Spectrophotometric, Turbidimetric and Gravimetric Estimation of Total Hydrocarbon Contamination of Soil


Petroleum hydrocarbons (PHCs) are among the common contaminants ofland, water and atmosphere. They are sampled and analyzed in their media asgroup of compounds usually referred to as total petroleum hydrocarbons, TPH. Soilsamples were collected from Baghdad and Babylon governorates from potentiallypolluted area near community power generators. Control samples were collectedfrom local gardens. Turbidimetric as well as infrared spectral methods wereemployed for their determination and the obtained results were compared with thatof the gravimetric method. For turbidimetric measurements TPH were extractedwith a solvent mixture (MeOH-EtOH), filtered and transferred into a glass cellcontaining an emulsifier aqueous solution. The TPH form an emulsion with waterthat is stable for certain time. The turbidity was then measured and correlated withthe TPH concentration, following a calibration step using diesel fuel in the sameextraction solvent. For FT-IR spectral investigation, the soil samples wereintroduced to the spectrophotometer in three forms: untreated soil powder; soilpowder after charring at 650o C until a constant weight; and soil extract with CCl4mixed with KBr crystals and dried. The comparison of the spectra indicated the IRabsorption of the hydrocarbon contaminant. The percentage loss on ignition valueswere also recorded and correlated with the results of the turbidimetricmeasurements R2= 0.7721). The soil samples of the gardens were not hydrocarbonfree because of the expected hydrocarbons precipitated from air.