Microbial Sulfate Reduction Enhances Arsenic Mobility Downstream of Zerovalent-Iron-Based Permeable Reactive Barrier.

We assessed the potential of zerovalent-iron- (Fe(0)) based permeable reactive barrier (PRB) systems for arsenic (As) remediation in the presence or absence of microbial sulfate reduction. We conducted long-term (200 day) flow-through column experiments to investigate the mechanisms of As transformation and mobility in aquifer sediment (in particular, the PRB downstream linkage). Changes in As speciation in the aqueous phase were monitored continuously. Speciation in the solid phase was determined at the end of the experiment using X-ray absorption near-edge structure (XANES) spectroscopy analysis. We identified thio-As species in solution and AsS in solid phase, which suggests that the As(V) was reduced to As(III) and precipitated as AsS under sulfate-reducing conditions and remained as As(V) under abiotic conditions, even with low redox potential and high Fe(II) content (4.5 mM). Our results suggest that the microbial sulfate reduction plays a key role in the mobilization of As from Fe-rich aquifer sediment under anoxic conditions. Furthermore, they illustrate that the upstream-downstream linkage of PRB affects the speciation and mobility of As in downstream aquifer sediment, where up to 47% of total As initially present in the sediment was leached out in the form of mobile thio-As species.

Lithium isotopic fingerprints of sources and processes in surface waters of the Ebro River Basin (Spain).

The Ebro River in north-eastern Spain is among the largest contributors of freshwater to the Mediterranean Sea and ends in the Ebro delta, one of the major wetlands in Europe. The bedrock of the Ebro River basin mainly consists of carbonate rocks and evaporites of Palaeozoic and Mesozoic age, and the river flows through several large cities, and agricultural and industrial areas. The Ebro outlet at Amposta was sampled once a month for a year (2006), and a field campaign in April of the same year sampled the Ebro along its main course as well as its principal tributaries. In the present study, the behaviour of Li and its isotopes was investigated at basin scale, with the objective of elucidating the processes controlling the lithium-isotope signatures of a large river draining mostly sedimentary bedrock. δ7Li values show a narrow range from +17.1 ‰ to +18.3 ‰ along the Ebro main stream, and between +16.3 and +18.9 ‰ at the outlet. In the major tributaries, the δ7Li values ranged from +12.9 ‰ to +20.9 ‰, with bedrock values ranging from +0.5 to +29.3 ‰. Comparing Li concentrations with Cl and SO4 ones, it appears that evaporite weathering plays an important role in controlling Li concentrations, but no anthropogenic agricultural or industrial influence on Li concentrations was detected. The Na/Li, Cl/Li and SO4/Li ratios clearly reflect the role of halite dissolution for some tributaries (Gallego, Ega and Aragon), gypsum dominating others (Guadalope, Matarrana, Huerva and Segre), and little influence of carbonate in all tributaries, the Ebro itself being a mixture of all tributaries. We tentatively applied the simple Rayleigh fractionation model, but most δ7Li values of the Ebro water samples plotted away from the fractionation line, reinforcing the major role of mixing processes in the Ebro basin, rather than fractionation processes during water/rock interactions. A comparison of δ7Li values and 87Sr/86Sr ratios further demonstrates the role of gypsum/anhydrite and limestone in the Ebro and its tributaries. Sr-isotopes show a non-negligible role of carbonate dissolution, generally considered to be weak in the control of the lithium cycle in catchments.

Impact of vaccination on the presence and severity of symptoms in hospitalized patients with an infection of the Omicron variant (B.1.1.529) of the SARS-CoV-2 (subvariant BA.1).

OBJECTIVES: The emergence of SARS-CoV-2 variants raised questions about the extent to which vaccines designed in 2020 have remained effective. We aimed to assess whether vaccine status was associated with the severity of Omicron SARS-CoV-2 infection in hospitalized patients. METHODS: We conducted an international, multi-centric, retrospective study in 14 centres (Bulgaria, Croatia, France, and Turkey). We collected data on patients hospitalized for ≥24 hours between 1 December 2021 and 3 March 2022 with PCR-confirmed infection at a time of exclusive Omicron circulation and hospitalization related or not related to the infection. Patients who had received prophylaxis by monoclonal antibodies were excluded. Patients were considered fully vaccinated if they had received at least two injections of either mRNA and/or ChAdOx1-S or one injection of Ad26.CoV2-S vaccines. RESULTS: Among 1215 patients (median age, 73.0 years; interquartile range, 57.0-84.0; 51.3% men), 746 (61.4%) were fully vaccinated. In multivariate analysis, being vaccinated was associated with lower 28-day mortality (Odds Ratio [95% Confidence Interval] (OR [95CI]) = 0.50 [0.32-0.77]), intensive care unit admission (OR [95CI] = 0.40 [0.26-0.62]), and oxygen requirement (OR [95CI] = 0.34 [0.25-0.46]), independent of age and comorbidities. When co-analysing these patients with Omicron infection with 948 patients with Delta infection from a study we recently conducted, Omicron infection was associated with lower 28-day mortality (OR [95CI] = 0.53 [0.37-0.76]), intensive care unit admission (OR [95CI] = 0.19 [0.12-0.28]), and oxygen requirements (OR [95CI] = 0.50 [0.38-0.67]), independent of age, comorbidities, and vaccination status. DISCUSSION: Originally designed vaccines have remained effective on the severity of Omicron SARS-CoV-2 infection. Omicron is associated with a lower risk of severe forms, independent of vaccination and patient characteristics.

WITHDRAWN: Special Issue on innovative methods for characterizing evolution and budgets in water - rock systems: A tribute to Tom Bullen and Stepan Shvartsev.

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.apgeochem.2021.104892. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Chemical and strontium isotope characterization of rainwater in France: influence of sources and hydrogeochemical implications.

Strontium isotope ratios and Ca2+, Na+, K+, Mg2+, Cl-, SO4(2-), NO3- and Sr2+ concentrations were measured in rainwater samples collected in four stations in France (Brest, Dax, Orleans and Clermont-Ferrand) over a period of 1 year. Each sample represented a monthly series of rain events. The chemical composition and the 87Sr/86Sr ratios of the rainwater samples varied considerably. Using Na concentrations as an indicator of marine origin, the proportion of marine and crustal elements was estimated from elemental ratios. Strontium isotopes were used to characterize the different sources using data from the four stations and the literature. Such sources include sea salts, crustal sources (carbonates, silicates and volcanic rocks) and anthropogenic sources (fertilizers, automobile exhausts, incinerators and urban heating).

Microbial and mineral evolution in zero valent iron-based permeable reactive barriers during long-term operations.

Impacts of subsurface biogeochemical processes over time have always been a concern for the long-term performance of zero valent iron (Fe(0))-based permeable reactive barriers (PRBs). To evaluate the biogeochemical impacts, laboratory experiments were performed using flow-through glass columns for 210 days at controlled temperature (20 °C). Two different particle sizes of Fe(0) were used in the columns, and to simulate indigenous microbial activity, extra carbon source was provided in the two columns (biotic columns) and the remaining two columns were kept abiotic using gamma radiations. Heavy metals (Zn, As) were removed efficiently in all the columns, and no exhaustion of treatment capability or clogging was observed during our experimental duration. Newly formed Fe mineral phases and precipitates were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and micro-XRF techniques in solid phase at the end of the experiment. In addition, 16S rRNA gene extraction was used for microbial community identification in biotic columns. During the incubation, microbial population shifted in favor of Desulfosporosinus species (sulfate-reducing bacteria) from initial dominance of Acidithiobacillus ferrooxidans in sediments. Dominant mineral phases detected in biotic columns were mackinawite (FeS) and sulfate green rust, while in abiotic columns, magnetite/maghemite phases were more prevalent.

Sulfur and oxygen isotope tracing in zero valent iron based In situ remediation system for metal contaminants.

In the present study, controlled laboratory column experiments were conducted to understand the biogeochemical changes during the microbial sulfate reduction. Sulfur and oxygen isotopes of sulfate were followed during sulfate reduction in zero valent iron incubated flow through columns at a constant temperature of 20±1°C for 90 d. Sulfur isotope signatures show considerable variation during biological sulfate reduction in our columns in comparison to abiotic columns where no changes were observed. The magnitude of the enrichment in δ(34)S values ranged from 9.4‰ to 10.3‰ compared to initial value of 2.3‰, having total fractionation δS between biotic and abiotic columns as much as 6.1‰. Sulfur isotope fractionation was directly proportional to the sulfate reduction rates in the columns. Oxygen isotopes in this experiment seem less sensitive to microbial activities and more likely to be influenced by isotopic exchange with ambient water. A linear relationship is observed between δ(34)S and δ(18)O in biotic conditions and we also highlight a good relationship between δ(34)S and sulfate reduction rate in biotic columns.

Influence of methane addition on selenium isotope sensitivity and their spectral interferences.

The measurements of stable selenium (Se) isotopic signatures by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) are very challenging, due to the presence of spectral interferences and the low abundance of Se in environmental samples. We systematically investigated the effect of methane addition on the signal of Se isotopes and their interferences. It is the first time that the effect of methane addition has been assessed for all Se isotopes and its potential interferences using hydride generator multi-collector inductively coupled plasma mass spectrometry (HG-MC-ICP-MS). Our results show that a small methane addition increases the sensitivity. However, the response differs between a hydride generator and a standard introduction system, which might be related to differences in the ionization processes. Both argon and hydrogen-based interferences, the most common spectral interferences on selenium isotopes in HG-MC-ICP-MS, decrease with increasing methane addition. Therefore, analyte-interference ratios and precision are improved. Methane addition has thus a high potential for the application to stable Se isotopes ratios by HG-MC-ICP-MS.

Isotope and ion selectivity in reverse osmosis desalination: geochemical tracers for man-made freshwater.

A systematic measurement of ions and 2H/1H, 7Li/6Li, 11B/10B, 18O/ 16O, and 87Sr/86Sr isotopes in feed-waters, permeates, and brines from commercial reverse osmosis (RO) desalination plants in Israel (Ashkelon, Eilat, and Nitzana) and Cyprus (Larnaca) reveals distinctive geochemical and isotopic fingerprints of fresh water generated from desalination of seawater (SWRO) and brackish water (BWRO). The degree of isotope fractionation during the passage of water and solutes through the RO membranes depends on the medium (solvent-water vs. solutes), chemical speciation of the solutes, their charge, and their mass difference. O, H, and Sr isotopes are not fractionated during the RO process. 7Li is preferentially rejected in low pH RO, and B isotope fractionation depends on the pH conditions. Under low pH conditions, B isotopes are not significantly fractionated, whereas at high pH, RO permeates are enriched by 20 per thousand in 11B due to selective rejection of borate ion and preferential permeation of 11B-enriched boric acid through the membrane. The specific geochemical and isotopic fingerprints of SWRO provide a unique tool for tracing "man-made" fresh water as an emerging recharge component of natural water resources.