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1.
《Atmospheric Research》2009,91(2-4):243-252
Aerosol size distributions were measured with Micro Orifice Uniform Deposit Impactor (MOUDI) cascade impactors at the rural Angiola and urban Fresno Supersites in California's San Joaquin Valley during the California Regional PM10/PM2.5 Air Quality Study (CRPAQS) winter campaign from December 15, 2000 to February 3, 2001. PM2.5 filter samples were collected concurrently at both sites with Sequential Filter Samplers (SFS). MOUDI nitrate (NO3−) concentrations reached 66 μg/m3 on January 6, 2001 during the 1000–1600 PST (GMT-8) period. Pair-wise comparisons between PM2.5 MOUDI and SFS concentrations revealed high correlations at the Angiola site (r > 0.93) but more variability (r < 0.85) at the Fresno site for NO3−, sulfate (SO4=), and ammonium (NH4+). Correlations were higher at Fresno (r > 0.87) than at Angiola (r < 0.7) for organic carbon (OC), elemental carbon (EC), and total carbon (TC). NO3− and SO4= size distributions in Fresno were multi-modal and wider than the uni-modal distributions observed at Angiola. Geometric mean diameters (GMD) were smaller for OC and EC than for NO3− and SO4= at both sites. OC and EC were more concentrated on the lowest MOUDI stage (0.056 µm) at Angiola than at Fresno. The NO3− GMD increased from 0.97 to 1.02 µm as the NO3− concentration at Angiola increased from 43 to 66 µg m− 3 during a PM2.5 episode from January 4–7, 2001. There was a direct relationship between GMD and NO3− and SO4= concentrations at Angiola but no such relationships for OC or EC. This demonstrates that secondary aerosol formation increases both concentration and particle size for the rural California environment.  相似文献   

2.
Shanghai is the largest industrial and commercial city in China, and its air quality has been deteriorating for several decades. However, there are scarce researches on the level and seasonal variation of fine particle (PM2.5) as well as the carbonaceous fractions when compared with other cities in China and around the world. In the present paper, abundance and seasonal characteristics of PM2.5, organic carbon (OC) and elemental carbon (EC) were studied at urban and suburban sites in Shanghai during four season-representative months in 2005–2006 year. PM2.5 samples were collected with high-vol samplers and analyzed for OC and EC using thermal-optical transmittance (TOT) protocol. Results showed that the annual average PM2.5 concentrations were 90.3–95.5 μg/m3 at both sites, while OC and EC were 14.7–17.4 μg/m3 and 2.8–3.0 μg/m3, respectively, with the OC/EC ratios of 5.0–5.6. The carbonaceous levels ranked by the order of Beijing > Guangzhou > Shanghai > Hong Kong. The carbonaceous aerosol accounted for  30% of the PM2.5 mass. On seasonal average, the highest OC and EC levels occurred during fall, and they were higher than the values in summer by a factor of 2. Strong correlations (r = 0.79–0.93) between OC and EC were found in the four seasons. Average level of secondary organic carbon (SOC) was 5.7–7.2 μg/m3, accounting for  30% of the total OC. Strong seasonal variation was observed for SOC with the highest value during fall, which was about two times the annual average.  相似文献   

3.
Chemical characteristics of haze during summer and winter in Guangzhou   总被引：33，自引：0，他引：33  
Airborne particles were collected with a 10-stage MOUDI and a PM10 sampler in Guangzhou, China, during both haze and normal days in the summer of 2002 and 2003, and winter 2002. The characteristics of PAHs, organic carbon, elemental carbon and water-soluble inorganic ions were studied under four periods (summer normal, summer haze, winter normal and winter haze). In this study, secondary pollutants (OC, SO42−, NO3− and NH4+) were the major chemical components and appeared to show a remarkably rapid increase from normal to haze days. The particle mass size distributions were bimodal and dominated by fine particles in haze days. A significantly higher OC/EC ratio was found in haze days (3.2–4.7) compared to normal days (1.8–2.8), indicating secondary organic aerosol formation might be significant during haze days. Correlation analysis between visibility and chemical species showed that the major scattering species were TC (total carbon) and sulfate in normal days and nitrate and TC in haze days, respectively. Simultaneously, correlation analysis between visibility and meteorological factors demonstrated that visibility increased with both temperature and wind speed, while it decreased with relative humidity. Furthermore, the relatively higher value of IcdP/(BghiP + IcdP) and the low value of Cmax, CPI, and BghiP/BeP in winter haze could be due to the growth of motor vehicle usage and energy consumption in winter.  相似文献   

4.
Organic and elemental carbon (OC and EC) content in PM10 was studied at two sites in Prague, which were located in a suburb and in the downtown. Similar overall average levels were found for both species and also for the PM10 mass at the two sites (i.e., 5.5 and 4.8 μg/m3 for OC, 0.74 and 0.80 μg/m3 for EC, and 33 μg/m3 and 37 μg/m3 for the PM10 mass at the suburb and downtown site, respectively), but substantial differences were observed between the two sites in some seasons and/or meteorological situations. Approximately three times higher values were found for OC in winter compared to summer, with a higher winter/summer ratio for the suburban site. The differences for EC were smaller, but still, compared to summer, more than two times higher EC levels were observed during autumn at the suburban site and 1.5 higher EC levels in winter and autumn at the downtown site. The lowest OC to EC ratios at the suburban site were 3.4, while they were around 1.3 for the downtown site. It was found that the origin of the air masses had a major impact on the observed PM10 mass and OC levels, with largest concentrations noted for air masses recirculating over central Europe and arriving from southeastern Europe in winter. Trajectories coming from the west and northwest originating above the Atlantic Ocean and the Artic brought the cleanest air masses to the sites. For EC the largest difference between the two sites was observed for northwesterly winds during the non-heating season when the suburban site was upwind of Prague.  相似文献   

5.
In the present study, the wet and dry depositions of particulate NO3−, SO42−, Cl− and NH4+ were measured using a wet/dry sampler as a surrogate surface. Gas phase compounds of nitrogen, sulfur and chloride (HNO3, NH3, SO2 and HCl) were measured by an annular denuder system (ADS) equipped with a back up filter for the collection of particles with diameter ≤ 5 μm. Ambient concentrations of NO, NO2 and SO2 were also taken into consideration. Sampling was conducted at an urban site in the center of the city of Thessaloniki, northern Greece. The presence of the aerosol species was examined by cold/warm period and the possible compounds in dry deposits were also considered. Dry deposition fluxes were found to be well correlated with ambient particle concentrations in order to be used for the calculation of particle deposition velocity. Average particulate deposition velocities calculated were 0.36, 0.20, 0.20 and 0.10 cm s− 1 for Cl−, NO3−, SO42− and NH4+, respectively. Total dry deposition fluxes (gas and particles) were estimated at 3.24 kg ha− 1 year− 1 for chloride (HCl + p-Cl), 9.97 kg ha− 1 year− 1 for nitrogen oxidized (NO + NO2 + HNO3 + p-NO3), 5.32 kg ha− 1 year− 1 for nitrogen reduced (NH3 + p-NH4) and 15.77 kg ha− 1 year− 1 for sulfur (SO2 + p-SO4). 70–90% total dry deposition was due to gaseous species deposition. The contribution of dry deposition to the total (wet + dry) was at the level of 60–70% for sulfur and nitrogen (oxidized and reduced), whereas dry chloride deposition contributed 35% to the total. The dry-to-wet deposition ratio of all the studied species was found to be significantly associated with the precipitation amount, with nitrogen species being better and higher correlated. Wet, dry and total depositions measured in Thessaloniki, were compared with other countries of Europe, US and Asia.  相似文献   

6.
In this paper warm cloud microphysical parameters including cloud droplet number concentration (Nc), liquid water content (ql) and effective radius (re) from 75 flights around the Beijing area during 2005 and 2006 are summarized. Average Nc (cm− 3) for Cu, Sc, Ac, As and Ns are 376 ± 290, 257 ± 226, 147 ± 112, 60 ± 35 and 60 ± 84, respectively. Many records of high Nc above 1000 cm− 3 are observed. The large standard deviations indicate a large variation of Nc and ql in this region. The maxima of ql reach 1.4 g m− 3 in Cu and 1.0 g m− 3 in Sc, respectively. Different parameterizations of effective radius are examined with the in-situ data in this area. There are different ways to obtain the prefactor representing the relationship between effective radius and mean volume radius. Significant systematic errors are found to be at the large sizes when the prefactor is expressed with relative dispersion under the Gamma Distribution. Fixed prefactor of 1, which was widely used, even produces much larger error. A prefactor of 1.22 is found to be better than the former two methods by fitting with the observed data. The effective radius is further parameterized as functions of mean volume radius, liquid water content and cloud droplet number concentration. We suggest that the effective radius can be parameterized as re,p ≈ 1.20rv + 0.22–1.28/rv2, which is a practical and more accurate scheme without too much computation complexity.  相似文献   

7.
A high-volume cascade impactor, equipped with a PM10 inlet, was used to collect size-segregated aerosol samples during the summer of 2004 at two Portuguese locations: a coastal-rural area (Moitinhos) and an urban area (Oporto). Concentrations of airborne particulate matter (PM), total carbon (TC), organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were determined for the following particle size ranges: < 0.49, 0.49–0.95, 0.95–3.0, and 3.0–10 µm. The total PM mass concentrations at the urban and coastal-rural sites ranged from 22.8 to 79.6 μg m− 3 and 19.9 to 28.2 μg m− 3, respectively, and more than 56% of the total aerosol mass was found in the fractions below 3.0 μm. At both locations the highest concentrations of OC and EC were found in the submicrometer size range. The regional variability for the OC and EC concentrations, with the highest concentrations being found in the urban area, was related to the contribution of local primary sources (mostly traffic emissions). It was also verified an enrichment of the small size particles in WSOC, representing on average 37.3(± 12.4)% and 59.7(± 18.0)% of OC in the very fine aerosol at the coastal-rural and urban areas, respectively. The amount of secondary OC calculated by the minimum OC/EC ratio method indicates that secondary organic aerosol formation was important throughout the study at both sites. The obtained results suggest that long-range transport and favourable summer conditions for photochemical oxidation are key factors determining secondary OC formation in the coastal-rural and urban areas. The ultraviolet absorption properties of the chromophoric constituents of the WSOC fractions were also different among the different particle size ranges and also between the two sampling locations, thus suggesting the strong impact of the diverse emission sources into the composition of the size-segregated organic aerosol.  相似文献   

8.
Particle light absorption (bap), black carbon (BC), and elemental carbon (EC) measurements at the Fresno Supersite during the summer of 2005 were compared to examine the equivalency of current techniques, evaluate filter-based bap correction methods, and determine the EC mass absorption efficiency (σap) and the spectral dependence of bap. The photoacoustic analyzer (PA) was used as a benchmark for in-situ bap. Most bap measurement techniques were well correlated (r ≥ 0.95). Unadjusted Aethalometer (AE) and Particle Soot Absorption Photometer (PSAP) bap were up to seven times higher than PA bap at similar wavelengths because of absorption enhancement by backscattering and multiple scattering. Applying published algorithms to correct for these effects reduced the differences to 24 and 17% for the AE and PSAP, respectively, at 532 nm. The Multi-Angle Absorption Photometer (MAAP), which accounts for backscattering effects, overestimated bap relative to the PA by 51%. BC concentrations determined by the AE, MAAP, and Sunset Laboratory semi-continuous carbon analyzer were also highly correlated (r ≥ 0.93) but differed by up to 57%. EC measured with the IMPROVE/STN thermal/optical protocols, and the French two-step thermal protocol agreed to within 29%. Absorption efficiencies determined from PA bap and EC measured with different analytical protocols averaged 7.9 ± 1.5, 5.4 ± 1.1, and 2.8 ± 0.6 m2/g at 532, 670, and 1047 nm, respectively. The Angström exponent (α) determined from adjusted AE and PA bap ranged from 1.19 to 1.46. The largest values of α occurred during the afternoon hours when the organic fraction of total carbon was highest. Significant biases associated with filter-based measurements of bap, BC, and EC are method-specific. Correcting for these biases must take into account differences in aerosol concentration, composition, and sources.  相似文献   

9.
The chemical composition of regional background aerosols, and the time variability and sources in the Western Mediterranean are interpreted in this study. To this end 2002–2007 PM speciation data from an European Supersite for Atmospheric Aerosol Research (Montseny, MSY, located 40 km NNE of Barcelona in NE Spain) were evaluated, with these data being considered representative of regional background aerosols in the Western Mediterranean Basin. The mean PM10, PM2.5 and PM1 levels at MSY during 2002–2007 were 16, 14 and 11 µg/m3, respectively. After compiling data on regional background PM speciation from Europe to compare our data, it is evidenced that the Western Mediterranean aerosol is characterised by higher concentrations of crustal material but lower levels of OM + EC and ammonium nitrate than at central European sites. Relatively high PM2.5 concentrations due to the transport of anthropogenic aerosols (mostly carbonaceous and sulphate) from populated coastal areas were recorded, especially during winter anticyclonic episodes and summer midday PM highs (the latter associated with the transport of the breeze and the expansion of the mixing layer). Source apportionment analyses indicated that the major contributors to PM2.5 and PM10 were secondary sulphate, secondary nitrate and crustal material, whereas the higher load of the anthropogenic component in PM2.5 reflects the influence of regional (traffic and industrial) emissions. Levels of mineral, sulphate, sea spray and carbonaceous aerosols were higher in summer, whereas nitrate levels and Cl/Na were higher in winter. A considerably high OC/EC ratio (14 in summer, 10 in winter) was detected, which could be due to a combination of high biogenic emissions of secondary organic aerosol, SOA precursors, ozone levels and insolation, and intensive recirculation of aged air masses. Compared with more locally derived crustal geological dusts, African dust intrusions introduce relatively quartz-poor but clay mineral-rich silicate PM, with more kaolinitic clays from central North Africa in summer, and more smectitic clays from NW Africa in spring.  相似文献   

10.
Intensive measurements of gas and aerosol for 2 weeks were carried out at Qingdao (gas and aerosol in 2000, 2001 and 2002), Fenghuangshan (gas and aerosol in 2000 and 2001), and Dalian (aerosol in 2002) in the winter–spring period. High SO2 episodes were observed on 18 January 2000 at both Qingdao and Fenghuangshan. According to back trajectory calculations and analysis of gaseous species, high SO2 episodes were caused by local pollution and transport.Nitrate, sulfate and ammonium were the major species in PM2.5. Mass fractions of NO3−, nss-SO42− and NH4+ at Qingdao in 2002 were 10%, 12% and 5.5% for PM2.5, respectively, which were higher than that of nss-Ca2+ (1%). Chemical compositions observed at Dalian and Fenghuangshan were similar to those at Qingdao. The mass ratio of nss-SO42−/SO2 at Qingdao in winter was low (< 1.2), indicating that sulfate was probably produced by the slow oxidation of SO2 in the gas phase and/or was transported from outside of Qingdao in winter. The equivalent ratio of NH4+ to nss-SO42− was 1.39, suggesting that ammonium sulfate was one of the major chemical compositions in PM2.5. The NO3−/SO42− ratio at Qingdao was higher than that at remote places in East Asia. Gas and aerosol data obtained at Fenghuangshan were similar to data at Qingdao, suggesting that emissions from small cities may have a great influence on pollution in northern China.  相似文献   

11.
This paper presents the development of a simple and precise analytical method for the determination of nitrogen dioxide in ambient air. In this method nitrogen dioxide is determined in the form of nitrite. The determination of nitrogen dioxide needs no reagents except for a solution of sodium hydroxide mixed with sodium arsenite (NaOH–Na2As2O3) which is used as an absorbing reagent for trapping the nitrogen dioxide from the atmosphere in the form of nitrite, i.e., a prior analysis step. The determination of submicrogram levels of nitrogen dioxide is based on the selection of a strong and sharp quantitative analytical peak at 1380 cm− 1 using diffuse reflectance infrared spectroscopy (DRS-FTIR). The limit of detection (LOD) and the limit of quantification of the method are found to be 0.008 μg g− 1 NO2− and 0.05 μg g− 1 NO2−, respectively. The precision in terms of standard deviation and relative standard deviation value at a level of 2 μg NO2− / 0.1 g KBr for n = 10 is found to be 0.036 μg NO2− and 1.8%, respectively. The relative standard deviation (n = 10) for the determination of nitrogen dioxide in ambient air was observed to be in the range 2.6–3.8%. The method proposed is time-saving and eliminates the slow and cumbersome steps of pH maintenance of the reaction mixture and color formation of the EPA recommended spectrophotometric and other methods for quantitative determination of nitrogen dioxide.  相似文献   

12.
A total of 48 precipitation samples have been collected from individual precipitation events at the Nam Co Monitoring and Research Station for Multisphere Interactions (Nam Co Station, 30°47′N, 90°58′E; 4730 m a.s.l) located in the central Tibetan Plateau from August 2005 to August 2006. All samples were analyzed for major cations (NH4+, Na+, K+, Ca2+ and Mg2+) and anions (Cl−, NO3− and SO42−), conductivity and pH. Precipitation pH values ranged from 6.03 to 7.38 with an average value of 6.59. The high pH is due to large inputs of crustal aerosols in the atmosphere, which contain a large fraction of carbonate. Ca2+ is the dominant cation in precipitation with an average value of 65.58 μeq L− 1 (4.91–301.41 μeq L− 1), accounting for 54% of the total cations in precipitation. HCO3− is the predominant anion, accounting for 62% of the total anions. When compared with data from a snow pit in the Zhadang Glacier 50 km away (5800 m a.s.l), major ion concentration in precipitation at the Nam Co Station is much higher due to local aerosol inputs. Correlation and empirical orthogonal function (EOF) analysis indicate that regional crustal aerosols and species from combustion emissions of residents are the major sources for these ions, lake salt aerosols from the Nam Co nearby and regional mineral aerosols from dry lake sediments are secondary sources, and sea salt contribution is the least due to the long distance transport.  相似文献   

13.
Black carbon relationships with emissions and meteorology in Xi'an, China   总被引：4，自引：0，他引：4  
Aerosol black carbon (BC) was measured every 5 min at Xi'an, China from September 2003 to August 2005. Daily BC concentrations ranged from 2 to 65 μg m− 3, averaging 14.7 ± 9.5 μg m− 3 and displayed clear summer minima and winter maxima. BC typically peaked between 0800 and 1000 LST and again between 2000 and 2200 LST, corresponding with morning and evening traffic combined with nighttime residential cooking and heating. The nocturnal peak was especially evident in winter, when more domestic heating is used and pollutant-trapping surface-inversions form earlier than in summer. BC frequency distributions the most commonly occurring concentrations occurred between 5 and 10 μg m− 3 in all four seasons. BC ranged from 1.6% and 15.6%, and averaged 8.3% of PM2.5. A clear inverse relationship between BC and wind speed (WS) was found when WS was below 2.5 to 3.0 m s− 1, implying a local origin for BC. Mixed layer depths (MLDs) were shallower during BC episodes compared to cleaner conditions.  相似文献   

14.
Zhang  Xiaoyu  Ji  Guixiang  Peng  Xiaowu  Kong  Lingya  Zhao  Xin  Ying  Rongrong  Yin  Wenjun  Xu  Tian  Cheng  Juan  Wang  Lin 《Journal of Atmospheric Chemistry》2022,79(2):101-115

In this study, 123 PM2.5 filter samples were collected in Wuhan, Hubei province from December 2014 to November 2015. Water- soluble inorganic ions (WSIIs), elemental carbon (EC), organic carbon (OC) and inorganic elements were measured. Source apportionment and back trajectory was investigated by the positive matrix factorization (PMF) model and the hybrid single particle lagrangian integrated trajectory (HYSPLIT) model, respectively. The annual PM2.5 concentration was 80.5?±?38.2 μg/m3, with higher PM2.5 in winter and lower in summer. WSIIs, OC, EC, as well as elements contributed 46.8%, 14.8%, 6.7% and 8% to PM2.5 mass concentration, respectively. SO42?, NO3? and NH4+ were the dominant components, accounting for 40.2% of PM2.5 concentrations. S, K, Cl, Ba, Fe, Ca and I were the main inorganic elements, and accounted for 65.2% of the elemental composition. The ratio of NO3?/SO42? was 0.86?±?0.72, indicating that stationary sources play dominant role on PM2.5 concentration. The ratio of OC/EC was 2.9?±?1.4, suggesting the existence of secondary organic carbon (SOC). Five sources were identified using PMF model, which included secondary inorganic aerosols (SIA), coal combustion, industry, vehicle emission, fugitive dust. SIA, coal combustion, as well as industry were the dominant contributors to PM2.5 pollution, accounting for 34.7%, 20.5%, 19.6%, respectively.

  相似文献   

15.
Major ion concentrations and strontium isotopic ratios (87Sr/86Sr) were measured in rainwater samples collected at the urban site of Lanzhou, a city located on the Loess Plateau in the arid and semi-arid areas of northwest China. The rainwater samples possessed alkaline pH, at a reference level of 5.6, with a range of 6.82 to 8.28 and a volume-weighted mean (VWM) pH value of 7.70. The alkaline character of rainwater in Lanzhou is due to the result of neutralization caused by the alkaline soil dusts which contain large amount of CaCO3. It was observed that Ca2+ was the most abundant cation with a VWM value of 886 µeq l− 1 (115–2184 µeq l− 1), accounting for 87.8% of the total cations. Without considering HCO3−, SO42− and NO3− were dominant among the anions, accounting for 64.2% and 23.0%, respectively, of the total measured anions. Using Na as an indicator of marine origin and Al for terrestrial inputs, the proportions of sea salt and non-sea-salt elements were estimated from elemental ratios. The precipitation in this region has typical continental characteristics. The Sr concentrations varied from 0.004 to 0.885 µmol l− 1, and strontium isotopic ratios (87Sr/86Sr) lay in the range of 0.71025–0.71302, with an average of 0.71143. The 87Sr/86Sr ratios of Lanzhou rainwater are higher than that of seawater, which reflects contributions from the radiogenic Sr sources of the aerosols. The most suitable candidate for the source would be the soil dust originating from local and distant loess and desert areas. The 87Sr/86Sr ratios were used to characterize different sources of base cations in rainwater, suggesting that the samples could be interpreted in terms of combinations of at least three components: soil dust derived from the Loess Plateau and desert areas in northwest China (with 87Sr/86Sr ~ 0.7130), seawater (with 87Sr/86Sr ~ 0.70917), and anthropogenic inputs (with 87Sr/86Sr ~ 0.7103). The high 87Sr/86Sr ratio and Ca and Sr content in the rainwater from Lanzhou can be attributed to the dissolution of calcium carbonate in soil dust.  相似文献   

16.
The changing chemical composition of cloud water and precipitation in the Western Sudety Mountains are discussed against the background of air-pollution changes in the Black Triangle since the 1980s until September 2004. A marked reduction of sulphur dioxide emissions between the early 1990's and the present (from almost 2 million tons to around 0.2 million tons) has been observed, with a substantial decline of sulphate and hydrogen concentration in cloud water (SO42− from more than 200 to around 70 μmol l− 1; H+ from 150 to 50 μmol l− 1) and precipitation (SO42− from around 80 to 20–30 μmol l− 1; H+ from around 60 to 10–15 μmol l− 1) samples. At some sites, where fog/cloud becomes the major source of pollutants, deposition hot spots are still observed where, for example, nitrogen deposition can exceed 20 times the relevant critical load. The results show that monitoring of cloud water chemistry can be a sensitive indicator of pollutant emissions.  相似文献   

17.
Normal alkanes and PAHs in atmospheric PM10 aerosols collected during 2008 winter and spring in Baoji, a mid-scale inland city of China, were determined on a molecular level. Concentrations of n-alkanes ranged from 232 to 3583 ng/m3 with an average of 1733 ng/m3 in winter and from 124 to 1160 ng/m3 with an average of 449 ng/m3 in spring, while PAHs in the PM10 samples were 594 ± 405 and 128 ± 82 ng/m3 in the two seasons. Molecular compositions showed that CPI (odd/even) values of n-alkanes were close to unity for all the samples especially in winter, and diagnostic ratios of PAHs (e.g., Phe/(Phe + Ant), CPAH/ΣPAHs and IcdP/(IcdP + BghiP)) were found similar to those in coal burning smoke with a strong linear relationship (R2 ≥ 0.85) between PAHs and fossil fuel derived n-alkanes, demonstrating that coal burning is the main source of n-alkanes and PAHs in the city, especially in winter due to house heating. Concentrations of the determined compounds in Baoji are much higher than those in Chinese mega-cities, suggesting that air pollution in small cities in the country is more serious and need more attention.  相似文献   

18.
Beijing is one of the largest and most densely populated cities in China. PM2.5 (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 PM2.5 and to discuss the formation mechanisms of secondary particles, SO2, NO2, PM2.5, and chemical components of PM2.5 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+, NH4 +, NO3 ?, SO4 2?, Cl?, Al, Ca, Fe, Mg, Na, Pb, Si, and Zn, were selected for analysis. Overall, OC, SO4 2?, NO3 ?, and NH4 + 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 NH4 + 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 [NO3 ?]/[SO4 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 ([SO4 2?]/([SO4 2?] + [SO2])) and NOR ([NO3 ?]/([NO3 ?] + [NO2])) indicated that gas-phase oxidation reactions were the major formation mechanism of SO4 2? in spring and summer in urban Beijing, whereas slow gas-phase oxidation reactions and heterogeneous reactions both occurred in autumn and winter. NO3 ? was mainly formed through year-round heterogeneous reactions in urban Beijing.  相似文献   

19.
The main objective of this study is to investigate the chemical characteristics of biomass burning aerosol and its impact on regional air quality during an agricultural waste burning period in early summer in the rural areas of Korea. A 12-h integrated intensive sampling of biomass burning aerosol in the fine and coarse modes was conducted on 2–20 June 2003 in Gwangju, Korea. The collected samples were analyzed for concentrations of mass, ionic, elemental, and carbonaceous species. Average concentrations of fine and coarse mass were measured to be 67.9 and 18.7 μg m− 3 during the biomass burning period, 41.9 and 18.8 μg m− 3 during the haze period, and 35.6 and 13.3 μg m− 3 during the normal period, respectively. An exceptionally high PM2.5 concentration of 110.3 μg m− 3 with a PM2.5/PM10 ratio of 0.79 was observed on 6 June 2003 during the biomass burning period. The potassium ratio method was used to identify biomass burning samples. The average ratio of potassium in the fine mode to the coarse mode (FK/CK) was 23.8 during the biomass burning period, 6.0 during the haze period, and 4.7 during the normal period, respectively. A FK/CK ratio above 9.2 was considered a criterion for biomass burning event in this study. Particulate matter from the open field burning of agricultural waste has an adverse impact on visibility, human health, and regional air quality.  相似文献   

20.
In November 2004–January 2005, a micro orifice uniform deposit impactor (MOUDI) and a Nanometer (nanometer)-MOUDI were used in the center of Taiwan to measure particle size (18 nm particle size 18 μm) distributions of atmospheric aerosols at a traffic site during the winter period. The average Mass in Media Aerodynamic Diameter (MMAD) of suspended particles is 0.99 μm this study. As for the ultra fine and nanometer (nanometer) particle mode, the composition order for these major ions species was SO42− NH4+ NO3− Mg2+ Ca2+ Na+ K+ Cl−. An ion Chromatography (DIONEX-100) was used to analyze major anion species, Cl−, NO3−, SO42− and cation species, NH4+Na+, K+, Ca2+Mg2+. Their concentrations were also extracted from various particles size modes (nanometer (nanometer), ultra fine, fine and coarse). The results obtained in this study also indicated that the average portions for the major ionic species (SO42−, NH4+ and Mg2+) in the nanometer (nanometer), ultra fine, fine and coarse particulate modes are about 34%, 37%, 63% and 30%, respectively at this traffic sampling site during the winter period.  相似文献   

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