| 1. |
- Krecl, Patricia, et al.
(author)
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A feasibility study of mapping light-absorbing carbon using a taxi fleet as a mobile platform
- 2014
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In: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 66, s. 23533-
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Journal article (peer-reviewed)abstract
- Carbon-containing particles are associated with adverse health effects, and their light-absorbing fractions were recently estimated to be the second largest contributor to global warming after carbon dioxide. Knowledge on the spatiotemporal variability of light-absorbing carbon (LAC) particles in urban areas is relevant for air quality management and to better diagnose the population exposure to these particles. This work reports on the first mobile LAC mass concentrations (M-LAC) measured on-board four taxis in the Stockholm metropolitan area in November 2011. On average, concentrations were higher and more variable during daytime (median of 1.9 mu g m(-3) and median absolute deviation of 2.3 mu g m(-3)). Night-time (21:00-05:00) measurements were very similar for all road types and also compared to levels monitored at an urban background fixed site (median of 0.9 mu g m(-3)). We observed a large intra-urban variability in concentrations, with maxima levels inside road tunnels (median and 95th percentile of 7.5 and 40.1 mu g m(-3), respectively). Highways presented the second ranked concentrations (median and 95th percentile of 3.2 and 9.7 mu g m(-3), respectively) associated with highest vehicle speed (median of 65 km h(-1)), traffic rates (median of 62 000 vehicles day(-1) and 1500 vehicles h(-1)) and diesel vehicles share (7-10%) when compared to main roads, canyon streets, and local roads. Multiple regression modelling identified hourly traffic rate and M-LAC concentration measured at an urban background site as the best predictors of on-road concentrations, but explained only 25% of the observed variability. This feasibility study proved to be a time-and cost-effective approach to map out ambient M-LAC concentrations in Stockholm and more research is required to represent the distribution in other periods of the year. Simultaneous monitoring of other pollutants, closely correlated to M-LAC levels in traffic-polluted environments, and including video recording of road and traffic changes would be an asset.
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| 2. |
- Krecl, Patricia, et al.
(author)
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Spatiotemporal distribution of light-absorbing carbon and its relationship to other atmospheric pollutants in Stockholm
- 2011
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:22, s. 11553-11567
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Journal article (peer-reviewed)abstract
- Carbon-containing particles have deleterious effects on both Earth's climate and human health. In Europe, the main sources of light-absorbing carbon (LAC) emissions are the transport (67%) and residential (25%) sectors. Information on the spatiotemporal variability of LAC particles in urban areas is relevant for air quality management and to better diagnose the population exposure to these particles. This study reports on results of an intensive field campaign conducted at four sites (two kerbside stations, one urban background site and a rural station) in Stockholm, Sweden, during the spring 2006. Light-absorbing carbon mass (M(LAC)) concentrations were measured with custom-built Particle Soot Absorption Photometers (PSAP). The spatiotemporal variability of M(LAC) concentrations was explored by examining correlation coefficients (R), coefficients of divergence (COD), and diurnal patterns at all sites. Simultaneous measurements of NO(x), PM(10), PM(2.5), and meteorological variables were also carried out at the same locations to help characterize the LAC emission sources. Hourly mean (+/- standard deviation) M(LAC) concentrations ranged from 0.36 +/- 0.50 at the rural site to 5.39 +/- 3.60 mu g m(-3) at the street canyon site. Concentrations of LAC between urban sites were poorly correlated even for daily averages (R<0.70), combined with highly heterogeneously distributed concentrations (COD>0.30) even at spatial scales of few kilometers. This high variability is connected to the distribution of emission sources and processes contributing to the LAC fraction at these sites. At urban sites, M(LAC) tracked NO(x) levels and traffic density well and mean M(LAC)/PM(2.5) ratios were larger (26-38%) than at the background sites (4-10 %). The results suggest that vehicle exhaust emissions are the main responsible for the high M(LAC) concentrations found at the urban locations whereas long-range transport (LRT) episodes of combustion-derived particles can generate a strong increase of levels at background sites. To decrease pollution levels at kerbside and urban background locations in Stockholm, we recommend abatement strategies that target reductions of vehicle exhaust emissions, which are the main contributors to M(LAC) and NO(x) concentrations.
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| 3. |
- Krecl, Patricia, et al.
(author)
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Spatiotemporal Variability of Light-Absorbing Carbon Concentration in a Residential Area Impacted by Woodsmoke
- 2010
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In: Journal of the Air & Waste Management Association. - : Informa UK Limited. - 1047-3289 .- 1096-2247 .- 2162-2906. ; 60:3, s. 356-368
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Journal article (peer-reviewed)abstract
- Residential wood combustion (RWC) is responsible for 33% of the total carbon mass emitted in Europe. With the new European targets to increase the use of renewable energy, there is a growing concern that the population exposure to woodsmoke will also increase. This study investigates observed and simulated light-absorbing carbon mass (M-LAC) concentrations in a residential neighborhood (Lycksele, Sweden) where RWC is a major air pollution source during winter. The measurement analysis included descriptive statistics, correlation coefficient, coefficient of divergence, linear regression, concentration roses, diurnal pattern, and weekend versus weekday concentration ratios. Hourly RWC and road traffic contributions to M-LAC were simulated with a Gaussian dispersion model to assess whether the model was able to mimic the observations. Hourly mean and standard deviation concentrations measured at six sites ranged from 0.58 to 0.74 mu g m(-3) and from 0.59 to 0.79 mu g m(-3), respectively. The temporal and spatial variability decreased with increasing averaging time. Low-wind periods with relatively high M-LAC concentrations correlated more strongly than high-wind periods with low concentrations. On average, the model overestimated the observations by 3- to 5-fold and explained less than 10% of the measured hourly variability at all sites. Large residual concentrations were associated with weak winds and relatively high M-LAC loadings. The explanation of the observed variability increased to 31-45% when daily mean concentrations were compared. When the contribution from the boilers within the neighborhood was excluded from the simulations, the model overestimation decreased to 16-71%. When assessing the exposure to light-absorbing carbon particles using this type of model, the authors suggest using a longer averaging period (i.e., daily concentrations) in a larger area with an updated and very detailed emission inventory.
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| 4. |
- Targino, Admir C., et al.
(author)
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Deterioration of air quality across Sweden due to transboundary agricultural burning emissions
- 2013
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In: Boreal environment research. - 1239-6095 .- 1797-2469. ; 18:1, s. 19-36
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Journal article (peer-reviewed)abstract
- Targino, A. C., Krecl, P., Johansson, C., Swietlicki, E., Massling, A., Coraiola, G. C. & Lihavainen, H. 2013: Deterioration of air quality across Sweden due to transboundary agricultural burning emissions. Boreal Env. Res. 18: 19-36. We analyzed measurements of aerosol and trace-gas concentrations from sites across Sweden before and during a series of agricultural wildland fires in eastern Europe in spring 2006. During the burning episodes, concentrations of background particulate matter (PM) and trace gases, such as carbon monoxide and ozone, increased, affecting air quality across the country and violating national air quality standards. The European Union PM10 daily limit value of 50 mu g m(-3) was exceeded during the pollution episodes even at the background stations, resulting in a nearly four-fold increase as compared with that in non-episode conditions. In relation to a non-episode period, the concentration rise in the accumulation-mode particles was from 40% at an urban site to 340% at a rural site, causing an increase in total particle number concentrations. The fires also boosted ground-level ozone, increasing concentrations of this pollutant by up to 100% at the background stations, which exceeded national air quality standards. Both elemental (EC) and organic carbon (OC) levels increased, with OC making a larger contribution to the total carbonaceous concentrations during the biomass burning episodes. The large-scale atmospheric circulation determined the strength and timing of the pollution events, with the eastern and northern sectors of Sweden experiencing two pollution pulses, whilst sites in the western and southern sectors were affected by one shorter episode. The results show that regional air quality deteriorated due to the long-range transport of pollutants emitted during agricultural wildfires.
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