The Shimensi tungsten-polymetallic deposit, located in Lower Yangtze mineralization province, is a recently-discovered world-class deposit. It is necessary to clarify the source and the evolution of the ore forming fluid. We report Pb isotope results form scheelite, wolframite, molybdenite and chalcopyrite samples as well as K-feldspars from Neoproterozoic biotite granodiorite, and Mesozoic porphyritic biotite granite, fine-grained biotite granite, and granite porphyry. Results show that the Pb isotopes from both the ore minerals and granite K-felspar can be divided into 3 groups. Pb isotope ratios from the ore minerals are similar to those from the early Cretaceous prophyritic biotite granite and fine-grained biotite granite, indicating that the ore components for the Shimensi deposit were mainly originated from these two types of granites. The O isotope equilibrium temperature of the quartz-scheelite ranges from ∼295.89°C to 435.97°C, the δ¹⁸O from ∼7.0‰ to 9.6‰, indicating that the mineralization occurred under the condition of high temperature and O isotope equilibrium exchange. It is concluded that the ore-forming fluids for the Shimensi deposite had a magmatic-hydrothermal origin, related to the Early Cretaceous magmatism in an extensional tectonic environment in East China. The granites themselves were probably generated from partially melting of the Neoproterozoic Shuangqiaoshan Group, which contains of 9.13 ppm high tungsten background content.

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Cyanobacteria induced biomineralization of atmospheric CO₂ is a natural process leading to the formation of carbonates by spontaneous precipitation or through the presence of nucleation sites, under supersaturated conditions. As importance of basaltic rocks in the carbon cycle has already been highlighted, basaltic glass was chosen to test its ability to release cations needed for carbonate formation in presence of Synechococcus sp. cyanobacteria. Active cyanobacteria were expected to generate a local alkaline environment through photosynthetic metabolism. This process produces oxygen and hydroxide ions as waste products, raising the pH of the immediate cell surface vicinity and indirectly enhancing the carbonate CO₃^2- concentration and providing the a degree of saturation that can lead to the formation of calcite CaCO₃ or magnesite MgCO₃. In the presence of active cells, the saturation index (SI) increased from -10.56 to -9.48 for calcite and from -13.6 to -12.5 for magnesite, however they remained negative due to the low Ca²⁺ and Mg²⁺ activities. Dead cells were expected to act as nucleation sites by the stepwise binding of carbonate with Ca²⁺ and Mg²⁺ on their surface. In the presence of inactive cells, SI values were closer to 0 but still negative due to the low pH and cation concentrations. Our results highlight that our current understanding of the carbon cycle suggests that Earth’s climate is stabilized by a negative feedback involving CO₂ consumption and especially during chemical weathering of silicate minerals.

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Recent interest in geochemical maps produced for environmental assessment has led to multi-purpose applications of such maps in various other fields including provenance studies for agriculture and archaeology. Research subjects of these provenance studies closely relate to surficial rocks. Fine stream sediment samples used for Japanese geochemical mapping originate from parent rocks present in the corresponding drainage basins. Consequently, as well as the chemical composition of stream sediment samples, information regarding the parent lithology is imperative for the applications mentioned above. In this work, the exposed areas of different lithologies in river drainage basins were calculated using a digitalized geological map and watershed polygons obtained using a hydrologic model. Stream sediment samples were classified into 18 different types in a larger-scale classification and into 92 more specific types in a smaller-scale classification based on the following assumption: when a specific rock type crops out over more than 50% of the watershed area, it is the dominant rock type controlling the chemical composition of stream sediments. This assumption was confirmed to be reasonable using a one-way analysis of variance. Chemical Index Alteration values suggest that the chemical weathering process is not dominant in the formation of stream sediments from their source rocks. Accordingly, the chemical compositions of stream sediments are approximately comparable to that of their source rocks. Finally, the percentages of the different lithologies in the watershed areas were tabulated for all stream sediment samples (n = 3024). The median values of 53 elemental concentrations were calculated for samples classified according to the dominant lithology. This new database lists the chemical compositions and the dominant lithology in the watershed area for each sample and constitutes an extensive source of information relevant to understanding of the chemical, mineralogical, and petrological variety of surface materials in this island arc setting, which helps to respond to existing academic or industrial requests.

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Reactive oxygen species (ROS) are photochemically generated in sunlit natural water and are involved in degradation of organic matter, redox reactions, and biological processes. Hydroxyl radicals (·OH), nitric oxide radicals (NO·), and singlet oxygen (¹O₂) are some of the dominant ROS in natural water. In this study, these three ROS were measured in samples collected from nine rivers across 65 stations along the west to east axis of Japan. Quantification of ·OH, NO·, and ¹O₂ was performed by High-Performance Liquid Chromatography using benzene, 4, 5-diaminofluorescein-2, and furfuryl alcohol as chemical probes, respectively. The absorption coefficient at 300 nm (a₃₀₀, m^-1), which ranged from 2.44 to 36.2 m^-1, was used to investigate the chromophoric dissolved organic matter (CDOM) properties of the rivers. The photoformation rate ranges were (13.9-944) × 10^-12 M s^-1 for ·OH, (2.76-2610) × 10^-12 M s^-1 for NO·, and (9.48-133) × 10^-9 M s^-1 for ¹O₂. The steady-state concentration ranges were (1.53-16) × 10^-16 M for ·OH, (10.2-1520) × 10^-12 M for NO·, and (3.79-53.4) × 10^-14 M for ¹O₂. The results showed that nitrite was a major source for both ·OH and NO·, and CDOM was a major source for ¹O₂ across all the rivers. According to significant relationships with these sources, models were generated to predict the formation rates of the ROS (in M s^-1) from known concentrations of source compounds using the equations R·OH (10^-12) = 19.2 [NO₂^-1]-μM + 36.9, RNO· (10^-12) = 41.4 [NO₂^-1]-μM + 44, and R_¹O2)(10^-9) = 3.52 (a₃₀₀)-m^-1 + 1.61. Dissolved organic matter, escape to the atmosphere, and water molecules were the major sinks for river ·OH, NO·, and ¹O₂, respectively. A general scavenging rate constant of ·OH as a function of the dissolved organic carbon concentration was obtained [k_C,OH = [(7.5 ± 6.8) × 10⁸ L (mol C)^-1 s^-1]. These models will allow for easy prediction of ROS concentrations on a large-scale.

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The research proved the capacity of mangrove soils (of Boca del Zorro Spout) to sorb and desorb two low molecular weight PAHs, fluorene and phenanthrene. In order to evaluate this capacity, we determined the total organic carbon (TOC wt%) and the maturity of soil organic matter (SOM) by calculating the maximum vitrinite reflectance (R_{o max}). Additionally, batch-reactor experiments, water leaching and ultrasonication were conducted to study the sorption and desorption process. The mangrove soil presents a TOC content of 25% and a humification range of SOM that has reached the range of peat. Sorption isotherms were nonlinear following the Freundlich model. The values of the isotherm nonlinearity index (N) and organic carbon normalized sorption coefficients (log K_oc) are similar for fluorene and phenanthrene; therefore, they follow the same sorption mechanism in the mangrove soil. The log K_oc values obtained suggest that the soil is composed of a mixture of both recent organic matter and organic matter with an advanced degree of maturity. For this reason, for both polycyclic aromatic hydrocarbons (PAHs), the process responded to a non-linear model with limited sorption sites with variable potential energy. Both fluorene and phenanthrene presented a desorption percentage between 6-7% in mangrove soil sample. This allows us to infer that the bonds presented in the sorption process are associated with the insertion of fluorene and phenanthrene into the pores of the humified mangrove soil material. The research into mangrove soil displayed significant heterogeneity in composition and strong sorption of PAHs, as a result, mangrove soil presents natural filters in this area of the Venezuelan Caribbean.

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