Christoph Hueglin

Pushing the spatio-temporal resolution limit of urban air pollution maps

Up-to-date information on urban air pollution is of great importance for health protection agencies to assess air quality and provide advice to the general public in a timely manner. In particular, ultrafine particles (UFPs) are widely spread in urban environments and may have a severe impact on human health. However, the lack of knowledge about the spatio-temporal distribution of UFPs hampers profound evaluation of these effects. In this paper, we analyze one of the largest spatially resolved UFP data set publicly available today containing over 25 million measurements. We collected the measurements throughout more than a year using mobile sensor nodes installed on top of public transport vehicles in the city of Zurich, Switzerland. Based on these data, we develop land-use regression models to create pollution maps with a high spatial resolution of 100m × 100 m. We compare the accuracy of the derived models across various time scales and observe a rapid drop in accuracy for maps with subweekly temporal resolution. To address this problem, we propose a novel modeling approach that incorporates past measurements annotated with metadata into the modeling process. In this way, we achieve a 26% reduction in the root-mean-square error-a standard metric to evaluate the accuracy of air quality models-of pollution maps with semi-daily temporal resolution. We believe that our findings can help epidemiologists to better understand the adverse health effects related to UFPs and serve as a stepping stone towards detailed real-time pollution assessment.

In vitro estrogenicity of ambient particulate matter: contribution of hydroxylated polycyclic aromatic hydrocarbons.

Atmospheric particulate matter (PM1) was collected at an urban and a rural site in Switzerland during a hibernal high air pollution episode and was investigated for estrogenicity using an estrogen‐sensitive reporter gene assay (ER‐CALUX). All samples that were tested induced estrogen receptor‐mediated gene expression in T47D human breast adenocarcinoma cells. Observed estrogenic activities corresponded to 17β‐estradiol (E2) CALUX equivalent concentrations ranging from 2 to 23 ng E2‐CEQ per gram of PM1 (particulate matter of ≤ 1 µm aerodynamic diameter) and from 0.07 to 1.25 pg E2‐CEQ per m3 of sampled air. There was a strong correlation between the PM1 estrogenicity of the urban and rural sites (r = 0.92). Five hydroxylated polycyclic aromatic hydrocarbons (hydroxy‐PAHs), which show structural similarities to E2, were assessed for their estrogenic activity. The following order of estrogenic potency was found: 2‐hydroxychrysene > 2‐hydroxyphenanthrene > 1‐hydroxypyrene > 2‐hydroxynaphthalene > 1‐hydroxynaphthalene. Three of these hydroxy‐PAHs, namely 2‐hydroxyphenanthrene, 2‐hydroxynaphthalene and 1‐hydroxynaphthalene, were detected in all PM1 extracts. However, they contributed only 0.01–0.2% to the overall estrogenic activity. Hence, mainly other estrogenic compounds not yet identified by chemical analysis must be responsible for the observed activity. The temporal trend of PM1 estrogenicity at the urban and rural site, respectively, was compared with the time course of several air pollutants (NO2, NO, SO2, O3, CO) and meteorological parameters (temperature, humidity, air pressure, solar irradiation, wind velocity). However, specific emission sources and formation processes of atmospheric xenoestrogens could not be elucidated. This study showed that ambient particulate matter contains compounds that are able to interact with estrogen receptors in vitro and potentially also interfere with estrogen‐regulated pathways in vivo. Copyright

Source apportionment of PM10, organic carbon and elemental carbon at Swiss sites: An intercomparison of different approaches

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.

Size-Resolved Identification, Characterization, and Quantification of Primary Biological Organic Aerosol at a European Rural Site

Primary biological organic aerosols (PBOA) represent a major component of the coarse organic matter (OMCOARSE, aerodynamic diameter > 2.5 μm). Although this fraction affects human health and the climate, its quantification and chemical characterization currently remain elusive. We present the first quantification of the entire PBOACOARSE mass and its main sources by analyzing size-segregated filter samples collected during the summer and winter at the rural site of Payerne (Switzerland), representing a continental Europe background environment. The size-segregated water-soluble OM was analyzed by a newly developed offline aerosol mass spectrometric technique (AMS). Collected spectra were analyzed by three-dimensional positive matrix factorization (3D-PMF), showing that PBOA represented the main OMCOARSE source during summer and its contribution to PM10 was comparable to that of secondary organic aerosol. We found substantial cellulose contributions to OMCOARSE, which in combination with gas chromatography mass spectrometry molecular markers quantification, underlined the predominance of plant debris. Quantitative polymerase chain reaction (qPCR) analysis instead revealed that the sum of bacterial and fungal spores mass represented only a minor OMCOARSE fraction (<0.1%). X-ray photoelectron spectroscopic (XPS) analysis of C and N binding energies throughout the size fractions revealed an organic N increase in the PM10 compared to PM1 consistent with AMS observations.

Contribution of road traffic to ambient fine particle concentrations (PM10) in Switzerland

A multivariate receptor model was applied to estimate the contribution of road traffic to ambient levels of fine particles (PM10) at different locations in Switzerland. At two roadside sites with heavy local traffic, the road traffic was found to account for 46% and 64% of PM10. At an urban background site, the estimated average road traffic contribution was 34%, whereas a slightly higher value was obtained at a suburban site (36%). These results are in agreement with the findings of a recent study, where a conceptually different approach (dispersion modelling) was applied.

Performance of NO, NO 2 low cost sensors and three calibrationapproaches within a real world application

approaches within a real world application Alessandro Bigi1, Michael Mueller2, Stuart K. Grange3, Grazia Ghermandi1, and Christoph Hueglin2 1‘Enzo Ferrari’ Department of Engineering, University of Modena and Reggio Emilia, Modena, Italy 2Empa, Swiss Federal Institute for Materials Science and Technology, Duebendorf, Switzerland 3Wolfson Atmospheric Chemistry Laboratory, University of York, York, United Kingdom Correspondence to: Alessandro Bigi (alessandro.bigi@unimore.it)

Increases in Wintertime Oxidation Capacity Counteract the Success of Emission Reduction Measures in Europe with Respect to Secondary Inorganic Aerosols

Air pollution reduction measures in Europe have led to marked decreases in the levels of primary pollutants such as SO2 and NOx since the 1980s while for secondary pollutants like ozone and secondary inorganic aerosols (SIA) the effects of these measures are much less obvious. A recent extensive comparison of the composition of particulate matter smaller than 10 μm (PM10) in Switzerland between the years 1998/1999 and 2008/2009, for example, revealed no changes in the levels of nitrates despite large NOx emission reductions over this period. Similarly, aerosol sulphates decreased much less strongly than the precursor gas SO2.

Revealing the limits of spatio-temporal high-resolution pollution maps

Up-to-date information on urban air pollution, such as reliable pollution maps, is of great importance for health protection agencies to timely assess the air quality situation and provide advice to the general public. Ultrafine particles (UFPs) are widely spread in urban environments and believed to have severe impact on the human health. However, the lack of spatially resolved data hampers profound evaluation of these effects. In this work, we introduce one of the largest spatially resolved UFP data set available today, with over 25 million measurements to build high-resolution pollution maps for an urban area of 100 km2. The data is collected throughout more than one year using mobile sensor nodes, which are installed on top of public transport vehicles in the city of Zurich, Switzerland. We develop land-use regression models to create pollution maps with a high spatial resolution and study their temporal resolution limit.

Holzfeuerungen: eine bedeutende Quelle von Feinstaub in der Schweiz

Wood combustion: a substantial source of airborne particulate matter in Switzerland Wood is a renewable energy source. Wood combustion for heating purposes therefore helps in reducing CO2 emissions. However, it often results in high emissions of particulate matter (PM) which includes both black carbon (BC) and organic carbon (OC). PM has adverse health effects and should therefore be minimized. This paper reports on the latest methods to quantify the contribution of wood combustion to PM load and gives values for PM, BC, and OC from wood combustion at a number of different sites in Switzerland. State of the art methods to characterize emissions are presented and examples are given. It is shown that a major fraction of the emissions stems from small wood stoves, where the emissions are especially high during the starting phase. In addition, these small furnaces emit large amounts of gases which are rapidly oxidized and form secondary aerosols in the atmosphere. Improvements in the emissions of small wood s...

Residential Wood Burning: A Major Source of Fine Particulate Matter in Alpine Valleys in Central Europe

Residential wood burning is one of the important sources of ambient particulate matter (PM) in many European regions. Besides total PM, residential wood burning is at many locations an important source of other air pollutants such as polycyclic aromatic hydrocarbons (PAHs), benzene, particulate organic carbon (OC), and black carbon (BC), especially in regions such as the Alpine region, where wood fuel is, on one hand, traditionally used for domestic heating during the cold season in small stoves and, on the other hand, meteorological conditions during winter are often favourable for accumulation of wood smoke in a shallow boundary layer. As a consequence, wood burning in the Alpine region can be the dominating source of PM, OC, and BC during the cold season. This is true for both larger cities and small villages in rural areas. The absolute contribution of wood burning emissions to particulate air pollutants tends in rural environments to be even larger than in urban areas. This chapter gives an overview about the results of studies on ambient particulate pollutants from residential wood burning in the Alpine region.