Measurements of OVOCs and NMHCs in a Swiss highway tunnel for estimation of road transport emissions.

Eighteen oxygenated volatile organic compounds (OVOCs) and eight nonmethane hydrocarbons (NMHCs) were measured continuously during a two-week campaign in 2004 in the Gubrist highway tunnel (Switzerland). The study aimed to estimate selected OVOC and NMHC emissions of the current vehicle fleet under highway conditions. For the measured OVOCs the highest EFs were found for ethanol (9.7 mg/km), isopropanol (3.2 mg/km), and acetaldehyde (2.5 mg/km), followed by acetone, benzaldehyde, and acrolein. Formaldehyde, the most abundant OVOC measured in other studies, was not measured by the method applied. Relative emissions of the measured OVOCs were estimated to contribute approximately 6 and 4% to the total road traffic VOC emissions from Switzerland and Europe, respectively. Results are compared with those from previous studies from the same tunnel performed in 1993 and 2002, and from campaigns in other tunnels. A continuous reduction in the emission factors (EFs) was determined for all measured compounds from 1993 until 2004. The relative contributions of light-duty vehicles (LDV) and heavy-duty vehicles (HDV) to the total emissions indicated that OVOCs were mainly produced by the HDVs, whereas LDVs dominated the production of the NMHCs.

European emissions of HFC-365mfc, a chlorine-free substitute for the foam blowing agents HCFC-141b and CFC-11.

HFC-365mfc (1,1,1,3,3-pentafluorobutane) is an industrial chemical used for polyurethane foam blowing. From early 2003, HFC-365mfc has been commercially produced as a substitute for HCFC-141b, whose use in Europe has been banned since January 2004. We describe the first detection of HFC-365mfc in the atmosphere and report on a 2 year long record at the high Alpine station of Jungfraujoch (Switzerland) and the Atlantic coast station of Mace Head (Ireland). The measurements at Jungfraujoch are used to estimate the central European emissions of HFC-365mfc, HCFC-141b, and CFC-11. For HFC-365mfc, we estimate the central European emissions (Germany, France, Italy, Switzerland, The Netherlands, Belgium, and Luxembourg) in 2003 and 2004 as 400-500 tonnes year(-1). These emissions are about one-third lower on a per capita basis than what we estimate from the Mace Head measurements for the total of Europe. The estimated emissions of HCFC-141b for central Europe are higher (i.e., 7.2-3.5 ktonnes year(-1)) with a decreasing trend in the period from 2000 to 2004. Residual emissions of CFC-11 are estimated at 2.4-4.7 ktonnes year(-1) in the same time period. The Po Valley (northern Italy) appears to be a main source region for HFC-365mfc and for the former blowing agents HCFC-141b and CFC-11. In 2004, the emissions of HFC-365mfc arose from a wider region of Europe, which we attribute to an increased penetration of HFC-365mfc into the European market.

Photosensitized reduction of nitrogen dioxide on humic acid as a source of nitrous acid.

Nitrous acid is a significant photochemical precursor of the hydroxyl radical, the key oxidant in the degradation of most air pollutants in the troposphere. The sources of nitrous acid in the troposphere, however, are still poorly understood. Recent atmospheric measurements revealed a strongly enhanced formation of nitrous acid during daytime via unknown mechanisms. Here we expose humic acid films to nitrogen dioxide in an irradiated tubular gas flow reactor and find that reduction of nitrogen dioxide on light-activated humic acids is an important source of gaseous nitrous acid. Our findings indicate that soil and other surfaces containing humic acid exhibit an organic surface photochemistry that produces reductive surface species, which react selectively with nitrogen dioxide. The observed rate of nitrous acid formation could explain the recently observed high daytime concentrations of nitrous acid in the boundary layer, the photolysis of which accounts for up to 60 per cent of the integrated hydroxyl radical source strengths. We suggest that this photo-induced nitrous acid production on humic acid could have a potentially significant impact on the chemistry of the lowermost troposphere.

Low European methyl chloroform emissions inferred from long-term atmospheric measurements.

Methyl chloroform (CH3CCl3, 1,1,1,-trichloroethane) was used widely as a solvent before it was recognized to be an ozone-depleting substance and its phase-out was introduced under the Montreal Protocol. Subsequently, its atmospheric concentration has declined steadily and recent European methyl chloroform consumption and emissions were estimated to be less than 0.1 gigagrams per year. However, data from a short-term tropospheric measurement campaign (EXPORT) indicated that European methyl chloroform emissions could have been over 20 gigagrams in 2000 (ref. 6), almost doubling previously estimated global emissions. Such enhanced emissions would significantly affect results from the CH3CC13 method of deriving global abundances of hydroxyl radicals (OH) (refs 7-12)-the dominant reactive atmospheric chemical for removing trace gases related to air pollution, ozone depletion and the greenhouse effect. Here we use long-term, high-frequency data from Mace Head, Ireland and Jungfraujoch, Switzerland, to infer European methyl chloroform emissions. We find that European emission estimates declined from about 60 gigagrams per year in the mid-1990s to 0.3-1.4 and 1.9-3.4 gigagrams per year in 2000-03, based on Mace Head and Jungfraujoch data, respectively. Our European methyl chloroform emission estimates are therefore higher than calculated from consumption data, but are considerably lower than those derived from the EXPORT campaign in 2000 (ref. 6).

Emissions of the refrigerants HFC-134a, HCFC-22, and CFC-12 from road traffic: results from a tunnel study (Gubrist Tunnel, Switzerland).

This study presents the quantification of the emissions of the refrigerants CFC-12 (CCl2F2), HCFC-22 (CHClF2), and HFC-134a (CF3CH2F) from road traffic in Switzerland. These gases are used as refrigerants in car air conditioning systems (A/C-systems) and in cool aggregates for refrigeration transport. All three substances act as greenhouse gases, and CFC-12 and HCFC-22 are in addition stratospheric ozone depleting chemicals. The measurements have been performed in a highway tunnel in the area of Zürich and cover a large number of individual vehicles, which are thought to be representative of a typical European car fleet. The average emission rates per vehicle were found to be 1.0 +/- 0.2 mg h(-1) for CFC-12, 0.6 +/- 0.4 mg h(-1) for HCFC-22, and 6.2 +/- 0.8 mg h(-1) for HFC-134a. These emission factors have been measured for driving vehicles and represent an average emission rate for all types of vehicles regardless of whether they are equipped with an A/C-unit or not. For an average vehicle equipped with an A/C-unit, these results translate into losses of about 14 mg h(-1) for HFC-134a and 20-30 mg h(-1) for CFC-12, when the estimated distribution of HFC-134a-A/C-units (45%) and CFC-12-A/C-units (3-5%) in the car fleet were taken into account. The emissions of CFC-12 and HFC-134a were mainly attributed to the losses from A/C-systems of passenger cars, whereas the emissions of HCFC-22 originate from losses of refrigeration systems of transport trucks. The observed emissions are discussed in respect to their environmental impact and compared to the overall greenhouse gas emissions of road traffic.