[Distribution character of polycyclic aromatic hydrocarbons in soils from the karst cavity, Guilin City, South China].

We investigated the distribution characteristic of polycyclic aromatic hydrocarbons (PAHs) of soils from Dayan cave, a karst cavity in Guilin City, South China. The total PAHs concentrations from the inner cave ranged from 7.22 to 117.29 ng x g(-1) were much lower than those of outside cave (range of 51.35-235.73 ng x g(-1)). PAHs in studied area polluted slightly compared with other area. PAHs contents outside the cave and near cave gate were much higher than those within the cave with a little concentration change. In outside cave soils, the heavy molecular weight PAH (HMW) concentrations were higher than those of the light molecular weight PAH (LMW) (mean value 69.25 ng x g(-1) > 38.81 ngx g(-1)) while it was reverse inside cave (mean value 3.93 ng x g(-1) < 7.41 ng x g(-1)),which indicated the inner PAHs might came from atmosphere introduction and rainwater filtering from the top of the cave too. PAHs concentration distribution in the soils presented "trap effect" near the cave gate and a concentration superposition from the slope in the north cave wicket. HMW concentration near the cave gate was even larger by three times than that outside cave gate and a positive relation was found between PAH molecular weight and its falling tendence (R2 = 0.49). Deducing from the analysed data, PAHs concentration contributed by the cave gate was about 17 times of that of the slope. Temperature and molecular weight diversity were important factors influencing PAH concentration distribution.