n-Alkanes in surficial soils of Basrah city, Southern Iraq

A study has been carried out to determine the distribution of aliphatic hydrocarbons in surface soils of Basrah city, southern Iraq. One hundred twenty eight surface soil samples (0-10 cm depth) were collected from sixteen sites around Basrah city covering commercial ports, industrial and oil operational locations, urban and rural areas. Hydrocarbons were extracted with mixture of benzene: methanol using soxhlet technique and fractioned with silica-alumina column. Characterization of individual hydrocarbon components was carried out using gas chromatography-flame ionization detector. Average of the total identified n- alkanes concentrations in soil samples were found ranging from 03.575 to 21.266 µg g -1 dry weight. Carbon Preference Index (CPI) values for n-alkanes varied between 0.893 and 5.57. The isoprenoids, pristane and phytane were detected in most soil samples. Unresolved Complex Mixture (UCM) values ranged from 5.2 to 12.3 µg g -1 dry weight. No significant correlation between soil , % Total Organic Carbon (% TOC) and the concentrations of n- alkanes was observed. Results indicated that the aliphatic hydrocarbons were from both biogenic and anthropogenic sources. Generally, the results show that the total n-alkanes concentrations were higher in winter and autumn than that recorded for spring and summer.