Performance assessment of serial dilutions for the determination of backscattering properties in highly turbid waters

The ECO BB9, an instrument designed for characterizing the particulate backscattering coefficient (b(bp)) of waters in situ, saturates frequently in water with high concentrations of particles. These water types are of increasing interest in water optics research due to the complexity of their contents and gaps in the knowledge of their interactions with the light field. Through serial dilutions, the concentrations of particles can be brought into the instrument range and linear extrapolation can be used to yield a prediction of b(bp) for the original undiluted solution. The efficacy of this simple approach is explored here using natural and synthetic waters in a controlled laboratory setting. b(bp) is a key inherent optical property used in validating and calibrating water quality parameters commonly estimated by remote sensing inversion algorithms. For this reason, the synthetic waters were constructed to test the method across water types characteristic of colored dissolved organic matter, non-algal particulates, and phytoplankton. The dilution method was evaluated by assessment of dilution series accuracy, precision, and constancy of the backscattering spectral slope. It was found to be effective with all water types in this paper.