Reliability of solid phase microextraction in estimating bioavailability of pyrene in soil.

Solid phase microextraction (SPME) coupled with gas chromatography was employed to estimate bioavailability of pyrene in soils with different properties of textures, organic matter contents (SOM) and aging periods. Experimental results indicated that biodegradation rates increased from 0.10 (sandy loam) to 0.15 (silty loam) μg g-1 hr-1. By contrast, biodegradation rate decreased from 0.10 (1.3% SOM) to 0.04 (7.6% SOM) μg g-1 hr-1. The amounts of pyrene biodegraded decreased 27% when SOM was modified from 1.3 to 7.6%, indicating that distributions of pyrene in soils at biodegradation end points were affected by the SOM. Sequestration as measured by sonication extraction had evidently occurred in aged soil samples. SPME measurements slightly overestimated the amount of pyrene degraded by indigenous and seeded microorganisms, in soils with the different properties (correlation coefficient, R2 = 0.74). The present study demonstrates that the SPME method can not replace biodegradation tests commonly used for predicting bioremediation efficacy.

Effect of applying biosolids on the biodegradation of toluene and naphthalene contaminated soils.

Biosolids contain nutrients, organic matters and micro-organisms that can provide soil benefits. In this study, toluene and naphthalene-contaminated soils were used to investigate the effect of applying biosolids on the enhancement of the biodegradation rate. The oxygen uptake rate (OUR) was determined with a respirometer and was used to calculate the oxygen uptake percentage of substrate in biosolids (a value) using a two-phase respirogram. Experimental result showed that the application of biosolids had positive effect on the enhancement of the biodegradation rate of toluene and naphthalene in the contaminated soils. The biodegradation rates of toluene and naphthalene were 15% and 20% in soils without applying biosolids, respectively. With the biosolids, its biodegradation rate for the two contaminants was about 4-fold higher in relative to control and the maximum value occurred in a soil to biosolids ratio as 1: 0.5. The a value for toluene and naphthalene was in the levels of 10-20% which revealed that the biosolids used in this study was mainly composed by micro-organism.