Terrestrial Ecosystems Impact and Hazard Assessment

Leader: Patricia Holden

The main goals of Theme 4 are to develop approaches to study, and to determine the impacts of, selected manufactured nanomaterials (NMs) that may affect terrestrial processes involving soils, microbes, and plants, and to model processes for predicting hazards at population, community and ecosystem scales. Theme 4 researches ecologically meaningful scenarios through which NM exposure and hazards could have important societal implications. TiO2, ZnO, CeO2, Ag- and Cu-based NMs, multiwalled carbon nanotubes (MWCNTs), graphene, carbon black (CB), and boron nitride (BN) are focal NMs because of either their high production volumes as per Themes 1 and 4, their hazards as per high throughput screening (HTS) in Themes 2 - 5, or their propensity to migrate into terrestrial environments as per material flow analyses and transport simulations (Themes 5 and 6).

Progress over the last year has been in studying multiple NM variants (e.g. MOx, carbonaceous including MWCNTs, Ag- and Cu-based) for their impacts on microbial and plant populations, microbial communities and trophic transfer, and plant-microbe interactions. We assessed NM impacts on environmental microorganisms including bacteria and protists, and broadened the understanding of how NMs are translocated into plants, and how they affect plant health, food quality, and soil microbial populations and communities that support plant growth. We completed an assessment of soybean plant damage from nanoCeO2 amended to soil. A dynamic energy budget (DEB) model was developed that simulates soybean growth dose-dependency from NMs affecting aboveground biomass with feedbacks to root nodule symbioses. Several plant species were studied for their uptake and intoxication by bare and coated NMs, and for how environmental factors mitigate or exacerbate NM hazards to plants.

Theme 4 leads the Carbonaceous NM Working Group (C WG, including participants from CEIN, US EPA, NIST and Lawrence Livermore National Laboratory or LLNL). In association, a soil-grown soybean mesocosm study was completed for comparing effects of MWCNTs, graphene, and CB on this major food crop’s yield, food quality, N2-fixing root symbioses, plant health, and soil microbial communities. In collaboration with NIST and LLNL, trophic transfer was quantified for 14C-labeled MWCNTs from bacteria to protozoans. An environmental strain of Pseudomonas aeruginosa was studied for its resistance to carbonaceous NMs and BN, and transcriptomic analyses were initiated to determine resistance mechanisms. Theme 4’s overall impact derives from emphasizing hazard assessment of food crops, using a transferable ecological nanotoxicology system that begins with screening NM hazards using environmentally-relevant bacteria and hydroponic plants, mechanistically predicting hazards across terrestrial exposures, quantifying the potential for trophic transfer via base microbial food chains, judiciously examining bioavailability and trophic interactions using terrestrial mesocosms, and developing research approaches.