The Influence of Soil Mechanical Redesigning on Polycyclic Aromatic Hydrocarbon (PAH) Release: a Column Approach

Abstract

Intrinsic molecular parameters (solubility, chemical structure, etc.) as well as physico-chemical properties of the medium (lithology, permeability, organic matter content, etc.) and hydrological specificities (rainfall regimes) are usually put forward to characterize the mobility of polycyclic aromatic hydrocarbons (PAHs). Here, we study the role of aggregate mechanical redesigning on the ability of anciently impacted soils to release polycyclic hydrocarbons. Soil columns were collected in a heavily impacted wasteland (Villeneuve la Garenne, France) for this purpose and submitted to continuous and sequential leaching regimes. The soil’s organo-mineral properties were characterized with suited techniques (Rock Eval, FT/IR) prior to the leaching experiments. The release of 18 PAHs (naphthalene, 1 methyl naphthalene, 2 methyl naphthalene, acenaphtylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benz(b)fluoranthene, benz(k)fluoranthene; benzo(a)pyrene, indeno[1,2,3-cd]pyrene, dibenz(a,h)anthracene, benzo(g,h,i) perylene) was assayed under non-disturbed configuration of the columns, then under reshuffled (10 mm), and finely sieved (4 mm) states in order to evaluate the impact of grain redistribution on the mobilization of the aromatic molecules. For both sequential and continuous leaching regimes, results showed a substantial increase of released amounts when the systems were disturbed. Significant increases of PAH concentrations were indeed observed when the columns were reshuffled (10 mm). The release was more intense when the mechanical reworking was performed with a smaller threshold (4 mm). Greater accessibility of the molecules drove very likely PAH release during the mechanical reworking operations.