“…The application of oil-refinery effluent over a prolonged period on certain types of soil has been reported to cause an increase in the soil's heavy metal content (Zn, Fe, Cu, Mn, Cr, Pb, and Ni), with levels potentially accumulating to toxic levels, which could make the soil become phytotoxic (Rajesh et al 2009). Such changes should be a cause for concern in countries that use refinery wastewater for irrigation, such as in Jordan (Mohsen and Jaber 2002).…”