Matti Johansson

Application of nitrogen transfer matrices for integrated assessment

Abstract Linear transfer matrices for nitrogen compounds were constructed from the results of the regional air quality model of the Finnish Meteorological Institute (FMI-RM). The matrices are implemented into the integrated assessment model DAIQUIRI used at the Finnish Environment Institute. The deposition fields of oxidised and reduced nitrogen calculated with both models for year 1990 are compared with each other and against measured deposition. Both models give higher depositions than the measurements, and DAIQUIRI often more than FMI-RM. DAIQUIRI currently tends to overestimate nearby deposition of oxidised and reduced nitrogen in areas where land use types other than forest dominate.

Development of an Integrated Model for the Assessment of Acidification in Finland

An integrated model to consider the future development of acidifying emissions and their impacts on forest soils and lakes is being prepared in close collaboration with several Finnish research institutes and IIASA. The model system (HAKOMA) covers SO2 and NOx emissions from energy use, industrial processes, and transportation, and also NH3 emissions from agriculture, animal farming, and industry. Future emissions are estimated on the basis of different scenarios for energy, traffic, industry and agriculture and on the basis of alternative reduction strategies.

Long-term base cation balances of forest mineral soils in Finland

Long-term base cation balances (Ca, Mg and K) for forest mineral soils in Finland were calculated with mass balance methods. The aim of the study was to identify the areas in which weathering and base cation deposition do not support leaching and uptake of base cations by vegetation. The effect of stem harvesting and whole-tree harvesting on the base cation balances was studied and preliminary calculations were made about the amounts of ash needed for compensation of the potential base cation depletion. The effect of sulphur emission reduction till 2010 was also considered. The study demonstrated that there would be depletion of base cations in forest mineral soils in southern, central and northeastern Finland (40–50% of the grids) in the long term if whole-tree harvesting would be practised. Theoretical calculations showed that ash application would be most useful in those areas to compensate the base cation depletion. If stem harvesting is practised, only small areas (20%) in southwestern and southeastern Finland and northeastern Lapland would show depletion of base cations in the long term.

Critical Loads of Acidity for Forest Soils: Tentative Modifications

We reviewed the current methods for calculatingcritical loads of acidity for forest soils. The consequencesof four sets of assumptions concerning the soil modelstructure, parameter values and the critical loads criterionwere explored by comparing the values of the averageaccumulated exceedance (AAE) calculated for Finland withdeposition values for the year 1995. The AAE index is given inthe unit of deposition and is a measure of how far a region isfrom being protected in terms of fulfilling a certaincriterion, taking into account the size of the ecosystem areas.Using a critical limit for the molar ratio of theconcentrations of base cations to aluminium in soil solutiongave the lowest average accumulated exceedance. Assumingorgano-aluminium complexes and leaching of organic anions gaveAAE = 4 eq ha-1 a-1, which was close to the valueobtained with the standard approach used in Finland, assuminggibbsite equilibrium and no leaching of organic anions,yielding AAE = 5 eq ha-1 a-1. With a critical basesaturation limit, instead of the concentrations criterion, theAAE index was 17 eq ha-1 a-1. The highest averageaccumulated exceedance (AAE = 25 eq ha-1 a-1),corresponding to the lowest critical load, was obtained whenthe effects-based criterion (critical concentration or criticalbase saturation) was substituted with one restricting thedeterioration of the neutralizing capacity of the soil, ANCle(crit) = 0. These tests illustrate the variabilityof the critical load values for acidity that can be introducedby changing the criterion or by varying the calculation method,without, however, representing the extreme values of criticalloads that could be derived.

Modeling potential long-term responses of a small catchment in Lapland to changes in sulfur deposition

Abstract The SMART model (Simulation Model for Acidifications Regional Trends) was developed to estimate long-term chemical changes in soil and lake water in response to changes in atmospheric deposition. Its major outputs include base saturation, pH, and the molar Al/Ca ratio for soils, and major cations and anions for soil and lake water. The model structure is based on the anion mobility concept and the charge balance principle. SMART was applied to the Christmas Lakes, a chain of small oligotrophic catchments in northeast subarctic Finnish Lapland (69°25′N, 29°11′E), located close to the border with Norway and 40 km from the Nikel smelter in Russia, a major source of sulfur emissions. The Christmas Lakes are less than 60 ha in size, have clear water, and are low in base cations and alkalinity. At present, the lakes are not very acidic, the pH being around 6.5 in autumn. The SMART model was calibrated to present soil and water quality data, using best estimates for historical deposition patterns for the period 1890–1990. The model applications in this paper are intended to demonstrate the range of potential catchment responses in northern Lapland for different assumptions concerning sulfur. The two calibrations of the model, assuming (1) a high sulfur deposition in combination with sulfate adsorption and (2) a lower present deposition with no adsorption, revealed that the present sulfur deposition has to lie between 0.4 and 0.8 g S/m2/year. The model results for both calibrations indicate that future sulfur deposition would have to be very low to stop and reverse the ongoing acidification. However, since the present base saturation is fairly high (>50%), there is still time (several years) to reduce the sulfur deposition to values the system can tolerate.

Sensitivity of soil acidification model to deposition and forest growth.

We report an investigation concerning the impacts of acid deposition and forest growth scenarios on simulated soil effective base saturation for a forested catchment in eastern Finland. These forests have not been managed during the last 150 yr and the area receives low levels of acidifying deposition. The fluxes of sulphur, nitrogen and base cations were assessed with models simulating historic and future deposition, stand uptake and leaching. We tested the effects of calibrating the modelled deposition time series to high and low estimates of current levels of deposition. The highest future soil base saturation was predicted when using the year with the lowest observed sulphur and nitrogen deposition (1993) as representative of the present deposition. The lowest historical and future soil base saturation resulted for using the year with the highest observed deposition of sulphur and nitrogen (1988). All scenarios concerning nutrient uptake, emission reduction levels and timing of the reductions resulted in simulated future soil base saturation values located between those predicted with the high and low observed present deposition. The standard deviation in the soil base saturation introduced by varying the present forest biomass and growth was smaller than that produced by varying the present deposition values.

Integrated assessment modeling of air pollution in four european countries

The integrated assessment modeling on acid rain has incorporated several related effects and pollutants into a multi-pollutant/multi-effect approach, resulting in complex integrated models and policy assessments. The development and implementation of effects-oriented cost-effective emission reduction strategies in Europe are based on integrated assessment models. The project on national integrated assessment modeling in Finland, Denmark, Spain and Sweden aimed to support the national evaluation of European emission reduction strategies. The tasks covered the comparison of inventories and projections for emissions of sulfur, nitrogen oxides, ammonia and volatile organic compounds, assessment of control techniques and related costs, concentration and deposition scenarios to estimate environmental effects of acidification, eutrophication and ground-level ozone and their temporal aspects, uncertainty analyses on both individual modules and whole integrated models, and dissemination of results to stakeholders. The integrated assessment modeling provided a consistent framework for the harmonization of input data and in-depth scientific research tasks on emissions, pollutant loading and impacts including comprehensive uncertainty analyses, and facilitated the dissemination of knowledge to policy-makers.

A Module to Calculate Primary Particulate Matter Emissions and Abatement Measures in Europe

Primary particulate matter is emitted directly into the atmosphere from various anthropogenic and natural sources such as power plants (combustion of fossil fuels) or forest fires. Secondary particles are formed by transformation of SO2, NOx, NH3, and VOC in the atmosphere. They both contribute to ambient particulate matter concentrations, which may have adverse effects on human health. Health hazards are caused by small particulate size, high number of especially fine (< 2.5 µm) and ultra-fine (< 0.1 µm) particles and/or their chemical composition. As part of an integrated assessment model developed at IIASA, a module on primary particulate matter (PM) emissions has been added to the existing SO2, NOx, NH3 and VOC sections. The module considers so far primary emissions of total suspended particles (TSP), PM10 and PM2.5 from aggregated stationary and mobile sources. A primary PM emission database has been established. Country specific emission factors for stationary sources have been calculated within the module using the ash content of solid fuels.

The Importance of Nitrogen Oxides for the Exceedance of Critical Thresholds in the Nordic Countries

Impacts of air pollutants and especially acidification in ecosystems have been of serious concern in the Nordic countries since the 1970s. The current approach to assess several pollutants (sulfur and nitrogen oxides, ammonia, volatile organic compounds) and their effects (acidification, eutrophication and ground-level ozone) simultaneously is extremely complex. This study explored the relative role of nitrogen oxides in environmental impacts in the Nordic countries. The share of NOx in the exceedances of critical loads, the long-term ecosystem protection targets, was found to be roughly 25% in acidification and 50% in eutrophication. The contribution of NOx emissions to ground-level ozone formation was considered important, as NOx is the limiting precursor in ozone formation in the Nordic countries. The comparison of observed and modeled accumulated ozone concentrations (AOT40) for the early 1990s shows noticeable differences in the Nordic area, partly due to the sensitivity of the AOT40 indicator to the 40 ppb threshold value.

Nitrogen Deposition Effects on Ecosystem Services and Interactions with other Pollutants and Climate Change

Ecosystem services are defined as the ecological and socio-economic value of goods and services provided by natural and semi-natural ecosystems. Ecosystem services are being impacted by many human induced stresses, one of them being nitrogen (N) deposition and its interactions with other pollutants and climate change. It is concluded that N directly or indirectly affects a wide range of provisioning, regulating, supporting and cultural ecosystem services, many of which are interrelated. When considering the effects of N on ecosystem services, it is important to distinguish between different types of ecosystems/species and the protection against N impacts should include other aspects related to N, in addition to biodiversity. The Working Group considered the following priorities of ecosystem services in relation to N: biodiversity; air quality/atmosphere; ecosystem changes; NO3 leaching; climate regulation and cultural issues. These are the services for which the best evidence is available in the literature. There is a conflicting interest between greenhouse gas ecosystem services and biodiversity protection; up to some point of increasing N inputs, net greenhouse gas uptake is improved, while biodiversity is already adversely affected.