Estimation of bioavailability and potential risks of naphthalene in soils with solid phase microextraction.

A series of batch experiments were conducted to observe the variations of bioavailability of naphthalene in different types of soil with indigenous microorganisms. Solid phase microextraction (SPME) was employed to estimate the bioavailability of naphthalene in the soils. Various soil properties were attained by artificially modifying soil organic matter (SOM) with the addition of bagasse compost and textures with the addition of original silt and clay to determine the correlation between the amount of biodegraded naphthalene after 300 h and the amount of extractable naphthalene by SPME. Experimental results indicated that the biodegradation rate increased from 0.30 (sandy loam) to 0.48 (silty loam) μg g(-1) h(-1) when soils had more silt/clay. In contrast, the biodegradation rate slightly decreased from 0.30 (1.3% SOM) to 0.20 (5.2% SOM) μg g(-1) h(-1) when the SOM was high. Distributions of naphthalene in soils after biodegradation were affected by the addition of bagasse compost. It showed that the bioavailability of naphthalene in soils decreased with an increase in SOM. Sequestration as measured by ultrasonic extractability evidently occurred within 4 months in aged soil samples. However, the amounts extracted by sonication after 4 and 16 months of aging did not statistically differ from each other. The SPME measurements correlated well with the amount of biodegraded naphthalene by indigenous microorganisms. Results of this study demonstrate that SPME is a promising method to estimate the bioremediation efficacy of naphthalene-contaminated soils with various properties.