Aquatic Geochemistry最新文献

Advancing underground hydrogen storage (UHS) is essential for a sustainable, emission-free future, with its success highly contingent on the unique properties of each subsurface reservoir. To ensure optimal storage, detailed site assessments are required. One of the critical gaps in knowledge necessary for ensuring safe storage is geochemical redox reactions, especially those involving iron. These redox reactions are crucial as they influence hydrogen retention or loss in the subsurface environments. In this study, we have theoretically addressed hydrogen consumption via abiotic reduction of a Fe³⁺ oxide under different Fe²⁺ activities. Simulations indicate that in scenarios, where the initial hydrogen partial pressure is extremely low (around 10⁻⁵ bars), decreasing the activity of Fe²⁺ by a factor of 10 can lead to a marked decrease in the initial hydrogen pressure by a maximum factor of 1000 within a few years. Variations in Fe²⁺ activity can significantly influence abiotic hydrogen consumption only under very low hydrogen partial pressures. This is primarily due to enhanced dissolution of Fe³⁺ oxides. In comparison, in conditions where hydrogen partial pressure is higher (> 10⁻² bars), reduction of Fe³⁺ oxide can yield magnetite, resulting in a muted loss of hydrogen over time. The transition in the reduction behavior of Fe³⁺ oxide from a ‘dissolution-driven’ process to ‘magnetite crystallization,’ which also determines the fate of stored hydrogen, depends on initial hydrogen partial pressure. Our results demonstrate that low quantities of hydrogen can be maintained within typical storage cycles spanning less than a year, depending upon aqueous Fe content.

Hydromagnesite (HM for short) is a natural carbonate mineral that is widely distributed. It is a high-quality mineral raw material for preparing flame retardants, magnesium oxides, heavy/light basic magnesium carbonates, magnesium hydroxides, and other Mg products. The evaluation of HM resources is of great significance to the development and utilization of salt lake resources. Using remote sensing technology to observe HM resources in salt lake can overcome the shortcomings of traditional prospecting methods such as discontinuous spatial data, time and effort. In addition, spectral analysis is the basis of hyperspectral remote sensing, and more detailed analysis of the spectral characteristics of HM is still lacking; therefore, we measured the reflection spectral curve of HM samples in the area of Jiezechaka by ASD FieldSpec4 short-wave infrared spectrometer and determined the mineral composition and content of HM samples by X-ray diffraction. The analysis indicated three and seven absorption valleys with high and low absorption intensities, respectively, in the reflectance spectral curves of the HM samples in the Jiezechaka area. Then, on this basis, the Landsat8 OLI multispectral data and ZY1-02D AHSI hyperspectral data were used as the basic data of remote sensing inversion. As the ZY1-02D AHSI data have 166 bands, which is much more than Landsat8 OLI data, it has a stronger ability to characterize the spectral characteristics of HM and can better meet the requirements of remote sensing inversion. The end member spectra were selected based on PPI and SMACC methods, respectively. The HM information around Jiezechaka Salt Lake in Tibet was extracted by the mixture tuned matched filtering method, and the regional distribution map of HM was made. A confusion matrix operation was used to compare the determination results of the two types of data. Among them, based on Landsat8 data, PPI method was used to obtain end members, and the overall accuracy of HM extraction results was > 69%, and the kappa coefficient was 0.688. Based on Landsat8 data, SMACC method was used to obtain end members, and the overall accuracy of HM extraction results was > 67%, and the kappa coefficient was 0.667. Based on ZY1-02D AHSI data, PPI method was used to obtain end members, and the overall accuracy of HM extraction results was > 76%, and the kappa coefficient was 0.743. Based on ZY1-02D AHSI data, SMACC method was used to obtain end members, and the overall accuracy of HM extraction results was > 73%, and the kappa coefficient was 0.728. It shows that the end members selected by PPI method can better express HM information in the image. Finally, through the overlay analysis of the four results, we concluded that HM outcrops in the Jiezechaka area are mainly distributed in the northwestern and southeastern regions of the lake. This study provides a rapid assessment technique for measuring HM information from salt lakes.

The Tataleng River (TTR), as an important tributary of the Da Qaidam Salt Lake (DQSL) and Xiao Qaidam Salt Lake (XQSL) in the Qaidam Basin (QB), has an exceptionally high B content. However, the solute sources and the provenance of B in the TTR are still unclear, which significantly hinders a deeper understanding of the source–sink processes of the boron deposits in the QB. In this study, water samples were collected from tributaries, mainstreams, mud volcanoes, hot springs, and rainwater in the TTR area. Through hydrochemical analysis, forward modeling, and B isotope geochemistry methods, combined with the previous research results, some findings were obtained. The hydrochemical type of TTR is Ca–Mg–Cl, and the major mechanism of controlling chemical composition is rock weathering. The solute sources in the TTR are mainly from dissolution of evaporites (75.9%), atmospheric precipitation (20.8%), and a minor contribution from carbonates (3.1%) and silicates weathering (0.6%). The higher B content (0.89–4.30 mg/L, mean = 2.13 mg/L) and lower δ¹¹B value (0.79‰–4.71‰, mean = 4.17‰) of the TTR indicate that the B sources are mainly from mixture of mud volcanic waters (56.19–199.98 mg/L, mean = 113.51 mg/L, − 1.26‰–2.22‰, mean = 0.85‰) in the upper reaches, and the deep groundwater near the Indosinian granite in the lower reaches. The significant difference in boron resources between the two lakes may be due to the enrichment of B in the late Pleistocene in the DQSL, which received exceptionally rich soluble B carried by the ancient TTR during an active tectonic period, while the weakening of tectonic activity and the diversion of the ancient TTR resulted in the supply of B with significantly reduced content to the XQSL. These results are helpful for a deeper understanding of the ore-forming mechanisms of the boron deposits in salt lake.

Mahai Basin (MH), located in the northern Qaidam Basin (QB), possesses abundant K-rich brine resources. The investigation on the origin of deep K-rich confined brine and the variations in K–Mg elements corresponding to the evolution in MH shed light on the significance of assessment and utilization of brine deposits. This study presents multiple isotopes (δ¹⁸O–δD, ⁸⁷Sr/⁸⁶Sr) and hydrochemical characteristics for various waters (including river water, surface brine, intercrystalline brine, confined brine and anticlinal brine) in the MH. Our findings corroborate that: (1) confined brine exhibits relatively high K⁺ (average value of 6.88 g/L) and low Ca²⁺–Sr²⁺ concentrations, compared to anticlinal brine, and its chemical composition resembles the evolution of Yuqia River in Ca–SO₄–HCO₃ diagram, suggesting that contemporary river water is the primary source of confined brine. (2) The δ¹⁸O–δD values of confined brine in MH ranged from − 17.80 to − 27.40‰ and 1.50 to 2.40‰, respectively, and fall on the right field of the local evaporation line, indicating successive evaporation and concentration processes. (3) The ⁸⁷Sr/⁸⁶Sr ratios (0.71142–0.71145) of confined brine fall between river water (0.71150–0.71183) and anticlinal brine (0.71135), combining with river water and confined brine which exhibit low Sr content, and further confirming the origin of confined brine is a mixture by river and anticlinal brine and much river recharge budget. (4) Considering the evolution of sedimentary facies (Dezongmahai Lake area as an example) and the gradual increase in K and Mg contents in MH, the enrichment of K and Mg exhibits a certain correlation with the evolution of MH. Notably, the brine in the northeast of the basin displays the highest levels of K and Mg, indicating that this region serves as the ultimate depositional center.

Brine groundwater in Quaternary salt lakes is widely exploited to extract potassium, lithium, and boron; the complex hydrogeological parameters of brine aquifers could cause significant difficulties in brine resource assessment and exploitation. However, the origin and porosity of brine aquifers remain unclear. This study presents an approach that utilizes geochemical indicator analysis with paleogeographic reconstruction to better assess porosity in salt lake aquifers. We identified 15 representative boreholes in Mahai Salt Lake, and the lithology, porosity, and chloride contents of their respective sediments, the pore porosity of each borehole in the study area ranges from 38.17 to 0.51%, the average chloride content of each borehole ranges from 26.63 to 38.74%, found that the vertical porosity fluctuations of halite deposits were significantly larger than those of detrital deposits, the sediments in the boreholes consisted predominantly of halite-containing debris or fine-debris-containing halite, reflecting the paleoenvironmental signatures of the salt lake. According to lithology and sedimentary environment, four brine aquifers were classified and the chloride and porosity distribution characteristics in the I–IV brine aquifers were further illustrated. Based on information of paleolake evolution in Qaidam Basin, we established a conceptual model to identify the impact factors for the porosity distribution pattern in the I–IV brine aquifers.

There are typical salt lake-type borate deposits in the northern Qaidam Basin, which are mainly distributed in Da Qaidam Lake (DQL), Xiao Qaidam Lake, and Mahai Basin (MHB). DQL has deposited famous solid borates and enriched a large number of brine boron deposits. It is the earliest industrial production base in China. Nanbaxian (NBX) to the west of DQL is a unique area where solid borates are deposited in MHB. Although there are three salt lakes in the MHB, borate deposits were only deposited in the salt pits of NBX, and the formation process of these borate deposits remains to be clarified. In this study, the major elements, boron contents, and d¹¹B values in the water and sediments of NBX were investigated in conjunction with the B-Na-Mg equivalence diagrams and relevant data from other salt lakes to elucidate the source of boron in MHB and the depositional conditions of borate minerals in NBX. The results are as follows: (1) The source of boron in NBX differs from that in three salt lakes in MHB. The source in NBX is mainly constrained by the weathering and fluid-rock (Boron-bearing ultra-high pressure metamorphic belt) interaction, while that in Dezongmahai and Niulangzhinv–Balunmahai lakes are primarily controlled by river water and anticlinal brine, respectively. (2) The high boron content (0.28 to 41.38 mg/L) and low d¹¹B values (- 34.71‰ to - 6.14‰) of the water-soluble phase of sediments in NBX are consistent with geochemical characteristics (d¹¹B: - 23.67‰ to - 3.0‰) of borates in DQL, demonstrating that the re-dissolution of borate deposits in NBX. (3) Deposition of borate minerals in the MHB requires ionic equivalents of Mg, Na, and B to 0.02 to 0.4, 0.25 to 0.75, and 0.2 to 0.7, respectively. Additionally, the brine hydrochemistry in which the borate are deposited must be of the carbonate or sulfate type, and the brine water should be greater than 8 in pH and 400 mg/L in boron content. This study provides a theoretical basis for exploring and exploiting salt lake-type borate deposits.

Soil-derived dissolved organic matter (DOM) has a significant impact on aquatic ecosystems. Identifying the fluorescence signatures of DOM from different soils in river and sea waters can provide valuable insights into its migration patterns. This makes crucial assessing the contributions of pH, salinity, and other milieu parameters to the variability of DOM optical properties. Present study investigates the changes in DOM of Chernozems under varying salinity using UV–visible absorbance spectroscopy and 3D-fluorescence spectroscopy coupled with parallel factor analysis (EEMs-PARAFAC). Water-extractable organic matter (WEOM) extracted from soils of two field experiments of contrasting land use: long-term bare fallow (LTBF) and annually mown steppe (Steppe), was used as a proxy for DOM. Diluted extracts were incubated with varying NaCl concentrations in the dark and then examined. Steppe WEOM exhibited fair constancy of optical parameters under increasing salinity, while significant changes of the optical indices and of PARAFAC components’s loadings were observed for LTBF WEOM. The remarkable stability of the Steppe WEOM can be attributed to its chemical diversity. Two distinct and sufficiently stable humic-like PARAFAC components have the potential to serve as markers of Chernozem DOM. The findings clearly demonstrate that salinity itself slightly reduces absorption and fluorescence and changes some optical indices of WEOM of Chernozems.

The solid-liquid phase equilibria of aqueous system containing the sulfates of lithium and potassium (Li₂SO₄ + K₂SO₄ + H₂O) at T = 303.2 and 318.2 K were done by isothermal dissolution method. The phase equilibria data (solubility, density, and refractive index) of the system were determined experimentally. The corresponding solid-liquid phase diagram, density/refractive index versus composition diagrams, were plotted. There are two ternary invariant points and three crystallization regions corresponding to Li₂SO₄·H₂O, LiKSO₄, and K₂SO₄ in the phase diagram of system Li₂SO₄ + K₂SO₄ + H₂O at 303.2 and 318.2 K. A comparision of system Li₂SO₄ + K₂SO₄ + H₂O at different temperature (T = 288.2, 303.2, 318.2 and 348.2 K) shown that the double salt LiKSO₄ was formed in the above mentioned temperatures, and the crystallization region of the LiKSO₄ increases gradually with the increase of temperature.

There is growing concern about the effects of ocean acidification (OA) on coral reefs, with many studies indicating decreasing calcium carbonate production and reef growth. However, to accurately predict how coral reefs will respond to OA, it is necessary to characterize natural carbonate chemistry conditions, including the spatiotemporal mean and variability and the physical and biogeochemical drivers across different environments. In this study, spatial and temporal physiochemical variability was characterized at two contrasting reef locations in Bocas del Toro, Panama, that differed in their benthic community composition, reef morphology, and exposure to open ocean conditions, using a combination of approaches including autonomous sensors and spatial surveys during November 2015. Mean and diurnal temporal variability in both physical and chemical seawater parameters were similar between sites and sampling depths, but with occasional differences in extreme values. The magnitude of spatial variability was different between the two sites, which reflected the cumulative effect from terrestrial runoff and benthic metabolism. Based on graphical vector analysis of TA–DIC data, reef metabolism was dominated by organic over inorganic carbon cycling at both sites, with net heterotrophy and net calcium carbonate dissolution dominating the majority of observations. The results also highlight the potentially strong influence of terrestrial freshwater runoff on surface seawater conditions, and the challenges associated with evaluating and characterizing this influence on benthic habitats. The Bocas del Toro reef is a unique system that deserves attention to better understand the mechanisms that allow corals and coral reefs to persist under increasingly challenging environmental conditions.