Dissolved and particulate thorium-234, particulate organic carbon in the upper 150 m of water columns from five stations in the Prydz Bay, the Southern Ocean were determined during the 22nd Chinese National Antarctic ...Dissolved and particulate thorium-234, particulate organic carbon in the upper 150 m of water columns from five stations in the Prydz Bay, the Southern Ocean were determined during the 22nd Chinese National Antarctic Research Expedition （from November 2005 to March 2006 ）. The disequilibria between thorium-234 and its parent uranium-238 in upper layer was used to derive the averaged residence time of thorium-234, which decreased along with the latitude to the south and a minimum value, 1 - 8 d for particulate thorium-234 and 29 - 48 d for dissolved thorium-234, appeared at the medium latitude station, and the export fluxes of thorium-234 were calculated too and ＇a maximum value, 0. 35 -0. 63 Bq/（m^3 · d） for the particulate thorium-234 and 0. 44 -0. 65 Bq/ （m^3 ·d） for the dissolved thorium-234, appeared at the same station. The export fluxes of particulate organic carbon at different water columns were derived by two methods with irreversible scavenging model, and the averaged values were 104. 7 mmol/ （ m2 · d ） （ E method） and 120. 6 mmol/（ m2·d ） （ B method ）, respectively, indicating that a relatively high new production would exist in summer in the Prydz Bay where it will play a potential significant role in sequestering the absorption CO2 to deeper ocean.展开更多
A low-level β counting-or spectrum apparatus used for the detection of the β radiation of thorium-234 and α spectrum of thorium- 228 simultaneously and an easy operating procedure for the enrichment, radiochemical ...A low-level β counting-or spectrum apparatus used for the detection of the β radiation of thorium-234 and α spectrum of thorium- 228 simultaneously and an easy operating procedure for the enrichment, radiochemical separating, sampling and measurement of thorium-234 and uranium-238 in the ocean are developed based on the requirements of analyzing export productivity in the eupho- ric zone via thorium-234 - uranium-238 radioactivity disequilibrium. The detecting efficiency both of 13 and α radiation is higher than 20%. The background of βradiation is less than 0. 5 min ^-1 , and the energy resolution of ct detector is better than 1%. Total recycle ratio of thorium-234 is about 75%. Using the above apparatus and procedure, the radioactivities of dissolved thorium-234 and uranium-238, particle thorium-234 and uranium-238 in seawater of the South China Sea, the Southern Ocean and the Arctic Ocean were analyzed.展开更多
基金The Scientific Research Foundation of Third Institute of Oceanography,State Oceanic Administration under contract NoTIO2007003the Natural Science Foundation of Fujian Province of China under contract No2006J0287+1 种基金the National Natural Science Foundation of China fromkey program under contract No 40531007 and from general program under contract Nos40406014 and 40276001the State Social Commonweal Foundationof China under contract No 2004DIB5178
文摘Dissolved and particulate thorium-234, particulate organic carbon in the upper 150 m of water columns from five stations in the Prydz Bay, the Southern Ocean were determined during the 22nd Chinese National Antarctic Research Expedition （from November 2005 to March 2006 ）. The disequilibria between thorium-234 and its parent uranium-238 in upper layer was used to derive the averaged residence time of thorium-234, which decreased along with the latitude to the south and a minimum value, 1 - 8 d for particulate thorium-234 and 29 - 48 d for dissolved thorium-234, appeared at the medium latitude station, and the export fluxes of thorium-234 were calculated too and ＇a maximum value, 0. 35 -0. 63 Bq/（m^3 · d） for the particulate thorium-234 and 0. 44 -0. 65 Bq/ （m^3 ·d） for the dissolved thorium-234, appeared at the same station. The export fluxes of particulate organic carbon at different water columns were derived by two methods with irreversible scavenging model, and the averaged values were 104. 7 mmol/ （ m2 · d ） （ E method） and 120. 6 mmol/（ m2·d ） （ B method ）, respectively, indicating that a relatively high new production would exist in summer in the Prydz Bay where it will play a potential significant role in sequestering the absorption CO2 to deeper ocean.
基金This project was supported by the State Social Commonweal Grant(project name:the comprehensive investigation of Nansha Islands waters)the Natural Science Foundation of Fujian Province of China under contract No.2006J0287+2 种基金This study was also supported,in part,by the National Natural Science Foundation of China from key program under contract No.40531007general program under contract Nos 40406014 and 40276001State Social Commonweal Grant under contract No.2004DIB5178.
文摘A low-level β counting-or spectrum apparatus used for the detection of the β radiation of thorium-234 and α spectrum of thorium- 228 simultaneously and an easy operating procedure for the enrichment, radiochemical separating, sampling and measurement of thorium-234 and uranium-238 in the ocean are developed based on the requirements of analyzing export productivity in the eupho- ric zone via thorium-234 - uranium-238 radioactivity disequilibrium. The detecting efficiency both of 13 and α radiation is higher than 20%. The background of βradiation is less than 0. 5 min ^-1 , and the energy resolution of ct detector is better than 1%. Total recycle ratio of thorium-234 is about 75%. Using the above apparatus and procedure, the radioactivities of dissolved thorium-234 and uranium-238, particle thorium-234 and uranium-238 in seawater of the South China Sea, the Southern Ocean and the Arctic Ocean were analyzed.
