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Global sea to air iodine emissions, along with organic emissions and their oxidation products, have increased tremendously. This work presents a comprehensive analysis of the humidity mediated changes in ageing aerosols comprising iodide and water soluble dicarboxylic acid using aerosol micro-Raman spectroscopy. The studies in the model system, sodium iodide-malonic acid mixed aerosols, unveiled the depletion in iodide. Mechanistic insights gleaned through comparative studies conducted under inert (nitrogen) and oxidative (air) atmospheres reveal the iodide depletion occurs possibly via oxidation to molecular iodine. The reaction involves gaseous components, diffusion of which across the particles will be impacted by the physical state of the particles, such as viscosity, which in turn is intricately linked to ambient humidity levels. To this end, studies on the temporal evolution of the reaction at three distinct RHs covering 30–80% revealed the enhanced progression of the reaction with increasing humidity. Given that geographical locations serving as major sources for atmospheric iodine typically experience high humidity, these reactions could emerge as an additional process controlling iodine speciation in ageing aerosols. [Display omitted] • Humidity mediated changes observed in aerosols comprising iodide and dicarboxylic acid. • Studies on NaI-malonic acid mixed aerosols unveiled the depletion in iodide. • Iodide depletion occurs possibly via oxidation to molecular iodine. • Enhanced progression of the reaction observed with increasing humidity. [ABSTRACT FROM AUTHOR]

Concurrent heavy metals remediation in natural environments poses significant challenges due to factors like metal speciation and interactions with soil moisture. This review focuses on strategies for immobilizing both anionic and cationic metals simultaneously in soil-crop systems. Key approaches include water management, biochar utilization, stabilizing agents, nanotechnology, fertilization, and bioremediation. Sprinkler or intermittent irrigation combined with soil amendments/biochar effectively immobilizes As/Cd/Pb simultaneously. This immobilization occurs through continuous adsorption-desorption, oxidation-reduction, and precipitation mechanisms influenced by soil pH, redox reactions, and Fe-oxides. Biochar from sources like wine lees, sewage sludge, spent coffee, and Fe-nanoparticles can immobilize As/Cd/Pb/Cr/Co/Cu/Zn together via precipitation. In addition, biochar from rice, wheat, corn straw, rice husk, sawdust, and wood chips, modified with chemicals or nanoparticles, simultaneously immobilizes As and Cd, containing higher Fe 3 O 4 , Fe-oxide, and OH groups. Ligand exchange immobilizes As, while ion exchange immobilizes Cd. Furthermore, combining biochar especially with iron, hydroxyapatite, magnetite, goethite, silicon, graphene, alginate, compost, and microbes—can achieve simultaneous immobilization. Other effective amendments are selenium fertilizer, Ge-nanocomposites, Fe–Si materials, ash, hormone, and sterilization. Notably, combining nano-biochar with microbes and/or fertilizers with Fe-containing higher adsorption sites, metal-binding cores, and maintaining a neutral pH could stimulate simultaneous immobilization. The amendments have a positive impact on soil physio-chemical improvement and crop development. Crops enhance production of growth metabolites, hormones, and xylem tissue thickening, forming a protective barrier by root Fe-plaque containing higher Fe-oxide, restricting upward metal movement. Therefore, a holistic immobilization mechanism reduces plant oxidative damage, improves soil and crop quality, and reduces food contamination. [Display omitted] • Simultaneous metals immobilization is challenging for various factors. • Soil pH and redox reaction greatly influence the immobilization. • Fertilization with sprinkler or intermittent irrigation can reduce both As and Cd. • Nano-biochar with microbes can initiate simultaneous immobilization. • The pathways of anionic metalloids and cationic metals are discussed. [ABSTRACT FROM AUTHOR]

We explain here that the authors of the article cited in the title have misrepresented the species of As(III) and As(V) in solutions and, in particular, have neglected their speciation as a function of pH. Their discussion of (ad)sorption mechanisms is therefore unsatisfactory, especially since organic matter (flower waste) and the presence of iron oxyhydroxides should be taken into account. Furthermore, the modeling of (ad)sorption kinetics and isotherms was based on linearized equations, whereas the corresponding nonlinear equations should have been used. Therefore, we believe that the authors of the original article should make corrections and additions to it. This Letter to the Editor is motivated by a concern to avoid the dissemination of approximate or even incorrect concepts in the scientific literature, which could mislead novice researchers. [Display omitted] • As shares some similarities with N and P (belonging to Group 15 elements). • NaAsO 2 and NaH 2 AsO 4 are covalent compounds (not ionic compounds). • Oxidation state of elements: writing As(III) and As(V) rather than As3+ and As5+. • PFO model: r 2 = 0.992, but q e,experiment (4.98 mg/g) is very different from q e,PFO (71.4 mg/g), which results from applying linear method. • IUPAC recommends symbol (⇌) for chemical equilibria. Symbol (↔) is used for resonance structures. [ABSTRACT FROM AUTHOR]

Uranium (U) is a chemical and radioactive toxic contaminant affecting many groundwater systems. The focus of this study was to evaluate the suitability of forward osmosis (FO) for uranium rejection from contaminated groundwater under field-relevant conditions. Laboratory experiments with aqueous solution containing uranium were performed with FO membrane to understand the uranium rejection mechanism under varied pH, draw solution concentration, and presence of co-ions. Further, experiments were performed with U-contaminated field groundwater. Results of the hydrogeochemcial modelling using PHREEQC indicated that the rejection mechanism of uranium was highly dependent on aqueous speciation. Uranium rejection was maximum at alkaline pH with ca. 99% rejection due to charge-based interactions between membrane and dominant uranyl complexes. The results of the co-ion study indicated that nitrate and phosphate ions decrease uranium rejection. Whereas, bicarbonates, calcium, and magnesium ions concentrated uranium in feed solution. Further, the uranium adsorption onto the membrane surface primarily depended on pH of the aqueous solution with maximum adsorption at pH 5.5. Our results show that the World Health Organization's drinking water guideline value of 30 μ gL−1 for U could be achieved via FO process in field groundwater containing low dissolved solids. [Display omitted] • Uranium mitigation in field relevant (Na+ - HCO 3 -) low TDS (< 500 mgL−1) groundwater. • Uranium rejection was maximum at alkaline pH (i.e. 99.2% for pH 10.0). • Co-ions viz. nitrate and phosphate reduce uranium rejection. • Bicarbonates, calcium, and magnesium lead to concentrating uranium in feed solution. • WHO's drinking water guidelines were achieved in contaminated groundwater using FO. [ABSTRACT FROM AUTHOR]

The arsenic (As) content of seaweed has been extensively studied due to its toxicological concerns. As a primary producer, seaweed plays a vital role in the biochemical cycling of As in marine environments. Several studies have focused on the growth and behavior of seaweed under a salinity gradient; however, information related to the impact of salinity on As uptake, biotransformation mechanism, and time-dependent speciation patterns of these plants is limited. This study aimed to investigate the temporal effects of salinity on these factors in seaweed. Three seaweed species, Sargassum fusiforme , Sargassum thunbergii, and Sargassum horneri , were maintained in a 1% Provasoli-enriched seawater medium for 14 d under 5‰, 15‰, 25‰, and 34‰ salinities. The results revealed that the high salinity media promoted a rapid uptake of As by all three species. Arsenic accumulation inside the cell approached 100% within seven days of culture for S. thunbergii, irrespective of the salinity content of the media. In addition, As(V) biotransformation and release by S. fusiforme and S. thunbergii were time-dependent, while S. horneri released dimethylarsinic acid (DMAA) from day 3 of the culture. All seaweed species showed methylation of As(V) to DMAA during the culture period. Furthermore, S. thunbergii released DMAA when As(V) was completely depleted from the culture media, whereas the release by S. fusiforme and S. horneri was relatively earlier than that of S. thunbergii. S. horneri showed minimal tolerance to low salinity, as the cells revealed significant damage. Based on the results of this study, a conceptual model was developed that demonstrated the effects of salinity on As uptake and the biotransformation mechanism of seaweed. [Display omitted] • As(V) uptake by seaweed increased with greater salinity of the medium. • As(V) uptake was faster in Sargassum thunbergii than in S. fusiforme and S. horneri. • Speciation and release of two species depended on time and not As(V) and salinity. • Hyposalinity promoted DMAA(V) release over As(V) uptake. • Sargassum horneri was the least saline-tolerant of the three species. [ABSTRACT FROM AUTHOR]

The aim of the present study was to find environmentally friendly solutions for the disposal of problematic and toxic textile sludge (TS) by producing textile sludge biochar (TSB) by pyrolysis and evaluating its chemical properties, polycyclic aromatic hydrocarbon (PAH) content, heavy metals (HMs) speciation, environmental risks, and effects on seed germination. Pyrolysis of TS at temperatures ranging from 300 to 700 °C significantly reduced (85–95%) or eliminated certain PAHs in the biochar, enriched heavy metal content within land use limits, and increased bioavailability of HMs in biochar produced at 300 °C and decreased leaching capacity of HMs in biochar produced at 700 °C. The speciation of HMs and their bioavailability during pyrolysis processes was strongly temperature dependent, with lower temperatures increasing the toxic and bioavailable forms of Zn and Ni, while higher temperatures converted the bioavailable Ni to a more stable form, while Cu, Cr, and Pb were transformed from stable to toxic and bioavailable forms. The ecological risk index (RI) values of TSB-300 and TSB-700 are below the threshold value of 150, indicating a low-risk level, and the risk level decreases at temperatures above 500 °C. Further, the extracts of TSB-300 and TSB-700 had the highest percentage of germinating seeds, while the extracts of TS and TSB-500 inhibited seed germination by 20–30% compared to the control. These results indicate that pyrolysis effectively reduces PAHs and binds leachable HMs in biochar, however, the specific pyrolysis temperature influences metal speciation, bioavailability, seed germination, and environmental risk. [Display omitted] • Disposal of TS containing HMs poses a high environmental risk. • PAHs are reduced significantly by pyrolysis of TS into biochar. • Higher temperatures produce biochar with a stable form of Ni. • Environmental risk index of 700 °C biochar was the lowest. • Extracts of biochar produced at 700 °C promote plant growth. [ABSTRACT FROM AUTHOR]

Current human health risk assessments of soil arsenic (As) contamination rarely consider bioaccessibility (IVBA), which may overestimate the health risks of soil As. The IVBA of As (As-IVBA) may differ among various soil types. This investigation of As-IVBA focused As from geological origin in a typical subtropical soil, lateritic red soil, and its risk control values. The study used the SBRC gastric phase in vitro digestion method and As speciation sequential extraction based upon phosphorus speciation extraction method. Two construction land sites (CH and HD sites) in the Pearl River Delta region were surveyed. The results revealed a high content of residual As (including scorodite, mansfieldite, orpiment, realgar, and aluminum arsenite) in the lateritic red soils at both sites (CH: 84.9%, HD: 91.7%). The content of adsorbed aluminum arsenate (CH: 3.24%, HD: 0.228%), adsorbed ferrum arsenate (CH: 8.55%, HD: 5.01%), and calcium arsenate (CH: 7.33%, HD: 3.01%) were found to be low. The bioaccessible As content was significantly positively correlated with the As content in adsorbed aluminum arsenate, adsorbed ferrum arsenate, and calcium arsenate. A small portion of these sequential extractable As speciation could be absorbed by the human body (CH: 14.9%, HD: 3.16%), posing a certain health risk. Adsorbed aluminum arsenate had the highest IVBA, followed by calcium arsenate, and adsorbed ferrum arsenate had the lowest IVBA. The aforementioned speciation characteristics of As from geological origin in lateritic red soil contributed to its lower IVBA compared to other soils. The oxidation state of As did not significantly affect As-IVBA. Based on As-IVBA, the carcinogenic and non-carcinogenic risks of soil As in the CH and HD sites decreased greatly in human health risk assessment. The results suggest that As-IVBA in lateritic red soil should be considered when assessing human health risks on construction land. [Display omitted] • In lateritic red soil, As from geological origin has low bioaccessibility. • SBET can mainly extract the adsorbed arsenate on Al, Fe and Ca arsenate. • The bioaccessibility of soil As is not related to its oxidation state. • The occurrence of As in Lateritic red soil is dominated by low solubility minerals. • Soil remediation target values can be significantly promoted based on As-IVBA. [ABSTRACT FROM AUTHOR]

Mercury (Hg) stable isotope ratios supplemented by Hg solid speciation data were determined in soils in a former Fe–Hg mining/smelting area (Jedová hora, Czech Republic, Central Europe). The dominant Hg phase in the studied soils was found to be cinnabar (HgS). A secondary form of soil Hg(II) was represented by Hg weakly and strongly bound to mineral (micro)particles, as revealed by thermo-desorption analysis. These Hg species probably play a key role in local soil Hg processes and biogeochemical cycling. The Hg isotopic data generally showed small differences between HgS (−1.1 to −0.8‰; δ202Hg) and the soil samples (−1.4 to −0.9‰; δ202Hg), as well as limited isotopic variability within the two studied soil profiles. On the other hand, the detected negative δ202Hg shift (∼0.4‰) in organic horizons compared to mineral soils in the highly contaminated profile suggests the presence of secondary post-depositional Hg processes, such as sorption or redox changes. For the less contaminated profile, the observed Hg isotopic variation (∼0.3‰; δ202Hg) in the subsurface mineral soil compared to both overlying and underlying horizons is likely due to cyclic redox reactions associated with Hg isotopic fractionation. We assume that the adsorption of Hg(II) to secondary Fe(III)/Mn(III,IV)-oxides could be of major importance in such cases. [Display omitted] • Cinnabar and Hg(II) bound to mineral particles were the main Hg forms in soils. • Generally small δ202Hg variations in contaminated soil profiles. • Post-depositional soil processes (sorption, redox changes) cause Hg fractionation. • First determination of Hg isotopic ratios in Fe(III)-containing ore. [ABSTRACT FROM AUTHOR]

Chromium is widely recognized as a significant pollutant discharged into the environment by various industrial activities. The toxicity of this element is dependent on its oxidation state, making speciation analysis crucial for monitoring the quality of environmental water and assessing the potential risks associated with industrial waste. This study introduces a single-well fluorometric sensor that utilizes orange emissive thioglycolic acid stabilized CdTe quantum dots (TGA-QDs) and blue emissive carbon dots (CDs) to detect and differentiate between various chromium species, such as Cr (III) and Cr (VI) (i.e., CrO 4 2− and Cr 2 O 7 2−). The variations of fluorescence spectra of the proposed probe upon chromium species addition were analyzed using machine learning techniques such as linear discriminant analysis and partial least squares regression as a classification and multivariate calibration technique, respectively. Linear discriminant analysis (LDA) demonstrated exceptional accuracy in differentiating single-component and bicomponent samples. Additionally, the findings from the partial least squares regression (PLSR) showed that the sensor created has strong linearity within the 1.0–100.0, 1.0–100.0, and 0.1–15 μM range for Cr 2 O 7 2−, CrO 4 2−, and Cr3+, respectively. Furthermore, appropriate detection limits were successfully achieved, which were 2.6, 2.9, and 0.7 μM for Cr 2 O 7 2−, CrO 4 2−, and Cr3+, respectively. Ultimately, the successful capability of the sensing platform in the identification and quantification of chromium species in environmental water samples provides innovative insights into general speciation analytics. [Display omitted] • This study utilizes a single-well fluorometric sensor for chromium speciation. • The probe was developed by mixing TGA-QDs and CDs in an appropriate proportion. • The probe benefits from Machine Learning techniques for chromium speciation. • The probe monitors chromium pollution in environmental water samples in real-time. [ABSTRACT FROM AUTHOR]

The oxidation of pyrite results in the formation of a solid film passivation layer on its surface. This layer effectively hinders the direct interaction between H 2 O, O 2 , and the pyrite surface, thereby impeding the oxidation dissolution of pyrite. There are few studies on whether alumina (Al 2 O 3), a common aluminum-containing oxide, affects the formation of a solid film passivation layer on the surface of pyrite and inhibits the oxidation dissolution of pyrite. This research investigates the impact of Al 2 O 3 incorporation on the speciation transformation of S, Fe, and Al on the surface of pyrite during oxygen pyrite process. The oxidation of pyrite followed the "polysulfide-thiosulfate" complex oxidation pathway. When <1.5 g/L Al 2 O 3 was introduced, it increase pyrite oxidation, whereas ≥1.5 g/L Al 2 O 3 prevented pyrite oxidation. The process of Al 2 O 3 dissolution results in the consumption of H+ and the subsequent release of Al3+. This, in turn, facilitates the hydrolysis of Fe3+ and Al3+ to generate a secondary mineral layer on the pyrite surface. As a result of the accumulation of S promotes the formation of polysulfide chemical (FeS n) or iron deficiency sulfide (Fe 1-x S), resulting in the formation of a solid film passivation layer composed of sulfur film and secondary mineral layer. The results demonstrated that Al 2 O 3 can promote the formation of a solid film passivation layer on the surface of pyrite, which has significant implications for controlling the oxidation dissolution process of pyrite and offers a new perspective for the source control of acid mine drainage. [Display omitted] • Morphological transformation of S, Fe and Al during pyrite oxidation were influenced by Al 2 O 3. • Al 2 O 3 was found to promote the development of a secondary mineral layer on the pyrite surface. • The secondary mineral layer facilitated the formation of a sulfur film on the pyrite surface. • The oxidation of pyrite followed the "polysulfide-thiosulfate" composite oxidation process. • The formation of solid film passivation inhibited the oxidative dissolution of pyrite. [ABSTRACT FROM AUTHOR]

Oxides of silicon (Si), manganese (Mn), and zinc (Zn) have been used as soil amendments to reduce As mobility and uptake in paddy soil systems. However, these amendments are hypothesized to be affected differently depending on the soil pH and their effect on As speciation in rice paddy systems is not fully understood. Herein, we used a microcosm experiment to investigate the effects of natural Si-rich fly ash and synthetic Mn and Zn oxides on the temporal development of porewater chemistry, including aqueous As speciation (As(III), As(V), MMA, DMA, and DMMTA) and solid-phase As solubility, in a naturally calcareous soil with or without soil acidification (with sulfuric acid) during 28 days of flooding and subsequent 14 days of drainage. We found that soil acidification to pH 4.5 considerably increased the solubility of Si, Fe, Mn, and Zn compared to the non-acidified soil. Additions of Mn and Zn oxides decreased the concentrations of dissolved arsenite and arsenate in the non-acidified soil whereas additions of Zn oxide and combined Si–Zn oxides increased them in the acidified soil. The Si-rich fly ash did not increase dissolved Si and As in the acidified and non-acidified soils. Dimethylated monothioarsenate (DMMTA) was mainly observed in the acidified soil during the later stage of soil flooding. The initial 28 days of soil flooding decreased the levels of soluble and exchangeable As and increased As associated with Mn oxides, whereas the subsequent 14 days of soil drainage reversed the trend. This study highlighted that soil acidification considerably controlled the solubilization of Ca and Fe, thus influencing the soil pH-Eh buffering capacity, the solubility of Si, Mn, and Zn oxides, and the mobility of different As species in carbonate-rich and acidic soils under redox fluctuations. [Display omitted] • Solubilities of Si, Mn, and Zn oxides differed in acidified and non-acidified soils. • Soil acidification greatly impacted As, Si, Mn, and Zn solubility in paddy soils. • Mn and Zn oxides decreased arsenite and arsenate in non-acidified soil. • Zn oxide increased dissolved arsenite and arsenate in acidified soil. • Soil acidification and reaeration synergistically increased H 4 SiO 4 -to-H 3 AsO 3 ratio. [ABSTRACT FROM AUTHOR]

The leaching of heavy metals from abandoned mine tailings can pose a severe threat to surrounding areas, especially in the regions influenced by acid rain with high frequency. In this study, the potential risks of heavy metals in the tailings collected from a small-scale abandoned multi-metal mine was assessed, and their leaching behavior and mechanism were investigated by batch, semi-dynamic and in situ leaching experiments under simulated and natural rainfall conditions. The results suggested that Zn, Cu, Pb, and Cd in the tailings could cause high/very high risks. Both batch and semi-dynamic leaching tests consistently confirmed that the leaching of heavy metals (particularly Cd) could lead to serious pollution of the surrounding environment. The leaching rates of heavy metals were pH-dependent and related to their chemical speciations in the mine tailings. The leaching behavior of Cu and Cd was dominated by surface wash-off, Zn was controlled by diffusion initially and then surface wash-off, and the leaching mechanisms of Pb and As varied with the pH conditions. It was estimated that acid rain could greatly elevate the release fluxes of Zn (20.8%), Cu (36.7%), Pb (49.9%) and Cd (35.3%) in the study area. These findings could improve the understanding of the leaching behavior of heavy metals from mine tailings and assist in developing appropriate management strategies. [Display omitted] • Cu, Zn, Pb and Cd in tailings posed high risks to surrounding areas. • Metal leaching under rainfall was correlated to the acid soluble form. • Leaching behavior and mechanism varied with elements and pH conditions. • Acid rain promoted the release fluxes of Cu, Zn, Pb, and Cd from tailings. • The predictions of release fluxes were verified by the in-situ experiments. [ABSTRACT FROM AUTHOR]

Monochloramine (NH 2 Cl) is applied upstream of reverse osmosis (RO) membranes for biofouling control. Residual NH 2 Cl can undergo UV photolysis downstream, generating reactive species for an AOP to occur. At the bench-scale, NH 2 Cl is typically generated from combining sodium hypochlorite and ammonium chloride or sulfate. This study investigated the degradation of four compounds of interest – acetaminophen, caffeine, sucralose and 1,4-dioxane – in UV/NH 2 Cl at the bench scale to study their reactivity with reactive chlorine species (RCS) and reactive nitrogen species (RNS). With methanol acting as a scavenger of •OH radicals, the performance of UV/NH 2 Cl was compared to UV/H 2 O 2 and UV/HOCl. In UV/H 2 O 2 , dioxane was severely inhibited at 1–2 mg/L H 2 O 2 and comparable at 5 mg/L to UV/NH 2 Cl. When ammonium sulfate ((NH 4) 2 SO 4) was used as the ammonia source over ammonium chloride (NH 4 Cl), the overall degradation of micropollutants was higher and caffeine was exclusively degraded. At 1–2 mg/L NH 2 Cl, dioxane degraded by 16.2–17.8% and 2.92–5.29% from (NH 4) 2 SO 4 and NH 4 Cl respectively while caffeine degraded by 7.45–9.61% with NH 2 Cl ((NH 4) 2 SO 4), but not degrade with NH 2 Cl (NH 4 Cl). The higher concentration of chloride ions from NH 4 Cl significantly influenced the speciation of generated radicals and impacted micropollutant degradation. This suggests that the reactivity of more selective RCS (Cl 2 •−, •ClO, ClOH•−) and RNS (•NH 2 , •NO, •NO 2 , etc.) varies with micropollutants of interest. The presence of higher chloride concentration from the ammonia source inhibited the generation of •OH radicals with •OH consumed by RNS to form NO 3 − (μg/L levels), showing the impact of the choice of ammonia source and the water matrix on UV/NH 2 Cl performance. [Display omitted] • Micropollutant degradation in UV/NH 2 Cl depends on its individual reactivity with reactive species. • Chloride contribution from ammonia reagent influences speciation of reactive chlorine species. • Caffeine degraded in UV/NH 2 Cl ((NH 4) 2 SO 4) systems with lower chloride concentrations. [ABSTRACT FROM AUTHOR]

In this study, we systematically explore coagulation behavior, ultrafiltration membrane fouling behavior and the mechanism involved in during the process of pre-oxidation of potassium permanganate and coagulation of aluminum chloride at different condition to treat model pollutants (humic acid, HA) and natural water. The KMnO 4 pre-oxidation significantly enhances flocs formation, and for HA artificial water the flocs size increases from 82 to 122 μm at pH 5.5, from 63 to 185 μm at pH 7.0 and from 0 to 75 μm at pH 8.5, respectively, as for natural water it increases from 72 to 139 μm. The enhanced coagulation at pH 5.5 is attributed to the increased polymeric Al speciation after pre-oxidation along with the generated Mn2+ damaging the electric double layer structure. And for pH 8.5 it is mainly caused by the in-situ MnO 2 as combination nuclei during pre-oxidation. Besides, for pH 7.0, the combined effect of in-situ MnO 2 and the increased polymeric Al speciation both contribute to improvement of the coagulation. What's more, the enhanced Al coagulation by pre-oxidation of KMnO 4 also helps alleviate the membrane fouling for both HA artificial water and natural water, and a much rougher surface with larger flocs forms after KMnO 4 -aided Al coagulation filtration. This study provides an alternative perspective on the mechanism of pre-oxidation coagulation process. [Display omitted] • Pre-oxidation by KMnO 4 significantly enhances Al coagulation. • For alkaline condition it mainly results from the in-situ MnO 2. • For weak acid it is the aluminum speciation change along with the generated Mn2+. • For neutral condition both the in-situ MnO 2 and aluminum speciation change matter. • The KMnO 4 aided Al coagulation help alleviate the membrane fouling. [ABSTRACT FROM AUTHOR]

Daytime volatilization of gaseous elemental mercury (Hg(0) aq) is a significant mechanism for mercury removal from aquatic systems and potentially limits the production and bioaccumulation of methylmercury. Changes in incoming solar radiation (in the ultraviolet range), dissolved organic matter, salinity, and total suspended particles were investigated concurrently with several mercury species (Hg(0) aq , dissolved total mercury (THg), easily reducible mercury (ERM), and mercury associated with total suspended solids (THg TSS)) during daylight hours near the mouth of a hypertidal river. There were no predictable temporal changes observed for Hg(0) aq in unfiltered surface water. Hg(0) aq ranged from 0 to 12 pg L−1, THg ranged from 0 to 492 pg L−1, ERM ranged from 13 to 381 pg L−1, and THg TSS ranged from <1.58 ng g−1 to 261.32 ng g−1. The range of Hg(0) aq predicted by the empirical model was similar to measured ERM concentrations, but it was shown that ERM did not significantly predict in-situ photoreducible Hg(II) (Hg(II) RED). Production of Hg(0) aq appears to largely be suppressed by suspended solids, which limits ultraviolet radiation transmission through surface water. Comparison of these results to an empirical model developed for this site to predict Hg(0) aq indicates that significantly more mercury is available for photoreduction near the mouth of the tidal river, and that Hg(II) will likely photoreduce quickly when TSS levels decrease with ocean mixing. [Display omitted] • Divalent mercury photoreduction lessens mercury concentrations in ecosystems. • Estuarine water samples were taken every 0.5 h from sunrise to sunset. • Empirical model predicts higher mercury photoreduction than measured in the field. • High suspended solids limited mercury photoreduction. [ABSTRACT FROM AUTHOR]

This study concerns total arsenic (TAs) and arsenic species determination in three species of mushrooms collected in Yunnan, China. The purpose of this study was to check concentration level of arsenic in Boletus edulis , Tricholoma matsutake and Suillellus luridus , estimate arsenic bioaccessibility and find out which arsenic species occur in mushrooms to assess if they may pose a threat to human health. An analytical methodology based on ion chromatography (IC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS) with dynamic reaction cell (DRC) and size exclusion chromatography (SEC) with UV–Vis detection and ICP-DRC-MS detection. Ultrasound assisted extraction (UAE), microwave assisted extraction (MAE) and enzymatic assisted extraction (EAE) were applied. Quantification of As species in extracts was performed by IC/ICP-DRC-MS in the first dimension. Slightly better extraction efficiencies were obtained for MAE (from 75% to 90%) then for UAE. EAE was used for estimation of bioaccessibility by application of a modified BARGE bioaccessibility method (UBM) for in vitro studies. Bioaccessibility values were in the ranges of 73%–102%, 74%–115% and 18%–87% for step 1 (S1), for step 2 (S2) and for step 3 (S3) of EAE, respectively. Extracts obtained after EAE were subjected to SEC-UV-Vis/ICP-DRC-MS analysis as the second dimension. The main signal was obtained in the area of a molecular mass of ∼5 kDa for all mushroom extracts. Monitoring of an 50SO+ ion confirmed that this signal comes from As-protein. In sample of Boletus edulis additional signal occurred which is classified as unknown As-compound. Both signals require identification with another analytical technique. Image 1 • Speciation of As in mushroom samples from Yunnan, China. • Speciation analysis by IEC-ICP-DRC-MS and SEC-UV-Vis/ICP-DRC-MS. • Ultrasound, microwave and enzymatic assisted extraction of arsenic from mushroom samples. • Bioaccessibility of As from mushroom samples using modified BARGE method. [ABSTRACT FROM AUTHOR]

To constrain the resuspension influence to the biogeochemical behavior of trace metals (TMs) in settling materials, the concentrations and chemical speciations of macro-elements (Al, Fe, Mn) and selected particulate TMs (V, Cr, Co, Cu, Zn, Ga, Sr, Cd, Ba, Tl, Pb, U) in trap-collected particles (TCPs), surface sediments (SS) and core sediment samples (CS5) of the Jiaozhou Bay were compared. Two approaches, mass conservation method and vertical two end-members mixing model, both calculated a resuspension ratio of more than 90%. Greater TM concentrations and Al-normalization levels than SS/CS5 determined the TCPs an important TM-sink, predominantly owing to grain-size effects and TCP-specific characteristics, i.e., structural capacity of organic-Fe associations for TMs' scavenging, preferential remineralization of TM than biogenic elements in autochthonous microorganisms. Comparison revealed distinct, Fe mineral controls on TM sequestration patterns: higher metal sequestration associated with amorphous Fe oxyhydroxides, while less reactive crystalline Fe oxides hold less metal. Nevertheless, turbulent hydrodynamics muted the wide TM retention divergences between TCP and SS, which should have happened based on different Fe minerals distribution for TCP/SS. The net effect of TM release by the organic carrier phase and then adsorption principally onto Mn/Fe oxyhydroxide phase for raised overall TCP-TM concentrations was also identified. • The resuspended ratios from sediments were estimated over 90% for Jiaozhou Bay. • Resuspended particles were important trace metal sinks for higher concentrations. • Effects of iron cycling and organic remineralization were evaluated. [ABSTRACT FROM AUTHOR]

Abstract Freshwater and marine organisms are capable of metabolizing arsenic (As) efficiently and regulating the As biogeochemical cycles. In this study, Undaria pinnatifida was exposed to As(V) (0, 0.1, and 1 μM) and phosphate (P; 1 and 10 μM) in seawater under laboratory-controlled conditions for up to seven days to analyze As biotransformation. The growth rates and chlorophyll fluorescence of the alga were unaffected by As stress, and statistically insignificant differences were observed among the cultures (p > 0.05). As(V) was readily accumulated by this macroalga through phosphate transporters, transformed intracellularly, and excreted into the medium, depending on the As(V) to P molar ratios. The concentration of As(V) and biotransformed species As(III) and DMAA(V) varied significantly in the algal cultures on the basis of the exposure period (p < 0.05). The concentration of As(III) was initially higher but decreased with the incubation period, whereas the concentration of DMAA(V) increased gradually. At the end of the incubation, 0.04 and 0.32 μM DMAA(V) were recorded in the media containing 0.1 and 1 μM As(V) with a constant 1.0 μM P, respectively. The results also indicated that the cellular uptake of As(V) and subsequent release of DMAA(V) were inhibited by P in the medium. The biotransformation was consistent with the As(V) detoxification mechanism based on reduction and methylation, which was enhanced by the lower As(V) to P molar ratios. These findings can be helpful in understanding the contribution of macroalgae to As biogeochemistry in marine environments and the potential risks of As dietary intake. Graphical abstract Image 1 Highlights • The growth rate was significantly unchanged up to seven days with 1.0 μM of As(V). • The overall biotransformation of As(V) was coupled with reduction and methylation. • As(V) uptake and its biotransformation was enhanced by low levels of P in culture. • The intracellular accumulation of As was minimum at initial high levels of P. • The presence of Fe in medium can lead to adsorb As and P on the surface of algae. [ABSTRACT FROM AUTHOR]

Abstract Increasing attention is being paid to Sb as a primary hazardous substance, and further systematic studies of Sb behavior in freshwater wetlands are required. The plain wetlands in Lake Taihu basin located in lower Yangtze River valley, are heavily populated and economically developed area in China. The plain wetlands receive polluted water from point sources (textile and printing plants). In this study, Sb speciation in plain wetlands was investigated and the potential ecological risk of 8 metal(loid)s (As, Cd, Cr, Cu, Ni, Pb, Zn, Sb) were assessed. The mean Sb concentration in the wetlands water is 7.03 μg L−1, which consist of pentavalent, trivalent, organic Sb dissolved in water and a great part that attached to suspend solids (SS). Statistical analysis indicated that Sb(Ⅲ) is dissolved from SS and then further oxided to Sb(V) accompanied with tailing water discharged into wetlands; presence of organic Sb is related to microorganic in eutrophic environment; precipitation of SS is the dominant factor for distribution of bioavailable Sb in surficial sediment. The toxicity coefficient factor for Sb is proposed as 10 and ambient background of 8 metal(loid)s are set up. The potential ecological risk for plain wetlands was 135, which was low level. As, Cd and Sb were main contributors to the ecological risks. The wetlands are threatened by Sb pollution, which should be restrict by reducing the concentration of SS and Sb in tailing water from local water treatment facilities. Graphical abstract Image 10115 Highlights • Sb's toxicity coefficient of 10 was determined and was used to evaluate potential ecological risk of plain wetlands. • Sb speciation in water and sediment of plain wetlands were performed. • The factors affecting the distribution of Sb species in water were analyzed. • The fate of Sb pollutants from textile mill and printing industries plain wetlands was illustrated. [ABSTRACT FROM AUTHOR]

Abstract Formation potential and speciation characteristics of two important groups of disinfection byproducts (DBPs), namely, trihalomethanes (THMs) and haloacetic acids (HAA S), during Cl 2 and ClO 2 treatment of water samples collected from three different sources, namely, sea, river, and reservoir, were investigated with reference to key controlling parameters. Formation of inorganic DBPs such as chlorate and chlorite was evaluated. Dissolved organic carbon (DOC) and UV absorbance (UV 254) of the sea, river, and reservoir samples were 3.35 ± 0.05, 3.12 ± 0.05, and 3.23 ± 0.05 mg/L and 0.062 ± 0.01, 0.074 ± 0.01, and 0.055 ± 0.01 cm−1, respectively. For Cl 2 and ClO 2 treatments, the respective formation potential of THMs and HAAs from the three water sources studied exhibited unidentical trend suggesting that higher THM formation was not necessarily associated with higher HAA formation. On chlorination, the concentrations of total HAAs formed were 9.8 μg/L (sea), 12.8 μg/L (river), and 20.6 μg/L (reservoir) and total THM yields were 38.3 μg/L (sea), 18.8 μg/L (river), and 21.5 μg/L (reservoir) for a Cl 2 dose of 1 mg/L and 30 min reaction time. The trend of formation of THMs and HAAs for Cl 2 treatment was similar to that for ClO 2 treatment. However, the amount of HAAs (3.5 μg/L (sea), 1.8 μg/L (river), and 1.9 μg/L (reservoir)) and THMs (not detected) formed was much lower than that formed during chlorination. Regardless of source water type, di-HAAs were the most favored HAAs, followed by tri-HAAs with a small amount of mono-HAAs formed for both Cl 2 and ClO 2 treatment. Chlorination yielded more THMs than HAAs, whereas it was reverse for chlorine dioxide treatment. Irrespective of treatment with ClO 2 or Cl 2 , seawater samples showed the highest bromine incorporation percentage (BIP) in both THMs and HAAs followed by that for river and reservoir water samples. HAAs were found to be always associated with lower amount of BIP than THMs. Graphical abstract Image 1 Highlights • Di-HAAs were the dominant HAAs formed, followed by tri-HAAs. • ClO 2 treatment was associated with higher BIP than Cl 2 treatment. • ClO 2 : [HAAs] > [THMs], whereas Cl 2 : [THMs] > [HAAs]. • Major sources in treated water – ClO 3 −: contaminated hypochlorite; ClO 2 −: chlorine dioxide disinfection. [ABSTRACT FROM AUTHOR]

Abstract Clouds are complex multiphasic media where efficient chemical reactions take place and where microorganisms have been found to be metabolically active. Hydroxyl radical is the main oxidant in cloud water, and more generally in the atmosphere, during the day and drives the cloud oxidative capacity. However, only one measurement of the steady state hydroxyl radical concentrations in cloud water has been reported so far. Cloud chemistry models are used to estimate the hydroxyl radical concentrations with values ranging from 10−12 to 10−15 M that are surely overestimated due to a lack of knowledge about the speciation of the organic matter acting as a sink for hydroxyl radicals. The aim of this work is to quantify the concentration of hydroxyl radicals at steady state in rain and cloud waters and to measure the impact of native microflora on this concentration. First, the non-toxicity of terephthalic acid as probe is controlled before the analysis in real atmospheric water samples. Higher concentrations of hydroxyl radicals are found in cloud waters than in rain waters, with a mean value "1.6 ± 1.5" × 10−16 M and "7.2 ± 5.0" × 10−16 M for rain and cloud waters respectively and no real impact of microorganisms was observed. This method allows the measurement of steady state hydroxyl radical levels at very low concentrations (down to 10−17 M) and it is biocompatible, fast and easy to handle. It is a useful tool, complementary to other methods, to give a better overview of atmospheric water oxidant capacity. Highlights • New method is proposed for the determination of hydroxyl radical concentration present in atmospheric natural waters. • It allows to evaluate steady state OH radical concentrations at very low concentrations (10−17 M) and is biocompatible. • Steady state concentration of hydroxyl radicals are determined in 5 different samples of cloud and rain waters. • Mean value in cloud water of 7.2 ± 5.0 × 10−16 M are more than four times higher than in rain water 1.6 ± 1.5 × 10−16 M. • The evaluated values are much lower than most of the values estimated by cloud chemistry models. [ABSTRACT FROM AUTHOR]

Increasing loading of phosphorus (P) into freshwater systems is deemed as one of the key drivers triggering harmful algal blooms (HABs). However, conventional water quality monitoring of P normally uses the operational cutoff (e.g., 450-nm filter membrane) to separate particulate and dissolved phases (entities passing through the 450-nm membrane are regarded as dissolved phase), which completely neglects the roles of small colloids (450–100 nm) and nanoparticles (100–1 nm). Herein, a new particle size separation approach was used to separate water samples collected from catfish aquaculture ponds in west Alabama into six size fractions: large particles (>1000 nm), large colloids (1000–450 nm), small colloids (450–100 nm), large nanoparticles (100–50 nm), small nanoparticles (50–1 nm), and the truly dissolved phase (<1 nm). The speciation and concentration of P in these six size fractions were then investigated using Hedley's sequential extraction method. The new particle size separation results showed that particle loading (mass) followed the order: >1000 nm, 450–100 nm, 1000–450 nm, 100–50 nm, and 50–1 nm. This is mainly due to the abundance of large-sized (>1000 nm) zooplankton and phytoplankton such as algae and cyanobacteria in the catfish aquaculture ponds. Importantly, the small colloid (450–100 nm) and nanoparticle (100–1 nm) size fractions, which were previously regarded as the dissolved phase using the 450-nm membrane filtration operation, accounted for ∼41.8% of the total particle mass. The Hedley's sequential extraction results showed that sodium hydroxide (NaOH)-extracted P represented the largest P pool, followed by water (H 2 O)- and sodium bicarbonate (NaHCO 3)-extracted P pools. Smaller particles exhibited a higher loading of P due to their large surface areas. These new findings suggest that the new particle size separation approach needs to be adopted for future water quality monitoring and mitigation of HABs in freshwater ecosystems. [Display omitted] • A new particle size separation approach of water samples was used to separate particles in water samples collected from catfish aquaculture ponds in west Alabama. • The speciation and concentration of phosphorus on particles in different size fractions of water samples were determined by Hedley's sequential extraction method. • Small colloids and nanoparticles play an important role in the loading of phosphorus in catfish aquaculture ponds in west Alabama. [ABSTRACT FROM AUTHOR]

Trace minerals such as copper (Cu) and zinc (Zn) are animal nutrition supplements necessary for livestock health and breeding performance, yet they also have environmental impacts via animal excretion. Here we investigated changes in Cu and Zn speciation from the feed additive to the broiler excreta stages. The aim of this study was to assess whether different Cu and Zn feed additives induce different Cu and Zn speciation patterns, and to determine the extent to which this speciation is preserved throughout the feed-animal-excreta system. Synchrotron-based X-ray absorption spectroscopy (XAS) was used for this investigation. The principal findings were: (i) in feed, Cu and Zn speciation changed rapidly from the feed additive signature (Cu and Zn oxides or Cu and Zn sulfates) to Cu and Zn organic complexes (Cu phytate and Zn phytate). (ii) in the digestive tract, we showed that Cu and Zn phytate were major Cu and Zn species; Cu sulfide and Zn amorphous phosphate species were detected but remained minor species. (iii) in fresh excreta, Cu sulfide and Zn amorphous phosphate were major species. These results should help to: (i) enhance the design of future research studies comparing different feed additive performances; (ii) assess Cu and Zn bioavailability in the digestive tract; (iii) gain further insight into the fate of Cu and Zn in cultivated soils when poultry manure is used as fertilizer. [Display omitted] • Cu and Zn speciation of feed additives changed rapidly after mixture with basal diet. • In the broiler digestive tract Cu and Zn are mainly associated with phytate. • In fresh excreta Zn precipitates in Zn amorphous phosphate. • In fresh excreta Cu forms Cu(II) octahedral complexes and Cu(I) sulfides. [ABSTRACT FROM AUTHOR]

The redox capabilities of birnessite minerals are contingent upon the physical characteristics of the solid, indicating that different allotropes have various reactivities. Here, the role of these structural differences on the oxidation of iodine, a risk driving environmental contaminant in several federal complexes, was investigated. The mechanism of which can be seen here, with one of the minerals of study, acid birnessite. The pH range chosen for this study was pH 5–6. Throughout the experiments it was seen that the average oxidation state (AOS) had the greatest contribution to the differences in redox capabilities of the various birnessite minerals. Several trends were observed throughout this study: as AOS decreased, oxidation of iodide (I−) increased; as specific surface area (SSA) increased, the sorption of iodate (IO 3 −) increased. Additional experiments were conducted at trace levels of iodine, to better model environmental conditions. In that case, a one-step conversion of I− to IO 3 − occurred, to a greater extent than under artificially elevated concentrations. [Display omitted] • Birnessite structure affects extent of oxidation of I− to IO 3 − and speciation. • Oxidation reaction forms an intermediate I 2 species under higher concentrations. • There is a one-step transformation of I− to IO 3 − under dilute concentrations. [ABSTRACT FROM AUTHOR]

This study investigated heavy metal chemical speciation and leaching behavior from a board-type spent selective catalytic reduction (SCR) catalyst containing high concentrations of vanadium, chromium, nickel, copper, zinc, and lead. A three-step sequential extraction method, standard toxicity characteristic leaching procedure (TCLP), and leaching characteristic tests have been performed. It was found that the mobility of six heavy metals in the spent SCR catalyst was significantly different. The mobility of the six heavy metals exhibited the following order: Ni > Zn > V > Cr > As > Cu. Meanwhile, TCLP test results revealed relatively high Zn and Cr leaching rate of 83.20% and 10.35%, respectively. It was found that leaching rate was positively correlated with available contents (sum of acid soluble, reducible and oxidizable fractions). Leaching characteristics tests indicated that pH substantially affected the leaching of these heavy metals. In particular, the leaching of Cr, Ni, Cu, and Zn was positively influenced by strong acid, while V and As were easily released in the presence of strong acid and strong alkali (pH < 3 or pH > 11). In terms of kinetics, the leaching of Cr, Ni, Cu, Zn, and As within the spent catalyst was dominated by erosion and dissolution processes, which were rapid reaction processes. V was released in large amounts within 1 h, but its leaching amount sharply decreased with time due to readsorption. [ABSTRACT FROM AUTHOR]

In order to clarify some of the assumptions and approximations about the use of the distribution coefficient K d for 226 Ra in soils, a systematic study has been performed using centrifugation to extract the soil solution. The separated fractions of the soil solution have different kinetics with respect to the sorption process in the soil, which may in turn condition the final chemical composition and even the speciation of the radionuclides in solution. In the experimental design of this study three factors were considered: the moisture level in the incubation process, incubation time and the speed of centrifugation. Also, three levels were chosen for each factor. In order to analyze the influence of the structural characteristics of the soil, this study was performed with three textural fractions: coarse sand, fine sand, and silt and clay, obtained from an only soil. Also, the soil was naturally enriched with radionuclides of the 238 U series. An analysis of variance (ANOVA) was performed in order to assess the influence of the factors studied on the distribution coefficient of 226 Ra. The results indicate that different behaviors can be observed depending on the structural characteristic of the soil. In the case of particle size, the soil with the largest grain size showed that the incubation process parameters influence the equilibrium level achieved, while in the case of the smallest edaphic particles, radium is not homogeneously distributed in the soil solution and the K d value is dependent on the speed of centrifugation. [ABSTRACT FROM AUTHOR]

The influence of humic substances (specifically humic and fulvic acids, referred to as HS-HA and HS-FA) as well as other factors, such as major nutrient concentrations of total dissolved nitrogen (TDN), total dissolved phosphate (TDP) and hydrologic factors, on the distribution of total dissolved iron (DFe) and the chemical speciation of DFe was studied in the East China Sea (ECS) during a summer cruise in 2013. As the wide rage fraction of nature organic matter, the HS-HA, HS-FA in ESC contains most part of the organic ligand (Lt) of DFe. The concentrations of HS-HA, DFe and Lt in coastal water masses were higher than those in the water masses affected by the Kuroshio Current. The highest concentrations of HS-HA and DFe were observed in surface water at stations MT1 and MC4, with the value of 336.5 μg SRHA/L and 20.3 nmol/L, respectively, whereas, the lowest concentrations of HS-HA and DFe were observed in surface waters with the value of 149.6 μg SRHA/L and 0.4 nmol/L, respectively. HS-HA concentrations were more conservative than that of DFe. The DFe which were combined by unit weight HS-HA (mg −1 , IB) in the surface and bottom waters quickly decreased with increasing salinities from the Yangtze River estuary to the southeast of the ECS. Average IB values in bottom waters were higher than those in surface waters. This study indicated that Yangtze River dilution water and cold water from the Yellow Sea were the main source of HS-HA and DFe in ECS. [ABSTRACT FROM AUTHOR]

Pig manure has been utilized as a good feedstock to produce biochar. However, the pig manure-derived biochar from intensive pig cultivation contains high levels of total and bioavailable heavy metals. In this study, the co-pyrolysis of pig manure with other biomass (e.g. rice straw) at 300–700 °C was investigated to solve the above-mentioned topic. The ammonium acetate (CH 3 COONH 4 ), Tessier sequential extraction procedure and hydrogen peroxide were adopted to evaluate the bioavailability, chemical speciation, and potential risk of Cu and Zn in the biochars. Results showed that the addition of rice straw significantly reduced the concentrations of total, exchangeable and carbonate-associated Cu and Zn in the biochars compared to the single pig manure biochars. Co-pyrolysis of pig manure with rice straw at a mass ratio of 1:3 and at 600 °C could be most effective to reduce the concentrations of CH 3 COONH 4 -extractable and potential released Cu and Zn in the biochars. In conclusion, the co-pyrolysis process is a feasible management for the safe disposal of metal-polluted pig manure in an attempt to reduce the bioavailability and potential risk of heavy metals at relatively high pyrolysis temperatures. [ABSTRACT FROM AUTHOR]

In this study, we tested 123 groundwater wells from five different areas of Punjab, Pakistan for arsenic (As) contamination level and species, as well as delineated hydrogeochemical behaviour of As in aquifers. Results revealed that 75% and 41% of the groundwater wells exceeded the safe As limit of World Health Organisation (WHO, 10 μg L −1 ) and Pakistan-EPA (50 μg L −1 ), respectively. Arsenite (As(III)) and arsenate (As(V)) spanned 0–80% and 20–100% of total As (1.2–206 μg L −1 ), respectively. The mean As content (5.2 μg L −1 ) of shallow wells at 9–40 m depth did not exceed the WHO safe limit, representing a safe aquifer zone for pumping of groundwater compared to deeper wells at 41–90 m (51 μg L −1 ) and >90 m (23 μg L −1 ) depths. Piper-plot elucidated that the aqueous chemistry was dominated with Na-SO 4 , Na-Ca-SO 4 , Na-Mg-SO 4 type saline water. Principal component analysis grouped As concentration with well depth, pH, salinity, Fe and CO 3 , exhibiting that these hydrogeochemical factors could have potential role in controlling As release/sequestration into the aquifers of study area. Geochemical modeling showed positive saturation indices only for iron (Fe) oxide-phases, indicating Fe oxides as the major carriers of As. Overall, this study provides insights to tackle emerging As threat to the communities in Punjab, Pakistan, as well as help develop suitable management/mitigation strategies – based on the baseline knowledge of As levels/species and factors governing As contamination in the study area. [ABSTRACT FROM AUTHOR]

This study presents the effect of aqueous uranium speciation (U-hydroxides and U-hydroxo-carbonates) on the interaction of this radionuclide with the cells of the yeast Rhodotorula mucigilanosa BII-R8. This strain was isolated from Spanish bentonites considered as reference materials for the engineered barrier components of the future deep geological repository of radioactive waste. X-ray absorption and infrared spectroscopy showed that the aqueous uranium speciation has no effect on the uranium binding process by this yeast strain. The cells bind mobile uranium species (U-hydroxides and U-hydroxo-carbonates) from solution via a time-dependent process initiated by the adsorption of uranium species to carboxyl groups. This leads to the subsequent involvement of organic phosphate groups forming uranium complexes with a local coordination similar to that of the uranyl mineral phase meta-autunite. Scanning transmission electron microscopy with high angle annular dark field analysis showed uranium accumulations at the cell surface associated with phosphorus containing ligands. Moreover, the effect of uranium mobile species on the cell viability and metabolic activity was examined by means of flow cytometry techniques, revealing that the cell metabolism is more affected by higher concentrations of uranium than the cell viability. The results obtained in this work provide new insights on the interaction of uranium with bentonite natural yeast from genus Rhodotorula under deep geological repository relevant conditions. [ABSTRACT FROM AUTHOR]

Sediments contaminated by Hg and As from two historical mining areas have been deposited in the Nalón estuary (Asturias, northern Spain) since 1850. Total mercury (Hg total ) concentrations in the sediments range from 0.20 μg g −1 to 1.33 μg g −1 , most of it in the form of sulphides. Concentrations of methylmercury (303.20–865.40 pg g −1 ) are up to two orders of magnitude lower than the concentration of Hg total . Total As concentration (As total ) is enriched compared to the background level for the area. The relative abundance of As(V) on As(III) in the sediments ranges from 97.6% to 100%, whereas inorganic Hg accounts for more than 99% of the total Hg. The occurrence of the most toxic species, inorganic As(III) and organic methylmercury, seem to be related to redox conditions together with the amounts of sulphur which act as natural barriers which inhibit the biological and chemical speciation processes. Despite the high amounts of Hg and As present in the sediments, their transference to the water column appear to be limited thus converting sediments in an effective sink of both elements. Special attention should be paid to potential variations of the environmental conditions which might increase the element mobility and exchange between sediments and the water column. [ABSTRACT FROM AUTHOR]

Lake Nahuel Huapi (NH) is a large, ultraoligotrophic deep system located in Nahuel Huapi National Park (NHNP) and collecting a major headwater network of Northwestern Patagonia (Argentina). Brazo Rincón (BR), the westernmost branch of NH, is close to the active volcanic formation Puyehue-Cordón Caulle. In BR, aquatic biota and sediments display high levels of total Hg (THg), ranging in contamination levels although it is an unpolluted region. In this survey, Hg species and fractionation were assessed in association with dissolved organic matter (DOM) in several aquatic systems draining to BR. THg varied between 16.8 and 363 ng L −1 , with inorganic Hg (Hg 2+ ) contributing up to 99.8% and methyl mercury (MeHg) up to 2.10%. DOC levels were low (0.31–1.02 mg L −1 ) resulting in high THg:DOC and reflecting in high Hg 2+ availability for binding particles (partitioning coefficient log K d up to 6.03). In streams, Hg fractionation and speciation related directly with DOM terrestrial prints, indicating coupled Hg-DOM inputs from the catchment. In the lake, DOM quality and photochemical and biological processing drive Hg fractionation, speciation and vertical levels. Dissolved gaseous Hg (Hg 0 ) reached higher values in BR (up to 3.8%), particularly in upper lake layers where solar radiation enhances the photoreduction of Hg 2+ and Hg-DOM complexes. The environmental conditions in BR catchment promote Hg 2+ binding to abiotic particles and bioaccumulation and the production of Hg 0 , features enhancing Hg mobilization among ecosystem compartments. Overall, the aquatic network studied can be considered a “natural Hg hotspot” within NHNP. [ABSTRACT FROM AUTHOR]

An original methodology to quantitatively explore exchangeability of hydrogen isotopes in carbohydrate molecules is proposed. To access the speciation of organically bound hydrogen isotopes, isotopic exchanges were carried out under a soft path regime in the vapor phase at 20 °C with set (D,T/H) vapor pressure ratios. When steady states were reached, the fraction of exchangeable hydrogen of microcrystalline cellulose, alpha-cellulose and wheat grains were obtained and ranged from 13 to 31% (versus a theoretical value of 30%). In cellulose, and more specifically in microcrystalline cellulose, the molecular hydrogen bonds as well as the different conformations of the network seemed to decrease the hydroxyl groups of glucose units available for isotopic exchange. On the contrary, the assumed enzymatic hydrolysis of the constitutive molecules of wheat starch into low-molecular weight carbohydrate molecules enhanced the exchangeable pool. An average value of the activity between non-exchangeable organically bound tritium (NE-OBT) and non-exchangeable organically bound hydrogen was calculated for wheat grains, ( T H ) NE  = 0.55 ± 0.03 Bq.g −1 of hydrogen atoms. [ABSTRACT FROM AUTHOR]

The abandoned mining area of Valdicastello Carducci (Tuscany, Italy) is characterized by the massive presence of thallium in the acid mine drainages and in the valley stream crossing the region. We previously found that Tl(III), generally considered the less stable oxidation state of thallium, is present both in the stream and in tap water distributed in the area, whereas acid mine drainages only contain Tl(I). These findings posed some concern related to the reactivity and dispersion of this toxic element in the environment. Since the valence state of thallium determines its toxicity, distribution and mobility, the study of thallium redox speciation appears crucial to understand its environmental behaviour. In this work, water samples collected from the mine drainages and the contaminated stream were adopted as model to study the distribution of aqueous Tl(I)/Tl(III) as a function of light exposure and solution properties and composition. The influence of three light sources and organic acids was evaluated. Thallium speciation was also assessed in tap water after treatment with common oxidizing agents, and in the rust crust collected from the public waterworks. [ABSTRACT FROM AUTHOR]

A soft material formed by multiwall carbon nanotubes and 1-butyl-3-methyl imidazolium chloride was used as sorbent material to perform the chromium speciation in natural waters. This soft material was not yet used for the speciation of metals as chromium. Thus, a multicommutated flow system containing a minicolumn packed with the soft material was designed. The procedure was based on the capacity of the sorbent to retain Cr(VI) as Cr 2 O 7 = and allow to pass Cr(III) through the column. Then, a fully automated flow-batch analysis system was developed to quantify both species using chemiluminescence detection. Thus, Cr(III) was determined as catalyst of the luminol and hydrogen peroxide reaction and Cr(VI) as oxidant of luminol reaction. This represents a new approach because the oxidation of luminol using Cr 2 O 7 = has not been reported in literature. The variables of the two systems were optimized. The limits of detection were 1.4 μg L −1 for Cr(VI) and 4.0 μg L −1 for Cr(III). The precision of the method was 3.8% and 7.0% for Cr(VI) and Cr(III), respectively. The present method was applied to real water samples with recoveries between 95% and 107%. Besides, these results were in accordance with those obtained using inductive coupled plasma-optical emission spectrometry technique. [ABSTRACT FROM AUTHOR]

Phosphate rock in Guiyang (Southwest of China) is used for the phosphate production, and hence generating a by-product phosphogypsum (PG). From 2007, part of the PG was used as main raw material for cemented backfill. The main objective of this paper is to investigate the geochemical evolution of metals before and after the PG inclusion into the backfill matrix. A sequential extraction procedure was selected to determine the chemical speciation of metals in phosphate rock, PG, binder and field backfill samples. Dynamics of metals going from phosphate rock and PG to backfill have been evaluated. The results showed that almost all the metals in the PG and binder had been effectively transferred to the backfill. Furthermore, compared to metals taken out along with phosphate rock exploitation, PG-based cemented backfill might bring some metals back but with only little metals in mobile fraction. Additionally, in order to determine the long-term behavior of metals in PG-based cemented backfill, the field samples which were backfilled from 2007 to 2016 were collected and analyzed. The results showed that total amounts of metals in backfill were all within similar range, indicating that the cemented PG backfill could be an effective method to solidify/stabilize metals in PG. Nevertheless, Due to the high water-soluble fractions detected, the concentrations of As, Mn and Zn should be continuously monitored. [ABSTRACT FROM AUTHOR]

In North Sea and Port Açu (Brazil) coastal areas, high arsenic (As) concentrations were observed in water, soil and sediments. Therefore, the impact of this contamination on fish and shellfish species bought from local fishermen was studied. Total As was assessed with ICP-OES (Brazil) and ICP-MS (North Sea) after microwave digestion. Toxic As was assessed with liquid chromatography-ICP-MS (Brazil) and hydride generation-atomic fluorescence spectrometry (North Sea). All analytical methods comply with Quality Assurance/Quality Control procedures. Several fish species have average Total As concentrations above 1 μg g-1 wet weight (ww), but the highest concentrations are found in less spotted dogfish, lemon sole and whelks from the North Sea, with respectively 50, 49 and 50 μg g-1 ww. High Total As concentrations correspond to high Toxic As concentrations, except for scallops having increased Toxic As concentrations. Toxic As fractions are highest in scallops (almost 10%) but rarely exceeds 2% in all other species. Liver samples were only analyzed in ray, dogfish and catfish and their Toxic As fractions are between 2 and 4 times higher than in muscle. For a consumption of 150 g of seafood, only 3 samples exceed the provisional total daily intake of 2 μg kg-1 bw, however, cancer risks are non-negligible. Using mean Toxic As concentrations for each of the different fish and shellfish species studied, Lifetime Cancer Risk values at the actual global seafood consumption rate of 54 g day-1 are above 10–4 for whelks, scallops, dogfish, ray and lemon sole. [ABSTRACT FROM AUTHOR]

Chromium is a common soil contaminant and, although it has been studied widely, questions about its speciation and dissolutions kinetics remain unanswered. We combined information from an irrigation experiment performed with intact soil columns with data from batch experiments to evaluate solubility and mobilization mechanisms of Cr(III) in a historically contaminated soil (>65 years). Particulate and colloidal Cr(III) forms dominated transport in this soil, but their concentrations were independent of irrigation intensity (2–20 mm h −1 ). Extended X-ray absorption fine structure (EXAFS) measurements indicated that Cr(III) associated with colloids and particles, and with the solid phase, mainly existed as dimeric hydrolyzed Cr(III) bound to natural organic matter. Dissolution kinetics of this species were fast (≤1 day) at low pH (<3) and slightly slower (≤5 days) at neutral pH. Furthermore, it proved possible to describe the solubility of the dimeric Cr(III) organic matter complex with a geochemical equilibrium model using only generic binding parameters, opening the way for use of geochemical models in risk assessments of Cr(III)-contaminated sites. [ABSTRACT FROM AUTHOR]

The rapid expansion of biomass power generation has resulted in a large amount of ash, which need to be treated urgently. The trace elements in ash also have environmental risks during treatment. Therefore, the essential characteristics and potential environmental risks of biomass ash generated by direct combustion of agricultural straw were studied. The leaching characteristics of elements, including major elements (Mg, K, Ca) and trace elements (V, Cr, Mn, Co, Ni, Cu, Zn, Cd, As, Pb and Ba), in fly ash and slag produced by biomass power plant were analyzed through the static leaching experiments of simulating the possible pH value of natural water in the laboratory. The results show that the trace elements are enriched in fly ash and slag, which may be related to the volatility of elements during combustion. And during the leaching test, the leaching concentration of major and trace elements in fly ash is higher than that in slag. Sequential chemical extraction is used to reveal the occurrence forms of trace elements in biomass ash. Except for residue, Mn, Co, Zn, Cd, and Pb in fly ash mainly exist in carbonate bound, V and As are Fe–Mn oxides bound, and Cr, Ni, Cu, and Ba are mainly organic matter bound. In the slag, Cd is mainly carbonate bound, Cu is mainly organic matter bound, while other elements are mainly Fe–Mn oxides bound. The Risk Assessment Code values calculated based on the existing forms of elements show that As and Cd in slag and Mn, Co, Pb and Cd in fly ash need special attention during utilization. The research results can provide reference for the management and utilization of biomass ash. [Display omitted] • The toxic leaching concentration of biomass ash is lower than the standard limit. • The major elements and trace elements in biomass ash show different leaching laws. • There are different occurrence forms of elements in biomass ash. • Mn, Co, Cd, Pb in fly ash and As, Cd in slag have potential environmental risks. [ABSTRACT FROM AUTHOR]

Iron-modified biochar (Fe-biochar) has been widely developed to attenuate Cr(VI) pollution in both acid and alkaline environments. However, there are few comprehensive studies on how the iron speciation in Fe-biochar and chromium speciation in solution influencing the removal of Cr(VI) and Cr(III) under varying pH. Here, multiple Fe-biochar containing Fe 3 O 4 or Fe(0) were prepared and applied to remove aqueous Cr(VI). Kinetics and isotherms suggested that all Fe-biochar could efficiently remove Cr(VI) and Cr(III) via adsorption-reduction-adsorption. The Fe 3 O 4 -biochar immobilized Cr(III) by forming FeCr 2 O 4 , while amorphous Fe–Cr coprecipitate and Cr(OH) 3 was formed when using Fe(0)-biochar. Density functional theory (DFT) analysis further indicated that pH increase caused more negative adsorption energies between Fe(0)-biochar and the pH-dependent Cr(VI)/Cr(III) species. Consequently, the adsorption and immobilization of Cr(VI) and Cr(III) species by Fe(0)-biochar was more favored at higher pH. In comparison, Fe 3 O 4 -biochar exhibited weaker adsorption abilities for Cr(VI) and Cr(III), which were in consistent with their less negative adsorption energies. Nonetheless, Fe(0)-biochar merely reduced ∼70% of adsorbed Cr(VI), while ∼90% of adsorbed Cr(VI) was reduced by Fe 3 O 4 -biochar. These results unveiled the importance of iron and chromium speciation for chromium removal under varying pH, and might guide the application-oriented design of multifunctional Fe-biochar for broad environmental remediation. [Display omitted] • Fe-biochar efficiently removed aqueous Cr via adsorption-reduction-adsorption. • Fe speciation altered the contribution of adsorption and reduction to Cr removal. • The role of Fe speciation in Cr removal process was dependent on pH. • The interaction between Cr species and Fe-biochar at varying pH was analyzed by DFT. [ABSTRACT FROM AUTHOR]

The occurrence of high arsenic concentrations (up to 3000 μg L−1) in water of soda lakes of the Pantanal wetland is a remarkable case of natural arsenic contamination in South America. However, little is known about arsenic speciation in this environment, particularly regarding speciation changes related to lake trophic status and seasonal variations. To fill this gap, arsenic speciation analysis was carried out in surface (SW) and subsurface (SSW) waters sampled in five soda lakes with different eutrophication status, in two dry and one wet season. As(V) was the dominant species in these waters, while As(III), DMA, MMA and likely complex organic species were present in lower amounts. The results allow to conclude that the arsenic speciation in SW and SSW varies seasonally according to the regional wet or dry periods and lake water levels. In eutrophic turbid and in oligotrophic vegetated soda lakes, arsenic speciation was also characterized by spatial differences between edge and center or between the SW and SSW. Cyanobacteria or macrophytes/algae are involved in arsenic biotransformation in soda lakes through its metabolic and detoxification processes. Significant variation in surface water arsenic speciation occurs as a result of seasonal primary production fluctuation or water arsenic concentration changes in the soda lakes, increasing organoarsenics in dry periods, whereas in flood periods, As(V) prevails. Spatial distribution of arsenic species is significantly impacted by biogeochemical conditions at the water/sediment interface in soda lakes. [Display omitted] • Arsenic species largely varied in surface and subsurface water of soda lakes. • Cyanobacteria or macrophytes/algae are involved in As biotransformation. • Arsenic speciation varies seasonally with lake water level and trophic condition. • Spatial distribution of As species varies with biogeochemical conditions. [ABSTRACT FROM AUTHOR]

Bioaccumulation through diet is the predominant source of metal(loid)s in fishes; however, the trophic transfer of metal(loid)s from the diet to aquatic organisms remains largely unclear. In this study, aquatic organisms and five potential food sources (leaf litter, coarse and fine particulate organic matter (CPOM and FPOM, respectively), epilithon and fish) were collected around the Shimen Realgar Mine of China. Stomach content analysis and stable nitrogen and carbon isotope analysis, combined with a new Bayesian mixing model (MixSIAR), were used to quantify diet compositions of aquatic organisms. The δ13C and δ15N values varied among fish sizes and sampling sites and were probably related to the diet shift of aquatic organisms. The MixSIAR modelling results showed that the aquatic organisms' food sources were mainly composed of FPOM (9%–68%) and epilithon (15%–65%), with leaf litter, CPOM and fish accounting for smaller proportions (2%–30%). Concentrations ranged from 0.91 to 1298 mg/kg for As, 0.01–1.30 mg/kg for Cd, 0.12–37.79 mg/kg for Pb, 0.63–1158 mg/kg for Cr, 1.22–411 mg/kg for Cu, 0.82–1772 mg/kg for Mn, 0.31–542 mg/kg for Ni and 21.84–1414 mg/kg for Zn in all the collected samples, including the aquatic organisms and the relevant food sources. The metal(loid) concentrations in the CPOM, FPOM and epilithon were significantly higher than those in aquatic organisms and leaf litter. In addition, the biomagnification factors were all less than 1, indicating a biodilution from diet to freshwater organisms. The predominant As species were organic As in aquatic organisms, while inorganic As was common in their food sources, indicating that As biotransformation occurred within the freshwater food chain. [Display omitted] • Quantifying diet composition by the MixSIAR model based on δ13C and δ15N analysis. • Higher metal(loid) concentrations were found in potential food sources than in aquatic organisms. • The BMF of metal(loid)s was <1 and showed biodilution from the diet to aquatic organisms. • Higher proportion of organic As were found in biota muscle than in its potential food sources. [ABSTRACT FROM AUTHOR]

The sulfide-induced change in arsenic speciation is often coupled to iron geochemical processes, including redox reaction, adsorption/desorption and precipitation/dissolution. Knowledge about how sulfide influenced the coupled geochemistry of iron and arsenic was not explored well up to now. In this work, retention and mobilization of As(III) and As(V) on ferrihydrite in sulfide-rich environment was studied. The initial oxidation states of arsenic and the contact order of sulfide notably influenced arsenic sequestration on ferrihydrite. For As(III) systems, pre-sulfidation of As(III) decreased arsenic sequestration mostly. The arsenic adsorption capacity decreased about 50% in comparison with the system without sulfide addition. For As(V) systems, pre-sulfidation of ferrihydrite decreased 30% sequestration of arsenic on ferrihydrite. Reduction of ferrihydrite by sulfide in As(V) system was higher than that in As(III) system. Geochemical modeling calculations identified formation of thioarsenite in the pre-sulfidation of As(III) system. Formation of arsenic thioanions enhanced As solubility in the pre-sulfidation of As(III) system. The high concentration of sulfide and Fe(II) in pre-sulfidation of ferrihydrite system contributed to saturation of FeS. This supplied new solid phase to immobilize soluble arsenic in aqueous phase. X-ray absorption near edge spectroscopy (XANES) of sulfur K-edge, arsenic K-edge and iron L-edge analysis gave the consistent evidence for the sulfidation reaction of arsenic and ferrihydrite under specific geochemical settings. [ABSTRACT FROM AUTHOR]

The article describes the unique studies of the chemical composition changes of new geological object (tsunami deposits in south Thailand – Andaman Sea Coast) during four years (2005–2008) from the beginning of formation of it (deposition of tsunami transported material, 26 December 2004). The chemical composition of the acid leachable fraction of the tsunami deposits has been studied in the scope of concentration macrocompounds – concentration of calcium, magnesium, iron, manganese and iron speciation – the occurrence of Fe(II), Fe(III) and non-ionic iron species described as complexed iron (Fe complex). The changes of chemical composition and iron speciation in the acid leachable fraction of tsunami deposits have been observed with not clear tendencies of changes direction. For iron speciation changes the transformation of the Fe complex to Fe(III) has been recorded with no significant changes of the level of Fe(II). [ABSTRACT FROM AUTHOR]

Phytostabilisation strategies have proven to be an efficient remediation option for mine tailings, but the adequate plant species and amendments have to be carefully selected. A remediation experiment was carried out at the semi-field level in tailings (pH 3.2, ≈1100, 4700 and 5000 mg kg −1 of As, Pb and Zn, respectively) from the mining district of La Unión-Cartagena (SE Spain). A red mud derivative (Fe/Al oxides), its combination with compost, and hydrated lime (Ca hydroxide) were applied in field plots of 0.25 m 2 . After four months of field stabilisation, tailings were transferred unaltered to a plant growth facility, and Atriplex halimus and Zygophyllum fabago (halophytes) were sown. Three months later, trace element (TE) solubility, plant accumulation and chemical speciation in the tailings pore water were studied. In unamended tailings, soluble TEs concentrations were very high (e.g., 40 mg Zn l −1 ), the dominant species being free ions and SO 4 2- - complexes (>70%). The addition of amendments increased tailings pH (6.7–7), reduced TEs solubility and extractability (>80–99%) and changed the dominant species of soluble Al, Cu, Pb and Zn to hydroxides and/or organo-metallic complexes, but increased slightly the extractable As and soluble Tl concentrations. Plants were able to grow only in amended tailings, and both species presented low levels of Al, As, Cd and Zn. Therefore, the use of combined red mud derivative and compost and halophytes was shown to be a good phytostabilisation strategy, although the dose applied must be carefully chosen in order to avoid possible solubilisation of As and Tl. [ABSTRACT FROM AUTHOR]

Knowledge of elemental localization and speciation in rice ( Oryza sativa L.) roots is crucial for elucidating the mechanisms of Cu accumulation so as to facilitate the development of strategies to inhibit Cu accumulation in rice grain grown in contaminated soils. Using synchrotron-based X-ray microfluorescence and X-ray absorption spectroscopy, we investigated the distribution patterns and speciation of Cu in rice roots treated with 50 μM Cu for 7 days. A clear preferential localization of Cu in the meristematic zone was observed in root tips as compared with the elongation zone. Investigation of Cu in the root cross sections revealed that the intensity of Cu in the vascular bundles was more than 10-fold higher than that in the other scanned sites (epidermis and cortex) in rice roots. The dominant chemical form of Cu (79.1%) in rice roots was similar to that in the Cu-cell wall compounds. These results suggest that although Cu can be easily transported into the vascular tissues in rice roots, most of the metal absorbed by plants is retained in the roots owing to its high binding to the cell wall compounds, thus preventing metal translocation to the aerial parts of the plants. [ABSTRACT FROM AUTHOR]

The co-combustion of sludge (sewage and dredged sludge) with rice husk is expected to become a trend because of its economic and environmental benefits. However, the massive residues from the co-combustion process and the mobility of heavy metals (HMs) warrant special attention. The basic performance and environmental properties of the trace elements (Cr, Cu, Fe, Mn, Ba and Zn) from the co-combustion ashes were studied to promote the further utilization of these materials. These ashes have a shell particle shape, high specific area, high amorphous content and low crystalline phase content. The investigation mainly focused on the environmental properties of these ashes to evaluate the risk of these by-products to the environment. Results show Cu, Mn, and Zn have cumulative leaching concentrations of 1.033, 23.32, and 3.363 mg/L for W, by contrast, Cr, Cu, Fe, Mn, Ba, and Zn have cumulative leaching concentrations of 0.488, 0.296, 8.069, 10.44, 2.568, and 2.691 mg/L for H, which are much greater than the Chinese ground water standard (GB/T14848-93). Meanwhile Mn, Zn, Ba, Cr, and Fe all pose a very high risk for H, while Cu only poses a medium risk, and all HMs in W exhibit much lower contamination levels than those in H by the method of risk assessment code (RAC). It indicates that these ashes have undesirably high levels of HMs that demonstrate high mobility and pose environmental risks according to their leachability and chemical speciation. And the HMs in W show lower mobility and environmental hazards than those in H. [ABSTRACT FROM AUTHOR]

The water level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) in China experiences a drying and wetting rotation every year, and the water level induced redox variation may influence inorganic sulfur speciation and mercury methylation. In this work, a simulative flooding and drying experiment and a sulfate added flooding experiment were conducted to study this topic. The results showed that sulfate was reduced from the 10th d during the flooding period based on the detected sulfide in water and the increased elemental sulfur (S 0 ) in sediment. Sulfate reduction and sulfide re-oxidation led to the increase of S 0 contents with the maximal values of 1.86 and 0.46 mg kg −1 during the flooding and drying period, respectively. Methylmercury (MeHg) content in sediment displayed a rising trend (0.16–0.28 μg kg −1 ) in the first 40 d during the flooding period, and then declined from 0.28 to 0.15 μg kg −1 . A positive correlation between MeHg content and S 0 content in soil ( r = 0.53 , p < 0.05) was found during the flooding period, and a positive but not significant correlation between the percent of MeHg in THg (%MeHg) and S 0 content ( r = 0.85 , p = 0.08). In sulfate added flooding simulation, MeHg content in sediment did not increase with the sulfate concentration increasing. The increased pyrite in high-sulfate treatment may fix mercury through adsorption process. This study demonstrated that inorganic sulfur species especially S 0 and chromium reducible sulfur (CRS) play an important role on mercury methylation in the WLFZ of the TGR. [ABSTRACT FROM AUTHOR]

Deep-sea hydrothermal vent communities, revealing patterns of niche partitioning, live in a limited area characterised by sharp physico-chemical gradients. In this study, we investigated carbon, sulfur, nitrogen stable isotopes as well as arsenic (As) speciations and concentrations for two snails (Alviniconcha sp. and Ifremeria nautilei) and a crustacean, (Eochionelasmus ohtai manusensis), occupying distinct niches in the hydrothermal vent field of the Vienna Woods, Manus Basin, Western Pacific. δ13C values of Alviniconcha sp. (foot), I. nautilei (foot and chitin) and E. o. manusensis (soft tissue) are similar, from −28 to −33‰ (V-PDB). The δ15N values of Alviniconcha sp. (foot and chitin), I. nautilei (foot and chitin) and E. o. manusensis (soft tissue) range from 8.4 to 10.6‰. The δ34S values of Alviniconcha sp. (foot and chitin), I. nautilei (foot) and E. o. manusensis (soft tissue) range from 5.9 to 11.1‰. Using stable isotopes, for the first time, we inferred a Calvin-Benson (RuBisCo) metabolic pathway for Alviniconcha sp. along with the presence of γ- Proteobacteria symbionts for the Vienna Woods communities. For I. nautilei, a feeding pattern is proposed with γ- Proteobacteria symbiosis and a Calvin–Benson–Bassham diet with mixotrophic feeding. E. ohtai manusensis is filtering bacteria with a CBB feeding strategy, with δ15N values indicating possible higher position in the trophic chain. Arsenic concentrations in the dry tissue of Alviniconcha (foot), I. nautilei (foot) and E. o. manusensis (soft tissue) are high, from 4134 to 8478 μg/g, with inorganic As concentrations of 607, 492 and 104 μg/g, respectively and dimethyl arsenic (DMA) concentrations of 11.12, 0.25 and 11.2 μg/g, respectively. Snails occurring in a vent proximal position have higher As concentration than barnacles, a pattern not observed for S concentrations. Arsenosugars were not put in evidence indicating that the available organic material for the vent organisms are not surface derived. [Display omitted] • Sources of nutrition and survival strategies at the active hydrothermal site Vienna Woods, Manus Basin. • d13C, d15N, d34S and element concentrations for the dominant assemblage Alviniconcha sp, I. nautilei , E. ohtai manusensis • Insights into the process of metalloid As bioaccumulation and biotransformation in the investigated marine organisms. • Comparisons with adjacent vent areas of the Manus Basin in order to identify mechanism acting at regional scale. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a toxic metalloid that is a significant global pollutant of the environment and a persistent bioaccumulation carcinogen. Earthworms are frequently employed as sentinel organisms to investigate the bioavailability of As in contaminated soils. However, the process of As accumulation in earthworms and the mechanism of transformation of As species in their bodies are not well understood. The accumulation of As and variation of As species in the earthworms (Eisenia fetida) exposed to sodium arsenite (0, 20, and 80 mg kg−1 As) were investigated in this study. The total As concentration of earthworms in the three treatments at various sample times was dose-dependent on soil As content. After 56 days of exposure, the high concentration treatment had the highest total As content (772 ± 21 mg kg−1) in earthworms, followed by the low concentration treatment (579 ± 42 mg kg−1) and control (31 ± 1 mg kg−1). During 56 days, the proportion of trivalent As in earthworms increased from 70% to more than 90%, while pentavalent As decreased by 11–18%. On day 28, the sum of the four organic As species reached a maximum (<1%). Changes in soil As species and an increase in bioavailable As cause earthworms to accumulate more As. The total As in soil after 56 days of exposure was 9.51 ± 0.50, 25.6 ± 0.60, and 82.8 ± 0.28 mg kg−1, which was not significantly different from the total As in soil before the experiment. These findings are useful in assessing the risk of earthworm exposure to sodium arsenite in the soil. [Display omitted] • Total As concentration in earthworms was dose-dependent on soil As content. • The trivalent arsenic increased and pentavalent arsenic decreased in earthworms. • The sum of the four organic As species reached a maximum (<1%). • The more soil Av-As and Olsen-P, the more As accumulated by earthworms. [ABSTRACT FROM AUTHOR]