Removal of mercury from sediment by ultrasound combined with biomass (transgenic Chlamydomonas reinhardtii)

As one of the most pervasive environmental problems, Hg pollution in sediment is particularly difficult to remediate because it cannot be decomposed. The application of ultrasound combined with biomass (transgenic Chlamydomonas reinhardtii (C. reinhardtii), a green alga) for the removal of Hg from model and contaminated sediments (Al₂O₃, α-HgS, and PACS-2 marine sediment) was investigated in this study. Ultrasound was found to enhance Hg release from Al₂O₃, α-HgS, and PACS-2 marine sediment into the aqueous phase compared to mechanical shaking. A transgenic C. reinhardtii (2AMT-2) expressing a plasmamembrane-anchored metallothionein polymer effectively recovered Hg(II) released into the aqueous phase by sonication over a broad pH range from 2.0 to 9.0. The results showed that this combined technique of ultrasound and alga biomass (2AMT-2) engineered for enhanced metal recovery was effective to remove Hg from solids and sediments, especially from Al₂O₃ and α-HgS with no natural organic matter. The results of this study are discussed with respect to the development of in situ remediation techniques for Hg-contaminated sediments.     

Comparison of municipal solid waste management systems in Canada and Ghana: A case study of the cities of London, Ontario, and Kumasi, Ghana

Integrated waste management has been accepted as a sustainable approach to solid waste management in any region. It can be applied in both developed and developing countries. The difference is the approach taken to develop the integrated waste management system. This review looks at the integrated waste management system operating in the city of London, Ontario-Canada and how lessons can be drawn from the system’s development and operation that will help implement a sustainable waste management system in the city of Kumasi, Ghana. The waste management system in London is designed such that all waste generated in the city is handled and disposed of appropriately. The responsibility of each sector handling waste is clearly defined and monitored. All major services are provided and delivered by a combination of public and private sector forces.The sustainability of the waste management in the city of London is attributed to the continuous improvement strategy framework adopted by the city based on the principles of integrated waste management. It is perceived that adopting a strategic framework based on the principles of integrated waste management with a strong political and social will, can transform the current waste management in Kumasi and other cities in developing countries in the bid for finding lasting solutions to the problems that have plagued the waste management system in these cities.     

Assessment of arsenic immobilization in synthetically prepared cemented paste backfill specimens

Mine tailings coming from the exploitation of sulphide and/or gold deposits can contain significant amounts of arsenic (As), highly soluble in conditions of weathering. Open mine voids backfilling techniques are now widely practiced by modern mining companies to manage the tailings. The most common one is called cemented paste backfill (CPB), and consists of tailings mixed with low amounts of hydraulic binders (3-5%) and a high proportion of water (typically 25%). The CPB is transported through a pipe network, to be placed in the mine openings. CPB provides storage benefits and underground support during mining operations. Moreover, this technique could also enhance contaminant stabilization, by fixing the contaminants in the binder matrix. CPB composites artificially spiked with As were synthesized in laboratory, using two types of hydraulic binders: a Portland cement, and a mix of fly ash and Portland cement. After curing duration of 66 days, the CPB samples were subjected to several leaching tests in various experimental conditions in order to better understand and then predict the As geochemical behaviour within CPBs. The assessment of the As release indicates that this element is better stabilized in Portland cement-based matrices rather than fly ash-based matrices. The As mobility differs in these two matrices, mainly because of the different As-bearing minerals formed during hydration processes. However, the total As depletion does not exceed 5% at the end of the most aggressive leaching test, indicating that As is well immobilized in the two types of CPB.     

Water Quality and Plankton in the United States Nearshore Waters of Lake Huron

Our goal in the development of a nearshore monitoring method has been to evaluate and refine an in situ mapping approach to assess the nearshore waters across the Great Lakes. The report here for Lake Huron is part of a broader effort being conducted across all five Great Lakes. We conducted an intensive survey for the United States nearshore of Lake Huron along a continuous shoreline transect (523?km) from Port Huron, Michigan, to Detour Passage. A depth contour of 20?m was towed with a conductivity-temperature depth profiler, fluorometer, transmissometer, and laser optical plankton counter. Multiple cross-contour tows (10-30?m) on the cruise dates were used to characterize the variability across a broader range of the nearshore. The cross-contour tows were comparable with the alongshore contour indicating that the 20-m contour does a good job of representing the nearshore region (10-30?m). Strong correlations were observed between water quality and spatially associated watershed land use. A repeat tow separated by several weeks investigated temporal variability in spatial patterns within a summer season. Strong correlations were observed across each variable for the temporal repeat across broad- and fine-scale spatial dimensions. The survey results for Lake Huron nearshore are briefly compared with a similar nearshore survey in Lake Superior. The biomass concentrations of lower food web components of Lake Huron were notably approximately 54-59?% of those in Lake Superior. The towed instrumentation survey supported the recent view of a change in Lake Huron to an ultra-oligotrophic state, which has been uncharacteristic in recent history.     

Carcinogenicity of Organic Extracts of Atmospheric Pollutants

The carcinogenicity of atmospheric pollutants from various urban sources in the U.S.A. has been demonstrated by the subcutaneous injection of trace quantities of organic extracts in newborn mice. The incidence of tumors, which included hepatomas, multiple pulmonary adenomas, and lymphomas, varied widely with the source of the pollutant. The results of these experiments indicate that, besides benzo[α] pyrene, other major classes of carcinogens are also present in polluted air. These experiments also indicate a high potential carcinogenic hazard of polluted air to man.     

The Correlation between Light Scattering and Mass Concentration of Tobacco Smoke

Reports by others^1,2 have pointed to tobacco smoke as a significant source of air pollution in indoor spaces. Studies by Charlson, et al., ³ Kretzschmar,⁴ and Eccleston, et al. ⁵ have yielded mass concentration-light scattering correlations for several natural aerosols. This note presents a value for the mass concentration/ light scattering ratio for tobacco smoke. This ratio provides a means of assessing air quality in indoor spaces using an instrument with a fairly short (?1 min) time constant.     

Emission and Fate Assessment of Methyl Tertiary Butyl Ether in the Boston Area Airshed Using a Simple Multimedia Box Model: Comparison with Urban Air Measurements

Abstract

Expected urban air concentrations of the gasoline additive methyl tertiary butyl ether (MTBE) were calculated using volatile emissions estimates and screening transport models, and these predictions were compared with Boston, MA, area urban air measurements. The total volatile flux of MTBE into the Boston primary metropolitan statistical area (PMSA) airshed was calculated based on estimated automobile nontailpipe emissions and the Universal Quasi-Chemical Functional-Group Activity Coefficient computed abundance of MTBE in gasoline vapor. The fate of MTBE in the Boston PMSA was assessed using both the European Union System for the Evaluation of Substances, which is a steady-state multimedia box model, and a simple airshed box model. Both models were parameterized based on the meteorological conditions observed during air sampling in the Boston area. Measured average urban air concentrations of 0.1 and 1 [H9262]g/m³ MTBE during February and September of 2000, respectively, were comparable to corresponding model predictions of 0.3 and 1 μg/m³ and could be essentially explained from estimated temperature-dependent volatile emissions rates, observed average wind speed (the airshed flushing rate), and reaction with ambient tropospheric hydroxyl radical (.OH), within model uncertainty. These findings support the proposition that one can estimate gasoline component source fluxes and use simple multimedia models to screen the potential impact of future proposed gasoline additives on urban airsheds.     

Pathogen and indicator organism reduction through secondary effluent filtration: implications for reclaimed water production

The reduction of pathogens and indicator organisms through secondary effluent filtration was investigated at six full-scale treatment facilities, ranging in capacity from 0.04 to 1 m3/s (1 to 25 mgd). Grab samples were assayed for pathogens (cultivable enteric viruses, Giardia, and Cryptosporidium) and indicator organisms (coliforms, enterococci, Clostridium perfringens, and coliphages) quarterly under peak flow conditions from each facility over the course of 1 calendar year. Log10 removals resulting from filtration averaged 0.3 to 0.8 log10 for cultivable enteric viruses, 0.4 to 1.5 log10 for protozoan parasites, 0.01 to 3.7 log10 for indicator bacteria, and 0.3 to 1.1 log10 for coliphages. In addition to filter design (cloth, monomedium shallow- or deep-bed, or dual-media filters), differences in reduction of pathogens and indicators could be attributed to the combined effects of hydraulic loading rates, chemical addition practices, backwashing and postbackwashing operating strategies, and the effectiveness of upstream biological treatment and sedimentation.