Respiration Zone Research Articles

Exposure characteristics and risk assessment of VOCs from Chinese residential cooking

In comparison with various restaurant cuisines, common cooking methods are more represented in residential cooking. Rather than the exhaust pipe or the ambient environment in the cooking room, the respiration zone better reflects the health risks for operators. In this study, the concentrations of total volatile organic compound (TVOC) released from six typical cooking methods were monitored online in the respiratory zone, and the VOCs were analysed by GC-MS. The results demonstrated that the intensities of exposure to TVOC for the different cooking methods decreased as follows: stir-frying (3.809 mg/m3) > quick-frying (2.724 mg/m3) > deep-frying (2.465 mg/m3) > boiling (1.161 mg/m3)≈stewing (1.149 mg/m3) > limit in China (0.600 mg/m3) > steaming (0.440 mg/m3). The intense ventilation mode of the ventilator reduced exposure to TVOC by 45–63% relative to the medium mode. Eleven types of VOCs (approximately 200 compounds) were found in Chinese residential cooking fumes, and the predominant contaminants were aldehydes, followed by alkanes, unsaturated aldehydes, alcohols and alkenes. The mass percentage of aromatic hydrocarbons in all VOCs emitted from Chinese residential cooking was only 1%, while the value was 17–48% for commercial restaurants. The results of a health risk assessment revealed that the total potential carcinogenic risk level for VOCs released by six residential cooking methods decreased as follows: deep-frying (5.75) > stir-frying (3.95) > quick-frying (2.94) > stewing (1.99) > boiling (1.73) > steaming (1.48). Chinese residential cooking, and especially deep frying, has potential health impacts for the operator.

Can Primary Ferroan Dolomite and Ankerite Be Precipitated? Its Implications for Formation of Submarine Methane-Derived Authigenic Carbonate (MDAC) Chimney

Microbes can mediate the precipitation of primary dolomite under surface conditions. Meanwhile, primary dolomite mediated by microbes often contains more Fe2+ than standard dolomite in modern microbial culture experiments. Ferroan dolomite and ankerite have been regarded as secondary products. This paper reviews the process and possible mechanisms of microbial mediated precipitation of primary ferroan dolomite and/or ankerite. In the microbial geochemical Fe cycle, many dissimilatory iron-reducing bacteria (DIRB), sulfate-reducing bacteria (SRB), and methanogens can reduce Fe3+ to Fe2+, while SRB and methanogens can also promote the precipitation of primary dolomite. There are an oxygen respiration zone (ORZ), an iron reduction zone (IRZ), a sulfate reduction zone (SRZ), and a methanogenesis zone (MZ) from top to bottom in the muddy sediment diagenesis zone. DIRB in IRZ provide the lower section with Fe2+, which composes many enzymes and proteins to participate in metabolic processes of SRB and methanogens. Lastly, heterogeneous nucleation of ferroan dolomite on extracellular polymeric substances (EPS) and cell surfaces is mediated by SRB and methanogens. Exploring the origin of microbial ferroan dolomite may help to solve the “dolomite problem”.

Assessment of the Atmospheric Air Quality Within the Main Вus Stations Kharkiv

Purpose. The aim of the paper is determine of atmospheric air quality withim the main Bus Stations in Kharkiv. Methods. The following methods were used: filed, laboratory and statistical ones. Results. The results of the researches was found that the content of dust, carbon monoxide and nitrogen dioxide in the atmospheric air of the city of Kharkiv around Bus stations №1 " Avtovokzal", № 3 " Kinnyj Rynok", № 6 "Zavodska", and Kholodna Gora Terminal higher than MACs. The highest concentrations of pollutants were identified around Bus stations Nr 6 “Zavodska” and Kholodna Gora Terminal. It have shown a tendency to increase in atmospheric air concentrations of gasoline, carbon monoxide, nitrogen dioxide. The temporal tendency to increase in atmospheric air concentrations of gasoline, carbon monoxide, nitrogen dioxide was revealed. Conclusions. The detected excess of the MPC of harmful substances in the atmospheric air of the city of Kharkiv in the districts of the bus stations indicates a difficult situation with the quality of atmospheric air in the cities of intensive traffic, especially in the respiration zone of children. Recommendations aimed at improvement of air quality was proposed.

Origin of facies zonation in microbial carbonate platform slopes: Clues from trace element and stable isotope geochemistry (Middle Triassic, Dolomites, Italy)

AbstractLimestones containing radiaxial fibrous cements were sampled along the southern slope of the late Anisian (Middle Triassic) Latemar carbonate platform in the Dolomites, northern Italy. The Latemar upper slopes comprise massive microbial boundstone, whereas lower slopes are made of clinostratified grainstone, rudstone and breccia. Samples are representative of a seawater column from near sea‐level to an aphotic zone at about 500 m water depth. Radiaxial fibrous cements were analyzed for carbon (δ13C) and oxygen (δ18O) stable isotopic composition, as well as major and trace element content, to shed light on the origin of the slope facies zonation. The δ13C vary between 1·7‰ and 2·3‰ (Vienna Pee‐Dee Belemnite), with lowest values at palaeo‐water depths between 70 m and 300 m. Radiaxial fibrous cements yielded seawater‐like rare earth element patterns with light rare earth element depletion (NdSN/YbSN ≈ 0·4), superchondritic yttrium/holmium ratios (≈55) and negative cerium anomalies. Cadmium reaches maximum values of ca 0·5 to 0·7 μg/g at palaeo‐water depths between 70 m and 300 m; barium contents (0·8 to 1·8 μg/g) increase linearly with depth. The downslope patterns of δ13C and cadmium suggest increased nutrient and organic matter contents at depths between ca 70 m and 300 m and point to an active biological pump. The peak in cadmium and the minimum of δ13C mark a zone of maximum organic matter respiration and high nutrient and organic matter availability. The base of this zone at ca 300 m depth corresponds with the transition from massive microbial boundstone to clinostratified grainstone, rudstone and breccia. The microbial boundstone facies apparently formed only in seawater enriched in organic matter, possibly because this organic matter sustained benthic microbial communities at Latemar. The base of slope microbialites on high‐relief microbial carbonate platforms may be a proxy for the depth to maximum respiration zones of Palaeozoic and Mesozoic periplatform basins.

Sensitivity tests of biological safety cabinets' contaminant contention to variations on indoor flow parameters in biosafety level laboratories

Laboratory buildings demand from 4 to 6 times more energy use than conventional applications, and near 50% of this energy use is due to its ventilation system. Previous studies have demonstrated that the strategy of increasing ventilation rates, in mixing ventilation mode, has limited effectiveness on airborne infection control and that the local airflow patterns are more important than a global ventilation rate for that purpose. The primary objective of this research was to assess the sensitivity of contaminant contention to variations on indoor flow parameters, for biosafety level (BSL-Biosafety level) laboratories. Selected testing scenarios were modeled, and the only contaminant source was located inside the biological safety cabinet (BSC-Biological safety cabinets). Numerical modeling, using computational fluid dynamics was performed, in order to assess the sensitivity of BSC's contaminant contention to different values on: generation rate; room thermal load; downflow turbulence; inflow velocity; and room air change rate. Another objective of this research was to assess the time scale related to contaminant transport from the BSC interior to the operator respiration zone, after a concentration build up has taken place inside the BSC. The results showed that BSC's contaminant contention is dependent on room indoor flow pattern, room turbulence level and inflow velocity. The use of higher values of ventilation rates in biosafety level laboratories should be analyzed with caution, because increasing the ventilation rate, with mixed ventilation, decreases the BSC's contaminant contention, due to the enhanced turbulent level, and may increase personnel exposure to hazardous contaminants that leak from the BSC.

Advanced statistical models commonly applied in aerobiology cannot accurately predict the exposure of people to Ganoderma spore-related allergies

The genus Ganoderma commonly comprises wood decay fungal species that actively produce a large number of spores liberated from basidiocarps thereby contributing significantly to fungal air spora worldwide. Basidiospores of Ganoderma incite disease of tree species, and constitute aeroallergens hazardous to people. Earlier forecasting models to predict high concentrations of Ganoderma spores pointed out the dew point temperature, maximum and average wind speed and precipitation as significant meteorological parameters that affect the basidiospore release. The main aim of this work was to study relationships between basidiospore counts and meteorological conditions and to verify whether regression models based on data collected at aerobiological studies accurately predict the risk of exposure of people with spore-related allergies. Basidiospores were captured over three autumn months from 2006 to 2008 using two Hirst-type volumetric spore traps with identical sampling protocols and evaluation methods. Daily spore concentrations were sampled and the dynamics of changes in Ganoderma spore concentrations sampled at heights used in standard aerobiological studies, located several meters above the ground level (a.g.l.), were compared with those recorded at the same site, but at the human respiration zone, much closer to the ground. Relationships between basidiospore concentrations and weather variables were investigated with the Spearman's rank correlation analysis. To reveal differences in meteorological parameters and Ganoderma spore content between consecutive years and months studied, the non-parametric Mann–Whitney U, Kruskal–Wallis and Dunn's tests were applied. Furthermore artificial neural networks and multivariate regression trees were used, for which meteorological parameters were input variables, while Ganoderma basidiospore abundance was an output variable.Considerable differences were observed between Ganoderma spore concentrations at people's respiratory zone and 18 a.g.l., a height used in standard aerobiological studies. At 1m a.g.l. the concentrations were 1.2 to 6 times higher than those at 18m a.g.l. Moreover, the dynamics of changes throughout spore trapping seasons were different; at 18m a.g.l. they fluctuations were similar across all years sampled, whereas at 1m a.g.l. there were wide variations between years. The correlation between weather variables and concentrations of captured basidiospores at these levels was significant but rather low. The results questioned the usefulness of models based on spore samplings performed at several meters a.g.l. and suggested that the real numbers of basidiospores that are inhaled by people might depend on parameters that were as yet not included in the models.

A Measurement Study on the Indoor Climate of a College Classroom

To clarify the indoor climate in Japanese college classrooms, an air-conditioned, mechanically ventilated classroom of a university was surveyed. Temperatures, humidity and carbon dioxide (CO2) concentration in winter and summer were measured before, during and after lessons. The airtightness of the room and the airflow rate of the ventilation system were also measured. In winter, at an outdoor air temperature around 0 °C and with the thermostat temperature of the air conditioners set to 30 °C, the vertical difference in room air temperature exceeded 10 °C. The relative humidity (RH) was about 30% during lesson hours. After half an hour of occupancy, the CO2 concentration exceeded 1500 ppm in the respiration zone. It subsequently reached 2500 ppm, as measured within the respiration zone at half room height, after a continued 1.5 hours of occupancy. No special thermal or humidity problems were found in the summer survey. However, the CO2 level was very close to that of winter. The CO2 concentration decays indicated that the air change rate was 0.82 to 0.87 ac/h, which satisfied the Japanese criterion of 0.3 ac/h for the prevention of formaldehyde, yet it was far below the national criterion of 4.4 ac/h for college classrooms.

Method to assess quality and quantity of outdoor ventilation airflow received by occupants

Ventilation with outdoor air is one important way to improve indoor air quality and keep occupants healthy and comfortable. Assessment of ventilation performance and effective outdoor ventilation airflow received by occupants at their workspace or respiration zone is necessary. A new scale, the first factor of outdoor air effect (FFOAE), was developed for this purpose and is based on the relationship between local components composition and the combined effect of outdoor air stream and contamination sources. The transfer efficiency of the outdoor air component,the time efficiency of indoor airflow, and the transfer efficiency of the contaminant component were reflected simultaneously in the first factor of outdoor air effect. With the aid of the FFOAE, impacts of indoor airflow pattern, supplied outdoor airflow rate, contamination sources emission intensities, and their distribution on ventilation performance, quality, and quantity of outdoor ventilation airflow received by occupants are discussed by numerical simulations.

Denitrification efficiency for defining critical loads of carbon in shallow coastal ecosystems

Denitrification efficiency [DE; (N2 − N/(DIN + N2 − N) × 100%)] as an indicator of change associated with nutrient over-enrichment was evaluated for 22 shallow coastal ecosystems in Australia. The rate of carbon decomposition (which can be considered a proxy for carbon loading) is an important control on the efficiency with which coastal sediments in depositional mud basins with low water column nitrate concentrations recycle nitrogen as N2. The relationship between DE and carbon loading is due to changes in carbon and nitrate (NO3) supply associated with sediment biocomplexity. At the DE optimum (500–1,000 µmol m−2 h−1), there is an overlap of aerobic and anaerobic respiration zones (caused primarily by the existence of anaerobic micro-niches within the oxic zone, and oxidized burrow structures penetrating into the anaerobic zone), which enhances denitrification by improving both the organic carbon and nitrate supply to denitrifiers. On either side of the DE optimum zone, there is a reduction in denitrification sites as the sediment loses its three-dimensional complexity. At low organic carbon loadings, a thick oxic zone with low macrofauna biomass exists, resulting in limited anoxic sites for denitrification, and at high carbon loadings, there is a thick anoxic zone and a resultant lack of oxygen for nitrification and associated NO3 production. We propose a trophic scheme for defining critical (sustainable) carbon loading rates and possible thresholds for shallow coastal ecosystems based on the relationship between denitrification efficiency and carbon loading for 17 of the 22 Australian coastal ecosystems. The denitrification efficiency “optimum” occurs between carbon loadings of about 50 and 100 g C m−2 year−1. Coastal managers can use this simple trophic scheme to classify the current state of their shallow coastal ecosystems and for determining what carbon loading rate is necessary to achieve any future state.

Safety of Phenol Vapor Inhalation during Performance of Chemical Matrixectomy to Treat Ingrown Toenails

Phenol is commonly used in chemical matrixectomies to treat ingrown toenails. Although many studies have documented the safety of phenol matrixectomy for the patient, few studies have investigated the procedure's safety for the physician and auxiliary health care personnel. This study was undertaken to evaluate the safety of phenol vapor inhalation for health care personnel during performance of chemical matrixectomy. The environmental concentrations of phenol in the respiration zones of the physician and an assistant were measured during an in-office surgical procedure consisting of two partial chemical matrixectomies using a 95% phenol solution. The samples were analyzed using gas chromatography with a flame ionization detector. The phenol concentration measured in the physician's respiration zone was close to Spain's established environmental limit of daily exposure, with an index of exposure of 60%. The concentration measured in the assistant's respiration zone was well below the environmental limit of daily exposure, with an index of exposure of only 10%. The performance of chemical matrixectomies is safe for health care personnel when they are exposed to the vapor of phenol solutions of up to 95% concentration for up to 21 minutes. The degree of safety would be greater with lower phenol concentrations and shorter exposure times.

Effect of nitrite and nitrate on biogenic sulfide production in sewer biofilms determined by the use of microelectrodes

The effects of O2 and NO3- concentrations on in situ sulfate reduction and sulfide reoxidation in microaerophilic wastewater biofilms grown on rotating disk reactors were investigated by the use of microelectrodes for O2, S2-, NO3-, NO2-, and pH. Microelectrode measurements showed the vertical microzonation of O2 respiration, NO3- respiration, H2S oxidation and SO4(2-) reduction in the biofilms. The microelectrode measurements indicate that sulfate reducing activity was largely restricted to a narrow anaerobic zone located about 500 microm below the biofilm surface. An addition of nitrate forced the sulfate reduction zone deeper in the biofilm and reduced the specific sulfate reduction rate as well. The sulfate reduction zone was consequently separated from the O2 and NO3- respiration zones. Anaerobic H2S oxidation with NO3- was also induced by addition of nitrate to the medium. Measurements of the reduced inorganic sulfur compounds (FeS, FeS2 and S0), total-Mn and total-Fe in the biofilm indicated that the produced H2S became immediately oxidized with O2, NO3- and other oxidants, mainly ferric/ferrous hydrates. On the basis of the present results, it was estimated that of all sulfide produced, 13% of the sulfide was precipitated by metal ions as FeS and S0 just above the sulfate reduction zone, 65% was anaerobically oxidized to SO4(2-) with NO3- as an electron acceptor and 22% was aerobically oxidized within the biofilm incubated in 70 micromol l(-1) of DO and 280 micromol l(-1) of NO3-.

Effect of nitrite and nitrate on in situ sulfide production in an activated sludge immobilized agar gel film as determined by use of microelectrodes.

Microelectrode, fluorescence in situ hybridization (FISH), and denaturing gradient gel electrophoresis (DGGE) analyses were used to investigate the effect of nitrite and nitrate on in situ sulfide production in an activated sludge immobilized agar gel film. Microelectrode measurements of O(2), H(2)S, NO(3)(-), NO(2)(-), and pH revealed that the addition of NO(2)(-) and NO(3)(-) forced sulfate reduction zones deeper in the agar gel and significantly reduced the in situ sulfide production levels. The sulfate reduction zone was consequently separated from O(2) and NO(2)(-) or NO(3)(-) respiration zones with increasing the concentrations of NO(2)(-) and NO(3)(-). These NO(2)(-) and NO(3)(-) treatments had only a transient effect on sulfide production. The in situ sulfide production quickly recovered to the previous levels when NO(2)(-) and NO(3)(-) were removed. The PCR-DGGE and FISH analyses revealed that 2-day-continuous addition of 500 microM NO(3)(-) did not change the metabolically active sulfate-reducing bacterial (SRB) community. On the basis of these data, it could be concluded that the addition of NO(2)(-) and NO(3)(-) did not kill SRB, but induced the interspecies competition for common carbon source (i.e., acetate) between nitrate-reducing heterotrophic bacteria and SRB and enhanced the oxidation of the produced sulfide, which were main possible causes of the suppression of in situ sulfide production in the agar gel.

Microbial ecology of sulfate-reducing bacteria in wastewater biofilms analyzed by microelectrodes and fish (fluorescent in situ hybridization) technique

The vertical distribution of sulfate-reducing bacteria (SRB) in microaerophilic wastewater biofilms grown on fully submerged rotating disk reactors (RDR) was determined by the conventional culture-dependent MPN method and in situ hybridization of fluorescently-labelled 16S rRNA-targeted oligonucleotide probes for SRB in parallel. Chemical concentration profiles within the biofilm were also measured using microelectrodes for O2, S2-, NO3- and pH. In situ hybridization revealed that the SRB probe-stained cells were distributed throughout the biofilm even in the oxic surface zone in all states from single scattered cells to clustered cells. The higher fluorescence intensity and abundance of SRB probe-stained cells were found in the middle part of the biofilm. This result corresponded well with O2 and H2S concentration profiles measured by microelectrodes, showing sulfate reduction was restricted to a narrow anaerobic zone located about 500 μm below the biofilm surface. Results of the MPN and potential sulfate reducing activity (culture-dependent approaches) indicated a similar distribution of cultivable SRB in the biofilm. The majority of the general SRB probe-stained cells were hybridized with SRB 660 probe, suggesting that one important member of the SRB in the wastewater biofilm could be the genus Desulfobulbus. An addition of nitrate forced the sulfate reduction zone deeper in the biofilm and reduced the specific sulfate reduction rate as well. The sulfate reduction zone was consequently separated from O2 and NO3- respiration zones. Anaerobic H2S oxidation with NO3- was also induced by addition of nitrate to the medium.

Microbial ecology of sulfate-reducing bacteria in wastewater biofilms analyzed by microelectrodes and fish (fluorescent in situ hybridization) technique

The vertical distribution of sulfate-reducing bacteria (SRB) in microaerophilic wastewater biofilms grown on fully submerged rotating disk reactors (RDR) was determined by the conventional culture-dependent MPN method and in situhybridization of fluorescently-labelled I6S rRNA-targeted oligonucleotide probes for SRB in parallel. Chemical concentration profiles within the biofilm were also measured using microelectrodes for O2, S2−, NO3− and pH. in situ hybridization revealed that the SRB probe-stained cells were distributed throughout the biofilm even m the oxic surface zone in all states from single scattered cells to clustered cells. The higher fluorescence intensity and abundance of SRB probe-stained cells were found in the middle part of the biofihn This result corresponded well with O2 and H2S concentration profiles measured by microelectrodes, showing sulfate reduction was restricted to a narrow anaerobic zone located about 500 µm below the biofilm surface. Results of the MPN and potential sulfate reducing activity (culturedependent approaches) indicated a similar distribution of cultivable SRB in the biofilm. The majority of the general SRB probe-stained cells were hybridized with SRB 660 probe, suggesting that one important member of the SRB in the wastewater biofilm could be the genus Desulfobulbus. An addition of nitrate forced the sulfate reduction zone deeper in the biofilm and reduced the specific sulfate reduction rate as well. The sulfate reduction zone was consequently separated from O2 and NO3− respiration zones. Anaerobic H2S oxidation with NO3− was also induced by addition of nitrate to the medium.

A H2S microsensor for profiling biofilms and sediments: application in an acidic lake sediment

We developed a microsensor for the amperometric detection of dissolved hydrogen sulfide, H,S, in sedirnents and biofilms. The mlcrosensor exhibits a fast ( tgO c0.2 to 0.5 S) and linear response to H2S over a concentration range of 1 to >l000 pm01 H2S I-', and has a low stirring dependency of the microsensor signal (c1 to 2%). We used the new mlcrosensor to obtain the first microprofiles of H2S in an acidic lake sediment with a several cm thick flocculant surface layer. Despite the low pH of 4.6, a relative low SO,'level in the lake water, and a broad O2 respiration zone of ca 6 mm, we were able to measure H2S depth profiles in the sediment at a good resolution, that allowed for calculation of specific sulfate reduction and H2S oxidation activities. Such calculations showed highest sulfate reduction activity in the anoxic sediment down to ca 20 mm depth A comparison of calculated area1 rates of O2 consumption and sulfate reduction Indicated that sulfate reduction accounted for up to 13 % of total organic carbon mineralization in the acidic sediment. All produced H2S was reoxldized aerobically with O2 at the oxic-anoxic interface. In addition to its good performance in acidic environments, the new H2S microsensor has proven useful for sulfide measurements in neutral and moderate alkaline (pH < 9) biofilms and sediments, and thus is a true alternative to the traditionally used potentiometric Ag/Ag2S microelectrode for most applications in aquatic ecology and biogeochemistry.