Comparison of characteristics of heavy metals in different grain sizes of intertidalite sediment by using grid sampling method

384 surface sediment samples were collected from mud flat, silt flat and mud-silt flat of Bohai Bay by 1 m and 10 m interval using grid sampling method. Concentrations of Al, Fe, Ti, Mn, Ba, Sr, Zn, Cr, Ni and Cu in each sample were measured by ICP-AES. To figure out the random distribution and concentration characteristics of these heavy metals, concentration of them were compared between districts with different grain size. The results show that varieties of grain size cause the remarkable difference in the concentration of heavy metals. Total concentration of heavy metals are 147.37 g·kg^-1, 98.68 g·kg^-1 and 94.27 g·kg^-1 in mud flat, mud-silt flat and silt flat respectively. Majority of heavy metals inclines to concentrate in fine grained mud, while Ba and Sr have a tendency to concentrate in coast grained silt which contains more K₂O·Al₂ O₃·6SiO₂. Concentration of Sr is affected significantly by the grain size, while concentration of Cr and Ti are affected a little by the grain size.