A risk-based screening approach for prioritizing contaminants and exposure pathways at Superfund sites

Contamination at Superfund sites can involve mixtures of chemicals and radionuclides in a variety of environmental media. Determining priorities for evaluation and remediation of various contaminants is an important part of the initial phases of any site investigation. An effective screening analysis at the beginning of the project can help by identifying both those situations in need of immediate remedial attention and those which require further sampling and evaluation. The screening approach discussed here is made up of two sets of calculations designed to provide upper- and lower-bound estimates of health risk to individuals likely to receive the highest exposures. This approach allows rapid identification of contaminants which pose a negligible risk and can be assigned a low priority for remedial attention or which pose a substantial risk and should be given the highest priority for appropriate remediation efforts. Contaminants designated as neither high- nor low-priority should be investigated in more detail prior to making decisions regarding the need for or method of remediation. The utility of this approach has already been demonstrated in the evaluation of contamination in the Clinch and Tennessee River systems originating from historical operations of atomic weapons and energy research facilities near Oak Ridge, Tennessee.     

The effects of ethylene chlorohydrin on fatty acid synthesis

Male chicks weighing 700 to 900 g. received an acute or eight doses IG of 60 or 40 mg/kg ethylene chlorohydrin (ECH) respectively and were sacrificed eighteen hours after the last dose. Mitochondrial elongation of fatty acids was decreased significantly while fatty acid synthetase activity was not significantly affected by ECH treatment. Cytochrome c oxidase activity in fresh whole liver homogenate was significantly higher in chicks subjected to acute exposure with ECH when compared to the controls. Upon freezing and thawing of homogenates, cytochrome c oxidase activity increased significantly in the control group but was unchanged in the ECH group which suggests that the mitochondrial membrane integrity is compromised by the ECH treatment. Serum and liver triglyceride levels were significantly elevated in both the single and multiple ECH dose groups. Liver to body weight ratios were significantly higher in both treatment groups when compared to their controls. Histological examination of the liver of ECH-treated chicks showed cytoplasmic clearing of the cells but no vacuolization or centrilobular necrosis. Serum isocitrate dehydrogenase levels were significantly higher in the multiple treatment ECH group than in the control group.     

Teratogenic evaluation and fetal deposition of hexabromobenzene (HBB) and hexafluorobenzene (HFB) in CD-1 mice

HBB (hexabromobenzene) and HFB (hexafluorobenzene) were tested for their teratogenic potential in CD-1 mice. HBB and HFB were administered to pregnant mice from the 6th to the 16th day of gestation by gastric intubation. Neither HBB nor HFB were teratogenic or fetotoxic at doses up to 98.6 mg HBB/kg and 65.3 mg HFB/kg. No maternal toxicity was noted. HBB concentration in the fetuses indicated little, if any accumulation. No HFB was detected in the fetal or maternal tissues 24 hours after the last dose.     

The economics of uranium demand

The major characteristics of the demand for uranium are identified, and a number of factors which determine the actual level of uranium requirements of the nuclear power industry are discussed. Since the role of inventories is central to the process of short-term price formation, by comparing projections of uranium production and apparent consumption, the relative level of total inventories is calculated and an assessment is made of its likely impact on the uranium market during the 1980s.     

A simulation model of rhizome networks for Fallopia japonica (Japanese knotweed) in the United Kingdom

Fallopia japonica (Japanese knotweed) is an aggressively invasive herbaceous perennial that causes substantial economic and environmental damage in the United Kingdom (UK). As such, it is of considerable concern to councils, environmental groups, private landowners and property developers. We construct a 3D correlated random walk model of the development of the subterranean rhizome network for a single stand of F. japonica. The formulation of this model uses detailed knowledge of the morphology and physiology of the plant, both of which differ in the UK to that of its native habitat due to factors including a lack of predation and competition, longer growth seasons and favourable environmental conditions in the UK. Field data obtained as a part of this study are discussed and used in the model for parameterisation and validation. The simulation captures the field data well and predicts, for example, quadratic growth in time for the stand area. Furthermore, the role of a selection of parameters on long-term stand development are discussed, highlighting some key factors affecting vegetative spread rates.     

Seasonal and areal changes in standing stocks of phytoplankton,zooplankton and micronekton in the eastern tropical pacific

Five standing stocks were measured together at similar latitudes and longitudes on seasonally repetitive cruises in 3 areas — western, eastern, and southern — of the eastern tropical Pacific. The stocks were chlorophyll a at 0 to 150 m depth (mg/m²), night and day zooplankton at 0 to 200 m depth (ml/1000 m³), and night crustacean micronekton and fish-pluscephalopod micronekton at 0 to 200 m depth (ml/1000 m³). The logarithms of the measurements of each stock in each area were subjected to analysis of variance with the following factors: season (2 month period), latitude, and longitude. Seasonal coverage was most comprehensive, with 7 successive periods, in the western area (approximately 16° N to 3° S latitude, 100° to 122° W longitude). Most stocks in most parts of the western area had a simple seasonal cycle of low amplitude, with a single maximum and minimum that usually differed by a factor <2; some stocks in some parts of the area exhibited no seasonal cycle; all statistically significant cycles, except for fish-plus-cephalopod micronekton, were similar in phase. In the other two areas, located broadly to the east and south of the western area, suitable measurements were made at only 2 periods (opposite seasons) of the year. There were indications of phase differences between chlorophyll a and zooplankton in the eastern area, which should be further investigated. Most standing stocks declined gradually from east to west, and were higher in known upwelling areas and areas of shoal thermocline than elsewhere.     

Soil quality: a review of the science and experiences in the USA

An increasing human population is placing greater demand on soil resources, and as a result degradation is taking place in many regions of the world. This is critical because soils perform a number of essential processes including supporting food and fiber production, influencing air quality through interaction with the atmosphere, and serving as a medium for storage and purification of water. The soil quality concept was introduced to complement soil science research by making our understanding of soils more complete and helping guide the use and allocation of labor, energy, fiscal, and other inputs as agriculture intensifies and expands to meet increasing world demands. Soil quality thus provides a unifying concept for educating professionals, producers, and the public about the important processes that soils perform. It also provides an assessment tool for evaluating current management practices and comparing alternative management practices. Soil attributes comprising a minimum data set have been identified, and both laboratory and field methods have been developed for measuring them. A soil quality index is being developed to normalize measured soil quality indicator data and generate a numeric value that can be used to compare various management practices or to assess management-induced changes over time. Using previously published data, we evaluated the soil quality index as a tool to assess a wide range of management practices in the Northern Great Plains. The index ranked the treatments: grazed fertilized tame pasture > moderately grazed > ungrazed > heavily grazed > annual cropping with no-tillage > conventionally tilled crop-fallow which agrees with the way they were subjectively ranked in the publications. The soil quality index shows potential for use as a management assessment tool.