Toxicokinetics and Toxicodynamics of Radium-226 in an Estuarine Sentinel Species Geukensia demissa

Author

Sarah DonaherFollow

Date of Award

5-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Engineering and Earth Science

Committee Chair/Advisor

Nicole Martinez

Committee Member

Brian Powell

Committee Member

Cindy Lee

Committee Member

Peter Van den Hurk

Committee Member

Teresa Mathews

Abstract

The historical use of radioluminescent objects, most notably those containing radium-226 (²²⁶Ra)-based paint, has contributed to contemporary environmental contamination of radioactive material, often near naval installations or other military-associated coastal sites. The risk to both human and environmental health from this small-scale, discrete radioactive material is challenging to predict due to large uncertainties in the source terms, bioavailability, and toxicity of these objects. The objective of this study was to provide information on the accumulation and toxicity of acute ²²⁶Ra exposure in a sentinel species to improve risk assessments for small-scale, coastal radiological contamination. The sentinel species approach is characterized by four stages: 1) the presence of some environmental hazard, 2) the selection of an appropriate sentinel species, 3) the measurement of some detectable response(s) in the sentinel, and 4) the making of an informed decision based on these responses. The estuarine mussel Geukensia demissa (Atlantic ribbed mussel) was chosen for this study as it is tolerant to a range of environmental stressors and capable of accumulating both aqueous and particulate contaminants. The first study quantified the concentrations, mobility, and bioavailability of 16 metals and metalloids, including two naturally occurring radionuclides, in a native salt marsh habitat of G. demissa. Notable findings included markedly higher sediment metal concentrations but lower metal macrophyte bioavailability for the low marsh zone compared to the high marsh zone, and distinct differences in the sediment fractionation between transition and heavy metals. G. demissa was an appropriate bioindicator for 12 of 16 target metal(loid)s, indicated by strongly positive correlations between sediment and soft tissue concentrations. Heavy metals preferentially accumulated in the byssus of the mussel relative to the soft tissue, whereas transition metals were more homogenously distributed. In controlled laboratory exposure studies, mussels rapidly accumulated and eliminated aqueous ²²⁶Ra from their soft tissues, reaching equilibrium within 7 days for most organ groups. Tissue ²²⁶Ra concentrations were directly proportional to water ²²⁶Ra concentrations, with a bioconcentration factor (BCF) of 0.83 ± 0.15. Mussels were also exposed to radiolabeled sediment and algae; subsequent preferential tissue accumulation was observed in organ groups associated with particle discrimination and digestion, respectively. Finally, dose-dependent impacts on both radical scavenging activity and filter-feeding were observed in mussels exposed to aqueous ²²⁶Ra, but no impacts to secondary cellular oxidative stress markers were noted. The present dissertation provides the first mechanistic study of the toxicokinetics and toxicodynamics of ²²⁶Ra in a marine mollusk, with the intention of informing biomonitoring schemes to ensure adequate protection of environmental health from legacy radioactive material.

Recommended Citation

Donaher, Sarah, "Toxicokinetics and Toxicodynamics of Radium-226 in an Estuarine Sentinel Species Geukensia demissa" (2024). All Dissertations. 3592.
https://open.clemson.edu/all_dissertations/3592

Author ORCID Identifier

0000-0002-3691-319X