Study On Transport And Export Processes Of Marine Particles In The Southern Ocean And South China Sea Using Isotope Tracers

The transport and export process of marine particles now plays a key part in the study on marine carbon cycle, of which particulate carbon (POC) export flux, as a critical index to evaluate the efficiency of the biological pump, determines the biogeochemical cycle rate of marine particle-reactive elements and chemical constituents. Intensive research in the field is significant for understanding functions of marine ecosystem and predicting trends of global climate change.²³⁴Th specific activities were determined by Fe(OH)3 co-precipitation method with anαspectrum-βcounter device. Applying ²³⁴Th-²³⁸U disequilibrium to investigate the transport and export process of particles in the euphotic zone in the Prydz Bay of the Southern Ocean and South China Sea as well as ²³⁴Th scavenging and removal process in the surface water of the world ocean promoted the understanding of the carbon cycle process in the South China sea, advanced our research on cycle and export process of the particles and biogenic elements in the Prydz Bay of the Southern Ocean and descriped an image of ²³⁴Th scanveging and removal process The results are as follows:The average value of POC export flux from the euphotic zone were 169.31 and 55.42 mmol C m-2 d-1 for the continental shelf and slope of the Prydz Bay in the Southern Ocean respectively. Moreover, the ThE ratio of the two regions were 0.61 and 0.25 on average, indicating that scavenging and removal process of particles in the shelf were more active than in the slope region. The biological pump ran actively in summer in the Prydz Bay, which may be a potential CO2 sink.The average value of POC export flux from the euphotic zone were 15.98 and 10.40 mmol C m-2 d-1 for the northwest South China Sea and Nansha Islands sea area respectively. Moreover, the ThE ratio were 0.18 and 0.27 on average for the above-mentioned sea areas respectively. Obviously, POC export flux and the ThE ratio in the South China Sea which was a typical oligoltrophic region were lower than those in the continental shelf of the Prydz Bay with high productivity in summer.There were stratified euphotic zone with temporal and spatial variations in the northwest South China Sea, Nansha Islands and continental slope of the Prydz Bay, accompanied by stratified scavenging and removal rates of ²³⁴Th as well as POC export fluxes.²³⁴Th scavenging and removal rates as well as POC export fluxes in the surface water of the Southern Ocean were lower than those of the western Pacific Ocean, which might be due to lack of biogenic particles in the water of the Southern Ocean characterized by high nutrients and low chlorophyll resulting that ²³⁴Th could not be scavenged and removed quickly from the surface water.