Applied Geochemistry最新文献

Helium (He) in hydrological systems is used to constrain the deep structure and improve interpretations of geophysical techniques beneath the Cathaysia Block (CB), of which the Cenozoic tectonic and geodynamic processes are controversial. The air-corrected ³He/⁴He ratio of both geothermal and non-geothermal waters in the CB range from 0.10 to 6.41Ra (Ra is the atmospheric ³He/⁴He ratio), displaying an increasing trend from inland to coastal area, aligning with thinning crust and younger magmatic activities. Mantle-derived He fluxes in the CB vary from 0.11 to 33.41 × 10¹⁰ atoms m⁻²s⁻¹, surpassing those in stable continental areas by up to three orders of magnitude. Due to the absence of active volcanic surface manifestations and identifiable crustal magma chambers, the mantle-derived volatiles are possibly transported from the mantle through the faults with advective flow rates ranging from 1.26 to 154 mm y⁻¹. Two distinct modes of mantle He releases lead to differences in mantle He fluxes between the interior and coastal CB. Seismic activity enhances permeability in the interior CB, leading to the leakage of mantle He. In the coastal CB, high mantle He fluxes with characteristics of volcanic degassing imply degassing from the partial mantle melting. The presence of high ³He/⁴He ratios (up to 6.41 Ra) and regional thermal anomaly provide evidence for an ongoing process of crustal underplating by mantle melting. Combined with the underplate layer revealed by geophysical results, this implies the continuous compensation mechanism involving mantle influx to counter extension-induced crustal thinning since the Mesozoic–Cenozoic in the coastal CB.

This study presents the riverine ¹²⁹I concentrations and fluxes during high-flow events. The river water samples obtained by a previous study were subjected to ¹²⁹I analyses. River water samples were collected at the midstream of the Abukuma River for five and seven times during high-flow events in July 2018 and October 2018, respectively. Suspended solids and filtered water samples were measured for ¹²⁹I/¹²⁷I ratios using an accelerator mass spectrometer system and for ¹²⁷I concentrations using ICP-MS. Aggregated mean values of dissolved ¹²⁹I concentration and ¹²⁹I concentrations in suspended solids were 0.11 μBq/L (n = 12) and 0.60 mBq/kg (n = 12), respectively. Corresponding values of ¹²⁹I/¹²⁷I ratios were in 2.2 × 10⁻⁹ (n = 12) and 3.7 × 10⁻⁹ (n = 12), respectively. These concentrations and ratios were comparable to those at the background level before the Fukushima Dai-ichi nuclear power plant accident. Positive correlations with dissolved ¹³⁷Cs and Cl⁻ concentrations suggested that the dissolved ¹²⁹I concentration decreased due to dilution of the river water during the events. A positive correlation with total carbon content suggested that organic matter contents determine ¹²⁹I concentrations in suspended solids. The total ¹²⁹I fluxes during JUL18 and OCT18 were 9.9 × 10³ and 2.2 × 10⁴ Bq, respectively. Although dissolved ¹²⁹I was predominant under low-flow conditions, the particulate ¹²⁹I flux increased by one or two orders of magnitude during the peak water discharge phases. These results underline the importance of particulate ¹²⁹I dynamics during high-flow events for quantitative evaluation of the ¹²⁹I cycle.

The Oyu Tolgoi world-class porphyry copper-gold deposits in Mongolian are that supergene and epithermal hydrothermal system superimposed in the early stage of porphyry system. Lithofacies of alterations, mineral and geochemical comprehensive methods were employed. Objective of this article are to investigate their formation environment of alteration rocks and mineralization in order to establish REEs and comprehensive prospecting indicators of alteration lithofacies, especially to find ore-forming center for this superimposed mineralization systems. Based on this study, REEs and geochemical prospecting indicators of alteration veins are of evident positive Eu anomaly, and are higher in concentrations of Fe₂O₃, CaO, S and TiO₂, with obvious positive U–K, Pb, P and Ti anomalies. It is very useful to catch the advanced argillic alteration lithofacies to delineate coverage of the later stage epithermal system, in which they are characterized by “U”-shape pattern normalized by chondrite as well as obviously anomalous concentrations of Cu, As, Se, Ba, Pb and Bi, with higher concentrations of K₂O, Al₂O₃ and S. Moreover, it is very valuable to discovery the intermediate argillization lithofacies to outline the mineralized center in which are typified by veinlets and brecciated hematite-magnetite silicification rock, and hematite-ferrocarbonatization rock. The mineralized center is typified by silicification altered rock in structure of veinlets-shape or the lithocap. The hydrothermal breccia zone may be an indicator of structure-lithology for the excrete channel and feeder of metallogenic fluid transportation in the epithermal system. Therefore, it is very more important that they are characterized by noticeable negative Eu anomaly (Eu*＝－0.57) and smooth-shape pattern normalized by chondrite. Copper mineralized center is implied by transitional environment of oxidation-reduction characterized by the ratios of Fe³⁺/Fe²⁺ from 0.72 to 2.13, plus Cu、As、Se、Ba、Pb and Bi anomalies, occurred lithofacies of the intermediate argillic alteration are considered to be localization markers whenever associations of Cu、V、Zn、Se and Mo anomalies may be signs for orebody finder.

In this study, a functional ionic liquid system was successfully applied to extract lithium from the Canadian oil and gas produced water samples without further dilution at ambient conditions. The effects of interference cations, dissolved organics and other factors on the extraction were studied in detail. Chemical precipitation method was applied to reduce the concentrations of divalent ions before the ionic liquid extraction. The extraction efficiency is about 70% on average and can be as high as 90%. It appears that this extraction method can be directly applied to the oilfield brine samples with both high Na/Li and Mg/Li ratios. In addition, it seems that the dissolved organics in the produced water did not impact the extraction efficiency. Efforts shall be made in the future to reduce the cost by replacing the diluent with another type of solvent and further improving the recycle and reuse of the IL systems. In summary, the technology can achieve satisfactory lithium extraction from the Canadian oil and gas produced water.

The uptake kinetics of ³²Si and ⁴⁵Ca on cement minerals including C-S-H phases, portlandite, AFm phases, ettringite, and aged hardened cement paste were determined through batch sorption experiments. A two-step uptake kinetics was observed, with a fast initial step during ∼1 day followed by a much slower second step, not yet completed after one year. The working hypothesis that the fast uptake is caused by exchange of the radioisotopes with stable isotopes adsorbed on the mineral surface, whereas the slow uptake step is due to uptake in the crystal lattice during recrystallisation, was tested with the help of phenomenological models that combine surface adsorption and homogeneous recrystallisation. The experimental data could be reproduced satisfactorily using a refined version of the formerly published continuous homogeneous recrystallisation (CHOR) model, supporting the working hypothesis and allowing equilibrium sorption coefficients (R_d; L kg⁻¹) for these radionuclides to be calculated on a mechanistic basis. This provides insight into the intrinsic rates and mechanisms of interaction between cementitious materials and their pore fluids which contain dissolved calcium and silicon.

Heavy metal and metalloid contamination of farmland soils are closely related to human health. Soil contamination caused by small-scale mining activities has been largely neglected, especially in developing countries. This research studies the characteristics and the source of heavy metals and metalloids in farmland soils in the Bailing Cu–Zn deposit area in Northeastern China through multiple approaches. Geochemical mapping conducted by portable X-ray fluorescence (pXRF) spectrometry and elemental fractionation analysis (sequential extraction) revealed the spatial variations in elemental concentration and fractionation of the farmland soils. The elemental variations in the sediment and water samples in a stream passing by the farmland were determined by inductively coupled plasma mass spectroscopy (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Results indicate elevated As, Zn, Fe, and Mn concentrations in the west bank of the farmland and the associated environmental risks caused by extremely high As concentrations (>500 mg kg⁻¹). The upstream mining activities are identified as a dominated source of contamination in the studied farmland based on the variations of elemental concentrations and fractionations, as well as multivariate analysis results. This study revealed potential ecological risks caused by heavy metal and metalloid contamination in farmland soils in the metal mine impacted area and the stream as a primary pathway for the migration of pollutants associated with mining activities.

Birnessite is a phyllomangante mineral widely found in surficial environments. Its morphology not only affects its adsorption and oxidation properties but also indicate changes in the climatic conditions of ancient Earth. This study explored how preparative parameters affect the morphology and reactivity birnessite. Synthesized at boiling temperatures, birnessite nanoflowers measured 265 nm with a specific surface area (SSA) of 34.87 m²/g, while at 65 °C, they increase to 2251 nm with a similar SSA of 30.33 m²/g. Lowering KMnO₄ or HCl concentrations increased nanoflower size. Reduced concentration of KMnO₄ hindered Coulombic forces, fostering a parallel petal arrangement and a higher SSA (59.11 m²/g). Lower concentration of HCl led to perpendicular petals and a reduced SSA (12.33 m²/g). Decreased concentrations of both KMnO₄ and HCl reduced initial δ-MnO₂ concentration, allowing time for edge-to-edge assembly and nanoflake substrate formation. Subsequently, δ-MnO₂ vertically assembled on substrates to form microwalls with SSA of 85.39 m²/g. Organic acids as capping agents disrupted this assembly. Adsorption tests for Cd²⁺ revealed microwalls achieved 7102 mmol/kg, surpassing original birnessite nanoflowers at 2114 mmol/kg. These results provide insights into the crystallization processes and reactivity of natural birnessite, as well as methods for the controllable synthesis of nanoflowers.

Carbon capture and storage (CCS) is a promising technology for reducing CO₂ emissions. Significant concerns have emerged about the potential leakage of CO₂ into shallow aquifers, highlighting the risk to water quality and environmental safety. This underscores the importance of finding monitoring tools suitable for different geological scenarios. If leakage occurs in the context of depleted reservoirs being used for CO₂ storage, residual CH₄ from the storage complex will likely be entrained together with CO₂. However, few studies have addressed the implications of CH₄ presence and its potential as a monitoring parameter during CO₂ leakage.

To address this gap, we simulated a leakage event by injecting water enriched with CO₂ and CH₄ into a shallow limestone aquifer. The impact of the injection was monitored using a combination of laboratory measurements on water samples and in-situ sensors located downstream from the injection well.

All parameters were affected by the simulated leakage. Some monitoring tools allowed us to differentiate the leakage event from natural variations. A key finding of this study was that at 7 m from the injection well, the CH₄ breakthrough occurred roughly one day before the CO₂ breakthrough, highlighting the potential of CH₄ as an early indicator of CO₂ leakage and suggesting interesting prospectives for industrial-scale sites. However, further research is needed to confirm the potential of CH₄ as a CO₂ leakage indicator at industrial scales, due to potential methane oxidation and loss of the signal with longer times and distances.

This study contributes to a better understanding of the potential risks and effective monitoring strategies associated with CO₂-CH₄ leakage in carbonate aquifers.

Geochemical surveys are a cornerstone for data generation in geosciences, facilitating resource exploration. Geochemical data is essential for identifying mineralized areas, understanding local geology and assessing environmental impacts. This paper aims to: (1) review the process of geochemical data generation to gain an appreciation of the characteristics of traditional geochemical data; (2) review recent developments in the usage of geochemical data, particularly the disruption brought forth by those in data science and artificial intelligence; and (3) envision a future specification of geochemical data that would be fit-for-purpose for modern and emerging data users. This review reveals that benefits brought by advancements in automation, analytical technique and computing capability have unlocked unprecedented insights from geochemical data. However, the sustainability of re-purposing small geochemical data for big data methods is intrinsically questionable. The mismatch stems from rapidly changing data requirements in geochemistry, which is brought forth by: (1) a pivot away from scientific reduction through the adoption of system-level methods; (2) developments in geometallurgy; (3) skill gaps in geoscientific education; and (4) a growing demand of raw materials. While traditional methods will likely continue to serve many scientific needs, new strategies and techniques must be developed and implemented to cost effectively and efficiently generate bigger geochemical data. Bigger geochemical data must emerge in response to the already changing landscape of geochemical data usage. Solutions are multidimensional, from evolving geoscientific education, leveraging modern technology, explicating and differentiating data user and generator roles and responsibilities, to modernizing data management.

The river infiltration zone is a mixed area of surface water and groundwater under the riverbed and along the riverbank, which is greatly affected by river infiltration. Currently, there is a lack of understanding regarding the migration and transformation processes of Fe, Mn, and As, along with their correlation with organic carbon in the river infiltration zone affected by riverbed scouring and siltation processes. In this study, based on techniques such as pore water sampling and the Tessier sequential extraction, the spatiotemporal variations in Fe, Mn, and As concentrations and possible geochemical processes at the riverbed sediment–water interface and along the river infiltration flow path were revealed. The results indicated that the potential geochemical activity of Fe, Mn, and As and the distribution of organic carbon in the riverbed sediment responded to riverbed scouring–siltation processes. Compared to the high water level period, the potential geochemical activity of Fe, Mn, As, and organic carbon in the riverbed sediment generally exhibited an upward trend during the low water level period, indicating more intense Fe and Mn biogeochemical reactions. During river infiltration, the labile organic carbon (LOC) was preferentially utilized, and with increasing depth, the sedimentary organic carbon (SOC) continuously transformed into LOC and dissolved organic carbon (DOC). Affected by riverbed scouring processes, the transition time from oxidizing to reducing conditions in the pore water increased, and the Fe, Mn, and As reduction zones moved deeper and farther from the riverbank, resulting in a significant expansion of the groundwater pollution area. The reductive dissolution of iron and manganese oxides/hydroxides and the oxidation of organic matter–bound Fe, Mn, and As were the main biogeochemical processes contributing to the release of Fe, Mn, and As in the river infiltration zone. These research results have crucial theoretical significance and practical application value for the sustainable utilization of groundwater resources and the remediation of groundwater pollution.