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1.
The objective of the study was to quantify the concentration and emission levels of sulfuric odorous compounds emitted from pig-feeding operations. Five types of pig-housing rooms were studied: gestation, farrowing, nursery, growing and fattening rooms. The concentration range of sulfuric odorous compounds in these pig-housing rooms were 30–200 ppb for hydrogen sulfide (H2S), 2.5–20 ppb for methyl mercaptan (CH3SH), 1.5–12 ppb for dimethyl sulfide (DMS; CH3SCH3) and 0.5–7 ppb for dimethyl disulfide (DMDS; CH3S2CH3), respectively. The emission rates of H2S, CH3SH, DMS and DMDS were estimated by multiplying the average concentration (mg m−3) measured near the air outlet by the mean ventilation rate (m3 h−1) and expressed either per area (mg m−2 h−1) or animal unit (AU; liveweight of the pig, 500 kg) (mg pig−1 h−1). As a result, the emission rates of H2S, CH3SH, DMS and DMDS in the pig-housing rooms were 14–64, 0.8–7.3, 0.4–3.4 and 0.2–1.9 mg m−2 h−1, respectively, based on pig's activity space and 310–723, 18–80, 9–39 and 5–22 mg AU−1 h−1, respectively, based on pig's liveweight, which indicates that their emission rates were similar, whether based upon the pig's activity space or liveweight. In conclusion, the concentrations and emission rates of H2S were highest in the fattening room followed by the growing, nursery, farrowing and gestation rooms whereas those of CH3SH, DMS and DMDS concentrations were largest in the growing room followed by the nursery, gestation and farrowing rooms.  相似文献   

2.
A series of source tests were conducted to characterize emissions of particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and total hydrocarbon (THC ) from five types of portable combustion devices. Tested combustion devices included a kerosene lamp, an oil lamp, a kerosene space heater, a portable gas range, and four unscented candles. All tests were conducted either in a well-mixed chamber or a well-mixed room, which enables us to determine emission rates and emission factors using a single-compartment mass balance model. Particle mass concentrations and number concentrations were measured using a nephelometric particle monitor and an eight-channel optical particle counter, respectively. Real-time CO concentrations were measured with an electrochemical sensor CO monitor. CO2, CH4, and THC were measured using a GC-FID technique. The results indicate that all particles emitted during steady burning in each of the tested devices were smaller than 1.0 μm in diameter with the vast majority in the range between 0.1 and 0.3 μm. The PM mass emission rates and emission factors for the tested devices ranged from 5.6±0.1 to 142.3±40.8 mg h−1 and from 0.35±0.06 to 9.04±4.0 mg g−1, respectively. The CO emission rates and emission factors ranged from 4.7±3.0 to 226.7±100 mg h−1 and from 0.25±0.12 to 1.56±0.7 mg g−1, respectively. The CO2 emission rates and emission factors ranged from 5500±700 to 210,000±90,000 mg h−1 and from 387±45 to 1689±640 mg g−1, respectively. The contributions of CH4 and THC to emission inventories are expected to be insignificant due both to the small emission factors and to the relatively small quantity of fuel consumed by these portable devices. An exposure scenario analysis indicates that every-day use of the kerosene lamp in a village house can generate fine PM exposures easily exceeding the US promulgated NAAQS for PM2.5.  相似文献   

3.
Measurements of ammonia (NH3), nitrous oxide (N2O) and methane (CH4) were made from 11 outdoor concrete yards used by livestock. Measurements of NH3 emission were made using the equilibrium concentration technique while closed chambers were used to measure N2O and CH4 emissions. Outdoor yards used by livestock proved to be an important source of NH3 emission. Greatest emission rates were measured from dairy cow feeding yards, with a mean of 690 mg NH3-N m−2 h−1. Smaller emission rates were measured from sheep handling areas, dairy cow collecting yards, beef feeding yards and a pig loading area, with respective mean emission rates of 440, 280, 220 and 140 mg NH3-N m−2 h−1. Emission rates of N2O and CH4 were much smaller and for CH4, in particular, emission rates were influenced greatly by the presence or absence of dung on the measurement area.  相似文献   

4.
To investigate the characteristics of mercury exchange between soil and air in the heavily air-polluted area, total gaseous mercury (TGM) concentration in air and Hg exchange flux were measured in Wanshan Hg mining area (WMMA) in November, 2002 and July–August, 2004. The results showed that the average TGM concentrations in the ambient air (17.8–1101.8 ng m−3), average Hg emission flux (162–27827 ng m−2 h−1) and average Hg dry deposition flux (0–9434 ng m−2 h−1) in WMMA were 1–4 orders of magnitude higher than those in the background area. It is said that mercury-enriched soil is a significant Hg source of the atmosphere in WMMA. It was also found that widely distributed roasted cinnabar banks are net Hg sources of the atmosphere in WMMA. Relationships between mercury exchange flux and environmental parameters were investigated. The results indicated that the rate of mercury emission from soil could be accelerated by high total soil mercury concentration and solar irradiation. Whereas, highly elevated TGM concentrations in the ambient air can restrain Hg emission from soil and even lead to strongly atmospheric Hg deposition to soil surface. A great amount of gaseous mercury in the heavily polluted atmosphere may cycle between soil and air quickly and locally. Vegetation can inhibit mercury emission from soil and are important sinks of atmospheric mercury in heavily air-polluted area.  相似文献   

5.
A 3-year research project was established in 1999 to create numerical reference data for material emissions during the time of construction and during the first year. Seven buildings, representing the present construction practice in Finland, were investigated. Material emissions were measured by using the field and laboratory cell (FLEC) during the time of construction, in the newly finished, and in the 6- and 12-month-old buildings. The emission rates for volatile organic compounds (VOCs), formaldehyde, and ammonia were determined.The highest total VOCs (TVOC) emissions were measured in the newly finished buildings from the ceiling structure and from some of the PVC floor coverings. These emissions were up to 1300–2000 μg m−2 h−1. Individual VOCs with emission rates above 50 μg m−2 h−1 included 2-(2-butoxyethoxy) ethanol and its acetate, C4–C16-substituted alkylbenzenes, and xylenes. The mean TVOC emission decreased at least to the Finnish M1-class level (200 μg m−2 h−1) from all surfaces and in all the buildings in 6–12 months. The ammonia and formaldehyde emissions from the ceiling structure were 20–60 μg m−2 h−1 in the newly finished buildings and the M1-levels (30/50 μg m−2 h−1) were exceeded in some cases. These emissions even increased in some buildings during the follow-up period indicating the difference between emissions measured in the laboratory and on site from real structures. Reference values based on the means and 95th percentile are presented to be utilised in both quality control and while investigating indoor air quality problems which are suspected to be caused by a defect structure.  相似文献   

6.
Carbonyl compounds exist in the atmosphere as either gases or aerosols. Some of them are water soluble and known as oxidation products of biogenic and/or anthropogenic hydrocarbons. Five carbonyl compounds, glyoxal (GO), 4-oxopentanal (4-OPA), glycolaldehyde (GA), hydroxyacetone (HA) and methylglyoxal (MG) have been identified in a temporal series of 12 rain samples. The concentrations of the compounds in the samples were high at the beginning of the rain event and decreased with time to relatively low and fairly constant levels, indicating that the compounds were washed out from the atmosphere at the start of the rain event. Possibly, these compounds also existed in the cloud condensation nuclei (CCN). Wet deposition rates of the carbonyl compounds were calculated for nine samples collected during a 20 h period. The deposition rates ranged from 0 (4-OPA) to 1.2×10−1 mg C m−2 h−1 (MG) with the average of 2.9×10−2 mg C m−2 h−1. Production rates of isoprene oxidation products (GA, HA and MG) in the area surrounding the sampling site were estimated with a chemical box model. The deposition rates exceeded the production rates in most samples. This indicates that the rainfall causes a large net flux of the water soluble compounds from the atmosphere to the ground. Insoluble carbonyl compounds such as n-nonanal and n-decanal were expected to be present in the atmosphere, but were not detected in the rain during the sampling period, suggesting that an aerosol containing these insoluble compounds does not effectively act as a CCN.  相似文献   

7.
Carbonyl sulphide (COS) concentrations in air and dissolved in seawater were determined during a cruise in summer 1997 in the northeast Atlantic Ocean. Seawater characteristics and meteorological parameters were monitored. Dissolved COS concentrations throughout the entire cruise exhibited a strong diel cycle with maximum concentrations in late afternoon and minimum concentrations at sunrise. This is in good agreement with the theory that COS is photochemically produced from dissolved organic matter during the day and removed by hydrolysis. The overall mean concentration of dissolved COS was 23.6 pmol dm-3; the daily mean varied according to water mass characteristics and was highest in upwelling areas owing to increased dissolved organic matter. Atmospheric COS concentrations, varying from about 450 to 800 pptv with an average value of 657 pptv, showed some dependency on air mass history and local COS flux from the sea surface. The exchange of COS between the ocean and the atmosphere depended on dissolved COS concentrations and wind speed. The daily integrated flux was always from the sea into the air, and the average was 1.3±0.8 g COS km-2 d-2. The collected data were used to test a mixed layer box model and a one-dimensional model, both describing the behaviour of COS in seawater. We found that the one-dimensional model simulates the data more closely, especially during the night.  相似文献   

8.
To understand the effect of water level on CH4 emissions from an invasive Spartina alterniflora coastal brackish marsh, we measured CH4 emissions from intermittently and permanently (5 cm water depth) inundated mesocosms with or without N fertilizer added at a rate of 2.7 g N m?2. Dissolved CH4 concentrations in porewater and vertically-profiled sediment redox potential were measured, as were aboveground biomass and stem density of S. alterniflora. Mean CH4 fluxes during the growing season in permanently inundated mesocosms without and with N fertilizer were 1.03 and 1.73 mg CH4 m?2 h?1, respectively, which were significantly higher than in the intermittently inundated mesocosms. This response indicates that prolonged submergence of sediment, up to a water depth of 5 cm, stimulated CH4 release. Inundation did not greatly affect aboveground biomass and stem density, but did significantly reduce redox potential in sediment, which in turn stimulated CH4 production and increased the CH4 concentration of porewater, resulting in higher CH4 emission in the mesocosm. Our data showed that the stimulatory effect of shallow, permanent inundation on CH4 emission in S. alterniflora marsh sediment was due primarily to an improved methanogenic environment rather than an increase in plant-derived substrates and/or the number of gas emission pathways through the plant’s aerenchymal system.  相似文献   

9.
A gas monitoring system based on broadband absorption spectroscopic techniques in the ultraviolet region is described and tested. The system was employed in real-time continuous concentration measurements of sulfur dioxide (SO2) and nitric oxide (NO) from a 220-ton h?1 circulating fluidized bed (CFB) boiler in Shandong province, China. The emission coefficients (per kg of coal and per kWh of electricity) and the total emission of the two pollutant gases were evaluated. The measurement results showed that the emission concentrations of SO2 and NO from the CFB boiler fluctuated in the range of 750–1300 mg m?3 and 100–220 mg m?3, respectively. Compared with the specified emission standards of air pollutants from thermal power plants in China, the values were generally higher for SO2 and lower for NO. The relatively high emission concentrations of SO2 were found to mainly depend on the sulfur content of the fuel and the poor desulfurization efficiency. This study indicates that the broadband UV spectroscopy system is suitable for industrial emission monitoring and pollution control.  相似文献   

10.
We determined hourly emissions of isoprene, monoterpenes and sesquiterpenes from Siberian larch, one of the major tree species in Siberian forests. Summer volatile organic compounds (VOCs) emission from Siberian larch consisted mainly of monoterpenes (about 90%). The monoterpene emission spectrum remained constant during the measurement period, almost half was sabinene and other major monoterpenes were Δ3-carene, β- and α-pinene. During spring and summer, about 10% of the VOCs were sesquiterpenes, mainly α-farnesene. The sesquiterpene emissions declined to 3% in the fall. Isoprene, 2-methyl-3-buten-2-ol (MBO) and 1,8-cineole contributed to less than 3% of the VOC emission during the whole period. The diurnal variation of the emissions could be explained using a temperature-dependent parameterization. Emission potentials normalized to 30 °C were 5.2–21 μg gdw−1 h−1 (using β-value of 0.09 °C−1) for monoterpenes and 0.4–1.8 μg gdw−1 h−1 (using β-value of 0.143 °C−1, mean of determined values) for sesquiterpenes. Normalized monoterpene emission potentials were highest in late summer and elevated again in late fall. Sesquiterpene emission potentials were also highest in late summer, but decreased towards fall.  相似文献   

11.
Direct emissions and emission of precursor compounds of acetic and formic acid from higher plants are a significant source of these acids in the atmosphere. To travel from the plant cell to the atmosphere, a gas molecule must first leave the liquid phase and then enter the internal leaf gas phase. The apoplast (cell wall) is the last barrier before the molecule can escape through the stomata. During field experiments we monitored the gas exchange (H2O, CO2, organic acids) of Quercus ilex L. leaves. The exchange rates of acetic and formic acid under field conditions followed a typical diurnal pattern and ranged between −10 (uptake) and 52 (emission) nmol m-2 leaf area min-1 with the maximum around noon. Growth chamber experiments indicate that the emission is related to the stomatal conductance. We discussed the exchange rate of organic acids between the cell wall and the atmosphere in connection with Henry’s law, and the physicochemical conditions in the cell wall. The evaluation showed that for apoplastic pH values between 4 and 5, 26–130% of the measured acetic acid emission based on leaf area could be predicted.  相似文献   

12.
This paper characterizes the emission rates of size fractionated particulate matter, inorganic aerosols, acid gases, ammonia and methane measured over four flocks at a commercial broiler chicken facility. Mean emission rates of each pollutant, along with sampling notes, were reported in this paper, the first in a series of two. Sampling notes were needed because inherent gaps in data may bias the mean emission rates.The mean emission rates of PM10 and PM2.5 were 5.0 and 0.78 g day?1 [Animal Unit, AU]?1, respectively, while inorganic aerosols mean emission rates ranged from 0.15 to 0.46 g day?1 AU?1 depending on the season. The average total acid gas emission rate was 0.43 g day?1 AU?1 with the greatest contribution from nitrous and nitric acids and little contribution from sulfuric acid (as SO2).Ammonia emissions were seasonally dependent, with a mean emission rate of 66.0 g day?1 AU?1 in the cooler seasons and 94.5 g day?1 AU?1 during the warmer seasons. Methane emissions were relatively consistent with a mean emission rate of 208 g day?1 AU?1.The diurnal pattern in each pollutant’s emission rate was relatively consistent after normalizing the hourly emissions according to each daily mean emission rate. Over the duration of a production cycle, all the measured pollutants’ emissions increased proportionally to the total live mass of birds in the house, with the exception of ammonia.Interrelationships between pollutants provide evidence of mutually dependent release mechanisms, which suggests that it may be possible to fill data gaps with minimal data requirements. In the second paper (Roumeliotis, T.S., Dixon, B.J., Van Heyst, B.J. Characterization of gaseous pollutants and particulate matter emission rates from a commercial broiler operation part II: correlated emission rates. Atmospheric Environment, 2010.), regression correlations are developed to estimate daily mean emission rates for data gaps and, using the normalized hourly diurnal patterns from this paper, emission factors were generated for each pollutant.  相似文献   

13.
Spartina alterniflora exhibits great invading potential in the coastal marsh ecosystems. Also, nitrogen (N) deposition shows an apparent increase in the east of China. To evaluate CH4 emissions in the coastal marsh as affected by the invasion of S. alterniflora and N deposition, we measured CH4 emission from brackish marsh mesocosms vegetated with S. alterniflora and a native plant, Suaeda salsa, and fertilized with exogenous N at the rates of 0 and 2.7 g N m?2, respectively. Dissolved porewater CH4 concentration and redox potentials in soils as well as aboveground biomass and stem density of plants were also monitored. The averaged rate of CH4 emission during the growing season in the S. alterniflora and S. salsa mesocosms without N application was 0.88 and 0.54 mg CH4 m?2 h?1, respectively, suggesting that S. alterniflora plants significantly increased CH4 emission mainly because of higher plant biomass rather than stem density compared to S. salsa, which delivered more substrates to the soil for methanogenesis. Exogenous N input dramatically stimulated CH4 emission by 71.7% in the S. alterniflora mesocosm. This increase was attributable to enhancement in biomass and particularly stem density of S. alterniflora driven by N application, which transported greater photosynthesis products than oxygen into soils for CH4 production and provided more pathways for CH4 emission. In contrast, there was no significant effect of N fertilization on CH4 emission in the S. salsa mesocosm. Although N fertilization significantly stimulated CH4 production by increasing S. salsa biomass, no significant increase in stem density was observed. This fact, along with the low gas transport capacity of S. salsa, failed to efficiently transport CH4 from wetlands into the atmosphere. Thus we argue that the stimulatory or inhibitory effect of N fertilization on CH4 emission from wetlands might depend on the gas transport capacity of plants and their relative contribution to substrates for CH4 production and oxygen for CH4 oxidation in soil.  相似文献   

14.
The emission of isoprene (2-methyl-1,3-butadiene) by terrestrial vegetation is an important biosphere–atmosphere exchange which significantly impacts tropospheric chemistry. Isoprene emissions from Chapman oak (Quercus chapmanii) grown for over two years in elevated CO2 levels were measured and compared to emissions from trees grown in ambient CO2 levels in identical open-topped chambers, and emissions from ambient-grown trees were compared to emissions from trees grown in chamberless control plots. Emission rates were adjusted to 30 μmol m−2 s−1 of light intensity and 30°C, and standard T-tests were performed to compare emission rates. No significant differences in isoprene emission were found in ambient vs. elevated CO2 grown trees, while emissions from ambient vs. control trees showed a significant chamber effect.  相似文献   

15.
The object of this study was to develop an accurate estimation method to evaluate the contribution of the various compartments of swine husbandry to dust and GHG (greenhouse gases, CO2, CH4 and N2O) emission into the atmosphere during one year of observation.A weaning, a gestation, a farrowing and a fattening room in an intensive pig house were observed in three different periods (Autumn–Winter, Springtime and Summer, monitoring at least 60% of each period (20% at the beginning, in the middle and at the end) of each cycle).During monitoring, live weight, average live weight gain, number of animals and its variation, type of feed and feeding time were taken into account to evaluate their influence on PM10, or the fraction of suspended particulate matter with an aerodynamic diameter less than or equal to 10 μm [Emission Inventory Guidebook, 2007. B1100 Particle Emissions from Animal Husbandry Activities. Available from: <http://reports.eea.europa.eu/EMEPCORINAIR5/en/B1100vs1.pdf> (accessed October 2008)] and to define GHG emission.The selected piggery had a ventilation control system using a free running impeller to monitor continuously real-time environmental and management parameters with an accuracy of 5%.PM10 concentration was monitored by a sampler (Haz Dust EPAM 5000), either continuously or through traditional gravimetric technique, and the mean value of dust amount collected on the membranes was utilized as a correction factor to be applied to continuously collected data.PM10 concentration amount incoming from inlets was removed from PM10 emission calculation, to estimate the real contribution of pig house dust pollution into atmosphere.Mean yearly emission factor of PM10 was measured in 2 g d?1 LU?1 for the weaning room, 0.09 g d?1 LU?1 for the farrowing room, 2.59 g d?1 LU?1 for the fattening room and 1.23 g d?1 LU?1 for the gestation room. The highest PM10 concentration and emission per LU was recorded in the fattening compartment while the lowest value was recorded in the farrowing room.CO2, CH4 and N2O concentrations were continuously measured in the exhaust ducts using an infrared photoacoustic detector IPD (Brüel & Kjaer, Multi-gas Monitor Type 1302, Multipoint Sampler and Doser Type 1303) sampling data every 15 min, for the 60% of the cycles.Yearly emission factor for CO2 was measured in 5997 g d?1 LU?1 for the weaning room, 1278 g d?1 LU?1 for the farrowing room, 13,636 g d?1 LU?1 for the fattening room and 8851 g d?1 LU?1 for the gestation room.Yearly emission factor for CH4 was measured in 24.57 g d?1 LU?1 for the weaning room, 4.68 g d?1 LU?1 for the farrowing room, 189.82 g d?1 LU?1 for the fattening room and 132.12 g d?1 LU?1 for the gestation room.Yearly emission factor for N2O was measured in 3.62 g d?1 LU?1 for the weaning room, 0.66 g d?1 LU?1 for the farrowing room, 3.26 g d?1 LU?1 for the fattening room and 2.72 g d?1 LU?1 for the gestation room.  相似文献   

16.
The emissions of CO2 and H2S from the aqueous solutions and wastewater were studied to determine and compare the times required to reach the equilibrium of H2S and CO2 between water and gas phases. The solutions of NaHCO3 and NaHS were acidified and the change in the pressure of emitted gases was measured with a manometric OxiTop® system. The average time required to achieve the equilibrium state of distribution of CO2 between two phases was 16.7±1.5 min, and it did not depend on the initial amount of NaHCO3 in the solution. The average time required to achieve the equilibrium of H2S (sulfide) was 19.5±5.5 min, having the same value for solutions with different initial contents of sulfide ions. The average time required to achieve the equilibrium of H2S in the wastewater was 16.2±3.6 min, and it showed the faster emission of gaseous H2S to decrease the oversaturation of the solution. The ratio of measured values of pressure to the calculated values did not depend on the concentration of NaHS in the initial solution, and its average value was 0.86±0.14. The results showed that measured values of pressure of H2S emitted from the wastewater were twice lower than the calculated values and it is necessary to take into account the catalyzed formation of polysulfide in the solution of sulfides.  相似文献   

17.
In the United States, fertilized corn fields, which make up approximately 5% of the total land area, account for approximately 45% of total soil NOx emissions. Leaf chamber measurements were conducted of NO and NO2 fluxes between individual corn leaves and the atmosphere in (1) field-grown plants near Champaign, IL (USA) in order to assess the potential role of corn canopies in mitigating soil–NOx emissions to the atmosphere, and (2) greenhouse-grown plants in order to study the influence of various environmental variables and physiological factors on the dynamics of NO2 flux. In field-grown plants, fluxes of NO were small and inconsistent from plant to plant. At ambient NO concentrations between 0.1 and 0.3 ppbv, average fluxes were zero. At ambient NO concentrations above 1 ppbv, NO uptake occurred, but fluxes were so small (14.3±0.0 pmol m−2 s−1) as to be insignificant in the NOx inventory for this site. In field-grown plants, NO2 was emitted to the atmosphere at ambient NO2 concentrations below 0.9 ppbv (the NO2 compensation point), with the highest rate of emission being 50 pmol m−2 s−1 at 0.2 ppbv. NO2 was assimilated by corn leaves at ambient NO2 concentrations above 0.9 ppbv, with the maximum observed uptake rate being 643 pmol m−2 s−1 at 6 ppbv. When fluxes above 0.9 ppbv are standardized for ambient NO2 concentration, the resultant deposition velocity was 1.2±0.1 mm s−1. When scaled to the entire corn canopy, NO2 uptake rates can be estimated to be as much as 27% of the soil-emitted NOx. In greenhouse-grown and field-grown leaves, NO2 deposition velocity was dependent on incident photosynthetic photon flux density (PPFD; 400–700 nm), whether measured above or below the NO2 compensation point. The shape of the PPFD dependence, and its response to ambient humidity in an experiment with greenhouse-grown plants, led to the conclusion that stomatal conductance is a primary determinant of the PPFD response. However, in field-grown leaves, measured NO2 deposition velocities were always lower than those predicted by a model solely dependent on stomatal conductance. It is concluded that NO2 uptake rate is highest when N availability is highest, not when the leaf deficit for N is highest. It is also concluded that the primary limitations to leaf-level NO2 uptake concern both stomatal and mesophyll components.  相似文献   

18.
Real-world emissions of a traffic fleet on a transit route in Austria were determined in the Tauerntunnel experiment in October 1997. The total number of vehicles and the average speed was nearly the same on both measuring days (465 vehicles 30 min−1 and 76 km h−1 on the workday, 477 and 78 km h−1 on Sunday). The average workday fleet contained 17.6% heavy-duty vehicles (HDV) and the average Sunday fleet 2.8% HDV resulting in up to four times higher emission rates per vehicle per km on the workday than on Sunday for most of the regulated components (CO2, CO, NOx, SO2, and particulate matter-PM10). Emission rates of NMVOC accounted for 200 mg vehicle−1 km−1 on both days. The relative contributions of light-duty vehicles (LDV) and HDV to the total emissions indicated that aldehydes, BTEX (benzene, toluene, ethylbenzene, xylenes), and alkanes are mainly produced by LDV, while HDV dominated emissions of CO, NOx, SO2, and PM10. Emissions of NOx caused by HDV were 16,100 mg vehicle−1 km−1 (as NO2). Produced by LDV they were much lower at 360 mg vehicle−1 km−1. Comparing the emission rates to the results that were obtained by the 1988 experiment at the same place significant changes in the emission levels of hydrocarbons and CO, which accounted 1997 to only 10% of the levels in 1988, were noticed. However, the decrease of PM has been modest leading to values of 80 and 60% of the levels in 1988 on the workday and on Sunday, respectively. Emission rates of NOx determined on the workday in 1997 were 3130 mg vehicle−1 km−1 and even higher than in 1988 (2630 mg vehicle−1 km−1), presumable due to the increase of the HD-traffic.  相似文献   

19.
Uptake of aromatic hydrocarbons (AH) by ice crystals during vapor deposit growth was investigated in a walk-in cold chamber at temperatures of 242, 251, and 260 K, respectively. Ice crystals were grown from ambient air in the presence of gaseous AH namely: benzene (C6H6), toluene (methylbenzene, C7H8), the C8H10 isomers ethylbenzene, o-, m-, p-xylene (dimethylbenzenes), the C9H12 isomers n-propylbenzene, 4-ethyltoluene, 1,3,5-trimethylbenzene (1,3,5-TMB), 1,2,4-trimethylbenzene (1,2,4-TMB), 1,2,3-trimethylbenzene (1,2,3-TMB), and the C10H14 compound tert.-butylbenzene. Gas-phase concentrations calculated at 295 K were 10.3–20.8 μg m−3. Uptake of AH was detected by analyzing vapor deposited ice with a very sensitive method composed of solid-phase micro-extraction (SPME), followed by gas chromatography/mass spectrometry (GC/MS).Ice crystal size was lower than 1 cm. At water vapor extents of 5.8, 6.0 and 8.1 g m−3, ice crystal shape changed with decreasing temperatures from a column at a temperature of 260 K, to a plate at 251 K, and to a dendrite at 242 K. Experimentally observed ice growth rates were between 3.3 and 13.3×10−3 g s−1 m−2 and decreased at lower temperatures and lower value of water vapor concentration. Predicted growth rates were mostly slightly higher.Benzene, toluene, ethylbenzene, and xylenes (BTEX) were not detected in ice above their detection limits (DLs) of 25 pg gice−1 (toluene, ethylbenzene, xylenes) and 125 pg gice−1 (benzene) over the entire temperature range. Median concentrations of n-propylbenzene, 4-ethyltoluene, 1,3,5-TMB, tert.-butylbenzene, 1,2,4-TMB, and 1,2,3-TMB were between 4 and 176 pg gice−1 at gas concentrations of 10.3–10.7 μg m−3 calculated at 295 K. Uptake coefficients (K) defined as the product of concentration of AH in ice and density of ice related to the product of their concentration in the gas phase and ice mass varied between 0.40 and 10.23. K increased with decreasing temperatures. Values of Gibbs energy (ΔG) were between −4.5 and 2.4 kJ mol−1 and decreased as temperatures were lowered. From the uptake experiments, the uptake enthalpy (ΔH) could be determined between −70.6 and −33.9 kJ mol−1. The uptake entropy (ΔS) was between −281.3 and −126.8 J mol−1 K−1. Values of ΔH and ΔS were rather similar for 4-ethlytoluene, 1,3,5-TMB and tert.-butylbenzene, whereas 1,2,3-TMB showed much higher values.  相似文献   

20.
The effects of natural compounds on reducing formaldehyde emission from plywood were investigated. Urea, catechin and vanillin were examined as the natural formaldehyde reducers. The microemission cell, with an internal volume of 35 ml, the maximum exposed test surface area of 177 cm2 and an air purge flow rate of 50 ml min−1, was used to measure specific emission rate (SER). In the case of no reducer treatment, formaldehyde emission from plywood was fast and SERs were 4.4 mg m−2 h−1 at 30 °C and 15 mg m−2 h−1 at 60 °C. When this plywood was treated with the natural compounds, the SERs of formaldehyde were decreased at all temperatures. In the case of urea treatment, the SERs of formaldehyde decreased to 0.30 mg m−2 h−1 at 30 °C and 0.65 mg m−2 h−1 at 60 °C. When the urea treatment was applied to the inside of kitchen cabinet (made from plywood; 270 cm wide, 60 cm deep, 250 cm high), the concentration of formaldehyde was reduced substantially from 1600 to 130 μg m−3. The reducing effect of formaldehyde continued during the observation period (6 months), with a mean concentration of 100 μg m−3. Reducers in the plywood would react with released formaldehyde. Application of natural compounds such as urea, catechin and vanillin could provide a simple and effective approach for suppressing formaldehyde emission from plywood.  相似文献   

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