Salminen, S. & Paatero, J. 2009: Concentrations of ²³⁸Pu, ^239+240Pu and ²⁴¹Pu in the surface air in Finnish Lapland in 1963. Boreal Env. Res. 14: 827–836.

Activity concentrations of ²³⁸Pu, ^239+240Pu and ²⁴¹Pu (measured both directly by liquid scintillation counting and indirectly by buildup of ²⁴¹Am) were determined with the aid of archived air filters sampled at Sodankylä (67°22'N, 26°39'E) in 1963. Atmospheric concentrations of ²³⁸Pu, ^239+240Pu and ²⁴¹Pu were < 0.1–3.6(± 0.5) µBq m^–3, 0.4(± 0.1)–95(± 3) µBq m^–3 and < 16–1730(± 70) µBq m^–3, respectively. The plutonium concentrations varied seasonally, being highest in spring and summer due to the springtime-enhanced transportation of radioactive aerosols from the stratosphere to the troposphere. Contrary to some earlier assumptions, the ^239+240Pu activity concentration in the air was practically at the same level in northern and southern Finland. The ²³⁸Pu/^239+240Pu activity ratio in the air was 0.014(± 0.003)–0.32(± 0.11), typically close to that of global fallout from the nuclear weapons testing. The ²⁴¹Pu/^239+240Pu activity ratio varied between 7.7(± 1.2) and 41(± 8). According to these isotope ratios, plutonium in Sodankylä originated mainly from global nuclear test fallout, even though the effect of the Soviet tests at the end of 1962 were observed at the beginning of 1963. However, direct atmospheric transport from Novaya Zemlya to Finnish Lapland could not be detected.

Setälä, O., Sopanen, S., Autio, R. & Erler, K. 2009: Grazing and food selection of the calanoid copepods Eurytemora affinis and Acartia bifilosa feeding on plankton assemblages containing Dinophysis spp. Boreal Env. Res. 14: 837–849.

Grazing of Eurytemora affinis and Acartia bifilosa on plankton communities containing toxic dinoflagellates of the genus Dinophysis was experimentally studied in the northern Baltic Sea. The experiments were carried out in plankton communities with different concentrations and relative proportions of microplankton. In the experiments with high total cell concentrations, the dinoflagellate Heterocapsa triquetra predominated, and in these experiments they formed the main part of the copepod diet. When the total cell concentrations were lower and the relative Dinophysis spp. concentrations higher, the role of Dinophysis spp. as food became more important, although no marked change in the ingestion rates were found. Eurytemora affinis consumed up to 226 Dinophysis spp. cells (0.50 µg C) ind^–1 day^–1, and A. bifilosa up to 64 cells (0.1 µg C) ind^–1 day^–1. No positive selection for Dinophysis spp. was detected, and in fact, other species were preferred. Pectenotoxin-2 (PTX2) was found in two pooled samples of copepods after incubation (53 and 142 pg PTX2 ind^–1, respectively). Although no positive selection for Dinophysis spp. was detected, these dinoflagellates formed an important part of the copepod's diet at low food concentrations in these experiments. It is thus possible that in environmental conditions characterized by low microplankton biomass, the copepods can have a minor role in toxin transfer in planktonic food webs of the northern Baltic Sea by accumulating toxins in their tissues or transferring them to faecal pellets.

Tainio, M., Karvosenoja, N., Porvari, P., Raateland, A., Tuomisto, J. T., Johansson, M., Kukkonen, J. & Kupiainen, K. 2009: A simple concept for GIS-based estimation of population exposure to primary fine particles from vehicular traffic and domestic wood combustion. Boreal Env. Res. 14: 850–860.

We introduce a simple concept called Population-based Time-Average Inhalation (PTAI) intended to evaluate the relative effect of emission sources on population exposure. The PTAI is defined as the sum of the individual time-average inhalations at a particular distance from an air pollution source. We demonstrate this concept by evaluating the PTAI's for primary fine particulate matter emission from vehicular traffic and domestic wood combustion in Finland. The PTAI's for these two pollution categories were evaluated by combining the emission volume and location data with population location data and with the time-average inhalation per person. The PTAI for the vehicular traffic was significantly higher than that for domestic wood combustion. The result suggests that there is a difference in the exposure potency (per emission volume) between these two sources. The PTAI differences between domestic wood combustion sub-sectors imply that there is a significant difference also in exposure potency between different sub-sectors.

Derome, J., Saarsalmi, A. & Kukkola, M. 2009: Effects of nitrogen and sulphur "stress" treatment on soil acidity and growth response of a Scots pine stand. Boreal Env. Res. 14: 861–874.

In the early 1990s, revitalization fertilization experiments were established in Finland to investigate the possibilities of mitigating the effects of acidifying deposition. Annual treatments (ammonium sulphate) equivalent to 5-fold annual N and S deposition were also included during 1991–2000. The results presented here are from a replicated experiment in a Scots pine stand growing on a relatively infertile, coarse-textured soil in southern Finland. The N + S treatment strongly increased stand growth and litterfall production, indicating that the pines were still suffering from a serious shortage of nitrogen. There were no indications of nitrogen saturation, and no signs of nitrification. The serious leaching losses of Ca and Mg from the surface soil appeared to be primarily due to the addition of large amounts of sulphate. According to the results from the control plots, levels of acidifying N and S deposition in southern Finland had not been high enough to cause a threat to site fertility through soil acidification.

Liu, C. & Westman, C. J. 2009: Biomass in a Norway spruce–Scots pine forest: a comparison of estimation methods. Boreal Env. Res. 14: 875–888.

In order to compare different methods for estimating forest biomass, the dry mass of needles, branches, stem and roots at tree to stand levels was investigated in a mixed Norway spruce (Picea abies)–Scots pine (Pinus sylvestris) stand in southern Finland by means of direct weighing to allometric functions. The results revealed a substantial difference among estimations made with various methods. For instance, at the stand level, with the above-ground tree biomass (170.8 Mg ha^–1) estimated using partial harvesting methodas a baseline, tree biomass had a higher estimate (+10%) based on the dry mass of selected understorey, medium and dominant trees as the sample trees, but a lower estimate (–18%) by means of the allometric functions established based on the data gathered from nearby trees. At the individual tree level, the allometric functions overestimated dry weight of needles and branches by 20%–207% and 38%–263% for dominant pine and understorey spruce, respectively, but underestimated the stem weight. These results imply the utmost importance of considering the estimate error when calculating the tree biomass in a forest stand with an indirect approach.

Tang, L., Chen, D., Karlsson, P.-E., Gu, Y. & Ou, T. 2009: Synoptic circulation and its influence on spring and summer surface ozone concentrations in southern Sweden. Boreal Env. Res. 14: 889–902.

The influence of synoptic circulation patterns on surface ozone concentrations at three monitoring sites in southern Sweden was investigated for the spring (April–May) and summer (June–August) periods 1990–2005. Synoptic circulation patterns were classified into six groups based on the Lamb Weather Types (LWTs). The analyses show that the anticyclonic weather pattern (A) and the directional flows from southeast/east (SEE) and southwest/south (SWS) were most frequently associated with high ozone levels. It was estimated that 85.5%, 73.3% and 83.5% of the ozone episode days at Rörvik/Råö, Norra Kvill and Vavihill, respectively, were observed under these three circulation patterns. There were apparent spatial differences in the ozone concentrations during nighttime under condition A that were related to the high altitude position of Norra Kvill and Vavihill. The wind component indices u and v, and the total vorticity index [zeta] for each circulation pattern reflect the intensity of synoptic circulation and they all have an impact on the variation of surface ozone concentrations. The total vorticity index seems to be the key variable in terms of synoptic influence on surface ozone. A statistic model for the relations between synoptic circulation and ozone concentrations was established based on the frequencies and intensities of the six LWTs. It is able to explain 85% and 71% of the total variances in the observed mean ozone concentrations in spring and summer, respectively, over the period 1998–2005. The results demonstrated the strong impacts of synoptic circulations on surface ozone concentrations in southern Sweden.

Viljanen, M., Holopainen, A.-L., Rahkola-Sorsa, M., Avinsky, V., Ruuska, M., Leppänen, S., Rasmus, K. & Voutilainen, A. 2009: Temporal and spatial heterogeneity of pelagic plankton in Lake Pyhäselkä, Finland. Boreal Env. Res. 14: 903–913.

Phytoplankton and zooplankton constitute a cascade in which relationships and the behavioural strategies of organisms are involved in complex and dynamic ways on various temporal and spatial scales. In this study, we used a combination of short-interval sampling and spatial data analysis to investigate the distribution patterns of pelagic phyto- and zooplankton in Lake Pyhäselkä, a moderately large (263 km²) mesotrophic and humic lake in eastern Finland. The general goal of this work was to improve our understanding of pelagic plankton interactions and dynamics in large lakes. The specific objective was to reveal and verify the short-interval day-to-day temporal and spatial distribution patterns of pelagic plankton in 2005 in Lake Pyhäselkä. We can conclude from our results that phytoplankton and zooplankton exhibit seasonally and spatially heterogeneous distribution; the most obvious differences in phytoplankton and zooplankton abundance and biomass, and in the water quality parameters, were seasonal ones, and these were statistically highly significant; there were obvious small-scale, short-interval day-to-day variations in temperature and the horizontal and vertical distribution of phytoplankton and zooplankton; and the validity of a comparative inter-lake approach and long term monitoring of one lake would greatly depend on the question of whether the samples had been taken in the same month, at the same place and at comparable points in the vertical water column.