Assessing Biological Interactions and Potential Impacts of Emerging Carbonaceous Materials to Terrestrial Organisms
Alvarez, Pedro J.
Doctor of Philosophy thesis
This research addresses the potential ecotoxicity of two emerging carbonaceous materials: C 60 and biochar. The use of these materials is rapidly increasing, as well as their potential for widespread applications. Thus, information about unintended consequences associated the widespread use, incidental or accidental release, and disposal of these emerging materials is needed. The environmental impacts of C 60 , its stable water suspension (nC 60 ), and biochar are assessed here using bacteria and earthworms as model receptors. The antibacterial activity of nC 60 can be mitigated by the presence of natural organic matter as a soil constituent or dissolved in the water column. Sorption to soil might decrease the bioavailability of nC 60 and thus its toxicity to bacteria. Aqueous organic matter also may mitigate nC 60 toxicity. Pristine C 60 showed toxicity to the earthworm's reproduction and was rapidly bioaccumulated by earthworms, although to a lower extent than smaller phenanthrene molecules that are more hydrophobic; thus, the large molecular size of C 60 hinders its bioaccumulation. Less bioaccumulation occurred at higher C 60 concentration in soil, which is counterintuitive and reflects that higher C 60 concentrations that exceed the soil sorption capacity exist as larger precipitates that are less bioavailable. Earthworms avoided soils amended with high concentrations of dry biochar, and experienced significant weight loss after 28-day exposure. The avoidance response was likely to avert desiccation rather than to avoid potential toxicants (i.e., PAHs formed during biochar production by pyrolysis) or nutrient scarcity. By wetting the biochar to field capacity before exposing the worms, this adverse effect can be completely mitigated. Overall, this research provides a foundation for ecotoxicity assessment associated with exposure to C 60 or biochar, and establishes a method by which other emerging materials can be evaluated for their potential environmental impacts.