Browsing by Author "Schnoor, Jerald L."

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    Critical Uncertainties and Gaps in the Environmental- and Social-Impact Assessment of the Proposed Interoceanic Canal through Nicaragua
    (Oxford University Press, 2016) Huete-Pérez, Jorge A.; Ortega-Hegg, Manuel; Urquhart, Gerald R.; Covich, Alan P.; Vammen, Katherine; Rittmann, Bruce E.; Miranda, Julio C.; Espinoza-Corriols, Sergio; Acevedo, Adolfo; Acosta, María L.; Gómez, Juan P.; Brett, Michael T.; Hanemann, Michael; Härer, Andreas; Incer-Barquero, Jaime; Joyce, Frank J.; Lauer, J. Wesley; Maes, Jean Michel; Tomson, Mason B.; Meyer, Axel; Montenegro-Guillén, Salvador; Whitlow, W. Lindsay; Schnoor, Jerald L.; Alvarez, Pedro J.J.
    The proposed interoceanic canal will connect the Caribbean Sea with the Pacific Ocean, traversing Lake Nicaragua, the major freshwater reservoir in Central America. If completed, the canal would be the largest infrastructure-related excavation project on Earth. In November 2015, the Nicaraguan government approved an environmental and social impact assessment (ESIA) for the canal. A group of international experts participated in a workshop organized by the Academy of Sciences of Nicaragua to review this ESIA. The group concluded that the ESIA does not meet international standards; essential information is lacking regarding the potential impacts on the lake, freshwater and marine environments, and biodiversity. The ESIA presents an inadequate assessment of natural hazards and socioeconomic disruptions. The panel recommends that work on the canal project be suspended until an appropriate ESIA is completed. The project should be resumed only if it is demonstrated to be economically feasible, environmentally acceptable, and socially beneficial.
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    Engineered nanomaterials and plant interactions: uptake, translocation, transformation and physiological effects
    (2014-11-12) Wang, Jing; Alvarez, Pedro J.J.; Schnoor, Jerald L.; Braam, Janet; Li, Qilin
    The increasing likelihood of engineered nanomaterial (ENM) releases to the environment and their potential applications in agriculture highlight the importance of understanding ENM interactions with plants, which are cornerstone of most ecosystems. This study investigated how silver nanoparticles (Ag NPs) of different sizes affect plant growth over a wide range of concentrations and how coating charge affects quantum dots (QDs) uptake, translocation and transformation within woody plants. Even though both Ag NPs (5, 10, and 25 nm) and silver ion (Ag+) were phytotoxic to poplars and Arabidopsis above a specific concentration, a stimulatory effect was observed on root elongation, fresh weight and evapotranspiration of both plants at a narrow range of sub-lethal concentrations. Plants were most susceptible to the toxic effects of Ag+, but Ag NPs also showed some toxicity at higher concentrations and this susceptibility increased with decreasing Ag NP size. Both poplars and Arabidopsis accumulated silver, but silver distribution in shoot organs varied between plant species. Arabidopsis accumulated silver primarily in leaves (at ten-fold higher concentrations than in the stem or flower tissues), whereas poplars accumulated silver at similar concentrations in leaves and stems. Uptake of cationic QDs by poplar was faster than anionic QDs, possibly due to electrostatic attraction of cationic QDs to the negatively charged root cell wall. QDs aggregated upon root uptake, and their translocation to poplar shoots was likely limited by the endodermis. After 2-day exposure, both cationic and anionic coatings were likely degraded from the internalized QDs inside the plant, leading to the aggregation of the metallic cores and a “red-shift” of fluorescence. The fluorescence of cationic QD aggregates inside roots was stable through the 11-day exposure period, while that of the anionic QD aggregates was quenched probably due to destabilization of the coating inside the plant, even though these QDs were more stable in the hydroponic solution. Overall, the phyto-stimulatory effect observed in this study precludes the generalization of the phytotoxicity of Ag NPs. The QDs study highlights the importance of coating properties in the rate and extent to which NPs are assimilated by plants and potentially introduced into food webs.
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    Rapid Metabolism of 1,4-Dioxane to below Health Advisory Levels by Thiamine-Amended Rhodococcus ruber Strain 219
    (American Chemical Society, 2021) Simmer, Reid A.; Richards, Patrick M.; Ewald, Jessica M.; Schwarz, Cory; da Silva, Marcio L.B.; Mathieu, Jacques; Alvarez, Pedro J.J.; Schnoor, Jerald L.
    Bioremediation is a promising treatment technology for 1,4-dioxane-contaminated groundwater. However, metabolic dioxane-degrading bacteria identified to date are limited by their slow kinetics and inability to sustain growth at low dioxane concentrations (<100 μg/L). Furthermore, strains may underperform because of missing growth factors, such as amino acids or vitamins. In this work, we reevaluate Rhodococcus ruber strain 219 as a dioxane-degrading strain with bioaugmentation potential. We report rapid growth and metabolic dioxane degradation by R. ruber 219 when supplemented with thiamine (vitamin B1). We also discern that the strain lacks a complete de novo thiamine synthesis pathway, indicating that R. ruber 219 is a probable thiamine auxotroph. However, when supplemented with thiamine, the strain’s Monod kinetics (Ks = 0.015 ± 0.03 μg/L) and exceedingly low Smin (0.49 ± 1.16 μg/L) suggest this strain can maintain growth at very low dioxane concentrations (<100 μg/L). Accordingly, we demonstrate that thiamine-grown R. ruber 219 sustains degradation of dilute dioxane (<100 μg/L) to below health advisory levels. This is the first study to report sustained metabolic dioxane biodegradation to below health advisory levels of 0.35 μg/L. Overall, our findings solidify R. ruber 219 as a promising candidate for bioremediation of dioxane-contaminated groundwater.
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    Transport of Gold Nanoparticles through Plasmodesmata and Precipitation of Gold Ions in Woody Poplar
    (American Chemical Society, 2014) Zhai, Guangshu; Walters, Katherine S.; Peate, David W.; Alvarez, Pedro J.J.; Schnoor, Jerald L.
    Poplar plants (Populus deltoides × nigra, DN-34) were used as a model to explore vegetative uptake of commercially available gold nanoparticles (AuNPs) and their subsequent translocation and transport into plant cells. AuNPs were directly taken up and translocated from hydroponic solution to poplar roots, stems, and leaves. Total gold concentrations in leaves of plants treated with 15, 25, and 50 nm AuNPs at exposure concentrations of 498 ± 50.5, 247 ± 94.5, and 263 ± 157 ng/mL in solutions were 0.023 ± 0.006, 0.0218 ± 0.004, and 0.005 ± 0.0003 μg/g of dry weight, respectively, which accounted for 0.05, 0.10, and 0.03%, respectively, of the total gold mass added. The presence of total gold in plant tissues was measured by inductively coupled plasma mass spectrometry, while AuNPs were observed by transmission electron microscopy in plant tissues. In solution, AuNPs were distinguished from Au(III) ions by membrane separation and centrifugation. AuNPs behaved conservatively inside the plants and were not dissolved into gold ions. On the other hand, Au(III) ions were taken up and reduced into AuNPs inside whole plants. AuNPs were observed in the cytoplasm and various organelles of root and leaf cells. A distinct change in color from yellow to pink was observed as Au(III) ions were reduced and precipitated in a hydroponic solution. The accumulation of AuNPs in the plasmodesma of the phloem complex in root cells clearly suggests ease of transport between cells and translocation throughout the whole plant, inferring the potential for entry and transfer in food webs.