ASLO Aquatic Sciences 2005

Topical session TS48

organized by:

Ben Hodges, University of Texas at Austin, hodges@mail.utexas.edu;

Sveinn Palmarsson, University of California Davis, sopalmarsson@ucdavis.edu;

Jose Romero, University of Western Australia, romero@cwr.uwa.edu.au

Fate and Transport of Nutrients and Contaminants: Recent Advances

Understanding the bioavailability of nutrients and contaminants in the aquatic environment requires a cross-disciplinary view of the sources and sinks of these chemicals, how they are transported within the system, how different environmental conditions impact their biochemistry, and how they alter physiological characteristics within an ecosystem. Readily available commercial field instrumentation has resulted in the expansion of worldwide ability to characterize transport and mixing. This session will provide a forum for presentations that contribute, in a specific or interdisciplinary manner, to the understanding of fate and transport of nutrients and contaminants in rivers, lakes, and oceanic waters. Both empirical and modeling studies are encouraged.
For more information , contact Ben Hodges.

ASLO Aquatic Sciences 2005

February 20-25, 2005, Salt Lake City, Utah, USA

Conference web site:
http://aslo.org/meetings/slc2005/index.html

Form of contributions:
Abstracts of talks and poster presentations are published in the conference proceedings.

Tutorial Speaker: Carolyn Oldham, Centre for Water Research, University of Western Australia

Contaminant Fate and Transport – An Interdisciplinary Systems Approach

Over the past 50 years there has been pressure for detailed process understanding to allow prediction of contaminant fate and transport in both aquatic and terrestrial systems. The development of deterministic numerical models has focused a large body of field measurement on the understanding of small-scale processes. Yet the increased focus on small-scale processes has not necessarily improved our predictive capability. It is now time to implement an inter-disciplinary systems approach to aquatic sciences and in particular to define, describe and analyze the time and space scales of interactions between physical, chemical and biological processes. A systems approach will force an explicit focus on the spatial and temporal connectivity between processes across landscape components and ecosystems. I will review contaminant research over the past decade and then argue for a ‘top-down’ approach with an aim to develop the simplest possible model that explicitly focuses on connectivity, and that will allow good prediction of the ecosystem response to contamination. Such a working model will require iterative engagement between physical, chemical and biological limnologists as well as catchment scientists.

Invited Speaker: Diane McKnight, Institute for Arctic and Alpine Research, University of Colorado

Dissolved humic substances can act as electron acceptors and electron shuttlers across redox gradients in aquatic ecosystems. We studied changes in redox state of dissolved fulvic acid and other species in the hyporheic zone of an alpine stream with an adjacent wetland. We identified hyporheic locations with rapid exchange through chemical and isotopic characterization of water from wetland wells and by conducting a tracer experiment, which confirmed that there were high rates of exchange (a = 1e-3) between the main stream channel and a large storage zone (1e-9 m^2). Fluorescence spectra of dissolved fulvic acid changes with redox state and we analyzed excitation-emission matrices (EEMs) of stream and well samples using PARAFAC to determine redox trends in the hyporheic zone. Oxidized species of fulvic acid and inorganic nitrogen are more abundant in locations with rapid hyporheic zone exchange with the main channel than in other locations, whereas iron concentrations were lower. These results show that hyporheic exchange carries water containing reduced fulvic acid back to the main stream channel, and suggest that these processes influence nitrogen and metal transport.