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At least 973 records · Page 54Linked to original sources

PubMed2000

Use of benzo[a]pyrene relative abundance ratios to assess exposure to polycyclic aromatic hydrocarbons in the ambient atmosphere in the vicinity of a Söderberg aluminum smelter.

The purpose of this study was to investigate the use of benzo[a]pyrene (B[a]P) relative abundance ratios (RARs) to assess exposure to polycyclic aromatic hydrocarbons (PAHs) in the urban atmospheric air in the vicinity of a horizontal stud Söderberg aluminum reduction facility. The B[a]P RARs refer to the concentration of individual PAHs measured in a given sample divided by the concentration of B[a]P found in the same sample. This study compared the B[a]P RARs calculated for the facility stack and three sites near the Söderberg aluminum smelter for three different sampling periods. Interperiod differences were significant for many of the PAHs, and the differences between the stations proved insignificant at p < 0.05. The differences between each individual station and the facility stack were significant for all PAHs. B[a]P RARs increased in value at the stations compared with the stack, indicating that B[a]P may be degraded or removed from the atmosphere at a rate greater than that of the majority of the measured PAHs. It is concluded that B[a]P and B[a]P RARs may be poor markers of exposure to PAHs in the vicinity of this Söderberg aluminum refinery for the entire mixture of PAHs present in the ambient atmosphere.

Air Pollution↗

PubMed2004

Determination of levoglucosan in atmospheric fine particulate matter.

A microanalytical method suitable for the quantitative determination of the sugar anhydride levoglucosan in low-volume samples of atmospheric fine particulate matter (PM) has been developed and validated. The method incorporates two sugar anhydrides as quality control standards. The recovery standard sedoheptulosan (2,7-anhydro-beta-D-altro-heptulopyranose) in 20 microL solvent is added onto samples of the atmospheric fine PM and aged for 1 hr before ultrasonic extraction with ethylacetate/ triethylamine. The extract is reduced in volume, an internal standard is added (1,5-anhydro-D-mannitol), and a portion of the extract is derivatized with 10% by volume N-trimethylsilylimidazole. The derivatized extract is analyzed by gas chromatography/mass spectrometry (GC/MS). The recovery of levoglucosan using this procedure was 69 +/- 6% from five filters amended with 2 microg levoglucosan, and the reproducibility of the assay is 9%. The limit of detection is approximately 0.1 microg/mL, which is equivalent to approximately 3.5 ng/m3 for a 10 L/min sampler or approximately 8.7 ng/m3 for a 4 L/min personal sampler (assuming 24-hr integrated samples). We demonstrated that levoglucosan concentrations in collocated samples (expressed as ng/m3) were identical irrespective of whether samples were collected by PM with aerodynamic diameter < or = 2.5 microm or PM with aerodynamic diameter < or = 10 microm impactors. It was also demonstrated that X-ray fluorescence analysis of samples of atmospheric PM, before levoglucosan determinations, did not alter the levels of levoglucosan.

Aerosols↗

PubMed1979

Measurement of atmospheric vinyl chloride.

Methods for atmospheric vinyl chloride measurement have been reviewed. The lowest detection limits and most specific measurement are achieved by scrubbing atmospheric samples with activated charcoal, desorbing the vinyl chloride, and assaying it by gas chromatography (GC). NIOSH currently recommends collecting samples using tubes packed with 150 mg of coconut shell charcoal, desorbing with carbon disulfide, and analyzing by GC equipped with flame-ionization detection (FID); the method is capable of detecting less than 1 ppm vinyl chloride and has an apparent recovery of abo the ppb level with no loss of accuracy or precision. Some field methods, such as infrared analysis and conductivity measurement, are capable of detecting 1 ppm or lower but are subject to interferences by other contaminants; th-y could be useful for evaluating sources of vinyl chloride leaks and for continuous monitoring. Permeation tubes are superior to gravimetric or volumetric methods for generating atmospheres of known vinyl chloride concentration.

Air Pollutants↗

PubMed1992

Evaluation of OSHA method 5 for measuring chloroform in pulp and paper industry workplace and ambient atmospheres.

As a result of the recent lowering of the Occupational Safety and Health Administration's (OSHA's) permissible exposure limit (PEL) for chloroform from 50 ppm to 2 ppm, interest has increased in measuring chloroform in pulp and paper industry workplace atmospheres. OSHA suggested that its Method 5 should be used for measuring chloroform concentrations in the range of the new PEL. There are some potential problems with using Method 5 for this purpose. Pulp and paper industry atmospheres may interfere with the measurement because of high temperature, high humidity, and the presence of chlorine. The charcoal sorbent tubes specified in OSHA Method 5 were challenged in the laboratory with a test gas containing 0.1, 0.5, 1, and 2 times the PEL of chloroform at 38 degrees C with 80% to 93% relative humidity and ca. 0.5 ppm chlorine. Application of the National Institute for Occupational Safety and Health (NIOSH) validation protocol to the results indicated a bias of -8.2% and a pooled coefficient of variation (CV) of 0.0274. The method CV is less than the critical CV; thus, the method is acceptable by the NIOSH validation protocol under these conditions. Field testing of OSHA Method 5 was successful and did not reveal any unexpected problems. Additional tests showed that with some modification, OSHA Method 5 can be used to measure chloroform concentrations in ambient atmospheres down to 0.1 ppb.

Air Pollutants, Occupational↗

PubMed2003

Purification characteristics of golden pothos for atmospheric gasoline.

Previous studies have shown that plants have the ability to purify various atmospheric chemicals. Gasoline is one of the more serious pollutants. Soil and atmospheric pollution caused by gasoline is increasing due to the widespread use of automobiles. In this article, the purification characteristic of the pothos plant for atmospheric gasoline is investigated using a tin oxide gas sensor. The purification rate (Pr), defined as the purification ability per hour as described by a differential coefficient, has a maximum value at longer time intervals as the pollutant concentration becomes higher. Pr can be represented by an exponential function of lapsed time and its characteristic in soil is similar. A golden pothos plant growing in a 30-cm diameter pot of was placed in a 300-I experimental chamber to examine its purification ability. Pr had a maximum value 40 h after a 0.04-ml injection of gasoline into the chamber. The total purification ability (Pa) is also used in this study and is derived using the peak value (h) and the full width (tw) at half maximum of the tin oxide gas-sensor characteristic, namely Pa = h/tw x 100. The Pa of the pothos for gasoline was about 7, with the value decreasing as the pollutant concentration increased.

Araceae↗

PubMed2005

Measurement of volatile organic compounds in the urban atmosphere of Harris County, Texas, USA.

Volatile organic compounds (VOCs) are a major component of urban air pollution. It is well documented that exposure to certain types of VOCs can cause adverse health effects such as cancer, immune and neurological damage, and reproductive and endocrine disorders. Urban air samples were collected at five locations in Harris County, Texas to determine the measurement of VOCs in the ambient air of residential areas in close proximity to industrial facilities that emit toxic air pollutants into the air. Three locations used in this study were located along the Houston Ship Channel (HSC), in the heart of one of the largest petrochemical complexes in the nation. Two other sampling locations were located many miles away from the ship channel and any industrial facilities that are required to report toxic air emissions. Air samples were collected daily over an 8-h period from December 2002 to March 2003. The samples were collected in 6-L stainless steel Silonite-coated canisters and analyzed using a modified version of EPA Method TO-15. A total of 53 compounds was quantitated using a gas chromatograph mass spectrometer system coupled to a cryogenic preconcentrator. Eighteen alkanes and oxygenated compounds were identified, along with 7 alkenes and 5 aromatic compounds. Several alkanes such as butane, isobutane, 2-methyl butane, and pentane were detected at all five sites. The total VOC concentrations determined were highest at two of the industrial sites and lowest at the site farthest away from the ship channel and any industrial facilities. This study concluded that the atmosphere near Harris County's industrial complex had higher concentrations of VOCs than the atmosphere in areas farther away from the HSC. The atmosphere of areas downwind from emission sources were found to be directly affected by toxic air emissions from industrial process but not at the levels seen in areas closer to the HSC.

Air↗

PubMed2000

Diffusion in the Atmospheres of Blue Horizontal-Branch Stars.

We investigate the effects of diffusion in the atmospheres of hot horizontal-branch stars using a model atmosphere code including diffusion self-consistently. Equilibrium stratifications (i.e., for which the diffusion velocity equals zero in each layer) are computed for models of effective temperatures between 10,000 and 25,000 K. The stratified models provide much better agreement with many observational features [jump in the (u, u-y) color-magnitude diagram, gaps, lower spectroscopic gravities] in comparison with classical horizontal-branch models. The observed abundance anomalies are also consistent with the amounts that can be supported in the atmospheres.

Journal Article↗

PubMed2001

Presence for design: conveying atmosphere through video collages.

Product designers use imagery for inspiration in their creative design process. To support creativity, designers apply many tools and techniques, which often rely on their ability to be inspired by found and previously made visual material and to experience the atmosphere of the user environment. Computer tools and developments in VR offer perspectives to support this kind of imagery and presence in the design process. But currently these possibilities come at too high a technological overhead and price to be usable in the design practice. This article proposes an expressive and technically lightweight approach using the possibilities of VR and computer tools, by creating a sketchy environment using video collages. Instead of relying on highly realistic or even "hyperreal" graphics, these video collages use lessons learned from theater and cinema to get a sense of atmosphere across. Product designers can use these video collages to reexperience their observations in the environment in which a product is to be used, and to communicate this atmosphere to their colleagues and clients. For user-centered design, video collages can also provide an environmental context for concept testing with prospective user groups.

Communication↗

PubMed2002

Generation of controlled atmospheres for the determination of the irritant potency of peroxyacetic acid.

Given the physical properties of peroxyacetic acid, which decomposes into acetic acid and hydrogen peroxide, the generation and analysis of controlled atmospheres used to test the irritant potency of this peracid in mice require specific developments. The sampling and analytical method was based on the simultaneous sampling on a titanyl sulphate-impregnated silica gel tube (allowing the determination of total peroxides, peroxyacetic acid and hydrogen peroxide) and in an impinger containing a methyl-p-tolyl sulphide solution (of which the analysis yields the concentration of total acids, peroxyacetic acid and acetic acid, and peroxyacetic alone). From these results the concentrations of the different products can be inferred without interference. A special device composed of inert materials was designed for the generation of the controlled atmosphere. Buffering the peroxyacetic solution at pH 7 with a phosphate buffer allowed the generation of peroxyacetic acid atmospheres with negligible concentrations of acetic acid and hydrogen peroxide.

Acetic Acid↗

PubMed2006

Impact of urban atmospheric pollution on coronary disease.

Recent epidemiological findings have suggested that urban atmospheric pollution may have adverse effects on the cardiovascular system as well as on the respiratory system. We carried out an exhaustive search of published studies investigating links between coronary heart disease and urban atmospheric pollution. The review was conducted on cited articles published between 1994 and 2005 and whose main objective was to measure the risk of ischaemic heart diseases related to urban pollution. Of the 236 references identified, 46 epidemiological studies were selected for analysis on the basis of pre-defined criteria. The studies were analysed according to short-term effects (time series and case-crossover designs) and long-term effects (case-control and cohort studies). A link between coronary heart disease and at least one of the pollutants studied (PM10, O3, NOx, CO, SO2) emerged in 40 publications. Particulate matter, nitrogen oxides, and carbon monoxide were the pollutants most often linked with coronary heart disease. The association was inconstant for O3. Although the mean mortality or morbidity risk related to urban atmospheric pollution is low compared with that associated with other better-known risk factors, its impact on health is nevertheless major because of the large number of people who are exposed. This exhaustive review supports the possibility that urban pollution is indeed an environmental cardiovascular risk factor and should be considered as such by the cardiologists.

Air Pollution↗

PubMed2002

Carbon isotope discrimination and bundle sheath leakiness in three C(4) subtypes grown under variable nitrogen, water and atmospheric CO(2) supply.

The changes in composition and productivity of semi-arid C(4) grassland, anticipated with rising atmospheric CO(2), will depend on soil water and nutrient availability. The interactive effects of soil resource limitation and elevated CO(2 )on these grasses, furthermore, may vary among C(4) biochemical subtypes (NADP-ME, NAD-ME, PCK) that differ in bundle sheath leakiness (Phi) responses to drought and nitrogen supply. To address C(4) subtype responses to soil resource gradients, the carbon isotope discrimination (Delta), bundle sheath leakiness (Phi), leaf gas exchange (A, g(s), c(i)/c(a)) and above-ground biomass accumulation were measured on three dominant grasses of semi-desert grassland in south-eastern Arizona. Bouteloua curtipendula (PCK), Aristida glabrata (NADP-ME) and the non-native Eragrostis lehmanniana (NAD-ME) were grown in controlled-environment chambers from seed under a complete, multi-factorial combination of present ambient (370 ppm) and elevated (690 ppm) CO(2) concentration and under high and low water and nitrogen supply. E. lehmanniana (NAD-ME) had the highest photosynthetic rate (A) and lowest Phi compared to the other two grasses when grown under low nitrogen and water availability. However, favourable water and nitrogen supply and elevated atmospheric CO(2) enhanced photosynthetic performance and above-ground biomass production of B. curtipendula (PCK) to a greater extent than in A. glabrata and E. lehmanniana. Contrary to pre vious studies, Phi and Delta in the NADP-ME subtype (A. glabrata) were most affected by changing environmental conditions compared to the other subtypes; deviations from the classic NADP-ME anatomy in Aristida could have accounted for this result. Overall, response of semi-arid grasslands to rising atmospheric CO(2) may depend more on species-specific responses to drought and nitrogen limitation than on general C(4) subtype responses.

Algorithms↗

PubMed2003

A quick method for estimation of long-lived alpha activity in work atmospheres.

In an operating plant quick reporting of the status of long-lived alpha activity concentrations in the work atmosphere is required. This will help in taking any corrective control measures if required. Radon and thoron progeny concentrations prevalent in the general atmosphere predominantly interfere in measurement of long-lived alpha activity in air. The alpha counts due to radon and thoron progeny vary widely in many atmospheric conditions. Therefore, conventionally, 5 days delay is allowed for all interfering activity to decay completely and true alpha air activity is then estimated. An approach for quick assessment of long-lived alpha activity by eliminating interference due to radon and thoron progeny in air, is made here. Based on the study of the pattern of alpha count rate due to radon and thoron progeny in air, a method for estimation of long-lived alpha activity within 8 hours delay time is suggested in this paper.

Air Pollutants, Radioactive↗

PubMed2001

The effects of electrical and controlled atmosphere stunning methods on meat and liver quality of geese.

The objective of this research was to investigate the effects of electrical and gas stunning on the meat and liver quality characteristics of liver geese. Sixty birds were slaughtered at 12 wk of age, in groups of 20 at three different times. Thirty birds each were subjected to one of the two stunning methods. Deboned breast fillets and thigh muscles were evaluated for hemorrhaging, amount of blood in the veins, and color by using a visual grading system. Livers were removed from carcasses during evisceration and were subsequently graded. Besides external color and hemorrhaging, the degree of liver weight loss due to removal of blood vessels was also determined. The use of controlled atmosphere stunning significantly reduced the incidence of muscle hemorrhages when compared to electrical stunning. However, no significant difference was found for color or amount of blood remaining in the veins of muscles between geese receiving electrical or controlled atmosphere stunning. The hemorrhaging and color scores of livers from gas-stunned birds did not differ from those of electrically stunned birds. As for the liver weight loss caused by removal of veins and capillaries, stunning treatment had no significant effect on this parameter. These results suggest that controlled atmosphere stunning produced slightly better quality goose meat but did not improve liver quality when compared to the electrical stunning method used.

Animal Welfare↗

PubMed1999

Influence of increased atmospheric CO(2) concentration on quality of plant material and litter decomposition.

Nitrogen (N) and lignin concentrations in plant tissues and litter of plants grown in greenhouses or open-top chambers in elevated atmospheric CO(2) concentration were compared with those of plants grown in ambient air in short-term studies. We also compared the N concentration of plant material of Quercus ilex L. and Q. pubescens Willd. growing in the vicinity of natural CO(2)-springs with that of the same species growing at a control site. In the short-term studies, elevated CO(2) caused significant decreases in tissue N concentration and the extent of the decrease varied with species. Nitrogen amendment of the soil lessened the CO(2)-enrichment effect. Lignin concentration was modified by elevated CO(2) and the effect was species specific, but no general positive or negative trend was evident. A comparison of trees growing under natural conditions near a natural CO(2)-spring and at a control site revealed no site differences in N concentration of the plant material. A comparison of published results on decomposition rates of litter produced in elevated atmospheric CO(2) and in ambient air indicated that CO(2) enrichment can cause both enhancements and decreases of carbon mineralization. We conclude that (1) long-term responses to elevated CO(2) could differ from the results obtained from short-term studies and that (2) biodiversity could be an important factor altering the sign of the feedback on atmospheric CO(2) concentration. We also discuss the implications of our finding of a long-term, inhibitory effect of the initial N concentration of litter on the decomposition rate of litter and its consequence on ecosystem feedback.

Journal Article↗

PubMed2000

Kinetics of nitrogen uptake by Populus tremuloides in relation to atmospheric CO(2) and soil nitrogen availability.

Sustained increases in plant production in response to elevated atmospheric carbon dioxide (CO(2)) concentration may be constrained by the availability of soil nitrogen (N). However, it is possible that plants will respond to N limitation at elevated CO(2) concentration by increasing the specific N uptake capacity of their roots. To explore this possibility, we examined the kinetics of (15)NH(4) (+) and (15)NO(3) (-) uptake by excised roots of Populus tremuloides Michx. grown in ambient and twice-ambient CO(2) concentrations, and in soils of low- and high-N availability. Elevated CO(2) concentration had no effect on either NH(4) (+) or NO(3) (-) uptake, whereas high-N availability decreased the capacity of roots to take up both NH(4) (+) and NO(3) (-). The maximal rate of NH(4) (+) uptake decreased from 12 to 8 &mgr;mol g(-1) h(-1), and K(m) increased from 49 to 162 &mgr;mol l(-1), from low to high soil N availability.Because NO(3) (-) uptake exhibited mixedkinetics over the concentration range we used (10-500 &mgr;mol l( -1)), it was not possible to calculate V(max) and K(m). Instead, we used an uptake rate of 100 &mgr;mol g(-1) h(-1) as our metric of NO(3) (-) uptake capacity, which averaged 0.45 and 0.23 &mgr;mol g(-1) h(-1) at low- and high-N availability, respectively. The proximal mechanisms for decreased N uptake capacity at high-N availability appeared to be an increase in fine-root carbohydrate status and a decrease in fine-root N concentration. Both NH(4) (+) and NO(3) (-) uptake were inversely related to fine-root N concentration, and positively related to fine-root total nonstructural carbohydrate concentration. We conclude that soil N availability, through its effects on fine-root N and carbohydrate status, has a much greater influence on the specific uptake capacity of P. tremuloides fine roots than elevated atmospheric CO(2). In elevated atmospheric CO(2), changes in N acquisition by P. tremuloides appeared to be driven by changes in root architecture and biomass, rather than by changes in the amount or activity of N-uptake enzymes.

Journal Article↗

PubMed2002

Responses of deciduous broadleaf trees to defoliation in a CO2 enriched atmosphere.

Relatively little is known about the implications of atmospheric CO2 enrichment for tree responses to biotic disturbances such as folivory. We examined the combined effects of elevated CO2 concentration ([CO2]) and defoliation on growth and physiology of sugar maple (Acer saccharum Marsh.) and trembling aspen (Populus tremuloides Michx.). Seedlings were planted in the ground in eight open-top chambers. Four chambers were ventilated with CO2-enriched air (ambient + 283 micromol mol-1) and four chambers were supplied with ambient air. After 6 weeks of growth, half of the leaf area was removed on a subset of seedlings of each species in each CO2 treatment. We monitored subsequent biomass gain and allocation, along with leaf gas exchange and chemistry. Defoliation did not significantly affect final seedling biomass in either species or CO2 treatment. Growth recovery following defoliation was associated with increased allocation to leaf mass in maple and a slight enhancement of mean photosynthesis in aspen. Elevated [CO2] did not significantly affect aspen growth, and the observed stimulation of maple growth was significant only in mid-season. Correspondingly, simulated responses of whole-tree photosynthesis to elevated [CO2] were constrained by a decrease in photosynthetic capacity in maple, and were partially offset by reductions in specific leaf area and biomass allocation to foliage in aspen. There was a significant interaction between [CO2] and defoliation on only a few of the measured traits. Thus, the data do not support the hypothesis that atmospheric CO2 enrichment will substantially alter tree responses to folivory. However, our findings do provide further indication that regeneration-stage growth rates of certain temperate tree species may respond only moderately to a near doubling of atmospheric [CO2].

Acer↗

PubMed1989

Chernobyl source term, atmospheric dispersion, and dose estimation.

The Chernobyl source term available for long-range transport was estimated by integration of radiological measurements with atmospheric dispersion modeling and by reactor core radionuclide inventory estimation in conjunction with WASH-1400 release fractions associated with specific chemical groups. These analyses indicated that essentially all of the noble gases, 60% of the radioiodines, 40% of the radiocesium, 10% of the tellurium, and about 1% or less of the more refractory elements were released. Atmospheric dispersion modeling of the radioactive cloud over the Northern Hemisphere revealed that the cloud became segmented during the first day, with the lower section heading toward Scandinavia and the upper part heading in a southeasterly direction with subsequent transport across Asia to Japan, the North Pacific, and the west coast of North America. The inhalation doses due to direct cloud exposure were estimated to exceed 10 mGy near the Chernobyl area, to range between 0.1 and 0.001 mGy within most of Europe, and to be generally less than 0.00001 mGy within the United States. The Chernobyl source term was several orders of magnitude greater than those associated with the Windscale and TMI reactor accidents. However, the 137Cs from the Chernobyl event is about 6% of that released by the U.S. and U.S.S.R. atmospheric nuclear weapon tests, while the 131I and 90Sr released by the Chernobyl accident was only about 0.1% of that released by the weapon tests.

Accidents↗

PubMed1997

Anomaly in atmospheric radon concentration: a possible precursor of the 1995 Kobe, Japan, earthquake.

Clear seismic-related anomalies in the radon (222Rn) concentration of the atmosphere were observed prior to the Kobe earthquake (magnitude 7.2) on 17 January 1995. The radon anomalies were observed at a monitoring station in Kobe, which is located about 20 km away from the epicenter. The means of radon concentration in the atmosphere for each day were calculated using the data observed between April 1984 and March 1994, in order to obtain the normal radon variation. The difference between the smoothed radon concentration and the smoothed mean radon concentration is the residual value. Using the weekly averages of residual values in the historical period, the weekly residual value in the validation period were predicted. The historical period was from April 1984 to March 1994. The validation period was from April 1994 to January 1996. The seismic-related radon anomaly higher than the 99% confidence limit of the residual value of radon concentration in the atmosphere was observed beginning about 2 mo before the earthquake.

Air↗