Alkanes in the sediments of Al-Gharraf River, Southern Iraq

The study aimed to determine the concentrations of alkanes compounds using a gas chromatograph with high-precision separation techniques. Samples were collected from four stations in the Al-Gharraf River in southern Iraq during 2018-2019. A seasonal variation was observed in the concentrations of alkanes, which is the highest in the winter. The total alkanes concentrations were the lowest at 0.079 μg/g at station 1 in summer. The highest total concentration of alkanes was in station 3 in winter reaching 2.215 μg/g. There was a dominance of individual carbon compounds of C17, C19, and C21 indicating the source of hydrocarbon from phytoplankton, plant, and bacteria. The presence of carbon compounds higher than C25 reveals that organic matter is derived from land and aquatic plants. The results also indicate that the source of petroleum hydrocarbons in the sediments of the Al-Garraf River is a common biogenic and anthropogenic based CPI index and the pri/phy guide that was less than 1 in the second and third stations for all seasons, and greater than 1 in the first and fourth stations.