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- Creator:
- Gaston, Emily
- Description:
- The abundance and distribution of microplastic (<5 mm) has become a growing concern, particularly over the past decade. Research to date has focused on water, soil, and organism matrices but generally disregarded air. We explored airborne microplastic inside and outside of buildings in coastal California by filtering known volumes of air through glass fiber filters, which were then subsequently characterized with a variety of microscopy techniques: gross traditional microscopy, fluorescent microscopy following staining with Nile red, micro-Raman spectroscopy, and micro-Fourier transform infrared (FT-IR) spectroscopy. Microplastics permeated the air, with indoor (3.3±2.9 fibers and 12.6±8.0 fragments m–3; mean±1 SD) harboring twice as much as outdoor air (0.6 ±0.6 fibers and 5.6±3.2 fragments m–3). Microplastic fiber length did not differ significantly between indoor and outdoor air, but indoor microplastic fragments (58.6±55 µm) were half the size of outdoor fragments (104.8±64.9 µm). Micro-Raman and FT-IR painted slightly different pictures of airborne plastic compounds, with micro-Raman suggesting polyvinyl chloride dominates indoor air, followed by polyethylene (PE) and microFT-IR showing polystyrene dominates followed by PE and polyethylene terephthalate. The ubiquity of airborne microplastic points to significant new potential sources of plastic inputs to terrestrial and marine ecosystems and raises significant concerns about inhalation exposure to humans both indoors and out.
- Resource Type:
- Article
- Campus Tesim:
- Channel Islands
- Department:
- Environmental Science & Resource Management
- Creator:
- Gledhill, Michelle
- Description:
- A primary goal in ecotoxicology is the prediction of population-level effects of contaminant exposure based on individual-level response. Assessment of toxicity at the population level has predominately focused on the population growth rate (PGR), but the PGR may not be a relevant toxicological endpoint for populations at equilibrium. Equilibrium population size may be a more meaningful endpoint than the PGR because a population with smaller equilibrium (i.e., long-term mean) size is more susceptible to the negative effects of environmental variability. I address the ecotoxicology individual-to-population extrapolation problem with modeling. I developed and analyzed a general model applicable to many freshwater fish species that includes density-dependent juvenile survival and additional juvenile mortality due to toxicity exposure, and I quantified its effect on equilibrium population size as a means of assessing toxicity. I then used selenium toxicity in bluegill sunfish as an example to assess the effects of environmental stochasticity on toxicity response with simulation modeling. Individual-level effects are typically greater than population-level effects until the individual effect is large, due to compensatory density-dependent relationships. These effects are sensitive to the recruitment potential of a population, in particular the low-density first-year survival rate S_b. Assuming high S_b could result in underestimating effects of population-level toxicity. The equilibrium size depends directly on S_b, the reproductive potential, the toxin concentration at which mean mortality is 50% (LC50), and the rate at which individual mortality increases with increasing toxin concentration. More experimental data are needed to decrease the uncertainty in estimating these parameters. Effects of environmental variability resulted in simulated extinctions at much lower toxin concentrations than predicted deterministically.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Humboldt
- Department:
- Mathematical Modeling
- Creator:
- Ramirez, Nicolas
- Description:
- Ecotoxicology is the study of toxic chemicals, natural or synthetic, on populations and communities. Despite numerous texts and journal articles which discuss ecotoxicological principles and methods, there are relatively few studies conducted on the use of GIS technology as it applies to spatially modeling ecotoxicological systems. Modeling ecotoxicological systems using GIS allows us to account for simultaneous processes of distribution and transformation. In order to be useful for a large number of end users, a GIS tool set should be generalized, allowing users to adjust specific parameters based on the specific scenario. The objective of this study was to explore the use of GIS for ecotoxicological applications through the development of new analytical tools for future studies in ecotoxicology and environmental management and planning. The result was the CALCULATE EXPONENTIAL DECAY script tool developed using the PYTHON programming language for use in ESRI ArcMap software environment. This tool was developed while working on “Understanding the Cumulative Affects of Environmental and Psycho-social Stressors that Threaten the Pohlik-lah and Ner-er-ner Lifeway: The Yurok Tribe’s Approach”, an EPA Star Grant project which began in 2008.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Humboldt
- Department:
- Natural Resources Planning and Interpretation