Comparison of Inherent Optical Properties as Surrogate for Particulate Matter Concentration in Coastal Waters

Particulate matter concentration (PM, often referred to as total suspended solids [TSS]) is an important parameterin the evaluation of water quality. Several optical measurements used to provide an estimate of water turbidity havealso been used to estimate PM, among them light transmission, backscattering, and side-scattering. Here we analyzesuch measurements performed by the Alliance for Coastal Technologies (ACT) at various coastal locations to estab-lish whether a given optical method performs better than others for the estimation of PM. All the technologies werefound to perform well, predicting PM within less than 55% relative difference for 95% of samples (n= 85, four loca-tions). Backscattering performed best as a predictor of PM, predicting PM with less than 37% relative difference for95% of samples. The correlation coefficient (R) was between 0.96 and 0.98 for all methods with PM data rangingbetween 1.2 to 82.4 g m–3. In addition, co-located measurements of backscattering and attenuation improves PM pre-diction and provides compositional information about the suspended particles; when their ratio is high, the bulk par-ticulate matter is dominated by inorganic material while when low, dominated by organic materia