An investigation of the presence and mobility of pollutants at sites used for land treatment of oily residues /

Abstract

The purpose of this study was to evaluate the conditions which exist at sites used for the land treatment of oily residues, after closure. Three sites, which had closed for different periods of time were selected and the site soil was analyzed for priority pollutants, and evaluated for the characteristic of Extraction Procedure (E.P.) Toxicity. Soil samples from the sites were also analyzed for oil content, pH, CEC, T.O.C., Cl('-) and heavy metals. Soil pore water and deep core samples were analyzed for heavy metals, oil content and selected priority pollutants, to determine whether or not pollutants were reaching the unsaturated zone.

The results show that the priority pollutants present at these sites were primarily PNA's and phenolics, and that the metals and oil were generally immobilized in the top 25-50 cm of soil. However, some metals were mobilized and could present a pollution threat. Analysis of soil pore water and deep core samples indicated the presence of trace amounts of several organics in the unsaturated zone up to a depth of 150 cm. Further analysis of soil and water samples from the unsaturated zone below 150 cm is required to determine the extent to which organics are penetrating the unsaturated zone.

The results show that no appreciable degradation of the oil present at the sites took place over a 15 month period. The soil pore water contained Cl('-) at concentrations from 12 mg/l to 5000 gm/l, Fe and Mn at concentrations from trace amounts to 12 mg/l, Zn and Ba at concentrations up to 5 mg/l. The E.P. Toxicity extract of the site soils did not contain any compounds above the allowed levels. Thus, the sites did not exhibit the characteristic of E.P. Toxicity. In addition there was no correlation between the concentration of metals in the E.P. Extract and the concentration in the soil pore water, showing that the test does not model the leaching of metals under the conditions existing at these sites.