Real-time measurements of non-refractory submicron aerosols (NR-PM1 ) were conducted within the greater Alpine region (Switzerland, Germany, Austria, France and Liechtenstein) during several ...week-long field campaigns in 2002-2009. This region represents one of the most important economic and recreational spaces in Europe. A large variety of sites was covered including urban backgrounds, motorways, rural, remote, and high-alpine stations, and also mobile on-road measurements were performed. Inorganic and organic aerosol (OA) fractions were determined by means of aerosol mass spectrometry (AMS). The data originating from 13 different field campaigns and the combined data have been utilized for providing an improved temporal and spatial data coverage. The average mass concentration of NR-PM1 for the different campaigns typically ranged between 10 and 30 μg m-3 . Overall, the organic portion was most abundant, ranging from 36% to 81% of NR-PM1 . Other main constituents comprised ammonium (5-15%), nitrate (8-36%), sulfate (3-26%), and chloride (0-5%). These latter anions were, on average, fully neutralized by ammonium. As a major result, time of the year (winter vs. summer) and location of the site (Alpine valleys vs. Plateau) could largely explain the variability in aerosol chemical composition for the different campaigns and were found to be better descriptors for aerosol composition than the type of site (urban, rural etc.). Thus, a reassessment of classifications of measurements sites might be considered in the future, possibly also for other regions of the world. The OA data was further analyzed using positive matrix factorization (PMF) and the multi-linear engine ME (factor analysis) separating the total OA into its underlying components, such as oxygenated (mostly secondary) organic aerosol (OOA), hydrocarbon-like and freshly emitted organic aerosol (HOA), as well as OA from biomass burning (BBOA). OOA was ubiquitous, ranged between 36% and 94% of OA, and could be separated into a low-volatility and a semi-volatile fraction (LV-OOA and SV-OOA) for all summer campaigns at low altitude sites. Wood combustion (BBOA) accounted for a considerable fraction during wintertime (17-49% OA), particularly in narrow Alpine valleys BBOA was often the most abundant OA component. HOA/OA ratios were comparatively low for all campaigns (6-16%) with the exception of on-road, mobile measurements (23%) in the Rhine Valley. The abundance of the aerosol components and the retrievability of SV-OOA and LV-OOA are discussed in the light of atmospheric chemistry and physics.
In this study, the results of source apportionment of particulate matter (PM10), organic carbon (OC), and elemental carbon (EC) — as obtained through different approaches at different types of sites ...(urban background, urban roadside, and two rural sites in Switzerland) — are compared. The methods included in this intercomparison are positive matrix factorisation modelling (PMF, applied to chemical composition data including trace elements, inorganic ions, OC, and EC), molecular marker chemical mass balance modelling (MM-CMB), and the aethalometer model (AeM).
At all sites, the agreement of the obtained source contributions was reasonable for OC, EC, and PM10. Based on an annual average, and at most of the considered sites, secondary organic carbon (SOC) is the component with the largest contribution to total OC; the most important primary source of OC is wood combustion, followed by road traffic. Secondary aerosols predominate in PM10. All considered techniques identified road traffic as the dominant source of EC, while wood combustion emissions are of minor importance for this constituent.
The intercomparison of different source apportionment approaches is helpful to identify the strengths and the weaknesses of the different methods. Application of PMF has limitations when source emissions have a strong temporal correlation, or when meteorology has a strong impact on PM variability. In these cases, the use of PMF can result in mixed source profiles and consequently in the under- or overestimation of the real-world sources. The application of CMB models can be hampered by the unavailability of source profiles and the non-representativeness of the available profiles for local source emissions.
This study also underlines that chemical transformations of molecular markers in the atmosphere can lead to the underestimation of contributions from primary sources, in particular during the summer period or when emission sources are far away from the receptor sites.
► Source apportionment results for PM10, OC and EC by PMF, MM-CMB and AeM are compared. ► Generally good agreement of source contributions as estimated with the different approaches is obtained. ► The strengths and the limitations of the different approaches are investigated. ► PMF: correlated source activities are an obstacle for a correct identification of PM source. ► MM-CMB: degradation of organic tracers can lead to an underestimation of source impacts.
In this study, the chemical composition of PM10 at various sites in Switzerland during a one year period in 2008/2009 and changes since the time of a similar characterisation campaign in 1998/1999 ...are investigated. The concentrations of main components of PM10 were found to be similar at different site types north of the Alps (i.e. urban background, suburban and rural sites). Secondary inorganic PM10 components (nitrate, sulphate and ammonium) constituted the largest PM10 mass fraction, followed by carbonaceous matter (OM and EC), while the abundance of mineral dust and trace elements was small (both <10%). At a rural site south of the Alps the concentrations of secondary inorganic components were much lower and the concentrations of OM and EC clearly higher than north of the Alps. Enhanced concentrations of EC, trace elements and to a lesser extent of OM and mineral dust were found at an urban roadside site. At this site, typical traffic related trace elements like Cu, Fe, Mo, Sb and Ba were highly enriched.
This paper indicates clear positive effects of emission reduction strategies for PM10 and precursors implemented during the past ten and more years. The concentrations of sulphate and EC declined during the considered time period, EC reductions were especially strong at the urban roadside site (−2.4μgm−3). In contrast, the concentration of nitrate slightly increased at all of the considered sites (0.2–0.5μgm−3). Large reductions in the concentrations of many trace elements in PM10 during the past ten years are evident. As an example, the observed relative decrease of Pb is about −80%, which is a success of the ban of leaded gasoline in Switzerland and in the EU.
► Chemical composition of PM10 at different site types in Switzerland is investigated. ► The results are compared with data from ten years before. ► Sulphate, elemental carbon and various trace elements declined during past ten years. ► In contrast, nitrate concentrations slightly increased. ► The observed changes allow an assessment of implemented emission control measures.
During the past years, actions implemented for the reduction of particulate matter emissions have in many European countries focused on road traffic emissions. Much less attention was paid to ...emissions from domestic wood combustion though the importance of residential wood burning as a source of atmospheric particulate matter (PM) in the Alpine region has been shown in many studies.
Here we review the current knowledge about the contribution of wood burning emissions to ambient concentrations of elemental carbon (EC), organic carbon (OC) and PM in the Alpine region. The published results obtained by different approaches (e.g. macro-tracer method, multivariate receptor modeling, chemical mass balance modelling, and so-called Aethalometer modeling) are used in an ambient mono-tracer approach to estimate representative relationships between wood burning tracers (levoglucosan and mannosan) and EC, OC and PM from wood burning. The relationships found are applied to available ambient measurements of levoglucosan and mannosan at Alpine sites for estimation of the contributions of wood burning emissions to average levels of carbonaceous aerosols and PM at these sites. Our results imply that PM from wood burning alone adds often up to 50% and more of the EU daily limit value for PM10 in several alpine valleys during days in winter. Concentrations of carbonaceous aerosols in these valleys are often up to six times higher than in urban or rural sites at the foothills of the Alps.
•Review of current knowledge about wood burning emissions in the alpine region.•Ambient mono-tracer approach combining data from source apportionment studies.•Compared concentrations of EC, OC and PM from wood burning at 23 measurement sites.•50% and more of EU daily limit value for PM10 reached due to wood burning emissions.
PM10 speciation data from various sites in Switzerland for two time periods (January 1998–March 1999 and August 2008–July 2009) have been analysed for major sources by receptor modelling using ...Positive Matrix Factorisation (PMF). For the 2008/2009 period, it was found that secondary aerosols (sulphate- and nitrate-rich secondary aerosols, SSA and NSA) are the most abundant components of PM10 at sites north of the Alps. Road traffic and wood combustion were found to be the largest sources of PM10 at these sites. Except at the urban roadside site where road traffic is dominating (40% of PM10 -- including road salt), the annual average contribution of these two sources is of similar importance (17% and 14% of PM10, respectively). At a rural site south of the Alps wood combustion and road traffic contributions to PM10 were higher (31% and 24%, respectively), and the fraction of secondary aerosols lower (29%) than at similar site types north of the Alps.
Comparison of PMF analyses for the two time periods (1998/1999 and 2008/2009) revealed decreasing average contributions of road traffic and SSA to PM10 at all sites. This indicates that the measures that were implemented in Switzerland and in neighbouring countries to reduce emissions of sulphur dioxide and PM10 from road traffic were successful. On the other hand, contributions of wood combustion did not change during this ten year period, and the contribution of nitrate-rich secondary aerosols has even increased. It is shown that PMF can be a helpful tool for the assessment of long-term changes of source contributions to ambient particulate matter.
► Road traffic and wood combustion are the largest sources of PM10 in Switzerland. ► Road traffic related PM10 clearly declined during past ten years. ► In contrast, contribution of wood combustion remained about constant. ► Receptor modelling can be very useful for assessment of long-term changes.
The European Photon Imaging Camera (EPIC) consortium has provided the focal plane instruments for the three X-ray mirror systems on XMM-Newton. Two cameras with a reflecting grating spectrometer in ...the optical path are equipped with MOS type CCDs as focal plane detectors (Turner CITE), the telescope with the full photon flux operates the novel pn-CCD as an imaging X-ray spectrometer. The pn-CCD camera system was developed under the leadership of the Max-Planck-Institut für extraterrestrische Physik (MPE), Garching. The concept of the pn-CCD is described as well as the different operational modes of the camera system. The electrical, mechanical and thermal design of the focal plane and camera is briefly treated. The in-orbit performance is described in terms of energy resolution, quantum efficiency, time resolution, long term stability and charged particle background. Special emphasis is given to the radiation hardening of the devices and the measured and expected degradation due to radiation damage of ionizing particles in the first 9 months of in orbit operation.
Linear and non-linear microwave active devices are usually modelled with an equivalent circuit for CAD applications. The circuit is composed of parasitic (bias-independent) and intrinsic ...(bias-dependent) elements; the correct evaluation of both types of elements is required not only for the extraction of a non-linear model, but also for the extraction of a linear bias-dependent one, as necessary for foundry use. The evaluation of parasitics is usually performed prior to the standard full-bias measurements, for a special condition of the active device (Vds = 0, 'cold FET' measurements) 1. The standard technique for inductances evaluation however does not take into account a correction term due to parasitic resistances and capacitances, that is equivalent to a negative inductive tern even in the low and medium frequency range, where evaluation is made. This can lead to incorrect gate, source and drain parasitic inductance values, especially for small transistors. In some cases the magnitude of the error can be comparable to the small via-hole inductance, that therefore may appear to be negative if evaluated with the standard technique; it can also represent a substantial fraction of gate and drain inductances. In this paper the underlying theory and experimental data are exposed.
Repetitive transcranial magnetic stimulation (rTMS) is used to modulate neural systems and provides the opportunity for experimental tests of hypotheses regarding mechanisms underlying anorexia ...nervosa (AN). The present pilot study has investigated whether high‐frequency repetitive transcranial magnetic stimulation (HF‐rTMS) to a region of the right dorsolateral prefrontal cortex (DLPFC) might be associated with change in food selection among adult inpatients with AN. Ten women received one session of sham and one session of HF‐rTMS targeting the right DLPFC while completing a computerized Food Choice Task. Compared to sham, HF‐rTMS was associated with changes in food ratings and food choice: inpatients reported higher healthiness ratings of low‐ and high‐fat foods and selected a significantly greater proportion of high‐fat foods over a neutrally rated reference item while receiving HF‐rTMS. Findings suggest that HF‐rTMS to the right DLPFC was associated with a reduction of fat avoidance on a food choice task among inpatients with AN and provide additional support for the possibility that this region, and related neural circuits, may underlie restrictive food choice. Research using rTMS to experimentally test neural mechanisms is needed to elucidate the underpinnings of AN and supports the development of novel treatment targets.
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