Desorption of polycyclic aromatic hydrocarbons from field-contaminated soil to a two-dimensional hydrophobic surface before and after bioremediation

Abstract

Dermal exposure can represent a significant health risk in settings involving potential contact with soil contaminated with polycyclic aromatic hydrocarbons (PAHs). However, there is limited work on the ability of PAHs in contaminated soil to reach the skin surface via desorption from the soil. We evaluated PAH desorption from a field-contaminated soil to a two-dimensional hydrophobic surface (C18 extraction disk) as a measure of potential dermal exposure as a function of soil loading (5 to 100 mg dry soil/cm2), temperature (20 °C to 40 °C), and soil moisture content (2% to 40%) over periods up to 16 d. The efficacy of bioremediation in removing the most readily desorbable PAH fractions was also evaluated. Desorption kinetics were described well by an empirical two-compartment kinetic model. PAH mass desorbed to the C18 disk kept increasing at soil loadings well above the estimated monolayer coverage, suggesting mechanisms for PAH transport to the surface other than by direct contact. Such mechanisms were reinforced by observations that desorption occurred even with dry or moist glass microfiber filters placed between the C18 disk and the soil. Desorption of all PAHs was substantially reduced at a soil moisture content corresponding to field capacity, suggesting that transport through pore air contributed to PAH transport to the C18 disk. The lower molecular weight PAHs had greater potential to desorb from soil than higher molecular weight PAHs. Biological treatment of the soil in a slurry-phase bioreactor completely eliminated PAH desorption to the C18 disks.

Selection of oxidant doses for in situ chemical oxidation of soils contaminated by polycyclic aromatic hydrocarbons (PAHs): A review

“…Sequestration is due mainly to sorption to fresh natural and fossil organic matter, adsorption onto mineral surfaces, diffusion into soil micropores and encapsulation [46,[84][85][86][87]. Its extent depends on the chemical properties of individual PAHs [39,88,89] and on the physical and chemical characteristics of the soil [39,74,[90][91][92][93][94][95][96][97][98][99][100]. In particular, sorption of hydrophobic organic compounds to fossil or anthropogenic organic matter is much slower but much stronger than sorption to other materials [101][102][103][104][105][106][107].…”

Using Low Molecular Weight Organic Acids to Enhance Microbial Degradation of Polycyclic Aromatic Hydrocarbons: Current Understanding and Future Perspectives

“…Over the past decades, increasing amounts of PAHs have been generated from the incomplete combustion of organic substances, such as coal, oil, wood, and tobacco [2,3]. The strong genotoxic, mutagenic, and carcinogenic properties of PAHs pose a severe threat to human health and, therefore, raise global concerns [4][5][6]. In total, 16 widespread PAHs compounds were listed as priority pollutants by the US EPA (United States Environmental Protection Agency) [7,8].…”

Polycyclic aromatic hydrocarbons bioavailability in industrial and agricultural soils: Linking SPME and Tenax extraction with bioassays

“…PAHs are found at high levels in soils at manufactured gas plants (MGP) (Arp et al 2014;Barnier et al 2014), and some agricultural soils are also contaminated with PAHs (Bayat et al 2015, Duan et al 2015, Guo et al 2017. Generally, PAH bioavailability is often assessed in industrial contaminated soils (Gomez-Eyles et al 2012, Hu & Aitken 2012. There have been no studies predicting the bioavailability of PAHs in field contaminated agricultural soil to earthworms, although the bioavailability of PAHs at relatively low concentrations (up to 9.9 mg kg -1 ) has been studied in urban soil and sludge (Oleszczuk 2009).…”