Impact of soil properties on bioavailabilities of organic chemicals

Xinzhu Pu, Purdue University

Abstract

To examine the impact of soil properties on the bioavailabilities of soil-bound organic chemicals, three specific aims were proposed: (1) generate bioavailability data for selected chemicals; (2) investigate the influence of soil properties on the bioavailability of organic chemicals; (3) examine the relationship between the in vivo animal model and the in vitro physiologically-based extraction test (PBET). The bioavailability of pentachlorophenol (PCP), phenanthrene (PA), 2,3′,4,4 ′,5-pentachlorobiphenyl (PCB 118) and 2,2′,5,5 ′-tetrachlorobiphenyl (PCB52), from soils with varying characteristics was investigated using rat model and for the latter three using PBET. The areas under the blood or plasma concentration versus time curves (AUC) for these chemicals from soils were significantly lower than the AUCs following iv injection, demonstrating that the soil matrix significantly reduced the bioavailabilities. No differences in the bioavailability of PCP were observed among soils except for WNC1, a field contaminated soil, where PCP showed significantly lower bioavailability, which may be related to the aging effect. The fractions of PA, PCB52 and PCB118 mobilized by the synthetic digestive fluids in PBET were significantly different among soils, suggesting the soil properties impacted the extractability of soil-bound PA and PCBs. There were no significant differences among soils for the in vivo bioavailabilities of PA and PCBs. There was a trend for the soils with higher organic carbon contents to have a lower mobilization and bioavailability of soil-bound PA, PCB52 and PCB118, suggesting OC content might decrease absorption of the chemicals after oral administration. An inverse relationship between the soil clay content and lability with the higher clay content resulting in lower mobilization of PA indicated that the clay might also decrease the oral absorption of PA. The range and rank order of the bioavailabilities of the four chemicals from the same group of soils were different, indicating that the chemical properties impacted bioavailability. Good agreement between the PBET and rat model was observed for PA, but not for PCBs, suggesting that PBET assay might be a useful alternative to predict the bioavailability of certain soil-bound organic chemicals, but might be chemical class dependent.

Degree

Ph.D.

Advisors

Carlson, Purdue University.

Subject Area

Toxicology|Soil sciences|Environmental science

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