黄河口新生湿地沉积物放射性核素及其对沉积过程变化指示作用解析  

Radionuclides in the Sediments of the Newly Created Wetlands of Yellow River Estuary and Its Indication to Environmental Change

作　　者：王启栋[1,2] 宋金明[1] 李学刚[1] 袁华茂[1] 李宁[1] 曹磊[1,2] 

机构地区：[1]中国科学院海洋研究所生态与环境科学重点实验室,山东青岛266071 [2]中国科学院大学,北京100049

出　　处：《地质论评》2014年第3期635-645,共11页Geological Review

基　　金：国家海洋公益性项目(201205008);国家海洋局环境评价项目(DOMEP(MEA)-01-01)的成果

摘　　要：为探讨放射性核素对沉积速率、沉积环境变化以及重大环境历史事件的指示作用,本文首次报道了用HPGeγ谱仪测定黄河口新生湿地柱状沉积物中6种放射性核素活度的结果,并根据137Cs的垂直分布估算了沉积速率,探讨了放射性核素与有机质的关系及其垂直变化与沉积过程变化的对应关系。结果表明,黄河口新生湿地柱状沉积物中6种放射性核素的平均比活度分别为40K(687.33±54.59)Bq/kg、137Cs(8.60±1.35)Bq/kg、226Ra(29.96±4.23)Bq/kg、228Ra(69.96±6.63)Bq/kg、228Th(45.35±4.58)Bq/kg和238U(60.52±15.37)Bq/kg,与其他区域相比,黄河口新生湿地137Cs、238U含量偏高。除137Cs外,其他5种核素均与TOC呈显著正相关,表明有机质有利于核素在沉积物中的保留。137Cs的垂直分布与黄河口净造陆速率的年际变化具有一致性,据此估算获得近20年该区域平均沉积速率为2.8cm/a,其中河口湿地形成初期沉积速率较高,而后逐渐减小并保持相对稳定。放射性核素比活度的垂直变化可反映沉积过程中黄河断流、黄河调沙以及大的洪水等重大环境事件,可以作为指示沉积变化特征的重要指标。Radionuclides could serve as powful proxies to determine the sedimentation rate and to indicate sedimentary enviornment change and major enviornmental events in the history. The activities of six radionuclides determined by HPGe γ Spectrometer in the core sediments of the newly created wetlands of the Yellow River Estuary were firstly reported in this paper. The sedimentation rate was estimated according to the depth profile of 137Cs. The vertical distribution of radionuclides and their relationships with TOC and the sedimentary process were investigated. The result showed that the average activities of 40K, 137Cs, 226Ra,228Ra, 228Th and 238U in the newly created Yellow River Estuary wetlands were （ 687.33 ± 54.59 ）, （ 8.60 ± 1.35 ）, （ 29.96 ± 4. 23 ）, （ 69.96± 6. 63 ）, （45.35 ± 4.58 ） and （60.52± 15.37 ） Bq/kg, respectively, among which 137Cs and 238 U were higher than other areas along the coast of China. All the radionuclides showed significant positive correlations with TOC, suggesting that the present of organic matter had the potential to promote the retention of radionuclides in the sediment. The vertical variation of 137 Cs was highly consistent with the average annual net epeirogenic rate of the Yellow River Estuary, according to which we estimated the average sedimentation rate of this area being 2.8cm/a. The sediment deposited very quickly at the initial stage of the estuary wetlands formation, and then the deposition rate gradually decressed to a relatively stable level. As the vertical variations of radionuelides＇ specific activities may reflect major enviornmental events such as long-time river cutoff, water and sediment regulation and severe flooding events during the sedimentary history, they could serve as important indicators indicating the sedimentary change characteristics.

关 键 词：放射性核素 沉积速率 沉积环境变化 新生湿地 黄河口 

分 类 号：P597.1[天文地球—地球化学] P512.2[天文地球—地质学]