Considerations for realistic atmospheric environments: An application to corrosion testing.

Measured salt compositions in dust collected over roughly the last decade from surfaces of in-service stainless-steel alloys at four locations around the United States are presented, along with the predicted brine compositions that would result from deliquescence of these salts. The salt compositions vary greatly from ASTM seawater and from laboratory salts (i.e., NaCl or MgCl2) commonly used on corrosion testing. The salts contained relatively high amounts of sulfates and nitrates, evolved to basic pH values, and exhibited deliquescence relative humidity values (RH) higher than seawater. Additionally, inert dust in components were quantified and considerations for laboratory testing are presented. The observed dust compositions are discussed in terms of the potential corrosion behavior and are compared to commonly used accelerated testing protocols. Finally, ambient weather conditions and their influence on diurnal fluctuations in temperature (T) and RH on heated metal surfaces are evaluated and a relevant diurnal cycle for laboratory testing a heated surface has been developed. Suggestions for future accelerated tests are proposed that include exploration of the effects of inert dust particles on atmospheric corrosion, chemistry considerations, and realistic diurnal fluctuations in T and RH. Understanding mechanisms in both realistic and accelerated environments will allow development of a corrosion factor (i.e., scaling factor) for the extrapolation of laboratory-scale test results to real world applications.

Physical and chemical properties of sea salt deliquescent brines as a function of temperature and relative humidity.

Thermodynamic modeling has been used to predict chemical compositions of brines formed by the deliquescence of sea salt aerosols. Representative brines have been mixed, and physical and chemical properties have been measured over a range of temperatures. Brine properties are discussed in terms of atmospheric corrosion of austenitic stainless steel, using spent nuclear fuel dry storage canisters as an example. After initial loading with spent fuel, during dry storage, the canisters cool over time, leading to increased surface relative humidities and evolving brine chemistries and properties. These parameters affect corrosion kinetics and damage distributions, and may offer important constraints on the expected timing, rate, and long-term impacts of canister corrosion.

Polonium-210 accumulates in a lake receiving coal mine discharges-anthropogenic or natural?

Coal is an integral part of global energy production; however, coal mining is associated with numerous environmental health impacts. It is well documented that coal-mine waste can contaminate the environment with naturally-occurring radionuclides from the uranium-238 (238U) decay series. However, the behavior of the final radionuclide in the 238U-series, i.e., polonium-210 (210Po) arising from coal-mine waste-water discharge is largely unexplored. Here, results of a year-long (2014-2015) field study, in which the concentrations of 210Po in sediments and surface water of a lake that receives coal-mine waste-water discharge in West Virginia are presented. Initial measurements identified levels of 210Po in the lake sediments that were in excess of that which could be attributed to ambient U-series parent radionuclides; and were indicative of discharge site contamination of the lake ecosystem. However, control sediment obtained from a similar lake system in Iowa (an area with no coal mining or unconventional drilling) suggests that the levels of 210Po in the lake are a natural phenomenon; and are likely unrelated to waste-water treatment discharges. Elevated levels of 210Po have been reported in lake bottom sediments previously, yet very little information is available on the radioecological implications of 210Po accumulation in lake bottom sediments. The findings of this study suggest that (Monthly Energy Review, 2016) the natural accumulation and retention of 210Po in lake sediments may be a greater than previously considered (Chadwick et al., 2013) careful selection of control sites is important to prevent the inappropriate attribution of elevated levels of NORM in lake bottom ecosystems to industrial sources; and (Van Hook, 1979) further investigation of the source-terms and potential impacts on elevated 210Po in lake-sediment ecosystems is warranted.

Biological responses to contaminants in the Humber Estuary: disentangling complex relationships.

Due to the ecological importance of estuaries, it is necessary to understand the biological effects that potentially toxic contaminants induce in bioindicator species. A key aspect is whether effects at lower levels of biological organisation transfer through the system to higher levels. In understanding such processes, characterising multivariate relationships between contaminants, sediment toxicities and detoxification processes are important. Worms (Hediste diversicolor) and sediments were collected along the Humber Estuary, England, and inorganic and organic contaminants were quantified. Sediment toxicities and glutathione-S-transferases (GSTs) activity in the ragworm were analysed. Concentrations of metals were highest near urban and industrial areas, whereas organic contaminants appeared at upstream locations. GST activity correlated with heavy metals. The genotoxicity, oestrogenicity, dioxin and dioxin-like activity were higher at upstream locations. Oestrogenicity correlated with alkylphenols and some organochlorines, whilst genotoxicity correlated with organochlorines and heavy metals. Despite this, higher level biological responses could not be predicted, indicating that homeostasis is operating.

An assessment of the utility of the yeast GreenScreen assay in pharmaceutical screening.

In this paper we describe an initial reproducibility study of 12 proprietary compounds followed by the assessment of 51 marketed pharmaceuticals and, lastly, a summary of the data so far from 2698 proprietary compounds from the Johnson & Johnson (J&J) compound library, in the yeast GreenScreen assay (GSA). In this assay, a reporter system in the yeast cells employs the DNA damage inducible promoter of the RAD54 gene, fused to the extremely stable green fluorescent protein (GFP). The assay proved to be very robust, the Excel templates provided by Gentronix with the assay interfaced well with in-house J&J systems with little adaptation, the assay was very rapid to perform and used very little compound. The results confirm previous work which suggests that the yeast GSA detects different classes of genotoxic compounds to the Ames assay and as a result can help screen out important genotoxic compounds at the pre-regulatory test phase that are missed by Ames-test-based screens alone. A combination of SAR evaluation of genotoxicity plus an Ames-test-based screen and the GSA provides a powerful pre-regulatory test battery to aid in the selection of successful drug candidates.

Genetic modification and variations in solvent increase the sensitivity of the yeast RAD54-GFP genotoxicity assay.

The yeast (Saccharomyces cerevisiae) RAD54-GFP DNA repair reporter assay (GreenScreen assay, GSA) can be used for early genotoxicity screening in drug discovery. During the initial validation of this preregulatory assay, a subset of known genotoxic compounds that did not give reproducibly clear positive GSA results was identified. Cell permeability, inherent drug resistance mechanisms, metabolic activation and compound solubility were identified as possible barriers to the detection of specific compounds. In this study three types of modification to the existing assay protocol were explored in order to address these possibilities: (i) modification of the reporter host strain by deletion of genes involved in cell wall integrity or with products functioning as efflux pumps (PDR5, ERG6, SNQ2, YOR1); (ii) expression in the host yeast of human phase I metabolic activation genes and (iii) variation in the test solvent system for compounds with poor aqueous solubility. The modifications described and the assay results presented show how the assay may be tailored to suit specific classes of test compound in a more analytical mode. Improvements in assay sensitivity were seen in the detection of some genotoxins using yeast cell wall mutants and those expressing human cytochrome P450 genes.

Results of a technology demonstration project to compare rapid aquatic toxicity screening tests in the analysis of industrial effluents.

The results of a 'BioWise' demonstration project to assess the comparative sensitivity and practicality of seven new assays for the direct assessment of ecotoxicity in industrial effluents are presented. In addition the aim of the project was to validate the results of the new assays against benchmark data generated from non-proprietary, rapid, microplate screening assays using the regulatory species; freshwater crustacean Daphnia magna and green algae Selenastrum capricornutum, chosen in view of their environmental relevance. The new commercial test assays were: Daphnia magna, Selenastrum capricornutum and Thamnocephalus platyurus Toxkits supplied by Vickers Laboratories Ltd, containing dormant, immobilised life stages of the test species; GreenScreen EM, a yeast based assay for genotoxicity and general acute toxicity supplied by Gentronix Ltd; and CellSense a mediated, amperometric whole cell biosensor based on immobilised activated sludge and E. coli. 38 effluent samples supplied by members of SOCSA (Specialised Organic Chemicals Sector Association) were examined over a period of 13 months, in the project co-ordinated by the AstraZeneca Brixham Environmental Laboratory, and part funded by BioWise via the UK Government Department of Trade and Industry.

The GreenScreen genotoxicity assay: a screening validation programme.

A yeast (Saccharomyces cerevisiae) DNA repair reporter assay termed the GreenScreen assay (GSA) is described. This is a novel, cost-effective genotoxicity screen, developed to provide a pre-regulatory screening assay for use by the pharmaceutical industry and in other applications where significant numbers of compounds need to be tested. It provides a higher throughput and a lower compound consumption than existing eukaryotic genotoxicity assays and is sensitive to a broad spectrum of mutagens and, importantly, clastogens. We describe a simple, robust assay protocol and a validation study. The end-point of the test reflects the typically eukaryotic chromosomes and DNA metabolizing enzymes of yeast. The capacity for metabolic activation (MA) in yeast is limited compared with the mammalian liver or its extracts, but the assay does detect a subset of compounds that would require MA in existing genotoxicity tests. The GSA detects a different spectrum of compounds to bacterial genotoxicity assays and thus, together with an in silico structure-activity relationship (SAR) screen, and possibly a high throughput bacterial screen, would provide an effective preview of the regulatory battery of genotoxicity tests.

Selenium bioaccumulation by the water boatman Trichocorixa reticulata (Guerin-Meneville).

The input of selenium from subsurface agricultural drainage into surface water systems can result in the accumulation of toxic concentrations of selenium in aquatic food chains. Elevated selenium concentrations in aquatic systems is a significant environmental problem in many areas of the United States. A laboratory investigation was conducted to determine the dominant route of selenium bioaccumulation by the corixid Trichocorixa reticulata, an important food chain organism. The roles of waterborne and foodborne exposure in selenium bioaccumulation were examined using 48-h bioassays. Waterborne selenium concentrations ranged from 0 to 1,000 microgram Se/L as selenate. A mixture of two species of blue-green algae cultured in media with selenium concentrations ranging from 0 to 1,000 microgram Se/L as selenate was used as a corixid diet in the foodborne treatments. Corixids exposed to waterborne selenate did not accumulate selenium above control concentrations. Corixids fed algae exposed to >/=100 microgram Se/L as selenate had significantly higher selenium concentrations than control organisms. These data suggest that corixids may be effectively isolated from the water and selenium accumulation is solely through dietary exposure.

The use of bioassays and toxicity identification evaluation (TIE) procedures to assess recovery and effectiveness of remedial activities in a mine drainage-impacted stream system.

Effluents from Walker Mine and its tailings pile have resulted in toxic concentrations of metals in Dolly and Little Grizzly Creeks. Recent remedial structures have greatly reduced metal loading, however the need to assess recovery of the receiving aquatic ecosystem exists so that future remediation priorities can be established. The objective was to contribute to this assessment using Toxicity Identification Evaluation procedures. Water samples were collected at several sites in Dolly and Little Grizzly Creeks. Untreated samples and samples passed through ion exchange columns, which remove cationic metals, were compared in side-by-side bioassays using Pimephales promelas, Ceriodaphnia dubia, and Selenastrum capricornutum. Samples were analyzed for total and dissolved copper, cadmium, zinc, and iron. Copper was the element responsible for toxicity. Toxicity was detected in the mine discharge and immediately downstream from the tailings where dissolved copper concentrations were 250 microg/L and 415 microg/L, respectively. Toxicity decreased at downstream sites but extended at least 6.4 km downstream. Improvement in bioassay performance by the treated waters verified metal toxicity. The results indicate that the mine effluent and tailings pile currently have the heaviest impact on Dolly and Little Grizzly Creeks and should be given the highest priority in future remedial programs.

Development of a green fluorescent protein reporter for a yeast genotoxicity biosensor.

A reporter system, constructed for a laboratory screen for new genes involved in DNA repair in the brewer's yeast Saccharomyces cerevisiae, has been developed for use in a genotoxicity biosensor. The strain produces green fluorescent protein (yEGFP) when DNA damage has occurred. yEGFP is codon optimised for yeasts. The reporter does not respond to chemicals which delay mitosis, and responds appropriately to the genetic regulation of DNA repair. Data is presented which demonstrate strain improvements appropriate to biosensor technology: improved signal to noise ratio, ease of data collection and uncomplicated material handling.

Ecotoxicology of selenium in freshwater systems.

The toxicology, environmental impacts and risk assessment of Se in freshwater systems are a high priority for research and regulatory agencies. However, understanding Se in freshwater systems is a challenging endeavor. The accurate risk assessment and determination of a water-quality criterion for any freshwater ecosystem are difficult for many reasons. First, the understanding of the structure and energy dynamics in ecosystems is limited. Second, knowledge of Se cycling and transformations in aquatic ecosystems is rudimentary. Third, the role of various environmental factors affecting its bioaccumulation, biotransformation, and toxicology in aquatic ecosystems is largely unknown. Fourth, the extrapolation and use of existing data in commonly used formulas for risk assessment and calculations of water quality criteria is difficult because of the demonstrated species differences in the bioaccumulation, metabolism, and tolerance of Se. There are many aspects of Se ecotoxicology that need to be addressed to develop more accurate environmental risk assessments and determine appropriate water-quality criteria to protect aquatic ecosystems. Studies evaluating the biochemical speciation of Se in aquatic ecosystems, and determination of the role of microbial communities in its cycling, bioaccumulation, transformation, transfer, and toxicity in aquatic systems, appear to be priorities for future research. These would include a broad exploration of Se effects on ecosystems, e.g., exposure regime, direct and indirect biologic effects, and ecosystem level effects. There are, however, ecological uncertainties that tend to confound such endeavors, e.g., insufficient data, extrapolation issues, and environmental stochasticity (Harwell and Harwell 1989). There are several concepts concerning the ecotoxicology of Se that can be stated. Elevated concentrations have degraded many freshwater ecosystems throughout the United States, and additional systems are expected to be affected as anthropogenic activities increasingly mobilize Se into aquatic systems. Se is a very toxic essential trace element. Toxic threshold concentrations in water, dietary items, and tissues are only 2-5 times normal background concentrations. Toxicity in freshwater ecosystems is the result of bioaccumulation, biotransformation, and cycling of Se in aquatic food chains. Thus, environmental risk assessment and development of effective water-quality criteria to protect freshwater ecosystems become formidable tasks.

The toxicity of waterborne boron to Daphnia magna and Chironomus decorus and the effects of water hardness and sulfate on boron toxicity.

The concentrations of many elements, including boron, are increasing in aquatic ecosystems due to anthropogenic activities. Laboratory studies were undertaken to evaluate the toxicity of waterborne boron to two key freshwater macroinvertebrates and to evaluate the effects of water hardness and sulfate on boron toxicity. Acute toxicity evaluations of waterborne sodium tetraborate resulted in 48 h. LC50 values of 141 and 1376 mg B/L for neonate Daphnia magna and fourth instar Chironomus decorus, respectively. Chronic sublethal studies demonstrated a significant decrease in C. decorus growth rate at 20 mg B/L. Further studies showed that increasing water hardness (10.6 to 170 mg/L as CaCO3) and sulfate (10.2 to 325.4 mg SO4(-2)/L) concentrations did not affect boron toxicity to D. magna. These results, in conjunction with a review of the literature, suggest that aquatic macrophytes may be more sensitive to boron than macroinvertebrates and thus would be better choices for aquatic risk assessment evaluations for this element.

Effects of elevated foodborne selenium on growth and reproduction of the fathead minnow (Pimephales promelas).

Several field studies of selenium-contaminated lakes and reservoirs have indicated the possibility of selenium-induced reproductive failure in important populations of fish. These investigators have hypothesized that bioaccumulation of selenium through the food chain led to fish selenium levels high enough to elicit toxic responses. The present investigation was designed to determine the effects of elevated foodborne selenium on the fathead minnow (Pimephales promelas). Fish were fed a diet spiked with a mixture of inorganic (selenite and selenate) and organic (seleno-L-methionine) selenium and effects on growth and reproduction were determined. Growth was significantly inhibited at the highest selenium treatment levels evaluated (20 and 30 ppm Se). There were no significant treatment effects on any of the reproductive parameters measured. Reasons for the disparity between selenium-induced reproductive impairment observed in other species and apparent lack of impairment in fathead minnows may involve reduced bioaccumulation of selenium by minnows due to differences in gut morphology and physiology.

Protein and nitrate content of lemna sp. As a function of developmental stage and incubation temperature.

Lemna protein per frond and per root increases with developmental stage until plants are at least two generations old. Protein per frond, per root, and per unit dry weight is greater in plants grown at 23.9 C than at 18.3 C. More protein is found in fronds than in roots, and more nitrate occurs in roots than in fronds. Nitrate per root increases with developmental stage and is higher (per root) in plants grown at 23.9 C than in those grown at 18.3 C. The distribution of generations within a growing population is constant for at least eight doubling times. Whether populations multiply slowly at 15.6 C or more rapidly at 23.9 C, fronds which have not yet produced progeny form 62% of the population; fronds which are one generation old form 24% of the population; and fronds which are two generations old form 9% of the population.