Seasonal Remote Sensing Retrieval Of Suspended Matter And Chlorophyll-A Concentration In Poyang Lake

Poyang Lake is the largest freshwater lake in China.Its ecological functions such as water conservation and sustaining of biodiversity have significant effects to ecological security and sustainable development of the society.With the development of urbanization and the increasing frequency of human activities,the water environment of Poyang Lake has also been greatly affected.The Chlorophyll-a concentration and total suspended matter concentration are the important indicators for assessing the water quality of lakes.In this study takes Poyang Lake as the study area.The in-situ measured spectral data and water samples were sampling in four seasons to obtain the Chlorophyll-a concentration and total suspended matter concentration through laboratory water sample processing.The study analyzed the spectral features of field collected water samples and conducted correlation analysis to obtain the sensitive spectral bands for inverting the chlorophyll-a and total suspended matter concentrations in Poyang Lake.Combined with GF-1 satellite imagery,the Chlorophyll-a and total suspended matter concentrations of Poyang Lake in different seasons were established.The study analyzed spatial and temporal distribution of Chlorophyll-a and total suspended matter concentrations.The main conclutions of this study are as follows:(1)Based on the field sampling data,the correlations between Chlorophyll-a and total suspended matter concentrations and water surface reflectance in Poyang Lake were established,respectively.The correlation coefficient between total suspended matter concentration and water surface reflectance is higher,while that for chlorophyll-a concentration is lower.The red and the infrared spectral bands are more sensitive and can be used as the feature spectral bands to establish the retrieval model.(2)The two spectral indices of ratio and difference were established,and the sensitive band inversion of chlorophyll-a concentration was approximately consistent with the first,third and fourth bands of GF-1 satellite data.Therefore,the APPEL model was used to construct the inversion band combination factor,and a Chlorophyll-a concentration retrieval model was established.The quadratic equation has the highest degree of fitting and the precision verification result is well.(3)The highest correlation between the total suspended matter concentration and the water surface reflectance correspondeds to the third band of the GF-1 satellite image data.A single-band model for retrieval of total suspended matter concentration was established accordingly.The summer retrieval model had the highest fitting degree with the quadratic equation,the autumn and winter season retrieval models had the highest fitting degree with the power equation,and the spring retrieval model had the highest fitting degree with the exponential equation.(4)The high value areas of Chlorophyll-a concentration in Poyang Lake are mainly concentrated in the northern channel area,the waters near the entrance to the five tributary rivers,and the nearshore water of Poyang Lake.The concentration of Chlorophyll-a in the central area of the lake is relatively low,and the distribution is relatively uniform.The seasonal distribution is the highest value of chlorophyll-a concentration in summer and the lowest in winter.The pattern of changes of water temperature and water level have determined the seasonal variation of Chlorophyll-a concentration.(5)The high value areas of total suspended solids concentration in Poyang Lake water are mainly distributed on the northern channel area and the center of the lake.The concentration of total suspended matter in the south is relatively low,with little change.The seasonal distribution of total suspended sediment concentration in Poyang Lake is highest in autumn and lowest in summer.The change of water level is one of the factors that influence the seasonal change of total suspended matter concentration.