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| 3. |
- Hultengren, S., et al.
(författare)
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Recovery of the epiphytic lichen flora following air quality improvement in south-west Sweden
- 2004
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Ingår i: Water Air and Soil Pollution. - 0049-6979. ; 154:1-4, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- The development of the epiphytic lichen vegetation on tree trunks inside and nearby twelve towns and industrial areas in south-west Sweden was investigated 1986/ 88 and 1997 using a photographic technique. The lichen vegetation studied in terms of area cover as well as the air pollution sensitivity and preference for nitrogen of the individual lichens. During both surveys the lichen flora was strongly impoverished in urban areas compared to suburban areas and especially to the countryside ( reference) areas nearby. The air pollution situation has improved in the area both before and during the study period. This holds especially for SO2, to a lesser extent also for NO2. Following the improvement of the air quality, an increased lichen area cover on the tree trunks was observed. Also the cumulative pollution sensitivity of the lichens present was higher in 1997 compared to 1986/ 88 in suburban and countryside areas. For the nitrogen impact, the increase from 1986/ 88 to 1997 was smaller than for pollution sensitivity, but still statistically significant. The trends are interpreted as signs of a normalisation of the lichen flora. It is concluded that the observed pattern of lichen recovery reflects the fact that the reduction of the air pollution level in the central parts of the towns is still not large enough to permit a large-scale recovery of the lichen flora, while in the suburban areas and the countryside next to the towns, the air quality has now improved to an extent, which permits the reinvasion of a number of lichens.
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| 4. |
- 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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| 5. |
- Karlsson, Per Erik, 1957, et al.
(författare)
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A cumulative ozone uptake-response relationship for the growth of Norway spruce saplings
- 2004
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 128:3, s. 405-417
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Tidskriftsartikel (refereegranskat)abstract
- Norway spruce saplings [Picea abies (L.) Karst.] were exposed during four growing seasons to different ozone treatments in open-top chambers: charcoal filtered air (CF), non-filtered air (NF) and non-filtered air with extra ozone (NF+, 1.4xambient concentrations). The CF and NF + ozone treatments were combined with phosphorous deficiency and drought stress treatments. The total biomass of the trees was harvested at different intervals during the experimental period. The ozone uptake to current-year needles of the Norway spruce saplings was estimated using a multiplicative stomatal conductance simulation model. There was a highly significant correlation between the reduction of total biomass and the estimated cumulative ozone uptake, which did not vary when different thresholds were applied for the rate of ozone uptake. The reduction of the total biomass was estimated to 1 per 10 mmol m(-2) cumulated ozone uptake, on a projected needle area basis. (C) 2003 Elsevier Ltd. All rights reserved.
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| 6. |
- Piikki, Kristin, 1975, et al.
(författare)
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The impact of tropospheric O3 on leaf number duration and tuber yield of the potato (Solanum tuberosum L.) cultivars Bintje and Kardal
- 2004
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Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 0167-8809. ; 104:3, s. 483-492
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Tidskriftsartikel (refereegranskat)abstract
- Ozone (O3) is a major phytotoxic air pollutant with the potential to cause severe yield losses in potato (Solanum tubersosum L.) and in other crops. The present study was aimed (i) to investigate the O3 sensitivity of two potato cultivars (Bintje and Kardal) in relation to their earliness in maturation, and (ii) to analyse possible O3 effects on potato tuber dry mass (DM) production in relation to leaf duration. The experiment was performed in the southwest of Sweden using open-top chamber (OTC) technique. The crops were exposed to three levels of O3: charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air + 26 nmol mol−1 O3 (NF+). In addition, ambient air plots were used to monitor the impact of the OTC enclosure. Leaf number duration (LND) was calculated as the number of leaves integrated over the temperature sum accumulation during the season. In the present study, the O3 effects on potato were characterised by visible injury of the leaves and earlier leaf senescence. The haulm/plant DM ratio was significantly lower in NF+ compared to CF and NF. The conclusions were (i) that the early to intermediate maturing cultivar Bintje tended to suffer more from O3 injury than the late maturing cultivar Kardal, (ii) that this was due to a difference in the ability to compensate for haulm damage by the development of new leaves rather than to a difference in leaf O3 sensitivity, and (iii) that a rather low O3 exposure can induce a significant reduction in LND in potato. The O3 effects on tuber DM (−2% in NF+ and +31% increase in CF, both compared to NF) could not be statistically demonstrated, although there was a strong correlation between LND and tuber DM.
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| 7. |
- Pleijel, Håkan, 1958, et al.
(författare)
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On the logarithmic relationship between NO2 concentration and the distance from a highroad
- 2004
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 332:1-3, s. 261-264
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of nitrogen dioxide (NO2) concentrations, performed with passive diffusion samplers in gradients from a highway in South-west Sweden, were used to test the assumption that the NO2 concentration contributed by the highway varies with the logarithm of the distance from the highway. The five data sets used corroborated the hypothesis, and it was shown that all data could be accommodated to a common relationship with high correlation (R-2=0.95) using the concentration of 10 to away from the highroad as the reference. The data were also well in accordance with a recently published study from Canada, although the slope of the relationship between the NO2 concentration contributed by a highway and the logarithm of the distance was somewhat stronger for the Swedish data compared to the Canadian. The regression slope is likely to be sensitive to wind speed, atmospheric stability, surface roughness and the background ozone concentrations of the area. (C) 2004 Elsevier B.V. All rights reserved.
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| 8. |
- Pleijel, Håkan, 1958, et al.
(författare)
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Relationships between ozone exposure and yield loss in European wheat and potato - a comparison of concentration- and flux-based exposure indices
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:15, s. 2259-2269
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Tidskriftsartikel (refereegranskat)abstract
- Data from open-top chamber experiments with field grown crops, performed in Sweden, Finland, Belgium, Italy and Germany, were combined to derive relationships between yield and ozone exposure for wheat (Triticum aestivum L.) and potato (Solanum tuberosum L.). Three different exposure indices were compared: AOT40 (accumulated exposure over a threshold ozone concentration of 40 nmol mol(-1)), CUOt (cumulative stomatal uptake of ozone, using a constant ozone uptake rate threshold of t nmol m(-2) s(-1)) and mAOTc(0) (conductance modified AOT using a threshold concentration for ozone of c(0) nmol mol(-1)). The latter is essentially a combination of AOT and CUO. Ozone uptake was estimated using a Jarvis-type multiplicative model for stomatal conductance. In terms of correlation between relative yield (RY) and ozone exposure, CUO5, the CUO index with an ozone uptake rate threshold of 5 nmol m(-2) s(-1), performed best for both wheat and potato, resulting in r(2) values of 0.77 and 0.64, respectively. CUO5 performed considerably better in terms of the correlation between RY and ozone exposure, than AOT40 for wheat, while mAOT10, the best performing mAOT index in this case, was intermediate in performance for this crop. For potato, the differences between the different ozone exposure indices AOT40, CUO5 and mAOT20 (the mAOT index performing best for potato) in the correlation between RY and ozone exposure were relatively small. To test the assumption that the non-stomatal deposition of ozone was negligible for the uppermost, sunlit leaves, measurements of ozone uptake in relation to leaf conductance for water vapor of wheat leaves in a cuvette system were used. The non-stomatal deposition of ozone to the leaves turned out to be comparatively small. Based on the non-stomatal conductance (g(ns) = 15 mmol m(-2) s(-1)) estimated for the wheat leaves in the cuvette system, it was concluded that the consequence of omitting the non-stomatal conductance is small. In conclusion the study indicated that the ozone uptake based approach showed a high degree of fitting along a north-south European transect of pedoclimatic conditions, and represents a better and more relevant approach to the quantification of ozone effects on crops growth than the use of ozone exposure indices purely based on ozone concentrations. (C) 2004 Elsevier Ltd. All rights reserved.
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| 9. |
- Skarby, L., et al.
(författare)
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Growth of Norway spruce (Picea abies) in relation to different ozone exposure indices: a synthesis
- 2004
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Ingår i: Atmospheric Environment. - 1352-2310. ; 38:15, s. 2225-2236
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Tidskriftsartikel (refereegranskat)abstract
- In the Goteborg Ozone-Spruce Project (GOSP), two independent open-top chamber experiments were conducted during four growing seasons, using one clone of Norway spruce (Picea abies). The experiments tested the impact of ozone, alone and in combination with low phosphorus supply and in combination with drought stress, respectively, on biomass accumulation. In this paper, the results from both experiments were combined for the first time in order to analyse the relationship between relative biomass accumulation and different exposure indices (accumulated exposure over a threshold (AOT) with different cut-off concentrations, and the sum of ozone concentrations above 60 nl l(-1), referred to as SUM06). In addition, a pooled analysis was made on several European studies of Norway spruce as a first effort to synthesize independent data and test the relative growth in relation to the AOT40 index. Significant negative relationships between the relative biomass of the GOSP-clone and the different indices were obtained. AOT20 and AOT30 resulted in the highest correlations. Based on the regression model, ozone is predicted to reduce the biomass of the GOSP-clone by 1% at the critical level for forest trees in Europe, a seasonal AOT40 of 10 mul l(-1) h. A significant negative relationship between relative growth and AOT40 was obtained also with the European data set. At the present ozone critical level, the model predicted a 6% reduction in growth for the most sensitive Norway spruce trees in this data set. (C) 2004 Elsevier Ltd. All rights reserved.
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| 10. |
- Uddling, Johan, 1972, et al.
(författare)
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Biomass reduction of juvenile birch is more strongly related to stomatal uptake of ozone than to indices based on external exposure
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:28, s. 4709-4719
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Tidskriftsartikel (refereegranskat)abstract
- In order to test the hypothesis that ozone-induced limitation of biomass production in juvenile silver birch (Betula pendula Roth) is driven by stomatal uptake of ozone (O-3) rather than external exposure, biomass reduction was related to the cumulative uptake of O-3 through stomata over an uptake cut-off threshold of x nmol O-3 m(-2) s(-1) (CUO > x), to the accumulated exposure to O-3 over a threshold of y nmol mol(-1) during daylight hours (daylight AOTy) or during 24 h (24 h AOTy), and to the sum of daytime concentrations exceeding 60 nmol mol(-1) (SUM06). The analysis included data from nine different experiments conducted in Sweden, Finland and Switzerland. Stomatal uptake of O-3 was estimated using a stomatal conductance (g,) model including g, response functions for photosynthetic photon flux density, water vapour pressure deficit of the air and air temperature. Experiment-specific maximum g(s) (g(max)) as well as g(s) in darkness (g(dark)) were assessed through local measurements. Biomass reduction Was more strongly related to CUO > x than to SUM06 and daylight or 24 h AOTy, but the difference between CUO > x and 24 h AOTy was small. The better performance of CUO > x was dependent on the use of site- and experiment-specific g(max) and g(dark) values, and there was a positive relationship between g(max) and biomass reduction per unit AOT40. Daylight AOTy and SUM06 could not account for the growth limiting impact of nocturnal O-3 uptake in the Swiss experiments. A sensitivity analysis revealed that the CUO > x estimates were largely insensitive to the estimate of the conductance for non-stomatal leaf surface deposition of O-3, as a result of turbulent conditions at the experimental plots. In summary, we conclude that CUO > x was more successful in accounting for the variation in biomass reduction in juvenile birch as compared to indices based on external exposure, if g(max) and g(dark) were locally parameterised. (C) 2004 Elsevier Ltd. All rights reserved.
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