Standing stock and mass balance of marine litter in the Seto Inland Sea, Japan.

The basin of Seto Inland Sea has a population of 31 million people. The standing stock and mass balance of marine litter in this area was estimated using rapid assessment for beach litter, questionnaire surveys on removed amounts of marine litter, and existing data. The mass balance of marine litter was explained by using a single box model, assuming complete mixing and uniform density. If the standing stock of drifting and beach litter combined was 3400 tons, the inflow of litter from rivers was 3000 tons/year, generation of litter at sea was 1200 tons/year, and inflow from the open sea was 300 tons/year. The amount of marine litter removed from the beach and sea surface was 1400 tons/year, outflow to the open sea was 2400 tons/year, and deposition on the sea bottom was 700 tons/year.