Objective:

The objective of this project is to demonstrate a sediment friction-sound probe (SED-FSP) for direct, in-situ measurement of grain size at contaminated sediment and groundwater-surface water interaction (GSI) sites. Specific objectives include development of a commercial prototype friction-sound probe, verification of sensor performance in the laboratory, and field demonstration and verification at three Department of Defense sites.

Technology Description:

Friction-sound is a simple and robust technique for in-situ, screening-level measurement of grain size. Friction-sound is believed to be generated when phonons are produced by the breaking or excitation of atomic or molecular bonds as the probe moves over or through the sediment. Theory and previous empirical studies suggest that friction-sound intensity is linearly related to grain size and probe velocity. A prototype SED-FSP has been constructed and tested in the laboratory. In the prototype SED-FSP, the acoustic pickup was integrated into an existing Trident porewater probe that had been sealed to preclude damage to the microphone. The results confirmed that a Trident-based SED-FSP provides a sensitive measure of grain size and that the amplitude of the sound intensity can clearly delineate between sediments with mean diameters in the clay, silt, and sand size ranges. In the prototype embodiment to be demonstrated in this project, the SED-FSP will be integrated with the Trident Probe for GSI sites and a Sediment Profile Imaging (SPI) system for traditional contaminated sediment sites. The Trident Probe is a screening probe for identifying groundwater discharge zones. Its configuration will provide an effective platform for rapid in-situ screening of both contaminated sediment sites and GSI sites. The SPI system is a profiling camera system that provides a rapid, cost-effective method for optically mapping physical, chemical, and biological characteristics of the surface of the seafloor. The SPI platform provides another ideal deployment strategy to demonstrate the SED-FSP.

Expected Benefits:

Development of the capability to measure grain size in situ at contaminated sediment and GSI sites provides two significant benefits. First, cost savings are associated with the ability to quickly and easily map grain size distributions in the field. The cost savings stem from the reduced sampling time, sample handling, sample shipping, and sample analysis efforts. Rough estimates suggest that per sample costs, including field sampling and analysis, could be reduced by more than 50%. Second, the ability to obtain the data while in the field creates an opportunity for adaptive sampling in accordance with TRIAD principles, leading to more focused and thus less expensive characterization for both contaminated sediment and GSI sites. Because the Trident sampling platform has already been demonstrated and commercialized, the costs to integrate the friction-sound grain size sensor should be minimized. (Anticipated Project Completion - 2012) 

Principal Investigator:

Dr. Bart Chadwick
SPAWAR Systems Center, San Diego
Environmental Sciences Branch, Code 7175
53560 Hull Street
San Diego, CA 92152
Telephone: (619) 553-5333
Fax: (619) 553-3097
E-mail: bart.chadwick@navy.mil