Applied Geochemistry最新文献

Tectono-geochemical data measured from tectonites host a wealth of information that is closely related to the accumulation and dispersion of ore-forming materials, while structure system is the only pathway to connect the deep orebody with the surficial tectono-geochemical anomaly, and both have correspondence and consistency. Based on the geological precondition that structure system and ore-forming process are closely associated with each other, the study proposed a method of sequential Gaussian co-simulation of tectono-geochemical anomaly, which integrates the tectono-geochemical anomaly with the ore-controlling structure system to solve two basic geological prospecting problems that are closely associated with ore-forming space and ore-forming material migration. A case study for concealed Pb–Zn prospecting based on tectono-geochemical data in the Huangzhuguang ore cluster (China) was employed to examine the potential applications of the proposed method. Firstly, centered logratio transformation was employed to remove the closure effect of tectono-geochemical data and to make the data conform to an approximate normal distribution. Secondly, sequential Gaussian co-simulation was applied to improve the simulation results of the tectono-geochemical anomaly by introducing the ore-controlling structure system. Thirdly, the probability distribution of tectono-geochemical anomalies was quantified by uncertainty modeling technique. The case study demonstrated that the proposed method can significantly improve the performance of the primary variable in predicting concealed ore deposits.

Sea spray aerosols (SSA) are important contributors to the global aerosol load, and they have a significant impact on the global climate system and chemical processes. To better assess the environmental impact of SSA emissions, it is important to quantitatively characterize the parametric dependence of SSA production fluxes on other environmental variables, and assess their role in global climate models (GCMs) and chemical transport models (CTMs). There are currently significant differences in the simulation of global SSA production fluxes in various models, and these differences are mainly attributed to the differences in the sea spray source functions (SSSFs). Research in the literature over the last decade has greatly broadened the knowledge of SSSFs and improved our understanding of SSA production fluxes and how they are applied in models. This paper clarifies the derivation process of different SSSFs, and provides a critical review of the application progress of different SSSFs in different models, which plays an important role in improving the accuracy of model simulations to evaluate the impact of SSA. More specifically, we review the studies related to the parameterization of sea spray aerosol production fluxes in the last decade, mainly focusing on the influencing factors of SSA production, the research progress of SSSFs, and the application of SSSFs in the models. The main environmental factors that alter the production flux in SSA include wind speed, sea surface temperature, wave state, salinity, surface active organic matter, etc. To better parameterize the SSA production flux, different expressions of SSSFs have been proposed. This paper mainly summarizes from different variables such as particle size distribution dependence, whitecap coverage, sea surface temperature dependence and wave state dependence. Moreover, many studies have incorporated different SSSFs in different GCMs and CTMs to evaluate the reasonableness of SSSFs and the climate impact of SSA emissions. Finally, we summarize the current results and inadequacy of SSA production flux parameterization, and put forward the prospect of future research direction.

Travertine samples deposited in Earth's surface environments can be used as an effective archive for paleo-climatic reconstruction. As a common element in carbonates, magnesium (Mg) and its isotopic composition in travertine could provide useful information for evaluating paleo-environment changes. In this study, we investigate the Mg isotope systematics in both endogenic travertines (mainly calcite) and spring/stream waters at Baishuitai, Yunnan, SW China. Our results show a systematic increase in δ²⁶Mg value from −1.37 to −1.26‰ for water samples downstream, but varied δ²⁶Mg values between −4.12 and −3.95‰ (average −4.02‰) for solid carbonates, thus a corresponding fractionation Δ²⁶Mg_{calcite-water} between −2.76 to −2.59‰ (mean value of −2.69‰). Therefore, the solid carbonates preferentially incorporate light Mg isotopes during travertine formation. More interestingly, the Mg distribution coefficient (K_Mg/Ca) between travertine and water exhibits two variation trends with the calcite deposition rate (R_p) along the canal, which can be explained by the change of calcite formation mechanism from direct nucleation to precipitation via amorphous calcium carbonate (ACC) intermediate. In the upper-stream, the direct nucleation of calcite results in the rapid incorporation of Mg ions into crystal lattice, while a relatively slow precipitation of calcite downstream would incorporate Mg via ACC formation pathway in a quasi-equilibrium pattern. This is consistent with the grain size distribution and crystal morphology observed under SEM. Our results show the important control of water Mg/Ca ratios on the calcite precipitation during travertine formation, and imply the potential and complexity of using Mg isotopes of travertine deposits to reconstruct paleo-environments.

We validated the recently updated Caltech Isoprene Mechanism (CIM), which represents the complex dynamics of isoprene peroxy isomers through repetitive O₂ addition and dissociation reactions, using a dataset synthesized from two field measurements taken place in both urban and rural areas of East China. The dataset covers a large span of nitric oxide (NO) levels ranging from tens of ppt characteristic of clean rural air to tens of ppb typically found in the polluted urban environment. An observationally constrained zero-dimensional box model that incorporates the CIM mechanism was constructed to simulate the daytime profiles of methacrolein (MACR) and methyl vinyl ketone (MVK), two major first-generation products that account for over half of the total carbon oxidation flow of isoprene. A closer agreement with the measurements was found compared with the traditional mechanism that prescribes a fixed yield of MACR and MVK across all NO levels. This result demonstrates that the isoprene peroxy dynamics operate competitively in the area and play a governing role in the final distribution of isoprene oxidation products. The atmospheric implication is that, with effective measures taken to reduce pollutant emissions in East China, the prevailing chemical regime at play has evolved and implementing the updated isoprene mechanism into regional models will have a profound impact on the predicted radical cycling and ozone production of the local atmosphere.

N-nitrosamines are a new class of disinfection byproducts with significant toxicity and carcinogenicity that have attracted extensive attention worldwide in recent years. N-nitrosamines in natural and drinking water would have adverse effects on people. The occurrence of N-nitrosamines in surface water, groundwater, and tap water of the Liujiang River Basin was investigated to disclose the source, fate, and cancer risk of N-nitrosamines in a typical karstic river. The origins of N-nitrosamines contamination were investigated using principal component analysis and multiple linear regression (PCA-MLRA). The results indicated that the concentrations of nine N-nitrosamines species were NDMA (1.7–342 ng/L), NMEA (ND, ND represents not detected), NPYR (2.5–53 ng/L), NDBA (ND-87 ng/L), NDEA (0.2–5.7 ng/L), NDPA (ND-34 ng/L), NPIP (ND-32 ng/L), NMOR (0.1–5.2 ng/L), and NDPhA (ND-0.3 ng/L). 71% of N-nitrosamines in the surface water samples of the Liujiang River's mainstream could be attributed to industrial and aquaculture effluents. Furthermore, 29% of N-nitrosamines could originate from domestic sewage and agricultural operations. In addition, we estimated the cancer risks associated with N-nitrosamines in groundwater and drinking water. For lifetime exposure (from birth to age 70), the average estimated carcinogenic risks of groundwater and tap water from oral intake were 7.4 × 10⁻⁵ (7.4 extra cancer cases per 100,000 persons exposed) and 9.7 × 10⁻⁵, respectively, which were greater than the US EPA standard (1 × 10⁻⁵). N-nitrosamines posed the highest cancer risk to children aged one to six. The experimental results would serve as a data foundation for environmental governance in typical karst regions.

Acid mine drainage (AMD) is a well-known source of toxic trace metals in freshwaters. Traditional passive treatment systems rely on AMD neutralization with limestone and removal of most common toxic transition metals such as Cu and Zn with little attention to rare earth elements (REE). Alkaline waste materials now receive increasing attention as low cost AMD treatment alternatives in the circular economy. This study was set up to identify the efficiency of alkaline waste materials remediating AMD and scavenging REE in addition to other toxic trace elements. An AMD sample was collected from a lixiviate coming from pyrite heaps in the Iberian Pyrite Belt (pH = 1.8, 30 μM ∑REY). The sample was treated with either blast furnace slag (BFS) generated during smelting of iron ore in a blast furnace or biomass ashes (BA) derived from combustion of biomass, thereby using analytical grade CaCO₃, and NaOH as reference products. The batch alkalinization experiments were conducted by adding each alkaline material at an amount to obtain an equal pH to ≈6.5. The required amounts of the products were NaOH < CaCO₃<BFS < BA in line with their acid neutralizing capacities. The largest removal of sulfate from water was obtained in the CaCO₃ treatment suggesting gypsum precipitation which was lower with BA and BFS and virtually absent with NaOH, these trends were confirmed by SEM-EDX and XRD. Both BFS and BA removed more Fe than CaCO₃ and NaOH. The REE elements were well removed by all treatments (>99%) and the remaining REE concentrations in the solutions were clearly lower than values for Cu and Zn. The Zn and Cu removals were not consistently high enough (except with NaOH) to meet environmental limits in the discharge waters. The largest efficiency for REE removals was obtained with CaCO₃. Indirect evidence here suggests that gypsum is a better host for the trivalent REE than Fe(III) minerals in the precipitates. The ionic radii of trivalent REE are more similar to Ca²⁺ than to Fe³⁺, explaining the better potential of gypsum as REE host. This study showed also the potential of BFS as alkaline agent for the remediation of AMD in terms of its higher alkalinity generation potential as compared to BA, thus making BA less promising than BFS.

δD and δ¹⁸O isotope signatures were widely used as tracers to investigate recharge processes of rainfall transfer into caves in the vadose zones of karst regions. The present research systematically monitored rainfall, soil water, and drip water at the Liangfeng Cave in Guilin City, China, from January 2020 to September 2022, as these aspects remain poorly quantified. The δD and δ¹⁸O compositions of rainfall were depleted during the rainy season and enriched during the dry season. The local meteoric water line (LMWL) was described as δD = 7.98δ¹⁸O + 11.52. The dry season is mainly characterized by resident soil water, with little mobile soil water, whereas the primary source of recharged drip water is stored bedrock water on the top of the cave. During the rainy season, resident and mobile soil water exchanged with each other, resulting in homogenous δD and δ¹⁸O compositions across different soil depths and indicating a lack of ecohydrological separation; however, δD and δ¹⁸O signature in drip water may differ from the original observed in rainfall, suggesting that the residence time affected the response time of the drip water to rain. Moreover, mixed stored older water in the overlying bedrock was the primary drip water recharge source each season; thus, drip water's isotope amplitude values were more depleted than rainfall's. Distinct flow paths also created differences in the lag time and amplitude at each drip site. During high-intensity rain, the isotopic signals were rapidly transmitted by preferential flow at different soil depths and via drip water. The δD and δ¹⁸O signals in the drip water showed significant depleted excursions several months after high-intensity rainfall. These findings indicate that ecohydrological separation did not occur under any circumstances within the study area, and care should be taken when interpreting significant depleted excursions of δD and δ¹⁸O signals in drip water during the summer monsoon or the amount of rainfall in stalagmites across seasonal or interannual scales.

This study aimed to identify the origins of crude oils by analyzing the δ¹³C values of phenanthrene (Phen) and methylphenanthrenes (9-MP and 1-MP) in some selected oils from the Tarim Basin (NW China), Termit Basin (Niger), Bongor Basin (Chad), and Fushan Depression (South China Sea). The study showed that oils with low 9-MP/1-MP ratios (<2.0), phenanthrene (Phen) δ¹³C values below −30.0‰, and Δ¹³C_(9MP-Phen) and Δ¹³C_(1MP-Phen) values above zero are marine-originated oils, while oils with high 9-MP/1-MP ratios (>2.0), phenanthrene (Phen) δ¹³C values above −20.0‰, and Δ¹³C_(9MP-Phen) and Δ¹³C_(1MP-Phen) values below zero are terrestrial-originated oils. Oil samples with high 9-MP/1-MP ratios (>2.0), phenanthrene (Phen) δ¹³C values ranging from −30.0‰ to −20.0‰, and Δ¹³C_(9MP−Phen) and Δ¹³C_(1MP-Phen) plots below zero are mixed-originated oils with higher terrestrial contribution. In contrast, oils with low 9-MP/1-MP ratios, phenanthrene (Phen) δ¹³C values ranging from −30.0‰ to −20.0‰, and plotting above and below Δ¹³C_{(9-MP−Phen)} and Δ¹³C_{(1-MP−Phen)} vice versa, are mixed-originated oils with higher contribution from marine sources.

In combination with the geological settings, the results indicated that the oils from the Tarim Basin have three distinct origins. The majority of the oils are marine-sourced oils derived from the Lower-Paleozoic marine carbonate rocks. Oil samples *T2, *T3, and *T4 are mixed-originated oils with higher terrestrial contribution generated from the Mesozoic lacustrine shales/mudstones in the Tarim Basin. The oil samples *T1 (XH1) and *T9 (S94) are from a mixed origin with higher marine material, are derived from Upper-Paleozoic marine shale source rocks in the Tarim Basin. In Termit Basin, most of the selected oils are mixed oils with higher marine organism contribution from YSQ₁ and YSQ₂ source rocks from the Mesozoic Yogou Shale Formations, except for *T27 oil sample (Douwani-1), which is a mixed oil with higher terrestrial contribution from YSQ₃ source rocks of the Mesozoic Yogou Shale Formations. As for the selected oils from Bongor Basin and Fushan Depression, they are mixed oils with higher contributions from aquatic organisms generated from the Mesozoic and Cenozoic lacustrine shale rocks, respectively.

This approach allowed to identify for the first time the mixed origin with higher contribution of marine organic matter of the oil samples *T1 (XH1) and *T9 (S94) from the Tarim Basin, and the mixed origin with higher contribution of terrestrial organic matter of the oil sample *T27 (Douwani-1) from the Termit Basin.

Sr and Nd isotopic ratios along with (REE + Y) and other trace elements were measured in bedded travertines from three quarries at Tivoli Terme, Latium, aimed at deciphering their chemical and isotopic characteristics for the origin and evolution of fluids. Travertines, which were deposited between ∼81 and ∼54 ka BP, display high Sr and low REY contents along with REY_PAAS patterns, supporting their fluid origin mainly from marine rocks, in particular the Upper Triassic Burano Evaporite Fm. This has been confirmed by the narrow ranges of δ⁸⁷Sr and ε_Nd values, close to those of that formation and other Mesozoic marine carbonates from central Italy. A sample of today's thermal water from Tivoli Terme provided a REY_PAAS pattern and a δ⁸⁷Sr value comparable with travertines, both features supporting that today's water is analog to past hydrothermal fluids. The overlap of the chemical and Sr–Nd isotopic compositions of coeval travertines and thermal waters from Tivoli and Acquasanta Terme, Marche, suggests a common fluid origin, ruling out any significant contribution from magmatic fluids/rocks to Tivoli travertines, yet deposited at the periphery of the Alban Hills volcano. Lastly, the geochemical results provide implications for regional neotectonics and the role of CO₂-rich fluid pressure in fault activation, even in mildly active to almost inactive tectonic domains.

Hydrolysis of Sn is a pivotal step during the precipitation of cassiterite, the primary Sn-bearing mineral and thermodynamically stable Sn-oxide on Earth's surface. In this contribution, we investigated the reaction kinetics of Sn(IV) chloride hydrolysis by systematic experiments at temperatures of 6.4 °C to 28.6 °C. Experimental results show that the hydrolysis reactions of Sn(IV) chloride follow a first-order kinetics model, with rate constants (0.12 h⁻¹ to 5.5 h⁻¹) strongly controlled by temperature. Based on the obtained reaction constants at different temperatures and the Arrhenius equation, the activation energy of the Sn(IV) chloride hydrolysis reaction is calculated to be 26.05 ± 2.25 kcal/mol, indicating a surface-controlled reaction mechanism. Additionally, the Sn(IV) chloride hydrolysis rate increases with the ionic strength. No significant Sn isotope fractionation between aqueous Sn(IV) and the solid hydrolysis product was observed during the Sn(IV) hydrolysis experiments in this study. The activation energy data and Sn isotope behavior associated with Sn(IV) chloride hydrolysis may be used to better understand the behavior of Sn during various mineralization and weathering processes.