Abstract: Sediment samples at 0-10 cm and 10-20 cm depths were collected from Shantou mangrove wetland, and their particle sizes and the contents of polycyclic aromatic hydrocarbons (PAHs), organic carbon, and black carbon were determined by the methods of ultrasonic solvent extraction and GC-MS. The two sediment layers were dominated by 4-ring PAHs, followed by moderate molecular weight PAHs, and lower or molecular weight PAHs. The contents of PAHs, organic carbon, and black carbon, and the percentages of silt and clay were higher in 0-10 cm than in 10-20 cm layer, but the pH value had no difference between the two layers. Correlation analysis showed that in the two layers, PAHs content had no correlation with organic carbon content but significantly correlated with black carbon content (P<0.01), and significant correlations were observed among the contents of silt, black carbon, and PAHs (P<0.05), suggesting that silt content was the main factor affecting the PAHs distribution in Shantou mangrove sediments, and black carbon could be the essential factor for the stratification of PAHs in different sediment layers.

Key words: Dryland, Apple orchard, Desiccation, Nitrate accumulation