The degradation of plastic litter in rivers: Implications for beaches

Abstract

Polythene sheeting is a major litter component on estuarine beaches and river banks. Sanitary towel backing strips, which are one of the commonest items of sewage related debris found on beaches, enter the riverine system via combined sewer overflows. Investigations on these items, positioned at natural riverine stranding levels, showed that after an initial rapid breakdown little further loss of tensile strength occurred. Experiments carried out on backing strips, buried in the bank, suspended from a tree and tethered to the bank, showed significant change. Buried samples retained the greatest tensile strength retention, dropping no lower than 90 %, the other samples showed similar retention rates at 80 %. The difference is probably due to photodegradation as biodeg- radation effects were minimal. Probably, the longevity of such plastics is a major reason for their abundance and widespread distribution both on river banks and beaches.