In the ocean, typical concentrations of suspended particulates are between 10 and 200 mg/liter. Light-scattering nephelometers have been used for over 15 years to infer concentration and particulate perturbations. The nephelometers are sensitive to about particle concentration of 1 to 2 mg/liter. These particle concentrations can also be remotely sensed by ocean penetrating lidar. The particulate concentrations relate to the turbidity of the water, increasing the backscattering and attenuation of incident laser radiation; the attenuation is usually characterized by K, the diffuse attenuation coefficient. By appropriate processing of the lidar return waveforms, we can remotely infer the K, and thus the particulate concentrations - to a few mg/liter.
Richard F. Lutomirski,
"Lidar remote sensing of ocean waters", Proc. SPIE 2222, Atmospheric Propagation and Remote Sensing III, (29 June 1994); doi: 10.1117/12.177986; https://doi.org/10.1117/12.177986