[Retrieving for chlorophyll-a concentration and suspended substance concentration based on HJ-1A HIS image].

Based on geometry correction using ERDAS software and radiation correction using 6S model for HJ-1A hyper-spectrum image (HSI) on May 2 in 2010 and the analysis of spectrum for water data and spectral data of hyper-spectrum image, this paper processes original spectrum data of 28 sample points using method of normalization and method of first-order derivation. Single-band and band combination are selected to establish inversion models of the concentration of chlorophyll-a and solid suspensions. Choosing the model with biggest correlation coefficient, the spatial distribution map of the concentration of chlorophyll-a and solid suspensions content in Taihu Lake is acquired. The research results show: Band-73 of hyper-spectrum image which has been normalized shows the biggest correlation coefficient of the concentration of chlorophyll-a, remote sensing sediment parameter shows the biggest correlation coefficient of the concentration of solid suspensions, the result is consistent with analysis of spectral data of hyper-spectrum image. Average relative errors of predicted and measured values are within 30 percent. Spatial distribution map of water quality is consistent with the result of field surveys. Therefore, based on reference of the analysis of sensitive band of spectrum for water data, HJ-1A hyper-spectrum image can give quantitative estimation of water quality parameters in Taihu Lake.

[Effect of inherent optical parameters on average penetration depth of photon flux and the integral average cosine of underwater light field in lake Taihu during summer].

Based on the inherent optical parameters of the water and water quality data in lake Taihu from 2006-07-29 to 2006-08-01, the effect of scattering on the penetration path along the original direction of the flux and the Integral average cosine of underwater light field were study by the radiative transfer theory, and the possible mechanism was analyzed. There were increasing trend from northwest to southeast of them. There were a nonlinear relation between them and concentration of Chl-a, suspended matter, inorganism matter, organism matter. The relation was described by logarithmic function. The study was helpful for bio-optical model and the environmental effects of photosynthetic active radiation in waters.

[Analysis on the spatial characteristics of the light quantum yields in Lake Taihu in spring].

Based on the primary productions and underwater irradiance in the head of the jetty in a station of the Lake Taihu ecology network of the Chinese academia, Zhihugang estuary area, the center of Lake Taihu and Xukou Bay at April 28, May 4, May 5, May 6 in 2009, the light quantum yields of algae and P-I curve were calculated. Then the spatial characteristics were analyzed. There was significant photoinhibition in the head of the jetty in a station of the Lake Taihu ecology network of the Chinese academia; there was not appreciable photoinhibition in Zhihugang estuary area and the center of Xukou Bay; and there was only light-saturation phenomena in the center of Lake Taihu. The order of the light quantum yield per Chl-a was the center of Lake Taihu, the head of the jetty, Zhihugang estuary area and the center of Xukou Bay.

[Variation of spectrum of photosynthesis available radiation absorbed by underwater optical medium with depth in Lake Taihu in summer].

Normalized spectrum of photosynthesis available radiation (PAR), which was absorbed by all kinds of medium per unit volume of water at different depths, was calculated by the data from downward and upward irradiance and absorption coefficients of phytoplankton, non-algae particles and chromophoric dissolved organic matter (CDOM) in 41 locations in Lake Taihu from July 29 to August 1, 2006. The results showed that there were two peaks at about 450 nm and 675 nm in the normalized spectrum of PAR absorbed by phytoplankton per unit volume of water, respectively. With the increasing of the depth, the peak at about 450 nm gradually weakened, and red-shift appeared from 450 nm. The above phenomena were much more obvious in the algae-type zone and the center of Lake Taihu. The PAR absorbed by phytoplankton per unit volume of water was shift to 600-700 nm which mainly originated from 400-500 nm to 600-700 nm. The transitional speed was slower in the grass-type zone but it was faster in Meiliang Bay(algae-type zone)and the center of Lake Taihu. In the above water, the PAR absorbed by non-algae particles per unit volume of water mainly originated from 400-500 nm, but energy source gradually shifted to 500-600 nm with the increasing of depth. The variable characteristics of normalized spectrum of PAR absorbed by CDOM per unit volume of water were similar to that of non-algae particles. However, the advantage in grass-type zone which CDOM per unit volume of water absorbed PAR between 500 and 600 nm was less significant than that of non-algae particles per unit volume of water.