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1.
《Atmospheric environment (Oxford, England : 1994)》1999,33(8):1177-1185
Monitoring of nitrogen dioxide (NO2) by passive sampling on the Danish island Funen (Fyn) show that the concentration of nitrogen dioxide is low (2–20 ppb). The level of NO2 in rural and suburban areas is governed by imported airpollution, and elevated NO2 concentrations due to local traffic are of limited importance. These results are supported by diffusion denuder measurements of nitric acid (HNO3) and particulate nitrate. Measurements of NO2 with chemiluminescence and diffusive passive sampling showed good agreement between the methods. The special mounting device for the diffusive samplers used in this work seem to have reduced the turbulence at the open end of the tube. The product from the reaction between nitrogen dioxide and triethanolamine was investigated and tentatively identified as triethanolamine N-oxide, which is in accordance with the observed 1 : 1 stoechiometry in the conversion of NO2 to nitrite ions. 相似文献
2.
《Atmospheric environment (Oxford, England : 1994)》2002,36(20):3289-3298
For over one year, the Environmental Protection Commission of Hillsborough County (EPCHC) in Tampa, Florida, operated two dichotomous sequential particulate matter air samplers collocated with a manual Federal Reference Method (FRM) air sampler at a waterfront site on Tampa Bay. The FRM was alternately configured as a PM2.5, then as a PM10 sampler. For the dichotomous sampler measurements, daily 24-h integrated PM2.5 and PM10–2.5 ambient air samples were collected at a total flow rate of 16.7 l min−1. A virtual impactor split the air into flow rates of 1.67 and 15.0 l min−1 onto PM10–2.5 and PM2.5 47-mm diameter PTFE® filters, respectively. Between the two dichotomous air samplers, the average concentration, relative bias and relative precision were 13.3 μg m−3, 0.02% and 5.2% for PM2.5 concentrations (n=282), and 12.3 μg m−3, 3.9% and 7.7% for PM10–2.5 concentrations (n=282). FRM measurements were alternate day 24-h integrated PM2.5 or PM10 ambient air samples collected onto 47-mm diameter PTFE® filters at a flow rate of 16.7 l min−1. Between a dichotomous and a PM2.5 FRM air sampler, the average concentration, relative bias and relative precision were 12.4 μg m−3, −5.6% and 8.2% (n=43); and between a dichotomous and a PM10 FRM air sampler, the average concentration, relative bias and relative precision were 25.7 μg m−3, −4.0% and 5.8% (n=102). The PM2.5 concentration measurement standard errors were 0.95, 0.79 and 1.02 μg m−3; for PM10 the standard errors were 1.06, 1.59, and 1.70 μg m−3 for two dichotomous and one FRM samplers, respectively, which indicate the dichotomous samplers have superior technical merit. These results reveal the potential for the dichotomous sequential air sampler to replace the combination of the PM2.5 and PM10 FRM air samplers, offering the capability of making simultaneous, self-consistent determinations of these particulate matter fractions in a routine ambient monitoring mode. 相似文献
3.
Zhao-Yang Meng Xiao-Bin Xu Tao Wang Xing-Ying Zhang Xiao-Lan Yu Shu-Feng Wang Wei-Li Lin Yi-Zhen Chen Yi-An Jiang Xing-Qin An 《Atmospheric environment (Oxford, England : 1994)》2010,44(21-22):2625-2631
We present two years (January 2007–December 2008) of atmospheric SO2, NO2 and NH3 measurements from ten background or rural sites in nine provinces in China. The measurements were made on a monthly basis using passive samplers under careful quality control. The results show large geographical and seasonal variations in the concentrations of these gases. The mean SO2 concentration varied from 0.7 ± 0.4 ppb at Waliguan on Qinghai Plateau to 67.3 ± 31.1 ppb at Kaili in Guizhou province. The mean NO2 concentration ranged from 0.6 ± 0.4 ppb at Waliguan to 23.9 ± 6.9 ppb at Houma in southern Shanxi. The mean NH3 concentration ranged from 2.8 ± 3.0 ppb at Shangdianzi in northeastern Beijing to 13.7 ± 8.4 ppb at Houma. At most sites, SO2 and NO2 peaked in winter and reached minima in summer, while NH3 showed maximum values in summer and lower values in cold seasons. On the whole, the geographical distributions of the observed gas concentrations are consistent with those of emissions. The ground measurements of SO2 and NO2 are contrasted to the SCIAMACHY SO2 and OMI NO2 tropospheric columns, respectively. Although the satellite data can capture the main features of emissions and concentrations of SO2, they do not reflect the variations of SO2 in the surface layer. The situation is better for the case of NO2. The OMI NO2 columns capture the geographical differences in the ground NO2 and correlate fairly well with the ground levels of NO2 at six of the ten sites. 相似文献
4.
《Atmospheric environment (Oxford, England : 1994)》2001,35(20):3405-3412
Personal exposures, residential indoor, outdoor and workplace levels of nitrogen dioxide (NO2) 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 NO2 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 NO2 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 NO2 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 NO2 exposure variation. Regression models based on ambient fixed site concentrations alone explained only 11–19% of personal NO2 exposure variation. Thus, ambient fixed site monitoring alone was a poor predictor for personal NO2 exposure variation, but adding personal questionnaire information can significantly improve the predicting power. 相似文献
5.
《Atmospheric environment (Oxford, England : 1994)》1999,33(24-25):4101-4108
The influence of traffic-induced pollutants (e.g. CO, NO, NO2 and O3) on the air quality of urban areas was investigated in the city of Essen, North Rhine-Westphalia (NRW), Germany. Twelve air hygiene profile measuring trips were made to analyse the trace gas distribution in the urban area with high spatial resolution and to compare the air hygiene situation of urban green areas with the overall situation of urban pollution. Seventeen measurements were made to determine the diurnal concentration courses within urban parks (summer conditions: 13 measurements, 530 30 min mean values, winter conditions: 4 measurements, 128 30 min mean values). The measurements were carried out during mainly calm wind and cloudless conditions between February 1995 and March 1996. It was possible to establish highly differentiated spatial concentration patterns within the urban area. These patterns were correlated with five general types of land use (motorway, main road, secondary road, residential area, green area) which were influenced to varying degrees by traffic emissions. Urban parks downwind from the main emission sources show the following typical temporal concentration courses: In summer rush-hour-dependent CO, NO and NO2 maxima only occurred in the morning. A high NO2/NO ratio was established during weather conditions with high global radiation intensities (K>800 W m−2), which may result in a high O3 formation potential. Some of the values measured found in one of the parks investigated (Gruga Park, Essen, area: 0.7 km2), which were as high as 275 μg m−3 O3 (30-min mean value) were significantly higher than the German air quality standard of 120 μg m−3 (30-min mean value, VDI Guideline 2310, 1996) which currently applies in Germany and about 20% above the maximum values measured on the same day by the network of the North Rhine–Westphalian State Environment Agency. In winter high CO and NO concentrations occur in the morning and during the afternoon rush-hour. The highest concentrations (CO=4.3 mg m−3, NO=368 μg m−3, 30-min mean values) coincide with the increase in the evening inversion. The maximum measured values for CO, NO and NO2 do not, however, exceed the German air quality standards in winter and summer. 相似文献
6.
Yu Ren Aijun Ding Tao Wang Xinhua Shen Jia Guo Jiamin Zhang Yan Wang Pengju Xu Xinfeng Wang Jian Gao Jeffrey L. Collett 《Atmospheric environment (Oxford, England : 1994)》2009,43(9):1702-1711
Measurement of ambient gas-phase total peroxides was performed at the summit of Mount Tai (Mt. Tai, 1534 m above sea level) in central-eastern China during March 22–April 24 and June 16–July 20, 2007. The hourly averaged concentration of peroxides was 0.17 ppbv (± 0.16 ppbv, maximum: 1.28 ppbv) and 0.55 ppbv (± 0.67 ppbv, maximum: 3.55 ppbv) in the spring and summer campaigns, respectively. The average concentration of peroxides at Mt. Tai, which is in a heavily polluted region, was much lower than hydrogen peroxide measurements made at some rural mountain sites, suggesting that significant removal processes took place in this region. An examination of diurnal variation and a correlation analysis suggest that these removal processes could include chemical suppression of peroxide production due to the scavenging of peroxy and hydroxy radicals by high NOx, wet removal by clouds/fogs rich in dissolved sulfur dioxide which reacts quickly with peroxides, and photolysis. These sinks competed with photochemical sources of peroxides, resulting in different mean concentrations and diurnal pattern of peroxides in the spring and summer. A principal component analysis was conducted to quantify the major processes that influenced the variation of peroxide concentrations. This analysis shows that in the spring photochemical production was an important source of peroxides, and the major sink was scavenging during upslope transport of polluted and humid air from the lower part of the planetary boundary layer (PBL) and wet removal by synoptic scale clouds. During the summer, highly polluted PBL air (with high NOx) was often associated with very low peroxides due to the chemical suppression of HO2 by high NOx and wet-removal by clouds/fogs in this sulfur-rich atmosphere, especially during the daytime. Higher concentrations of peroxides, which often appeared at mid-nighttime, were mainly associated with subsidence of air masses containing relatively lower concentrations of NOy. 相似文献
7.
《Atmospheric environment (Oxford, England : 1994)》2001,35(21):3619-3631
Long-term observations of the nitrate radical concentration and supporting parameters in the continental boundary layer at the rural site Lindenberg near Berlin, Germany, were performed using differential optical absorption spectroscopy (DOAS). Average nighttime NO3 levels were 4.6 ppt, while NO3 steady-state lifetimes (calculated from the NO2–O3 product and the NO3 concentration) varied between 5 s and 615 s with an average of 92 s. The long-term observations offered the possibility to study the importance of NO3 for the oxidation of VOCs (volatile organic compounds) and its contribution in the non-photochemical removal of NOx from the atmosphere in different seasons. Analysis of the data showed, that NO3 was depleted by both, reactions with VOCs and indirectly by loss of N2O5 on aerosol surfaces. A clear seasonal variation of the sink distribution was found. The VOC sink dominated during summer while indirect loss was of major importance during the winter months. The results are compared with former long-term campaigns of NO3 in the marine boundary layer. 相似文献
8.
《Atmospheric environment (Oxford, England : 1994)》1999,33(28):4637-4650
NOx emissions from a medium speed diesel engine on board a servicing passenger ferry have been indirectly measured using a predictive emission monitoring system (PEMS) over a 1-yr period. Conventional NOx measurements were carried out with a continuous emission monitoring system (CEMS) at the start of the study to provide historical data for the empirical PEMS function. On three other occasions during the year the CEMS was also used to verify the PEMS and follow any changes in emission signature of the engine. The PEMS consisted of monitoring exhaust O2 concentrations (in situ electrochemical probe), engine load, combustion air temperature and humidity, and barometric pressure. Practical experiences with the PEMS equipment were positive and measurement data were transferred to a land-based office by using a modem data communication system. The initial PEMS function (PEMS1) gave systematic differences of 1.1–6.9% of the calibration domain (0–1725 ppm) and a relative accuracy of 6.7% when compared with CEMS for whole journeys and varying load situations. Further improvements on the performance could be obtained by updating this function. The calculated yearly emission for a total engine running time of 4618 h was 316 t NOx±38 t and the average NOx emission corrected for ambient conditions 14.3 g kWhcorr−1. The exhaust profile of the engine in terms of NOx, CO and CO2 emissions as determined by CEMS was similar for most of the year. Towards the end of the study period, a significantly lower NOx emission was detected which was probably caused by replacement of fuel injector nozzles. The study suggests that PEMS can be a viable option for continuous, long-term NOx measurements on board ships. 相似文献
9.
《Atmospheric environment (Oxford, England : 1994)》2007,41(12):2549-2558
Atmospheric concentrations of and personal exposure to benzene have been measured in four French metropolitan areas for 210 subjects over two seasons. Half of the volunteers were 6–13-year-old children. The adult subjects were non-smokers, not occupationally exposed and they live and work in the monitored areas. Measurements were performed using diffusive samplers followed by GC-FID analysis. The average values for ambient air concentrations (μg m−3) were: Rouen: 1.5; Île de France (Paris area): 1.6; Grenoble: 2.3 and Strasbourg: 2.6, showing that benzene concentrations in the ambient air of the four cities satisfy the requirements of the European Directive 2000/69EC of the European Parliament which stipulates a limit value of 5 μg m−3. However, the 48 h exposures measured were found to be between 2.7 and 3.5 times higher than ambient air concentrations. As a consequence, 60% of the subjects investigated, including children, were exposed to concentrations higher than the ambient air limit value. This work confirms that air monitoring data collected by fixed stations should be used with caution when assessing population exposure to benzene, especially given the influence of indoor sources and other polluted microenvironments where people spend part of their time. 相似文献
10.
Cesare Dari-Salisburgo Piero Di Carlo Franco Giammaria Yoshizumi Kajii Alfonso D'Altorio 《Atmospheric environment (Oxford, England : 1994)》2009,43(4):970-977
A laser induced fluorescence (LIF) instrument has been developed to measure tropospheric NO2 with low detection limit. The instrument design, development and first measurements are reported. There are also details of the temporal gate system built for the fluorescence acquisition. The instrument is able to make fast measurements (up to 4 Hz) and shows a limit of detection of 10 pptv/60 s. Continuous observations (2 weeks in summer 2007) in a small town in central Italy were used to test the performance of the instrument and to study the photochemistry of ozone in a background site. LIF and a commercial chemiluminescence (CL) instrument simultaneous observations of NO2 show a good linearity (LIF = 1.02 CL + 0.6 (ppb), R2 = 0.98) but there is a bias of the commercial instrument of about 0.60 ppbv on average. The overestimation of the CL system is probably due to conversion of NOy species into NO by the molybdenum converter used in the CL instrument to detect NO2. Analysis of 1 s data is used to test the instrument response and the coupling between nitrogen oxides and ozone. 相似文献
11.
《Atmospheric environment (Oxford, England : 1994)》2007,41(8):1627-1633
To evaluate the tropical wetlands contribution to the methane (CH4) burden better, field campaigns were performed during 2004 and 2005 near the Miranda River, in five sites inside the Brazilian Pantanal region. The CH4 fluxes were determined using the static chamber technique. Environmental variables that may affect CH4 emissions, as the water depth, the water and air temperatures were also measured. The overall average of the 320 individual CH4 flux measurements made between March/2004 and March/2005 was 142±314 mg CH4 m−2 d−1, which is a value near the ones observed in other tropical flooded regions. About 47% of the fluxes measurements presented nonlinear increases in the chamber concentrations, which were assumed to be linked to CH4 losses through bubbles. The bubble flux represented about 90% of the total CH4 losses in the measurements and ranged from 1 to 2187 mg CH4 m−2 d−1 with an average of 292±410 mg CH4 m−2 d−1 (median: 153 mg CH4 m−2 d−1). The diffusive flux ranged from 1 to 124 mg CH4 m−2 d−1, with an average of 10±17 mg CH4 m−2 d−1 (median: 5 mg CH4 m−2 d−1). The fluxes from lakes were smaller than those observed in the floodplains, where the flooding was more dependent on the seasonal cycle. The diffusive flux showed a slight, but not statistically significant seasonal variation, following the seasonal variation of the flooding of the Pantanal region. A rough estimative of the total annual CH4 emission shows that the contribution of the Pantanal is about 3.3 Tg CH4 yr−1, which represents about 3.3% of the total CH4 emissions estimated to be originated in wetlands ecosystems. It may be a conservative estimate, which may present a large interannual variation, since it was obtained during one of the lowest flood of the Pantanal in recent years. 相似文献
12.
《Atmospheric environment (Oxford, England : 1994)》2001,35(7):1203-1215
Comparisons were made between the predictions of six photochemical air quality simulation models (PAQSMs) and three indicators of ozone response to emission reductions: the ratios of O3/NOz and O3/NOy and the extent of reaction. The values of the two indicator ratios and the extent of reaction were computed from the model-predicted mixing ratios of ozone and oxidized nitrogen species and were compared to the changes in peak 1 and 8 h ozone mixing ratios predicted by the PAQSMs. The ozone changes were determined from the ozone levels predicted for base-case emission levels and for reduced emissions of volatile organic compounds (VOCs) and oxides of nitrogen (NOx). For all simulations, the model-predicted responses of peak 1 and 8 h ozone mixing ratios to VOC or NOx emission reductions were correlated with the base-case extent of reaction and ratios of O3/NOz and O3/NOy. Peak ozone values increased following NOx control in 95% (median over all simulations) of the high-ozone (>80 ppbv hourly mixing ratio in the base-case) grid cells having mean afternoon O3/NOz ratios less than 5 : 1, O3/NOy less than 4 : 1, or extent less than 0.6. Peak ozone levels decreased in response to NOx reductions in 95% (median over all simulations) of the grid cells having peak hourly ozone mixing ratios greater than 80 ppbv and where mean afternoon O3/NOz exceeded 10 : 1, O3/NOy was greater than 8 : 1, or extent exceeded 0.8. Ozone responses varied in grid cells where O3/NOz was between 5 : 1 and 10 : 1, O3/NOy was between 4 : 1 and 8 : 1, or extent was between 0.6 and 0.8. The responses in such grid cells were affected by ozone responses in upwind grid cells and by the changes in ozone levels along the upwind boundaries of the modeling domains. 相似文献
13.
《Atmospheric environment (Oxford, England : 1994)》2004,38(10):1459-1471
Twelve hours integrated fine particles (PM2.5) and 24-h average size-segregated particles were collected to investigate the chemical characteristics and to determine the size distribution of ionic species during October–December 1999 in three cities of different urban scale; Chongju, Kwangju, and Seoul, Korea. Concentrations of 5-min PM2.5 black carbon (BC) and hourly criteria air pollutants (PM10, CO, NOx, SO2, and O3) were also measured using the Aethalometer and ambient air monitoring system, respectively.Highest PM2.5 mass concentrations at Chongju, Kwangju, and Seoul sites were 63.0, 77.9, and 143.7 μg m−3, respectively. For the time period when highest PM2.5 mass occurred, BC level out of PM2.5 chemical species was highest at both Chongju and Kwangju, and highest NO3− (23.6 μg m−3) followed by BC (23.1 μg m−3) were observed at Seoul site, indicating that highest PM2.5 pollution is closely associated with the traffic emissions. Strong relationships of Fe with BC and Zn at both Kwangju and Seoul sites support that the Fe and Zn measured there are originated partly from same source as BC, i.e. diesel traffics. However, it is suggested that the Fe measured at Chongju is most likely derived from dispersion of soil dust.The size distributions of SO42−, NO3−, and NH4+ ionic species indicated similar unimodal distributions at all sampling sites. However, different unimodal patterns in the accumulation mode size range with a peak in the smaller size (0.28–0.53 μm, condensation mode) in both Kwangju and Seoul, and in the relatively larger size (0.53–1.0 μm, droplet mode) in Chongju, were found. The potassium ion under the study sites dominates in the fine mode, and its size distribution showed unimodal character with a maximum in the size range 0.56–1.0 μm. 相似文献
14.
Fuhai Geng Qiang Zhang Xuexi Tie Mengyu Huang Xincheng Ma Zhaoze Deng Qiong Yu Jiannong Quan Chunsheng Zhao 《Atmospheric environment (Oxford, England : 1994)》2009,43(3):584-593
In this study, air pollutants, including ozone (O3), nitrogen oxides (NOx = NO + NO2), carbon monoxides (CO), sulfur dioxide (SO2), and volatile organic compounds (VOCs) measured in the Yangtze River Delta (YRD) region during several air flights between September/30 and October/11 are analyzed. This measurement provides horizontal and vertical distributions of air pollutants in the YRD region. The analysis of the result shows that the measured O3 concentrations range from 20 to 60 ppbv. These values are generally below the US national standard (84 ppbv), suggesting that at the present, the O3 pollutions are modest in this region. The NOx concentrations have strong spatial and temporal variations, ranging from 3 to 40 ppbv. The SO2 concentrations also have large spatial and temporal variations, ranging from 1 to 35 ppbv. The high concentrations of CO are measured with small variations, ranging from 3 to 7 ppmv. The concentrations of VOCs are relatively low, with the total VOC concentrations of less than 6 ppbv. The relative small VOC concentrations and the relative large NOx concentrations suggest that the O3 chemical formation is under a strong VOC-limited regime in the YRD region. The measured O3 and NOx concentrations are strongly anti-correlated, indicating that enhancement in NOx concentrations leads to decrease in O3 concentrations. Moreover, the O3 concentrations are more sensitive to NOx concentrations in the rural region than in the city region. The ratios of Δ[O3]/Δ[NOx] are ?2.3 and ?0.25 in the rural and in the city region, respectively. In addition, the measured NOx and SO2 concentrations are strongly correlated, highlighting that the NOx and SO2 are probably originated from same emission sources. Because SO2 emissions are significantly originated from coal burnings, the strong correlation between SO2 and NOx concentrations suggests that the NOx emission sources are mostly from coal burned sources. As a result, the future automobile increases could lead to rapid enhancements in O3 concentrations in the YRD region. 相似文献
15.
《Atmospheric environment (Oxford, England : 1994)》2001,35(5):975-983
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
16.
《Atmospheric environment (Oxford, England : 1994)》2001,35(21):3585-3593
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
17.
Litao Wang Carey Jang Yang Zhang Kai Wang Qiang Zhang David Streets Joshua Fu Yu Lei Jeremy Schreifels Kebin He Jiming Hao Yun-Fat Lam Jerry Lin Nicholas Meskhidze Scott Voorhees Dale Evarts Sharon Phillips 《Atmospheric environment (Oxford, England : 1994)》2010,44(28):3449-3457
Following the meteorological evaluation in Part I, this Part II paper presents the statistical evaluation of air quality predictions by the U.S. Environmental Protection Agency (U.S. EPA)’s Community Multi-Scale Air Quality (Models-3/CMAQ) model for the four simulated months in the base year 2005. The surface predictions were evaluated using the Air Pollution Index (API) data published by the China Ministry of Environmental Protection (MEP) for 31 capital cities and daily fine particulate matter (PM2.5, particles with aerodiameter less than or equal to 2.5 μm) observations of an individual site in Tsinghua University (THU). To overcome the shortage in surface observations, satellite data are used to assess the column predictions including tropospheric nitrogen dioxide (NO2) column abundance and aerosol optical depth (AOD). The result shows that CMAQ gives reasonably good predictions for the air quality.The air quality improvement that would result from the targeted sulfur dioxide (SO2) and nitrogen oxides (NOx) emission controls in China were assessed for the objective year 2010. The results show that the emission controls can lead to significant air quality benefits. SO2 concentrations in highly polluted areas of East China in 2010 are estimated to be decreased by 30–60% compared to the levels in the 2010 Business-As-Usual (BAU) case. The annual PM2.5 can also decline by 3–15 μg m?3 (4–25%) due to the lower SO2 and sulfate concentrations. If similar controls are implemented for NOx emissions, NOx concentrations are estimated to decrease by 30–60% as compared with the 2010 BAU scenario. The annual mean PM2.5 concentrations will also decline by 2–14 μg m?3 (3–12%). In addition, the number of ozone (O3) non-attainment areas in the northern China is projected to be much lower, with the maximum 1-h average O3 concentrations in the summer reduced by 8–30 ppb. 相似文献
18.
《Atmospheric environment (Oxford, England : 1994)》2001,35(31):5339-5346
A fast response analyzer for HNO3 in highly polluted air is described. The time resolution attainable was 12 s. The method is based on the difference in a technique for HNO3-scrubbed and non-scrubbed air and the reduction of HNO3 to NO with the use of a line of catalytic converters and a method for the subsequent NO-ozone chemiluminescence. A sample air stream, in which particulates are removed with a Teflon filter, is divided into two channels. CH-1 is directly connected to the converter line, and CH-2 contains a HNO3 scrubber packed with a nylon fiber that goes to another converter line. Each converter line is composed of a hot quartz-bead converter (QBC) and a molybdenum converter (MC) in a series. A QBC reduces HNO3 to (NO+NO2), which is called NOx. The MC reduces the NOx to NO.For CH-1, the analyzer detects most compounds that typically comprise NOy (J. Geophys. Res. 91 (1986) 9781). These CH-1 compounds are called NOy′ hereafter (NOy-particulate nitrate) because the particulates are removed by the filter. A difference in the detector signal for the two channels indicates HNO3. For a blank test, atmospheric air in which HNO3 was pre-scrubbed by an extra nylon fiber was introduced to the analyzer. Variations in the blank value were 0.38±0.42 and 0.34±0.55 ppb during the high readings (NOy′-HNO3 ) (called NOy* hereafter) (111±12 ppb, N=180), and low NOy* readings (62±8 ppb, N=180), respectively, indicating that the lowest detection limit of the analyzer is 1.1 ppb (2σ). When the data obtained with the analyzer is compared to the data using the denuder method, a linear correlation with the regression of Y=0.973X+0.077 (r2=0.916 (N=20)) in the range of 0–6.5 ppb HNO3 is obtained, which is an excellent agreement. Atmospheric monitoring was carried out at Kobe. Although the average concentration of HNO3 was 2.6±1.3 ppb, ca.10 ppb for a HNO3 concentration was occasionally observed when the NOy* concentration was high, i.e., more than 100 ppb. 相似文献
19.
《Atmospheric environment (Oxford, England : 1994)》2005,39(35):6664-6672
Atmospheric nitric acid does not only contribute to acidification and eutrophication but causes also deterioration of many materials. Material belonging to our cultural heritage is irreplaceable and its lifetime can depend on the corrosion rate. Nowadays, only very few long-term measurements of nitric acid concentration in Europe and elsewhere have been published so far. Due to the fact that atmospheric corrosion is a long-term effect, the relevant research does not necessarily require monitoring of nitric acid on a daily basis. Moreover, power supply is often not available at sites where it is of interest to study the corrosion rate of objects belonging to our cultural heritage. Besides, such measurements must not disturb the impression of the objects. In this context, the diffusive sampling technique provides average concentrations over long-term periods at a low cost. In addition, the samplers used are noiseless, comparatively small in size, and thus, their ambient exposure can be made inconspicuously and with discretion. The present paper is focussed on an intensive corrosion study, which was performed at 11 rural and 23 urban sites in Europe and one rural site in Canada during 2002/2003. For the above-mentioned reasons, the diffusive sampler's technique was employed for the nitric acid monitoring, where the diffusive samplers were first tested against the denuder technique and bi-monthly measurements of nitric acid were thus obtained. The bi-monthly concentrations varied from 0.05 to 4.3 μg m−3 and the annual averages from 0.16 to 2.0 μg m−3. The observations collected, depicted a summertime maximum and a wintertime minimum in the nitric acid concentrations, except at the northern rural sites, where a maximum in the winter was observed. Furthermore, the observed nitric acid concentrations in Southern Europe were higher than in Northern Europe. In a few places, close to the sites of urban measurements, rural measurements of nitric acid were also performed. The obtained nitric acid concentrations were higher in the cities, especially during the period of maximum concentrations. 相似文献
20.
《Atmospheric environment (Oxford, England : 1994)》2001,35(6):1001-1013
A field experiment was conducted in August 1998 to investigate the concentrations of isoprene and isoprene reaction products in the surface and mixed layers of the atmosphere in Central Texas. Measured near ground-level concentrations of isoprene ranged from 0.3 (lower limit of detection – LLD) to 10.2 ppbv in rural regions and from 0.3 to 6.0 ppbv in the Austin urban area. Rural ambient formaldehyde levels ranged from 0.4 ppbv (LLD) to 20.0 ppbv for 160 rural samples collected, while the observed range was smaller at Austin (0.4–3.4 ppbv) for a smaller set of samples (37 urban samples collected). Methacrolein levels did not vary as widely, with rural measurements from 0.1 ppbv (LLD) to 3.7 ppbv and urban concentrations varying between 0.2 and 5.7 ppbv. Isoprene flux measurements, calculated using a simple box model and measured mixed-layer isoprene concentrations, were in reasonable agreement with emission estimates based on local ground cover data. Ozone formation attributable to biogenic hydrocarbon oxidation was also calculated. The calculations indicated that if the ozone formation occurred at low VOC/NOx ratios, up to 20 ppbv of ozone formed could be attributable to biogenic photooxidation. In contrast, if the biogenic hydrocarbon reaction products were formed under low NOx conditions, ozone production attributable to biogenics oxidation would be as low as 1 ppbv. This variability in ozone formation potentials implies that biogenic emissions in rural areas will not lead to peak ozone levels in the absence of transport of NOx from urban centers or large rural NOx sources. 相似文献