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Your search keyword '"Vollmer, M.K."' showing total 8 results
Start Over Author "Vollmer, M.K." Journal science of the total environment
8 results on '"Vollmer, M.K."'

5. The importance of mobile, mobilisable and pseudo total heavy metal fractions in soil for three-level risk assessment and risk management

Author

Gupta, S.K., Vollmer, M.K., Krebs, R., Gupta, S.K., Vollmer, M.K., and Krebs, R.

Abstract

Heavy metals which accumulate in soils may be harmful to soil and its boundary ecosystems. In this paper a unified risk assessment and risk management concept is proposed followed by a discussion on its practical implementation. To assess and manage risk, the application of a three-level evaluation system is presented, incorporating the degree of metal contamination. Levels for guide values, trigger values and clean up values are used. In order to assess exposure to heavy metals, three metal fractions like mobile, mobilisable and pseudo total metal fractions are introduced. Exceeding trigger and guide values at a site may be harmful to the risk receptors. Adequate site-specific mild remediation measures aim to diminish or eliminate risk without adversely affecting basic functions of soil. The importance of mobile and mobilisable metal concentrations is discussed in relation to the development of ecological and economical sound remediation techniques.

Published
2018

8. Molecular hydrogen (H2) emissions from gasoline and diesel vehicles

Author

Bond, S.W., Alvarez, R., Vollmer, M.K., Steinbacher, M., Weilenmann, M., and Reimann, S.

Subjects
*MOLECULAR microbiology, *EMISSIONS (Air pollution), *HYDROGEN, *GASOLINE, *DIESEL motor vehicle engines, *DIESEL motor exhaust gas, *DYNAMOMETER, *HYDROGEN economy
Abstract

Abstract: This study assesses individual-vehicle molecular hydrogen (H2) emissions in exhaust gas from current gasoline and diesel vehicles measured on a chassis dynamometer. Absolute H2 emissions were found to be highest for motorcycles and scooters (141±38.6mg km−1), approximately 5 times higher than for gasoline-powered automobiles (26.5±12.1mg km−1). All diesel-powered vehicles emitted marginal amounts of H2 (∼0.1mg km−1). For automobiles, the highest emission factors were observed for sub-cycles subject to a cold-start (mean of 53.1±17.0mg km−1). High speeds also caused elevated H2 emission factors for sub-cycles reaching at least 150km h−1 (mean of 40.4±7.1mg km−1). We show that H2/CO ratios (mol mol−1) from gasoline-powered vehicles are variable (sub-cycle means of 0.44–5.69) and are typically higher (mean for automobiles 1.02, for 2-wheelers 0.59) than previous atmospheric ratios characteristic of traffic-influenced measurements. The lowest mean individual sub-cycle ratios, which correspond to high absolute emissions of both H2 and CO, were observed during cold starts (for automobiles 0.48, for 2-wheelers 0.44) and at high vehicle speeds (for automobiles 0.73, for 2-wheelers 0.45). This finding illustrates the importance of these conditions to observed H2/CO ratios in ambient air. Overall, 2-wheelers displayed lower H2/CO ratios (0.48–0.69) than those from gasoline-powered automobiles (0.75–3.18). This observation, along with the lower H2/CO ratios observed through studies without catalytic converters, suggests that less developed (e.g. 2-wheelers) and older vehicle technologies are largely responsible for the atmospheric H2/CO ratios reported in past literature. [Copyright &y& Elsevier]

Published
2010
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