Terrestrial Ecosystems Impact and Hazard Assessment - Theme 4 (TER)
Leader: Patricia Holden
The overarching goal of Theme 4 is to discover and understand the effects of ENMs on terrestrial environments, with an aim to predict and avoid such effects. The societal drivers for studying effects of ENMs in terrestrial environments are: maintenance of ecosystem services (e.g. nutrient cycling, pollutant biodegradation, and plant fertility), agricultural crop production and food quality, and water quality (i.e. groundwater, used as a drinking water source). ENMs are expected to enter terrestrial environments in the U.S. mainly via land application of wastewater treatment plant (WWTP) biosolids; ENMs may also deposit to lands from the atmosphere (e.g. automobile exhaust carrying nano-CeO2 from catalytic converters) and from direct water-to-land processes (e.g. spills near manufacturing sites, painted facades, or personal care products released into recreational water bodies). Theme 4 researches the feedbacks between ENMs and terrestrial environments—and thus seeks to describe not only effects on organisms, but also bioprocessing of ENMs in soils and plants. In this regard Theme 4 results can inform ENM fates which are foci of Theme 3. Otherwise, Theme 4 research is comparatively source-blind, and seeks to understand what effects ENMs can have in terrestrial systems once ENMs have been transported into, and have accumulated in, soils. Terrestrial environments are comprised of soil minerals, organic matter, water, dissolved nutrients, microbiota, macrofauna, and plants. Theme 4 research appropriately addresses all relevant biological (macromolecular to whole organism) and ecological (individual, to population, to community, to ecosystem) scales, and is attentive to the physical, biological, and chemical processes influencing ENM impacts. To date, across published nanotoxicology, there have been relatively few studies focusing on terrestrial environments. Inaugural studies suggested that ENMs, if applied at realistic concentrations to soils, would not be sufficiently bioavailable to affect microbes or plants. However, work from Theme 4 is revealing that: a broad range of ENMs are toxic to bacteria in the dark (as in soils); ENMs associate with, and damage, bacterial membranes; bacterial membrane damage inhibits bacterial growth with extents that can be predicted by mathematical models incorporating ROS amounts; ENMs attached to, or within, bacteria are trophically-transferred to protozoan predators which also bioprocess ENMs; bacterial consortia in soils are altered by ENMs including losses of functionally-narrow taxa in N and C cycling; soil water holding characteristics are altered by ENMs with implications to drought tolerance of ENM-contaminated soils; plants bioaccumulate and process specific ENMs with variations by plant and ENM type; ENMs can genetically alter hydroponic plants; ENMs negatively impact important crop plants and soil microbial processes relevant to soil fertility.
Overall, the goals of Theme 4 are consistent with the Center goals of delivering understanding that is mechanistic and transferable; Theme 4 goals and findings are highly responsive to prior critiques that holistic, as well as reductionist, inquiries should be made to improve the relevance of our research.
1. Nanotoxicology in Terrestrial Microcosms
2. Trophic Transfer, Bioaccumulation and Biomagnification of Engineered Nanomaterials in Basal Levels of Environmental Food Webs
3. Engineered Nanoparticle Biosorption, Toxicity, and Toxicity Mechanisms in Planktonic and Biofilm Bacteria
4. Toxicity and Uptake of Nanoparticles by Terrestrial Plant Species
5. Dynamic Energy Budget (DEB) Modeling of Toxic Effects of CdSe Quantum Dots