545-551 Lindell

L. Vättern is the second largest lake (approx. 130 x 30 km surface) in Sweden and one of the largest freshwater bodies (volume 74 km) in Europe (Fig. 1). The lake is of great national interest and is protected by law for recreation, national defense, natural and cultural interests, etc. L. Vättern is a unique ecosystem with glacial relicts as, e.g. the amphipods Monoporeia affinis, Gammaracanthus lacustris, Mysis relicta and some fish species as well. The Arctic char (Salvelinus salvelinus) is a key species for the lake and it is an important species in the commercial fishery. Due to the long theoretical hydraulic residence time (ca. 60 yrs) and a long history as a recipient of discharges from both cities and paper mills, L. Vättern is a suitable site for studies of long-term accumulation and degradation of persistent organic pollutants (POPs). The environmental monitoring program has been running regularly since 1966, but is primarily aimed to monitor nutrient status and related parameters. The program does not include regular measurements of persistent organic pollutants, such as PCBs, DDT and dioxins. However, due to the importance of the commercial and recreational fishery, pollutants like POPs and mercury have, on an irregular basis, been monitored since the late 1960s. The concentration of POPs in fish from L. Vättern has been high during the last 30 yrs and, therefore, human fish consumption, mainly char, is subjected to restrictions by the Swedish National Food Administration (SNFA). Persistent organic pollutants (POPs) are lipophilic and have a tendency to bioaccumulate in biota (1). Thus, it is recommended that women should not consume char from L. Vättern more than once a month, and during pregnancy and breast-feeding periods they should not consume char from the lake at all. These recommendations are the same as those for the consumption of Atlantic salmon (Salmo salar) from the Baltic Sea, which is also an ecosystem known to be highly contaminated with POPs (1). There are several sources of the POPs in L. Vättern. Historically, point sources and release from the technosphere were probably dominant. In recent years, more diffuse sources are more important. Mass-balance estimates of POPs are complicated because of the large lake surface compared to the whole drainage area (40%). This ratio makes the lake sensitive to atmospheric deposition of the substances as well as volatilization, as the water surface–air exchange is very difficult to quantify. Industrial production of PCBs began in 1929, although they had been used on a small scale even earlier. In the 1960s these substances were recorded in biota for the first time, although they had been noted earlier, but were difficult to identify (1). The use of PCBs was restricted by law in Sweden in 1972, which resulted in declining concentrations in biota in the country (2). Since 1995, it is also illegal to use PCBs in old applications. Today, discussions involve determinations of background levels as the persistent properties of PCBs result in long half-lives in the environment (2). PCBs were not spread in the environment on purpose, but reached the environment due to their excellent properties and use in various technical and industrial applications (Box 1). Monitoring of Persistent Organic Pollutants (POPs): Examples from Lake Vättern, Sweden Måns J. Lindell, Gudrun Bremle, Ola Broberg and Per Larsson