A Low-Cost Fluorometer Applied to the Gulf of Saint Lawrence Rhodamine Tracer Experiment

In order to increase the spatiotemporal resolution and accessibility of freshwater and marine data, low-cost in situ fluorometers are required. The devices must be robust, fully submersible, and sensitive in the 1 ppb–1 ppm range for compounds such as Rhodamine water tracer (RWT), a dye used in time of travel, and substance dispersal measurements. In this work, we introduce a deployment-ready, low-cost, small form-factor RWT fluorometer prototype based on the principle of lock-in amplification. Using measurements collected from remotely operated underwater vehicle (ROV) deployments during a dye-tracer experiment in the Gulf of Saint Lawrence, we compare its performance against that of a widely used commercial fluorometer. The results of the prototype’s calibration and deployment show competitive performance against commercial instruments, with a limit of detection (LOD) below 0.2 ppb and for a cost of U.S.
$\$ $
744.70, a fraction of the cost of relevant commercially available in situ fluorometers.