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Measurement of Particle Size Distribution in Turbid Solutions by Dynamic Light Scattering Microscopy
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Variability of relationship between the volume scattering function at 180° and the backscattering coefficient for
Applied Optics
|May 14, 2020
Summary
The key parameter for interpreting lidar signals, χp(π), is sensitive to particle shape and internal structure. Using a fixed value can lead to significant errors when analyzing lidar data from diverse waters.
Area of Science:
- Ocean Optics
- Remote Sensing
- Particle Characterization
Background:
- Accurate interpretation of lidar (light detection and ranging) signals for particle distribution relies on the parameter χp(π).
- This parameter links the particulate volume scattering function (VSF) at 180° (βp(π)) to the particulate backscattering coefficient (bbp).
- χp(π) has been understudied due to challenges in simultaneous field measurements of βp(π) and bbp.
Purpose of the Study:
- To re-examine χp(π) and its spectral dependence using in situ VSF measurements across various waters.
- To investigate the influence of particle shape and internal structure on the inversion of χp(π).
- To assess the impact of using fixed χp(π) values for lidar data interpretation.
Main Methods:
- In situ measurement of VSFs at high angular resolution in diverse aquatic environments.
- Inference of βp(π) using a validated VSF-inversion method.
- Testing inversion kernels based on homogeneous spheres, asymmetric hexahedra, and coated spheres to model particle phase functions.
Main Results:
- Reconstructed VSFs showed good agreement (<5% difference) with measured VSFs for scattering angles <170° across all tested kernels.
- Inferred βp(π) near 180° was strongly dependent on the inversion kernel, with sphere kernels capturing backscattering enhancement.
- χp(π) values derived from sphere kernels aligned with direct measurements, while dependence on particle shape and internal structure was observed.
Conclusions:
- χp(π) is sensitive to particle shape and internal structure, necessitating careful consideration for accurate lidar signal interpretation.
- Employing a single, fixed value for χp(π) across different water types can introduce significant errors in lidar data analysis.
- χp(π) exhibited minimal spectral dependence in the studied waters.
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