Inggard Arne Blakar

Radiocaesium in the sediments of Øvre Heimdalsvatn, a Norwegian subalpine lake

Abstract Lake sediment cores and samples of stream sediments from the catchment of Ovre Heimdalsvatn have been collected. The lake sediments exhibit apparently unsystematic spatial distribution of radiocaesium. This is ascribed to irregular bathygraphy. However, the radiocaesium concentration increased with increasing percentage of organic matter, water content, and with distance from the main inlet. There was no correlation with lake depth. Stream sediments were scarce because of torrential conditions but those present had activities in line with the lake sediments. Therefore they constitute a small potential for further supply of radiocaesium to the lake. Measurements of export from the catchment and retention in the lake show that the total radiocaesium activity in the sediments may remain unchanged or even increase during the years to come.

Chernobyl cesium in the sediments of lake Høysjøen, Central Norway

Abstract The distribution of radiocesium in the sediments of Lake Hoysjoen was analysed 18 months after the Chernobyl fallout event. The concentration in the sediment was similar to concentrations in surrounding terrestrial soils. Local accumulation in a riverine plume is explained by surface runoff from frozen wetland when the snow in the drainage area melted. Most of the radiocesium in the lake was bound in the upper centimetre of sediment.

Decline of acid rain enhances mercury concentrations in fish.

M efforts have been made to reduce sulfur emissions in Europe. Acid rain pollution in Norway has diminished substantially, thanks to the 1979 Geneva Convention on Longrange Transboundary Air Pollution, which was implemented starting in 1983. Parallel with the reduction in acid rain, atmospheric concentrations and deposition of mercury (Hg) have also been reduced. Here, we show that reduced acid rain may have increased dissolved organic carbon in runoff, and enhanced transport of mercury from catchments, and increased in-lake Hg methylation. Together, these enhanced processes result in higher concentrations of methymercury in fish. Mercury pollution in Norway mainly originates from distant sources in other European countries. Similar to acid rain, the long-range atmospheric transport of Hg has declined significantly during the past decades. It was therefore unexpected when a recent nationwide survey showed strong increased Hg concentrations in brown trout (Salmo trutta) and European perch (Perca f luviatilis) in a representative set of lakes in southern Norway. We selected two of these lakes for further case studies based on the availability of historic lake chemistry data. The selection includes the lake with the highest Hgincrease in perch as well as one with a slight decline. The greatest health threat to human consumers comes from methyl-mercury (MeHg), a potent neurotoxin which is easily incorporated into living tissues. The methylation process is a key to the understanding of the potential danger posed by environmental Hg. Environmental Hg is methylated predominantly by naturally occurring bacteria known as sulfatereducing bacteria. The process occurs in saturated soils, anoxic lake waters, and in anoxic sediments, although the factors that control the methylation process are not fully understood. In October 2010 we sampled and analyzed modern sediments from two lakes in Norway (Figure 1).

On the chemical water quality in Høylandet, a reference area for acidification research

Chemical and physical water quality parameters havebeen analyzed in a synoptic study of 101 lakes and103 rivers and streams in Høylandet, a coastalcatchment in Central Norway. The area is sparselypopulated and most sites were unaffected by localpollution. Cambro-Silurian sedimentary rocks,porphyric granites and migmatitic gneisses arerepresented within the area and gave variableconcentrations of dissolved salts in surface water.Conductivity varied from 0.6 to 20 mS m-1 and pHfrom 5.0 to 7.6. Salt from sea spray dominated indilute water in more elevated parts of the catchmentwhile chemical weathering products were dominant inlower. The concentrations of all major ions and pHdecreased with increasing elevation. Non marinesulfate occurred in moderate concentrations. pHvalues less than 5.5 were rare and the area as a wholedid not seem to be subject to acidification.

A flexible gravity corer based on a plastic funnel closing principle

A highly flexible and efficient gravity corer, easy to construct from inexpensive and readily available material, is described. Barrels of various length can be swiftly interchanged according to requirements in the field. Hollow weights can easily be adjusted to the most appropriate height of the barrel. The simple but reliable closing valve (constructed of two plastic funnels) can be adapted to other types of gravity corers as well. Several useful modifications of the corer are discussed.

TOC concentrations in Norwegian lakes: The effect of sea-salts and anthropogenic acid components

Concentrations of organic matter have increased in several lakes on the northern hemisphere since the mid 1970s. This is an important feature, since organic matter is an essential constituent for a range of biological, chemical and physical processes in water bodies. There have been several explanations for this increase, including climate change issues. There has however been no uniform increase o f TOC concentrations in lakes (similar situation in several countries on the northern hemisphere; i.e. EvANS et al. 2006, RouLET et al. 2006, SKJELKVÂLE et al. 2001). Changes in ionic strength in precipitation is mainly been controlled by natural sea-salt episodes and anthropogenic acid rain components, and the ionic strength has declined significantly in precipitation over the past decades, mainly due to the decline in sulphate emission from anthropogenic sources. Since the solubility of organic matter is reduced with increased ionic strength (e.g. TIPPING & HURLEY 1988), we have looked at the effect of changes in ionic strength in precipitation, and hence also in catchment surface waters, in Norwegian lakes. We have also looked at the importance of catchment buffer capacity, since pH might control the solubility o f soi l organic matter (i. e. DE WIT et al. 200 l). Our hypothesis has been that lakes with low buffer capacity, and in where sulphate has been a major inorganic constituent, have been the ones with the most pronounced percentage increase in TOC concentrations. Other types of lakes, either with different chemical composition or with some buffer capacity, were thought to have been less affected by the decline in anthropogenic acid components in precipitation.