Marine sediment is considered any deposit of insoluble material, primarily rock and soil particles, transported from land areas to the ocean by wind, ice, and rivers, as well as the remains of marine organisms, products of submarine volcanism, chemical precipitates from seawater, and materials from outer space (e.g., meteorites) that accumulate on the seafloor. This data collection activity covers baseline, geographical and temporal trend monitoring of heavy metals and chlorinated hydrocarbons in sediments from the marine chemistry monitoring programme. Data for sediments covers foreshore and offshore areas around Ireland and in the North Atlantic Ocean between Ireland and Canada. Sediment sample stations have been collected since 1992. Contaminants in sediments monitoring has been undertaken by the Marine Chemistry team of the Marine Environment and Food Safety Services (MEFSS) section of the Marine Institute. Data 100% complete for surveys since 1992.