[A-HW28] Hydrology and Water Environment

[AHW28-03] Improving Water Quality Analysis Through Reflection Components Separation with Spectro-Polarimetric Measurements

*Ahmad Shaqeer Mohamed Thaheer¹, Yukihiro Takahashi¹ (1.Department of Cosmosciences, Faculty of Science, Hokkaido University)

Keywords:Polarization, Spectral Analysis, Contaminant, Chlorophyll, Suspended Sediment

Water bodies play a vital role in maintaining ecological balance, serving as habitats for diverse species and providing essential resources for human and environmental sustainability. However, increasing anthropogenic activities, including agricultural runoff and industrial waste, pose significant threats to water quality. Natural water systems exhibit significant variability due to the presence of organic and inorganic constituents. Traditional in-situ measurements often fail to capture the full complexity of these systems. Current remote sensing techniques, while promising, frequently neglect the impact of surface light components influenced by factors such as solar radiation and wave dynamics. Here, we demonstrate an innovative approach that utilizing spectral reflectance and polarization in the visible and near-infrared regions to improve water quality monitoring. By employing a line spectrometer equipped with a polarization filter, we conducted hyperspectral measurements under simulated wave conditions to assess the reflectance of chlorophyll (Chl) and suspended sediment (SS) contaminants at varying concentrations. To ensure consistent and accurate spectral analysis, normalization and continuum removal techniques were applied, enabling reliable comparisons across the spectra. The spectral angle mapper (SAM) algorithm was utilized to quantify the similarity between unpolarized components (in wave conditions) and total components (in calm conditions) of the reflectance spectra. Additionally, spectral entropy was employed to evaluate the effects of wave dynamics compared to calm water conditions. The results revealed that polarized components of contaminant reflectance, particularly at lower wavelengths, were minimal in calm water but increased significantly under wave conditions. Higher contaminant concentrations exhibited greater spectral similarity, characterized by reduced specular reflections and distinct features in the Degree of Linear Polarization (DoLP). These findings suggest that wave dynamics amplify polarized scattering, providing new insights into contaminant behavior under real-world conditions. This approach adds a crucial dimension to water quality monitoring by addressing the influence of surface variations, offering improved accuracy over traditional techniques.