ABSTRACT: Sediments from Lakes Pontchartrain and Maurepas: Database Development and Preliminary Synthesis of Historical Chemical and Other Environmental Data

MANHEIM, FRANK T., ANDREW MCINTIRE, GEORGE C. FLOWERS, MARCY MAROT, and CHARLES W. HOLMES

This research is pan of a larger USGS-led cooperative program on Lake Pontchartrain. It seeks to compile available data on concentrations of metals and organic compounds, and other background information related to bottom sediments in Lakes Pontchartrain and Maurepas. The goal a comprehensive, widely-accessible database is designed to permit quantitative assessment of environmental (toxicity), scientific, and management questions related to bottom sediments.

The data organization, processing and validation system utilizes methodology that was earlier developed for work along the U.S. Atlantic margin, as well as methodologies used by other federal agencies. It draws on cooperation with many regional organizations, including Tulane University, Louisiana State University, the Louisiana Dept. of Environmental Quality, USGS-Water Resources Division, U.S. EPA, U.S. Army Corps of Engineers, and the University of New Orleans. Currently, 385 stations with 775 samples have been identified, including 472 with chemical data and 270 with texture information.

Assessment of current data suggests that many of Lake Pontchartrain's sediments have relatively low levels of major toxic metals and organic contaminants. This is unlike other urban estuaries that have been found to be heavily contaminated. For example, no samples had copper concentrations that exceeded effects-based sediment toxicity criteria for bulk sediments (70 ug Cu/g). On the other hand, samples distributed over wide areas exceeded toxicity screening criteria for lead. The contrast suggests lead sources in air pollution. Accessible data coverage is still sparse in areas near urbanized areas like New Orleans and more industrialized inland waterways. An exception to the latter is Bayou Trepagnier, from which samples having as much as 5000 ug/g lead have been reported.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana