ANALYSIS AND TEMPORAL VARIATIONS OF TRACE-METALS IN PRECIPITATION AT AN ATLANTIC STATION

Weekly and half-monthly bulk samples have been collected over one year at an Atlantic station and routinely analysed for 0.08 M HNO3-leachab le trace metals Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn by direct electrothe rmal atomic absorption spectrometry. In the presence of sea salt, inte rference effects may lead to important erroneous metal concentrations if peak height measurements and direct calibration with aqueous standa rds are used. Interference effects are minimized (to about 5%) by usin g integrated absorbance measurements for sea salt solutions having C-N a < 100 mg/l and using standards prepared in the presence of sea salt (20 mg/l in Na). The variability of trace-metal determinations obtaine d for six bulk collectors for each sampling event shows that our entir e analytical protocol, sampling and analysis, permits to follow their temporal variations at a coastal station for weekly or half-monthly sa mpling periods. A high correlation is obtained for anthropogenic metal s Cd, Cu, Ni, Pb and Zn. For Cr, Fe and Mn, significant correlations w ith anthropogenic metals indicate both anthropogenic and crustal sourc es. No correlation with Na is observed. At this Atlantic station, trac e-metal concentrations and annual deposition densities are significant ly lower than at European stations around the North Sea which are more subject to industrial emissions.