New Directions for NOAA/NS&T Program: Historical Reconstruction of Sediment Contamination Using Dated Cores

Sediment cores sampled in coastal and estuarine areas can be used to reconstruct historical trends in sediment contamination. The sediment cores have to be undisturbed in order to obtain a good continuous chronological record. The core layers are dated using various techniques: shifts in pollen species related to known climatic or local changes, known natural events such as storm or hurricane, natural or man made radioactive isotopes (such as 210 pb, 137 Cs, or 238-24OPu). The analysis of trace metals or organic compounds in the dated horizons leads to a chronology of the sediment contamination of the area. Such studies, performed between 1970 and 1980, showed that the most contaminated sediment strata were those deposited between 1960 and 1975 in the coastal United States as well as around the world. After a careful review of the available literature on the subject, the National Oceanic and Atmospheric Administration (NOAA) National Status and Trends Program (NS&T), decided to included such studies in its monitoring efforts in order to get contamination trends in the marine sediments. These new studies should help in monitoring what happened in the last decade and in particular if the worldwide decrease noticed in recent years for the Pb pollution in marine sediments is also observed for the other contaminants monitored by NS&T.