Use of Isotope Dilution Method To Predict Bioavailability of Organic Pollutants in Historically Contaminated Sediments

Abstract

Many cases of severe environmental contamination arise from historical episodes, where recalcitrant contaminants have resided in the environment for a prolonged time, leading to potentially decreased bioavailability. Use of bioavailable concentrations over bulk chemical levels improves risk assessment and may play a critical role in determining the need for remediation or assessing the effectiveness of risk mitigation operations. In this study, we applied the principle of isotope dilution to quantify bioaccessibility of legacy contaminants DDT and PCBs in marine sediments from a Superfund site. After addition of 13C or deuterated analogues to a sediment sample, the isotope dilution reached a steady state within 24 h of mixing. At the steady state, the accessible fraction (E) derived by the isotope dilution method (IDM) ranged from 0.28 to 0.89 and was substantially smaller than 1 for most compounds, indicating reduced availability of the extensively aged residues. A strong linear relationship (R2 = 0.86) was found between E and the sum of rapid (Fr) and slow (Fs) desorption fractions determined by sequential Tenax desorption. The IDM-derived accessible concentration (Ce) was further shown to correlate closely with tissue residue in the marine benthic polychaete Neanthes arenaceodentata exposed in the same sediments. As shown in this study, the IDM approach involves only a few simple steps and may be readily adopted in laboratories equipped with mass spectrometers. This novel method is expected to be especially useful for historically contaminated sediments or soils, for which contaminant bioavailability may have changed significantly due to aging and other sequestration processes.

Evaluation of different methods for assessing bioavailability of DDT residues during soil remediation

“…The observation suggested that 48 h of mixing under the experimental conditions appeared to be adequate for attaining apparent distribution equilibrium between the native HOCs and the externally introduced *HOCs. This finding was in agreement with previous studies using sediments and with other HOCs (Delgado-Moreno and Gan, 2013; Jia et al, 2014). Therefore, IDM may be used for assessing the accessible concentration of HOCs in soil with an equilibration time as short as 48 h, lending a great advantage to the applicability of this method in comparison with most other methods.…”

“…The principle of IDM for estimating bioaccessibility was given in Delgado-Moreno and Gan (2013) and Jia et al (2014). Briefly, IDM operates on the presumption that the phase distribution of native HOC and the externally added isotope-labeled analogue (*HOC) for the accessible phase reach an apparent equilibrium after a shortterm equilibration.…”

“…The isotope dilution method (IDM), which is based on similar equilibrium behavior between a native HOC and its isotope-labeled analogue in the accessible phase, has been successfully developed and validated in freshwater and marine sediments (DelgadoMoreno and Gan, 2013;Jia et al, 2014). Compared to other methods, IDM only involves a few simple steps and may be easily adopted in laboratories with mass spectrometry facilities (DelgadoMoreno and Gan, 2013;Jia et al, 2014).…”

“…Compared to other methods, IDM only involves a few simple steps and may be easily adopted in laboratories with mass spectrometry facilities (DelgadoMoreno and Gan, 2013;Jia et al, 2014). In this study, we explored the application of IDM to both spiked and field contaminated soils.…”

Sustainable exposure prevention through innovative detection and remediation technologies from the NIEHS Superfund Research Program

“…This approach yields a strong correlation between the derived equilibrium concentrations on the SPME fiber and bioaccumulation (lipid-normalized tissue residues) for DDTs in worms, showing that this method can rapidly measure reductions in bioavailable contaminants. Related work on PBDEs shows how this methodology can assess remediation effectiveness (8).…”