Selective migration of low and medium molecular weight hydrocarbons in petroleum-contaminated terrestrial environments

A vertical selective migration of low and medium molecular weight hydrocarbons is demonstrated in the depth of a tropical forest soil heavily impacted by a crude oil spill. An identical pattern of horizontal migration is observed in the lateral zone of the polluted area and in the sediments of a shallow river which received the contaminated water runoff of the forest. The differential migration, which is attributed to the chromatographic properties of the media, resulted in the formation of a residual contaminant similar in composition to a gas-oil cut. The environmental contamination by this fraction extended far beyond the area initially polluted by the crude oil.