Total petroleum hydrocarbon (TPH) concentrations and their fractional composition (medium fraction: n-alkane chain-length C15 to C27, heavy fraction: >C27) were determined at distances from 1 to 60？m from roads and at soil depths from 0.5 to 15？cm. The traffic intensities were up to 25000 vehicles per day. Soil TPH concentrations were highest within 15？m distance (665 and 3198？mg kg？1 at the windward and leeward sides, resp.), followed by a rapid drop to background values beyond (196 and 115？mg kg？1 in 60？m distance at the windward and leeward sides, resp.). The data variability was lowest at distances of 1？m and highest within tree plantations at distances of 15？m from the road. The TPH concentrations decreased with depth but were significantly higher than the background at all depths investigated. A principal component analysis revealed a positive relation between the medium-to-heavy fraction ratio and soil depth. A fractional differentiation of hydrocarbons with distance from road was not observed. It was concluded that the assessment of the potential of hydrocarbons to translocate, accumulate, or degrade in soil necessitates their subdivision into fractions based on their physicochemical and metabolic properties. 1. Introduction The widespread use of hydrocarbons in fuels causes their predominance among organic atmospheric pollutants, and petroleum products are the major source of anthropogenic hydrocarbon pollutants found in the atmosphere [1–3]. Total petroleum hydrocarbons (TPH) from fossil sources are not readily biodegradable as compared to biomass or soil organic matter, which have been demonstrated to be consumed during hydrocarbon degradation [4, 5]. Once deposited to the surface, hydrocarbons may persist and bioaccumulate in environmental media [6] and infiltrate into groundwater aquifers via leaching or into surface aquifers by runoff with severe effects on plants [7, 8], humans, and animals [9, 10]. Organic contaminants in roadside soils have been receiving considerable attention as a result of traffic intensity [1, 2, 11, 12]. Hydrocarbon deposition to ecosystems is of more complex nature, because it is influenced by meteorological and further peripheral conditions, like wind, geomorphology, road construction, buildings, or vegetation, resulting in atmospheric dilution, turbulent exchange, possible wind channeling, and so forth [12]. Apart from studies dealing with individual substances, TPH have been treated in the literature as one class of substances so far. However, as a diverse mix of numerous individual aliphatic hydrocarbons,
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