Abstract: Through laboratory simulation, different amounts of exogenous polycyclic aromatic hydrocarbons (PAHs) monomer standard substances were added to peat soil and farmland soil. After freeze-drying and natural air drying, 16 kinds of exogenous PAHs monomers in the soil were determined by gas chromatography-mass spectrometry (GC-MS),  and the effects of two drying methods on the recovery rate of exogenous PAHs and the  isomer ratio in soil were analyzed to reflect the accuracy of PAHs  determination in the soil and the difference of source determination of PAHs in natural soil under different drying methods. The experimental results show that    with the increase of the amount of exogenous PAHs in peat soil,  the total recovery rate of PAHs  decrease first and then increase. The total recovery rate (56.29%—80.15%) of PAHs after the air-drying treatment is higher than that of freeze-drying treatment (52.82%—78.31%) under the same addition amount, and recover rate of its monomer PAHs low-ring component after air-drying treatment is higher than that of  freeze-drying treatment,  recovery rate of high-ring component after freeze-drying treatment  is higher than that of air-drying treatment. The recovery rate of total PAHs in farmland soil  is significantly different (P<0.05) under different drying methods. The total recovery rate after freeze-drying treatment is  64.40%—73.81%,  and the total recovery rate after air-drying treatment  is  40.88%—57.01%,  and the recovery rate of the monomer PAHs after freeze-drying treatment is higher than that of air-drying treatment. The difference of organic matter mass ratio and water content of the two soils may be the main factors that lead to the difference of  total and monomer recovery rate of PAHs. There is no significant difference in the ratios of PAHs isomers in peat soil,  while the ratios of the PAHs isomers in farmland soil are significantly affected by the drying method.

Key words: soil; , drying method; , polycyclic aromatic hydrocarbons;  , recovery rate; , isomer ratio