Comparisons of acoustic and optical sensors for suspended sediment concentration measurements under non-homogeneous solutions

A set of acoustic and optical turbidity sensors was tested and compared in laboratory conditions under suspended sediment concentrations of the range 0.1-10 g/l. Various well sorted, mixed, as well as natural sediments (including clay, mud and sand) were used to cover a wide range of conditions, with emphasis on bimodal sediments. All optical sensors showed good performance with post-calibration RMS errors typically below 10% of the range and R² Pearson coefficients exceeding 95% (a=0.1). The Wetlabs produced the smallest RMS errors, followed by the Troll (overall average ∼4.3% and 5.8%, respectively), but the differences were not significant. OBS-3+ performance was also good (overall average RMS error ∼3%), while the Vector ADV produced measurements with average RMS errors ∼10.7% of the range for SSC up to 1 g/l, above which signal saturation is likely to occur.