Manganese, cerium and iron in the Sulu, Celebes and Philippine Seas

Abstract

This study was undertaken to investigate trace metals in southeast Asian seas that have different hydrographic settings: the Philippine, the Celebes, and the Sulu seas. Results reveal characteristics of dissolved and leachable manganese, dissolved cerium, and leachable iron in the water column. Remarkable increases of Mn, Ce, and Fe exist at the bottom layer of the water column in the Celebes Sea. The Ce/Mn molar ratios in the bottom waters of the Celebes Sea are identical to those in the porewaters of the underlying sediment. Both Ce and Mn show similar geochemical cycles in these deep waters of the Celebes Sea. In the Sulu Sea's deep waters, the leachable particulate fractions are dominant for Fe and Mn. The residence time of Fe in the Sulu Sea is estimated as 12 years. This residence time estimate is very similar to the particle residence time in the water column, implying that resuspension of sediment-derived particles affects leachable Fe distributions in the Sulu Sea.