Abstract
This study investigated the occurrence and sources of aliphatic hydrocarbons (AHCs) in soils within the vicinity of hot mix asphalt (HMA) plants. Soil samples were collected from two HMA plants and analysed with gas chromatography - flame ionisation detector (GC-FID). Sample collection was from both surface (0-15 cm) and subsurface (15-30 cm) soils at an increasing distance of 10 m from the HMA plants while the control samples at both depths were collected at 1 km away from the plants. The AHCs concentration (nC9-nC38) in soils from both HMA Plants ranged from 8.16 - 433.04 mg/kg and 5.91-177.83 mg/kg for surface and subsurface soils respectively while the concentration in the control samples ranged from 5.97 - 23.95 mg/kg and 2.52 - 13.31 for surface and subsurface soil respectively. The sources of the AHCs were determined using isoprenoid ratios, carbon preference index (CPI) and maximum carbon chain (Cmax). The isoprenoid ratios and CPI values of the samples closer ( 20 m from the HMA plants showed mixture of both anthropogenic and biogenic sources. Keywords : Asphalt Plants; Soil; Aliphatic hydrocarbons; Pristane; Phytane.
Highlights
MATERIALS AND METHODSSamples were collected at both surface (0-15cm) and subsurface (15-30cm) depths
Hot mix asphalt (HMA) plant is an assemblage of mechanical equipment where aggregates or inert mineral materials such as sand, gravel, crushed stones, Slag, rock dust or powder are blended, heated, dried and mixed with bitumen in measured quantities (Mamlouk and Zaniewski, 2011)
Petroleum hydrocarbons ranging from light products like diesel to heavy residues such as bitumen are used in asphalt production process
Summary
Samples were collected at both surface (0-15cm) and subsurface (15-30cm) depths. They were randomly collected across the plant vicinities and blended to form a homogenous mix. The extracts were concentrated to 1 ml using a rotary evaporator. The column was eluted with 20 ml of hexane to obtain the aliphatic fractions. Each of these fractions was concentrated to 1 ml using a rotary evaporator. One microlitre (1μl) of each sample extract was analysed with AGILENT 6890 gas chromatography equipped with flame ionization detector (FID) under the following operational conditions: capillary column of length 25.0 m, diameter 320 μm, stationary phase; phenyl methylsiloxane, film thickness 0.17 μm.
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