| Abstrakt: |
The bioavailability of hydrophobic organic chemicals decreases with aging in soil because of sequestration. However, assessments of the risk of exposure to contaminated soils are usually dependent on eitherchemical concentrations, which are measured using vigorous extraction methods, or models that assume an equilibrium without considering the actual conditions. The objective of this research was to determinethe availability and desorption kinetics of freshly added and aged naphthalene from a peat and a mineral soil; naphthalene was desorbed into solutions with pH levels that approximate those found in different gastric regions. Soil and peat samples were spiked with radiolabeled and unlabeled naphthalene at 2 and 20 mug/g and were aged from 0 to135 d. Desorption kinetics were determined using a simulated stomachsolution (0.1 M NaCl, 0.1 M HCl, 0.01 M NH4Ac, pH = 1.0) and a neutral solution (0.2 M NaCl, pH = 6.7) that represented the pHof intestinal conditions and most soils. Peat sorbed much more naphthalene than did soil, and it allowed little desorption. Though both acidic and neutral extracting solutions could desorb naphthalene, little apparent effect of aging was observed in peat, whereas desorption from soil declined markedly with aging. In addition, the percentage of naphthalene that desorbed from soil was greater for the higher incubation concentration. The desorption of naphthalene from the peat andsoil was higher into the neutral solution than into the gastric solution. These results suggest that aging, exposure conditions, concentration effect, and organic matter content should be taken into accountin predictive models and risk assessments. [ABSTRACT FROM AUTHOR] |
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