Long-term exposure to increased levels of reactive nitrogen compounds (RNCs) and particulate matter (PM) affect human health. Many cities are currently not able to fulfill European air quality standards for these critical pollutants. Meanwhile, promising new abatement technologies such as diesel particle filters (DPFs) and selective catalytic reduction (SCR) catalysts are developed to reduce PM and RNC emissions. Herein, effects of a urea-based SCR system on RNC emissions are discussed and we quantified the highly reactive intermediates isocyanic acid (HNCO) and ammonia (NH3), both potential secondary pollutants of the urea-based SCR chemistry. A diesel engine (3.0 L, 100 kW), operated in the ISO 8178/4 Cl, cycle was used as test platform. A V2O5-based SCR catalyst was either applied as such or down-stream of a high oxidation potential-DPF (hox-DPF). With active SCR, nitric oxide (NO) and nitrogen dioxide (NO2) conversion efficiencies of 0.86-0.94 and 0.86-0.99 were obtained. On the other hand, mean HNCO and NH3 emissions increased to 240-280 and 1800-1900 mg h(-1). On a molar basis, HNCO accounted for 0.8-1.4% and NH3 for 14-25% of the emitted RNCs. On roads, SCR systems will partly be inactive when exhaust temperatures drop below 220 degrees C. The system was active only during 75% of the test cycle, and urea dosing was stopped and restarted several times. Consequently. NO conversion stopped but interestingly, NO2 was still converted. Such light-off and shutdown events are frequent in urban driving, compromising the overall deNO(x) efficiency. Another important effect of the SCR technology is illustrated by the NH3/NO2 ratio, which was >1 with active SCR, indicating that exhaust is basic rather than acidic after the SCR catalyst. Under these conditions, isocyanic acid is stable. The widespread use of various converter technologies already affected RNC release. Diesel oxidation catalysts (DOCs) and hox-DPFs increased NO2 emissions, three-way catalysts (TWCs) those of NH3. The investigated SCR technology substantially lowered NO and NO2 emissions, while NH3 levels were comparable to those of TWC vehicles (300-1500 mg h(-1)). If applied in the future, the combined DPF/SCR technology will change ambient RNC levels, PM compositions and atmospheric redox- and acid/base-chemistry in traffic-affected areas. (C) 2011 Elsevier Ltd. All rights reserved.

Diesel exhaust contains several genotoxic compounds that may or may not penetrate diesel particulate filters (DPFs). Furthermore, the DPF-supported combustion of soot and adsorbed compounds may lead to the formation of additional pollutants. Herein, we compare the impact of 14 different DPFs on emissions of known genotoxic compounds. During a four year period, these DPFs were tested on a heavy duty diesel engine, operated in the ISO 8178/4 C1 cycle. Integral samples, including gas-phase and particle-bound matter were taken. All DPFs were efficient wall-flow filters with solid particulate number filtration efficiencies eta > 98%. On the basis of their CO, NO, and NO(2) emission characteristics, two different filter families were distinguished. DPFs with high oxidation potential (hox, n = 8) converted CO and NO besides hydrocarbons, whereas low oxidation potential DPFs (lox, n = 6) did not support CO and NO oxidation but still converted hydrocarbons. Lox-DPFs reduced NO(2) from 1.0 +/- 0.3 (engine-out) to 0.42 +/- 0.11 g/kWh (eta = 0.59), whereas hox-DPFs induced a NO(2) formation up to 3.3 +/- 0.7 g/kWh (eta = -2.16). Emissions of genotoxic PAHs decreased for both filter families. Conversion efficiencies varied for individual PAHs and were lower for lox- (eta = 0.31-0.87) than for hox-DPFs (eta = 0.75-0.98). Certain nitro-PAHs were formed indicating that nitration is an important step along PAH oxidation. For example, 1-nitronaphthalene emissions increased from 11 to 17 to 21 microg/L without, with lox-, and hox-DPFs respectively, whereas 2-nitronaphthalene emissions decreased from 25 to 19 to 4.7 microg/L. In contrast to our expectations, the nitration potential of lox-DPFs was higher than the one of hox-DPFs, despite the intense NO(2) formation of the latter. The filters converted most genotoxic PAHs and nitro-PAHs and most soot particles, acting as carriers for these compounds. Hox-DPF exhaust remains oxidizing and therefore is expected to support atmospheric oxidation reactions, whereas lox-DPF exhaust is reducing and consuming oxidants such as ozone, when mixed with ambient air.

Diesel particulate filters (DPFs) are a promising technology to detoxify diesel exhaust. However, the secondary combustion of diesel soot and associated compounds may also induce the formation of new pollutants. Diesel soot is rated as carcinogenic to humans and also acts as a carrier for a variety of genotoxic compounds such as certain polycyclic aromatic hydrocarbons (PAHs) or nitrated PAHs (nitro-PAHs). Furthermore, diesel exhaust contains considerable amounts of nitric oxide (NO), which can be converted to more powerful nitrating species like nitrogen dioxide (NO2), nitric acid (HNO3), and others. This mix of compounds may support nitration reactions in DPFs. Herein we report effects of two cordierite-based, monolithic, wall-flow DPFs on emissions of genotoxic PAHs and nitro-PAHs and compare these findings with those of a reporter gene bioassay sensitive to aryl hydrocarbons (AHs). Soot combustion was either catalyzed with an iron- or a copper/iron-based fuel additive (fuel-borne catalysts). A heavy duty diesel engine, operated according to the 8-stage ISO 8178/4 C1 cycle, was used as test platform. Emissions of all investigated 4- to 6-ring PAHs were reduced by about 40-90%, including those rated as carcinogenic. Emissions of 1- and 2-nitronaphthalene increased by about 20-100%. Among the 3-ring nitro-PAHs, emissions of 3-nitrophenanthrene decreased by about 30%, whereas 9-nitrophenanthrene and 9-nitroanthracene were found only after DPFs. In case of 4-ring nitro-PAHs, emissions of 3-nitrofluoranthene, 1-nitropyrene, and 4-nitropyrene decreased by about 40-60% with DPFs. Total AH-receptor (AHR) agonist concentrations of diesel exhaust were lowered by 80-90%, when using the iron- and copper-based DPFs. The tested PAHs accounted for < 1% of the total AHR-mediated response, indicating that considerable amounts of other aryl hydrocarbons must be present in filtered and unfiltered exhaust. We conclude that both DPFs detoxified diesel exhaust with respect to total aryl hydrocarbons, including the investigated carcinogenic PAHs, but we also noticed a secondary formation of selected nitro-PAHs. Nitration reactions were found to be stereoselective with a preferential substitution of hydrogen atoms at peri-positions. The stereoisomers obtained are related to combustion chemistry, but differ from those formed upon atmospheric nitration of PAHs.

Potential risks of a secondary formation of polychlorinated dibenzodioxins/furans (PCDD/Fs) were assessed for two cordierite-based, wall-through diesel particulate filters (DPFs) for which soot combustion was either catalyzed with an iron- or a copper-based fuel additive. A heavy duty diesel engine was used as test platform, applying the eight-stage ISO 8178/4 C1 cycle. DPF applications neither affected the engine performance, nor did they increase NO, NO2, CO, and CO2 emissions. The latter is a metric for fuel consumption. THC emissions decreased by about 40% when deploying DPFs. PCDD/F emissions, with a focus on tetra- to octachlorinated congeners, were compared under standard and worst case conditions (enhanced chlorine uptake). The iron-catalyzed DPF neither increased PCDD/F emissions, nor did it change the congener pattern, even when traces of chlorine became available. In case of copper, PCDD/F emissions increased by up to 3 orders of magnitude from 22 to 200 to 12 700 pg I-TEQ/L with fuels of < 2, 14, and 110 microg/g chlorine, respectively. Mainly lower chlorinated DD/Fs were formed. Based on these substantial effects on PCDD/F emissions, the copper-catalyzed DPF system was not approved for workplace applications, whereas the iron system fulfilled all the specifications of the Swiss procedures for DPF approval (VERT).

A novel sensor system, the photoelectrical aerosol sensor (PAS), was checked for its applicability in the field of investigations of diesel particulate matter in workplace air. The work was sponsored by the German federation of institutions for statutory accident insurance and prevention (Hauptverband der gewerblichen Berufsgenossenschaften). As comparing method the coulometric determination of elementary carbon in the respirable dust fraction was used. Several measurement campaigns were performed on an engine test stand as well as in different types of workplaces. The PAS were found to be well-suited for certain types of measurement tasks. Recommendations for use are given. A detailed research report is available.

Anlaesslich des Umbaues der Kreuzung General-Guisan-Platz in Biel vom Rechtsvortritt auf Kreisvortritt wurden in einer Diplomarbeit des Nachdiplomstudiums Umwelttechnik der Ingenieurschule Biel, die Fahrzyklen verschiedener Befahrungsvarianten dieser Kreuzung vor und nach dem Umbau aufgenommen.In der vorliegenden Arbeit wurden diese Messdaten mit Hilfe des Rechners ausgewertet und es wurden entsprechende mittlere Fahrzyklen festgelegt. Bei diesen Fahrzyklen wurden anschliessend die Messungen einiger Fahrzeuge auf dem Abgasrollenpruefstand der AISB durchgefuehrt, was die Abschaetzung der totalen Schadstoffemissionen und des Kraftstoffverbrauches in der Kreuzung ermoeglichte. Anhand der erarbeiteten Ergebnisse kann die verkehrsberuhigende und emissionsmindernde Wirkung des Kreisels bestaetigt werden. Verglichen mit dem Rechtsvortritt werden im Mittel der Kraftstoffverbrauch um 6 Prozent und die Schadstoffemissionen um 9 Prozent reduziert. Die Auswirkungen des Kreuzungsumbaues werden von anderen, zum Teil entgegenwirkenden Einfluessen ueberlagert. Dies sind vor allem: die Fahrweise, die Gangwahl, das Verkehrsaufkommen, die Flottenzusammensetzung und die Fussgaenger. Aus diesen Gruenden kann aus den Ergebnissen der Analyse einer Kreuzung nicht vorbehaltlos auf andere Kreuzungen geschlossen werden. Die direkte Messung des Fahrverhaltens vor und nach dem Umbau der Kreuzung mit anschliessender Abgas-Verbrauchsanalyse ist neben verschiedenen Simulationsverfahren ein gutes Mittel zur Beurteilung der Umweltvertraeglichkeit und auch der Subventionswuerdigkeit des Umbaus. (A)

This paper reviews results from field surveys of over 200 sites on ski segments in the central Swiss Alps. Terrain modification during piste construction is shown to encourage soil erosion, especially in long, concave, linear hollows, on high-angle slopes, shallow or poorly drained soils and on long pistes. Erosion inhibits regeneration of the vegetation, especially above 2200 m a.m.s.l.; below 1600 m a.m.s.l. natural and/or artificial revegetation is generally more successful. On the basis of these observations, recommendations are presented for the siting and design of ski pistes.