Engineering validation of a novel trace metal clean sampler for profiling and mobile deployment in pressure chamber tests

Amy V Mueller, Northeastern University, Civil & Env Engineering / Marine & Env Science, Boston, MA, United States, John Crusius, USGS at U Washington, Seattle, WA, United States and Fizzah Shaikh, Northeastern University, Boston, United States
The Portable Remote In-Situ Metal (PRISM) sampler is a modular sampler designed for affordability, minimum number of moving parts, and flexible deployment (7.5" outer diameter, for use on stationary, profiling, and mobile platforms). The PRISM sampler was developed to enable higher-frequency sampling for trace metals, both to improve understanding of trace metal cycling (e.g., Fe, Cu) in relation to daily-to-weekly scale ocean events as well as to begin to provide data for metals that can more readily be compared to data already being collected using sensors for physical, chemical, and meteorological parameters. Initial testing on profiling and mobile platforms took place in Puget Sound during summer 2017, and while preliminary work focused on assessing cleanliness with respect to Fe, this presentation will provide insights garnered with respect to Cu for samples collected in the same deployments. However, deployments were constrained by bathymetry (20-65m depth) and a lack of cameras on the equipment made it impossible to verify timing precisely during deployments. This presentation provides details of the associated lab-based testing that provides a more rigorous assessment of the behavior of the sampler (e.g., pumping rates, sample collection process, resiliency against leakage) as a function of depth, profiling rate, etc. Several series of tests were undertaken in a lab-situated pressure vessel capable of pressurization to 220psi (~135 m). Leakage was tested by pre-filling syringes (the sample-collection containers) with synthetic seawater followed by pressure cycling (simulating profiling). Pumping rates (number of seconds needed to collect 10mL water sample) and sample collection timing (with respect to schedule set in the program at deployment) were validated using a custom 360-degree imaging platform, necessary to record behavior of the cylindrical PRISM sampler, consisting of two GoPro cameras and a series of mirrors. Results to be presented include evaluation of system design with respect to pressure effects on pumping and leakage, as well as validation of the burn wire/melt wire triggering system, and cleanliness of sample collection (analyses of field samples) for Cu.