摘要：Distribution of Cu, Cr, Pb, Zn, Cd, Ni, and Hg in mud of Japanese rivers of first category was investigated with 178 mud samples from the mouth of 91 rivers, collected from August to September, 1973. The mud from the rivers in San-in district on the Japan Sea coast showed the lowest amount of all the heavy metals. The samples obtained from the Tsurumi or the Yodo River, near the industrial area, showed a very high concentration of all the metals. From the calculated values of the mean and standard deviation of each metal, it was considered that the higher these two values were, the more the river was polluted. The mean value of fignition loss was 5.03%. On the basis of this value, all the river were grouped into two classes. The first group had below 5.03% of ignition loss and the other with higher value. The mean and standard deviation of heavy metals of the former group were smaller than those of latter. Marked difference in concentration of Cd and Hg was observed between the two groups, while no difference was observed in the concentration of Ni. These results indicate that the mean of each metal in the first group river may be considered as approximate value for Japanese river mud in natural state.
