The critical levels for ozone effects on vegetation have been reviewed and revised by the LRTAP Convention. Eight new or revised critical levels based on the accumulated stomatal flux of ozone (POD
Y
..., the Phytotoxic Ozone Dose above a threshold flux of
Y nmol m
−2 PLA s
−1, where PLA is the projected leaf area) have been agreed. For each receptor, data were combined from experiments conducted under naturally fluctuating environmental conditions in 2–4 countries, resulting in linear dose–response relationships with response variables specific to each receptor (
r
2 = 0.49–0.87,
p < 0.001 for all). For crops, critical levels were derived for effects on wheat (grain yield, grain mass, and protein yield), potato (tuber yield) and tomato (fruit yield). For forest trees, critical levels were derived for effects on changes in annual increment in whole tree biomass for beech and birch, and Norway spruce. For (semi-)natural vegetation, the critical level for effects on productive and high conservation value perennial grasslands was based on effects on important component species of the genus
Trifolium (clover species). These critical levels can be used to assess protection against the damaging effects of ozone on food security, important ecosystem services provided by forest trees (roundwood production, C sequestration, soil stability and flood prevention) and the vitality of pasture.
Field measurements and open-top chamber experiments using nine current European winter wheat cultivars provided a data set that was used to revise and improve the parameterisation of a stomatal ...conductance model for wheat, including a revised value for maximum stomatal conductance and new functions for phenology and soil moisture. For the calculation of stomatal conductance for ozone a diffusivity ratio between O3 and H2O in air of 0.663 was applied, based on a critical review of the literature. By applying the improved parameterisation for stomatal conductance, new flux-effect relationships for grain yield, grain mass and protein yield were developed for use in ozone risk assessments including effects on food security. An example of application of the flux model at the local scale in Germany shows that negative effects of ozone on wheat grain yield were likely each year and on protein yield in most years since the mid 1980s.
► Revised parameterisation of the LRTAP stomatal conductance model for wheat. ► More appropriate value for the diffusivity ratio between ozone and water vapour. ► Functions describing the influence of phenology and soil moisture on stomatal flux. ► New flux-effect relationships for wheat grain yield, grain mass and protein yield.
Improved parameterizations of ozone stomatal conductance model for wheat and new ozone flux-effect relationships for risk assessments.
This study explores the statistical relations between the concentration of nine heavy metals (HM) (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), ...vanadium (V), zinc (Zn)), and nitrogen (N) in moss and potential explanatory variables (predictors) which were then used for mapping spatial patterns across Europe. Based on moss specimens collected in 2010 throughout Europe, the statistical relation between a set of potential predictors (such as the atmospheric deposition calculated by use of two chemical transport models (CTM), distance from emission sources, density of different land uses, population density, elevation, precipitation, clay content of soils) and concentrations of HMs and nitrogen (N) in moss (response variables) were evaluated by the use of Random Forests (RF) and Classification and Regression Trees (CART). Four spatial scales were regarded: Europe as a whole, ecological land classes covering Europe, single countries participating in the European Moss Survey (EMS), and moss species at sampling sites. Spatial patterns were estimated by applying a series of RF models on data on potential predictors covering Europe. Statistical values and resulting maps were used to investigate to what extent the models are specific for countries, units of the Ecological Land Classification of Europe (ELCE), and moss species. Conclusions: RF is an eligible method identifying and ranking boundary conditions of element concentrations in moss and related mapping including the influence of the environmental factors.
A central topic of recent research in ground-level ozone (O3) effects on plants is the shift from exposure based on concentrations to a physiologically more realistic approach based on O3 uptake. ...Critical test of the evidence for the benefits of the latter approach is of utmost importance for the development of O3 risk assessment. We explored the variability in O3 sensitivity in the wheat response function used for risk assessment by the Convention on Long-Range Transport of Air Pollution (LRTAP). The variation in O3 sensitivity among individual experiments was a factor of six larger when using the concentration-based index AOT40 compared to stomatal O3 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 O3 response among experiments regardless of cultivar differences. Response-functions based on daytime O3 concentrations for the experiments of the POD response function was compared with the corresponding response function including available global data for O3 effects on field grown wheat yield. On average, there was no difference in O3 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.
Moss surveys provide spatially dense data on environmental concentrations of heavy metals and nitrogen which, together with other biomonitoring and modelling data, can be used for indicating ...deposition to terrestrial ecosystems and related effects across time and areas of different spatial extension. For enhancing the spatial resolution of measuring and mapping atmospheric deposition by technical devices and by modelling, moss is used complementarily as bio-monitor. This paper investigated whether nitrogen and heavy metal concentrations derived by biomonitoring of atmospheric deposition are statistically meaningful in terms of compliance with minimum sample size across several spatial levels, whether this is also true in terms of geostatistical criteria such as spatial auto-correlation and, by this, estimated values for unsampled locations and whether moss indicates atmospheric deposition in a similar way as modelled deposition, tree foliage and natural surface soil at the European and country level, and whether they indicate site-specific variance due to canopy drip. Data from modelling and biomonitoring atmospheric deposition were statistically analysed by means of minimum sample size calculation, by geostatistics as well as by bivariate correlation analyses and by multivariate correlation analyses using the Classification and Regression Tree approach and the Random Forests method. It was found that the compliance of measurements with the minimum sample size varies by spatial scale and element measured. For unsampled locations, estimation could be derived. Statistically significant correlations between concentrations of heavy metals and nitrogen in moss and modelled atmospheric deposition, and concentrations in leaves, needles and soil were found. Significant influence of canopy drip on nitrogen concentration in moss was proven. Moss surveys should complement modelled atmospheric deposition data as well as other biomonitoring approaches and offer a great potential for various terrestrial monitoring programmes dealing with exposure and effects.
English title: Purposes and contingencies in the lower and upper secondary school lab: A study of how students act in relation to the goals of the activityStudies have shown that students’ awareness ...of the goals and purposes of the laboratory activity is important for their possibility to participate in and learn from the activity. While practical activities often have been considered to be a central part of science education, relatively few studies have examined laboratory work in situ. In this paper we addressed these issues by examining (a) what purposes are distinguished when students’ work with a laboratory assignment and (b) how these purposes are made continuous with the teacher’s aim with the assignment. The data was based on classroom observations from two ordinary laboratory settings, one from a chemistry class in lower secondary school and one from a physics class in the natural science programme in upper secondary school. Although both student groups acknowledged their teacher’s intentions with the practical and could act towards the more student centered purposes of the activity, e.g. describe what happens with the copper and measure the speed of a small vessel respectively, there were differences regarding the possibilities the students had to act toward the activity’s final aim. The results showed that these factors can be referred to the amount of purposes introduced by the teacher as well as those that arose because of contingences, and the connection of these purposes to students’ prior experiences.
HIV‐1 protease is an important target for treatment of AIDS, and efficient drugs have been developed. However, the resistance and negative side effects of the current drugs has necessitated the ...development of new compounds with different binding patterns. In this study, nine C‐terminally duplicated HIV‐1 protease inhibitors were cocrystallised with the enzyme, the crystal structures analysed at 1.8–2.3 Å resolution, and the inhibitory activity of the compounds characterized in order to evaluate the effects of the individual modifications. These compounds comprise two central hydroxy groups that mimic the geminal hydroxy groups of a cleavage‐reaction intermediate. One of the hydroxy groups is located between the δ‐oxygen atoms of the two catalytic aspartic acid residues, and the other in the gauche position relative to the first. The asymmetric binding of the two central inhibitory hydroxyls induced a small deviation from exact C2 symmetry in the whole enzyme–inhibitor complex. The study shows that the protease molecule could accommodate its structure to different sizes of the P2/P2′ groups. The structural alterations were, however, relatively conservative and limited. The binding capacity of the S3/S3′ sites was exploited by elongation of the compounds with groups in the P3/P3′ positions or by extension of the P1/P1′ groups. Furthermore, water molecules were shown to be important binding links between the protease and the inhibitors. This study produced a number of inhibitors with Ki values in the 100 picomolar range.
Ground level ozone concentrations, in combination with the prevailing climate, at the estate Östads Säteri in southwestern Sweden were estimated to reduce the yield of wheat and potato ranging ...between 5% and 10%. Occasionally, in years with the highest ozone concentrations and/or climatic conditions favoring high rates of ozone uptake to the leaves, yield loss levels above 10% may occur. Based on simple extrapolation, these ozone-induced reductions of crop yields at Östads Säteri represent a potential total annual yield loss in Sweden in the range of 24.5 million Euro for wheat and 7.3 million Euro for potato, respectively. A simulation of forest growth at Östad Säteri predicted that prevailing mean ozone exposure during 1993–2003 had the potential to reduce forest growth by 2.2% and the economic return of forest production by 2.6%. Using this value for extrapolation to the national level, the potential annual economic loss for Sweden due to negative impacts of ozone on forest production would be in the range of 56 million Euro (2004 prices).
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