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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 NO 2 , CO, PM 10 , as well as O 3 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 (R 2 in the range 0.52–0.90). Some negative (annual average [NO 2 ], ammonia bulk deposition) or positive (average urban [O 3 ]) temporal trends became statistically significant (p < 0.05) when the LWT adjustment was applied. In all the cases but one (NH 4 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. [ABSTRACT FROM AUTHOR]

A key part of the uncertainty in terrestrial feedbacks on climate change is related to how and to what extent nitrogen (N) availability constrains the stimulation of terrestrial productivity by elevated CO2 ( eCO2), and whether or not this constraint will become stronger over time. We explored the ecosystem-scale relationship between responses of plant productivity and N acquisition to eCO2 in free-air CO2 enrichment ( FACE) experiments in grassland, cropland and forest ecosystems and found that: (i) in all three ecosystem types, this relationship was positive, linear and strong ( r2 = 0.68), but exhibited a negative intercept such that plant N acquisition was decreased by 10% when eCO2 caused neutral or modest changes in productivity. As the ecosystems were markedly N limited, plants with minimal productivity responses to eCO2 likely acquired less N than ambient CO2-grown counterparts because access was decreased, and not because demand was lower. (ii) Plant N concentration was lower under eCO2, and this decrease was independent of the presence or magnitude of eCO2-induced productivity enhancement, refuting the long-held hypothesis that this effect results from growth dilution. (iii) Effects of eCO2 on productivity and N acquisition did not diminish over time, while the typical eCO2-induced decrease in plant N concentration did. Our results suggest that, at the decennial timescale covered by FACE studies, N limitation of eCO2-induced terrestrial productivity enhancement is associated with negative effects of eCO2 on plant N acquisition rather than with growth dilution of plant N or processes leading to progressive N limitation. [ABSTRACT FROM AUTHOR]

Data from three Swedish open-top chamber and four German FACE experiments were combined to derive response functions for elevated CO 2 (eCO 2 ) effects on Cd, Zn, Mn, protein, grain yield, grain mass and grain number of wheat. Grain yield and grain number were increased by ∼6% and ∼7%, respectively, per 100 ppm CO 2 ; the former effect was linked to plant nitrogen status. Grain mass was not influenced by eCO 2 , whereas Cd concentration was reduced. Unlike Zn, Mn and protein, effects on Cd yield were not related to effects on grain yield. Yields of Mn, Zn and (weakly) protein were positively affected by eCO 2 . For protein, grain yield, grain mass and grain number, the results were consistent among the FACE and OTC experiments. A key conclusion was that yields of essential nutrients were enhanced (Mn > Zn > protein), although less than grain yield, which would not be expected from a simple dilution model. [ABSTRACT FROM AUTHOR]

Concentrations of NO2 and O3 were measured inside and outside a dense broad-leaved forest canopy adjacent to a busy traffic route in the City of Gothenburg, Sweden, with duplicate passive diffusion samplers during six one-week periods starting well before leaf senescence and ending when leaves were largely senescent. Concentrations of NO2 were lower inside the forest canopy during all periods (representing a significant effect, p = 0.016), on average by 7% or 2.7 μg m−3. O3 showed a more variable response with an average non-significant effect of 2% lower in the forest stand. There was no systematic trend of the difference in concentrations inside and outside the forest stand of the pollutants with the progression of autumn leaf senescence. Our study indicates that the effect of urban vegetation on air pollution concentrations is small, although it seems to exist for NO2 in a traffic polluted environment. [Copyright &y& Elsevier]

Although it is established that there exist potential trade-offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide ( CO2) and ozone ( O3), their underlying causes remain poorly explored. To investigate the processes affecting grain quality under altered CO2 and O3, we analysed 57 experiments with CO2 or O3 exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O3 was associated with a change in grain protein yield of 8.1% ( R2 = 0.96), whereas a change in yield effect of 10% by CO2 was linked to a change in grain protein yield effect of 7.5% ( R2 = 0.74). Superimposed on this effect, elevated CO2, but not O3, had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO2 restricts grain protein accumulation, which is absent for O3. Grain mass, another quality trait, was more strongly affected by O3 than grain number, whereas the opposite was true for CO2. Harvest index was strongly and negatively influenced by O3, but was unaffected by CO2. We conclude that yield vs. protein trade-offs for wheat in response to CO2 and O3 are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO2 has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO2-induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade-offs are very different in wheat exposed to elevated O3 compared with elevated CO2. [ABSTRACT FROM AUTHOR]

Abstract: Wheat (Triticum aestivum L.) grain Zn data from six open-top chamber experiments performed in south-west Sweden were combined to study the relationship between Zn accumulation and grain yield, grain protein, and yield components. Treatments included, in addition to open-top chamber controls, elevated CO2, elevated O3, combined CO2 and O3 exposure, combined elevated CO2 and supplemental irrigation, supplemental irrigation, and ambient air comparison plots. The grain Zn concentration was strongly correlated with grain protein (R 2 =0.90) over the range of the experimental treatments, representing non-soil factors. A significant yield dilution effect was found for Zn. For a 10% increase in grain yield, Zn yield was increased by 6.8% on average. Effects on Zn yield correlated strongly with effects on grain protein yield, with a slope close to unity, showing that yield dilution effects for grain Zn and grain protein were similar. Treatment effects on grain Zn concentration were related to effects on grain weight (P <0.01) and grain number (P <0.05), but not to harvest index. It was concluded that yield stimulation caused by rising CO2 concentrations is likely to lead to reduced Zn concentrations of wheat grain, thus reducing the nutritional quality. [Copyright &y& Elsevier]

Effects of different concentrations of ozone on grain filling, flag leaf senescence and final grain yield in field-grown spring wheat (Triticum aestivum L. cv. Dragon) were studied using open-top chambers. The hypothesis tested was that an ozone-induced reduction in grain yield is mainly related to an enhanced senescence and a shortening of the grain-filling period. The plants were exposed to filtered air (F), non-filtered air without extra ozone (NF) or non-filtered air with 3 different levels of ozone added (NF1+, NF2+ and NF3+). The mean daytime (08.00–20.00 h) ozone concentrations during the exposure period (31 days) were 7, 20, 34, 48 and 62 nmol mol-1 in F, NF, NF1+, NF2+ and NF3+, respectively. The corresponding ozone doses, expressed as the accumulated exposure over a concentration threshold of 40 nmol mol-1 (AOT40), were 0, 12, 1 989, 5 881 and 10 375 nmol mol-1 h, respectively, and 884, 2 594, 4 557, 6 188 and 7 900 μmol m-2, respectively, expressed as the calculated cumulative flag leaf ozone flux (CFO30). The flag leaves senesced earlier and the grain-filling duration was significantly shorter at higher ozone exposure compared to F (-5, -13 and -18% in NF1+, NF2+ and NF3+, respectively). The relative grain-filling rate did not differ between the treatments. The 1000-grain weights were 10, 28 and 37% lower, and the grain yields were 15, 29 and 46% lower than F in NF1+, NF2+ and NF3+, respectively. Ozone exposure had no significant effect on the number of grains per unit ground area or on straw yield, but significantly reduced the harvest index and increased the grain protein concentration in NF2+ and NF3+ compared to F. The grain yield was negatively correlated with the ozone dose, expressed either as AOT40 or as CFO3 with or without an ozone flux threshold. The 1000-grain weight was positively correlated with the grain-filling duration (R2=0.998), which in turn was positively correlated with the leaf area duration (R2=0.989). [ABSTRACT FROM AUTHOR]

A central topic of recent research in ground-level ozone (O 3) effects on plants is the shift from exposure based on concentrations to a physiologically more realistic approach based on O 3 uptake. Critical test of the evidence for the benefits of the latter approach is of utmost importance for the development of O 3 risk assessment. We explored the variability in O 3 sensitivity in the wheat response function used for risk assessment by the Convention on Long-Range Transport of Air Pollution (LRTAP). The variation in O 3 sensitivity among individual experiments was a factor of six larger when using the concentration-based index AOT40 compared to stomatal O 3 uptake based Phytotoxic Ozone Dose (POD). Thus, consideration of environmental variables affecting stomatal conductance, such as solar radiation, air humidity and temperature, explained a substantial part of the variation in O 3 response among experiments regardless of cultivar differences. Response-functions based on daytime O 3 concentrations for the experiments of the POD response function was compared with the corresponding response function including available global data for O 3 effects on field grown wheat yield. On average, there was no difference in O 3 sensitivity between the two data sets, although the variation in response was substantially larger for global data. We conclude that POD represents a strong improvement over AOT40. The strength and representativeness of the POD approach highlighted is significant for the development and application of models used for risk assessment of ozone impact on crops. • We compared the phytotoxic dose (POD) with concentration based ozone index AOT40. • Ozone sensitivity in wheat varied much less when using POD compared to AOT40. • Our analysis shows that POD leads to more accurate ozone risk assessment. [ABSTRACT FROM AUTHOR]

Potted subterranean clover (Trifolium subterraneum) plants of different ages were exposed to 70 nl l-1 ozone for 6 h, either during the light or during the dark period in a laboratory-based climate chamber. There was limited visible leaf injury on plants which were 14-20 and 28-34 d old and no significant decrease in biomass after daytime ozone exposure. The oldest leaves of 22-26 d old plants exhibited severe visible injury, which was associated with a significant reduction in biomass in 24-26 d old plants. Thus, ozone-induced visible injury of different magnitude developed in all plants, but was associated with biomass reduction only during a limited period of the plants life-span. Apart from modifying ozone uptake by plants, climatic conditions are important as growth modifiers. It is suggested that subterranean clover plants of defined developmental stages should be used in bioindication of ozone. Night ozone exposure injured significantly fewer leaves than day exposure. However, some leaves developed visible injury even after night ozone exposure. Night uptake of ozone may be of more importance in northern than in central and southern Europe, because summer nights are short and, for a certain period, never completely dark. [ABSTRACT FROM AUTHOR]

Five modern cultivars of winter wheat ( Triticum aestivum L.): Yangmai16 (Y16), Yangmai 15 (Y15), Yangfumai 2 (Y2), Yannong 19 (Y19) and Jiaxing 002 (J2) were investigated to determine the impacts of elevated ozone concentration (E-O 3 ) on photosynthesis-related parameters and the antioxidant system under fully open-air field conditions in China. The plants were exposed to E-O 3 at 1.5 times the ambient ozone concentration (A-O 3 ) from the initiation of tillering to final harvest. Pigments, gas exchange rates, chlorophyll a fluorescence, antioxidants contents, antioxidative enzyme activity and lipid oxidation were measured in three replicated plots throughout flag leaf development. Results showed that significant O 3 effects on most variables were only found during the mid-grain filling stage. Across five cultivars, E-O 3 significantly accelerated leaf senescence, as indicated by increased lipid oxidation as well as faster declines in pigment amounts and photosynthetic rates. The lower photosynthetic rates were mainly due to non-stomatal factors, e.g. lower maximum carboxylation capacity and electron transport rates. There were strong interactions between O 3 and cultivar in photosynthetic pigments, light-saturated photosynthesis rate and chlorophyll a fluorescence with O 3 -sensitive (Y19, Y2 and Y15) and O 3 -tolerant (J2, Y16) cultivars being clearly differentiated in their responses to E-O 3 . E-O 3 significantly influenced the antioxidative enzymes but not antioxidant contents. Significant interactions between O 3 and cultivar were found in antioxidative enzymes, such as SOD and CAT, but not in stomatal conductance ( g s ). Therefore, it can be concluded that antioxidative enzymes rather than g s or antioxidants are responsible for the differential responses to E-O 3 among cultivars. These findings provide important information for the development of accurate modeling O 3 effects on crops, especially with respect to the developmental stage when O 3 damage to photosynthesis becomes manifest. [ABSTRACT FROM AUTHOR]

A key part of the uncertainty in terrestrial feedbacks on climate change is related to how and to what extent nitrogen (N) availability constrains the stimulation of terrestrial productivity by elevated CO2 ( eCO2), and whether or not this constraint will become stronger over time. We explored the ecosystem-scale relationship between responses of plant productivity and N acquisition to eCO2 in free-air CO2 enrichment ( FACE) experiments in grassland, cropland and forest ecosystems and found that: (i) in all three ecosystem types, this relationship was positive, linear and strong ( r2 = 0.68), but exhibited a negative intercept such that plant N acquisition was decreased by 10% when eCO2 caused neutral or modest changes in productivity. As the ecosystems were markedly N limited, plants with minimal productivity responses to eCO2 likely acquired less N than ambient CO2-grown counterparts because access was decreased, and not because demand was lower. (ii) Plant N concentration was lower under eCO2, and this decrease was independent of the presence or magnitude of eCO2-induced productivity enhancement, refuting the long-held hypothesis that this effect results from growth dilution. (iii) Effects of eCO2 on productivity and N acquisition did not diminish over time, while the typical eCO2-induced decrease in plant N concentration did. Our results suggest that, at the decennial timescale covered by FACE studies, N limitation of eCO2-induced terrestrial productivity enhancement is associated with negative effects of eCO2 on plant N acquisition rather than with growth dilution of plant N or processes leading to progressive N limitation. [ABSTRACT FROM AUTHOR]

Urban air quality is influenced by vegetation through alterations in airflow and pollutant deposition processes. We investigated these interactions by integrating the Vegetation Impact Dynamic Assessment model (VIDA) with the Large-Eddy Simulation model PALM. Our analysis focus on nitrogen dioxide (NO₂) and particulate matter (PM) concentrations at the local scale, considering three tree genera. Our findings reveal the necessity of accounting for both gaseous pollutants and particles separately due to their differing mechanisms of deposition onto leaves. The coupled PALM-VIDA model demonstrates a significant reduction in PM levels across the modelling domain and within street canyons when deposition to vegetation is incorporated. Reduction in NO₂ through deposition to vegetation is lower but human NO 2 exposure can still be decreased if tree species selection and placement leads to desirable effects on air flow. Sparse tree arrangements or species with sparse crowns facilitate ventilation and are often better at reducing NO₂ concentrations in street canyons compared to denser vegetation with higher deposition but negative effects on ventilation. Our study informs urban planning and green infrastructure design, underscoring the multifaceted role of urban greenery in air pollution mitigation strategies. Its main conclusion is that both deposition processes and the influence of air mixing and ventilation need to be considered to accurately assess the effects of urban trees on local air quality. Ill-considered placement and species selection may cause a net increase in pollutants underneath the trees. However, careful planning can address this risk and instead improve overall air quality. • Deposition of particles and NO 2 to vegetation was integrated in an urban air quality model • Both deposition and air flow processes must be considered in assessments of urban tree effects on air quality • Deposition to trees was more important for particle removal compared to NO 2 • The choice of tree species is significant for the effect of vegetation on air quality • Sparsely planted trees can balance deposition and ventilation in street canyons [ABSTRACT FROM AUTHOR]

Urban greenery is identified as a potential tool in air pollution mitigation. However, the impact is still debated. This paper introduces the innovative VIDA (Vegetation Impact Dynamic Assessment) model, specifically designed to quantify air pollution removal through deposition on vegetation. The VIDA model offers an advanced representation of vegetation that could be integrated into urban air quality dispersion models in the future. Furthermore, the model serves as a valuable tool for exploring the intricate interactions among deposition, resuspension, and wash-off processes, as well as understanding how meteorological conditions and various leaf traits influence these processes. The current version of the model focuses on particulate matter (PM) and encompasses a range of processes, including deposition on vegetation surfaces, encapsulation within the waxy cuticle, wind-driven resuspension, and wash-off. Additionally, the model takes into consideration dynamic changes in PM concentrations on the leaf surface over time, incorporating factors such as PM size fractions, meteorological conditions, and leaf characteristics. This comprehensive approach allows for the evaluation of various species or species groups based on their distinct traits. The VIDA model effectively reproduces measured data, yet continued evaluation remains crucial as new data emerges. Notably, challenges were encountered due to data scarcity and the absence of standardized methods for characterizing vegetation traits. Addressing these challenges and refining the representation of wash-off process will enhance the VIDA model's utility in predicting the dynamic relationship between vegetation and air quality. The introduction of VIDA provides a significant advancement in modelling air pollution removal by deposition to vegetation at a relevant local scale and enables inclusion of urban greenery as tool in urban planning for air pollution mitigation. • The VIDA model quantifies air pollution removal through deposition on vegetation. • VIDA models particle deposition, cuticle encapsulation, resuspension, and wash-off. • VIDA enables inclusion of urban greenery in air pollution mitigation. [ABSTRACT FROM AUTHOR]

Highlights • Elevated CO 2 decreases the concentrations of most nutrients in non-legume C 3 crops. • The effects are correlated for nutrients mostly found in proteins: N, Zn, Fe, S. • None of the suggested mechanisms and processes can explain the effect on N. • Decreased concentrations of protein, Zn and Fe have implications for food security. Crops grown under elevated CO 2 (eCO 2) typically exhibit enhanced yields but at the same time decreased nutritional quality. The latter effect has often been explained as a growth dilution phenomenon, but this cannot be the only process involved since crop nutrient concentrations are decreased also when production is unaffected by eCO 2. We review the current knowledge on eCO 2 effects on crop nutritional quality with focus on the current understanding of the possible mechanisms and processes causing these effects. Emphasis is on crop nitrogen (N) and protein concentrations but effects on other nutrients and how they compare with those on N are also covered. [ABSTRACT FROM AUTHOR]

Ongoing urban exploitation is increasing pressure to transform urban green spaces, while there is increasing awareness that greenery provides a range of important benefits to city residents. In efforts to help resolve associated problems we have developed a framework for integrated assessments of ecosystem service (ES) benefits and values provided by urban greenery, based on the ecosystem service cascade model. The aim is to provide a method for assessing the contribution to, and valuing, multiple ES provided by urban greenery that can be readily applied in routine planning processes. The framework is unique as it recognizes that an urban greenery comprises several components and functions that can contribute to multiple ecosystem services in one or more ways via different functional traits (e.g. foliage characteristics) for which readily measured indicators have been identified. The framework consists of five steps including compilation of an inventory of indicator; application of effectivity factors to rate indicators' effectiveness; estimation of effects; estimation of benefits for each ES; estimation of the total ES value of the ecosystem. The framework was applied to assess ecosystem services provided by trees, shrubs, herbs, birds, and bees, in green areas spanning an urban gradient in Gothenburg, Sweden. Estimates of perceived values of ecosystem services were obtained from interviews with the public and workshop activities with civil servants. The framework is systematic and transparent at all stages and appears to have potential utility in the existing spatial planning processes. [ABSTRACT FROM AUTHOR]

Inefficient use of fertilizers by crops increases the risk of nutrient leaching from agro-ecosystems, resulting in economic loss and environmental contamination. We investigated how ground-level ozone affects the efficiency by which wheat used applied nitrogen (N) fertilizer to produce grain protein (NE P , N efficiency with respect to protein yield) and grain yield (NE Y , N efficiency with respect to grain yield) across a large number of open-top chamber field experiments. Our results show significant negative ozone effects on NE P and NE Y , both for a larger data set obtained from data mining (21 experiments, 70 treatments), and a subset of data for which stomatal ozone flux estimates were available (7 experiments, 22 treatments). For one experiment, we report new data on N content of different above-ground plant fractions as well as grain K and P content. Our analysis of the combined dataset demonstrates that the grain yield return for a certain investment in N fertilizer is reduced by ozone. Results from the experiment with more detailed data further show that translocation of accumulated N from straw and leaves to grains is significantly and negatively affected by ozone, and that ozone decreases fertilizer efficiency also for K and P. As a result of lower N fertilization efficiency, ozone causes a risk of increased N losses from agroecosystems, e.g. through nitrate leaching and nitrous oxide emissions, a hitherto neglected negative effect of ozone. This impact of ozone on the N cycle implies that society is facing a dilemma where it either (i) accepts increased N pollution and counteracts ozone-induced yield reductions by increasing fertilization or (ii) counteracts N pollution under elevated ozone by reducing fertilization, accepting further yield loss adding to the direct effect of ozone on yield. [ABSTRACT FROM AUTHOR]

Air pollution levels (NO 2 , PAHs, O 3 ) were investigated, before (BLE) and after (ALE) leaf emergence, in the urban landscape of Gothenburg, Sweden. The aims were to study the 1) spatial and temporal variation in pollution levels between urban green areas, 2) effect of urban vegetation on air pollution levels at the same distance from a major emission source (traffic route), 3) improvement of urban air quality in urban parks compared to adjacent sites near traffic, 4) correlation between air pollution and noise in a park. O 3 varied little over the urban landscape. NO 2 varied strongly and was higher in situations strongly influenced by traffic. Four PAH variables were included: total PAH, total particle-bound PAH, the quantitatively important gaseous phenanthrene and the highly toxic particle-bound benzo(a)pyrene. The variation of PAHs was similar to NO 2 , but for certain PAHs the difference between highly and less polluted sites was larger than for NO 2 . At a vegetated site, NO 2 and particulate PAH levels were lower than at a non-vegetated site at a certain distance from a busy traffic route. This effect was significantly larger ALE compared to BLE for NO 2 , indicating green leaf area to be highly significant factor for air quality improvement. For particulate PAHs, the effect was similar BLE and ALE, indicating that tree bark and branches also could be an important factor in reducing air pollution. Parks represented considerably cleaner local environments (park effect), which is likely to be a consequence of both a dilution (distance effect) and deposition. Noise and air pollution (NO 2 and PAH) levels were strongly correlated. Comparison of noise levels BLE and ALE also showed that the presence of leaves significantly reduced noise levels. Our results are evidence that urban green spaces are beneficial for urban environmental quality, which is important to consider in urban planning. [ABSTRACT FROM AUTHOR]

This review summarizes new information on the current status of ground-level ozone in Europe north of the Alps. There has been a re-distribution in the hourly ozone concentrations in northern Europe during 1990–2015. The highest concentrations during summer daytime hours have decreased while the summer night-time and winter day- and night-time concentrations have increased. The yearly maximum 8-h mean concentrations ([O 3 ] 8h,max ), a metric used to assess ozone impacts on human health, have decreased significantly during 1990–2015 at four out of eight studied sites in Fennoscandia and northern UK. Also the annual number of days when the yearly [O 3 ] 8h,max exceeded the EU Environmental Quality Standard (EQS) target value of 60 ppb has decreased. In contrast, the number of days per year when the yearly [O 3 ] 8h,max exceeded 35 ppb has increased significantly at two sites, while it decreased at one far northern site. [O 3 ] 8h,max is predicted not to exceed 60 ppb in northern UK and Fennoscandia after 2020. However, the WHO EQS target value of 50 ppb will still be exceeded. The AOT40 May–July and AOT40 April–September metrics, used for the protection of vegetation, have decreased significantly at three and four sites, respectively. The EQS for the protection of forests, AOT40 April–September 5000 ppb h, is projected to no longer be exceeded for most of northern Europe sometime before the time period 2040–2059. However, if the EQS is based on Phytotoxic Ozone Dose (POD), POD 1 , it may still be exceeded by 2050. The increasing trend for low and medium range ozone concentrations in combination with a decrease in high concentrations indicate that a new control strategy, with a larger geographical scale than Europe and including methane, is needed for ozone abatement in northern Europe. [ABSTRACT FROM AUTHOR]

In this paper we investigate the effects of the temporal variation of pollution dispersion, traffic flows and vehicular emissions on pollution concentration and illustrate the need for temporally differentiated road pricing through an application to the case of the congestion charge in Stockholm, Sweden. By accounting explicitly for the role of pollution dispersion on optimal road pricing, we allow for a more comprehensive view of the economy–ecology interactions at stake, showing that price differentiation is an optimal response to the physical environment. Most congestion charges in place incorporate price bands to mitigate congestion. Our analysis indicates that, to ensure compliance with air quality standards, such price variations should also be a response to limited pollution dispersion. [ABSTRACT FROM AUTHOR]

• Model errors were similar for predicted potato yield at ambient and elevated CO 2 concentration. • Models with least calibration error provided the most accurate response to elevated CO 2. • Top performing models were representative of three different model structural groups. • Four models outperformed the ensemble mean and median for more than half of the datasets. • More data on yield response to elevated CO 2 under field conditions is still needed. A multi-model inter-comparison study was conducted to evaluate the performance of ten potato crop models to accurately predict potato yield in response to elevated CO 2 (Ce) when calibrated with ambient CO 2 data (Ca). Experimental data from seven open-top chambers (OTC) and free-air−CO 2 -enrichment (FACE) facilities across continental Europe were used. Model ensemble percent errors averaged over all datasets for simulated yields were 26.5 % for Ca and 27.2 % Ce data. Metrics such as Wilmott's index of agreement (IA) and root mean square relative error (RMSRE) ranged broadly among individual models and locations, such that four of the ten models outperformed the median or mean of the ensemble for about half of the Ce datasets. These top performing models were representative of three different model structural groups, including radiation use efficiency, transpiration efficiency, or leaf-level based approaches. Relative response to an increase in CO 2 was more accurately modeled than absolute yield responses when averaged across all locations, and within 3.3 kg ppm−1 (or 5%) of observed values. Specific targets in the model structure needed for improvement were not identified due to large and inconsistent variation in the accuracy of yield predictions across locations. However, models with the lowest calibration errors tended to be top performers for Ce predictions as well. Such results suggest calibration is at least as important as model structure. Where possible, modelers using potato models to estimate Ce responses should use Ce calibration data to improve confidence in such predictions. [ABSTRACT FROM AUTHOR]

Oxidative stress from ozone (O 3 ) causes plants to alter their emission of biogenic volatile organic compounds (BVOC) and their photosynthetic rate. Stress reactions from O 3 on birch trees can result in prohibited plant growth and lead to increased BVOC emission rates as well as changes in their compound blend to emit more monoterpenes (MT) and sesquiterpenes (SQT). BVOCs take part in atmospheric reactions such as enhancing the production of secondary organic aerosols (SOA). As the compound blend and emission rate change with O 3 stress, this can influence the atmospheric conditions by affecting the production of SOA. Studying the stress responses of plants provides important information on how these reactions might change, which is vital to making better predictions of the future climate. In this study, measurements were taken to find out how the leaves of mature mountain birch trees ( Betula pubescens ssp. czerepanovii ) respond to different levels of elevated O 3 exposure in situ depending on leaf age. We found that leaves from both early and late summers responded with induced SQT emission after exposure to 120 ppb O 3 . Early leaves were, however, more sensitive to increased O 3 concentrations, with enhanced emission of green leaf volatiles (GLV) and tendencies of both induced leaf senescence as well as poor recovery in the photosynthetic rate between exposures. Late leaves had more stable photosynthetic rates throughout the experiment and responded less to exposure at different O 3 levels., Competing Interests: The authors declare that they have no conflict of interest., (© 2024 The Authors. Plant‐Environment Interactions published by New Phytologist Foundation and John Wiley & Sons Ltd.)

Antimony (Sb) is a toxic metalloid, which has been increasingly used in the brake lining of vehicles, and increased concentrations have been found in soils near abundant traffic. However, since very few investigations of Sb accumulation in urban vegetation have been undertaken there exists a knowledge gap. We studied the concentrations of Sb in leaves and needles of trees in the Gothenburg City area, Sweden. In addition, lead (Pb), also associated with traffic, was investigated. Sb and Pb concentrations of Quercus palustris leaves at seven sites with contrasting traffic intensity varied substantially, correlated with the traffic-related PAH (polycyclic aromatic hydrocarbon) air pollution at the sites and increased during the growing season. Sb but not Pb concentrations were significantly higher in needles of Picea abies and Pinus sylvestris near major roads compared to sites at larger distances. In Pinus nigra needles at two urban streets both Sb and Pb were higher compared to an urban nature park environment, emphasising the role of traffic emissions for these elements. A continued accumulation of Sb and Pb in three years old needles of Pinus nigra , two years old needles of Pinus sylvestris and eleven years old needles of Picea abies was observed. Our data suggest a pronounced link between traffic pollution and Sb accumulation in leaves and needles, where the particles carrying Sb seem not to be transported very far from the source. We also conclude that there exists a strong potential for Sb and Pb bioaccumulation over time in leaves and needles. Implications of these findings are that increased concentrations of toxic Sb and Pb are likely to prevail in environments with high traffic intensity and that Sb can enter the ecological food chain by accumulation in leaves and needles, which is important for the biogeochemical cycling., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)

Plant responses to rising atmospheric carbon dioxide (CO 2 ) concentrations, together with projected variations in temperature and precipitation will determine future agricultural production. Estimates of the impacts of climate change on agriculture provide essential information to design effective adaptation strategies, and develop sustainable food systems. Here, we review the current experimental evidence and crop models on the effects of elevated CO 2 concentrations. Recent concerted efforts have narrowed the uncertainties in CO 2 -induced crop responses so that climate change impact simulations omitting CO 2 can now be eliminated. To address remaining knowledge gaps and uncertainties in estimating the effects of elevated CO 2 and climate change on crops, future research should expand experiments on more crop species under a wider range of growing conditions, improve the representation of responses to climate extremes in crop models, and simulate additional crop physiological processes related to nutritional quality., (© 2020. Springer Nature Limited.)

A stomatal ozone (O 3 ) flux-response relationship for relative yield of maize was established by parameterizing a Jarvis stomatal conductance model. For the function (f VPD ) describing the limitation of stomatal conductance by vapor pressure deficit (VPD, kPa), cumulative VPD during daylight hours was superior to hourly VPD. The latter function is proposed as a methodological improvement of this multiplicative model when stomatal conductance peaks during the morning and it is reduced later as it is the case of maize in this experiment. The model agreed relatively well with the measured stomatal conductance (R 2  = 0.63). Based on the comparison of R 2 values of the response functions, POD 6 (Phytotoxic Ozone Dose over an hourly threshold 6 nmol m -2 s -1 ) and AOT40 (accumulated hourly O 3 concentrations over a threshold of 40 ppb) performed similarly. The critical levels based on POD 6 and AOT40 for 5% reduction in maize yield were 1.17 mmol m -2 PLA and 8.70 ppm h, respectively. In comparison with other important crops, the ranking of sensitivity of maize strongly differed depending on the O 3 metric used, AOT40 or POD 6 . The newly proposed response functions are relevant for O 3 risk assessment for this crop in Asia., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Data from experiments where field-grown wheat was exposed to ozone were collated in order to compare the effects in Europe, Asia and North America using dose-response regression. In addition to grain yield, average grain mass and harvest index were included to reflect the influence of ozone on the crop growth pattern. In order to include as many experiments as possible, daytime average ozone concentration was used as the ozone exposure index, but AOT40, estimated from average ozone concentrations, was also used to compare the performance of the two exposure metrics. The response to ozone differed significantly between the continents only for grain yield when using AOT40 as the exposure index. North American wheat was less sensitive than European and Asian that responded similarly. The variation in responses across all three continents was smallest for harvest index, followed by grain mass and grain yield. The highly consistent effect on harvest index shows that not only effects on biomass accumulation, but also on the partitioning of biomass, are important for the ozone-induced grain yield loss in wheat. The average duration of daily ozone exposure was longer in European experiments compared to North American and Asian. It cannot be excluded that this contributed to the indicated higher ozone sensitivity in European wheat in relation to North American. The main conclusions from this study are that on the average the response of wheat to ozone was lower for the older North American experiments and that the ozone response of the growth pattern reflected by grain mass and harvest index did not differ between continents., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Tropospheric ozone is known to adversely affect crops and other vegetation. Most studies have focussed on the effects of elevated ozone levels vs. present ambient. We investigated the effect of present ambient surface ozone (O 3 ) concentrations vs. preindustrial on a range of agronomically important response variables in field-grown wheat, using results from 33 experiments (representing 9 countries, 3 continents, 17 cultivars plus one set of 4 cultivars) having both charcoal filtered (CF) and non-filtered (NF) air treatments. Average filtration efficiency was 62%, reducing the O 3 concentration from 35.6±10.6SDppb in NF to 13.7±8.8SDppb in CF. Average CF concentrations were in the range of levels believed to represent pre-industrial conditions, while NF concentrations were 7% lower than in the ambient air at plant height on the experimental sites. NF had significant (p<0.05) negative effects compared to CF on grain yield (-8.4%), grain mass (-3.7%), harvest index (-2.4%), total above-ground biomass (-5.4%), starch concentration (-3.0%), starch yield (-10.9%), and protein yield (-6.2%). No significant effect was found for grain number and protein concentration. There was a significant relationship between the effect of filtration on grain yield and the difference in O 3 concentration between NF and CF treatments. The average yield loss per ppb O 3 removed was 0.38% and did not systematically vary with year of experiment (ranging from 1982 to 2010) or with the average O 3 level in the experiments. Although there are many differences among the field experiments included in this meta-analysis (e.g. genotype, degree of O 3 pollution of the site and year, nutrient and soil condition, filtration efficiency), our study clearly shows that there is a consistent and significant effect of present ambient O 3 exposure on a range of important response variables in wheat, the most strongly affected being starch yield., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Exposure to elevated air pollution levels can aggravate pollen allergy symptoms. The aim of this study was to investigate the relationships between airborne birch ( Betula ) pollen, urban air pollutants NO 2 , O 3 and PM 10 and their effects on antihistamine demand in Gothenburg and Malmö, Sweden, 2006-2012. Further, the influence of large-scale weather pattern on pollen-/pollution-related risk, using Lamb weather types (LWTs), was analysed. Daily LWTs were obtained by comparing the atmospheric pressure over a 16-point grid system over southern Sweden (scale ~3000 km). They include two non-directional types, cyclonic (C) and anticyclonic (A) and eight directional types depending on the wind direction (N, NE, E…). Birch pollen levels were exceptionally high under LWTs E and SE in both cities. Furthermore, LWTs with dry and moderately calm meteorological character (A, NE, E, SE) were associated with strongly elevated air pollution (NO 2 and PM 10 ) in Gothenburg. For most weather situations in both cities, simultaneously high birch pollen together with high air pollution had larger over-the-counter (OTC) sales of antihistamines than situations with high birch pollen alone. LWTs NE, E, SE and S had the highest OTC sales in both cities. In Gothenburg, the city with a higher load of both birch pollen and air pollution, the higher OTC sales were especially obvious and indicate an increased effect on allergic symptoms from air pollution. Furthermore, Gothenburg LWTs A, NE, E and SE were associated with high pollen and air pollution levels and thus classified as high-risk weather types. In Malmö, corresponding high-risk LWTs were NE, E, SE and S. Furthermore, occurrence of high pollen and air pollutants as well as OTC sales correlated strongly with vapour pressure deficit and temperature in Gothenburg (much less so in Malmö). This provides evidence that the combination of meteorological properties associated with LWTs can explain high levels of birch pollen and air pollution. Our study shows that LWTs represent a useful tool for integrated daily air quality forecasting/warning.

We synthesized the effects of ozone on wheat quality based on 42 experiments performed in Asia, Europe and North America. Data were analysed using meta-analysis and by deriving response functions between observed effects and daytime ozone concentration. There was a strong negative effect on 1000-grain weight and weaker but significant negative effects on starch concentration and volume weight. For protein and several nutritionally important minerals (K, Mg, Ca, P, Zn, Mn, Cu) concentration was significantly increased, but yields were significantly decreased by ozone. For other minerals (Fe, S, Na) effects were not significant or results inconclusive. The concentration and yield of potentially toxic Cd were negatively affected by ozone. Some baking properties (Zeleny value, Hagberg falling number) were positively influenced by ozone. Effects were similar in different exposure systems and for spring and winter wheat. Ozone effects on quality should be considered in future assessments of food security/safety., (Copyright © 2014 Elsevier Ltd. All rights reserved.)