## 4 Concluding Remarks  
Our laboratory measurements combined with Mie scattering calculations for samples of standard polystyrene beads illustrate the value of such an approach for evaluating the calibration and performance of light scattering instruments. For the specific version of LISST-VSF instrument and data processing code used in our study, we determined the calibration correction functions for improved determinations of the particulate volume scattering function \(\beta_{p}(\psi)\) and the degree of linear polarization \(DoLP_{p}(\psi)\). The required correction was found to be particularly significant for \(\beta_{p}(\psi)\) (a correction factor of ~1.7 to 1.9). The improved determinations of \(\beta_{p}(\psi)\) and \(DoLP_{p}(\psi)\) were validated with measurements on independent samples, and also using another independently-calibrated light scattering instrument, DAWN-EOS. Although the correction functions developed in this study are applicable only to the specific version of LISST-VSF instrument and the data processing code used in this study, our results emphasize a general need for evaluating the performance of light scattering instruments and minimizing the associated uncertainties in quantitative determinations from measurements. The improved protocol for measurements of light scattering with our LISST-VSF instrument was applied to measurements taken on 17 natural seawater samples from coastal and offshore marine environments characterized by contrasting assemblages of suspended particles. The particulate volume scattering function, degree of linear polarization, and backscattering ratio were determined from LISST-VSF measurements. For our dataset, these light scattering properties exhibit significant variations related to a broad range of measured particle properties characterizing the organic vs. inorganic composition and size distribution of particulate assemblages. For example, we observed negative relational trends between the particulate backscattering ratio and the increasing proportions of organic particles or phytoplankton in the total particulate assemblage. These proportions were parameterized in terms of the measured ratio of particulate organic carbon (POC) or chlorophyll-_a_ (Chla) concentration to the total dry mass concentration of suspended particulate matter (SPM). The observed trends can be useful in the development of optical approaches for characterizing the composition of particulate assemblages. Our results also suggest a potential trend between the maximum degree of linear polarization of light scattered by particles and particle size metrics. Specifically, the decrease in the maximum degree of linear polarization observed at scattering angles close to 90\({}^{\text{o}}\) tends to be associated with particulate assemblages exhibiting a higher proportion of large-sized particles. Earlier theoretical studies have shown that changes in the angular shape and the maximum value of the degree of linear polarization depend on particle refractive index and size distribution [82, 83]; however, the experimental data of the degree of linear polarization of scattered light for natural marine  
Figure 13: Similar to Figure 12, but with optical quantities shown as a function of the particle size metrics (**a**,**c**) \(D_{V}^{90}\), representing the diameter corresponding to the 90\({}^{\text{th}}\) percentile of the particle volume distribution, and (**b**,**d**) \(\zeta\), the power law slope of the particle number distribution. particle assemblages are very scarce. Our results provide a contribution to filling this gap. This type of data can also be useful for improving an understanding of the polarization properties of marine light fields including polarization of water-leaving radiance and advancing related applications, including remote sensing applications [84; 85; 86; 87; 88; 89; 90].