Direct determination of soil surface bound polycyclic aromatic hydrocarbons in petroleum-contaminated soils by real time aerosol mass spectrometry

Soil surface-bound polycyclic aromatic hydrocarbons (PAHs) were identified by use of Real-Tune Aerosol Mass Spectrometry (RTAMS) in two NIST standard research material (SRM) soils (Montana SRM 2710 and Peruvian SRM 4355) each contaminated separately with three common petroleum hydrocarbons (diesel f uel, gasoline, and kerosene). The described contaminated soil analysis requ ired no sample preparation. Direct laser desorption/ionization mass spectro metric analysis of individual soil particles contaminated with each of the petroleum hydro-carbons at three different contamination levels (0.8, 8, an d 80 ppth (wt/wt)) yielded detectable PAH cation distributions that ranged from m/z 128 to 234, depending on the fuel contaminant. The same analysis p erformed on uncontaminated SRM soils revealed very little (Peruvian) to no (Montana) detectable PAH species. Size analysis showed that most of the ind ividual soil particles analyzed were between 1 and 5 pm in diameter. Tandem mass spectrometry (MS/MS) experiments identified alkyl-substituted two- an d three-ringed PAHs in all three petroleum hydrocarbon contaminated soils. However, due to similarities in fragmentation patterns, MS/MS analysis of h igher MW species (m/z > 200) was unable to distinguish between the possibil ity of highly alkyl-substituted three-ringed PAHs and hydrogenated four-rin ged PAHs, The described technique offers the direct, rapid determination an d characterization of surface-bound PAHs in petroleum-contaminated soils at part-per-million levels without prior extraction, separation, or other sam ple preparation methods.