RESUMEN
This study was undertaken to document the impact of heavy metal pollution on the Libyan jird, Meriones libycus and to contribute to an environmental impact statement for the rapidly growing City of Riyadh. All metal concentrations in surface soil of a polluted site (within Riyadh City) were higher than those from a reference site (outside the city). Although Pb declined versus earlier reports on Riyadh soil, Cd (0.97 Ag g-1) and Hg (0.28 Ag g-1) were above some of the most stringent quality guidelines (0.07- 0.62 Ag g-1 for Cd and 0.14- 0.18 Ag g-1 for Hg). Metal distribution in M. libycus proved site-related and organ-specific, recognizing a higher affinity of most tested metals towards the kidneys, liver and brain than the lung and heart. The comparatively lower sitespecific accumulation of Pb in soft tissues was attributed primarily to its major hypothetical accumulation in bones, whereas, the transition rate of Hg from the liver was suggested to be lower to the brain than to the kidneys. Although a non hazardous status was assumed for Cu (11.27-13.16 Ag g-1) and Hg (up to 0.207 Ag g-1) in tissues of M. libycus, a potential risk was imposed by mean tissue concentrations of Cd (up to 3.29 Ag g-1), Ni (up to 1.48 Ag g-1) and Pb (up to 1.94 Ag g-1). On the grounds of the significantly higher metal levels in polluted soft tissues versus reference subjects, Libyan jirds possess high exposure potential and can be useful biomonitors of environmental metal contamination.