Strong organic ligand in oceanic Particulate Matter (PM), as determined from amount of thorium adsorption onto PM in 0.1 M HCl, was measured for surface waters of mid-latitude region (ca. 32.5°S) in the South Pacific Ocean. The Particulate Organic Ligand (POL) concentrations in surface waters of the South Pacific, ranging from 2.6 to 13.3 nM, showed a longitudinal variation with low concentrations in the South Pacific subtropical gyre (180°-100°W) and high in the eastern South Pacific. The POL

more »

... oncentrations in the South Pacific surface waters increased with increasing nutrients (nitrate and phosphate) and chlorophyll concentration, which means that POL in surface waters is closely related to biological activity in the ocean; the high POL occurs in highly productivity region, whereas the low POL appears in the oligotrophic ocean. This is a first basin-scale measurement of POL in surface waters of the South Pacific. POL is a useful tool for better understanding of biological activity, particle dynamics and trace metal cycling in surface layer, if we have more detail knowledge on chemical and biogeochemical properties of POL, as do factors controlling spatial and temporal variability.