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Complete removal of nitrogen, sulfur and carbon in wastewaters by denitrifying sulfide removal (DSR) process can be achieved at stoichiometry sulfide to nitrate ratio (S/N) of 1:1 in expanded granular sludge bed reactor. Wastewaters with varying S/N ratios can adversely impact the DSR performances with deterioration of synergetic cooperation between autotrophic and heterotrophic denitrifiers. DO (dissolved oxygen) serves effectively as supplementary electron receiver for sulfide oxidation, leaving more nitrate for heterotrophic denitrifiers to utilize acetate. The optimal oxygen to sulfide molar ratio (DO/S) is 0.5:1 for complete removal of sulfide, nitrate and acetate at different S/N ratios. The heterotrophic denitrification rate was decreased to 0.03 ± 0.002, 0.24 ± 0.011 and 0.35 ± 0.027 NO 3 − -N·h −1 ·gVSS −1 at S/N ratio of 5:2, 5:5 and 5:8, respectively, when DO/S of 3:1 was performed. This optimal condition was proposed as an easy-to-implement control criterion for subsiding the adverse impact by varying S/N ratios in handling real wastewaters. [ABSTRACT FROM AUTHOR]

Land disposal of dredged sulfide-rich coastal sediments generates secondary coastal acid sulfate soils (CASS), as previously reduced sulfide minerals oxidise to produce acidic drainage rich in Fe, SO 4 2− and rare-earth elements (REEs). Few studies investigate both the source and the sink of REEs in the context of interpreting their mobilisation and potential use in tracing anthropogenic activity. Here we investigate REE signatures in estuarine sediments (and overlying surface waters) that have received acute, long-term (>15 years) acidic drainage from legacy sulfuric dredge spoils. It was found that the dredge spoil continues to act as a source of acidity (pH 3.5–5.5), Fe and REEs during development of CASS, and contains negligible acid volatile sulfide (AVS, a proxy for FeS) and relatively low concentrations of ΣREE (mean 44.5 mg/kg, range 4.1–362 mg/kg). In the receiving sediments, high AVS concentrations (mean 92.2 μmol/g, range 0.38–278 μmol/g) reflect elevated FeS content, likely due to high inputs of Fe and SO 4 2− from the acidic drainage, and correspond with a high concentration of total S (mean 852 μmol/g, range 105–2209 μmol/g) and an accumulation of ΣREE (mean 670 mg/kg, range 19.9–1819 mg/kg). Importantly, where drain sediments that were previously enriched in highly reactive sulfidic minerals and trace elements and have become exposed to the atmosphere (e.g. Site 3) and partially oxidised, they provide a further source of acidification, remobilising the REEs to the downstream sediments. Interestingly, we also found a clear positive correlation between phosphorous and REEs both in the dredge spoil and sediment, suggesting phosphate minerals may act as a sink for REEs in CASS influenced drain sediments. This is further supported by strong positive gadolinium anomalies (1.1–1.6) and high calculated anthropogenic Gd values (12–38%), which may reflect the influence of phosphate fertiliser on this eutrophic system. [ABSTRACT FROM AUTHOR]

Several sulfur compounds are thought to play important roles in the plant tolerance to cadmium (Cd), but the role of inorganic sulfide in Cd tolerance remains largely unknown. In this study, we found that Cd exposure increased the accumulation of soluble sulfide in Arabidopsis plants. When exogenous sulfide, in the form of NaHS, was foliarly applied, Cd-induced growth inhibition and oxidative stress were alleviated. In addition, although the foliar application of sulfide did not affect the total Cd levels, it significantly decreased the soluble Cd fractions in plants. Furthermore, foliar applications of sulfide decreased Cd distribution in the cytoplasm and organelles, but increased Cd retention in the cell wall, which is a less sensitive compartment. These results suggest that the Cd-induced accumulation of soluble sulfide alleviates Cd toxicity in plants by inactivating Cd and sequestering it into the cell wall. [ABSTRACT FROM AUTHOR]

The mining industry produces a huge quantity of sulphidic mine tailings, which cause several short- and long-term environmental problems when disposed by landfilling in impounding lakes. The possibility of immobilizing several heavy metals from gold mine tailings by reactive geopolymerization technique has been investigated in the present study. The chemical stability of geopolymers synthetized by the alkali activation of metakaolin and blast furnace slag and the addition of 40–50 wt% gold mine tailings is demonstrated. The geopolymers were cured at room temperature, and the effects of different Si/Al and Na/Al molar ratios and curing times were investigated. The inertization effectiveness was evaluated by means of leaching tests carried out according to standard EN 12457 after 7 and 28 days and after 18 months. The samples were immersed into the water for 1 day, and the leachable metals in the test solution were determined by ICP-OES. The results show that various elements (Cr, Cu, Ni, Zn and Mn) from gold mine tailings are able to immobilize almost completely by alkali activation with proper co-binder material. The immobilization efficiency were highly improved with longer curing period also for the problematic elements As, V, Sb and B. [ABSTRACT FROM AUTHOR]

The determination of organics biodegradability and corresponding biodegradation kinetics provides valuable information on the optimal design and operation of anaerobic biotechnology especially for sulfidogenesis. This study proposes a deterministic method, i.e. a biochemical sulfide potential (BSP) test, and compares it to the conventional biochemical methane potential (BMP) test in terms of their ability to characterize sulfate-laden organic waste biodegradability. It demonstrated 1.48 times higher degradation of volatile suspended solids (VSS) and 2.60 times more chemical oxygen demand (COD) conversion in its major metabolites than the BMP test. Moreover, it required only four days to complete, compared to the 35 days required by the BMP test. Through the two-substrate first-order hydrolysis model, it was revealed that the shortened time was attributed to the enhanced degradation rates from both readily (eight times) and slowly (nearly 10 times) biodegradable organic substrates in the BSP test compared with the BMP test for the same sulfate-laden organic waste. The findings highlight the inappropriateness of the BMP test to sulfidogenic applications due to the underestimated predictions of organic waste biodegradability and excessive time requirements. Furthermore, the ability of the BSP test to identify the average elemental composition ( C x H y O z N a P b S c ) of substrate biodegradable particulate organics (BPO) is explored and verified using a casein-based validation test. Using BPO elemental composition as the input variable, a BSP biochemical kinetic model is thereby developed to predict BSR performance and possible dynamic process control. Overall, this study demonstrates the applicability and advantages of the BSP test in sulfidogenic applications for characterization of organics biodegradability and identification of BPO average elemental composition, furthermore develops a process model utilizing the derived BPO average elemental composition to provide optimized reactor retention time and substrates feed mixture for optimum performance. [ABSTRACT FROM AUTHOR]

Sulfide at mine tailing ponds poses a source of contamination to the surrounding environment. This study was designed to investigate and assess the fresh and weathered tailings pollution in the vicinity of the Dabaoshan Mine in Guangdong Province, China for in situ rehabilitation. Characterization of the fresh and weathered tailings was performed using geochemical and mineralogical analysis. Results indicated that low sulfur weathered and fresh tailing samples still presented a relatively high acid-production potential. Cu, Zn, Pb, and Cd in fresh tailing samples mainly existed in sulfides, whereas residual silicates were the dominant chemical forms of the four metals in weathered tailing samples. According to Hakanson's ecological risk index assessment, the potential risk individual coefficients of four heavy metals similarly ranked as follows: Cd > Cu > Zn > Pb. The tailing samples in the Dabaoshan Mine presented a much high potential ecological risk. The health risk assessment showed that the carcinogenic risk and non-carcinogenic risk levels of heavy metals in tailing were both lower than 10 −6 and 1.0, respectively. The main exposure route of total non-carcinogenic risk from the tailing was the ingestion of tailing particles. [ABSTRACT FROM AUTHOR]

Environmental pollution caused by sulfide compounds has become a major problem for public health. Hence, there is an urgent need to explore a sensitive, selective, and simple sulfide detection method for environmental monitoring and protection. Here, a novel microbial biosensor was developed using recombinant Escherichia coli BL21 ( E. coli BL21) expressing sulfide:quinone oxidoreductase (SQR) for sulfide detection. As an important enzyme involved in the initial step of sulfide metabolism, SQR oxidizes sulfides to polysulfides and transfers electrons to the electron transport chain. Nanoporous gold (NPG) with its unique properties was selected for recombinant E. coli BL21 cells immobilization, and then glassy carbon electrode (GCE) was modified by the resulting E. coli /NPG biocomposites to construct an E. coli /NPG/GCE bioelectrode. Due to the catalytic oxidation properties of NPG for sulfide, the electrochemical reaction of the E. coli /NPG/GCE bioelectrode is attributed to the co-catalysis of SQR and NPG. For sulfide detection, the E. coli /NPG/GCE bioelectrode showed a good linear response ranging from 50 μM to 5 mM, with a high sensitivity of 18.35 μA mM −1 cm −2 and a low detection limit of 2.55 μM. The anti-interference ability of the E. coli /NPG/GCE bioelectrode is better than that of enzyme-based inhibitive biosensors. Further, the E. coli /NPG/GCE bioelectrode was successfully applied to the detection of sulfide in wastewater. These unique properties potentially make the E. coli /NPG/GCE bioelectrode an excellent choice for reliable sulfide detection. [ABSTRACT FROM AUTHOR]

The production of dimethyl sulfide (DMS) is poorly quantified in tropical reef environments but forms an essential process that couples marine and terrestrial sulfur cycles and affects climate. Here we quantified net aqueous DMS production and the concentration of its cellular precursor dimethylsulfoniopropionate (DMSP) in the sea anemone Aiptasia sp., a model organism to study coral-related processes. Bleached anemones did not show net DMS production whereas symbiotic anemones produced DMS concentrations (mean ± standard error) of 160.7 ± 44.22 nmol g-1 dry weight (DW) after 48 h incubation. Symbiotic and bleached individuals showed DMSP concentrations of 32.7 ± 6.00 and 0.6 ± 0.19 μmol g-1 DW, respectively. We applied these findings to a Monte Carlo simulation to demonstrate that net aqueous DMS production accounts for only 20% of gross aqueous DMS production. Monte Carlo-based estimations of sea-to-air fluxes of gaseous DMS showed that reefs may release 0.1 to 26.3 μmol DMSm-2 coral surface area (CSA) d-1 into the atmosphere with 40% probability for rates between 0.5 and 1.5 μmolm-2 CSA d-1. These predictions were in agreement with directly quantified fluxes in previous studies. Conversion to a flux normalised to sea surface area (SSA) (range 0.1 to 17.4, with the highest probability for 0.3 to 1.0 μmol DMSm-2 SSA d-1 (suggests that coral reefs emit gaseous DMS at lower rates than the average global oceanic DMS flux of 4.6 μmolm-2 SSA d-1 (19.6 Tg sulfur per year). The large difference between simulated gross and quantified net aqueous DMS production in corals suggests that the current and future potential for its production in tropical reefs is critically governed by DMS consumption processes. Hence, more research is required to assess the sensitivity of DMS-consumption pathways to ongoing environmental change in order to address the impact of predicted degradation of coral reefs on DMS production in tropical coastal ecosystems and its impact on future atmospheric DMS concentrations and climate. [ABSTRACT FROM AUTHOR]

The Zheyaoshan deposit is the largest within the Baiyinchang (BYC) volcanic-hosted massive sulfide (VHMS) district, located in the northern Qilian orogenic belt of North China. The deposit is hosted by quartz keratophyre tuffs, with wall-rock alteration mainly comprising chlorite, sericite, quartz, pyrite and epidote. Mineral assemblages within the altered host rocks can be divided into a sericite-quartz-dominant assemblage (sericite-silicified zone), a chlorite-dominant assemblage (chlorite-dominant zone) and a pyrite-dominant assemblage (mineralized zone) based on geochemical analysis and alteration characteristics. We have conducted detailed processing and critical analysis of the geochemical data of both the altered and least-altered host rocks in order to investigate the problem of closure in the geochemical dataset to eliminate the influence that each component has on the other in terms of mass change, and have applied the standardized method of the mass change calculation to analyze this data. The results show that: (1) the sericite-silicified zone formed along fissures due to the ingress of hydrothermal fluids, with MnO 2 , Na 2 O and CaO being mobilized into the hydrothermal fluids leached and MgO, Fe 2 O 3 , SiO 2 , K 2 O, BaO deposited. Additionally, Ag, Cu and chalcophile elements (Ag, As and Bi) were enriched while Pb, Zn and large ion lithophile elements (LILEs) (Cs, Sr, Eu, Be) were mobilized into hydrothermal fluids; (2) the physiochemical conditions and pH levels of the hydrothermal fluids changed during sericitization, with MgO, Fe 2 O 3 , BaO being further enriched and MnO, Na 2 O, CaO further depleted, leading to formation of chlorite and the initial precipitation of metallogenic the (Cu, Zn, Pb) and chalcophile elements (Ag, As, Bi); (3) the negative Eu anomaly was mainly due to its strong activity when Eu is mobilized into the hydrothermal fluids during since plagioclase break-down during the sericite-silicification process; (4) AI and CCPI values gradually increase towards the orebody. The chlorite-dominant assemblage and sericite-quartz-dominant assemblage on the periphery of the chlorite-dominant zone can all be used as vectors towards the volcanic massive sulfide orebody and for regional-scale mineral exploration. Either leached elements or enriched elements can be considered as significant indicator elements and as prospective indicators for geochemical exploration within the BYC district. The Eu anomaly may be especially useful as an indicator for distinguishing the least-altered rocks which has great significance for exploration on the regional scale. [ABSTRACT FROM AUTHOR]

The organic enrichment of surficial sediments has a known effect on benthic faunal communities due largely to oxygen depletion and sulfide toxicity. Total dissolved sulfide (free S − 2 = H 2 S + HS − + S 2 − ) concentrations in sediments are widely measured as a practical indicator of community effects. However, the standard ion selective electrode (ISE) method for free S − 2 analysis can provide biased results owing to the inclusion of non-toxic mineral sulfides and the oxidation and volatilization of free S − 2 . A rapid field protocol was developed that alleviates these problems while also providing data on dissolved oxygen concentrations. Sediments collected near salmon aquaculture pens over cohesive and permeable substrates were analysed using the standard and new protocols. The results confirm previous conclusions of artifacts with the standard ISE method, while the dual indicator approach more accurately describes the stages, spatial extent and magnitude of sediment geochemical alterations affecting benthic communities. [ABSTRACT FROM AUTHOR]

In this study, the effect of natural organic matter (NOM) composition (humic acid (HA) or fulvic acid (FA)) on dissolution, reactive oxygen species (ROS) generation, and toxicity of sulfide nanoparticles (NPs) was investigated under UV irradiation. NOM acted as a UV filter or antioxidant, decreasing ROS (O 2 − , OH, and 1 O 2 ) generation by WS 2 and MoS 2 NPs. The higher light-absorbing fractions of HA in NP/HA mixtures and the faster reaction rate of HA with ROS resulted in higher inhibition effect of HA than FA on O 2 − and OH generation by WS 2 and MoS 2 NPs. Both HA and FA completely inhibited 1 O 2 generation by WS 2 and MoS 2 NPs. NOM could transfer electrons to CdS and promote its O 2 − generation. No measurable amount of OH was generated by CdS with or without NOM. FA decreased 1 O 2 generation by CdS more significantly than HA due to the higher reaction rate between FA and 1 O 2 . HA showed a higher inhibition effect on the dissolution rate of CdS and WS 2 NPs than FA. Both HA and FA played minor roles in the toxicity of CdS toward Escherichia coli but decreased the toxicity of MoS 2 and WS 2 due to the reduced ROS generation and/or dissolution concentrations. [ABSTRACT FROM AUTHOR]

Sulfide is highly toxic, corrosive, malodorous and may cause many other hazards; therefore, it is necessary to take effective measures to control its emission to the environment. Many physicochemical processes have been devised to separate sulfur from wastewaters. Compared with those traditional methods, biological sulfide removal processes not only have high removal rates, but also generate elemental sulfur, thus recovering mineral resources from wastes. In the paper, the generation methods of elemental sulfur in biological sulfide removal process are reviewed and the characteristics of biologically produced sulfur are described, accordingly the recovery methods of elemental sulfur from wastewater are discussed. [ABSTRACT FROM AUTHOR]

This study investigates the morphology, mineralogy, and geochemistry of seafloor massive sulfide (SMS) deposits from six back-arc hydrothermal vent fields along the Eastern Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) in the context of endmember vent fluid chemistry and proximity to the Tonga Subduction Zone. To complement deposit geochemistry, vent fluid analyses of Cu, Zn, Ba, Pb and H 2,(aq) were completed to supplement existing data and enable thermodynamic calculations of mineral saturation states at in situ conditions. Results document southward increases in the abundance of mantle-incompatible elements in hydrothermal fluids (Ba and Pb) and SMS deposits (Ba, Pb, As, and Sb), which is also expressed in the abundance of barite (BaSO 4 ) and galena (PbS) in SMS deposits. These increases correspond to a decrease in distance between the ELSC/VFR and the Tonga Subduction Zone that correlates with a change in crustal lithology from back-arc basin basalt in the north to mixed andesite, rhyolite, and dacite in the south. Barite influences deposit morphology, contributing to the formation of horizontal flanges and squat terraces. Results are also consistent with a regional-scale lowering of hydrothermal reaction zone temperatures from north to south (except at the southernmost Mariner vent field) that leads to lower-temperature, higher-pH vent fluids relative to mid-ocean ridges of similar spreading rates (Mottl et al., 2011). These fluids are Cu- and Zn-poor and the deposits formed from these fluids are Cu-poor but Zn-rich. In contrast, at the Mariner vent field, higher-temperature and lower pH vent fluids are hypothesized to result from higher reaction zone temperatures and the localized addition of acidic magmatic volatiles (Mottl et al., 2011). The Mariner fluids are Cu- and Zn-rich and vent from SMS deposits that are rich in Cu but poor in Zn with moderate amounts of Pb. Thermodynamic calculations indicate that the contrasting metal contents of vent fluids and SMS deposits can be accounted for by vent fluid pH. Wurtzite/sphalerite ((Zn, Fe)S) and galena (PbS) are saturated at higher temperatures in higher-pH, Zn-, Cu-, and Pb-poor ELSC/VFR vent fluids, but are undersaturated at similar temperatures in low-pH, Zn-, Cu-, and Pb-rich vent fluids from the Mariner vent field. Indicators of pH in the ELSC and VFR SMS deposits include the presence of co-precipitated wurtzite and chalcopyrite along conduit linings in deposits formed from higher pH fluids, and different correlations between concentrations of Zn and Ag in bulk geochemical analyses. Significant positive bulk geochemical Zn:Ag correlations occur for deposits at vent fields where hydrothermal fluids have a minimum pH (at 25 °C) < 3.3, while correlations of Zn:Ag are weak or negative for deposits at vent fields where the minimum vent fluid pH (at 25 °C) > 3.6. Data show that the compositions of the mineral linings of open conduit chimneys (minerals present, mol% FeS in (Zn,Fe)S) that precipitate directly from hydrothermal fluids closely reflect the temperature and sulfur fugacity of sampled hydrothermal fluids. These mineral lining compositions thus can be used as indicators of hydrothermal fluid temperature and composition (pH, metal content, sulfur fugacity). [ABSTRACT FROM AUTHOR]

A comprehensive study of the organic chemistry and mineralogy of an ultracarbonaceous micrometeorite (UCAMM D05IB80) collected from near the Dome Fuji Station, Antarctica, was carried out to understand the genetic relationship among organic materials, silicates, and water. The micrometeorite is composed of a dense aggregate of ∼5 µm-sized hollow ellipsoidal organic material containing submicrometer-sized phases such as glass with embedded metal and sulfides (GEMS) and mineral grains. There is a wide area of organic material (∼15 × 15 μm) in its interior. Low-Ca pyroxene is much more abundant than olivine and shows various Mg/(Mg + Fe) ratios ranging from ∼1.0 to 0.78, which is common to previous works on UCAMMs. By contrast, GEMS grains in this UCAMM have unusual chemical compositions. They are depleted in both Mg and S, which suggests that these elements were leached out from the GEMS grains during very weak aqueous alteration, without the formation of phyllosilicates. The organic materials have two textures—smooth and globular with an irregular outline—and these are composed of imine, nitrile and/or aromatic nitrogen heterocycles, and amide. The ratio of nitrogen to carbon (N/C) in the smooth region of the organics is ∼0.15, which is five times higher than that of insoluble organic macromolecules in types 1 and 2 carbonaceous chondritic meteorites. In addition, the UCAMM organic materials are soluble in epoxy and are thus hydrophilic; this polar nature indicates that they are very primitive. The surface of the material is coated with an inorganic layer, a few nanometers thick, that consists of C, O, Si, S, and Fe. Sulfur is also contained in the interior, implying the presence of organosulfur moieties. There are no isotopic anomalies of D, 13 C, or 15 N in the organic material. Interstellar photochemistry alone would not be sufficient to explain the N/C ratio of the UCAMM organics; therefore, we suggest that a very small amount of fluid on a comet must have been necessary for the formation of the UCAMM. The GEMS grains depleted in Mg and S in the UCAMM prove a very weak degree of aqueous alteration; weaker than that of carbonaceous chondrites. Short-duration weak alteration probably caused by planetesimal shock locally melted cometary ice grains and released water that dissolved the organics; the fluid would likely have not mobilized because of the very low thermal conductivity of the porous icy body. This event allowed the formation of the large organic puddle of the UCAMM, as well as organic matter sulfurization, formation of thin membrane-like layers of minerals, and deformation of organic nanoglobules. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries have attracted considerable attention due to its high theoretical specific capacity, low cost, environmental friendliness, etc. However, the dissolution of polysulfide intermediate in the electrolyte leads to rapid capacity decay in the charge-discharge process. A sulfur-based cathode with the specific discharge capacity of 630 mAh g−1 and ultrahigh capacity retention ratio of 0.11% per cycle after 400 cycles at 0.5 C that simply blend the sublimed sulfur and acetylene black in the mortar with the polyamide-6 (PA6) as binder is reported. The intense complexation between the lithium polysulfide and amide groups (CONH) in PA6 can effectively inhibit the 'shuttling effect' and reduce the loss of active materials during the charge-discharge process. The discovery provides a handy and practicable strategy for developing the excellent cycling stability lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

A novel denitrifying sulfide removal microbial fuel cell (MFC), using sulfide and nitrate separately as the anodic electron donor and the cathodic electron acceptor, was explored to recover power coupled with pollutants removal. Power recovery coupled with sulfide and nitrate removal in this MFC was achieved under different buffers, hydraulic retention times (HRTs) and temperatures. Bicarbonate was deemed as a suitable alternative buffer to phosphate in this MFC, obtaining comparable power recovery and pollutant removal loadings but without potential secondary pollution. Shortening HRT from 5.54 h to 2.27 h or increasing temperature from 20 °C to 30 °C favored both power recovery and pollutants removal. The suitable HRT and temperature for this MFC were found to be 2.77 h and 30 °C, achieving a power density of 2.80 ± 0.05 W/m 3 NC, a sulfide removal loading of 1.07 ± 0.03 kg S/(m 3 NC d), and a nitrate removal loading of 14.4 ± 0.3 g N/(m 3 NC d). Shortening HRT and lowering temperature would be beneficial to suppress sulfate formation, but more than 71.9% of sulfide was oxidized to sulfate in current study. [ABSTRACT FROM AUTHOR]

Fungi include a vast group of eukaryotic organisms able to colonise different natural, anthropised and extreme environments, including marine areas contaminated by metals. The present study aims to give a first multidisciplinary characterisation of marine bottom sediments contaminated by metals (Cd, Co, Cr, Cu, Ni, and Zn), originating in the water leakage from an abandoned Fe-Cu sulphide mine (Libiola, north-western Italy), and evaluate how the chemical and physical parameters of water and sediments may affect the benthic fungal communities. Our preliminary results showed the high mycodiversity of the marine sediments studied (13 genera and 23 species of marine fungi isolated), and the great physiological adaptability that this mycobiota evolved in reaction to the effects of the ecotoxic bottom sediment contamination, and associated changes in the seawater parameters. [ABSTRACT FROM AUTHOR]

Most of the existing Life Cycle Assessment studies addressing the environmental impacts of copper production exclude the emissions generated by tailings. This study aims at compiling the life cycle inventory related to the storage of tailings from sulfidic copper ore concentration, in the specific case of a plant located in south-west Poland. The environmental impacts induced by these tailings are compared with the rest of the environmental impacts of copper production. This study demonstrates that, when considering toxicity-related environmental impact categories, the potential impacts related to the storage of tailings in dedicated facilities are a key issue in the life cycle impact assessment of copper concentrate production, and consequently of copper production. Depending on the temporal perspective considered in the study, the disposal of sulfidic tailings induces impacts that may be several orders of magnitude larger than those of copper concentrate production. Yet, when limiting the considered temporal perspective to 100 years, tailings storage has a relatively low contribution to the impacts of concentrate production. The discrepancy between the impacts related to copper concentrate production and those of tailings disposal is highly dependent on both the temporal perspective considered in the LCA study and the actual conditions of tailings management in the future. [ABSTRACT FROM AUTHOR]

Severe metal pollution due to industrial effluents releases has been documented in Jiulong River estuary, Southern China. However, integrated understanding of trace metal behavior in the sediment is lacking. In the present study, DGT (diffusive gradients in thin films) technique was employed together with sediment cores to study the porewater dynamics of trace metals as well as the benthic exchange fluxes from four sampling sites over three different months. The sedimentary environment showed distinct spatial and temporal variations due to effluent discharge and biological activities. Metal behavior was controlled by early diagenetic reactions below the interface, in suboxic layer and in deeper sediment. Precipitation as sulfides and adsorption onto Mn/Fe (hydr)oxides were important in scavenging trace metals. Estimated exchange fluxes at sediment-water interface in this estuary indicated that the overlying water was a major source for trace metals, whereas sediments could also be the source if surface remobilization (Mn/Fe reduction) dominated. Our results highlighted the impacts of both natural and anthropogenic processes on the source, fate and transformation of trace metals in this dynamic system. [ABSTRACT FROM AUTHOR]

The inhibitory effects of sulfide on microbial processes during anaerobic digestion have been widely addressed. However, other effects of sulfide are less explored, given that sulfide is a potential sulfur source for microorganisms and its high reactivity triggers a suit of abiotic reactions. We demonstrated that sulfide interaction with Fe regulates the dynamics and activities of microbial community during anaerobic digestion. This was manifested by the S:Fe molar ratio, whose increase adversely influenced the acetoclastic methanogens, Methanosaeta , and turnover of acetate. Dynamics of hydrogenotrophic methanogens, Methanoculleus and Methanobrevibacter , were presumably influenced by sulfide-induced changes in the partial pressure of hydrogen. Interestingly, conversion of the long-chain fatty acid (LCFA), oleate, to methane was enhanced together with the abundance of LCFA-degrading, β-oxidizing Syntrophomonas at an elevated S:Fe molar ratio. The results suggested that sulfur chemical speciation is a controlling factor for microbial community functions in anaerobic digestion processes. [ABSTRACT FROM AUTHOR]

Deep-sea hydrothermal vent ecosystems are known to support remarkably diverse microbial communities, ranging from chemoautotrophic prokaryotes to heterotrophic prokaryotes and microeukaryotes. While fungi have generally been identified as an important component of various microbial communities in the environment, little is known about the species richness and abundance of such microorganisms in deep-sea hydrothermal vent ecosystems. In this study, a combined culture-dependent and culture-independent sequence-based approach was used to investigate fungal distribution and diversity at a deep-sea hydrothermal vent site located at the Mid-Atlantic Ridge of the South Atlantic Ocean. Sequence analyses showed that the fungal community was dominated by members of the Ascomycota and the Basidiomycota. Several new phylotypes (28 of 65 total fungal OTUs and 2 of 19 culturable fungal phylotypes) were identified, contributing to the literally unknown diversity of fungi in this understudied habitat. The fungal community structures in the chimney samples were distinct from those in three sulfide samples. The qPCR results revealed that fungal LSU rRNA gene copy numbers ranged from 5.88×10 5 to 6.77×10 6 copies/gram rock (wet weight), and the Ascomycota was significantly more abundant 2–3 orders) than the Basidiomycota. Our findings provide new insights into the diversity and abundance of fungi in deep-sea hydrothermal vent ecosystems, which increases our knowledge and understanding of the fungal diversity in deep-sea environments. [ABSTRACT FROM AUTHOR]

Seafloor hydrothermal polymetallic sulfide deposits are a new type of resource, with great potential economic value and good prospect development. This paper discusses turbidity, oxidation-reduction potential, and temperature anomalies of hydrothermal plumes from the Zouyu-1 and Zouyu-2 hydrothermal fields on the southern Mid-Atlantic Ridge. We use the known location of these vent fields and plume data collected in multiple years (2009, 2011, 2013) to demonstrate how real-time plume exploration can be used to locate active vent fields, and thus associated sulfide deposits. Turbidity anomalies can be detected 10 s of km from an active source, but the location precision is no better than a few kilometers because fine-grained particles are quasi-conservative over periods of many days. Temperature and oxidation-reduction potential anomalies provide location precision of a few hundred meters. Temperature anomalies are generally weak and difficult to reliably detect, except by chance encounters of a buoyant plume. Oxidation-reduction potential is highly sensitive (nmol concentrations of reduced hydrothermal chemicals) to discharges of all temperatures and responds immediately to a plume encounter. Real-time surveys using continuous tows of turbidity and oxidation-reduction potential sensors offer the most efficient and precise surface ship exploration presently possible. [ABSTRACT FROM AUTHOR]

Enzymatic dehairing in aqueous medium is in demand over lime-sulphide based conventional method of leather making due to the environmental concerns. However, the use of water not only depletes precious natural resource but also leads to incomplete hair removal. Here, we report the enzyme-only dehairing of sheepskins in chosen green solvents. The enzyme showed better activity in the presence of heptane and propylene glycol than in aqueous medium. This was substantiated with a limited computational study involving protease-solvent interface. Further, it is demonstrated that the solvent-enzyme mixture removed hair more efficiently without any sulphide and lime than aqueous enzyme-lime-sulphide system and produced leathers with properties similar to conventional method. Also, a complete elimination of sulphide emission and reduction in the pollution loads such as lime and total dissolved solids is observed. Recycling studies demonstrate that it is industrially feasible to replace water with green solvents for enzymatic dehairing process. The findings have great implications for not only leather industry but also other industries where usage of enzyme is contemplated. [ABSTRACT FROM AUTHOR]

Magnesium hydroxide [Mg(OH)2 is a commonly used chemical for controlling corrosion and odor problems in sewers by reducing the transfer of hydrogen sulfide from the liquid to the gas phase through pH elevation. The effectiveness of many current dosing practices is unsatisfactory due to negligence of the dynamics of sewage flow and characteristics, and their effects on sewage pH. This paper reports the design and validation of the first online control algorithm for [Mg(OH)2 dosing to sewers. The control algorithm consists of a combination of feedforward and feedback loops. A feedback controller is used to calculate the [Mg(OH)2 dosing rate to raise the sewage pH at the pumping station to the set-point. A feedforward controller is then used to calculate the additional [Mg(OH)2 dose based on the prediction of acid production in the downstream sewer pipe due to in-sewer processes. A further feedback controller is used to adjust the [Mg(OH)2 dosing rate to correct the error between the sewage pH at the end of the pipe and the pH set-point. Following comprehensive assessment using modeling and simulation, the control was successfully validated and its effectiveness demonstrated in a 2-month field study. The online control algorithm reduced the variation of pH at the discharge point, i.e., from 8.73 ± 0.21 to 8.59 ± 0.10. In addition to improved sulfide control, the controller also resulted in 15% saving in chemical consumption, leading to significant financial benefits and lower environmental footprint. It was also found that the sewage flow rate should be predicted online for sewers influenced by rainwater infiltration as the variation of flow rate and sewage dilution are important disturbances for the controller. [ABSTRACT FROM AUTHOR]

Bizerte Lagoon is a southern Mediterranean semi-enclosed lagoon with a maximum depth of 12 m. After assessing sediment quality, the authors report on the physicochemical characteristics of the lagoon's surface sediment using SEM (simultaneously extracted metals) and AVS (acid volatile sulfides) as proxies. Biogeochemical tools are used to investigate the environmental disturbance at the water-sediment interface by means of SEM and AVS to seek conclusions concerning the study area's pollution status. Results confirm accumulation of trace elements in sediment. The use of the SEM-AVS model with organic matter in sediment (ƒOC) confirms possible bioavailability of accumulated trace elements, especially Zn, in the southern part of the lagoon, with organic matter playing an important role in SEM excess correction to affirm a nontoxic total metal sediment state. Individual trace element toxicity is dependent on the bioavailable fraction of SEM on sediment, as is the influence of lagoon inflow from southern water sources on element bioavailability. Appropriate management strategies are highly recommended to mitigate any potential harmful effects on health from this heavy-metal-based pollution. [ABSTRACT FROM AUTHOR]

The present study investigates the impact of tannery effluents on the self-purification capacity and the local macroinvertebrate community of one natural stream. As the concentration of chromium and sulfide increased from up- to downstream sites, the reduction of suspended solids, 5-days biological oxygen demand (BOD), chemical oxygen demand and nitrification capacity decreased by 61 %, 21 %, 30 % and 74 %, respectively. Similarly, the share of Ephemeroptera, Plecoptera, and Trichoptera on the macroinvertebrate community decreased from 24 % to 0 %. Also the diversity (Simpson's) index and the correlation between the physicochemical parameters, BOD reduction, the macroinvertebrate abundance and the chromium concentration underpin the importance of the contamination by tannery effluents for the degradation of the stream habitat quality. In conclusion, although the physicochemical parameters indicate that the self-purification of the river can be maintained for a certain stream section, the biodiversity of the river is severely compromised. [ABSTRACT FROM AUTHOR]

The Ediacaran-Cambrian interval was an eventful transitional period, when dynamic interactions between the biosphere and its physical environment allowed the Earth System to cross into a new state, characterized by the presence of metazoans, more equable climates and more expansive oxygenation of the oceans. Due to the retreat of widespread sulphidic conditions, redox-sensitive trace-metals could accumulate to a greater extent in 'black shales' deposited in localized anoxic/euxinic environments, such as highly productive ocean margins. This study investigates the concentrations of the redox-sensitive trace-metals molybdenum and vanadium in organic-rich sedimentary rocks from seven sections of the Yangtze Platform, slope and basin. Iron speciation analyses were carried out in order to distinguish oxic, anoxic-ferruginous and anoxic-sulphidic settings, while sulphur and nitrogen isotope ratios were measured to gain insight into sulphate and nitrate availability, respectively, in the context of changing redox conditions. The data herein demonstrate an overall increase in redox-sensitive trace-metal contents in black shales across the Ediacaran-Cambrian transition, but with marked temporal and spatial variability. Euxinia is evident in South China before 551 Ma in the Ediacaran, and again in the early Cambrian. However, some time-equivalent sections are not enriched in redox-sensitive trace-metals, and also exhibit contrasting S-isotope and N-isotope systematics. A more complex configuration of the Yangtze Platform, for example with vast intra-shelf basins, together with changing (generally rising) eustatic sea-level may account for this variability. In this regard, it is proposed that a mid-depth sulphidic wedge, caused by nutrient upwelling over the south-east platform margins, migrated over time (but generally landward), leading to spatially variable redox conditions determined by sea-level, currents and bathymetric constraints. The changing extents of anoxia and euxinia appear to have limited the distribution of emerging Ediacaran and Cambrian ecosystems. [ABSTRACT FROM AUTHOR]

In order to characterize the sulfide-derived SO 4 fluxes in the Rio Grande, we collected seasonally (from 2009 to 2011) riverine, agricultural drain and groundwater samples and analyzed them for their major element chemistries and the δ 34 S and δ 18 O of dissolved SO 4 . The observed variation of δ 34 S (− 4 to + 8‰) and δ 18 O (− 2 to + 7‰) in the Rio Grande mainly resulted from mixing between sulfide- and sulfate-derived SO 4 of volcanic and sedimentary origin. Our S isotope mass balance suggests that the average sulfide-derived SO 4 flux usually accounted for 83–94% (± 10–20%) of the sulfate source in the upstream Rio Grande and decreased downstream to 45–51% because of increasing contributions of sulfate-derived SO 4 . The sulfide-derived SO 4 was related to snow melt in the high elevation watersheds and recycling of surficial sulfate-rich salts by episodic water activity in dry areas at lower elevations. Additionally, elevated bedrock sulfide contents in volcanic and some sedimentary terrains of the studied area have been recognized as important factors contributing to sulfide-derived SO 4 in the Rio Grande. [ABSTRACT FROM AUTHOR]

The aerobic biotransformation pathways of 4:2, 6:2, and 8:2 fluorotelomer thioether amido sulfonate (FtTAoS) were characterized by determining the fate of the compounds in soil and medium microcosms amended with an aqueous film-forming foam (AFFF) solution. The biotransformation of FtTAoS occurred in live microcosms over approximately 40 days and produced 4:2, 6:2, and 8:2 fluorotelomer sulfonate (FtS), 6:2 fluorotelomer unsaturated carboxylic acid (FtUCA), 5:3 fluorotelomer carboxylic acid (FtCA), and C4 to C8 perfluorinated carboxylic acids (PFCAs). Two biotransformation products corresponding to singly and doubly oxygenated forms of 6:2 FtTAoS were also identified through high resolution mass spectrometry (MS) analysis and liquid chromatography tandem-MS. An oxidative assay was used to indirectly quantify the total concentration of polyfluorinated compounds and check the mass balance. The assay produced near complete mass recovery of FtTAoS after biotransformation, with 10% (mol/mol) of the amended FtTAoS accounted for in FtS, FtCA, and PFCA products. The transformation rates of identified products appear to be slow relative to FtTAoS, indicating that some intermediates may persist in the environment. This study confirms some of the sources of FtS and PFCAs in groundwater and soil at AFFF-impacted sites and suggests that fluorinated intermediates that are not routinely measured during the biotransformation of PFASs may accumulate. [ABSTRACT FROM AUTHOR]

Sulfide-modified nanoscale zerovalent iron (S-nZVI) is attracting a lot of attention due to its ease of production and high reactivity with organic pollutants. However, its structure is still poorly understood and its potential application in heavy metal remediation has not been explored. Herein, the structure of S-nZVI and its cadmium (Cd) removal performance under different aqueous conditions were carefully investigated. Transmission electron microscopy (TEM) with an energy-dispersive X-ray spectroscopy (EDS) analysis suggested that sulfur was incorporated into the zerovalent iron core. Scanning electron microscopy (SEM) with EDS analysis demonstrated that sulfur was also homogeneously distributed within the nanoparticles. When the concentration of Na 2 S 2 O 4 was increased during synthesis, a flake-like structure (FeS x ) increased significantly. S-nZVI had an optimal Cd removal capacity of 85 mg/g, which was >100% higher than for pristine nZVI. Even at pH 5, over 95% removal efficiency was observed, indicating sulfide compounds played a crucial role in metal ion removal and particle chemical stability. Oxygen impaired the structure of S-nZVI but enhanced Cd removal capacity to about 120 mg/g. Particle aging had no negative effect on removal capacity of S-nZVI, and Cd-containing mixtures remained stable in a two months experiment. S-nZVI can efficiently sequester dissolved metal ions from different contaminated water matrices. [ABSTRACT FROM AUTHOR]

Reduced water consumption (RWC), for water conservation purposes, is expected to change the wastewater composition and flow conditions in sewer networks and affect the in-sewer transformation processes. In this study, the impact of reduced water consumption on sulfide and methane production in rising main sewers was investigated. Two lab-scale rising main sewer systems fed with wastewater of different strength and flow rates were operated to mimic sewers under normal and RWC conditions (water consumption reduced by 40%). Sulfide concentration under the RWC condition increased by 0.7–8.0 mg-S/L, depending on the time of a day. Batch test results showed that the RWC did not change the sulfate-reducing activity of sewer biofilms, the increased sulfide production being mainly due to longer hydraulic retention time (HRT). pH in the RWC system was about 0.2 units lower than that in the normal system, indicating that more sulfide would be in molecular form under the RWC condition, which would result in increased sulfide emission to the atmosphere as confirmed by the model simulation. Model based analysis showed that the cost for chemical dosage for sulfide mitigation would increase significantly per unit volume of sewage, although the total cost would decrease due to a lower sewage flow. The dissolved methane concentration under the RWC condition was over two times higher than that under the normal flow condition and the total methane discharge was about 1.5 times higher, which would potentially result in higher greenhouse gas emissions. Batch tests showed that the methanogenic activity of sewer biofilms increased under the RWC condition, which along with the longer HRT, led to increased methane production. [ABSTRACT FROM AUTHOR]

Nickel-, copper-, and platinum group element (PGE)-enriched sulphide mineralization in large igneous provinces has attracted numerous PGE studies. However, the distribution and behavior of PGEs as well as the history of sulphide saturation are less clear in oxide-dominated mineralization. Platinum group elements of oxide-bearing layered mafic intrusions from the Emeishan large igneous province are examined in this study. Samples collected from the Baima and Taihe oxide-bearing layered gabbroic intrusions reveal contrasting results. The samples from Baima gabbroic rocks have low total PGE abundances (ΣPGE < 4 ppb) whereas the Taihe gabbroic rocks, on average, have more than double the concentration but are variable ranging from ΣPGE < 2 ppb to ΣPGE ∼300 ppb. The Baima gabbro is platinum-subgroup PGE (PPGE = Rh, Pt and Pd) enriched and iridium-subgroup PGE (IPGE = Os, Ir and Ru) depleted, with a distinct positive Ru anomaly on a primitive mantle normalized multi-element plot. The Taihe gabbros are also PPGE enriched but with negative Ru and Pd anomalies on a primitive mantle normalized multi-element plot. The PGE concentrations of Baima rocks are indicative of fractionation of a relatively evolved, mafic, S-undersaturated parental magma that was affected by earlier sulphide segregation. In contrast, the Taihe rocks record evidence of both S-saturated and S-undersaturated conditions and that the parental magma was likely emplaced very close to S-saturation. Comparisons of the platinum group element contents in the Emeishan flood basalts and the Emeishan oxide-bearing intrusions suggest that the PGE budget in a magma is not controlled by magma series (high-Ti vs. low-Ti), but very much by crustal contamination. The unlikelihood of substantial crustal contamination in the Taihe magma allowed the magma to remain S-undersaturated for a longer duration. PGE and sulphide mineralization was not identified in the Taihe intrusion but the presence of one PGE-enriched sample (Pt + Pd = ∼300 ppb) suggests that the parental magma likely did not experience sulphide segregation and is a potential target for further prospecting. [ABSTRACT FROM AUTHOR]

Sulfide-bearing mill wastes are sources of high concentrations of acid, soluble metals, Sb, and As. Contents of Cu, Zn, Fe, Pb, Cd, As, and Sb in wastes of the Belovo Zn-processing and the Karabash mineral-processing plants (Russia) exceed the average content in the upper continental crust and background soils. High-dissolved metal and As concentrations are found in acid drainages, which form as a result of interaction between sulfide wastes and water. Monitoring research using geochemical and geophysical methods was performed to evaluate the contamination of the surrounding area (water and bottom sediments in the contaminated rivers and snow cover). Zones of geochemical anomalies were identified where the concentrations of Fe, Cu, Zn, Cd, Pb, and As are 2–3 orders of magnitude higher than in drinking water standards (for rivers) and background levels (for snow). The use of geophysical methods allowed us to prove penetration of drainage solutions into the groundwaters. The total environmental damage caused by the pollution of water and land resources in the Belovo Zn-processing plant waste disposal area amounted to $156 million at the time of 2011, and could reach $480 million by 2030, if steps are not taken in recycling and remediation of disturbed areas. [ABSTRACT FROM AUTHOR]

The stability of Cu-Al-5Ni ternary alloy used in the manufacture of NaCl and Na2SO4 from the Lake Qaroun in Egypt was investigated in 3.5% NaCl in the presence of sulfide ions. The electrochemical reactions of Cu-Al-5Ni electrode in the test solutions were studied using electrochemical impedance spectroscopy measurements. In addition surface examination and morphological studies were applied using scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The results of impedance measurements at open circuit potential have shown that the overall impedance of the system decreases with the increase in sulfide ion concentration and increases with immersion time due to continuous growth of the passive film on the alloy surface. The EDAX analysis showed the presence of copper, aluminum and nickel compounds, Cu-oxides, Cu-chlorides and Cu2S on the alloy surface. [ABSTRACT FROM AUTHOR]

Snottites are extremely acidic (pH 0–2) biofilms that form on the walls and ceilings of hydrogen sulfide-rich caves. Recent work suggests that microbial communities including snottites and related cave wall biofilms accelerate cave formation by oxidizing sulfide to sulfuric acid. Therefore, we used full-cycle rRNA methods and metagenomics to explore the community composition and sulfur metabolism of snottites from the sulfidic Frasassi and Acquasanta cave systems, Italy. Acquasanta snottites were dominated by strains ofAcidithiobacillus thiooxidans, with a smaller population ofFerroplasmasp. Frasassi snottites were also dominated byAt. thiooxidansbut with a more diverse community including relatives of ‘G-plasma’ (Thermoplasmatales),Acidimicrobium, and rare taxa. We identified diverse homologues of sulfide:quinone oxidoreductase (SQR) in the metagenomic datasets. Based on phylogenetic analysis, the numerically dominantAt. thiooxidanspopulations have four different types of SQR, whileFerroplasmahas two andAcidimicrobiumand G-plasma each have one. No other genetic evidence for sulfur oxidation was detected for eitherAcidimicrobiumor G-plasma, suggesting that they do not generate sulfuric acid. Our results confirm earlier findings thatAt. thiooxidansis the dominant primary producer and sulfide oxidizer in sulfidic cave snottites. [ABSTRACT FROM PUBLISHER]

We conducted a species-level study of molluscs associated with a 5-m long carcass of a minke whale at a depth of 125 m in the Kosterfjord (North Sea, Sweden). The whale-fall community was quantitatively compared with the community commonly living in the surrounding soft-bottom sediments. Five years after the deployment of the dead whale at the sea floor, the sediments around the carcass were dominated by the bivalveThyasira sarsi, which is known to contain endosymbiotic sulphur-oxidizing bacteria, while background sediments were dominated by another thyasirid,T. equalis, less dependent on chemosynthesis for its nutrition. The Kosterfjord samples were further compared at the species level with mollusc abundance data derived from the literature, including samples from different marine settings of the west coast of Sweden (active methane seep, fjords, coastal and open marine environments). The results show high similarity between the Kosterfjord whale-fall community and the community that developed in one of the Swedish fjords (Gullmar Fjord) during hypoxic conditions. This study indicates that at shallow-water whale-falls, the sulphophilic stage of the ecological succession is characterized by generalist chemosynthetic bivalves commonly living in organic-rich, sulphidic environments. [ABSTRACT FROM AUTHOR]

Because of its broad usage in industry and medical science, as well as the potential toxicity in the environment, the detection of sulfide, including hydrogen sulfide, metal sulfide and organic sulfide, has long attracted the attention of scientists working in diverse areas. Compared with other detection methods, electrochemical detection represents a highly sensitive, rapid, affordable, and simple technique. In this regard, the main objective of this report is to provide an up-to-date review of the electrochemical detection of sulfide. This review details different electrochemical approaches investigated between 2010 and 2012, together with the development of various electrodes. In addition to the commonly used techniques, such as, anodic stripping voltammetry (ASV), amperometry, cyclic voltammetry (CV), photoelectrochemical methods, and electrochemical detection methods coupled with other devices, have also been discussed, within the context of detection limit, linear detection range, and applicable conditions. [ABSTRACT FROM AUTHOR]

Here we describe biogeochemical processes that lead to the generation of acid rock drainage (ARD) and rock weathering on the Antarctic landmass and describe why they are important sources of iron into the Antarctic Ocean. During three expeditions, 2009-2011, we examined three sites on the South Shetland Islands in Antarctica. Two of them displayed intensive sulfide mineralization and generated acidic (pH 3.2-4.5), iron-rich drainage waters (up to 1.78 mM Fe), which infiltrated as groundwater (as Fe2+) and as superficial runoff (as Fe3+) into the sea, the latter with the formation of schwertmannite in the sea-ice. The formation of ARD in the Antarctic was catalyzed by acid mine drainage microorganisms found in cold climates, including Acidithiobacillus ferrivorans and Thiobacillus plumbophilus. The dissolved iron (DFe) flux from rock weathering (nonmineralized control site) was calculated to be 0.45 × 109 g DFe yr-1 for the nowadays 5468 km of ice-free Antarctic rock coastline which is of the same order of magnitude as glacial or aeolian input to the Southern Ocean. Additionally, the two ARD sites alone liberate 0.026 and 0.057 × 109 g DFe yr-1 as point sources to the sea. The increased iron input correlates with increased phytoplankton production close to the source. This might even be enhanced in the future by a global warming scenario, and could be a process counterbalancing global warming. [ABSTRACT FROM AUTHOR]

The trace metal pollution of sediments in Chaohu Lake, one of the most highly eutrophic lakes in East China, was investigated. Surface sediment (0-5 cm) samples were collected from 35 different positions and analyzed by inductively coupled plasma optical emission spectrometry to determine trace metal contents. Results showed that the mean content of trace metals was as follows: Cr, 85.09 mg kg-1; Cu, 34.49 mg kg-1; Ni, 26.46 mg kg-1; Pb, 34.17 mg kg-1 and Zn, 107.46 mg kg-1. The trace metal concentrations from different sampling sites displayed spatial diversity; the heavily polluted sampling sites were close to where estuaries flow in to the lake. A four-step sequential extraction was used to examine the partitioning of the trace metals. Results demonstrated that the percentage of the species bound to the oxidizable phase for all trace metals ranged from 15.6 to 37.7%, while for Cu, Cr and Ni, the main forms were residual (41.3, 62.3 and 69.8%, respectively). Trace metals in the oxidizable fraction may mainly exist in the form of sulfides. The ecological potential risks of trace metals decreased as follows: Pb>Zn >Cu>Cr>Ni. [ABSTRACT FROM AUTHOR]

Abstract: Cultures of the sulfate reducing bacteria Desulfovibrio desulfuricans were grown under anoxic conditions to study the effect of added sulfide, selenite and mercuric ions. A chemical trap consisting in a CuSO4 solution was used to control the poisoning effect induced by the bacterial production of hydrogen sulfide via the precipitation of CuS. Following the addition of Hg2+, the formation of methylmercury (MeHg) was correlated to bacterial proliferation with most of MeHg found in the culture medium. A large fraction (50–80%) of added Hg2+ to a culture ended up in a solid phase (Hg0 and likely HgS) limiting its bioavailability to cells with elemental Hg representing ~40% of the solid. Following the addition of selenite, a small fraction was converted into Se(0) inside the cells and, even though the conversion to this selenium species increased with the increase of added selenite, it never reached more than 49% of the added amount. The formation of volatile dimethylselenide is suggested as another detoxification mechanism. In cultures containing both added selenite and mercuric ions, elemental forms of the two compounds were still produced and the increase of selenium in the residual fraction of the culture suggests the formation of mercuric selenite limiting the bioavailability of both elements to cells. [Copyright &y& Elsevier]

During subsurface bioremediation of uranium-contaminated sites, indigenous metal and sulfate-reducing bacteria may utilize a variety of electron acceptors, including ferric iron and sulfate that could lead to the formation of various biogenic minerals in situ. Sulfides, as well as structural and adsorbed Fe(II) associated with biogenic Fe(II)-sulfide phases, can potentially catalyze abiotic U(VI) reduction via direct electron transfer processes. In the present work, the propensity of biogenic mackinawite (Fe1+xS, x = 0 to 0.11) to reduce U(VI) abiotically was investigated. The biogenic mackinawite produced by Shewanella putrefaciens strain CN32 was characterized by employing a suite of analytical techniques including TEM, SEM, XAS, and Mössbauer analyses. Nanoscale and bulk analyses (microscopic and spectroscopic techniques, respectively) of biogenic mackinawite after exposure to U(VI) indicate the formation of nanoparticulate UO2. This study suggests the relevance of sulfide-bearing biogenic minerals in mediating abiotic U(VI) reduction, an alternative pathway in addition to direct enzymatic U(VI) reduction. [ABSTRACT FROM AUTHOR]

Background: Alvinella pompejana is an annelid worm that inhabits deep-sea hydrothermal vent sites in the Pacific Ocean. Living at a depth of approximately 2500 meters, these worms experience extreme environmental conditions, including high temperature and pressure as well as high levels of sulfide and heavy metals. A. pompejana is one of the most thermotolerant metazoans, making this animal a subject of great interest for studies of eukaryotic thermoadaptation. Results: In order to complement existing EST resources we performed deep sequencing of the A. pompejana transcriptome. We identified several thousand novel protein-coding transcripts, nearly doubling the sequence data for this annelid. We then performed an extensive survey of previously established prokaryotic thermoadaptation measures to search for global signals of thermoadaptation in A. pompejana in comparison with mesophilic eukaryotes. In an orthologous set of 457 proteins, we found that the best indicator of thermoadaptation was the difference in frequency of charged versus polar residues (CvP-bias), which was highest in A. pompejana. CvP-bias robustly distinguished prokaryotic thermophiles from prokaryotic mesophiles, as well as the thermophilic fungus Chaetomium thermophilum from mesophilic eukaryotes. Experimental values for thermophilic proteins supported higher CvP-bias as a measure of thermal stability when compared to their mesophilic orthologs. Proteome-wide mean CvP-bias also correlated with the body temperatures of homeothermic birds and mammals. Conclusions: Our work extends the transcriptome resources for A. pompejana and identifies the CvP-bias as a robust and widely applicable measure of eukaryotic thermoadaptation. [ABSTRACT FROM AUTHOR]

Abstract: The effectiveness of three bioproducts (also known as biomaterials) for liquid-phase biological treatment (LPBT) of sewer biofilms to control detrimental build-up of sulphide (H2S) and methane (CH4) in sewers was tested in a laboratory system mimicking a rising/force main sewer pipe. Bioproduct A claims to disrupt cell-to-cell communication of sewer anaerobic biofilms while Bioproducts B and C claim to enhance sulphidotrophic (sulphide-oxidising) capacity of the sewer biofilm, to avoid sulphide accumulation. The results demonstrated that all three bioproducts tested had no or negligible impact on sulphide or methane control, as opposed to traditional sulphide-controlling chemicals widely used by the wastewater industry such as oxygen, nitrate, iron salts and magnesium hydroxide. Those had previously been demonstrated to be effective using the same laboratory system with the same testing protocol. The implications of the findings are discussed. It is concluded that field application/trials of these three bioproducts are not warranted. It is recommended that other bioproducts should be subject to similar rigorous tests prior to being taken up by the water industry for field trials/application. [Copyright &y& Elsevier]

In this study a sequencing batch reactor was used to simultaneously remove both sulphide and nitrate via an autotrophic denitrification process. The sulphide loading rates were gradually increased from 200 mg S2− L−1 d−1–450 mg S2− L−1d−1while the nitrogen loading rates were kept at 450 mg NO3 −–N L−1d−1. The obtained results demonstrated that it was possible to carry out autotrophic denitrification in a Sequencing Batch Reactor with removal efficiencies of sulphide and nitrogen of 100% and 67%, respectively. The efficiency of the process was influenced by the pH value in the reactor. The operation at pH values higher than 9.0 decreased the efficiency of sulphide oxidation into sulphate to 11.3%. The main bacteria populations present in the sludge belonged to Thiobacillus genus. [Copyright &y& Elsevier]

The accumulation of monosulfidic sediments in inland waterways is emerging as a major environmental issue. Mobilisation and suspension of monosulfidic sediments can result in deoxygenation, acidification of the water column and mobilisation of trace metals. The controls on monosulfidic sediment mobilisation and the critical thresholds for its scour and entrainment have not been established. This study examines the effect of a minor flood event (average return interval of 5 years) on sulfidic sediment scour in the Wakool River in southern NSW, Australia. Five profiles were sampled within a small (∼300 m) reach before and after a minor flood event to determine the degree of sediment scour and transport. The results indicate substantial scour of both monosulfidic sediments and underlying bed sediments (approximately 2100 m3). Changes in the sediment geochemistry suggest large concentrations of monosulfidic sediments had been suspended in the water column, partially-oxidised and redeposited. This is supported by 210Pb results from one of the profiles. These results suggest that these monosulfidic sediments can move as bed load during minor flood events. [Copyright &y& Elsevier]

Sulfide produced in marine sediments by sulfate reduction is toxic for several macrophytes, and high sediment sulfide concentrations have been associated with seagrass die-off events. Sulfide has been shown to reduce growth in a number of seagrasses, but little is known about its effect on the photosynthetic and respiratory metabolism. Consequently, the aim of this research was to evaluate the effect of sulfide on photosynthesis and respiration of the seagrass Zostera marina. Photosynthetic oxygen evolution and respiration were determined polarographically, while the optimum quantum yield was used as a measure of the photosynthetic performance of photosystem II in the leaves of Z. marina. The results showed that sulfide concentrations of approximately 1000 µM could be considered an upper threshold limit for the survival of Z. marina in the coastal lagoons of Baja California (Mexico) studied. Respiration was not inhibited by sulfide concentrations up to 1000 µM during 48-h incubations, while photosynthetic performance was reduced by short exposure to sulfide concentrations of 25 µM but also by long exposure to concentrations as low as 50 µM. This is the first study that shows that the photosynthetic capacity of Z. marina is not recovered once the sulfide-free conditions have been re-established. [ABSTRACT FROM AUTHOR]

This study is aimed at evaluating the availability and mobility of arsenic in sulfidic materials from gold mining areas in Minas Gerais State, Brazil. Eight extraction media were employed in a sequential extraction scheme, as follows: exchangeable As; strongly adsorbed As; As coprecipitated with acid-volatile sulfide, carbonates, MnO, and AlO; As coprecipitated with amorphous iron; As linked to crystalline iron oxide; As coprecipitated with silicates; As coprecipitated with amorphous FeS and AsS, and residual As, which was determined by GFAAS. Results demonstrated that in spite of differences in arsenic concentrations, the availability of the metalloid was found to be low for all samples. In general, arsenic was found in less available forms. Nevertheless, most of the arsenic in the environment is retained in the fractions 3, 4, and 5 which are susceptible to dissolution in acid medium, which in turn might be due to oxidation of the sulfide present in the samples. [ABSTRACT FROM AUTHOR]

Abstract: Twenty-nine congeners of polychlorinated diphenyl sulfide (PCDPS) theoretically possible were synthesized and purified, and their octanol–water partition coefficients (log K ow) and high performance liquid chromatography capacity factors (HPLC-log k′) were determined. Then the constitutional and structural descriptors were obtained respectively to establish 2D models and comparative molecular similarity indices analysis (CoMSIA) method was used to establish 3D models. All the models were robust and predictive, indicating that the electrostatic effect may be the primary factor influencing the two properties of PCDPS. The log K ow and log k′ values of all PCDPS congeners were predicted based on these models. The establishment of linear equation on log K ow between PCDPS and chlorinated or brominated diphenyl ether (PCDE, PBDE) was attempted, and the hydrophobic differences were considered to relate with the size of the molecules. [Copyright &y& Elsevier]