2021 article
Incorporating Oil / Water Partitioning in Risk Calculations for PAHs in Petroleum Impacted Soils and Sediments
Pietari, J., O'Reilly, K., Shea, D., & Kamath, R. (2021, April 30). SOIL & SEDIMENT CONTAMINATION.
author keywords: Polycyclic aromatic hydrocarbons; crude oil; weathering; groundwater; leaching
UN Sustainable Development Goal Categories
2. Zero Hunger
(Web of Science)
Source: Web Of Science
Added: June 10, 2021
ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) may drive remediation at impacted soil or sediment sites. Current equations for calculating the PAH concentrations in soil that are protective of underlying groundwater (i.e., soil screening levels, or SSLs) generally assume a three-phase partitioning model, wherein PAHs partition among the soil matrix, porewater, and pore air. This simplified model does not consider the oil phase, and therefore overestimates the dissolved PAH concentration, and consequently, overpredicts the mobility and toxicity of PAHs to receptors especially when the source of PAHs is oil. This results in unnecessarily stringent cleanup goals and adds to the cost of treatment and management of impacted soils. Complicating factors leading to the overestimation of dissolved PAH are that oil weathering (1) decreases to the effective solubility of the lower molecular weight PAHs, and (2) the presence of the oil itself increases PAH retention in the oil phase, thereby reducing aqueous/dissolved PAH concentrations. This is particularly important when oil is both the source and the factor controlling its solubility. In this paper, we have incorporated additional partitioning factors into existing SSL equations to capture the impact of oil weathering on PAH partitioning: The oil-water partitioning coefficient (KOIL ) for crude oils was measured at different stages of weathering using a passive sampling device (PSD). Results confirm that current methods for deriving SSLs are highly conservative and that the aqueous concentrations and mobility of PAHs are lower in soils and sediments that contain weathered oils. Thus, the mobility of PAHs in historically impacted soils is much lower than what is assumed when calculating SSLs for soil-leaching-to-groundwater scenarios.