Clay - % clay