南海与厦门湾海水中^(210)Po和^(210)Pb的粒级分布

Size-fractionated ^(210)Po and ^(210)Pb in the South China Sea and Xiamen Bay

对南海和厦门湾表层水中210Po和210Pb的粒级分布特征进行了研究.结果表明,南海海水中210Po和210Pb在不同粒级颗粒物中的体积比活度高低顺序为:(<0.4μm)>(0.4~2.0μm)>(2.0~10μm)>(>10μm).210Po2、10Pb主要存在于<2.0μm粒级颗粒物中.厦门湾210Po体积比活度高低顺序为:(2.0~10μm)>(<1.2μm)>(>10μm)>(1.2~2.0μm),210Po主要存在于>2.0μm粒级颗粒物中.南海不同粒级颗粒物中210Pb的质量比活度差异不大,0.4~2.0μm和2.0~10μm粒级210Po质量比活度约为10μm粒级210Po比活度的3倍.厦门湾210Po的质量比活度比南海相应粒级210Po低约1个数量级,且各粒级间差异不大,表明不同粒径颗粒物在210Po和210Pb清除过程中的作用不同.210Po和210Pb的固-液分配系数(Kd)及分馏因子(α)进一步证实南海0.4~2.0μm粒级颗粒物对210Po的清除能力比其它粒级颗粒物更强,而>10μm粒级颗粒物对210Pb的清除能力比其它粒级颗粒物更强.不同粒级颗粒物中210Po与210Pb之间的不平衡状况揭示了不同粒级颗粒物不同的来源,为210Po/210Pb不平衡示踪颗粒物来源提供了依据.

Size-fractionated ^210Po and ^210Pb have been examined in the South China Sea （SCS） and the 〈 0. 4μm fraction becomes a major component of the total ^210Po and ^210Pb. In contrast, size-fractionated ^210Po in order of activities were 2.0-10μm 〉 （ 〈 1.2μm） 〉 （ 〉 10μm） 〉 1.2-2.0μm in Xiamen Bay and 〉2. 0μm fraction makes the majority of total ^210Po. In the SCS, the mass specific activities （MSA, Bq/kg SPM） of the size-fractionated ^210Pb have no evident differences but the MSA of ^210Po with 0.4 -2.0μm and 2.0 - 10μm size classes were three times higher than that of ^210Po with 〉 10μm size class. In Xiamen Bay ,the MSA of ^210Po was an order of magnitude lower than that in the SCS, but the MSA for all size classes showed no apparent differences. These results suggested that both of the size and chemical composition of the SPM play important roles in the scavenging processes of ^210PPo and ^210Pb. The solid-liquid partition coefficients of size-fractionated ^210Po and ^210Pb and the fractionation factor between^210Po and ^210Pb, indicated that 0.4 - 2.0μm SPM scavenge ^210Po more than ^210Pb while 〉 10μm SPM have stronger affinities for ^210Pb than for ^210Po in the SCS. In addition, the disequilibria between size-fractionated ^210Po and ^210Pb shed new light on the application of ^210Po/^210Pb to reveal the sources of the particulate with different size classes.