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1.
(NH 4) 2SO 4, CaCl 2, Na 2SiO 3 and NaNO 3 were selected as surrogates of inorganic seed aerosols of ambient atmosphere of Chinese urban areas, respectively, to study their effects on the formation of secondary organic aerosol (SOA) in the toluene/CH 3ONO/NO x photooxidation system. The SMPS and aerosol laser time-of-flight mass spectrometer (ALTOFMS) was used to measure the aerodynamic size and chemical composition of individual SOA particles in real-time. Experimental results indicate that either the growth or products of SOA is affected by the presence of inorganic seed aerosol. Inorganic seed aerosols would promote growth rates of SOA formation at the start of the reaction and inhibits its formation rate with prolonging the reaction time. In the case of about 100 μg m ?3 seed aerosol load, the addition of Na 2SiO 3 induced a same growth rate of SOA formation as NaNO 3. The influence of four individual seed aerosols on the generation of SOA decreased in the order of CaCl 2 > (NH 4) 2SO 4 > NaNO 3, Na 2SiO 3. The presence of Na 2SiO 3 or NaNO 3 has no obvious effect on the growth rates of SOA formation, but it does increase the yield of organic acid and nitrogen-containing organic compounds, respectively. Besides the significantly effect on the growth rate of SOA formation, the presence of CaCl 2 or (NH 4) 2SO 4 can lead to the formation of high-molecular weight species which is found to be positively correlated with the hygroscopic behavior of seed aerosols. The CaCl 2 shows the strongest hygroscopic behavior among the four individual seed aerosols, and the most significant promotion effect on the formation of the high-molecular weight species. It is proposed that the SOA generation enhancement and high-molecular weight products are achieved by particle-phase heterogeneous reactions induced and catalyzed by the acidity of CaCl 2 and (NH 4) 2SO 4 seed aerosols. 相似文献
2.
Nitrogen-containing organic compounds (NOC) formed from secondary organic aerosols (SOA) age via reaction with reduced nitrogen species are a vital class of brown carbon compounds. NOC compounds from ammonia (NH 3) gas-aging of benzene SOA were investigated in present study, and the experiments were performed by irradiating benzene/CH 3ONO/NO/NH 3 air mixtures in a home-made smog chamber. The particulate NOC products of aged benzene SOA in the presence of NH 3 were measured by UV-Vis spectrophotometer, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with Fuzzy C-Means (FCM) clustering algorithm, respectively. Experimental results demonstrated that NH 3 has significant promotion effect on benzene SOA formation. Organic ammonium salts, such as ammonium glyoxylate, ammonium 6-oxo-2,4-hexadienoiclate, which are formed from NH 3 reactions with gaseous organic acids were detected as the major particulate NOC products of NH 3-aged benzene SOA. 1H–imidazole, 1H–imidazole-2-carbaldehyde and other imidazole products via the heterogeneous reactions between NH 3 and dialdehydes of benzene SOA were successfully detected as important brown carbon constituents. The formation of imidazole products suggests that some ambient particles contained organonitrogen compounds may be come from this mechanism. The results of this study may provide valuable information for discussing NH 3 deposition and SOA aging mechanisms. 相似文献
3.
To characterize atmospheric particulate matter equal or less than 2.5 μm in diameter (PM 2.5) over the Tropical Atlantic Ocean, aerosol sampling was carried out in Puerto Rico during August and September, 2006. Aerosols were analyzed by ion chromatography for water-soluble inorganic and organic ions (including Na +, NH 4 +, Mg 2+, Ca 2+, K +, Cl ?, SO 4 2?, NH 4 +, F ?, methanesulfonate (MSA), and oxalate), by inductive coupled plasma mass spectrometry (ICPMS) for trace elements (Al, Fe, Zn, Mn, Cu, Ni, V, Pb, Cr, Sb, Co, Sc, Cd), and by scanning electron microscopy for individual aerosol particle composition and morphology. The results show that the dominant cations in aerosols were Na +, (mean: 631 ng m ?3), accounting for 63.8 % of the total cation and NH 4 + (mean: 164 ng m ?3), accounting for 13.8 % of the total cation measured in this study. The main inorganic anions were Cl ? (576 ng m ?3, 54.1 %) and SO 4 2? (596 ng m ?3, 38.0 %). The main organic anion was oxalate (18 ng m ?3). Crustal enrichment factor calculations identified 62 % of the trace elements measured (Cu, Ni, V, Co, Al, Mn, Fe, Sc, and Cr) with crustal origin. Single particle analysis demonstrated that 40 % of the aerosol particles examined were Cl ? rich particles as sodium chloride from seawater and 34 % of the total particles were Si-rich particles, mainly in the form of aluminosilicates from dust material. Based on the combination of air-mass trajectories, cluster analysis and principal component analysis, the major sources of these PM 2.5 particles include marine, Saharan dust and biomass burning from West Africa; however, volcanic emissions from the Soufriere Hills in Montserrat had significant impact on aerosol composition in this region at the time of sample collection. 相似文献
4.
In the present paper, we have characterized the ambient ammonia over Delhi along with other trace gases (NH 3, NO, NO 2, SO 2 and CO) and particulates (PM 2.5 and PM 10) measured during December 2011 to June 2012. The average mixing ratios of ambient NH 3, NO, NO 2, SO 2 and CO were recorded as 21.2 ± 5.4, 19.5 ± 4.9, 17.4 ± 1.4, 1.7 ± 0.5 ppb and 1.6 ± 0.7 ppm, respectively, during winter, whereas the average mixing ratios of ambient NH 3, NO, NO 2, SO 2 and CO were recorded as 20.8 ± 4.7, 21.7 ± 6.3, 16.8 ± 3.1, 2.2 ± 0.8 ppb and 1.8 ± 0.9 ppm, respectively, during summer. In the present case, non-significant seasonal and diurnal variations of NH 3, NO, NO 2, SO 2 and CO were observed during both the seasons. The average monthly NH 3/NH 4 + ratios varied from 0.28 to 2.56 with an average value of 1.46 in winter. The higher NH 3/NH 4 + ratio (3.5) observed in summer indicates the abundance of NH 3 in the atmosphere during summer. The higher fraction of particulate NH 4 + observed in winter than summer attributes to the conversion of gaseous NH 3 into NH 4 +. The results emphasized that the traffic could be one of the significant sources of ambient NH 3 at the urban site of Delhi as illustrated by positive correlations of NH 3 with traffic-related pollutants (NO, NO 2 and CO). Surface wind analysis and wind directions also support the roadside traffic and agricultural activities at the nearby area indicating possible major sources of ambient NH 3 at the study site. 相似文献
5.
Measurements of aerosol physical, chemical and optical parameters
were carried out in Guangzhou, China from 1 July to 31 July 2006 during the
Pearl River Delta Campaign. The dry aerosol scattering coefficient was measured
using an integrating nephelometer and the aerosol scattering coefficient for
wet conditions was determined by subtracting the sum of the aerosol absorption
coefficient, gas scattering coefficient and gas absorption coefficient from the
atmospheric extinction coefficient. Following this, the aerosol hygroscopic
growth factor, f(RH), was calculated as the ratio of wet and dry aerosol
scattering coefficients. Measurements of size-resolved chemical composition,
relative humidity (RH), and published functional relationships between particle
chemical composition and water uptake were likewise used to find the aerosol
scattering coefficients in wet and dry conditions using Mie theory for
internally- or externally-mixed particle species [(NH 4) 2SO 4, NH 4NO 3, NaCl, POM, EC and residue]. Closure was obtained by comparing
the measured f(RH) values from the nephelometer and other in situ optical
instruments with those computed from chemical composition and thermodynamics.
Results show that the model can represent the observed f(RH) and is
appropriate for use as a component in other higher-order models. 相似文献
6.
In this study bulk airborne aerosol composition measured by the PILS-IC (integration time of 3 min 24 s) during TRACE-P P3B Flight 10 are used to investigate the ionic chemical composition and mixing state of biomass burning particles. A biomass burning plume, roughly 3–4 days old, moderately influenced by urban pollution aerosols recorded in the Philippine Sea is investigated. Focusing on the fine particle NO 3−, SO 42−, K +, NH 4+, and water-soluble organics, the observed correlations and nearly 1-to-1 molar ratios between K + and NO 3− and between NH 4+ and (SO 42−+ inferred Organics) suggest the presence of fine-mode KNO 3, (NH 4) 2SO 4, and NH 4(Organics) aerosols. Under the assumption that these ion pairs existed, and because KNO 3 is thermodynamically less favored than K 2SO 4 in a mixture of NO 3−, SO 42−, K +, NH 4+, and Organic anions, the measurements suggest that aerosols could be composed of biomass burning particles (KNO 3) mixed to a large degree externally with the (NH 4) 2SO 4 aerosols. A “closed-mode” thermodynamic aerosol simulation predicts that a degree of external mixing (by SO 42− mass) of 60 to 100% is necessary to achieve the observed ionic associations in terms of the existence of KNO 3. However, the degree of external mixing is most likely larger than 90%, based on both the presence of KNO 3 and the amounts of NH 4NO 3. Calculations are also shown that the aerosol mixing state significantly impacts particle growth by water condensation/evaporation. In the case of P3B Flight #10, the internal mixture is generally more hygroscopic than the external mixture. This method for estimating particle mixing state from bulk aerosol data is less definitive than single particle analysis, but because the data are quantitative, it may provide a complementary method to single particle chemical analysis. 相似文献
7.
This paper presents the application of a Monte-Carlo simulation for assessing the uncertainties of German 2005 emissions of particulate matter (PM 10 & PM 2.5) and aerosol precursors (SO 2, NO x, NH 3 and NMVOC) carried out in the PAREST (PArticle REduction STrategies) research project. For the uncertainty analysis the German Federal Environment Agency’s emission inventory was amended and integrated with a model on the disaggregation of energy balance data. A series of algorithms was developed in order to make efficient and pragmatic use of available literature and expert judgement data for uncertainties of emission model input data. The inventories for PM 10 (95 %-confidence interval: ?16 %/+23 %), PM 2.5 (?15 %/+19 %) and NO x (?10 %/+23 %) appear most uncertain, while the inventories for SO 2 (?9 %/+9 %), NMVOC (?10 %/+12 %) and NH 3 (?13 %/+13 %) show a higher accuracy. The source categories adding the most relevant contributions to overall uncertainty vary across the pollutants and comprise agriculture, mobile machinery in agriculture and forestry, construction sites, small businesses/carpentries, cigarette smoke and fireworks, road traffic, solvent use and stationary combustion. The PAREST results on relative uncertainties have been quoted in the German Informative Inventory Reports since 2012. A comparison shows that the PAREST results for Germany are within the range of (for NH 3: close below) other European countries’ results on air pollutant inventory uncertainties as reported in the 2013 Informative Inventory Reports. 相似文献
8.
The chemical compositions (Na +, NH 4 +, K +, Mg 2+, Ca 2+, Cl ?, NO 2 ?, NO 3 ?, SO 4 2?, HCO 3 ?) of wet precipitation and nitrogen isotope compositions δ 15N(NH 4 +) were studied from January to December 2010 in Wroc?aw (SW Poland). Results of a principle component analysis show that 82 % of the data variability can be explained by three main factors: 1) F1 (40 %) observed during vegetative season (electrical conductivity, HCO 3 ?, NO 3 ?, NO 2 ?, NH 4 + and SO 4 2?), mainly controlling rainwater mineralization; 2) F2 (26 %) observed during vegetative and heating seasons (K +, Ca 2+ and Mg 2+), probably representing a combination of two processes: anthropogenic dusts and fertilizers application in agricultural fields, and 3) F3 (16 %) reported mainly during heating season (Na + and Cl ?) probably indicating the influence of marine aerosols. Variations of δ 15N(NH 4 +) from ?11.5 to 18.5?‰ identify three main pathways for the formation of NH 4 +: 1) equilibrium fractionation between NH 3 and NH 4 +; 2) kinetic exchange between NH 3 and NH 4 +; 3) NH 4 + exchange between atmospheric salts particles and precipitation. The coupled chemical/statistical analysis and δ 15N(NH 4 +) approach shows that while fossil fuels burning is the main source of NH 4 + in precipitation during the heating season, during the vegetative season NH 4 + originates from local sewage irrigation fields in Osobowice or agricultural fertilizers. 相似文献
9.
Daily rainwater samples collected at Lijiang in 2009 were analyzed for pH, electrical conductivity, major ion (SO 4 2?, Cl ?, NO 3 ?, Na +, Ca 2+, Mg 2+, and NH 4 +) concentrations, and δ 18O. The rainwater was alkaline with the volume-weighted mean pH of 6.34 (range: 5.71 to 7.11). Ion concentrations and δ 18O during the pre-monsoon period were higher than in the monsoon. Air mass trajectories indicated that water vapor from South Asia was polluted with biomass burning emissions during the pre-monsoon. Precipitation during the monsoon was mainly transported by flow from the Bay of Bengal, and it showed high sea salt ion concentrations. Some precipitation brought by southwest monsoon originated from Burma; it was characterized by low δ 18O and low sea salt, indicating that the water vapor from the region was mainly recycled monsoon precipitation. Water vapor from South China contained large quantities of SO 4 2?, NO 3 ?, and NH 4 +. Throughout the study, Ca 2+ was the main neutralizing agent. Positive matrix factorization analysis indicated that crustal dust sources contributed the following percentages of the ions Ca 2+ 85 %, Mg 2+ 75 %, K + 61 %, NO 3 ? 32 % and SO 4 2? 21 %. Anthropogenic sources accounted for 79 %, 68 %, and 76 % of the SO 4 2?, NO 3 ? and NH 4 +, respectively; and approximately 93 %, 99 %, and 37 % of the Cl ?, Na +, and K + were from a sea salt source. 相似文献
10.
Secondary aerosol formation was studied at Allahabad in the Indo-Gangetic region during a field campaign called Land Campaign-II
in December 2004 (northern winter). Regional source locations of the ionic species in PM 10 were identified by using Potential Source Contribution Function (PSCF analysis). On an average, the concentration of water
soluble inorganic ions (sum of anions and cations) was 63.2 μgm −3. Amongst the water soluble ions, average NO 3− concentration was the highest (25.0 μgm −3) followed by SO 42− (15.8 μgm −3) and NH 4+ (13.8 μgm −3) concentrations. These species, contributed 87% of the total mass of water soluble species, indicating that most of the water
soluble PM 10 was composed of NH 4NO 3 and (NH 4) 2SO 4/NH 4HSO 4 or (NH 4) 3H(SO 4) 2 particles. Further, the concentrations of SO 42−, NO 3−, and NH4 + aerosols increased at high relative humidity levels up to the deliquescence point (∼63% RH) for salts of these species suggesting
that high humidity levels favor the conversion and partitioning of gaseous SO 2, NO x, and NH 3 to their aerosol phase. Additionally, lowering of ambient temperature as the winter progressed also resulted in an increase
of NO 3− and NH 4+ concentrations, probably due to the semi volatile nature of ammonium nitrate. PSCF analysis identified regions along the
Indo-Gangetic Plain (IGP) including Northern and Central Uttar Pradesh, Punjab, Haryana, Northern Pakistan, and parts of Rajasthan
as source regions of airborne nitrate. Similar source regions, along with Northeastern Madhya Pradesh were identified for
sulfate. 相似文献
11.
Aerosols consist of organic and inorganic species, and the composition and concentration of these species depends on their sources, chemical transformation and sinks. In this study an assessment of major inorganic ions determined in three aerosol particle size ranges collected for 1 year at Welgegund in South Africa was conducted. SO 42? and ammonium (NH 4+) dominated the PM 1 size fraction, while SO 42? and nitrate (NO 3) dominated the PM 1–2.5 and PM 2.5–10 size fractions. SO 42? had the highest contribution in the two smaller size fractions, while NO 3? had the highest contribution in the PM 2.5–10 size fraction. SO 42? and NO 3? levels were attributed to the impacts of aged air masses passing over major anthropogenic source regions. Comparison of inorganic ion concentrations to levels thereof within a source region influencing Welgegund, indicated higher levels of most species within the source region. However, the comparative ratio of SO 42? was significantly lower due to SO 42? being formed distant from SO 2 emissions and submicron SO 42? having longer atmospheric residencies. The PM at Welgegund was determined to be acidic, mainly due to high concentrations of SO 42?. PM 1 and PM 1–2.5 fractions revealed a seasonal pattern, with higher inorganic ion concentrations measured from May to September. Higher concentrations were attributed to decreased wet removal, more pronounced inversion layers trapping pollutants, and increases in household combustion and wild fires during winter. Back trajectory analysis also revealed higher concentrations of inorganic ionic species corresponding to air mass movements over anthropogenic source regions. 相似文献
12.
Ions can speed up the formation of aerosol particles. The former studies have mainly concerned on the role of the ion charge itself. We have studied the possible (additional) role of the actual small air ion spectrum shape, and the quantitative role of ion–ion recombination pathway. By means of our ion evolution model, formation of new species (H 2SO 4) n(NH 3) m(HNO 3) k via ion–ion recombination was investigated. The model shows how the generation rate of the new species depends on the concentrations of H 2SO 4 and NH 3, and how it depends on the tropospheric background aerosol situation. The rate can be up to a few new neutral complexes per cubic centimeter and per second. New particle generation via ion–ion recombination provides an extra channel, especially for the clean atmosphere. Former results have shown that such situations are often present in Antarctica. Our aerosol spectrum measurements reveal a number of similar non-Antarctic results. Sometimes, such situations are followed by aerosol bursts, which may be (partly) due to an ion–ion recombination channel. 相似文献
13.
This study systematically analyzed the concentrations of cations and anions and determined the pH in the rainwater at Guiyang from Oct. 2008 to Sep. 2009. The pH in the rainwater varied between 3.35 and 9.99 with a volume-weighted mean value of 4.23. The volume-weighted mean concentrations of anions followed the order SO 4 2->Cl ->F ->NO 3 -, whereas the volume-weighted mean concentrations of cations followed the order Ca 2+>NH 4 +>Na +>Mg 2+>K +. This finding indicates that SO 4 2- was the main anion and that Ca 2+ and NH 4 + were the main cations. Significant correlations between each pair of ions (SO 4 2-, NO 3 -, NH 4 +, Ca 2+, and Mg 2+) were observed, suggesting that CaSO 4, Ca(NO 3) 2, MgSO 4, Mg(NO 3) 2, NH 4NO 3, (NH 4) 2SO 4, and/or NH 4HSO 4 exist in the atmosphere at Guiyang. The soil-derived species (such as Ca 2+) played an important role in the neutralization of the acidity in rainwater. The SO 4 2- and NO 3 - in the rainwater were mainly from anthropogenic sources, and their contributions accounted for 98.1 % and 94.7 %, respectively. NH 4 + was also most likely derived from anthropogenic sources, such as domestic and commercial sewage, and played an important role in the neutralization of the rainwater at Guiyang. 相似文献
14.
Beijing is one of the largest and most densely populated cities in China. PM 2.5 (fine particulates with aerodynamic diameters less than 2.5 μm) pollution has been a serious problem in Beijing in recent years. To study the temporal and spatial variations in the chemical components of PM 2.5 and to discuss the formation mechanisms of secondary particles, SO 2, NO 2, PM 2.5, and chemical components of PM 2.5 were measured at four sites in Beijing, Dingling (DL), Chegongzhuang (CG), Fangshan (FS), and Yufa (YF), over four seasons from 2012 to 2013. Fifteen chemical components, including organic carbon (OC), elemental carbon (EC), K +, NH 4 +, NO 3 ?, SO 4 2?, Cl ?, Al, Ca, Fe, Mg, Na, Pb, Si, and Zn, were selected for analysis. Overall, OC, SO 4 2?, NO 3 ?, and NH 4 + were dominant among 15 components, the annual average concentrations of which were 22.62 ± 21.86, 19.39 ± 21.06, 18.89 ± 19.82, and 13.20 ± 12.80 μg·m ?3, respectively. Compared with previous studies, the concentrations of NH 4 + were significantly higher in this study. In winter, the average concentrations of OC and EC were, respectively, 3 and 2.5 times higher than in summer, a result of coal combustion during winter. The average OC/EC ratios over the four sites were 4.9, 7.0, 8.1, and 8.4 in spring, summer, autumn, and winter, respectively. The annual average [NO 3 ?]/[SO 4 2?] ratios in DL, CG, FS, and YF were 1.01, 1.25, 1.08, and 1.12, respectively, which were significantly higher than previous studies in Beijing, indicating that the contribution ratio of mobile source increased in recent years in Beijing. Analysis of correlations between temperature and relative humidity and between SOR ([SO 4 2?]/([SO 4 2?] + [SO 2])) and NOR ([NO 3 ?]/([NO 3 ?] + [NO 2])) indicated that gas-phase oxidation reactions were the major formation mechanism of SO 4 2? in spring and summer in urban Beijing, whereas slow gas-phase oxidation reactions and heterogeneous reactions both occurred in autumn and winter. NO 3 ? was mainly formed through year-round heterogeneous reactions in urban Beijing. 相似文献
15.
Haze-fog conditions over northern India are associated with visibility degradation and severe attenuation of solar radiation by airborne particles with various chemical compositions. PM 2.5 samples have been collected in Delhi, India from December 2011 to November 2012 and analyzed for carbonaceous and inorganic species. PM 10 measurements were made simultaneously such that PM 10–2.5 could be estimated by difference. This study analyzes the temporal variation of PM 2.5 and carbonaceous particles (CP), focusing on identification of the primary and secondary aerosol emissions, estimations of light extinction coefficient (b ext) and the contributions by the major PM 2.5 chemical components. The annual mean concentrations of PM 2.5, organic carbon (OC), elemental carbon (EC) and PM 10–2.5 were found to be 153.6 ± 59.8, 33.5 ± 15.9, 6.9 ± 3.9 and 91.1 ± 99.9 μg m ?3, respectively. Total CP, secondary organic aerosols and major anions (e.g., SO 4 2? and NO 3 ?) maximize during the post-monsoon and winter due to fossil fuel combustion and biomass burning. PM 10–2.5 is more abundant during the pre-monsoon and post-monsoon. The OC/EC varies from 2.45 to 9.26 (mean of 5.18 ± 1.47), indicating the influence of multiple combustion sources. The b ext exhibits highest values (910 ± 280 and 1221 ± 371 Mm ?1) in post-monsoon and winter and lowest in monsoon (363 ± 110 and 457 ± 133 Mm ?1) as estimated via the original and revised IMPROVE algorithms, respectively. Organic matter (OM =1.6 × OC) accounts for ~39 % and ~48 % of the b ext, followed by (NH 4) 2SO 4 (~21 % and ~24 %) and EC (~13 % and ~10 %), according to the original and revised algorithms, respectively. The b ext estimates via the two IMPROVE versions are highly correlated (R 2 = 0.95, root mean square error = 38 % and mean bias error = 28 %) and are strongly related to visibility impairment ( r = ?0.72), mostly associated with anthropogenic rather than natural PM contributions. Therefore, reduction of CP and precursor gas emissions represents an urgent opportunity for air quality improvement across Delhi. 相似文献
16.
Ions can speed up the formation of aerosol particles. The former studies have mainly concerned on the role of the ion charge itself. We have studied the possible (additional) role of the actual small air ion spectrum shape, and the quantitative role of ion–ion recombination pathway. By means of our ion evolution model, formation of new species (H 2SO 4) n(NH 3) m(HNO 3) k via ion–ion recombination was investigated. The model shows how the generation rate of the new species depends on the concentrations of H 2SO 4 and NH 3, and how it depends on the tropospheric background aerosol situation. The rate can be up to a few new neutral complexes per cubic centimeter and per second. New particle generation via ion–ion recombination provides an extra channel, especially for the clean atmosphere. Former results have shown that such situations are often present in Antarctica. Our aerosol spectrum measurements reveal a number of similar non-Antarctic results. Sometimes, such situations are followed by aerosol bursts, which may be (partly) due to an ion–ion recombination channel. 相似文献
17.
This paper reports aerosol chemical properties for the first time over a Korean Global Atmosphere Watch (GAW) supersite, Anmyeon (36°32′N; 126° 19′E), during 2003–2004 period. Total suspended Particulates (TSP) showed significant seasonal variation with consistent higher mass concentrations during spring season (average of up to 230?±?190 μg/m 3). PM 10 also followed similar trend with higher concentrations during spring (average of up to 170?±?130 μg/m 3) and showed reduced concentrations during summer. PM 2.5 showed a significant increase during summer (average of up to 60?±?25 μg/m 3), which could be due to the influx of fine mode sea salt aerosols associated with the Changma front (summer monsoon). Chemical composition analysis showed enhanced presence of acidic fractions, majorly contributed by sulphates (SO 4 2- ) and nitrates (NO 3 - ) in TSP, PM 10 and PM 2.5 during different seasons. Enhanced presence of Calcium (Ca 2+) was observed during sand storm days during spring. The high correlation obtained on matrix analysis between crustal ions and acidic ions suggests that the ionic compositions over the site are mainly contributed by terrestrial sources of similar origin. The neutralization factors has been estimated to find the extend of neutralization of acidicity by main basic components, and found to have higher value for Ammonium (up to 1.1) in different seasons, indicating significant neutralization of acidic components over the region by NH 4 + . Back trajectory analysis has been performed during different seasons to constrain the possible sources of aerosol origin and the results are discussed in detail. 相似文献
18.
We investigated the acidity and concentrations of water-soluble ions in PM 2.5 aerosol samples collected from an urban site in Beijing and a rural site in Gucheng, Hebei Province from November 2016 to January 2017 to gain an insight into the formation of secondary inorganic species. The average SO 42–, NO 3–, and NH 4+ concentrations were 8.3, 12.5, and 14.1 μg m –3, respectively, at the urban site and 14.0, 14.2, and 24.2 μg m –3, respectively, at the rural site. The nitrogen and sulfur oxidation ratios in urban Beijing were correlated with relative humidity (with correlation coefficient r = 0.79 and 0.67, respectively) and the aerosol loadings. Based on a parameterization model, we found that the rate constant of the heterogeneous reactions for SO 2 on polluted days was about 10 times higher than that on clear days, suggesting that the heterogeneous reactions in the aerosol water played an essential role in haze events. The ISORROPIA II model was used to predict the aerosol pH, which had a mean (range) of 5.0 (4.9–5.2) and 5.3 (4.6–6.3) at the urban and rural site, respectively. Under the conditions with this predicted pH value, oxidation by dissolved NO 2 and the hydrolysis of N 2O 5 may be the major heterogeneous reactions forming SO 42– and NO 3– in haze. We also analyzed the sensitivity of the aerosol pH to changes in the concentrations of SO 42–, NO 3–, and NH 4+ under haze conditions. The aerosol pH was more sensitive to the SO 42– and NH 4+ concentrations with opposing trends, than to the NO 3– concentrations. The sensitivity of the pH was relatively weak overall, which was attributed to the buffering effect of NH 3 partitioning. 相似文献
19.
Our long-term study provides an unequivocal evidence for near-quantitative (80–100%) depletion of chloride from sea-salts in the marine atmospheric boundary layer (MABL) of tropical Bay of Bengal. During the late NE-monsoon (Jan-Mar), continental outflow from south and south-east Asia dominate the wide-spread dispersal of pollutants over the Bay of Bengal. Among anthropogenic constituents, SO 4 2? (range: 0.6–35 μg m ?3) is the most dominant. The non-sea-salt SO 4 2? (nss-SO 4 2? ) constitutes a major fraction (55–65%) of the aerosol water-soluble ionic composition (WSIC), whereas contribution of NO 3 ? is relatively minor. The magnitude of Cl-deficit (with respect to its sea-salt proportion) exhibits linear increase with the excess-nss-SO 4 2? (excess over NH 4 + ). We propose that displacement of HCl from sea-salt aerosols by H 2SO 4 is a dominant reaction mechanism for the chloride-depletion. These results also suggest that sea-salts could serve as a potential sink for anthropogenic SO 2 in the downwind polluted marine environment. Furthermore, loss of hydrogen chloride, representing a large source of reactive chlorine, has implications to the oxidant chemistry in the MABL (oxidation of hydrocarbons and dimethyl sulphide). 相似文献
20.
Size-segregated aerosol particles were collected using a high volume MOUDI sampler at a coastal urban site in Xiamen Bay, China, from March 2018 to June 2020 to examine the seasonal characteristics of aerosol and water-soluble inorganic ions (WSIIs) and the dry deposition of nitrogen species. During the study period, the annual average concentrations of PM1, PM2.5, PM10, and TSP were 14.8?±?5.6, 21.1?±?9.0, 35.4?±?14.2 μg m?3, and 45.2?±?21.3 μg m?3, respectively. The seasonal variations of aerosol concentrations were impacted by the monsoon with the lowest value in summer and the higher values in other seasons. For WSIIs, the annual average concentrations were 6.3?±?3.3, 2.1?±?1.2, 3.3?±?1.5, and 1.6?±?0.8 μg m?3 in PM1, PM1-2.5, PM2.5–10, and PM>10, respectively. In addition, pronounced seasonal variations of WSIIs in PM1 and PM1-2.5 were observed, with the highest concentration in spring-winter and the lowest in summer. The size distribution showed that SO42?, NH4+ and K+ were consistently present in the submicron particles while Ca2+, Mg2+, Na+ and Cl? mainly accumulated in the size range of 2.5–10 μm, reflecting their different dominant sources. In spring, fall and winter, a bimodal distribution of NO3? was observed with one peak at 2.5–10 μm and another peak at 0.44–1 μm. In summer, however, the fine mode peak disappeared, likely due to the unfavorable conditions for the formation of NH4NO3. For NH4+ and SO42?, their dominant peak at 0.25–0.44 μm in summer and fall shifted to 0.44–1 μm in spring and winter. Although the concentration of NO3–N was lower than NH4–N, the dry deposition flux of NO3–N (35.77?±?24.49 μmol N m?2 d?1) was much higher than that of NH4–N (10.95?±?11.89 μmol N m?2 d?1), mainly due to the larger deposition velocities of NO3–N. The contribution of sea-salt particles to the total particulate inorganic N deposition was estimated to be 23.9—52.8%. Dry deposition of particulate inorganic N accounted for 0.95% of other terrestrial N influxes. The annual total N deposition can create a new productivity of 3.55 mgC m?2 d?1, accounting for 1.3–4.7% of the primary productivity in Xiamen Bay. In light of these results, atmospheric N deposition could have a significant influence on biogeochemistry cycle of nutrients with respect to projected increase of anthropogenic emissions from mobile sources in coastal region. 相似文献
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