The study of production and depletion of chemical species is vital for the understanding of composition and evolution of planetary atmospheres. We present an implementation of photoinduced isotopic effects into the PATMO code (Ávila et al., 2021) code designed for the study of stable isotopes and photo-induced isotopic effects. With respect to the original code PATMO, where the photochemistry was not included, this report extends capability of the model to set photochemical processes for stable isotopes and thus enhancing its applicability. The PATMO code is flexible and allows the edition of new chemical reactions without need for hard code them. We also test how changes in spectral resolution affects the calculation of isotopic effects during the photodissociation of oxygen. We found that for a highly structured spectrum such as the Schumann-Runge band a spectral resolution larger than 0.005 nm is necessary for accurately modeling these isotopic effects. We also show that SO₂ and SO photodissociation couples in a complex shielding fashion and significantly affects the photo-induced isotopic effects. The model was also benchmarked against today’s Earth atmosphere, where the solar UV flux and the ozone profile of the US Standard atmosphere of 1976 was reproduced with the simple Chapman mechanism and improved with the implementation of NOx and HOx radicals.

To clarify the sources and fate of CH₄ enriched in coastal seawaters, we determined the distribution of both the concentrations and dual stable isotope compositions (δ¹³C and δ²H) of dissolved CH₄ in the bays of Ise and Mikawa in Japan during five sampling campaigns from 2013 to 2020, together with those in the major inflows of the Kiso, Nagara, and Yahagi Rivers. Excess CH₄ were found in the surface layer of Ise Bay, and their δ¹³C and δ²H values were close to those of CH₄ enriched in the major inflows, but deviated from those of CH₄ in the sedimentary layer at the bottom of Ise Bay. The oxidation rates of CH₄ in the water columns were negligibly small during the incubation experiments. In conclusion, the excess CH₄ in the surface layer of Ise Bay was derived from the inflows. The CH₄ enrichment in the freshwater sediments of the inflows showing up to four orders of magnitude higher CH₄ concentrations than those in the sediments of Ise Bay supported this conclusion. Similar results were obtained in Mikawa Bay. The total emission flux of CH₄ from the estuary area of Ise Bay was larger than the influx of CH₄ into Ise Bay via the inflows, suggesting that the CH₄ dissolved in the inflows was emitted into the atmosphere immediately after inflowing into the bay water.

An optimised and improved process is presented for the sequential separation of Pb, Sr, and light rare earth elements (LREEs) from a single aliquot of digested silicate sample. Cation exchange resin, Sr resin, and Ln resin columns are used to achieve 80–90% recovery yield of each element with high purity. Pb and Sr are recovered using a miniaturised Sr column after the separation of the Pb-Sr fraction from the digested silicate sample using cation exchange resin (AG50W-X8). The rare earth elements (REE) fraction recovered from the same step is used to separate Nd using Ln resin. We have used dilute HNO₃ to elute a Ce and Sm free Nd fraction (Ce/Nd < 10^–5). The REE fraction was oxidised with >5 mM NaBrO₃ solution prior to loading on the Ln resin. The required concentration of NaBrO₃ was tested using reference rock JB-2 and 5 mM was found to be sufficient for REE from 20 mg rock powder. The separation process also yields highly pure Ba, La, Ce, and Sm as by-products which can be used for isotopic analyses. The activity of the NaBrO₃ solution degrades rapidly, and therefore should be used within 2–3 days of preparation. Pb-Sr-Nd isotopic ratios of nine reference rocks and sediments from GSJ and USGS were measured using TIMS and are found to be accurate and reproducible. We also report the first Pb-Sr-Nd isotopic ratios for JSl-1 (slate from GSJ) and Pb isotopic ratio of SDO-1 (shale from USGS).

The chemical and isotopic characteristics of waters from typical landslide areas in Niigata and Nagano Prefectures, Japan, are described in this article. The study areas are Mushigame, Nigorisawa, Yomogihira (Niigata Pref.) and Kanayamazawa (Nagano Pref.) where landslides have often occurred. We present the chemical composition and δD-δ¹⁸O values of surface and groundwaters from the areas in order to characterize a geochemical nature of the waters involved in the landslides. The waters were of meteoric origin as indicated by the δD-δ¹⁸O values. The Mushigame waters were enriched in NaCl, suggesting contribution of fossil seawater trapped in oil-producing mudstone strata in the area. The Nigorisawa and Yomogihira waters are less in Cl^– and relatively more enriched in HCO₃^– and SO₄^2–. The Na-K-Mg relationship of all the waters except the Kanayamazawa waters indicated close equilibration with some minerals such as K-feldspar, K-mica, chlorite and silica in the rocks, suggesting water-rock interaction at deeper depths, although the waters were greatly diluted by surface groundwater on the way to the surface as indicated by their δD-δ¹⁸O signatures. Dissolved sulfate is a major anion and was originally produced by oxidation of sulfides in volcanic rocks. Variable δ³⁴S and δ¹⁸O values of sulfate suggest reduction of such sulfate to sulfide probably at shallow levels under different reducing conditions followed by re-oxidation, inducing the variability in the isotopic values. Thus, multiple oxidation-reduction processes may be common in the areas.

We measured the Raman spectra of CO₂ fluid at 30 MPa and room temperature (19.1–21.3°C). The spectra showed peaks attributed to the CO₂ combining various isotopes such as ¹²C¹⁶O₂, ¹³C¹⁶O₂, and ¹²C¹⁶O¹⁸O. The relative ratio of ¹²C¹⁶O₂ to ¹²C¹⁶O¹⁸O peaks represents the oxygen isotope ratio of CO₂. To evaluate the precision of the peak ratios, we measured the CO₂ Raman spectra at different exposure times. We examined the standard deviation (1 σ) of the peak intensity ratios and area ones for 20 measurements at each exposure time. The standard deviations of the intensity ratios and area ones were 2.7 and 3.1%, respectively, at a maximum exposure time of 494 s, conversion to peak intensity of ¹²C¹⁶O₂ yields about 2,000,000 counts. The uncertainties are 2.5–3 times greater than expected from the noise of a CCD camera and photon statistics. The oxygen isotope ratios (δ¹⁸O) of natural samples have a range of variation of about 16.6%. Compared to that value, the precision we obtained from this study is very small. Raman spectroscopy can be combined with microscopy to analyze areas as small as approx. 1 μm in diameter. Therefore, oxygen isotope measurement using Raman spectroscopy has potential for application to natural samples as a new method for small CO₂ fluids such as fluid inclusions.