Towards a Universal Open-Source In-Situ Fluorometer: The PIXIE

Abstract

This dissertation is centered on the design and application of a low-cost, open-source, submersible in-situ fluorometer, dubbed the PIXIE, that makes a transformative step in submersible fluorometry by providing accessible, state-of-the-art performance at a minimal barrier to entry. There is a need for larger data volumes of key fluorometric variables for the protection of costal communities and for the study of large-scale oceanographic interventions, which accessible fluorometry benefits directly. In this work, three main contributions to the advancement of the field of submersible in-situ fluorometry are presented. First, an accessible, holistic model of fluorometry is developed from first principles. The model is combined with a review of the state of contemporary in-situ fluorometry to inform the engineering characteristics of future designs. Testing data from three sample fluorometers is analyzed to reveal insight into fundamental device performance. Second, the model, review, and analysis are used to construct the PIXIE. All aspects of the fluorometer’s design are covered thoroughly. The device is calibrated to reveal its competitive measurement performance, and then validated in a live deployment. All source materials for the PIXIE are openly released to the public. Finally, the PIXIE is evaluated for use with optode sensor technology to expand the range of detectable variables to pH, and eventually pO2 and pCO2. A prototype is developed as a universal sensor-foil characterizer. A characterized sensor foil is applied to the PIXIE and its capacity for pH measurement is examined. The results presented in this dissertation are applicable to small- and large-scale oceanographic and limnological research teams, to citizen scientists, and to all stakeholders who benefit from higher spatio-temporal data pulled from our planet’s waterways. The PIXIE has already initiated international collaboration. The PIXIE is a step towards a universal measurement platform for many of these important data. With its direct applicability to tracer studies conducted in support of marine Carbon Dioxide Removal through Ocean Alkalinity Enhancement, the open-source PIXIE fluorometer aims to make a transformative contribution to work that affects us on a global scale.