Superfund Research Program

Assessment of Contaminant Concentrations and Ecologic Implications

Project Leader: Timothy Ford
Grant Number: P42ES005947
Funding Period: 1995 - 2000

Project-Specific Links

Final Progress Reports

Year:   1999 

Research in the past year has focused primarily on measurements of microbial diversity as indicators of exposure to bioavailable forms of contaminant. In particular, project investigators are currently focused on arsenic and cadmium resistance. These toxic, potentially carcinogenic metals are present at high concentrations in the sediments of New Bedford Harbor. The underlying premise of this work is that the presence of cadmium and arsenic in a bioavailable form (and thus an ecological, and consequently, human health concern), should result in increased expression of metal resistance genes. Screening for such a response at the molecular level is being investigated as an indicator of the bioavailability of contaminants and the potential for adverse biological effects.

Cadmium and arsenic resistant aerobic and anaerobic bacteria were isolated from an area of New Bedford Harbor characterized by high concentrations of metal contaminants. The 16S rRNA gene was amplified using PCR, and restriction fragment length polymorphism analysis was used to group the bacteria for further study. The isolates have been screened for their level of resistance to arsenic; growth has been observed at concentrations of arsenic up to 150 mM. Southern blotting is being used to screen for the presence of the ars resistance genes in all of the isolates. Thus far, researchers have observed arsC chromosomally encoded on several isolates.

Additional studies
Project investigators have completed studies of contaminant metal migration through capping material (remediation alternative). Under simulated conditions of submarine groundwater discharge (SGD), research has shown that advective transport of contaminants is highly significant. This provides critical information for management decisions on remediation approaches. Effects of groundwater chemistry on metal mobilization have demonstrated the importance of redox conditions, sulfide, pH, and organic carbon on capping efficiency under conditions of SGD. Researchers have examined response of clam larvae to exposure to PCBs; there is a clear dose-response relationship between concentration of PCBs and development of larval abnormalities. International work on fate of metals in Lake Chapala, Mexico, has shown that mercury concentrations in Chirostoma, a commercially important fish species, exceed WHO guidelines. Collaboration with the Bermuda Biological Station for Research resulted in a jointly funded conference on "Ocean and Human Health."