There is an increasing demand for quantitatively predictive (prognostic) models for describing the transport, fate, and bioavailability of elements in estuarine systems.  It is safe to say, however, that these models do not yet exist at the accuracy level required for environmental risk assessment.

Estuaries exhibit a tight coupling of chemistry, biology, and physics within and between the sediments and the water column, and there are several limitations which prevent us from developing comprehensive prognostic models, including:

• Many of the fundamental processes are still not fully understood.
• There is a weak understanding of elemental fluxes across dynamic sediment water interfaces (SWIs).
• Data from laboratory experiments do not directly "scale-up" to the real world.
• The non-linear interrelationships between processes can not be fully tested with current laboratory techniques.
• There is a prohibitive expense in the collection of sufficient spatial and temporal data in the field.

	and
diagnostic modeling		laboratory methodologies

The RALF project studies estuarine physics and biogeochemistry through the coupled use of :

• Biogeochemical Rotating Annular Flume (RALF)
• Allows for the study of dynamic sediment-water systems in the presence of a controlled 3-dimensional  flow field.
• Provides some degree of realtime or quasi-realtime data collection for physical, chemical, and biological parameters.
• Diagnostic Modeling (Virtual RALF)
• Fully 3-D model of flow-field and transport.
• Couples sediment diagenesis to surficial transport and transformations