福建罗源湾潮滩沉积过程对人类活动和台风事件的响应

Sedimentary Processes of Tidal Flat and the Responses to Typhoon Events and Anthropogenic Influences in the Luoyuan Bay of China

潮滩地区是人类活动和台风事件影响最为显著的地区之一,利用潮滩沉积记录可以提取影响区域重大人类活动和台风事件的历史变化。罗源湾潮滩中上部盐沼和光滩柱状沉积物粒度分析结果显示,罗源湾潮滩沉积物以细颗粒为主,盐沼内部和潮滩中上部光滩柱状沉积物平均粒径分别为5.41～45.00μm和5.4～68.82μm,但在不同深度出现多次沉积物变粗的现象;利用210Pb测试计算得到的沉积速率分别为1.96 cm/a和1.23 cm/a;近年来的围填海活动导致潮间带地区沉积速率显著增大,互花米草的引种也进一步导致潮间带上部沉积速率增大。台风的强烈影响使得潮间带沉积出现间断,在沉积间断界面出现沉积物粒度变粗的现象,由此推断了近170年来显著影响罗源湾地区的台风事件沉积层的位置,并由此计算了不同时段的沉积速率。根据柱状沉积物粒度分析结果,不仅可以反演近百年来的对罗源湾产生重要影响的台风事件,也可以反演20世纪50年代以来罗源湾经历的几次较大规模的人类活动。

Situated at the junction of land and sea,tidal flat is very sensitive to typhoon event and anthropogenic influence.In order to reveal the histories of regional typhoon events and strong anthropogenic influences,two sediment cores were collected in inner Spartina alterniflora marsh and middle-upper intertidal flat in the Luoyuan Bay for sedimentary records extraction.The sediment cores were cut with 1 cm interval for grain size and radio isotope dating.The results of grain size analysis indicate that the sediment on tidal flat of Luoyuan Bay is mainly composed by fine fractions.The mean grain sizes of core sediments in inner Spartina alterniflora marsh and middle-upper intertidal flat are 5.41 μm^45.00 μm and 5.4 μm^68.82 μm,respectively;however,there are several interfaces where sediment characteristics vary obviously.The mean sedimentation rates in inner Spartina alterniflora marsh and middle-upper intertidal flat calculated from 210Pb are 1.96 cm/a and 1.23 cm/a,respectively.However,the mean sedimentation rates increased from 0.56 cm/a during 1909~1946 to 2.36 cm/a during 1946~1966 at upper intertidal flat due to strong reclamations,and the introduction of Spartina alterniflora led to the mean sedimentation rate increased to 5.10 cm/a during the early marsh formation,and with increasing of the marsh age,the mean sedimentation rate decreased to 2.83 cm/a.The sedimentary records of core sediments collected from inner Spartina alterniflora marsh and middle-upper intertidal flat not only recorded the typhoon events which brought the strong effects on the Luoyuan Bay in recent 170 years,and but also recorded the several large scale reclamation from 1950＇s.