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1.
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   

2.
Black carbon concentration and weather data were online monitored continuously from March 2008 to February 2009 at the Akedala regional atmosphere station in the arid region of Central Asia. We present the daily, monthly and seasonal variations of BC concentration in the atmosphere and discuss the possible emission sources. Black carbon concentration in this region varies in the range of 43.7–1,559.2?ng/m3. A remarkable seasonal variation of BC in the aerosol was observed in the order of winter?>?spring?>?autumn?>?summer. The peak value of BC appeared at 10:00–13:00 while the lowest one at 7:00–9:00 each day. Air masses backward trajectories show the potential emission sources in the northwest from spring to autumn. Through back trajectory also revealed that BC in winter might be attributed to the emission from the anthropogenic activities, including domestic heating, cooking, combustion of oil and natural gas, and the medium-range transport from those cities in northern slope of Tianshan Mountains and Siberia. Some BC aerosols from the arid region of Central Asia were transported to the Pacific Ocean by the Westerlies.  相似文献   

3.
Carbon monoxide (CO), Ozone (O3) and Black Carbon (BC) aerosol mass concentrations in relation to planetary boundary layer (PBL) height measurements were analyzed from January–December, 2008 over tropical urban environment of Hyderabad, India. DMSP-OLS night-time satellite data were analyzed for fire occurrence over the region and its correlation with pollution concentrations over the urban region. Results of the study suggested considerable increase in CO and BC concentrations during early morning hours. Higher concentration of BC, CO and ozone was observed during pre-monsoon, post-monsoon and winter and lowest concentrations exhibited during monsoon season. NCEP/NCAR reanalysis winds suggested long range transport of aerosols and trace gases from forest fires are enhancing the pollutant concentrations over the study area.  相似文献   

4.
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   

5.
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   

6.
Direct physical measurements of particle mass and number concentration indicate an increase in overall aerosol mass resulting from cloud processing, most likely through aqueous-phase chemistry (e.g., SO2 oxidation). Measurements conducted in the Pennines of Northern England reveal an average increase of 14 to 20% in dry aerosol mass (0.003<particle diameter<0.9 μm) after aerosol passage through an orographic cloud. The rate of in-cloud mass production is most sensitive to changes in upwind particle size distributions, SO2 concentration, and cloud water acidity. Newly-formed mass appears in size range between 200 and 600 nm and enhances the bimodality of the particle number distribution after cloud processing. Furthermore, the cloud-produced mass is estimated to increase total light scattering, bsp, by 18 to 24%. The scattering efficiency of the dry, cloud-generated aerosol is 5.0±0.3 m2 g−1 and increases to 7.4±0.7 m2 g−1 when adjusted to 90% relative humidity by incorporating particle hygroscopicity data.  相似文献   

7.
Black carbon (BC) mass concentration variation has been studied, over a period of 2 years (June 2010–May 2012) at Bhubaneswar. Daily, monthly and seasonal measurements revealed a clear winter maxima (5.6 μg/m3) of BC followed by post-monsoon (4.05 μg/m3), monsoon (3.02 μg/m3) and pre-monsoon (2.46 μg/m3). Nighttime BC mass concentrations have been found to be distinctly higher during winter followed by post-monsoon and monsoon. Investigations reveal that the winter maxima are due to a stable atmospheric condition and long-range transport over the Indo-Gangetic Plain and Western Asia. Local boundary layer dynamics and anthropogenic activities have been assumed to have a pronounced effect on the diurnal cycle seasonally. Statistical analysis suggests significant variation of BC during the months and non-significant during the days. The study also gives an insight into importance of BC study from health angle and suggests an assessment and management framework. Source apportionment study suggests that BC mass concentration observed at Bhubaneswar is generally dominated by fossil fuel combustion.  相似文献   

8.
During the second Arctic Gas and Aerosol Sampling Program conducted in April 1986, we performed measurements of the optically absorbing carbonaceous component of the ambient aerosol from the NOAA WP-3D aircraft operating between sea level and 10 km altitude. We collected the aerosol of filters that were exposed for several hours; we also operated the aethalometer to measure the concentration of aerosol black carbon in real time. The filter analyses represent averages over the altitude range and time span during which the filter was collecting. The real-time results were sorted by altitude to calculate vertical profiles of black carbon concentration. Values typically ranged from 300 to 500 ng m–3 at lower altitudes, decreasing gradually to 25 to 100 ng m–3 at 8–10 km. Strong stratification at lower altitudes was frequently observed. The magnitude of these concentrations suggests that the sources are distant regions of considerable fuel consumption. The presence of this material in the tropospheric column and its probable deposition to the high-albedo surface may result in perturbations of the solar radiation balance. The concentrations measured at the highest altitudes may mean that particulate carbon and accompanying emissions for which it is a tracer are mixing into the stratosphere.  相似文献   

9.
The physical and chemical properties of aerosol particles were investigated at Plan d'Aups, one of the ESCOMPTE sites located in the St. Baume mountain area (700 m a.s.l.), 50 km east of Marseilles (France). The site is ideally located for assessing the vertical and horizontal extent of the pollution plume from the Marseilles–Berre area.Our study showed that polluted air masses from the Marseilles–Berre area are advected to Plan d'Aups in the early afternoon. Average daily concentration of particles reaches up to 40 μg m−3 while 1-h average particle number concentration is greater than 30,000 cm−3. Most of the particle mass is composed of SO42− and organic carbon (OC). The chemical properties of the particles revealed that an additional source, possibly from the industrial area of Gardanne, contributes to the aerosol mass. This last source is characterised by significant emissions of elements, such as Zn, V, Al and Si.In addition to transport, we found that gas-to-particle conversion takes place at the interface between the free troposphere and the boundary layer. We estimated that on average, 30% of the particle number is accounted for by direct nucleation. This is potentially a major aerosol source to the free troposphere.  相似文献   

10.
In this study, a regional air quality model system (RAQMS) was applied to investigate the spatial distributions and seasonal variations of atmospheric aerosols in 2006 over East Asia. Model validations demonstrated that RAQMS was able to reproduce the evolution processes of aerosol components reasonably well. Ground-level PM10 (particles with aerodynamic diameter ≤10 μm) concentrations were highest in spring and lowest in summer and were characterized by three maximum centers: the Taklimakan Desert (～1000 μg m-3), the Gobi Desert (～400 μg m-3), and the Huabei Plain (～300 μm-3) of China. Vertically, high PM10 concentrations ranging from 100 μg m-3 to 250 μg m-3 occurred from the surface to an altitude of 6000 m at 30o--45oN in spring. In winter, the vertical gradient was so large that most aerosols were restricted in the boundary layer. Both sulfate and ammonium reached their highest concentrations in autumn, while nitrate reached its maximum level in winter. Black carbon and organic carbon aerosol concentrations reached maximums in winter. Soil dust were strongest in spring, whereas sea salt exerted the strongest influence on the coastal regions of eastern China in summer. The estimated burden of anthropogenic aerosols was largest in winter (1621 Gg) and smallest in summer (1040 Gg). The sulfate burden accounted for ～42% of the total anthropogenic aerosol burden. The dust burden was about twice the anthropogenic aerosol burden, implying the potentially important impacts of the natural aerosols on air quality and climate over East Asia.  相似文献   

11.
Volatile organic compounds (VOCs) emissions by vegetation present in the Mediterranean area are not well known. They may contribute with anthropogenic VOC emissions to the tropospheric ozone formation that reaches important level in the European Mediterranean region. The present work, carried out as part of the European ESCOMPTE project «fiEld experimentS to COnstrain Models of atmospheric Pollution and Transport of Emissions», adds a new contribution to the inventory of the main natural hydrocarbons sources likely to participate in the ozone production. The corresponding measurement campaign was conducted in La Barben, a site close to Marseilles (France), with the aim to quantify the terpenic emission pattern and the behaviour of Pinus halepensis, an important Mediterranean species slightly studied.The determination of biogenic emissions from P. halepensis was done by the enclosure of an intact branch in a Teflon cuvette. Main emitted monoterpenes were β trans-ocimene and linalool. The total monoterpenic emission rates thus recorded were found to reach maximum values around 30 μg gdry weight−1 h−1. The normalized emission rates calculated at 30 °C and 1000 μmol m−2 s−1 with Guenther's algorithm was 14.76, 8.65 and 4.05 μg gdry weight−1 h−1, respectively, for the total monoterpenes, β trans-ocimene and linalool.  相似文献   

12.
On February 8, 1993, the NASA DC-8 aircraft profiled from 10,000 to 37,000 feet (3.1–11.3 km) pressure altitude in a stratified section of tropical cyclone “Oliver” over the Coral Sea northeast of Australia. Size, shape and phase of cloud and precipitation particles were measured with a 2-D Greyscale probe. Cloud/ precipitation particles changed from liquid to ice as soon as the freezing level was reached near 17,000 feet (5.2 km) pressure altitude. The cloud was completely glaciated at −5°C. There was no correlation between ice particle habit and ambient temperature. In the liquid phase, the precipitation-cloud drop concentration was 4.0 × 103 m−3, the geometric mean diameter Dg=0.5−0.7 mm, and the liquid water content 0.7−1.9 g m−3. The largest particles anywhere in the cloud, dominated by fused dendrites at concentrations similar to that of raindrops (2.5 × 103 m−3) but a higher condensed water content (5.4 g m−3 estimated) were found in the mixed phase; condensed water is removed very effectively from the mixed layer due to high settling velocities of the large mixed particles. The highest number concentration (4.9 × 104 m−3), smallest size (Dg=0.3−0.4 mm), largest surface area (up to 2.6 × 102 cm2 m−3 at 0.4−1.0 g m−3 of condensate) existed in the ice phase at the coldest temperature (−40°C) at 35,000 feet (10.7 km). Each cloud contained aerosol (haze particles) in addition to cloud particles. The aerosol total surface area exceeded that of the cirrus particles at the coldest temperature. Thus, aerosols must play a significant role in the upscattering of solar radiation. Light extinction (6.2 km−1) and backscatter (0.8 sr−1 km−1) was highest in the coldest portion of the cirrus cloud at the highest altitude.  相似文献   

13.
The potential resources on the ion-stimulated syntheses effects of aerosol particles of lower troposphere in test sites in the arctic, mountain, arid and forest areas as the function of irradiation time and gas-precursor concentration were experimentally and theoretically evaluated. The dust-free outdoor air was irradiated with an ionization current of 10− 6 A by α-rays from isotope 239Pu. The total output of radiolytic aerosols (RA) with a diameter of 3–1000 nm was found to be 0.05–0.1 molecules per 1 eV of absorbed radiation, while the physical upper limit is 0.25–0.4 molecules/eV. In an interval of exposition time from 6 to 800 s (adsorbed energy is 3 · 1012–1014 eV/cm3) the RA mass concentration at different sites was increased from 1–10 to 50–500 μg/m3. According to the liquid chromatography data the major RA material is the H2O/HNO3 solution with acid concentration  25%. The used physical model presents new aerosols as a product from small and intermediate ion association through formation of neutral clusters and describes adequately some of the peculiarities in field experiment data. Introducing SO2, NH3, and also hydrochloric, nitric and sulphuric acid vapours with concentration 0.1–1 mg/m3 in the irradiated air stimulated an increase of mass aerosol concentration by a factor of 8–30. The mean size also decreased by a factor of 3–5. These facts allowed us to expect that the chemical composition of radiolytic aerosols generated in outdoor air would noticeably differ after addition of the gas-precursors.  相似文献   

14.
Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased by about 1.4 times during intense foggy/hazy days. Concentrations of SO4 2−, NO3 −, NH4 + and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH4 aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 μm). AOD value at 0.5 μm wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63). OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing during intense foggy/hazy days (+75.8 W/m2) than that during clear sky or less foggy/hazy days (+38 W/m2), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m2 during clear sky or less foggy/hazy days to −76 W/m2 during intense foggy/hazy days, mainly due to the scattering aerosols like SO4 2-.  相似文献   

15.
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   

16.
A unified chemistry-aerosol-climate model is applied in this work to compare climate responses to chang- ing concentrations of long-lived greenhouse gases(GHGs,CO2,CH4,N2O),tropospheric O3,and aerosols during the years 1951–2000.Concentrations of sulfate,nitrate,primary organic carbon(POA),secondary organic carbon(SOA),black carbon(BC)aerosols,and tropospheric O3 for the years 1950 and 2000 are obtained a priori by coupled chemistry-aerosol-GCM simulations,and then monthly concentrations are in- terpolated ...  相似文献   

17.
Source attribution of urban smog episodes caused by coal combustion   总被引：1，自引：0，他引：1  
Stable weather conditions together with extensive use of coal combustion often lead to severe smog episodes in certain urban environments, especially in Eastern Europe. In order to identify the specific sources that cause the smog episodes in such environments, and to better understand the mixing state and atmospheric processing of aerosols, both single particle and bulk chemical characterization analysis of aerosols were performed in Krakow, Poland, during winter 2005.Real-time measurements of the bulk PM10 aerosol during a severe smog episode (PM10 mass > 400 µg m− 3) showed a stable concentration of black carbon in the aerosol, and an increase in the sulphate and chlorine mass contributions towards the end of the episode. Chemical characterization of single particles further helped to identify residential coal burning as the main source that caused this severe smog episode, consisting of single particles with major signals for carbon with simultaneous absence of sulphate, chlorine and calcium. Particles from industrial coal combustion gained importance towards the end of that episode, after residential coal combustion was switched off, indicated by an increase of the percentage of sulphate and chlorine containing particles. Traffic was not a significant source during the severe smog episode. During a lighter smog episode, residential and industrial coal combustion was still predominant, with an increased contribution of traffic and processed/aged aerosols. On a clean day, particle classes containing nitrate were the most abundant. In addition, the aerosol was more internally mixed showing that there were more sources contributing to the total aerosol population.  相似文献   

18.
As part of the second Arctic Gas and Aerosol Sampling Program (AGASP II) continuous measurements of atmospheric aerosol black carbon (BC) were made at the NOAA/GMCC observatory at Barrow, Alaska (71°19N, 156°36W) during the period March 21–April 22, 1986. Black carbon is produced only by incomplete combustion of carbonaceous materials and so is a particularly useful atmospheric indicator of anthropogenic activities. The BC data have been analyzed together with the concurrent measurements of carbon dioxide (CO2), methane (CH4), and condensation nuclei (CN) that are routinely made at the observatory. All four species showed elevated and highly variable concentrations due to local human activities, principally in the township of Barrow, 7 km to the southwest, and at the DEW Line radar installation 1 km to the northwest. We distinguish between those periods of the record that are affected by local activities and those that are not, on the basis of the short-term (periods of up to 1 hour) variability of the continuous CO2 and CN records, with large short-term variabilities indicating local sources. We identified seven periods of time (events) with durations ranging from 13 to 37 hours when the BC, CO2, and CH4 concentrations changed smoothly over time, were highly correlated with each other, and were not influenced by local activities. These events had BC/CO2 ratios in the range (50–103)×10–6. These ratios are dimensionless since we convert the CO2 concentrations to units of ng m–3 of carbon. Such values of BC/CO2 are characteristic of the combustion effluent from large installations burning heavy fuel oil or coal, automobiles, and domestic-scale natural gas usage. We conclude that these events are indicative of air masses that have been polluted with combustion emissions in a distant location and then transported to the Arctic. In the absence of species-selective loss mechanisms, these air masses will maintain their combustion effluent signatures during the transport. The BC/CO2 ratios found for the local combustion activities are consistent with those expected from known combustion processes.  相似文献   

19.
Physical characterization of atmospheric aerosols was carried out using various equipments like Grimm's spectrophotometer, Aetholometer and Microtops-II at Bhubaneswar, a coastal city in the east coast of India. Meteorological parameters were recorded on-line with an automatic weather station, which showed weather relatively free from extreme events with high humidity during the period. The pre-monsoon months showed an increase in aerosol mass in the higher size ranges. The black carbon (BC) showed maximum values during winter which may be due to various anthropogenic activities like biomass burning and forest fire as well as dry conditions conducive to transport from far off places. The α values representing aerosol size distribution and β values showing the total aerosol concentration in vertical air column rose simultaneously in pre-monsoon months to attain maximum values during February–March 2008. The AOD was also correlated with PM-10 and BC concentrations.  相似文献   

20.
Although it is believed that organic aerosols play a key role in cloud nucleation and make an important contribution to the cloud condensation nuclei (CCN) population, their specific species remain poorly characterized. This paper reviews the current knowledge of organic acids (mainly formic, acetic, pyruvic and oxalic acids). Without specification, organic acids in this paper refer to these four organic acids in the gas and aerosol phases. This paper analyzes the extent to which organic acids act as CCN and compares the physical and chemical properties of organic acids with those of CCN. The results show that aerosol formate and acetate concentrations range from 0.02 to 5.3 nmol m−3 and from 0.03 to 12.4 nmol m−3, respectively, and that between 34 to 77% of formate and between 21 to 66% of acetate are present in the fine fraction of aerosols. It was found that although most (98–99%) of these volatile organic acids are present in the gas phase, their concentrations in the aerosol particles are sufficient to make them a good candidate for CCN. The results also show that organic acids may make an important contribution to the formation of CCN in some special sources such as vegetation emissions and biomass-burning. Organic acids are expected to contribute significantly to the estimates of indirect (cloud-mediated) forcing due to aerosols.  相似文献   

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