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- Grundström, Maria, 1979, et al.
(author)
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Urban NO2 and NO pollution in relation to the North Atlantic Oscillation NAO
- 2011
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 45:4, s. 883-888
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Journal article (peer-reviewed)abstract
- The North Atlantic Oscillation (NAO), a measure of the strength of the zonal wind across the North Atlantic Ocean, strongly influences weather conditions in NW Europe, e.g. temperature, precipitation and wind, especially during winter. It was hypothesised that elevated concentrations of nitrogen oxides in Gothenburg would be enhanced during negative NAO index (NAOI) conditions, representing more anticyclonic weather situations and thus leading to limited air mixing in the urban atmosphere, than situations with NAOI > 0. Hourly wintertime (DecembereFebruary) concentrations (1997e2006) of NO2, NO, air pressure, temperature and wind direction from an urban rooftop (30mabove street level) in the centre of the City of Gothenburg were analysed in relation to NAOI. Air pressure, the average concentration of nitrogen oxides (NOx ¼ NO2 þ NO), as well as the fraction of hourly NO2 and NO concentrations exceeding 90 mg m_3 and the fraction of daily NO concentrations exceeding 60 mg m_3, were significantly and negatively related to NAOI. Air temperature was positively correlated with NAOI. Southerly and westerly winds were more common in months with positive NAOI, while easterly and northerly winds were overrepresented in months with negative NAOI. High pollution concentrations dominantly occurred in situations with northerly and easterly wind directions. High NO2 and NO concentrations were associated with negative NAOI, especially in the morning when the traffic rush coincided with restricted air mixing. Over the tenyear period there were trends for more negative NAOI and increased time fractions with hourly NO2 concentrations exceeding 90 mgm_3. The conclusion of this study is that a climate shift towards higher or lower NAOI has the potential to significantly influence urban air pollution in North-West Europe, and thus the possibility to reach air quality standards, even if emissions remain constant.
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- Grundström, Maria, 1979, et al.
(author)
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Variation and co-variation of PM10, particle number concentration, NOx and NO2 in the urban air - Relationships with wind speed, vertical temperature gradient and weather type
- 2015
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In: Atmospheric Environment. - : Elsevier Ltd. - 1352-2310. ; 120, s. 317-327
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Journal article (peer-reviewed)abstract
- Atmospheric ultrafine particles (UFP; diameter < 0.1 μm) represent a growing global health concern in urban environments and has a strong link to traffic related emissions. UFP is usually the dominating fraction of atmospheric particle number concentrations (PNC) despite being a minor part of total particle mass. The aim of this study was to empirically investigate the relationship between PNC and other air pollutants (NOX, NO2 and PM10) in the urban environment and their dependence on meteorology and weather type, using the Lamb Weather Type (LWT) classification scheme. The study was carried out in Gothenburg, Sweden, at an urban background site during April 2007-May 2008. It was found that daily average [PNC] correlated very well with [NOx] (R2 = 0.73) during inversion days, to a lesser extent with [NO2] (R2 = 0.58) and poorly with [PM10] (R2 = 0.07). Both PNC and NOx had similar response patterns to wind speed and to the strength of temperature inversions. PNC displayed two regimes, one strongly correlated to NOx and a second poorly correlated to NOx which was characterised by high wind speed. For concentration averages based on LWTs, the PNC-[NOx] relationship remained strong (R2 = 0.70) where the windy LWT W deviated noticeably. Exclusion of observations with wind speed >5 ms-1 or ΔT < 0 °C from LWTs produced more uniform and stronger relationships (R2 = 0.90; R2 = 0.93). Low wind speeds and positive vertical temperature gradients were most common during LWTs A, NW, N and NE. These weather types were also associated with the highest daily means of NOx (~30 ppb) and PNC (~10 000 # cm-3). A conclusion from this study is that NOx (but not PM10) is a good proxy for PNC especially during calm and stable conditions and that LWTs A, NW, N and NE are high risk weather types for elevated NOx and PNC. © 2015.
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| 6. |
- Harmens, H., et al.
(author)
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Wheat yield responses to stomatal uptake of ozone: Peak vs rising background ozone conditions
- 2018
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 173, s. 1-5
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Journal article (peer-reviewed)abstract
- Recent decades have seen a changing temporal profile of ground-level ozone (O-3) in Europe. While peaks in O-3 concentrations during summer months have been declining in amplitude, the background concentration has gradually increased as a result of the hemispheric transport of O-3 precursors from other world regions. Ground level O-3 is known to adversely affect O-3-sensitive vegetation, including reducing the yield of O-3-sensitive crops such as common wheat (Triticum aestivum L.). The reduction in wheat yield has been shown to be linearly related to the phytotoxic O-3 dose above a flux threshold of Y (PODY) accumulated over a specific period. In the current study, we tested whether the flux-effect relationships for wheat yield and 1,000-grain weight were affected by the temporal profile of O-3 exposure. A modern wheat cultivar (Skyfall) was exposed to eight different realistic O-3 profiles repeated weekly: four profiles with increasing background O-3 concentrations (ca. 30-60 ppb) including small peaks and four profiles with increasing O-3 peak concentrations (ca. 35-110 ppb). Both wheat yield and 1,000-grain weight declined linearly with increasing PODY. The slope of the flux-effect relationships was not affected significantly by the profile of O-3 exposure. Hence, flux-effect relationships developed for wheat based on exposure to enhanced peak O-3 concentrations are also valid for the changing European O-3 profile with higher background and lower peak concentrations. The current study also shows that the modern wheat cultivar Skyfall is more sensitive to O-3 than European wheat varieties tested for O-3 sensitivity in the 1980s and 1990s.
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| 7. |
- Karlsson, G. P., et al.
(author)
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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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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:15, s. 2237-2245
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Journal article (peer-reviewed)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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| 8. |
- Karlsson, Per Erik, 1957, et al.
(author)
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Ozone concentration gradients and wind conditions in Norway spruce (Picea abies) forests in Sweden
- 2006
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 40:9, s. 1610-1618
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Journal article (peer-reviewed)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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| 9. |
- Klingberg, Jenny, 1978, et al.
(author)
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Variation in ozone exposure in the landscape of southern Sweden with consideration of topography and coastal climate
- 2012
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 47, s. 252-260
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Journal article (peer-reviewed)abstract
- Ozone concentrations ([O3]) and meteorological parameters were measured with a mobile monitoring station at two coastal and five inland sites in southwest Sweden. Three of the five inland sites were located topographically low and two high compared to the surrounding landscape. In addition, [O3] data from six permanent monitoring stations in southern Sweden were analysed in relation to the positions of the measurement sites in the landscape. [O3] was also measured with passive diffusion samplers at two other sites. Both the diurnal temperature range (DTR) and the diurnal [O3] range (DOR) were to a large extent explained by the strength of the nocturnal temperature inversions at the sites. To investigate the influence of topography, the relative altitude of the sites was defined as the average altitude within a 3 km radius subtracted from the altitude of the site. Statistically significant relationships were obtained for average [O3] as well as DOR with relative altitude. Inland low sites experienced stronger nocturnal temperature inversions, lower average [O3] and larger DOR compared to inland high and coastal sites. Relative altitude was found to be superior to site altitude in explaining the variation of average [O3] and DOR in the landscape. This study underlines the importance of including local topography, as well as vicinity to the coast, in modelling [O3] and in O3 environmental risk assessments.
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| 10. |
- Mills, G., et al.
(author)
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A synthesis of AOT40-based response functions and critical levels of ozone for agricultural and horticultural crops
- 2007
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 41:12, s. 2630-2643
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Journal article (peer-reviewed)abstract
- Crop-response data from over 700 published papers and conference proceedings have been analysed with the aim of establishing ozone dose-response functions for a wide range of European agricultural and horticultural crops. Data that met rigorous selection criteria (e.g. field-based, ozone concentrations within European range, full season exposure period) were used to derive AOT40-yield response functions for 19 crops by first converting the published ozone concentration data into AOT40 (AOT40 is the hourly mean ozone concentration accumulated over a threshold ozone concentration of 40ppb during daylight hours, units ppmh). For any individual crop, there were no significant differences in the linear response functions derived for experiments conducted in the USA or Europe, or for individual cultivars. Three statistically independent groups were identified: ozone sensitive crops (wheat, water melon, pulses, cotton, turnip, tomato, onion, soybean and lettuce); moderately sensitive crops (sugar beet, potato, oilseed rape, tobacco, rice, maize, grape and broccoli) and ozone resistant (barley and fruit represented by plum and strawberry). Critical levels of a 3 month AOT40 of 3 ppm It and a 3.5 month AOT40 of 6ppm h were derived from the functions for wheat and tomato, respectively. (c) 2006 Elsevier Ltd. All rights reserved.
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