Ilus, E. 2007: The Chernobyl accident and the Baltic Sea. Boreal Env. Res. 12: 1–10.

The impact of the radioactive fallout caused by the accident at the Chernobyl NPP on the Baltic Sea is discussed in this paper. The fallout from Chernobyl was very unevenly distributed in the drainage area of the Baltic Sea; the Bothnian Sea and the eastern part of the Gulf of Finland received most of the deposition. This was reflected in the activity concentrations of the main fallout nuclides (especially ¹³⁷Cs) that have been found in the marine environment of the Baltic Sea since then. The maximum concentrations that were detected soon after the fallout decreased significantly in a short time, and the distribution pattern of the Chernobyl-derived ¹³⁷Cs has changed over the course of time as a consequence of river discharges, mixing of water masses, sea currents and sedimentation processes. Sea currents have transported caesium from the Gulf of Finland and the Gulf of Bothnia into the Baltic Proper and further out of the Baltic Sea into the North Sea. In addition, a considerable amount of ¹³⁷Cs has been bound in the seabed of the Baltic Sea. In general, the concentrations of man-made radionuclides in the sediments have been at or below the concentrations of naturally-occurring radionuclides, and are not expected to cause harmful effects on the wildlife in the Baltic Sea. The exposure of the population to radiation caused by the ingestion of Baltic Sea fish after the Chernobyl accident was considered to be low compared with the mean annual exposure of Finns to radiation or to the dose caused by natural radionuclides in the sea.

Vesterbacka, P. 2007: Natural radioactivity in drinking water in Finland. Boreal Env. Res. 12: 11–16.

The mean annual effective dose from natural radionuclides for users of drilled wells was estimated to be 0.41 mSv, for users of wells dug in the ground 0.05 mSv and for people using water from waterworks 0.02 mSv. The highest effective dose from drinking water was caused by ²²²Rn (Fig. 2) constituting 75% and 60% of the total effective dose caused by all natural radionuclides for drilled-well users for users of wells dug in the ground, respectively. ²¹⁰Po and ²¹⁰Pb contributed the most to the effective dose caused by the long-lived radionuclides. Contribution of the isotopes of radium (²²⁶Ra and ²²⁸Ra) to the total effective dose from drinking water was minor.

Saxén, R. L. 2007: ¹³⁷Cs in freshwater fish and lake water in Finland after the Chernobyl deposition. Boreal Env. Res. 12: 17–22.

The uneven deposition of ¹³⁷Cs from the Chernobyl accident caused a large variation in the activity concentrations of ¹³⁷Cs in Finnish lakes. The concentrations of ¹³⁷Cs in lake water had decreased by more than 90% until the end of 1986, and thereafter the decrease gradually slowed down. In 2002, activity concentrations of ¹³⁷Cs in lake waters varied from 4 to 330 Bq m^–3. The concentrations of ¹³⁷Cs in fish had been generally highest in 1987 or 1988 and decreased thereafter by on average about 70% until 2005. After the deposition, several environmental processes, such as the water flow, sedimentation and runoff, and other characteristics such as potassium concentration, other water chemical parameters and the water residence time of the lake, have changed the distribution of ¹³⁷Cs in the compartments of the aquatic environment. The results also show that the activity concentrations of ¹³⁷Cs decreased at various rates in different lakes; ¹³⁷Cs in fish decreased three times more rapidly in one lake compared to another lake. In 2000–2004, activity concentration of ¹³⁷Cs in fish ranged from 8 Bq kg^–1 to 7800 Bq kg^–1 f.w. (f.w. = fresh weight).

Kostiainen, E. 2007: ¹³⁷Cs in Finnish wild berries, mushrooms and game meat in 2000–2005. Boreal Env. Res. 12: 23–28.

Activity concentrations of ¹³⁷Cs in wild berries, mushrooms and game meat were measured in samples collected during 2000–2005 in areas with varying ¹³⁷Cs deposition levels in Finland. Depending on the ¹³⁷Cs deposition levels in the sampling areas, the areal-mean activity concentrations of ¹³⁷Cs were 10–230 Bq kg^–1 in wild berries, 20–240 Bq kg^–1 in moose meat and 10–3000 Bq kg^–1 in all mushroom species. Compared with the ¹³⁷Cs level of samples collected in 1986 in the corresponding areas, the reduction in the ¹³⁷Cs level was about one third for wild berries, equal to the rate of radioactive decay of ¹³⁷Cs. More reduction was observed in the activity concentrations of ¹³⁷Cs in moose meat, on average up to 50% since 1986. The aggregated transfer coefficients from soil to wild berries showed no change since 1986–1988, while there was about one third reduction in those from soil to game meat.

Puhakainen, M., Rahola, T., Heikkinen, T. & Illukka, E. 2007: ¹³⁴Cs and ¹³⁷Cs in lichen (Cladonia stellaris) in southern Finland. Boreal Env. Res. 12: 29–35.

The variation of the amounts of fallout radionuclides in reindeer lichen Cladonia stellaris (syn. Cladonia alpestris) and the underlying soil below the lichen was investigated in 1986–2004 at three locations in southern Finland. Samples from the lichen carpet were fractionated into three vertical layers and the distribution of radionuclides between the different fractions was investigated. The effective half-lives of ¹³⁷Cs in lichen were almost the same in all three layers and, as a whole, the effective half-life of lichen varied from 2.7 to 3.4 years.

Realo, K., Isakar, K., Lust, M. & Realo, E. 2007: Weekly variation of the ²¹⁰Pb air concentration in North Estonia. Boreal Env. Res. 12: 37–41.

We performed a gammaspectrometric analysis to determine the content of ²¹⁰Pb in aerosol filter samples collected weekly in Harku-Tallinn, North Estonia, in 2001–2005. Activity concentrations varied from 65 µBq m^–3 to 2020 µBq m^–3 with an arithmetic mean value of 366 µBq m^–3 and followed a log-normal distribution with a geometric mean value of 308 µBq m^–3 and dispersion factor of 0.52. The mean values were slightly higher than those expected at a location of comparable latitude and longitude. The analysis of monthly averaged concentrations revealed a dominant seasonal variation governed mainly by the origin of intruding air masses: high ²¹⁰Pb air concentrations in winter and low values in spring and summer. A multiple linear regression analysis confirms that significant correlations between the ²¹⁰Pb concentrations in the surface air and local meteorological parameters are observed only in winter.

Paatero, J., Kulmala, S., Jaakkola, T., SaxŽn, R. & Buyukay, M. 2007: Deposition of ¹²⁵Sb, ¹⁰⁶Ru, ¹⁴⁴Ce, ¹³⁴Cs and ¹³⁷Cs in Finland after the Chernobyl accident. Boreal Env. Res. 12: 43–54.

In this study the deposition characteristics of ¹²⁵Sb, ¹⁰⁶Ru, ¹⁴⁴Ce, ¹³⁴Cs and ¹³⁷Cs in Finland after the Chernobyl accident was investigated based on gamma spectrometric analysis of 97 lichen, peat and surface soil samples. The aim of this study was to determine the fallout pattern of ¹²⁵Sb, ¹⁰⁶Ru, ¹³⁴Cs, and ¹⁴⁴Ce in Finland, to verify the fallout pattern of ¹³⁷Cs reported in earlier works, and to obtain an estimate of the total amounts of these nuclides deposited in Finland. The highest deposition values of ¹⁴⁴Ce were found in a zone extending from southwestern Finland to Kuhmo area close to the Russian border. The deposition pattern of ¹⁴⁴Ce resembled the deposition patterns of refractory nuclides, such as ⁹⁵Zr and transuranium elements. The regional deposition of cesium isotopes 134 and 137 differed from that of ¹⁴⁴Ce owing to the different volatility properties of these nuclides. Our results confirm the earlier observations of high deposition values of ¹³⁷Cs in southwestern Finland, Varkaus–Kuopio region, Kuhmo region and Kotka–Kouvola region. A comparison of previous results to our results suggests an overestimated deposition in the Oulu region in this study due to the lack of samples in the region. The observed average ¹³⁴Cs to ¹³⁷Cs activity ratio, 0.527 ± 0.010 decay-corrected to 1 May 1986, is in agreement with earlier studies and corresponds to a burnup of 13 GWd tU^–1. Although ruthenium is a refractory element, the behaviour of ¹⁰³Ru and ¹⁰⁶Ru has been shown to resemble the behaviour of volatile elements. This has been explained by the formation of volatile ruthenium oxides. The deposition pattern of ¹²⁵Sb resembled those of cesium isotopes. This suggests that antimony behaved like volatile nuclides in the destroyed reactor. It was calculated that depending on the nuclide, 0.017%–1.5% of the reactor core inventory and 0.6%–13% of the atmospheric emissions were deposited in Finland. These percentages were proportional to the volatility of the nuclides.

Raunio, J. & Soininen, J. 2007: A practical and sensitive approach to large river periphyton monitoring: comparative performance of methods and taxonomic levels. Boreal Env. Res. 12: 55–63.

The reliability and sensitivity of two periphyton monitoring methods were assessed in the large boreal Kymi River. First, results from 11 years of monitoring of periphyton biomass on artificial substrates, expressed as chlorophyll a, were analysed. Second, in a one-year survey, the sensitivity of periphyton biomass was compared with the analysis of epilithic diatom community structure. Finally, diatom community analysis using three practical approaches based on different taxonomic resolutions was tested. The long-term monitoring results of periphyton biomass revealed significant differences among the sites and years. Although long-term results showed significant correlation in the annual nutrient concentrations and periphyton biomass, the diatom indices demonstrated a higher sensitivity to changes in water quality. Analysis of concordance showed that diatom community analysis based on generic level alone, or specifically combined with the identification of only the abundant species, could offer a practical and reliable biomonitoring tool for large rivers.

Tagesson, T. & Lindrot, A. 2007: High soil carbon efflux rates in several ecosystems in southern Sweden. Boreal Env. Res. 12: 65–80.

Soil C effluxes were measured at five forest stands with different vegetation and a meadow in southeastern Sweden (57¡5«N, 16¡7«E). Exponential regressions of soil respiration against air and soil temperatures were used to model soil respiration at forests stands. For the meadow, a light response curve with gross primary production (GPP) against PAR and a cubic regression with GPP against air temperature were used to model GPP. Soil water content limited soil respiration in all ecosystems but spruce where the limitation appeared only at high soil water content. In the forest ecosystems, the forest floor vegetation was scarce and its C uptake had no significant effect on soil C effluxes. Annual soil respiration in all sites was between 2.05 and 4.34 kg CO₂ m^–2 yr^–1, which is large as compared with that reported in many other studies. Annual GPP of meadow was between 1.81 and 1.99 kg CO₂ m^–2 yr^–1, which gives a NEE between 1.39 and 2.41 kg CO₂ m^–2 yr^–1, i.e. a significant loss of C.