Organic Sulfides Research Articles

Dyeing and finishing wastewater treatment in China: State of the art and perspective

China has the largest textile production and export in the world, with a massive amount of wastewater and related pollutants releasing. With an increasing concern to improve water quality, dyeing and finishing wastewater (DFW) requires better disposal or reclamation. In this review, the characteristics of wastewater in different natural and synthetic fiber production processes as well as the origins of their specific pollutants such as aniline, absorbable organic halogens (AOX), sulfide, hexavalent chromium and antimony were summarized. The discharge standards for DFW in China, have undergone complex evolution processes, which were discussed including the current standard, the revision detail and the one to be implemented. Furthermore, the current status of pollutant reduction in the textile industry, covering cleaner production and wastewater treatment, was targeted, in particular the state of the art of specific pollutant removal technologies and their feasibility of application for DFW treatment. Also, reclamation systems based on wastewater discharge characteristics and reclaimed water quality requirements were reviewed. Overall, the systematic solution of source reduction of wastewater and contaminants, coupled with subsequent treatment and recycling, is crucial for the sustainable development of the textile industry.

The underappreciated role of natural organic matter bond Hg(II) and nanoparticulate HgS as substrates for methylation in paddy soils across a Hg concentration gradient

Rice consumption is the major pathway for human methylmercury (MeHg) exposure in inland China, especially in mercury (Hg) contaminated regions. MeHg production, a microbially driven process, depends on both the chemical speciation of inorganic divalent mercury, Hg(II), that determines Hg bioavailability for methylation. Studies have shown that Hg(II) speciation in contaminated paddy soils is mostly controlled by natural organic matter and sulfide levels, which are typically thought to limit Hg mobility and bioavailability. Yet, high levels of MeHg are found in rice, calling for reconsideration of the nature of Hg species bioavailable to methylators in paddy soils. Here, we conducted incubation experiments using a multi-isotope tracer technique including 198Hg(NO3)2, natural organic matter bond Hg(II) (NOM-199Hg(II)), ferrous sulfide sorbed Hg(II) (≡FeS-200Hg(II)), and nanoparticulate mercuric sulfide (nano-202HgS), to investigate the relative importance of geochemically diverse yet relevant Hg(II) species on Hg methylation in paddy soils across a Hg concentration gradient. We show that methylation rates for all Hg(II) species tested decreased with increasing Hg concentrations, and that methylation rates using NOM-199Hg(II) and nano-202HgS as substrates were similar or greater than rates obtained using the labile 198Hg(NO3)2 substrate. ≡FeS-200Hg(II) yielded the lowest methylation rate in all sites, and thus the formation of FeS is likely a sink for labile 198Hg(NO3)2 in sulfide-rich paddy soils. Moreover, the variability in the methylation data for a given site (1 to 5-fold variation depending on the Hg species) was smaller than what was observed across the Hg concentration gradient (103–104 fold variation between sites). These findings emphasize that at broad spatial scales, site-specific characteristics, such as microbial community structure, need to be taken into consideration, alongside the nature of the Hg substrate available for methylation, to determine net MeHg production. This study highlights the importance of developing site-specific strategies for remediating Hg pollution.

Water Contamination in Petroleum Refinery Processes

<p>This study was conducted to assessment the environmental impacts in petroleum refineries due to the different processes. The paper presents the data obtained during a case study was achieved in Tobruk petroleum refinery. The main petroleum products of the refinery represented by diesel, light naphtha, heavy naphtha and kerosene with maximum production capacity concerning 21,500 bbl/day. The results of the study revealed that the waste water affected by high concentration of hydrocarbons. The heavy metals are also determined and represented by V, Fe, Ni and Cu with low contents in crude oil. Also the pollutants parameters in the disposal water e.g. biochemical oxygen demand, chemical oxygen demand, total organic carbon, suspended solids, phenols, ammonia and sulphides are determined, and the results are compared with other refinery types. The concentration of these parameters are higher than the standard values that recommended by Environmental Protection Agency (EPA), at the same time these values are less if they are compared with the other refinery types.</p>

Unveiling structure-function relationships in deep eutectic solvents based biomimetic catalysis for aerobic oxidative desulfurization

Organic sulfides in fuel oil result in the formation of environmentally hazardous sulfur oxide through the combustion in vehicle engine. Oxidative desulfurization is considered to be an effective technique to eliminate sulfides in fuel oil, whose core is the construction of efficient catalytic systems under mild conditions. Herein, a biomimetic catalytic system was designed for aerobic oxidative desulfurization via coupling ammonium molybdate polyoxometalate with four different deep eutectic solvents (DESs), obeying multi-step electron transfer mechanism. It was found that the desulfurization efficiency was not directly associated with conductivity, viscosity and hydrogen-bonding strength. In combination with density functional theory (DFT) calculation, the difference in desulfurization efficiency was ascribed to the distinguished intrinsic oxidation ability of organic acid in DES. The optimal catalytic system not only could resist the adverse effect of naphthaline and indole within suitable concentration scope, but also did not show obvious decrease in desulfurization performance after ten runs. More importantly, deep desulfurization was still afforded for actual diesels using this catalytic system, indicating its enormously potential applications on an industrial level under mild conditions.

AsIII-oxidizing and Cd-tolerant plant growth-promoting bacteria synergistically reduce arsenic translocation, toxicity and accumulation in KDML105 rice

Arsenic (As) contamination in rice grains, a staple food for the global human population, is a pervasive problem that leads to serious health risks. In this study, various combinations of AsIII-oxidizing bacteria (Pseudomonas stutzeri 4.25, 4.27, and 4.44) and Cd-tolerant bacteria (Cupriavidus taiwanensis KKU2500−3 and Delftia acidovorans KKU2500−12) affected the growth of KDML105 rice in pots containing As-contaminated soil under greenhouse conditions. All strains produced inorganic and organic sulfides and exhibited plant growth-promoting traits in vitro. The KKU2500−12/4.25, KKU2500−3/4.25, KKU2500−3/4.27 and KKU2500−3/4.44 combinations increased the oxidation rate of AsIII to AsV. Noninoculated and coinoculated rice was grown in soils collected from As-contaminated paddy fields containing non-detected As or low (29.13 mg/kg) or high (45.11 mg/kg) total As levels. Arsenic affected rice growth and productivity and As accumulation in rice tissues and grains. Bacterial inoculation significantly increased rice growth and yield and decreased the unfilled-grain percentage. KKU2500−3/4.44 was the most effective combination in decreasing As toxicity and accumulation, resulting in non-detected As or a 50 % reduction in As in rice grains grown in low- or high-As soils, respectively. The counts of inoculated bacteria on the root surface and interior were relatively high. Thus, bacteria reduced As availability in the rhizosphere and subsequently decreased As uptake by roots. The bacteria enhanced sulfide accumulation in roots and likely induced the formation of insoluble, nontoxic arsenic sulfide. Various Asx forms and compounds were likely induced by bacteria within roots and reduced AsIII translocation from roots to shoots, leaves and grains, resulting in decreased As toxicity during rice growth and decreased As accumulation in grains. A possible role for the inoculated bacteria in the serial root-xylem-phloem-leaf-phloem-grain translocation of AsIII is proposed. These findings demonstrate the potential for the use of these bacteria in fields with low levels of As contamination (below 29.13 mg/kg).

Microscale Toxicity Identification Evaluation (TIE) for interstitial water of estuarine sediments affected by multiple sources of pollution.

Estuaries in the world are affected by different contamination sources related to urbanisation and port/industrial activities. Identifying the substances responsible for the environmental toxicity in estuaries is challenging due to the multitude of stressors, both natural and anthropogenic. The Toxicity Identification and Evaluation (TIE) is a suitable way of determining causes of toxicity of sediments, but it poses difficulties since its application is labour intensive and time consuming. The aim of this study is to evaluate the diagnosis provided by a TIE based on microscale embryotoxicity tests with interstitial water (IW) to identify toxicants in estuarine sediments affected by multiple stressors. TIE showed toxicity due to different combinations of metals, apolar organic compounds, ammonia and sulphides, depending on the contamination source closest to the sampling station. The microscale TIE was able to discern different toxicants on sites subject to different contamination sources. There is good agreement between the results indicated in the TIE and the chemical analyses in whole sediment, although there are some disagreements, either due to the sensitivity of the test used, or due to the particularities of the use of interstitial water to assess the sediment toxicity. The improvement of TIE methods focused on identifying toxicants in multiple-stressed estuarine areas are crucial to discern contamination sources and subsidise management strategies.

Green synthesis of Cu/Fe3O4nanocomposite using Calendula extract and evaluation of its catalytic activity for chemoselective oxidation of sulfides to sulfoxides with aqueous hydrogen peroxide

Plant mediated biogenic synthesizednanoparticles have beenquite familiar as next generation prospective catalysts. In this work, we have demonstrated copper nanoparticles (Cu NP) immobilized magnetic Fe3O4 nanoparticles using Calendula extract as a reducing and stabilizing agent. The plant extract phytochemicals initially are adorned as a protective shell over the core ferrite NPs and further reduces the incoming Cu ions following a green pathway.The physicochemical characterizations of the nanocomposite was carried out through Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD) study.The as synthesized material was used as a competent and magnetically isolable catalyst in the controlled and selective oxidation of different organic sulfides to sulfoxides using hydrogen peroxide as the green oxidant at room temperature. A wide spectrum of aromatic, aliphatic and heterocyclic sulfides were oxidized to their corresponding sulfoxides with excellent yields without any over oxidized product to sulfones.Due to superparamagentic character, the materialwas easily magnetically decantable and reused for 8 consecutive times with retention of its catalytic activity.

Partial Nitrification in a Sequencing Moving Bed Biofilm Reactor (SMBBR) with Zeolite as Biomass Carrier: Effect of Sulfide Pulses and Organic Matter Presence

This work aimed to achieve partial nitrification (PN) in a Sequencing Moving Bed Biofilm Reactor SMBBR with zeolite as a biomass carrier by using sulfide pulses in the presence of organic matter as an inhibitor. Two conditions were evaluated: sulfide (HS−) = 5 mg S/L and vvm (air volume per liquid volume per minute, L of air L−1 of liquid min−1) = 0.1 (condition 1); and a HS− = 10 mg S/L and a vvm = 0.5 (condition 2). The simultaneous effect of organic matter and sulfide was evaluated at a Chemical Oxygen Demand (COD) = 350 mg/L and HS− = 5 mg S/L, with a vvm = 0.5. As a result, using the sulfide pulse improved the nitrite accumulation in both systems. However, Total Ammonia Nitrogen (TAN) oxidation in both processes decreased by up to 60%. The simultaneous presence of COD and sulfide significantly reduced the TAN and nitrite oxidation, with a COD removal yield of 80% and sulfide oxidation close to 20%. Thus, the use of a sulfide pulse enabled PN in a SMBBR with zeolite. Organic matter, together with the sulfide pulse, almost completely inhibited the nitrification process despite using zeolite.

Spatiotemporal Trends, Sources and Ecological Risks of Heavy Metals in the Surface Sediments of Weitou Bay, China

Heavy metals are extremely harmful materials to marine ecosystems and human health. To determine the anthropogenic contributions and ecological risks in Weitou Bay, China, the spatiotemporal variations in the concentrations of heavy metals in surface sediment were investigated during spring 2008 and 2017. The results indicated that high concentrations of pollutants were generally located near the river mouths and along the coast of industrial areas. Principal component analysis indicated that heavy metal contents were mainly affected by industrial waste drainage, urban development, natural weathering and erosion, and interactions between organic matter and sulfides. The potential ecological risk assessment demonstrated that, in 2008, 82% of the sampling sites were at low risk, while 18% were at moderate risk. The situation had deteriorated slightly by 2017, with 73%, 18%, and 9% of stations in Waytou Bay at low, moderate, and very high risk, respectively. Cd was the most harmful metal, followed by Hg. These two elements accounted for more than 80% of the potential ecological risk index (RI) value. The present work analyzed the source of heavy metals, identified the major pollution elements and high risk areas, and provides guidance for pollution control and ecological restoration in Weitou Bay.

Preliminary analysis on roles of metal\u2013organic compounds in the formation of invisible gold

The paper comprises new analytical data on the nature and occurrence of gold in solid pyrobitumen, closely associated with the main gold-bearing sulfide arsenic ores of the Bakyrchik gold deposit (Kazakhstan), related to post-collisional magmatic-hydrothermal origin. Gold mineralization of the deposit occurs mainly in the form of an “invisible” type of gold in the structures of arsenian pyrite and arsenopyrite, and the form of gold-organic compounds of pyrobitumen in carbonaceous-terrigenous sequences of Carboniferous formation. Microscopic and electron microscopic analysis, Raman and FT-Infrared analysis, mineralogical and three-step sequential extraction analysis (NH2OH·HCl, H2O2, HNO3 + HCl) has been carried out using 9 ore samples (from 3 different types of ores) for a comprehensive study of pyrobitumen and sulfide arsenic ores focusing mainly on organic matter. The sequentially extracted precious metal content of pyrobitumen reaches up to 7 ppm gold and other metals like Ag 4 ppm, Pt 31 ppb, and Pd 26 ppb, forming metal–organic compounds, while arsenic sulfide minerals incorporate 11 ppm gold, 39 ppm Ag, 0.49 ppm Pt. The enrichment of gold associating with organic matter and sulfide ore minerals was confirmed in this study. Organic matter was active in the migration of gold and the capture of gold by pyrobitumen. Moreover, the reductive organic matter agent released gold, most likely for the sulfide arsenic ore minerals. Pyrobitumen was a decisive factor in the concentration, transportation, and preservation of gold in the deposit.

2D sp2 carbon-conjugated triazine covalent organic framework photocatalysis for blue light-induced selective oxidation of sulfides with O2

Triazine, possessing planar and fully conjugated attributes, purveys ample space to construct well-defined crystalline polymers like graphic carbon nitrides (g-C3N4), covalent triazine frameworks (CTFs), and covalent organic frameworks (COFs). Herein, g-C3N4, CTF-1, and TP-COF were successfully synthesized and systematically confirmed by a series of characterizations, aiming at visible light photocatalytic activation of O2. Compared to CTF-1 and g-C3N4, TP-COF was endowed with the best photocatalytic performance by several inherent properties, including a large specific surface area, a suitable bandgap, and superior charge transfer. The blue light-induced selective conversion of organic sulfides has been achieved expeditiously with O2 over TP-COF photocatalyst. Moreover, rigorous control experiments and in situ electron paramagnetic resonance (EPR) suggest that electron and energy transfer pathways contribute to the selective formation of desired sulfoxides. This work emphasizes that the tailor-made trait of COFs provides an ideal plarform of customizing two-dimensional (2D) photoactive COFs based on triazine for visible light-induced selective chemical transformations.

Rapid, concurrent formation of organic sulfur and iron sulfides during experimental sulfurization of sinking marine particles.

Organic matter (OM) sulfurization can enhance the preservation and sequestration of carbon in anoxic sediments, and it has been observed in sinking marine particles from marine O2-deficient zones. The magnitude of this effect on carbon burial remains unclear, however, because the transformations that occur when sinking particles encounter sulfidic conditions remain undescribed. Here, we briefly expose sinking marine particles from the eastern tropical North Pacific O2-deficient zone to environmentally relevant sulfidic conditions (20°C, 0.5 mM [poly]sulfide, two days) and then characterize the resulting solid-phase organic and inorganic products in detail. During these experiments, the abundance of organic sulfur in both hydrolyzable and hydrolysis-resistant solids roughly triples, indicating extensive OM sulfurization. Lipids also sulfurize on this timescale, albeit less extensively. In all three pools, OM sulfurization produces organic monosulfides, thiols, and disulfides. Hydrolyzable sulfurization products appear within ≤ 200-μm regions of relatively homogenous composition that are suggestive of sulfurized extracellular polymeric substances (EPS). Concurrently, reactions with particulate iron oxyhydroxides generate low and fairly uniform concentrations of iron sulfide (FeS) within these same EPS-like materials. Iron oxyhydroxides were not fully consumed during the experiment, which demonstrates that organic materials can be competitive with reactive iron for sulfide. These experiments support the hypothesis that sinking, OM- and EPS-rich particles in a sulfidic water mass can sulfurize within days, potentially contributing to enhanced sedimentary carbon sequestration. Additionally, sulfur-isotope and chemical records of organic S and iron sulfides in sediments have the potential to incorporate signals from water column processes.

Temperature control on CO2 emissions from the weathering of sedimentary rocks

Sedimentary rocks can release carbon dioxide (CO2) during the weathering of rock organic carbon and sulfide minerals. This sedimentary carbon could act as a feedback on Earth’s climate over millennial to geological timescales, yet the environmental controls on the CO2 release from rocks are poorly constrained. Here, we directly measure CO2 flux from weathering of sedimentary rocks over 2.5 years at the Draix-Bléone Critical Zone Observatory, France. Total CO2 fluxes approached values reported for soil respiration, with radiocarbon analysis confirming the CO2 source from rock organic carbon and carbonate. The measured CO2 fluxes varied seasonally, with summer fluxes five times larger than winter fluxes, and were positively correlated with temperature. The CO2 release from rock organic carbon oxidation increased by a factor of 2.2 when temperature increased by 10 °C. This temperature sensitivity is similar to that of degradation of recent-plant-derived organic matter in soils. Our flux measurements identify sedimentary-rock weathering as a positive feedback to warming, which may have operated throughout Earth’s history to force the surface carbon cycle. The release of carbon dioxide during oxidative weathering of sedimentary rocks acts as a positive feedback to warming, according to 2.5 years of CO2 flux measurements from the Draix-Bléone Critical Zone Observatory, France.

Covalent Triazine Framework as an Efficient Photocatalyst for Regeneration of NAD(P)H and Selective Oxidation of Organic Sulfide.

Covalent triazine frameworks (CTFs), belonging to the super-family of covalent organic frameworks, have attracted significant attention as a new type of photosensitizer due to the superb light-harvesting ability and efficient charge transfer originating from the large surface area. However, the wide optical band gap in CTFs, which is larger than 3.0 eV, hinders the efficient light harvesting in the visible range. To overcome this limitation, we developed the new type CTFs photocatalyst based on the donor-acceptor conjugation scheme by using melamine (M) and 2,6-diaminoanthraquinone (AQ) as monomeric units. The melamine-2,6-diaminoanthraquinone-based covalent triazine frameworks (M-AQ-CTFs) photocatalyst shows the excellent light-harvesting capacity with high molar extinction coefficient, and the suitable optical band gap involving the internal charge transfer character. Combination of M-AQ-CTFs and artificial photosynthetic system including the organometallic rhodium complex, acting as an electron mediator, exhibited the excellent photocatalytic efficiency for the regeneration of the nicotinamide cofactors such as NAD(P)H. In addition, this photocatalyst showed the high photocatalytic efficiency for the metal-free aerobic oxidation of sulfide. This study demonstrates the high potential of CTFs photocatalyst with the donor-acceptor conjugated scheme can be actively used for artificial photosynthesis.

Singlet Oxygen Generation, Quenching and Reactivity with Metal Thiolates.

Metal thiolate complexes can act as photosensitizers for the generation of singlet oxygen, quenchers of singlet oxygen, and they may undergo chemical reactions with singlet oxygen leading to oxidized thiolate ligands. This review covers all of the chemical reactions of thiolate ligands with singlet oxygen (through early 2021). Since some of these reactions are self-sensitized photooxidations, singlet oxygen generation by metal complexes is also discussed. Mechanistic features such as the effects of protic vs. aprotic conditions are presented and compared with the comparatively well-understood photooxidation of organic sulfides. In general, the total rate of singlet oxygen removal correlates with the nucleophilicity of the thiolate ligand which in turn can be influenced by the metal. Some interesting patterns of reactivity have been noted as a result of this survey: Metal thiolate complexes bearing arylthiolate ligands appear to exclusively produce sulfinate (metal-bound sulfone) products upon reaction with singlet oxygen. In contrast, metal thiolate complexes bearing alkylthiolate ligands may produce sulfinate and/or sulfenate (metal-bound sulfoxide) products. Several mechanistic pathways have been proposed for these reactions, but the exact nature of any intermediates remains unknown at this time.

Gaseous and Particulate Content of Laser Tattoo Removal Plume.

There is increasing awareness of the potential hazards of surgical plumes. The plume associated with laser tattoo removal remains uncharacterized. To determine the gaseous, particulate, and microbiological content of the laser tattoo removal plume. Air sampling was performed during laser tattoo removal from pig skin and from patients. Measurement of metals, volatile organic compounds (VOCs), carbon monoxide (CO), hydrogen sulfide (HS), and ultrafine particulates (UPs) as well as bacterial 16S ribosomal DNA sequencing were performed. Metals were identified in the plume from both pig and human skin. Volatile organic compounds were found at similar levels within and outside the treatment room. Several bacterial phyla were detected in the treatment room, but not outside. High levels of UPs were measured throughout the treatment room during tattoo removal from pig skin. Ultrafine particulates were detected at low levels in the room periphery during tattoo removal from human skin, but at higher levels in the immediate treatment zone. HS and CO were not detected. Metals, VOCs, HS, and CO were found at levels below applicable occupational exposure limits. The presence of bacteria is of uncertain significance, but may be hazardous. High levels of UPs require further investigation.

Characterization and influence of odorous gases on the working surface of a typical landfill site: A case study in a Chinese megacity

Odor pollutants from a landfill can have serious impacts on the surrounding environment and nearby residents. Moreover, the variety and complexity of volatile organic compounds (VOCs) along with the landfill odor makes sampling and identifying compounds challenging. In this study, the authors monitored municipal solid waste (MSW)-related areas, sludge-related areas and waste coverage with the most malodorous compounds. In terms of all 120 VOCs, 67 malodorous VOCs with significant variations were categorized into six classes of compounds under all test conditions. Among the concentration characteristics, Site B concentrations were the highest. For the odor index (OI), the OI values of Site B were higher than those on other sites. The organic sulfides, organic acids and amine were the major malodorous pollutants emitted from landfill and influenced the residential area. Through a coefficient of divergence analysis, the CDjk values of Sites A (0.66) and B (0.69) were lower than others, indicating the effects of odor emission on the surrounding residential area were slightly more severe than on the other sites because of the meteorological condition during the study period. The results of this study can provide essential information to enhance understanding the actual odor emission intensity and characteristics of landfill and the migration, transportation and influence of odorant emissions on the working surface of the landfill.

Dysprosium (III) Supported on CoFe2O4 MNPs as a Heterogeneous Catalyst for the Selective Oxidation of Sulfides and Synthesis of Symmetrical Disulfides

A magnetic catalyst based on immobilization of dysprosium ions on the surface of CoFe2O4 nanoparticles has been reported and used as an efficient magnetic nanocatalyst for the selective oxidation of organic sulfides and synthesis of symmetrical disulfides containing aromatic and aliphatic sulfides and thiols. The magnetic solid catalyst has been identified using TGA, FT-IR, VSM, ICP, SEM, and XRD. Moreover, the catalyst can also be separated with an external magnet and recycled several times without any remarkable decrease in its catalyst activity.

Experimental pyrolysis of metalliferous coal: A contribution to the understanding of pyrometamorphism of organic matter and sulfides during coal waste heaps fires

Thermal metamorphism of original coal adjacent to burning centers in coal waste heaps is a common phenomenon, and semi-coke and coke are formed during this process. In this study, changes taking place during the pyrolysis of both organic and inorganic constituents of coal in burning heaps are interpreted, and the volatility of major and trace elements is assessed. Experimental pyrolysis of bituminous coal from the coal and uranium Novátor Mine (Czech Republic) was carried out at temperatures of 200 °C, 500 °C, 700 °C and 900 °C. Changes occurring at various temperatures of pyrolysis in the coal matrix were studied by methods of coal petrography, organic and inorganic geochemistry. Due to the high contents of sulfides of Fe, Cu Zn and Pb in coal, changes in their chemical composition which occur during their melting were also studied.The results showed that with rising temperature the amount of gas produced during the pyrolysis increased significantly while the amount of released nitrogen from coal organic substance and CO2 decreased and, conversely, the H2 content was increasing significantly. The largest amount of tar originated at a temperature of 500 °C. Coke and semi-coke appeared in the solid residue already at a temperature of 500 °C and, as the temperature increased, its porosity and optical reflectance were gradually increasing. The results of gas chromatography/mass spectroscopy (GC/MS) showed that the pyrolysis was associated with a rapid decline in the extractability of solid products of pyrolysis. The maximum concentration of polycyclic aromatic hydrocarbons (PAHs) in coke was recorded at 500 °C (28.5 rel.% of identified compounds), and then dropped to 11 rel.% at 900 °C.The concentration of Hg in the solid residue after the pyrolysis declined significantly even at temperatures of <500 °C. At higher temperatures, apart from Hg, the amount of In, Sb, Tl, Zn, As, Mo, Sn, Pb, Se, Hg and Cd in the pyrolysis residuum gradually decreased, which corresponds to the presence of sulfides of the above elements in the mats of coal fire gas minerals (CFGM) on the surface of many burnt coal heaps.Galena was partially melted during the pyrolysis already at a temperature of 700 °C to form metallic Pb. However, a significant increase in the volume of melts occurred when the temperature reached 900 °C with the formation of mineral assemblage consisting of galena – metallic Pb – pyrrhotite – sphalerite – intermediate Cu-Fe solid solution phase (iss) – bornite. Consequently, the melting of sulfides during the pyrolysis can be one of the reasons for high volatility of some chalcophile elements in the processes of coal pyrolysis in burning heaps.

Multiplexed Workplace Measurements in Biogas Plants Reveal Compositional Changes in Aerosol Properties.

Anaerobic digestion is an emerging technology producing energy from renewable resources or food waste. Exposure screenings, comprising hazardous substances and biological agents, at different workplaces are necessary for a comprehensive overview of potential hazards in order to assess the risk of employees in biogas plants. In order to analyse these parameters, workplace measurements were conducted in seven full-scale anaerobic digesters. Personal and stationary sampling was performed for inhalable and respirable particles, volatile organic compounds, ammonia, hydrogen sulphide, carbon monoxide, and carbon dioxide. Furthermore, concentrations of the total cell count, endotoxins, and fungi—down to species level—were determined in comparison to windward air. Sequencing of the 16S rRNA genes was utilized for the determination of the bacterial composition inside the biogas plants. Measurements of hazardous substances show hardly values reaching the specific occupational exposure limit value, except ammonia. An approximate 5-fold increase in the median of the total cell count, 15-fold in endotoxins, and 4-fold in fungi was monitored in the biogas plants compared with windward air. Specifying the comparison to selected workplaces showed the highest concentrations of these parameters for workplaces related to delivery and cleaning. Strikingly, the fungal composition drastically changed between windward air and burdened workplaces with an increase of Aspergillus species up to 250-fold and Penicillium species up to 400-fold. Sequence analyses of 16S rRNA genes revealed that many workplaces are dominated by the order of Bacillales or Lactobacillales, but many sequences were not assignable to known bacteria. Although significant changes inside the biogas plant compared with windward air were identified, that increase does not suggest stricter occupational safety measures at least when applying German policies. However, exposure to biological agents revealed wide ranges and specific workplace measurements should be conducted for risk assessment.