Lead and Arsenic Bioaccessibility and Speciation as a Function of Soil Particle Size

Journal Article · Wed Nov 01 00:00:00 EDT 2017 · Journal of Environmental Quality

DOI:https://doi.org/10.2134/jeq2016.10.0387· OSTI ID:1581850

Karna, Ranju R. ^[1]; Noerpel, Matt ^[1]; Betts, Aaron R. ^[2]; Scheckel, Kirk G. ^[3]

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1. Oak Ridge Institute of Science and Education National Risk Management Research Laboratory, Land Remediation and Pollution Control Division 5995 Center Hill Ave. Cincinnati OH 45224‐1701
2. Oak Ridge Institute of Science and Education National Risk Management Research Laboratory, Land Remediation and Pollution Control Division 5995 Center Hill Ave. Cincinnati OH 45224‐1701, Dep. of Soil and Plant Sciences Univ. of Delaware 221 Academy St. Newark DE 19711
3. USEPA, National Risk Management Research Laboratory, Land Remediation and Pollution Control Division 5995 Center Hill Ave. Cincinnati OH 45224‐1701

Bioavailability research of soil metals has advanced considerably from default values to validated in vitro bioaccessibility (IVBA) assays for site‐specific risk assessment. Previously, USEPA determined that the soil‐size fraction representative of dermal adherence and consequent soil ingestion was <250 μm. This size fraction was widely used in testing efforts for both in vivo and in vitro experiments. However, recent studies indicate the <150‐μm size fraction better represents the particle size that adheres to skin for potential ingestion. At issue is the relevance of validated in vivo and in vitro methods developed with <250 μm moving to the <150‐μm fraction. The objectives of this study were to investigate <250‐μm versus <150‐μm particle size and particle size groups for evaluating lead (Pb) and arsenic (As) IVBA and speciation. Soils with different properties were homogenized, oven dried, and sieved: <250 to > 150, <150 to >75, <75 to >38, and <38 μm. Sieved versus ground subsamples of <250‐μm and <150‐μm bulk soils were also used for IVBA and synchrotron‐based Pb and As speciation. Although we observed an increase in total and IVBA‐extractable Pb and As with decreased soil particle size, changes in %IVBA of Pb and As (dependent on the ratio extractable:total) remained consistent in all of the tested soils. No significant changes in Pb and As speciation were observed across the soil fractions. The results suggest that using the more relevant <150‐μm fraction will not undermine currently validated IVBA protocols in future bioavailability studies. Core Ideas Identified critical knowledge gaps regarding the <250‐μm vs. <150‐μm particle size used for IVBA. Wider implementation of the <150‐μm size fraction maintains past validation with <‐250 μm fraction. Regardless of increase in total and extractable Pb and As, %IVBA results remained consistent. Using <150‐μm particle size for IVBA requires much higher volumes/masses of soils. Synchrotron‐based speciation is significant in bioavailability studies to understand the fate and transport of contaminants.

• Sponsoring Organization: USDOE
• OSTI ID: 1581850
• Journal Information: Journal of Environmental Quality, Journal Name: Journal of Environmental Quality Vol. 46 Journal Issue: 6; ISSN 0047-2425
• Publisher: Wiley Blackwell (John Wiley & Sons)
• Country of Publication: United States
• Language: English