Abstract
Persistent man-made litter that has washed ashore becomes more serious in the Sea of Japan. In order to devise effective measures to prevent the outflow of land litter, information of the right quantities, types, and origins of the beached litter is essential. The measurements were carried out on two sites at the same time, and the confidence level was evaluated by means of the absolute percentage excess which is [100× (|Q1-Q2|)/(Q1+Q2)] where QN is the quantity of litter on Site N. Small debris is overwhelming in number, whereas large litter is overwhelming in weight. Since small fragments are generated from large litter of shaped polyolefin articles, a survey of large litter that has freshly washed up is important. The percentages of excesses of freshly washed-up bottles, large floats and heavy ropes were measured at two adjacent sites of 250m beach lines every month at 6 beaches for 3 years. The results indicated that the confidence index for the amount of litter that freshly washed up on the whole of the beach, including the monitored site, was obtained by monitoring a 500m beach line every month at several locations.
