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1.
The influences of relative humidity (RH) on the heterogeneous reaction of NO2 with soot were investigated by a coated wall flow tube reactor at ambient pressure. The initial uptake coefficient (γ
initial) of NO2 showed a significant decrease with increasing RH from 7 to 70%. The γ
initial on “fuel-rich” and “fuel-lean” soot at RH = 7% was (2.59 ± 0.20) × 10?5 and (5.92 ± 0.34) × 10?6, respectively, and it decreased to (5.49 ± 0.83) × 10?6 and (7.16 ± 0.73) × 10?7 at RH = 70%, respectively. Nevertheless, the HONO yields were almost independent of RH, with average values of (72 ± 3)% for the fuel-rich soot and (60 ± 2)% for the fuel-lean soot. The Langmuir-Hinshelwood mechanism was used to demonstrate the negative role of RH in the heterogeneous uptake of NO2 on soot. The species containing nitrogen formed on soot can undergo hydrolysis to produce carboxylic species or alcohols at high RH, accompanied by the release of little gas-phase HONO and NO. 相似文献
2.
In addition to direct photolysis studies, in this work the second-order reaction rate constants of pesticides imidacloprid (IMD) and ametryn (AMT) with hydroxyl radicals (HO●), singlet oxygen (1O2), and triplet excited states of chromophoric dissolved organic matter (3CDOM*) were determined by kinetic competition under sunlight. IMD and AMT exhibited low photolysis quantum yields: (1.23?±?0.07)?×?10–2 and (7.99?±?1.61)?×?10–3 mol Einstein?1, respectively. In contrast, reactions with HO● radicals and 3CDOM* dominate their degradation, with 1O2 exhibiting rates three to five orders of magnitude lower. The values of kIMD,HO● and kAMT,HO● were (3.51?±?0.06)?×?109 and (4.97?±?0.37)?×?109 L mol?1 s?1, respectively, while different rate constants were obtained using anthraquinone-2-sulfonate (AQ2S) or 4-carboxybenzophenone (CBBP) as CDOM proxies. For IMD this difference was significant, with kIMD,3AQ2S*?=?(1.02?±?0.08)?×?109 L mol?1 s?1 and kIMD,3CBBP*?=?(3.17?±?0.14)?×?108 L mol?1 s?1; on the contrary, the values found for AMT are close, kAMT,3AQ2S*?=?(8.13?±?0.35)?×?108 L mol?1 s?1 and kAMT,3CBBP*?=?(7.75?±?0.80)?×?108 L mol?1 s?1. Based on these results, mathematical simulations performed with the APEX model for typical levels of water constituents (NO3?, NO2?, CO32?, TOC, pH) indicate that the half-lives of these pesticides should vary between 24.1 and 18.8 days in the waters of the Paranapanema River (São Paulo, Brazil), which can therefore be impacted by intensive agricultural activity in the region. 相似文献
3.
On June 5 and 6 of 1980, two parallel plume oxidation studies were carried out in the vicinity of the Tennessee Valley Authority's Colbert Steam Plant. One study was performed in a smog chamber into which stack gases were injected and mixed with ambient air. The other study included direct airborne sampling of the power plant plume. Atmospheric oxidation rates for the conversion of SO 2 to SO 4 2- and the removal rates of NO x (which is presumably the rate of NO 3 - formation) were estimated for both studies. The SO 2 to SO 4 2- rate coefficients were found to be 0.022 ± 0.009 h -1 for both chamber experiments and the first airborne sampling day. For the second day, a rate constant of 0.041 ± 0.052 h -1 was estimated from the aircraft data. The large deviation in this value is explained by the fact that the plume from the power plant combined and reacted with the urban plume from the city of Florence, AL. The formation of a very large "O3 bulge" on this day is also attributed to the mixed plumes. The first order rate coefficients for NO x removal were estimated to be 0.27 ± 0.14 h -1 for both chamber experiments and the first airborne sampling day. A NO x removal rate could not be determined for the second airborne sampling day. 相似文献
5.
Bursa is one of the largest cities of Turkey and it hosts 17 organized industrial zones. Parallel to the increase in population, rapidly growing energy consumption, and increased numbers of transport vehicles have impacts on the air quality of the city. In this study, regularly calibrated automatic samplers were employed to get the levels of air pollution in Bursa. The concentrations of CH 4 and N-CH 4 as well as the major air pollutants including PM 10, PM 2.5, NO, NO 2, NO x, SO 2, CO, and O 3, were determined for 2016 and 2017 calendar years. Their levels were 1641.62?±?718.25, 33.11?±?5.45, 42.10?±?10.09, 26.41?±?9.01, 19.47?±?16.51, 46.73?±?16.56, 66.23?±?32.265, 7.60?±?3.43, 659.397?±?192.73, and 51.92?±?25.63 µg/m 3 for 2016, respectively. Except for O 3, seasonal concentrations were higher in winter and autumn for both years. O 3, CO, and SO 2 had never exceeded the limit values specified in the regulations yet PM 10, PM 2.5, and NO 2 had violated the limits in some days. The ratios of CO/NO x, SO 2/NO x, and PM 2.5/PM 10 were examined to characterize the emission sources. Generally, domestic and industrial emissions were dominated in the fall and winter seasons, yet traffic emissions were effective in spring and summer seasons. As a result of the correlation process between O x and NO x, it was concluded that the most important source of O x concentrations in winter was NO x and O 3 was in summer. 相似文献
6.
Simultaneous daily measurements of water-soluble organic nitrogen (WSON), ammonium and nitrate were made between July and November 2008 at a rural location in south-east Scotland, using a ‘Cofer’ nebulizing sampler for the gas phase and collection on an open-face PTFE membrane for the particle phase. Average concentrations of NH 3 were 82 ± 17 nmol N m ?3 (error is s.d. of triplicate samples), while oxidised N concentrations in the gas phase (from trapping NO 2 and HNO 3) were smaller, at 2.6 ± 2.2 nmol N m ?3, and gas-phase WSON concentrations were 18 ± 11 nmol N m ?3. The estimated collection efficiency of the nebulizing samplers for the gas phase was 88 (±8) % for NH 3, 37 (±16) % for NO 2 and 57 (±7) % for WSON; reported average concentrations have not been corrected for sampling efficiency. Concentrations in the particle phase were smaller, except for nitrate, at 21 ± 9, 10 ± 6 and 8 ± 9 nmol N m ?3, respectively. The absence of correlation in either phase between WSON and either (NH 3 + NH 4+) or NO 3? concentrations suggests atmospheric WSON has diverse sources. During wet days, concentrations of gas and particle-phase inorganic N were lower than on dry days, whereas the converse was true for WSON. These data represent the first reports of simultaneous measurements of gas and particle phase water-soluble nitrogen compounds in rural air on a daily basis, and show that WSON occurs in both phases, contributing 20–25% of the total water-soluble nitrogen in air, in good agreement with earlier data on the contribution of WSON to total dissolved N in rainfall in the UK. 相似文献
7.
Abstract The U.S. Environmental Protection Agency Clean Air Status and Trends Network (CASTNET) utilizes an open-face filter pack system to measure concentrations of atmospheric sulfur and nitrogen species. Concentration data for nitrogen species measured with filter pack systems sometimes deviate from data collected by other measurement systems used to measure the same species. The nature of these differences suggests that more than one sampling mechanism or atmospheric process is involved. The study presented here examines these differences by intercomparing CASTNET data with data from other studies, examining the results from earlier intercomparison studies, and conducting a field test to investigate the effect of particle size on filter pack measurement systems. Measurements of nitrogen species from the Maryland Aerosol Research and Characterization (MARCH) monitoring site were compared with nitrogen concentrations at three nearby CASTNET sites. Results indicate that CASTNET measured higher particulate nitrate (NO 3 -) and lower gaseous nitric acid (HNO 3) concentrations. Comparisons of NO 3 - from 34 collocated CASTNET and Inter-agency Monitoring of Protected Visual Environments (IMPROVE) sites show that CASTNET NO 3 - measurements were typically higher than the corresponding IM PROVE values. Also, results from the Lake Michigan Air Director’s Consortium Midwest Ammonia Monitoring Project demonstrated NO 3 - dissociation on Teflon filters. To investigate the effect of particle size, filter pack measurement systems were operated at three CASTNET sites with and without cyclones during six 7-day measurement periods from March to August 2006. Results indicate the size-selection cyclones had a significant effect on both NO 3 - and HNO 3 concentrations, but little effect on sulfate (SO 4 2-) and ammonium (NH 4 +) levels. NO 3 - concentrations sampled with the open-face filters were significantly higher than concentrations measured with a 2.5-μm cut point, as were HNO 3 concentrations. Although limited in spatial and temporal coverage, the field study showed that the use of an open-face filter pack may allow for the collection of coarse NO 3 - particles and for the reaction of HNO 3 with metals/salts on the Teflon filter. 相似文献
8.
In this study, fine particulate matter (PM 2.5) emitted from a municipal solid waste incinerator (MSWI) was collected using dilution sampling method. Chemical compositions of the collected PM 2.5 samples, including carbon content, metal elements, and water-soluble ions, were analyzed. Traditional in-stack hot sampling was simultaneously conducted to compare the influences of dilution on PM 2.5 emissions and the characteristics of the bonded chemical species. The results, established by a dilution sampling method, show that PM 2.5 and total particulate matter (TPM) emission factors were 61.6 ± 4.52 and 66.1 ± 5.27 g ton-waste ?1, respectively. The average ratio of PM 2.5/TPM is 0.93, indicating that more than 90% of PM emission from the MSWI was fine particulate. The major chemical species in PM 2.5 included organic carbon (OC), Cl ?, NH 4+, elemental carbon (EC) and Si, which account for 69.7% of PM 2.5 mass. OC was from the unburned carbon in the exhaust, which adsorbed onto the particulate during the cooling process. High Cl ? emission is primarily attributable to wastes containing plastic bags made of polyvinyl chloride, salt in kitchen refuse and waste biomass, and so on. Minor species that account for 0.01–1% of PM 2.5 mass included SO 42-, K +, Na, K, NO 3?, Al, Ca 2+, Zn, Ca, Cu, Fe, Pb, and Mg. The mean ratio of dilution method/in-stack hot method was 0.454. The contents of water-soluble ions (Cl ?, SO 42-, NO 3?) were significantly enriched in PM 2.5 via gas-to-particle conversion in the dilution process. Results indicate that in-stack hot sampling would underestimate levels of these species in PM 2.5. Implications: PM 2.5 samples from a municipal solid waste incinerator (MSWI) were collected simultaneously by a dilution sampling technique and a traditional in-stack method. PM 2.5 emission factors and chemical speciation profiles were established. Dilution sampling provides more reliable data than in-stack hot sampling. The results can be applied to estimate the PM 2.5 emission inventories of MSWI, and the source profile can be used for contribution estimate of chemical mass balance modeling. 相似文献
9.
Impacts of diazinon ( O, O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate), imidacloprid [1-(6-chloro-3-pyridylmethyl)- N-nitroimidazolidin-2-ylideneamine] and lindane (1,2,3,4,5.6-hexachlorocyclohexane) treatments on ammonium, nitrate, and nitrite nitrogen and nitrate reductase enzyme activities were determined in groundnut ( Arachis hypogaea L.) field for three consecutive years (1997 to 1999). Diazinon was applied for both seed- and soil-treatments but imidacloprid and lindane were used for seed treatments only at recommended rates. Diazinon residues persisted for 60 days in both the cases. Average half-lives (t 1/2) of diazinon were found 29.3 and 34.8 days respectively in seed and soil treatments. In diazinon seed treatment, NH 4 +, NO 3 ?, and NO 2 ? nitrogen and nitrate reductase activity were not affected. Whereas, diazinon soil treatment indicated significant increase in NH 4 +-N in a 1-day sample, which continued until 90 days. Some declines in NO 3 ?N were found from 15 to 60 days. Along with this decline, significant increases in NO 2 ?N and nitrate reductase activity were found between 1 and 30 days. Imidacloprid and lindane persisted for 90 and 120 days with average half-lives (t 1/2) of 40.9 and 53.3 days, respectively. Within 90 days, imidacloprid residues lost by 73.17% to 82.49% while such losses for lindane residues were found 78.19% to 79.86 % within 120 days. In imidacloprid seed-treated field, stimulation of NO 3 ?N and the decline in NH 4 +NO 2 ?-N and nitrate reductase enzyme activity were observed between 15 to 90 days. However, lindane seed treatment indicated significant increases in NH 4 +-N, NO 2 ?-N and nitrate reductase activity and some adverse effects on NO 3 ?N between 15 and 90 days. 相似文献
10.
Abstract The research objective was to adapt the ultraviolet (UV)photolysis method to determine dissolved organic nitrogen (DON) in aqueous extracts of aerosol samples. DON was assumed to be the difference in total concentration of inorganic nitrogen forms before and after sample irradiation. Using a 2 2 factorial design the authors found that the optimal conversion of urea, amino acids (alanine, aspartic acid, glycine, and serine), and methylamine for a reactor temperature of 44 °C occurred at pH 2.0 with a 24-hr irradiance period at concentrations < µM of organic nitrogen. Different decomposition mechanisms were evident: the photolysis of amino acids and methylamine released mainly ammonium (NH 4 +), but urea released a near equimolar ratio of NH 4 + and nitrate (NO 3 ?). The method was applied to measure DON in the extracts of aerosol samples from Tampa, FL, over a 32-day sampling period. Average dissolved inorganic (DIN) and DON concentrations in the particulate matter fraction PM 10 were 78.1 ± 29.2 nmol-Nm ?3and 8.3 ± 4.9 nmol-Nm ?3, respectively. The ratio between DON and total dissolved nitrogen ([TDN] = DIN + DON) was 10.1 ± 5.7%, and the majority of the DON (79.1 ± 18.2%) was found in the fine particulate matter (PM 2.5) fraction. The average concentrations of DIN and DON in the PM 2.5 fraction were 54.4 ± 25.6 nmol-Nm ?3 and 6.5 ± 4.4 nmol-Nm ?3, respectively. 相似文献
11.
Rates of CO 2 production in the reaction CO + OH and CO + OH + halocarbon have been used to determine rate constants for some OH + halocarbon reactions at 29.5°C relative to that of k(CO + OH) = 2.69 × 10 ?13 cm 3 molecule ?1 sec ?1. The following rate constants were obtained: k(OH + CH 3Cl) = 3.1 ± 0.8, k(OH + CH 2Cl 2) = 2.7 ± 1.0, k(OH + C 2H 5Cl) = 44.0 ± 25, k(OH + CICH 2CH 2CI) = 6.5, (<29) and k(OH + CH 3CCl 3) = 2.1 (<5.7) cm 3 molecule ?1 sec ?1 × 10 ?14. The k values, CH 2Cl 2 excepted, are in substantial agreement with determinations made in nonoxygen environments. The present results for CH 2Cl 2 are almost certainly in error due to difficulties with the competitive approach used. 相似文献
12.
The precision and accuracy of the determination of particu-late sulfate and fluoride, and gas phase SO 2 and HF are estimated from the results obtained from collocated replicate samples and from collocated comparison samples for high-and low-volume filter pack and annular diffusion denuder samplers. The results of replicate analysis of collocated samples and replicate analyses of a given sample for the determination of spherical aluminosilicate fly ash particles have also been compared. Each of these species is being used in the chemical mass balance source apportionment of sulfur oxides in the Grand Canyon region as part of Project MOHAVE, and the precision and accuracy analyses given in this paper provide input to that analysis. The precision of the various measurements reported here is ±1.8 nmol/m 3 and ±2.5 nmol/m 3 for the determination of SO 2 and sulfate, respectively, with an annular denuder. The precision is ±0.5 nmol/m 3 and ±2.0 nmol/m 3 for the determination of the same species with a high-volume or low-volume filter pack. The precision for the determination of the sum of HF(g) and fine particulate fluoride is ±0.3 nmol/m 3. The precision for the determination of aluminosilicate fly ash particles is ±100 particles/m 3. At high concentrations of the various species, reproducibility of the various measurements is ±10% to ±14% of the measured concentration. The concentrations of sulfate determined using filter pack samplers are frequently higher than those determined using diffusion denuder sampling systems. The magnitude of the difference (e.g., 2-10 nmol sulfate/m 3) is small, but important relative to the precision of the data and the concentrations of particulate sul-fate present (typically 5-20 nmol sulfate/m 3). The concentrations of SO 2(g) determined using a high-volume cascade impactor filter pack sampler are correspondingly lower than those obtained with diffusion denuder samplers. The concentrations of SO x (SO 2(g) plus particulate sulfate) determined using the two samplers during Project MOHAVE at the Spirit Mountain, NV, and Hopi Point, AZ, sampling sites were in agreement. However, for samples collected at Painted Desert, AZ, and Meadview, AZ, the concentrations of SO x and SO 2(g) determined with a high-volume cascade impactor filter pack sampler were frequently lower than those determined using a diffusion denuder sampling system. These two sites had very low ambient relative humidity, an average of 25%. Possible causes of observed differences in the SO 2(g) and sulfate results obtained from different types of samplers are given. 相似文献
13.
Denitrification is an important N removal process in aquatic systems but is also implicated as a potential source of global N 2O emissions. However, the key factors controlling this process as well as N 2O emissions remain unclear. In this study, we identified the main factors that regulate the production of net N 2 and N 2O in sediments collected from rivers with a large amount of sewage input in the Taihu Lake region. Net N 2 and N 2O production were strongly associated with the addition of NO 3 ?-N and NH 4 +-N. Specifically, NO 3 ?-N controlled net N 2 production following Michaelis–Menten kinetics. The maximum rate of net N 2 production ( V max) was 116.3 μmol N 2-N m ?2 h ?1, and the apparent half-saturation concentration ( k m) was 0.65 mg N L ?1. N 2O to N 2 ratios increased from 0.18?±?0.03 to 0.68?±?0.16 with the addition of NO 3 ?-N, suggesting that increasing NO 3 ?-N concentrations favored the production of N 2O more than N 2. The addition of acetate enhanced net N 2 production and N 2O to N 2 ratios, but the ratios decreased by about 59.5 % when acetate concentrations increased from 50 to 100 mg C L ?1, suggesting that the increase of N 2O to N 2 ratios had more to do with the net N 2 production rate rather than acetate addition in this experiment. The addition of Cl ? did not affect the net N 2 production rates, but significantly enhanced N 2O to N 2 ratios (the ratios increased from 0.02?±?0.00 to 0.10?±?0.00), demonstrating that the high salinity effect might have a significant regional effect on N 2O production. Our results suggest that the presence of N-enriching sewage discharges appear to stimulate N removal but also increase N 2O to N 2 ratios. 相似文献
14.
The interference in HNO 3 determination due to HNO 2 and NO x retention on nylon filters has been evaluated in laboratory and field conditions. Nitrous acid is retained on nylon filters with efficiencies varying from 25% at 12ℓ min −1 to 80% at 2ℓ min −1, yielding NO 2− ion. In ambient sampling performed during photochemical smog episodes, NO 2− is oxidized to NO 3− with conversion factors up to 100%, resulting in a positive bias in HNO 3 determination.NO 2 reacts heterogeneously with H 2O on nylon surfaces according to the reaction 2NO 2 + H 2O → HNO 2 + HNO 3 with a removal constant of about 1 × 10 −4 ms −1 at a H 2O concentration of 20,000 ppm. The resulting nitrite and nitrate are independent of the sampling flow rate, while NO 2 concentration, sampling time and exposed nylon surface area play a directly proportional role. Accordingly, the relative interference of NO 2 with respect to HNO 3 determination is almost negligible for nylon filters, usually run at relatively high flow rates, while it may be significant for nylon denuders, which are characterized by larger exposed surfaces and lower operating flow rates. 相似文献
15.
Gaseous nitrogen dioxide (NO 2) represents an oxidant that is present in relatively high concentrations in various indoor settings. Remarkably increased NO 2 levels up to 1.5 ppm are associated with homes using gas stoves. The heterogeneous reactions of NO 2 with adsorbed water on surfaces lead to the generation of nitrous acid (HONO). Here, we present a HONO source induced by heterogeneous reactions of NO 2 with selected indoor paint surfaces in the presence of light (300 nm?<? λ?<?400 nm). We demonstrate that the formation of HONO is much more pronounced at elevated relative humidity. In the presence of light (5.5 W m ?2), an increase of HONO production rate of up to 8.6?·?10 9 molecules cm ?2 s ?1 was observed at [NO 2]?=?60 ppb and 50 % relative humidity (RH). At higher light intensity of 10.6 (W m ?2), the HONO production rate increased to 2.1?·?10 10 molecules cm ?2 s ?1. A high NO 2 to HONO conversion yield of up to 84 % was observed. This result strongly suggests that a light-driven process of indoor HONO production is operational. This work highlights the potential of paint surfaces to generate HONO within indoor environments by light-induced NO 2 heterogeneous reactions. 相似文献
16.
The main objective of this atmospheric study was to determine the major sources of PM 1 (particles having aerodynamic diameter <1.0 μm) within and near the city of Kanpur, in the Indo-Gangetic Plain. Day and night, 10 h long each, filter-based aerosol samples were collected for 4 months (November 2009 to February 2010) throughout the winter season. These samples were subjected to gravimetric and quantitative chemical analyses for determining water-soluble ions (NH 4 +, F ?, Cl ?, NO 3 ?, and SO 4 2?) using an ion chromatograph and trace elements using an inductively coupled plasma–optical emission spectrometer. The mean PM 1 mass concentrations were recorded as 114?±?71 μg/m 3 (day) and 143?±?86 μg/m 3 (night), respectively. A significantly higher diurnal contribution of ions (NH 4 +, F ?, Cl ?, NO 3 ?, and SO 4 2?) in PM 1 mass was observed during the fog-affected days and nights throughout the winter season, for which the average values were recorded as 38.09?±?13.39 % (day) and 34.98?±?12.59 % (night), respectively, of the total PM 1 mass. This chemical dataset was then used in a source-receptor model, UNMIX, and the model results are described in detail. UNMIX provided a maximum number of five source factors, including crustal material, composite vehicle, secondary aerosol, coal combustion, and iron/steel production and metallurgical industries, as the dominant air pollution sources for this study. 相似文献
17.
ABSTRACT The Aerosol Research and Inhalation Epidemiology Study (ARIES) was designed to provide high-quality measurements of PM 25, its components, and co-varying pollutants for an air pollution epidemiology study in Atlanta, GA. Air pollution epidemiology studies have typically relied on available data on particle mass often collected using filter-based methods. Filter-based PM 2.5 sampling is susceptible to both positive and negative errors in the measurement of aerosol mass and particle-phase component concentrations in the undisturbed atmosphere. These biases are introduced by collection of gas-phase aerosol components on the filter media or by volatilization of particle phase components from collected particles. As part of the ARIES, we collected daily 24-hr PM 2.5 mass and speciation samples and continuous PM 2.5 data at a mixed residential-light industrial site in Atlanta. These data facilitate analysis of the effects of a wide variety of factors on sampler performance. We assess the relative importance of PM 2.5 components and consider associations and potential mechanistic linkages of PM 2.5 mass concentrations with several PM 2.5 components. For the 12 months of validated data collected to date (August 1, 1998-July 31, 1999), the monthly average Federal Reference Method (FRM) PM 2 5 mass always exceeded the proposed annual average standard (12-month average = 20.3 ± 9.5 ug/m 3). The particulate SO 4 2- fraction (as (NH 4) 2SO 4) was largest in the summer and exceeded 50% of the FRM mass. The contribution of (NH 4) 2SO 4 to FRM PM 2.5 mass dropped to less than 30% in winter. Particu-late NO 3 - collected on a denuded nylon filter averaged 1.1 ± 0.9 ug/m 3. Particle-phase organic compounds (as organic carbon × 1.4) measured on a denuded quartz filter sampler averaged 6.4 ± 3.1 ug/m 3 (32% of FRM PM 2 5 mass) with less seasonal variability than SO 4 2-. 相似文献
18.
Abstract The real-time ambient mass sampler (RAMS) is a continuous monitor based on particle concentrator, denuder, drier, and tapered element oscillating microbalance (TEOM) monitor technology. It is designed to measure PM 2.5 mass, including the semi-volatile species NH 4NO 3 and semi-volatile organic material, but not to measure PM 2.5 water content. The performance of the RAMS in an urban environment with high humidity was evaluated during the July 1999 NARSTO-Northeast Oxidant and Particles Study (NEOPS) intensive study at the Baxter water treatment plant in Philadelphia, PA. The results obtained with the RAMS were compared to mass measurements made with a TEOM monitor and to constructed mass obtained with a Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS) sampler designed to determine the chemical composition of fine particles, including the semi-volatile species. An average of 28% of the fine particulate material present during the study was semi-volatile organic material lost from a filter during particle collection, and 1% was NH 4NO 3 that was also lost from the particles during sampling. The remaining mass was dominantly nonvolatile (NH 4) 2SO 4 (31%) and organic material (37%), with minor amounts of soot, crustal material, and nonvolatile NH 4NO 3. Comparison of the RAMS and PC-BOSS results indicated that the RAMS correctly monitored for fine particulate mass, including the semi-volatile material. In contrast, the heated filter of the TEOM monitor did not measure the semi-volatile material. The comparison of the RAMS and PC-BOSS data had a precision of ±4.1 μg/m 3 (±9.6%). The precision of the RAMS data was limited by the uncertainty in the blank correction for the reversible adsorption of water by the charcoal-impregnated cellulose sorbent filter of the RAMS monitor. The precision of the measurement of fine par-ticulate components by the PC-BOSS was ±6-8%. 相似文献
19.
Personal exposures, residential indoor, outdoor and workplace levels of nitrogen dioxide (NO 2) were measured for 262 urban adult (25–55 years) participants in three EXPOLIS centres (Basel; Switzerland, Helsinki; Finland, and Prague; Czech Republic) using passive samplers for 48-h sampling periods during 1996–1997. The average residential outdoor and indoor NO 2 levels were lowest in Helsinki (24±12 and 18±11 μg m −3, respectively), highest in Prague (61±20 and 43±23 μg m −3), with Basel in between (36±13 and 27±13 μg m −3). Average workplace NO 2 levels, however, were highest in Basel (36±24 μg m −3), lowest in Helsinki (27±15 μg m −3), with Prague in between (30±18 μg m −3). A time-weighted microenvironmental exposure model explained 74% of the personal NO 2 exposure variation in all centres and in average 88% of the exposures. Log-linear regression models, using residential outdoor measurements (fixed site monitoring) combined with residential and work characteristics (i.e. work location, using gas appliances and keeping windows open), explained 48% (37%) of the personal NO 2 exposure variation. Regression models based on ambient fixed site concentrations alone explained only 11–19% of personal NO 2 exposure variation. Thus, ambient fixed site monitoring alone was a poor predictor for personal NO 2 exposure variation, but adding personal questionnaire information can significantly improve the predicting power. 相似文献
20.
Rate constants for the atmospheric reactions of 1-methyl-2-pyrrolidinone with OH radicals, NO 3 radicals and O 3 have been measured at 296±2 K and atmospheric pressure of air, and the products of the OH radical and NO 3 radical reactions investigated. Using relative rate techniques, rate constants for the gas-phase reactions of OH and NO 3 radicals with 1-methyl-2-pyrrolidinone of (2.15±0.36)×10 -11 cm 3 molecule -1 s -1 and (1.26±0.40)×10 -13 cm 3 molecule -1 s -1, respectively, were measured, where the indicated errors include the estimated overall uncertainties in the rate constants for the reference compounds. An upper limit to the rate constant for the O 3 reaction of <1×10 -19 cm 3 molecule -1 s -1 was also determined. These kinetic data lead to a calculated tropospheric lifetime of 1-methyl-2-pyrrolidinone of a few hours, with both the daytime OH radical reaction and the nighttime NO 3 radical reaction being important loss processes. Products of the OH radical and NO 3 radical reactions were analyzed by gas chromatography with flame ionization detection and combined gas chromatography–mass spectrometry. N-methylsuccinimide and (tentatively) 1-formyl-2-pyrrolidinone were identified as products of both of these reactions. The measured formation yields of N-methylsuccinimide and 1-formyl-2-pyrrolidinone were 44±12% and 41±12%, respectively, from the OH radical reaction and 59±16% and ∼4%, respectively, from the NO 3 radical reaction. Reaction mechanisms consistent with formation of these products are presented. 相似文献
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