THE DISTRIBUTION OF CHLOROBENZENES IN THE BOTTOM SEDIMENTS OF ISE BAY

The concentration of dichloro- to hexachlorobenzene in the surficial bottom sediments in Ise Bay were determined as a preliminary study of the behavior of these compounds in this coastal environment. The sediment samples were collected from 10 stations on the west coast and in Yokkaichi Port in March 1987 and from 44 stations all over the bay in October 1987. 1,2- and 1,3-Dichlorobenzene and 1,2,3- and 1,2,4-trichlorobenzene levels were highest in the vicinity of Yokkaichi Port and Tsu-Matsuzaka Port. Higher levels of these compounds were also found in the middle of the bay. The concentrations of tetrachlorobenzene isomers were generally low but they were also higher in the vicinity of the two ports. 1,3,5-Trichlorobenzene was higher only in the vicinity of Yokkaichi. The levels of these compounds were not higher around Nagoya City, the largest city in the bay. The stations with higher dichloro- and trichlorobenzenes concentrations in the middle of the bay covered the area where the sediment particle size was small. This was also the area where downward water flow was estimated to exit. These findings indicated that these congeners were adsorbed by suspended particulates and transported by water flow. The distribution patterns, therefore, could be explained by the following effects: the distance from the source, the horizontal transport caused by the river inflows and the sedimentation caused by downward water flow. Pentachlorobenzene concentration was very low and its distribution was not clear. Hexachlorobenzene had quite a different distribution pattern from other congeners, indicating that its sources were different.