Research scientists from Syracuse University, the State University of New York at Oswego and New York State Department of Health and State University at Albany have been working on the development of remedial technologies as a part of the NIEHS research program. Chemical engineers from Syracuse University have been working on the development of a process that uses carbon dioxide at very high pressures to create a supercritical fluid effective in extracting PCBs and other contaminants from soils. This technology has evolved to the point where it is now possible to effectively extract the PCBs from the solid materials and scientists are now working on ways to destroy the extracted PCBs.
Biochemists from the Department of Health and the Environmental Research Center at Oswego have been working for years to enhance the biodegradation of PCBs using bacteria. It is well known that microorganisms can degrade PCBs and other similar contaminants and that this process occurs in natural systems. What is not known is why degradation works better in certain environments than in others and how to enhance the process to ensure complete breakdown of the contaminants. Data developed during the past few years indicate anaerobic (absence of oxygen) bacteria are able to partially degrade PCBs, but the process is slow and will not work in all environments. Partial degradation may in fact create compounds that are more available to wildlife and eventually to humans. In situ, or in place, biodegradation is a preferred remedial technology because it does not require removal of the contaminated material to be treated. The ongoing debate amongst the biodegradation research community focuses on whether natural microbial processes work effectively to destroy PCBS sufficiently to reduce impacts to wildlife and humans. Industrial representatives who have been responsible for discharging PCBs to the environment favor in situ biodegradation technologies because of the obvious cost savings. If the process can be accomplished in place, there are large economic advantages for the responsible parties for remediating the impacted areas.
In addition to supercritical fluid and biodegradation remedial technologies, researchers at the College at Oswego have developed an advanced oxidative process(AOP) that is capable of degrading PCBS in sediments and water. Photocatalytic processes utilize light energy and a solid photo excitable catalyst to produce free radicals or superoxidizing compounds which aggressively degrade organic contaminants. Although this technology is currently being used to degrade contaminants in water and air, the Oswego laboratory is one of the few worldwide facilities that has successfully demonstrated the application of the technology to the treatment of contaminated sediments.
The Oswego researchers recently demonstrated the degradation of more than 90%
of PCBs and more than 99% of the total volatile organic compounds (VOCs) from a State Superfund Site in a matter of minutes using an
electrochemical treatment process (ECP). The electrochemical treatment involves introducing an electrical current into the suspended sediment and water mixture to accelerate the degradation process. Hydrogen peroxide additions to the electrolyzed slurry produces free radicals with aggressively attack PCBs attached to suspended solids and dissolved in water.
Oswego researchers recently determined that PCBs are far more volatile than is generally believed. Laboratory experiments conducted on PCB-contaminated sediments collected from the Massena area demonstrated that as much as 75% of the PCB can be lost to volatilization under normal temperatures. Investigators determined that the PCB loss was directly related to the loss in water and even when the PCB are submerged, the sediments rapidly lose the adsorbed contaminants as the water evaporates. This finding has significant implications since the PCB-contaminated sediments of the St. Lawrence River are being dredged and stored onshore allowing the sediments to air dry and therefore release their store of PCBs to the local air.
This finding provides answers to the sources of PCBs measured in polar animals and humans and conforms to air monitoring data collected near the General Motors hazardous waste landfill. Air monitoring data collected near the General Motors landfill indicate the PCB concentrations are elevated during late spring to early summer corresponding to the earths warming as well as when the soils are losing stored moisture through evapo-transpiration. Air exposure may prove to be a major source of contamination to area residents as the contaminated soils and dredged material lose water and accompanying PCBs through evaporation.
Although there has been a great deal of progress made in recent years in understanding how environmental contaminants move in the environment and how these substances can be destroyed, there is a great deal more to learn about how these compounds affect living things. What is clear, however, is that a broad class of environmental contaminants at very low exposures have subtle, non lethal health effects on animals, including humans, and on their behavior and mental abilities. Although subtle, these chronic effects impact not only the exposed populations, but their children as well.
