Isotope Hydrology Section, International Atomic Energy Agency, Vienna International Centre, 1400, Vienna, Austria.
Sci Rep. 2022 Jun 17;12(1):10271. doi: 10.1038/s41598-022-14227-5.
Tritium (H) in Earth's precipitation is vigilantly monitored since historical nuclear bomb tests because of radiological protection considerations and its invaluable role as a tracer of the global water cycle in quantifying surface, groundwater, and oceanic fluxes. For hydrological applications, accurate knowledge of H in contemporary local precipitation is prerequisite for dating of critical zone water and calibrating hydrogeologic transport and groundwater protection models. However, local tritium input in precipitation is hard to constrain due to few H observation sites. We present new high-spatial resolution global prediction maps of multi-year mean H in contemporary "post-bomb" (2008-2018) precipitation by using a robust regression model based on environmental and geospatial covariates. The model accurately predicted the mean annual H in precipitation, which allowed us to produce global H input maps for applications in hydrological and climate modelling. The spatial patterns revealed natural H in contemporary precipitation sufficient for practical hydrological applications (1-25 TU) but variable across continental regions and higher latitudes due to cumulative influences of cyclical neutron fluxes, stratospheric inputs, and distance from tropospheric moisture sources. The new H maps provide a foundational resource for improved calibration of groundwater flow models and critical zone vulnerability assessment and provides an operational baseline for quantifying the potential impact of future anthropogenic nuclear activities and hydroclimatic changes.
氚（H）在地球降水（量）中受到严密监测，这是出于辐射防护考虑，同时也是因为其作为全球水循环示踪剂在量化地表水、地下水和海洋通量方面的宝贵作用。对于水文应用而言，准确了解当代当地降水中的 H 是对关键带水进行年代测定和对水文地质输运和地下水保护模型进行校准的前提条件。然而，由于 H 观测站点较少，降水（量）中的本地氚输入（量）很难被约束。我们利用基于环境和地理空间协变量的稳健回归模型，为当代“后（核）炸弹时期”（2008-2018 年）降水提出了新的具有高空间分辨率的多年平均 H 全球预测图。该模型准确地预测了降水（量）中的年平均 H，这使我们能够制作全球 H 输入图，用于水文和气候建模应用。空间分布揭示了当代降水（量）中存在天然 H，足以满足实际水文应用的需要（1-25 TU），但由于循环中子通量、平流层输入和与对流层水汽源的距离的累积影响，在各大陆区域和高纬度地区存在变化。新的 H 图为改进地下水流动模型的校准和关键带脆弱性评估提供了基础资源，并为量化未来人为核活动和水文气候变化的潜在影响提供了一个操作基准。
