摘要:

Volatilization of low molecular weight components of spilled crude oil pollutes the atmosphere, but if volatilization can be prevented, these compounds can biodegrade in the soil. Various materials with the potential to act as bulking agents for the purpose of enhancing bioremediation of oil-contaminated soils were tested in the laboratory to determine their effectiveness as sorbents in reducing volatilization of crude oil components. Sawdust, chopped bermudagrass hay, peat, vermiculite, and activated carbon served as the bulking agents and were mixed into the soil at a 1:1 (v:v) ratio immediately after oil was applied. Soils used were a Bowie sandy loam (fine-loamy, siliceous, thermic Plinthic Paludult) and a Weswood clay loam (fine-silty, mixed thermic Fluventic Ustochent). Soil moisture was adjusted to −0.5 MPa potential, and East Texas crude oil was added to each soil to provide 8% oil on a dry soil weight basis. Incubation temperature was either 10° or 30°C during the 7-day period. Volatile hydrocarbons were analyzed using gas chromatography. At 30°C, soil reduced volatilization by 17%, compared with oil alone, but there was no significant difference between the two soils. Addition of peat or hay reduced oil volatilization further. Activated carbon reduced volatilization losses by 28%. Decreasing the temperature from 30° to 10°C reduced volatilization by approximately 20% for most treatments. Significant amounts of volatile hydrocarbons were lost within the first 4 h after addition of oil to the soil; therefore, it may not be practicable, in many situations, to add bulking agents quickly enough to reduce volatilization significantly.

ISSN:0038-075X    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Quick and reliable information about the engineering properties of soils is needed for evaluating soils for nonagricultural uses. The objectives of this preliminary study were, (i) to relate some engineering properties of typical tropical soils from Nigeria to their mineralogy, (ii) to develop simple models for predicting and characterizing these engineering properties from easily determinable soil properties, and (iii) to compare values of the swell potential of these soils estimated by various equations used in soil mechanics with values measured directly in the laboratory. Data from 30 soil samples collected across Nigeria were used for this study. The extent of the volumetric shrinkage (VS) hazard posed by the soils is influenced more by the dominant clay minerals than by the texture or soil order. Generally, soils containing only kaolinite (1:1 mineral) had low VS values (<10%), whereas those containing either low or trace concentrations of smectite or vermiculite (2:1 minerals) acted like expansive soils (VS = 10-30%) in spite of the dominance of the 1:1 mineral. Soils with substantial amounts of either smectite or vermiculite had very high VS values (>30%).There were strong linear relationships between VS, liquid limit (LL), and plastic limit (PL) on one hand and cation exchange capacity (CEC), organic matter (OM), and clay content on the other. Regression equations developed with CEC could not predict accurately the VS and LL of two of the 10 validation soils with <5 cmol(c)/kg CEC and dominated by kaolinite. The OM-based model could not provide good estimates of the PL of the two vertisols with >80% VS values. The relationships between the soil properties and plasticity index were weak. Some nonlinear equations used to predict the swell potential of soils grossly underestimated the measured shrink-swell hazard posed by these soils. These predictive empirical equations need to be tested on a wider range of tropical soils than were used in this study before any valid conclusions on their applicability can be made.

ISSN:0038-075X    

出版商:OVID    

年代:1998

数据来源: OVID