Abstract: Dissolved humic acids (DHAs) are widely found in nature, which affect the environmental fate of polycyclic aromatic hydrocarbons. Focusing on pyrene, one of the common polycyclic aromatic hydrocarbon pollutants, we used a multi-bag equilibrium system to compare the partition coefficients of different DHAs with pyrene to explore the relationship between the composition of humic acid (HA) and its ability to bind pyrene and the underlying mechanisms. The results showed that HA is mainly composed of aromatic carbon, aliphatic carbon, and oxygen-containing and nitrogen-containing functional groups. The ability of HA to bind pyrene (K_DOC is 120.36-172.40 μg·g^-1 C) increased with the increases of HA aromatic (SUVA254 is 2.51-4.18) and hydrophobic component content (A260 is 1.21-2.04), and decreased with the increases of its aliphatic (H/C is 1.02-1.34) and polar functional group \[(N+O)/C is 0.48-0.69\]. Our results suggest that DHA is a micelle-like structure with aromatic carbon as a hydrophobic core, and the aliphatic chain and the polar functional group distributed on the aliphatic chain being hydrophilic. Our results provide theoretical support for assessing ecological risk of polycyclic aromatic hydrocarbons.

Key words: urbanization, ecological stress, ecological protection., landscape pattern, regional ecological security