No data with location information were excluded. Hence, users are responsible for establishing their own quality standards in use of these data. However, since data quality and comparability are critical issues for contaminant analysis, we have provided annotations on the results of quality-screening tests in the database. These may assist users in choices of data for given purposes, as described in detail in the above publication. The concentrations of metals in Lake Pontchartrain sediments generally fall within background ranges, well below values associated with toxic effects in benthic organisms.
Exceptions occur for samples collected near New Orleans coastal canals.
Values close to shore may double or triple those in more centrally located environments. We normalized concentrations of metals in surface sediments of Lake Pontchartrain to concentrations in deeper sediments pre-dating European settlement to determine the percentage of samples containing metals of anthropogenic origin. Lake Maurepas is isolated from possible contamination emanating from the urban areas around New Orleans. The specific origin and transport of introduced barium is unclear. We find little difference between metal concentrations in sediments in the vicinity of the Spillway and other lake sediments.