Anthropogenic halocarbons, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), bromocarbons (halons) and long-lived chlorinated solvents have been ...measured continuously at the high-Alpine site of Jungfraujoch (Switzerland) since January 2000. Chloro- and bromo-containing halocarbons are responsible for the stratospheric ozone depletion and will be globally banned from usage within the next years. With the exception of the stable CFC-12 (CF
2Cl
2), all major CFCs and chlorinated solvents show a negative trend in recent years in their background concentrations at Jungfraujoch. HCFCs, as their first-generation substitute, are still increasing with a few percent per year. However, the frequency and the strength of HCFCs pollution events, which are caused by regional European emissions, are already declining. This can be seen as a sign of the impending ban of these gases within the next years in Europe. On the other hand, HFCs as the second-generation substitutes, are increasing with relative rates of at least 10% per year (e.g. almost 5 ppt per year for HFC-134a). An allocation of European sources was attempted by combining measured concentrations with trajectories of air masses reaching the Jungfraujoch during pollution events. Potential source regions could be detected in Italy, France, Spain and Germany.
A time series analysis of ozone monitoring data from several locations in Switzerland from 1991 to 1999 is presented. Different methods are used to address changes in the ozone level during these ...years and to account for the influence of changing meteorological conditions. The results show a slight decrease of the peaks but a highly significant increase of the mean value of around 0.5–0.9
ppb
yr
−1. The frequency distribution has changed in the sense that very low values have become less frequent and that there is a strong increase in frequency of occurrence of half-hourly mean values between about 45 and 55
ppb. A selection procedure reveals slight tendencies towards different trends of afternoon ozone peaks in summer depending on weather and pollution situations. Ozone peaks tend to decrease on fair weather days at rural sites (but increase at urban sites) and show a small increase on cloudy and windy days. A non-linear regression model is used to estimate trends of summertime afternoon ozone peaks in the presence of meteorological variability. In the model, the long-term signal is additively split into a linear part and a part which is modulated by global radiation. The coefficients for both terms are statistically significant at many sites, with an increasing linear trend at the sites north of the Alps of around 1
ppb
yr
−1 and a decrease of ozone peaks under fair weather conditions relative to cloudy conditions. When additionally considering the effect of precursor concentrations in the regression models, both trends are weakened, which means that they can partly be explained by changes in local to regional emissions. However, at the sites north of the Alps remains a tendency towards a positive linear “base trend” of around 0.4
ppb
yr
−1. This could possibly be due to increasing background ozone concentrations.
Motor vehicle combustion emissions of molecular hydrogen (H
2), carbon monoxide (CO), and carbon dioxide (CO
2) were measured during a 6-week period from November 2004 to January 2005 in Gubrist ...Tunnel, Switzerland, to determine vehicle emission factors for these trace gases and the ratios of the concentration growths
Δ
H
2
/
Δ
CO
and
Δ
H
2
/
Δ
CO
2
in the tunnel under real-world highway driving conditions. For H
2, molar mixing ratios at the tunnel exit were found to be 7–10
ppm (parts-per-million,
10
-
6
) during rush hours. Mean emission factors of
E
H
2
=
49.7
(
±
16.5
)
mg
km
-
1
,
E
CO
=
1.46
(
±
0.54
)
g
km
-
1
, and
E
CO
2
=
266
(
±
69
)
g
km
-
1
were calculated.
E
H
2
was largest during weekday rush-hour traffic, a consequence of the more frequent accelerations in congested traffic when fuel combustion is not optimal.
E
H
2
was smaller for heavy-duty vehicles (HDV) compared to light-duty vehicles (LDV), a finding which was attributed to the diesel vs. gasoline engine technology. The mean
Δ
H
2
/
Δ
CO
molecular ratio was
0.48
±
0.12
. This ratio increased to
∼
0.6
during rush hours, suggesting that H
2 yield is favored relative to CO under fuel-rich conditions, presumably a consequence of an increasing contribution of the water–gas-shift reaction. The mean
Δ
H
2
/
Δ
CO
2
molecular ratio was
4.4
×
10
-
3
but reduced to
2.5
×
10
-
3
when the relative HDV abundance was at maximum. Using three different approaches, road traffic H
2 emissions were estimated for 2004 for Switzerland at 5.0–6.6
Gg and globally at 4.2–8.1
Tg. Despite projections of increasing traffic, Swiss H
2 emissions are not expected to change significantly in the near future, and global emissions are likely to decrease due to improved exhaust gas clean-up technologies.
Automatic on-line monitors for particulate matter with an aerodynamic diameter up to 10
μm (PM10) (TEOM, beta attenuation) are widely used in air pollution monitoring networks. However, the data ...cannot always be considered equivalent to the manual gravimetric reference method, which is required in Europe as well as in US for compliance measurements. In this paper, a new method is described to obtain reference equivalent PM10 data series from automatic beta-attenuation monitors based on a limited number of gravimetric PM10 data. The correction procedure was tested with long-term data series from 5 Swiss sites with different exposure characters (urban street canyon, motorway, suburban, rural) and was shown to produce PM10 data, which fulfilled all requirements of EN12341, except at a background site with very low PM10 concentrations. At all sites, including the background site, the correction produced excellent agreement of the corrected monitor data for annual means and a satisfactory match of the number of days exceeding the short time limit value of 50
μg
m
−3 compared to reference equivalent PM10 data.
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.
The influence of meteorological transport processes on trace gas concentrations at the high‐Alpine site Jungfraujoch (3580 m above sea level) is investigated. These processes are subdivided into two ...categories: thermally driven transport, which takes place on a local scale, and transport on a regional (föhn) or synoptic scale (fronts). During thermally induced processes, which are mainly observed in summer and spring, the carbon monoxide (CO) mixing ratios show a diurnal variation with a maximum concentration at ≈ 1800 local time. Processes on the regional and synoptic scale which occur during the whole season induce large variability in the trace gas observations. The CO concentrations can be twice as large as the monthly median value during severe föhn episodes. The NOx values exhibit an even larger increase. Depending on the season, the O3 observations during these periods show an increase in summer and a pronounced decrease in winter. In addition, it is found that the calculated trajectories using the output of a mesoscale weather prediction model are a useful tool to detect and explain episodes with high NOx or CO concentrations. Altogether, the present results imply that meteorological transport processes on different spatial and timescales are important for the interpretation of the trace gas observations at the high‐Alpine site Jungfraujoch during the whole year.
Particle emissions caused by railway traffic have hardly been investigated in the past, due to their obviously minor influence on air quality compared to automotive traffic. In this study, emissions ...related to particle abrasion from wheels and tracks were investigated next to a busy railway line in Zuerich (Switzerland), where trains run nearly exclusively with electrical locomotives. Hourly size-segregated aerosol samples (0.1-1, 1-2.5 and 2.5-10 mu m) were collected with a rotating drum impactor (RDI) and subsequently analyzed by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). In this way, hourly elemental mass concentrations were obtained for chromium, manganese, iron and copper, which are the elements most relevant for railway abrasion. Additionally, daily aerosol filters were collected at the same site as well as at a background site for subsequent analysis by gravimetry and wavelength dispersive XRF (WD-XRF). Railway related ambient air concentrations of iron and manganese were calculated for the coarse (2.5-10 mu m) and fine (<2.5 mu m) particle fraction by means of a Mn/Fe ratio investigation. The comparison to train type and frequency data showed that 75% and 60% of the iron and manganese mass concentrations related to cargo and passenger trains, respectively, were found in the coarse mode. The railway related iron mass concentration normalized by the train frequency ranges between 10 and 100 ng m super(-3) h iron in 10 m distance to the tracks, depending on train type. It is estimated that the personal exposure next to a busy railway line above ground is more than a magnitude lower than inside a subway station.
In the Gubrist tunnel, located on the highway bypassing the town area of Zurich, Switzerland, air samples were collected continuously between September 17 and October 20, 2002, and concentrations of ...fluorinated refrigerants from automobile air-conditioning systems and transport refrigeration were quantified. The gases exhibited variable mixing ratios with higher concentrations during the day than at night and early morning. A reasonably good correlation between benzene concentrations and traffic density was found, whereas the correlations for hydrofluorocarbon (HFC)-134a, hydrochlorofluorocarbon (HCFC)-22, and CFC-12 were weaker. Highest emission factors were observed for HFC-134a, while the average emission factor for CFC-12 was lower by approximately a factor of six. For HFC-134a and HCFC-22, there was a substantial emission factor for heavy-duty vehicles. When the emission rates were applied to the Swiss car fleet, a total annual emission of 33 tpy of CFC-12 was estimated.
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