Development of an In Situ Pore Water Sampler for Scientific Ocean Drilling

Sediment pore waters, which are waters that exist between sediment particles, serve as the foundation for many significant discoveries through scientific ocean drilling. Yet, the same technique used to extract pore waters employed 50-years ago remains today, even though known sampling artifacts exist. The proposed project will develop, test, and deliver a novel fluid sampler that will provide pristine in situ pore waters for a range of chemical, microbial, and dissolved gas analyses.

The novel sampler will utilize inert materials to preserve pristine fluids, account for sampling procedures that minimize artifacts, and be operational within the context of standard procedures on a scientific drilling vessel. In addition, the sampler will also provide new functionality, suitable for conducting manipulative experiments to, for example, assess microbial metabolic rate and function and collect fluids in sandy sediment.

This new capability represents one of the needed innovations that will provide new data types to characterize and understand a broad range of interdisciplinary-linked processes in deep-sea sediment. Elucidating such processes will help to achieve goals and objectives outlined in the 2050 Scientific Framework, a document that was developed by an international consortium of scientists for seafloor scientific drilling and was well received within the National Science Foundation.

The proposed in situ fluid sampler will take advantage of a small space within the cutting shoe of the Advanced Piston Corer (APC), which is a standard tool for recovering shallow (< several hundred meters) sediment. The proposed sampler will be able to collect up to 52 ml of fluid within 15 minutes after the APC is injected into the sediment. To achieve this rate of fluid collection we will test various components of the sampler (shear pins, trigger spring, piston spring, and frit) in the context of sediment composition and porosity in a laboratory setting.

Results from these tests will guide a 7-day (1 day of transit) coring operation to assess performance and to compare chemical results with those from Rhizon-recovered pore waters from a variety of natural sediment types. Additional modifications and/or laboratory tests will be conducted prior to the production of four samplers for use with the US-IODP scientific drilling program, thus expanding the capability of shipboard science.

The proposed sampler will support a new type of fluid collection that will improve our understanding of biogeochemical processes (e.g., eliminating the Ca and alkalinity artifact in carbonate-rich sediment), provide fluids to test the potential for two different microbial populations (free-floating and grain-attached), allow one to prime the sampler with biocide, amendment, or enrichment solutions for microbial studies, or collect fluids for dissolved gas analysis. These new capabilities will provide new data types that will be necessary to achieve the goals and objectives in the 2050 Scientific Framework, an international guide to scientific priorities that can be achieved with seafloor scientific drilling.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.