Comparisons of Four Methods for Measuring Total Petroleum Hydrocarbons and Short-term Weathering Effect in Soils Contaminated by Crude Oil and Fuel Oils

Total petroleum hydrocarbons (TPH) is an important parameter for evaluating risk and establishing cleanup requirements at petroleum release sites. However, different analytical methods may provide incomparable results. To select more appropriate method and design cost-effective remediation strategy, a comparison study of four analytical methods (gravimetric method, infrared spectrometry (IR), gas chromatography-flame ionization detection (GC-FID), and ultraviolet spectrophotometer (UV)) is conducted for soil samples spiked by crude oil and fuel oils under both non-weathered and short-term weathered conditions. The gravimetric method produces higher TPH recovery for less volatile samples such as samples contaminated by motor oil and crude oil. The UV method reports very low TPH recovery and thus fails to provide the meaningful results in all tested samples. The IR method is a quick and relatively inexpensive screening tool and generally gives high TPH recovery, but the method precision and reproducibility are relatively low. The GC-FID method is relatively expensive and time consuming, but it has several advantages: (1) is more selective to hydrocarbons; (2) the method precision and reproducibility is relatively high; (3) is able to provide chemical fingerprint information. Therefore, appropriate method and should be chosen carefully depending on oil contamination type and investigation purpose. The results of short-term simulated weathering experiment showed 99.6% and 65.3% of TPH measured by the GC-FID method were removed for the kerosene and diesel contaminated soils after 14 days of weathering at 50oC, respectively. We have provided evidence that weathering is an important attenuation pathway at kerosene and diesel spill sites. We can design the most cost-effective remediation strategy according to different oil types spilled.