Association of 16 priority polycyclic aromatic hydrocarbons with humic acid and humin fractions in a peat soil and implications for their long-term retention

To elucidate the environmental fate of polycyclic aromatic hydrocarbons (PAHs) once released into soil, sixteen humic acids (HAs) and one humin (HM) fractions were sequentially extracted from a peat soil, and sixteen priority PAHs in these humic substances (HSs) were analyzed. It was found that the total concentration of 16 PAHs (Sigma 16PAHs) increased evidently from HAl to HA16, and then dramatically reached the highest value in HM. The trend of Sigma 16PAHs in HAs relates to surface carbon and C-H/C-C contents, the bulk aliphatic carbon content and aliphaticity, as well as the condensation enhancement of carbon domains, which were derived from elemental composition, XPS, C-13 NMR, as well as thermal analyses. HM was identified to be the dominant sink of 16 PAHs retention in soil, due to its aliphatic carbon-rich chemical composition and the highly condensed physical makeup of its carbon domains. This study highlights the joint roles of the physical and chemical properties of HSs in retention of PAHs in soil and the associated mechanisms; the results are of significance for PAH-polluted soil risk assessment and remediation. (C) 2017 Elsevier Ltd. All rights reserved.National Science Fund for Distinguished Young Scientist [41525005]; 973 Program [2014CB441104]; National Natural Science Foundation of China [41390240, 41629101]; Undergraduate Student Research Training Program; 111 Program [B14001]SCI(E)ARTICLE882-89023