Bioconcentration model for non-ionic, polar, and ionizable organic compounds in amphipod

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

4 Scopus Citations
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Detail(s)

Original languageEnglish
Pages (from-to)1378-1386
Journal / PublicationEnvironmental Toxicology and Chemistry
Volume37
Issue number5
Online published9 Jan 2018
Publication statusPublished - May 2018

Abstract

The present study presents a bioconcentration model for non-ionic, polar, and ionizable organic compounds in amphipod based on first-order kinetics. Uptake rate constant k1 is modeled as logk(1) = 1/0:81/logK(OW)+0.15 (root mean square error [RMSE] = 0.52). Biotransformation rate constant kM is estimated using an existing polyparameter linear free energy relationship model. Respiratory elimination k2 is calculated as modeled k1 over theoretical biota–water partition coefficient Kbiow considering the contributions of lipid, protein, carbohydrate, and water. With negligible contributions of growth and egestion over a typical amphipod bioconcentration experiment, the bioconcentration factor (BCF) is modeled as k1/(kM+ k2) (RMSE = 0.68). The proposed model performs well for non-ionic organic compounds (log KOW range = 3.3–7.62) within 1 log-unit error margin. Approximately 12% of the BCFs are underpredicted for polar and ionizable compounds. However, >50% of the estimated k2 values are found to exceed the total depuration rate constants. Analyses suggest that these excessive k2 values and underpredicted BCFs reflect underestimation in Kbiow, which may be improved by incorporating exoskeleton as a relevant partitioning component and refining the membrane–water partitioning model. The immediate needs to build up high-quality experimental kM values, explore the sorptive role of exoskeleton, and investigate the prevalence of k2 overestimation in other bioconcentration models are also identified. The resulting BCF model can support, within its limitations, the ecotoxicological and risk assessment of emerging polar and ionizable organic contaminants in aquatic environments and advance the science of invertebrate bioaccumulation.  

Research Area(s)

  • Amphipod, Aquatic invertebrate, Bioconcentration, Non-ionic organic compound, Polar and ionizable organic compound, Risk assessment