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1.
The contribution of emissions from agricultural facilities is rapidly becoming a major concern for local and regional air
quality. Characterization of particle properties such as physical size distribution and chemical composition can be valuable
in understanding the processes contributing to emissions and ultimate fate of particulate matter from agricultural facilities.
A measurement campaign was conducted at an Iowa, deep-pit, three-barn swine finishing facility to characterize near-source
ambient particulate matter. Size-specific mass concentrations were determined using minivol samplers, with additional size
distribution information obtain using optical particle counters. Particulate composition was determined via ion chromatographic
analysis of the collected filters. A thermal-CO 2 elemental/organic carbon analyzer measured particulate carbon. The chemical composition and size distribution of sub-micron
particles were determined via real-time aerosol mass spectrometry. Primary particulate was not found to be a major emission
from the examined facility, with filter-based impactor samples showing average near-source increases (~15–50 m) in ambient
PM 10 of 5.8 ± 2.9 μg m −3 above background levels. PM 2.5 also showed contribution attributable to the facility (1.7 ± 1.1 μg m −3). Optical particle counter analysis of the numerical size distributions showed bimodal distributions for both the upwind
and downwind conditions, with maximums around 2.5 μm and below the minimum quantified diameter of 0.3 μm. The distributions
showed increased numbers of coarse particles (PM 10) during periods when wind transport came from the barns, but the differences were not statistically significant at the 95%
confidence level. The PM 10 aerosols showed statistically increased concentrations of sulfate, nitrate, ammonium, calcium, organic carbon, and elemental
carbon when the samplers were downwind from the pig barns. Organic carbon was the major constituent of the barn-impacted particulate
matter in both sub-micron (54%) and coarse size (20%) ranges. The AMS PM 1 chemical speciation showed similar species increases, with the exception of and Ca +2, the latter not quantified by the AMS. 相似文献
2.
The concentrations of PM 10, PM 2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi
(28.63° N, 77.18° E), India. The annual mean PM 10 and PM 2.5 concentrations (± standard deviation) were about 219 (± 84) and 97 (±56) μgm −3 respectively, about twice the prescribed Indian National Ambient Air Quality Standards values. The monthly average ratio
of PM 2.5/PM 10 varied between 0.18 (June) and 0.86 (February) with an annual mean of ∼0.48 (±0.2), suggesting the dominance of coarser in
summer and fine size particles in winter. The difference between the concentrations of PM 10 and PM 2.5, is deemed as the contribution of the coarse fraction (PM 10−2.5). The analyzed coarse fractions mainly composed of secondary inorganic aerosols species (16.0 μgm −3, 13.07%), mineral matter (12.32 μgm −3, 10.06%) and salt particles (4.92 μgm −3, 4.02%). PM 2.5 are mainly made up of undetermined fractions (39.46 μgm −3, 40.9%), secondary inorganic aerosols (26.15 μgm −3, 27.1%), salt aerosols (22.48 μgm −3, 23.3%) and mineral matter (8.41 μgm −3, 8.7%). The black carbon aerosols concentrations measured at a nearby (∼300 m) location to aerosol sampling site, registered
an annual mean of ∼14 (±12) μgm −3, which is significantly large compared to those observed at other locations in India. The source identifications are made
for the ionic species in PM 10 and PM 2.5. The results are discussed by way of correlations and factor analyses. The significant correlations of Cl −, SO 42−, K +, Na +, Ca 2+, NO 3− and Mg 2+ with PM 2.5 on one hand and Mg 2+ with PM 10 on the other suggest the dominance of anthropogenic and soil origin aerosols in Delhi. 相似文献
3.
The fractions of local traffic (LT), urban background (UBG) and regional background (RBG) of the particle pollution at a traffic-influenced
kerbside in Dresden, Germany, were determined by measurements of size-segregated mass concentration, chemical composition
and particle size distributions in a network of five measurement stations partly existing and partly set up for this study.
Besides the kerbside station, one urban background site and three rural sites were included in the study. Using data from
these different sites, the LT, UBG, and RBG contributions were calculated, following the approach of Lenschow et al. ( 2001). At the kerbside site, 19% of the total number concentration (Dp St = 10–600 nm) could be attributed to the RBG, 15% to the UBG, and 66% to the LT immediately nearby. Particle mass concentrations
up to Dp aer = 420 nm RBG amounts to 68%, UBG to 21%, and LT only to 11%. Highest mass concentrations were observed at all stations in
autumn and winter during easterly inflow directions. The local traffic fraction of PM 10 mass at the kerbside station was found to be 30% for westerly inflow, but only 7% for southeasterly inflow due to the dominating
transport fraction from up to 80% of the particle mass at this inflow direction. Size-resolved investigation showed the main
fractions in both the particle size ranges of Dp aer = 0.42 to 1.2 and 0.14 to 0.42 μm at all stations. The main components sulphate, ammonium and total carbon showed higher
concentrations at south-eastern/eastern inflow in autumn at all stations, while nitrate at the kerbside and urban background
site was higher during westerly inflow in winter. The chemical composition at the regional background site at westerly inflow
(12% nitrate, 8% sulphate, 11% total carbon) was significantly different from that at easterly inflow (3% nitrate, 15% sulphate,
22% total carbon). The prevailing part of the ionic mass was always found in the fine particle range of Dp aer = 0.14 to 1.2 μm at all stations. For all inflow directions highest total carbon concentrations were observed at the kerbside
station, especially in the ultra-fine size range of Dp aer = 0.05 to 0.14 μm with up to 30% of the whole carbon. PAH concentrations were always higher at south-eastern/eastern inflow
especially during wintertime. Trace metal components and silicon were found mainly in the coarse mode fraction at the kerbside
resulting from abrasion or resuspension. 相似文献
4.
Long-term measurements of ambient particulate matter less than 2.5 μm in diameter (PM 2.5) and its chemical compositions were performed at a rural site in Korea from December 2005 to August 2009. The average PM 2.5 concentration was 31 μg m −3 for the whole sampling period, and showed a slightly downward annual trend. The major components of PM 2.5 were organic carbon, SO 42−, NO 3−, and NH 4+, which accounted for 55 % of total PM 2.5 mass on average. For the top 10 % of PM 2.5 samples, anionic constituents and trace elements clearly increased while carbonaceous constituents and NH 4+ remained relatively constant. Both Asian dust and fog events clearly increased PM 2.5 concentrations, but affected its chemical composition differently. While trace elements significantly increased during Asian
dust events, NO 3−, NH 4+ and Cl were dramatically enhanced during fog events due to the formation of saturated or supersaturated salt solution. The
back-trajectory based model, PSCF (Potential Source Contribution Function) identified the major industrial areas in Eastern
China as the possible source areas for the high PM 2.5 concentrations at the sampling site. Using factor analysis, soil, combustion processes, non-metal manufacture, and secondary
PM 2.5 sources accounted for 77 % of the total explained variance. 相似文献
5.
PM 10 samples were collected over three years at Monzenmachi, the Japan Sea coast, the Noto Peninsula, Ishikawa, Japan from January
17, 2001 to December 18, 2003, using a high volume air sampler with quartz filters. The concentrations of the water-soluble
inorganic ions in PM 10 were determined with using ion chromatography. By analyzing the characteristics of these, the evidences were found that the
Asian outflow had an obviously influence on the air quality at our study site. The results were as follows: the secondary
pollutants SO 42−, NO 3− and NH 4+ were the primary water-soluble inorganic ions at our study site. The monthly mean concentrations of SO 42−, NH 4+, NO 3− and Ca 2+ have prominent peak in spring due to the strong influence of the Asian continent outflow—these according to backward air
trajectory analysis, the maximum of which were 6.09 for nss-SO 42− in May, 2.87 for NO 3− and 0.68 μg m −3 for nss-Ca 2+ in April, respectively. Comparable to similar data reported from various points around East Asia, it had the characteristics
of a polluted coastal area at our study site. The concentration of nss-Ca 2+ in PM 10 drastically increased when the Asian dust invaded, the mean value during the Asian dust days(AD) was 0.86 μg m −3, about 4 times higher than those of normal days (NAD). Meanwhile, the mean concentrations of nss-SO 42−, NO 3− and NH 4+ in AD periods were higher than those in NAD periods which were 5.87, 1.76 and 1.82 μg m −3, respectively, it is due to the interaction between dust and secondary particles during the long-range transport of dust
storms. Finally, according to the source apportionment with positive matrix factorization (PMF) method in this study, the
major source profiles of PM 10 at our study site were categorized as (1) marine salt, (2) secondary sulfate, (3) secondary nitrate and (4) crustal source. 相似文献
6.
The new European Council Directive (PE-CONS 3696/07) frames the inhalable (PM 10) and fine particles (PM 2.5) on priority to chemically characterize these fractions in order to understand their possible relation with health effects.
Considering this, PM 2.5 was collected during four different seasons to evaluate the relative abundance of bulk elements (Cl, S, Si, Al, Br, Cu, Fe,
Ti, Ca, K, Pb, Zn, Ni, Mn, Cr and V) and water soluble ions (F −, Cl −, NO 2
−, NO 3
−, SO 4
2−, Na +, NH 4
+, Ca 2+ and Mg 2+) over Menen, a Belgian city near the French border. The air quality over Menen is influenced by industrialized regions on
both sides of the border. The most abundant ionic species were NO 3
−, SO 4
2− and NH 4
+, and they showed distinct seasonal variation. The elevated levels of NO 3
− during spring and summer were found to be related to the larger availability of the NO x precursor. The various elemental species analyzed were distinguished into crustal and anthropogenic source categories. The
dominating elements were S and Cl in the PM 2.5 particles. The anthropogenic fraction (e.g. Zn, Pb, and Cu) shows a more scattered abundance. Furthermore, the ions and elemental
data were also processed using principal component analysis and cluster analysis to identify their sources and chemistry.
These approach identifies anthropogenic (traffic and industrial) emissions as a major source for fine particles. The variations
in the natural/anthropogenic fractions of PM 2.5 were also found to be a function of meteorological conditions as well as of long-range transport of air masses from the industrialized
regions of the continent.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
The kinetics of heterogeneous reactions of NO 2 with 17 polycyclic aromatic hydrocarbons (PAHs) adsorbed on laboratory generated kerosene soot surface was studied over the
temperature range (255–330) K in a low pressure flow reactor combined with an electron-impact mass spectrometer. The kinetics
of soot-bound PAH consumption due to their desorption and reaction with NO 2 were monitored using off-line HPLC measurements of their concentrations in soot samples as a function of reaction time, NO 2 concentrations in the gas phase being analyzed by mass spectrometer. No measurable decay of PAHs due to the reaction with
NO 2 was observed under experimental conditions of the study (maximum NO 2 concentration of 5.5 × 10 14 molecule cm −3 and reaction time of 45 min), which allowed to determine the upper limits of the first-order rate constants for the heterogeneous
reactions of 17 soot-bound PAHs with NO 2: k < 5.0 × 10 −5 s −1 (for most PAHs studied). Comparison of these results to previous studies carried on different carbonaceous substrates, showed
that heterogeneous reactivity of PAHs towards NO 2 is, probably, dependent on the substrate nature even for resembling, although different carbonaceous materials. Results show
that particulate PAHs degradation by NO 2 alone is of minor importance in the atmosphere 相似文献
8.
We present mobile vehicle lidar observations in Tianjin, China during the spring, summer, and winter of 2016. Mobile observations were carried out along the city border road of Tianjin to obtain the vertical distribution characteristics of PM 2.5. Hygroscopic growth was not considered since relative humidity was less than 60% during the observation experiments. PM 2.5 profile was obtained with the linear regression equation between the particle extinction coefficient and PM 2.5 mass concentration. In spring, the vertical distribution of PM 2.5 exhibited a hierarchical structure. In addition to a layer of particles that gathered near the ground, a portion of particles floated at 0.6–2.5-km height. In summer and winter, the fine particles basically gathered below 1 km near the ground. In spring and summer, the concentration of fine particles in the south was higher than that in the north because of the influence of south wind. In winter, the distribution of fine particles was opposite to that measured during spring and summer. High concentrations of PM 2.5 were observed in the rural areas of North Tianjin with a maximum of 350 μg m –3 on 13 December 2016. It is shown that industrial and ship emissions in spring and summer and coal combustion in winter were the major sources of fine particles that polluted Tianjin. The results provide insights into the mechanisms of haze formation and the effects of meteorological conditions during haze–fog pollution episodes in the Tianjin area. 相似文献
9.
Ambient respirable particles (PM 10; aerodynamic diameter ≤10 μm) collected in a tropical urban environment (Delhi, India) during December 2008-November 2009
were characterized with respect to 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) and 8 major and trace metals
(Fe, Mn, Cd, Cu, Ni, Pb, Zn and Cr). Concentrations of Σ 16PAHs (annual mean: 74.7 ± 50.7 ng m −3, range 22.1–258.4 ng m −3) and most metallic species were at least an order of magnitude greater than values reported from similar locations worldwide.
Seasonal variations in Σ 16PAHs were significant ( p < 0.001) with highest levels in winter while crustal and anthropogenic metals showed significant but mutually opposite seasonal
dependence. Statistically significant associations were observed between chemical species and various meteorological parameters.
The PAH profile was dominated by combustion-derived large-ring species (~85%) that were essentially local in origin. Principal
component analysis–multiple linear regression (PCA-MLR) apportioned four sources: crustal dust (73%), vehicular emission (21%),
coal combustion (4%) and industrial emission (2%) that was further validated by hierarchical cluster analysis (HCA). Temporal
trend analysis showed that crustal sources were predominant in summer ( p < 0.05) while the remaining sources were most active in winter. Summertime intrusions of Saharan dust were identified with
the help of aerosol maps and air parcel backward trajectories. Inhalation cancer risk assessment showed that up to 3,907 excess
cancer cases (357 for PAHs, 122 for Cd, 2040 for Cr (VI) and 1387 for Ni) are likely in Delhi considering lifetime inhalation
exposure to these chemicals at their current concentrations. 相似文献
10.
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
11.
The levels of carbonyl compounds in Shanghai ambient air were measured in five periods from January 2007 to October 2007 (covering
winter, high-air-pollution days, spring, summer and autumn). A total of 114 samples were collected and eighteen carbonyls
were identified. Formaldehyde, acetaldehyde and acetone were the most abundant carbonyls and their mean concentrations of
19.40 ± 12.00, 15.92 ± 12.07 and 11.86 ± 7.04 μg m −3 respectively, in the daytime for five sampling periods. Formaldehyde and acetaldehyde showed similar diurnal profiles with
peak mixing ratios in the morning and early afternoon during the daytime. Their mean concentrations were highest in summer
and lowest in winter. Acetone showed reversed seasonal variation. The high molecular weight (HMW, ≥C5) carbonyls also showed
obvious diurnal variations with higher concentrations in the daytime in summer and autumn, while they were all not detected
in winter. Formaldehyde and acetaldehyde played an important role in removing OH radicals in the atmosphere, but the contribution
of acetone was below 1%. The carbonyls levels in high-air-pollution days were reported. More carbonyl species with higher
concentrations were found in high-air-pollution days than in spring. These carbonyls were transported with other pollutants
from north and northwest in March 27 to April 2, 2007 and then mixed with local sources. Comparing with Beijing and Guangzhou,
the concentrations of formaldehyde and acetaldehyde in Shanghai were the highest, which indicated that the air pollution in
Shanghai was even worse than expected. 相似文献
12.
Both aerosol and rainwater samples were collected and analyzed for ionic species at a coastal site in Southeast Asia over
a period of 9 months (January–September 2006) covering different monsoons. In general, the occurrence and distribution of
ionic species showed a distinct seasonal variation in response to changes in air mass origins. Real-time physical characterization
of aerosol particles during rain events showed changes in particle number distributions which were used to assess particle
removal processes associated with precipitation, or scavenging. The mean scavenging coefficients for particles in the range
10–500 nm and 500–10 μm were 7.0 × 10 −5 ± 2.8 × 10 −5 s −1 and 1.9 × 10 −4 ± 1.6 × 10 −5 s −1, respectively. A critical analysis of the scavenging coefficients obtained from this study suggested that the wet removal
of aerosol particles was greatly influenced by rain intensity, and was particle size-dependent as well. The scavenging ratios,
another parameter used to characterize particle removal processes by precipitation, for NH 4
+, Cl −, SO 4
2−, and NO 3
− were found to be higher than those of Na +, K +, and Ca 2+ of oceanic and crustal origins. This enrichment implied that gaseous species NH 3, HCl, and HNO 3 could also be washed out readily. These additional sources of ions in precipitation presumably counter-balanced the dilution
effect caused by high total precipitation volume in the marine and tropical area. 相似文献
13.
Summary Measurements of landscape-scale methane emission were made over an aapa mire near Kaamanen in Finnish Lapland (69° 8′ N,
27° 16′ E, 155 m ASL). Emissions were measured during the spring thaw, in summer and in autumn. No effect of water table position
on CH 4 emission was found as the water table remained at or above the surface of the peat. Methane emission fluxes increased with
surface temperature from which an activation energy of −99 kJ mol −1 was obtained. Annual emission from the site, modelled from temperature regression and short-term flux measurements made in
three separate years, was calculated to be 5.5 ± 0.4 g CH 4 m −2 y −1 of which 0.6 ± 0.1 g CH 4 m −2 y −1 (11%) was released during the spring thaw which lasted 20 to 30 days.
The effect of global warming on the CH 4 budget of the site was estimated using the central scenario of the SILMU (Finnish Research Programme on Climate Change) model
which predicts annual mean temperature increases of 1.2, 2.4 and 4.4 °C in 2020, 2050 and 2100, respectively. Maximum enhancements
in CH 4 emission due to warming were calculated to be 18, 40 and 84% for 2020, 2050 and 2100, respectively. Actual increases may
be smaller because prediction of changes in water table are highly uncertain.
Received September 17, 1999 Revised October 16, 2000 相似文献
14.
Size segregated sampling of aerosol particles at the coal-fired power station Šoštanj, Slovenia was performed by a newly developed
system. In addition, simultaneous sampling of particles was performed at two locations, Velenje and Veliki vrh, chosen on
the basis of long term monitoring of SO 2 in the influential area of power plant. The signature of the power plant (e.g. characteristic size distributions of some
typical trace elements) was identified. For elements, like As, Mo, Cd and Ga, which are typical for coal combustion, the highest
concentrations were observed in the size range between 1 and 4 μm. For Se and sometimes for Ga two modes were identified,
first between 0.1 and 0.5 μm and second between 1 and 4 μm. Ratios between the average concentrations of selected elements
in fine and coarse particles collected at Veliki vrh (the most influenced location) and Velenje (usually not influenced by
the thermo power station) were significantly higher than 1 in the case of Mo and Se for coarse and fine size range, while
for As the ratio was higher than 1 for the coarse fraction. Consequently, Mo, Se and As were found as the most important tracers
for the emissions from the investigated source. On the basis of the ratios between the concentrations of elements measured
in particles at low and high SO 2 concentrations at Veliki vrh, Cd was shown to be a typical tracer as well. Our results definitely showed that size segregated
measurements of particles at the source and in the influenced area give more precise information on the influence of source
to the surrounding region. It was found that patterns of size distributions for typical trace elements observed at the source
are found also in the influenced area, i.e. Veliki vrh. 相似文献
15.
This paper deals with the atmospheric concentrations of PM 5 and PM 2.5 particulate matter and its water soluble constituents along with the size distribution of ions and spatial variation at three
different residential environments in a semiarid region in India. Samples were collected from the indoors and outdoors of
urban, rural and roadside sites of Agra during October 2007–March 2008. The mean concentrations of PM 2.5 indoors and outdoors were 178 μgm −3 and 195 μgm −3 while the mean concentrations of PM 5 indoors and outdoors were 231.8 μgm −3 and 265.2 μgm −3 respectively. Out of the total aerosol mass, water soluble constituents contributed an average of 80% (33% anions, 50% cations)
in PM 5 and 70% (29% anions, 43% cations) in PM 2.5. The indoor–outdoor ratio of water soluble components suggested additional aerosol indoor sources at rural and roadside sites.
Indoor–outdoor correlations were also determined which show poor relationships among concentrations of aerosol ions at all
three sites. Univariate Pearson correlation coefficients among water soluble aerosols were determined to evaluate the relationship
between aerosol ions in indoor and outdoor air. 相似文献
16.
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
17.
Daily measurements of atmospheric aerosol characteristics were carried out in Dolgoprudny (Moscow region) in June–August 2010.
The particle concentrations at 11 size gradations within the range of 0.01–10 μm and the concentrations of cloud condensation
nuclei active at water vapor supersaturation of 0.2–1% were determined. It is shown that the long anticyclonic conditions
and the burning of forests and peat bogs resulted in the increase in total aerosol concentration in surface air by more than
1.5 times and in concentrations of particles with the diameter of 0.1–1 μm and > 1 μm by 5 and 10 times, respectively. The
fire smoke mainly consisted of the particles with the size of 0.1–3 μm. The particles with the size of more than 5 μm were
not observed. The recurrent visibility decrease up to hundreds of meters was caused by the increase in the concentration of
particles with the diameter of more than 0.32μm in the air. During the smoke blanketing, the concentration of active condensation
nuclei in aerosol increased almost by 20 times that created an opportunity for watering of aerosol particles and formation
of the acid smog. 相似文献
18.
Five aromatic hydrocarbons – benzene, toluene, ethylbenzene, p-xylene and 1,2,4-trimethylbenzene – were selected to investigate the laser desorption/ionization mass spectra of secondary
organic aerosols (SOA) resulting from OH-initiated photooxidation of aromatic compounds. The experiments were conducted by
irradiating aromatic hydrocarbon/CH 3ONO/NO
X
mixtures in a home-made smog chamber. The aerosol time-of-flight mass spectrometer (ATOFMS) was used to measure the aerodynamic
size and chemical composition of individual secondary organic aerosol particles in real-time. Experimental results showed
that aerosol created by aromatics photooxidation is predominantly in the form of fine particles, which have diameters less
than 2.5 μm (i.e. PM2.5), and different aromatic hydrocarbons SOA mass spectra have eight same positive laser desorption/ionization
mass spectra peaks: m/z = 18, 29, 43, 44, 46, 57, 67, 77. These mass spectra peaks may come from the fragment ions of the
SOA products: oxo-carboxylic acids, aldehydes and ketones, nitrogenated organic compounds, furanoid and aromatic compounds.
The possible reaction mechanisms leading to these products were also discussed. 相似文献
19.
Aerosol and rain samples were collected between 48°N and 55°S during the KH-08-2 and MR08-06 cruises conducted over the North
and South Pacific Ocean in 2008 and 2009, to estimate dry and wet deposition fluxes of atmospheric inorganic nitrogen (N).
Inorganic N in aerosols was composed of ~68% NH 4+ and ~32% NO 3– (median values for all data), with ~81% and ~45% of each species being present on fine mode aerosol, respectively. Concentrations
of NH 4+ and NO 3− in rainwater ranged from 1.7–55 μmol L −1 and 0.16–18 μmol L −1, respectively, accounting for ~87% by NH 4+ and ~13% by NO 3− of total inorganic N (median values for all data). A significant correlation ( r = 0.74, p < 0.05, n = 10) between NH 4+ and methanesulfonic acid (MSA) was found in rainwater samples collected over the South Pacific, whereas no significant correlations
were found between NH 4+ and MSA in rainwater collected over the subarctic ( r = 0.42, p > 0.1, n = 6) and subtropical ( r = 0.33, p > 0.5, n = 6) western North Pacific, suggesting that emissions of ammonia (NH 3) by marine biological activity from the ocean could become a significant source of NH 4+ over the South Pacific. While NO 3− was the dominant inorganic N species in dry deposition, inorganic N supplied to surface waters by wet deposition was predominantly
by NH 4+ (42–99% of the wet deposition fluxes for total inorganic N). We estimated mean total (dry + wet) deposition fluxes of atmospheric
total inorganic N in the Pacific Ocean to be 32–64 μmol m −2 d −1, with 66–99% of this by wet deposition, indicating that wet deposition plays a more important role in the supply of atmospheric
inorganic N than dry deposition. 相似文献
20.
Epidemiological studies initially considered the impact of total solid particles on human health, but according to the acquired
knowledge about the worse effect of smaller particles, those studies turned to consider the impact of PM 10. However, for the last decade PM 2.5 began to be more important, once as they are smaller they can penetrate deeper in the lungs, being possible their trapping
in alveoli and worse effects on human health. Therefore, more information on PM 2.5 should be provided namely concerning the levels and elemental composition. Considering the relevance of traffic on the emission
of particles of small sizes, this work included the detailed characterization of PM 10 and PM 2.5, sampled at two sites directly influenced by traffic, as well as at two reference sites, aiming a further evaluation of the
influence of PM 10 and PM 2.5 on public health. The specific objectives were to study the influence of traffic emission on PM 10 and PM 2.5 characteristics, considering concentration, size distribution and elemental composition. PM 10 and PM 2.5 samples were collected using low-volume samplers; the element analyses were performed by particle induced X-ray emission
(PIXE). At the sites influenced by traffic emissions PM 10 and PM 2.5 concentrations were 7–9 and 6–7 times higher than at the background sites. The presence of 17 elements (Mg, Al, Si, P, S,
Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb) was determined in both PM fractions; particle metal contents were 3–44 and
3–27 times higher for PM 10 and PM 2.5, respectively, than at the backgrounds sites. The elements originated mostly from anthropogenic activities (S, K, V, Mn,
Ni, Zn and Pb) were predominantly present in PM 2.5, while the elements mostly originated from crust (Mg, Al, Si and Ca) predominantly occurred in PM 2.5–10. The results also showed that in coastal areas sea salt spray is an important source of particles, influencing PM concentration
and distributions (PM 10 increased by 46%, PM 2.5/PM 10 decreased by 26%), as well as PM compositions (Cl in PM 10 was 11 times higher). 相似文献
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