University of California at Santa Cruz, 1156 High St., Santa Cruz, CA, 95064, USA.
GEOMAR Helmholtz Center for Ocean Research, Wischhofstrasse 1-3, 24148, Kiel, Germany.
Nat Commun. 2021 Jan 8;12(1):148. doi: 10.1038/s41467-020-20248-3.
Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models.
长期以来，在海洋同位素预算中，如果不是完全忽略不计，地下水溶质通量被认为是静态的，并且次于河流通量。在这里，我们呈现了沿海地下水中 Li、Mg、Ca、Sr 和 Ba 的浓度和同位素数据，以确定地下水排泄在调节陆地来源溶质通量到海洋的大小和同位素组成方面的重要性。我们使用三种独立的地下水排泄到沿海水域的体积估算方法，对全球数据进行了外推，据此我们估计，地下水来源的溶质通量至少占 Li、Mg、Ca、Sr 和 Ba 的河流通量的 5%。地下水来源的 Mg、Ca 和 Sr 通量的同位素组成与全球河流平均值明显不同，而 Li 和 Ba 通量的同位素与河流无法区分。这些差异反映了对沿海岩石学的强烈依赖，这应该优先在地球系统模型中进行参数化。
