Density of foliage mass and area in the boreal forest cover in Finland,with applications to the estimation of monoterpene and isoprene emissions

The distribution of the density of foliage mass and area in forest canopies throughout Finland (60–70°N) were determined on the basis of the permanent sample plots used in the Finnish National Forest Inventory. These parameters were linked to the long-term monthly mean air temperatures for 1961–1990, which had been converted to hourly temperature and radiation values with the help of a weather simulator in order to calculate the spatial distribution of mean yearly emissions of monoterpene and isoprene over Finland. The mean total density of foliage mass in southern Finland (60°⩽latitude<65°N) was around 500 g m⁻², equivalent to 4–5 m² of total foliage area per m² of land area. In northern Finland (65°⩽latitude<70°N), the maximum values remained below 200–300 g m⁻², or 2–3 m² m⁻². The highest values were achieved in forests dominated by mature Norway spruces. The higher temperatures and longer growing season in southern Finland led to greater emissions than in the rest of the country. Total annual emissions of monoterpene were 1070 kg km⁻² yr⁻¹ in southern Finland and 460 kg km⁻² yr⁻¹ in the north, and those of isoprene from Norway spruce canopies 150 and 40 kg km⁻² yr⁻¹, respectively.     

Impact of large scale circulation on European summer surface ozone and consequences for modelling forecast

In this study, we investigate the benefit for European ozone simulation of using day-to-day varying chemical boundary conditions produced by a global chemical weather forecast platform instead of climatological monthly means at the frontiers of a regional model. We performed two simulations over Europe using the regional (0.5 × 0.5°) CHIMERE CTM forced by global scale simulations based on the LMDz-INCA CTM. For summer 2005, ozone differences exceeding 20 ppb can be punctually found between these two simulations in the borders of the domain. The mean of the differences ranges between 0 and 3 ppb beyond 15° of the frontiers of the regional model.Correlations with ground-based ozone measurements at more than 400 stations are slightly increased by the use of daily boundary conditions. The simulation of the temporal variability is significantly enhanced in particular for the daily means and daily maxima. As expected, the gain is higher at the borders of the regional domain.The change of percentile distribution shows that the net impact of high temporal resolution boundary conditions is not of major concern for surface ozone peaks which are mainly due to local photochemistry. The use of daily boundary conditions is however necessary to correctly simulate concentrations in the 20–35 ppb range which are of crucial interest for human and vegetation exposure effects.     

Dry deposition of ozone on building materials. Chamber measurements and modelling of the time-dependent deposition

Tests of the dry deposition of ozone to the surfaces of a concrete floor tile and an activated carbon cloth (ACC) sample were performed in a deposition chamber. The time-dependent deposition of ozone to the material surfaces was modelled with an adsorption, desorption, reaction model. This made it possible to find deposition velocities at equilibrium, at t=∞, from shorter time runs of 48 h. The total equilibrium deposition velocity on the concrete floor tile was found to decrease from 0.08(10) to 0.057(10) cm s⁻¹ in three consecutive runs on the same sample, and was found to be 0.137(8) cm s⁻¹ on an ACC. All at a linear airflow velocity of 0.092 cm s⁻¹, RH=50% and T=22°C. Varying the airflow in the deposition chamber, the surface deposition velocity was found to equal to the total deposition velocity for the concrete floor tile. A surface deposition velocity of 0.186(8) cm s⁻¹ was found for the ACC sample. The total real area and the reaction rate constant for the decomposition of ozone was found to be larger, and the adsorption rate constant, the desorption rate constant and the mass of ozone on the surface smaller, on the ACC sample than on the concrete floor tile.     

Ground-level ozone and ozone vertical profile measurements close to the foothills of the Guadarrama mountain range (Spain)

Continuous measurements of ozone vertical profiles, OVP, in the low troposphere (around 500–2400 m) using an unattended commercial ozone profiler DIAL, were conducted during June–July 2004 in Segovia, SG, a small city in the upper plateau located close to the foothills of the Guadarrama mountain range, Guadarrama, in the Central Massif. The data obtained over almost 37 complete days have enabled us to characterise the ozone vertical exchange, describe the phenomenology of the main ozone peaks, OP, recorded in the city and their relationship with ozone transport/formation from the gas precursor emissions of the greater Madrid area across Guadarrama. To achieve the last objective concurrent measurements of ground-level ozone in SG and a representative monitoring station upwind from Guadarrama, Buitrago de Lozoya, BL, have been used. 72.2% of the concurrent maximum diurnal ozone peaks exceeding the 95 percentile hourly value in SG (OPSG) and BL (OPBL) were linked to ozone transport and formation from the greater Madrid area towards Guadarrama. An estimate of the contribution of the greater Madrid area on OPSG yielded 28 μg m⁻³.The most prominent ozone vertical stratification was linked to the mixing height, MH, and a frequent nocturnal stable layer formed, NSL. Three small ozone enriched-layers were identified at mean heights of 500, 700 and 1000 m, respectively. Ozone tended to decline versus altitude. The hourly patterns of the three layers showed two peak occurrences of similar amplitude in the early morning, 7–8 h, and mid-afternoon, 14–16 h. A minimum was also observed during daytime, 10–11 h, its origin being attributed to a dilution process induced by the “chimney effect” caused by the slopes heating during this period.The comparison between OPSG, and the maximum diurnal ozone peaks in the first layer, OL1P, showed a satisfactory relationship, correlation coefficient, r, of the linear fit 0.77, and comparable mean values, 127 and 130 μg m⁻³, respectively, revealing the presence of an uniform ozone vertical distribution in the 500 m atmospheric layer above ground level during mid-afternoon.     

Surface ozone background in the United States: Canadian and Mexican pollution influences

We use a global chemical transport model (GEOS-Chem) with 1° × 1° horizontal resolution to quantify the effects of anthropogenic emissions from Canada, Mexico, and outside North America on daily maximum 8-hour average ozone concentrations in US surface air. Simulations for summer 2001 indicate mean North American and US background concentrations of 26 ± 8 ppb and 30 ± 8 ppb, as obtained by eliminating anthropogenic emissions in North America vs. in the US only. The US background never exceeds 60 ppb in the model. The Canadian and Mexican pollution enhancement averages 3 ± 4 ppb in the US in summer but can be occasionally much higher in downwind regions of the northeast and southwest, peaking at 33 ppb in upstate New York (on a day with 75 ppb total ozone) and 18 ppb in southern California (on a day with 68 ppb total ozone). The model is successful in reproducing the observed variability of ozone in these regions, including the occurrence and magnitude of high-ozone episodes influenced by transboundary pollution. We find that exceedances of the 75 ppb US air quality standard in eastern Michigan, western New York, New Jersey, and southern California are often associated with Canadian and Mexican pollution enhancements in excess of 10 ppb. Sensitivity simulations with 2020 emission projections suggest that Canadian pollution influence in the Northeast US will become comparable in magnitude to that from domestic power plants.     

Trends in near-surface ozone concentrations in Switzerland: the 1990s

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.     

Transformation of diesel engine exhaust in an environmental chamber

Overnight aging experiments with diesel engine exhaust from a diesel power aggregate, with no or 9 kW load, and from a diesel-fueled vehicle were conducted in an environmental chamber. During a 24 h aging period the volatilities of monodisperse particles at 140, 250 and 360 °C heater temperatures were analyzed with volatility tandem differential mobility analysis (VTDMA). The particulate organic to total carbon ratio and organic carbon subfractions at 120, 250, 450 and 550 °C were analyzed with thermal-optical carbon analysis for samples from fresh, 8 or 18 h aged and 24 h aged aerosol. During the experiment also the particle size distribution, ozone and nitrogen oxide concentration, and temperature, relative humidity and total solar and total ultraviolet radiation in the chamber were monitored.After injection, the geometric mean diameter and number concentration of the particles in the chamber were 66–85 nm and 0.9–4.6×10⁵ cm⁻³, respectively. The particles were seen to grow fast, at a growth rate of 18–47 nm h⁻¹ during the first hour. The fresh particles from the diesel power aggregate contained 37–45% of apparent volume semi-volatile compounds with no load and 10–24% with 9 kW load. The semi-volatile apparent volume fraction at 360 °C for 50 nm particles produced by the diesel power aggregate was 57%. After 24 h of aging, the semi-volatile apparent volume fraction at 360 °C for 100 nm particles was 99%. This suggests that the particles in the 24 h aged aerosol at this size class are no more primary particles but particles that are formed in the chamber through nucleation and subsequent growth.     

A long-term study of background ozone concentrations in the central Mediterranean—diurnal and seasonal variations on the island of Gozo

A four and a half year study of ozone concentrations in the Central Mediterranean was carried out between January 1997 and August 2001 on a background monitoring station located on the island of Gozo midway between Southern Europe and North Africa.Seasonal and diurnal variations of background ozone are documented. They show the existence of seasonal cycles with a primary maximum in spring followed by a secondary, more variable maximum in summer which indicates that photochemically produced ozone is being transported over the Mediterranean to the rural island of Gozo. Although peak ozone concentrations seldom exceeded 100 ppbv during summer, the background ozone-mixing ratios (as monthly averages) are some of the highest values which can be found at low latitude sites throughout the world. An increasing trend in the annual background ozone concentration from 48.2 ppbv in 1997 to 52.2 ppbv in 2000 is observed. During wintertime the average ozone mixing-ratio (as monthly averages) of 44 ppbv in December is approximately twice as high as on the European continent. This may imply that on Malta, due to higher average ozone concentrations between autumn and spring (the main growing season), crop damage of high economic value may occur.     

Reactions between ozone and building products: Impact on primary and secondary emissions

Reactions of ozone on common building products were studied in a dedicated emission test chamber system. Fourteen new and unused products were exposed to 100–160 ppb of ozone at 23 °C and 50% RH during 48 h experiments. Ozone deposition velocities calculated at steady state were between 0.003 cm s⁻¹ (alkyd paint on polyester film) and 0.108 cm s⁻¹ (pine wood board). All tested product showed modified emissions when exposed to ozone and secondary emissions of several aldehydes were identified. Carpets and wall coverings emitted mainly C₅–C₁₀ n-aldehydes, typical by-products of surface reactions. Linoleum, polystyrene tiles and pine wood boards also showed increased emissions of formaldehyde, benzaldehyde and hexanal associated with reduced emissions of unsaturated compounds suggesting the occurrence of gas-phase reactions. The ozone removal on the different tested products was primarily associated with surface reactions. The relative contribution of gas-phase reactions to the total ozone removal was estimated to be between 5% and 30% for pine wood boards depending on relative humidity (RH) and on the incoming ozone concentration and 2% for polystyrene tiles. On pine wood board, decreasing ozone deposition velocities were measured with increasing ozone concentrations and with RH increasing in the range 30–50%.     

Temporal trends of black carbon concentrations and regional climate forcing in the southeastern United States

The effect of black carbon (BC) on climate forcing is potentially important, but its estimates have large uncertainties due to a lack of sufficient observational data. The BC mass concentration in the southeastern US was measured at a regionally representative site, Mount Gibbes (35.78°N, 82.29°W, 2006 m MSL). The air mass origin was determined using 48-h back trajectories obtained from the hybrid single-particle Lagrangian integrated trajectory model. The highest average concentration is seen in polluted continental air masses and the lowest in marine air masses. During the winter, the overall average BC value was 74.1 ng m⁻³, whereas the overall summer mean BC value is higher by a factor of 3. The main reason for the seasonal difference may be enhanced thermal convection during summer, which increases transport of air pollutants from the planetary boundary layer of the surrounding urban area to this rural site. In the spring of 1998, abnormally high BC concentrations from the continental sector were measured. These concentrations were originating from a biomass burning plume in Mexico. This was confirmed by the observations of the Earth probe total ozone mapping spectrometer. The BC average concentrations of air masses transported from the polluted continental sector during summer are low on Sunday to Tuesday with a minimum value of 256 ng m⁻³ occurring on Monday, and high on Wednesday to Friday with a maximum value of 379 ng m⁻³ occurring on Friday. The net aerosol radiative forcing (scattering effects plus absorption effects) per unit vertical depth at 2006 m MSL is calculated to be −1.38×10⁻³ W m⁻³ for the southeastern US. The magnitude of direct radiative forcing by aerosol scattering is reduced by 15±7% due to the BC absorption.     

Evidence of impact of aerosols on surface ozone concentration in Tianjin,China

In this study, we will present evidence that aerosol particles have strong effects on the surface ozone concentration in a highly polluted city in China. The measured aerosol (PM10), UV flux, and O₃ concentrations were analyzed from 1 November (1 Nov) to 7 November (7 Nov) 2005 in Tianjin, China. During this period, the aerosol concentration had a strong day-by-day variation, ranging from 0.2 to 0.6 mg m⁻³. The ozone concentration also shows a strong variability in correlation with the aerosol concentration. During 1 Nov, 2 Nov, 6 Nov, and 7 Nov, the ozone concentration was relatively high (about 30–35 ppbv; defined as a high-ozone period), and during 3 Nov to 5 Nov, the ozone concentration was relatively low (about 5–20 ppbv; defined as a low-ozone period). The analysis of the measurement shows that the ozone concentration is strongly correlated to the measured UV flux. Because there were near cloud-free conditions between 1 Nov and 7 Nov, the variation of the UV flux mainly resulted from the variation of aerosol concentration. The result shows that higher aerosol concentrations produce a lower UV flux and lower ozone concentrations. By contrast, the lower aerosol concentration leads to a higher UV flux and higher ozone concentrations. A chemical mechanism model (NCAR MM) is applied to interpret the measurement. The model result shows that the extremely high aerosol concentration in this polluted city has a very strong impact on photochemical activities and ozone formation. The correlation between aerosol and ozone concentrations appears in a non-linear feature. The O₃ concentration is very sensitive to aerosol loading when aerosol loading is high, and this sensitivity is reduced when aerosol loading is low. For example, the ratio of Δ[O₃]/Δ[AOD] is about −16 ppbv AOD⁻¹ when AOD is less than 2, and is only −4 ppbv AOD⁻¹ when AOD is between 2 and 5. This result implies that a future decrease in aerosol loading could lead to a rapid increase in the O₃ concentration in this region.     

Isoprene and monoterpene emission from the coniferous species Abies Borisii-regis—implications for regional air chemistry in Greece

The emission of isoprene has been studied from a forest of Abies Borisii-regis, a Mediterranean fir species previously thought to emit only monoterpenes. Emission studies from two independent enclosure experiments indicated a standardised isoprene emission rate of (18.4±3.8) μg g_dry-weight⁻¹ h⁻¹, similar in magnitude to species such as eucalyptus and oak which are considered to be strong isoprene emitters. Isoprene emission depended strongly on both leaf temperature (2°C–34°C) and photosynthetically active radiation (PAR) below 250 μmol m⁻² s⁻¹, becoming saturated with respect to PAR above this value. The annual isoprene emission rate was estimated to be (132±29) kT yr⁻¹ for those trees growing within Greece, comparable to current estimates of the total isoprene budget of Greece as a whole, and contributing significantly to regional ozone and carbon monoxide budgets. Monoterpene emission exhibited exponential temperature dependence, with 1,8-cineole, α-pinene, β-pinene and limonene forming the primary emissions. A standardised total monoterpene emission rate of (2.7±1.1) μg g_dry-weight⁻¹ h⁻¹ was calculated, corresponding to an annual monoterpene emission rate of (24±12) kT yr⁻¹. Research was conducted as part of the AEROBIC’97 (AEROsol formation from BIogenic organic Carbon) series of field campaigns.     

Variability in ultraviolet total optical depth during the Southern California Ozone Study (SCOS97)

Formation of photochemical air pollution is governed in part by the solar ultraviolet actinic radiation flux, but wavelength-resolved measurements of UV radiation in polluted urban atmospheres are rarely available. As part of the 1997 Southern California Ozone Study, cosine weighted solar irradiance was measured continuously at seven UV wavelengths (300, 306, 312, 318, 326, 333 and 368 nm) at two sites during the period 1 July to 1 November 1997. The first site was at Riverside (260 m a.s.l.) in the Los Angeles metropolitan area, which frequently experiences severe air pollution episodes. The second site was at Mt Wilson (1725 m a.s.l.), approximately 70 km northwest of Riverside, and located above much of the urban haze layer. Measurements of direct (i.e., total minus diffuse) solar irradiance were used to compute total atmospheric optical depths. At 300 nm, optical depths (mean±1 S.D.) measured over the entire study period were 4.3±0.3 at Riverside and 3.7±0.2 at Mt Wilson. Optical depth decreased with increasing wavelength, falling at 368 nm to values of 0.8±0.2 at Riverside and 0.5±0.1 at Mt Wilson. At all wavelengths, both the mean and the relative standard deviation of optical depths were larger at Riverside than at Mt Wilson. At 300 nm, the difference between the smallest and largest observed optical depths corresponds to over a factor 2 increase in the direct beam irradiance for overhead sun, and over a factor 7 increase for a solar zenith angle of 60°. Principal component analysis was used to reveal underlying factors contributing to variability in optical depths. PCA showed that a single factor (component) was responsible for the major part of the variability. At Riverside, the first component was responsible for 97% of the variability and the second component for 2%. At Mt Wilson, 89% of the variability could be attributed to the first component and 10% to the second. Dependence of the component contributions on wavelength allowed identification of probable physical causes: the first component is linked to light scattering and absorption by atmospheric aerosols, and the second component is linked to light absorption by ozone. These factors are expected to contribute to temporal and spatial variability in solar actinic flux and photodissociation rates of species including ozone, nitrogen dioxide, and formaldehyde.     

Interannual variability of methanesulfonate in rainwater at Amsterdam Island (Southern Indian Ocean)

Methanesulfonate (MS⁻), an exclusive oxidation product of dimethylsulfide (DMS), has been analyzed in rainwater at Amsterdam Island (37°50′S 77°32′E) in the Southern Indian Ocean from 1991 to 1999. Rainwater MS⁻ concentrations range from 0.004 to 4.59 μmol l⁻¹ with a volume weighted mean value of 0.24 μmol l⁻¹ and present a well distinguished seasonal variation with higher values in summer, in line with the seasonal variation of its gaseous precursor (DMS), which was measured on a daily basis since 1990. The interannual variability of MS⁻ in rainwater follows closely that of DMS, indicating that MS⁻ in rainwater can be used as a surrogate to study long-term variations of atmospheric DMS, and further confirms the findings of Sciare et al. (J. Geophys. Res. 105 (2000a) 26 369), that large-scale anomalies occurred in the biogenic sulfur cycle in the Southern Indian Ocean during the studied period. Furthermore, on a monthly basis, the MS⁻ anomalies in the rainwater were found to be closely related to sea-surface temperature (SST) anomalies. The correlation between MS⁻ and SST is consistent with that observed between gaseous DMS and SST in the area and indicates an important coupling between the oceanic and the atmospheric compartments of the biogeochemical sulfur cycle.     

A review of surface ozone in the polar regions

Surface ozone records from ten polar research stations were investigated for the dependencies of ozone on radiative processes, snow-photochemisty, and synoptic and stratospheric transport. A total of 146 annual data records for the Arctic sites Barrow, Alaska; Summit, Greenland; Alert, Canada; Zeppelinfjellet, Norway; and the Antarctic stations Halley, McMurdo, Neumayer, Sanae, Syowa, and South Pole were analyzed. Mean ozone at the Northern Hemisphere (NH) stations (excluding Summit) is ∼5 ppbv higher than in Antarctica. Statistical analysis yielded best estimates for the projected year 2005 median annual ozone mixing ratios, which for the Arctic stations were 33.5 ppbv at Alert, 28.6 ppbv at Barrow, 46.3 ppbv ppb at Summit and 33.7 ppbv at Zeppelinfjellet. For the Antarctic stations the corresponding ozone mixing ratios were 21.6 ppbv at Halley, 27.0 ppbv at McMurdo, 24.9 ppbv at Neumayer, 27.2 ppbv at Sanae, 29.4 ppbv at South Pole, and 25.8 ppbv at Syowa. At both Summit (3212 m asl) and South Pole (2830 m asl), annual mean ozone is higher than at the lower elevation and coastal stations. A trend analysis revealed that all sites in recent years have experienced low to moderate increases in surface ozone ranging from 0.02 to 0.26 ppbv yr⁻¹, albeit none of these changes were found to be statistically significant trends. A seasonal trend analysis showed above-average increases in ozone during the spring and early summer periods for both Arctic (Alert, Zeppelinfjellet) and Antarctic (McMurdo, Neumayer, South Pole) sites. In contrast, at Barrow, springtime ozone has been declining. All coastal stations experience springtime episodes with rapid depletion of ozone in the boundary layer, attributable to photochemically catalyzed ozone depletion from halogen chemistry. This effect is most obvious at Barrow, followed by Alert. Springtime depletion episodes are less pronounced at Antarctic stations. At South Pole, during the Antarctic spring and summer, photochemical ozone production yields frequent episodes with enhanced surface ozone. Other Antarctic stations show similar, though less frequent spring and summertime periods with enhanced ozone. The Antarctic data provide evidence that austral spring and summertime ozone production in Antarctica is widespread, respectively, affects all stations at least through transport events. This ozone production contributes to a several ppbv enhancement in the annual mean ozone over the Antarctic plateau; however, it is not the determining process in the Antarctic seasonal ozone cycle. Although Summit and South Pole have many similarities in their environmental conditions, this ozone production does not appear to be of equal importance at Summit. Amplitudes of diurnal, summertime ozone cycles at these polar sites are weaker than at lower latitude locations. Amplitudes of seasonal ozone changes are larger in the Southern Hemisphere (by ∼5 ppbv), most likely due to less summertime photochemical ozone loss and more transport of ozone-rich air to the Arctic during the NH spring and summer months.     

Surface ozone and NOx concentrations at a high altitude Mediterranean site,Greece

Ozone was measured in six- and NO_x in five sampling periods in 1996–97, mostly during summer, at a 1070 m altitude site in northern Peloponnese. Mean values in each sampling period ranged from 43–48 ppb exceeding the European Union 24 h plant protection standard. The background ozone concentration of 43 ppb derived from the correlation of ozone with NO^′_x also exceeded the EU plant protection standard. Ozone exhibited maxima in the afternoon and minima during the night; in certain 24–48 h periods, however, the ozone concentrations remained practically constant; in these short periods air mass back trajectories indicated air masses which originated in north Africa. NO^′_x concentrations had maximum of 24 h around noon. Their mean concentrations ranged from 0.5–0.7 ppb, smaller than respective concentrations in north-central Europe.     

Kinetic aspects and identification of by-products during the ozonation of bitertanol in agricultural wastewaters

The degradation of bitertanol by ozone treatment is investigated. Solutions of bitertanol (8.4 μg mL^?1) were prepared either by dissolution of the standard or by dilution of Gaucho Blé seed loading solution and then ozonated under different conditions. Evolution of the concentrations of bitertanol and its ozonation by-products in both solutions was monitored by HPLC–UV as a function of the treatment time for a concentration of 100 g m^?3 of ozone in the inlet gas. Bitertanol degradation was found to follow a pseudo-first order reaction in both cases. However, the rate of the reaction in diluted seed loading solution was much lower (0.19 vs. 0.27 min^?1 in standard solution) and was close to the reaction rate observed in the presence of a radical scavenger, tert-butanol (0.11 min^?1). Thus, it may be suggested that additives present in the seed loading solution may play the role of radical scavengers. Study of ozone concentration in the inlet gas (from 25 to 100 g m^?3) showed that ozone degradation is also a first-order reaction with respect to ozone. Four ozonation by-products were highlighted, collected and identified by HPLC coupled with an ion trap mass spectrometer using positive electrospray ionization mode. A degradation pathway of bitertanol was finally proposed.     

Inhomogeneities and trends in the surface ozone record (1988–1996) at Jungfraujoch in the Swiss Alps

Ozone data at the Jungfraujoch Observatory (3580 m asl) in the Swiss Alps have been recorded continuously since 1986 in the framework of the Swiss National Air Pollution Monitoring Network (NABEL), operated by the Swiss Federal Laboratories for Materials Testing and Research (EMPA). The long-term ozone record (1988–1996) was examined with regard to potential inhomogeneities using Zugspitze (2960 m asl), a neighbouring alpine site in Germany, as a reference site. The Alexandersson test (for shift) and the Easterling–Peterson test (for trend and shift) were applied to a difference times series, calculated from monthly ozone means at Jungfraujoch and Zugspitze. The Alexandersson test revealed a significant shift discontinuity in November 1989 and the Easterling–Peterson test a trend discontinuity in September 1991. It is assumed that the shift discontinuity may be related to an instrument change, but there is not firm evidence due to lack of detailed information from the instrumental history in the earlier years of the ozone record at Jungfraujoch. Monthly ozone means at Davos (1640 m asl) in eastern Switzerland indicate that part of the trend discontinuity in September 1991 may be of natural origin. Adjustment of the monthly ozone means at Jungfraujoch for the observed shift discontinuity removed the inhomogeneity in November 1989, and reduced the trend discontinuity by a factor of 4.8. A trend analysis on both adjusted (homogenised) and unadjusted monthly ozone means (1988–1996) at Jungfraujoch showed no statistically significant linear trend. The boundaries encompassing the true linear trend are indicated by two linear regression calculations on both adjusted and unadjusted data. Trends in the cold season are positive albeit not significant. The only statistically significant trends are found in October, December, and February for the adjusted data.