Life cycle assessment of mine tailings management in Canada

The effective management of mine tailings involves the control of several environmental impacts and legal requirements. Six tailings site management and closure scenarios were developed for a copper zinc underground mine located in Quebec (Canada) and compared using life cycle assessment (LCA). Two options are considered for the mine operation: tailings can be sent to the tailings disposal area where they are submerged or they can be partly used for backfilling. For each of these two operation options, three alternatives are presented for mine closure: (a) submerged tailings, (b) partial desulphurization with a cover of desulphurized material and (c) a cover with capillary barrier effects (CCBE) made of natural soils followed by revegetation. The goals of the study were to draw the inventory of these management scenarios from the development to the post-closure phase, to assess and compare their environmental impacts and to determine the importance of the land-use impact category. The potential impacts for each scenario were evaluated using the IMPACT 2002+ LCIA method. The results of the performed LCA indicate that for mine development and operation, scenarios where tailings are partly used as backfill for underground stopes appear to lead to larger impacts in 11 of the 14 midpoint categories since the backfill plant operation consumes a greater amount of material and energy. For a site closure period of 2 years, the CCBE option creates the greatest impacts, since it requires much more effort than the other techniques. The results for the post-closure phase have been analysed separately since they have a larger uncertainty. They appear to modify the comparative assessment results. The various results presented in the paper show the importance of taking land-use impacts into account.     

Evaluation of recycling waste materials and by-products in highway construction

SUMMARY

The generation, handling, and safe disposal of waste materials has become a major concern in North America. Approval of facilities for waste processing and proper disposal is becoming more difficult to obtain. Furthermore, there is a growing public awareness of the importance of conserving and preserving our valuable natural resources. This expanding awareness has given rise to the trend towards recycling or reuse of awide variety of solid wastes. Experiences with using waste materials in highway construction can vary considerably, depending on material characteristics, construction processes, and climatic differences. A number of waste materials may be suitable for use in highway construction, but others may not. The objective of this paper is introduced in two tasks. The first is to include a survey of the waste materials and by-products that have been used successfully, or may be used, as materials for highway construction or maintenance work. This also includes determination of the state of practice concerning economic and technical factors for these wastes. The second is to rank these materials based on three criteria: number of uses by State agencies, economic uses and performance aspects.     

Emissions from Carbureted and Timed Port Fuel Injected Engines

A comparison was made between the exhaust emission characteristics of a popular make car when equipped with the stock carburetor and when equipped with a timed-port fuel injection system. A brief optimization study was made to adjust the spark timing and fuel flow characteristics to minimize emissions. Performance and economy were compared between the fuel injected and carbureted versions. Emission measurements of CO, CO₂, and hydrocarbon were made in road tests by proportional sampling and through the California Cycle by continuous nondispersive infra red instrumentation.     

The non-target organism Caenorhabditis elegans withstands the impact of sulfamethoxazole

The widespread usage of antibiotics in agriculture leads to releases into the environment, but there is insufficient knowledge of the side-effects on non-target organisms. Therefore, we investigated the effects of the sulfonamide-antibiotic sulfamethoxazole (SMX) on Caenorhabditis elegans at phenotypic, biochemical and molecular biological levels. Multiple endpoints, including life history traits, thermal stress resistance and lipid peroxidation, as well as gene expression profiles, were determined after exposure of the nematodes to SMX. In contrast to expectations, SMX prolonged the lifespan and increased both the body size and pharynx pumping rate. On the other hand, SMX delayed reproductive timing and caused lipid peroxidation. The total number of offspring and thermal stress resistance were unaffected. The up-regulation of hsp-16.1 indicated stress in general and the increased lipid peroxidation oxidative stress in particular. This oxidative stress indicated that mitohormesis was the likely cause of the longevity and that enhanced pumping frequency was probably the reason for the increased growth. The sole adverse effect was delayed initial reproduction. This delay, however, can be crucial for r-strategists, such as the bacterivorous model animal used, in sustaining their populations in the environment in the presence of predators. Bacterivorous animals, in turn, are essential to maintaining nutrient recycling via the microbial loop.     

Calculating Air Quality and Its Control

Air quality is shown as a function of averaging times of five minutes to one year for carbon monoxide, hydrocarbons, nitric oxide, nitrogen dioxide, nitrogen oxides, oxidant, and sulfur dioxide in Chicago, Cincinnati, Los Angeles, New Orleans, Philadelphia, San Francisco, and Washington, D. C. Concentrations are approximately lognormally distributed for all pollutants in all cities for all averaging times. Maximum concentration is inversely proportional to averaging time to an exponent. The exponent is a function of the standard geometric deviation. General air quality and control parameters are derived and shown for one example, nitrogen oxides in Washington, D. C. These values are compared to one air quality standard.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.     

ESP Performance with Atmospheric Fluidized-Bed Combustion

Electric utilities considering atmospheric fluidized-bed combustion (AFBC) as an economic way to reduce SO₂ and NO_x emissions at coal-fired power plants must evaluate the impact AFBC will have on existing or planned plant systems and components. Because fly ash in AFBC units can have characteristics significantly different from that generated in pulverized-coal-fired boilers, a particular concern in this regard is the performance of the plant's particulate control equipment.     

An Air Quality Data Analysis System for Interrelating Effects,Standards, and Needed Source Reductions: Part 6. Calculating Concentration Reductions Needed to Achieve the New National Ozone Standard

The new ozone National Ambient Air Quality Standard specifies that the expected number of days per calendar year that the 1 hour average ozone concentration can exceed 0.12 ppm must be equal to or less than 1. This paper describes a method to calculate design frequency, design concentration, and the percentage concentration reduction necessary to achieve this standard. The design frequency is once per year (1/365) if daily maximum hour ozone concentrations are available at a particular site for an equal number of days in summer (April through September) and winter (October through March). An equation is used to adjust design frequency as a function of the number of summer and winter samples available. The design concentration (the ambient concentration measured at the design frequency) needs to be reduced to 0.12 ppm. Graphical and digital methods for determining the design concentration are presented. Percentage concentration reductions needed to achieve the standard are calculated for each site which has ozone concentration data available in the National Aerometric Data Bank for at least half of the days in one summer of years 1975 through 1977. The degree of reduction calculated for the site with the highest concentrations in each county is indicated by shading on a map of the United States.     

Herbicide impact on Hormosira banksii gametes measured by fluorescence and germination bioassays

The innovative bioassay described here involves chlorophyll a fluorescence measurements of gametes from the macroalgae, Hormosira banksii, where gametes (eggs) were exposed to Diuron, Irgarol and Bromacil. Response was assessed as percent inhibition from control of effective quantum yield (DeltaF/Fm') of photosystem II, herein referred to as % PSII Inhibition. This was measured with the dual-channelled pulse amplitude modulated (PAM) fluorometer, ToxY-PAM. The fluorescence bioassay was run simultaneously with an established H. banksii germination bioassay to compare sensitivity, precision, and time-to-result. The fluorescence bioassay gave highly sensitive results evidenced by EC(50)s (% PSII Inhibition) for Diuron, Irgarol and Bromacil being three, four and three orders of magnitude (respectively) lower than EC50s generated from the germination bioassays. Precision of the fluorescence bioassay was demonstrated with low coefficient of variations (<30%) for all three toxicants. With regard to time, the fluorescence bioassay gave results within 6h, as opposed to more than 50h for the germination bioassay.