Document Type

Thesis

Date of Award

5-31-1987

Degree Name

Master of Science in Environmental Engineering - (M.S.)

Department

Civil and Environmental Engineering

First Advisor

John R. Schuring

Second Advisor

Gordon Lewandowski

Third Advisor

Dorairaja Raghu

Abstract

This study addressed the problem of using volatile organics in geotechnical laboratory tests. Previous experiments with volatile organics such as benzene and trichloroethylene with soils had shown significant concentration losses during the tests. The purpose of the study was to identify the sources of loss and to quantify the magnitude of loss.

Vapor - liquid equilibrium was used to predict theoretical evaporation losses of benzene from aqueous solutions. Calculations were made for both an infinite volume of air and for a finite volume. Experiments were then performed to verify the theoretical predictions.

Other losses considered were those during solution preparation, sampling of the Flexible Wall Permeameter, and long term storage. All benzene concentrations were measured with a Gas Chromatograph.

The results of the experiments showed that losses during preparation range from 5% to 15% depending on the procedure and the time of mixing. Long term storage of the benzene solution in vials indicated that diffusion losses through the septum are less than 10% if the storage time is less than 13 days. Beyond this period, the rate of loss increases significantly. This is believed to be due to the softening of the elastic septum of the vial cap.

A series of correction curves were developed to interpret the data generated during flexible wall permeameter experiments. A comparison of the losses predicted by the curves with data from previous permeameter experiments showed approximate agreement with the concentration level observed.

In general, the study showed that the two most important parameters for benzene loss are exposure time and air volume above the solution. Improved test procedures are recommended to control the volatile losses during geotechnical laboratory testing.

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