Study On The Character And Inlfuencing Factor Of Marine Nepheloid Layer In Northern South China Sea

In upwelling area and shelf-slope area of northern South China Sea(NSCS),16sections are studied. By analyzing temperature、salinity、turbidity and chlorophyll ofwater, and composition、mean grain size and volume concentration of in-site particlesize, the character and controlled mechanism of nepheloid layer of NSCS are studied.Result shows that bottom nepheloid layer(BNL) is popular in the upwelling areaof NSCS, and surface nepheloid layer(SNL) exists in several sites. High energycoastal process and matter from bays and rivers provide matter source for SNL andBNL.BNL is also popular in shelf-slope area of NSCS; SNL often appears in innershelf off the Pearl River estuary and outer shelf-slope area; intermediate nepheloidlayer(INL) exists in the slope area. Particle matter sources of nepheloid layer aremainly from material of Pearl River, rivers of southwest Taiwan and Hainan Island,biogenous particle matter.The seaward extension of the BNLs in the slope areas is very obvious, and thelateral transport of nepheloid layers of the slope area is vital for the transport ofparticle matter from shelf to deep sea.The intensity and thickness of BNLs are mainly controlled by the hydrography ofthe shelf-slope waters、resuspension of fine deposites、dispersion of material by riverdischarge and so on.Mean grain size and volume concentration of in-site particle size of18-6、18-7section indicate that mean grain size range of nepheloid layers is30-110μm and50-110μm respectively, and high value area of volume concentration of lower layerwater is almost the same with the extent of the nepheloid layer.The EPMA analysis of suspended matter shows that particle matter of SNLs inshelf margin is mainly biogenous particle matter, while particle matter of INLs andBNLs is mainly terrigenous particle matter.The thesis is mainly supported by Chinese Offshore Investigation andAssessment（908-01-CJ13,908-01-CJ18,908-ZC-I-05）.