Major ions in Central European precipitation - Insight into changes in NO3-/SO42-, NH4+/NO3- and NH4+/SO42- ratios over the last four decades.

Knowledge of precipitation composition is important, among other things, to reveal changes in atmospheric chemistry. Here we present the long-term time trends in ratios of major ions in precipitation, namely nitrate to sulphate (NO3-/SO42-), ammonium to sulphate (NH4+/SO42-) and ammonium to nitrate (NH4+/NO3-). For this we explore the long-term time series recorded by the Czech Hydrometeorological Institute at eight monitoring sites situated in urban, rural and mountain regions of the Czech Republic between 1980 and 2020. To that end, we use innovative Bayesian inference with the Integrated Nested Laplace Approximation (INLA) computational method appropriate for investigating complicated large-scale data. Our results indicated: (i) increasing NO3-/SO42- ratio in precipitation over time and distinct seasonal behaviour with higher values in winter and lower values in summer, (ii) increasing NH4+/SO42- ratio in precipitation and distinct seasonal behaviour with higher values in summer and lower values in winter and (iii) relatively stable NH4+/NO3- ratio in precipitation with a mild recent increase and distinct seasonal behaviour with higher values in summer and lower values in winter. This behaviour pattern holds true for all the sites analysed, irrespective of their geographical position, altitude or environment. Though explored in detail rarely, the ion ratios are important to study as they reflect changes in atmospheric chemistry, mirroring changes in emissions and meteorology and suggesting changing impacts on ecosystems and the environment.

Ambient ozone at a rural Central European site and its vertical concentration gradient close to the ground.

The representativeness of ambient air quality of an in situ measurement is key in the use and correct interpretation of the measured concentration values. Though the horizontal representativeness aspect is generally not neglected in air pollution studies, a detailed, high-resolution vertical distribution of ambient air pollutant concentrations is rarely addressed. The aim of this study is twofold: (i) to explore the vertical distribution of ground-level ozone (O3) concentrations measured at four heights above the ground-namely at 2, 8, 50, and 230 m-and (ii) to examine in detail the vertical O3 concentration gradient in air columns between 2 and 8, 8 and 50, and 50 and 230 m above the ground. We use the daily mean O3 concentrations measured continuously at the Kosetice station, representing the rural Central European background ambient air quality observed during 2015-2021. We use the semiparametric GAM (generalised additive model) approach (with complexity or roughness-penalised splines implementation) to analyse the data with sufficient flexibility. Our models for both O3 concentrations and O3 gradients use (additive) decomposition into annual trend and seasonality (plus an overall intercept). The seasonal and year-to-year patterns of the modelled O3 concentrations look very similar at first glance. Nevertheless, a more detailed look through O3 gradients shows that they differ substantially with respect to their seasonal and long-term dynamics. The vertical O3 concentration gradient in 2-230 m is not uniform but changes substantially with increasing height and shows by far the highest dynamics near the ground between 2 and 8 m, differing in both the seasonal and annual aspects for all the air columns inspected. We speculate that non-linear changes of both seasonal and annual components of vertical O3 gradients are due to atmospheric-terrestrial interactions and to meteorological factors, which we will explore in a future study.

Ambient ozone - New threat to birds in mountain ecosystems?

Mountain ecosystems are inhabited by species with specific characteristics enabling survival at high altitudes, which make them at risk from various pressures. In order to study these pressures, birds represent excellent model organisms due to their high diversity and position at the top of food chains. The pressures upon mountain bird populations include climate change, human disturbance, land abandonment, and air pollution, whose impacts are little understood. Ambient ozone (O3) is one of the most important air pollutants occurring in elevated concentrations in mountain conditions. Although laboratory experiments and indirect course-scale evidence suggest its negative effects on birds, population-level impacts remain unknown. To fill this knowledge gap, we analysed a unique 25-years long time series of annual monitoring of bird populations conducted at fixed sites under constant effort in a Central European mountain range, the Giant Mountains, Czechia. We related annual population growth rates of 51 bird species to O3 concentrations measured during the breeding season and hypothesized (i) an overall negative relationship across all species, and (ii) more negative O3 effects at higher altitudes due to increasing O3 concentration along altitudinal gradient. After controlling for the influence of weather conditions on bird population growth rates, we found an indication of the overall negative effect of O3 concentration, but it was insignificant. However, the effect became stronger and significant when we performed a separate analysis of upland species occupying the alpine zone above treeline. In these species, populations growth rates were lower after the years experiencing higher O3 concentration indicating an adverse impact of O3 on bird breeding. This impact corresponds well to O3 behaviour and mountain bird ecology. Our study thus represents the first step towards mechanistic understanding of O3 impacts on animal populations in nature linking the experimental results with indirect indications at the country-level.

Comparison of vertical and horizontal atmospheric deposition of nitrate at Central European mountain-top sites during three consecutive winters.

Nitrogen (N) deposition, a key process of atmospheric self-cleaning, represents an important pathway for nutrients and pollutants to ecosystems. Enhanced N deposition flux contributes to acidification, eutrophication and loss of biodiversity. N-NO3- concentrations in rime and snow were measured at 10 Czech plots situated in borderline mountains in 2009-2011 winters. The results were put in context with data-driven geostatistical modelling results of annual wet vertical and horizontal deposition. Our hypotheses were that: (i) rime and snow would be more polluted in the highly industrialized north than in the south, (ii) the N-NO3- concentrations would differ in the three winters studied, and (iii), that N-NO3- rime deposition is not negligible in Central European mountain ranges. Our results indicated that winter N-NO3- concentrations were significantly higher in rime than in snow and that there were much larger between-site differences in N-NO3- concentrations for rime than for snow. Relatively large differences were found between individual years. Atmospheric input of N-NO3- in winter was dominated by vertical deposition, i.e., snow. Modelled results showed that mean winter rime deposition corresponded to about 6-25 %, and mean winter snow deposition made up 25-72.5 % of mean annual N-NO3- wet-only deposition. Model N-NO3-occult deposition estimated from throughfall and total (wet and dry) deposition is highly uncertain, however: N throughfall is not a relevant proxy for estimation of realistic total N deposition due to N exchange between the tree canopy and atmosphere.

Local fresh- and sea-water effects on fog occurrence.

Fog is an important atmospheric phenomenon highly relevant to ecosystems and/or the environment. Two essential prerequisites of fog formation are the presence of fog condensation nuclei and water in the atmosphere. The aim of our study was to examine in detail how fog occurrence is influenced by water areas in the immediate vicinity of the fog observation site. We have used as input data long-term observations on fog occurrence measured at 56 professional meteorological stations in Romania in 1981-2017 and GIS-derived information on water areas and on two topographical indices, TWI and TPI, in the neighbourhood of these stations. We formulated three alternative models of different complexity based on a semiparametric generalised additive logistic model for the probability of fog occurrence with potentially nonlinear, smooth effects modelled via penalised splines. A radius of 9 km appeared to be the most influential when considering the water area in a circle around the fog observation station. Based on our results, we concluded that (i) the water area in the vicinity of the station is a factor influencing fog occurrence, (ii) the water's effect differs according to water type (freshwater or seawater proximity), and (iii) GIS-derived topographical indices are informative for the explanation of fog occurrence and their inclusion enhanced the fit of the models substantially. Our findings, based on a reliable long-term data set of fog occurrence and recent GIS-derived data, explored by a relevant statistical approach will enhance further considerations related to fog formation and its environmental consequences.

Terrain and its effects on fog occurrence.

Fog is a very complex phenomenon, relevant to both atmospheric physics and chemistry, contributing to the atmospheric inputs of both nutrients and pollutants to the environment. Fog occurrence is affected by numerous factors. The aim of this study is to examine the effects of terrain on fog occurrence. Namely, we studied in detail how altitude, slope and landform influence the probability of fog occurrence using the generalized additive model. In particular, we investigated how different explanatory variables might modify (deform) the trend and the seasonal component of the probability of fog occurrence. We used long-term records of daily fog occurrence measured in 1981-2017 at 56 professional meteorological stations in Romania, reflecting different environments and geographical areas. The altitude of the sites under review ranged between 13 and 2504 m above sea level, the coverage of localities at different altitudes being highly uneven. Out of the terrain variables considered, the most decisive influence was found to be altitude. We have included information on slope and landform, which refined and bettered the basic model. Our model results indicated a significant decrease in the probability of fog occurrence over the examined period. The behaviour of fog differed according to the altitude, the most profound effects being observed for ground-level fog and fog above flat terrain. The probability of fog occurrence at different altitudes varied mostly in summer and autumn, whereas it was very similar in winter.

Trends in ambient O3 concentrations at twelve sites in the Czech Republic over the past three decades: Close inspection of development.

Ambient or ground-level ozone (O3), a key player in atmospheric chemistry, has been studied extensively throughout the world in recent decades due to its harmful effects on human health and the environment. The aim of this study is to examine in detail the time patterns of O3 in the Czech Republic, a Central European country with a long-term history of ambient air pollution. We have examined the interplay between annual trends and within-a-year seasonality in daily O3 concentrations at twelve stations representing different environments, geographical regions and altitudes in the Czech Republic in 1993-2018. We base our analysis on a generalised additive model (GAM) framework as a modern regression approach suitable for addressing non-linear trend shapes in a formalised and unified way. In particular, we use penalised splines. The inconsistent behaviour of the stations prior to 1998, two local maxima around 2003 and 2006 and a steady increase in O3 at all sites from 2014 to the present are the main features of our study. A seasonality O3 pattern with a clear maximum in May-June is similar for all stations. In parallel with the O3 concentration changes over the years, the deformation of seasonality profiles over a long period of time occurs, resulting in a shift of the peak O3 concentrations towards later days in the year. Our statistical modelling offers a detailed view of both long-term trend and seasonality components separately. Additionally, in a model with trend*seasonality interaction, we are able to study the gradual deformation of the seasonality profile over the years. Capsule: Our analysis of daily mean O3 concentrations at twelve Czech sites in 1993-2018 revealed a steady increase in O3 from 2014 and deformation of the seasonality O3 profiles over the year.

Long-term trends in fog occurrence in the Czech Republic, Central Europe.

Fog is a very important and complex atmospheric phenomenon of the utmost importance for the environment and for human society. For practical reasons, fog occurrence is observed regularly at meteorological stations worldwide. Decreasing trends in fog frequency reported from numerous regions have been often associated with either decreasing pollution or climate change, including increasing temperature and changes in atmospheric circulation. We have examined the data on fog occurrence from twelve Czech sites representing different environments (urban, rural, mountain), geographical areas, and altitudes across the country. For our analysis we used long-term records from the time period of 1961-2018, covering both the ambient air's heavily polluted periods of the 1970s and 1980s and the cleaner period, following the adoption of new, more stringent legislation and effective countermeasures after the 1990s. We applied a generalised additive model (GAM) framework as a flexible, semiparametric regression approach to address nonlinear trend shapes in a formalised and unified way. In particular, we employed a penalised spline approach with cross-validated penalty coefficient estimation. Our study confirmed non-linear behaviour for both year-to-year trends and annual seasonality. Our results showed further that over the analysed, almost sixty-year period, fog occurrence has decreased significantly at all the examined sites, though the pattern of the long-term change differed among individual sites. Moreover, we have found significant seasonality in fog occurrence, though it is different at individual sites. Furthermore, apart from the overall annual fog probability change over the years, at some sites the fog's seasonal profile has also deformed substantially over the long term.

Long-term trends in nitrogen oxides at different types of monitoring stations in the Czech Republic.

Nitrogen oxides (NOx) are important in atmospheric chemistry and have substantial environmental impacts. This study provides a detailed data analysis on long-term changes in ambient NOx levels within the framework of their emission pattern. We examined the trends in NOx, NO, NO2 and NO2/NOx ratio at 39 Czech sites representing different environments (urban, rural, mountain, industrial) in 1994-2016, i.e. a 23-year time series, using the non-parametric Man-Kendall test. The ambient air concentrations in NO, NO2 and NOx decreased significantly at most of the sites, as was assumed due to the substantial NOx emission decrease over the period under review. The largest decrease per year was detected at the urban site in capital Prague (decrease in the 98th percentile equal to 2.28 ppb, decrease in the annual median equal to 1.00 ppb). At some sites, however we observed a substantial equivocal temporal change in the NO2/NOx ratio. Whereas at some sites the NO2/NOx ratio was decreasing, at other sites the trend was increasing significantly. The highest increase per year in the annual median of the NO2/NOx ratio, equal to 0.0086 was detected at the urban Praha 1-nám-Rep. site; the highest increase per year in the 98th percentile, equal to 0.0126 was recorded at the rural Krupka site. Most sites (regardless of type) with generally increasing trends in the NO2/NOx ratio, are situated in the north-west portion of the Czech Republic The increasing NO2/NOx ratio detected at some sites is believed to implicate undesired changes in atmospheric chemistry, namely with respect to ambient O3 formation, promoting increasing O3 concentrations.

Assessment of air pollution origin based on year-long parallel measurement of PM2.5 and PM10 at two suburban sites in Prague, Czech Republic.

From 2nd April 2008 to 28th March 2009, a total 248 daily samples of the PM2.5 and PM10 were collected every sixth day parallel at two suburban sites (Libus and Suchdol) located at the two opposite sides (south and north, respectively) of Prague, Czech Republic. The PM2.5 samples were analyzed for ions by ion chromatography (IC), organic and elemental carbon (OC and EC) by OC/EC analyzer and PM10 samples also for 56 elements by inductively coupled plasma-mass spectrometry (ICP-MS). The average annual PM2.5 and PM10 was 24.4 ±â€¯13.0 µg m-3 and 26.7 ±â€¯15.1 µg m-3, respectively, in Prague-Libus, and 25.1 ±â€¯22.1 µg m-3 and 27.1 ±â€¯23.2 µg m-3, respectively, in Prague-Suchdol. Since the species forming large part of the aerosol mass were strongly correlated (Spearman's rank correlation coefficient rs > 0.80), the variability of PM2.5 and PM10 concentration was mainly driven by the local meteorology or regional and/or long range transport. PM10 mass closure was calculated based on analytical results with the average percentage of recalculated mass of 77 ±â€¯19% in Prague-Libus and 86 ±â€¯16% in Prague-Suchdol. The most abundant groups in PM10 at both sites during the four seasons were OM (Prague-Libus 34% and Prague-Suchdol 37%) and SIA (Prague-Libus 30% and Prague-Suchdol 34%). The Positive Matrix Factorization (PMF) was applied to the chemical composition of PM10 from both sites (124 samples) together to determine its sources. The nine factors were assigned as: mixed factor secondary sulphate and biomass burning, secondary sulphate, traffic, secondary nitrate, road dust, residential heating, aged sea salt, industry and mixed factor road salt along with aged sea salt. According to the polar plots and ventilation index (VI) east/west classification analysis the sources were separated based on origin to four categories local, urban agglomeration, regional and long range transport (LRT). The mixed source secondary sulphate and biomass burning, residential heating and industry were common sources of local origin at both sites. Prague-Suchdol was influenced by traffic related pollution from the urban agglomeration more than Prague-Libus where the traffic and road dust/salt were of local origin. The regional pollution by secondary sulphates and nitrate was also relevant at both sites along with long range transport of sea salt from North Atlantic Ocean, Norwegian Sea and North Sea. The contribution of the local sources to PM10 was significant mainly at Prague-Libus site. However, the sources of regional origin were also important and influence of urban agglomeration pollution to PM10 is not negligible as well.

Areas under high ozone and nitrogen loads are spatially disjunct in Czech forests.

It is widely accepted that excessive loads of nitrogen (N) deposition and ambient ozone (O3) endanger natural ecosystems and the environment. Despite substantial reductions in emissions since the early 1990s both in the Czech Republic and in neighbouring countries, neither O3 exposures nor N deposition have yet decreased to acceptable levels relative to the recommended thresholds. Based on long-term monitoring and high-quality data, we have indicated the areas of special risk due to high N deposition and O3 exposures in Czech forests in 2000-2015. The areas of potential risk denote those forests under the highest loads of N deposition and O3 exposure on a regular basis. The underlying classification approach is relativistic, i.e. based ultimately on quartiles of pollution intensities and not derived from critical limits or loads. The forest areas under the highest O3 exposures and N deposition are spatially disjunct. The highest O3 exposures are in the southern and the highest N deposition is in the northern Czech Republic. In contrast to our assumption, only 1322 km2, i.e. 4.6% of the total forested area (28,782 km2) are overlapping areas with a potential risk due both to high O3 exposures and to N deposition. Our results provide valuable input information for a more detailed environmental analysis, anticipated in the future, addressing to what extent the indicated areas at potential risk are associated with the actual negative impacts on forests.

Revisiting fog as an important constituent of the atmosphere.

We examined observation-based fog occurrence at three Czech monitoring sites: Praha 4 - Libus, Kosetice and Churánov, representing different environments - urban, rural and mountain - over a time span of 27 years (1989-2015). We searched for a simple model describing fog occurrence fitting the observed air pollution and meteorological data. For our analysis we used a generalized additive model, GAM, with (penalized) spline components to capture possible nonlinear and a priori unknown functional relationships. In order to cope with the binary nature of the data (indicators of fog presence on individual days), we employed a logistic regression GAM model fitted by a maximizing penalized likelihood (where the penalty coefficients were estimated via cross-validation). After testing several physically motivated models, being guided by AIC and physical interpretation of the components, we arrived at a model which uses the following explanatory variables: relative humidity, ambient SO2 concentrations, ambient NOx concentrations, air temperature and seasonality. All associations between the response and the analysed explanatory variables were highly significant. According to our results, the most important explanatory variables modelling the fog probability were relative humidity and air pollutants. Interestingly, we observed an increasing trend in fog occurrence at all three sites under review starting around the mid 2000s. CAPSULE: The most important explanatory variables modelling the fog probability at three Central European sites were humidity, SO2 and NOx. An increasing trend in fog occurrence has been observed since the mid 2000s.

Environmental factors exert strong control over the climate-growth relationships of Picea abies in Central Europe.

The growth response of trees to changing climate is frequently discussed as increasing temperatures and more severe droughts become major risks for forest ecosystems. However, the ability of trees to cope with the changing climate and the effects of other environmental factors on climate-growth relationships are still poorly understood. There is thus an increasing need to understand the ability of individual trees to cope with changing climate in various environments. To improve the current understanding, a large tree-ring network covering the whole area of the Czech Republic (in 7×7km grids) was utilized to investigate how the climate-growth relationships of Norway spruce are affected by 1) various geographical variables, 2) changing levels of acidic deposition, 3) soil characteristics and 4) age, tree diameter and neighbourhood competition. The period from 1930 to 2013 was divided into four, 21-year long intervals of differing levels of acidic deposition, which peaked in the 1972-1993 period. Our individual-based, spatiotemporal, multivariate analyses revealed that spruce growth was mostly affected by drought and warm summers. Drought plays the most important negative role at lower altitudes, while the positive effect of higher temperature was identified for trees at higher altitudes. Increased levels of acidic deposition, together with geographical variables, were identified as the most important factors affecting climate-growth association. Tree age, tree size and soil characteristics also significantly modulate climate-growth relationships. The importance of all environmental variables on climate-growth relationships was suppressed by acidic deposition during periods when this was at a high level; growth was significantly more enhanced by spring and summer temperatures during these periods. Our results suggest that spruce will undergo significant growth reduction under the predicted climate changes, especially at the lower altitudes which lie outside of its natural range.

Discerning environmental factors affecting current tree growth in Central Europe.

We examined the effect of individual environmental factors on the current spruce tree growth assessed from a repeated country-level statistical landscape (incl. forest) survey in the Czech Republic. An extensive set of variables related to tree size, competition, site characteristics including soil texture, chemistry, N deposition and climate was tested within a random-effect model to explain growth in the conditions of dominantly managed forest ecosystems. The current spruce basal area increment was assessed from two consecutive landscape surveys conducted in 2008/2009 and six years later in 2014/2015. Tree size, age and competition within forest stands were found to be the dominant explanatory variables, whereas the expression of site characteristics, environmental and climatic drives was weaker. The significant site variables affecting growth included soil C/N ratio and soil exchangeable acidity (pH KCl; positive response) reflecting soil chemistry, long-term N-deposition (averaged since 1975) in combination with soil texture (clay content) and Standardized Precipitation Index (SPI), a drought index expressing moisture conditions. Sensitivity of growth to N-deposition was positive, although weak. SPI was positively related to and significant in explaining tree growth when expressed for the growth season. Except SPI, no significant relation of growth was determined to altitude-related variables (temperature, growth season length). We identified the current spruce growth optimum at elevations about 800ma.s.l. or higher in the conditions of the country. This suggests that at lower elevations, limitation by a more pronounced water deficit dominates, whereas direct temperature limitation may concern the less frequent higher elevations. The mixed linear model of spruce tree growth explained 55 and 65% of the variability with fixed and random effects included, respectively, and provided new insights on the current spruce tree growth and factors affecting it within the environmental gradients of the country.

Towards a better spatial quantification of nitrogen deposition: A case study for Czech forests.

The quantification of atmospheric deposition flux is essential for assessment of its impact on ecosystems. We present an advanced approach for the estimation of the spatial pattern of atmospheric nitrogen deposition flux over the Czech forests, collating all available measured data and model results. The aim of the presented study is to provide an improved, more complete, more reliable and more realistic estimate of the spatial pattern of nitrogen deposition flux over one country. This has so far usually been based on measurements of ambient NOx concentrations as dry deposition proxy, and [Formula: see text] and [Formula: see text] in precipitation as wet deposition proxy. For estimation of unmeasured species contributing to dry deposition, we used the CAMx Eulerian photochemical dispersion model, coupled with the Aladin regional numeric weather prediction model. The contribution of fog and dissolved organic nitrogen was estimated using a geostatistical data driven model. We prepared individual maps for particular components applying the most relevant approach and then merged all layers to obtain a final map representing the best estimate of nitrogen deposition over the Czech Republic. Final maps accounting for unmeasured species clearly indicate that the approach used so far may result in a substantial underestimation of nitrogen deposition flux. Our results showed that nitrogen deposition over the Czech forested area in 2008 was well above 2 g N m(-2) yr(-1), with almost 70% of forested area receiving 3-4 g N m(-2) yr(-1). NH3 and gaseous HNO3, contributing about 80%, dominated the dry nitrogen deposition. Estimating the unmeasured nitrogen species by modeled values provides realistic approximations of total nitrogen deposition that also result in more realistic spatial patterns that could be used as input for further studies of likely nitrogen impacts on ecosystems.

Spatial and temporal trends of ozone distribution in the Jizerské hory Mountains of the Czech Republic.

We present results of the 5-year monitoring of ambient O3 concentrations in a Central European medium altitude mountain forested area. O3 levels were measured at 11 sites between 714 and 1000 m a.s.l. in 2006-2010 vegetation seasons using Ogawa diffusive samplers. Our results reveal that O3 exposure in the Jizerské hory Mts. was relatively high and comparable with polluted sites in Southern Europe and in higher altitudes. O3 concentrations differed significantly between individual sites and in individual years. O3 concentrations showed clear dependence on altitude at sites with similar aspect. Its gradient for the entire 5-year period under review equaled 3.5 ppb/100 m of altitude, ranging between nearly 5 ppb/100 m of altitude in 2006 and nearly 3 ppb/100 m of altitude in 2010. O3 concentrations at the site with northern aspect were consistently significantly lower than at the site at similar altitude with southern aspect. O3 concentrations measured at the forest edge were consistently lower than those measured at the same site but at the forest clearing. It is evident that the macro-setting of the O3 monitoring site is crucial for obtaining reliable results with high representativeness for the area.

Stomatal ozone flux and visible leaf injury in native juvenile trees of Fagus sylvatica L.: a field study from the Jizerske hory Mts., the Czech Republic.

The study was carried out at six sites in the Jizerskehory Mts. in the north of the Czech Republic. At all these sites, ranging in altitude between 460 and 962 m a. s. l., and during the period from June to September in 2008, O3 concentrations and environmental parameters important for accumulated stomatal O3 flux (AFst) into Fagus sylvatica leaves were measured. At five sites, visible injury on Fagus sylvatica L. juvenile tree leaves was observed. A combination of actual O3 levels in the Jizerkehory Mts. and environmental conditions, though relative air humidity and air temperature significantly limited stomatal conductance, has been sufficient enough to cause O3 uptake exceeding the critical level (CL) for forest ecosystems. The AFst values ranged between 13.4 and 22.3 mmol O3 m(-2). The CL for the accumulated stomatal flux of O3 above a flux threshold 1.6 nmol m(-2) s(-1) (AFst1.6) was exceeded at all sites from ca 45 to 270% (160% on average). The CL of 5 ppm h(-1) for AOT40 (accumulated O3 exposure above threshold of 40 ppb) was exceeded at four sites. The relationship between visible injury on O3 indices was found. The conclusions based on AOT40 and AFSt are not the same. AFSt has been determined as better predictor of visible injury than AOT40.

Trends in atmospheric deposition fluxes of sulphur and nitrogen in Czech forests.

We present the temporal trends and spatial changes of deposition of sulphur and nitrogen in Czech forests based on records from long-term monitoring. A statistically significant trend for sulphur was detected at most of the sites measuring for wet, dry, and total deposition fluxes and at many of these the trend was also present for the period after 2000. The spatial pattern of the changes in sulphur deposition flux between 1995 and 2011 shows the decrease over the entire forested area in a wide range of 18.1-0.2 g m(-2) year(-1) with the most pronounced improvement in formerly most impacted regions. Nitrogen still represents a considerable stress in many areas. The value of nitrogen deposition flux of 1 g m(-2) year(-1) is exceeded over a significant portion of the country. On an equivalent basis, the ion ratios of NO3(-)/SO4(2-) and NH4(+)/SO4(2-) in precipitation show significantly increasing trends in time similarly to those of pH.

Association between ambient ozone and health outcomes in Prague.

PURPOSE: Though numerous studies investigating ambient ozone (O(3)) effects on human health were published, such a study for Central Europe is still lacking. We have investigated the association between ozone (O(3)) levels and hospital admissions and mortality due to cardiovascular and respiratory diseases for Prague inhabitants for summer months (April-September) over the 5-year period 2002-2006. Our hypothesis was that ambient O(3) levels in Prague resulted in adverse health outcomes and were associated with increased mortality and hospital admissions. METHODS: The effect of O(3) on mortality and hospital admissions was investigated using the negative binomial regression after controlling for the influence of meteorological factors (air temperature and relative humidity) and calendar effects (seasonal patterns, long-term trends and day of week). RESULTS: We found a statistically significant association between O(3) levels and daily mortality from respiratory diseases. Relative risk of 1.080 (95% CI: 1.031-1.132) was observed for mortality from respiratory diseases per 10 µg m(-3) increase in 1-day lagged daily mean O(3) concentration. No statistically significant association was detected between O(3) concentrations and daily mortality from all causes, daily mortality from cardiovascular diseases and hospital admissions for respiratory and cardiovascular diseases. The O(3) effects differed in men and women, nevertheless, the results were ambiguous with respect to used lag and O(3) metrics. No significant confounding effects of PM(10) on the investigated association were observed. CONCLUSIONS: O(3) exposure in Prague, though lower as compared to many other cities in Europe, is high enough to cause adverse health effects.

The influence of climate change on stomatal ozone flux to a mountain Norway spruce forest.

Daily stomatal ozone flux to a mountain Norway spruce forest stand at the Bily Kriz experimental site in the Beskydy Mts. (Czech Republic) was modelled using a multiplicative model during the 2009 growing season. The multiplicative model was run with meteorological data for the growing season 2009 and ALADIN-CLIMATE/CZ model data for the 2030 growing season. The exceedance of the flux-based critical level of O(3) (Phytotoxic Ozone Dose) might be lower for Norway spruce at the Bily Kriz experimental site in a future climate (around 2030), due to increased stomatal closure induced by climate change, even when taking into account increased tropospheric background O(3) concentration. In contrast, exceedance of the concentration-based critical level (AOT40) of O(3) will increase with the projected increase in background O(3) concentration. Ozone concentration and stomatal flux of ozone significantly decreased NEP under both present and future climatic conditions, especially under high intensities of solar radiation.