| 141. |
- Johansson, Christer, et al.
(författare)
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Road traffic emission factors for heavy metals
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 43:31, s. 4681-4688
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Tidskriftsartikel (refereegranskat)abstract
- Quantifying the emissions and concentrations of heavy metals in urban air is a prerequisite for assessing their health effects. In this paper a combination of measurements and modelling is used to assess the contribution from road traffic emissions. Concentrations of particulate heavy metals in air were measured simultaneously during 1 year at a densely trafficked street and at an urban background site in Stockholm, Sweden. Annual mean concentrations of cadmium were 50 times lower than the EU directive and for nickel and arsenic concentrations were 10 and six times lower, respectively. More than a factor of two higher concentrations was in general observed at the street in comparison to roof levels indicating the strong influence from local road traffic emissions. The only compound with a significantly decreasing trend in the urban background was Pb with 9.1 ng m−3 in 1995/96 compared to 3.4 ng m−3 2003/04. This is likely due to decreased emissions from wear of brake linings and reduced emissions due to oil and coal combustion in central Europe. Total road traffic emission factors for heavy metals were estimated using parallel measurements of NOx concentrations and knowledge of NOx emission factors. In general, the emission factors for the street were higher than reported in road tunnel measurements. This could partly be due to different driving conditions, since especially for metals which are mainly emitted from brake wear, more stop and go driving in the street compared to in road tunnels is likely to increase emissions. Total emissions were compared with exhaust emissions, obtained from the COPERT model and brake wear emissions based on an earlier study in Stockholm. For Cu, Ni and Zn the sum of brake wear and exhaust emissions agreed very well with estimated total emission factors in this study. More than 90% of the road traffic emissions of Cu were due to brake wear. For Ni more than 80% is estimated to be due to exhaust emissions and for Zn around 40% of road traffic emissions are estimated to be due to exhaust emissions. Pb is also mainly due to exhaust emissions (90%); a fuel Pb content of only 0.5 mg L−1 would give similar emission factor as that based on the concentration increment at the street. This is the first study using simultaneous measurements of heavy metals at street and roof enabling calculations of emission factors using a tracer technique.
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| 142. |
- Johansson, Christer, et al.
(författare)
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The effects of congestions tax on air quality and health.
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 43:31, s. 4843-4854
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Tidskriftsartikel (refereegranskat)abstract
- The “Stockholm Trial” involved a road pricing system to improve the air quality and reduce traffic congestion. The test period of the trial was January 3–July 31, 2006. Vehicles travelling into and out of the charge cordon were charged for every passage during weekdays. The amount due varied during the day and was highest during rush hours (20 SEK = 2.2 EUR, maximum 60 SEK per day). Based on measured and modelled changes in road traffic it was estimated that this system resulted in a 15% reduction in total road use within the charged cordon. Total traffic emissions in this area of NOx and PM10 fell by 8.5% and 13%, respectively. Air quality dispersion modelling was applied to assess the effect of the emission reductions on ambient concentrations and population exposure. For the situations with and without the trial, meteorological conditions and other emissions than from road traffic were kept the same. The calculations show that, with a permanent congestion tax system like the Stockholm Trial, the annual average NOx concentrations would be lower by up to 12% along the most densely trafficked streets. PM10 concentrations would be up to 7% lower. The limit values for both PM10 and NO2 would still be exceeded along the most densely trafficked streets. The total population exposure of NOx in Greater Stockholm (35 × 35 km with 1.44 million people) is estimated to decrease with a rather modest 0.23 μg m−3. However, based on a long-term epidemiological study, that found an increased mortality risk of 8% per 10 μg m−3 NOx, it is estimated that 27 premature deaths would be avoided every year. According to life-table analysis this would correspond to 206 years of life gained over 10 years per 100 000 people following the trial if the effects on exposures would persist. The effect on mortality is attributed to road traffic emissions (likely vehicle exhaust particles); NOx is merely regarded as an indicator of traffic exposure. This is only the tip of the ice-berg since reductions are expected in both respiratory and cardiovascular morbidity. This study demonstrates the importance of not only assessing the effects on air quality limit values, but also to make quantitative estimates of health impacts, in order to justify actions to reduce air pollution.
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| 143. |
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| 144. |
- Jones, Stephanie H., et al.
(författare)
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Are organic films from atmospheric aerosol and sea water inert to oxidation by ozone at the air-water interface?
- 2017
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Ingår i: Atmospheric Environment. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1352-2310 .- 1873-2844. ; 161, s. 274-287
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Tidskriftsartikel (refereegranskat)abstract
- The heterogeneous oxidation of thin films of organic material extracted from real aerosol and sea-water samples was studied at the air-water interface using X-ray reflectivity. Oxidation of thin films of organic material extracted from real aerosol and sea-water is important in further understanding the impact of coated aerosols on the climate of the Earth. Surface active insoluble organic material extracted from the atmosphere was found to form stable films at the air-water interface (thickness measured as 10-14 nm). On exposure of the films to gas-phase ozone, no reaction (or change in the relative scattering length of the interface) was observed, indicating a potential lack of unsaturated organic material in the samples. Gas chromatography and electrospray ionization mass spectrometry showed the presence of saturated compounds in the samples. It is therefore proposed that the amount of unsaturated compounds as compared to saturated compounds in the atmospheric material is so low that the mass spectrometry analyses, as well as gas-phase oxidation are dominated by saturated material. A reaction was observed on exposure of the same films to aqueous phase hydroxyl and nitrate radicals and a film thinning mechanism is proposed to explain the change in scattering length of the film at the air-water interface. It can be suggested tentatively that oxidation by gas-phase ozone is not important in the atmosphere for organic films on aqueous atmospheric aerosol and that further studies should focus on radical induced oxidation of saturated organic material instead of unsaturated proxies that are typically studied.
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| 145. |
- Jonsson, Per, 1974, et al.
(författare)
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Suspended particulate matter and its relations to the urban climate in Dar es Salaam, Tanzania
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:25, s. 4175-4181
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Tidskriftsartikel (refereegranskat)abstract
- Relationships between sources and levels of particulate matter and climatic parameters (urban heat island intensity, wind speed, temperature and relative humidity) were investigated in the coastal city of Dar es Salaam, Tanzania's largest city. Measurements were made during the wet and dry seasons of 2001 at an urban and a rural site. Five elements were used to represent different sources: K in fine particles (biomass), Zn in fine particles (industry), Cl in coarse particles (sea spray), Ti in coarse particles (soil) and Pb in fine particles (traffic). The concentrations of these elements varied considerably between the urban and rural site during both the wet and dry season, with the urban site in the dry season having the highest concentrations. Diurnal differences are also apparent, although not as straightforward. In an attempt to explain these differences, correlations between all elements and the climatic parameters were investigated. The results show that the nocturnal urban heat island intensity was positively correlated and wind speed negatively correlated with particulate levels, presumably due to the increased atmospheric stability. (C) 2004 Elsevier Ltd. All rights reserved.
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| 146. |
- Jung, M. I., et al.
(författare)
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Contrasting synoptic weather patterns between non-dust high particulate matter events and Asian dust events in Seoul, South Korea
- 2019
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 214
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Tidskriftsartikel (refereegranskat)abstract
- The serious degradation of regional air quality is a critical social issue in East Asia despite continuous efforts to reduce the emission of pollutants and their precursors. To better understand high-pollution events in this region, the synoptic weather patterns associated with springtime non-dust high PM10 (High PM10) events and Asian Dust events in Seoul, South Korea, are examined for the 2001–2018 period. It is shown that the two high-pollution events accompany different atmospheric circulations. While High PM10 events are associated with weak surface cyclonic circulations over the Southeast China, Asian Dust events are characterized by strong cyclones over Northeast China. Composite weather maps show that mid-tropospheric circulation anomalies are exactly the opposite between the two events with anticyclonic anomalies over the Korean Peninsula for High PM10 events but cyclonic anomalies for Asian Dust events. The cluster analyses further reveal that High PM10 events are not determined by a single dominant weather pattern. They are associated with surface cyclonic circulations from southeastern China to the Sea of Okhotsk, anticyclonic circulations around the Korean Peninsula or their mixtures. This result is in contrast with the Asian Dust events which are primarily driven by vertically well-organized continental cyclones. © 2019 Elsevier Ltd
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| 147. |
- Karlsson, G. P., et al.
(författare)
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Test of the short-term critical levels for acute ozone injury on plants - improvements by ozone uptake modelling and the use of an effect threshold
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:15, s. 2237-2245
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Tidskriftsartikel (refereegranskat)abstract
- The current short-term critical levels for acute ozone injury on plants were evaluated based on 32 datasets from eastern Austria, Belgium and southern Sweden with subterranean clover (Trifolium subterraneum L., cv. Geraldton). Potential improvements using an exposure index related to ozone uptake (AF(st), Accumulated Stomatal Flux), a modified accumulated exposure over the threshold (mAOT) exposure index and the introduction of an effect threshold in the short-term critical level were investigated. The existing short-term critical levels did not accurately describe the effects in terms of observed visible injury. Using a mAOT based on solar radiation and vapour pressure deficit (VPD) improved the explanation of observed visible injury. However, using a simple stomatal conductance model, driven by solar radiation, air temperature, VPD and ozone uptake, the correlation between modelled and observed effects were considerably improved. The best performance was obtained when an ozone uptake rate threshold of 10 nmol m(-2) s(-1) (AF(st)10, per unit total leaf area) was used. The results suggested the use of an effect threshold of 10% leaf injury in order to minimise the risk of erroneously recorded visible injury due to observation technique or other injuries hard to distinguish from ozone injury. A new, AF(st) based exposure index was suggested, an ozone exposure of AF(st)10=75 mumol m(-2) during an exposure period of eight days was estimated to prevent more than 10% visible injury of the leaves. This study strongly suggests that a simple model for ozone uptake much better explains observed effects, compared to the currently used exposure index AOT40. However, if a lower degree of complexity, data requirements and also a lower extent of explanation of observed effects are to be considered a new short-term critical level, based on a mAOT may be suggested: a mAOT30 of 160 ppb h during an exposure period of 8 days is estimated to protect the leaves from visible injury on more than 10% of the leaves. (C) 2004 Elsevier Ltd. All rights reserved.
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| 148. |
- Karlsson, Per Erik, 1957, et al.
(författare)
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New critical levels for ozone effects on young trees based on AOT40 and simulated cumulative leaf uptake of ozone
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:15, s. 2283-2294
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Tidskriftsartikel (refereegranskat)abstract
- Leaf or needle ozone uptake was estimated for young trees at seven experimental sites across Europe using a stomatal conductance simulation model. Dose-response relationships based on cumulative leaf uptake of ozone (CUO) were calculated using different hourly ozone flux thresholds and these were compared to dose-response relationships based on daylight AOT40, which is currently used within the UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP). Regression analysis showed that the CUO-biomass response relationships were highly significant for both coniferous and broadleaf trees, and independent of which ozone flux threshold was applied. On the basis of this regressions analysis, an hourly flux threshold of 1.6 nmol m(-2) s(-1) (COO > 1.6) is proposed as the most appropriate for all species categories in deriving dose-response relationships. The analysis indicated that the current critical level for ozone impacts on European forests of AOT40 10 ppm h may not protect the most sensitive receptors and that critical levels for AOT40 and CUO > 1.6 of 5 ppm h and 4 mmol m(-2), respectively, are more appropriate. The research identified weaker dose-response relationships for the CUO exposure index compared with AOT40. Distinguishing between sensitive and less sensitive species substantially improved the CUO-biomass response relationships although, still, to a lesser extent than when exposure was expressed as AOT40. (C) 2004 Elsevier Ltd. All rights reserved.
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| 149. |
- Karlsson, Per Erik, 1957, et al.
(författare)
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Ozone concentration gradients and wind conditions in Norway spruce (Picea abies) forests in Sweden
- 2006
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 40:9, s. 1610-1618
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Tidskriftsartikel (refereegranskat)abstract
- Ozone concentrations and wind conditions were measured at different heights above ground inside two different Norway spruce forest canopies in Sweden and compared to those outside or above the forests. Compared to high above ground outside or above the canopies, the ozone concentrations inside the Norway spruce forests were reduced 3-8% during mid-day and 10-40% during nighttime. Daylight Accumulated exposure Over a Threshold 40ppb (AOT40) was reduced 15-45% inside as compared to outside the forest. The horizontal concentration differences between inside and outside the forest were in the order of 3-4%, independently of the height above ground. The ozone concentration difference inside and outside the forest depended on the air turbulence as well as the horizontal wind speed inside the forest. It also depended on the distance to the forest edge in relation to the wind direction. The ozone concentration differences inside and outside the Norway spruce forests were explained by the differences in the rate of dry deposition in relation to the rate of replacement of ozone from higher air layers or by the horizontal wind going into the forest. (c) 2005 Elsevier Ltd. All rights reserved.
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| 150. |
- Karlsson, Per Erik, et al.
(författare)
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Total deposition of inorganic nitrogen to Norway spruce forests – Applying a surrogate surface method across a deposition gradient in Sweden
- 2019
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 217, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The dry and wet deposition of nitrate, NO3−, and ammonium, NH4+, were estimated for Norway spruce forests at ten monitoring sites across Sweden for the years 2014–2017. The particulate dry deposition was estimated based on measurements using Teflon string samplers as surrogate surfaces, in combination with the net throughfall deposition for sodium (throughfall subtracted with wet deposition). The wet deposition was estimated from bulk deposition measurements, corrected for dry deposition to the collectors. There was a strong gradient for total inorganic nitrogen (N) deposition across Sweden from north to southwest, ranging from 2 to 20 kg N ha−1 yr−1. The values for N deposition derived from measurements were for most sites exceeding the corresponding values derived from modelling with the MATCH and EMEP models, in southern Sweden by up to 4–6 kg N ha−1 y−1. Based on comparisons between total and throughfall deposition, the canopy uptake of atmospheric N deposition to Norway spruce forests in Sweden was estimated to be in the range of 0–7 kg N ha−1 yr−1.
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