THE EFFECT OF RESIDUAL KEROSENE ON THE TRANSPORT OF AMMONIUM AND NITRATE IONS IN SANDY SOIL

Field and laboratory work have shown that the availability of electron accepters such as oxygen and/or nitrogen as well as of nutrients such as nitrogen and phosphorus is necessary for effective biodegradation of hydrocarbon compounds. Therefore, these compounds are frequently in jected into the contaminated subsurface to enhance in situ biodegradat ion. The effect of residual subsurface hydrocarbon (kerosene) contamin ation on the transport of an electron acceptor (NO3-) and a nutrient ( NH4+) was investigated. Soil column experiments were conducted using u ncontaminated and contaminated soil, and a one-dimensional solute tran sport model with multiprocess nonequilibrium sorption was used to pred ict the breakthrough curves. The presence of kerosene contamination wa s found to decrease the volumetric water content which in turn increas ed the pore-water velocity. An earlier breakthrough time for NO3- rela tive to the uncontaminated soil was observed and predicted by the tran sport model. The exchange isotherm involving NH4+ was not affected by the presence of kerosene; therefore, no significant difference in NH4 transport was observed or predicted. The results of this study indica te that the transport of NO3- will be increased by residual subsurface hydrocarbon contamination whereas NH4+ transport will be unaffected. Therefore the presence of residual subsurface contamination by hydroca rbons will have to be taken into account in NO3- transport models.