| Because of global climate change and human activities,coastal waters are facing a series of environmental problem include polution and eutrophication and human social economic activities are greatly affected.As most open and most developed areas in china,Guangzhou and its surrounding areas(the Pearl River Delta)have the largest trade port group,the largest populatio,and important Wetland Reserve.Waterway patency,drinking water safty and wetland ecosystem health would promote the local economic development,ensure social stability and protect the environment.However,because of the complex ocean-land-atmospheric environment conditions in the coastal waters,The long-term quantitative monitoring of water environment characteristics in the Pearl River estuary has not been effectively solved.Suspended sediment is not only an important pollutant bearing body,but also has a high sensitivity to a variety of environmental conditions.In this paper,the temporal and spatial pattern of suspended sediment in the Pearl River Estuary and its formation mechanism are studied by using the remote sensing data and the measured data.The main contents and conclusions of the study are as follows:1)A novel regional-based total suspended matter concentration(TSM)retrival model is proposed for long-term monitoring TSM in Pearl River estuary using MODIS remote sensing images.The results showed that the exponential model based on the Rayleigh-corrected reflectance ratio(Rrc(660)/Rrc(560))could achieve acceptable accuracy,with MRE of 15.67%and R2 of 0.925.2)The TSM environment data record(2003-2015)has be established to assess spatil-term distribution in Pearl River estuary.The spatial feature with Semi-circular striped distribution could be observed.The sediment concentration in the dry season is higher than that in the wet season.The sediment concentration increases obviously in the mouth of river during the high discharge period.Seasonal feature of sediment concentration were significant in different years.3)The main influencing factors of the suspended sediment in the Pearl River estuary are the wind speed and the wind direction.Northerly winds induce winter upwelling events which increase sediment concentration inshore and offshore.The precipitation and runoff are maximum in summer,when the sediment concentration increases obviously in the mouth of river.The low concentration of suspended sediment are observed because of low runoff and low wind speed in the spring and autumn.Cascade development of reservoirs in Pearl River basin is affecting the seasonal distribution of the runoff in and the interannual distribution of the sediment into the Pearl River estuary. |
