Using Polarization to Increase Contrast of Water OH Raman Scattering Relative to Fluorescence of Dissolved Organic Matter

Environmental fluorescence measurements sometimes use water Raman scattering as an internal standard to compensate for path length, lensing effects, and turbidity. Fluorescent dissolved organic matter (FDOM) in water may interfere strongly with the measurement of this reference. However, fluorescence in fluid solution is largely unpolarized, while the OH stretching Raman band of water is always strongly polarized. Using an environmental sample from Lake Wateree in South Carolina, USA, we demonstrate that judicious use of this polarization allows for a significant level of improvement in the contrast or visibility of the water Raman band relative to FDOM.