Chlorinated degreasing solvents: Physical-chemical properties affecting aquifer contamination and remediation

Chlorinated degreasing solvents are multicomponent liquids containing not o nly the chlorinated hydrocarbons with which their name is associated (e.g., trichloroethylene or [TCE], perchloroethylene or [PCE], 1,1,1-trichloroeth ane [TCA]) but also a number of organic additives included as corrosion inh ibitors and antioxidants. The additives. such as 1,4-dioxane, are likely to be of significant public-health importance as ground water contaminants du e to their toxicity solubility, and mobility. Following their use in vapor degreasing systems by industry, chlorinated degreasing solvents will also c ontain about 25% solubilized oil and grease. A number of physical-chemical properties become especially important in the light of the multicomponent nature of these solvents. First, the higher aq ueous solubility and lower sorption of the additives makes it is reasonable to expect that faster moving plumes of these solvent additives will preced e plumes of the chlorinated hydrocarbons. Second, due to high losses of chl orinated hydrocarbons by volatilization from vapor degreasers during years in the middle of the century, it is probable that background concentrations of these hydrocarbons are present in ground water flow systems due to thei r downwind washout. Finally, the solubilized oil and grease may cause profo und changes to the wettability of aquifer materials contacted by the solven ts during their subsurface migration. II is argued, therefore, that the wet tability of aquifer materials contaminated by chlorinated degreasing solven ts needs to be experimentally determined before remediation of DNAPL at eac h site, rather than being simply assumed as water wet.