Concentrations Of Sulfur Species Research Articles

Modeling study of the impact of SO<sub>2</sub> volcanic passive emissions on the tropospheric sulfur budget

Abstract. Well constrained volcanic emissions inventories in chemistry transport models are necessary to study the impacts induced by these sources on the tropospheric sulfur composition and on sulfur species concentrations and depositions at the surface. In this paper, the changes induced by the update of the volcanic sulfur emissions inventory are studied using the global chemistry transport model MOCAGE (MOdèle de Chimie Atmosphérique à Grande Échelle). Unlike the previous inventory (Andres and Kasgnoc, 1998), the updated one (Carn et al., 2016, 2017) uses more accurate information and includes contributions from both passive degassing and eruptive emissions. Eruptions are provided as daily total amounts of sulfur dioxide (SO2) emitted by volcanoes in the Carn et al. (2016, 2017) inventories, and degassing emissions are provided as annual averages with the related mean annual uncertainties of those emissions by volcano. Information on plume altitudes is also available and has been used in the model. We chose to analyze the year 2013, for which only a negligible amount of eruptive volcanic SO2 emissions is reported, allowing us to focus the study on the impact of passive degassing emissions on the tropospheric sulfur budget. An evaluation against the Ozone Monitoring Instrument (OMI) SO2 total column and MODIS (Moderate-Resolution Imaging Spectroradiometer) aerosol optical depth (AOD) observations shows the improvements of the model results with the updated inventory. Because the global volcanic SO2 flux changes from 13 Tg yr−1 in Andres and Kasgnoc (1998) to 23.6 Tg yr−1 in Carn et al. (2016, 2017), significant differences appear in the global sulfur budget, mainly in the free troposphere and in the tropics. Even though volcanic SO2 emissions represent 15 % of the total annual sulfur emissions, the volcanic contribution to the tropospheric sulfate aerosol burden is 25 %, which is due to the higher altitude of emissions from volcanoes. Moreover, a sensitivity study on passive degassing emissions, using the annual uncertainties of emissions per volcano, also confirmed the nonlinear link between tropospheric sulfur species content with respect to volcanic SO2 emissions. This study highlights the need for accurate estimates of volcanic sources in chemistry transport models in order to properly simulate tropospheric sulfur species.

Anaerobic Co-Digestion of Tannery and Slaughterhouse Wastewater for Solids Reduction and Resource Recovery: Effect of Sulfate Concentration and Inoculum to Substrate Ratio

Anaerobic digestion is considered unsuitable for the bioremediation of tannery effluent due to process inhibition, mainly due to high concentrations of sulfur species, and the accumulation of H2S and/or NH3. This study using the standardized biochemical methane potential protocol showed that efficient processing is possible with slaughterhouse wastewater, provided sufficient functional biomass is present at the start of the process and the SO42− concentration is below inhibition threshold. Methanogenic activity (K = 13.4–17.5 and µm = 0.15–0.27) and CH4 yields were high when reactors were operated ISR ≥ 3 and/or lower SO42− ≤ 710 mg/L while high SO42− ≥ 1960 mg/L and ISR < 3.0 caused almost complete inhibition regardless of corresponding ISR and SO42−. The theoretical optimum operating conditions (922 mg/L SO42−, ISR = 3.72) are expected to generate 361 mL biogas/gVS, 235 mL CH4/gVS with reduction efficiencies of 27.5% VS, 27.4% TS, 75.1% TOC, 75.6% SO42−, and 41.1% COD. This implies that tannery sludge will be reduced by about 27% (dry mass) and SO42− by 76%, with a fraction of it recovered as S0. The models displayed a perfect fit to the cumulative CH4 yields with high precision in the order Logistic > Cone > modified Gompertz > first order.

Simulation Study of the Formation of Corrosive Gases in Coal Combustion in an Entrained Flow Reactor

Gaseous sulfur species play a major role in high temperature corrosion of pulverized coal fired furnaces. The prediction of sulfur species concentrations by 3D-Computational Fluid Dynamics (CFD) simulation allows the identification of furnace wall regions that are exposed to corrosive gases, so that countermeasures against corrosion can be applied. In the present work, a model for the release of sulfur and chlorine species during coal combustion is presented. The model is based on the mineral matter transformation of sulfur and chlorine bearing minerals under coal combustion conditions. The model is appended to a detailed reaction mechanism for gaseous sulfur and chlorine species and hydrocarbon related reactions, as well as a global three-step mechanism for coal devolatilization, char combustion, and char gasification. Experiments in an entrained flow were carried out to validate the developed model. Three-dimensional numerical simulations of an entrained flow reactor were performed by CFD using the developed model. Calculated concentrations of SO2, H2S, COS, and HCl showed good agreement with the measurements. Hence, the developed model can be regarded as a reliable method for the prediction of corrosive sulfur and chlorine species in coal fired furnaces. Further improvement is needed in the prediction of some minor trace species.

Seasonality of aerosol chemical composition at King Sejong Station (Antarctic Peninsula) in 2013

Seasonal variations of ionic species concentrations in PM10 and PM2.5 aerosols were investigated at King Sejong Station (King George Island, Antarctic Peninsula) in 2013. Seasonal variations of PM2.5 mass were also determined, and found to be in the range: 2482.2 ± 944.4 ng m−3 (austral winter) to 3493.3 ± 1223.8 ng m−3 (austral fall). On a weight basis, the PM2.5 ionic species consisted mainly of primary ions from sea spray (~30% in summer, ~50% in winter) and partly from secondary ions (~20% in summer), with the ratios of sea spray and secondary ion components to PM2.5 mass showing clear seasonal variation. The seasonal cycle of sea spray components was not well defined, but was weakly correlated with wind speed (r2 = 0.38). This correlation was likely attributable to a combination of the seasonal properties of wind and the measurement site's location at the western tip of Barton Peninsula. The concentrations of sulphur species (CH3SO3− and non sea salt SO42−) were clearly higher during austral summer. Notably, these concentrations were ~2–3 times higher during in January 2013 than in other summer months of the field observation period. This was attributed to an increased biomass of algae in the ocean area surrounding King George Island and more frequent air mass passage over ocean areas with algae blooms. The NH4+ concentration was also clearly higher in austral summer 2013, mainly due to secondary formation from the NH3 released from local emission sources such as penguin colonies and ocean areas near the measurement site with acidic aerosol, but also affected by local meteorology specific to the summer of 2014.

Viral and metabolic controls on high rates of microbial sulfur and carbon cycling in wetland ecosystems

BackgroundMicroorganisms drive high rates of methanogenesis and carbon mineralization in wetland ecosystems. These signals are especially pronounced in the Prairie Pothole Region of North America, the tenth largest wetland ecosystem in the world. Sulfate reduction rates up to 22 μmol cm−3 day−1 have been measured in these wetland sediments, as well as methane fluxes up to 160 mg m−2 h−1—some of the highest emissions ever measured in North American wetlands. While pore waters from PPR wetlands are characterized by high concentrations of sulfur species and dissolved organic carbon, the constraints on microbial activity are poorly understood. Here, we utilized metagenomics to investigate candidate sulfate reducers and methanogens in this ecosystem and identify metabolic and viral controls on microbial activity.ResultsWe recovered 162 dsrA and 206 dsrD sequences from 18 sediment metagenomes and reconstructed 24 candidate sulfate reducer genomes assigned to seven phyla. These genomes encoded the potential for utilizing a wide variety of electron donors, such as methanol and other alcohols, methylamines, and glycine betaine. We also identified 37 mcrA sequences spanning five orders and recovered two putative methanogen genomes representing the most abundant taxa—Methanosaeta and Methanoregulaceae. However, given the abundance of Methanofollis-affiliated mcrA sequences, the detection of F420-dependent alcohol dehydrogenases, and millimolar concentrations of ethanol and 2-propanol in sediment pore fluids, we hypothesize that these alcohols may drive a significant fraction of methanogenesis in this ecosystem. Finally, extensive viral novelty was detected, with approximately 80% of viral populations being unclassified at any known taxonomic levels and absent from publicly available databases. Many of these viral populations were predicted to target dominant sulfate reducers and methanogens.ConclusionsOur results indicate that diversity is likely key to extremely high rates of methanogenesis and sulfate reduction observed in these wetlands. The inferred genomic diversity and metabolic versatility could result from dynamic environmental conditions, viral infections, and niche differentiation in the heterogeneous sediment matrix. These processes likely play an important role in modulating carbon and sulfur cycling in this ecosystem.

Effect of elevated pressure on ferric iron reduction coupled to sulfur oxidation by biomining microorganisms

Acidophiles, including a mixed mesophilic, iron-oxidizing culture (FIGB) and a thermophilic enrichment culture (TK65) from a black shale and sandstone copper ore (Kupferschiefer), were used to evaluate microbial ferric iron reduction coupled to oxidation of reduced inorganic sulfur compounds (RISCs) at elevated pressure to simulate potential biogeochemical processes in deep in situ leaching operations. Experiments were performed from atmospheric pressure (0.1 MPa) up to 36 MPa in different incubation chambers and high-pressure reactors. Microbial abundance and activity were determined by quantifying iron and sulfur species concentrations, by direct cell counting, terminal restriction fragment length polymorphism (T-RFLP) analysis and quantitative PCR (qPCR). The data indicate that the tested acidophilic cultures were able to reduce soluble ferric iron coupled to oxidation of sulfur compounds under anaerobic conditions. Even at high pressure (up to 36 MPa) these acidophiles were capable of growing, and microbial ferric iron reduction was only partially inhibited. These results show that the tested acidophiles are barotolerant and their activities may contribute to sulfur and iron cycling in anaerobic environments including deep ore deposits, which is relevant for in situ leaching operations.

Generalized parameter estimation and calibration for biokinetic models using correlation and single variable optimisations: Application to sulfate reduction modelling in anaerobic digestion

In this work, a generalized method for the estimation of biokinetic parameters in anaerobic digestion (AD) models is proposed. The method consists of a correlation-based approach to estimate specific groups of parameters mechanistically, followed by a sensitivity-based hierarchical and sequential single parameter optimisation (SHSSPO) calibration method for the remaining groups of parameters. The method was evaluated to estimate and calibrate the parameter values for sulfate reduction processes when included into the IWA Anaerobic Digestion Model No. 1 (ADM1) and simulations were compared with experimental data from literature. Under the proposed method, a large number of biokinetic parameters, namely biomass yields, maximum specific uptake rates, and half saturation constants, can first be estimated using mechanistic correlations. This achieves a significant reduction in the number of parameters to be fitted to data. For the remaining parameters, a method is proposed based on the overall sensitivity and degree of ubiquity of each parameter to establish a hierarchy in a sequential single parameter optimisation against the experimental data. This approach aims at eliminating the uncertainty on optimality (and therefore parameter identification) associated to multivariable parameter calibration problems. The method was applied to the sulfate reduction related parameters and led to the hydrogen sulfide inhibition parameters as the only ones requiring optimisation against experimental data. Comparison of the proposed SHSSPO performance with that of multi-dimensional parameter optimisation methods shows a superior performance in terms of overall error and computation times. Also, final simulation results led to model predictions of similar, if not better, quality than those achieved by multivariable parameter optimisation methods. The experimental variables optimized for included liquid effluent concentrations of sulfur species and volatile fatty acids as well as effluent methane gas flow. Overall, the proposed parameter estimation and calibration method provides a deterministic step-by-step approach to parameter estimation that decreases identifiability uncertainty at a very low computational effort. The results obtained suggest that the method could be generically applied with similar success to other biokinetic models frequently used in wastewater treatment.

Comparison of CFD Simulations with Measurements of Gaseous Sulfur Species Concentrations in a Pulverized Coal Fired 1 MWth Furnace

High temperature corrosion is a major issue in coal fired power plants. Gaseous sulfur species are one of the main causes of furnace wall corrosion. In order to take effective countermeasures, the identification of exposed furnace wall regions is necessary, which can be achieved by 3D-CFD simulations coupled with detailed sulfur and combustion chemistry. A model for the release of sulfur species during coal combustion, which is based on the mineral matter transformation of sulfur bearing minerals under coal combustion conditions, has been developed and is to be presented in this study. CFD simulations of a 1 MWth combustion chamber fired with pulverized hard coal have been carried out. Measurements of gas concentrations have been performed at different heights and radial positions as well as at the exit of the combustion chamber. The results of the simulations are in good agreement with measured concentrations of major gas species and sulfur species.

Spatial and temporal distributions of sulfur species in paddy soils affected by acid mine drainage in Dabaoshan sulfide mining area, South China

In paddy soils polluted by acid mine drainage (AMD), heavy metals contamination has been studied intensively, but little information has been gathered regarding the associated speciation of sulfur. Therefore, the concentrations of various sulfur species in paddy soil profiles were investigated at sites downstream of the Dabaoshan sulfide mining area, South China. No significant differences in water-soluble sulfate (WS), adsorbed sulfate (AS), or total sulfur (TS) were observed between upstream and downstream paddy soil profiles. A surprising finding was that seasonal change of WS in deeper soil may have contributed to the gradual decline in TS over the past 10years. The largest concentrations of AS was found in 20 to 30cm soil horizons, where a strong influence of large surface area soil particles, and abundant amorphous iron hydroxides and fine clays likely enhanced sulfate adsorption. Reduced inorganic sulfur (RIS) was found in highest concentrations at depths of 0 to 20cm and was significantly positively correlated with total soil C and N contents. Furthermore, ester sulfate (ES) was the dominating sulfur species in every layer, which may result from (i) abundant WS and AS promoted ES formation, and (ii) the presence of active Al and Fe oxides inhibited ES mineralization. Concentrations of sulfur species and other soil properties were used in principle component analysis to identify three geochemically distinct layers in these paddy soils (0 to 20cm, 20 to 30cm and 30 to 80cm). Due to AMD irrigation, differences in the speciation of sulfur among these layers illustrates how the chemical imprint of AMD irrigation has influenced and been affected by the background biogeochemistry of these soils. The present examination of the speciation and vertical and horizontal distribution of sulfur species provides valuable information for the continued management and remediation of these and other AMD-contaminated paddy soils.

Multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in Yellowstone National Park geothermal springs.

BackgroundThe paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling.ResultsWater samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (<6 μmol L-1) in the pools with low pH due to fast disproportionation of thiosulfate. In the pools with higher pH, the concentration of thiosulfate varies, depending on different geochemical pathways of thiosulfate formation. The δ34S values of sulfate in four systems were close to those calculated using a mixing line of the model based on dilution and boiling of a deep hot parent water body. In two pools δ34S values of sulfate varied significantly from the values calculated from this model. Sulfur isotope fractionation between ZVS and hydrogen sulfide was close to zero at pH < 4. At higher pH zero-valent sulfur is slightly heavier than hydrogen sulfide due to equilibration in the rhombic sulfur–polysulfide – hydrogen sulfide system. Triple sulfur isotope (32S, 33S, 34S) fractionation patterns in waters of hydrothermal pools are more consistent with redox processes involving intermediate sulfur species than with bacterial sulfate reduction. Small but resolved differences in ∆33S among species and between pools are observed.ConclusionsThe variation of sulfate isotopic composition, the origin of differences in isotopic composition of sulfide and zero–valent sulfur, as well as differences in ∆33S of sulfide and sulfate are likely due to a complex network of abiotic redox reactions, including disproportionation pathways.

Multi-Objective Optimization of Corrosion Rate Parameters in Refining Process Using Particle Swarm Optimization.

ABSTRACTIn this paper, a Particle Swarm Optimization (PSO) algorithm is presented to find the optimal combination of corrosion rate parameters for a refining process in the oil industry. The experimental data in this paper are constituted by results obtained from field tests. Maintenance control is a very important aspect in order to prevent substantial damage to facilities, equipment and people. Other important factor to consider is the cost of maintenance which tends to reduce the required actions. The main parameters in corrosion control are flow, concentration of sulfur species, total acid number (TAN), temperature, and chromium content. However it is not easy to know the combined effect of different variables due to synergistic effects. Particle swarm optimization (PSO) is a population based stochastic optimization technique, inspired by social behavior of bird flocking or fish schooling. The system is initialized with a population of random solutions and searches for optima by updating generations. In PSO, the potential solutions, called particles, fly through the problem space by following the current optimum particles.

Chemical analysis of sulfur species in geothermal waters

Analytical methods have been developed to determine sulfur species concentrations in natural geothermal waters using Reagent-Free™ Ion Chromatography (RF™-IC), titrations and spectrophotometry. The sulfur species include SO42−, S2O32−, and ∑S2− with additional determination of SO32− and SxO62− that remains somewhat semiquantitative. The observed workable limits of detections were ≤0.5μM depending on sample matrix and the analytical detection limits were 0.1μM. Due to changes in sulfur species concentrations upon storage, on-site analyses of natural water samples were preferred. Alternatively, the samples may be stabilized on resin for later elution and analysis in the laboratory. The analytical method further allowed simultaneous determination of other anions including F−, Cl−, dissolved inorganic carbon (DIC) and NO3− without sample preservation or stabilization. The power of the newly developed methods relies in routine analysis of sulfur speciation of importance in natural waters using techniques and facilities available in most laboratories doing water sample analysis. The new methods were successfully applied for the determination of sulfur species concentrations in samples of natural and synthetic waters.

Micron-scale Fe 2+/Fe 3+, intermediate sulfur species and O 2 gradients across the biofilm–solution–sediment interface control biofilm organization

We measured micron-scale Fe 2+/Fe 3+ and intermediate sulfur species gradients across the biofilm–solution interface and defined the microbial community composition in natural and bioreactor-cultivated acid mine drainage biofilms to investigate how community organization correlated with geochemical conditions. Intermediate sulfur species concentrations were also measured in associated sediments. Under initial conditions of high Fe 2+ and O 2 concentrations, the first biofilm colonists were Leptospirillum Group II, UBA genotype, and a few Archaea. Cytochrome 579 concentration in early formed biofilms was high, correlating with rapid Fe 2+ oxidation. As biofilm thickness increased, O 2 concentrations in the middle of biofilms decreased, indicating that diffusion limitation of O 2 may control activity levels of aerobic organisms. Calculated low O 2 and high Fe 3+ concentrations in the interior regions of biofilms may explain the previously reported suppression of the UBA genotype in mature biofilms. Instead, Leptospirillum Group II, 5-way CG genotype, dominated under these conditions. Leptospirillum Group III and eukaryotes appeared in the community as the biofilm thickened and Fe 3+/Fe 2+ increased. In mature biofilms, the architecture changed from planar to crenulated, perhaps to increase the surface area of biofilms and decrease O 2 diffusion limitation. In thick, mature biofilms, layering is associated with segregation of Leptospirillum Group II and Archaea and the concentration of cytochrome 579 is lower. The accumulation of Archaea close to the biofilm–air interface may facilitate their aerobic metabolism of waste carbon compounds. Sulfite, thiosulfate and polysulfides were detected in AMD sediments and thiosulfate was detected in solution. These compounds indicate the redox status of the system and represent potential energy sources. Temporal and spatial heterogeneity in community structure correlate with heterogeneity in geochemical conditions, implying active feedbacks between geochemical conditions and microbial species distribution and activity.

Influence of sulfur-bearing polyatomic species on high precision measurements of Cu isotopic composition

An increased interest in high precision Cu isotope ratio measurements using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has developed recently for various natural geologic systems and environmental applications, these typically contain high concentrations of sulfur, particularly in the form of sulfate (SO 4 2−) and sulfide (S). For example, Cu, Fe, and Zn concentrations in acid mine drainage (AMD) can range from 100 µg/L to greater than 50 mg/L with sulfur species concentrations reaching greater than 1000 mg/L. Routine separation of Cu, Fe and Zn from AMD, Cu–sulfide minerals and other geological matrices usually incorporates single anion exchange resin column chromatography for metal separation. During chromatographic separation, variable breakthrough of SO 4 2− during anion exchange resin column chromatography into the Cu fractions was observed as a function of the initial sulfur to Cu ratio, column properties, and the sample matrix. SO 4 2− present in the Cu fraction can form a polyatomic 32S– 14N– 16O– 1H species causing a direct mass interference with 63Cu and producing artificially light δ 65Cu values. Here we report the extent of the mass interference caused by SO 4 2− breakthrough when measuring δ 65Cu on natural samples and NIST SRM 976 Cu isotope spiked with SO 4 2− after both single anion column chromatography and double anion column chromatography. A set of five 100 µg/L Cu SRM 976 samples spiked with 500 mg/L SO 4 2− resulted in an average δ 65Cu of − 3.50‰ ± 5.42‰ following single anion column separation with variable SO 4 2− breakthrough but an average concentration of 770 µg/L. Following double anion column separation, the average SO 4 2−concentration of 13 µg/L resulted in better precision and accuracy for the measured δ 65Cu value of 0.01‰ ± 0.02‰ relative to the expected 0‰ for SRM 976. We conclude that attention to SO 4 2− breakthrough on sulfur-rich samples is necessary for accurate and precise measurements of δ 65Cu and may require the use of a double ion exchange column procedure.

Spontaneous potential and redox responses over a forest ring

Forest rings are large, circular features in boreal forests that commonly exceed [Formula: see text] in diameter and are visible on aerial photographs. A detailed study of redox conditions and spontaneous potential (SP) was carried out over a forest ring that overlies an [Formula: see text] accumulation. Studies included drilling, monitoring well installation, and downhole SP using both polarizing and nonpolarizing electrodes. Also measured were redox potential of groundwater and soils, concentrations of sulfur species in groundwater, and headspace concentrations of redox-sensitive gases in monitoring wells. The results show positive SP anomalies in the shallow subsurface and near-horizontal, negative-inward redox gradients in the water-saturated overburden at theedges of the ring. SP anomalies are spatially correlated with redox gradients, suggesting that the two are related. The SP anomalies may be produced in response to redox gradients as redox-active ions and polar molecules spontaneously align with the negative poles toward the oxidizing end of the gradient, i.e., toward their more electronegative neighbors. This orientation of dipoles imparts a macroscopic electrical polarity to the redox gradient and results in the observed positive electrical anomaly inside the forest ring. Ongoing oxidation reactions occurring around the periphery of the forest ring maintain strong [Formula: see text] concentration gradients, which result in an outward steady-state diffusive flux of [Formula: see text]. Electromigration of redox-active ions in the redox-induced electrical field may also contribute to maintenance of the redox gradient.

Natural Fluctuation of Sulfur Species in Volcanic Fumaroles

We describe and discuss the origin of short-term (hours) variations in the concentration of sulfur species (SO2, H2S, and S80) of crater fumaroles discharging at different temperatures (up to 410°C) from five volcanic systems. Sulfur species can be investigated as an independent subsystem within the whole composition characterizing the fumarolic fluids, their chemical behavior being governed by similar laws in volcanic systems. The measured data are time dependent and show regular oscillations whose amplitude is by far larger than the analytical error. The agreement between the theoretical and the measured concentrations of SO2, H2S, and S80 suggests that the formation of dissipative structures can explain the observed oscillations. Accordingly, the periodicity and the amplitude of the compositional oscillations were found to be in strong relation with the entropy excess of the non-equilibrium systems under investigation. The results of our study suggest that the amplitude and magnitude of short-term natural (self-induced) fluctuations of the sulfur species caused by the presence of the dissipative structures, and their comparison with the compositional variations of other subsystems, should be taken into serious account for geochemical monitoring purposes.

Speciation studies of copper in the Gulf of Elefsis: the role of the macroalgae Ulva rigida

The Gulf of Elefsis, situated in the vicinity of Athens, is a high productivity area regarding the biota. One of the most abundant algae existing there is Ulva rigida. Controlled laboratory simulation experiments, as well as field investigations indicated that copper is complexed to a high extent with organic substances released by U. rigida and other naturally occurring organic ligands. A significant part of these organic ligands exhibit surface active properties, i.e. the accumulation on different phase boundaries (e.g. seawater/atmosphere, seawater/living organisms, seawater/particulate suspended matter, seawater/sediments). The complexing capacity values of samples collected from different microenvironments within the Gulf of Elefsis, determined by the electrochemical method of differential pulse anodic stripping voltammetry (DPASV), vary between 0.04 and 0.43 μM Cu 2+. At the same time, the complexing capacities of samples obtained from the laboratory tanks in which U. rigida has been placed in order to be decomposed under controlled conditions, show much higher complexing capacity values (up to 13 μM Cu 2+), especially during the final stage of the experiment. The method of linear sweep voltammetry (LSV) was applied for the determination of the concentration of sulfur species (S 0+S 2−) present in nonaerated tanks containing U. rigida. The total concentration of sulfur species in tank No. 2 was 300 nM while in tank No. 3 it was 500 nM. As a result of the presence of sulfur species, a part of the complexing capacity of the substances released during algae biomass decomposition in these two tanks could be attributed to the formation of copper sulfides. Furthermore, the surfactant activity (amount of surface active substances (SAS) expressed in equivalents of the nonionic surfactant Triton-X-100) was determined by A.C. out of phase voltammetry. Higher amounts of SAS were detected in the tanks containing U. rigida (up to 0.70 mg/l eq. T-X-100), in comparison to samples originating from natural microenvironments which had values ranging between 0.10 and 0.17 mg/l eq. T-X-100. These results show that U. rigida, although definitely not the only or necessarily the major contributor to the organic ligand pool in the study area, contributes considerably to the production of ligands with high metal complexing capacity and/or high surfactant activity.

On-line process monitoring of water-soluble ions in pulp and paper machine waters by capillary electrophoresis

In this study, capillary electrophoresis (CE) was used for separation of inorganic and organic ions from waters of paper and paperboard machines at mills. The instrument was constructed for on-line measurements by building a batch-type sample feeding unit. Chloride, thiosulphate, sulphate, oxalate, sulphite, hydrogen sulphide, formate, carbonate, phosphate and acetate in the process water samples were separated using an ion-specific separation system in CE with dicarboxylic acid buffer (pH 8.2), with pyridinium-2,3-dicarboxylic acid modified with commercial NICE-Pak OFMOH solution (pH 12.0) or with a cetyltrimethylammonium bromide solution modified with chromate (pH 10.6). In addition, Analis CEofix Anions 8 electrolyte solution was tested in on-line studies at mills. It allowed 5 min separation time for the anions. Aluminium was determined at pH 3.6 in 10 min by using a laboratory-made imidazole buffer modified with 18-crown 6-ether. The developed CE systems were used to monitor the concentrations of sulphur species in dithionite degradation, to estimate corrosion degree in the water tanks, to monitor formaldehyde as the biocide chemical in wire washing and, in general, to observe process disturbances resulting from chemical feedings and their sites. The CE combination was on-line coupled to eight different process machines for continuous monitoring of concentrations for periods between two weeks and one month at paper and pulp mills in Finland.

The comparison of modelled surface level sulfur species concentrations from COSAM with observations

The comparison of modelled surface level sulfur species concentrations from COSAM with observations

A 3D model study of the global sulphur cycle: Contributions of anthropogenic and biogenic sources

The impact of anthropogenic emissions on the global distributions and budgets of the main atmospheric sulphur species [namely dimethylsulphide (DMS), sulphur dioxide (SO 2), and non-sea-salt (nss-) sulphates (SO 4 2−)] is investigated using the IMAGES three-dimensional. tropospheric chemistry-transport model. A previous study showed a broad consistency between modelled and observed concentrations of sulphur species for the present-day ( c. 1985) atmosphere. Here, in order to assess the relative contributions of biogenic and man-made sources, we compare distributions calculated for the preindustrial atmosphere with the present-day results. The calculations show a large increase in the concentrations of sulphur dioxide and nss-sulphates since preindustrial times, amounting to a factor of 2–3 on global average, and reaching more than two orders of magnitude at the surface in some parts of the Northern Hemisphere. Biogenic species such as DMS are also shown to be influenced by industrialization through changes in the oxidizing capacity of the atmosphere. Over the most polluted areas, the increase in sulphates deposition is found to have reached a factor of 30.