Strontium isotopes play a crucial role in geoscience, serving as valuable tools for tracing chemical weathering and its profound impact on the global carbon cycle and climate. By analyzing the ratios of ⁸⁷Sr/⁸⁶Sr in natural reservoirs such as rivers and marine carbonates, scientists can reconstruct past environmental conditions and gain insights into the intricate interplay between tectonics, weathering, and climate. This knowledge significantly enhances our ability to predict future climatic changes.

While radiogenic Sr isotopes exhibit remarkable sensitivity to variations in weathering sources, they lack the ability to detect biogeochemical reactions that occur during weathering. To address this gap, specialized techniques have been developed to measure the fractionation of stable Sr isotopes (δ^88/86Sr), providing valuable information about these post-weathering processes.

Stable isotopes in waters reflect both lithology (mixing of various weathering sources) and fractionation processes (such as biogeochemical reactions). Consequently, it’s challenging to isolate each individual effect, making it difficult to interpret changes in δ^88/86Sr in waters.

However, through extensive studies on understanding these processes in natural environments, we’ve developed a method to distinguish the signals of lithology from fractionation. We use triple Sr isotopes—⁸⁷Sr/⁸⁶Sr and δ^88/86Sr—to achieve this. We applied this methodology in a study conducted in SW Taiwan, where we focused on the impact of secondary carbonate precipitation in rivers and their associated CO₂ outgassing flux.

This new methodology enables us to accurately determine the precipitation-derived fractionation and, consequently, estimate CO₂ emissions. This case study demonstrates the effectiveness of applying triple Sr isotopes in studies related to mineral weathering and the carbon cycle.