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1.
Measurements of air pollutants from a background site in central London are analysed. These comprise hourly data for CO, NO, NO 2, O 3, SO 2 and PM 10 from 1996 to 2008 and particle number count from 2001 to 2008. The data are analysed in terms of long-term trends, annual, weekly and diurnal cycles, and autocorrelation and cross-correlation functions. CO, NO and NO 2 show a typical traffic-associated pattern with two daily peaks and lesser concentrations at the weekend. Particle number count and PM 10 show a similar cycle, but with smaller amplitude. Ozone has an annual cycle with a maximum in May, influenced by the spring maximum in background ozone, but the diurnal and weekly cycles are dominated by losses through reaction with nitric oxide. Particle number count shows a minimum corresponding with maximum air temperatures in August, whereas the CO, NO NO 2 and SO 2 show a minimum in June/July. There is a lower particle count to NO x ratio at the background site compared to a central London kerbside site (Marylebone Road) and a seasonal pattern in particle count to NO x and PM 10 ratios consistent with loss of nanoparticles by evaporation during atmospheric transport. Sulphur dioxide peaks in the morning in summer, but at midday in winter consistent with emissions from elevated sources mixing down from aloft as the diurnal mixed layer deepens. Implications for epidemiological studies of air quality and health are discussed. Sulphur dioxide, carbon monoxide, nitric oxide and nitrogen dioxide show clear downward trends over the measurement period, PM 10 declines initially before levels stabilised, and ozone concentrations increased. 相似文献
2.
On 17th February 2003, a congestion charging scheme (CCS), operating Monday–Friday, 07:00–18:00, was introduced in central London along with a programme of traffic management measures. We investigated the potential impact of the introduction of the CCS on measured pollutant concentrations (oxides of nitrogen (NO X, NO and NO 2), particles with a median diameter less than 10 microns (PM 10), carbon monoxide (CO) and ozone (O 3)) measured at roadside and background monitoring sites across Greater London. Temporal changes in pollution concentrations within the congestion charging zone were compared to changes, over the same time period, at monitors unlikely to be affected by the CCS (the control zone) and in the boundary zone between the two. Similar analyses were done for CCS hours during weekends (when the CCS was not operating).Based on the single roadside monitor with the CCS Zone, it was not possible to identify any relative changes in pollution concentrations associated with the introduction of the scheme. However, using background monitors, there was good evidence for a decrease in NO and increases in NO 2 and O 3 relative to the control zone. There was little change in background concentrations of NO X. There was also evidence of relative reductions in PM 10 and CO. Similar changes were observed during the same hours in weekends when the scheme was not operating.The causal attribution of these changes to the CCS per se is not appropriate since the scheme was introduced concurrently with other traffic and emissions interventions which might have had a more concentrated effect in central London. This study provides important pointers for study design and data requirements for the evaluation of similar schemes in terms of air quality. It also shows that results may be unexpected and that the overall effect on toxicity may not be entirely favourable. 相似文献
3.
An empirical model has been devised to predict concentrations of PM 10 at background and roadside locations in London. Factors to calculate primary PM 10 and PM 2.5 concentrations are derived from annual mean NO X, PM 2.5 and PM 10 measurements across London and south east England. These factors are used to calculate daily means for the primary and non-primary PM 10 fractions for the London area. The model accurately predicts daily mean PM 10 and EU Directive Limit values across a range of sites from kerbside to rural. Predictions of future PM 10 can be made using the expected reductions in secondary PM 10 and site specific annual mean NO X predicted from emission inventories and dispersion modelling. The model suggests that the EU Directive Limit values will be exceeded close to many of London's busiest roads, and perhaps at central background sites should there be a repeat of 1996 meteorological conditions during 2005. A repeat of 1997 meteorology conditions during 2005 would lead to the EU Limit Value being exceeded alongside the busiest central London roads only. The model is applicable for London and south east England but the methodology could be applied elsewhere at a city or regional level. The model relies on the currently observed ratio between NO X and PM 10. This ratio has remained constant over the last 4 years but might change in the future. The NO X:PM 10 ratio derived from measurements and used in this model, implies that emission inventories might over estimate primary PM 10 by more than 50%. 相似文献
4.
Under the National Ambient Air Quality Standards (NAAQS), put in place as a result of the Clean Air Amendments of 1990, three regions in the state of Utah are in violation of the NAAQS for PM 10 and PM 2.5 (Salt Lake County, Ogden City, and Utah County). These regions are susceptible to strong inversions that can persist for days to weeks. This meteorology, coupled with the metropolitan nature of these regions, contributes to its violation of the NAAQS for PM during the winter. During January–February 2009, 1-hr averaged concentrations of PM 10-2.5, PM 2.5, NO x, NO 2, NO, O 3, CO, and NH 3 were measured. Particulate-phase nitrate, nitrite, and sulfate and gas-phase HONO, HNO 3, and SO 2 were also measured on a 1-hr average basis. The results indicate that ammonium nitrate averages 40% of the total PM 2.5 mass in the absence of inversions and up to 69% during strong inversions. Also, the formation of ammonium nitrate is nitric acid limited. Overall, the lower boundary layer in the Salt Lake Valley appears to be oxidant and volatile organic carbon (VOC) limited with respect to ozone formation. The most effective way to reduce ammonium nitrate secondary particle formation during the inversions period is to reduce NO x emissions. However, a decrease in NO x will increase ozone concentrations. A better definition of the complete ozone isopleths would better inform this decision. Implications: Monitoring of air pollution constituents in Salt Lake City, UT, during periods in which PM2.5 concentrations exceeded the NAAQS, reveals that secondary aerosol formation for this region is NOx limited. Therefore, NOx emissions should be targeted in order to reduce secondary particle formation and PM2.5. Data also indicate that the highest concentrations of sulfur dioxide are associated with winds from the north-northwest, the location of several small refineries. 相似文献
5.
An ozone abatement strategy for the South Coast Air Basin (SoCAB) has been proposed by the South Coast Air Quality Management District (SCAQMD) and the California Air Resources Board (ARB). The proposed emissions reduction strategy is focused on the reduction of nitrogen oxide (NO x) emissions by the year 2030. Two high PM 2.5 concentration episodes with high ammonium nitrate compositions occurring during September and November 2008 were simulated with the Community Multi-scale Air Quality model (CMAQ). All simulations were made with same meteorological files provided by the SCAQMD to allow them to be more directly compared with their previous modeling studies. Although there was an overall under-prediction bias, the CMAQ simulations were within an overall normalized mean error of 50%; a range that is considered acceptable performance for PM modeling. A range of simulations of these episodes were made to evaluate sensitivity to NO x and ammonia emissions inputs for the future year 2030. It was found that the current ozone control strategy will reduce daily average PM 2.5 concentrations. However, the targeted NO x reductions for ozone were not found to be optimal for reducing PM 2.5 concentrations. Ammonia emission reductions reduced PM 2.5 and this might be considered as part of a PM 2.5 control strategy. Implications: The SCAQMD and the ARB have proposed an ozone abatement strategy for the SoCAB that focuses on NOx emission reductions. Their strategy will affect both ozone and PM2.5. Two episodes that occurred during September and November 2008 with high PM2.5 concentrations and high ammonium nitrate composition were selected for simulation with different levels of nitrogen oxide and ammonia emissions for the future year 2030. It was found that the ozone control strategy will reduce maximum daily average PM2.5 concentrations but its effect on PM2.5 concentrations is not optimal. 相似文献
6.
Air quality impacts of volatile organic compound (VOC) and nitrogen oxide (NO x) emissions from major sources over the northwestern United States are simulated. The comprehensive nested modeling system comprises three models: Community Multiscale Air Quality (CMAQ), Weather Research and Forecasting (WRF), and Sparse Matrix Operator Kernel Emissions (SMOKE). In addition, the decoupled direct method in three dimensions (DDM-3D) is used to determine the sensitivities of pollutant concentrations to changes in precursor emissions during a severe smog episode in July of 2006. The average simulated 8-hr daily maximum O 3 concentration is 48.9 ppb, with 1-hr O 3 maxima up to 106 ppb (40 km southeast of Seattle). The average simulated PM 2.5 (particulate matter with an aerodynamic diameter <2.5 μm) concentration at the measurement sites is 9.06 μg m ?3, which is in good agreement with the observed concentration (8.06 μg m ?3). In urban areas (i.e., Seattle, Vancouver, etc.), the model predicts that, on average, a reduction of NO x emissions is simulated to lead to an increase in average 8-hr daily maximum O 3 concentrations, and will be most prominent in Seattle (where the greatest sensitivity is??0.2 ppb per % change of mobile sources). On the other hand, decreasing NO x emissions is simulated to decrease the 8-hr maximum O 3 concentrations in remote and forested areas. Decreased NO x emissions are simulated to slightly increase PM 2.5 in major urban areas. In urban areas, a decrease in VOC emissions will result in a decrease of 8-hr maximum O 3 concentrations. The impact of decreased VOC emissions from biogenic, mobile, nonroad, and area sources on average 8-hr daily maximum O 3 concentrations is up to 0.05 ppb decrease per % of emission change, each. Decreased emissions of VOCs decrease average PM 2.5 concentrations in the entire modeling domain. In major cities, PM 2.5 concentrations are more sensitive to emissions of VOCs from biogenic sources than other sources of VOCs. These results can be used to interpret the effectiveness of VOC or NO x controls over pollutant concentrations, especially for localities that may exceed National Ambient Air Quality Standards (NAAQS). Implications: The effect of NO x and VOC controls on ozone and PM 2.5 concentrations in the northwestern United States is examined using the decoupled direct method in three dimensions (DDM-3D) in a state-of-the-art three-dimensional chemical transport model (CMAQ). NO x controls are predicted to increase PM 2.5 and ozone in major urban areas and decrease ozone in more remote and forested areas. VOC reductions are helpful in reducing ozone and PM 2.5 concentrations in urban areas. Biogenic VOC sources have the largest impact on O 3 and PM 2.5 concentrations. 相似文献
7.
Abstract It is important to understand the effects of emission controls on concentrations of ozone, fine particulate matter (PM 2.5), and hazardous air pollutants (HAPs) simultaneously, to evaluate the full range of health, ecosystem, and economic effects. Until recently, the capability to simultaneously evaluate interrelated atmospheric pollutants (“one atmosphere” analysis) was unavailable to air quality managers. In this work, we use an air quality model to examine the potential effect of three emission reductions on concentrations of ozone, PM 2.5, and four important HAPs (formaldehyde, acetaldehyde, acrolein, and benzene) over a domain centered on Philadelphia for 12-day episodes in July and January 2001. Although NO x controls are predicted to benefit PM 2.5 concentrations and sometimes benefit ozone, they have only a small effect on formaldehyde, slightly increase acetaldehyde and acrolein, and have no effect on benzene in the July episode. Concentrations of all pollutants except benzene increase slightly with NO x controls in the January simulation. Volatile organic compound controls alone are found to have a small effect on ozone and PM 2.5, a less than linear effect on decreasing aldehydes, and an approximately linear effect on acrolein and benzene in summer, but a slightly larger than linear effect on aldehydes and acrolein in winter. These simulations indicate the difficulty in assessing how toxic air pollutants might respond to emission reductions aimed at decreasing criteria pollutants such as ozone and PM 2.5. 相似文献
8.
Spread of air pollution sources and non-uniform mixing conditions in urban or regional air sheds often result in spatial variation of pollutant concentrations over different parts of the air sheds. A comprehensive understanding of this variation of concentrations is imperative for informed planning, monitoring and assessment in a range of critical areas including assessment of monitoring network efficiency or assessment of population exposure variation as a function of the location in the city. The aims of this work were to study the citywide variability of pollutants as measured by “urban background” type monitoring stations and to interpret the results in relation to the applicability of the data to population exposure assessments and the network efficiency. A comparison between ambient concentrations of NO x, ozone and PM 10 was made for three stations in the Brisbane air shed network. The best correlated between the three stations were ozone concentrations followed by NO x concentration, with the worst correlations observed for PM 10. With a few exceptions correlations of all pollutants between the stations were statistically significant. Marginally better were the correlations for the lower concentrations of pollutants that represent urban background, over the correlations for higher concentrations, representing peak values. Implications of these findings on application of the monitoring data to air-quality management, as well as the need for further investigations has been discussed. 相似文献
9.
Abstract One-hour average ambient concentrations of particulate matter (PM) with an aerodynamic diameter <2.5 μm (PM 2.5) were determined in Steubenville, OH, between June 2000 and May 2002 with a tapered element oscillating microbalance (TEOM). Hourly average gaseous copollutant [carbon monoxide (CO), sulfur dioxide (SO 2), nitrogen oxide (NO x), and ozone (O 3)] concentrations and meteorological conditions also were measured. Although 75% of the 14,682 hourly PM 2.5 concentrations measured during this period were ≤17 μg/m 3, concentrations >65 μg/m 3 were observed 76 times. On average, PM 2.5 concentrations at Steubenville exhibited a diurnal pattern of higher early morning concentrations and lower afternoon concentrations, similar to the diurnal profiles of CO and NO x. This pattern was highly variable; however, PM 2.5 concentrations >65 μg/m 3 were never observed during the mid-afternoon between 1:00 p.m. and 5:00 p.m. EST. Twenty-two episodes centered on one or more of these elevated concentrations were identified. Five episodes occurred during the months June through August; the maximum PM 2.5 concentration during these episodes was 76.6 μg/m 3. Episodes occurring during climatologically cooler months often featured higher peak concentrations (five had maximum concentrations between 95.0 and 139.6 μg/m 3), and many exhibited strong covariation between PM 2.5 and CO, NO x, or SO 2. Case studies suggested that nocturnal surface-based temperature inversions were influential in driving high nighttime concentrations of these species during several cool season episodes, which typically had dramatically lower afternoon concentrations. These findings provide insights that may be useful in the development of PM 2.5 reduction strategies for Steubenville, and suggest that studies assessing possible health effects of PM 2.5 should carefully consider exposure issues related to the intraday timing of PM 2.5 episodes, as well as the potential for toxicological interactions among PM 2.5 and primary gaseous pollutants. 相似文献
10.
Particulate matter mass (PM), trace gaseous pollutants, and select volatile organic compounds (VOCs) with meteorological variables were measured in Logan, Utah (Cache Valley), for >4 weeks during winter 2017 as part of the Utah Winter Fine Particle Study (UWFPS). Higher PM levels for short time periods and lower ozone (O 3) levels were present due to meteorological and mountain valley conditions. Nitrogenous pollutants were relatively strongly correlated with PM variables. Diurnal cycles of NO x, O 3, and fine PM(PM 2.5) (aerodynamic diameter <2.5 μm [PM 2.5]) suggested formation from NO x. O 3 levels increased from early morning into midafternoon, and NO x and PM 2.5 increased throughout the morning, followed by sharp decreases. Toluene/benzene and xylenes/benzene ratios and VOC correlations with nitrogenous and PM species were indicative of local traffic sources. Wind sector comparisons suggested that pollutant levels were lower when winds were from nearby mountains to the east versus winds from northerly or southerly origins. Implications: The Cache Valley in Idaho and Utah has been designated a PM2.5 nonattainment area that has been attributed to air pollution buildup during winter stagnation events. To inform state implementation plans for PM2.5 in Cache Valley and other PM2.5 nonattainment areas in Utah, a state and multiagency federal research effort known as the UWFPS was conducted in winter 2017. As part of the UWFPS, the U.S. Environmental Protection Agency (EPA) measured ground-based PM species and their precursors, VOCs, and meteorology in Logan, Utah. Results reported here from the EPA study in Logan provide additional understanding of wintertime air pollution conditions and possible sources of PM and gaseous pollutants as well as being useful for future PM control strategies in this area. 相似文献
11.
Yanbu, on the Red Sea, is an affluent Saudi Arabian industrial city of modest size. Substantial effort has been spent to balance environmental quality, especially air pollution, and industrial development. We have analyzed six years of observations of criteria pollutants O 3, SO 2, particles (PM 2.5 and PM 10) and the known ozone precursors—volatile organic compounds (VOCs) and nitrogen oxides (NO x). The results suggest frequent VOC-limited conditions in which ozone concentrations increase with decreasing NO x and with increasing VOCs when NO x is plentiful. For the remaining circumstances ozone has a complex non-linear relationship with the VOCs. The interactions between these factors at Yanbu cause measurable impacts on air pollution including the weekend effect in which ozone concentrations stay the same or even increase despite significantly lower emissions of the precursors on the weekends. Air pollution was lower during the Eids (al-Fitr and al-Adha), Ramadan and the Hajj periods. During Ramadan, there were substantial night time emissions as the cycle everyday living is almost reversed between night and day. The exceedances of air pollution standards were evaluated using criteria from the U.S. Environmental Protection Agency (EPA), World Health Organization (WHO), the Saudi Presidency of Meteorology and Environment (PME) and the Royal Commission Environmental Regulations (RCER). The latter are stricter standards set just for Yanbu and Jubail. For the fine particles (PM 2.5), an analysis of the winds showed a major impact from desert dust. This effect had to be taken into account but still left many occasions when standards were exceeded. Fewer exceedances were found for SO 2, and fewer still for ozone. The paper presents a comprehensive view of air quality at this isolated desert urban environment. Implications: Frequent VOC-limited conditions are found at Yanbu in Saudi Arabia that increase ozone pollution if NOx is are reduced. In this desert environment, increased nightlife produces the highest levels of VOCs and NOx at night rather than the day. The effects increase during Ramadan. Fine particles peak twice a day—the morning peak is caused by traffic and increases with decreasing wind, potentially representing health concerns, but the larger afternoon peak is caused by the wind, and it increases with increasing wind speeds. These features suggest that exposure to pollutants must be redefined for such an environment. 相似文献
12.
This study examined the effects of varying future reductions in emissions of oxides of nitrogen (NO x) and volatile organic compounds (VOC) on the location and magnitude of peak ozone levels within California’s South Coast Air Basin (SoCAB or Basin). As ozone formation is currently VOC-limited in the Basin, model simulations with 2030 baseline emissions (?61% for NO x and ?32% for VOC from 2008) predict 10–20% higher peak ozone levels (i.e., NO x disbenefit) in the western and central SoCAB compared with the 2008 base simulation. With additional NO x reductions of 50% beyond the 2030 baseline emissions (?81% from 2008), the predicted ozone levels are reduced by about 15% in the eastern SoCAB but remain comparable to 2008 levels in the western and central Basin. The Basin maximum ozone site shifts westward to more populated areas of the Basin and will result potentially in greater population-weighted exposure to ozone with even a relatively small shortfall in the required NO x reductions unless accompanied by additional VOC reductions beyond 2030 baseline levels. Once committed to a NO x-focused control strategy, NO x reductions exceeding 90% from 2008 levels will be necessary to attain the ozone National Ambient Air Quality Standards (NAAQS). The findings from this study and other recent work that the current VOC emission estimates are underestimated by about 50% suggest that greater future VOC reductions will be necessary to reach the projected 2030 baseline emissions. Increasing the base year VOC emissions by a factor of 1.5 result in higher 2008 baseline ozone predictions, lower relative response factors, and about 20% lower projected design values. If correct, these findings have important implications for the total and optimum mix of VOC and NO x emission reductions that will be required to attain the ozone NAAQS in the SoCAB. Implications: Results of this study indicate that ozone levels in the western and central SoCAB would remain the same or increase with even a relatively small shortfall in the projected NO x reductions under planned NO x-focused controls. This possibility, therefore, warrants a rigorous analysis of the costs and effects of varying reductions of VOC and NO x on the formation and combined health impacts of ozone and secondary particles. Given the nonlinearity of ozone formation, such analyses should include the implications of gradually increasing global background ozone concentrations and the Basin’s topography and meteorology on the practical limits of alternative emission control strategies. 相似文献
13.
Long-term measurements (2004–2011) of PM 10 (particulate matter with an aerodynamic diameter <10 μm) and trace gases (carbon monoxide [CO], ozone [O 3], nitrogen oxide [NO], oxides of nitrogen [NO x], nitrogen dioxide [NO 2], sulfur dioxide [SO 2], methane [CH 4], nonmethane hydrocarbon [NMHC]) have been conducted to study the effect of physicochemical factors on the PM 10 concentration. In addition, this study includes source apportionment of PM 10 in Kuala Lumpur urban environment. An advanced principal component analysis (PCA) technique coupled with absolute principal component scores (APCS) and multiple linear regression (MLR) has been applied. The average annual concentration of PM 10 for 8 yr is 51.3 ± 25.8 μg m ?3, which exceeds the Recommended Malaysian Air Quality Guideline (RMAQG) and international guideline values. Detail analysis shows the dependency of PM 10 on the linear changes of the motor vehicles in use and the amount of biomass burning, particularly from Sumatra, Indonesia, during southwesterly monsoon. The main sources of PM 10 identified by PCA-APCS-MLR are traffic combustion (28%), ozone coupled with meteorological factors (20%), and windblown particles (1%). However, the apportionment procedure left 28.0 μg m ?3, that is, 51% of PM 10 undetermined.Implications: Air quality is always a top concern around the globe. Especially in the South Asian regions, measures are not yet sufficient; as revealed in our studies, the concentrations of particulate matters exceed the tolerable limits. Long-term data analysis and characterization of particular matters and their sources will aid the policy makers and the concerned authority to adapt measures and policies according to the circumstances. Additionally, similar intensive studies will give insight about future implications of air quality management. 相似文献
14.
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
15.
A three-dimensional global chemical tracer model and a radiation transfer model have been used to study the role of NO x emissions for radiative forcing of climate. Through production of tropospheric O 3, NO x emissions lead to positive radiative forcing and warming. But by affecting the concentration of OH radicals, NO x also reduces the levels of CH 4, thereby giving negative forcing and cooling. The lifetime of NO x varies from hours to days, giving large spatial variations in the levels of NO x. We have selected geographical regions representing different chemical and physical conditions, and chemical and radiative effects of reducing NO x emissions by 20% in each region are studied. Due to nonlinearities in the O 3 chemistry as well as differences in convective activity, there are large geographical differences in the effect of NO x on O 3 as well as variations in the annual profile of the changes. The effect of NO x emissions on methane is also found to depend on the localisation of the emissions. The calculated ozone and methane forcing are of similar magnitude but of opposite sign. The methane effect acts on a global scale with a delay of approximately a decade, while the ozone effect is of regional character and occurs during weeks. 相似文献
16.
The ambient PM 10 and PM 2.5 data collected during the fall and winter portions of the 1995 Integrated Monitoring Study (IMS95) were used to conduct Chemical Mass Balance (CMB) Modeling to determine source contribution estimates. Data from the core and saturation monitoring sites provided an extensive database for evaluating the spatial and temporal variations of contributing sources. Geological sources dominated fall samples, while secondary ammonium nitrate and carbonaceous sources were the largest contributors for winter samples. Secondary ammonium nitrate concentrations were uniform across all sites during both the fall and winter. Site-to-site variability was primarily due to differences in geological contributions in the fall, and carbonaceous source contributions in the winter. During the winter, diurnal profiles of particulate matter (PM) were driven by variations in carbonaceous sources at urban sites, and by variations in secondary ammonium nitrate at rural sites. Although records of day-specific PM activities were recorded during the study, no correlation was observed between 24-h CMB results and specific activities. The ambient data collected during IMS95 was also used to evaluate the adequacy of the emissions inventory. Comparison of ambient and emissions based ratios of NMHC/NO x, PM/NO x, CO/NO x, and SO x/NO x suggested that emissions of NMHC and CO in some locations may be underestimated, while emissions for PM and SO x may be overestimated. Comparison of fractional primary CMB source contribution estimates to corresponding fractional emissions estimates indicated that geological sources were overemphasized in the inventory, while carbonaceous sources were underrepresented. 相似文献
17.
Abstract In this paper, we examine the changes in ambient ozone concentrations simulated by the Community Multiscale Air Quality (CMAQ) model for summer 2002 under three different nitrogen oxides (NO x) emission scenarios. Two emission scenarios represent best estimates of 2002 and 2004 emissions; they allow assessment of the impact of the NO x emissions reductions imposed on the utility sector by the NO x State Implementation Plan (SIP) Call. The third scenario represents a hypothetical rendering of what NO x emissions would have been in 2002 if no emission controls had been imposed on the utility sector. Examination of the modeled median and 95th percentile daily maximum 8-hr average ozone concentrations reveals that median ozone levels estimated for the 2004 emission scenario were less than those modeled for 2002 in the region most affected by the NO x SIP Call. Comparison of the “no-control” with the “2002” scenario revealed that ozone concentrations would have been much higher in much of the eastern United States if the utility sector had not implemented NO x emission controls; exceptions occurred in the immediate vicinity of major point sources where increased NO titration tends to lower ozone levels. 相似文献
18.
Air pollution has been an increasing concern within the Kingdom of Saudi Arabia and other Middle Eastern countries. In this work the authors present an analysis of daily ozone (O 3), nitrogen oxide (NO x), and particulate matter (<10 μm aerodynamic diameter; PM 10) concentrations for two years (2010 and 2011) at sites in and around the coastal city of Jeddah, as well as a remote background site for comparison. Monthly and weekly variations, along with their implications and consequences, were also examined. O 3 within Jeddah was remarkably low, and exhibited the so-called weekend effect—elevated O 3 levels on the weekends, despite reduced emissions of O 3 precursors on those days. Weekend O 3 increases averaged between 12% and 14% in the city, suggesting that NO x/volatile organic compound (VOC) ratios within cities such as Jeddah may be exceptionally high. Sites upwind or far removed from Jeddah did not display this weekend effect. Based on these results, emission control strategies in and around Jeddah must carefully address NO x/VOC ratios so as to reduce O 3 at downwind locations without increasing it within urban locations themselves. PM 10 concentrations within Jeddah were elevated compared with North American cites of similar climatology, though comparable to other large cities within the Middle East. Implications:Daily concentrations of O 3, PM 10, and NO x in and around the city of Jeddah, Saudi Arabia, are analyzed and compared with those of other reference cities. Extremely low O 3 levels, along with a significant urban weekend effect (higher weekend O 3, despite reduced NO x concentrations), is apparent, along with high levels of PM 10 within the city. Urban O 3 in Jeddah was found to be lower than that of other comparable cities, but the strong weekend effect suggests that care must be taken to reduce downwind O 3 levels without increasing them within the city itself. Further research into the emissions and chemistry contributing to the reduced O 3 levels within the city is warranted. 相似文献
19.
The intercomparison of seven chemical mechanisms for their suitability for air quality policy formulation and assessment is described. Box modeling techniques were employed using 44 sets of background environmental conditions covering North America to constrain the chemical development of the longer lived species. The selected mechanisms were modified to enable an unbiased assessment of the adequacy of the parameterizations of photochemical ozone production from volatile organic compound (VOC) oxidation in the presence of NO x. Photochemical ozone production rates responded differently to 30% NO x and VOC reductions with the different mechanisms, despite the striking similarities between the base-case ozone production rates. The 30% reductions in NO x and VOCs also produced changes in OH. The responses in OH to 30% reductions in NO x and VOCs appeared to be more sensitive to mechanism choice, compared with the responses in the photochemical ozone production rates. Although 30% NO x reductions generally led to decreases in OH, 30% reductions in VOCs led to increases in OH, irrespective of mechanism choice and background environmental conditions. The different mechanisms therefore gave different OH responses to NO x and VOC reductions and so would give different responses in terms of changes in the fate and behavior of air toxics, acidification and eutrophication, and fine particle formation compared with others, in response to ozone control strategies. Policymakers need to understand that there are likely to be inherent differences in the responses to ozone control strategies between different mechanisms, depending on background environmental conditions and the extents of NO x and VOC reductions under consideration. Implications: The purpose of this paper is to compare predicted ozone responses to NOx and VOC reductions with seven chemical mechanisms under North American conditions. The good agreement found between the tested mechanisms should provide some support for their application in the air quality models used for policymaking. 相似文献
20.
A highly resolved temporal and spatial Pearl River Delta (PRD) regional emission inventory for the year 2006 was developed with the use of best available domestic emission factors and activity data. The inventory covers major emission sources in the region and a bottom–up approach was adopted to compile the inventory for those sources where possible. The results show that the estimates for SO 2, NO x, CO, PM 10, PM 2.5 and VOC emissions in the PRD region for the year 2006 are 711.4 kt, 891.9 kt, 3840.6 kt, 418.4 kt, 204.6 kt, and 1180.1 kt, respectively. About 91.4% of SO 2 emissions were from power plant and industrial sources, and 87.2% of NO x emissions were from power plant and mobile sources. The industrial, mobile and power plant sources are major contributors to PM 10 and PM 2.5 emissions, accounting for 97.7% of the total PM 10 and 97.2% of PM 2.5 emissions, respectively. Mobile, biogenic and VOC product-related sources are responsible for 90.5% of the total VOC emissions. The emissions are spatially allocated onto grid cells with a resolution of 3 km × 3 km, showing that anthropogenic air pollutant emissions are mainly distributed over PRD central-southern city cluster areas. The preliminary temporal profiles were established for the power plant, industrial and on-road mobile sources. There is relatively low uncertainty in SO 2 emission estimates with a range of −16% to +21% from power plant sources, medium to high uncertainty for the NO x emissions, and high uncertainties in the VOC, PM 2.5, PM 10 and CO emissions. 相似文献
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