摘要
234Th was utilized as a tracer of particulate organic carbon （POC） export in the northwestern South China Sea （SCS） on the basis of the data collected at four stations during a spring cruise. Depth profiles of dissolved and particulate 234Th activities were measured in the upper 60m, showing a significant deficit relative to 23Su over the investigated stations. A stratified structure of 234Th-23su disequilibrium was in general observed in the upper 60 m water column, indicating that the euphotic zone of the northwestern SCS in this reason can be divided into two layers, an upper and lower layer, with different export rates. POC export fluxes were estimated from a one-dimensional steady state model of 234Th fluxes in combination with the measurement of POC/234Th ratios on suspended particles. The POC export in this region ranged from 8.2 to 20.0 mmol/（m2.d）, with an average of 16.0 mmol/（m2-d）, and was slightly higher than those previously reported in the southern SCS.
234Th was utilized as a tracer of particulate organic carbon （POC） export in the northwestern South China Sea （SCS） on the basis of the data collected at four stations during a spring cruise. Depth profiles of dissolved and particulate 234Th activities were measured in the upper 60m, showing a significant deficit relative to 23Su over the investigated stations. A stratified structure of 234Th-23su disequilibrium was in general observed in the upper 60 m water column, indicating that the euphotic zone of the northwestern SCS in this reason can be divided into two layers, an upper and lower layer, with different export rates. POC export fluxes were estimated from a one-dimensional steady state model of 234Th fluxes in combination with the measurement of POC/234Th ratios on suspended particles. The POC export in this region ranged from 8.2 to 20.0 mmol/（m2.d）, with an average of 16.0 mmol/（m2-d）, and was slightly higher than those previously reported in the southern SCS.
基金
The National Natural Science Foundation of China under grant Nos 40531007,40676062 and 10705019
the scientific research foundation of the Ministry of Science and Technology of China through commonweal grant No.2007050228
International Cooperation Program No.2009DFA22920
Open Fund of the Key Laboratory of Global Change and Marine-Atmospheric Chemistry
State Oceanic Administration under grant Nos 0807 and 0902
Tsinghua University Initiative Scientific Research Program
