Assessment of Pyrene Bioavailability in Soil by Mild Hydroxypropyl-β-Cyclodextrin Extraction

Abstract

Bioavailability of organic pollutants in soil is currently a much-debated issue in risk assessment of contaminated sites. Ecorisk of an organic pollutant in soil is strongly influenced by the properties of the soil and its contamination history. To evaluate the effect of aging on the availability of pyrene, earthworm (Eisenia fetida) accumulation and chemical extraction by exhaustive and nonexhaustive techniques in soil spiked with a range of pyrene levels (1.07, 9.72, 88.4, 152, and 429 μg g⁻¹ dry soil) were measured in this study using both unaged (i.e., 0 days) and aged (i.e., 69, 150, and 222 days) soil samples. The results showed that the amount of pyrene accumulated by earthworms did not change greatly with aging time under different high-dose contamination levels, but changed significantly at lower concentrations. Moreover, aging (after 222 days) significantly decreased biological and chemical availability of pyrene. Furthermore, the relationship between earthworm bioaccumulation, hydroxypropyl-β-cyclodextrin (HPCD), and organic solvent extraction was investigated in order to find a suitable and rapid method to predict pyrene bioavailability. Results showed that, at different levels of pyrene, the mean values of earthworm uptake and HPCD extractability were 10-40% and 10-65%, respectively. Correlation (r² = 0.985) and extraction results for pyrene suggested that mild HPCD extraction was a better method to predict bioavailability of pyrene in soil compared with organic solvent extraction.

Integration of Chemical Methods and Biomarkers for Assessment of Chlorimuron-Ethyl Bioavailability in Soil

“…This phenomenon might result from the change in the contamination states of chlorimuronethyl molecules in microsites within the soil matrix (Khan et al, 2011). For instance, chlorimuron-ethyl was redistributed from weaker to stronger sorption sites, which sequestrated or formed bound residues in soil and thus made the extraction very difficult.…”

Assessment of phenanthrene bioavailability in aged and unaged soils by mild extraction

“…Soil was spiked with five different concentrations of phenanthrene (1.12, 8.52, 73, 136, and 335 μg Phe g −1 dry soil) in triplicate according to Cheema et al (2010) and Khan et al (2011) with slight modifications. Briefly, 1-kg air-dried soil was contaminated with the stock solution of phenanthrene and placed in a jar to prepare each independent sample.…”

“…Hartnik et al (2008) also developed a HPCD extraction method for the currently used pesticides α-cypermethrin and chlorfenvinphos and found that HPCD extractability correlated well with those of earthworm uptake. Most recently, Khan et al (2011) successfully correlated HPCD extractability and earthworm uptake in pyrene-amended fresh and aged soils.…”

“…Aqueous solutions of cyclodextrin have been used to dissolve (form a host-guest inclusion complex) a range of low solubility contaminants to greater than their aqueous solubility limits (Hickman and Reid 2005;Allan et al 2006). Most recently, many studies have demonstrated that nonexhaustive extraction by aqueous hydroxypropyl-β-cyclodextrin (HPCD) was able to predict the bioavailable fraction of polycyclic aromatic hydrocarbons (PAHs) in a wide range of soils (Dupuy et al 2005;Allan et al 2006;Barthe and Pelletier 2007;Hickman et al 2008;Khan et al 2011). In many cases, a 1:1 correlation between HPCD extractability and microbial degradation rate or earthworm uptake was reported, and a scaling factor was not needed (Reid et al 2004;Allan et al 2006).…”

“…These include chemical assays such as mild organic solvent extraction (Swindell and Reid 2006;Bergknut et al 2007;Gomez-Eyles et al 2010;Khan et al 2011) and mild cyclodextrin extraction (Puglisi et al 2007; Barthe and Pelletier 2007;Barriuso et al 2008;Wong and Bidleman 2010;Khan et al 2011) and biological availability assays such as earthworm (EW) uptake (Parrish et al 2006;Bergknut et al 2007;Hartnik et al 2008;Gomez-Eyles et al 2010;Khan et al 2011). All these strategies are essentially based on the principle that bioavailability is governed by contaminant mass transfer from the soil solid phase to the aqueous phase.…”