Tracking a Surrogate Hazardous Agent (Rhodamine Dye) in a Coastal Ocean Environment Using In Situ Measurements and Concentration Estimates Derived from Drone Images

Abstract

New tools and technology are needed to track hazardous agents such as oil and red tides in our oceans. Rhodamine dye (a surrogate hazardous agent) was released into the Atlantic ocean in August 2018, and experiments were conducted to track the movement of the dye near the water surface within three hours following the release. A DrOne Water Sampling SystEm (DOWSE), consisting of a 3D-printed sampling device tethered to a drone, was used to collect 26 water samples at different locations around the dye plume. Rhodamine concentrations were measured from the drone water samples using a fluorometer and ranged from 1 to 93 ppb. Dye images were taken during the drone-sampling of surface water containing dye and at about 10 m above the sampling point. These images were post-processed to estimate dye concentrations across the sampling domain. A comparison of calibrated heat maps showed that the altitude images yielded dye distributions that were qualitatively similar to those from images taken near the ocean surface. Moreover, the association between red ratios and dye concentrations yielded trendlines explaining up to 67% of the variation. Drones may be used to detect, track and assist in mitigating hazardous agents in the future.

Drone-based water sampling and characterization of three freshwater harmful algal blooms in the United States

“…Correlations between pigment measurements (e.g., phycocyanin, PC and Chl-a) and cyanotoxins are difficult to predict, and studies thus far have focused on specific locations with historic water quality data that extends over several seasons (or years). Recently, drone imagery was used to detect and characterize rhodamine dye (a surrogate HAB) in the ocean (Filippi et al, 2021). This method could find use in freshwater lakes to pinpoint areas of sample collection that would be most useful in determining water quality metrics in lakes with a history of HABs.…”

“…Recent advances in uncrewed robotic systems offer one solution to many of these problems and have allowed researchers to conduct environmental research in aquatic systems at an unprecedented level of detail (Powers et al, 2018a;Powers et al 2018b;Powers et al, 2018c;Ribas-Ribas et al, 2019). Aerial and aquatic robots have been used to collect and characterize microorganisms (Powers et al, 2018b) and detect and track fluorescent dyes (surrogates for hazardous agents) in lakes (Powers et al, 2018a) and the ocean (Filippi et al, 2021). Ore et al (2015) developed a pump-driven drone water sampling platform for water quality measurements in a variety of aquatic environments.…”

“…Once the water sample was at the surface, a picture was taken from the drone showing the sampler in the water. Each drone image contains metadata that ultimately allows the precise location of the sampler in the lake to be determined (Filippi et al, 2021). This method was repeated for each sampling point along a 100-m transect (10-100 m) [e.g., transects as highlighted in (Benson et al, 2019)] from land or from an anchored boat until 10 samples were collected for each flight.…”

Remote Sensing of Visible Dye Concentrations During a Tracer Experiment on a Large, Turbid River

“…In a recent coastal application, Filippi et al. (2021) collected water samples from an sUAS and reported moderate correlations between the RWT concentrations in these samples and band ratios calculated from color images acquired from the sUAS at the same time.…”

“…Powers et al (2018) also used data from an sUAS to characterize diffusion of a pulse of fluorescein injected into a small inland reservoir. In a recent coastal application, Filippi et al (2021) collected water samples from an sUAS and reported moderate correlations between the RWT concentrations in these samples and band ratios calculated from color images acquired from the sUAS at the same time.…”