Towards integrated modeling of the long-term impacts of oil spills.

Although great progress has been made to advance the scientific understanding of oil spills, tools for integrated assessment modeling of the long-term impacts on ecosystems, socioeconomics and human health are lacking. The objective of this study was to develop a conceptual framework that could be used to answer stakeholder questions about oil spill impacts and to identify knowledge gaps and future integration priorities. The framework was initially separated into four knowledge domains (ocean environment, biological ecosystems, socioeconomics, and human health) whose interactions were explored by gathering stakeholder questions through public engagement, assimilating expert input about existing models, and consolidating information through a system dynamics approach. This synthesis resulted in a causal loop diagram from which the interconnectivity of the system could be visualized. Results of this analysis indicate that the system naturally separates into two tiers, ocean environment and biological ecosystems versus socioeconomics and human health. As a result, ocean environment and ecosystem models could be used to provide input to explore human health and socioeconomic variables in hypothetical scenarios. At decadal-plus time scales, the analysis emphasized that human domains influence the natural domains through changes in oil-spill related laws and regulations. Although data gaps were identified in all four model domains, the socioeconomics and human health domains are the least established. Considerable future work is needed to address research gaps and to create fully coupled quantitative integrative assessment models that can be used in strategic decision-making that will optimize recoveries from future large oil spills.

Establishment of a NORM baseline for selected seafood in the Gulf of Mexico.

Naturally occurring radioactive material was characterized in selected seafood samples from three areas in the Gulf of Mexico. Relatively desirable and abundant fish such as Red Snapper, Red Drum, Northern Whiting, and Spotted Trout as well as oysters were collected and analyzed using gamma spectroscopy to determine the concentration of 228Ra, 226Ra, and 40 K. Average total activity concentration from these radionuclides were 0.9 ±â€¯0.6, 1.6 ±â€¯1.2, and 132 ±â€¯57 Bq kg-1 respectively, in the edible portion of wet weight samples. The results were consistent with previous studies for other bodies of water. A small but statistically significant increase in 226Ra was found in comparison to similar research performed 20 years prior. These measurements provide a reasonable baseline for the examined species from the Gulf of Mexico.

Determination of Uranium Series Activity Before Secular Equilibrium Is Established.

Timely achievement of uranium series' secular equilibrium is not always feasible. Our objective is to mathematically justify methods for early uranium series gamma spectroscopy measurements that can accurately predict naturally occurring radioactive material equilibrium activities long before equilibrium is established. It was believed that, regardless of prior Rn escape, after sealing a sample for a few hours the activities of Rn, Ra, and U could theoretically be determined with a single measurement of both Pb and Bi. However, when accounting for error, this theory did not work as expected (CV = 14.0 in Ra simulation). A similar approach published by Li et al. in 2015 proved to be much more reliable with the error considered, using Pb activities measured at two different times gave significantly improved results when tested the same way (CV = 0.29 in Ra simulation). Because both Pb and Bi activities are typically available when using gamma spectrometry, we combine these approaches and further increased the accuracy of the calculated activities (CV = 0.21 in Ra simulation).

Dissecting the pattern of proton release from partial process involved in ubihydroquinone oxidation in the Q-cycle.

A key feature of the modified Q-cycle of the cytochrome bc1 and related complexes is a bifurcation of QH2 oxidation involving electron transfer to two different acceptor chains, each coupled to proton release. We have studied the kinetics of proton release in chromatophore vesicles from Rhodobacter sphaeroides, using the pH-sensitive dye neutral red to follow pH changes inside on activation of the photosynthetic chain, focusing on the bifurcated reaction, in which 4H+are released on complete turnover of the Q-cycle (2H+/ubiquinol (QH2) oxidized). We identified different partial processes of the Qo-site reaction, isolated through use of specific inhibitors, and correlated proton release with electron transfer processes by spectrophotometric measurement of cytochromes or electrochromic response. In the presence of myxothiazol or azoxystrobin, the proton release observed reflected oxidation of the Rieske iron­sulfur protein. In the absence of Qo-site inhibitors, the pH change measured represented the convolution of this proton release with release of protons on turnover of the Qo-site, involving formation of the ES-complex and oxidation of the semiquinone intermediate. Turnover also regenerated the reduced iron-sulfur protein, available for further oxidation on a second turnover. Proton release was well-matched with the rate limiting step on oxidation of QH2 on both turnovers. However, a minor lag in proton release found at pH 7 but not at pH 8 might suggest that a process linked to rapid proton release on oxidation of the intermediate semiquinone involves a group with a pK in that range.

Visualizing High-Order Decay after Disequilibria.

High-order decay equations are often difficult to study without significant care taken with variables and assumptions. As parent and progeny activities evolve over time, the effects of uncertainties and approximations confound the quality and interpretation of results. Of particular concern is the situation when decay equilibrium has been disturbed and progenies have arbitrary initial activities. To address this, code was created using Wolfram Mathematica to visualize the time-activity plots of the high order progenies of naturally occurring radioactive material after secular equilibrium is disturbed. The Bateman equation for an un-replenished parent was expanded to calculate activity vs. time for up to 13 progenies at different initial activities. The code uses the formula of Skrable et al., without parent production, expanded to the 13th progeny with arbitrary initial concentration. The code calculates and plots activity vs. time; it also reports the cumulative disintegrations of each progeny over a user-specified time period for comparison to counting measurements. The code could also be modified to incorporate additional production or branched decay schemes. We believe this code may be useful to health physicists and is intended to be accessible for anyone's use. This paper presents the code with explanations and examples on how to use it.

Evaluation of a Novel and Standardized Technique for Subcutaneous Upper Limb Dissection.

It is often necessary to dissect the subcutaneous tissues to confirm or exclude the presence of cutaneous bruising. We undertook a literature search that demonstrated that there is currently no standardized technique for subcutaneous dissection, and the specific incisions and dissections used probably vary between individual pathologists. It is our experience that dissections wider than the area of cutaneous bruising visible externally often reveal bruises not identified on external inspection. We propose a standardized technique for subcutaneous dissection of the upper limb that allows direct inspection of the subcutaneous tissues of the forearm and dorsum of the hand. We have evaluated this technique by comparing the number of bruises detected on external inspection with the number of bruises verified by subcutaneous dissection. Our study has shown a significant increase in the detection of bruises on subcutaneous dissection when compared with external inspection alone. One hundred sixteen forensic autopsies in which the technique was performed were included in our series. We recorded bruises seen on external examination alone and compared the number with additional bruises that were discovered on dissecting the upper limbs. In 49 cases (42%), the technique uncovered additional bruises that were missed on external examination alone.

Development of a human physiologically based pharmacokinetic (PBPK) model for dermal permeability for lindane.

Lindane is a neurotoxicant used for the treatment of lice and scabies present on human skin. Due to its pharmaceutical application, an extensive pharmacokinetic database exists in humans. Mathematical diffusion models allow for calculation of lindane skin permeability coefficients using human kinetic data obtained from in vitro and in vivo experimentation as well as a default compound-specific calculation based on physicochemical characteristics used in the absence of kinetic data. A dermal model was developed to describe lindane diffusion into the skin, where the skin compartment consisted of homogeneous dermal tissue. This study utilized Fick's law of diffusion along with chemical binding to protein and lipids to determine appropriate dermal absorption parameters which were then incorporated into a physiologically based pharmacokinetic (PBPK) model to describe in vivo kinetics. The estimation of permeability coefficients using chemical binding in combination with in vivo data demonstrates the advantages of combining physiochemical properties with a PBPK model to predict dermal absorption.

Using Geographic Information Systems to Determine Site Suitability for a Low-Level Radioactive Waste Storage Facility.

Radioactive waste is an inevitable product of using radioactive material in education and research activities, medical applications, energy generation, and weapons production. Low-level radioactive waste (LLW) makes up a majority of the radioactive waste produced in the United States. In 2010, over two million cubic feet of LLW were shipped to disposal sites. Despite efforts from several states and compacts as well as from private industry, the options for proper disposal of LLW remain limited. New methods for quickly identifying potential storage locations could alleviate current challenges and eventually provide additional sites and allow for adequate regional disposal of LLW. Furthermore, these methods need to be designed so that they are easily communicated to the public. A Geographic Information Systems (GIS) based method was developed to determine suitability of potential LLW disposal (or storage) sites. Criteria and other parameters of suitability were based on the Code of Federal Regulation (CFR) requirements as well as supporting literature and reports. The resultant method was used to assess areas suitable for further evaluation as prospective disposal sites in Louisiana. Criteria were derived from the 10 minimum requirements in 10 CFR Part 61.50, the Nuclear Regulatory Commission's Regulatory Guide 0902, and studies at existing disposal sites. A suitability formula was developed permitting the use of weighting factors and normalization of all criteria. Data were compiled into GIS data sets and analyzed on a cell grid of approximately 14,000 cells (covering 181,300 square kilometers) using the suitability formula. Requirements were analyzed for each cell using multiple criteria/sub-criteria as well as surrogates for unavailable datasets. Additional criteria were also added when appropriate. The method designed in this project proved to be sufficient for initial screening tests in determining the most suitable areas for prospective disposal (or storage) sites. Cells above 90%, 95%, and 99% suitability include respectively 404, 88, and 4 cells suitable for further analysis. With these areas identified, the next step in siting a LLW storage facility would be on-site analysis using additional requirements as specified by relevant regulatory guidelines. The GIS based method provides an easy, economic, efficient and effective means in evaluating potential sites for LLW storage facilities where sufficient GIS data exist.