| During the 30th and 31th Chinese Antarctic Research Expedition,seawater samples were collected for the measurements of 210Po and 210Pb in the Prydz Bay and its adjacent areas.The distribution of 210Pn and 210Pb,and their disequilibria were studied.The export flux of particulate orgalic carbon(POC)and particulate nitrogen(PN)were estimated based on the 210Po/210Pb disequilibria.Our results suggested that activity concentration and distribution of 210Po around the Prydz Bay were mainly controlled by biological assimilation,particle scavenging and removal,and remineralization of particulate organic matter,while those of 210Pb were mainly regulated by atmospheric deposition,particle scavenging and removal,and remineralization of particulate organic matter.The activity concentrations of dissolved 210Po(DPo).total 210Po(TPo),dissolved 210Pb(DPb)and total 210Pb(TPb)in the shelf were generally lower than those in the slope and basin,which confirmed that biological assimilation and particle scavenging and removal were stronger in the shelf than in the slope and basin.In the slope and basin,the activity concentration of DPo in the upper water column were low while those of particulate 210Po(PPo)were high,which indicated the role of biological assimilation and particle scavenging and removal.In contrast,activity concentrations of DPo,TPo,DPb and TPb were high in the mesopelagic water,indicating the effect of remineralization of particulate organic matter or the intrusion of the Circumpolar Deep Water.The activity concentrations of DPo,TPo,DPb and TPb in the deep water were mostly lower than those in the mesopelagic water,which confirmed that sediment resuspension or the addition of the Shelf Water enhanced the particle scavenging and removal of 210Po.Different characteristics of 210Po/210Pb disequilibria were observed in different water masses around the Prydz Bay.The ratios of the activity concentration of TPo to TPb(TPo/TPb)A.R.)in the Antarctic Surface Water,Winter residual Water,Shelf Water and Thermocline Water were less than 1,which reflected that the processes of biological assimilation and particle scavenging and removal remove 210Po preferentially.The activity concentrations of TPo and TPb were high in the Circumpolar Deep Water and the TPo/TPb)A.R.were close to 1 or in some case,the TPo was excess to TPb.The facts that TPo/TPb)A.R.of the Antarctic Bottom Water was less than 1 and their TPo/TPb)A.R.was between the Shelf Water and the Circumpolar Deep Water suggested the effect of sediment resuspension or the formation of Antarctic Bottom Water.The balance between the input by remineralization of particulate organic matter and the removals by biological assimilation and particle scavenging determined the disequilibria of 210Po and 210Pb.The effect of biological assimilation and particle scavenging on the 210Po/210Pb disequilibria was stronger than that of the remineralization of particulate organic matter in the upper 200 m water column in the shelf,slope and basin.On the contrary,the mesopelagic water in the slope and basin was manily regulated by the remineralization of particulate organic matter.Based on the 210Po/210Pb disequilibria,the export fluxes of POC and PN from the euphotic layer were estimated to be 0.35-47.82 mmolC/m2/d and 0.1 7-16.07 mmolN/m2/d respectively.In general,the export fluxes of POC and PN were the highest in the shelf while the lowest in the slope.The export fluxes of POC and PN in the thermocline and appeared to be the highest in the shelf while the lowest in the basin.However,the export flux of POC and PN in the deep water were higher than those in the mesopelagic,which indicated the effect of the extra input of particulate organic matter. |
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