Comparison of carbonyl compounds emissions from diesel engine fueled with biodiesel and diesel

The characteristics of carbonyl compounds emissions were investigated on a direct injection, turbocharged diesel engine fueled with pure biodiesel derived from soybean oil. The gas-phase carbonyls were collected by 2,4-dinitrophenylhydrazine (DNPH)-coated silica cartridges from diluted exhaust and analyzed by HPLC with UV detector. A commercial standard mixture including 14 carbonyl compounds was used for quantitative analysis. The experimental results indicate that biodiesel-fueled engine almost has triple carbonyls emissions of diesel-fueled engine. The weighted carbonyls emission of 8-mode test cycle of biodiesel is 90.8 mg (kW h)^?1 and that of diesel is 30.7 mg (kW h)^?1. The formaldehyde is the most abundant compound of carbonyls for both biodiesel and diesel, taking part for 46.2% and 62.7% respectively. The next most significant compounds are acetaldehyde, acrolein and acetone for both fuels. The engine fueled with biodiesel emits a comparatively high content of propionaldehyde and methacrolein. Biodiesel, as an alternative fuel, has lower specific reactivity (SR) caused by carbonyls compared with diesel. When fueled with biodiesel, carbonyl compounds make more contribution to total hydrocarbon emission.     

Emissions of isoprene,monoterpene and short-chained carbonyl compounds from Eucalyptus spp. in southern Australia

Eucalypts are among the highest emitters of biogenic volatile organic compounds, yet there is relatively little data available from field studies of this genus. Emissions of isoprene, monoterpenes and the short-chained carbonyls formaldehyde, acetaldehyde and acetone were determined from four species (Eucalyptus camaldulensis, Eucalyptus globulus, Eucalyptus grandis, and Eucalytpus viminalis) in Australia. A smaller comparative study was conducted on E. camaldulensis in south-eastern Australia. Carbonyl emissions, reported here for the first time from eucalypts, were generally comparable with rates reported for other species, with diurnal emissions peaking at about 4, 75 and 34 nmol m^?2 min^?1 for acetone, formaldehyde and acetaldehyde respectively. There was wide variation in diurnal isoprene and monoterpene emissions between species, but under standard conditions, isoprene emissions were much lower than previous reports. Conversely, standard emission rates of monoterpenes were as much as six times greater than previous reports for some species. Emission of each carbonyl was correlated with its ambient concentration across different species, but more weakly related to temperature. Acetaldehyde emission in particular was significantly correlated with transpiration, but not with sap flow or with ethanol concentrations in xylem sap, suggesting fermentation within the leaf and stomatal conductance are primary controlling processes. Differences in acetaldehyde exchange velocities between sites, in addition to transpiration differences, suggest stomata may indeed exert long term emission regulation, in contrast to compounds for which no biological sink exists.     

Variable emissions of microbial volatile organic compounds (MVOCs) from root-associated fungi isolated from Scots pine

Soils emit a large variety of volatile organic compounds. In natural ecosystems, measurements of microbial volatile organic compound (MVOC) exchange rates between soil and atmosphere are difficult due to e.g. the spatial heterogeneity of the belowground organisms, and due to the many potential sources for the same compounds. We measured in laboratory conditions the MVOC emission rates and spectra of eight typical fungi occurring in boreal forest soils. The studied species are decomposers (Gymnopilus penetrans, Ophiostoma abietinum), ectomycorrhizal (Cenococcum geophilum, Piloderma olivaceum, Suillus variegatus, Tomentellopsis submollis) and endophytic fungi (Meliniomyces variabilis, Phialocephala fortinii). The MVOC emissions contained altogether 21 known and 6 unidentified compounds whose emission rates were >0.1 μg g(DW)^?1 h^?1. The most abundant compounds were the short-chain carbonyl compounds (acetone and acetaldehyde). The greatest carbonyl emissions were measured from P. olivaceum (1.9 mg acetone g(DW)^?1 h^?1) and P. fortinii (0.114 mg acetaldehyde g(DW)^?1 h^?1). Terpenoid emissions (isoprene, mono- and sesquiterpenes) were detected from some fungal cultures, but in relatively small amounts. We conclude that soil micro-organisms can potentially be responsible for significant emissions of volatiles, especially short-chain oxygenated compounds, to the below-canopy atmosphere.     

Constituents of volatile organic compounds of evaporating essential oil

Essential oils containing aromatic compounds can affect air quality when used indoors. Five typical and popular essential oils—rose, lemon, rosemary, tea tree and lavender—were investigated in terms of composition, thermal characteristics, volatile organic compound (VOC) constituents, and emission factors. The activation energy was 6.3–8.6 kcal mol^?1, the reaction order was in the range of 0.6–0.8, and the frequency factor was 0.01–0.24 min^?1. Toluene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, n-undecane, p-diethylbenzene and m-diethylbenzene were the predominant VOCs of evaporating gas of essential oils at 40 °C. In addition, n-undecane, p-diethylbenzene, 1,2,4-trimethylbenzene, m-diethylbenzene, and 1,2,3-trimethylbenzene revealed high emission factors during the thermogravimetric (TG) analysis procedures. The sequence of the emission factors of 52 VOCs (137–173 mg g^?1) was rose ≈ rosemary > tea tree ≈ lemon ≈ lavender. The VOC group fraction of the emission factor of aromatics was 62–78%, paraffins were 21–37% and olefins were less than 1.5% during the TG process. Some unhealthy VOCs such as benzene and toluene were measured at low temperature; they reveal the potential effect on indoor air quality and human health.     

Trends of ambient carbonyl compounds in the urban environment of Hong Kong

The concentrations of C₁–C₈ carbonyl compounds were measured at two urban sites in Hong Kong from October 1997 to September 2000. The daily total carbonyl concentrations were found to range from 2.4 to 37 μg m⁻³. Formaldehyde was the most abundant species, which comprised from 36 to 43% of the total detected carbonyls, followed by acetaldehyde (18–21%) and acetone (8–20%). The highest 24-hour average concentrations measured were 10 and 7.7 μg m⁻³ for formaldehyde and acetaldehyde, respectively. Seasonal and temporal variations in the concentrations of formaldehyde and acetaldehyde were not obvious, but lowest concentrations often occurred from June to August. The mean formaldehyde/acetaldehyde molar ratios at the two sites in summer (2.8±1.1 and 2.5±1.2) were significantly higher (p⩽0.01) than those in winter periods (1.9±0.6 and 2.0±0.6). The phenomena were explained by influences of both photochemical reactions and local meteorological conditions. Better correlations between formaldehyde and acetaldehyde, and between NO_x and each of the two major carbonyls were obtained in winter periods indicating direct vehicular emissions were the principal sources. The ambient formaldehyde and acetaldehyde concentrations in the urban atmosphere of Hong Kong were within the normal ranges reported in the literature for other urban sites world-wide.     

Emission profile of 18 carbonyl compounds,CO, CO2, and NOx emitted by a diesel engine fuelled with diesel and ternary blends containing diesel,ethanol and biodiesel or vegetable oils

The impact of vehicular emissions on air depends, among other factors, on the composition of fuel and the technology used to build the engines. The reduction of vehicular emissions requires changes in the fuel composition, and improving the technologies used in the manufacturing of engines and for the after-treatment of gases. In general, improvements to diesel engines have targeted not only emission reductions, but also reductions in fuel consumption. However, changes in the fuel composition have been shown to be a more rapid and effective alternative to reduce pollution. Some factors should been taken into consideration when searching for an alternative fuel to be used in diesel engines, such as emissions, fuel stability, availability and its distribution, as well as its effects on the engine durability. In this work, 45 fuel blends were prepared and their stability was evaluated. The following mixtures (v/v/v) were stable for the 90-day period and were used in the emission study: diesel/ethanol – 90/10%, diesel/ethanol/soybean biodiesel – 80/15/5%, diesel/ethanol/castor biodiesel – 80/15/5%, diesel/ethanol/residual biodiesel – 80/15/5%, diesel/ethanol/soybean oil – 90/7/3%, and diesel/ethanol/castor oil – 90/7/3%. The diesel/ethanol fuel showed higher reduction of NO_x emission at a lower load (2 kW) when compared with pure diesel. The other fuels showed a decrease of NO_x emissions in the ranges of 6.9–75% and 4–85% at 1800 rpm and 2000 rpm, respectively. The combustion efficiencies of the diesel can be enhanced by the addition of the oxygenate fuels, like ethanol and biodiesel/vegetable oil, resulting in a more complete combustion in terms of NO_x emission. In the case of CO₂ the decreases were in the ranges of 5–24% and 4–6% at 1800 rpm and 2000 rpm, respectively. Meanwhile, no differences were observed in CO emission. The carbonyl compounds (CC) studied were formaldehyde, acetaldehyde, propionaldehyde, acrolein, acetone, crotonaldehyde, butyraldehyde, butanone, benzaldehyde, isovaleraldehyde, valeraldehyde, o-toluenaldehyde, m-toluenaldehyde, p-toluenaldehyde, hexaldehyde, octaldehyde, 2,5-dimethylbenzaldehyde, and decaldehyde. Among them, formaldehyde, acetaldehyde, acetone, and propionaldehyde showed the highest emission concentrations. When ternary blend contains vegetable oil, there is a strong tendency to increase the emissions of the high weight CC and decrease the emissions of the low weight CC. The highest concentration of acrolein was observed when the fuel contains diesel, ethanol and biodiesel. With the exception of NO_x, the use of ternary blended fuels resulted on the increase in the emission rates of the studied compounds.     

Reducing carbonyl emissions from a heavy-duty diesel engine at US transient cycle test by use of paraffinic/biodiesel blends

Formaldehyde and acetaldehyde are toxic carcinogens so their reductions in diesel-engine emissions are desirable. This study investigated emissions of carbonyl compounds (CBCs) from an HDDE (heavy-duty diesel engine) at US transient cycle test, using five test fuels: premium diesel fuel (D100), P100 (100% palm-biodiesel), P20 (20% palm-biodiesel + 80% premium diesel fuel), PF80P20 (80% paraffinic fuel + 20% palm-biodiesel), and PF95P05 (95% paraffinic fuel + 5% palm-biodiesel). Experimental results indicate that formaldehyde was the major carbonyl in the exhaust, accounting for 70.1–76.2% of total CBC concentrations for all test fuels. In comparison with D100 (172 mg BHP^?1 h^?1), the reductions of formaldehyde and acetaldehyde emission factor for P100, P20, PF80P20, and PF95P05 were (?16.8%, ?61.8%), (?10.0%, ?39.0%), (21.3%, 1.10%), and (31.1%, 19.5%), respectively. Using P100 and P20 instead of D100 in the HDDE increased CBC concentrations by 14.5% and 3.28%, respectively, but using PF80P20 and PF95P05 significantly reduced CBC concentrations by 30.3% and 23.7%, respectively. Using P100 and P20 instead of D100 (2867 ton yr^?1) in the HDDE increased CBC emissions by 240 and 224 ton yr^?1, respectively, but using PF80P20, and PF95P05 instead of D100 in the HDDE decreased CBC emissions by 711 and 899 ton yr^?1, respectively. The above results indicate that the wide usage of paraffinic–palmbiodiesel blends as alternative fuels could protect the environment.     

Indoor exposure from building materials: A field study

The present study has been conducted in the frame of BUMA (Prioritization of Building Materials Emissions as indoor pollution sources), a European funded project, aiming at assessing the exposure to emitted compounds in indoor air. Field campaigns in five (5) European cities (Milan, Copenhagen, Dublin, Athens and Nicosia) were carried out. These campaigns covered weekly winter and summer concentration measurements in two (2) public buildings and two (2) private houses in each city. BTEX, terpenes, and carbonyls were measured using passive sampling in two sites inside the building and one outside. VOC emission measurements on selected building material have also been performed using Field and Laboratory Emission Cell (FLEC). The results on indoor concentrations for compounds such as formaldehyde (1.2–62.6 μg m^?3), acetaldehyde (0.7–41.6 μg m^?3), toluene (0.9–163.5 μg m^?3), xylenes (0.2–177.5 μg m^?3) and acetone (2.8–308.8 μg m^?3) have shown diversity and relatively significant indoor sources depending on the building type, age etc. Indoor concentrations of these substances are varied depending on the building age and type. The percentage of approximately 40% of the indoor air quality levels originated from building materials.     

Characteristics of carbonyls: Concentrations and source strengths for indoor and outdoor residential microenvironments in China

Indoor and outdoor carbonyl concentrations were measured simultaneously in 12 urban dwellings in Beijing, Shanghai, Guangzhou, and Xi’an, China in summer (from July to September in 2004) and winter (from December 2004 to February 2005). Formaldehyde was the most abundant indoor carbonyls species, while formaldehyde, acetaldehyde and acetone were found to be the most abundant outdoor carbonyls species. The average formaldehyde concentrations in summer indoor air varied widely between cities, ranging from a low of 19.3 μg m⁻³ in Xi’an to a high of 92.8 μg m⁻³ in Beijing. The results showed that the dwellings with tobacco smoke, incense burning or poor ventilation had significantly higher indoor concentrations of certain carbonyls. It was noticed that although one half of the dwellings in this study installed with low emission building materials or furniture, the carbonyls levels were still significantly high. It was also noted that in winter both the indoor and outdoor acetone concentrations in two dwellings in Guangzhou were significantly high, which were mainly caused by the usage of acetone as industrial solvent in many paint manufacturing and other industries located around Guangzhou and relatively longer lifetime of acetone for removal by photolysis and OH reaction than other carbonyls species. The indoor carbonyls levels in Chinese dwellings were higher than that in dwellings in the other countries. The levels of indoor and ambient carbonyls showed great seasonal differences. Six carbonyls species were carried out the estimation of indoor source strengths. Formaldehyde had the largest indoor source strength, with an average of 5.25 mg h⁻¹ in summer and 1.98 mg h⁻¹ in winter, respectively. However, propionaldehyde, crotonaldehyde and benzaldehyde had the weakest indoor sources.     

Temporal variations of atmospheric carbonyls in urban ambient air and street canyons of a Mountainous city in Southwest China

Carbonyl compounds in urban ambient air and street canyons were measured from December 2008 to August 2009 in a mountainous city in southwest China (Guiyang). The formaldehyde yield from the photo-oxidation of isoprene emitted by vegetation was estimated to be in the range of 0.63–3.62 μg m^?3 from May to August, which accounted for 28.8–33.4% of ambient formaldehyde. Based on the calculation of photolysis rates and rates of reaction with the OH radical, it was found that photolysis was the predominant sink for formaldehyde and acetone in both summer and winter. For acetaldehyde, photo-oxidation by OH radicals and photolysis were the major sinks in summer while photo-oxidation by OH radicals was the dominant sink in winter. Wet precipitation was found to be an important removal process for the atmospheric carbonyls. In the urban ambient air, the average concentrations of formaldehyde, acetaldehyde, acetone and all carbonyls were 4.8 ± 2.1, 5.7 ± 3.3, 5.1 ± 2.5, and 25.1 ± 9.2 μg m^?3 (n = 139), respectively. The average concentrations of these species in street canyons were 18.8 ± 6.5, 9.4 ± 3.2, 10.9 ± 2.1, and 64.1 ± 16.3 μg m^?3 (n = 62), respectively. The significantly higher carbonyl levels on weekdays (compared to weekends) highlight the contribution of vehicle emissions to carbonyls in the street canyons.     

Emission factors and exposures from ground-level pyrotechnics

Potential exposures from ground-level pyrotechnics were assessed by air monitoring and developing emission factors. Total particulate matter, copper and SO₂ exposures exceeded occupational health guidelines at two outdoor performances using consumer pyrotechnics. Al, Ba, B, Bi, Mg, Sr, Zn, and aldehyde levels were elevated, but did not pose a health hazard based on occupational standards. Emission factors for total particulate matter, metals, inorganic ions, aldehydes, and polyaromatic hydrocarbons (PAHs) were determined for seven ground-supported pyrotechnics through air sampling in an airtight room after combustion. Particle generation ranged from 5 to 13% of the combusted mass. Emission factors (g Kg^?1) for metals common to pyrotechnics were also high: K, 23–45; Mg, 1–7; Cu, 0.05–7; and Ba, 0.03–6. Pb emission rates of 1.6 and 2.7% of the combusted mass for two devices were noteworthy. A high correlation (r² ≥ 0.89) between metal concentrations in pyrotechnic compositions and emission factors were noted for Pb, Cr, Mg, Sb, and Bi, whereas low correlations (r² ≤ 0.1) were observed for Ba, Sr, Fe, and Zn. This may be due to the inherent heterogeneity of multi-effect pyrotechnics. The generation of inorganic nitrogen in both the particulate (NO₂^?, NO₃^?) and gaseous (NO, NO₂) forms varied widely (<0.1–1000 mg Kg^?1). Aldehyde emission factors varied by two orders of magnitude even though the carbon source was carbohydrates and charcoal for all devices: formaldehyde (<7.0–82 mg Kg^?1), acetaldehyde (43–210 mg Kg^?1), and acrolein (1.9–12 mg Kg^?1). Formation of lower molecular weight PAHs such as naphthalene and acenaphthylene were favored, with their emission factors being comparable to that from the combustion of household refuse and agricultural debris. Ba, Sr, Cu, and Pb had emission factors that could produce exposures exceeding occupational exposure guidelines. Sb and unalloyed Mg, which are banned from consumer fireworks in the US, were present in significant amounts.     

Real-world emission factors of fifteen carbonyl compounds measured in a Hong Kong tunnel

Real-world vehicle emissions of carbonyls were determined in summer and winter of 2003 at the Shing Mun Tunnel, Hong Kong. Fifteen carbonyl species have been analyzed in this study. The total measured carbonyls emission factors ranged from 21.7 to 68.9 mg veh⁻¹ km⁻¹ among different measurement periods, with an average of 35.8±11.9 mg veh⁻¹ km⁻¹. Higher carbonyl emissions were found to be associated with a high proportion of diesel-fueled vehicles. Total measured carbonyl emissions from Diesel-fueled Vehicle (DV, 71.5 mg veh⁻¹ km⁻¹) were about 7 times higher than those from Non-Diesel-fueled Vehicle (NDV, 10 mg veh⁻¹ km⁻¹). The five carbonyls with the largest DV emission factor were, in decreasing order, formaldehyde (38.3 mg veh⁻¹ km⁻¹), acetaldehyde (11.4 mg veh⁻¹ km⁻¹), acetone (5.3 mg veh⁻¹ km⁻¹), crotonaldehyde (5.2 mg veh⁻¹ km⁻¹) and benzaldehyde (2.0 mg veh⁻¹ km⁻¹). These five carbonyl compounds together accounted for 87% of the sum of all DV carbonyl emission factors. For NDV, the five most abundant carbonyls in NDV emission at the tunnel were, in decreasing order, formaldehyde (3.5 mg veh⁻¹ km⁻¹), acetone (1.8 mg veh⁻¹ km⁻¹), methyl ethyl ketone (1.6 mg veh⁻¹ km⁻¹), m,p-tolualdehyde (1.0 mg veh⁻¹ km⁻¹) and acetaldehyde (mg veh⁻¹ km⁻¹). They accounted for 85% of the sum of all NDV carbonyl emission factors.     

Characteristics of carbonyl compounds in public vehicles of Beijing city: Concentrations,sources, and personal exposures

The characteristics of carbonyl compounds (carbonyls) including concentrations, major sources, and personal exposure were investigated for 29 vehicles including taxi, bus and subway in Beijing. It was found that the taxis (Xiali, TA) and buses (Huanghe, BA) fueled by gasoline with longer service years had the higher indoor carbonyl levels (178±42.7 and 188±31.6 μg m⁻³) while subways energized by electricity without exhaust and the jingwa buses (BB) driven in the suburb had the lower levels with total concentrations of 98.5±26.3 and 92.1±20.3 μg m⁻³, respectively. Outdoor carbonyls of taxi cars and buses were nearly at the same level with their total concentrations varying from 80 to 110 μg m⁻³. The level of outdoor subways carbonyls was equal with the ambient air levels. Exhaust leakage, indoor material emissions, photochemical formation, and infiltration of outdoor air were considered to be the major sources to in-vehicle carbonyls. Personal exposures and cancer risk to formaldehyde and acetaldehyde were calculated for professional bus and taxi drivers, respectively. Taxi drivers had the highest cancer risk with personal exposure to formaldehyde and acetaldehyde of 212 and 243 μg day⁻¹, respectively. The public concern should pay considerable attention to professional drivers’ health.     

Snowpack processing of acetaldehyde and acetone in the Arctic atmospheric boundary layer

Acetaldehyde (CH₃CHO) and acetone (CH₃C(O)CH₃) concentrations in ambient air, in snowpack air, and bulk snow were determined at Alert, Nunavut, Canada, as a part of the Polar Sunrise Experiment (PSE): ALERT 2000. During the period of continuous sunlight, vertical profiles of ambient and snowpack air exhibited large concentration gradients through the top ∼10 cm of the snowpack, implying a flux of carbonyl compounds from the surface to the atmosphere. From vertical profile and eddy diffusivity measurements made simultaneously on 22 April, acetaldehyde and acetone fluxes of 4.2(±2.1)×10⁸ and 6.2(±4.2)×10⁸ molecules cm⁻² s⁻¹ were derived, respectively. For this day, the sources and sinks of CH₃CHO from gas phase chemistry were estimated. The result showed that the snowpack flux of CH₃CHO to the atmosphere was as large as the calculated CH₃CHO loss rate from known atmospheric gas phase reactions, and at least 40 times larger (in the surface layer) than the volumetric rate of acetaldehyde produced from the assumed main atmospheric gas phase reaction, i.e. reaction of ethane with hydroxyl radicals. In addition, acetaldehyde bulk snow phase measurements showed that acetaldehyde was produced in or on the snow phase, likely from a photochemical origin. The time series for the observed CH₃C(O)CH₃, ozone (O₃), and propane during PSE 1995, PSE 1998, and ALERT 2000 showed a consistent anti-correlation between acetone and O₃ and between acetone and propane. However, our data and model simulations showed that the acetone increase during ozone depletion events cannot be explained by gas phase chemistry involving propane oxidation. These results suggest that the snowpack is a significant source of acetaldehyde and acetone to the Arctic boundary layer.     

Sources and photodecomposition of formaldehyde and acetaldehyde in Rome ambient air

Atmospheric levels of formaldehyde and acetaldehyde as well as their diurnal and seasonal variations were investigated from 1994 to 1997 in downtown Rome during sunny and wind calm days. Hourly concentrations of formaldehyde ranged from 8 to 28 ppbV in summer and 7 to 17 ppbv in winter; acetaldehyde concentrations varied correspondingly within the 3–18 and 2–7 ppbv intervals. Percentages of both aldehydes photochemically produced were estimated through a simple relationship based upon the comparison of individual ratios of formaldehyde and acetaldehyde to toluene in ambient air and automobile emission. Photochemical production was found to weigh upon atmospheric levels for 80–90% in summer days. It dropped below 35% in the winter period, when direct emission from traffic largely predominated. Photochemical summer source was more efficient for acetaldehyde than for formaldehyde, especially in the early morning. The importance of formaldehyde as the major source of hydroxyl radicals in Rome was also assessed.     

The effects of evaporating essential oils on indoor air quality

Essential oils, predominantly comprised of a group of aromatic chemicals, have attracted increasing attention as they are introduced into indoor environments through various forms of consumer products via different venues. Our study aimed to characterize the profiles and concentrations of emitted volatile organic compounds (VOCs) when evaporating essential oils indoors. Three popular essential oils in the market, lavender, eucalyptus, and tea tree, based on a nation-wide questionnaire survey, were tested. Specific aromatic compounds of interest were sampled during evaporating the essential oils, and analyzed by GC-MS. Indoor carbon monoxide (CO), carbon dioxide (CO₂), total volatile organic compounds (TVOCs), and particulate matters (PM₁₀) were measured by real-time, continuous monitors, and duplicate samples for airborne fungi and bacteria were collected in different periods of the evaporation. Indoor CO (average concentration 1.48 vs. 0.47 ppm at test vs. background), CO₂ (543.21 vs. 435.47 ppm), and TVOCs (0.74 vs. 0.48 ppm) levels have increased significantly after evaporating essential oils, but not the PM₁₀ (2.45 vs. 2.42 ppm). The anti-microbial activity on airborne microbes, an effect claimed by the use of many essential oils, could only be found at the first 30–60 min after the evaporation began as the highest levels of volatile components in these essential oils appeared to emit into the air, especially in the case of tea tree oil. High emissions of linalool (0.092–0.787 mg m⁻³), eucalyptol (0.007–0.856 mg m⁻³), d-limonene (0.004–0.153 mg m⁻³), ρ-cymene (0.019–0.141 mg m⁻³), and terpinene-4-ol-1 (0.029–0.978 mg m⁻³), all from the family of terpenes, were observed, and warranted for further examination for their health implications, especially for their potential contribution to the increasing indoor levels of secondary pollutants such as formaldehyde and secondary organic aerosols (SOAs) in the presence of ozone.     

Concentrations and Source Characteristics of Airborne Carbonyl Compounds Measured Outside Urban Residences

Abstract

This paper presents the analysis of ambient air concentrations of 10 carbonyl compounds (aldehydes and ketones) measured in the yards of 87 residences in the city of Elizabeth, NJ, throughout 1999–2001. Most of these residences were measured twice in different seasons; the sampling duration was 48 hr each time. The authors observed higher concentrations for most of the measured carbonyl compounds on warmer days, reflecting larger contributions of photochemical reactions on warmer days. The estimated contributions of photochemical production varied substantially across the measured carbonyl compounds and could be as high as 60%. Photochemical activity, however, resulted in a net loss for formaldehyde. The authors used stepwise multiple linear regression models to evaluate the impact of traffic sources and meteorological conditions on carbonyl concentrations using the data collected on colder days (with lower photochemical activities). They found that the concentrations of formal-dehyde, acetaldehyde, acrolein, propionaldehyde, crotonaldehyde, benzaldehyde, glyoxal, and methylglyoxal significantly decreased with increasing distance between a measured residence and one or more major roadways. They also found significant negative associations between concentrations for most of the measured carbonyl compounds and each of the following meteorological parameters: mixing height, wind speed, and precipitation.     

A study of photochemical and physical processes affecting carbonyl compounds in the Arctic atmospheric boundary layer

Experiments were conducted during the ALERT 2000 field campaign aimed at understanding the role of air–snow interactions in carbonyl compound chemistry and the associated ozone depletion in the atmospheric boundary layer. Under sunlit conditions, we find that formaldehyde, acetaldehyde and acetone exhibit a significant diel cycle with average ambient air concentrations of 166, 53 and 385 ppt, respectively. A box model of Arctic surface layer chemistry was used to understand the diel behavior of carbonyl compound concentrations at Alert, Nunavut, Canada, with a focus on the chemical and physical processes that affect carbonyl compounds. Results of the study showed that the measured carbonyl compound concentrations can only be simulated when a radiation-dependent snowpack source term (possibly photochemistry) and a temperature-dependent sink (physical uptake on snow grains) of carbonyl compounds were added to the model. We are able to simulate the concentration and amplitude of the observed diel cycle, but not the phase of the cycle. These results help confirm the importance of snowpack chemistry and physical processes with respect to carbonyl compound concentrations in the Arctic surface boundary layer, and reveal weakness in the details of our understanding.     

Light-absorbing aldol condensation products in acidic aerosols: Spectra,kinetics, and contribution to the absorption index

The radiative properties of aerosols that are transparent to light in the near-UV and visible, such as sulfate aerosols, can be dramatically modified when mixed with absorbing material such as soot. In a previous work we had shown that the aldol condensation of carbonyl compounds produces light-absorbing compounds in sulfuric acid solutions. In this work we report the spectroscopic and kinetic parameters necessary to estimate the effects of these reactions on the absorption index of sulfuric acid aerosols in the atmosphere. The absorption spectra obtained from the reactions of six different carbonyl compounds (acetaldehyde, acetone, propanal, butanal, 2-butanone, and trifluoroacetone) and their mixtures were compared over 190–1100 nm. The results indicated that most carbonyl compounds should be able to undergo aldol condensation. The products are oligomers absorbing light in the 300–500 nm region where few other compounds absorb, making them important for the radiative properties of aerosols. Kinetic experiments in 96–75 wt% H₂SO₄ solutions and between 273 and 314 K gave an activation energy for the rate constant of formation of the aldol products of acetaldehyde of −(70±15) kJ mol⁻¹ in 96 wt% solution and showed that the effect of acid concentration was exponential. A complete expression for this rate constant is proposed where the absolute value in 96 wt% H₂SO₄ and at 298 K is scaled to the Henry's law coefficient for acetaldehyde and the absorption cross-section for the aldol products assumed in this work. The absorption index of stratospheric sulfuric acid aerosols after a 2-year residence time was estimated to 2×10⁻⁴, optically equivalent to a content of 0.5% of soot and potentially significant for the radiative forcing of these aerosols and for satellite observations in channels where the aldol products absorb.     

Indoor and outdoor carbonyl compounds in the hotel ballrooms in Guangzhou,China

Twenty-one carbonyl compounds were measured simultaneously at four hotel ballrooms in urban Guangzhou during the autumn, 2002. In each ballroom, measurements were carried out in business hours in the evening (20:30–24:00) on 7 consecutive days without any disturbance of the ballroom's normal operation. Nineteen out of the 21 target carbonyl compounds were identified in indoor and outdoor air. In the outdoor environment, formaldehyde was the most abundant carbonyl, followed by acetaldehyde, and there existed a strong correlation between formaldehyde and acetaldehyde. In the indoor air, however, acetaldehyde was the most abundant carbonyl, its concentrations seemed to be affected significantly by smoking. The indoor concentrations of carbonyls were found higher than their outdoor counterparts with only a few exceptions. Further studies concerning the indoor/outdoor ratios and mutual correlation of the carbonyls indicated that apart from direct emission from indoor materials and infiltration of outdoor air, other anthropogenic sources, e.g. tobacco smoke, also significantly contributed to carbonyl compounds. The possible sources of some high molecular weight carbonyls, e.g. nonanaldehyde, were also discussed briefly. Preliminary estimate of the exposures and risks due to carbonyls in the ballrooms was made, which indicated that long-term exposure in such places might cause increased chance of developing cancers.