Polycyclic aromatic hydrocarbons in sediment cores from the Dashiwei Tiankeng reach in the Bailang underground river, South China

Sediment cores from the Dashiwei Tiankeng reach of the Bailang underground river were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs). The concentrations of total PAHs ranged from 35.34 to 280.17 ng/g (mean 107.65 ng/g), and the concentrations of benzo[a]pyrene ranged from 1.78 to 175.74 ng/g (mean 35.94 ng/g). Analyses on molecular markers inferred that the PAHs were sourced mainly from wood and coal combustion before 1998, but there were obvious petroleum and petroleum combustion inputs after 1999. The PAHs profile indicated that the Bailang underground river was polluted by two major events. One was steel smelting in the 1950s, and the other was rapid economic development in the 1990s. The relationship between the PAHs and the sediment organic matter (SOM) in the profile was negative. Factors that impacted the SOM contents in sediment core included vegetation, agriculture crops, wood and fossil fuel burning, and soil erosion caused by construction. The sediment cores from the Bailang underground river reflected the economic development of the region.