TIME TRENDS AND SOURCE FOR DIOXINS IN SEDIMENTS IN A LARGE-SCALE RICE PRODUCTION AREA, NIIGATA, JAPAN

Abstract

The age of a sediment core in Toyano lagoon was measured using radioisotope technique, and dioxins (TCDDs/Fs and co-PCB) amounts were measured. TEQs increased with time, reached its maximum in 1968 and decreased after that. The TEQs of layers from 1960 to 1975 exceeded the Japan environmental criteria for sediments, 150pgTEQ/g. Principal component analysis showed that dioxins from PCP, CNP and PCB products were the principal components. TCDDs/Fs from PCP and CNP accounted for almost all TEQ, and most of co-PCB came from PCB products used past. The results tell us that today's dioxins' pollution comes from the chemicals used not now but past.