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- Pleijel, Håkan, 1958, et al.
(författare)
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Surface Ozone in the Marine Environment—Horizontal Ozone Concentration Gradients in Coastal Areas
- 2013
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Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 224:7
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Tidskriftsartikel (refereegranskat)abstract
- Spring/summer surface ozone concentrations, [O3], in coastal environments were investigated: (1) by comparison of coastal and inland monitoring stations with data from a small island >5 km off the coast of southwest Sweden, (2) as a gradient from the coast towards inland in southernmost Sweden. Further, results from the chemical transport model MATCH were used to assess the marine influence on [O3]. It was hypothesised that [O3] is higher on the small island compared to the coast, especially during night and in offshore wind. Another hypothesis was that [O3] declines from the coast towards inland. Our hypotheses were based on observations that the deposition velocity of O3 to sea surfaces is lower than to terrestrial surfaces, and that vertical air mixing is stronger in the marine environment, especially during night. The island experienced 10 % higher [O3] compared to the coast. This difference was larger with offshore (15 %) than onshore wind (9 %). The concentration difference between island and coast was larger during night, but prevailed during day and could not be explained by differences in [NO2] between the sites. The difference in [O3] between the island and the inland site was 20 %. Higher [O3] over the sea, especially during night, was reproduced by MATCH. In the gradient study, [O3] declined from the coast towards inland. Both [O3] and [NO2] were elevated at the coast, indicating that the gradient in [O3] from the coast was not caused by NO titration. The conclusions were that surface [O3] in marine environments is higher than in coastal, and higher in coastal than inland areas, especially during night.
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| 2. |
- Karlsson, Per Erik, et al.
(författare)
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The vulnerability of northern European vegetation to ozone damage in a changing climate An assessment based on current knowledge
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The potential vulnerability of vegetation at northern latitudes to ozone damage was assessed based on current knowledge with regard to air ozone concentrations and leaf ozone uptake as well as to plant traits affecting ozone tolerance. The focus was on the northern European arctic, alpine and northern boreal vegetation zones, with a special focus on high-altitude vegetation. In particular, we analysed if there are increasing risks for ozone impacts on northern vegetation due to high spring ozone concentrations in relation to climate change induced shifts such as e.g. an earlier start of the growing season. The ozone concentrations in these regions are characterized by the influence of a combination of conditions caused by high latitudes and high altitudes. Ozone concentrations increase with altitude and the difference in ozone concentrations between day and night are smaller at high-altitude and high-latitude sites. Summer periods with long daylight conditions potentially promote the leaf ozone uptake through the open stomata. The aims of this report were: • To assess the current state of knowledge regarding the potential vulnerability of far northern vegetation to ozone damage, today and in the future • To provide advice for policy implications regarding necessary ozone precursor emission abatement • To provide advice for future research and monitoring of ozone impacts on the vegetation at northern latitudes Ongoing environmental changes affecting far northern latitude ecosystems were reviewed. Current and novel methods were described for how to estimate the time of year during which the ozone exposure for vegetation should be accumulated. Time trends for ozone concentrations at northern latitudes were analysed. Ozone episodes with high concentrations at far northern latitudes were described. Source attributions of northern ozone concentrations were analysed. Environmental conditions at far northern latitudes that might be important for ozone damage were evaluated. Plant traits that can influence the ozone vulnerability were discussed. Current experimental results for ozone injury on northern plant species were evaluated. Future scenarios for ozone impact on northern vegetation were discussed. Some important results from the analyses are described below. At high altitudes and high latitudes, the ozone concentrations are relatively similar during day- and night-time. Furthermore, at high latitudes, the long daylight duration during the summer has the potential to increase the duration of the daily period with plant gas exchange and leaf ozone uptake. Therefore, the absorption of ozone through the stomata may potentially be higher at northern latitudes. However, measurements of light intensity and quality at northern sites in combination with a simple calculation example illustrated that this probably was not the case, since the potential added ozone uptake in the early morning and late evening at northern sites may be cancelled out by a lower ozone uptake in the middle of the day, as compared to southern sites. Both data on budburst and data on ecosystem CO2 exchange as well as meteorological observations show that there has been a development towards an earlier start of the growing season during the year, with approximately 0.5 – 1 day per year. Thus, there is clear evidence for an earlier start of the growing season, which is likely to continue. However, the timing of the spring ozone maximum is also shifted towards earlier in the year. There is presently no evidence for an increasing overlap between the growing season and the ozone peak. Despite this, there is a potential for increased ozone uptake to vegetation in spring due to the earlier growing start of vegetation and increased uptake of ozone to vegetation in May. The impact of this on the accumulated phytotoxic ozone dose for northern vegetation needs to be investigated further. The overall conclusions about the present and near future ozone vulnerability of northern vegetation were: • There remain uncertainties regarding to what extent northern vegetation is affected by ozone exposure. • According to current knowledge, we could not find evidence that expected changes in ozone concentrations and climate would make the northern arctic, alpine and subalpine vegetation substantially more vulnerable to ozone than other types of European vegetation. • The risk of significant and lasting negative impact of the current exposure to ozone on northern boreal forests is most likely not greater than for boreonemoral and nemoral forests in southern Fennoscandia. • However, peak ozone concentrations occurring in spring and early summer may affect vegetation at northern latitudes in Fennoscandia since the start of the growing season in the future may occur earlier during the year. The policy implications that can be derived from these conclusions were: • The current state of knowledge implies that ecosystems in the far north are not more susceptible to ozone than vegetation in other parts of Europe. Hence, we cannot advocate for a stronger reduction of ozone precursors emissions based exclusively on the ozone sensitivity of vegetation in the far north. • Policies designed to reduce emissions of ozone precursors to protect vegetation in other parts of Europe as well as in the entire northern hemisphere are likely to suffice to protect vegetation in northern Fennoscandia. There are important remaining knowledge gaps. Our conclusions are based on important, but limited observations. Experimental evidence from investigations specifically designed to study ozone sensitivity of high-altitude vegetation in northern Europe are to a large extent lacking. It is recommended that further experimental research is undertaken to directly compare the ozone sensitivity of plants of high-latitude/high-altitude origin with that of plants (species, genotypes) representative of regions of the southern part of the Nordic region. This research should include the characteristics of the high-latitude climate and other conditions. A specific research question is if the new ozone critical levels for European vegetation based on PODYSPEC (Mapping Manual, 2017) are correct, both regarding calculation methodology as well as impact assessments? In particular, there is a lack of information about the degree of stomata closure during nights in high-latitude area plants. This is important for the modelling of ozone uptake (dry deposition) in these areas and requires coordinated measurement campaigns in close cooperation with modelers. Further research questions may be related to the future development of the northern regions – e.g. oil and gas extraction including flaring, shipping, more tourism and climate change – how will that affect the ozone exposure of in the northern vegetation? Do future ozone precursor emission scenarios describe this correctly? Will warm and dry summers like 2018 become more frequent in connection with climate change, and how will this affect ozone impacts on vegetation? There are currently very few, long term ozone monitoring stations in the arctic and alpine vegetation zones, in particular at high altitudes. Given the expected increase in anthropogenic activities in these areas in combination with climate change, it is strongly recommended to increase the number of high-altitude ozone monitoring sites in these regions.
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| 3. |
- Pleijel, Håkan, 1958, et al.
(författare)
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A method to assess the inter-annual weather-dependent variability in air pollution concentration and deposition based on weather typing
- 2016
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 126, s. 200-210
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Tidskriftsartikel (refereegranskat)abstract
- Annual anomalies in air pollutant concentrations, and deposition (bulk and throughfall) of sulphate, nitrate and ammonium, in the Gothenburg region, south-west Sweden, were correlated with optimized linear combinations of the yearly frequency of Lamb Weather Types (LWTs) to determine the extent to which the year-to-year variation in pollution exposure can be partly explained by weather related variability. Air concentrations of urban NO2, CO, PM10, as well as O3 at both an urban and a rural monitoring site, and the deposition of sulphate, nitrate and ammonium for the period 1997–2010 were included in the analysis. Linear detrending of the time series was performed to estimate trend-independent anomalies. These estimated anomalies were subtracted from observed annual values. Then the statistical significance of temporal trends with and without LWT adjustment was tested. For the pollutants studied, the annual anomaly was well correlated with the annual LWT combination (R2 in the range 0.52–0.90). Some negative (annual average [NO2], ammonia bulk deposition) or positive (average urban [O3]) temporal trends became statistically significant (p < 0.05) when the LWT adjustment was applied. In all the cases but one (NH4 throughfall, for which no temporal trend existed) the significance of temporal trends became stronger with LWT adjustment. For nitrate and ammonium, the LWT based adjustment explained a larger fraction of the inter-annual variation for bulk deposition than for throughfall. This is probably linked to the longer time scale of canopy related dry deposition processes influencing throughfall being explained to a lesser extent by LWTs than the meteorological factors controlling bulk deposition. The proposed novel methodology can be used by authorities responsible for air pollution management, and by researchers studying temporal trends in pollution, to evaluate e.g. the relative importance of changes in emissions and weather variability in annual air pollution exposure.
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| 5. |
- Etzold, Sophia, et al.
(författare)
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Nitrogen deposition is the most important environmental driver of growth of pure, even-aged and managed European forests
- 2020
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 458
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Tidskriftsartikel (refereegranskat)abstract
- Changing environmental conditions may substantially interact with site quality and forest stand characteristics, and impact forest growth and carbon sequestration. Understanding the impact of the various drivers of forest growth is therefore critical to predict how forest ecosystems can respond to climate change. We conducted a continental-scale analysis of recent (1995–2010) forest volume increment data (ΔVol, m3 ha−1 yr−1), obtained from ca. 100,000 coniferous and broadleaved trees in 442 even-aged, single-species stands across 23 European countries. We used multivariate statistical approaches, such as mixed effects models and structural equation modelling to investigate how European forest growth respond to changes in 11 predictors, including stand characteristics, climate conditions, air and site quality, as well as their interactions. We found that, despite the large environmental gradients encompassed by the forests examined, stand density and age were key drivers of forest growth. We further detected a positive, in some cases non-linear effect of N deposition, most pronounced for beech forests, with a tipping point at ca. 30 kg N ha−1 yr−1. With the exception of a consistent temperature signal on Norway spruce, climate-related predictors and ground-level ozone showed much less generalized relationships with ΔVol. Our results show that, together with the driving forces exerted by stand density and age, N deposition is at least as important as climate to modulate forest growth at continental scale in Europe, with a potential negative effect at sites with high N deposition.
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| 10. |
- Klingberg, Jenny, 1978, et al.
(författare)
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Declining ozone exposure of European vegetation under climate change and reduced precursor emissions
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11, s. 5269-5283
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Tidskriftsartikel (refereegranskat)abstract
- The impacts of changes in ozone precursor emissions as well as climate change on the future ozone exposure of the vegetation in Europe were investigated. The ozone exposure is expressed as AOT40 (Accumulated exposure Over a Threshold of 40 ppbO3) as well as PODY (Phytotoxic Ozone Dose above a threshold Y). A new method is suggested to express how the length of the period during the year when coniferous and evergreen trees are sensitive to ozone might be affected by climate change. Ozone precursor emission changes from the RCP4.5 scenario were combined with climate simulations based on the IPCC SRES A1B scenario and used as input to the Eulerian Chemistry Transport Model MATCH from which projections of ozone concentrations were derived. The ozone exposure of vegetation over Europe expressed as AOT40 was projected to be substantially reduced between the periods 1990–2009 and 2040–2059 to levels which are well below critical levels used for vegetation in the EU directive 2008/50/EC as well as for crops and forests used in the LRTAP convention, despite that the future climate resulted in prolonged yearly ozone sensitive periods. The reduction in AOT40 was mainly driven by the emission reductions, not changes in the climate. For the toxicologically more relevant POD1 index the projected reductions were smaller, but still significant. The values for POD1 for the time period 2040–2059 were not projected to decrease to levels which are below critical levels for forest trees, represented by Norway spruce. This study shows that substantial reductions of ozone precursor emissions have the potential to strongly reduce the future risk for ozone effects on the European vegetation, even if concurrent climate change promotes ozone formation.
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