海南岛小海潟湖沉积环境演变研究

Sedimentary Environment Evolvement of Xiaohai Lagoon in the Hainan Island

对小海潟湖南部和中部2个柱状沉积物XHK04-01和XHK04-04进行了粒度分析,210Pb分析,总有机碳、总氮、总硫的含量分析,并且利用C/N,C/S在沉积物中的不同研究了小海地区沉积环境的演变。结果表明,小海南部和中部地区以粉砂为主,近年来粘土含量增加,水动力条件变弱;海水对沉积环境的影响逐渐减小,沉积物上覆水体呈淡化趋势,但相对于小海南部,中部淡化程度小。小海南部沉积速率较大,达到0.623cm/a;总有机碳、总氮在20世纪60年代之前含量相对稳定,陆源有机碳占总有机碳80%左右,60年代之后含量迅速上升,特别是1973年以来,陆源有机碳只占到总有机碳45%左右,自生有机碳增加。小海中部沉积速率较小,为0.216cm/a;总有机碳、总氮在20世纪50年代以前含量相对稳定,陆源有机碳占到总有机碳70%左右,最近50a来总有机碳和总氮含量快速增加,陆源有机碳只占到总有机碳47%左右,自生有机碳增加。小海中部和南部沉积环境在20世纪50年代之前稳定,在最近50a发生了很大的变化,这与小海潟湖口门束窄、修筑防沙堤、入海河流改道等因素有关。

The paper analyzes granularity of column sediment XHK04-01 and XHK04-04, and their 210^pb and determine total organic carbon, nitrogen, sulfur content of column sediment XHK04-01 and XHK04-04, and finally using difference of C / N, C / S in sediments researches the evolvement of sediment environment. The results indicate： middle sediment and southern sediment of Xiaohai is mostly silver sand, illuminating that middle and southern hydrodynamic conditions of Xiaohai become weak; effects of seawater on sedimentary environment gradually decrease and the overlying water of sediment gradually desalt, but southern water is more desalted less salt than middle water. Southern sediment rates was 0.623 cm/a; total organic carbon and total nitrogen was steady before 60s in 20th century, and terrene organic carbon was about 80 per cent of total organic carbon; total organic carbon and total nitrogen rase rapid after 60s in 20th century, especially since 1973, and terrene organic carbon was about 45 per cent of total organic carbon. Autochthonic organic carbon rose. Middle Sediment rates was 0.216 cm/a, and total organic carbon and total nitrogen was steady before 50s in 20th century, terrene organic carbon was about 70 per cent of total organic carbon; total organic carbon and total nitrogen rose rapid after 50s in 20th century, and terrene organic carbon was about 47 percent of total organic carbon; autochthonic organic carbon rose. Southern and middle sedimentary environment of Xiaohai was steady from 1750s to 1950s, Southern and middle sedimentary environment of Xiaohai changed a lot in the past fifty years. The reasons are related to the narrow door of Xiaohai lagoon, building the dyke and the changing fluvial course.