Impact of Forest Combustion on Soil Contamination by PAHs Using QuEChERS and GC-MS/MSTQD

The present study was conducted in one of the most dense forest area of Asir region located in the southwest of Saudi Arabia to study the Impact of Forest Combustion on surface and subsurface soil contamination by Poly Aromatic Hydrocarbons (PAHs). The major toxic effects of PAHs including cancers, immunity suppression, loss of fertility, mutagenic and cardiovascular diseases. The extraction and analytical methods, have been developed and validated for quantification of trace levels of 17 PAHs namely, Naphthalene, Acenaphthylene, Acenaphthene, Fluorene, Phenanthrene, Anthracene, Fluoranthene, Pyrene, Retene, Benzo [b+j] fluoranthene, Benzo (a)pyrene, Benzo [k] fluoranthene, 3-methylchol-anthrene, Dibenz [a,h] acridine, Indeno [1,2,3-cd]pyrene, Dibenz [a,h] anthracene and Benzo [ghi] perylene. Surface and subsurface soil samples were collected from Alsaqa and Murir post-fire forests in Asir Province, Saudi Arabia, and extracted by Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and analyzed by Gas Chromatography-Mass Spectrometry Triple Quadrupole (GC-MS/MSTQD). The experimental results of 17 compounds of PAHs were highly satisfactory linearity, recovery and precision, especially with the tested soil samples. Recovery % ranged from 96.48±2.19 to 105.61±3.21%., the limit of detection (LOD) ranged from 3.71 to 6.77 µg kg-1. Meanwhile the limit of quantification (LOQ) for the analyzed PAHs were in the range of 10.47 to 16.42 µgkg-1. This method featured good sensitivity, lower quantification limits and the precision of the analyzed 17 PAHs.  The calibration curves were linear over wide concentration ranges with correlation coefficients (r2) 0.7478 to 0.9822 for 17 PAHs analyzed by GC-MS/MSTQD. The concentrations of the investigated PAHs in Alsaqa forest surface (S) and subsurface (SS) soils ranged from F24.81±4.29 to 57.28±3.56 and 24.10±2.31to 55.47±4.15 mg kg-1dry weight respectively. Meanwhile, the PAHs concertation in Murir surface and subsurface soils ranged from 12.48±2.37 to 28.83±3.35 and 12.83±1.37 to 25.59±4.31 mg kg-1 dry weight respectively. Retene compound was detected in Alsaqa, and Murir forest investigated surface, and subsurface soil sample ranged from 57.28, 55.47, and 28.83, 25.59 mg/kg-1(ppm) respectively. Meanwhile, Retene was not detected (ND) in the control surface and subsurface soil sample. The detected PAHs by applying the modified QuEChERS and GC-MS/MSTQD method were applied successfully for the extraction and determination of the 17 PAHs in burned forest soil samples.