Study On Soil Colloid And Phenanthrene Transportation Through Saturated Porous Media

Soil colloid is widespread in groundwater environment. Colloid transportation insubsurface environment has attracted considerable attention in recent years because ofits role in facilitating transport of strongly adsorbed contaminants to groundwater. Theinfluence of bulk solution pH and ionic strength on model colloid (i.e., latexmicrosphere, amorphous silica colloids) transport is well established, while littleattention has been paid to water-dispersible soil colloid. In this study, black soil,moisture soil and red soil which are three kinds of typical soil in China had beencollected, soil colloid was extracted by centrifugation, microscopic characterizationmethods and spectroscopic methods were used to analysis the physical and chemicalcharacteristics of soil colloid. Leaching experiments were conducted with the colloid inquartz sand saturated porous media to investigate the effects of solution pH and ionstrength and to explore the mechanism of transport and fate of water-dispersible soilcolloid and facilitating transport of phenanthrene.The results suggested that the physical and chemical characteristics of three kindsof soil colloid were very different and the transport and fate had significant differenceunder variation range of solution pH and ion strength. The breakthrough curves ofleaching experiments demonstrated that during pH variation range from4to9, neutralpH condition favor colloid mobility in saturated porous media, however acidity andbasicity pH condition impede colloid mobility. The fraction of colloid recovered (MR)increased and the deposition rate coefficient (k) decreased as the ionic strength of thebulk solution decreased from0.5mmol/L to0.001mmol/L. The mobility of red soilcolloid was mostly influenced by pH and ion strength. Leaching experiments whichsimulated phenanthrene-contaminated surface soil demonstrated that when the leachatecontained black soil colloid, the concentration of phenanthrene had gone up by an orderof magnitude10times than deionized water leaching experiment. The moisture soilcolloid had a litter weaker effect on the facilitating transport of phenanthrene than blacksoil colloid, however the red soil colloid was weakest. The transportation and fate ofthree kinds water-dispersible soil colloid were very different in the saturated porousmedia, and also the facilitating transport of pollutants.