Greener extraction of polycyclic aromatic hydrocarbons from soil and sediment using eucalyptus oil

Abstract

Polycyclic aromatic hydrocarbons are toxic pollutants which persist in the environment. Extraction of polycyclic aromatic hydrocarbons requires large volumes of toxic organic solvents, but the use of non-hazardous solvents provides a potentially cleaner approach to quantifying polycyclic aromatic hydrocarbons in environmental matrices. Here we investigated the efficiency of eucalyptus oil to extract polycyclic aromatic hydrocarbons from spiked soil and sediment. Eucalyptus oil extraction conditions including temperature, time, and volume of oil were optimized employing a Box–Behnken experimental design, and the desorption kinetics of phenanthrene, pyrene, chrysene, and benzo[a]pyrene were evaluated using an empirical first order kinetic model. Results show that extraction efficiency from soil, of 112% for phenanthrene, 108% for pyrene, 102% for chrysene and 98% for benzo[a]pyrene, is higher than that from sediment, of 90, 111, 84 and 82%, respectively. This may be due to soil possessing 12 times more organic carbon. Recoveries higher than 77% were obtained over the concentration range 0.5–10 mg/kg for the tested polycyclic aromatic hydrocarbons, with limits of detection lower than 63 µg/kg and limits of quantitation lower than 125 µg/kg. These findings suggest that eucalyptus oil has potential as a safer solvent to extract hydrophobic contaminants.

Optimization and Comparison of Microwave‐Assisted Extraction, Supercritical Fluid Extraction, and Eucalyptus Oil–Assisted Extraction of Polycyclic Aromatic Hydrocarbons from Soil and Sediment

“…Spiking of the soil and sediment was carried out as described by Kariyawasam, Prenzler, et al (2022) for MAE and SFE parameter optimization using the four PAH standards. Two grams of blank soil or sediment were weighed into glass screw‐cap scintillation vials (20 ml) in triplicate and covered with acetone (1800 µl).…”

“…Based on a factorial design, a total of 15 experiments for MAE and 27 for SFE were performed, including three center points, as described in Supporting Information, Tables S2 and S3. Optimization of EuAE was carried out as described in Kariyawasam, Prenzler, et al (2022).…”

“…Eucalyptus oil–assisted extraction was conducted under the conditions optimized in Kariyawasam, Prenzler, et al (2022). In brief, Eu‐oil (5 ml) was added to PAH‐spiked soil samples (2 g), and the soil slurries were mixed on a rotary shaker (23 rpm) for 5 days at 20 °C.…”

“…The potential to use vegetable oil as a nontoxic, biodegradable, and cost‐effective alternative solvent to extract PAHs from contaminated soils has been explored in recent studies (Arca‐Ramos et al, 2015; Gong et al, 2006; Lau et al, 2012; Pannu et al, 2004), which indicated that the oils have the ability to desorb and dissolve PAHs bound to environmental matrices, while potentially also acting as nutrients to support plant growth in remediated soils (Villemur et al, 2000). Another type of plant‐derived oils are the essential oils, and Kariyawasam, Prenzler, et al (2022) explored the application of eucalyptus oil (Eu‐oil) to extract PAHs from soils and sediments, which allowed direct analysis of the extract without the use of hazardous industrial organic solvents and sophisticated technology. The major compound in Eu‐oil is eucalyptol (84.39%), with 19 other compounds, including limonene and α‐terpineol occurring at <6% (Campos & Berteina‐Raboin, 2022).…”