ABSTRACT Chromium isotope and chemical compositions in runoff from two felsic rock catchments, the Lysina (LYS; Czech Republic) and the Neglinka (NEG; northwest Russia), were studied. Three types of water were identified: Na-Ca-SO4 type for the LYS, Mg-Ca-Cl-HCO3 type for the NEG downstream, and Mg-Ca-Cl to Mg-Ca-HCO3 type for the NEG upstream. The Cr (III) liberated during soil/bedrock weathering oxidized to Cr (VI), which was the main dissolved Cr species in both catchments. Variations in δ53Cr values for LYS runoff (–0.07‰ to +0.37‰) reflected a sole Cr source, seasonality of weathering and hydrologically controlled leaching/export processes. In the NEG catchment, back-reduction of Cr (VI) to Cr (III) during riverine transport resulted in a decrease in Cr concentrations (to 10–30%) and in an increase of δ53Cr values (+0.09 to +0.42‰ for the upstream to +0.72 to +1.73‰ for the downstream). Groundwater discharge could have influenced the chemical composition of the downstream NEG runoff to some extent.

中文翻译：

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长英质基岩下两个集水区径流中Cr的行为

摘要 研究了来自两个长英质岩石集水区 Lysina（LYS；捷克共和国）和 Neglinka（NEG；俄罗斯西北部）的径流中的铬同位素和化学成分。确定了三种类型的水：用于 LYS 的 Na-Ca-SO4 类型，用于 NEG 下游的 Mg-Ca-Cl-HCO3 类型，以及用于 NEG 上游的 Mg-Ca-Cl 到 Mg-Ca-HCO3 类型。土壤/基岩风化过程中释放的 Cr (III) 被氧化成 Cr (VI)，这是两个流域中主要溶解的 Cr 物质。LYS 径流的 δ53Cr 值的变化（–0.07‰ 到 +0.37‰）反映了唯一的 Cr 来源、风化的季节性和水文控制的浸出/出口过程。在 NEG 流域，河流运输过程中 Cr (VI) 向 Cr (III) 的逆还原导致 Cr 浓度降低（至 10-30%）和 δ53Cr 值增加（+0.09 至 +0.09）。上游为 42‰，下游为 +0.72 到 +1.73‰）。地下水排放可能在一定程度上影响了下游 NEG 径流的化学成分。