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PubMed2003

The application of proton transfer reaction-mass spectrometry (PTR-MS) to the monitoring and analysis of volatile organic compounds in the atmosphere.

Proton transfer reaction-mass spectrometry (PTR-MS) is a new and emerging technique for the measurement and monitoring of volatile organic compounds (VOCs) at low concentrations in gaseous samples in more-or-less real time. Utilising chemical ionisation, it combines the desirable attributes of high sensitivity and short integration times with good precision and accuracy. Recently it has been exploited in applications related to atmospheric science. Here, the principles of operation of the PTR-MS are described, its advantages and disadvantages discussed, its inherent uncertainties highlighted, some of its uses in atmospheric sciences reviewed, and some suggestions made on its future application to atmospheric chemistry.

Air Pollutants↗

PubMed2003

Pesticide vapours in confined atmospheres. Determination of dichlorvos by SPME-GC-MS at the microg m(-3) level.

A method based on SPME is described for assessing the gaseous dichlorvos concentration in confined atmospheres like a greenhouse after a pesticide application. Sampling was made by using SPME with PDMS fibres immersed into a 250 mL sampling flask into which air samples were dynamically pumped from the analysed atmosphere. Sampling duration was 40 min and samples were then analysed by GC-MS. Calibration was performed from a vapour saturated air sample and gas phase diluted samples, and this procedure afforded a curve with a regression coefficient (R2) higher than 0.98. The repeatability of these measurements was observed with an RSD of 2.5%. This analysis procedure was then applied for the determination of gaseous dichlorvos concentrations versus time, in the atmosphere of an experimental 8 m2 and 20 m3 greenhouse. The pesticide was sprayed according to real cultivation conditions and measurements were made from 2 up to 74 h after application affording observed concentrations in the range of decades and hundreds of microg m(-3) (corresponding limits of detection and quantification were found at the level of a few microg m(-3)).

Air Movements↗

PubMed2004

Identifying the sources and timing of ancient and medieval atmospheric lead pollution in England using a peat profile from Lindow bog, Manchester.

A peat core from Lindow bog near Manchester, England, was precisely cut into 2 cm slices to provide a high-resolution reconstruction of atmospheric Pb deposition. Radiocarbon and (210)Pb age dates show that the peat core represents the period ca. 2000 BC to AD 1800. Eleven radiocarbon age dates of bulk peat samples reveal a linear age-depth relationship with an average temporal resolution of 18.5 years per cm, or 37 years per sample. Using the Pb/Ti ratio to calculate the rates of anthropogenic, atmospheric Pb deposition, the profile reveals Pb contamination first appearing in peat samples dating from ca. 900 BC which clearly pre-date Roman mining activities. Using TIMS, MC-ICP-MS, and SF-ICP-MS to measure the isotopic composition of Pb, the (208)Pb/(206)Pb and (206)Pb/(207)Pb data indicate that English ores were the predominant sources during the pre-Roman, Roman, and Medieval Periods. The study shows that detailed studies of peat profiles from ombrotrophic bogs, using appropriate preparatory and analytical methods, can provide new insight into the timing, intensity, and predominant sources of atmospheric Pb contamination, even in samples dating from ancient times.

Carbon Radioisotopes↗

PubMed2004

Automated measurement and calibration of reactive volatile halogenated organic compounds in the atmosphere.

The automated calibration and analysis of very low mixing ratios of the reactive volatile organic halocarbons CH(3)I, CHCl(3), C(2)H(5)I, 2-C(3)H(7)I, CH(2)Br(2), CH(2)ClI, CHBr(2)Cl, 1-C(3)H(7)I, CH(2)BrI, CHBr(3) and CH(2)I(2) for long term atmospheric field measurements are described. Analytes were pre-concentrated from 3 l of air onto an adsorbent trap cooled to -10 [degree]C using Peltier plates, and rapidly transferred to a gas chromatograph (GC) by resistive heating. A two stage Carboxen 1016/Carbotrap C adsorbent trap allowed good analyte recovery and rapid desorption without the need for post-desorption cryofocussing. Halocarbons were detected using a mass spectrometer (MS) in selective ion mode. Detection limits were between 0.02 and 0.12 pptv (parts per trillion by volume) for approximately hourly samples of CHCl(3), CH(3)I, C(2)H(5)I, 1-C(3)H(7)I, 2-C(3)H(7)I, CH(2)ClI, CH(2)Br(2), CHBr(2)Cl, CH(2)BrI, CHBr(3) and CH(2)I(2) with a precision of 3-8%. A novel calibration system was constructed which utilised fixed volume (50 [micro sign]l) injections of the output of thermostatted permeation tubes into a stream of nitrogen gas in order to dilute parts per million by volume (ppmv) mixing ratios into pptv. The calibration was completely automated, allowing multi-point calibrations during routine operation. The overall accuracy of the measurements is estimated to be +/-15%. The instrument was used continuously for automated atmospheric measurements during a 4-month research cruise from Germany to Antarctica, and a 6 week field campaign at Mace Head, Ireland. The results for CHCl(3) during the latter campaign were within 13% of measurements made by a GC-MS operating continuously at the site within the long term Advanced Global Atmospherics Gases Experiment.

Air Pollutants↗

PubMed2005

Increasing atmospheric antimony contamination in the northern hemisphere: snow and ice evidence from Devon Island, Arctic Canada.

Adopting recently developed clean laboratory techniques, antimony (Sb) and scandium (Sc) deposition were measured in a 63.72 m-long ice core (1842-1996) and a 5 m deep snow pit (1994-2004) collected on Devon Island, Canadian High Arctic. Antimony concentrations ranged from 0.07 to 108 pg g(-1) with a median of 0.98 pg g(-1)(N= 510). Scandium, used as a conservative reference element, revealed that dust inputs were effectively constant during the last 160 years. The atmospheric Sb signal preserved in the ice core reflects contamination from industrialisation, the economic boom which followed WWII, as well as the comparatively recent introduction of flue gas filter technologies and emission reduction efforts. Natural contributions to the total Sb inventory are negligible, meaning that anthropogenic emissions have dominated atmospheric Sb deposition throughout the entire period. The seasonal resolution of the snow pit showed that aerosols deposited during the Arctic winter, when air masses are derived mainly from Eurasia, show the greatest Sb concentrations. Deposition during summer, when air masses come mainly from North America, is still enriched in Sb, but less so. Snow and ice provide unambiguous evidence that enrichments of Sb in Arctic air have increased 50% during the past three decades, with two-thirds being deposited during winter. Most Sb is produced in Asia, primarily from Sb sulfides such as stibnite (Sb2S3), but also as a by-product of lead and copper smelting. In addition there is a growing worldwide use of Sb in automobile brake pads, plastics and flame retardants. In contrast to Pb which has gone into decline during the same interval because of the gradual elimination of gasoline lead additives, the enrichments of Sb have been increasing and today clearly exceed those of Pb. Given that the toxicity of Sb is comparable to that of Pb, Sb has now replaced Pb in the rank of potentially toxic trace metals in the Arctic atmosphere.

Air Pollutants↗

PubMed2000

Atmospheric oxygen accelerates the induction of a post-mitotic phenotype in human dermal fibroblasts: the key protective role of glutathione.

It has been proposed that ageing of human dermal fibroblasts occurs as a multi-stage process during which cells progress from a mitotic to a post-mitotic state. We describe the development of a simple and novel cell-cloning model for identifying and quantifying the different fibroblast morphotypes associated with the induction of post mitotic behaviour. We have found that under atmospheric (20%) oxygen tension a significant proportion of human dermal fibroblasts are rapidly induced to switch from a mitotic to a post-mitotic phenotype. In contrast, under more physiological (4%) oxygen conditions, the induction of a post-mitotic phenotype is largely prevented. Increasing oxidative stress by addition of hydrogen peroxide or depletion of glutathione also induced a switch from a mitotic to a post-mitotic phenotype in these cells, whereas addition of the anti-oxidant N-acetylcysteine under atmospheric (20%) oxygen tension potently inhibited this process. In addition, a statistically significant correlation was observed between the magnitude of intracellular glutathione depletion and the reduction in the population of mitotic cells in this model. We propose that the switch from a mitotic to a post-mitotic phenotype represents a process of cellular ageing and that standard atmospheric oxygen tension imposes a substantial oxidative stress on dermal fibroblasts which accelerates this process in culture. The data also suggest that intracellular glutathione levels strongly influence the induction of a post-mitotic phenotype and that, by implication, depletion of glutathione may play a significant role in the progression of cellular ageing in human skin.

Acetylcysteine↗

PubMed2006

Modelling atmospheric pollution during the games of the XXVIII Olympiad: effects on elite competitors.

UNLABELLED: The present study investigated the specific atmospheric conditions expected in Athens during the summer of 2004 in relation to the performance of elite athletes. DESIGN: Atmospheric pollution and weather data for the period April 16th to September 30th covering the entire greater Athens area and collected from 1984 to 2003 were used for descriptive statistics and model fitting. The analysis was focused on carbon monoxide (CO), ozone (O3), sulfur dioxide (SO2), nitrogen oxide (NO), nitrogen dioxide (NO2), and particulate matter with a diameter of < 10 microm (PM10). Factor and cluster analysis were used to describe atmospheric pollution in the northern, central, and southern sector of Athens. Generalized estimated equations (GEE) analysis was used to predict mean August 2004 pollutant concentration. Increased concentrations of O3 and PM10 (mean 2003 values: 134.3 +/- 9.3, 44 +/- 1.9 microg/m3, respectively) may generate adverse health and performance effects. The highest O3 values were recorded in the northern Athenian sector during the period June 12th to July 23rd, peaking around mid-day (12:00-18:00) (p < 0.05). The highest PM10 concentrations were recorded in the central Athenian sector during the period August 20th to September 9th, peaking at late afternoon (14:00-22:00) (p < 0.05). Similar concentrations were observed during all days of the week (p > 0.05). GEE approximated mean August 2004 pollutant concentrations similar to: CO: 2.8 (mg/m3), O3: 136, SO2: 24, NO: 134, and NO2: 106 (microg/m3). Concentrations of O3 and PM10 during the XXVIII Olympiad may generate adverse health and performance effects on the cardiovascular function of the elite competitors. (The present manuscript was submitted shortly before the start of the Games and became published after their completion. In this light, the actual pollution rates in Athens during August 2004 are presented in the Note Added in Proof as credence to the statistics used).

Air Pollutants↗

PubMed2002

Successive bifurcations in a simple model of atmospheric zonal-flow vacillation.

Low-frequency variability of the atmospheric flow in the Southern Hemisphere is dominated by irregular changes in the latitude and intensity of the mid-latitude eastward jet about its climatological mean state. This phenomenon, known as atmospheric zonal-flow vacillation, is characterized by the existence of two persistent states of the zonal (i.e., east-west oriented) jet and irregular transitions between them. Nonlinear interactions between the mean flow and the waves play a key role in the dynamics of this vacillation. In the present study, we develop a low-order, deterministic model for the nonlinear dynamics of atmospheric zonal-flow vacillation. Multiple equilibria arise in this model's zonal-mean flow, that is, in the longitudinal flow averaged along a given latitude circle. These equilibria bear a strong resemblance to the two persistent flow regimes found in Southern Hemisphere observations. The two equilibrium states are maintained by wave forcing against surface drag, as in the observations. Successive bifurcations to periodic and chaotic zonal-mean flow regimes occur as the model's dissipation parameter is reduced. (c) 2002 American Institute of Physics.

Journal Article↗

PubMed2005

Culturing at atmospheric oxygen levels impacts lymphocyte function.

To determine whether culturing peripheral blood mononuclear cells at atmospheric oxygen levels skews responses in comparison with culturing lymphocytes at physiologic oxygen levels, we cultured peripheral blood mononuclear cells at 5%, 10%, and atmospheric (20%) gas-phase oxygen for 5 days. We found that incubator oxygen levels influenced lymphocyte proliferation stimulated by two commonly used stimuli: Con A and antibodies that crosslink surface CD3 and CD28 to mimic antigen presentation. In both cases, proliferation increased as gas-phase oxygen levels increased. In contrast, oxygen levels did not influence proliferation stimulated by phytohemagglutinin, another commonly used mitogen. Similarly, oxygen levels did not impact cell viability in unstimulated cultures. Thus, we conclude that the influence of oxygen levels on proliferation depends on the stimulus, and, most importantly from the standpoint of immune responses, culturing cells at atmospheric rather than physiologic oxygen levels results in significantly increased proliferation responses to the CD3/CD28 crosslinking, a proliferation stimulus commonly used to mimic T cell antigen receptor signaling.

CD28 Antigens↗

PubMed2006

Distinct metastable atmospheric regimes despite nearly Gaussian statistics: a paradigm model.

A controversial topic in the recent climate modeling literature is the fashion in which metastable low-frequency regimes in the atmosphere occur despite nearly Gaussian statistics for these planetary waves. Here a simple 57-mode paradigm model for such metastable atmospheric regime behavior is introduced and analyzed through hidden Markov model (HMM) analysis of the time series of suitable low-frequency planetary waves. The analysis of this paradigm model elucidates how statistically significant metastable regime transitions between blocked and zonal statistical states occur despite nearly Gaussian behavior in the associated probability distribution function and without a significant role for the low-order truncated nonlinear dynamics alone; turbulent backscatter onto the three-dimensional subspace of low-frequency modes is responsible for these effects. It also is demonstrated that suitable stochastic mode reduction strategies, which include both augmented cubic nonlinearity and multiplicative noise, are also capable of capturing the metastable low-frequency regime behavior through a single stochastic differential equation compared with the full turbulent chaotic 57-mode model. This feature is attractive for issues such as long-term weather predictability. Although there have been many applications of HMM in other sciences, this work presents a previously undescribed application of HMM analysis to atmospheric low-frequency variability and points the way for further applications including their use in extended range predictability.

Journal Article↗

PubMed2001

Morphological properties of atmospheric aerosol aggregates.

Ultrafine particles (smaller than about 0.1 microm) are often emitted from combustion and other high-temperature processes in the form of fractal-like aggregates composed of solid nanoparticles. Results of a study of atmospheric aggregates are reported. Particles were collected on transmission electron microscope grids fitted on the last two stages of a single-jet eight-stage low-pressure impactor for periods of a few minutes. Photomicrographs of transmission electron microscope grids from the impactor stages were analyzed to obtain the fractal dimension (D(f)) and prefactor (A) for aggregates. D(f) increased from near 1 to above 2 as the number of primary particles making up the aggregates increased from 10 to 180. Total particle concentrations in size ranges roughly equivalent to the low-pressure impactor stages were measured with a mobility analyzer and condensation particle counter. In one set of measurements, the fraction of the particles present as aggregates was about 60% for particles with aerodynamic diameters between 50 and 75 nm and 34% for the range 75 to 120 nm. The total aggregate concentration in the 50- to 120-nm size range was about 400 ml(-1). The primary particles that make up atmospheric aggregates are more polydisperse than soot aggregates generated from a single laboratory source, an ethane/oxygen flame. Most measurements were made in the Los Angeles area, where the aggregates may represent a signature for diesel emissions. Rural aggregate concentrations in the size range 50 to 120 nm were less than 1% of the concentrations at urban sites. The data will permit better estimates of atmospheric aggregate residence times, transport, and deposition in the lung, optical extinction, and heterogeneous nucleation.

Journal Article↗

PubMed1979

Autotrophic growth of H2-uptake-positive strains of Rhizobium japonicum in an atmosphere supplied with hydrogen gas.

Previous research from this laboratory has demonstrated CO(2)-fixing and H(2)-uptake capacities of certain strains of Rhizobium japonicum. In this report we have shown that SR, a H(2)-uptake-positive (Hup(+)) strain of R. japonicum, is capable of autotrophic growth with H(2) as the energy source. Growth occurred on mineral salts/vitamins/Noble agar, mineral salts/vitamins liquid medium (0.27 mug of C as vitamins per ml), and in mineral salts liquid medium with no added vitamins when cultures were provided with NH(4)Cl and incubated in an atmosphere containing H(2), CO(2), O(2), and N(2). Little or no growth occurred when either H(2) or CO(2) was omitted from the atmosphere or when the culture was inoculated with SR3, a Hup(-) mutant of SR. Growth was measured by protein synthesis, fixed organic carbon, and increase in cell number in liquid cultures. The organism that grew autotrophically was verified as R. japonicum by (i) apparent purity on streak plates; (ii) retention of the double antibiotic resistance markers; and (iii) its capability to nodulate soybeans. H(2)- and CO(2)-supported growth was demonstrated for three additional Hup(+) wild-type R. japonicum strains (USDA 136, 3I1b 6, and 3I1b 143), while three Hup(-) wild-type strains (USDA 120, 3I1b 144, and USDA 117) were incapable of growth on the Noble agar medium containing mineral salts/vitamins in the H(2)/CO(2)/O(2)/N(2) atmosphere. This demonstrated capability of Hup(+)R. japonicum strains to grow autotrophically requires revision of current concepts regarding conditions for survival and competition of these bacteria in the soil and their relationships to other microorganisms.

Biological Transport↗

PubMed1981

Tropospheric concentrations of methylchloroform, CH(3)CCl(3), in January 1978 and estimates of the atmospheric residence times for hydrohalocarbons.

The ground level tropospheric concentrations of CH(3)CCl(3) were measured from 55 degrees N to 53 degrees S during the time period around Jan. 1, 1978. The northern temperate zone concentration of CH(3)CCl(3) averaged 94.6 +/- 4.0 x 10(-12) by volume. The southern temperate zone concentration averaged 65.2 +/- 1.3 x 10(-12), for a worldwide average of 80 x 10(-12) by volume. The ratio of concentrations between the two zones is 1.45 +/- 0.07. The observed CH(3)CCl(3) concentrations correspond to 0.52 +/- 0.05 times the atmospheric release to that date, corresponding to an atmospheric residence time of 6.9 +/- 1.2 yr. The atmospheric residence times for 22 other hydrohalocarbon molecules were estimated in comparison to that of CH(3)CCl(3) through the relative rates of reaction with OH radicals.

Journal Article↗

PubMed1995

Characterization of aspen isoprene synthase, an enzyme responsible for leaf isoprene emission to the atmosphere.

Isoprene (2-methyl-1,3-butadiene) is a volatile hydrocarbon emitted from many plant species to the atmosphere, where it plays an important role in atmospheric chemistry. An enzyme extracted from aspen (Populus tremuloides) leaves was previously found to catalyze the Mg(2+)-dependent elimination of pyrophosphate from dimethylallyl diphosphate (DMAPP) to form isoprene (Silver, G. M., and Fall, R. (1991) Plant Physiol. 97, 1588-1591). This enzyme, isoprene synthase, has now been purified 4000-fold to near homogeneity. The enzyme had a native molecular mass of 98-137 kDa and isoelectric point of 4.7 and contained 58- and 62-kDa subunits, implying that it is a heterodimer. Partial amino acid sequences of the two subunits indicated they are closely related to each other and that they do not share a strong homology with any other reported proteins. The isoprene synthase reaction was dependent on Mg2+ or Mn2+, and the reaction products were shown to be isoprene and pyrophosphate with a stoichiometry close to 1:1. The Km for DMAPP was high at 8 mM, and the kcat of 1.7 s-1 was low, but similar to those of other allylic diphosphate-utilizing enzymes. It is argued that the isoprene synthase reaction may be much more efficient in vivo, where it is under light-dependent control. It seems probable that this unique enzyme, rather than non-enzymatic reactions, can account for the emission of hundreds of millions of metric tons of isoprene from plants to the global atmosphere each year.

Alkyl and Aryl Transferases↗

PubMed1991

Preferential feeding behaviour of hens in different gaseous atmospheres.

1. The object of this study was to identify the concentrations of carbon dioxide (CO2) and hypoxia (induced by argon) which hens could detect and by preference avoid. 2. Hens were housed in an apparatus consisting of an upper roosting chamber connected to two descending passages which led to separate identical feeding chambers. The gas concentration in both these feeding chambers could be regulated. 3. The hens were allowed to feed in either a normal air atmosphere or an altered atmosphere containing a sub-stunning concentration of CO2 or argon. The birds' preference for feeding in the two chambers was used as an indicator of the concentration which they chose to avoid. 4. The study involved two experiments. In the first it was found that when the concentration of CO2 was raised above 5%, or the concentration of oxygen was reduced to 10% or below, the occupancy of that chamber was significantly reduced. 5. The results of the second experiment confirmed that a concentration of above 7.5% CO2 or oxygen levels of 10% or below can be detectable to hens and, given a free choice, the hens learnt to avoid such atmospheres. 6. The presence of a dominant bird in the roosting chamber or in the feeding chamber containing air caused the subordinate birds to enter the treatment chamber containing gas. This would imply that the unpleasantness of the stunning gases at the concentrations used in this study was less severe than the social pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2000

Shelf-life extension of cod fillets with an acetate buffer spray prior to packaging under modified atmospheres.

Fresh cod fillets (Gadus morhua) were sprayed with a 10% acetate buffer (pH 5.6), packed with an industrial gas-flushing packaging machine under modified atmospheres (50% CO2--45% O2--5% N2, 2 cm3/1 g gas/product ratio) and stored at 7 degrees C for 12 days. Control cod fillets were directly packed and stored under the same conditions. A reduction of the aerobic plate counts was observed immediately after the cod fillets had been sprayed. During storage under modified atmospheres, there was complete inhibition of H2S-producing bacteria and Enterobacteriaceae in the treated cod fillets. Production of total volatile bases and trimethylamine (TMA) was inhibited in treated fillets for 10 days' storage under modified atmospheres. Inhibition of TMA production can be attributed to growth inhibition of H2S-producing bacteria, inhibition of the trimethylamine oxide (TMAO)-dependent metabolism of TMAO-reducing bacteria and the stable pH during storage. The shelf-life, at 7 degrees C, of treated cod fillets, based on cooked flavour score, was almost 12 days, ca 8 days more than shelf-life of the control fillets.

Acetic Acid↗

PubMed2003

Ward atmosphere in acute psychiatric inpatient care: differences and similarities between patient and staff perceptions.

The purpose of the study was to compare patient and staff perceptions of the social climate in a psychiatric department, in order to investigate to what extent the two groups agree in their view of the ward milieu. Ninety-six patients and 66 staff members answered the Ward Atmosphere Scale (WAS) questionnaire, comprising a 100-item "real-form" concerning the ward atmosphere as it is actually perceived and a 100-item "ideal-form" concerning the atmosphere in an imagined "best of all" ward. Staff scores were significantly higher than patient scores on the WAS-R subscales Involvement, Spontaneity, Practical orientation, Personal problems orientation and Program clarity, and on the WAS-I subscales Spontaneity, Practical orientation, and Anger and aggression. Patient scores were significantly higher than staff scores on the WAS-R subscale Staff control and on the WAS-I subscales Support, Autonomy and Staff control. At the same time, the findings showed that the WAS-profiles of the two groups were highly concordant regarding both "realities" and "ideals". In conclusion, patients and staff do to some extent differ in their perception of the social climate in the ward. However, the differences seem to reflect nuances in views rather than fundamental differences in opinion. From an overall point of view, the findings suggest a basic agreement between patients and staff regarding the valuation of the treatment environment as well as the general preferences concerning the ward milieu.

Adult↗

PubMed2006

Lead isotopes decipher multiple origins within single PM10 samples in the atmosphere of Paris.

The atmospheric concentration of lead (Pb) in France has strongly decreased since its legal reduction in gasoline in 2000. Pb-isotope ratios are effective tracers of its origin. Pb in atmospheric particulate matter with a diameter <10 microm (PM10) in Paris is shown to have a dual origin: (1) an intrinsic fraction (leached by hydrofluoric acid) forms the cores of particles and (2) a labile fraction (complexation with hydrobromic acid) represents generally >90 % (mass) of the bulk Pb and aggregates on pre-existing particles in the atmosphere. Characterisation of the emissions from different pollution sources, however, indicates that Pb is entirely contained in the labile fraction. Our results show that, in air, the intrinsic fraction is consistently more radiogenic (the degree of enrichment being greater in summer), hinting at different origins. The labile fraction clearly identifies industrial activity as its main source, but the intrinsic fraction may result from either a different industrial-pollution source or, more likely, from a natural end-member (i.e. pre-industrial sediment).

Air Pollutants↗