Thesis Defense - Alec Johnson

Apr 22 2021 9:00 am
Zoom Virtual Meeting

Development of an In-Situ Chemical Sampler for Aquatic Systems
Alec Johnson, Thesis Defense
Thursday, April 22nd at 9 a.m.
Via Zoom:  https://umontana.zoom.us/j/95470410896

This defense will outline an in-situ aquatic sampler, named the Deployable Underwater Chemical Sampler (DUCS). The DUCS uses a smart sampling method where an acid preservative is mixed with collected samples, and acidified samples are then stored within a long length of tubing. The preservative acts as a tracer to determine where samples start and stop, while simultaneously correcting for dilution factor using conductivity. Following deployment, samples from the DUCS storage are dispensed into a series of small vials and conductivity measurements for these vials are determined using a small volume conductivity probe. Individual sample locations within the small vials, along with the associated dilution factors, are determined from these conductivity measurements. Using this smart sampling approach, the DUCS can collect preserved samples at higher frequencies than other commercially available samplers, making this sampler ideal for high-frequency organic carbon sampling. The DUCS could also potentially be used for in situ sampling and preservation of other chemical species, such as trace metals. The high-frequency sampling capable by the DUCS will allow for better understanding of the variability of these important chemical species in aquatic systems. In addition to evaluating this sampler in-lab for organic carbon sampling, data from DUCS deployments in the Clark Fork River (CFR) near Missoula, MT will also be presented.