Enhanced Accessibility of Polycyclic Aromatic Hydrocarbons (PAHs) and Heterocyclic PAHs in Industrially Contaminated Soil after Passive Dosing of a Competitive Sorbate

Abstract

To assess the exposure to polycyclic aromatic hydrocarbons (PAHs) it is important to understand the binding mechanisms between specific soil constituents and the organic pollutant. In this study, sorptive bioaccessibility extraction (SBE) was applied to quantify the accessible PAH fraction in industrially contaminated soil with and without passive dosing of a competitive sorbate. SBE experiments revealed an accessible PAH fraction of 41 ± 1% (∑16 US EPA PAHs + 5 further PAHs). The passive dosing of toluene below its saturation level revealed competitive binding and resulted in an average increase of the accessible fraction to 49 ± 2%, whereby primarily the accessibility of higher molecular weight PAHs (log K > 6) was affected. Competitive binding was verified using the same soil with only desorption-resistant PAHs present. In this experiment, passive dosing of toluene resulted in desorption of 13 ± 0.4% PAH. We explain increased PAH desorption after addition of toluene by competitive adsorption to high-affinity sorption sites while acknowledging that toluene could additionally have increased PAH mobility within the soil matrix. Findings suggest that the presence of copollutants at contaminated sites deserves specific considerations as these may increase accessibility and thereby exposure and mobility of PAHs.

Equilibrium sampling reveals increasing thermodynamic potential of polycyclic aromatic hydrocarbons during sewage sludge digestion

“…Comparing to industrially contaminated soils, PAH levels were on average 1000 (Bartolomé et al, 2018. ) and 50-400 times (Humel et al, 2017) higher in Swiss soils and landfill-contaminated Austrian soil, respectively (Table 2) than the measured levels in the digested sludge.…”

“…Total concentration data was kindly provided by the WWTPs and is listed in Table 1, and C free was calculated from Eq. (1) using the C silicone data obtained by equilibrium sampling and silicone to water partition coefficients by Humel et al (2017).…”

“…C free was calculated in digested sludge from the four WWTPs by applying Eq. (1) and silicone-specific partition coefficients (Humel et al, 2017) (Table 2). As digested sludge is applied to agricultural land, sludge is a potential source of PAHs to the soil as well as to the aquatic environment, having the sea sediment as final recipient.…”

“…Freely dissolved concentrations of selected PAHs (ng/L) in digested sludge calculated from Eq. (1), applying partition coefficients from Humel et al, 2017(Should be Humel et al, (2017)) For WWTP IV, C free from both one and three weeks of equilibration are included in the table.…”

Pollution Characteristics of Polycyclic Aromatic Hydrocarbons in Unsaturated Zone of the Different Workshops at a Large Iron and Steel Industrial Site of Beijing, China

“…As a common coking by-product, phenol also could promote the solubility of PAHs in aqueous phase [39]. Humel et al [40] found passive dosing of toluene induced an increase in the fraction of accessible PAHs but also enhanced the release rate of PAHs from soil through competitive adsorption, in particular, with more than 4-ring. This study also tested BTEX concentrations in unsaturated zone sampled at C1 and Table 3).…”