作者：Li, M., Zhang, G., Zhang, X., Chen, X., Zheng, C., Yang, H., Li, Q. & Fan, Q.

As an arid inland watershed in the alpine regions, the Golmud River Basin (GRB) on the northern Tibetan Plateau exhibit large hydrological catchment and diverse geomorphic units. Previous studies have focused on respective sections of the GRB, especially from the mountainous area to the fine soil plain (zones 1-4) as well as the terminal salt lake (zone 6), however, the pivotal role of the salt marsh plain (zone 5) in regulating hydrological circulation and solute migration has been unclear. This study employs integrated geochemical characteristics of major-trace elements and multiple isotopes (delta D-delta O-18-delta C-13-delta Cl-37-C-14) for examining the hydrogeochemical evolution on the watershed-scale, hydrological circulation and salinity enrichment in the salt marsh plain area. Several key conclusions have been obtained: (1) a transition in water chemistry from Ca-Mg-Cl-HCO3 type in zones 1-3 to Na-Cl type in zones 4-5 and Na-Ca-Cl type in zone 6, along with the stepwise increasing (zones 1-3) and significantly elevated salinity (zones 4-6), reflecting controlling effect shifts from water-rock interaction to evaporation on the catchment scale and further to recharge of Ca-Sr-high fluids in the sink basin. Na-Cl ions dominated in river water and groundwater in the entire GRB, indicating dissolution of halite occurred in this typical arid watershed. (2) Spatial trace element patterns, with Sr dominance in mountainous source giving way to B, Li and Sr enrichment in salt marsh plain linked to lakeshore lithology, evaporation and the recharge of residual groundwater. (3) An "increase-decrease-increase" trend in delta D and delta O-18 isotopes, with significant isotopic depletion in the salt marsh plain attributed to the recharge of groundwater. (4) The sharp enrichment of salinity (383-286,400 mg/L), wide variation in delta Cl-37 values (-0.41 parts per thousand similar to+0.75 parts per thousand), characteristic C-O isotopic distribution pattern transitioning from upstream freshwater signatures to downstream salt lake field, and average C-14 age of 15.6 ka of confined groundwater show the salt-bearing solutes of groundwater in the salt marsh plain primarily controlled by effects of dissolution of evaporite in paleolacustrine strata and recharge of groundwater since Last Glacial Period. (5) Significant differences in delta Cl-37 values were observed among different water types: atmospheric precipitation (+2.45 parts per thousand), river water (-0.36 parts per thousand to +0.01 parts per thousand), confined groundwater (-0.41 parts per thousand to +0.75 parts per thousand) in the salt marsh plain, and intercrystalline brine (-0.56 parts per thousand to -0.35 parts per thousand) in terminal salt lakes. These distinct isotopic signatures effectively distinguish various hydrogeochemical evolution processes, including atmospheric input, strong evaporation, dissolution of evaporites, and salt precipitation. This isotopic variability provides a precise tracing archive for investigating salinity evolution mechanisms in arid inland basins. This work aims to shed light on salinity enrichment and soil salinization processes in arid alpine watersheds.

作为青藏高原北部高寒地区的一个干旱内陆流域，格尔木河流域拥有广阔的集水区和多样的地貌单元。以往研究多关注该流域的各个分段，尤其是从山区到细土平原（1–4区）以及终端盐湖（6区），然而，盐沼平原（5区）在调节水文循环和溶质迁移中的关键作用一直不明确。本研究综合利用主微量元素和多种同位素（δD–δ¹⁸O–δ¹³C–δ³⁷Cl–¹⁴C）的地球化学特征，考察流域尺度的水文地球化学演化、盐沼平原区的水文循环和盐分富集过程。研究获得以下主要结论：（1）水化学类型从1–3区的Ca-Mg-Cl-HCO₃型过渡为4–5区的Na-Cl型及6区的Na-Ca-Cl型，同时盐度在1–3区逐步升高，在4–6区显著上升，反映了控制作用从流域尺度的水岩相互作用转变为蒸发作用，并进一步转变为汇水盆地中高Ca-Sr流体的补给。整个格尔木河流域的河水和地下水中Na-Cl离子占主导，表明该典型干旱流域发生了石盐溶解。（2）微量元素的空间分布格局显示，山区源区以Sr为主，而在盐沼平原，B、Li和Sr的富集则与湖岸岩性、蒸发作用及残余地下水的补给有关。（3）δD和δ¹⁸O同位素呈“升高—降低—升高”的变化趋势，盐沼平原显著的同位素贫化归因于地下水的补给。（4）盐度的急剧富集（383–286,400 mg/L）、δ³⁷Cl值的宽幅变化（−0.41‰至+0.75‰）、碳氧同位素从上游淡水特征向下游盐湖区过渡的特征分布模式，以及承压地下水平均¹⁴C年龄15.6 ka，均表明盐沼平原地下水中的含盐溶质主要受控于古湖相地层蒸发岩的溶解以及末次冰期以来的地下水补给。（5）不同水体间的δ³⁷Cl值存在显著差异：大气降水（+2.45‰）、河水（−0.36‰至+0.01‰）、盐沼平原承压地下水（−0.41‰至+0.75‰）和终端盐湖晶间卤水（−0.56‰至−0.35‰）。这些独特的同位素特征有效区分了大气输入、强烈蒸发、蒸发岩溶解和盐类沉淀等多种水文地球化学演化过程。这种同位素变异性为研究干旱内陆盆地盐分演化机制提供了精准的示踪档案。本研究旨在揭示干旱高寒流域的盐分富集与土壤盐渍化过程。

（来源：Journal of Hydrology 2026  DOI: 10.1016/j.jhydrol.2025.134029）