中文摘要：

海岸盐沼广泛分布在海岸和河口环境,滩面有盐生植被覆盖,并且被潮水沟分割成片.研究海岸盐沼沉积过程和沉积速率,对于深入认识人类活动与海岸系统之间的相互作用具有非常重要的意义.137Cs测年技术是近20年用来测定现代沉积速率的一个有效方法,人工核试验产生的137Cs被释放到大气中,再经气-水、水-沉积物界面的交换和吸附而沉淀在地层里,通过几次出现的峰值年代来计算不同时段的沉积速率;该方法在计算湖泊沉积速率方面取得了成功,在陆架、海湾、潮滩等区域也取得了较好的成果.但由于该方法对研究区域地层记录的稳定性有较高的要求,沉积物黏土含量、分选程度均对137Cs含量有显著影响;海岸盐沼由于植被生长茂盛,根系伸入地层深处,对沉积地层有较大扰动,因此,很难分辨出特征峰值,需要借助其他手段来综合判断特征沉降峰值.

英文摘要：

Salt marshes are a widespread coastal and estuarine environment, and geomorphologically are composed of an approximately leveling, vegetated platform dissected by network of typically blind-ended channels. It is important for studying the depositional processes and sedimentation rates to understand deeply the interaction between human activities and coastal system. ^137Cs chronology is an effective technique for studying modern sedimentation rates since 20 years. 137 Cs is an artificial radioactive isotope intro- duced into the natural environment since the start of the atmospheric nuclear weapon testing in the 1950s. 137 Cs can be exchanged and adsorbed in the surface sediment and buried through the air-water interface and water-sediment interface,and four dating markers（1954,1963,1974 and 1986）which correspond to the on- set and peaks discharge of 137 Cs can be identified and the sedimentation rates in different periods can be calculated. 137Cs chronology is used widely to study sedimentation rates in lakes,continental shelves, bays and tidal flats,and gives better study results. The 137 Cs chronology needs high stability of strata in study area, and its concentration is influenced by clay content and sorting degree of sediments. The root system of the salt marsh vegetation can extend deeply downwards and disturb the stratum sequence. Then it is difficult to identify the characteristic peak, and thus other techniques are needed to do comprehensive estimation.