Changes In Speciation Research Articles

Uranium Repartitioning during Microbial Driven Reductive Transformation of U(VI)-Sorbed Schwertmannite and Jarosite.

This study exposes U(VI)-sorbed schwertmannite and jarosite to biotic reductive incubations under field-relevant conditions and examines the changes in aqueous and solid-phase speciation of U, Fe, and S as well as associated microbial communities over 180 days. The chemical, X-ray absorption spectroscopy, X-ray diffraction, and microscopic data demonstrated that the U(VI)-sorbed schwertmannite underwent a rapid reductive dissolution and solid-phase transformation to goethite, during which the surface-sorbed U(VI) was partly reduced and mostly repartitioned to monomeric U(VI)/U(IV) complexes by carboxyl and phosphoryl ligands on biomass or organic substances. Furthermore, the microbial data suggest that these processes were likely driven by the consecutive developments of fermentative and sulfate- and iron- reducing microbial communities. In contrast, the U(VI)-sorbed jarosite only stimulated the growth of some fermentative communities and underwent very limited reductive dissolution and thus, remaining in its initial state with no detectable mineralogical transformation and solid-phase U reduction/repartitioning. Accordingly, these two biotic incubations did not induce increased risk of U reliberation to the aqueous phase. These findings have important implications for understanding the interactions of schwertmannite/jarosite with microbial communities and colinked behavior and fate of U following the establishment of reducing conditions in various acidic and U-rich settings.

Fate of As(V) and Cr(VI) adsorbed on goethite in a mangrove‐microcosm experiment

AbstractMangroves provide fundamental ecosystem services; however, the growing impact of human activities has resulted in increased pollution pressure, such as chemical contaminants. The redox processes are major biogeochemical players in the fate of contaminants. We investigate the effects of the redox environment on As(V) and Cr(VI) adsorbed on goethite (i.e., Fe(III)‐oxide) over 40 days of incubation in columns containing mangrove soil subjected to seawater saturation cycles. Our spectroscopic data highlighted a less Fe(III)‐ordered arrangement on goethite over time; As(V) is strongly bound to goethite, which delayed until 20 days its remobilization and reduction to As(III). After 40 days, the goethite held ∼50% of the initial As, but it was 15% as As(III). On the other hand, Cr(VI) was desorbed almost completely in less than 10 days, and the residual Cr ions bound to goethite were almost totally converted to Cr(III). Our study stresses the importance of individual time‐dependence in evaluating chemical speciation changes among potential toxic elements in wetland systems, such as mangroves and artificial wetlands designed to water treatment or soil remediation.

XANES spectroscopy proofs pH‐dependent P sorption partitioning to Fe oxyhydroxides versus montmorillonite in acidic soils

AbstractBackgroundFe and Al oxyhydroxides are well‐known phosphorus (P)‐retaining minerals in soils. Little information is available regarding the relevance of clay minerals for the sorption of P in mixed oxyhydroxide–clay mineral systems and pH effects on P sorption partitioning.Aims and MethodsWe wanted to investigate pH effects on P sorption partitioning between Fe oxyhydroxides and high‐activity clay minerals in mixed‐mineral systems. We quantified the relative contribution of ferrihydrite or goethite versus Al‐saturated montmorillonite (Al‐MT) to the retention of orthophosphate (oPO4) and inositol hexakisphosphate (IHP) at different pH values (3–6). We combined the analysis of P solution concentration changes with the quantification of P bound to Fe(III) versus Al in the Fe oxyhydroxide/Al‐MT mixtures by X‐ray absorption near‐edge structure (XANES) spectroscopy.ResultsOrthophosphate was preferentially retained by ferrihydrite, compared to Al‐MT at pH 3–6. The opposite was observed for goethite at low P solution concentrations. The contribution of Al‐MT versus Fe oxyhydroxides to oPO4 retention increased with pH. This is attributed to a speciation change of clay‐adsorbed Al from monomeric Al3+ to polynuclear Al hydroxy species. IHP was predominantly retained by Al‐MT rather than ferrihydrite at pH 3–6, probably by the formation of adsorbed and surface‐precipitated Al phytate complexes.ConclusionsSynchrotron‐based XANES spectroscopy allows for quantifying P adsorbed to co‐existing pedogenic Fe(III) oxyhydroxides versus Al‐MT in mixed‐mineral systems. Soil P retention partitioning to these minerals depends on (1) dominating P form (oPO4, IHP), (2) relative abundance of high‐activity clay minerals, short‐range ordered and crystalline Fe oxyhydroxides, and (3) solution pH.

Evolution of Cu and Zn speciation in agricultural soil amended by digested sludge over time and repeated crop growth

Metals such as Zn and Cu present in sewage sludge applied to agricultural land can accumulate in soils and potentially mobilise into crops. Sequential extractions and X-ray absorption spectroscopy results are presented that show the speciation changes of Cu and Zn sorbed to anaerobic digestion sludge after mixing with soils over three consecutive 6-week cropping cycles, with and without spring barley (Hordeum vulgare). Cu and Zn in digested sewage sludge are primarily in metal sulphide phases formed during anaerobic digestion. When Cu and Zn spiked sludge was mixed with the soil, about 40% of Cu(I)-S phases and all Zn(II)-S phases in the amended sludge were converted to other phases (mainly Cu(I)-O and outer sphere Zn(II)-O phases). Further transformations occurred over time, and with crop growth. After 18 weeks of crop growth, about 60% of Cu added as Cu(I)-S phases was converted to other phases, with an increase in organo-Cu(II) phases. As a result, Cu and Zn extractability in the sludge-amended soil decreased with time and crop growth. Over 18 weeks, the proportions of Cu and Zn in the exchangeable fraction decreased from 36% and 70%, respectively, in freshly amended soil, to 28% and 59% without crop growth, and to 24% and 53% with crop growth. Overall, while sewage sludge application to land will probably increase the overall metal concentrations, metal bioavailability tends to reduce over time. Therefore, safety assessments for sludge application in agriculture should be based on both metal concentrations present and their specific binding strength within the amended soil.

Impacts of Selenium Supplementation on Soil Mercury Speciation, Soil Properties and Mercury-Resistant Microorganisms and Resistant Genes

Soil mercury (Hg) contamination is a serious threat to local ecology and public health. Exogenous selenium (Se) supplementation can effectively reduce the toxicity of Hg. However, the mechanisms affecting the changes in soil Hg speciation, soil properties and the microbial Hg-resistant system during the Se–Hg interaction after exogenous Se supplementation are not clear. Therefore, in this study, soil culture experiments were conducted to analyze the effects of different Se additions on the transformation of Hg speciation, soil properties and Hg-resistant microorganisms and resistant genes (mer operon). The results indicated that Se supplementation facilitated the transformation of soil Hg from bioavailable (exchangeable and carbonate-bound) to stable forms (organic material-bound and residual), significantly reducing Hg bioavailability. Se supplementation notably decreased the electrical conductivity of Hg-contaminated soil, but had no significant effect on the soil pH, organic matter content, cation exchange capacity or alkaline phosphatase and catalase activities. The maximum activity levels of soil sucrase and urease were observed when 1 mg kg−1 Se was added. Se significantly inhibited soil peroxidase and ascorbate oxidase activities, thereby alleviating the oxidative stress in the soil system caused by Hg. Additionally, Se significantly activated the Hg-resistant system in soil microorganisms by either decreasing or increasing the regulatory genes merD and merR, and it significantly upregulated the cytoplasmic protein gene merP and the membrane protein genes merC, merF and merT. This further increased the abundance of the organomercury lyase gene merB and the mercuric reductase gene merA, promoting the conversion of Hg species to Hg⁰. Furthermore, the abundance of mer operon-containing microorganisms, such as Thiobacillus ferrooxidants, Pseudomonas, Streptomyces and Cryptococcus, significantly increased with Se addition, explaining the role of soil microorganisms in mitigating soil Hg stress via Se supplementation.

Phytoavailability, translocation, and accompanying isotopic fractionation of cadmium in soil and rice plants in paddy fields

Rice consumption is a major pathway for human cadmium (Cd) exposure. Understanding Cd behavior in the soil-rice system, especially under field conditions, is pivotal for controlling Cd accumulation. This study analyzed Cd concentrations and isotope compositions (δ114/110Cd) in rice plants and surface soil sampled at different times, along with urinary Cd of residents from typical Cd-contaminated paddy fields in Youxian, Hunan, China. Soil water-soluble Cd concentrations varied across sampling times, with δ114/110Cdwater lighter under drained than flooded conditions, suggesting supplementation of water-soluble Cd by isotopically lighter Cd pools, increasing Cd phytoavailability. Both water-soluble Cd and atmospheric deposition contributed to rice Cd accumulation. Water-soluble Cd’s contribution increased from 28‐52% under flooded to 58‐87% under drained conditions due to increased soil Cd phytoavailability. Atmospheric deposition’s contribution (12‐72%) increased with potential atmospheric deposition flux among sampling areas. The enrichment of heavy Cd isotopes occurred from root-stem-grain to prevent rice Cd accumulation. The different extent of enrichment of heavy isotopes in urine indicated different Cd exposure sources. These findings provide valuable insights into the speciation and phytoavailability changes of Cd in the soil-rice system and highlight the potential application of Cd isotopic fingerprinting in understanding the environmental fate of Cd.

Revising VOC emissions speciation improves the simulation of global background ethane and propane.

Non-Methane Volatile Organic Compounds (NMVOCs) generate ozone (O3) when they are oxidized in the presence of oxides of nitrogen, modulate the oxidative capacity of the atmosphere and can lead to the formation of aerosol. Here, we assess the capability of a chemical transport model (GEOS-Chem) to simulate NMVOC concentrations by comparing ethane, propane and higher alkane observations in remote regions from the NOAA Flask Network and the World Meteorological Organization's Global Atmosphere Watch (GAW) network. Using the Community Emissions Data System (CEDS) inventory we find a significant underestimate in the simulated concentration of both ethane (35%) and propane (64%), consistent with previous studies. We run a new simulation where the total mass of anthropogenic NMVOC emitted in a grid box is the same as that used in CEDS, but with the NMVOC speciation derived from regional inventories. For US emissions we use the National Emissions Inventory (NEI), for Europe we use the UK National Atmospheric Emissions Inventory (NAEI), and for China, the Multi-resolution Emission Inventory for China (MEIC). These changes lead to a large increase in the modelled concentrations of ethane, improving the mean model bias from -35% to -4%. Simulated propane also improves (from -64% to -48% mean model bias), but there remains a substantial model underestimate. There were relatively minor changes to other NMVOCs. The low bias in simulated global ethane concentration is essentially removed, resolving one long-term issue in global simulations. Propane concentrations are improved but remain significantly underestimated, suggesting the potential for a missing global propane source. The change in the NMVOC emission speciation results in only minor changes in tropospheric O3 and OH concentrations.

Phosphorous speciation in EPS extracted from Aerobic Granular Sludge

Wastewater treatment technologies opened the door for recovery of extracellular polymeric substances (EPS), presenting novel opportunities for use across diverse industrial sectors. Earlier studies showed that a significant amount of phosphorus (P) is recovered within extracted EPS. P recovered within the extracted EPS is an intrinsic part of the recovered material that potentially influences its properties. Understanding the P speciation in extracted EPS lays the foundation for leveraging the incorporated P in EPS to manipulate its properties and industrial applications. This study evaluated P speciation in EPS extracted from aerobic granular sludge (AGS). A fractionation lab protocol was established to consistently distinguish P species in extracted EPS liquid phase and polymer chains. 31P nuclear magnetic resonance (NMR) spectroscopy was used as a complementary technique to provide additional information on P speciation and track changes in P species during the EPS extraction process. Findings showed the dominance of organic phosphorus and orthophosphates within EPS, besides other minor fractions. On average, 25% orthophosphates in the polymer liquid phase, 52% organic phosphorus (equal ratio of mono and diesters) covalently bound to the polymer chains, 16% non-apatite inorganic phosphorus (NAIP) precipitates mainly FeP and AlP, and 7% pyrophosphates (6% in the liquid phase and 1% attached to the polymer chains) were identified. Polyphosphates were detected in initial AGS but hydrolyzed to orthophosphates, pyrophosphates, and possibly organic P (forming new esters) during the EPS extraction process. The knowledge created in this study is a step towards the goal of EPS engineering, manipulating P chemistry along the extraction process and enriching certain P species in EPS based on target properties and industrial applications.

Transitioning from Regular Electrolytes to Solvate Ionic Liquids to High-Concentration Electrolytes: Changes in Transport Properties and Ionic Speciation.

Glyme-based lithium-ion electrolytes have received considerable attention from the scientific community due to their improved safety, as well as electrochemical and thermal stability over carbonate-based electrolytes. However, these electrolytes suffer from major drawbacks such as high viscosities. To overcome the challenges that hinder their full potential, the molecular description of glyme-based lithium electrolytes in the high-concentration regime, particularly in the solvate ionic liquid (SIL) and high-concentration electrolyte (HCE) regimes, is needed. In this study, model glyme-based electrolytes based on a lithium thiocyanate and either tetraglyme (G4) or a mixture of monoglyme (G1) and diglyme (G2) were investigated as a function of the solvent-to-lithium ratio using linear and nonlinear IR spectroscopies, in combination with ab initio computations as well as electrochemical methods . The transport properties reveal enhanced ionicities in the HCE and SIL regimes ([O]/[Li] ≤ 5) compared to the regular electrolytes (REs, with [O]/[Li] > 5) in both pure (G4) and mixed (G1:G2) glymes. IR and ab initio computations relate these larger ionicities to the higher concentration of charged aggregates in the HCE and SIL electrolytes ([O]/[Li] ≤ 5). Moreover, it was observed that the use of mixed glymes appears to have a minimal effect on the transport properties of REs but exhibits deleterious effects on SILs. Overall, the results provide a molecular framework for describing the local structure of lithium glyme-based electrolytes and demonstrate the key role that the nature of glyme solvation plays in the molecular structure and consequently the macroscopic properties of the Li-glyme SILs, HCEs, and REs.

Low-Temperature Thermal Treatment and Boron Speciation Analysis from Coals

Despite urgent calls for decarbonization, the continued increasing demand for electricity, primarily from coals, has presented challenges in managing coal-derived wastes such as coal fly ash (CFA), which are enriched with environmentally hazardous substances like boron. This study explores a low-temperature heating process to remove boron from coal, aimed at preventing its condensation and enrichment into CFA during combustion. Initial boron concentrations in coals varied widely from 50 to 500 ppm by weight and were found to correlate with fixed carbon content (FC) through the following polynomial equation: [B]o = 0.0929(FC)2 − 14.388(FC) + 601.85; R2 = 0.9173. This relationship suggests that as coal undergoes coalification, boron-containing compounds are decomposed and released, resulting in a decline in boron levels as the coal matures. Boron-removal efficiency was investigated by drying coal samples at 110 °C, 160 °C, and 210 °C under natural air convection, and nuclear magnetic resonance (NMR) spectroscopy was used to assess changes in boron speciation during heating. Our results demonstrate that boron removal ranged from 5% to 82%, with minimal improvements observed beyond 110 °C. In addition, the 11B MAS-NMR spectra of the coal samples showed four peaks at isotropic chemical shift values of −1.0, 2.0, 8.0, and 14.0 ppm and suggested that the species of boron volatilized at low temperatures is the inorganic BO4 assigned to peak no. 0 at −1.0 ppm. The association of boron with inorganic components in coal suggests potential for efficient removal, particularly in coals with higher fixed carbon content. These findings highlight the viability of low-temperature thermal treatment as a cost-effective method for boron removal, which is crucial in mitigating the risks associated with coal combustion by-products.

Effect of biochar-derived DOM on contrasting redistribution of chromate during Schwertmannite dissolution and recrystallization

Biochar-derived dissolved organic matter (BDOM), is extensively involved in the recrystallization of minerals and the speciation alteration of associated toxic metals. This study investigates how BDOM extracted from tobacco petiole (TP) or tobacco stalk (TS) biochar influences the speciation repartitioning of Cr(VI) in environments impacted by acid mine drainage (AMD), focusing on interactions with secondary minerals during Schwertmannite (Sch) dissolution and recrystallization. TP-BDOM, rich in lignin-like substances, slowed down the Cr-Sch dissolution and Cr release under acidic conditions compared to TS-BDOM. TP-BDOM's higher O/C component exerts a delayed impact on Cr-Sch stability and Cr(VI) reduction. In-situ ATR-FTIR and 2D-COS analysis showed that carboxylic and aromatic N-OH groups in BDOM could interact with Cr-Sch surfaces, affecting sulfate and Cr(VI) release. It was also observed that slight recrystallization occurred from Cr-Sch to goethite, along with increased Cr incorporation into secondary minerals within TS-BDOM. This enhances our understanding of BDOM's role in Cr(VI) speciation changes in AMD-contaminated sites.

Mechanisms and influential factors of soil chromium long-term stability by an accelerated aging system after chemical stabilization

Chemical stabilization is one of the most widely used remediation strategies for chromium (Cr)-contaminated soils by reducing Cr(VI) to Cr(III), and its performance is affected by human and natural processes in a prolonged period, challenging long-term Cr stability. In this work, we established a method for evaluating the long-term effectiveness of remediation of Cr-contaminated soils, and developed an accelerated aging system to simultaneously simulate acid rain leaching and freeze-thaw cycles. The mechanisms and influencing factors of long-term (50-year) change in soil Cr speciation were unravelled after stabilization with Metafix®. Chemical stabilization remarkably decreased the contents of Cr(VI)soil, Crtotal-leach and Cr(VI)leach, among which the removal rate of Cr(VI) in soil was up to 89.70 %, but it also aggravated soil Cr instability. During the accelerated aging process, Crtotal-leach change rates in chemically stabilized soil samples were 0.0462–0.0587 mg/(L·a), and soil Cr became instable after 20-year accelerated aging. The proportion of Cr bound to organic matter and residual Cr increased in soil, and exchangeable Cr decreased. Linear combination fitting results of XANES also showed that Cr(VI) and Cr3+ were transformed into OM-Cr(III), Fh-Cr(III) and CrFeO3 after restoration. During the accelerated aging process, acid rain leaching activated Cr(III) and dissolved Cr(VI), whereas freeze-thaw cycle mainly affected OM-Cr. Chemical stabilization, acid rain leaching and aging time were the major factors influencing the stability of soil Cr, and the freeze-thaw cycle promoted the influence of acid rain leaching. This study provided a new way to explore the long-term effectiveness and instability mechanisms at Cr-contaminated site after chemical stabilization.

Maize straw increases while its biochar decreases native organic carbon mineralization in a subtropical forest soil

Organic soil amendments have been widely adopted to enhance soil organic carbon (SOC) stocks in agroforestry ecosystems. However, the contrasting impacts of pyrogenic and fresh organic matter on native SOC mineralization and the underlying mechanisms mediating those processes remain poorly understood. Here, an 80-day experiment was conducted to compare the effects of maize straw and its derived biochar on native SOC mineralization within a Moso bamboo (Phyllostachys edulis) forest soil. The quantity and quality of SOC, the expression of microbial functional genes concerning soil C cycling, and the activity of associated enzymes were determined. Maize straw enhanced while its biochar decreased the emissions of native SOC-derived CO2. The addition of maize straw (cf. control) enhanced the O-alkyl C proportion, activities of β-glucosidase (BG), cellobiohydrolase (CBH) and dehydrogenase (DH), and abundances of GH48 and cbhI genes, while lowered aromatic C proportion, RubisCO enzyme activity, and cbbL abundance; the application of biochar induced the opposite effects. In all treatments, the cumulative native SOC-derived CO2 efflux increased with enhanced O-alkyl C proportion, activities of BG, CBH, and DH, and abundances of GH48 and cbhI genes, and with decreases in aromatic C, RubisCO enzyme activity and cbbL gene abundance. The enhanced emissions of native SOC-derived CO2 by the maize straw were associated with a higher O-alkyl C proportion, activities of BG and CBH, and abundance of GH48 and cbhI genes, as well as a lower aromatic C proportion and cbbL gene abundance, while biochar induced the opposite effects. We concluded that maize straw induced positive priming, while its biochar induced negative priming within a subtropical forest soil, due to the contrasting microbial responses resulted from changes in SOC speciation and compositions. Our findings highlight that biochar application is an effective approach for enhancing soil C stocks in subtropical forests.

The impact of multi-decadal changes in VOC speciation on urban ozone chemistry: a case study in Birmingham, United Kingdom

Abstract. Anthropogenic non-methane volatile organic compounds (VOCs) in the United Kingdom have been substantially reduced since 1990, which is, in part, attributed to controls on evaporative and vehicle tailpipe emissions. Over time, other sources with a different speciation (for example, alcohols from solvent use and industry processes) have grown in both relative importance and, in some cases, in absolute terms. The impact of this change in speciation and the resulting photochemical reactivities of VOCs are evaluated using a photochemical box model constrained by observational data during a summertime ozone event (Birmingham, UK) and apportionment of sources based on the UK National Atmospheric Emission Inventory (NAEI) data over the period 1990–2019. Despite road transport sources representing only 3.3 % of UK VOC emissions in 2019, road transport continued being the sector with the largest influence on the local O3 production rate (P(O3)). Under case study conditions, the 96 % reduction in road transport VOC emissions that has been achieved between 1990 and 2019 has likely reduced daytime P(O3) by ∼ 1.67 ppbv h−1. Further abatement of fuel fugitive emissions was modeled to have had less impact on P(O3) reduction than abatement of VOCs from industrial processes and solvent use. The long-term trend of increased emissions of ethanol and methanol has somewhat weakened the benefits of reducing road transport emissions, increasing P(O3) by ∼ 0.19 ppbv h−1 in the case study. Abatement of VOC emissions from multiple sources has been a notable technical and policy success in the UK, but some future benefits (from an ozone perspective) of the phase-out of internal combustion engine passenger cars may be offset if domestic and commercial solvent use of VOCs continue to increase.

Potential availability of metals in anaerobic mono- and co-digestion of pig manure and maize

This study aims to analyse the potential availability of essential metals including as Co, Fe, Ni, Zn, Mn, and Cu and non-essential metals such as Pb, Cr, and Cd within anaerobic mono- and co-digestion of pig manure and maize. The metals partitioning was determined using the Modified BCR (European Community Bureau of Reference) sequential extraction at defined intervals over a 45-days period, correlating changes in metals speciation with key digestion variables. The findings revealed that Cr, Cu, Fe, and Pb were predominantly associated with the oxidisable fraction, while Zn, Mn, and Cd were potentially available in both processes. Notably, NH4+-N and the VFAs, except propionic acid, correlated significantly with the available fractions of Co, Mn, Ni, Zn, Cr, and Pb during mono-digestion of pig manure. The wider pH range and the chemical properties of the feedstock in co-digestion resulted in varied correlations between the metals availability and the digestion variables.

Analysis of the Structure of Heavy Ion Irradiated LaFeO3 Using Grazing Angle X-ray Absorption Spectroscopy.

Crystalline ceramics are candidate materials for the immobilization of radionuclides, particularly transuranics (such as U, Pu, and Am), arising from the nuclear fuel cycle. Due to the α-decay of transuranics and the associated recoil of the parent nucleus, crystalline materials may eventually be rendered amorphous through changes to the crystal lattice caused by these recoil events. Previous work has shown irradiation of titanate-based ceramics to change the local cation environment significantly, particularly in the case of Ti which was shown to change from 6- to 5-fold coordination. Here, this work expands the Ti-based study to investigate the behavior in Fe-based materials, using LaFeO3 as an example material. Irradiation was simulated by heavy ion implantation of the bulk LaFeO3 ceramic, with the resulting amorphous layer characterized with grazing angle X-ray absorption spectroscopy (GA-XAS). Insights into the Fe speciation changes exhibited by the amorphized surface layer were provided through quantitative analysis, including pre-edge analysis, and modeling of the extended X-ray absorption fine structure (EXAFS), of the GA-XAS data.

Comparing the adsorption of micropollutants on activated carbon from anaerobically stored, organics-depleted, and nitrified urine

Separate collection and treatment of urine optimizes nutrient recovery and enhances micropollutant removal from municipal wastewater. One typical urine treatment train includes nutrient recovery in three biological processes: anaerobic storage, followed by aerobic organics degradation concurrently with nitrification. These are usually followed by activated carbon adsorption to remove micropollutants. However, removing micropollutants prior to nitrification would protect nitrifiers from potential inhibition by pharmaceuticals. In addition, combining simplified biological treatment with activated carbon adsorption could offer a cheap and robust process for removing micropollutants where nutrient recovery is not the first priority, as a partial loss of ammonia occurs without nitrification. In this study, we investigated whether activated carbon adsorption could also take place between the three biological treatment steps. We tested the effectiveness of micropollutant removal with activated carbon after each biological treatment step by conducting experiments with anaerobically stored urine, organics-depleted urine, and nitrified urine. The urine solutions were spiked with 19 pharmaceuticals: amisulpride, atenolol, atenolol acid, candesartan, carbamazepine, citalopram, clarithromycin, darunavir, diclofenac, emtricitabine, fexofenadine, hydrochlorothiazide, irbesartan, lidocaine, metoprolol, N4-acetylsulfamethoxazole, sulfamethoxazole, trimethoprim, venlafaxine, and two artificial sweeteners, acesulfame and sucralose. Batch experiments were conducted with powdered activated carbon (PAC) to determine how much activated carbon achieve which degree of micropollutant removal and how organics, pH, and speciation change from ammonium to nitrate influence adsorption. Micropollutant removal was also tested in granular activated carbon (GAC) columns, which is the preferred technology for micropollutant removal from urine. The carbon usage rates (CUR) per person were lower for all urine solutions than for municipal wastewater. The results showed that organics depletion would be needed when micropollutant removal was the sole aim of urine treatment, as the degradation of easily biodegradable organics prevented clogging of GAC columns. However, CUR did hardly improve with organics-depleted urine compared to stored urine. The lowest CUR was achieved with nitrified urine. This resulted from the additional organics removal during nitrification and not the lower pH or the partial conversion of ammonium to nitrate. In addition, we showed that the relative pharmaceutical removal in all solutions was independent of the initial pharmaceutical concentration unless the background organics matrix changed considerably. We conclude that removal of micropollutants in GAC columns from organics-depleted urine can be performed without clogging, but with the drawback of a higher carbon usage compared to removal from nitrified urine.

The Dynamics of the Concentration and Speciation of Arsenic in Private Drinking Water Wells in Eastern Wisconsin, USA

About 2.5 billion people rely on groundwater as their main drinking water source, and arsenic pollution within the groundwater system can cause serious short- and long-term health issues. Within the natural environment, arsenic generally exists as oxyanions which have two oxidation states, As(III) and As(V). Under ambient pH conditions, As(V) is primarily present as an anion (i.e., H2AsO4−) while As(III) tends to be uncharged (i.e., H3AsO3), making it much more difficult to remove As(III) through existing treatment techniques such as adsorption and reverse osmosis (RO). In Eastern Wisconsin, the dolomite and dolomite/sandstone aquifers represent a major drinking water source and high arsenic concentrations have been observed. Previous studies showed that arsenic can be released into private drinking water wells due to the oxidation of sulfide-bearing minerals with arsenic impurities that are usually dispersed within the dolomite and sandstone bedrock. However, there is a lack of information on the concentrations of each arsenic species as well as arsenic dynamics during water pumping/usage. The primary goals of this research were (1) to quantify the baseline concentrations of each arsenic species within selected Eastern Wisconsin private drinking water wells, and (2) to determine how the arsenic concentrations and species could be affected by continuous water usage. Our results showed that As(III) was the dominant species of arsenic, and during continuous water usage, there could be an upward trend in arsenic concentration (there was minimal change in arsenic speciation). Upon the completion of water pumping, arsenic concentrations decreased over time and returned to pre-pumping levels. Our findings highlighted the importance of quantifying the speciation and dynamics of arsenic during water use to the assessment of public health risks and the design of appropriate water treatment techniques.

The influence of cation exchange on the possible mechanism of erionite toxicity: A synchrotron-based micro-X-ray fluorescence study on THP-1-derived macrophages exposed to erionite-Na

Fibrous erionite is the only zeolite classified as Group 1 carcinogen by the International Agency for Research on Cancer (IARC). Carcinogenesis induced by erionite is thought to involve several factors as biopersistence, the iron role and cation exchange processes. To better understand these mechanisms, a detailed investigation at the micro scale was performed, collecting elemental information on iron and cation release and their distribution in biological systems by synchrotron micro-X-ray fluorescence mapping (SR-micro-XRF) and synchrotron micro-X-ray absorption spectroscopy (SR-micro-XANES) at the TwinMic beamline (Elettra synchrotron) and at the ID21 beamline of the European Synchrotron Radiation Facility (ESRF). By microscopy and chemical mapping, highly detailed maps of the chemical and morphological interaction of biological systems with fibres could be produced. In detail, THP-1 cell line derived macrophages, used as in vitro model, were analysed during erionite-Na phagocytosis at different time intervals, after single dose exposure. For comparison, cellular fluorescent probes were also used to evaluate the intracellular free sodium and calcium concentrations. Synchrotron analyses visualised the spatial distribution of both fibre and mineral particle associated metals during the phagocytosis, describing the mechanism of internalisation of erionite-Na and its accessory mineral phases. The intracellular distribution of metals and other cations was mapped to evaluate metal release, speciation changes and/or cation exchange during phagocytosis. The fluorescent probes complemented microchemical data clarifying, and confirming, the cation distribution observed in the SR-micro-XRF maps. The significant cytoplasmic calcium decrease, and the concomitant sodium increase, after the fibre phagocytosis seemed due to activation of plasma membrane cations exchangers triggered by the internalisation while, surprisingly, the ion-exchange capacity of erionite-Na could play a minor role in the disruption of the two cations intracellular homeostasis. These results help to elucidate the role of cations in the toxicity of erionite-treated THP-1 macrophages and add knowledge to its carcinogenicity process.

Assessment of Hg Speciation Changes in the Sedimentary Rock Record From Thermal Desorption Characteristics

AbstractSedimentary mercury (Hg) has become a widely used proxy for paleo‐volcanic activity. However, scavenging and drawdown of Hg by organic‐matter (OM) and sulfides are important non‐volcanic factors determining variability in such records. Most studies, therefore, normalize total Hg (HgT) to a Hg “host‐phase” proxy (e.g., HgT/TOC for OM, HgT/TS for sulfides), with the dominant host‐phase determined based on the strongest observed (linear) correlations. This approach suffers from various non‐linearities in Hg‐host‐phase behavior and does not account for succession‐level, let alone sample‐level, Hg speciation changes. Thermal desorption characteristics or “profiles” (TDPs) for many Hg species during pyrolysis analysis are well‐established with applications including distinguishing between OM‐bound Hg and different Hg sulfides and oxides in (sub‐)recent sediments. We explore the use of TDPs for geological sediment (rock) samples and illustrate the presence of multiple release phases (Hg species)—correlated to geochemical host‐phase—in (almost) all the 65 analyzed Tithonian (146–145 Ma) silt and mudrock samples. By quantifying the Hg in each release phase for every sample, we find TOC concentration may determine ∼60% of the variability in the first (lower temperature) Hg TDP release phase: a stark difference with the total Hg released from these samples, where ∼20% of variation is explained by TOC variability. TDPs provide insight on sample‐level Hg speciation and demonstrate that, while the common assumption of single‐phase Hg speciation in sedimentary rocks is problematic, differences in Hg speciation can be detected, quantified, and accounted for using commonly applied techniques—opening potential for routine assessment.