This study investigates the degradation pathway of gamma-hexachlorocyclohexane (gamma-HCH) in spiked soil using carboxymethyl cellulose stabilized Pd/Fe-0 bimetallic nanoparticles (CMC-Pd/nFe(0)). GC-MS analysis of gamma-HCH degradation products showed the formation of pentachlorocyclohexene. tri- and dichlorobenzene as intermediate products while benzene was formed as the most stable end product. On the basis of identified intermediates and final products, degradation pathway of gamma-HCH has been proposed. Batch studies showed complete gamma-HCH degradation at a loading of 0.20 g/L CMC-Pd/nFe(0) within 6 h of incubation. The surface area normalized rate constant (k(SA)) was found to be 7.6 x 10(-2) L min(-1) m(-2). CMC-Pd/nFe(0) displayed similar to 7-fold greater efficiency for gamma-HCH degradation in comparison to Fe-0 nanoparticles (nFe(0)), synthesized without CMC and Pd. Further studies showed that increase in CMC-Pd/nFe(0) loading and reaction temperature facilitates gamma-HCH degradation, whereas a declining trend in degradation was noticed with the increase in pH, initial gamma-HCH concentration and in the presence of cations. The data on activation energy (33.7 kJ/mol) suggests that gamma-HCH degradation is a surface mediated reaction. The significance of the study with respect to remediation of gamma-HCH contaminated soil using CMC-Pd/nFe(0) has been discussed. (C) 2012 Elsevier B.V. All rights reserved.