A study has been performed to explore the origin, spatiotemporal behaviour and mobilisation mechanism of the elevated arsenic (As) concentrations found in ground water and drinking ponds of the Doñana National Park, Southern Spain. At a larger scale, 13 piezometers and surface water samples of about 50 artificial drinking ponds and freshwater lagoons throughout the National Park were collected and analysed for major ions, metals and trace elements. At a smaller scale, 5 locations were equipped with piezometers and groundwater was sampled up to 4 times for ambient parameters, major ions, metals, trace elements and iron (Fe) speciation. As was analysed for inorganic and organic speciation. Undisturbed sediment samples were analysed for physical parameters, mineralogy, geochemistry as well as As species. Sediment analyses yielded total As between 0.1 and 18 mg/kg and are not correlated with As concentration in water. Results of the surface- and groundwater sampling revealed elevated concentration of As up to 302 μg/L within a restricted area of the National Park. Results of groundwater sampling reveals strong correlation of As with Fe(2+) pointing to As mobilisation due to reductive dissolution of hydroferric oxides (HFO) in areas of locally elevated amounts of organic matter within the sediments. High As concentrations in surface water ponds are correlated with elevated alkalinity and pH attributed to algae metabolism, leading to As desorption from HFO. The algae metabolism is responsible for the presence of methylated arsenic species in surface water, in contrast to ground water in which only inorganic As species was found. Temporal variations in surface water and groundwater are also related to changes in pH and alkalinity as a result of enhanced algae metabolism in surface water or related to changes in the redox level in the case of groundwater.
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http://dx.doi.org/10.1016/j.scitotenv.2015.11.138 | DOI Listing |
Proc Natl Acad Sci U S A
February 2025
School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China.
Bubbles present in saline water typically exhibit a prolonged lifetime, making them attractive for various engineering processes. Herein, we unveil a transition from delayed bubble coalescence to rapid bursting within about one millisecond in salty solutions. The key aspect in understanding this transition lies in the combined influences of surface deformation and ion surface excess instead of characterizing the ions alone.
View Article and Find Full Text PDFACS Appl Mater Interfaces
January 2025
State Key Laboratory of Advanced Chemical Power Sources (Chongqing University), Chongqing 400044, China.
Investigating how the size of carbon support pores influences the three-phase interface of platinum (Pt) particles in fuel cells is essential for enhancing catalyst utilization. This study employed molecular dynamics simulations and density functional theory calculation to examine the effects of mesoporous carbon support size, specifically its pore diameter, on Nafion ionomer distribution, as well as on proton and gas/liquid transport channels, and the utilization of Pt active sites. The findings show that when Pt particles are located within the pores of carbon support (Pt/PC), there is a significant enhancement in the spatial distribution of Nafion ionomer, along with a reduction in encapsulation around the Pt particles, compared to when Pt particles are positioned on the surface or in excessively large pores of the carbon support.
View Article and Find Full Text PDFEnviron Sci Technol
January 2025
National High Magnetic Field Laboratory Geochemistry Group and Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, Florida 32306, United States.
Intensification of wastewater treatment residual (i.e., biosolid) applications to watersheds can alter the amount and composition of organic matter (OM) mobilized into waterways.
View Article and Find Full Text PDFACS Appl Mater Interfaces
January 2025
Department of Applied Chemistry, Chuo University, Tokyo 112-8551, Japan.
We employed machine learning (ML) techniques combined with potential-dependent photoelectrochemical impedance spectroscopy (pot-PEIS) to gain deeper insights into the charge transport mechanisms of hematite (α-FeO) photoanodes. By the Shapley Additive exPlanations (SHAP) analysis from the ML model constructed from a small data set (dozens of samples) of electrical parameters obtained from pot-PEIS and the PEC performance, we identified the dominant factors influencing the electron transport to the back contact in the bulk and hole transfer to a solution at the hematite/electrolyte interface. The results revealed that shallow defect states significantly enhance electron transport, while deep defect states impede it, and also one of the surface states enhances the hole transfer to the electrolyte solution.
View Article and Find Full Text PDFLangmuir
January 2025
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany.
Catechol-derived polymers form stable coatings on a wide range of materials including challenging to coat low surface energy polymers. Whether modification of the coating polymer with fluorophilic or hydrophobic groups is a successful approach to further favor the coating of hydrophobic or fluorophilic surfaces with catechol-based polymers remains ambiguous. Herein, we report the effect of a series of catechol-derived polyglycerol (PG)-based coatings and monolayer coatings on the wettability of polytetrafluoroethylene (PTFE), polystyrene, and poly(methyl methacrylate) surfaces.
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