In situ real-time optical sensing device for three-dimensional water chemistry surveillance

Abstract

Assessing the aquatic chemistry of water bodies through sample collection is labor- and time-intensive with limits on discrete spatial coverage that may not provide a detailed representation of the system. A practical approach is to develop in situ sensors deployed aboard autonomous underwater vehicles (AUVs) for three-dimensional water chemistry mapping. For this purpose, a compact optical instrument (LEDIF) measuring fluorescence, absorbance, and scattering to quantify contaminants and natural substances in water bodies is packaged inside a pressure hull and attached to a highly modular and flexible AUV (Small Team of Autonomous Robotic FISH (STARFISH)). LEDIF-STARFISH was deployed at a reservoir in Singapore for in situ real-time chlorophyll a and turbidity data collection. Locations of potential algal hot spots were observed, providing unprecedented insight into the plankton biomass distribution of the reservoir at different times. The results showcase the instrument's potential in tracking spatiotemporal variability of substances in large water bodies.

A Multi-Platform Optical Sensor for In Vivo and In Vitro Algae Classification

“…Ng et al developed and field tested a multi-platform optical sensing technology utilizing multi-excitation fluorescence, broadband absorbance, and scattering to observe both spatial pattern and temporal trend of contaminants and natural substances in the water [ 11 , 12 , 13 , 14 , 15 ]. This work extends and characterizes the technology for in vivo algae classification to provide a comprehensive spectrum of water quality information.…”

Interactive monitoring in reservoirs using NUSwan – preliminary field results

“…Fixed stations are capable of providing high-resolution temporal data in real-time, but they lack mobility. Although AUV and USV are competent in supporting general spatiotemporal surveys (Ellison & Slocum 2008;Dunbabin et al 2009;Brown et al 2011;Koay et al 2011;Ng et al 2015), they tend to be too expensive and logistically demanding to be used for daily operations. Hence, their deployment for water quality measurements are typically focused on ad-hoc studies that involve conducting multiple survey trips over carefully selected time intervals and locations (Ishikawa et al 2005;Zhang & Sukhatme 2007;Hemond et al 2008).…”