Abstract
PCDD/DFs were included as the impurities of the organochlorine herbicides, and very large amount of them are left in Japanese recent paddy soil yet. They will flow out from rice pad into coastal region by way of adjacent river system, going with operation stages like the paddy soil mixing or rice transplanting, so they will have great implications for coastal environment and organisms in there.
Judging from the relation between particle size distribution and PCDD/DFs concentrations, those compounds move with particles of ≤10 μm in diameter and it is supposed that they will be adsorbed or absorbed by particles of this size.
In the vicinity of the river mouth, ≤10 μm particles in diameter and PCDD/DFs concentrations were decreased simultaneously, therefore, there is high possibilty that they must be exported from river mouth to the coastal region. Consequently, it is important to know the behaviour of the particles of ≤10 μm in order to understand the fate of PCDD/DFs in coastal environment.
