Vertical Characteristics And Remote Sensing Inversion Of Suspended Matter Concentration In Poyang Lake

Suspended particulate matter concentration is an important evaluation factor for measuring the quality of lake water environment.It can be quickly and effectively realized by means of water color remote sensing technology.At present,most studies on water color remote sensing assume that the water components are evenly distributed in the vertical direction.Poyang Lake is affected by natural and man-made factors,resulting in a non-uniform distribution of water components in the vertical direction.Based on the three-cruise measured data of Poyang Lake water body,this paper classifies the vertical distribution of suspended particulate matter concentration in Poyang Lake,quantitatively analyzes the influence degree of different vertical distribution types on the reflectivity above the water meter,and conducts the vertical concentration of suspended particulate matter on Poyang Lake.The distribution type of partition,the inversion model of suspended particle concentration is established and applied to the Sentinel-2A satellite image,revealing the planar and vertical distribution characteristics and effects of the concentration of suspended particulate matter in Poyang Lake at different periods.The main research contents and results of this paper are as follows:(1)The relationship between the vertical concentration of suspended particles in Poyang Lake and the optical parameters of water is revealed.By analyzing the measured data,it can be known that the vertical distribution of the total suspended particulate matter concentration in Poyang Lake can be divided into mixed type,linear type,first increase and then decrease type,and first increase and then mix type.The absorption coefficient of total suspended particulates in the same band increases with water depth,where the increase at the short wave is large and the increase at the long wave is small.The backscattering coefficient of the total suspended particles at the same band increases with the water depth,and the backscattering coefficient of the total suspended particles decreases with the increase of the wavelength.(2)The principle of water body division of Poyang Lake based on vertical characteristics.The Hydrolight software was used to simulate the remote sensing reflectivity under the vertical linear distribution of suspended particulate matter concentration,and the influence of the vertical distribution type on the reflectivity above the water meter was quantitatively analyzed.The regional distribution of different vertical distribution types of stations is analyzed.The Poyang Lake is divided into three lake areas: North,Middle and South.The northern lake area is linear;the southern lake area is mixed;Different types of stations in the lake area are staggered.(3)A remote sensing inversion model for the concentration of suspended particulate matter in Poyang Lake based on vertical feature stratification was constructed.The correlation analysis and curve fitting of suspended particulate matter concentration and remote sensing emissivity were used to establish a remote sensing inversion model of the partition.The models built in the three lakes have good inversion effects,and the model is feasible.The inversion accuracy of the models built in the northern and southern lakes is significantly higher than that in the central lake.Through the comparison of the accuracy of the three lake area models,the accuracy of the inversion model based on the partition of the vertical distribution type of suspended particulate matter concentration can be effectively improved.(4)The Application of Remote Sensing Inversion Model of Suspended Particulate Concentration in Poyang Lake.The results of remote sensing inversion of suspended particles were used to reveal the plane and vertical distribution of suspended particulate matter concentration in different periods of Poyang Lake.The horizontal and vertical distribution of suspended particulate matter concentration in the same period was ranked from the largest to the smallest: Central Lake District > Northern Lake Region > Southern Lake Region.The overall level of suspended particulate matter in Poyang Lake during the low water level(10~April)is greater than that during the high water level(May to September),and the sand mining points in the northern part of Huaiyin and Songmen Mountain during high water level and the impact of sand mining.In the downstream area,there is an extremely high value area,which can exceed 200 mg/L.The extremely high value areas in the low water level are mainly found in the bare disc-shaped lake.The vertical variation of the concentration of suspended particles in Poyang Lake is different in different periods.The total trend of vertical variation is that the surface layer is small and the bottom layer is large.Sand mining activity is an important factor affecting the vertical variation of suspended particulate matter concentration in Poyang Lake.The vertical variation of the concentration value in the sand mining area is the largest,and the vertical variation of the concentration within the sand mining influence area is the second,and the vertical concentration in the affected area is not affected by the sand mining.The change is minimal.