33 research outputs found
Nine years of UV aerosol optical depth measurements at Thessaloniki, Greece
Spectral measurements of the aerosol optical depth (AOD) and the Ångström coefficient were conducted at Thessaloniki, Greece (40.5° N, 22.9° E) between January 1997 and December 2005 with a Brewer MKIII double-monochromator spectroradiometer. The dataset was compared with collocated measurements of a second spectroradiometer (Brewer MKII) and a CIMEL sun-photometer, showing correlations of 0.93 and 0.98, respectively. A seasonal variation of the AOD was observed at Thessaloniki, with AOD values at 340 nm of 0.52 and 0.28 for August and December respectively. Back trajectories of air masses for up to 4 days were used to assess the influence of long-range transport from various regions to the aerosol load over Thessaloniki. It is shown that part of the observed seasonality can be attributed to air masses with high AOD originating from North-Eastern and Eastern directions during summertime. The analysis of the long-term record (9 years) of AOD showed a downward tendency. A similar decreasing tendency was found in the record of the PM aerosol measurements, which are conducted near the surface at 4 air-quality monitoring stations in the area of the city of Thessaloniki
The risks of acute exposure to black carbon in Southern Europe: Results from the med-particles project
Objectives: While several studies have reported associations of daily exposures to PM2.5 (particles less than 2.5 μm) with mortality, few studies have examined the impact of its constituents such as black carbon (BC), which is also a significant contributor to global climate change. Methods: We assessed the association between daily concentrations of BC and total, cardiovascular and respiratory mortality in two southern Mediterranean cities. Daily averages of BC were collected for 2 years in Barcelona, Spain and Athens, Greece. We used case-crossover analysis and examined single and cumulative lags up to 3 days. Results: We observed associations between BC and all mortality measures. For a 3-day moving average, cardiovascular mortality increased by 4.5% (95% CI 0.7 to 8.5) and 2.0% (95% CI 0 to 4.0) for an interquartile change in BC in Athens and Barcelona, respectively. Considerably higher effects for respiratory mortality and for those above age 65 were observed. In addition, BC exhibited much greater toxicity per microgram than generic PM2.5. Conclusions: Our findings suggest that BC, derived in western industrialised nations primarily from diesel engines and biomass burning, poses a significant burden to public health, particularly in European cities with high-traffic density.Peer reviewe
Ca-rich garnets and associated symplectites in mafic peraluminous granulites from the Gföhl Nappe System, Austria
Mafic peraluminous granulites associated with the mantle-derived peridotites
of the Dunkelsteiner Wald provide evidence of the tectono-metamorphic
evolution of the Gföhl Nappe System, Austria. They contain the primary
assemblage garnet + Al-rich clinopyroxene + kyanite. Large Ca- and
Mg-rich garnets are embedded in a granoblastic matrix of Al-rich
clinopyroxene, Ca-rich plagioclase and minor hornblende. They were
partially replaced by different generations of symplectites: (a) corundum +
sapphirine + spinel + plagioclase formed around kyanite inclusions,
(b) orthopyroxene + spinel + plagioclase ± hornblende formed at their
rims and (c) clinopyroxene + orthopyroxene + spinel + plagioclase ±
hornblende formed within cracks.
Large garnets show complex compositional structure comprising several
repeatedly occurring garnet types, which are characterized by specific
compositions. The areal extent and the cross-cutting relations observed in
element distribution maps allowed for the derivation of the relative timing
of the formation of the different garnet types. The compositional features of
the garnets indicate post-formational modification by intra-crystalline
diffusion and metasomatic agents.
The garnet composition isopleths in equilibrium assemblage diagrams are in
line with compositions modification as indicated by the element distribution
maps. They confirm the deviation of composition from equilibrium for all
garnet types. Furthermore, at least the youngest garnet types show evidence of
metasomatic (Fe + Mg) loss affecting their Ca content. Pressure–temperature (P–T) estimates
are based on equilibrium assemblage diagrams that reproduce satisfactorily
the observed mineral assemblages and measured mineral compositions. Criteria
for checking the existence of preserved equilibrium compositions are
suggested. The results call into question the invariability of the assumption
that the Ca content and/or zoning in garnet preserves primary
P–T information from garnet growth in every case.
Recrystallization and compositional readjustment of the reactive garnet
volume during symplectite formation led to the development of pronounced,
secondary diffusion-induced zoning profiles overprinting the different garnet
types and post-dating the complex garnet compositional structure. The primary
assemblage is stable between 760 and 880 °C and pressures
> 11 kbar. The bulk composition of the crack symplectites is almost
isochemical to the oldest, broken-down garnet type. These symplectites were
formed above 730 °C and pressures between 5 and 7.5 kbar. The rocks
studied underwent more or less isothermal decompression from pressures above
11 to ∼ 6 kbar at temperatures of about 800 °C. Crack and rim
symplectites were formed after decompression during the early stage of
approximately isobaric cooling under conditions of low differential stress.
Due to limited availability of fluids promoting symplectite formation, the
timescale of symplectite formation calculated from secondary diffusion
profiles associated with crack symplectites is shown to be geologically very
short (< 0.5 ka)
Synoptic and local scale atmospheric circulation associated with air pollution episodes in an urban Mediterranean area
Air pollution episodes in urban coastal areas follow certain pre-determined patterns, being associated with certain local meteorological conditions and emission of primary pollutants. In this study, the synoptic and local scale atmospheric circulation that prevails during air pollution episodes in a coastal major city in Greece, Thessaloniki, is examined for a period of 15 years (1989-2004). The study signifies the importance of studying air pollution meteorological patterns between coastal areas with different terrain characteristics. For Thessaloniki, it was found that the episodes occur mainly during the cold period of the year, while four types of synoptic scale circulation were recognized (I, II, III, IV) and five patterns of the local scale circulation (A1, A2, B1, B2 and B3). The highest percentage of episodes is associated with the presence of an anticyclone over the northern Greece (types I and IV), being characterized by weak or very weak surface pressure gradient intensity, according to the position and extension of the anticyclone. Moreover, a temperature increase of at least 1°C during the previous 3 days is required in the lower troposphere. Consistent with the synoptic conditions, the development of the sea breeze plays a crucial role in the occurrence of the episodes, even in the cold period of the year, when the sea breeze can still develop with smaller frequency and intensity. Finally, it was found that a small number of episodes is related with the advection of polluted air masses from the industrial area in the northwest of the city and from the Eordaia area in the west, which is the largest lignite producing area of Balkans. © Springer-Verlag 2008
Nine years of UV aerosol optical depth measurements at Thessaloniki, Greece
Spectral measurements of the aerosol optical depth (AOD) and the Ångström coefficient were conducted at Thessaloniki, Greece (40.5° N, 22.9° E) between January 1997 and December 2005 with a Brewer MKIII double-monochromator spectroradiometer. The dataset was compared with collocated measurements of a second spectroradiometer (Brewer MKII) and a CIMEL sun-photometer, showing correlations of 0.93 and 0.98, respectively. A seasonal variation of the AOD was observed at Thessaloniki, with AOD values at 340 nm of 0.52 and 0.28 for August and December respectively. Back trajectories of air masses for up to 4 days were used to assess the influence of long-range transport from various regions to the aerosol load over Thessaloniki. It is shown that part of the observed seasonality can be attributed to air masses with high AOD originating from North-Eastern and Eastern directions during summer-time. The analysis of the long-term record (9 years) of AOD showed a downward tendency. A similar decreasing tendency was found in the record of the PM10 aerosol measurements, which are conducted near the surface at 4 air-quality monitoring stations in the area of the city of Thessaloniki