Antti-Jussi Lindroos

Effects of heavy metal contamination on macronutrient availability and acidification parameters in forest soil in the vicinity of the Harjavalta CuNi smelter, SW Finland

Four experiments were established (1992) in Scots pine stands at distances of 0.5, 2, 4 and 8 km along a line running to the SE of the Cu-Ni smelter at Harjavalta, SW Finland, in order to investigate the effects of Cu and Ni emissions on macronutrient availability and estimates of cation exchange capacity (CEC) and base saturation (BS). The accumulation of Cu and Ni (total, exchangeable) in forest soil close to the smelter has resulted in a deficit of base cations (exchangeable Ca, Mg, K and BS) in the organic layer caused by inhibition of mineralisation and the displacement of base cations from cation exchange sites by Cu and Ni cations. No signs of soil acidification were found in the topmost layers of the soil measured as a change in pH, exchangeable acidity and Al. The determination of CEC by the summation method in heavy-metal polluted forest soils is not recommended unless heavy metal cations are also included in the calculations.

Ectomycorrhizal root tips in relation to site and stand characteristics in Norway spruce and Scots pine stands in boreal forests

Variations in ectomycorrhizal (EcM) short root tips of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in 16 stands throughout Finland were studied, and their relationships with latitude, organic layer C:N ratio, temperature sum and foliage biomass were determined. There were no significant differences in EcM root tip frequency (number per milligram of fine roots) or root tip mass between tree species or between northern and southern sites. The EcM root tip number per unit area of the organic layer plus the 0-30 cm mineral soil layer varied between 0.8 and 2.4 million per m(2) for Norway spruce and between 0.7 and 2.9 million per m(2) for Scots pine, and it was higher in the northern Scots pine stands than in the southern Scots pine stands. Over 80% of the EcM root tips of both species were in the organic layer and the upper 0-10 cm mineral soil layer. We related EcM root tips to foliage mass because these two components are the most important functional units in boreal tree physiology. Both species, especially the Scots pine trees, had more EcM root tips in relation to foliage mass in northern Finland than in southern Finland. Scots pine trees had more EcM root tips in relation to foliage mass than Norway spruce in the same climatic region. The EcM root tip:foliage biomass ratio of Norway spruce was positively related to the C:N ratio in the organic layer, whereas that of Scots pine was negatively related to the temperature sum. The number of EcM root tips per milligram of fine root biomass was constant, implying that trees of both species increase nutrient uptake by increasing fine root production and hence their total number of EcM tips and the area of soil occupied by mycelia. Both tree species responded to nitrogen (N) deficiency by maintaining more EcM tips per foliage unit, and this may be related to a higher proportion of N uptake in an organic form.

Weathering release of heavy metals from soil in comparison to deposition, litterfall and leaching fluxes in a remote, boreal coniferous forest

Soil weathering release rates of Cd, Cu, Ni, Pb and Zn were determined at 4 plots in a forested catchment located in eastern Finland. The rates are compared with atmospheric deposition, litterfall and leaching fluxes at two of the plots. The soils were Haplic Podzols and developed in glaciofluvial deposits or glacial till having sandy loam to loamy sand fine-earth (<2 mm) textures. The bedrock in the area consists of granodiorites. Total concentrations of heavy metals in the <2 mm fraction of the parent material were determined from a mixed acid (HF and HClO4) digestion using ICP–MS. Weathering rates were calculated assuming that the molar ratio of heavy metal to base cation (Ca+Mg) weathering rates (previously determined by the Zr depletion method) equalled the molar ratio of heavy metal to base cation concentrations in the parent material. The mean weathering release rates were 8.3 μmol m−2 a−1 for Zn, 5.2 for Ni, 4.3 for Cu, 1.5 for Pb, and 0.011 for Cd. These rates were similar to the deposition, litterfall, and leaching fluxes for each metal. Weathering is therefore an important process in the heavy metal biogeochemistry of boreal, forest ecosystems.

Changes in dissolved organic carbon during artificial recharge of groundwater in a forested esker in Southern Finland

Sprinkling infiltration in a forested esker leading to artificial recharge of groundwater was studied in Southern Finland. Changes in dissolved organic carbon (DOC) and the molecular size distribution and chemical properties of the organic carbon were investigated during the infiltration process. Artificial groundwater was produced using sprinkling infiltration directly onto the forest floor. One result of lake water infiltration through the organic horizon and I m thick mineral soil layer was a slight net increase in the DOC concentrations from 9.4 mg/L in the infiltration water to 13.2 mg/ L in percolation water. This indicates that the forest soil represents a potential input of organic matter into infiltration water. However, the DOC concentrations decreased by 27-38% as the infiltration water percolated down through the unsaturated soil layer into the groundwater zone. At a distance of 1450 m from the infiltration area, the mean DOC concentration in the groundwater was below the recommended value for drinking water in Finland of 2.0 mg/L. There was a strong reduction in the concentrations of hydrophilic and hydrophobic acids, but only a slight decrease in hydrophilic neutral organic compounds during the infiltration process. The DOC in the production well consisted of low molecular size fractions. Larger molecular size fractions were removed effectively from the water during the infiltration process.

The Weathering of Mineral Soil by Natural Soil Solutions

Chemical weathering is an important neutralisation process and sourceof cations in forest soil. The presence of dissolved organic matter in the soil solution can have a considerable influence on weathering release. The aim of this study is to compare the weathering potentialof natural soil solutions, collected from Norway spruce, Scots pine and birch sites, to release Al, Ca, Mg, K, Na, and Si from the fine fraction in the C horizon of a podzol. Residual organic matter in the mineral soil was removed with H2O2. The <0.06 mm fraction of the mineral soil was suspended in soil solution, collected from the three sites, for 11 days with continuous agitation. Ultrapure water was used as a control. The pH of the suspensions was maintained at 5.4 by bubbling with CO2. The initial mean DOC concentrations in the soil solutions were 65, 56 and 40 mg L-1 for the spruce, pine and birch sites, respectively. The presence of DOM in the soil solution did not significantly enhance the capacity to weather mineral soil material, and no systematic differences were found between the three sites. However, Al release from the mineral soil was slightly higher in the soil solutions containing DOM compared to the control solution with no DOM. The proportions of DOM fractions capable of enhancing weathering were comparable with those reported in earlier studies. The weathering of metals was found to be primarily due to pH-driven processes. The lack of considerable weathering enhancement by DOM could be due to the fact that the cation-binding sites of the organic ligands were already saturated by e.g. Al and Fe in the soil solution derived from these podzolic, Al- and Fe-rich soils.

Exceedance of critical loads and of critical limits impacts tree nutrition across Europe

Key messageExceedance of critical limits in soil solution samples was more frequent in intensively monitored forest plots across Europe with critical loads for acidity and eutrophication exceeded compared to other plots from the same network. Elevated inorganic nitrogen concentrations in soil solution tended to be related to less favourable nutritional status.ContextForests have been exposed to elevated atmospheric deposition of acidifying and eutrophying sulphur and nitrogen compounds for decades. Critical loads have been identified, below which damage due to acidification and eutrophication are not expected to occur.AimsWe explored the relationship between the exceedance of critical loads and inorganic nitrogen concentration, the base cation to aluminium ratio in soil solutions, as well as the nutritional status of trees.MethodsWe used recent data describing deposition, elemental concentrations in soil solution and foliage, as well as the level of damage to foliage recorded at forest plots of the ICP Forests intensive monitoring network across Europe.ResultsCritical loads for inorganic nitrogen deposition were exceeded on about a third to half of the forest plots. Elevated inorganic nitrogen concentrations in soil solution occurred more frequently among these plots. Indications of nutrient imbalances, such as low magnesium concentration in foliage or discolouration of needles and leaves, were seldom but appeared more frequently on plots where the critical limits for soil solution were exceeded.ConclusionThe findings support the hypothesis that elevated nitrogen and sulphur deposition can lead to imbalances in tree nutrition.

Spatio-temporal Trends in Soil Solution Bc/Al and N in Relation to Critical Limits in European Forest Soils

Chemical composition of soil solution provides information on the availability of nutrients and potentially toxic substances to plant roots and mycorrhizas. It is therefore used to monitor impacts of air pollutants on soils. In this study we examined two soil solution parameters, base cations/aluminium ratio (Bc/Altot ratio) and inorganic nitrogen concentration (N), in samples collected at 300 intensive monitoring plots of the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) from the early 1990s to 2006 in order to detect possible critical limit exceedances (CLimE). CLimE for Bc/Altot ratio indicating negative effects for tree growth were only rarely detected. Quite the contrary was observed in CLimE for inorganic N concentrations where the safety limits were frequently exceeded in parts of Europe. Especially noteworthy is the number of the plots where leaching of N from forest soils occurred over the studied period. With ongoing high atmospheric N input into forest soils, we expect critical limits to be exceeded in the future as well.

Snowpack quality as an indicator of air pollution in Finnish Lapland and the Kola Peninsula, NW Russia

Bulk snow samples were collected from the snowpack in open areas along two sampling lines running to the west from the Cu-Ni smelters at Nikel and Monchegorsk, NW Russia, during 1991–1993. The aim of the study was to estimate the area affected by sulphur and heavy metal deposition from the smelters. Snowpack quality was used as an indicator of deposition during winter time. The total sulphur, copper and nickel concentrations in the snowpack decreased significantly (p<0.001) with increasing distance from the smelters along the sampling line running directly to the west from Monchegorsk. The deposition pattern was similar each winter during 1991–1993. The pH values did not correlate with the corresponding sulphur concentrations, and there was no decreasing pH gradient in the snowpack on moving towards Monchegorsk. The effects of sulphur emissions from Monchegorsk on snowpack chemistry were not detectable on the Finnish side of the border. The 3-year mean of the total sulphur concentration was 0.27 mg/kg, and of the pH values 4.92, along the sampling line running to the west of Monchegorsk. The total sulphur concentrations near the smelters (< 20 km) varied between 0.37 and 0.95 mg/kg. The effect of the Cu-Ni smelters at Nikel on snowpack quality was not detectable in northern Finnish Lapland. The 3-year mean for total sulphur was 0.20 mg/kg and for pH 4.96 along the sampling line running to the west of Nikel.

Soil Acidity Parameters and Defoliation Degree in Six Norway Spruce Stands in Finland

Soil acidity parameters (pH, basesaturation, exchangeable Al) in the organic and mineralsoil layers and in soil water (pH, dissolved organiccarbon, total Al, Al3+ and molar Ca/Al ratios) insix Norway spruce stands in different parts of Finlandwere compared. An attempt was also made to relate thedegree of defoliation in the tree stand to N and Sdeposition and soil parameters. No relationship was foundbetween soil acidity parameters and defoliation in thesix stands. Defoliation was positively correlated withstand age and the C/N ratio of the organic layer, andnegatively with the cation exchange capacity. The plotlocated on a so-called sulphate soil on the west coast ofFinland had very low soil pH values, and extremely highAl and SO42- concentrations and molar Ca/Alratios of well below 1.0 in soil water. Despite the highnatural acidity in the soil on this plot, defoliation inthe spruce stand was the lowest (mean 8.6%) of all sixplots. The results of this study indicate that soilacidity is not a major factor affecting stand conditionin these spruce stands, and that the variation in soilacidity parameters is closely related to climatic factorsand natural soil formation processes.

Techniques for preserving and determining aluminium fractions in soil solution from podzolic forest soils

Abstract The purpose of the study was 1) to determine techniques for minimising the effects of transportation and storage on the concentrations of different A1 fractions in soil solution samples, and 2) to determine a suitable method for analysing monomeric A1 concentrations in water samples from humus-rich podzolic soils. Aluminium fractionation was performed on a cation exchange column and the fractions were analysed by ICP/AES and FIA. A time lag of a few hours to two days between sampling and pretreatment appeared to have no effect on total A1 concentrations, even though the samples were not preserved with acid. Freezing the samples was not an appropriate storage technique because it resulted in a strong decrease in total A1 concentrations. Storage (+4°C) had a detrimental effect on the proportion of exchangeable monomeric A1, but this problem was overcome by fractionating the samples immediately on arrival at the laboratory. Adjustment of sample pH to