Pathogen indicator microbes and heavy metals in Lake Pontchartrain following Hurricane Katrina.

Storm surge and several breaches of the New Orleans, Louisiana levee system caused flooding of more than 80% of the city following Hurricane Katrina in August 2005. Most of the floodwaters pumped out of the city were discharged to Lake Pontchartrain. Lake water and sediment samples were collected during September 19 to October 9, 2005 to determine the possible impact of the dewatering operation on Lake Pontchartrain. Surface water E. coli and enterococcus counts were high at stations near the mouth of the 17th Street Canal (geometric means = 6.0 x 10(3) CFU/100 mL and 1.7 x 10(2) CFU/100 mL, respectively) but decreased by factors of 40 and 5, respectively, at stations 5 km from the mouth of the canal. Priority heavy metal concentrations were generally undetectable or below U.S. EPA criterion maximum and criterion continuous concentrations. Surface sediments near the mouth of the canal contained generally higher concentrations of enterococcus, E. coli, and Al-normalized metals than points further from the canal. The impact of the discharged floodwaters on heavy metal concentrations and indicator organism counts in the water column of Lake Pontchartrain appears to have been small and short-lived. Historically, however, the canal has been a significant contributor of pollutants to the sediments.