Chemical weathering in the Himalayan river basins plays a key role in the global carbon cycle that controls the climate. In this contribution, the spatial distribution of dissolved major ions and (inorganic) carbon isotopic compositions of the Teesta River, a major tributary of the Brahmaputra River, has been investigated to constrain solute sources, weathering patterns, and acids involved in these processes. Mixing diagrams and piper plots of major ions indicate a dominant solutes supply by weathering of silicates and carbonates. The average sulfate concentration of the Teesta samples (92 ± 47 µM) is significantly higher than that reported earlier for atmospheric deposition (∼5 µM) in this basin. The carbon isotopic compositions of the dissolved inorganic fractions (δ¹³C_DIC) of the samples vary between −11.87‰ and −3.82‰ (mean: −7‰ ± 2‰). Comparison of δ¹³C_DIC – SO₄/(SO₄ + HCO₃) – HCO₃/(Ca + Mg) trends with their corresponding values expected for H₂SO₄ and H₂CO₃ acid‐mediated weathering indicates that both these acids contribute to chemical weathering in the Teesta river catchment. Inversion modeling of major ions and δ¹³C_DIC data have been used to quantify the impact of carbonic (H₂CO₃) and sulfuric acids (H₂SO₄) on the Teesta water chemistry. On average, the fractions of cations derived from H₂CO₃‐mediated weathering of carbonates (0.27 ± 0.14) and silicates (0.20 ± 0.09) are comparable with H₂SO₄‐mediated carbonate (0.38 ± 0.18) and silicate (0.15 ± 0.11) weathering in this basin. These results show that the amount of CO₂ uptake (via H₂CO₃‐mediated silicate weathering) and release (via H₂SO₄‐mediated carbonate weathering) are in balance for the Teesta River.

中文翻译：

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硫酸在大陆风化中的作用：下雅鲁藏布江特埃斯塔河中溶解的主要离子和无机碳同位素的见解

喜马拉雅河流域的化学风化在控制气候的全球碳循环中起着关键作用。在这一贡献中，对雅鲁藏布江的主要支流河Teesta河中溶解的主要离子和（无机）碳同位素组成的空间分布进行了研究，以限制这些过程中涉及的溶质源，风化模式和酸。主要离子的混合图和吹管图表明，通过风化硅酸盐和碳酸盐可以提供主要的溶质供应。Teesta样品的平均硫酸盐浓度（92±47 µM）显着高于早先报道的该盆地大气沉积的平均硫酸盐浓度（〜5 µM）。溶解的无机级分的碳同位素组成（δ ¹³ C ^ _DIC）的样本在-11.87‰和-3.82‰之间变化（平均值：-7‰±2‰）。比较δ ¹³ Ç _DIC  - SO ₄ /（SO ₄  + HCO ₃） - HCO ₃ /（CA + Mg）的与预期用于h它们相应的值的趋势₂ SO ₄和H ₂ CO ₃酸介导的耐候表明这两种酸有助于Teesta河流域的化学风化。主要离子和反演模型δ ^13个Ç _DIC数据已被用于量化的碳酸（H冲击₂ CO ₃）和硫酸（H₂ SO ₄）关于Teesta水化学。平均而言，由H ₂ CO ₃介导的碳酸盐（0.27±0.14）和硅酸盐（0.20±0.09）的风化产生的阳离子分数与H ₂ SO ₄介导的碳酸盐（0.38±0.18）和硅酸盐（0.15± 0.11）在该盆地中风化。这些结果表明，Teesta河的CO ₂吸收量（通过H ₂ CO ₃介导的硅酸盐风化）和释放量（通过H ₂ SO ₄介导的碳酸盐化风化）是平衡的。