| Total suspended matter(TSM)is one of the important optical active substances in water body,which largely determines the absorption,scattering and attenuation of light in water column and adsorbs nutrients,heavy metals and toxic and harmful substances.Therefore,TSM is of great important to biogeochemical processes of water substance,lake sediment burial dynamics and lake environment evolution.This study developed TSM estimation model in Lake Taihu based on satellite-ground synchronous experiment and Geostationary Ocean Color Imager(GOCI)image,estimated the total suspended matter(TSM)of Lake Taihu from 2012 to 2017 using GOCI data,analyzed the temporal and spatial variations in total suspended matter(TSM)in Lake Taihu and discussed the potential affecting factors,and further analyzed TSM short-term dynamics in Lake Taihu during its typical wind-waves process and typical heavy-rainfall process.The results showed that:(1)the band 7(745 nm)and band 8(865 nm)of GOCI data were the sensitive bands of TSM estimation in Lake Taihu with the linear correlation determination coefficients of 0.72 and 0.55,respectively.A single band empirical model based on GOCI band 7 was used to estimate the TSM concentration of Lake Taihu and its relative root mean square error and average absolute percentage error were 28.3%and 24.4%,respectively.(2)Long-term TSM concentration maps estimated from the GOCI data demonstrated marked temporal and spatial variations.TSM concentration has obvious intraday changes in lake Taihu.In July 21,2012,the TSM concentration in the lake Taihu northwest is higher than others,and showed a decreasing trend from early to late.Monthly variation of TSM concentration in the lake Taihu shows an obvious single peak distribution pattern changes from January to December,the changes experienced a process of up down up,The highest mean TSM value(65.6 mg/L)for the entire lake was found in March,whereas the lowest mean TSM value(44.1 mg/L)appeared in September.The waters in Lake Taihu were characterized by high TSM in all four seasons,the TSM distribution showing higher values in the winter and spring seasons and lower values in the summer and autumn seasons.The inter-annual variation,the lowest annual mean TSM ’value was 56.25 mg/L in 2014 and the highest value was 64.44 mg/L in 2013.Relative to other Bay area,the highest annual mean TSM value was in open area and the lowest value was in Zhushan Bay.The significantly correlated relationships between TSM and Kd(PAR)and between TSM and SDD,which was derived from a large number of field measurements taking in Lake Taihu,the linear correlation determination coefficients was 0.79 and 0.73,respectively.(3)Significant short-term TSM dynamic change was observed in Lake Taihu,and wind direction and wind speed were the important factors determining TSM concentration.TSM concentration increased with the increase of wind speed and diffused along with wind direction.High-frequency continuous GOCI images showed that the short-term dynamics of TSM concentration had a certain lag in response to wind-wave disturbance.The lag time ranged from several hours to one day,and the critical wind speed of TSM settling and sediment resuspension was about 3.4 m/s.(4)Significant rainfall TSM dynamic change was observed in Lake Taihu,and rainfall amount was the important factors determining the plume area near River Tiaoxi.From the TSM concentration distribution after heavy rainfall in lake Taihu,the high value region of the TSM concentration in lake Taihu gradually decreased with the change of time. |
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