共查询到20条相似文献,搜索用时 476 毫秒
1.
A wintertime episode during the 2000 California Regional PM Air Quality Study (CRPAQS) was simulated with the air quality model CMAQ–MADRID. Model performance was evaluated with 24-h average measurements available from CRPAQS. Modeled organic matter (OM) was dominated by emissions, which were probably significantly under-represented, especially in urban areas. In one urban area, modeled daytime nitrate concentrations were low and evening concentrations were high. This diurnal profile was not explained by the partition of nitrate between the gas and particle phases, because gaseous nitric acid concentrations were low compared to PM nitrate. Both measured and simulated nitrate concentrations aloft were lower than at the surface at two tower locations during this episode. Heterogeneous reactions involving NO 3 and N 2O 5 accounted for significant nitrate production in the model, resulting in a nighttime peak. The sensitivity of PM nitrate to precursor emissions varied with time and space. Nitrate formation was on average sensitive to NO x emissions. However, for some periods at urban locations, reductions in NO x caused the contrary response of nitrate increases. Nitrate was only weakly sensitive to reductions in anthropogenic VOC emissions. Nitrate formation tended to be insensitive to the availability of ammonia at locations with high nitrate, although the spatial extent of the nitrate plume was reduced when ammonia was reduced. Reductions in PM emissions caused OM to decrease, but had no effect on nitrate despite the role of heterogeneous reactions. A control strategy that focuses on NO x and PM emissions would be effective on average, but reductions in VOC and NH 3 emissions would also be beneficial for certain times and locations. 相似文献
2.
Improvement of air quality models is required so that they can be utilized to design effective control strategies for fine particulate matter (PM 2.5). The Community Multiscale Air Quality modeling system was applied to the Greater Tokyo Area of Japan in winter 2010 and summer 2011. The model results were compared with observed concentrations of PM 2.5 sulfate (SO 42-), nitrate (NO 3?) and ammonium, and gaseous nitric acid (HNO 3) and ammonia (NH 3). The model approximately reproduced PM 2.5 SO 42? concentration, but clearly overestimated PM 2.5 NO 3? concentration, which was attributed to overestimation of production of ammonium nitrate (NH 4NO 3). This study conducted sensitivity analyses of factors associated with the model performance for PM 2.5 NO 3? concentration, including temperature and relative humidity, emission of nitrogen oxides, seasonal variation of NH 3 emission, HNO 3 and NH 3 dry deposition velocities, and heterogeneous reaction probability of dinitrogen pentoxide. Change in NH 3 emission directly affected NH 3 concentration, and substantially affected NH 4NO 3 concentration. Higher dry deposition velocities of HNO 3 and NH 3 led to substantial reductions of concentrations of the gaseous species and NH 4NO 3. Because uncertainties in NH 3 emission and dry deposition processes are probably large, these processes may be key factors for improvement of the model performance for PM 2.5 NO 3?. Implications: The Community Multiscale Air Quality modeling system clearly overestimated the concentration of fine particulate nitrate in the Greater Tokyo Area of Japan, which was attributed to overestimation of production of ammonium nitrate. Sensitivity analyses were conducted for factors associated with the model performance for nitrate. Ammonia emission and dry deposition of nitric acid and ammonia may be key factors for improvement of the model performance. 相似文献
3.
A reactive plume model that treats secondary aerosol formation is used to investigate the major physical and chemical processes that affect the rate of sulfate and nitrate aerosol formation in power plant plumes. The reactive plume model is evaluated with experimental data collected in three power plant plumes, and model performance is shown to be quite satisfactory. One of these case studies is used to perform singleparameter and multi-parameter analyses of the sensitivity of sulfate and nitrate aerosol concentrations to various meteorological, air quality and chemical kinetic parameters. The results suggest that sulfate aerosol concentrations are most sensitive to relative humidity and temperature at high relative humidity, whereas nitrate aerosol concentrations are most sensitive to temperature, particularly at low relative humidity. The importance of the NO x/reactive hydrocarbon chemistry to sulfate and nitrate aerosol formation is examined. 相似文献
4.
We use an inorganic aerosol thermodynamic equilibrium model in a three-dimensional chemical transport model to understand the roles of ammonia chemistry and natural aerosols on the global distribution of aerosols. The thermodynamic equilibrium model partitions gas-phase precursors among modeled aerosol species self-consistently with ambient relative humidity and natural and anthropogenic aerosol emissions during the 1990s.Model simulations show that accounting for aerosol inorganic thermodynamic equilibrium, ammonia chemistry and dust and sea-salt aerosols improve agreement with observed SO 4, NO 3, and NH 4 aerosols especially at North American sites. This study shows that the presence of sea salt, dust aerosol and ammonia chemistry significantly increases sulfate over polluted continental regions. In all regions and seasons, representation of ammonia chemistry is required to obtain reasonable agreement between modeled and observed sulfate and nitrate concentrations. Observed and modeled correlations of sulfate and nitrate with ammonium confirm that the sulfate and nitrate are strongly coupled with ammonium. SO 4 concentrations over East China peak in winter, while North American SO 4 peaks in summer. Seasonal variations of NO 3 and SO 4 are the same in East China. In North America, the seasonal variation is much stronger for NO 3 than SO 4 and peaks in winter.Natural sea salt and dust aerosol significantly alter the regional distributions of other aerosols in three main ways. First, they increase sulfate formation by 10–70% in polluted areas. Second, they increase modeled nitrate over oceans and reduce nitrate over Northern hemisphere continents. Third, they reduce ammonium formation over oceans and increase ammonium over Northern Hemisphere continents. Comparisons of SO 4, NO 3 and NH 4 deposition between pre-industrial, present, and year 2100 scenarios show that the present NO 3 and NH 4 deposition are twice pre-industrial deposition and present SO 4 deposition is almost five times pre-industrial deposition. 相似文献
5.
As models of the composition and heterogeneous chemical reactions of the troposphere undergo refinement, novel application of state-of-the-art analytical techniques will be necessary to propound realistic characterizations of mineral dust chemistry. In this study, strontium carbonate particles treated with gaseous nitric acid and nitrogen dioxide were examined with X-ray absorption fine structure analysis (EXAFS). The X-ray spectra of carbonate and nitrate standards were fitted to ab initio calculations, which were used to determine the structure and consistency of strontium nitrate formed on strontium carbonate. By examining differences in mean square radial displacement and lattice spacing values obtained for bulk Sr(NO 3) 2 as compared to Sr(NO 3) 2 formed on SrCO 3, EXAFS proves effective as a tool for investigating the local structure and composition of heterogeneous aerosol particles. The implications of findings on reacted strontium carbonate for atmospheric models of calcium carbonate aerosol are discussed. 相似文献
6.
Quantitative information from the 1995 Integrated Monitoring Study (IMS95) is used to develop a conceptual model, which describes the chemical characteristics and the physical processes responsible for the accumulation of PM in the San Joaquin Valley of California. One significant finding of the conceptual model is the sensitivity of ammonium nitrate (46% of winter PM 2.5) and nitric acid to oxidants, which may be VOC-sensitive rather than NO x-sensitive. Key gaps in current knowledge are identified using the conceptual model, e.g., the relative sensitivity of winter oxidants to VOC and NO x, mechanistic details of secondary organic aerosol formation, mechanisms of dispersion under calm conditions, and the importance of dry deposition. Some recommendations are also provided for the formulation of air quality models suitable to address the accumulation of PM in the San Joaquin Valley. 相似文献
7.
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
8.
Bromine chemistry in the marine boundary layer is recognized to play an important role through catalytic ozone destruction, changes to the atmospheric oxidising capacity (by changing the OH/HO 2 and NO/NO 2 ratio) and oxidation of compounds such as dimethyl sulphide (DMS). However, the chemistry of bromine in polluted environments is not well understood and its effects are thought to be inhibited by reactions involving NO x (NO 2 & NO). This paper describes long-path Differential Optical Absorption Spectroscopy (DOAS) observations of bromine oxide (BrO) at a semi-polluted coastal site in Roscoff, France. Significant concentrations of BrO (up to 7.5 ± 1.0 pptv) were measured during daytime, indicating the presence of unknown sources or efficient recycling of reactive bromine from bromine nitrate (BrONO 2), which should be the major reservoir for bromine in a high NO x environment. These measurements indicate that bromine chemistry can play an important role in polluted environments. 相似文献
9.
A mathematical model is used to study the fate of nitrogen oxides (NO x) emissions and the reactions responsible for the formation of nitric acid (HNO 3). Model results indicate that the majority of the NO x inserted into an air parcel in the Los Angeles basin is removed by dry deposition at the ground during the first 24 h of travel, and that HNO 3 is the largest single contributor to this deposition flux. A significant amount of the nitric acid is produced at night by N 2O 5 hydrolysis. Perturbation of the N 2O 5 hydrolysis rate constant within the chemical mechanism results in redistribution of the pathway by which HNO 3 is formed, but does not greatly affect the total amount of HNO 3 produced. Inclusion of NO 3-aerosol and N 2O 5-aerosol reactions does not affect the system greatly at collision efficiencies, α, of 0.001, but at α = 0.1 or α = 1.0, a great deal of nitric acid could be produced by heterogeneous chemical processes.Ability to account for the observed nitrate radical (NO 3) concentrations in the atmosphere provides a key test of the air quality modeling procedure. Predicted NO 3 concentrations compare well with those measured by Platt et al. ( Geophys. Res. Lett.7, 89–92, 1980). Analysis shows that transport, deposition and emissions, as well as chemistry, are important in explaining the behavior of NO 3 in the atmosphere. 相似文献
11.
Assessing the public health benefits from air pollution control measures is assisted by understanding the relationship between mobile source emissions and subsequent fine particulate matter (PM 2.5) exposure. Since this relationship varies by location, we characterized its magnitude and geographic distribution using the intake fraction (iF) concept. We considered emissions of primary PM 2.5 as well as particle precursors SO 2 and NO x from each of 3080 counties in the US. We modeled the relationship between these emissions and total US population exposure to PM 2.5, making use of a source–receptor matrix developed for health risk assessment. For primary PM 2.5, we found a median iF of 1.2 per million, with a range of 0.12–25. Half of the total exposure was reached by a median distance of 150 km from the county where mobile source emissions originated, though this spatial extent varied across counties from within the county borders to 1800 km away. For secondary ammonium sulfate from SO 2 emissions, the median iF was 0.41 per million (range: 0.050–10), versus 0.068 per million for secondary ammonium nitrate from NO x emissions (range: 0.00092–1.3). The median distance to half of the total exposure was greater for secondary PM 2.5 (450 km for sulfate, 390 km for nitrate). Regression analyses using exhaustive population predictors explained much of the variation in primary PM 2.5 iF ( R2=0.83) as well as secondary sulfate and nitrate iF ( R2=0.74 and 0.60), with greater near-source contribution for primary than for secondary PM 2.5. We conclude that long-range dispersion models with coarse geographic resolution are appropriate for risk assessments of secondary PM 2.5 or primary PM 2.5 emitted from mobile sources in rural areas, but that more resolved dispersion models are warranted for primary PM 2.5 in urban areas due to the substantial contribution of near-source populations. 相似文献
12.
This paper synthesizes data on aerosol (particulate matter, PM) physical and chemical characteristics, which were obtained over the past decade in aerosol research and monitoring activities at more than 60 natural background, rural, near-city, urban, and kerbside sites across Europe. The data include simultaneously measured PM 10 and/or PM 2.5 mass on the one hand, and aerosol particle number concentrations or PM chemistry on the other hand. The aerosol data presented in our previous works (Van Dingenen et al., 2004, Putaud et al., 2004) were updated and merged to those collected in the framework of the EU supported European Cooperation in the field of Scientific and Technical action COST633 ( Particulate matter: Properties related to health effects). A number of conclusions from our previous studies were confirmed. There is no single ratio between PM 2.5 and PM 10 mass concentrations valid for all sites, although fairly constant ratios ranging from 0.5 to 0.9 are observed at most individual sites. There is no general correlation between PM mass and particle number concentrations, although particle number concentrations increase with PM 2.5 levels at most sites. The main constituents of both PM 10 and PM 2.5 are generally organic matter, sulfate and nitrate. Mineral dust can also be a major constituent of PM 10 at kerbside sites and in Southern Europe. There is a clear decreasing gradient in SO 42? and NO 3? contribution to PM 10 when moving from rural to urban to kerbside sites. In contrast, the total carbon/PM 10 ratio increases from rural to kerbside sites. Some new conclusions were also drawn from this work: the ratio between ultrafine particle and total particle number concentration decreases with PM 2.5 concentration at all sites but one, and significant gradients in PM chemistry are observed when moving from Northwestern, to Southern to Central Europe. Compiling an even larger number of data sets would have further increased the significance of our conclusions, but collecting all the aerosol data sets obtained also through research projects remains a tedious task. 相似文献
13.
Gaseous nitrogen dioxide (NO 2) represents an oxidant that is present in relatively high concentrations in various indoor settings. Remarkably increased NO 2 levels up to 1.5 ppm are associated with homes using gas stoves. The heterogeneous reactions of NO 2 with adsorbed water on surfaces lead to the generation of nitrous acid (HONO). Here, we present a HONO source induced by heterogeneous reactions of NO 2 with selected indoor paint surfaces in the presence of light (300 nm?<? λ?<?400 nm). We demonstrate that the formation of HONO is much more pronounced at elevated relative humidity. In the presence of light (5.5 W m ?2), an increase of HONO production rate of up to 8.6?·?10 9 molecules cm ?2 s ?1 was observed at [NO 2]?=?60 ppb and 50 % relative humidity (RH). At higher light intensity of 10.6 (W m ?2), the HONO production rate increased to 2.1?·?10 10 molecules cm ?2 s ?1. A high NO 2 to HONO conversion yield of up to 84 % was observed. This result strongly suggests that a light-driven process of indoor HONO production is operational. This work highlights the potential of paint surfaces to generate HONO within indoor environments by light-induced NO 2 heterogeneous reactions. 相似文献
14.
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
15.
In situ measurements of nitric acid (HNO 3), reactive nitrogen (NO y), nitric oxide (NO), and ozone (O 3) made in the upper troposphere (UT) and lower stratosphere (LS) between 29° and 33°N latitudes during September 1999 are used to examine NO y partitioning and correlations between the measured species in these regions. The fast-response (1 s) HNO 3 measurements are acquired with a new autonomous CIMS instrument. In the LS, HNO 3 accounts for the majority of NO y, and the sum of HNO 3 and NO x accounts for approximately 90% of NO y. In the UT, the sum of HNO 3 and NO x varies between 40% and 100% of NO y. Both HNO 3 and NO y are strongly positively correlated with O 3, with larger correlation slopes in the UT than in the LS. In the UT at low values of the quantity (NO y–NO x–HNO 3), it is uncorrelated with O 3, while at higher values, a positive correlation with O 3 is found. Of these two air mass types, those with higher (NO y–NO x–HNO 3) mixing ratios are likely associated with the presence of peroxyacetyl nitrate (PAN) that is produced by NO x-hydrocarbon chemistry. 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.
A simple, five-species algorithm to model the chemistry of oxides of nitrogen during long-range transport has been developed and used in the Eastern North America Model of Air Pollution (ENAMAP). The algorithm models the reactions and the physical depositions of NO and NO 2 as the primary pollutants, HNO 3 and particulate nitrate as the reaction products, and peroxyacetyl nitrate (PAN). PAN is utilized as a temporary reservoir for NO x, reacting during the day to form HNO 3, nitrate, and itself, then decomposing back to NO 2 at night. The NO and NO 2 are kept at equilibrium, and the NO 2 reacts to form PAN, HNO 3, and nitrate. The reaction rates and NO: NO 2 equilibrium constant vary diurnally. The model has been run for the months of January and August 1977, and has produced NO 2 concentration patterns that have characteristics consistent with the limited existing measurements of atmospheric nitrogen compounds. 相似文献
18.
The effects of the burning of fireworks on air quality in Beijing was firstly assessed from the ambient concentrations of various air pollutants (SO 2, NO 2, PM 2.5, PM 10 and chemical components in the particles) during the lantern festival in 2006. Eighteen ions, 20 elements, and black carbon were measured in PM 2.5 and PM 10, and the levels of organic carbon could be well estimated from the concentrations of dicarboxylic acids. Primary components of Ba, K, Sr, Cl −, Pb, Mg and secondary components of C 5H 6O 42−, C 3H 2O 42−, C 2O 42−, C 4H 4O 42−, SO 42−, NO 3− were over five times higher in the lantern days than in the normal days. The firework particles were acidic and of inorganic matter mostly with less amounts of secondary components. Primary aerosols from the burning of fireworks were mainly in the fine mode, while secondary formation of acidic anions mainly took place on the coarse particles. Nitrate was mainly formed through homogeneous gas-phase reactions of NO 2, while sulfate was largely from heterogeneous catalytic transformations of SO 2. Fe could catalyze the formation of nitrate through the reaction of α-Fe 2O 3 with HNO 3, while in the formation of sulfate, Fe is not only the catalyst, but also the oxidant. A simple method using the concentration of potassium and a modified method using the ratio of Mg/Al have been developed to quantify the source contribution of fireworks. It was found that over 90% of the total mineral aerosol and 98% of Pb, 43% of total carbon, 28% of Zn, 8% of NO 3−, and 3% of SO 42− in PM 2.5 were from the emissions of fireworks on the lantern night. 相似文献
19.
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
20.
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
|