^(210)Pb法测定东海大陆架现代沉积速率

DETERMINATION OF RECENT SEDIMENTATION RATES ON THE CONTINENTAL SHELF OF THE EAST CHINA SEA USING ^(210)Pb METHOD

一、前言自从七十年代初期(Krishnaswami等,Koide等)。210Pb法首次用于测定湖泊和海洋沉积速率以来,它已成功地用于湖泊、河口、峡湾、潮间带、大陆架和大陆斜坡等不同环境的沉积作用研究(Bruland,Robbins,)。在实际应用中,210Pb法与纹泥法,树木年轮法,孢粉法及某些放射胜同位素法一样,已被证实是一种较可靠的测年方法。这种方法尤其适用于近百年内现代沉积速率的测定。测定沉积物年龄的210Pb法不仅在近代沉积作用的研究方面,而且在解释工业革命以来人类活动对近代地球化学过程的影响方面均有显著的进展。

Three undisturbed cores were taken with a static corer(Model LDC 1—1)from the continental shelf of the East China Sea.The excess(unsupported)210Pb profiles of the cores revealed three characteristic regions:a surface mixed layer,a region of radioactive decay,and a region of low background activities.In the region of radioactive decay,the distribution of excess 210Pb decreased exponentially with depth.The compressive effect of the sediment was corrected based on the porosity of the surface layer.The corresponding sedimentation rates of the three cores were 0.83,0.39 and 0.48cm/yr respectively and the sedimentation fluxes were 0.42,0.28 and 0.21g/cm2/yr respectively.