Lakes and Watercourses

Lakes and Watercourses Lakes and Watercourses

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Assessment of mercury in fish should be based on analysis of pike weighing 0.4 – 1.6 kg. In lakes with a surface area of up to 10 km 2 , at least five fish should be used; in larger lakes, at least ten fish. Concentrations in sediment (present concentrations) refer to the level 0 – 1 cm on accumulation bottoms (loss of ignition >10%, ds < 25%). Metals in aquatic moss refer to concentrations in annual growth. Moss growing locally as well as planted specimens can be used. Exposure should have lasted for at least three weeks in the latter case. Where possible, it is recommended that local background concentrations recorded upstream or in a nearby aquatic area be used to determine present regional background concentrations. This applies particularly to aquatic moss, about which little is known in relation to regional background concentrations. Natural concentrations in sediment should primarily be determined using local values obtained from deeper strata of sediment, which reflect pristine concentrations in the area. In the case of most metals, these concentrations are found in sediments some 15 – 30 cm deep. But in eutrophied waters (where sedimentation occurs rapidly), the 150-yearold sediment will be found much deeper down. Much older sedimentary strata must be analysed for lead, since the environmental load of this metal has been accumulating for much longer. When analysing sediment, it is very important that the quantity of organic matter measured as loss on ignition is approximately as great in the sediment to be compared. This is particularly important with Pb and Hg, since the concentration of these metals in particular is correlated to the concentration of organic matter in the sediment. References Alm, G., Bengtson, M., Borg, H., Göthberg, A., Johansson, K., Lindeström, L. & Lithner, G. (1998): Metaller (”Metals”). From: T. Wiederholm (Ed.). Bedömningsgrunder för miljökvalitet – Sjöar och vattendrag. Bakgrundsrapport 1 – Kemiska och fysikaliska parametrar (”Environmental Quality Criteria – Lakes and Watercourses. Background report 1 – Chemical and physical parameters”). Swedish EPA Report 4920. Canadian Council of Resource and Environmental Ministers (CCME) (1987): Canadian water quality guidelines. Ottawa, (updated in April 1991 and May 1996). Lithner, G. (1989): Bedömningsgrunder för sjöar och vattendrag. Bakgrundsrapport 2 – metaller (”Quality criteria for lakes and watercourses. Background report 2 – Metals”). Swedish EPA Report 3628. National Food Administration (1992): Statens livsmedelsverk kungörelse med allmänna råd om konsumtion av fisk (”National Food Administration Regulations on Consumption of Fish”), SLU FS 1991:25. – Vår Föda 44(4):173 – 177. 49

Swedish EPA (1993): Metals and the Environment – Status and Trends, Swedish EPA Report 4245. Norwegian EPA (1997): Klassifisering av miljøkvalitet i ferskvann. – Veiledning (”Classification of freshwater quality - Guidelines”) 97:04. 50

Swedish EPA (1993): Metals <strong>and</strong> the Environment – Status <strong>and</strong> Trends, Swedish<br />

EPA Report 4245.<br />

Norwegian EPA (1997): Klassifisering av miljøkvalitet i ferskvann. – Veiledning<br />

(”Classification of freshwater quality - Guidelines”) 97:04.<br />

50

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