Partitioning of Hydrophobic Organic Contaminants and Microbial Communities on Microplastics

Microplastic contamination of aquatic environments has only recently caught the attention of scientists, regulators and the public. Microplastics are typically more recalcitrant than naturally occurring polymers and so have the potential to cause a range of issues, including increased exposure of marine life to chemical contaminants sorbed to or leached from microplastics, negative impacts due to ingestion of microplastics by biota, and the potential to carry and transport pathogenic and invasive species long distances. Bio-based, bio-degradable polymers have begun to gain market share as an alternative to traditional petrochemical-based plastics, but not much is known about their impacts in marine environments. The overall objective of this thesis was to improve our understanding of how bio-based microplastics compare to petrochemical-based plastics in the marine environment. This information could be used to evaluate the overall sustainability of bio-based polymers as replacements for petrochemical-based polymers. The first chapter of this work investigated the potential of four types of microplastics, polyethylene (PE), polyvinyl chloride (PVC) and two bio-based polymers, poly-3-hydroxybutyrate (PHB) and polylactic acid (PLA), to sorb hydrophobic organic contaminants (pyrene, PCB-153, and BDE-47) from the surrounding water column. It also examined how co-exposure to several of these contaminants influenced their sorption. The bio-based polymers used in this work, exhibited lower affinity for the organic contaminants investigated compared to the more widely used, petrochemical-derived microplastics. This may be due to several factors including hydrophobicity of the plastic surfaces and the chemical structure of each plastic. Further, competition between several co-exposed contaminants led to an overall decrease in chemical partitioning on polyethylene microplastics. The second chapter reported on the microbial composition of biofilm communities that form on bio-based (PHB and PLA) and petrochemical-based (PE and PVC) microplastics in comparison to a naturally occurring polymer, chitin. Microbial compositions of biofilms that formed on the different plastics were similar during the first and second week of growth, but chitin exhibited a distinct community from the microplastics. By the fourth week of growth, all substrates had a similar community composition. Diversity was generally higher on bio-based plastics. Genera harboring marine pathogens and hydrocarbon-degrading bacteria were identified on all substrates. This work has implications to policy surrounding marine debris issues, exploring the more nuanced differences between bio-based polymers and petrochemical polymers, introducing concerns over additive use in bio-based polymers, and reinforcing the need for “eco-cyclable” materials in single-use items

2016 Greenhouse Gas Inventory Report: Virginia Institute of Marine Science

During summer 2016 the VIMS Green Team completed an inventory of greenhouse gas (GHG) emissions from the Virginia Institute of Marine Science (VIMS) Gloucester Point campus during FY2015. GHG emissions were estimated using the Campus Carbon Calculator maintained by the Sustainability Institute at the University of New Hampshire, and compared to a previous GHG audit from FY2010

Risks to human and animal health related to the presence of deoxynivalenol and its acetylated and modified forms in food and feed

Deoxynivalenol (DON) is a mycotoxin primarily produced by Fusarium fungi, occurring predominantly in cereal grains. Following the request of the European Commission, the CONTAM Panel assessed the risk to animal and human health related to DON, 3-acetyl-DON (3-Ac-DON), 15-acetyl-DON (15-Ac-DON) and DON-3-glucoside in food and feed. A total of 27,537, 13,892, 7,270 and 2,266 analytical data for DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside, respectively, in food, feed and unprocessed grains collected from 2007 to 2014 were used. For human exposure, grains and grain-based products were main sources, whereas in farm and companion animals, cereal grains, cereal by-products and forage maize contributed most. DON is rapidly absorbed, distributed, and excreted. Since 3-Ac-DON and 15-Ac-DON are largely deacetylated and DON-3-glucoside cleaved in the intestines the same toxic effects as DON can be expected. The TDI of 1 μg/kg bw per day, that was established for DON based on reduced body weight gain in mice, was therefore used as a group-TDI for the sum of DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside. In order to assess acute human health risk, epidemiological data from mycotoxicoses were assessed and a group-ARfD of 8 μg/kg bw per eating occasion was calculated. Estimates of acute dietary exposures were below this dose and did not raise a health concern in humans. The estimated mean chronic dietary exposure was above the group-TDI in infants, toddlers and other children, and at high exposure also in adolescents and adults, indicating a potential health concern. Based on estimated mean dietary concentrations in ruminants, poultry, rabbits, dogs and cats, most farmed fish species and horses, adverse effects are not expected. At the high dietary concentrations, there is a potential risk for chronic adverse effects in pigs and fish and for acute adverse effects in cats and farmed mink

Electrical Forces Determine Glomerular Permeability

There is ongoing controversy about the mechanisms that determine the characteristics of the glomerular filter. Here, we tested whether flow across the glomerular filter generates extracellular electrical potential differences, which could be an important determinant of glomerular filtration. In micropuncture experiments in Necturus maculosus, we measured a potential difference across the glomerular filtration barrier that was proportional to filtration pressure (−0.045 mV/10 cm H2O). The filtration-dependent potential was generated without temporal delay and was negative within Bowman's space. Perfusion with the cationic polymer protamine abolished the potential difference. We propose a mathematical model that considers the relative contributions of diffusion, convection, and electrophoretic effects on the total flux of albumin across the filter. According to this model, potential differences of −0.02 to −0.05 mV can induce electrophoretic effects that significantly influence the glomerular sieving coefficient of albumin. This model of glomerular filtration has the potential to provide a mechanistic theory, based on experimental data, about the filtration characteristics of the glomerular filtration barrier. It provides a unique approach to the microanatomy of the glomerulus, renal autoregulation, and the pathogenesis of proteinuria

Introducing Dimensionality to the Archetypical Mn₁₂ Single-Molecule Magnet: a Family of [Mn₁₂]_<i>n</i> Chains

The [Mn₁₂O₁₂(O₂CR)₁₆(L₄)] family (R = various; L = terminal ligand) of clusters holds a special place in molecular magnetism; they are the most well-studied single-molecule magnets (SMMs). Targeted linkage of these SMMs has now been achieved for the first time. The resulting chain structures have been confirmed crystallographically, and the magnetic properties, up to 1.14 GPa, and high-field electron paramagnetic resonance spectra have been collected and analyzed