You are here: Home › Stressors › Pollution › COAST › Assessment Studies
Sediment Coring Study
This study addresses historical trends in contaminants of estuarine and coastal sediments. The composition of surface waters in rivers, lakes, and coastal areas has changed over time. In particular, changes due to the Industrial Revolution, dating from the middle of the 19th century, are very well known. These changes are expressed by increased levels of natural components, such as trace metals and nutrients, but also by the increase of anthropogenic compounds, such as polychlorinated biphenyls (PCBs) and pesticides.
Since the early 1960s, regulatory measures have been taken to decrease the amount of pollutants entering our waterways, but the bulk of these environmental measures were not enacted until the 1970s. Because of the scarcity of accurate data, due to lack of sensitive techniques or of regular data collection in the past, the extent of the past pollution and the effect of the recent legislative limitations is often difficult to access.
The analysis of sediment cores presents a way out of this dilemma. Most pollutants have an affinity for and adsorb easily onto sediments and fine particles. Therefore, by analyzing cores of undistributed sediments it is possible to assess the historic pollution of a given system. Sediment cores reflect not only the history of pollutant concentrations but also register the changes in the ecology of a water body. For example, changes in estuarine eutrophication are reflected in the concentration of organic matter, nitrogen, and phosphorus, while lake acidification is translated into changes in diatom assemblages.
The use of cored sediments to reconstruct the chronology of coastal and estuarine contamination is not, however, devoid of problems and caution must be exercised. Sediment mixing by physical or biological processes can obscure the results obtained by such studies, and sophisticated methods must be used in cases to tease out the desired information.
Areas for which coring data exist include; East Coast: Hudson-Raritan Estuary, Long Island Sound marshes, Chesapeake Bay and Savannah Estuary; Gulf Coast: Tampa Bay, Mississippi River Delta, and Galveston Bay; West Coast: Southern California Bight, San Francisco Bay, and Puget Sound.