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The fallout radionuclide 210 Pb has been widely used as an environment tracer for estimating deposition rates and revealing sedimentary processes. However, a comprehensive evaluation of different grain size fractions effects on the adsorption of 210 Pb is a prerequisite for effective utilization of the tracer. In this paper, 11 cores were collected from different sub-sedimentary environments in the Yangtze Estuary and its adjacent area, x-radiographs of the sediment cores were taken, and the grain size and radioactive 210 Pb levels were analyzed systematically; the relationship between grain size and 210 Pb was discussed in detail. The results indicated that 226 Ra was relatively stable, with no systematic variation from the Yangtze Estuary to inner shelf region or with depth and was unaffected by grain size. In contrast to 226 Ra, significant positive correlations between the fine fraction (<32 µm) and 210 Pb ex were found, particularly between the clay component (<4 µm) and 210 Pb ex , in all the sediment cores. The 210 Pb ex profiles were improved significantly after using the linear relationships for quantitatively normalizing the activities to the <4 µm components, and the calibrating 210 Pb ex profiles of different zones matched the sub-sedimentary environments of the recent reduction in sediment discharge after Three Gorges Dam (TGD) impoundment very well. Also, through the normalization procedure, it was found that the Yangtze-derived clay component may play the most important role in the distribution of 210 Pb ex in sediments, especially in upper layer 10-15 cm of the cores. When applying 210 Pb data to establish the geochronology or study sedimentary processes in the East China Sea or similar sedimentary environments, the grain size effect should be fully considered.

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