Irreversible adsorption of PCB to natural and simulated sediment
Conference
·
OSTI ID:455287
- Rice Univ., Houston, TX (United States)
In sediment and soil systems many mechanisms have been proposed to explain the slow release of irreversible fraction of hydrophobic organic contaminants. However, the complexity of soils and sediments has made it difficult to determine specifically what causes the bound fraction. A surrogate sediment was produced to alleviate some of the complexity and consists of anatase coated with an anionic surfactant. The surfactant coating of the surrogate sediment was observed to reproduce the adsorption/desorption behavior of the humic material present in a natural sediment. A desorption-resistant solid phase concentration of hydrophobic contaminant has been observed to exist for natural and surrogate sediments. This bound fraction could not be explained by artifacts of the procedure or commonly invoked kinetic models. The size of this compartment has been determined and was measured by repetitively exposing the sediment to the contaminant. The desorption which is bimodal has a labile phase which appears to be reversible and a resistant phase which desorbs at a low equilibrium concentration of 0.6 to 0.7 ppb--after the resistant compartment has been filled-- for both sediments. Literature reported field observations appear to be consistent with the laboratory observations of a resistant fraction which is released at ppb residual solution concentration. The remediation of sediments contaminated by hydrophobic organic chemicals may be severely limited by the existence of an irreversibly bound fraction. These results may significantly alter soil quality limits as currently set in the US EPA.
- OSTI ID:
- 455287
- Report Number(s):
- CONF-961149--
- Country of Publication:
- United States
- Language:
- English
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