The Geochemistry of River Particulate Matter from High-Standing Oceanic Islands (EPSCoR)

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9725543 Lyons Recent sediment flux work by Milliman and Syvitski (1992) suggest that rivers draining high-standing oceanic islands between Australia and Asia may contribute 50% of the total sediment flux to the oceans. This material is likely to be transferred directly into the deep ocean due, in part, to the narrow coastal-shelf areas associated with the active margins surrounding these islands. If this is true, terrestrial geochemical inputs to the ocean, and, hence, balances based on sediment measurements from larger river systems may be in error. We have collected and analyzed riverine sediments from four river systems in New Zealand. Our data indicate that these river sediments are depleted in Ba, Co, Cu, Hg, Mo, Ni, Zn and Pb and enriched in Sr, relative to marine clays. Shele-normalized REE patterns show intermediate REE enrichments with positive Eu anomalies. Our preliminary results indicate that these New Zealand sediments have different geochemical signatures than marine clastic sediments. During the three years of support for the research, the PIs plan to collect 200 to 300 riverine particulate matter (RPM) samples from streams and rivers in New Zealand. These samples will be analyzed, using state-of-the-art techniques in order to establish if the RPM geochemical flux to the oceans from these high-standing islands are different than from the major riverine flux established by Martin and Meybeck (1979). If they are, new flux calculations will be undertaken in order to better quantify the importance of RPM on marine geochemistry. In addition, samples will be collected from watersheds of similar geology and climate but of different area and sediment yield in order to evaluate the importance of storage on the RPM geochemistry. In Year 2, samples from watersheds of differing geology but similar climate will be compared in order to establish the linkage between bedrock types and RPM chemistry. All this work will be done in close cooperation with colleagues at the National Institute for Water and Atmospheric Research Ltd. in Christchurch, New Zealand.