The Chemical and Aqueous Transport (CAT) Meter Program
	Michael Tryon and Kevin Brown Scripps Institution of Oceanography, UCSD

Significant quantities of fluids and dissolved geochemical components are expelled through sediments in ocean margin and sedimented ridge environments. Previous work has focused on the most actively flowing sites which represent a very small fraction of the surface area in these settings. The diffuse component of flow, while orders of magnitude lower in rate, may be greater in terms of total mass flux because of the greater areas involved. Direct quantification and comparison of the diffuse and focused components of fluid convection have been difficult, fundamentally limiting our ability to constrain the complete hydrologic system and geochemical fluxes in many environments. To address this need, we have developed a new type of benthic aqueous flux meter that is capable of measuring diffuse linear fluid flow through the sediment surface on the order of 0.1 mm/yr to >15 m/yr. The system measures fluid flow by injection of a chemical tracer at a known rate into the fluids venting out of or into a collection chamber situated on the sea bed. The dilution of the tracer is subsequently analyzed to obtain the flow rate. These meters are optimized for measurement of low to moderate flow rates covering a range from that associated with diffuse regional flow through that of moderately active cold seeps.