Environmental science & technology
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Environ. Sci. Technol. · Apr 2007
Near-infrared spectroscopy (NIRS) of epilithic material in streams has a potential for monitoring impact from mining.
There is an increasing demand for cost-effective methods for environmental monitoring, and here we assess the potential of near-infrared spectroscopy (NIRS) on epilithic material from streams (material covering submerged stones) as a new method for monitoring the impact of pollution from mining and mining-related industries. NIRS, a routine technique in industry, registers the chemical properties of organic material on a molecular level and can detect minute alterations in the composition of epilithic material. Epilithic samples from 65 stream sites (42 uncontaminated and 23 contaminated) in northern Sweden were analyzed. ⋯ Of the streams designated a priori as contaminated, 74% were identified as contaminated by NIRS, 65% were identified by chemical analysis, and 26% were identified by diatom analysis. Unlike chemical analyses of water samples, NIRS data reflect biological impacts in the streams, and the epilithic material integrates impact over time. Given that, and the simplicity of NIRS-analyses, further studies to assess the use of NIRS of epilithic material as an inexpensive environmental monitoring method are justified.
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Environ. Sci. Technol. · Dec 2005
Comparative StudyImpact of environmental factors on efficacy of upper-room air ultraviolet germicidal irradiation for inactivating airborne mycobacteria.
This study evaluated the efficacy of an upper-room air ultraviolet germicidal irradiation (UVGI) system for inactivating airborne bacteria, which irradiates the upper part of a room while minimizing radiation exposure to persons in the lower part of the room. A full-scale test room (87 m3), fitted with a UVGI system consisting of 9 louvered wall and ceiling fixtures (504 W all lamps operating) was operated at 24 and 34 degrees C, between 25 and 90% relative humidity, and at three ventilation rates. ⋯ Performance of the UVGI system degraded significantly when the relative humidity was increased from 50% to 75-90% RH, the horizontal UV fluence rate distribution was skewed to one side compared to being evenly dispersed, and the room air temperature was stratified from hot at the ceiling to cold at the floor. The inactivation rate increased linearly with effective UV fluence rate up to 5 microW cm(-2); an increase in the fluence rate above this level did not yield a proportional increase in inactivation rate.
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Environ. Sci. Technol. · Nov 2005
Naphthenic acids in athabasca oil sands tailings waters are less biodegradable than commercial naphthenic acids.
Naphthenic acids (NAs) are natural constituents in many petroleum sources, including bitumen in the oil sands of Northern Alberta, Canada. Bitumen extraction processes produce tailings waters that cannot be discharged to the environment because NAs are acutely toxic to aquatic species. However, aerobic biodegradation reduces the toxic character of NAs. ⋯ The commercial NAs were biodegraded within 14 days, but only about 25% of the NAs native to the tailings waters were removed after 40-49 days. These results show that low molecular mass NAs (C < or =17) are more readily biodegraded than high molecular mass NAs (C > or =18). Moreover, the results indicate that biodegradation studies using commercial NAs alone will not accurately reflect the potential biodegradability of NAs in the oil sands tailings waters.
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Environ. Sci. Technol. · Sep 2005
Reducing CO2 emissions and energy consumption of heat-integrated distillation systems.
Distillation systems are energy and power intensive processes and contribute significantly to the greenhouse gases emissions (e.g. carbon dioxide). Reducing CO2 emissions is an absolute necessity and expensive challenge to the chemical process industries in orderto meetthe environmental targets as agreed in the Kyoto Protocol. A simple model for the calculation of CO2 emissions from heat-integrated distillation systems is introduced, considering typical process industry utility devices such as boilers, furnaces, and turbines. ⋯ Energy savings can reach up to 100% with respect to reboiler heat requirements. Emissions of these configurations are cut down by up to 83%, compared to conventional units, and by 36%, with respect to heat pump alternatives. Importantly, cost savings and more profit are gained in parallel to emissions minimization.