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PubMed2002

Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere.

Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations < 10(-5) times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations > or = 10(-5) PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga.

Archaea↗
PubMed2002

Carbon in the atmosphere and terrestrial biosphere in the 21st century.

The release of carbon dioxide from fossil-fuel combustion and land-use change has caused a significant perturbation in the natural cycling of carbon between land, atmosphere and oceans. Understanding and managing the effects of this disruption on atmospheric composition and global climate are likely to be amongst the most pressing issues of the 21st century. However, the present-day carbon cycle is still poorly understood. One remarkable feature is that an increasing amount of atmospheric carbon dioxide appears to be being absorbed by terrestrial vegetation. I review the recent evidence for the magnitude and spatial distribution of this 'terrestrial carbon sink', drawing on current research on the global atmospheric distribution and transport of carbon dioxide, oxygen and their isotopes; direct measurement of CO(2) fluxes above various biomes; and inventories of forest biomass and composition. I review the likely causes of these carbon sinks and sources and their implications for the ecology and stability of these biomes. Finally, I examine prospects and key issues over coming decades. Within a few years, satellite measurements of atmospheric CO(2) and forest biomass, coupled with 'real-time' biosphere-atmosphere models, will revolutionize our understanding of the terrestrial carbon cycle. Controlling deforestation and managing forests has the potential to play a significant but limited part in reaching the goal of stabilizing atmospheric CO(2) concentrations. However, there are likely to be limits to the amount of carbon storage possible in natural vegetation, and, in the long term, terrestrial carbon storage may be unstable, with the potential to accelerate rather than brake global warming.

Atmosphere↗
PubMed2002

Potential trace metal-organic complexation in the atmosphere.

It is possible that metal-organic complexation enhances the uptake of gaseous organic compounds and the solubility of metals in aerosols and atmospheric water. We investigated potential atmospheric organic ligands and the enhanced uptake of hydroxy-, oxo-, and dicarboxylic acids as well as dicarbonyls into atmospheric aqueous aerosol. We examined complexation with transition metals (iron, manganese, nickel, copper, zinc) and lead on the basis of available references and our experimental data. Humic-like substances are most likely ligands in the atmosphere, although this is a poorly characterized material. A number of polycarboxylic acids and hydroxy forms (e.g., citric and tartronic acids) effectively complex metals such as copper in atmospheric aerosols. The simple equilibrium model calculations show that the effect of the complexation on the gas-aqueous phase partition of gaseous atmospheric ligands is quite small for the ligands with the high physical Henry's law constants, e.g., dicarboxylic acids represented by oxalic acid, even if they have high affinity with metal ions. The lower Henry's law constants of the alpha-dicarbonyls, such as glyoxal and methylglyoxal, mean that the complexation could lead to profound increases in their partition into the aqueous phase. Despite quantum mechanical arguments for copper-glyoxal complexes, experiments showed no evidence of complexation between either hydrated or unhydrated alpha-dicarbonyls and the cupric ion. By contrast the beta-dicarbonyl, malondialdehyde, has properties that would allow it to partition into atmospheric water via the complexation with metal ions under some conditions.

Aerosols↗
PubMed2002

Atmospheric deposition of phosphorus to the everglades: concepts, constraints, and published deposition rates for ecosystem management.

This paper summarizes concepts underlying the atmospheric input of phosphorus (P) to ecosystems, published rates of P deposition, measurement methods, and approaches to future monitoring and research. P conveyed through the atmosphere can be a significant nutrient source for some freshwater and marine ecosystems. Particle sources and sinks at the land-air interface produce variation in P deposition from the atmosphere across temporal and spatial scales. Natural plant canopies can affect deposition rates by changing the physical environment and surface area for particle deposition. Land-use patterns can alter P deposition rates by changing particle concentrations in the atmosphere. The vast majority of P in dry atmospheric deposition is conveyed by coarse (2.5 to 10 m) and giant (10 to 100 m) particles, and yet these size fractions represent a challenge for long-term atmospheric monitoring in the absence of accepted methods for routine sampling. Most information on P deposition is from bulk precipitation collectors and wet/dry bucket sampling, both with questionable precision and accuracy. Most published annual rates of P deposition are gross estimates derived from bulk precipitation sampling in locations around the globe and range from about 5 to well over 100 mg P m(-2) year(-1), although most inland ecosystems receive between 20 and 80 mg P m(-2) year(-1). Rates below 30 mg P m(-2) year-1 are found in remote areas and near coastlines. Intermediate rates of 30 to 50 mg P m(-2) year(-1) are associated with forests or mixed land use, and rates of 50 to 100 mg P m(-2) year(-1) or more are often recorded from urban or agricultural settings. Comparison w ith other methods suggests that these bulk precipitation estimates provide crude boundaries around actual P deposition rates for various land uses. However, data screening cannot remove all positive bias caused by contamination of bucket or bulk collectors. As a consequence, continued sampling with these standard collectors in a region will not reduce the large uncertainty in rates derived from existing data. Calibrated surface accumulation methods hold promise as a primary means to estimate P flux in future monitoring. New methods for long-term P deposition monitoring will require an intercomparison of P flux estimates from surrogate surfaces, impactor sampling of particle concentrations combined with deposition models, and "throughfall" estimates for natural canopies. With better sampling methods and more long-term monitoring data, the importance of atmospheric P deposition in ecosystem dynamics and management can be better understood and predicted.

Atmosphere↗
PubMed2001

Consistent land- and atmosphere-based U.S. carbon sink estimates.

For the period 1980-89, we estimate a carbon sink in the coterminous United States between 0.30 and 0.58 petagrams of carbon per year (petagrams of carbon = 10(15) grams of carbon). The net carbon flux from the atmosphere to the land was higher, 0.37 to 0.71 petagrams of carbon per year, because a net flux of 0.07 to 0.13 petagrams of carbon per year was exported by rivers and commerce and returned to the atmosphere elsewhere. These land-based estimates are larger than those from previous studies (0.08 to 0.35 petagrams of carbon per year) because of the inclusion of additional processes and revised estimates of some component fluxes. Although component estimates are uncertain, about one-half of the total is outside the forest sector. We also estimated the sink using atmospheric models and the atmospheric concentration of carbon dioxide (the tracer-transport inversion method). The range of results from the atmosphere-based inversions contains the land-based estimates. Atmosphere- and land-based estimates are thus consistent, within the large ranges of uncertainty for both methods. Atmosphere-based results for 1980-89 are similar to those for 1985-89 and 1990-94, indicating a relatively stable U.S. sink throughout the period.

Agriculture↗
PubMed1996

Evidence in pre-2.2 Ga paleosols for the early evolution of atmospheric oxygen and terrestrial biota

The loss of Fe from some pre-2.2 Ga paleosols has been considered by previous investigators as the best evidence for a reduced atmosphere prior to 2.2 Ga. I have examined the behavior of Fe in both pre- and post-2.2 Ga paleosols from depth profiles of Fe3+/Ti, Fe2+/Ti, and sigma Fe/Ti ratios, and Fe3+/Ti vs. Fe2+/Ti plots. This new approach reveals a previously unrecognized history of paleosols. Essentially all paleosols, regardless of age, retain some characteristics of soils formed under an oxic atmosphere, such as increased Fe3+/Ti ratios from their parental rocks. The minimum oxygen pressure (PO2) for the 3.0-2.2 Ga atmosphere is calculated to be about 1.5% of the present atmospheric level, which is the same as that for the post-1.9 Ga atmosphere. The loss of sigma Fe, common in paleosol sections of all ages, was not due to a reducing atmosphere, but to reductive dissolution of ferric hydroxides formed under an oxic atmosphere. This reductive dissolution of ferric hydroxides occurred either (1) after soil formation by hydrothermal fluids or (2) during and/or after soil formation by organic acids generated from the decay of terrestrial organic matter. Terrestrial biomass on the early continents may have been more extensive than previously recognized.

Atmosphere↗
PubMed1991

Studies on the relationship between the pathogenicity of Paracoccidioides brasiliensis in mice and its growth rate under different oxygen atmospheres.

We performed comparative studies of the pathogenicity of six strains of Paracoccidioides brasiliensis (Bt-9, Bt-4, Pb-9, Pb-18, Bt-7 and B-1183) for young adult male ddY mice and the growth rate of each strain under different oxygen atmospheres (aerobic, micro-aerobic and anaerobic atmospheres) at 37 degrees C. 10(6) units of yeast cells were intravenously injected into each mouse. The pathogenicity of each isolate was determined by a scoring system based on organ culture and histopathological findings. The growth rates under different oxygen atmospheres were determined by a scoring system in which 300 fungal units per strain were counted. The strain Bt-9 showed the greatest pathogenicity, followed by Bt-4, Pb-9 and Pb-18 had on intermediate rank of pathogenicity. Bt-7 and B-1183 were the least pathogenic of the strains tested. Except for strain Bt-7 all strains showed an excellent growth under an aerobic atmosphere. Bt-4 and Bt-9 also showed excellent growth under a micro-aerobic atmosphere, followed by Pb-9, whereas the growth of Pb-18, Bt-7 and B-1183 was limited. There was a correlation between the growth rate under a micro-aerobic atmosphere and the pathogenicity of a strain. The growth rate of P. brasiliensis under a micro-aerobic atmosphere strongly correlated to its pathogenicity.

Aerobiosis↗
PubMed2002

Atmospheric lead and bromine in Germany: post-abatement levels, variabilities and trends.

INTENTION, GOAL, SCOPE, BACKGROUND: Abatement measures since the 1970s have depleted lead and bromine levels in the atmosphere over large parts of Europe. Our knowledge of the atmospheric cycling of these elements while a several decade-long period of intensive mobilization reaches its end is incomplete. OBJECTIVE: We have characterized the trends in the atmospheric levels of Pb and Br and present-day temporal and spatial variabilities. METHODS: This was achieved by short-term (weeks) and long-term (years) measurements of particulate Pb and Br at various sites in Germany. Samples of atmospheric particulate matter were collected on filter membranes and analyzed by x-ray fluorescence. RESULTS AND DISCUSSION: Average Pb levels at rural and urban inland sites did not exceed concentrations in background aerosols, sampled at a Baltic Sea coastal site, by more than a factor of 3. Due to sea salt, bromide inland particulate Br levels are below those at a coastal site. There, non-sea salt Br, however, is significant as well. Urban Pb and Br levels are not necessarily higher than rural levels. The concentration levels have decreased in such a way that the previously common source, local vehicular traffic emissions, is no longer predominant. Regional rather than local sources have been increasingly determining the concentrations since the 1990s. This is more pronounced for Br than for Pb. We found indications for coal burning and long-range transport as significant Pb sources. For particulate Pb species, a range of ages (elapsed time since Pb emission) has been found. This range shows two maxima corresponding to characteristic times of 72 and 24 h. CONCLUSIONS: The (mean) atmospheric residence time of particulate Pb is longer than the residence time of Br, in particular in the wintertime. The chemical species contributing to atmospheric Pb should be addressed in future studies. RECOMMENDATION AND OUTLOOK: Clearly, despite effective abatement measures, atmospheric Pb will continue to be dominated by anthropogenic mobilization. The influence from long-range transport can be expected to decrease with the effectiveness of abatement programmes in neighbouring countries of the region.

Aerosols↗
PubMed2002

How the inner world is reflected in relation to perceived ward atmosphere among patients with psychosis.

BACKGROUND: This study focused on how cognitive ability, personality traits, self-rated psychiatric symptoms, and social functioning were related to the way in which patients with psychosis perceived supportive aspects of the ward atmosphere. METHODS: Patients at a psychiatric rehabilitation unit (PRU) in southern Sweden completed a ward atmosphere questionnaire (COPES), rated their psychiatric symptoms (SCL-90), self-image (SASB), and were tested on cognitive functioning (WAIS-R) and global social functioning (GAF). They were diagnosed according to ICD-10. Data were analysed by means of logistic regression analyses. RESULTS: Self-monitoring and restraining (self-control), one cluster in the SASB, was the strongest factor associated with how the patients perceived the ward atmosphere. A perceived high level of self-control indicated high levels of perceived Support, Practical orientation, and Order and organisation of the ward atmosphere. A high level of self-rated paranoid symptoms (SCL-90) increased the risk of perceiving a high level of Anger and aggression and a low level of Program clarity. Regarding cognitive ability (WAIS-R), two factors were important for predicting perceived ward atmosphere. A low level of social competence was associated with a low level of perceived Order and organisation. Furthermore, a low level of abstract thinking was related to a low level of perceived Anger and aggression, while a high level of abstract thinking was associated with a low level of Program clarity. Patients with schizophrenia exhibited a lower level of Self-monitoring and restraining than patients with other psychoses. CONCLUSION: The results from this study indicate that individual factors such as self-control, paranoid symptoms and social competence may be important for how the ward atmosphere is perceived. This is important knowledge when monitoring the ward atmosphere to better fit a unit's target group.

Adult↗
PubMed1990

Growth of Listeria monocytogenes Scott A, serotype 4 and competitive spoilage organisms in raw chicken packaged under modified atmospheres and in air.

The development of Listeria monocytogenes Scott A, serotype 4 and aerobic plate counts on minced raw chicken were determined independently at 4, 10 and 27 degrees C. Samples were packaged in flexible film under two modified atmospheres (one containing oxygen and one containing no oxygen) or air. The anaerobic modified atmosphere (75:25, CO2:N2) resulted in the failure of both the aerobic plate counts and L. monocytogenes to grow at all temperatures. Both the L. monocytogenes and aerobic plate counts grew in air at all temperatures. The aerobic modified atmosphere (72.5:22.5:5, CO2:N2:O2), which more closely duplicates commercial practice, inhibited the increase in aerobic plate counts by more than 4 log10 cfu/g compared to air at 4 degrees C. However, the L. monocytogenes was not affected by this atmosphere and increased in numbers by nearly 6 log10 cfu/g at 4 degrees C in 21 days. Regression analysis of the log10 growth and 95% confidence intervals showed that the differences between aerobic plate counts and L. monocytogenes in modified atmosphere were large. The ability of L. monocytogenes to grow in the aerobic modified atmosphere was not affected by level of the L. monocytogenes inoculum nor by the initial level of aerobic plate counts. These data show that modified atmosphere packaging of raw chicken (and probably other meats) can substantially inhibit the aerobic spoilage flora while allowing pathogenic L. monocytogenes to increase.

Animals↗
PubMed2004

Polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) and monobromo-polychlorinated dibenzo-p-dioxins/dibenzofurans (MoBPXDD/Fs) in the atmosphere and bulk deposition in Kyoto, Japan.

Polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) and monobromo-polychlorinated dibenzo-p-dioxins/dibenzofurans (MoBPXDD/Fs) in atmosphere, bulk atmospheric deposition and soil in Kyoto, which is an urban city in Japan, were measured. Decabromodiphenyl ether (D(10)BDE, BDE-209) was detected in relatively high concentrations compared to other PBDE congeners in most samples. Similar results, in which D(10)BDE was predominantly detected, were reported in other studies in Japan. However, these homologue profiles differ from those of studies conducted in North America. The partitioning of semivolatile organic compounds between atmospheric gas phase and particulate-associated phase is an important factor in their environmental behavior. In this study, atmospheric particulate phase fraction (f(P)) of the brominated compounds increased with increasing bromine number, and f(P) was higher in samples collected in winter than in those collected in summer. Moreover, f(P) of PBDFs and MoBPXDFs was higher than that of PCDFs with the same halogen number. These results agree well with expectations from the vapor pressure of the brominated compounds and PCDD/Fs. Among the brominated compounds in the atmosphere, the level of MoBPXDD/Fs correlates positively with that of PCDD/Fs. This relationship has been previously observed in waste incineration samples. These results suggest that one of the sources of MoBPXDD/Fs in the atmosphere is incineration byproduct. The level of PBDD/Fs seems to correlate positively with that of PBDEs. This relationship suggest that the PBDD/Fs in the atmosphere relate to PBDEs, which is an impurity of PBDE products, or formed by the manufacture or combustion of plastics containing PBDEs.

Air Pollutants↗
PubMed2005

Atmospheric fall-out of POPs (PCDD-Fs, PCBs, HCB, PAHs) around the industrial district of Porto Marghera, Italy.

In order to estimate the importance of atmospheric fall-out of persistent organic pollutants (POPs) around the industrial district of Porto Marghera, Italy, atmospheric depositions of POPs were collected using bulk samplers inside the Lagoon of Venice. Seventy-seven atmospheric deposition samples were collected monthly over a 12-month period (March 2003-March 2004) at seven sites located close to the industrial area of Porto Marghera. Samples were analysed by HRGC/HRMS for PCDD-Fs, PCBs, HCB and PAHs. Differences in mean daily fluxes of all organic pollutants between industrial, urban and lagoonal stations were clear, atmospheric depositions at industrial sites being higher than target values for dioxin deposition recommended by the EU strategy on dioxins, furans and polychlorobiphenyls. In order to calculate atmospheric loadings of POPs around the industrial district, we considered an area defined by a distance of 10 km from the hypothetical centre-point of the main sources of atmospheric emissions from Porto Marghera. The calculated loadings, compared with the previous estimates, show that annual loadings of POPs are 12, 510, 90 and 130 kg of PCDD-Fs, PCBs, HCB and PAHs, respectively, corresponding to 350-500 mg TEQ, thus indicating a slight decrease in PCBs and a great decrease in HCB with respect to 1998-99. The input coming from the atmosphere is of the same order of magnitude of that due to the watershed runoff and approximately one-half of the direct industrial discharges.

Air Movements↗
PubMed2006

Modelling of the long term fate of pesticide residues in agricultural soils and their surface exchange with the atmosphere: Part I. Model description and evaluation.

Sources of pesticides in the atmosphere can be releases of new material through current use, or emission/reemission from soil residues resulting from historical use. It is the latter aspect, soil residues, that is the focus of this study. This paper describes the application of a simple coupled atmosphere-soil pesticide exchange model that can assist in the interpretation of soil residue and air concentration measurements, and in the projection of short period field measurements to larger spatial scales and longer time periods. Only dry gaseous exchange (emission and deposition) between bare agricultural lands and the atmosphere is modelled. Wet deposition and particle associated deposition of pesticide are not included. Model results are compared with published co-located air and soil pesticide concentration measurements made on agricultural lands in the southern U.S. that have soil residues of lindane and the following six highly persistent pesticides: cis-, trans-chlordane, p,p'-DDE, dieldrin, trans-nonachlor and toxaphene. The study results show: (i) that measured air concentrations of toxaphene and p,p'-DDE above agricultural soils in the southern U.S. can be attributed to emissions due to local soil residues of these pesticides rather than to the regional background air concentrations; (ii) that both soil emissions and background air concentrations of dieldrin contribute significantly to the measured air concentrations; (iii) that measured air concentrations of cis- and trans-chlordane as well as trans-nonachlor and lindane are mainly due to the regional background with little contribution from local soil residues. An analysis of modelled summer day and night average soil-air exchange fluxes shows that toxaphene and p,p'-DDE soil residues are strong sources of emission to the atmosphere during both the day and night while the chlordanes, trans-nonachlor, lindane and dieldrin are deposited from the atmosphere to the soil during the night hours and emitted to the atmosphere during the day time. This result illustrates the model's capability to simulate the processes that lead to the 'grasshopper' effect whereby persistent pesticides in soils can be transported in the atmosphere by successive periods of emission and deposition to terrestrial surfaces. In the second part to this paper, the model is used to study the trends of pesticide residues and air concentrations over a twenty year period.

Agriculture↗
PubMed2003

Input of atmospheric lead to marine sediments in a south-east Pacific coastal area (approximately 36 degrees S).

Atmospheric input of Pb to coastal sediments in the south-east Pacific (approximately 36 degrees S) was estimated using: (1) a salt marsh (non-local emission sources) as a natural collector of atmospheric fluxes and (2) Pb concentrations in rain and air samples, both considered to be representative of the atmospheric input in the study area. A radioisotopic geochronology technique ((210)Pb) was used to estimate the total Pb atmospheric supply to the sediments. The results show that atmospheric input to Concepción Bay accounts for 13-68% of Pb in near shore sediments, evaluated through salt marsh and rain, both showing comparable results. Consequently, there are other relevant Pb sources to explain the higher concentrations in this area. Sediments in the shelf are subject to important influence of upwelling waters, estimated by Salamanca [Sources and sinks of (210)Pb in Concepción Bay, Chile (1993) PhD thesis, Marine Science Research Center, State University of New York at Stony Brook, USA] using (210)Pb. The atmospheric input, however, is mainly responsible for the total Pb input, since the salt marsh (natural atmospheric collector) shows similar Pb(xs) inventories than the shelf, corresponding to a regional-scale Pb emissions.

Aerosols↗
PubMed1997

The communication atmosphere between physician colleagues: competitive perfectionism or supportive dialogue? A Norwegian study.

Open and supportive communication is probably one of the most important promotors of learning, coping and satisfaction at the workplace. The aim of this paper is to describe and predict the communication atmosphere between Norwegian physicians. Twenty statements describing communication, as perceived by the physicians themselves, were presented to a random sample of the members of the Norwegian Medical Association of which more than 90% of the physicians in the country are members (N = 2628). In general, this investigation indicates that the communication atmosphere among Norwegian physicians is characterised by support and mutual respect. More than half of the respondents fully agreed that communication between colleagues in the workplace is marked by solidarity, and that experienced colleagues show respect for the less experienced in both personal and professional matters. Physicians working in hospitals described the communication atmosphere as substantially more selfish and competitive than non-hospital physicians, whilst general practitioners considered the atmosphere between colleagues to be more supportive than non-specialists. In addition, high perceived stress was associated with the perception of a less supportive atmosphere. However, the strongest predictor of the communication atmosphere was clearly the physician's perceived autonomy. The comprehensive retrenchment programmes implemented in Norwegian hospitals during recent years have increased stress and restricted professional autonomy among both physicians and other occupational groups. Our findings indicate that the communication atmosphere necessary to secure continuity of knowledge within the medical profession may have been jeopardised by this process. In the long term, this may prove hazardous to the quality of medical care.

Adult↗
PubMed2000

Interpreting atmospheric pollen counts for use in clinical allergy: spatial variability.

BACKGROUND: Atmospheric pollen counts are ubiquitous data, however, few guidelines exist for interpreting them. A fundamental problem involves appreciating spatial variability in atmospheric pollen concentrations, for example, differences in pollen conditions between neighborhoods within a metropolitan area. The significance of this problem is perhaps most manifest in clinical allergy where pollen counts from a single rooftop pollen sampler are often applied to an entire city. OBJECTIVES: This review will consider experimental data concerning spatial variability in atmospheric pollen concentrations. Several guidelines for interpreting pollen counts with respect to this spatial variability will be presented. DATA SOURCES: This review will consider three independent bodies of literature concerning spatial variability in atmospheric pollen concentrations: (1) controlled-release experiments, (2) the paleoecology literature, and (3) atmospheric surveys. RESULTS: Four principal results emerged. First, pollen concentrations in the atmosphere appear to be inherently heterogeneous. Differences in pollen recovery between adjacent points increase in a predictable manner as a function of distance. Second, spatial variability decreases as the distance between pollen sources and destination regions increases. Pollen recovery across a city is most similar when pollen is transported from distant source regions. Third, the size of the source area represented by a pollen sampler depends on the distance between the sampler and the nearest vegetation. Samplers located near vegetation reflect small source areas; source areas expand considerably when the distance to the nearest vegetation increases. Last, individual pollen types travel characteristic distances from their source. Heavy pollen types collected at a particular point reflect a smaller source areas than lighter types which represent much larger source areas. CONCLUSIONS: These conclusions allow allergists to interpret their atmospheric pollen counts with greater sophistication than was previously possible. Mathematical equations presented in this review permit rough calculations concerning source areas.

Air Pollution↗
PubMed2001

Carbonyl sulfide derived from catalytic oxidation of carbon disulfide over atmospheric particles.

The formation of carbonyl sulfide (COS) by catalytic oxidization of carbon disulfide (CS2) over atmospheric particle catalysts was explored through FT-IR, MS (mass spectrometry), and a fixed-bed stainless steel reactor. Also the crystallizing conditions and specific surfaces (areas) of the catalysts were investigated by means of X-ray diffraction (XRD) and BET. Some oxides such as CaO, Fe2O3, Al2O3, and SiO2 were investigated under the conditions similar to the atmospheric particles as a comparison. The results showed that atmospheric particles and the oxide catalysts exhibited considerable oxidizing activity for CS2 at ambient temperature to form COS. Elemental sulfur as well as COS was one of the main products; even CO2 could be produced by a secondary reaction on some catalysts. Among the catalysts, CaO showed the strongest catalytic activity for oxidizing CS2. The catalytic activities of Fe2O3 and Al2O3 decreased considerably as compared with CaO, and SiO2 had the weakest catalytic activity. Atmospheric particles' catalytic activity is between Fe2O3's and Al2O3's. The atmospheric particles we collected mainly consist of Ca(Al2Si2O8).4H2O, which is also the main component of cement. COS, the main product, is formed by the catalytic oxidizing reaction of CS2 with adsorbed "molecular" oxygen overthe catalysts' surfaces. The concentration of adsorbed oxygen over catalysts' surfaces may be the key factor contributed to the oxidizing activities. This paper first revealed that CS2 could be catalytically oxidized over atmospheric particles to form COS. It induced that this reaction may be another important source of atmospheric COS from CS2.

Air Pollutants↗
PubMed2002

Transboundary atmospheric lead pollution.

A high-temporal resolution collection technique was applied to refine aerosol sampling in Jerusalem, Israel. Using stable lead isotopes, lead concentrations, synoptic data, and atmospheric modeling, we demonstrate that lead detected in the atmosphere of Jerusalem is not only anthropogenic lead of local origin but also lead emitted in other countries. Fifty-seven percent of the collected samples contained a nontrivial fraction of foreign atmospheric lead and had 206Pb/207Pb values which deviated from the local petrol-lead value (206Pb/207Pb = 1.113) by more than two standard deviations (0.016). Foreign 206Pb/207Pb values were recorded in Jerusalem on several occasions. The synoptic conditions on these dates and reported values of the isotopic composition of lead emitted in various countries around Israel suggest that the foreign lead was transported to Jerusalem from Egypt, Turkey, and East Europe. The average concentration of foreign atmospheric lead in Jerusalem was 23 +/- 17 ng/m3, similar to the average concentration of local atmospheric lead, 21 +/- 18 ng/ m3. Hence, the load of foreign atmospheric lead is similar to the load of local atmospheric lead in Jerusalem.

Air Movements↗