ABSTRACT
The fate of buried stranded Amoco Cadiz oil within sandy beaches has been investigated during a 3-year follow-up study after the tanker breakup. Observations at eight sandy North Brittany beaches have shown that oil, in discrete layers 1 to 2 centimeters thick, persists in several beaches. Followup studies have shown that such buried oil layers can migrate downwards within the beach sediment, eventually to stabilize deep within the beach at or near the water table.
Detailed data are presented on three beaches, including a dune-beach system and a transport-beach system, including observations on oil distribution and movement, residual contamination of sediments and underlying water table, and rates of oil movement.
The vertical migration of buried oil layers within these beaches appears to be a function of water table movement during the tidal cycles, and of the porosity (grain size) of the beach sediments. Rate of downward migration calculated for two beaches (Centre Héliomarin north beach, Pen Ar Mez beach) range from 0.25 to 1.0 millimeter per tidal cycle, with a residual fluctuation of 0.1 millimeter per tidal cycle. In beaches containing an impermeable basement of loam, silt, or bedrock (transport-beaches), the downward movement of the oil layer is interrupted at the basement interface, with subsequent movement along the basement and emergence of the oil in the lower intertidal and subtidal sediments at the foot of the beach.
These observations enable the prediction of the route and fate of stranded buried oil in sandy beach systems, and indicate the location of potential oil traps.
Sources and fate of microplastics in marine and beach sediments of the Southern Baltic Sea—a preliminary study
