U-Pb zircon age spectra determined for detrital zircon from the Shimanto Accretionary Complex suggest that the sediments forming the Shimanto belt are derived from essentially the same sources as the protoliths of the Sanbagawa Belt. The prominent Early Jurassic peaks seen in the age spectra of both belts suggest that SE China is not a major source of the detrital zircons. The age spectrum of our sample from the east coast of Shikoku indicates that the outcrop of the Tochidani Unit of the Shimanto Belt extends over a larger distance than previously thought, i.e. eastwards to the coast. The age barcode of the sample from the western coast of the Kii Peninsula agrees well with that of the overlying unit, whereas the age distribution of the sample from the south coast of the Kii Peninsular is unique. Hf isotopic compositions determined for a subset of the dated zircons fall into two groups, one with εHf(t) = –8 to +12 and the other with εHf(t) = –22 to –12. The former may be derived from sources located within the current Japanese archipelago and the latter from outside sources. These outside sources may be largely located in southern/south-eastern South Korea as indicated by the abundance of Early to Middle Jurassic zircon in the Shimanto Belt and the highly and negative εHf(t) values measured for zircon from Korean plutons.

Exacerbation of Cd contamination in soil is exerting a threat to food safety. Recently, Cd isotope geochemistry has been suggested for tracing the fate of this heavy metal in soil systems. However, its utility as a tool for evaluating the effectiveness of pollution remediation efforts has not been carefully considered. In the present work, first principle calculations based on density functional theory were employed to probe the most stable geometries of Cd-containing species including aqueous Cd²⁺, Cd(OH)_2(s), Cd²⁺ adsorbed on kaolinite edge surfaces, and Cd²⁺ incorporated into apatite lattice sites. Meanwhile, equilibrium Cd isotopic fractionations during conversions of free Cd²⁺ to immobile species were precisely quantified. At room temperature, equilibrium Cd isotopic fractionations between Cd(OH)_2(s), Cd²⁺ adsorbed on kaolinite edge surfaces, Cd²⁺ incorporated into apatite lattice sites (Ca1 and Ca2 sites), and aqueous Cd²⁺ were 0.58–0.64‰, –0.13‰, –0.88‰, and –0.72‰, respectively. During an in situ remediation, with the aid of these isotopic fractionation factors, we predicted a gradual decreasing trend in δ¹¹⁴Cd in soil with decreased fractions of mobile species (free Cd²⁺, exchangeable Cd²⁺, and non-specific adsorbed Cd²⁺). These results may provide a theoretical framework for future observations in field experiments.

In recent years, the Wufeng and Longmaxi Formations were identified as the favorable shale gas horizons. In order to further investigate the pore system and its controlling factor(s) in marine shales, twenty outcrop samples were collected from southwest of the Sichuan basin. The TOC content and mineral compositions were examined via geochemical analysis and the pore parameters were determined by the combined low-pressure nitrogen and carbon dioxide adsorption experiments. In addition, the fractal dimensions were calculated by the adsorption data. Our results show that the organic matter is the most significant factor controlling the development of nanoscale-pore in shales. The impacts of mineral compositions on pore system can be negligible. The poor correlations between fractal dimensions and TOC content and mineral compositions suggest that the fractal dimensions are not decided by the “relative content” of different shales components. The different correlations between fractal dimensions and average pore size and other pore parameters imply that the fractal dimensions are determined by the development of pores with different scales in shales. Particularly, the micro- and mesopore have opposite effects on the fractal dimensions. Based on the comparison of fractal dimensions observed in Wufeng and Logmaxi Formations, we suggest that the Longmaxi Formation has greater potential of exploration and development for the shale gas resource.

To better understand the distributions of low molecular weight (LMW) organic acids and their sources as well as their contribution to fog acidity that may decline a Japanese birch in mountain site (somma of Lake Mashu) of northeastern Hokkaido, Japan, we collected fog water samples at Lake Mashu site in May and July, 2015. The samples were analyzed for various organic species such as LMW monocarboxylic acids, dicarboxylic acids, oxocarboxylic acids, biogenic secondary organic aerosol (SOA)-tracers (isoprene- and α-pinene-oxidation products), and tracers of primary biological aerosol particles (PBAPs, e.g., saccharides), together with inorganic ions. Formic, acetic, and oxalic acids were detected as dominant carboxylic acids. Their concentrations in the fog samples were significantly lower than those from urban area in North America, Asia, and Europe and from forest area in Taiwan, except for oxalic acid in May. Concentrations of oxalic acid in May were higher than those in July, being consistent with higher values of SO₄²⁻ and NO₃⁻. Based on the air mass back trajectories, the Asian continent is suggested to contribute higher levels of dicarboxylic acids in fog water in spring. Concentrations of formic and acetic acids together with biogenic tracers in the present study were higher in July than in May. In July samples, concentrations of formic plus acetic acids showed positive correlations with biogenic SOA tracers and PBAPs. Oxalic acid also correlated with biogenic SOA tracers and PBAPs. Primary emission from biogenic sources and secondary formation are important factors to control the levels of LMW mono- and di-carboxylic acids in fog from Lake Mashu in July. pH of fog water ranged from 3.8 to 5.9. Total cation equivalents (Na⁺, NH₄⁺, K⁺, Ca²⁺, Mg⁺, and H⁺) were comparable to total anion equivalents (SO₄²⁻, NO₃⁻, Cl⁻, and detected organic anions). Contributions of organic acid equivalents to organic plus inorganic acid equivalents were low (range: 4–17%). Major ions in fog water of Lake Mashu were inorganic during the sampling periods. This study demonstrates that levels of organic and inorganic acids are not high enough to cause a damage on the tree ecosystem in the surroundings of Lake Mashu.

The present investigations of δ¹⁸O and δD values of Teesta river system (glacier fed; Eastern Indian Himalaya) along a steep altitudinal gradient has helped to better understand the spatial variability of the isotopic composition in water and moisture sources. We have used the stable isotope composition of the main Teesta River, its major tributaries, glacial melt streams (nallah) and few high altitude lakes. As the region is dominated by Indian Summer Monsoon precipitation brought by the Bay of Bengal Branch, the δ¹⁸O values ranges from ~–11 to –15‰ and δD from ~–41 to –128‰ in the main Teesta River. We propose that as the monsoonal moisture penetrates along the river valleys towards higher Himalaya, a progressive depletion in ¹⁸O and D isotopes take place during orographic lifting, resultant cooling and progressive rainout. It is observed that d-excess values range between –1 to 18 and suggests mixed moisture source having contributions from moisture originating in Bay of Bengal and mid-latitude westerlies.

Determination of ferrous iron (FeO) is important across a wide breadth of disciplines in geochemistry. The certified values of FeO in geochemical reference materials have been determined mainly by wet chemistry. During this procedure, special attention is needed to prevent oxidation of Fe²⁺ to Fe³⁺, which may lead to underestimations of FeO mass fractions. Here, we revisited a traditional titrimetric method to provide a better method of determining the FeO mass fractions in geochemical reference materials. We investigated the effect of duration of decomposition, sand bath temperature, and sample weight. Among these, we found that the effect of sample weight on the FeO values is most significant. The FeO values increase with increasing sample weight, indicating that vapor and foam effectively prevent oxidation. This is supported by yield tests and experiments involving the addition of SiO₂ powder to the samples. Thus, we suggest the use of greater amounts of sample to minimize oxidation. We further compare our results with the published recommended values for reference materials, demonstrating that the latter need be considered carefully. The approach described here is not only applicable to geochemical reference materials but also useful to unknown geological samples.