Abstract

Natural attenuation is a major ecosystem function allowing to abate soil organic contaminants such as polycyclic aromatic hydrocarbons (PAHs). Biodegradation of PAHs is classically considered as the major driver of natural attenuation, yet the role of abiotic transformation, including photodegradation, chemical oxidation, formation of non-extractable residues, and polymerization, has been overlooked due to the lack of investigations until recently. This paper reviews PAHs dissipation in soils by abiotic processes such as photodegradation and oxidation catalyzed by inorganic minerals and organic matters. The role of soil components on degradation rates, pathways, and mechanisms are discussed. The products of PAHs abiotic transformation and their potential risks are also described. Abiotic transformations are mainly controlled by interactions between PAHs and clay minerals, metal oxides/hydroxides, and soil organic matter. PAH photodegradation proceeds by both direct and indirect photolysis processes, which are enhanced in the presence of natural photosensitizers, for example, organic matter, and photocatalysts, for example, metal oxides/hydroxides. PAHs can also be chemically/catalytically oxidized by metal oxides/hydroxides, for example, MnO₂, Fe_xO_y, and clay minerals without light irradiation. Overall, PAHs transformation depends on their electron-donating properties, mineral electron-accepting properties, pH, temperature, moisture, and oxygen content. Following the elucidation of the transformative mechanism, knowledge to understand the impact of abiotic transformation on biodegradation are delineated. Future investigations are needed to advance the correlation of laboratory generated rates to the field applications, and the potential applications of natural attenuation based on abiotic processes are proposed.

摘要

自然衰减是一种主要的生态系统功能，可以减少多环芳烃 (PAH) 等土壤有机污染物。多环芳烃的生物降解通常被认为是自然衰减的主要驱动因素，但直到最近，由于缺乏研究，非生物转化的作用，包括光降解、化学氧化、不可提取残留物的形成和聚合，一直被忽视。本文综述了 PAHs 通过非生物过程（如无机矿物质和有机物催化的光降解和氧化）在土壤中的消散。讨论了土壤成分对降解率、途径和机制的作用。还描述了多环芳烃非生物转化的产物及其潜在风险。非生物转化主要受多环芳烃与粘土矿物、金属氧化物/氢氧化物和土壤有机质之间相互作用的控制。PAH 光降解通过直接和间接光解过程进行，这些过程在天然光敏剂（例如有机物）和光催化剂（例如金属氧化物/氢氧化物）的存在下得到增强。PAH 也可以被金属氧化物/氢氧化物化学/催化氧化，例如 MnO₂、Fe _x O _y和粘土矿物未经光照。总的来说，多环芳烃的转化取决于它们的供电子特性、矿物电子接受特性、pH 值、温度、水分和氧含量。在阐明转化机制之后，描述了了解非生物转化对生物降解影响的知识。未来的研究需要推进实验室产生率与现场应用的相关性，并提出了基于非生物过程的自然衰减的潜在应用。