Speed-dependent emission of air pollutants from gasoline-powered passenger cars

Zero-valent iron-facilitated reduction of nitrate: Chemical kinetics and reaction pathways

The kinetics and mechanisms of the reduction of NO₃^- in solution to NH₃ by 1.5μm diameter zero-valent iron (ZVI_1.5) particles has been examined. The effects of initial pH, ZVI_1.5 particle concentration and initial NO₃^- concentration were also investigated. Results indicate that denitrification by ZVI_1.5 is primarily a pH-dependent, surface-mediated process. At an initial ZVI_1.5 concentrations of 0.832g/L, and an optimal initial pH of 1.62, the NO₃^- concentration was reduced by 95% from 12.50mg/L-N to 0.65mg/L-N, in 120min. Several kinetic models were used to describe the denitrification process based on the ZVI_1.5:NO₃^- ratio. Based on mineralogical and surface analysis of the reacted ZVI_1.5, and detailed solution chemical analysis, the denitrification reaction pathway involves oxidation and partial dissolution of the ZVI_1.5 with the generation of Fe²⁺ and NO₂^- intermediates prior to formation of Fe³⁺ oxyhydroxide (goethite) and NH₃.

Characterization of particulate matter from diesel passenger cars tested on chassis dynamometers

Emission characterization of particle number as well as particle mass from three diesel passenger cars equipped with diesel particulate filter (DPF), diesel oxidation catalyst (DOC) and exhaust gas recirculation (EGR) under the vehicle driving cycles and regulatory cycle. Total particle number emissions (PNEs) decreased gradually during speed-up of vehicle from 17.3 to 97.3km/hr. As the average vehicle speed increases, the size-segregated peak of particle number concentration shifts to smaller size ranges of particles. The correlation analysis with various particulate components such as particle number concentration (PNC), ultrafine particle number concentration (UFPNC) and particulate matter (PM) mass was conducted to compare gaseous compounds (CO, CO₂, HC and NO_x). The UFPNC and PM were not only emitted highly in Seoul during severe traffic jam conditions, but also have good correlation with hydrocarbons and NO_x influencing high potential on secondary aerosol generation. The effect of the dilution temperature on total PNC under the New European Driving Cycle (NEDC), was slightly higher than the dilution ratio. In addition, the nuclei mode (D_P: ≤13nm) was confirmed to be more sensitive to the dilution temperature rather than other particle size ranges. Comparison with particle composition between vehicle speed cycles and regulatory cycle showed that sulfate was slightly increased at regulatory cycle, while other components were relatively similar. During cold start test, semivolatile nucleation particles were increased due to effect of cold environment. Research on particle formation dependent on dilution conditions of diesel passenger cars under the NEDC is important to verify impact on vehicular traffic and secondary aerosol formation in Seoul.

On-board measurement of emissions from liquefied petroleum gas, gasoline and diesel powered passenger cars in Algeria

On-board measurements of unit emissions of CO, HC, NOx and CO₂ were conducted on 17 private cars powered by different types of fuels including gasoline, dual gasoline-liquefied petroleum gas (LPG), gasoline, and diesel. The tests performed revealed the effect of LPG injection technology on unit emissions and made it possible to compare the measured emissions to the European Artemis emission model. A sequential multipoint injection LPG kit with no catalyst installed was found to be the most efficient pollutant reduction device for all of the pollutants, with the exception of the NOx. Specific test results for a sub-group of LPG vehicles revealed that LPG-fueled engines with no catalyst cannot compete with catalyzed gasoline and diesel engines. Vehicle age does not appear to be a determining parameter with regard to vehicle pollutant emissions. A fuel switch to LPG offers many advantages as far as pollutant emissions are concerned, due to LPG's intrinsic characteristics. However, these advantages are being rapidly offset by the strong development of both gasoline and diesel engine technologies and catalyst converters. The LPG's performance on a chassis dynamometer under real driving conditions was better than expected. The enforcement of pollutant emission standards in developing countries is an important step towards introducing clean technology and reducing vehicle emissions.