Treatments of polluted emissions from incinerator gases: a succinct review

Due to the incomplete mineralisation of some organic compounds during the incineration of municipal solid waste, gaseous emissions are loaded with a large amount of particulate matter, undesirable elements and toxic molecules. Typically, an incinerator of urban solid waste produces large flows of hot gaseous emissions to be purified before being released into the atmosphere. In this paper, treatments of flue gas from a typical municipal waste incinerator are described. The first step is an energy recovery system through heat exchangers to make steam or hot water. Steam is used to produce electricity via a turbine. The economic balance of the total system is very often dependent on the heat recovery. The second step involves particle removal technologies. Different systems are available such as cyclones, scrubbers, electrostatic precipitators or baghouse filters. The third step is the removal of numerous molecule families such as acid compounds (SO_x, HCl, HF), nitrogen oxides (NO_x), metal species and many organic compounds. The latter include dioxins, furans and volatile organic compounds. Some treatment processes are described according to the pollutant family.     

Activated sludge biotreatment of sulphurous waste emissions

Odours from wastewater treatment plants are comprised of a mixture of various gases, of which hydrogen sulphide (H₂S) is the main constituent. Sulphurous compounds can be degraded by microorganisms commonly found in wastewater. The use of activated sludge (AS) diffusion as a dual-role system, for the treatment of wastewater and for odour control, offers an alternative to traditional sulphurous waste gas treatment processes, such as biofilters, bioscrubbers and biotrickling filters, both in practical terms (use of existing facilities) and economically (minimal capital cost). Activated sludge diffusion avoids the common problems associated with these processes such as media plugging, excess biomass accumulation, gas short-circuiting, and moisture control and maintaining the correct biofilm thickness. The design issues to be considered when using AS diffusion for odour abatement, comprise odourous air pre-treatment,blowers and diffuser types, corrosion protection and increase in odour emission intensity. Nitrification inhibition depends on the composition and acclimation of the biomass, the concentration of H₂S and other components of the wastewater. Hydrogen sulphide removal rates of >98% were consistently achieved for loads of 3–34 mg H₂S/g MLSS/h, in two case studies, which also showed that sludge type has an impact on the ability of the sludge to degrade H₂S. Wastewater process performance measured as five-day biological oxygen demand (BOD₅), chemical oxygen demand (COD) and effluent suspended solids removal was not affected by H₂S diffusionat 5 ppm. A change in the microorganism population dynamics of anactivated sludge was observed when it was exposed to H₂S for aperiod of more than 21 days.     

Release of volatiles during the flowering period of Hydrosme rivieri (Araceae)

The release of volatile compounds from a flower of Hydrosme rivieri was recorded during the whole flowering period (7 days). The quantities of six odour components (dimethyl disulphide, dimethyl trisulphide, n-alkanes C₁₀, C₁₁, C₁₂ and C₁₃) forming the main part of emanating volatiles were plotted versus time. n-Alkanes started to emanate 3 days before the release of dimethyl disulphide and dimethyl trisulphide (the components with a rotting meat odour).     

Effect of Dimethyl Sulfides on the Induction of Apoptosis in Human Leukemia Jurkat Cells and HL-60 Cells

Organosulfur compounds have been established to possess anticancer effects. To provide a better understanding of the biological function of dimethyl sulfides, dimethyl monosulfide (Me₂S), dimethyl disulfide (Me₂S₂), dimethyl trisulfide (Me₂S₃) and dimethyl tetrasulfide (Me₂S₄) were used as experimental materials to investigate their effects on apoptosis induction in human leukemia Jurkat cells and HL-60 cells. Treatment with 20 μM dimethyl sulfides for 24 h decreased the viability of both cells. The cell viability-reducing effect of these sulfides was in the following order: Me₂S₄ ≈ Me₂S₃ > Me₂S₂ ≈ Me₂S for Jurkat cells and Me₂S₄ > Me₂S₃ > Me₂S₂ ≈ Me₂S for HL-60 cells. Me₂S₃ and Me₂S₄ significantly induced DNA fragmentation and caspase-3 activation. The addition of GSH or NAC completely suppressed the sulfide-induced apoptosis. Our results indicate that dimethyl sulfides with a larger number of sulfur atoms more strongly induced apoptosis in both human leukemia cells via ROS production and caspase-3 activation.     

Seasonal changes in fluxes of methane and volatile sulfur compounds from rice paddies and their concentrations in soil water

Rice paddies emit not only methane but also several volatile sulfur compounds such as dimethyl sulfide (DMS: CH₃SCH₃). However, little is known about DMS emission from rice paddies. Fluxes of methane and DMS, and the concentrations of methane and several volatile sulfur compounds including hydrogen sulfide (H₂S), carbonyl disulfide (CS₂), methyl mercaptan (CH₃SH) and DMS in soil water and flood water were measured in four lysimeter rice paddies (2.5 × 4 m, depth 2.0 m) once per week throughout the entire cultivation period in 1995 in Tsukuba, Japan. The addition of exogenous organic matter (rice straw) was also examined for its influence on methane or DMS emissions. Methane fluxes greatly differed between treatments in which rice straw had been incorporated into the paddy soil (rice straw plot) and plots without rice straw (mineral fertilizer plot). The annual methane emission from the rice straw plots (37.7 g m^-2) was approximately 8 times higher than that from the mineral fertilizer plots (4.8 g m^-2). Application of rice straw had little influence on DMS fluxes. Significant diurnal and seasonal changes in DMS fluxes were observed. Peak DMS fluxes were found around noon. DMS was emitted from the flood water in the early growth stage of rice and began to be emitted from rice plants during the middle stage. DMS fluxes increased with the growth of rice plants and the highest flux, 15.1 µg m^-2 h^-1, was recorded before heading. DMS in the soil water was negligible during the entire cultivation period. These facts indicate that the DMS emitted from rice paddies is produced by metabolic processes in rice plants. The total amount of DMS emitted from rice paddies over the cultivated period was estimated to be approximately 5–6 mg m^-2. CH₃SH was emitted only from flood water during the first month after flooding.     

Evolution of Volatile Sulfur Compounds during Laboratory-Scale Incubations and Indoor Preparation of Compost Used as a Substrate in Mushroom Cultivation

Volatile sulfur compounds are known to be produced during the preparation of compost used as a substrate in mushroom cultivation. Because they cause odor problems, attempts have been made to reduce the production of these compounds. The influences of temperature and various additions on the production of volatile sulfur compounds from composting material were tested on laboratory-scale preparations. The production of H₂S, COS, CH₃SH, and (CH₃)₂S was proven to be a biological process with an optimal temperature that coincides with the optimal temperature for biological activity. The formation of CS₂ and (CH₃)₂S₂ was shown to be a nonbiological process. The emission of volatile sulfur compounds during the indoor preparation of mushroom compost appeared to be remarkably reduced (about 90%) as compared with the emission during the conventional outdoor process. Introduction of this indoor composting process would result in a significant reduction in environmental pollution.     

Pollinator attraction of the wasp-flower Scrophularia umbrosa (Scrophulariaceae)

Certain species of Scrophularia (Scrophulariaceae), such as S. nodosa and S. umbrosa, are mainly pollinated by social wasps and are consequently described as wasp-flowers. Because plants attract their pollinators with the help of various floral cues, such as floral odour and/or optical cues, we have investigated the role of olfactory and visual floral signals responsible for wasp attraction in S. umbrosa. Using a combination of chemical (GC, GC-MS) and electrophysiological analyses (GC-EAD), we identified ten compounds in the complex floral odour bouquet that are detectable by the wasps' antennae. As in the wasp-flower Epipactis helleborine, we found so-called 'green leaf volatiles' (GLVs) in the floral odour; these GLVs are highly attractive to the wasps. GLVs, mostly six-carbon aldehydes, alcohols and acetates, and other volatile organic compounds (VOCs), are emitted by many plants infested with herbivores, e.g. caterpillars. In contrast to other investigated wasp-flowers, behavioural experiments have demonstrated that, in addition to the floral odour of S. umbrosa, visual cues are involved in pollinator attraction.     

Simultaneous feeding by aboveground and belowground herbivores attenuates plant-mediated attraction of their respective natural enemies

Herbivore-damaged plants emit volatile organic compounds that attract natural enemies of the herbivores. This form of indirect plant defence occurs aboveground as well as belowground, but it remains unclear how simultaneous feeding by different herbivores attacking leaves and roots may affect the production of the respective defence signals. We employed a setup that combines trapping of volatile organic signals and simultaneous measurements of the attractiveness of these signals to above and belowground natural enemies. Young maize plants were infested with either the foliar herbivore Spodoptera littoralis , the root herbivore Diabrotica virgifera virgifera , or with both these important pest insects. The parasitic wasp Cotesia marginiventris and the entomopathogenic nematode Heterorhabditis megidis were strongly attracted if their respective host was feeding on a plant, but this attraction was significantly reduced if both herbivores were on a plant. The emission of the principal root attractant was indeed reduced due to double infestation, but this was not evident for the leaf volatiles. The parasitoid showed an ability to learn the differences in odour emissions and increased its response to the odour of a doubly infested plant after experiencing this odour during an encounter with hosts. This first study to measure effects of belowground herbivory on aboveground tritrophic signalling and vice-versa reemphasizes the important role of plants in bridging interactions between spatially distinct components of the ecosystem.     

Isoprene is more affected by climate drivers than monoterpenes: A meta‐analytic review on plant isoprenoid emissions

Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatile organic compounds produced by plants (biogenic volatile organic compounds). We conducted a meta‐analysis to quantify the mean effect of environmental factors associated to climate change (warming, drought, elevated CO₂, and O₃) on the emission of isoprene and MTs. Results indicated that all single factors except warming inhibited isoprene emission. When subsets of data collected in experiments run under similar change of a given environmental factor were compared, isoprene and photosynthesis responded negatively to elevated O₃ (?8% and ?10%, respectively) and drought (?15% and ?42%), and in opposite ways to elevated CO₂ (?23% and +55%) and warming (+53% and ?23%, respectively). Effects on MTs emission were usually not significant, with the exceptions of a significant stimulation caused by warming (+39%) and by elevated O₃ (limited to O₃‐insensitive plants, and evergreen species with storage organs). Our results clearly highlight individual effects of environmental factors on isoprene and MT emissions, and an overall uncoupling between these secondary metabolites produced by the same methylerythritol 4‐phosphate pathway. Future results from manipulative experiments and long‐term observations may help untangling the interactive effects of these factors and filling gaps featured in the current meta‐analysis.     

Odorous Sulfur Compounds Emitted during Production of Compost Used as a Substrate in Mushroom Cultivation

Large-scale composting facilities are known to cause environmental problems, mainly through pungent air emitted by composting material. In air samples taken above stacks set up to prepare compost used as a substrate in mushroom cultivation, several volatile compounds were identified by means of the coupled techniques of gas chromatography and mass spectrography. Among the compounds identified, sulfur-containing compounds [H₂S, COS, CH₃SH, CS₂, (CH₃)₂S, (CH₃)₂S₂, and (CH₃)₂S₃] are the most conspicuous in causing a nuisance. Quantification of these compounds was performed by concentrating a relatively small air sample on Tenax GC. The sampling method appeared to be very useful under field conditions. During the composting process, the concentration of the volatile sulfur compounds in emitted air ranged from 1 to 35 μmol/m³. The highest concentrations were obtained at the end of the outdoor process. Total sulfur emission amounted to 8.3 mg of sulfur per kg (fresh weight) of compost. The end product still contained 2.58 g of sulfur per kg (fresh weight) of compost. Suggestions about the origin of the volatile sulfur compounds are made.     

Production of volatile sulfur compounds during the decomposition of algal mats.

Blue-green algal mats incubated anaerobically rapidly produce large amounts of volatile sulfur compounds, including hydrogen sulfide, methyl mercaptan, and dimethyl sulfide. The major organic sulfur compound is methyl mercaptan, in contrast to previous results with marine eucaryotic algae. Light inhibited production of volatile sulfur compounds, apparently because the algae then produced O2, rendering the system aerobic.     

Production of volatile sulfur compounds during the decomposition of algal mats.

Blue-green algal mats incubated anaerobically rapidly produce large amounts of volatile sulfur compounds, including hydrogen sulfide, methyl mercaptan, and dimethyl sulfide. The major organic sulfur compound is methyl mercaptan, in contrast to previous results with marine eucaryotic algae. Light inhibited production of volatile sulfur compounds, apparently because the algae then produced O2, rendering the system aerobic.     

Isobutyraldehyde as a competitor of the dimethyl sulfide degrading activity in biofilters

Upon inoculation with Hyphomicrobium MS3, theelimination capacity of a lab-scale biofilter for theodorant dimethyl sulfide (Me₂S) can be stronglyincreased from less than 10 to more than 35 and 1000 gm^-3d^-1 using wood bark and compost as acarrier material, respectively. However, uponsupplementation of isobutyraldehyde (IBA) as a secondgaseous substrate, sequential degradation profiles of IBAand Me₂S in physically separated sections wereobserved in the Hyphomicrobium MS3-inoculatedwood bark and compost biofilters. Contrary to this, thebiofiltration efficiency for Me₂S remainedunaffected upon the supplementation of toluene as asecond gaseous substrate. Batch experiments with theliquid Hyphomicrobium MS3 culture confirmed thecompetitive effect of IBA on the Me₂S degradingactivity: in the presence of both compounds, Hyphomicrobium MS3 preferred degradation of thecarbonyl compound. In technical terms, this means thatthe complete purification of a waste gas stream containingboth IBA and Me₂S should be performed usingsufficiently high or bistage HyphomicrobiumMS3-inoculated biofilters. Design criteria have to beconceived in this respect.     

On-line detection of root-induced volatiles in Brassica nigra plants infested with Delia radicum L. root fly larvae

Plants emit various volatile organic compounds (VOCs) upon herbivore attack. These VOC emissions often show temporal dynamics which may influence the behavior of natural enemies using these volatiles as cues. This study analyzes on-line VOC emissions by roots of Brassica nigra plants under attack by cabbage root fly larvae, Delia radicum. Root emitted VOCs were detected using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and Gas Chromatography–Mass Spectrometry (GC–MS). These analyses showed that several sulfur containing compounds, such as methanethiol, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS) and glucosinolate breakdown products, such as thiocyanates (TC) and isothiocyanates (ITC), were emitted by the roots in response to infestation. The emissions were subdivided into early responses, emerging within 1–6 h after infestation, and late responses, evolving only after 6–12 h. The marker for rapid responses was detected at m/z 60. The ion detected at m/z 60 was identified as thiocyanic acid, which is also a prominent fragment in some TC or ITC spectra. The emission of m/z 60 stopped when the larvae had pupated, which makes it an excellent indicator for actively feeding larvae. Methanethiol, DMS and DMDS levels increased much later in infested roots, indicating that activation of enzymes or genes involved in the production of these compounds may be required. Earlier studies have shown that both early and late responses can play a role in tritrophic interactions associated with Brassica species. Moreover, the identification of these root induced responses will help to design non-invasive analytical procedures to assess root infestations.     

生物净化废气技术的进展

生物技术以其能在常温常压下将污染物降解为无毒无害的简单物质、无二次污染、运行费用低等优点,目前已应用于许多废气处理,并已经形成了一套关于可生化气体的净化原理和工业应用经验的重要体系。文中介绍了生物技术处理污水处理厂、养殖场排放的恶臭气体、工厂排放的硫化物的发展,并分析了解决生物膜堵塞的途径,以及分子生物学在废气生物处理中的应用研究,提出生物净化废气技术的发展方向,期待该技术在国内能得到更广泛的应用。     

生物净化废气技术的进展

生物技术以其能在常温常压下将污染物降解为无毒无害的简单物质、无二次污染、运行费用低等优点,目前已应用于许多废气处理,并已经形成了一套关于可生化气体的净化原理和工业应用经验的重要体系。文中介绍了生物技术处理污水处理厂、养殖场排放的恶臭气体、工厂排放的硫化物的发展,并分析了解决生物膜堵塞的途径,以及分子生物学在废气生物处理中的应用研究,提出生物净化废气技术的发展方向,期待该技术在国内能得到更广泛的应用。     

What makes Allium species effective against pathogenic microbes?

The antimicrobial activity of garlic (Allium sativum L.) has been known since ancient times. The first citation dates back to the Egyptian period of fifteenth century BC when garlic was reported to be used in folk medicine as a remedy for microbial infections. Scientific investigations on garlic started in 1858 with the work of Pasteur who first noted antibacterial properties of garlic extracts. From that date to the discovery of antibiotics, garlic has been used against amoebic dysentery and epidemic diseases such as typhus, cholera, diphtheria, and tuberculosis. But what makes garlic and Allium species effective against pathogenic microbes? The volatile allicin and other thiosulfinates, giving pungency to Allium plants, are well-studied antimicrobial agents. The thiosulfinates can decompose to form additional sulfur constituents, including diallyl, methyl allyl, and dipropyl mono-, di-, tri- e tetra-sulfides, and (E)- and (Z)-ajoene without losing antimicrobial activity. Besides these compounds, onion and garlic are characterized by polar compounds of steroidal and phenolic origin, often glycosilated, not pungent and more stable during cooking, showing also antimicrobial activity. Recently, there has been increasing scientific attention given to such compounds. Nitrogen organic compounds, like alkaloids and polypeptides, have also been isolated from these plants and have shown antimicrobial activity. In this paper, the literature about the major volatile and non-volatile organic compounds of garlic and other Allium plants has been reviewed. Particular attention is given to the compounds possessing antimicrobial activity and to the correlation between the observed activity and the chemical structure of the tested compounds.     

Temporal and sexual variation of leaf-produced pollinator-attracting odours in the dwarf palm

Information on intra-specific variation in pollinator-attracting floral traits provides clues to selective pressures imposed by pollinators. However, these traits also reflect constraints related to floral phenology or morphology. The specific weevil pollinator Derelomus chamaeropsis of the dioecious Mediterranean dwarf palm Chamaerops humilis is attracted by volatile compounds that leaves, and not flowers, release during anthesis. Production of these olfactory cues is thus probably not constrained by any other floral function. This provides the opportunity to study variation of a floral trait that is not produced by a floral organ. We studied volatile compounds emitted by leaves of 12 individual C. humilis over the whole flowering season. The quantity of volatile compounds emitted by leaves reached a maximum when plants required pollinator visits. The relationship between odour emission and floral phenology was slightly different between male and female plants, probably reflecting differences in the exact time at which females and males benefit from pollinator visitation. Male plants produced higher quantities of volatile compounds than females. Odour composition was highly variable among individuals but did not differ between male and female plants. In this system, female C. humilis are pollinated by deceit and pollinators should be selected to avoid visiting them. The absence of sexual difference in blend composition may thus prevent pollinators from discriminating between male and female plants.An erratum to this article can be found at     

Volatile constituents and fatty acid composition of lipids in Durio zibethinus

The predominating flavour compounds in the fruit pulp of Durio zibethinus were hydrogen sulfide, ethyl hydrodisulfide and several dialkyl polysulfides, particularly (C₂H₅)₂S_n, where n = 2 or 3. Ethyl acetate, 1,1-diethoxyethane and ethyl 2-methylbutanoate contribute to an additional fruity odour note. Hydrodisulfides are probably the precursors of the dialkyl sulfides. In the pericarp and seed no volatile sulfur compounds could be detected. The fatty acid composition of the lipids in pericarp, pulp and seed depended on the origin and/or harvest season of the fruit. The main components were oleic and palmitic acids or arachidic acid together with appreciable quantities of palmitoleic, stearic, linoleic and linolenic acids.