Distribution of Macro- and Micro-Components in the Water Column of the Antarctic Ross Sea and in Surface Antarctic Snow

Abstract

Sample of Antarctic Ross Sea water were collected during the 1990/91 Italian Antarctic expedition: near the coast (74°40′ S, 164°07′ E) both with and without pack ice above the water column, and in the open ocean (70°53′ S, 177°21′ E) at different depths. In addition to alkaline and alkaline-earth elements, Se(IV), total inorganic Se, V, Cd, Pb and Cu were determined along the water column depth.

In the open sea the concentrations of the macro components increased by ca, 3% from 0 to 500 m in depth and then decreased lightly (1%) for all these analytes from 500 to 1500 m. Both soluble selenium (IV) and total inorganic Se, increased with increasing depth whereas the concentration of V was fairly constant when normalized to the sodium concentration of V. The dilution effect due to the pack ice under the water column could no longer be measured at a depth of 25 m.

Surface snow samples collected during the same expedition at varying distances from the sea, showed that the ionic concentration ratios relating to sodium are from two to five times higher than in sea water for potassium, two to four times for calcium, six to ten for magnesium, about 10⁴ for lead and cadmium, and 10⁵ for copper. In particular, it was found that alkaline and alkaline-earth elements exhibited the highest concentrations at a station 10 Km from the sea (100 m a.s.l.) and the lowest ones at a station 60 Km from the sea (700 m a.s.l.). No precise correlation was generally found among the normalized concentrations of heavy metals at the various sampling stations. For instance, the highest concentrations of lead, cadmium and copper were found at the last station, they were about 2.5 or 9 times higher than in the former, according to whether absolute or relative (to sodium) concentrations were considered.

Key Words:

• Antarctica
• sea water
• snow
• metals