Jacqueline A. MacDonald

Evaluating natural attenuation for groundwater cleanup

The National Research Council has issued the first comprehensive assessment of when natural attenuation works.

The effects of energy availability on the conjugative-transfer kinetics of plasmid RP4

Abstract Batch kinetic experiments were carried out to measure conjugative-transfer kinetics for plasmid RP4, which encodes resistance to kanamycin, tetracycline and ampicillin. The donor species was Rhodobacter capsulatus, while the recipient was a Pseudomonas strain obtained in our laboratory. Evaluated was a mass-action kinetic model that had a donor-to-recipient rate coefficient k11 and a transconjugant-to-recipient rate coefficient k2. Experimental results demonstrated that k11 and k12 were of similar magnitudes and could be reasonably large: e.g. up to 0.03 l gT/gD gR day for k11. However, the rate coefficients were not constants. Instead, they increased dramatically as the energy availability increased. Energy was made available in kinetic experiments from the energy substrates and from internal storage materials, carried over from prior batch growth cultures.

Natural attenuation strategy for groundwater cleanup focuses on demonstrating cause and effect

In the 20 years since cleanup of contaminated groundwater has been a high priority in the United States, recognition of both the scope of the problem and the technical difficulties involved has grown steadily Estimates of the number of hazardous waste sites where groundwater may be contaminated vary between 300,000 and 400,000 nationwide [NRC, 1994]. Legislation passed in the 1980s by Congress and the states generally required that groundwater in contaminated aquifers be restored to background or drinking water standards. Unfortunately attempts to meet these goals using conventional methods, such as pump and treat systems, frequently have been unsuccessful [NRC, 1994].

Peer Reviewed: Cleaning up unexploded ordnance

Technological limitations, cost uncertainties, regulatory disputes, environmental issues, and public safety concerns plague the transfer of military bases to civilian control.

Peer reviewed: hard times for innovative cleanup technology.

What can be done to remove market barriers to new groundwater and soil remediation technologies?

Peer reviewed: cleaning up the nuclear weapons complex.

Progress on groundwater and soil restoration is limited, and new technologies are needed.

Freshwater Science: A Discipline Divided

Without a central academic home or funding source, limnology is a fragmented and struggling field.