Hussein, T, Mølgaard, B., Hannuniemi, H., Martikainen, J., Järvi, L., Wegner, T., Ripamonti, G., Weber, S., Vesala, T. & Hämeri, K. 2014: Fingerprints of the urban particle number size distribution in Helsinki, Finland: Local versus regional characteristics. Boreal Env. Res. 19: 1–20.
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Heino, J., Ilmonen, J. & Paasivirta, L. 2014: Continuous variation of macroinvertebrate communities along environmental gradients in northern streams. Boreal Env. Res. 19: 21–38.
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Isomaa, M., Kaitala, V. & Laakso, J. 2014: Precautionary management of Baltic Sea cod (Gadus morhua callarias) under different environmental noise and harvesting strategies. Boreal Env. Res. 19: 39–50.
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Salminen-Paatero, S., Paatero, J. & Jaakkola, T. 2014: ²⁴¹Pu and ²⁴¹Pu/^239+240Pu activity ratio in environmental samples from Finland as evaluated by the ingrowth of ²⁴¹Am. Boreal Env. Res. 19: 51–65.
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Pätynen, A., Elliott, J. A., Kiuru, P., Sarvala, J., Ventelä, A.-M. & Jones, R. I. 2014: Modelling the impact of higher temperature on the phytoplankton of a boreal lake. Boreal Env. Res. 19: 66–78.
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Hussein, T, Mølgaard, B., Hannuniemi, H., Martikainen, J., Järvi, L., Wegner, T., Ripamonti, G., Weber, S., Vesala, T. & Hämeri, K. 2014: Fingerprints of the urban particle number size distribution in Helsinki, Finland: Local versus regional characteristics. Boreal Env. Res. 19: 1–20.

Understanding the fingerprints of urban aerosols is very important in urban model development. Cluster analysis combined with visual classification, air mass back-trajectories, and local meteorology form a comprehensive analysis tool to understand the fingerprints of urban aerosol particles and relate them to their source origin as local or regional. Here we identified seven fingerprints of urban aerosols in Helsinki during 2006. The fingerprints of fresh emissions (Clusters 1–2) from local sources including traffic are characterized by a dominant nucleation mode (GMD < 25 nm and 62%–82% of the submicron particle number concentration). Cluster 3 is characterized by aged ultrafine particle modes with a dominant Aitken mode (diameter 25–100 nm). The fingerprint (Cluster 0) of New Particle Formation (NPF) events is characterized by a second nucleation mode (GMD < 10 nm and a fraction more than 65% of the submicron particle number concentration); the inclusion of particles with D_p < 7 nm in the analysis is important to identify this unique fingerprint. The fingerprints (Clusters 4–5) of aerosols originated via Short-Range or Long-Range Transport (SRT/LRT) from Russia; middle Europe and the Baltic Sea are characterized by dominant Aitken and accumulation modes (as high as 70% of the submicron particle number concentration). Cluster 6 emerged from a mixture between locally emitted aerosols and those originated via SRT/LRT with roughly 50% contribution of the nucleation mode in the submicron particle number concentration. While the data used in this analysis were for the year 2006 only, we foresee the fingerprints are generally valid for the Helsinki Metropolitan Area.

Heino, J., Ilmonen, J. & Paasivirta, L. 2014: Continuous variation of macroinvertebrate communities along environmental gradients in northern streams. Boreal Env. Res. 19: 21–38.

Our aim was to examine the nature of macroinvertebrate community variation across a set of streams in three drainage basins in Finland. We found that there were no clearly discrete community types, but rather macroinvertebrate communities varied continuously along environmental gradients. Local environmental factors and geographical location were strongly collinear and both were important in accounting for variation in macroinvertebrate community structure in the multivariate regression tree analysis and based on a combination of k-means clustering and discriminant analysis. We conclude (i) that geographical location and local environmental factors are strongly intertwined and both are associated with variation in macroinvertebrate communities across northern streams at the spatial scale of the three drainage basins studied; and (ii) that environmental assessment and conservation studies should not rely too much on delineating “community types”, but rather acknowledge the continuous variation of stream macroinvertebrate communities.

Isomaa, M., Kaitala, V. & Laakso, J. 2014: Precautionary management of Baltic Sea cod (Gadus morhua callarias) under different environmental noise and harvesting strategies. Boreal Env. Res. 19: 39–50.

Many cod stocks have decreased during the last decades due to heavy exploitation. One reason is the difficulty to fit complex population dynamics, assessment methods and economic interests together. Moreover, strong environmental fluctuations, such as climate change, affect the success of population management. We consider precautionary harvest strategies in the management of Baltic cod (Gadus morhua callarias). We address the following questions: How does the frequency structure in environmental noise affect cod abundance under alternative harvesting strategies? What are the possibilities and limits for precautionary management of Baltic cod? We compare proportional and two threshold harvest strategies. The proportional strategy creates more stable economy while the threshold strategies produce higher sustainable yield and spawning stock biomass, although annual catch may vary substantially.

Salminen-Paatero, S., Paatero, J. & Jaakkola, T. 2014: ²⁴¹Pu and ²⁴¹Pu/^239+240Pu activity ratio in environmental samples from Finland as evaluated by the ingrowth of ²⁴¹Am. Boreal Env. Res. 19: 51–65.

The activity concentrations of ²⁴¹Pu and the ²⁴¹Pu/^239+240Pu activity ratios were determined from environmental samples to complete the study of transuranium nuclide distribution in environment in Finland. The activity of ²⁴¹Pu was determined by measuring the activity of its decay product, ²⁴¹Am, using α-spectrometry. The activity concentrations of ²⁴¹Pu in lichens from 1967–1976 were from 2.3 to 93 mBq g^–1 (in the sampling year) and from < 0.7 to 686 mBq g^–1 in lichen, peat, and grass samples from 1986 (on 1 May 1986). The ²⁴¹Pu/^239+240Pu activity ratios for the corresponding samples were from 4.1 to 167. The comparison of the ²⁴¹Pu results obtained in the present study and those from earlier analyzes (liquid scintillation counting) indicated a fairly good agreement. Regression analysis indicated that the activity concentrations of mainly Chernobyl-derived nuclides ²³⁸Pu, ²⁴¹Pu, and ²⁴²Cm correlated significantly with each other in the samples of 1986, the r² values being 0.89 and 0.67 for ²⁴¹Pu/^239+240Pu vs. ²³⁸Pu/^239+240Pu and ²⁴²Cm/^239+240Pu vs. ²⁴¹Pu/^239+240Pu, respectively.

Pätynen, A., Elliott, J. A., Kiuru, P., Sarvala, J., Ventelä, A.-M. & Jones, R. I. 2014: Modelling the impact of higher temperature on the phytoplankton of a boreal lake. Boreal Env. Res. 19: 66–78.

We linked the models PROTECH and MyLake to test potential impacts of climate-change-induced warming on the phytoplankton community of Pyhäjärvi, a lake in southwest Finland. First, we calibrated the models for the present conditions, which revealed an apparent high significance of internal nutrient loading for Pyhäjärvi. We then estimated the effect of two climate change scenarios on lake water temperatures and ice cover duration with MyLake. Finally, we used those outputs to drive PROTECH to predict the resultant phytoplankton community. It was evident that cyanobacteria will grow significantly better in warmer water, especially in the summer. Even if phosphorus and nitrogen loads to the lake remain the same and there is little change in the total chlorophyll a concentrations, a higher proportion of the phytoplankton community could be dominated by cyanobacteria. The model outputs provided no clear evidence that earlier ice break would advance the timing of the diatom spring bloom.