Effects of Site Selection Strategy on Freshwater Critical Load Exceedances in Wales

Critical loads are used in international negotiations to reduce acid deposition resulting from emissions of sulphur and nitrogen compounds within Europe. For freshwater ecosystems, the First-order Acidity Balance (FAB) model is used to generate national maps of critical loads and exceedances for both sulphur (S) and nitrogen (N). In Wales, two survey datasets have been used to calculate critical loads and exceedances; one based on water bodies selected to be "most-sensitive" to acidification within a 10 km grid and the other based on a random selection of standing waters. Both datasets indicate that critical loads were exceeded in 1990 in a significant proportion of Welsh lakes and streams; 36% of sites in the grid-based survey and 31% of sites in the random survey. However, implementation of the Gothenburg Protocol would protect all but 6% of sites in the grid-based survey and all sites in the random survey. Assessment of the relative success of the Gothenburg Protocol in protecting Welsh freshwater ecosystems therefore depends on the site selection strategy employed.     

Effects of Environmental Stress on Forest Crown Condition in Europe. Part III: Estimation of Critical Deposition and Concentration Levels and Their Exceedances

The stress by air pollution at the systematicPan-European 16 × 16 km² forest (crown) condition monitoring network, is discussed by comparingsite-specific estimates of critical and presentconcentration and deposition levels for S and Ncompounds and ozone. Results indicate that theexceedance of critical levels, related to directabove-ground impacts, decrease going from O₃ >SO₂ > N compounds. Critical N loads related toeffects on the forest understorey are exceeded atapproximately 25% of the plots, located mainly inWestern and Central Europe. Critical N loads relatedto effects on trees are hardly ever exceeded, but mostlikely, this is an under estimate. Critical aciddeposition levels are exceeded at approximately 30%of the plots with a low base saturation, where acidinputs may release toxic Al. This is especially thecase in Central and Eastern Europe, where presentloads are high and in boreal forest in SouthernScandinavia where critical loads are low. Although theuncertainties in the calculated exceedances is large,the spatial pattern, which is most important for acorrelative study, seems reliable, implying that thecritical load concept is suitable for regional risk assessments.     

Determination and Mapping Critical Loads of Acidity and Exceedances for Upland Forest Soils in Eastern Canada

Critical loads of acidity were estimated for upland forests in Eastern Canada using the steady-state Simple Mass Balance (SMB) Model. A consistent methodology was applied to the entire region, although critical loads were estimated separately for the Atlantic provinces (New Brunswick, Nova Scotia, Prince Edward Island and Newfoundland), Quebec and Ontario using different data sources. In this project, critical load estimates and steady-state exceedance values did not include the effect of forest fire and forest harvesting, which could have a considerable impact on critical loads in Eastern Canada. The observed soil pH – base saturation relationship for forest soils indicated that the constants used into the calculation of alkalinity leaching should be set to 10 (M/M) for the molar Bc/Al ratio in soil leachate and 10⁹ (mol L^?1)² for the gibbsite dissolution constant. The area-weighted median critical load for each province varied between 519 (Quebec) and 2063 eq ha^?1 y^?1 (Prince Edward Island), with a median critical load value for Eastern Canada of 559 eq ha^?1 y^?1. It is estimated that approximately 52% of the mapped area is exceeded in terms of acidity according to the 1994–1998 average total (wet + dry) atmospheric deposition. Greatest exceedances occurred in Ontario and Quebec and in the south of Nova Scotia, due to low critical loads and high loads of acid deposition.     

Acid Deposition and Critical Load Map of Tokyo

Acid deposition has been monitored in the natural vegetation of the western part of Tokyo, especially in the Okutama Mountains and surrounding areas. However, it is difficult to grasp the condition of acid deposition and the possible impacts on the vegetation in the whole area. Therefore, we attempted to make gridded acidic deposition maps and critical load maps. The grid size was 30 seconds latitude and 45 seconds longitude. Monthly wet deposition in the fiscal year of 1997 was calculated by multiplying concentration of wet deposition and precipitation. Concentration of wet deposition was estimated by averaging the data monitored at the nearest three stations with the inverse of distance as the weight. Precipitation was estimated by step-wise multiple regression with geographical factors as explanatory variables. Critical loads were estimated using the steady-state mass balance model with some modifications. As result, it was found that sulfur deposition had exceeded in most of the western part of Tokyo.     

Multi-Effect Critical Loads Used in Multi-Pollutant Reduction Agreements in Europe

The scientific support of negotiations on emission reductions under the framework of the Convention on Long-range Transboundary Air Pollution of the UN Economic Commission for Europe has been based during the last decade on the integrated assessment of sources, including abatement costs, and risks to receptors (e.g. forests, lakes) quantified by critical loads. The shift from a single-pollutant (sulfur) protocol in 1994 to a multi-pollutant protocol in 1999 necessitated an extension of the methods by which critical loads were computed and mapped. Instead of a single critical load for acidification, methods were now developed to assess the risk of acidifying effects of both sulfur and nitrogen deposition as well as the eutrophying effects of nitrogen on sensitive elements of the environment. Collaboration with a scientific network of 24 national institutions ensured a successful implementation of the proposed methodology across countries. This paper summarizes the methodology, describes the latest input data and presents critical load maps on the basis of which about 98% and 78% of European ecosystems would be protected against acidification and eutrophication, respectively, by the year 2010 according to the multi-pollutant multi-effect protocol.     

Critical limits of acidification to invertebrates in different regions of Europe

The International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes (ICP-Water) started in 1987. The main aim of the programme is to establish degree and geographical extent of acidification of surface waters and evaluate dose/response relationships to aquatic biota attributable to acidic deposition. The sample frequency in each locality is from a few — to a large number every year. Samples of invertebrates are taken from 108 localities. One time samples as well as regularly seasonal samples over years exist in the database. The acidity score (Raddum index) is determined for the different sites and regions, and compared with the corresponding chemical data. The analysis show a strong relationship between water quality and fauna. Sensitive species/taxa are associated with high ANC and pH, while tolerant species/taxa are associated with low pH and ANC. The diversity of the fauna in less acidified areas varies from region to region depending on the native water quality and the adaptions of the fauna. In areas with strongly oligotrophic water, low in ionic strength, the sensitive fauna tolerate lower ANC and pH than in areas with originally high ionic strength and high pH. The critical load of ANC, 20 μeq/1, developed for the oligotrophic water in Norway, should therefore be increased in watersheds with high ionic strength. In Central Europe the data indicate a critical level of ANC ≈50 μeq/1.     

Latent Process Modelling of Threshold Exceedances in Hourly Rainfall Series

Two features are often observed in analyses of both daily and hourly rainfall series. One is the tendency for the strength of temporal dependence to decrease when looking at the series above increasing thresholds. The other is the empirical evidence for rainfall extremes to approach independence at high enough levels. To account for these features, Bortot and Gaetan (Scand J Stat 41:606–621, 2014) focus on rainfall exceedances above a fixed high threshold and model their dynamics through a hierarchical approach that allows for changes in the temporal dependence properties when moving further into the right tail. It is found that this modelling procedure performs generally well in analyses of daily rainfalls, but has some inherent theoretical limitations that affect its goodness of fit in the context of hourly data. In order to overcome this drawback, we develop here a modification of the Bortot and Gaetan model derived from a copula-type technique. Application of both model versions to rainfall series recorded in Camborne, England, shows that they provide similar results when studying daily data, but in the analysis of hourly data the modified version is superior.     

Estimation of the Maximum Critical Load for Sulfur in South Korea

The maximum critical load of sulfur and its exceedance by the sulfur deposition of 1994–1997 were mapped for South Korea with a spatial resolution of 11 × 14 km using the steady-state mass balance method. The Korean soil and geological maps were used as basis for the estimations of the critical alkalinity leaching and the weathering rate of base cations. The normalized difference vegetation index data obtained from the Advanced Very High Resolution Radiometer (AVHRR) together with the observed primary productivity of plants were used for the estimation of the critical uptake of base cations. Wet deposition of the non-sea-salt base cations was derived from measured base cation concentrations in precipitation, precipitation rate and air concentration of total suspended particulate while dry deposition of base cations was estimated using the inferential technique using scavenging ratios. The predominant ranges of base cation weathering, uptake and deposition were estimated to be of 200 – 600 eq ha^?1 yr^?1, 200 – 400 eq ha^?1 yr^?1 and 400 – 600 eq ha^?1 yr^?1, respectively. Critical alkalinity leaching was mainly in the range of 1000 – 2000 eq ha^?1 yr^?1 due to relatively high value of precipitation runoff. Exceedance of sulfur critical load was found at 40 % of the ecosystems considered mainly in the southeastern part of Korea, and about 60 % of Korea ecosystems were sustainable against sulfur acidity loadings.     

Critical Limit of Acidifying Compounds to Invertebrates in Different Regions of Europe

The International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes (ICP Waters) was established in July 1985 under the Executive Body of the Convention on Long-Range Transboundary Air Pollution (LRTAP). The main aim of the Programme is to assess, on a regional basis, the degree and geographical extent of acidification of surface waters. Dose/response relationship of acid deposition to aquatic invertebrates is discussed for different regions of Europe. The bases for the study are the occurrence of the most sensitive species in their geographical areas. Critical limit will vary depending on definition of acceptable damage level. To minimise this discussion we have used the presence of the most sensitive species for defining the critical limit. The study shows that critical limit of acid neutralisation capacity (ANC) vary depending on the typical fauna of sensitive species and their adaptations to the native water chemistry. In areas with different composition of sensitive species, different critical limit is suggested, varying from ANC < 20 µeq/L to ANC >50 µeq/L.     

Effects of Data Uncertainty in the Swedish Critical Load Assessment for Forest Soils

The effects of input data uncertainty on the critical loads andexceedance estimates for Swedish forest soils was assessed usingMonte Carlo simulations of the PROFILE model. The study focuseson the effects of data uncertainty on the 5%-ile critical loadat 150 × 150 km resolution and the 95%-ile exceedance at150 × 150 km and 50 × 50 km resolution.The results indicate that datauncertainty limits the possibility to differentiate grid cellson 150 × 150 km resolution. The confidence interval for agiven percentile can generally be reduced if the uncertaintiesin calculated critical loads are addressed simultaneously forall sites in a grid cell. The resulting best estimates of the5%-ile critical load were found to be lowered, therebyadvocating larger deposition reductions to comply with a givengap closure of exceedance. The results further indicate that thenumber of sites within the grid cells is important for the rangeof the confidence interval for a given percentile.Re-aggregation of exceedance estimate in 50 × 50 km gridcells showed that differentiation may be improved as compared to150 × 150 km resolution. For 70% of the grid cells on 50× 50 km resolution, the confidence interval forcalculated exceedance covers both negative and positive values.     

Identifying Potentials for Reducing Uncertainty in Critical Load Calculations using the PROFILE Model

A sensitivity analysis was performed testingweathering rates, critical loads andexceedances for Swedish forest soils using Monte Carlosimulations of the PROFILE model. Different subsetsof input data were investigated with respect to theirpotential to reduce data uncertainty at site level butalso for modified estimates of the 5%-ile critical load andthe 95%-ile exceedance on 150×150 kmresolution. Physical soil properties were of dominantimportance for all sites and yield up to 62%reduction of the output standard deviation in weathering rate.The study showed that the critical ratio ofbase cations to inorganic aluminium (Bc/Al ratio) in the soilsolution was of major importance for reducingdata uncertainty in critical loads and exceedance estimates.The critical Bc/Al ratio was found to beimportant for reducing data uncertainties in modifiedestimates of the 5%-ile critical load and the95%-ile exceedance, in particular in the northern part ofSweden. Atmospheric deposition, uptake andlitterfall were more important for reducing data uncertaintyin the southern part. Physical soil propertiesand especially mineral content were found to be less importantfor reducing data uncertainties in criticalloads and exceedance estimates. The greatest scope forreducing data uncertainties in an applied perspectiveis to improve estimates of atmospheric deposition of anionsand cations as well as uptake and litterfall ofbase cations and nitrogen.     

Are Indicators for Critical Load Exceedance Related to Forest Condition?

The aim of this study was to evaluate the suitability of the (Ca?+?Mg?+?K)/Al and the Ca/Al ratios in soil solution as chemical criteria for forest condition in critical load calculations for forest ecosystems. The tree species Norway spruce, Sitka spruce and beech were studied in an area with high deposition of sea salt and nitrogen in the south-western part of Jutland, Denmark. Throughfall and soil water were collected monthly and analysed for pH, NO₃-N, NH₄-N, K, Ca, Mg, DOC and Al_tot. Organic Al was estimated using DOC concentrations. Increment and defoliation were determined annually, and foliar element concentrations were determined every other year. The throughfall deposition was highest in the Sitka spruce stand (maximum of 40 kg N ha^?1yr^?1) and lowest in the beech stand (maximum of 11 kg N ha^?1yr^?1). The Sitka spruce stand leached on average 12 kg N ha^?1yr^?1 during the period 1988–1997 and leaching increased throughout the period. Only small amounts of N were leached from the Norway spruce stand whereas almost no N was leached from the beech stand. For all tree species, both (Ca?+?Mg?+?K)/Al and Ca/Al ratios decreased in soil solution at 90 cm depth between 1989 and 1999, which was mainly caused by a decrease in concentrations of base cations. The toxic inorganic Al species were by far the most abundant Al species at 90 cm depth. At the end of the measurement period, the (Ca?+?Mg?+?K)/Al ratio was approximately 1 for all species while the Ca/Al ratio was approximately 0.2. The lack of a trend in the increment rates, a decrease in defoliation as well as sufficient levels of Mg and Ca in foliage suggested an unchanged or even slightly improved health condition, despite the decreasing and very low (Ca?+?Mg?+?K)/Al and Ca/Al ratios. The suitability of these soil solution element ratios is questioned as the chemical criteria for soil acidification under field conditions in areas with elevated deposition rates of sea salts, in particular Mg.     

Point Pattern Analysis of Spatial Deformation and Blurring Effects on Exceedances

Structural characteristics of random field threshold exceedance sets (e.g., size, connectivity, and boundary regularity) are used in practice for definition of different indicators in spatial and spatio-temporal risk analysis. In this work, point process techniques are applied to study the structural changes derived from random field deformations and blurring transformations, meaningful from both physical and methodological points of view in a variety of contexts. Specifically, based on simulations from a flexible random field model class, features such as aggregation/inhibition of patterns defined by centroids of connected components, as well as by boundary A-exit points, are investigated in relation to the local contraction/dilation effects of deformation and the smoothing properties of blurring. Supplementary materials accompanying this paper appear online.     

Critical Loads of Sulphur and Nitrogen for Terrestrial Ecosystems in Europe and Northern Asia Using Different Soil Chemical Criteria

A critical load data base was developed for Europe and Northern Asia using the latest data bases on soils, vegetation, climate and forest growth. Critical loads for acidity and nutrient nitrogen for terrestrial ecosystems were computed with the Simple Mass Balance model. The resulting critical loads are in accordance with critical loads from previous global empirical studies, but have a much higher spatial resolution. Critical loads of acidity are sensitive to both the chemical criterion and the critical limit chosen. Therefore a sensitivity analysis of critical loads was performed by employing different chemical criteria. A critical limit based on an acid neutralizing capacity (ANC) of zero resulted in critical loads that protect ecosystems against toxic concentrations of aluminium and unfavourable Al/Bc ratios, suggesting that ANC could be an alternative to the commonly used Al/Bc ratio. Critical loads of nutrient nitrogen are sensitive to the specified critical nitrate concentration, especially in areas with a high precipitation surplus. If limits of 3–6 mg N l^?1 are used for Western Europe instead of the widely used 0.2 mg N l^?1, critical loads double on average. In low precipitation areas, the increase is less than 50%. The strong dependence on precipitation surplus is a consequence of the simple modelling approach. Future models should explore other nitrogen parameters (such as nitrogen availability) instead of leaching as the factor influencing vegetation changes in terrestrial ecosystems.     

Characterization of organic matter fractions in the top layer of soils under different land uses in Central‐Eastern Europe

The objective of this study was to investigate differences in organic matter fractions, such as dissolved organic carbon and humic substances, in soils under different land uses. Soil samples were collected from the upper layer of arable lands and grasslands. Humic substances (HS) were chemically fractionated into fulvic acids (FA), humic acids (HA) and humins (HUM), and based on the separated fractions, the humification index (HI) and the degree of HS transformation (DT) were calculated. Dissolved organic carbon (DOC) was determined by cold (CWE) and hot water (HWE) extractions. Regardless of land use, the results indicated significant differences in soil organic carbon (SOC) and HS composition, with HA and HUM as the dominant fractions. Total SOC was higher in grassland (median = 17.51 g kg^?1) than arable soils (median = 9.98 g kg^?1); the HI and DT indices did not differ significantly between land uses (HI = 0.3–10.3 and DT = 0.2–6.2 for grasslands, p > 0.05; HI = 0.3–3.9 and DT = 0.2–20.1 for arable lands, p > 0.05). This indicates the relatively high stability of organic carbon and efficient humification processes in both land uses. Additionally, in arable soils lower CWE‐C (0.75 g kg^?1) and higher HWE‐C (2.59 g kg^?1) than in grasslands (CWE‐C = 1.13 g kg^?1, HWE‐C = 1.60 g kg^?1) can be related to farming practice and application of soil amendments. The results showed that both labile and humified organic matter are better protected in grassland soils and are consequently less vulnerable to mineralization.     

Conservation Agriculture in Europe

The adoption of Conservation Agriculture (CA) in Europe varies according to the ecological regions of the continent. Although Europe is behind other countries in adoption of CA, the indicators for future progress are encouraging. The area where CA is applied is growing rapidly because of increasing environmental awareness, including soil protection, and because of the need to reduce production costs. The European Conservation Agriculture Federation (ECAF) plays an important role in the adoption and dissemination of CA practices, and in discussions involving CA and the EU Common Agricultural Policy (CAP) reform.Yield performance and stability, operating costs, environmental policies and programs of the Common Agricultural Policy (CAP), and climate change will likely be the major driving forces defining the direction and for the extension of CA in Europe. The role of agriculture in climate change mitigation in the EU is discussed in the paper.     

Ozone measurements in Europe

Ozone measurements have been apart of EMEP since its third phase in 1984–1986 and since 1988 data have been collected systematically. By 1992 data for 76 sites were being collected by the Chemical Co-ordinating Centre in NILU. The mean ozone concentration increases from 20–25ppb in the western and northern fringes to 30–35 in central areas of Europe. There is also evidence from the last decade of an upward trend of up to 0.5ppb y^?1 at rural sites in the UK. The data have been analysed to estimate the spatial patterns in AOT 40 for ozone effects on crops and forests. The data show that the critical level for cereal crops of 5300 ppb.h above a threshold of 40 ppb is exceeded over almost all of continental Europe south of 65°N and over most of S.Britain. A similar exercise for the AOT 40 for the forest again shows exceedances of the critical load of 10⁴ ppb.h across all the mapped area of Continental Europe south of 65°N including S.Britian. As land use for forestry and ozone dose both increase with altitude, and these effects have not so far been incorporated in the AOT 40 assessment for forests, the degree of exceedence for forests may have been significantly under-estimated.     

A Critical Evaluation of Sample Pretreatment for Storage of Contaminated Sediments to be Investigated for the Potential Mobility of their Heavy Metal Load

The identification of the geochemical forms of heavy metals in contaminated sediments gives information on their availability. This requires the use of a geochemical speciation procedure such as the one developed by Tessier et al. (1979). In addition to the imperfections of these protocols, their results can vary depending on the technique used for the preservation of sediments which must be suited to the materials studied and to particularities of the investigation. This study was carried out on superficial river sediments, seriously polluted by Cu, Cd and Pb. Compared to fresh sediment, none of the drying methods studied (freeze-drying, air-drying and oven-drying at 105 °C) completely preserve the distribution of Cu, Pb, Zn and Cd in the various geochemical fractions of the sediment. The modifications depend directly on the quantities of metals present in the various fractions of the sediment, the effects being more marked when the quantity is smallest. This results in a decrease in metals in the exchangeable fraction and in those bound to carbonates under the action of atmospheric oxygen and a corresponding increase in the other fractions. To minimize this, freeze-drying and air-drying are satisfactory techniques which enable preservation of sediments representative of the environment.     

Testing the Feasibility of Using the ForSAFE-VEG Model to Map the Critical Load of Nitrogen to Protect Plant Biodiversity in the Rocky Mountains Region, USA

The ForSAFE-VEG model was used to estimate atmospheric nitrogen deposition and climate effects on soil chemistry and ground vegetation in alpine and subalpine zones of the northern and central Rocky Mountains region in the USA from 1750 to 2500. Model simulations for a generalized site illustrated how the critical load of atmospheric nitrogen deposition could be estimated to protect plant biodiversity. The results appear reasonable compared with past model applications in northern Europe. Atmospheric N deposition critical loads estimated to protect plant biodiversity were 1 to 2 kg N/ha/year. This range could be greater, depending on the values selected for critical site-specific parameters (precipitation, temperature, soil chemistry, plant nutrient uptake, and any eventual harvest of biomass) and the amount of biodiversity change allowed.