Formaldehyde determination in seawater. Preliminary application to coastal samples at Terra Nova Bay (Antarctica)

A sensitive spectro. uorimetric-FIA (flow injection analysis) method for formaldehyde ( HCHO) determination was improved with the aim of analysing seawater samples. The fluorescence emission versus HCHO concentration shows a linear pattern from sub mu g L-1 to about 1000 mg L-1. The reproducibility at 15 ppb level is about 2%. Interferences from other aldehydes were checked; only glyoxal shows a significative interference, but only when its concentration is about 6000 times higher than that of formaldehyde. Superficial ( microlayer, just sub-pack or sea-ice free sea surface) and deep ( along the water column, sub-pack or in sea-ice free areas) seawater samples were collected near the coast at Terra Nova Bay ( Ross Sea, Antarctica) during the 1998/1999 and 2001/2002 Italian Antarctic Expedition. We report here the preliminary results of the spectrofluorimetric-FIA determination of the HCHO content. The mean seawater superficial formaldehyde concentration was 15 mg L-1; the concentration along the water column ranged between 4.5 to over 40 mg L-1 ( 20 mg L-1 mean concentration), usually with a maximum value for the 30 m depth, corresponding to a fluorescence maximum. The sampling was repeated 7 times in the austral summer in order to evaluate seasonal changes in the formaldehyde concentration/seawater depth profiles. The results show changes in the formaldehyde concentration at different depths.