TANG

The highest value of Cd observed in the seaweed surveys surveys of the Tosen and Trondheim fjords was found at site 334. It is recommended that this value be confirmed by analysis of the duplicate sample and if it is confirmed, an investigation should be carried out to determine the source of the Cd. From preliminary estimates of the decrease of heavy metal concentration with distance from the mouth of the river entering the Osan arm, it is suggested that a uniform sample distance from the mouth may be taken equal to: Ds=aM1/2 where Ds is the sample distance, M is the river magnitude, and a is the constant connecting them. Preliminary values of (a) estimated from this study for maps of scales 1:500 000, and 1:50 000 are 446, 200, and 140 (meters) respectively.

A regional heavy-metal survey of the Trondheim (1:500 000) map sheet was carried out using seaweed as a sample medium. No values elevated above that explainable as regional background were observed for ash, Mo,Pb,Hg or As. Analyses were also performed for Ca,Na,and F but are not reported here. Significant variations in Zn,V,Cd,Co,Cu.Mn, and Fe were observed; elevated values usually being associated with the mouths of the major river systems suggesting an excess of these elements is being supplied by fresh water. Elevated values of Ni and V show an areal distribution dependent on the rock substrate while very high values of Zn od Cu appear to be derived from mine wastes along the Orkla river. No individual element seems to be diagnostic of incoming sea water. Recommendations are made for follow-up surveys of Ag and V in Halsafjord, V in Aafjorden, and U on Hitra. Although the initial impetus for this survey was for prospecting the region for metallic ore deposit, it would appear that, because of extensive mining in the past, the method is better suited for monitoring heavy-metal contamination, establishing regional backgrounds, and defining chemically distinct water masses within fjord systems.