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1.
This paper is Part II in a pair of papers that examines the results of the Community Multiscale Air Quality (CMAQ) model version 4.5 (v4.5) and discusses the potential explanations for the model performance characteristics seen. The focus of this paper is on fine particulate matter (PM 2.5) and its chemical composition. Improvements made to the dry deposition velocity and cloud treatment in CMAQ v4.5 addressing compensating errors in 36-km simulations improved particulate sulfate (SO 42−) predictions. Large overpredictions of particulate nitrate (NO 3−) and ammonium (NH 4+) in the fall are likely due to a gross overestimation of seasonal ammonia (NH 3) emissions. Carbonaceous aerosol concentrations are substantially underpredicted during the late spring and summer months, most likely due, in part, to a lack of some secondary organic aerosol (SOA) formation pathways in the model. Comparisons of CMAQ PM 2.5 predictions with observed PM 2.5 mass show mixed seasonal performance. Spring and summer show the best overall performance, while performance in the winter and fall is relatively poor, with significant overpredictions of total PM 2.5 mass in those seasons. The model biases in PM 2.5 mass cannot be explained by summing the model biases for the major inorganic ions plus carbon. Errors in the prediction of other unspeciated PM 2.5 (PM Other) are largely to blame for the errors in total PM 2.5 mass predictions, and efforts are underway to identify the cause of these errors. 相似文献
2.
The concentrations of PM 2.5−10, PM 2.5 and associated water-soluble inorganic species (WSIS) were determined in a coastal site of the metropolitan region of Rio de Janeiro, Southeastern Brazil, from October 1998 to September 1999 ( n=50). Samples were dissolved in water and analyzed for major inorganic ions. The mean (± standard deviation; median) concentrations of PM 2.5−10 and PM 2.5 were, respectively, 26 (± 16; 21) μg m −3 and 17 (± 13; 14) μg m −3. Their mean concentrations were 1.7–1.8 times higher in dry season (May–October) than in rainy season (November–April). The WSIS comprised, respectively, 34% and 28% of the PM 2.5−10 and PM 2.5 masses. Chloride, Na + and Mg 2+ were the predominant ions in PM 2.5−10, indicating a significant influence of sea-salt aerosols. In PM 2.5, SO 42− (∼97% nss-SO 42−) and NH 4+ were the most abundant ions and their equivalent concentration ratio (SO 42−/NH 4+ ∼1.0) suggests that they were present as (NH 4) 2SO 4 particles. The mean concentration of (NH 4) 2SO 4 was 3.4 μg m −3. The mean equivalent PM 2.5 NO 3− concentration was eight times smaller than those of SO 42− and NH 4+. The PM 2.5 NO 3− concentration in dry season was three times higher than in rainy season, probably due to reaction of NaCl (sea salt) with HNO 3 as a result of higher levels of NO y during the dry season and/or reduced volatilization of NH 4NO 3 due to lower wintertime temperature. Chloride depletion was observed in both size ranges, although more pronouncely in PM 2.5. 相似文献
3.
A mathematical model was developed to evaluate HNO 3 artifact of the annular denuder system due to evaporation and diffusional deposition of nitrate-containing aerosols. The model performance was validated by comparing its numerical solutions with laboratory and numerical data available in the literature for evaporation and diffusional deposition of monodisperse and polydisperse NH 4NO 3 aerosols. Measurement artifacts were evaluated by varying typical sampling ranges of ambient temperature, HNO 3 gas concentration, aerosol number concentration, aerosol mass median diameter, and nitrate mass fraction of <2.5 μm aerosols to see their respective effects. Potential application of the present model on estimating HNO 3 artifacts was demonstrated using literature data sampled in USA, Taiwan, Netherlands, Korea and Japan. Significant measurement artifact could be found in Taiwan and Netherlands due either to low HNO 3 gas concentration and high nitrate concentration in <2.5 μm aerosols or to high ambient temperature. 相似文献
4.
Abstract The Reedy River branch of Lake Greenwood, SC, has repeatedly experienced summertime algal blooms, upsetting the natural system. A series of experiments were carried out to investigate atmospheric nitrogen (N) input into the lake. N was examined because of the insignificant phosphorus dry atmospheric flux and the unique nutrient demands of the dominant algae ( Pithophora oedogonia) contributing to the blooms. Episodic atmospheric measurements during January and March 2001 have shown that the dry N flux onto the lake ranged from 0.9 to 17.4 kg N/ha-yr, and on average is caused by nitric acid (HNO 3; 31%), followed by nitrogen dioxide (NO 2; 23%), fine ammonium (NH 4 +; 20%), coarse nitrate (NO 3 ?; 16%), fine NO 3 + (5%), and coarse NH 4 + (5%). Similar measurements in Greenville, SC (the upper watershed of the Reedy River), showed that the dry N deposition flux there ranged from 1.4 to 9.7 kg N/ha-yr and was mostly caused by gaseous deposition (40% NO 2 and 40% HNO 3). The magnitude of this dry N deposition flux is comparable to wet N flux as well as other point sources in the area. Thermodynamic modeling showed low concentrations of ammonia, relative to the particulate NH 4 + concentrations. 相似文献
5.
Monthly nitrogen isotopes of ammonium and nitrate in wet deposition in the city of Guangzhou, and the causes of their variability, are reported in this paper. Nitrate δ 15N showed nearly constant values around zero in the dry season (October to April), but oscillating values from negative to positive in the rainy season (May to September). By contrast, ammonium δ 15N displayed lower values during the rainy season than in the dry season. The rural area north of the city was considered as the prominent source of ammonium and nitrate in spring and early summer (May and June), as suggested by their concurrent negative isotopic trends and higher NH 4+/NO 3? ratios. From July to September, different dominating sources from the city, i.e., fossil fuel combustion for nitrate, and sewage and waste emission for ammonium, caused disparate δ 15N trends of the two species, showing positive nitrate δ 15N, but still negative ammonium δ 15N. During the cool dry season, the high values of ammonium δ 15N and concurrently low NH 4+/NO 3? ratios suggested the decrease in NH 3 volatilization and relatively important thermogenic origin of ammonium, but the intermediate nitrate δ 15N values around zero may be a result of a balanced emission of NO x from the city and the rural areas. The isotopic effects of chemical conversion of NO x to nitrate and washout of nitrate were ruled out as significant causes of nitrate δ 15N variability, but ammonium washout, during which 15N is assumed to be preferentially removed, may partly contribute to the ammonium δ 15N variability. 相似文献
6.
Nitric acid and ammonium-containing particulate species were measured by the annular denuder-filter pack technique at Manndorf, a rural site in South Germany, in July 1990. The analyses of filter packs indicated that nitrate was present as ammonium salt which mostly dissociated during sampling. Moreover, due to the NH +4/NO −3 ratios higher than unity found in back-up filters, NH 4Cl was assumed to represent an appreciable fraction of the total particulate ammonium. Finally, the molar ratios NH +4/SO 2−4 found on front (Teflon) filters, suggested a large predominance of (NH 4) 2SO 4 among the different forms of sulphate. The concentration levels of gaseous HNO 3 observed in the daytime were characterised by a maximum after midday, whereas particulate nitrate showed five times out of eight days an opposite trend with early afternoon minima. The total nitrate (HNO 3+NH 4NO 3) showed in turn a diurnal pattern similar to that of sulphate. These findings led to the conclusion that a significant HNO 3 production pathway involved the thermal dissociation of NH 4NO 3 rather than the reaction of NO 2 with OH radical. 相似文献
7.
Increased reactive nitrogen (N r) deposition due to expansion of agro-industry was investigated considering emission sources, atmospheric transport and chemical reactions. Measurements of the main inorganic nitrogen species (NO 2, NH 3, HNO 3, and aerosol nitrate and ammonium) were made over a period of one year at six sites distributed across an area of ∼130,000 km 2 in southeast Brazil. Oxidized species were estimated to account for ∼90% of dry deposited N r, due to the region’s large emissions of nitrogen oxides from biomass burning and road transport. NO 2-N was important closer to urban areas, however overall HNO 3-N represented the largest component of dry deposited N r. A simple mathematical modeling procedure was developed to enable estimates of total N r dry deposition to be made from knowledge of NO 2 concentrations. The technique, whose accuracy here ranged from <1% to 29%, provides a useful new tool for the mapping of reactive nitrogen deposition. 相似文献
8.
Health studies have shown premature death is statistically associated with exposure to particulate matter <2.5 μm in diameter (PM2.5). The United States Environmental Protection Agency requires all States with PM2.5 non-attainment counties or with sources contributing to visibility impairment at Class I areas to submit an emissions control plan. These emission control plans will likely focus on reducing emissions of sulfur oxides and nitrogen oxides, which form two of the largest chemical components of PM2.5 in the eastern United States: ammonium sulfate and ammonium nitrate. Emission control strategies are simulated using three-dimensional Eulerian photochemical transport models.A monitor study was established using one urban (Detroit) and nine rural locations in the central and eastern United States to simultaneously measure PM2.5 sulfate ion (SO 42−), nitrate ion (NO 3−), ammonium ion (NH 4+), and precursor species sulfur dioxide (SO 2), nitric acid (HNO 3), and ammonia (NH 3). This monitor study provides a unique opportunity to assess how well the modeling system predicts the spatial and temporal variability of important precursor species and co-located PM2.5 ions, which is not well characterized in the central and eastern United States.The modeling system performs well at estimating the PM2.5 species, but does not perform quite as well for the precursor species. Ammonia is under-predicted in the coldest months, nitric acid tends to be over-predicted in the summer months, and sulfur dioxide appears to be systematically over-predicted. Several indicators of PM2.5 ammonium sulfate and ammonium nitrate formation and chemical composition are estimated with the ambient data and photochemical model output. PM2.5 sulfate ion is usually not fully neutralized to ammonium sulfate in ambient measurements and is usually fully neutralized in model estimates. The model and ambient estimates agree that the ammonia study monitors tend to be nitric acid limited for PM2.5 nitrate formation. Regulatory strategies in this part of the country should focus on reductions in NO X rather than ammonia to control PM2.5 ammonium nitrate. 相似文献
9.
The annular denuder system (ADS) was used to characterize seasonal variations of acidic air pollutants in Seoul, South Korea. Fifty- four 24 h samples were collected over four seasons from October 1996 to September 1997. The annual mean concentrations of HNO 3, HNO 2, SO 2 and NH 3 in the gas phase were 1.09, 4.51, 17.3 and 4.34 μg m -3, respectively. The annual mean concentrations of PM 2.5( dp≤2.5 μm in aerodynamic diameter, 50% cutoff), SO 2-4, NO -3 and NH +4 in the particulate phase were 56.9, 8.70, 5.97 and 4.19 μg m -3, respectively. All chemical species monitored from this study showed statistical seasonal variations. Nitric acid (HNO 3) and ammonia (NH 3) exhibited substantially higher concentrations during the summer, while nitrous acid (HNO 2) and sulfur dioxide(SO 2) were higher during the winter. Concentrations of PM 2.5, SO 2-4, NO -3 and NH +4 in the particulate phase were higher during the winter months. SO 2-4, NO -3 and NH +4 accounted for 26–38% of PM 2.5. High correlations were found among PM 2.5, SO 2-4, NO -3 and NH +4. The mean H + concentration measured only in the fall was 5.19 nmole m -3. 相似文献
10.
In order to discuss the dry deposition fluxes of atmospheric fixed nitrogen species, observations of aerosol chemistry including nitrate (NO 3?) and ammonium (NH 4+) were conducted at two islands, Rishiri Island and Sado Island, over the Sea of Japan. Although the atmospheric concentrations of particulate NH 4+–N showed higher values than those of particulate NO 3?–N at both sites, the dry deposition fluxes of the particulate NO 3?–N were estimated to be higher than those of the particulate NH 4+–N. This was caused by the difference of particle sizes between the particulate NO 3? and NH 4+; NH 4+ was almost totally contained in fine particles ( d < 2.5 μm) with smaller deposition velocity, whereas NO 3? was mainly contained in coarse particles ( d > 2.5 μm) with greater deposition velocity. Fine mode NO 3? was strongly associated with fine mode sea-salt and mineral particles, of which higher concentrations shifted the size of particulate NO 3? toward the fine mode range. This size shift would decrease the dry deposition flux of the fixed nitrogen species on coastal waters and accelerate atmospheric transport of them to the remote oceanic areas. 相似文献
11.
Abstract The Models-3 Community Multiscale Air Quality (CMAQ) Modeling System and the Particulate Matter Comprehensive Air Quality Model with extensions (PMCAMx) were applied to simulate the period June 29–July 10, 1999, of the Southern Oxidants Study episode with two nested horizontal grid sizes: a coarse resolution of 32 km and a fine resolution of 8 km. The predicted spatial variations of ozone (O 3), particulate matter with an aerodynamic diameter less than or equal to 2.5 μm (PM 2.5), and particulate matter with an aerodynamic diameter less than or equal to 10 μm (PM 10) by both models are similar in rural areas but differ from one another significantly over some urban/suburban areas in the eastern and southern United States, where PMCAMx tends to predict higher values of O 3 and PM than CMAQ. Both models tend to predict O 3 values that are higher than those observed. For observed O 3 values above 60 ppb, O 3 performance meets the U.S. Environmental Protection Agency's criteria for CMAQ with both grids and for PMCAMx with the fine grid only. It becomes unsatisfactory for PMCAMx and marginally satisfactory for CMAQ for observed O 3 values above 40 ppb. Both models predict similar amounts of sulfate (SO 4 2?) and organic matter, and both predict SO 4 2? to be the largest contributor to PM 2.5. PMCAMx generally predicts higher amounts of ammonium (NH 4 +), nitrate (NO 3 ?), and black carbon (BC) than does CMAQ. PM performance for CMAQ is generally consistent with that of other PM models, whereas PMCAMx predicts higher concentrations of NO 3 ?,NH 4 +, and BC than observed, which degrades its performance. For PM 10 and PM 2.5 predictions over the southeastern U.S. domain, the ranges of mean normalized gross errors (MNGEs) and mean normalized bias are 37–43% and –33–4% for CMAQ and 50–59% and 7–30% for PMCAMx. Both models predict the largest MNGEs for NO 3 ? (98–104% for CMAQ, 138–338% for PMCAMx). The inaccurate NO 3 ? predictions by both models may be caused by the inaccuracies in the ammonia emission inventory and the uncertainties in the gas/particle partitioning under some conditions. In addition to these uncertainties, the significant PM overpredictions by PMCAMx may be attributed to the lack of wet removal for PM and a likely underprediction in the vertical mixing during the daytime. 相似文献
12.
Abstract This paper presents measurements of daily sampling of fine particulate matter (PM 2.5) and its major chemical components at three urban and one rural locations in North Carolina during 2002. At both urban and rural sites, the major insoluble component of PM 2.5 is organic matter, and the major soluble components are sulfate (SO 4 2?), ammonium (NH 4 +), and nitrate (NO 3 ?). NH 4 + is neutralized mainly by SO 4 2? rather than by NO 3 ?, except in winter when SO 4 2? concentration is relatively low, whereas NO 3 ? concentration is high. The equivalent ratio of NH 4 + to the sum of SO 4 2? and NO 3 ? is <1, suggesting that SO 4 2?and NO 3 ?are not completely neutralized by NH 4 +. At both rural and urban sites, SO 4 2?concentration displays a maximum in summer and a minimum in winter, whereas NO 3 ?displays an opposite seasonal trend. Mass ratio of NO 3 ? to SO 4 2?is consistently <1 at all sites, suggesting that stationary source emissions may play an important role in PM 2.5 formation in those areas. Organic carbon and elemental carbon are well correlated at three urban sites although they are poorly correlated at the agriculture site. Other than the daily samples, hourly samples were measured at one urban site. PM 2.5 mass concen trations display a peak in early morning, and a second peak in late afternoon. Back trajectory analysis shows that air masses with lower PM 2.5 mass content mainly originate from the marine environment or from a continental environment but with a strong subsidence from the upper troposphere. Air masses with high PM 2.5 mass concentrations are largely from continental sources. Our study of fine particulate matter and its chemical composition in North Carolina provides crucial information that may be used to determine the efficacy of the new National Ambient Air Quality Standard (NAAQS) for PM fine. Moreover, the gas-to-particle conversion processes provide improved prediction of long-range transport of pollutants and air quality. 相似文献
13.
Totally nine measurement campaigns for ambient particles and SO 2 have been conducted during the period of 1997–2000 in Qingdao in order to understand the characteristics of the particulate matter in coastal areas of China. The mass fractions of PM 2.5, PM 2.5−10 and PM >10 in TSP are 49%, 25% and 26%, respectively. The size distribution of particles mass concentrations in Qingdao shows bi-modal distribution. Mass fraction percentages of water-soluble ions in PM 2.5, PM 2.5−10 and PM >10 decreased from 62% to 35% and 21%. In fine particles, sulfate, nitrate and ammonium, secondary formed compounds, are major components, totally accounting for 50% of PM 2.5 mass concentration.The ratios of sulfate, chloride, ammonium and potassium in PM 2.5 for heating versus non-heating periods are 1.34, 1.80, 1.56 and 1.44, respectively. The ratio of nitrate is 3.02 and this high ratio could be caused by reduced volatilization at lower temperature. Sulfate concentrations are higher than nitrate in PM 2.5. The chemical forms of sulfate and nitrate are probably (NH 4) 2SO 4 and NH 4NO 3 and chloride depletion was observed.Backward trajectory analysis reflected possible influence of air pollutant transport to Qingdao local aerosol pollution. 相似文献
14.
Abstract Particle infiltration is a key determinant of the indoor concentrations of ambient particles. Few studies have examined the influence of particle composition on infiltration, particularly in areas with high concentrations of volatile particles, such as ammonium nitrate (NH 4NO 3). A comprehensive indoor monitoring study was conducted in 17 Los Angeles–area homes. As part of this study, indoor/outdoor concentration ratios during overnight (nonindoor source) periods were used to estimate the fraction of ambient particles remaining airborne indoors, or the particle infiltration factor (F INF), for fine particles (PM 2.5), its nonvolatile (i.e., black carbon [BC]) and volatile (i.e., nitrate [NO 3 ?]) components, and particle sizes ranging between 0.02 and 10 μm. F INF was highest for BC (median = 0.84) and lowest for NO 3 ? (median = 0.18). The low F INF for NO 3 ? was likely because of volatilization of NO 3 ? particles once indoors, in addition to depositional losses upon building entry. The F INF for PM 2.5 (median = 0.48) fell between those for BC and NO 3 ?, reflecting the contributions of both particle components to PM 2.5. F INF varied with particle size, air-exchange rate, and outdoor NO 3 ? concentrations. The F INF for particles between 0.7 and 2 μm in size was considerably lower during periods of high as compared with low outdoor NO 3 ? concentrations, suggesting that outdoor NO 3 ? particles were of this size. This study demonstrates that infiltration of PM 2.5 varies by particle component and is lowest for volatile species, such as NH 4NO 3. Our results suggest that volatile particle components may influence the ability for outdoor PM concentrations to represent indoor and, thus, personal exposures to particles of ambient origin, because volatilization of these particles causes the composition of PM 2.5 to differ indoors and outdoors. Consequently, particle composition likely influences observed epidemiologic relationships based on outdoor PM concentrations, especially in areas with high concentrations of NH 4NO 3 and other volatile particles. 相似文献
15.
PM 2.5 sampling was conducted at a curbside location in Delhi city for summer and winter seasons, to evaluate the effect of PM 2.5 and its chemical components on the visibility impairment. The PM 2.5 concentrations were observed to be higher than the National Ambient Air Quality Standards (NAAQS), indicating poor air quality. The chemical constituents of PM 2.5 (the water-soluble ionic species SO 42-, NO 3?, Cl ?, and NH 4+, and carbonaceous species: organic carbon, elemental carbon) were analyzed to study their impact on visibility impairment by reconstructing the light extinction coefficient, b ext. The visibility was found to be negatively correlated with PM 2.5 and its components. The reconstructed b ext showed that organic matter was the largest contributor to b ext in both the seasons which may be attributed to combustion sources. In summer season, it was followed by elemental carbon and ammonium sulfate; however, in winter, major contributions were from ammonium nitrate and elemental carbon. Higher elemental carbon in both seasons may be attributed to traffic sources, while lower concentrations of nitrate during summer, may be attributed to volatility because of higher atmospheric temperatures. Implications: The chemical constituents of PM 2.5 that majorly effect the visibility impairment are organic matter and elemental carbon, both of which are products of combustion processes. Secondary formations that lead to ammonium sulfate and ammonium nitrate production also impair the visibility. 相似文献
16.
AbstractTo determine the sources of particulate matter less than 2.5?μm (PM 2.5 in different ambient atmospheres (urban, roadside, industrial, and rural sites), the chemical components of PM 2.5 such as ions (Cl -, NO 3-, SO 42-, NH 4+, Na +, K +, Ca 2+, and Mg 2+), carbonaceous species, and elements (Al, As, Ba, Cd, Cu, Fe, Mn, Ni, Pb, Se, V, and Zn) were measured. The average mass concentrations of PM 2.5 at the urban, roadside, industrial, and rural sites were 31.5?±?14.8, 31.6?±?22.3, 31.4?±?16.0, and 25.8?±?12.4?μg/m 3, respectively. Except for secondary ammonium sulfate and ammonium nitrate, the model results showed that the traffic source (i.e., the sum of gasoline and diesel vehicle sources) was the most dominant source of PM 2.5 (17.1%) followed by biomass burning (13.8%) at the urban site. The major primary sources of PM 2.5 were consistent with the site characteristics (diesel vehicle source at the roadside site, coal-fired plants at the industrial site, and biomass burning at the rural site). Seasonal data from the urban site suggested that ammonium sulfate and ammonium nitrate were the most dominant sources of PM 2.5 during all seasons. Further, the contribution of road dust source to PM 2.5 increased during spring and fall seasons. We conclude that the determination of the major PM 2.5 sources is useful for establishing efficient control strategies for PM 2.5 in different regions and seasons. 相似文献
17.
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
18.
Continuous measurement of PM 10, PM 2.5 and carbon (organic, elemental composition) concentrations, and samples of PM 10 and PM 2.5 collected on a polycarbonate membrane filter (Nuclepore ®, pore size: 0.8 μm), were carried out during a period from December 1998 to January 1999 at Shinjuku in Tokyo in order to investigate the chemical characterization of particles in winter-night smog within a large area of the Japan Kanto Plain including the Tokyo Metropolitan area. These were measured using an ambient particulate monitor (tapered element oscillating microbalance—TEOM) and a carbon particulate monitor. Elemental compositions in the filter samples of PM 10 and PM 2.5 were determined by means of particle-induced X-ray emission (PIXE) analysis. Ionic species (anion: F −, Cl −, NO 3−, SO 42− and C 2O 42−; cation: Na +, NH 4+, K +, Ca 2+ and Mg 2+) in the filter samples were analyzed by ion chromatography. The temporal variation patterns of PM 2.5 were similar to those of PM 10 and carbon. PM 2.5 made up 90% of the PM 10 at a high concentration, and 70% at a low concentration. Concentrations of 22 elements in both the PM 10 and PM 2.5 samples were consistently determined by PIXE, and Na, Mg, Al, Si, S, Cl, K, Ca, Fe, Zn and Pb were found to be the major components. Among these S and Cl were the most dominant elements of the PM 2.5 and PM 10 at high concentrations. Ionic species were mainly composed of Cl −, NO 3−, SO 42− and NH 4+. The component proportion of carbon, the other elements (total amount of measured elements other than S and Cl) and secondary-formed particles of PM 2.5 was similar to that of PM 10. The major component was carbon particles at a low concentration and secondary-formed particles at a high concentration. The proportion of NH 4NO 3 and NH 4Cl plus HCl in secondary-formed particles at a high concentration, in particular, was as high as 90%. 相似文献
19.
Vertical concentration profiles for NH 3, HNO 3 and HCl-gas and for NH 4+, NO 3−, SO 2−4, Cl − and Na + aerosol were obtained from a meteorological tower in the central part of the Netherlands. An upward NH 3 flux of 0.12 μgm −2 s −1 was calculated from the NH 3 profiles and meteorological data. From the HNO 3 profiles a maximum HNO 3 dry deposition velocity of 4 cm s −1 was calculated. Good agreement was found between the measured concentration products [NH 3] (g) × [HNO 3] (g) and the theoretical values at temperatures above 0°C and relative humidities below 80%. In other cases, higher NH 3 and/or HNO concentrations in the gas phase were measured than theoretically predicted. 相似文献
20.
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
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