百年来黄河三角洲东北部毗邻海域沉积记录演化及其影响因素

通过对黄河三角洲东北部毗邻海域采集的多个沉积物岩心,开展系统的沉积物粒度、有机碳氮及其同位素特征的分析,结合210Pb年代测定,探讨研究区近百年来高分辨率的沉积记录及其变化的主要因素。研究表明:岩心O3、M2和B63处于相对稳定的沉积环境中,沉积物的粒度分布都呈阶段性变化但表现出差异性,O3和M2自1976年以来沉积物粒度出现粗化,而距离现行河口较近的B63则变细之后粒度粗化,在沉积物的上段C/N和δ13C的变化都反映了陆源有机质输入的增加。黄河1976年改道使三角洲北部和东部海域的沉积环境发生改变,O3和M2受再悬浮泥沙的影响粒度变粗,废弃三角洲叶瓣再悬浮泥沙对研究区的供给量增加,导致O3和M2接受更多陆源有机质的供给。而B63受到更多较细粒黄河入海泥沙影响,粒度变细,陆源有机质输入也增加。黄河入海水沙的阶段性递减和调水调沙工程导致输运至研究区的细粒物质减少,使岩心B63沉积物上段层位的粒度变粗。

HIGH-RESOLUTION DEPOSITIONAL RECORDS IN THE NORTHEASTERN ADJACENT AREA OFF THE HUANGHE (YELLOW RIVER) DELTA FOR THE PAST HUNDRED YEARS AND THEIR INFLUENCE FACTORS

In this study,sediment cores collected from the area off the northeastern corner of the Huanghe(Yellow River) delta are comprehensively analyzed,including the characteristics of particle sizes, total organic carbon (TOC),total nitrogen (TN) and 210Pb dating.High-resolution depositional records for the past one hundred years were reconstructed for revealing the main factors that control their temporal variation in sedimentation. The results show that the hydrodynamic conditions at the locations of the cores O3, M2 and B63 are relatively stable, while the vertical variations in grain sizes show multi-stage patterns. The grain size of the cores O3 and M2 became coarser after 1976,while the sediment particle size at B63 had decreased since 1976 and increased after 1998.The variations in C/N ratio and δ13C suggest that terrigenous organic matter at the upper layer show an increasing trend for all three cores. The shift of Huanghe river channel in 1976 played important role in the formation of the depositional records in study area. After 1976,especially in recent decades, coarser sediment from erosion of the abandoned Diaokou-Shenxiangou deltaic lobe became the predominant sediment source. As the result,the grain size and terrigenous organic matter of cores O3 and M2 increased after 1976. Both the stepwise decreases in water and sediment discharges from the Huanghe to the sea and the water-sediment regulation of the Yellow River are probably the major reasons, which result in the increase in sediment particle size at B63 in recent decades.