Water Quality Parameters Characteristics And Inversion Of Erlonglake

Hydrosphere is one of the circle structures of the earth that links atmosphere,biosphere and lithophere closely. And lakes play an important role in hydrosphere for itsunique function and structure. Since the environment of the lakes has been polluted anddamaged in recent years, its area decreases and function retrogrades gradually. Therevitalization of northeast old industrial influences the lakes tremendously, so regionallake management becomes more and more significant. As one of the means for inspectingthe lake environment, remote sensing is developing greatly. However the technique thatwas used by marine remote sensing is adopted by the research in the water quality ofinland lakes. Nowadays, the retrival methods taken in lakes quality remote sensing aremainly classified into experienced and semi-analytical methods.This article takes ErlongLake as research object and obtains three periods of spectraldata and the concentration data of water quality parameters and water absorption datathrough outside measure and laboratory experiment. Moreover, the single-wavechlorophyll a concentration and total suspending solids concentration are established onthe base of the results of the experiments. Meanwhile, the retrival is done by means ofLandsat TM image data. Here are some conclusions as following by analyzing the changeof two parameters of time and space distribution:1In September, the concentrations of suspending solids and chlorophyll in ErlongHu are the highest. The scope of chlorophyll concentration swings greatly in thesemonths. The absorption of CDOM’s fluctuation range is small at440nm wavelength,however, the maximum appears in June.2In June, CDOM and the planktonic green plant pigment dominate the waterabsorption. In September, the planktonic green plant pigment does, nevertheless thecontribution rate of the three kind of substances are almost the same. Palace of variablerelations among the three substances and the total of generation between the twopigments are identical. This phonomenon has something to do with human’s agriculturalactivities and it can reflect CDOM’s resource.3The value of water reflectivity in300~500nm is relatively low, however thereflectance value of500~600nm sways obviously and it is much greater than that of300~500nm. The spectral of600~700nm displays various traits: there is a reflectancevalley near the band of620nm. Such a reflectance valley is caused by the absorption ofthe algae and algae in water green protein. Between690~690nm exist an obvious reflection peak, usually referred as the fluorescent peak. And it moves towards thedirection of long wave with the increase of chlorophyll a. This is the most significantspectral characteristic of the water containing algae.The reflectance rate oscilitatessignificantly in the infrared band which near700~750nm. The reflectivity of the band ismainly affected by the particle scattering, mirroring that the suspending solidsconcentration in Erlong Hu changes greatly.4The absorption of pigment particles and the absorption of CDOM decayexponentially as the wave length grows. It is discovered that there is no obviousrelationship between the absorption of pigment particle index and proportion of organicmatter in the pigment particles by the study of the absorption of CDOM slope. Throughstudy the absorption of CDOM slope, it is concluded that the spectral absorptiondecreases exponentially as CDOM increases. Humic acid is mainly the production ofwater phytoplankton degradation, nevertheless fulvic acid is mainly influenced byterrigenous material. As the CDOM absorption slope Sg value grows, the greater theproportion of fulvic acid becomes, the less the the proportion of humic acid does. Due toSg-10>Sg-9>Sg-6, the source of CDOM changes as the seasons change alternately.5The single band algorithm accuracy is generally low under the circumstance thatthe measured spectral data is used for retrival. The highest decision coefficient is only0.39when the chlorophyll a concentration is retrived. However, when the totalsuspending solids concentration,the total suspended solids concentration can reach0.66.The equation’s highest decision coefficient reach0.73and0.89respectively while theband ratio method is adopted in retriving chlorophyll a concentration and totalsuspending solids concentration. Obviously, the ratio algorithm works better than thesingle band algorithm.6The multiple regression model is established between the primary parameters andthe reflectance ratio of the band reflectance while the remote sensing image is used forretriving water quality indexes. And the result of the retrival is ideal. As it can be seenfrom the chart of parameters’ distribution, chlorophyll a concentration is inclined toreduce from the coast of the lake to the northeast corner and to the lake center finally.While the total suspending solids concentration ‘s value is small and the numericaldistribution is relatively even. So it can be known that,the water in Erlong Hu isrelatively clear.