Mineral Weathering & Carbon Cycle

Wastewater treatment plant effluent weakens alkalinity buffering and enhances CO₂ evasion in a carbonate-weathering-dominated river

ACS ES&T Water, doi:10.1021/acsestwater.6c00385

Rivers affected by carbonate weathering usually have high alkalinity, which helps buffer pH changes. However, wastewater treatment plant (WWTP) effluent can strongly alter river chemistry. In the Yanshui River in SW Taiwan, WWTP effluent from a major semiconductor park exceeds natural river flow by about 1.5 times. Our observations show that the river shifts from an upstream carbonate-weathering system, rich in Ca²⁺ and HCO₃^-, to a downstream urban system dominated by Na⁺ and Cl^- from WWTP effluent. Because the effluent has lower alkalinity, it dilutes the river’s buffering capacity. Together with organic matter decomposition, this raises the DIC/TA ratio, lowers pH, and increases downstream CO₂ levels. Modeling shows that WWTP effluent dilution greatly reduces alkalinity and buffering capacity, making the river more vulnerable to acidification and CO₂ release.

  Affordable & Clean Energy

A refined calibration of the Na-Li geothermometer for pelitic lithologies before and after orogenic metamorphism

Geothermics, doi:10.1016/j.geothermics.2025.103482

Geothermal exploration is hindered by the poor performance of classic geothermometers in metamorphic settings. Na-K geothermometers become unreliable due to K-feldspar transformed to illite during metamorphism. To address this, we assessed the Na-Li geothermometer using global geothermal well data. Results show a consistent relationship between temperature and Na/Li ratios across sedimentary, igneous, and metamorphic rocks, indicating metamorphism has limited effect on fluid Na/Li. A refined calibration validated by the Chingshui metapelitic field, Taiwan (<5.6% deviation), and applied in SW Taiwan confirms Na-Li estimates align with Na-K where valid. Na-Li thus provides a robust tool for pelitic reservoirs, even after orogenic metamorphism.

  Sustainable Cities & Communities

Potential geological risks from mud diatremes in the orogen regime of Southwestern Taiwan

Scientific Reports, doi:10.1038/s41598-025-91915-y

Recent evidence indicates that mudstone intrusions play a significant role in surface deformation and fault development. In southwestern Taiwan, drilling data verify that sediment originating from about 3 km deep ascends, causing positive gravity anomalies and local uplift. Resistivity surveys further reveal scattered mud intrusions capable of damaging structures. By measuring core porosity, we confirmed compression processes, while isotope geochemical and synchronous X-ray absorption methods traced the sediment source. Collectively, these multi-disciplinary findings show that mud diapirs can reach shallow depths, with fractures acting as conduits (mud diatremes). Such phenomena occur in both collisional and extensional settings, influencing fault development and posing geological risks to urban areas.

  Mineral Weathering & Carbon Cycle

Carbonate precipitation-derived CO₂ outgassing offsets the mineral weathering sink in the orogenic regime of southwestern Taiwan: Insights from triple Sr isotopes

Science of the Total Environment, doi:10.1016/j.scitotenv.2024.177370

Carbonate precipitation in saturated rivers significantly influences CO₂ outgassing and the short-term terrestrial carbon cycle. In this study, we applied triple strontium isotopes (⁸⁷Sr/⁸⁶Sr and δ^88/86Sr) to accurately determine the δ^88/86Sr fractionation derived from carbonate precipitation in rivers. This approach allows us to quantify the amount of metal incorporated into carbonates and thus the quantity of carbonate precipitated. Consequently, in southwestern Taiwan, 69% of weathered calcium was removed via precipitation, associated with increased HCO₃^- concentrations. High river discharge during wet periods enhances carbonate dissolution and precipitation, leading to elevated CO₂ outgassing. Machine learning estimates suggest that precipitation-derived CO₂ outgassing from rivers is nearly twice the long-term emission flux, highlighting its significant role in the terrestrial carbon cycle of orogenic regions.

  Mineral Weathering & Carbon Cycle

Hydrology controls sulfuric acid-mediated weathering in an orogenic regime of ​southwestern Taiwan

Science of the Total Environment, doi:10.1016/j.scitotenv.2024.175630

Chemical weathering, driven by river flow, plays a crucial role in shaping carbon dynamics, particularly in mountain-building landscapes. We explore how river discharge affects chemical weathering and its impact on carbon cycling and climate in southwestern Taiwan's critical zone. Carbonate minerals significantly contribute to weathering in SW Taiwan, driven largely by sulfuric acid. Increased river discharge correlates with enhanced sulfuric acid-mediated carbonate weathering, with a critical threshold of 4.6 m³/s marking a shift from CO₂ sink to source. Over a decade, the region has been a net CO₂ source, with rising discharge amplifying CO₂ emissions. This pattern likely applies to other mountainous regions, highlighting hydrology's key role in the carbon cycle.

  Stable Sr Isotope Geochemistry

Stable strontium isotope fractionation in hydroponically grown mung and soy bean sprouts

Journal of Food Composition and Analysis, doi:10.1016/j.jfca.2022.105081

Plant utilization is one of the essential processes dominating the migration, distribution, and accumulation of metals in the critical zone. Defining the isotopic fractionation factor of metals during plant utilization aims to constrain the plant fluxes during metal cycling, especially under different climatic conditions. The KBSI (Korea Basic Science Institute) has mature techniques for hydroponic experiments, and the NCKU NSI team has robust techniques for acid digestion and matrix separation of organic materials and high precision stable Sr isotopic determination . This research collaboration suggests that the changes in the Sr isotope composition of the plants are due to the combination of mixing and isotope fractionation processes between bean seeds and nutrient solution, providing an important inside into the Sr isotope behavior during the growth of plants.

  Stable Sr Isotope Geochemistry

Adsorption and desorption behaviors of Sr on montmorillonite: A triple Sr isotope perspective

ACS Earth and Space Chemistry, doi:10.1021/acsearthspacechem.2c00222

Montmorillonite is a widespread mineral, which affects the migration of Sr in the critical zone. Hydrochemical factors influencing Sr adsorption have been evaluated in the literature through laboratory batch experiments. Since those experiments were conducted using high-concentration and high-purity standard solutions, the influences of chemical matrices or element relative concentrations in water remain unclear. Here, we reassessed the adsorption and desorption behaviors of Sr on montmorillonite using natural waters with various chemical matrices and ionic strengths. The triple Sr isotopic tracers provide perspectives on how montmorillonite minerals adsorb Sr and release it to aqueous environments at various hydrochemical conditions.

  Stable Sr Isotope Geochemistry

Precise δ^88/86Sr determination on MC-ICP-MS by an improved method combined Zr-empirical external normalization isobaric interference correction and ⁸⁴Sr-⁸⁷Sr double spike

Journal of Analytical Atomic Spectrometry, doi:10.1039/D1JA00224D

The most accurate and precise δ^88/86Sr determination is performed by using the double spikes (DS) technique on TIMS. However, TIMS is always subjected to its long data acquisition time over MC-ICP-MS. We present a novel approach, combing the use of Zr-EEN for Kr and Rb isobaric interference correction and ⁸⁴Sr-⁸⁷Sr DS to overcome the severe mass bias effects on the measured ⁸⁸Sr/⁸⁶Sr ratios, to improve the analytical accuracy of MC-ICP-MS δ^88/86Sr determination.