Applied Geochemistry最新文献

The association of dissolved organic matter (DOM) with natural watershed backgrounds and anthropogenic activities is crucial for environmental assessment and sustainable development of basins. This study investigated the catchment-driven trend of DOM characteristics in the Hailar River basin, China. The results identified three fluorescent components through EEM-PARAFAC models: a terrestrial humic-like component (C1), a humic-like component related to microbial activity (C2), and a UVA humic-like component (C3), which were influenced by Cl⁻ and HCO₃⁻ derived from rock weathering. The contents of water-extractable organic carbon (WEOC) extracted from soils surrounding the watershed significantly correlated with the concentrations of DOC and COD_Cr. Furthermore, COD_Cr exhibits heightened sensitivity to precipitation and temperature fluctuations, revealing the synergistic effects of environmental factors and natural background. The hydrochemical composition and DOM characteristics are predominantly influenced by their origins from the Greater Khingan forests, indicating a catchment-driven trend of DOM in the studied river. What's more, COD in Hailar river basin was mainly controlled by refractory dissolved organic matter (RDOM). This research underscores the need for context-specific environmental standards rather than a “one-size-fits-all” approach and offers scientific insights and methodologies for the rational assessment of water quality and aquatic ecosystem health in similar riverine systems.

This study aims to comprehensively characterize the hydro-geochemical and isotopic features of the complex groundwater system in the Pordenone Plain (northeastern Italy). The area is an important industrial and agricultural area exposed to severe anthropogenic pressure and climate change, which put its water resources at risk in terms of quantity and quality, making it of high scientific and social interest. The hydrogeological setting of the Pordenone Plain has been previously simplified as a phreatic continuous aquifer in the High Plain that changes into a multilayered aquifer system towards the Low Plain. However, this study reveals significant lithological and structural heterogeneities in the High Plain that exert a strong influence on its subsurface hydrodynamics. All waters exhibit a Ca(Mg)–HCO₃ composition with relatively high Na–K values in the aquifers of the Low Plain likely related to cation exchange processes. Water stable isotopes (δ²H–H₂O and δ¹⁸O–H₂O) indicate that the deep aquifers in the Low Plain are confined by impermeable geological formations, such as clays and siltstones, which entirely restrict water mixing with shallower aquifers. Concurrently, tritium analysis provides evidence of slow recharge and flow rate. Three primary groundwater flows have been identified within the plain, as follows: 1) a surface flow that affects the unconfined or semi-confined aquifers of the High Plain hosted in gravelly sediments; 2) an intermediate flow fed by the pedemontane zone, which includes unconfined deep aquifers of the High Plain, semi-confined/shallow aquifers (at a depth of 40–50 m) located near the resurgence belt area and karst springs located in eastern pedemontane of the Cansiglio Plateau; 3) a deep flow fed by the mountainous zone that affects the deep confined aquifers of the Low Plain. A reliable hydrogeochemical conceptual model has been developed to explain the compositional variability of the studied waters, providing valuable insights for the sustainable management of groundwater resources in the Pordenone Plain.

Deposits enriched in rare earth elements (REEs) are abundant and diverse in mineralogy, but those of current economic value have extremely limited geographic distribution. Due to rapidly increasing demand and concerns about supply chain security, new and improved methods of prospecting, beneficiation, separation, purification, and recycling are needed. By overviewing the types and geographic distribution of REE deposits globally, their petrogenesis and major mineralogic assemblages, this review aims to deepen understanding of different types of REE deposits and distribution characteristics at the global level. Our review also seeks to provide a concise summary of important background information that is accessible to researchers from a variety of disciplines who are seeking to engage this rapidly expanding field.

We carried out density functional computations to investigate experimentally suggested ternary Ca–Am(III)–OH and possible Mg–Am(III)–OH complexes in water. We confirmed the experimental stoichiometry for the Ca complexes and their relative stability. For the Mg complexes, we find comparable or weaker complexation. This finding is in agreement with experimental observations. We demonstrate that explicit solvation of counterions is important when comparing Ca and Mg species. For the Ca complexes this has a minimal effect on their relative stability. Contrariwise, Mg complexes exhibit a lower stability and are highly sensitive to explicit short-range solvation effects. Explicit Mg²⁺ solvation significantly altered both absolute and relative formation energies compared to a simpler model. These findings highlight the crucial role of incorporating explicit short-range solvation effects in accurate computational modeling when small and highly charged ions are treated.

Rice and wheat, being major food crops worldwide, are susceptible to pollution risks associated with potentially toxic elements (PTEs). However, the accumulation and transfer patterns of different PTEs within rice and wheat systems remain a topic of debate. In this study, we conducted a holistic investigation of the risk flow of seven PTEs (As, Cd, Cr, Cu, Ni, Pb, and Zn) in the soil-root-straw-grain continuum of a typical rice-wheat rotation system. Laboratory analyses were performed on a total of 72 samples, comprising complete rice and wheat plants as well as paired soil samples. These samples were collected from nine cropland sites located in the Yangtze River Delta (YRD), a highly industrialized region in China. Our results revealed that Cd and Pb levels in the soils exceeded acceptable limits. Additionally, Cd, Cr, Ni, Pb, and Zn levels in wheat grains, as well as Cd in rice grains, exceeded food safety standards. Based on their behaviors within the soil-root-straw-grain continuum of rice and wheat, the seven PTEs can be classified into three categories: (1) The siderophile elements, Cr and Ni, exhibited higher concentrations in wheat roots, straws, and grains than in rice. (2) The chalcophile elements, Cd, Cu, Zn, and Pb, showed higher contents in rice roots and straws but lower contents in rice grains than in wheat. (3) The metalloid element, As, exhibited significantly higher concentrations and uptake capacity in rice than in wheat. Our findings suggest that wheat has a greater internal translocation capacity for PTEs than rice, leading to higher contamination levels and lower risk resistances for wheat crops. This study provides insights into agronomic regulations of different PTEs in rice and wheat cultivation areas.

The mineralogy, bulk geochemical composition, chemistry and U–Pb ages of detrital zircons in sediments from the La Pesca (LP) and Tesoro Altamira (TA) beaches, NW Gulf of Mexico are analyzed. The aim of this study is to infer the weathering history and provenance of sediments, and to identify the potential source terranes that are contributing sediments to the LP and TA beach areas. The beach sediments are rich in quartz and aluminosilicates. The Chemical Index of Weathering (CIW') and trace elements such as Th, Sr, U, and Ba reveal high weathering intensity for the LP and TA beach sediments. Major-element based diagrams and trace elemental ratios based on Co, Cr, Sc, La, and Th contents in sediments indicate felsic provenance, which is further supported by a negative europium anomaly and rare earth element (REE) patterns. The Th/U ratios (>0.3) together with positive cerium and negative europium anomalies of zircons in the LP and TA beaches indicate igneous origin. The comparison of zircon U–Pb ages of this study with ages reported from the adjacent terranes revealed that the Proterozoic (Paleoproterozoic: 1607.07–1943.45 Ma and Mesoproterozoic: 1021.19–1586.52 Ma) zircons are derived from the Oaxaquia, Mesa Central, Sierra Madre Oriental Provinces of Mexico and Mazatzal–Yavapai Province of the USA. On the other hand, Mesozoic (Jurassic 146.49–199.43 Ma and Cretaceous 68.46–136.82 Ma) and Cenozoic (Eocene 33.97–51.46 Ma and Oligocene 23.39–33.86 Ma) zircons are contributed by the Mexican volcanic rocks, Mesa Central and Sierra Madre Oriental Provinces in Mexico, and Mogollon-Datil Volcanic field and Colorado Plateau in USA. The rivers and their tributaries draining from the source areas are considered as a carrier and agent of distributing sediments along the northwestern Gulf of Mexico coastal areas, which are subsequently mixed by littoral currents.

Rare earth elements (REEs), a significant subset of critical minerals, play an indispensable role in modern society and are regarded as “industrial vitamins,” making them crucial for global sustainability. Geochemical survey data proves highly effective in delineating metallic mineral prospects. Separating geochemical anomalies associated with specific types of mineralization from the background reflecting geological processes has long been a significant subject in exploration geochemistry. The processing of high-dimensional, non-linear geochemical survey data necessitates a systematic framework to address common issues, including missing values, the closure effect, the selection of appropriate multivariate analysis methods, and anomaly detection techniques in order to detect geochemical anomalies associated with mineral occurrences. The Curnamona Province in South Australia is considered an emerging REE province with significant REE mineralization potential. In this study, we use data from this region to evaluate the performance of a novel machine learning-based framework that incorporates data pre-processing, multivariate statistical analysis, and anomaly recognition to address challenges such as missing data, noise interference, data imbalance and high non-linearity. We utilize lithogeochemical data to map potential greenfield regions of REE mineralization. The primary advantages of our framework lie in its provision of an effective random forest-based data imputation method, utilization of isometric log-ratio transformation to eliminate the closure effect, and reduction of the impact of outliers on data interpretation through robust principal component analysis. Additionally, the framework utilizes a deviation network to learn anomaly scores from complex, non-linear data under imbalanced data conditions, identifying geochemical anomalies associated with REE occurrences by leveraging prior knowledge rather than those caused by data noise or anthropogenic factors. The anomalous areas identified by this framework delineate all known REE deposits and extend to the surrounding regions. Furthermore, a close spatial coupling relationship exists between these strongly anomalous areas and the felsic granite intrusions. The comprehensive workflow for processing geochemical data proposed in this study can effectively address common challenges in the geochemical exploration of critical minerals. The identified geochemical anomalies can provide important clues for subsequent exploration.

Claystone formations are candidate host rocks for high-level heat-emitting nuclear waste (HLW). Temperatures from 90 to 150 °C at the canister surface are discussed internationally as potential emplacement and storage conditions. The thermal energy emitted from waste containers will be transported into the host rock formation, accelerating chemical reactions including the release of sorbed and dissolved gases and the generation of new gases. This study investigated gas release and generation in Opalinus Clay from Mont Terri (Switzerland) at elevated temperature and pressure conditions relevant for HLW storage and beyond. Hydrous pyrolysis experiments were conducted in Dickson-type flexible gold-titanium reaction cells and gold capsules in the temperature range of 80–345 °C and at 20 MPa. CO_2(g) was the predominant product, followed by C₁–C₄ hydrocarbons, which decrease in abundance with increasing carbon atom number. Neither CO nor H₂S was detected. H₂ was generated only in high temperature experiments at 315 °C and 345 °C, respectively. A combination of CO_2(g) quantification, stable carbon isotopic composition data, thermodynamic calculations and aqueous fluid composition (dissolved ions, pH) demonstrated that ≥80 % of the measured CO_2(g) originated from carbonate mineral dissolution. The model calculations also suggest that the fraction of CO_2(aq) in DIC increases from ∼50 % at 80 °C to nearly 100 % at higher temperatures. Thermal transformation of organic matter represented an additional source for CO_2(g) and was the predominant process yielding the C₁–C₄ hydrocarbons. Our findings stress the importance of quantitative geochemical data for the safety assessment of potential host rocks for HLW storage. We demonstrated that two sources are involved in gas release and generation at temperatures relevant for HLW storage, e.g., in the Opalinus Clay – organic matter and carbonate minerals. Our data will contribute to numerical modelling studies and the refinement of feature, events, and processes (FEP) catalogues.

The germanium content and its isotope ratio in thermal waters, aquifer rocks and main silicate minerals in a terrestrial groundwater system located in a granitic pluton (Karkonosze granitoid, Sudetes, Poland) have been investigated. This is the first extensive Ge isotope study carried out in both groundwater and aquifer rocks to better understand previously the identified enrichment of groundwater relative to rocks. This research also provides the first data on δ^74/70Ge for hybrid acid rocks formed by mixing magmas from two different sources (mantle- and crustal-derived) and main silicate minerals. The Ge isotopic composition in different facies of granite (porphyritic, equigranular) is comparable (δ⁷⁴/⁷⁰Ge of 0.43–1.23‰) to its hybrid rocks (quartz diorite–granodiorite, microgranular magmatic enclaves, composite dykes) – 0.79–1.27‰. However, the range of variability of this feature is quite wide. The minerals have δ^74/70Ge values of 1.01–1.04‰ in quartz, 0.84–0.90‰ in alkali feldspars, 0.76–0.88‰ in plagioclase, and 0.36–0.39‰ in biotite. The thermal waters are enriched in heavy Ge isotopes (δ^74/70Ge of 1.21–2.78‰) relative to the aquifer rocks (δ^74/70Ge of 0.43–1.27‰). Currently, the most likely explanation for this is the influence of secondary mineral phases formed in the geothermal granitic system. This comprises the preferential incorporation and adsorption of light Ge isotopes in/onto iron oxide/hydroxides and clay minerals. The other theoretical explanation, i.e., sulfide formation, is unlikely due to the unfavourable hydrogeochemical conditions in the studied system. The δ^74/70Ge values of thermal waters are similar to those of previously studied continental geothermal waters (1.65–3.29‰; Siebert et al., 2011) and fresh groundwater (2.24–4.02‰; Baronas et al., 2020), confirming that groundwater enrichment in heavy Ge isotopes relative to aquifer rocks may be widespread in the upper continental crust. Variation in the isotopic composition of the studied thermal waters is a result of the aquifer rock mineralogy and, in some cases, mixing of the old deep-circulating thermal water with the shallow modern cold groundwater. The general similarities in the chemical composition of the studied waters are due to the influence of porphyritic granite, which is the dominant rock type in this aquifer system. Some differences in chemical composition, including differences in the Ge isotopic composition, are related to the local distribution of hybrid rocks and sulfides. The δ^74/70Ge and Ge/Si ratios have been shown to be sensitive indicators of local hydrogeochemical conditions in an alimentation zone and a near-borehole zone of particular water intakes.