The IAEA worldwide intercomparison exercises (1990-1997): determination oftrace elements in marine sediments and biological samples

Four major worldwide intercomparison exercises for the determination of tra ce elements in various environmental matrices acre completed by the IAEA Ma rine Environment Laboratory since 1990: SD-M-2/TM, deep sea marine sediment ; IAEA-350, tuna fish homogenate; IAEA-356, contaminated coastal sediment a nd IAEA-140, sea plant (Fucus sp.). These intercomparison exercises aim at enabling individual laboratories to monitor their performance. The results of these exercises allowed us to make an overall evaluation of the quality of data provided for environmental assessment and to identify the trends of analytical performance in the determination of trace elements over the yea rs. The number of participants in each exercise varied between 68 and 130, and permits statistical evaluation of the performance for a number of eleme nts. For each intercomparison exercise, the performance of the participant laboratories was assessed by comparing reported results with established re ference values calculating 'Z-scores'. The results show that for each sampl e matrix, the values reported by some laboratories were far from satisfacto ry in the earlier exercises, in particular for Cd, Cr and Pb. Nevertheless, over time, a general improvement of performance can clearly be seen for al l elements. Moreover, there was a noticeable increase in the number of labo ratories with good performance in the two most recent exercises, observed b oth for biological and for sediment matrices. However, the determination of trace elements such as Cd, Cr, Pb and Hg in low level environmental sample s still remains a major challenge to the analysts. For this reason and in o rder to assess the current performance of laboratories for low environmenta l levels of contaminants, the future intercomparison exercises will concent rate on low level sediment and fish samples. (C) 1999 Elsevier Science B.V. All rights reserved.