Trends in Sulphur and Nitrogen Deposition Fluxes in the GEOMON Network, Czech Republic, between 1994 and 2000

Deposition fluxes of sulphur and nitrogen in bulk and throughfall precipitation were monitored for the 1994–2000 period for seven small forest catchments in the GEOMON network, Czech Republic (CR). Four catchments are situated at similar elevations (roughly between 800 and 1000 m) and represent three areas: the Black Triangle near the Kru?né hory Mts. coalfield (catchments JEZ and LYS), the Orlické hory Mts., close to the Polish industrial regions (UDL), and the ?umava Mts., a relatively unpolluted area (LIZ). Three catments (GEM, POM, LES) lie at lower elevations (400–600 m) in Central Bohemia. A substantial decrease in the bulk and throughfall deposition of pollutants occurred as a result of the desulphurisation programme implemented in the Czech Republic between 1996 and 1998. A reduction has been described mainly in the Kru?né hory Mts. (JEZ), in Slavkovský les (LYS) and also in Central Bohemia (GEM). The decrease in the throughfall to less than one half within a single year in POM (Central Bohemia) was an example of a direct response to the local emission reduction in the nearby Chvaletice power plant. However, in some areas, the throughfall deposition of sulphur, which includes wet and dry deposition, is still significant, especially at higher elevations. Recent forest degradation was observed in the Orlické hory Mts., where, particularly in 1998, as much as 91.1 kg S was found in coniferous throughfall. The fraction of dry deposition in the coniferous forests of CR represents 30–70% of the total deposition. The difference between coniferous (higher) and deciduous (lower) throughfall fluxes is significant because of the larger surface area of conifers and year-round exposure to air-borne sulphur. At several of the GEOMON sites, the flux of nitrogen via throughfall increased during the observation period and, at the end of the studied period (2000), nitrogen became the main source of acidification, replacing sulphur compounds. The highest fluxes (81.7 kg N ha^-1 yr^-1)were measured in 2000 in the Orlické hory Mts., which provide an example of multiple causes of forest decline – the direct impact of air pollution, abundance of nitrogen, acidification and secondary stressors (weather changes, insect pests, fungal infections). A comparison is given with data from other countries.     

Synthesis of Nitrogen Pools and Fluxes from European Forest Ecosystems

To investigate which ecosystem parameters determine the risk and magnitude of nitrate leaching we compiled data from published and unpublished sources on dissolved inorganic nitrogen (DIN: NO₃ ^-) in throughfall, DIN leaching loss in runoff or seepage water, and other ecosystem characteristics from 139 European forests. Not all data were available for all sites: 126 sites had at least one year's data on DIN inputs and DIN leaching loss; 40-50 sites had some data on soil chemistry and/or vegetation pools of N. DIN inputs in throughfall range between <1 and about 70 kg N ha-1 yr-1 and the losses with seepage or runoff range between <1 and 50 kg N ha-1 yr-1. Retention of N within the ecosystem increases with increasing DIN deposition and increasing proportion of NH₄ ⁺ in deposition. The amount of N in needles and litterfall shows a significant linear relationship with throughfall deposition of DIN, whereas the C:N ratio of the organic (OH) horizon is uncorrelated to the level of throughfall-DIN flux. About 50% of the variability in DIN leaching loss can be explained by the flux of DIN in throughfall. Alternatively, about 60% of the variability in DIN leaching loss can be explained in a two-variable multiple regression combining the C:N ratio of the organic soil and the pH of the mineral soil. The survey data suggest that leaching of DIN from forest ecosystems in Europe is related in part to current DIN deposition and in part to the longer-term internal ecosystem N status as reflected in the chemistry of the humus and acidification status of the soil.     

Spatial variation in nitrogen deposition over five adjacent catchments in a larch forest

Abstract

In this report, we propose a new method of evaluating the effect of nitrogen deposition on forest ecosystems, namely the spatial variation in nitrogen deposition enables to detect readily the effect of anthropogenic N deposition on biogeochemical processes in forest ecosystems. We analyzed the nitrogen deposition (throughfall fluxes) and stream water chemistry over five adjacent small catchments in which soil types (Hapludants) and vegetation composition (50 to 60 years old larch plantation) were fairly identical. Thirty-two throughfall collectors were set up in the five catchments (six to eight collectors in each catchment) and throughfall samples were collected after a rain event, while stream water samples were collected once or twice a month. The monitoring was carried out during a period of 6 months (2002 June to 2002 November). Throughfall dissolved inorganic nitrogen (DIN) fluxes were highly variable: the highest N input, 1.32 kg N ha^?1 6 months^?1, was sixty-six times higher than the lowest input, 0.02 kg N ha^?1 6 months^?1. The mean DIN inputs and the mean nitrate concentrations in streams showed a three-time variation across the five catchments. In addition, the DIN inputs showed a high correlation with the stream nitrate concentrations (r = 0.88).     

Beryllium Chemistry in the Lysina Catchment,Czech Republic

The environmental chemistry of beryllium (Be) was investigated at the Lysina catchment in western Bohemia, Czech Republic, a forest ecosystem with high loadings of acidic atmospheric deposition. The catchment supports Norway spruce plantations; it is underlain by leucogranite and the soils are Spodosols. Average concentrations of Be were high in groundwater (3.3 µg L-1) and in stream water (1.5 µg L-1), in comparison to the drinking water standard of the Czech Republic (0.2 µg L-1). Chemical equilibrium calculations suggest that aquoberyllium Be2+ was the prevailing inorganic species in drainage waters at the site. Atmospheric deposition of Be (45 µg m-2 yr-1) was small in comparison to drainage outflow (586 µg m-2 yr-1) at Lysina. Elevated Be concentrations in drainage water appear to be the result of the mobilization of Be from soils and weathered bedrock due to acidic atmospheric deposition. Increased mobility of Be due to acidification may have serious ecological consequences in acid-sensitive areas with terrestrial pools of available Be.     

Ion mass budgets for small forested catchments in Finland

Ion mass and H⁺ budgets were calculated for three pristine forested catchments using bulk deposition, throughfall and runoff data. The catchments have different soil and forest type characteristics. A forest canopy filtering factor for each catchment was estimated for base cations, H⁺, Cl^? and SO ₄ ^2? by taking into account the specific filtering abilities of different stands based on the throughfall quality and the distribution of forest types. Output fluxes from the catchments were calculated from the quality and quantity of the runoff water. Deposition, weathering, ion exchange, retention and biological accumulation processes were taken into account to calculate catchment H⁺ budgets, and the ratio between external (anthropogenic) and internal H⁺ sources. In general, output exceeded input for Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO ₃ ^? (if present) and A^? (organic anions), whereas retention was observed in the case of H⁺, NH ₄ ⁺ , NO ₃ ^? and SO ₄ ^2? . The range in the annual input of H⁺ was 22.8–26.3 meq m^?2 yr^?1, and in the annual output, 0.3–3.9 meq m^?2 yr^?1. Compared with some forested sites located in high acid deposition areas in southern Scandinavia, Scotland and Canada, the catchments receive rather moderate loads of acidic deposition. The consumption of H⁺ was dominated by base cation exchange plus weathering reactions (41–79 %), and by the retention of SO ₄ ^2? (17–49 %). The maximum net retention of SO ₄ ^2? was 87% in the HietajÄrvi 2 catchment, having the highest proportion of peatlands. Nitrogen transformations played a rather minor role in the H⁺ budgets. The ratio between external and internal H⁺ sources (excluding net base cation uptake by forests) varied between 0.74 and 2.62, depending on catchment characteristics and acidic deposition loads. The impact of the acidic deposition was most evident for the southern Valkeakotinen catchment, where the anthropogenic acidification has been documented also by palaeolimnological methods.     

Water chemistry in forested catchments after topsoil treatment with liming agents in South Sweden

Critical loads of sulphur and nitrogen are exceeded in South Sweden, and nutritional imbalances are expected to appear with time in forests. During 1984 paired catchments were established in a northwestern-southeastern gradient in South Sweden. The aim was to study long-term liming effects on throughfall, soil water, groundwater and runoff. Dolomitic limestone and wood ash were tested at one locality, Hagfors (59° N). Three adjacent catchments were used; one reference area, one treated with dolomitic lime (0.5 kg/m²) in 1985, and one with wood fly ash (0.22 kg/m²) in 1988. The lime and the fly ash was granulated and applied by a helicopter in the end of May. Measurements concerning chemistry of the precipitation, throughfall, soil water and runoff has been conducted since spring 1984. The results showed that top-soil spreading of liming agents, besides the desired effects on soil chemistry, after some years also affected the quality of the recipient water. In the dolomitic lime treated catchment the positive effects were most obvious, with raised pH-, Ca-, and Mg-values and lowered Al-, Fe- and Mn-values. A positive trend regarding lower nitrogen (NO₃ ^?) leaching could also be calculated. Wood ash in the used amount affected only slowly, but after six years the runoff water indicated increased pH-values as well as increased Ca- and K-values and Ca/Al-ratios. Dolomitic lime in the amounts of 0.5 kg/m² was concluded to be sufficient to achieve positive effects in catchments of the present type. Wood ash in the amount of 0.22 kg/m² although enough for recycling purposes, was not sufficient enough in increasing pH in runoff to prevent acid leaching from the forest soils.     

中国南方典型地区阔叶林大气氮沉降通量研究

A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen （N） fluxes of typical N compounds （NH3, NH4-N, NO3-N, and NO2） and contribution of three sources （gas, rainwater, and particles） to N deposition. From July 2003 to June 2004, the total atmospheric N deposition was 70.7 kg N ha^-1, with dry deposition accounting for 75% of the total deposition. Dry NH3 deposition accounted for 73% of the dry deposition and 55% of the total deposition. Moreover, NO2 contributed 11% of the dry deposition and 8% of the total deposition. Reduced N compounds （NH4^＋ and NH3） were the predominate contributors, accounting for 66% of the total deposition. Therefore, atmospheric N deposition should be considered when soil acidification and critical loads of atmospheric deposition on soils are estimated.     

Elevational trends in the fluxes of sulphur and nitrogen in throughfall in the Southern Appalachian Mountains: Some surprising results

From 1986–1989, a team of scientists measured atmospheric concentrations and fluxes in precipitation and throughfall, and modeled dry and cloudwater deposition in a spruce-fir forest of the Great Smoky Mountains National Park which is located in the Southern Appalachian Region of the United States. The work was part of the Integrated Forest Study (IFS) conducted at 12 forests in N. America and Europe. The spruce-fir forest at 1740 m consistently received the highest total deposition rates (～2200, 1200, and 700 eq ha^?1 yr^?1 for SO₄ ^2?, NO₃ ^?, and NH₄ ⁺). During the summers of 1989 and 1990 we used multiple samplers to measure hydrologie, SO₄ ^2?, and NO₃ ^? fluxes in rain and throughfall events beneath spruce forests above (1940 m) and below (1720 m) cloud base. Throughfall was used to estimate total deposition using relationships determined during the IFS. Although the SO₄ ^2? fluxes increased with elevation by a factor of ～2 due to higher cloudwater interception at 1940 m, the NO₃ ^? fluxes decreased with elevation by ～30%. To investigate further, we began year round measurements of fluxes of all major ions in throughfall below spruce-fir forests at 1740 m and at 1920 m in 1993–1994. The fluxes of most ions showed a 10–50% increase with elevation due to the ～70 cm yr^?1 cloudwater input at 1920 m. However, total inorganic nitrogen exhibited a 40% lower flux in throughfall at 1920 m than at 1740 m suggesting either higher dry deposition to trees at 1740 m or much higher canopy uptake of nitrogen by trees at 1920 m. Differential canopy absorption of N by trees at different elevations would have significant consequences for the use of throughfall N fluxes to estimate deposition. We used artificial trees to understand the foliar interactions of N.     

Comparison of the Suspended Sediment Dynamics in Two Loess Plateau Catchments,China

Changes in runoff and sediment loads are of great importance for the management of river basins and the implementation of soil and water conservation measures. This study compared the suspended sediment dynamics in the Huangfuchuan and Yanhe catchments on the Loess Plateau. Both annual runoff and sediment load displayed significant reductions from 1955 to 2012. The decreasing rates were −0·88 mm a⁻¹ and −2·72 Mg ha⁻¹ a⁻¹ in the Huangfuchuan catchment, respectively, and ‐0.31 mm a⁻¹ and −1·20 Mg ha⁻¹ a⁻¹ in the Yanhe catchment. A total of 183 and 195 events, respectively, were selected to assess the suspended sediment dynamics in both catchments during the periods of 1971–1989 and 2006–2012. The results showed a good linear relationship between the sediment yield and runoff depth in both catchments from 1971 to 1989 and a relatively worse relationship in the Yanhe catchment from 2006 to 2012. The magnitude and frequency of the hyper‐concentrated sediment flow obviously decreased in the 2000s compared with that between 1971 and 1989. A hysteresis analysis suggested that complex and counter‐clockwise loops were the dominant patterns. Various soil and water conservation measures (e.g., afforestation, grassing, terraces, and check dams) played a critical role in runoff and sediment load changes in both catchments. The two catchments showed obvious heterogeneities in runoff and sediment yield because of different lithologies, soil types, and vegetation. The results of this study provide valuable information on suspended sediment dynamics and could be used to improve soil erosion control measures on the Loess Plateau. Copyright © 2016 John Wiley & Sons, Ltd.     

A Global Analysis of Acidification and Eutrophication of Terrestrial Ecosystems

This paper presents an explorative, quantitative analysis of acidification and eutrophication of natural terrestrial ecosystems caused by excess sulfur (S) and nitrogen (N) deposition. The analysis is based on a steady-state approach, involving the comparison of deposition fluxes with critical loads to identify areas where critical loads are exceeded. Deposition fields for sulfur and nitrogen were obtained from the STOCHEM global chemistry-transport model, and they were combined with estimated base cation deposition to derive net acid deposition fluxes. The results indicate that the critical loads for acidification are exceeded in 7–17% of the global area of natural ecosystems. In addition, comparison of nitrogen deposition with critical loads for eutrophication yielded an exceedance in 7–18% of the global natural ecosystems. Apart from serious problems in the heavily industrialized regions of eastern USA, Europe, the former Soviet Union, and large parts of Asia, risks are also found in parts of South America, and West, East and Southern Africa. Both acidification and eutrophication risks could significantly increase in Asia, Africa and South America in the near future, and decrease in North America and Western Europe. Accounting for the effects of N in the analysis of acidification significantly enlarges the potentially affected areas and moves them away from highly industrialized areas compared to studies considering S deposition alone. Major uncertainties in the approach followed are associated with upscaling, the estimates of S, N and base cation emission and deposition fluxes, the critical loads to describe ecosystem vulnerability and the treatment of soil N immobilization and denitrification.     

The Impact of Climate Change on Metal Transport in a Lowland Catchment

This study investigates the impact of future climate change on heavy metal (i.e., Cd and Zn) transport from soils to surface waters in a contaminated lowland catchment. The WALRUS hydrological model is employed in a semi-distributed manner to simulate current and future hydrological fluxes in the Dommel catchment in the Netherlands. The model is forced with climate change projections and the simulated fluxes are used as input to a metal transport model that simulates heavy metal concentrations and loads in quickflow and baseflow pathways. Metal transport is simulated under baseline climate (“2000–2010”) and future climate (“2090–2099”) conditions including scenarios for no climate change and climate change. The outcomes show an increase in Cd and Zn loads and the mean flux-weighted Cd and Zn concentrations in the discharged runoff, which is attributed to breakthrough of heavy metals from the soil system. Due to climate change, runoff enhances and leaching is accelerated, resulting in enhanced Cd and Zn loads. Mean flux-weighted concentrations in the discharged runoff increase during early summer and decrease during late summer and early autumn under the most extreme scenario of climate change. The results of this study provide improved understanding on the processes responsible for future changes in heavy metal contamination in lowland catchments.     

Critical loads of sulfur and nitrogen for lakes I: Model description and estimation of uncertainty

Presently considerable effort is devoted to the development of methods for estimating critical loads of acidic deposition. In this paper a steady-state mass balance model for lakes is presented, allowing the simultaneous calculation of critical loads of acidifying S and N deposition and their exceedance. Special emphasis is given to the derivation of model inputs and parameters and the quantification of their uncertainties. The inclusion of rate-limited processes in the model leads to the dependence of the critical loads not only on catchment properties but also on the loading to the ecosystem. As a consequence, critical load values have to be re-calculated whenever deposition patterns change. The methods presented in this study are used in an accompanying paper to derive regional distributions of critical loads of S and N for lakes in Finland and to quantify their uncertainties.     

Leaching of Nutrients,Organic Carbon and Iron from Finnish Forestry Land

This study provides an assessment of the spatial variability of the long-term leaching of nutrients, total organic carbon (TOC) and iron (Fetot) from 22 forested catchments (0.69-56 km2), distributed across all but the northenmost areas of Finland. The natural, unmanaged Kruunuoja catchment is located in a national park, while the other catchments represent Finnish forestry land. The average leaching of Ptot (4.2 kg km-2 yr^-1) from the Kruunuoja catchment was small compared to the catchments representing forestry land (on average 10 kg km-2 yr^-1). Moreover, P fertilization was the most important predictor for the spatial variation in Ptot leaching (r2=0.45). Leaching of TOC, Fetot and N compounds was not closely related to forestry practices. Median C/N ratio in the study streams was high (range 34-66). The average inorganic N proportion and leaching of P_tot were lowest in the Kruunuoja catchment (7.3 % and 2.8 kg km-2 yr^-1, respectively) and highest in the southernmost Teeressuonoja catchment (54 % and 100 kg km-2 yr^-1, respectively) located in the highest N deposition area. The most important forestry practices since the 1960's have affected about 2.4 % of the area of study sites per year (cf. 2% in the entire country in 1991). Moreover, the mean annual runoff from the catchments (230-430 mm yr^-1) agrees with the mean annual runoff from Finland (301 mm yr^-1). Consequently, the results of the study catchments can be used to estimate average total annual leaching from Finnish forestry land: 2,700 t of Ptot, 48,000 t of Ntot, 110,000 t of Fetot and 1.5 million t of TOC.     

Recovery of acidified catchments in the extremely polluted Krusne hory Mountains,Czech Republic

Runoff and atmospheric chemistry in the Krusne hory Mts. have changed significantly from 1978 to 1994. Forest die-back related deforestation resulted in decreased dry deposition of SO₂ and changes in streamwater chemical composition. Atmospheric sulphur (S) deposition decreased from extremely high values of 66.6 kg S ha^?1 year^?1, in the early 1980s to 35.5 kg S ha^?1 year^?1 in 1994. Decreasing S input is reflected in decrease of streamwater sulphate (SO₄ ^2?) concentrations, which decreased from 1560 μeq l^?1 to 1164 μeq l^?1. Runoff export of S was 53 kg S ha^?1 year^?1 in 1993, S is not retained in the catchments. Nitrogen (N) budget indicates accumulation in the catchment, which is attributed to forest regrowth.     

Elevational Patterns of Acid Deposition into a Forest and Nitrogen Saturation on Mt. Oyama, Japan

Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 – 23.5 kg ha^?1 yr^?1 (annual inorganic total N deposition: 9.6 – 10.7 kgN ha^?1 yr^?1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 µg g^?1 (the range: 21.1 – 429 µg g^?1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L^?1 (the range: 2.38 – 20.6 mg L^?1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.     

Factors affecting streamwater chemistry in The Great Smoky Mountains,USA

The Great Smoky Mountains in the southeastern U.S. receive high total atmospheric deposition of sulphur and nitrogen (N) and contain large areas of shallow, poorly buffered soils. Results from extensive surveys conducted in October 1993 and March 1994 showed mat stream pH values were near or below 5.5 and Acid Neutralizing Capacity (ANC) was below SO μeq·L^?1 at high elevations. Mechanisms of acidification varies among stream systems in the study. We classified each study catchment into one of five water quality districts based upon within-basin elevational gradients of streamwater quality. Geologic factors, cf. the presence of calcareous or pyritic bedrock types exhibited a major influence on water quality and within-basin elevational gradients. Atmospheric deposition is an important factor affecting water quality at high elevations in all districts. Nitrate was the dominant strong acid anion in streamwater in many catchments, particularly at high elevation and especially in basins draining old growth forests. Most high elevation catchments appear to be N saturated. Continued high atmospheric loadings of N will likely spread N saturation of catchments downslope into areas where second growth forests are now maturing. Stream sulphate concentrations were lower than expected at higher elevations and may be related to the N saturation status of fliese systems.     

Factors Controlling Mercury Transport in an Upland Forested Catchment

Total mercury (Hg) deposition and input/output relationships were investigated in an 11-ha deciduous forested catchment in northern Vermont as part of ongoing evaluations of Hg cycling and transport in the Lake Champlain basin. Atmospheric Hg deposition (precipitation + modeled vapor phase downward flux) was 425 mg ha-1 during the one-year period March 1994 through February 1995 and 463 mg ha-1 from March 1995 through February 1996. In the same periods, stream export of total Hg was 32 mg ha-1, respectively. Thus, there was a net retention of Hg by the catchment of 92% the first year and 95% the second year. In the first year, 16.9 mg ha-1 or about half of the annual stream export, occurred on the single day of peak spring snowmelt in April. In contrast, the maximum daily export in the second year, when peak stream flow was somewhat lower, was 3.5 mg ha-1 during a January thaw. The fate of the Hg retained by this forested catchment is not known. Dissolved (< 0.22 µm) Hg concentrations in stream water ranged from 0.5-2.6 ng L-1, even when total (unfiltered) concentrations were greater than 10 ng L-1 during high flow events. Total Hg concentrations in stream water were correlated with the total organic fraction of suspended sediment, suggesting the importance of organic material in Hg transport within the catchment. High flow events and transport with organic material may be especially important mechanisms for the movement of Hg through forested ecosystems.     

Deposition of acidifying compounds in Sweden

The Swedish Environmental Research Institute (IVL) has monitored deposition of acidifying compounds in Sweden. The monitoring programmes were initiated by various air quality protection associations, and regional forest and environmental authorities. The purpose is to quantify sulphur (S) and nitrogen (N) deposition to forests, and to illustrate possible acidification of the soil. Actual deposition of S and N is compared with critical loads. Deposition is investigated by precipitation studies in open field areas and by throughfall studies in forest stands. Soilwater chemistry is examined in the forest stands and used as indication of soil conditions. For most of the study sites, data on needle loss, forest growth, and soil chemistry are available from the National Board of Forestry. All available data are combined in a computer database for evaluation. Evaluation of data during 1985–94 shows that regional deposition monitoring illustrates the size and distributional pattern of S and seasalts. Monitoring data can identify certain regions receiving heavy loads of N, which can be found mainly in southern Sweden. Soilwater analyses indicates that large areas in Sweden have heavily acidified forest soils, low pH-values, low levels of calcium (Ca²⁺), magnesium (Mg²⁺), and potassium (K⁺), and raised levels of inorganic aluminium (iAl). Forest sites in the coastal regions of southern and south-western Sweden also showed raised inorganic N levels in soilwater. The relationship between deposition load and effects on soil chemistry is recognised by a correlation between S deposition and iAl levels in soilwater. Another correlation was found between N deposition (throughfall) and N levels in soilwater.     

Predicting Freshwater Critical Loads of Acidification at the Catchment Scale: An Empirical Model

Current applications of the critical loads concept are geared primarily toward targeting emission control strategies at a national and international level. Maps of critical loads for freshwaters have been produced in grid form based on water samples of representative sites within each grid square. However, the water chemistry data required to calculate freshwater critical loads are not always readily available at a national level and maps are therefore limited to catchments where such data exist. This paper describes the development of an approach that uses nationally available secondary data to predict freshwater critical loads for catchments lacking the appropriate water chemistry information. An empirical statistical model is calibrated using data from 78 catchments throughout Scotland. Water chemistry for each catchment has been determined. Each catchment is characterized according to a number of attributes. Redundancy analysis of these data shows clear relationships between catchment attributes and the critical load derived from the water chemistry. The key variables that explain most of the variation in critical load relate to soil, geology and land use within the catchment. Using these variables as predictors in a regression analysis, the critical load can be predicted across a broad gradient of sensitivity (R² _adj=0.81). The predictive power of the model was maintained when different combinations of explanatory variables were used. This accords the approach a degree of flexibility in that model parameterization can be geared toward availability of secondary data. There are limitations with the model as presently calibrated. However, the approach offers considerable scope for environmental managers to undertake national inventories of catchment sensitivity and specific assessments of individual catchments.     

Deposition gradients and foliar and soil leachate concentrations of air pollutants in Scots pine stands of S.-E. Finland and the Karelian Isthmus,N.-W. Russia

Bulk precipitation and throughfall analyses in 50–100-year-old Scots pine stands revealed decreasing sulphur, nitrogen, calcium and magnesium deposition gradients, which extend from the St. Petersburg-Leningrad region and N.-E. Estonia to S.-E. Finland. The Ca and Mg deposition alleviate the acidifying effect of sulphur and nitrogen. The Scots pine canopies acted as a sink for ammonium and nitrate, while the canopy interactions increased sulphur, calcium and magnesium content in throughfall. Foliar S, N and Ca concentrations correlated positively with the corresponding deposition loads. In contrast, low foliar magnesium concentrations were detected in the vicinity of St. Petersburg. The results indicate that the sulphur and calcium deposition may have increased soil leachate S and Ca concentrations in the most polluted Scots pine stands.