HR: 1340h
AN: B23B-1050    [Abstracts]
TI: Geochemical Controls on the Mobility of Lead and Silver in Tropical Floodplain Sediments.
AU: * Watson, E A
EM: Elizabeth.Watson@csiro.au
AF: CSIRO Energy Technology, Private Mail Bag 7, Bangor, NSW 2234 Australia
AU: * Watson, E A
EM: Elizabeth.Watson@csiro.au
AF: Department of Physical Geography, Macquarie University, Macquarie University, North Ryde, NSW 2109 Australia
AU: Apte, S C
EM: Simon.Apte@csiro.au
AF: CSIRO Energy Technology, Private Mail Bag 7, Bangor, NSW 2234 Australia
AU: Dietrich, W E
EM: bill@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California, University of California, Berkeley, CA 94720-4767 United States
AU: Taylor, M P
EM: mtaylor@els.mq.edu.au
AF: Department of Physical Geography, Macquarie University, Macquarie University, North Ryde, NSW 2109 Australia
AB: The Strickland River, Papua New Guinea, which is the dominant drainage to the Fly River delta, receives inputs of mine tailings and waste rock from the Porgera gold mine, which is situated at an elevation of 2,500 meters in the upper catchment of the river system. While the contribution to the overall sediment load of the river is small, the mine derived sediments contain elevated concentrations of particulate silver and lead. The vertical core profiles of these elements were used as part of collaborative investigation among an NSF sponsored Margins Source to Sink research group, University of Papua New Guinea researchers, Porgera Joint Venture (PNG), CSIRO (Australia) and Macquarie University (Australia), to map the extent and rate of overbank deposition along the Strickland River. A key question is what proportion of the rivers sediment load is deposited on the lowland floodplain before the river joins the Fly River. An important property of any suitable particulate tracer is its low mobility following deposition. The aim of this study was to investigate the geochemical factors that may affect post-depositional mobility of lead and silver in floodplain sediments. Laboratory modelling studies were conducted to examine the effects of key parameters such as pH, dissolved organic carbon and redox changes resulting from wet/dry cycling of sediments during flooding and drying events. The solid phase speciation of silver and lead in floodplain sediments was also assessed by measurement of acid volatile sulphide concentrations and application of acid leaching procedures. A conceptual model of the geochemical processes affecting particulate silver and lead cycling in floodplain sediments will be presented.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0420 Biomolecular and chemical tracers
DE: 0461 Metals
DE: 0489 Trace element cycling (4875)
DE: 1030 Geochemical cycles (0330)
SC: Biogeosciences [B]
MN: Fall Meeting 2005