堆肥过程中挥发性有机物的产生与释放

总结了堆肥过程中挥发性有机物(VOCs)的产生及其影响因素.堆肥产生的VOCs中,氮化物、硫化物及挥发性脂肪酸属于臭味物质,但大部分VOCs不产生臭味,其中甲胺、二甲胺、甲硫醇、乙硫醇、2-甲基呋喃和甲醛应作为堆肥厂职业健康安全评价时的参考指标.温度、通气状况是影响堆肥过程中VOCs释放的重要因素,温度升高可促使VOCs产生,适当通风可减少VOCs释放.     

Critical components of odors in evaluating the performance of food waste composting plants

The current Taiwan government policy toward food waste management encourages composting for resource recovery. This study used olfactometry, gas chromatography-mass spectrometry (GC-MS) and gas detector tubes to evaluate the ambient air at three of the largest food waste composting plants in Taiwan. Ambient air inside the plants, at exhaust outlets and plant boundaries was examined to determine the comprehensive odor performance, critical components, and odor elimination efficiencies of various odor control engineering. Analytical results identified 29 compounds, including ammonia, amines, acetic acid, and multiple volatile organic compounds (VOCs) (hydrocarbons, ketones, esters, terpenes and S-compounds) in the odor from food waste composting plants. Concentrations of six components--ammonia, amines, dimethyl sulfide, acetic acid, ethyl benzene and p-Cymene--exceeded human olfactory thresholds. Ammonia, amines, dimethyl sulfide and acetic acid accounted for most odors compared to numerous VOCs. The results also show that the biotrickling filter was better at eliminating the concentrations of odor, NH(3), amines, S-compounds and VOCs than the chemical scrubber and biofilters. All levels measured by olfactometry at the boundaries of food waste composting plants (range, 74-115 Odor Concentration (OC)) exceeded Taiwan's EPA standard of 50 OC. This study indicated that the malodor problem continued to be a significant problem for food waste recovery.     

Environmental aspects of VOCs evolved in the early stages of human decomposition

In the present study, the time profile, measured as "accumulation", of volatile organic compounds (VOCs) produced during the early stages of human decomposition was investigated. A human cadaver was placed in a sealed bag at approximately the 4th day after death. Evolved VOCs were monitored for 24 h by sampling at different time intervals. VOCs produced were analyzed by thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS). Over 30 substances were identified in total. These included mainly aliphatic and aromatic hydrocarbons, oxygenated compounds (alcohols, aldehydes, ketones) and organic sulfides. The last were the most prominent class of compounds identified. Eleven compounds were present in all the sampling cycles and constitute a "common core": ethanol, 2-propanone, dimethyl disulfide, methyl benzene, octane, 2-butanone, methyl ethyl disulfide, dimethyl trisulfide and o-, m- and p-xylenes. The last sampling cycle yielded the most abundant compounds in number and quantities. Inorganic gases such as CO2, CO, NH3 and H2S were also determined. The fundamental physicochemical properties of the evolved VOCs were used for evaluating their environmental impacts. It appears that the decay process, which is a dynamic procedure, can provide chemical signals that might be detected and properly evaluated by experts in the fields of forensic sciences, search and rescue units and environmental scientists.     

Exposure to volatile organic compounds for individuals with occupations associated with potential exposure to motor vehicle exhaust and/or gasoline vapor emissions

Workers who work near volatile organic compounds (VOCs) source(s), motor vehicle exhausts and/or gasoline vapor emissions, are suspected to be exposed to highly-elevated VOC levels during their work-time. This study confirmed this suspicion and evaluated the work-time exposure VOCs for traffic police officers, parking garage attendants, service station attendants, roadside storekeepers and underground storekeepers, by measuring the concentrations of six aromatic VOCs in workplace air, or personal air and breath samples. For nearly all target VOCs, the post-work breath concentrations of the workers were slightly or significantly higher than the pre-work breath concentrations, depending on the compound and occupation. Furthermore, both the pre- and post-work breath concentrations of the workers showed elevated levels compared with a control group of college students. The post-work breath concentrations were significantly correlated with the personal air concentrations, while the pre-work breath concentrations were not. Smoking workers were not always exposed to higher aromatic VOC levels than non-smoking workers. The breath and personal air concentrations for all the target compounds were both higher for underground parking garage attendants than for ground-level parking attendants. For all the target compounds except toluene, storekeepers exhibited similar levels of exposure for all store types. Print shopkeepers recorded the highest toluene exposure.     

Secondary organic aerosol formation from a large number of reactive man-made organic compounds

A photochemical trajectory model has been used to examine the relative propensities of a wide variety of volatile organic compounds (VOCs) emitted by human activities to form secondary organic aerosol (SOA) under one set of highly idealised conditions representing northwest Europe. This study applied a detailed speciated VOC emission inventory and the Master Chemical Mechanism version 3.1 (MCM v3.1) gas phase chemistry, coupled with an optimised representation of gas-aerosol absorptive partitioning of 365 oxygenated chemical reaction product species. In all, SOA formation was estimated from the atmospheric oxidation of 113 emitted VOCs. A number of aromatic compounds, together with some alkanes and terpenes, showed significant propensities to form SOA. When these propensities were folded into a detailed speciated emission inventory, 15 organic compounds together accounted for 97% of the SOA formation potential of UK man made VOC emissions and 30 emission source categories accounted for 87% of this potential. After road transport and the chemical industry, SOA formation was dominated by the solvents sector which accounted for 28% of the SOA formation potential.     

Total Volatile Organic Compounds (TVOC) in Indoor Air Quality Investigations*

Abstract The amount of volatile organic compounds (VOCs) in indoor air, usually called TVOC (total volatile organic compounds), has been measured using different definitions and techniques which yield different results. This report recommends a definition of TVOC referring to a specified range of VOCs and it proposes a method for the measurement of this TVOC entity. Within the specified range, the measured concentrations of identified VOCs (including 64 target compounds) are summed up, concentrations of non-identified compounds in toluene equivalents are added and, together with the identified VOCs, they give the TVOC value. The report reviews the TVOC concept with respect to its usefulness for exposure assessment and control and for the prediction of health or comfort effects. Although the report concludes that at present it is not possible to use TVOC as an effect predictor, it affirms the usefulness of TVOC for characterizing indoor pollution and for improving source control as required from the points of view of health, comfort, energy efficiency and sustainability.     

Factors controlling volatile organic compounds in dwellings in Melbourne,Australia

This study characterized indoor volatile organic compounds (VOCs) and investigated the effects of the dwelling characteristics, building materials, occupant activities, and environmental conditions on indoor VOC concentrations in 40 dwellings located in Melbourne, Australia, in 2008 and 2009. A total of 97 VOCs were identified. Nine VOCs, n‐butane, 2‐methylbutane, toluene, formaldehyde, acetaldehyde, d‐limonene, ethanol, 2‐propanol, and acetic acid, accounted for 68% of the sum of all VOCs. The median indoor concentrations of all VOCs were greater than those measured outdoors. The occupant density was positively associated with indoor VOC concentrations via occupant activities, including respiration and combustion. Terpenes were associated with the use of household cleaning and laundry products. A petroleum‐like indoor VOC signature of alkanes and aromatics was associated with the proximity of major roads. The indoor VOC concentrations were negatively correlated (P < 0.05) with ventilation. Levels of VOCs in these Australian dwellings were lower than those from previous studies in North America and Europe, probably due to a combination of an ongoing temporal decrease in indoor VOC concentrations and the leakier nature of Australian dwellings.     

堆肥过程中臭气的产生和释放过程研究进展

堆肥过程中产生的臭气容易导致恶臭污染问题.总结了堆肥过程中主要臭气物质的产生机理、物理化学性质、影响因素及调控措施.堆肥过程中产生的臭气物质主要包括NH<,3>、H<,2>S和部分挥发性有机物;H<,2>S是堆肥过程产生的恶臭潜力最高的臭气;NH<,3>的最大释放浓度可达6 000 mg/m<'3>.堆肥原料的C/N值、调理剂种类、通风条件是影响氨气挥发的重要因素.指出过程控制是解决臭气问题的根本措施.     

Indoor levels of volatile organic compounds at Florentine museum environments in Italy

Indoor Air Quality monitoring in cultural institutions is of particular concern to protect these places and the cultural heritage content. An indoor monitoring campaign was performed in three museums in Florence (Italy) to determine the occurrence and levels of volatile organic compounds (VOCs). VOCs of interest included BTEX (benzene, toluene, ethylbenzene, xylenes), terpenes, aldehydes, organic acids, and cyclic volatile methyl siloxanes (cVMS). The most abundant VOCs in all samples analyzed were BTEX, which were strictly related to the traffic source, followed by siloxanes and terpenes. Among BTEX, toluene was always the most abundant followed by xylenes, ethylbenzene, and benzene. cVMS in exhibition rooms with the presence of visitors showed higher values compared to samples collected when the museums were closed. Terpenes showed not only the influence of vegetation-biogenic sources surrounding a museum but could also be related to the wood used for the construction of showcases and furniture and the use of cleaning products. Data obtained also showed the presence of organic acids and aldehydes whose source can be traced back to exhibits themselves and wood-based furniture. Assessing the levels of organic acids in museums is important because, over time, it can cause deterioration of the artifacts.     

Identification and transport investigation of microbial volatile organic compounds in full-scale stud cavities

An experimental project was conducted to investigate mold products, namely spores and volatile organic compounds (VOCs) in the cavity of full-scale stud wall assemblies. Twenty specimens were constructed and tested to inquire the capacity of wall cavities to restrain mold products, emanating from studs with 10% of their surface covered with mold, from penetrating into the indoor space. The tests were designed primarily to study the movement of spores. The project was subsequently extended to investigate the identification of microbial volatile organic compounds (MVOCs) and their transport through the building envelope. This paper presents the experimental design, testing procedure and a summary of the analysis conducted to identify mold related VOCs and their transport from the cavity to the indoor space, and the evaluation of the influence of experimental factors on this transport. Six experimental factors were investigated: air leakage path; mold presence; wall construction configurations (insulation, vapor barrier and sheathing material) and ambient conditions (dry and wet conditions). The chemical analysis of VOCs (volatile organic compounds) was performed using gas chromatography/mass spectrometry (GC/MS). Results are analyzed using multiple regression analysis to identify the mold related VOCs, and to determine the transport through the building envelope. Five VOCs are confirmed to be related to the mold presence in the cavity and the transport of these MVOCs is supported by the data. However, no significant effect of the construction factors on MVOC transport is detected.     

Volatile organic compounds in 169 energy-efficient dwellings in Switzerland

Exposure to elevated levels of certain volatile organic compounds (VOCs) in households has been linked to deleterious health effects. This study presents the first large-scale investigation of VOC levels in 169 energy-efficient dwellings in Switzerland. Through a combination of physical measurements and questionnaire surveys, we investigated the influence of diverse building characteristics on indoor VOCs. Among 74 detected compounds, carbonyls, alkanes, and alkenes were the most abundant. Median concentration levels of formaldehyde (14 μg/m³), TVOC (212 μg/m³), benzene (<0.1 μg/m³), and toluene (22 μg/m³) were below the upper exposure limits. Nonetheless, 90% and 50% of dwellings exceeded the chronic exposure limits for formaldehyde (9 μg/m³) and TVOC (200 μg/m³), respectively. There was a strong positive correlation among VOCs that likely originated from common sources. Dwellings built between 1950s and 1990s, and especially, those with attached garages had higher TVOC concentrations. Interior thermal retrofit of dwellings and absence of mechanical ventilation system were associated with elevated levels of formaldehyde, aromatics, and alkanes. Overall, energy-renovated homes had higher levels of certain VOCs compared with newly built homes. The results suggest that energy efficiency measures in dwellings should be accompanied by actions to mitigate VOC exposures as to avoid adverse health outcomes.     

Volatile organic compound (VOC) adsorption on material: influence of gas phase concentration, relative humidity and VOC type

This paper presents the results of a factorial experiment design analysis to investigate volatile organic compounds (VOC) adsorption on a ceiling tile. The impacts of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on adsorption have been investigated. Cyclohexane, toluene, ethyl acetate, isopropyl alcohol and methanol were the five VOCs used in this study. A factor significant level was determined through evaluating its F value and comparing it with the critical value of F distribution at 95% confidence level. It was found that: (i) neither the relative humidity and gas phase concentration nor any interaction effect between them had significant impacts on toluene adsorption on the ceiling tile; (ii) the adsorption isotherm appeared to be linear for the non-polar compounds and non-linear for the semi-polar and polar compounds; (iii) no significant impact of relative humidity on adsorption was observed for most VOC compounds except for methanol; and (iv) the ceiling tile had the highest adsorption capacity toward the polar compounds, followed by the aromatic compounds and aliphatic compounds. In addition, the statistical analysis regarding the experimental results of toluene as a single compound or as a part of a mixture showed that toluene adsorption capacity on the ceiling tile as a single compound was higher than as a part of a mixture. PRACTICAL IMPLICATIONS: Building materials and furnishings may act as source and sink of VOCs in the indoor environment. In this study, a factorial experiment design analysis technique was used to show the impact of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on the adsorption process (sink effect). The aim was to better understand the interaction between these parameters and to verify the common assumptions made in the model development and measurement of indoor air quality.     

Fate of aromatic hydrocarbons in Italian municipal wastewater systems: An overview of wastewater treatment using conventional activated-sludge processes (CASP) and membrane bioreactors (MBRs)

We studied the occurrence, removal, and fate of 16 polycyclic aromatic hydrocarbons (PAHs) and 23 volatile organic compounds (VOCs) in Italian municipal wastewater treatment systems in terms of their common contents and forms, and their apparent and actual removal in both conventional activated-sludge processes (CASP) and membrane bioreactors (MBRs). We studied five representative full-scale CASP treatment plants (design capacities of 12 000 to 700 000 population-equivalent), three of which included MBR systems (one full-scale and two pilot-scale) operating in parallel with the conventional systems. We studied the solid-liquid partitioning and fates of these substances using both conventional samples and a novel membrane-equipped automatic sampler. Among the VOCs, toluene, ethylbenzene, xylenes, styrene, 1,2,4-trimethylbenzene, and 4-chlorotoluene were ubiquitous, whereas naphthalene, acenaphthene, fluorene, and phenanthrene were the most common PAHs. Both PAHs and aromatic VOCs had removal efficiencies of 40-60% in the headworks, even in plants without primary sedimentation. Mainly due to volatilization, aromatic VOCs had comparable removal efficiencies in CASP and MBRs, even for different sludge ages. MBRs did not enhance the retention of PAHs sorbed to suspended particulates compared with CASPs. On the other hand, the specific daily accumulation of PAHs in the MBR’s activated sludge decreased logarithmically with increasing sludge age, indicating enhanced biodegradation of PAHs. The PAH and aromatic VOC contents in the final effluent are not a major driver for widespread municipal adoption of MBRs, but MBRs may enhance the biodegradation of PAHs and their removal from the environment.     

VOCs and PAHs emissions from creosote-treated wood in a field storage area

In this study, the emissions of volatile organic compounds (VOCs, in this case aromatic hydrocarbons containing one benzene ring and furans) and polycyclic aromatic hydrocarbons (PAHs) from wood recently treated with creosote are examined. The VOCs and PAHs were identified and quantified in the gas phase. Additionally, the PAHs were quantified in the particulate phase. Glass multi-sorbent tubes (Carbotrap, Carbopack X, Carboxen-569) were used to hold the VOCs. The analysis was performed using automatic thermal desorption (ATD) coupled with capillary gas chromatography/mass spectrometry (GC/MS). PAHs vapours were collected on XAD-2 resin, and particulate matter was collected on glass fibre filters. The PAHs were analysed using GC/MS. The main components of the vapours released from the creosote-treated wood were naphthalene, toluene, m+p-xylene, ethylbenzene, o-xylene, isopropylbenzene, benzene and 2-methylnaphthalene. VOCs emission concentrations ranged from 35 mg m(-3) of air on the day of treatment to 5 mg m(-3) eight days later. PAHs emission concentrations ranged from 28 microg m(-3) of air on the day of treatment to 4 microg m(-3) eight days later. The air concentrations of PAHs in particulate matter were composed predominantly of benzo[b+j]fluoranthene, benzo[a]anthracene, chrysene, fluoranthene, benzo[e]pyrene and 1-methylnaphthalene. The emission concentrations of particulate polycyclic aromatic hydrocarbons varied between 0.2 and 43.5 ng m(-3). Finally, the emission factors of VOCs and PAHs were determined.     

Iron (III) aquacomplexes as effective photocatalysts for the degradation of pesticides in homogeneous aqueous solutions

This study evaluated in-car and in-bus exposures to methyl-tertiary butyl ether (MTBE), benzene, and toluene on actual commuting routes, not hypothetical routes as used in many previous in-vehicle exposure studies of volatile organic compounds (VOCs). It focuses on four potentially influencing factors (transportation mode, passenger-car type, time of day, and season). A total of 40 passenger car commuters and 20 public bus commuters were recruited. The same commuters participated in both the summer and winter studies. The transportation mode, passenger-car type and commute season were all found to affect the in-vehicle levels of the target VOCs. Conversely, the commute time of day had little effect on the in-car and in-bus levels of the target compounds. The present study also confirmed that under Korean commuting conditions, passenger car and public bus interiors are important microenvironments for exposure to MTBE, benzene and toluene. This is supported by a previous finding that both in-car and in-bus air levels of the target VOCs tend to be much higher than ambient air levels of the compounds. Meanwhile, some spurious gasoline sold during the experimental periods appears to have elevated the in-car and in-bus exposures to toluene compared with those reported by some previous studies conducted in the same study area.     

Investigation of volatile organic compounds in office buildings in Bangkok,Thailand: Concentrations,sources, and occupant symptoms

To conserve energy, office buildings with air-conditioning systems in Thailand are operated with a tight thermal envelope. This leads to low fresh-air ventilation rates and is thought to be partly responsible for the sick building syndrome symptoms reported by occupants. The objectives of this study are to measure concentrations and to determine sources of 13 volatile organic compounds (VOCs) in office buildings with air-conditioning systems in the business area of Bangkok. Indoor and outdoor air samples from 17 buildings were collected on Tenax-TA^™ sorbent tubes and analyzed for individual VOCs by thermal desorption-gas chromatography/mass spectrometry (TD–GC/MS). Building ventilation was measured with a constant injection technique using hexafluorobenzene as a tracer gas. The results show that the VOC concentrations varied significantly among the studied buildings. The two most dominant VOCs were toluene and limonene with average concentrations of 110 and 60.5 μg m⁻³, respectively. A Wilcoxon sum rank test indicated that the indoor concentrations of aromatic compounds and limonene were statistically higher than outdoor concentrations at the 0.05 level, while the indoor concentrations of chlorinated compounds were not. Indoor emission factors of toluene and limonene were found to be highest with the average values of 80.9 and 18.9 μg m⁻² h⁻¹, respectively. Principal component analysis was applied to the emission factors of 13 VOCs, producing three components based on source similarities. Furthermore, a questionnaire survey investigation and field measurements of building air exchange pointed to indoor air complaints related to inadequate ventilation.     

Monitoring of indoor volatile organic compounds and polycyclic aromatic hydrocarbons arising from kerosene cooking fuel.

Air samples, representing indoor environments of a kitchen in which a kerosene stove was used were collected and analysed for volatile organic compounds (VOCs) viz., n-hexane, benzene, heptane, toluene, p- and o-xylene and n-decane using a cryogenic preconcentration system and a gas chromatograph with a flame-ionisation detector. Simultaneous outdoor samples were also collected to determine indoor to outdoor (I/O) ratios for each compound. Reversed phase high performance liquid chromatography (HPLC) with ultra violet absorption detection was optimised for separation and quantification of polycyclic aromatic hydrocarbons (PAHs) in air particulate matter. Concentration of total suspended particulate matter (TSPM), benzene soluble organics and the PAHs in air samples collected in indoor environment of some tenements at Trombay, Mumbai where kerosene is used as cooking fuel are discussed in relation to the concentration of the same in outdoor environment in vicinity of the tenement. VOCs and PAHs results from samples collected in kitchens in Trombay are discussed in relation to indoor air pollution.     

Treatment of VOCs in high strength wastes using an anaerobic expanded-bed GAC reactor

The potential of the expanded-bed granular activated carbon (GAC) anaerobic reactor in treating a high strength waste containing RCRA volatile organic compounds (VOCs) was studied. A total of six VOCs, methylene chloride, chlorobenzene, carbon tetrachloride, chloroform, toluene and tetrachloroethylene, were fed to the reactor in a high strength matrix of background solvents. Performance was evaluated. The reactor was found to effect excellent removal of all VOCs (97%). Chloroform, while itself removed at levels in excess of 97%, was found to inhibit the degradation of acetate and acetone, two of the background solvents. Without any source of chloroform in the feed, excellent COD removals were obtained in addition to near-complete removal of all the VOCs.     

The vertical distributions of VOCs in the atmosphere of Beijing in autumn

Volatile organic compounds (VOCs) in the air of Beijing City were measured at the heights of 8, 32, 140 and 280 m on the Beijing 325 m meteorological tower in autumn 2005. Concentrations of fifty-five compounds were determined by quantitative analytical methods. Our study utilized GC/MS analysis of 0.5 l air sample that were cryo-concentrated prior to analysis. The vertical distributions of VOCs were also investigated using 1-butene, isopentane, dichloromethane and toluene as representative compounds of several different categories. It is shown that 1-butene followed by 2-butene, isopentane followed by n-pentane, dichloromethane followed by chloroform and toluene followed by benzene are the most abundant compounds in the categories of alkene, alkane, halocarbon and aromatic hydrocarbon, respectively. The concentrations of TVOCs range from 51.2+/-39.7 ppb to 83.6+/-44.4 ppb on clear days, but from 62.9+/-19.0 ppb to 105.0+/-59.2 ppb on haze days. While alkenes and halocarbons contribute little to TVOCs, alkanes provide the largest percentage, ranging from about 46% to 63% at four different heights, which are followed by aromatic hydrocarbons ranging from about 15% to 27%. The vertical distributions of VOCs are complex. On clear days most distribution profiles show a decreasing trend with increasing height. On haze days, however, they exhibit first a decrease with increasing altitude from 8 m to 140 m and then a significant increase at 280 m. These results are understood by analyzing how the vertical distributions of VOCs are affected jointly by several factors such as meteorological parameters and transport property. In addition, principal components analysis (PCA) and cluster analysis show that VOCs have different origins at different heights.     

Emissions of VOCs,SVOCs, and mold during the construction process: Contribution to indoor air quality and future occupants’ exposure

Building materials and human activities are important sources of contamination indoors, but little information is available regarding contamination during construction process which could persist during the whole life of buildings. In this study, six construction stages on two construction sites were investigated regarding the emissions of 43 volatile organic compounds (VOCs), 46 semi-volatile organic compounds (SVOCs), and the presence of 4 genera of mold. Results show that the future indoor air quality does not only depend on the emissions of each building product but that it is also closely related to the whole implementation process. Mold spore measurements can reach 1400 CFU/m³, which is particularly high compared with the concentrations usually measured in indoor environments. Relatively low concentrations of VOCs were observed, in relation to the use of low emissive materials. Among SVOCs analyzed, some phthalates, permethrin, and hydrocarbons were found in significant concentrations upon the delivery of building as well as triclosan, suspected to be endocrine disruptor, and yet prohibited in the treatment of materials and construction since 2014. As some regulations exist for VOC emissions, it is necessary to implement them for SVOCs due to their toxicity.