Applied Geochemistry最新文献

We present an analytical workflow scheme to trace the source of lead and to estimate risks to lead contaminated soil and demonstrate the methods with test sites from the city of Turku. This workflow includes lead concentration, sequential extractions, mineralogical characterization, and isotope composition. Lead concentrations higher than 100 mg/kg were found in 16 out of 219 urban topsoil samples in the city of Turku during soil geochemical baseline mapping. Ten samples were selected for detailed geochemical and mineralogical studies. Most of the elevated Pb concentrations were measured from fill-derived soils. Mineralogical investigations using FE-SEM-EDS demonstrated that Pb exists in various types of particles and compounds in the Turku topsoil samples. Most of the particles appear to be of anthropogenic origin. The Pb isotopic compositions measured on individual Pb-bearing particles using laser ablation MC-ICP-MS in Turku soil rule out their origin from Finnish and Swedish bedrock. Thus, Pb in the fill-derived soils must have been imported from other regions. Based on the combined use of traditional geochemical study and advanced micro-analytical techniques, it was found that Pb in urban fill-derived soils is bound to various carrier phases and has several pollution sources. When Pb-containing urban soil is reused in city constructions, care should be taken to prevent direct contact with the Pb-containing soil and dust generation at such sites.

The Ulubelu geothermal field is located in Lampung Province, Indonesia, about 125 km west of Bandar Lampung City. This field is utilized as a power plant with an installed capacity of 220 MW operated since 2012. The Ulubelu geothermal system is a high enthalpy water-dominated reservoir and has temperature around 265 °C. This study aims to determine the elevation of the recharge area in the Ulubelu geothermal system based on the values of δ²H and δ¹⁸O isotopes to support the geothermal use sustainability. Major ions, δ²H, δ¹⁸O, and δ¹³C_(DIC) isotopes analysis were carried out on hot springs, lake water, cold springs, and rainwater. The content of the major anions and cations indicates that the hot springs from the Way Panas Group are chloride-type water originating from the reservoir meanwhile the Danau Hijau and Pagar Alam groups are condensates acid-sulphate fluids. Moreover, the calculation using a Na/K and silica geothermometer shows that the reservoir has a temperature around 229 ± 4 °C. Analysis of the δ²H and δ¹⁸O isotopes content informs that the origin meteoric water seeped into the geothermal reservoir was δ¹⁸O −6.65‰ and δ²H −39.5‰ ranging from 1108 to 1570 masl elevation. Overlaying with the surface terrain map depicts that the recharge area originates from the peak of Mt. Rendingan in the north of Ulubelu and Mt. Sula in the west with 42.9 km² total area. In conclusion, this study elucidates the recharge area elevation in the Ulubelu geothermal system, offering crucial insights for sustainable geothermal resource management and reservoir origin understanding, thus highlighting its potential for sustainable energy production.

Groundwater sulfate contamination becomes a big concern in urbanized areas where urbanization expansion continues. This study investigates the spatial distribution of sulfate in shallow groundwater of the Pearl River Delta (PRD) where urbanization has lasted for more than 40 years, and discusses sources and factors for groundwater sulfate contamination in various aquifers and areas with different land-use types by using hydrochemistry and principal component analysis. A total of 330 groundwater samples, 19 river samples, and 9 landfill leachate samples were collected from the PRD. The results show that groundwater SO₄²⁻ concentration in the PRD is up to 857.57 mg/L, and the SO₄²⁻-rich (>150 mg/L) groundwater accounts for 7.27%. SO₄²⁻-rich groundwater in the coastal alluvial aquifers is 3.8 times that in the alluvial-proluvial aquifers, while fissured and karst aquifers are absence of SO₄²⁻-rich groundwater. In coastal alluvial aquifers, SO₄²⁻-rich groundwater in urbanized areas is 8.5 times that in peri-urban areas. By contrast, in alluvial-proluvial aquifers, SO₄²-rich groundwater just occurs in urbanized areas rather than other areas. Exogenous input driven by urbanization is the primary factor for SO₄²⁻-rich groundwater in the PRD. The occurrence of SO₄²⁻-rich groundwater in urbanized and peri-urban areas of the PRD is mainly attributed to the industrial wastewater infiltration and acid precipitation. Lateral flow from rivers is another prominent source for SO₄²-rich groundwater in the PRD. As a consequence, in order to reduce the emergence of SO₄²⁻-rich groundwater in areas of accelerated urban expansion such as the PRD, strengthening the treatment and supervision of wastewater from township enterprises and waste gas from industrial enterprises is recommended.

When reduced sulfidic parent sediments are oxidized, they become acid sulfate soils and discharge metal laden acidic solutions that can damage the environment, infrastructure, and human health. Consequently, methods to mitigate the effect of acid sulfate soils are a priority in affected areas. In this study, acid sulfate soil core samples, consisting of a natural network of preferential-flow soil macropores with defined macropore surfaces and inner cores of denser clay, were characterized and subjected to treatments with calcium carbonate and peat suspensions, or combinations thereof. The effects on the geochemistry and microbial communities were examined on both macropore surfaces and in inner cores. Although transport of treatment substances into the inner cores was demonstrated, no substantial effects were found on the geochemistry and microbial community that consisted of bacterial taxa commonly identified in acid mine drainage. In contrast, positive treatment effects were clearly detected on macropore surfaces and the most promising mitigation effects were detected for treatments combining calcium carbonate and peat suspensions. These treatments increased the pH of the macropore surfaces, added an electron donor in the form of peat, and significantly decreased the relative abundance of acidophilic bacterial populations while shifting the microbial community towards species typically growing at circumneutral pH values. These new environmental conditions were favorable for iron reduction that resulted in a positive effect on permeate quality. The study presents novel data regarding the important differences between acid sulfate soil macropore surfaces and inner cores, as well as their diverse biogeochemical characteristics. It further establishes that the major oxidation-reduction processes occur at the macropore surfaces, and that the combination treatment was the most effective at mitigating the negative environmental effects.

The supply of technologically important rare earth elements (REE) is a concern in Europe, hence the recovery of REE from alternative sources has recently become widely investigated. One of the problems is the lack of cost-effective technologies for REE recovery from leaching solutions. The present work investigated the potential for recovering REE and Th from leaching solutions by co-precipitation with Pb phosphates. A set of four experiments were conducted using analytical reagent grade chemicals to analyze the effects of Pb and different pH on the efficiency of REE and Th removal from aqueous solutions. After selecting the best conditions, two additional experiments were performed using solutions obtained from leaching REE-rich apatite mine waste.

The precipitates resulting from the experiments as well as the solutions before and after precipitation were analyzed. It was found that the formation of a crystalline mixture of REE- and Th- enriched pyromorphite, Pb₅(PO₄)₃Cl, and Pb-phosphates, about which little has been known so far, was responsible for complete (>99%) removal of REE and Th from aqueous solutions at pH 4 and 6. At lower pH, the removal is incomplete except for Sc and Th, which probably form a distinct phases. Besides that, no fractionation of LREE and HREE was observed. The experiments included the study of solutions resulting from the leaching of REE-rich apatite waste, which may contribute to the development of new technologies for REE recovery from wastes.

Geofluids from natural springs connect with the crust and/or mantle in many cases, and their geochemical anomalies could be significant for the study on faults activity and even earthquakes. Several natural springs are distributed along the Lenglongling fault zone (LLLFZ) in the northeastern margin of the Tibetan Plateau, where the Ms 6.9 Menyuan earthquake occurred on January 8th, 2022. Based on chemical and isotopic compositions (δD, δ¹⁸O, δ¹³C, and ³He/⁴He) of water and gas samples, the origin of geofluids and their potential correlation with fault activity even including earthquakes are preliminarily assessed in this paper. The δ¹³C_CO2 values and ³He/⁴He ratios showed that the gas originating from the crust was associated with the metamorphism of carbonate rocks, whereas the δ¹⁸O and δD values of water samples indicated that the natural springs were predominantly infiltrated with precipitations from local mountains ranging 3.7 - 5.5 km in height. Obvious changes of Ca²⁺ and HCO₃⁻ concentrations in SZK spring waters in the surface rupture zones were observed in a short period (about three months) after the main shock, in contrast to those of the GSK springs far from the surface rupture zones. Such variations might be correlated with the stress increase prior to the 2022 Menyuan Ms 6.9 earthquake. The mechanical fracturing of surrounding limestone rocks during the slipping movement of LLLF could facilitate the water-rock interactions. Compared to three-month observations after the main shock, relatively higher concentrations of HCO₃⁻ and heavier δ¹⁸O_H2O values of the LHG springs were also observed in the short-term period. The shallow stored formation water might be squeezed along the cracks and rose to the surface during earthquake tremors, causing a sandblasting water phenomenon.

Hydrochemistry and carbon isotopic (δ¹³C_DIC) compositions of dissolved inorganic carbon (DIC) were investigated in the Upper Jhelum River Basin (UJRB) in the western Himalayan region, to better understand the mechanisms and controlling factors of chemical weathering and carbon dynamics. A forward model was used to estimate the contributions of various sources of dissolved loads. Carbonate weathering dominated the riverine solute generation with a contribution of 69.5 ± 5.9%, and ions derived from carbonate weathering show strong chemostatic behavior in response to changes in discharge. Ions derived from silicate weathering demonstrate a significant dilution impact and silicate weathering contributed 8.9 ± 3.1% of the riverine solutes. We estimated the annual discharge weighted weathering rates of carbonate (52.8 t/km²/y) and silicate (12.0 t/km²/y), and then estimated CO₂ consumption rates by carbonate weathering (7.0 10⁵ mol/km²/y), silicate weathering (2.2 10⁵ mol/km²/y), and net CO₂ consumption flux (6.5 mol/km²/y). The cation flux of 126.5 × 10⁴ t/km²/y accounts for 0.1% of the total cation budget of ocean water. The δ¹³C_DIC values are primarily controlled by carbonate weathering by carbonic acid and show a lower sensitivity than DIC contents in response to various hydrological conditions. However, biological carbon influx during higher temperatures in summer and autumn and evasion to the atmosphere during spring are secondary processes controlling DIC and δ¹³C_DIC in the region. This study provides insights into chemical weathering processes and carbon dynamics, highlights the impacts of hydrological variability that controls the generation and transport of solutes and aids in understanding of the global carbon cycle.

Although high arsenic (As) groundwater has been widely observed in sedimentary aquifers, arsenite (As(III)) and arsenate (As(V)) mobilization in fissured bedrock aquifers are less documented, and different mobilization behaviors of As(III) and As(V) in groundwater from those aquifers are little known. Thus, geochemical and isotopic characteristics of high As groundwater in fissured bedrock aquifers in the Xunhua-Hualong basin were investigated. Results showed that fissured bedrock aquifer hosted high As groundwater. Total As concentrations in spring waters were up to 628 μg/L being dominated by As(V) with high ORP values (from 87.2 to 212 mV). As(III) dominated dissolved As in deep groundwater (up to 22.5 μg/L) with low ORP values (−217 and −288 mV). The positive correlation between As concentration and δ¹⁸O in spring water revealed that oxidation of As-bearing pyritic minerals in the fissured bedrock aquifers released As into groundwater. In deep groundwater under anoxic conditions recharged by shallow aquifers, high As groundwater usually had high concentrations of dissolved Fe, suggesting that reductive dissolution of Fe (oxyhydr)oxide minerals mobilized As into groundwater. Elevated concentrations of PO₄³⁻ in high As spring water and deep groundwater indicated the competition adsorption between PO₄³⁻ and As(V) (and As(III)). Insignificant correlations were observed between As(V) and pH, HCO₃⁻, and Na⁺/Ca²⁺ in spring water, revealing that desorption induced by pH and HCO₃⁻ and cation exchange between Ca²⁺ and Na ⁺ had negligible effects on As(V) mobilization. However, alkaline pH caused the desorption of As(III), and the presence of HCO₃⁻ was conducive to As(III) desorption in deep groundwater. A conceptual model was established to explain As distribution in fissured bedrock aquifers, emphasizing contributions of mineral dissolution, desorption, and hydrogeological conditions to As mobilization. This paper highlights different mobilization behaviors of As(III) and As(V) in groundwater from fissured bedrock aquifers, requiring the different strategies to ensure the safety of drinking water in those areas.

We have investigated the hydrothermal alteration of polished wafers of tuff reacted with dilute groundwater at 90 °C, 150 °C and 250 °C for time periods ranging from 2 months to nearly 1 year. The polished rock wafer provided a convenient surface upon which to grow secondary minerals. Reaction product minerals were identified and analyzed at the end of each experiment and, along with the evolving fluid chemistry, were compared to computational results from corresponding reaction progress models.

At 250 °C after a few months the run products in the experiment were dominantly the mordenite group zeolite minerals: dachiardite (a Ca-rich variety) and mordenite, itself. At 150 °C after a few months of reaction only minor amounts of clay were produced, but after 1 year of reaction at this temperature both mordenite group zeolites were again present. At this lower temperature the total amount of run products was much smaller. At 90 °C no run products could be seen at all, even after 1 year of reaction. The reaction progress modeling results for reaction products were in good relative agreement with the experimental results.

The higher the temperature, and the greater the extent of reaction, the better the fluid phase modeling results agreed with the actual experimental results. At 250 °C the agreement was good for nearly all elements. At 150 °C agreement for pH, SiO₂, Na and K were good, but less good for Al, Mg and Ca, especially after short reaction times. At 90 °C agreement for pH, SiO₂ and Na was reasonable, but not as good for the other elements, and all modeling results for short reaction times did not match experimental results as well as the longer time results.

This study demonstrates that reaction progress modeling provides a powerful tool for predicting hydrothermal rock-water interactions, with results expected to improve, as more and better quality thermodynamic and kinetic data become available and as process-oriented simulators incorporate better and more comprehensive sub-models for mineral dissolution and growth.

Understanding the origins of groundwater and its movement from mountain to plain during different high intensity rainfall events is critical for conserving water supplies, determining water-use policies and controlling pollution. These factors are also the keys for understanding the dominant processes in hydrological models. In this study, groundwater resources and recharge processes during heavy precipitation were explored by using stable isotope tracers in the hilly area of Taihang Mountain. It was found that the δ²H and δ¹⁸O values of precipitation exhibited obvious precipitation amount effect during different precipitation intensity events. The stable isotopic values in groundwater and river water showed significantly varied during the single extreme heavy precipitation and the continuous heavy precipitation events. In the rainy season, precipitation amounts greater than 40 mm/d could effectively recharge the shallow groundwater in the study area. By comparing the spatial isotopic distribution of groundwater, soil water, and river water with precipitation, we showed distinct groundwater recharge patterns in terms of their water resources, timing, and the degree of river water and groundwater interaction during the single extreme heavy precipitation and the continuous heavy precipitation. After the single extreme heavy precipitation, the δ²H and δ¹⁸O values of groundwater, soil water, and river water showed stable over time and had the same similar variations, suggested that the groundwater recharge was mainly dominated by precipitation with preferential flow or bypass flow. While after the continuous heavy precipitation, the variation of δ²H and δ¹⁸O in all water is consistent with the previous precipitation, which shown a mixing effect of previous enrich precipitation and depleted heavy precipitation, suggested that groundwater source was dominated by a continuous recharge of previous heavier precipitation with translatory flow. The groundwater main recharge mechanism is not constant, but changes with rainfall intensity. The rainfall intensity play an important role in groundwater recharge change affecting runoff process. Overall, this paper presents a new insight to understand the effect of rainfall intensity on hydrological process, which could be used to provide vital information in the semi-humid and semi-arid regions where water resources are critical in climate change adaptation strategies.