Year of Award

2021

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Chemistry (Analytical/Environmental Option)

Department or School/College

Department of Chemistry and Biochemistry

Committee Chair

Michael DeGrandpre

Commitee Members

Michael DeGrandpre, Lu Hu, Ben Colman

Keywords

Dissolved Organic Carbon, Aquatic Sampler, Missoula Montana, High Frequency Sampling, Long Term Sampling

Subject Categories

Analytical Chemistry | Environmental Chemistry

Abstract

There has been a long-standing need to study Dissolved Organic Carbon (DOC) within aquatic systems. DOC is an important water quality parameter that provides insights into ecological and carbon cycle processes in aquatic systems. DOC is not easily studied due to traditional, labor-intensive sampling methods. Often, optical (e.g. fluorescence) proxy estimations for DOC are used instead of directly sampling for DOC. Using either low frequency measurements or proxy estimations for DOC can lead to inadequate understanding of the natural processes that control DOC in aquatic systems.

This thesis outlines a in-situ sampler that will be capable of collecting, preserving, and storing aquatic samples, with a special focus on Total Organic Carbon (TOC). In this initial phase of development, TOC is sampled instead of DOC due to issues encountered with in-line filtration. Employing a novel “smart sampling” technique that uses conductivity as a conservative tracer, this system collects and preserves the sample in real-time. The novel technique employed by the DUCS could be expanded to sample for other important aquatic species, and such the sampler has been tentatively named the Deployable Underwater Chemical Sampler (DUCS). The high frequency datasets that can be generated using the DUCS will be able to provide greater into ecological and carbon cycle processes.

Chapters in this thesis will primarily describe the design and performance of the DUCS for TOC sampling, as well as discuss possible future improvements. The performance of the DUCS both in and outside of laboratory settings is explored. A chapter describing initial experimental design for an in-situ UV-Persulfate based DOC sensor is also included.

There was an overall average DUCS accuracy error of ~25-30% when using the DUCS for TOC sampling versus collected QC samples during deployments in the Clark Fork River (CFR). The TOC sampling uncertainty of the DUCS for these initial deployments was shown to be close to compliance for standard method 5310 and USEPA method 415.3. This data, along with data collected during lab studies, provides evidence for the effectiveness of the prototype DUCS sampling system. With future improvements, this prototype could be improved into a commercially viable sampling system.

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