Single particle analysis of suspended matter in the Makasar Strait and Flores Sea with particular reference to tin-bearing particles

Suspended matter samples filtered from surface waters and two depth profile s from the Flores Sea and Makasar Strait were investigated by electron prob e X-ray microanalysis (EPXMA) and laser microprobe mass analysis (LAMMA). E PXMA yielded discrete morphological and chemical analysis of the major part icle types of suspended matter. Cluster analysis revealed that thirteen mai n particle types described the composition of suspended matter of the Flore s Sea and Makasar Strait. Silicates, aluminosilicates and Fe-oxyhydroxides were the predominant particle types. Suspended matter of the basins studied contained high levels of tin-bearing particles. On the basis of their comp osition, tin particles can be divided into three groups: (1) tin oxide/hydr oxides (cassiterite, romarchite, hydroromarchite); (2) iron-oxyhydroxides w ith adsorbed tin; and (3) mixed oxidation state tin hydroxysulphates. Only ultra-fine cassiterite particles enter the seawater in suspended state. Dis solved tin species entering the sea have three alternatives: (1) to be scav enged by Fe-oxyhydroxides; (2) to precipitate as tin oxide/hydroxides (roma rchite, hydroromarchite); (3) to precipitate as tin hydroxysulphates. The c onclusion is that dissolved and suspended tin originate from local sources in the land frame of the basins as well as from remote sources in the Indon esian Archipelago. Four different sectors of the waters studied have suspen ded matter with different composition: (1) the Mahakam River-Delta zone; (2 ) the open Flores Sea; (3) the landlocked Saleh Bay; (4) the Makasar Strait proper. The depth distribution of suspended particle types is mainly influ enced by: (1) the bottom nepheloid layer and calcite lysocline in the Flore s Sea; (2) the high bioproduction in the surface water layer and the vertic al distribution of organic matter in the Makasar Strait. (C) 1999 Elsevier Science B.V. All rights reserved.