Identification Of The Dominated Soil Structure Factors For Diesel Migration And Residual Under Leaking Condition

Soil contaminations caused by sudden chemicals spill such as tank corrosion, pipes broken, facilities explosion and transportation accident have been increasing in frequency and harmness. In this study, the simulated accidental spill of diesel was performed in 14 types of Chinese soil samples. The residual concentration and vertical distribution of diesel were investigated. Meanwhile, the soil particle size distribution and pore characteristics in 14 types of soils were identified quantitatively and systematically. Based upon different morphology of soil types in China, the multivariate linear relations of diesel residual amount and migration depth with the parameters of soil structure characteristics are established through SPSS statistical analysis, and the sensitive factors which affect the migration depth and residual amount of diesel are identified as well. The study will be benefit to further comprehend the discipline and mechanic underlying the formation of residual NAPL in soil pore space.The soil structural features and basic physical-chemical properties determined by mercury intrusion porosimetry, nitrogen adsorption method, geotechnical test and laser diffraction method showed that basic physical-chemical properties were significantly different due to the effect of soil parent material, climate, land use and human activities. There is strong correlation between the parameters of particle size distribution calculated according PSD curve. Two principal components factors were obtained through factor analysis, defined as size factor and shape factor, which can explain 93.3% of soil particle size information There is also strong correlation between the parameters of pore size distribution. Three principal components factors which can explain 92.6% of soil larger pore information were obtained by principal component analysis. According to the adsorption and desorption isotherm linear plot, the pore shape of various types of soil mainly contain either tubular capillary with both ends open or pore with narrow neck.After leaking for three days, the residual concentration of diesel in soil approximately reached steady state. The kinetic curves of diesel wetting front in one-dimensional columns were fitted well using third-order exponential equation. The migration distance was negatively correlated with fractal dimension, medium and large pore volume, while positively correlated with huge pore volume. The infiltration rates of diesel decreased over time, and the tendency fitted well with the power function. The residual amount of diesel in different soil decreased with the depth. But the maximum residual amounts did not appear in the surface.The multivariate linear relations of diesel residual amount and migration depth with the parameters of soil structure characteristics are established through SPSS statistical analysis. The volume of large pores between 0.05 and 0.5 μm had great effect on the migration depth. The volume of large pores between 0.5 and 7.5 μm was the main factor affecting the residual diesel concentration in topsoil. While the residual diesel concentration under topsoil was affected by the volume of medium pores smaller than 0.05 μm significantly.