Relationship between different size classes of particulate matter and meteorology in three European cities

Evidence on the correlation between particle mass and (ultrafine) particle number concentrations is limited. Winter- and spring-time measurements of urban background air pollution were performed in Amsterdam (The Netherlands), Erfurt (Germany) and Helsinki (Finland), within the framework of the EU funded ULTRA study. Daily average concentrations of ambient particulate matter with a 50% cut off of 2.5 microm (PM2.5), total particle number concentrations and particle number concentrations in different size classes were collected at fixed monitoring sites. The aim of this paper is to assess differences in particle concentrations in several size classes across cities, the correlation between different particle fractions and to assess the differential impact of meteorological factors on their concentrations. The medians of ultrafine particle number concentrations were similar across the three cities (range 15.1 x 10(3)-18.3 x 10(3) counts cm(-3)). Within the ultrafine particle fraction, the sub fraction (10-30 nm) made a higher contribution to particle number concentrations in Erfurt than in Helsinki and Amsterdam. Larger differences across the cities were found for PM2.5(range 11-17 microg m(-3)). PM2.5 and ultrafine particle concentrations were weakly (Amsterdam, Helsinki) to moderately (Erfurt) correlated. The inconsistent correlation for PM2.5 and ultrafine particle concentrations between the three cities was partly explained by the larger impact of more local sources from the city on ultrafine particle concentrations than on PM2.5, suggesting that the upwind or downwind location of the measuring site in regard to potential particle sources has to be considered. Also, relationship with wind direction and meteorological data differed, suggesting that particle number and particle mass are two separate indicators of airborne particulate matter. Both decreased with increasing wind speed, but ultrafine particle number counts consistently decreased with increasing relative humidity, whereas PM2.5 increased with increasing barometric pressure. Within the ultrafine particle mode, nucleation mode (10-30 nm) and Aitken mode (30-100 nm) had distinctly different relationships with accumulation mode particles and weather conditions. Since the composition of these particle fractions also differs, it is of interest to test in future epidemiological studies whether they have different health effects.     

Aspiration and sampling efficiencies of the TSP and louvered particulate matter inlets

An experimental system was developed for the rapid measurement of the aspiration/transfer efficiency of aerosol samplers in a wind tunnel. We attempted to measure the aspiration and particle transfer characteristics of two inlets commonly used for sampling airborne Particulate Matter (PM): the 'Total Suspended Particulate' or TSP inlet, and the louvered 'dichotomous sampler inlet' typically used in sampling PM10 or PM2.5. We were able to determine the fraction of the external aerosol that enters the inlet and is transferred through it, and hence is available for collection by a filter, or further size fractionation into PM10 or PM2.5. This 'sampling efficiency' was analysed as a function of dimensionless aerodynamic parameters in order to understand the factors governing inlet performance. We found that for the louvered inlet the sampling efficiency increases as the external wind increases. Under all conditions expected in practical use the louvered inlet aspirates sufficient PM to allow either PM10 or PM2.5 to be selected downstream. The TSP inlet's sampling efficiency decreases with increasing external wind, and the TSP inlet is likely to under-sample the coarse end of the PM10 fraction at moderate and high external winds. As this inlet is generally not used with a downstream size fractionator, changes in sampling efficiency directly affect the measured aerosol concentration. We also investigated whether it is possible to dimensionally scale the PM inlets to operate at either higher or lower flow rates, while preserving the same sampling characteristics as the current full-scale, 16.67 L min(-1) versions. In the case of the louvered inlet, our results indicate that scaling to lower flow rates is possible; scaling to higher flow rates was not tested. For the TSP sampler, the sampling efficiency changes if the sampler is scaled to operate at smaller or larger flow rates, leading to unreliable performance.     

Seasonal variability of endotoxin in ambient fine particulate matter

Endotoxin is a toxic, pro-inflammatory compound that has been detected in indoor air and dust in homes and occupational settings, and also in outdoor air. Data on the outdoor sampling of endotoxin are limited. Currently, little is known about the seasonal variation and influence of temperature on outdoor endotoxin levels. In the present study, we report endotoxin levels in fine fraction particulate matter with a 50% aerodynamic cutoff diameter of 2.5 microm (PM2.5) and describe the seasonal variation of endotoxin in Munich, Germany. In 1999-2000, PM2.5 was collected at forty outdoor monitoring sites across Munich. Approximately four samples were collected at each site for a total of 158 samples. Endotoxin concentrations in the PM2.5 samples were determined using the kinetic chromogenic Limulus Amebocyte Lysate (LAL) assay. The geometric mean endotoxin concentration was 1.07 EU mg PM2.5(-1) (95% C.I.: 0.915-1.251) or 0.015 EU m(-3) of sampled air (95% C.I.: 0.013-0.018). Munich endotoxin levels were significantly related to ambient temperature (p < 0.0001) and percent relative humidity (p < 0.0001). Sampling periods with higher average temperatures yielded higher levels of endotoxin in PM2.5 (r = 0.641), whereas decreases in percent relative humidity were associated with increased endotoxin levels in PM2.5 (r = -0.388). Endotoxin levels were significantly higher during the warmer seasons of spring [means ratio (MR): 2.5-2.7] and summer (MR: 2.1-3.0) than during winter. Although temperature and relative humidity do not explain all of the variability in endotoxin levels, their effects were significant in our data set. Temperature effects and seasonal variation of endotoxin should be considered in future studies of outdoor endotoxin.     

Persistent organic pollutants in soil density fractions: distribution and sorption strength

The sorption strength of persistent organic pollutants in soils may vary among different soil organic matter (SOM) pools. We hypothesized that polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were unevenly distributed and had different soil organic carbon (SOC)-water partition coefficients (K(OC)) among soil density fractions. We determined the concentrations and K(OC) values of 20 PAHs and 12 PCBs in bulk samples and three density fractions (light, <2.0, medium, 2.0-2.4, and heavy, >2.4 g cm(-3)) of 11 urban topsoils (0-5 cm) from Bayreuth, Germany. The K(OC) values were determined using sequential extraction with methanol-water mixtures (35% and 65% methanol) at 60 degrees C. The sum of 20 PAH concentrations in bulk soil ranged 0.4-186 mg kg(-1), and that of 12 PCB concentrations 1.2-158 microg kg(-1). The concentrations of all PAHs and PCBs decreased in the order light>medium>heavy fraction. When normalized to the SOC concentrations, PAH concentrations were significantly higher in the heavy than in the other density fractions. The K(OC) values of the PAHs in density fractions were 3-20 times higher than those of the PCBs with similar octanol-water partition coefficients (K(OW)). The K(OC) values of individual PAHs and PCBs varied up to a factor of 1000 among the studied soils and density fractions. The K(OC) values of 5- and 6-ring PAHs tended to be highest in the heavy fraction, coinciding with their enrichment in this fraction. For the other PAHs and all PCBs, the K(OC) values did not differ among the density fractions. Thus, there is no relationship between sorption strength and distribution among density fractions, indicating that density fractionation is not a suitable tool to distinguish among differently reactive PAH and PCB pools in soils.     

Background levels of heavy metals in surficial sediments of the Gulf of Lions (NW Mediterranean): an approach based on 133Cs normalization and lead isotope measurements

This paper presents an attempt to reach natural background levels of heavy metals in surficial sediments of the Gulf of Lions (NW Mediterranean). To correct for the grain-size effect, normalization procedures based on a clay mineral indicator element are commonly used, after a first grain size separation by sieving. In our study, we tested the applicability of this method with respect to commonly used normalizer elements, and found that stable Cs shows the best ability to reflect the fine sediment fraction. Background levels were successfully reached for Co, Cr, Cu, Ni and Pb, compared to various literature references. Nevertheless, in the case of lead, the normalized data depicted a general enrichment in all samples, and the natural levels could only be reached when concentrations were corrected for the atmospheric contribution by analysing lead isotope ratios. Also for Zn, a general enrichment was found in our samples, although less important.     

Dioxin?hnliche polychlorierte Biphenyle (PCB) in der Umwelt

Zusammenfassung Ziel und Absicht  Der derzeitige Kenntnisstand zu Quellen, Verbleib in der Umwelt, Exposition des Menschen und gesundheitlicher Bewertung von dioxin?hnlichen polychlorierten Biphenylen (PCB) und nicht dioxin?hnlichen PCB wird mit Fokus auf den deutschsprachigen Raum dargestellt und zusammengefasst. Methoden  Grundlage für den aktuellen Kenntnisstand sind die Vortr?ge und Diskussionsergebnisse eines zweit?gigen bundesweiten Statuskolloquiums. Die Bedeutung der dioxin?hnlichen PCB wird insbesondere in Relation zu den polychlorlerten Dibenzo-p-dioxinen (PCDD) und Dibenzofuranen (PCDF) betrachtet. Dazu dient in erster Linie ein Vergleich der Toxizit?ts?quivalentkonzentrationen (TEQ) beider Stoffgruppen in den betrachteten Umweltmatrices. Ergebnisse und Schlussfolgerungen  In vielen Umweltmedien sind die TEQ-Werte der dioxin?hnlichen PCB ?hnlich hoch wie die PCDD/PCDF-Gehalte, in den meisten Lebensmitteln tierischen Ursprungs sogar h?her. In den meisten Medien hat das nichtortho substituierte PCB 126 aufgrund seines hohen Toxizit?ts?quivalenzfaktors von 0,1 den mit Abstand h?chsten Beitrag zum PCB-TEQ. Für die gro?fl?chige Umweltbelastung mit PCB ist offensichtlich der atmosph?rische (Fern) Transport wesentlich. Für den Eintritt der dioxin?hnlichen, PCB in terrestrische Nahrungsketten ist der Transfer Atmosph?re-Pflanze wahrscheinlich der entscheidende Schritt. Empfehlungen und Ausblick  Trotz des Rückgangs der Umweltbelastung mit PCB und PCDD/PCDF überschreitet ein erheblicher Teil der Bev?lkerung in Deutschland und anderen europ?ischen Staaten gegenw?rtig noch die duldbare Aufnahme an, dioxin?hnlichen Substanzen. Aber auch aufgrund einer aktuellen toxikologischen Neubewertung der nicht-dioxin?hnlichen PCB muss die Verminderung der PCB-Exposition weiter betrieben werden. OnlineFirst: 11. April 2005     

Free Energy Reduction by Molecular Interface Crossing: Novel Mechanism for the Transport of Material Across the Interface of Nanoscale Droplets Induced by Competing Intermolecular Forces for Application in Perfluorocarbon Blood Substitutes

 Perfluorocarbons (PFCs) are inert liquids which can dissolve – and release – approximately 50 times more oxygen than blood plasma. Oxygen carriers based on PFCs are easy to produce, free of biological components, and more rigorously sterilizable than blood. PFCs injected into the body are eliminated by expiration through the lungs. Before reaching the lungs, PFCs accumulate in storage organs such as liver and spleen. In these organs nanoscale PFC droplets reduce their free energy by unifying to microscopic drops, thus indirectly lowering the rate of their expiration. The model of free energy reduction by molecular interface crossing (FERMIC), a novel emulsion breaking mechanism derived from first principles as presented here, leads to a better understanding of the structure formation processes relevant in perfluorocarbons (PFCs) in vivo. Received: 11 November 1998 / Accepted in revised form: 18 February 1999