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PubMed2005

Source apportionment of fine and coarse atmospheric particles in Auckland, New Zealand.

Atmospheric fine particles (with a diameter less than 2.5 microm) and coarse particles (with a diameter between 2.5 and 10 microm) were collected simultaneously at an urban background site in Auckland, New Zealand, in the summer and winter of 2003. Major water-soluble ions, black carbon (BC), and some elements in the samples were analysed, and the data compiled into two sets. Selected trace gases (NH3, HONO, HNO3, and SO2) were also collected at the same time. Application of positive matrix factorisation to the particle data resolved five sources for the fine particles and five for the coarse particles. Weighted multiple linear regression was used to investigate the mass contributions of the sources. It was found that although natural sources had significant contributions to the coarse particles, anthropogenic sources dominated the contributions to the fine particles, particularly in winter. Significant seasonal changes of the sources were observed. Overall, sea salt and wind-blown soil had significantly stronger contributions in the summer; in contrast, the winter contribution of vehicle emissions, road dust, and industry and incineration sources was significantly higher. These seasonal changes may be explained by variations in meteorological conditions and atmospheric chemistry. The nonparametric correlations between the atmospheric concentrations of the trace gases and the mass contributions of the resolved sources demonstrate that these sources are realistic, providing a useful supplementary approach for the assessment of receptor modelling.

Journal Article↗
PubMed2005

Atmospheric fate of phthalate esters in an urban area (Paris-France).

The atmospheric fate of six phthalate esters was investigated in the urban area of Paris (France). Total atmospheric levels (ng m-3) were as follows: DMP, 0.5; DEP, 10.7; DnBP, 22.2; BBP, 4.6; DEHP, 18.9; and DnOP, 0.5 ng m-3, showing a predominance of DnBP and next, DEHP. They are mainly present in the vapour phase, from 93.8% to 64.9%, particularly for the esters with alkyl chain length of less than six C. An inverse correlation was found between the vapour phase concentrations and the molecular weight and also a direct correlation between the vapour phase concentrations and the log [vapour pressure] of the compounds. Seasonal variations were displayed by principal component analysis (PCA), due to significant correlation between phthalate concentrations and air temperature. Rain water concentrations (ng L-1) were as follows: DMP, 116; DEP, 333; DnBP, 592; BBP, 81; DEHP, 423; and DnOP, 10. PCA analysis showed a seasonal variation of these concentrations correlated to the air temperature. The experimental water/air scavenging ratio was calculated and was in accordance with the theoretical one obtained from the vapour pressure and the Henry's law constant for each phthalate ester. The global trend was a decrease of the washout coefficient in relation with the rise of alkyl chain length. Yearly balances for rainwater and bulk deposition allowed the estimation of dry deposits that represented about half of total. Our findings highlight the major part played by particles in atmospheric deposition processes.

Air Pollutants↗
PubMed2005

Atmospheric gaseous mercury in Northern Taiwan.

The first attempt to systematically investigate the atmospheric mercury over the territory of Taiwan has been undertaken. Four sampling sites were selected in localities qualified as urban, suburban, industrial-rural and rural ones, within the northern part of Taiwan. The sites were monitored for atmospheric gaseous mercury alternately from September to December 2003 and from April to June 2004, by using a portable automated mercury analyzer Model Gardis-3. The results have shown rather high atmospheric gaseous mercury levels (up to 30 ng/m3 at the urban site, up to 22 ng/m3 at the rural site, up to 24 ng/m3 at the industrial-rural site, and up to 90 ng/m3 at the suburban site) which may indicate the presence of considerably strong point and area mercury sources whose origin still has to be detected more precisely.

Air Pollutants↗
PubMed2006

The relative influence of the anthropogenic air pollutants on the atmospheric turbidity factors measured at an urban monitoring station.

This work is based on simultaneous measurements of direct solar radiation along with other chemical measurements, with the objective of investigating the diurnal and seasonal variations of atmospheric turbidity factors (i.e., Linke's factor, Angström's coefficient, and aerosol optical depth). Relationships between atmospheric turbidity factors, expressing the solar radiation extinction, and anthropogenic air pollutants were also evaluated. The frequency of occurrence of the individual indices has been established to describe the sky conditions. The preliminary results obtained indicate high variability of aerosol loading, leading to high turbidity for most of the year. Annual averages of 0.2 and 6 with standard deviations of 0.096 and 0.98 were found for Angström and Linke turbidities, respectively. On the base of the frequency of occurrence, it has been found that over 50% of the dataset are around 0.25 and 6.3 for Angström and Linke turbidities, respectively. On average, the month of September experienced the highest turbidity, while December experienced the lowest. A possible reason for this is that the vertical distribution of the aerosol particles moves up in September due to the extent of the Sudan monsoon trough. We also note that spring values of the turbidity factors are closer to summer values, whereas the pronounced difference between the summer values in comparison with the winter values may be attributed to relatively greater difference in the water vapor level in the atmosphere.

Air Movements↗
PubMed2004

Investigation of influence of gas atmosphere and pressure upon non-contact atomic force microscopy.

Resonance measurements and atomic force microscopy (AFM) observations were carried out by the non-contact AFM operating in various gas atmospheres (hydrogen, helium, nitrogen and argon) over the range of pressures from 0.1 to 1.1 MPa. In each atmosphere, the resonance frequency of the AFM cantilever depended on the pressure of gases studied. The plots of the relative resonance frequency at a constant pressure vs. the gas density gave a straight line. It was found that the characteristic of the resonance frequency for the AFM cantilever were dependent on the density of the gas species. The resolution of the AFM was hardly influenced by the gas atmosphere under the present experimental conditions.

Journal Article↗
PubMed1997

Dissolution of powdered human enamel suspended in acid solutions at a high solid/solution ratio under a 5% CO2 atmosphere at 20 degrees C.

The aim was to examine the nature of enamel dissolution in aqueous suspensions with a high solid/solution ratio and in a CO2-rich atmosphere. Before experimentation, a water-saturated mixture of 95% N2-5% CO2 was passed through the acid solutions for 24 hr. Samples of 2 g of powdered enamel were suspended in 7 ml of either 5 or 10 mmol/l HClO4, with or without 2 parts/10(6) fluoride and kept gently agitated for 24 hr in the above atmosphere. The same enamel samples were repeatedly exposed to fresh acid for 26 runs. All experiments were duplicated. The aqueous phase was analysed after 20 min and 24 hr for calcium, phosphate, fluoride, chloride, sodium and magnesium. It was found that after 20 min the fluoride was invariably taken up in the enamel and the solution was supersaturated with respect to hydroxyapatite with pH ranging 6.7-5.6. During the following 24 hr pH increased further, the supersaturation remained unchanged and the concentrations of calcium and phosphate in solution decreased. In contrast, sodium, magnesium and chloride were released from enamel during the entire period. In the later runs, the supersaturation with respect to hydroxyapatite was only modest and the decrease of calcium and phosphate concentrations limited, as were the release of sodium, magnesium and chloride. It is concluded that despite a CO2-rich atmosphere, calcium, phosphate and carbonate were released from enamel and quickly established a supersaturation with respect to hydroxyapatite with a secondary reprecipitation of mineral. It indicates that within the dental caries lesion in vivo, lesion fluid cannot exist undersaturated with respect to enamel apatite.

Acids↗
PubMed1989

The toxic effect of short exposures to the atmospheric oxygen concentration on early mouse embryonic development.

When culture conditions of mouse preembryos include an O2 concentration of 20%, preembryos that initiate in vitro culture at the 1-cell stage have a lower survival rate than preembryos that are harvested for culture at the 2-cell stage. This "toxic" effect of O2 is not seen at 5% O2 concentrations, suggesting that atmospheric O2 concentrations are toxic to preembryos. The present study examined the effect of short-term exposures to 20% O2, as may occur during in vitro fertilization procedures. The results demonstrated that when 1-cell preembryos were exposed to the atmospheric oxygen concentration for as little as 1 hour, their development was inhibited. Furthermore, such toxic effects did not become apparent until after four to five divisions. The authors conclude that it is critical to minimize exposure of zygotes to the atmospheric O2 concentration for optimal development to continue past the 8- to 16-cell stage, at least in the mouse.

Animals↗
PubMed2001

Atmospheric water vapour processor designs for potable water production: a review.

Atmospheric water vapour processing (AWVP) technology is reviewed. These processors are machines which extract water molecules from the atmosphere, ultimately causing a phase change from vapour to liquid. Three classes of machines have been proposed. The machines either cool a surface below the dewpoint of the ambient air, concentrate water vapour through use of solid or liquid desiccants, or induce and control convection in a tower structure. Patented devices vary in scale and potable water output from small units suitable for one person's daily needs to structures as large as multi-story office buildings capable of supplying drinking water to an urban neighbourhood. Energy and mass cascades (flowcharts) are presented for the three types of water vapour processors. The flowcharts assist in classifying designs and discussing their strengths and limitations. Practicality and appropriateness of the various designs for contributing to water supplies are considered along with water cost estimates. Prototypes that have been tested successfully are highlighted. Absolute humidity (meteorological normals) ranges from 4.0 g of water vapour per cubic metre of surface air in the atmosphere (Las Vegas, Nevada, USA) to 21.2 g m-3 (Djibouti, Republic of Djibouti). Antofagasta, Chile has a normal absolute humidity of 10.9 g m-3. A 40% efficient machine in the vicinity of Antofagasta requires an airflow of 10 m3 s-1 to produce 3767 l of water per day. At a consumption of 50 l per person per day, 75 people could have basic water requirements for drinking, sanitation, bathing, and cooking met by a decentralized and simplified water supply infrastructure with attendant economic and societal benefits.

Air↗
PubMedDate not supplied

QSAR approach to POPs screening for atmospheric persistence.

The environmental behaviour of a persistent organic pollutant (POP) is mainly controlled by its persistence, its tendency to undergo long-range transport (LRT) and its physicochemical properties. Atmospheric half-life is one of the criteria commonly used to study air persistence and LRT potential. For the 12 UNEP POPs and another 48 possible POPs, the mean and maximum half-life estimations for degradation in air are modelled using different molecular structure descriptors (atom and fragment counts, topological and WHIM descriptors), selected by Genetic Algorithm, in QSAR regression models. Both values are modelled to obtain an average estimate and a precautionary value for ranking and screening purposes. The models, validated for their predictivity, could be applied to predict unavailable data. Principal component analysis (PCA) was then used to explore the half-life data in addition to the physicochemical properties that are most relevant to atmospheric mobility; the aim has been to screen and rank POPs with regard to their tendency towards atmospheric persistence and mobility, and to obtain a persistence index in air and an LRT index. These indexes were also modelled by molecular descriptors, thus allowing a preliminary screening of new compounds.

Air Movements↗
PubMed2002

Organic aerosols in the Miami area, USA: temporal variability of atmospheric particles and wet/dry deposition.

Atmospheric particulate matter and both wet and dry deposition was collected over a period of nine months at one location in the metropolitan area of Miami, Florida. Molecular distributions and concentrations of n-alkanes, fatty acids, polycyclic aromatic hydrocarbons (PAHs) and hopanes were determined using weekly composite samples over this time period in order to determine temporal variability, and their possible dependence on climatic parameters such as temperature, rainfall and wind direction and frequency. Based on molecular distributions of the compounds studied, potential emission sources for the atmospheric particles were assessed and suggested to be mainly derived from automobile exhaust and natural sources. Although wet and dry deposition processes were observed to remove about equal amounts of organic aerosols from the Miami atmosphere, dry deposition was dominant in the removal of anthropogenically derived compounds such as PAHs and hopanes. Only very limited seasonal trends were observed, while wind direction and frequency was found to be the most important meteorological parameter controlling the temporal variability of the organic aerosols. This is the first detailed report of this nature for the Miami area.

Aerosols↗
PubMed2003

Characterization of atmospheric PM10 and related chemical species in southern Taiwan during the episode days.

The concentrations of atmospheric PM10 on days with episodes of pollution were examined at four different sampling sites (CC, DL, LY, and HK) in southern Taiwan. The related to particulates water-soluble ionic species (Na+, K+, Mg2+, Ca2+, NH4+, Cl-, NO3-, SO4(2-)), carbonaceous species (EC and OC) and metallic species (Zn, Ni, Pb, Fe, Mn, Al, Si, V) were also analyzed. On the episode days of this study, the PM10 mass concentration ranged from 155 to 210 microgm(-3), from 150 to 208 microgm(-3), from 182 to 249 microgm(-3), and from 166 to 228 microgm(-3) at CC, DL, LY, and HK, respectively. The results indicate that the dominant water-soluble species were SO4(2-), NO3-, NH4+, and Cl- at the four sampling sites on these days. Moreover, the high sulfate and nitrate conversion values (SOR and NOR) presented herein suggest that secondary formations from SO2 to SO4(2-) and from NO2 to NO3- are present in significant quantities in the atmosphere of southern Taiwan on episode days. In particular, high SOR and NOR verified that both SO4(2-) and NO3- dominated the increase of atmospheric PM10 concentration in southern Taiwan on episode days.

Air Pollutants↗
PubMed2000

Assessment of atmospheric mercury emissions in Finland

This paper is part of the study of atmospheric emissions of heavy metals conducted by the Finnish Environment Institute in collaboration with the Technical Research Centre of Finland (VTT) under the umbrella of the Finnish Ministry of the Environment. The scope of our study is limited solely to anthropogenic mercury that is emitted directly to the atmosphere. This article addresses emission factors and trends of atmospheric mercury emissions during the 1990s and is based mainly on the database of the Finnish Environmental Administration. In addition, data based on the measurements taken by the VTT regarding emission factors have been used to estimate emissions of mercury from the incineration of waste. The study indicates that the total emission of mercury has decreased from 1140 kg in 1990 to 620 kg in 1997, while industrial and energy production have been on the increase simultaneously. The 45% emission reduction is due to improved gas cleaning equipment, process changes, automation, the installation of flue gas desulfurization process in coal-fired power plants and strict pollution control laws. In the past, some authors have estimated a higher mercury emission in Finland. In this study, it is also observed that there are no big changes in the quality of raw materials. Estimated emission factors can be of great help to management for estimating mercury emissions and also its risk assessment.

Journal Article↗
PubMed2000

Assessing the contribution of natural sources to regional atmospheric mercury budgets

Naturally mercury-enriched substrate is a long-lived source of mercury to the global atmospheric mercury cycle. Field flux chambers, laboratory gas exchange chambers and micrometeorological methods may be applied to estimate emissions from these sources. However, field chamber experimental design may affect the magnitude of the fluxes measured, and the laboratory chamber only provides a minimum estimate of flux. Many factors, such as mercury concentration and speciation in substrate, light, precipitation, and temperature, influence the emission of mercury from the substrate. Mercury concentration in the substrate is a dominant factor controlling emissions and may be used to predict emissions from regions of mercury enrichment. Mercury fluxes measured from three areas of natural enrichment and three areas with low levels of mercury enrichment are 1-5 orders of magnitude greater than the value applied to global belts of natural enrichment. Preliminary scaling of emissions from one of these areas and for western North America indicates that mercury enriched areas may be significant sources of mercury to the atmosphere, and that their contribution to regional and global atmospheric budgets needs to be reassessed.

Journal Article↗
PubMed2000

Atmospheric mercury deposition in Guizhou, China

The atmospheric deposition of mercury including total gas phase mercury (TGM), gas phase divalent mercury (Hg2+), and gas phase monomethyl mercury (MMHg) was investigated. Samples were collected from central cities and nature reserve areas across the province. Techniques and equipment including moss bags, KCl-coated denuder and GARDIS-1A portable mercury vapor analyzer were employed for sample collection and analysis. The reliability of techniques and analytical methods used for the project was evaluated. The deposition of atmospheric mercury was reported in species in this important mercury polluted province for the first time. The spatial and temporal variability of mercury emissions were investigated and reported. Contribution of coal mercury emissions to the atmosphere mercury deposition of the province was also investigated.

Journal Article↗
PubMed2002

The chronology of anthropogenic, atmospheric Pb deposition recorded by peat cores in three minerogenic peat deposits from Switzerland.

Peat cores were collected from three minerogenic peatlands in Switzerland: La Tourbière des Genevez (TGE), in Canton Jura; Gola di Lago (GDL), in Canton Ticino; and Mauntschas (MAU), in Canton Grisons. Chemical analyses of the pore waters and the peats document the increasingly minerogenic character with depth. In particular, the Sr concentration profile in the peats reflects the growing importance of mineral sediment dissolution with increasing distance below the peat surface. Despite this circumstance, Pb concentrations are greatest in the surface layers, and decrease with depth. Thus, dissolution of the basal sediments at these sites appears to be an unimportant source of Pb, compared with atmospheric deposition. Twenty-one new radiocarbon age dates for the three cores provide a chronology of Pb enrichment, and these are consistent with the record of atmospheric Pb deposition recorded by the ombrotrophic peat bog 'Etang de la Gruère' (EGR). Sediment samples from TGE and EGR were reacted at pH 5 with ammonium acetate to dissolve the carbonate fraction, filtered, and the residues analyzed using XRF. These analyses show that much of the Ca, Mg, Sr and Mn is lost when the carbonate fraction is dissolved, but this process does not measurably affect Pb. This finding suggests that carbonate dissolution dominates the weathering of the sediments underlying these peat deposits, but this fraction does not contain significant concentrations of Pb. Minerogenic peat deposits such as those described here, therefore, can serve as reliable archives of atmospheric Pb deposition, provided that mineral dissolution in the underlying sediments does not contribute measurably to the Pb inventory of the peat profile.

Air Pollutants↗
PubMed2003

PCBs in the atmosphere of King George Island, Antarctica.

Polychlorinated biphenyls (PCBs) are ubiquitous anthropogenic compounds found even in the polar regions, mainly due to long-range atmospheric transport. In order to assess the occurrence of atmospheric PCBs in the vicinity of the Brazilian Antarctic Research Station (62 degrees 05'S, 58 degrees 23'W), a sampling survey was undertaken in the austral summer of 1995-1996. The concentrations of the PCB congeners in the air ranged from not detected to 33.2 pgm(-3). The lower chlorinated congeners (PCB-101 and below), which are more volatile and subject to long-range transport, predominated in the air samples and represented 66.7% of the total PCB concentrations. Atmospheric levels of PCBs were correlated with meteorological conditions and the highest levels were associated with the passage of the frontal systems coming from South America.

Journal Article↗
PubMed2003

First national survey of atmospheric heavy metal deposition in Hungary by the analysis of mosses.

The atmospheric deposition of Cd, Cr, Cu, Fe, Ni, Pb, V and Zn in Hungary was investigated by using moss species as bioindicators. Our research was part of an international mapping project (Atmospheric Heavy Metal Deposition in Europe) [NORD 21 (1987) 1-44; NORD 9 (1994)] carried out in the most European countries in the 1990s to determine and to compare atmospheric heavy metal background pollution by standardized methods. Sampling was performed at 116 sites distributed over Hungary in the autumn of 1997. Moss species of Hypnum cupressiforme (72.4%) were preferred. But where it could not be collected, other species were taken. Unwashed, dried samples were digested with H(2)O(2)/HNO(3), and the concentrations of heavy metals were determined by ICP-AES. The results reflect local emission points. Background mean levels of Cd, Fe and Ni were mildly elevated in comparison to European means [NORD 9 (1994)]. Probably, that was due not only to pollution, but to the use of Hypnum cupressiforme, which can accumulate higher concentrations of heavy metals compared to other species. The results are presented on colored contour maps obtained with the SURFER program (Golden Software Inc. Co).

Air Pollutants↗
PubMed2000

A new approach for quantifying cumulative, anthropogenic, atmospheric lead deposition using peat cores from bogs: Pb in eight Swiss peat bog profiles.

Peat cores taken from eight Swiss peatlands were used to calculate inventories of anthropogenic Pb using either Sc or Zr to quantify Pb derived from rock weathering. The shapes of the Pb/Sc and Pb/Zr profiles suggest that Pb was supplied exclusively by atmospheric deposition at all sites. At one of the sites (Etang de la Gruère), anthropogenic Pb was calculated using both Sc and Zr as the conservative reference element. Lithogenic Pb determined using Sc was twice that obtained using Zr, possibly because Zr resides only in zircons which are dense compared to pyroxene and amphibole which are the main Sc-bearing phases in the earth's crust. However, the inventory of 'natural' Pb (supplied almost entirely by soil dust) is dwarfed by the anthropogenic inventory such that anthropogenic Pb calculated using Sc and Zr agree to within 5%. The total amount of anthropogenic Pb accumulated in the bogs was calculated by simply adding the mass of anthropogenic Pb for each peat slice over the length of each core. Cumulative, anthropogenic Pb calculated in this way ranged from 1.0 to 9.7 g/m2 and showed pronounced regional differences: the site south of the Alps (Gola di Lago in Canton Ticino) with direct exposure to the heavily industrialized region of northern Italy received nearly 10 times more anthropogenic Pb as the sites in more remote alpine regions (Schöpfenwaldmoor in Canton Berne, and Mauntschas in Canton Grisons). The approach used here to calculate cumulative, anthropogenic, atmospheric Pb (CAAPb) is simple and robust, independent of the chronology of Pb deposition, and makes no assumptions about the immobility of Pb within the peat profile. Given the worldwide distribution of peat bogs, it should be possible to undertake continental and global inventories of atmospheric metal deposition, for both the natural and anthropogenic components of most trace metals of environmental interest.

Air Pollutants↗