Ontario Ministry of Transportation

About: Ontario Ministry of Transportation is a government organization based out in Toronto, Ontario, Canada. It is known for research contribution in the topics: Poison control & Asphalt. The organization has 4652 authors who have published 3882 publications receiving 59011 citations.

Stress Evaluation for Rocks and Structural Concrete Members through Ultrasonic Wave Analysis: Review

Abstract: The preferable way to monitor structural behavior is to measure the actual stress in the structural members. Unfortunately, stress relieving by cutting holes or slots has been the only meth...

Heavy metal transport in large river systems: heavy metal emissions and loads in the Rhine and Elbe river basins

Abstract: Pollutant transport and management in the Rhine and Elbe basins is still of international concern, since certain target levels set by the international committees for protection of both rivers have not been reached. The analysis of the chain of emissions of point and diffuse sources to river loads will provide policy makers with a tool for effective management of river basins. The analysis of large river basins such as the Elbe and Rhine requires information on the spatial and temporal characteristics of both emissions and physical information of the entire river basin. In this paper, an analysis has been made of heavy metal emissions from various point and diffuse sources in the Rhine and Elbe drainage areas. Different point and diffuse pathways are considered in the model, such as inputs from industry, wastewater treatment plants, urban areas, erosion, groundwater, atmospheric deposition, tile drainage, and runoff. In most cases the measured heavy metal loads at monitoring stations are lower than the sum of the heavy metal emissions. This behaviour in large river systems can largely be explained by retention processes (e.g. sedimentation) and is dependent on the specific runoff of a catchment. Independent of the method used to estimate emissions, the source apportionment analysis of observed loads was used to determine the share of point and diffuse sources in the heavy metal load at a monitoring station by establishing a discharge dependency. The results from both the emission analysis and the source apportionment analysis of observed loads were compared and gave similar results. Between 51% (for Hg) and 74% (for Pb) of the total transport in the Elbe basin is supplied by inputs from diffuse sources. In the Rhine basin diffuse source inputs dominate the total transport and deliver more than 70% of the total transport. The diffuse hydrological pathways with the highest share are erosion and urban areas. Copyright © 2002 John Wiley & Sons, Ltd.

Genotoxicity testing using the Mutatox™ assay: Evaluation of benzo[a]pyrene as a positive control

Abstract: In a study on bioassay-directed chemical factionation of sediment extracts, problems were encountered using benzo(a)pyrene (BaP) as a positive control in the Mutatox™ bacterial genotoxicity assay. Genotoxic responses of tests with this compound, prescribed by the Mutatox supplier, could only be measured using supersaturated concentrations that exceeded its aqueous solubility more than 250 times. Additional to three obvious requirements for a positive control of this test system (it should demonstrate that the bacteria are alive and grow after reconstitution, that the bacteria are mutated, and that the bacteria emit light), a positive control should meet two criteria: the metabolic routes of genotoxic response induction for positive control and test compound(s) should be identical, and test concentrations (of both positive control and test compound) should be at environmentally relevant concentrations, i.e., below the aqueous solubilities. As BaP does not meet this last criterion, it does not fully qualify as a positive control in testing genotoxicity of solutes with the Mutatox assay. Testing of other unsubstituted polycyclic aromatic hydrocarbon (PAHS) did not yield another PAH as choice for positive control. Furthermore, the results of our study imply that calculating the bioavailability of BaP from the aqueous solubility alone is not sufficient, as this tends to underestimate the amount of BaP available to either the S9 enzyme system or the bacteria, whereas the interference between toxic and genotoxic effects hampered the interpretation of test results, as variations in toxicity may be interpreted as variations in genotoxicity. Quantitative S9-mediated genotoxicity assessments using the Mutatox test appeared difficult to make, as the two parameters that are proposed by the supplier (CMR, concentration of maximum genotoxic response, and LOEC, lowest observable [genotoxic] effect concentration) showed significant dependency on the sensitivity of the S9 system toward the test compound (CMR) or the initial test compound concentration (LOEC)