长江口崇明东滩沉积物中生源硅的地球化学分布特征  

THE GEOCHEMISTRY OF BIOGENIC SILICA IN SEDIMENT OF DONGTAN INTERTIDAL FLAT IN CHANGJIANG(YANGTZE) RIVER ESTUARY

作　　者：高磊[1,2] 李道季[3] 余立华[3] 孔定江[3] 王延明[3] 

机构地区：[1]同济大学海洋地质国家重点实验室 [2]华东师范大学河口海岸国家重点实验室上海200062 [3]华东师范大学河口海岸国家重点实验室

出　　处：《海洋与湖沼》2007年第5期411-419,共9页Oceanologia Et Limnologia Sinica

基　　金：国家重点基础研究发展规划项目"中国典型河口-近海陆海相互作用及其环境效应";2002CB412405号。

摘　　要：对采集自长江口崇明东滩潮间带的沉积物柱状样进行了生源硅含量(BSi)测定。BSi的测定采用了7h的碱液连续提取法以校正样品中粘土矿物非生源硅的溶出对测定结果的影响。结果表明,与渤海和黄海沉积物类似,研究区域沉积物BSi含量也处在较低水平(<0.5Si%),沉积物中所含有的陆源粘土矿物也使SiO32?在间隙水中的浓度(<250μmol/L)远远低于纯BSi的溶解度。沉积物中含氮量以及N/BSi摩尔比等指标随深度呈现出降低的趋势,这反映了沉积物中的有机物在早期成岩过程中的降解,并且N比BSi降解得快。沉积物中δ15N值与含氮量、N/BSi摩尔比等指标都具有一定的正相关关系,显示在早期成岩过程中,与14N相比,15N更容易从有机物中释放出来。此外,在沉积物10—15cm深度处,发现含氮量、N/BSi比值等指标异常的变化,可能反映了修坝、台风等偶然事件对沉积过程的影响。Biogenic silica （BSi） was determined in two sediment columns in Dongtan intertidal flat in Chang-jiang （Yangtze） River estuary. Due to abundant terrestrial material inputs that cause a clay effect, sequential extraction was carried out in BSi measurement. Results indicate that, similar to the sediments in the Bohai Sea and the Yellow Sea, BSi content in Dongtan sediments was relatively lower （〈 0.5Si%）, than those of other regions of the world. The high clay content of the sediment decreased the solubility; and the highest SiO3^2- concentrations in the porewater was no more than 250 μmol/L, much lower than the solubility greater than 1000μmol/L in pure opal in similar environmental conditions. A consistent tendency was found that particulate N （%） and all molar ratio of N/BSi （mol/mol） decreased with depth, which might reflected the decomposition of N and BSi in early diagenesis process and that element N was of higher decomposition rate than BSi. The positive relationship between δ^15N （%0） and N or N/BSi revealed in the study suggests that 15N was released more readily from the organic matter than laN did. Moreover, the sedimentation was greatly influenced by events such as typhoon, artificial dam, and so on, which has been demonstrated by the irregular data found in the profiles.

关 键 词：生源硅 沉积物 崇明东滩潮间带 长江口 

分 类 号：P731[天文地球—海洋科学]