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881.
Shelly L. Miller Peter Scaramella Joseph Campe Cynthia W. Goss Sandra Diaz-Castillo Ed Hendrikson Carolyn DiGuiseppi Jill Litt 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5661-5667
An indoor air quality assessment was conducted on 100 homes of recent Mexican immigrants in Commerce City, Colorado, an urban industrial community north of Denver. Head of households were administered a family health survey, filled out an activity diary, and participated in a home inspection. Carbon monoxide (CO) and carbon dioxide (CO2) were measured for 24 h inside the main living area and outside of the homes. Harvard Impactors were used to collect 24-h samples of PM2.5 at the same locations for gravimetric analysis. Dust samples were collected by vacuuming carpeting and flooring at four locations within the home and analyzed by ELISA for seven allergens. Mean indoor and outdoor PM2.5 levels were 27.2 and 8.5 μg m−3, respectively. Indoor PM2.5 and CO2 were elevated in homes for which the number of hours with door/window open was zero compared to homes in which the number of hours was high (>15 h). Indoor PM2.5 levels did not correlate with outdoor levels and tended to increase with number of inhabitants, and results indicate that the source of indoor particles were occupants and their activities, excluding smoking and cooking. Mean indoor CO2 and CO levels were 1170 and 2.4 ppm, respectively. Carbon monoxide was higher than the 24-h National Ambient Air Quality Standard in 3 of the homes. The predominant allergens were cat (Fel d 1) and mouse (Mus m 1) allergens, found in 20 and 34 homes, respectively. 相似文献
882.
Zhi-Ping Wang Yang Song Jay Gulledge Qiang Yu Hong-Sheng Liu Xing-Guo Han 《Atmospheric environment (Oxford, England : 1994)》2009,43(13):2148-2153
A budget for the methane (CH4) cycle in the Xilin River basin of Inner Mongolia is presented. The annual CH4 budget in this region depends primarily on the sum of atmospheric CH4 uptake by upland soils, emission from small wetlands, and emission from grazing ruminants (sheep, goats, and cattle). Flux rates for these processes were averaged over multiple years with differing summer rainfall. Although uplands constitute the vast majority of land area, they consume much less CH4 per unit area than is emitted by wetlands and ruminants. Atmospheric CH4 uptake by upland soils was ?3.3 and ?4.8 kg CH4 ha?1 y?1 in grazed and ungrazed areas, respectively. Average CH4 emission was 791.0 kg CH4 ha?1 y?1 from wetlands and 8.6 kg CH4 ha?1 y?1 from ruminants. The basin area-weighted average of all three processes was 6.8 kg CH4 ha?1 y?1, indicating that ruminant production has converted this basin to a net source of atmospheric CH4. The total CH4 emission from the Xilin River basin was 7.29 Gg CH4 y?1. The current grazing intensity is about eightfold higher than that which would result in a net zero CH4 flux. Since grazing intensity has increased throughout western China, it is likely that ruminant production has converted China's grazed temperate grasslands to a net source of atmospheric CH4 overall. 相似文献
883.
J.P. Bitog I.-B. Lee M.-H. Shin S.-W. Hong H.-S. Hwang I.-H. Seo J.-I. Yoo K.-S. Kwon Y.-H. Kim J.-W. Han 《Atmospheric environment (Oxford, England : 1994)》2009,43(30):4612-4621
This paper discusses about the quantitative effect of windbreak fences on wind velocity in the reclaimed land at Saemangeum in South Korea. Windbreak fences were constructed in the reclaimed land to reduce the wind velocity to prevent the generation and diffusion of dust. However, up to this time, no in-depth studies were conducted to quantitatively measure the effect of the windbreak fences on wind velocity thus an optimum windbreak structure is not yet determined. Using CFD simulations, the effects of fence porosity, fence height, and the distance between the adjacent fences were investigated. A wind tunnel experiment was initially conducted and data gathered were used to develop the CFD models. From the experiments and CFD simulations, the overall percentage difference of the measured velocities was 7.20% which is generally acceptable to establishing the reliability of the CFD models. The reduction effect on wind velocity was measured in between the adjacent fences up to a height of 0.6 m from the ground surface. In terms of porosity ( = 0, 0.2, 0.4, 0.6), 0.2 was found to be the optimum value. Conversely, the effect of fence height (0.6, 0.8 and 1.0 m) showed no significant difference; therefore, 0.6 m height is recommended. In addition, the reduction effect of distance between the adjacent fences (2, 4 and 6 m) on wind velocity having a 0.2 porosity has decreased to about 75% regardless of the distance. In the case of the reclaimed land in Saemangeum, a decrease of 75% can prevent the generation and diffusion of dusts. However, the source of dusts is very large. Therefore, constructing an array of windbreak with 6 m distance between them is deemed necessary. 相似文献
884.
A new direct thermal desorption-GC/MS method: Organic speciation of ambient particulate matter collected in Golden, BC 总被引:1,自引:0,他引:1
Luyi C. Ding Fu Ke Daniel K.W. Wang Tom Dann Claire C. Austin 《Atmospheric environment (Oxford, England : 1994)》2009,43(32):4894-4902
Particulate matter having an aerodynamic diameter less than 2.5 μm (PM2.5) is thought to be implicated in a number of medical conditions, including cancer, rheumatoid arthritis, heart attack, and aging. However, very little chemical speciation data is available for the organic fraction of ambient aerosols. A new direct thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) method was developed for the analysis of the organic fraction of PM2.5. Samples were collected in Golden, British Columbia, over a 15-month period. n-Alkanes constituted 33–98% by mass of the organic compounds identified. PAHs accounted for 1–65% and biomarkers (hopanes and steranes) 1–8% of the organic mass. Annual mean concentrations were: n-alkanes (0.07–1.55 ng m−3), 16 PAHs (0.02–1.83 ng m−3), and biomarkers (0.02–0.18 ng m−3). Daily levels of these organics were 4.89–74.38 ng m−3, 0.27–100.24 ng m−3, 0.14–4.39 ng m−3, respectively. Ratios of organic carbon to elemental carbon (OC/EC) and trends over time were similar to those observed for PM2.5. There was no clear seasonal variation in the distribution of petroleum biomarkers, but elevated levels of other organic species were observed during the winter. Strong correlations between PAHs and EC, and between petroleum biomarkers and EC, suggest a common emission source – most likely motor vehicles and space heating. 相似文献
885.
G.S.W. Hagler R.W. Baldauf E.D. Thoma T.R. Long R.F. Snow J.S. Kinsey L. Oudejans B.K. Gullett 《Atmospheric environment (Oxford, England : 1994)》2009,43(6):1229-1234
Ultrafine particles (UFPs, diameter < 100 nm) and co-emitted pollutants from traffic are a potential health threat to nearby populations. During summertime in Raleigh, North Carolina, UFPs were simultaneously measured upwind and downwind of a major roadway using a spatial matrix of five portable industrial hygiene samplers (measuring total counts of 20–1000 nm particles). While the upper sampling range of the portable samplers extends past the defined “ultrafine” upper limit (100 nm), the 20–1000 nm number counts had high correlation (Pearson R = 0.7–0.9) with UFPs (10–70 nm) measured by a co-located research-grade analyzer and thus appear to be driven by the ultrafine range. Highest UFP concentrations were observed during weekday morning work commutes, with levels at 20 m downwind from the road nearly fivefold higher than at an upwind station. A strong downwind spatial gradient was observed, linearly approximated over the first 100 m as an 8% drop in UFP counts per 10 m distance. This result agreed well with UFP spatial gradients estimated from past studies (ranging 5–12% drop per 10 m). Linear regression of other vehicle-related air pollutants measured in near real-time (10-min averages) against UFPs yielded moderate to high correlation with benzene (R2 = 0.76), toluene (R2 = 0.49), carbon monoxide (R2 = 0.74), nitric oxide (R2 = 0.80), and black carbon (R2 = 0.65). Overall, these results support the notion that near-road levels of UFPs are heavily influenced by traffic emissions and correlate with other vehicle-produced pollutants, including certain air toxics. 相似文献
886.
Yongxiang Han Xiaomin Fang Tianliang Zhao Huzhi Bai Shichang Kang Lianchun Song 《Atmospheric environment (Oxford, England : 1994)》2009,43(3):568-574
Dust aerosols play an important role in modulating the hydrologic cycle. The Tibetan Plateau (TP) is little polluted by human activities as an ideal site to study the effect of dust aerosol on precipitation. In this study, observational data of dust storms and precipitation in the TP and its vicinities as well as CALIPSO satellite data were used to analyze the distributions and vertical structure of dust storms on the plateau. The results showed that dust storms occur with high frequency and raise dust particles into the troposphere from ground level to a height of 5–9 km to modulate the hydrologic cycle in the TP. There are significant negative correlations between dust aerosol and precipitation in the dust source regions during the period of both 40 and 200 years. It is found that the role of precipitation in suppressing dust storms could be unimportant, while dust aerosol may play an important role in suppressing precipitation in the hinterland of the TP. Our study provides a potential approach to better understand the climate changes in the TP. 相似文献
887.
Claire L. Martin Ian D. Longley James R. Dorsey Rick M. Thomas Martin W. Gallagher Eiko Nemitz 《Atmospheric environment (Oxford, England : 1994)》2009,43(31):4714-4721
Little information is known about the behaviour of ultrafine particles (UFP) on a citywide scale. Total particle number flux, dominated by UFP, and other meteorological parameters were collected from tower sites in Manchester, London, Edinburgh and Gothenburg between 1999 and 2006 using the eddy covariance technique. Averaged diurnal cycles were produced for particle number flux, concentration, sensible heat flux, emission velocity, friction velocity, wind speed and temperature. UFP flux cycles showed clear diurnal trends which were linked to traffic activity and local sources. Wind sector analysis showed contributions to flux from local heavily urbanised areas. A simple parameterised model linking UFP flux to traffic activity, sensible heat and friction velocity above the city was produced. 相似文献
888.
Chester W. Spicer Michael W. Holdren Kenneth A. Cowen Darrell W. Joseph Jan Satola Bradley Goodwin Howard Mayfield Alexander Laskin M. Lizabeth Alexander John V. Ortega Matthew Newburn Robert Kagann Ram Hashmonay 《Atmospheric environment (Oxford, England : 1994)》2009,43(16):2612-2622
Aircraft emissions affect air quality on scales from local to global. More than 20% of the jet fuel used in the U.S. is consumed by military aircraft, and emissions from this source are facing increasingly stringent environmental regulations, so improved methods for quickly and accurately determining emissions from existing and new engines are needed. This paper reports results of a study to advance the methods used for detailed characterization of military aircraft emissions, and provides emission factors for two aircraft: the F-15 fighter and the C-130 cargo plane. The measurements involved outdoor ground-level sampling downstream behind operational military aircraft. This permits rapid change-out of the aircraft so that engines can be tested quickly on operational aircraft. Measurements were made at throttle settings from idle to afterburner using a simple extractive probe in the dilute exhaust. Emission factors determined using this approach agree very well with those from the traditional method of extractive sampling at the exhaust exit. Emission factors are reported for CO2, CO, NO, NOx, and more than 60 hazardous and/or reactive organic gases. Particle size, mass and composition also were measured and are being reported separately. Comparison of the emissions of nine hazardous air pollutants from these two engines with emissions from nine other aircraft engines is discussed. 相似文献
889.
T.L. O'Halloran J.D. Fuentes D.R. Collins M.J. Cleveland W.C. Keene 《Atmospheric environment (Oxford, England : 1994)》2009,43(22-23):3586-3595
During autumn, 2006, variation in the frequency of aerosol nucleation events, as inferred from nanoparticle growth events, and associated hygroscopicity were investigated as a function of air mass transport history at a mixed deciduous forest in central Virginia, U.S. Above-canopy size distributions of aerosols between 0.012 and 0.700 μm diameter, size-resolved particle hygroscopicity at eight dry diameters between 0.012 and 0.400 μm, and cloud condensation nuclei (CCN) activity were characterized. Air mass back trajectories were clustered to identify source regions. Growth events were most frequent in fast-moving air masses (mean = 9 m s?1) that originated over the north central U.S. Under these flow regimes, mean values for preexisting sub-μm aerosol number concentrations (4700 cm?3), corresponding surface area (142 μm2 cm?3), air temperature (6.2 °C), and relative humidity (RH, 49.4%) were relatively low compared to other regimes. Under stagnant flow conditions (mean = 3 m s?1), mean number concentrations were higher (>6000 cm?3) and size fractions <0.1 μm diameter exhibited enhanced hygroscopicity compared to other source regions. These results indicate that precursors emitted into relatively clean, cold, and dry air transported over the southeastern U.S. reacted to form condensable intermediates that subsequently produced new aerosols via nucleation and growth. This pathway was an important source for CCN. During events in October, nanoparticles were produced in greater numbers and grew more rapidly compared to November and December. 相似文献
890.
Ionic composition of TSP and PM2.5 during dust storms and air pollution episodes at Xi'an,China 总被引:1,自引:0,他引:1
Zhenxing Shen Junji Cao Richard Arimoto Zhiwei Han Renjian Zhang Yuemei Han Suixin Liu Tomoaki Okuda Shunsuke Nakao Shigeru Tanaka 《Atmospheric environment (Oxford, England : 1994)》2009,43(18):2911-2918
TSP and PM2.5 samples were collected at Xi'an, China during dust storms (DSs) and several types of pollution events, including haze, biomass burning, and firework displays. Aerosol mass concentrations were up to 2 times higher during the particulate matter (PM) events than on normal days (NDs), and all types of PM led to decreased visibility. Water-soluble ions (Na+, NH4+, K+, Mg2+, Ca2+, F?, Cl?, NO3?, and SO42?). were major aerosol components during the pollution episodes, but their concentrations were lower during DSs. NH4+, K+, F?, Cl?, NO3?, and SO42? were more abundant in PM2.5 than TSP but the opposite was true for Mg2+ and Ca2+. PM collected on hazy days was enriched with secondary species (NH4+, NO3?, and SO42) while PM from straw combustion showed high K+ and Cl?. Firework displays caused increases in K+ and also enrichments of NO3? relative to SO42?. During DSs, the concentrations of secondary aerosol components were low, but Ca2+ was abundant. Ion balance calculations indicate that PM from haze and straw combustion was acidic while the DSs samples were alkaline and the fireworks' PM was close to neutral. Ion ratios (SO42?/K+, NO3?/SO42?, and Cl?/K+) proved effective as indicators for different pollution episodes. 相似文献