Evaluation of soil flushing potential for clean-up of desert soil contaminated by industrial wastewater Shai Arnon a,b, * , Zeev Ronen a , Alexander Yakirevich a , Eilon Adar a,b a Department of Environmental Hydrology and Microbiology, Zuckerberg Institute for Water Research, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede-Boqer Campus 84990, Israel b Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Israel Received 13 January 2005; received in revised form 28 March 2005; accepted 6 April 2005 Available online 9 June 2005 Abstract The flushing potential of a desert loess soil contaminated by the flame retardant Tetrabromobisphenol A (TBBPA), chloride (Cl  ) and bromide (Br  ) was studied in undisturbed laboratory column experiments (20 cm diameter, 45 cm long) and a small field plot (2 · 2 m). While the soluble inorganic ions (Cl  and Br  ) were efficiently flushed from the soil profile after less than three pore volumes (PV) of water, about 50% of the initial amount of TBBPA in the soil was also flushed, despite its hydrophobic nature. TBBPA leaching was made possible due to a significant increase in the pH of the soil solution from 7.5 to 9, which increased TBBPA aqueous solubility. The remaining TBBPA mass in the soil was not mobilized from its initial location in the topsoil due to the decrease in pH at this horizon. In situ soil flushing demonstrated that this method is a feasible treatment for reducing soil contamination at this site. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Tetrabromobisphenol A; Loess; Leaching; Ionizable organic compounds 1. Introduction In recent years, inappropriate waste disposal has become a major environmental problem that requires cost-effective remediation solutions. The ability of contami- nants to reach groundwater and put water resources at risk lies in their inherent physico-chemical properties, as well as their resistance to removal by complex physi- cal, chemical and biological reactions in unsaturated and saturated geological media (Mackay et al., 1985; Saint- Fort, 1991; Schwarzenbach et al., 1993). Applying water, with or without additives, is frequently used for soil flushing in order to clean up the vadose zone (Thom- sen et al., 1989; MacKay et al., 1996). In situ soil flush- ing can be limited due to several reasons, primarily: (1) soils that have been contaminated for a long period of time exhibit a bi-phasic pattern of desorption with an initial fast stage (min–h) and a subsequent longer slow phase (days–years) (Pavlostathis and Jaglal, 1991); (2) the heterogeneous nature of soil implies that regions with low hydraulic conductivity may exist, from which contaminants must diffuse over a long period of time to the more effectively flushed layers (MacKay et al., 1996); and (3) the slow solubility rates of hydrophobic 0045-6535/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2005.04.050 * Corresponding author. Address: Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3109, USA. Tel.: +1 847 467 4980; fax: +1 847 491 4011. E-mail addresses: s-arnon@northwestern.edu (S. Arnon), zeevrone@bgumail.bgu.ac.il (Z. Ronen), alexy@bgumail.bgu. ac.il (A. Yakirevich), eilon@bgumail.bgu.ac.il (E. Adar). Chemosphere 62 (2006) 17–25 www.elsevier.com/locate/chemosphere