Rainfall, groundwater, and surface water isotope data from extreme tropical cyclones (2016-2019) within the Caribbean Sea and Atlantic Ocean basins

Short-lived natural radionuclides as tracers in hydrogeological studies - A review

Fundamental approaches to the study of groundwater rely on investigating the spatial and temporal distribution of stable and radioactive isotopes and other anthropogenic compounds in natural waterbodies. The most often used tracers for estimating groundwater flow paths and residence times, groundwater/surface water interaction as well as tracing chemical (contamination) sources include stable isotopes of water (δ 18O and δ 2H), radiocarbon (14C; t1/2 = 5730 a), tritium (3H; t1/2 = 12.43 a) as well as unreactive fluorine-containing gases (e.g., chlorofluorocarbons CCl3F or CFC-11; CCl2F3 or CFC-12; C2Cl3F3 or CFC-113; and SF6). While gas tracers are usually referred to as transient tracers and are appropriate for investigating modern flow systems, the isotopic tracers are often used to investigated paleo or regional flow systems. Stable isotopes of water can also be used to investigate groundwater/surface water interactions. Another, thus far been less frequently used group of groundwater tracers, are cosmo- and geo- genic short-lived radioisotopes. These isotopes are uniquely suited for studying a wide range of groundwater problems that have short time scales including high aquifer vulnerability to quantitative and qualitative impacts and groundwater discharge to surface waters. Here, we discuss and compare the applications of radio‑sulphur (35S; half-life t1/2 = 87 d), radio‑beryllium (7Be; t1/2 = 53 d), radio‑phosphorus (32/33P; combined t1/2 = 33 d), natural tritium (3H; t1/2 = 12.43 a), radon (222Rn; t1/2 = 3.8 d) and short-lived radium (224/223Ra; combined t1/2 = 5.2 d). The paper discusses the principles of the individual tracer methods, focusing on the isotopes' input functions or values, on sampling techniques, and on methods of analyses. Case studies that applied a combined use of the tracers are referred to for readers who wish to learn more about the application of the so far underused cosmo- and geo- genic radioisotopes as aquatic tracers.

In situ measurement of water vapor isotope ratios in air with a laser-based spectrometer

Simultaneous measurement of H₂¹⁷O/H₂¹⁶O, H₂¹⁸O/H₂¹⁶O, and HDO/H₂¹⁶O in air with a compact spectrometer based on a mid-infrared distributed feedback (DFB) laser was described. The obtained mixing ratios of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O agreed reasonably well with those measured by a hygrometer. The precision and repeatability of the spectrometer were analyzed. Indoor air tests demonstrated that its 220-s precision was 0.08 ‰, 0.06 ‰, and 0.14 ‰ for δ¹⁸O, δ¹⁷O, and δ²H respectively. The measured values of δ¹⁸O, δ¹⁷O, and δ²H in indoor air were highly correlated with the water vapor mixing ratios. The compact spectrometer provides in situ measurements of water vapor isotopes with high precision and fast time response, which opens new possibilities for its application in atmospheric and hydrological research in the future.