EFFECT OF pH ON Cr(VI) LEACHING FROM SOIL ENRICHED IN CHROMITE ORE PROCESSING RESIDUE CHIH-HUANG WENG 1∗ , C. P. HUANG 2 and PAUL F. SANDERS 3 1 Department of Civil Engineering, I-Shou University, Ta-Hsu Hsiang, Kaohsiung, 84008 Taiwan 2 Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716, USA 3 Division of Science & Research, New Jersey Department of Environmental Protection, Trenton, NJ 08625, USA ( ∗ author for correspondence: e-mail: chweng@isu.edu.tw; fax: + 886-7-6577461) (Received 18 October 2000; accepted in revised form 16 April 2001) Key words: chromium, COPR, leaching, soil 1. Introduction Over 400 chromium-contaminated sites related to the chromite ore processing residue (COPR) have been identified in Hudson County and other areas in northern New Jersey, USA (MEMT, 1990). At these contaminated sites, chromium is con- tinually leached from soils enriched in COPR even after decades of weathering. It is of interest to understand the major parameters affecting the Cr leaching pro- cess and to simulate the process. Although chromium behaviour in soil has been studied over several decades, there is limited information about the dynamics of chromium leaching from Cr-soils. The objectives of this study were to characterise the leaching behavior of Cr-soils as affected by the solution pH and to simulate the Cr(VI) leaching process using a solute-transport model and a series of column experiments. The results of this study would provide further understanding of the dynamic Cr(VI) leaching from Cr-soil. The information will also be helpful for the evaluation of the potential hazard of chromium-contaminated sites and in the establishment of effective remediation plans. 2. Materials and methods The Cr-soil was collected from the Liberty State Park in Hudson County, New Jersey, USA. Composite soil samples were taken to a depth of approximately 6 cm at three different locations. The properties of the Cr-soil are as follows: weight average particle size 250 μm, soil pH 8.5, organic matter content 8.6%, pH zpc 6.8, BET-N 2 specific surface area 22.0 m 2 g -1 , Cr 25.5 g kg -1 , Fe 222.2 g kg -1 , Mg Environmental Geochemistry and Health 23: 207–211, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands.