摘要
于2003年3月在厦门湾一个时间系列研究站(24°25.88'N,118°04.72'E)采集了高潮时不同深度的海水,用聚碳酸酯膜分离不同粒级悬浮颗粒物(SPM),用α能谱法测定各粒级悬浮颗粒物的铀同位素,研究了海水中238U和234U的体积比活度(AV)、质量比活度(Am)、活度比值[AR(234U/238U)]及238U、234U条件分配系数的粒级与深度分布特征.研究结果揭示了以下海洋学信息:(1)各粒级悬浮颗粒物中238U、234U的体积比活度和质量比活度的深度分布均表明,这两核素的深度分布趋势一致,反映出它们地球化学行为的一致性.(2)在所研究的不同水深处,在0.2～0.4、0.4～2.0、2.0～10.0、>10.0μm等4个粒级的SPM中,238U体积比活度AV(238U)的变化范围分别为0.04±0.00～0.15±0.01、0.04±0.00～0.13±0.01、0.29±0.02～0.43±0.02、1.06±0.06～4.11±0.24 Bq/m3;AV(234U)的相应值分别为0.08±0.00～0.08±0.00、0.05±0.00～0.13±0.01、0.27±0.01～0.37±0.02、0.84±0.05～3.95±0.24 Bq/m3.(3)在所研究的4个水深处的0.2～0.4、0.4～2.0、2.0～10.0、>10.0μm等4个粒级的SPM中,238U质量比活度Am(238U)的变化范围分别为0.100±0.000～0.319±0.021、0.022±0.000～0.167±0.013、0.049±0.003～0.113±0.005、0.024±0.002～0.081±0.005 Bq/g,而Am(234U)的相应值分别为0.114±0.014～0.364±0.045、0.027±0.005～0.168±0.013、0.052±0.003～0.098±0.008、0.029±0.002～0.064±0.005 Bq/g.(4)与238U、234U体积比活度的粒级变化顺序[也就是AV(>10.0μm)AV(2.0～10.0μm)>AV(0.4～2.0μm)=AV(0.2～0.4μm)]相反,这两核素质量比活度的粒级变化顺序为Am(0.2～0.4μm)≥Am(0.4～2.0μm)>Am(2.0～10.0μm)>Am(>10.0μm)≈Am(>0.2μm).(5)溶解态铀控制着总铀的地球化学行为,而颗粒态铀的地球化学行为则受控于大粒级颗粒物.(6)表层各粒级颗粒态AR(234U/238U)值均<1.0,而溶解态铀和总铀的AR(234U/238U)值均介于1.10～1.17之间.(7)不同粒级238U的条件分配系数(Kd)介于802～11 406 dm3/kg之间,Kd值随粒径减小而增大,意味着铀更有效地与小颗粒物相结合.
With high tide seawater samples collected at different depth of a timeseries station（24°25.88＇ N, 118° 04.72＇ E）in Xiamen Bay in March 2003, the sizefractionated suspended particulate matter（SPM） were separated with polycarbonate filter membrane and U isotopes were determined with ot spectrametry in the sizefractionated SPM. The depth profiles of the volumespecific activities A v, massspecific activities A,, ,AR（234U/238U） , and condition distribution coefficient （ Ka ） of the sizefraetionated 238^ U and 234^ U were studied. The following oceanographic information were revealed ： （ 1 ） The volumeand massspecific activities of the sizefractionated ^238 U and ^234 U showed a similar depth distribution feature, which reflected the consistent geochemical behavior of 23s U and 234 U. （ 2 ） At the different depth studied, Av （23Su） in the sizefraetionated SPM of 0.2 -0.4 μm,0.4 -2.0 Ixm,2.0 - 10.0 1μm and 〉 10.0 Ixm ranged from 0.04 _＋0.00 to 0.15 ±0.01 ,from 0.04 ±0.00 to 0.13 ±0.01 ,from 0.29 ±0.02 to 0.43 ±0.02 and from 1.06 ±0.06 to 4.11 ±0.24 Bq/m3 ,respectively,and the corresponding Av（234^U） were from 0.08 ±0.00 to 0.08 ±0.00 ,from 0.05 ±0.00 to 0.13 ±0.01 ,from 0.27 ±0.01 to 0.37 ±0.02 and from 0.84 ±0.05 to 3.95 ± 0.24 Bq/μ3, respectively. （3） At the different depth,Am （238 ^U） in the sizefractionated SPM of 0.2 ±0.4 Ixm,0.4 ±2.0 m,2.0 ± 10.0 txm and 〉 10.0 μm ranged from 0. 100 ±0. 000 to 0. 319 ±0. 021 ,from 0. 022 ±0. 000 to 0. 167 ±0. 013 ,from 0. 049 ±0. 003 to 0. 113 ±0. 005 and from 0. 024±0. 002 to 0. 081 ±0. 005 Bq/g, respectively, and the corresponding A_V, （ 234 U ） were 0.114± 0.014 - 0. 364 ± 0. 045,0. 027 ± 0. 005 - 0.168 ±0. 013,0. 052 ±0. 003 -0. 098 ±0. 008 and 0. 029 ＋0. 002 ±0. 064 ±0. 005 Bq/g,respeetively. （4） In contrast to the variation trends of Av （ 238 ^U ） and A,, （ 234^ U ） the trends of sizefractionation of Av （ 238 U） and Am （ 234^ U ） was （0.2-0.4 μm） （0.4-2.0μm） 〉（2.0±10.0 μm） 〉（ 〉10.0 μm） （ 〉0.2 μm）. （5） While dissolved U controls the total U geochemical behavior, the particulate U geochemical behavior was controlled by large SPM. （6） All sizefractionated AR （ 234^ U/238^ U ） in the surface seawater were lower than 1.0, but AR （ z34 U/238 U） of the dissolved and total U were all in values of 1.10 -1.17. （7） The condition distribution coefficient（ K_d） of the sizefraetionated 238U varied from 802 to 11 406 dm3/kg and it increased with the decrease of sizefractionation, which suggest more effective combination of U with small SPM than with large.
出处
《台湾海峡》
CAS
CSCD
2012年第1期3-11,共9页
Journal of Oceanography In Taiwan Strait
基金
国家自然科学基金资助项目(40806031)
南华大学科研资助项目(WT-KF-2010-01
2007×QD36)
关键词
海洋化学
238U
234U
粒级分布
深度分布
海水
厦门湾
238 ^U
234 ^U
marine chemistry
size fractionation distribution
profile
seawater
Xiamen Bay
