Reflection Spectra Coupling Analysis and Polarized Modeling of Optically Active Particles in Lakes

Abstract

The coupling between optically active substances of algae particles and inorganic suspended solids of water makes the characteristics of reflection spectra of water complex and changeable. This makes modeling and inversion of polarization remote sensing in class II water difficult. In our study, considering the influence of the mixing ratio of algae particles and inorganic suspended solids, the sensor incidence angle, and the solar zenith angle on the polarization reflection spectrum, we analyzed the coupling characteristics of the polarized bidirectional reflectance of particulate matter through control experiments of mixed components of water particles in the laboratory. With Chaohu Lake in China as an example, the polarized reflectance coupling characteristics of water particles was investigated by the water-leaving radiation. The results showed that in the characteristic bands of 570, 675, and 705 nm, the degree of linear polarization (DOLP) was sensitive to the water-leaving radiation of the particles rather than to the reflectance. With the variation of observation angle, the reflection spectra were strongly interfered with by solar flare when the sensor zenith angle was close to 50° on the meridian plane with an azimuth angle of 180°, but DOLP was less affected, while also having a low correlation in the high concentration region. Combined with the coupling characteristics of particles at 675 and 705 nm, the model of DOLP ratio was established by partial least squares regression (PLSR) with a determination coefficient (R2) of 0.91, root mean square error (RMSE) 0.035, and a verification accuracy of 0.959. This shows that the model has better prediction ability for the coupling characteristics of water particles by the polarization reflection spectra and provides good support for mixed spectral unmixing of class II water.

Crystallinity Control and Strain Release in Wide-Bandgap Perovskite Film via Seed-Induced Growth for Efficient Photovoltaics

“…The results indicated that a small amount of antisolvent could be well dispersed in the perovskite precursor. , However, particle size in dynamic light scattering (DLS) measurement (Figure a) gradually grew from 200–300 nm (control precursor) to 300–2000 nm (precursor with IPA additive). The precursors with EA and CB additives also showed larger particle sizes than the control, which indicates the growth of particle under different antisolvent additives. , In addition, there is an observable peak at about 1 nm in Figure a, which indicates that there are smaller clusters in the precursor, and the formation of smaller clusters may be caused by the distribution of residual antisolvents and the dissolution of larger colloidal particles. − The ultraviolet–visible (UV–vis) reflectance spectrum of the antisolvent-added precursor was higher than that of the reference precursor (Figure b), indicating the presence of perovskite seeds increased light reflection; the higher the seed concentration, the larger the volume and the stronger the reflectivity. , The seeds act as nucleation sites in the film formation process. The residual antisolvent promotes solvent volatilization, accelerating the formation of supersaturated state in the initial spin coating process. , …”

“…29−31 The ultraviolet−visible (UV−vis) reflectance spectrum of the antisolvent-added precursor was higher than that of the reference precursor (Figure 1b), indicating the presence of perovskite seeds increased light reflection; the higher the seed concentration, the larger the volume and the stronger the reflectivity. 32,33 The seeds act as nucleation sites in the film formation process. The residual antisolvent promotes solvent volatilization, accelerating the formation of supersaturated state in the initial spin coating process.…”