Kennecott Utah Copper

About: Kennecott Utah Copper is a based out in . It is known for research contribution in the topics: Copper & Aqueous solution. The organization has 487 authors who have published 447 publications receiving 10059 citations.

Inverse relationship between bioconcentration factor and exposure concentration for metals: implications for hazard assessment of metals in the aquatic environment.

Abstract: The bioconcentration factor (BCF) and bioaccumulation factor (BAF) are used as the criteria for bioaccumulation in the context of identifying and classifying substances that are hazardous to the aquatic environment. The BCF/BAF criteria, while developed as surrogates for chronic toxicity and/or biomagnification of anthropogenic organic substances, are applied to all substances including metals. This work examines the theoretical and experimental basis for the use of BCF/BAF in the hazard assessment of Zn, Cd, Cu, Pb, Ni, and Ag. As well, BCF/BAFs for Hg (methyl and inorganic forms) and hexachlorobenzene (HCB) were evaluated. The BCF/BAF data for Zn, Cd, Cu, Pb, Ni, and Ag were characterized by extreme variability in mean BCF/BAF values and a clear inverse relationship between BCF/BAF and aqueous exposure. The high variability persisted when even when data were limited to an exposure range where chronic toxicity would be expected. Mean BCF/BAF values for Hg were also variable, but the inverse relationship was equivocal, in contrast with HCB, which conformed to the BCF model. This study illustrates that the BCF/BAF criteria, as currently applied, are inappropriate for the hazard identification and classification of metals. Furthermore, using BCF and BAF data leads to conclusions that are inconsistent with the toxicological data, as values are highest (indicating hazard) at low exposure concentrations and are lowest (indicating no hazard) at high exposure concentrations, where impacts are likely. Bioconcentration and bioaccumulation factors do not distinguish between essential mineral nutrient, normal background metal bioaccumulation, the adaptive capabilities of animals to vary uptake and elimination within the spectrum of exposure regimes, nor the specific ability to sequester, detoxify, and store internalized metal from metal uptake that results in adverse effect. An alternative to BCF, the accumulation factor (ACF), for metals was assessed and, while providing an improvement, it did not provide a complete solution. A bioaccumulation criterion for the hazard identification of metals is required, and work directed at linking chronic toxicity and bioaccumulation may provide some solutions.

An analysis of the cooling of intrusives by ground-water convection which includes boiling

Abstract: A finite difference model of the cooling of an igneous intrusive of limited volume is developed and used to investigate the relation between igneous intrusion, the formation of liquid and vapor dominated geothermal systems, and the formation of porphyry-type ore deposits. The model takes into account the properties of pure water and accommodates the phenomena of boiling and condensation. Permeability, level of intrusion, and pluton volume are systematically varied. Pressure, temperature, and fluid velocity are computed as functions of time.It is found that a self-supported, vapor dominated steam zone is commonly (but briefly) formed above the intrusive. Condensed water bounds the steam zone above, and if the hydrothermal solutions are saline, a zone of boiling bounds the steam zone below. For pure water condensation is far more important than boiling--the solutions circulate around the critical point of water to become gaseous without boiling. Despite large temperature variations, convection causes fluid pressures throughout the whole uniform permeability system to be close to normal cold-water hydrostatic values. Thus, even in an active converting system with moderate permeability variations, fluid pressure will tend toward normal hydrostatic values. Fluid circulation appears easily sufficient to produce a typical porphyry copper ore shell, but base metal precipitation probably must be controlled by mechanisms other than simple temperature drop.

Aquatic toxicity of eighteen phthalate esters

Abstract: The extensive database of acute and chronic aquatic toxicity data for 18 phthalate esters was reviewed and summarized for freshwater and saltwater aquatic microorganisms, algae, invertebrates, and fish. Phthalate esters have been tested with six species of microorganisms, including bacteria and protozoans. Fifteen algal species have been tested, including green and bluegreen algae in both freshwater and saltwater. Nineteen freshwater and saltwater invertebrate species inhabiting surface waters and sediments and 21 freshwater and saltwater fish inhabiting cold and warm water bodies have been tested. The results of most studies indicate that acute and chronic toxicity to microorganisms, algae, aquatic invertebrates, and fish are limited to the lower molecular weight phthalate esters (i.e., dimethyl-, diethyl-, diallyl-, dipropyl-, dibutyl-, diisobutyl-, and butylbenzylphthalate). In contrast, higher molecular weight phthalate esters are not acutely or chronically toxic to aquatic organisms. Although conflicting data on chronic effects for high molecular weight phthalate esters have been reported for daphnids, these inconsistencies are attributed to physical effects imposed on daphnids when exposed to test concentrations in excess of true water solubilities. Altogether, nearly 400 test results covering more than 60 species of microorganisms, algae, invertebrates, and fish are reported for both freshwater and saltwater aquatic species. While most investigators used several common species and standard protocols to assay conventional endpoints, many nontraditional species and toxicological endpoints were also used. This has created a toxicological database of both sufficient depth to compare many similar tests and sufficient breadth to encompass virtually all important types of aquatic habitats and classes of aquatic species.