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This article in JEQ

  1. Vol. 31 No. 4, p. 1309-1315
     
    Received: Nov 5, 2001


    * Corresponding author(s): ckhachi@calstatela.edu
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doi:10.2134/jeq2002.1309

Long-Term Studies on the Effects of Nonvolatile Organic Compounds on Porous Media Surface Areas

  1. Crist S. Khachikian *a and
  2. Thomas C. Harmonb
  1. a Dep. of Civil Engineering, California State Univ. Los Angeles, 5151 State University Drive, Los Angeles, CA 90032-8151
    b Dep. of Civil and Environmental Engineering, Univ. of California Los Angeles

Abstract

This paper investigates the long-term behavior of porous media contaminated by nonvolatile organic compounds (NVOC) in terms of specific interfacial surface area. Specifically, a natural sand, Moffett sand (MS), was contaminated with naphthalene and the surface area was measured repeatedly over time using nitrogen adsorption–desorption techniques. A field-contaminated sand affected by lampblack material (LB) from former manufactured gas plant operations was also studied. Lampblack is a carbonaceous skeleton containing polycyclic aromatic hydrocarbons (PAHs) and other hydrocarbons. It is hypothesized that soils contaminated by these types of chemicals will exhibit significantly less surface area than their clean counterparts. The surface areas for the contaminated MS samples increased toward their clean-MS values during the 700-h aging period, but achieved the clean values only after pentane extraction or heating at 60°C. Heating at 50°C failed to achieve a similar recovery of the clean-MS surface area value. Nonspecific mass loss tracked the increase in surface area as indirect evidence that naphthalene loss was the cause of the surface area increase. For the LB samples, aging at 100°C produced a slight decrease in surface area and mass while aging at 250°C caused the surface area to increase roughly threefold while the mass decreased by approximately 1%. These results suggest that, under moderate heating and over the time scale of this investigation, there is a redistribution of the complex contaminant mixture on the solid matrix. Greater temperatures remove mass more efficiently and therefore exhibited the surface area increase expected in this experiment.

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Copyright © 2002. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.31:1309–1315.