The composition of suspended particulate matter from the Magela Creek system, northern Australia

Samples of suspended particulate matter were collected from the Magela Creek system during the 1982/83 wet season using a continuous flow centrifuge technique. Suspended particulate matter transported by the creek during flood events characteristically contained approximately 25% organic matter, 15% iron oxide, and the remainder consisting of varying amounts of clay (predominantly kaolinite with some chlorite), quartz and aluminium oxide. The enrichment of aluminium and iron found in these particulate samples has also been observed in other tropical systems. The major difference between the particulate matter collected from the creek and that collected from the slower moving water on the floodplain was the higher organic matter content (ca. 30–50%) in the latter samples, probably due to phytoplankton. The organic content of all samples was greater than measured in catchment soils or billabong sedimentsfrom this region. The suspended particulate matter was also enriched in trace metals compared with billabong sediments from the Magela system. Sequential chemical extraction of the samples indicated that a considerable proportion of the Mn, Cd, Cu, Pb and Zn were potentially biologically available.