Estimation of benthic dissolved organic carbon flux from wetlands and N estuaries using a novel technique
PI: Aria Amirbahman, Ph.D., P.E.

Department of Civil and Environmental Engineering, UMaine

National need
Dissolved organic carbon (DOC), which typically originates from the breakdown of organic matter, is a water quality concern in estuarine environments, as DOC facilitates transport of metals and organics in sediments and creates toxic byproducts during drinking water treatment.  Benthic DOC flux, or the rate of exchange of DOC across the sediment-water interface (SWI), can vary with changing environmental conditions, including wetland restoration and rising sea levels.  Therefore, it is important to quantify flux of DOC across the SWI.

Program overview and objectives
Existing DOC flux measurement techniques, such as measurement from porewater extraction, are intrusive to the sediment environment and underestimate flux by only capturing certain flux contributions.  Therefore, methods have been developed at the University of Maine using a novel technique, called eddy correlation, to estimate benthic DOC flux.  The eddy-correlation technique, first developed for use in atmospheric sciences and later applied to aquatic flux measurement, is a non-intrusive, field-based method that relies on measurement of turbulent fluctuations of properties such as fluid velocity, contaminant concentration, and temperature.
Preliminary DOC fluxes obtained using eddy correlation were typically an order of magnitude higher than the fluxes calculated from porewater extraction, a technique that is thought to underestimate flux, as turbulent fluctuations dominate vertical transport in these aquatic systems.

Acoustic Doppler velocimeter (ADV) and chromophoric dissolved organic matter (CDOM) fluorometer deployed to collect data for eddy correlation measurements

Typical plot of cumulative flux calculated using the eddy correlation technique

Project plan
The approach in the project is to develop and demonstrate application of the eddy-correlation technique to quantify vertical flux of DOC in several natural settings, and to validate those measurements by conducting well-controlled laboratory experiments, where the benthic DOC flux may be determined independently.  In particular, we will apply the eddy-correlation technique in bottom types which are prevalent in wetlands and estuaries but do not lend themselves to traditional sampling techniques.

Contact Information
Aria Amirbahman, Ph.D., P.E.
Professor of Environmental Engineering
Department of Civil and Environmental Engineering
University of Maine, Orono, ME 04469
Tel: 207-581-1277
Fax: 207-581-3888
E-mail: aria@umit.maine.edu

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