Report on intercalibration analyses in ICES North Sea and North Atlantic baseline studies

Following several proposals that baseline studies of pollutants in the marine environment should be established (see ICES, 1974), ICES set up a Working Group in 1971 with the responsibility of organising and implementing an International Study of the Pollution of the North Sea. Earlier ad hoc meetings in 1971 had planned a baseline survey of pollutant levels in food fish, and an associated intercalibration exercise to compare the analyses of heavy metal and organochlorine residues in two specially-prepared samples representative of the types of biological materials examined in the survey. 

The results of this first international study were re ported in 1973 (ICES, 1974), following w.hich the Working Group recommended that monitoring should continue at a national level, but that further intercalibration of analytical procedures was essential. A second intercalibration of heavy metal analyses was therefore developed towards the end of 1973, although it was not possible to find a satisfactory matrix oil for a further organochlorine intercalibration sample. The countries which analysed the second heavy metal reference sample were those which had examined the first sample and the results of this second intercalibration were reported to ICES in 1975 (Topping, 1975). In January 1975 the Working Group was replaced by a new Group* which planned a further baseline survey of heavy metals and organochlorines in fish and shellfish in the North Atlantic and North Sea, and a further intercalibration exercise for both types of residues was recommended. The results of this exercise were reported in ICES(1977b). 

This report presents, statistically analyses, and discusses the results obtained from all of the intercalibration programmes. As the samples used and the analytical techniques involved in the determination of the two types of residues are quite unrelated, the first  section of the report deals with the trace metal analyses and the following sectionwith those for organochlorine residues.