| Vivo algal plays an important role in natural water due to its wide distribution and large number. It captures carbon dioxide through photosynthesis and store carbon in their tissues, which is one of the best ways of carbon sequestering. Then, it’s important for the study of the global carbon cycle and carbon storage. Once some harmful algal blooms in the surface of water, it will form water blooms or red tides, which will cause enormous damage to ecological environment. Monitoring the distribution of algal via satellite images can make up the deficiencies of traditional monitoring methods, so algae inversion model should be built. Then bio-optical properties of some algaes are required to have more in-depth understanding. The author measured inherent optical properties of primary algal in freshwater lakes, then analyzed their impact factors and error, and built model of homogenous spherical and two-layered spherical for microcystis aeruginosa and chlorella based on the Mie and Aden-Kerker theory.Calculate the capabilities of scattering and back scattering of algal via measuring absorption coefficient, scattering coefficient and back scattering coefficient. Capability of scattering and back scattering of cyanobacteria is the strongest, diatom takes the second place, and the weakest is cryptophyta. The ratio of back scattering is also calculated. The ratio of back scattering of cyanobacteria and diatom are higher than chlorophyta and cryptophyta. The uncertainty of the ratio of back scattering comes from measurement and error caused by leading into conversion factors. It is concluded that cell number and pigment formation are main impact factors of back scattering. Back scattering coefficient increases as the cell number and chlorophyll a content increases. The relevant coefficient between particle size and back scattering coefficient is not higher.The complex index of refraction is determined based on the theory of Mie, ADA and Kramer-Kronig, together with the function of particle size, and forward model of homogenous spherical is then built. It is showed that root mean square error and relative error between simulated and observed values of absorption coefficient about chlorella is0.000273and0.022%, while root mean square error and relative error about microcystis aeruginosa is4.8%and0.048. Root mean square error and relative error between simulated and observed values of average scattering efficiency about chlorella is0.01006and7.01%, while chlorella is0.072and5.9%.Considering polydispersity of particle size based on the theory of Aden-Kerker and Kramer-Kronig, we obtain complex refractive index and volume ratio of chlorophyll in two-layered spherical model by loop iteration, and conduct simulation of two-layered spherical model. It is showed that root mean square error and average relative error between simulated and observed values of absorption efficiency about microcystis aeruginosa is0.043and3.48%, while root mean square error and average relative error between simulated and observed values of scattering efficiency is0.034and2.92%, root mean square error and average relative error between simulated and observed values of absorption efficiency about chlorella is0.187and10.6%, while root mean square error and average relative error between simulated and observed values of scattering efficiency is0.114and10.2%.Using the particle size inversion model which built based on scattering simulation model, author inversed the particle size distribution of Microcystis aeruginosa and Chlorella. The inversion center particle size of Microcystis aeruginosa is4.216um, and variance is1. Compared with the measured and modeled results of particle center size, the relative error is21.57%of the center size and20.48%of the variance. The inversion center particle size of Chlorella is3.31um, and variance is1.5. Compared with the measured and modeled results of particle center size, the relative error is14.53%of the center size and16.67%of the variance. The result of Chlorella perform better. |
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