Monte Cimone Research Articles

Influence of deep stratosphere-to-troposphere transport on atmospheric carbon dioxide and methane at the Mt. Cimone WMO/GAW global station (2165 m a.s.l., Italy): A multi-year (2015–2022) investigation

This work was dedicated to provide a first systematic assessment of the role played by deep stratosphere-to-troposphere transport events (denoted as “stratospheric intrusions–SIs”) in influencing the CO2 and CH4 variability at a high-elevation site in Italy (Monte Cimone, CMN, 2165 m a.s.l.). To select SI events, we used a methodology based on the analysis of the temporal variability of in-situ observed stratospheric tracers (O3, CO and RH), modeled PV along 5-day back-trajectories starting at the measurement site, and satellite measurements of total column ozone (TCO). The analysis of two case studies revealed clear fingerprints of the stratospheric air masses on the atmospheric composition at CMN: CO2 and CH4 decreases were observed in winter, while CO2CH4 increased (decreased) in summer. For 2015–2022, 9.8% of the hourly data were selected as influenced by SI events. The systematic analysis of the SI effect on CO2 confirmed differences between vegetative and non-vegetative seasons: during May–September, air masses from the stratosphere were richer in CO2 (+1.2 ± 0.1 ppm, average ±σ/N). On the other hand, during winter, air masses from higher altitudes were characterised by a lower amount of CO2 (−1.5 ± 0.1 ppm). Furthermore, SI events were usually characterised by an overall decrease in CH4 compared to the remaining data throughout the solar year (with average values ranging from −7.6 to −16.1 ppb as a function of the seasonal period). However, based on the analysis of seasonal anomalies of residuals, it looks that SI events did not play a major role in determining the interannual variability of CO2 and CH4 at CMN.

Western European emission estimates of CFC-11, CFC-12 and CCl4 derived from atmospheric measurements from 2008 to 2021

Abstract. Production and consumption of CFC-11 (trichlorofluoromethane, CCl3F), CFC-12 (dichlorodifluoromethane, CCl2F2) and CCl4 (carbon tetrachloride) are controlled under the regulations of the Montreal Protocol and have been phased out globally since 2010. Only CCl4 is still widely produced as a chemical feedstock. After 2010, emissions of CFC-11 and CFC-12 should therefore mostly originate from existing banks (e.g. from foams, mobile air conditioning units and refrigerators); however evidence has emerged of an increase in global emissions of CFC-11 in the last decade, some of which has not been fully accounted for. The motivation for this work was to assess the emissions of CFC-11, CFC-12 and CCl4 from western Europe. All countries in this region have been subject to the controls of the Montreal Protocol since the late 1980s and, as non-Article 5 Parties, have been prohibited from producing CFCs and CCl4 for dispersive use since 1996. Four different inverse modelling systems are used to estimate emissions of these gases from 2008 to 2021 using data from four atmospheric measurement stations: Mace Head (Ireland), Jungfraujoch (Switzerland), Monte Cimone (Italy) and Tacolneston (UK). The average of the four model studies found that western European emissions of CFC-11, CFC-12 and CCl4 between 2008 and 2021 were declining at 3.5 % yr−1 (2.7 % yr−1–4.8 % yr−1), 7.7 % yr−1 (6.3 % yr−1–8.0 % yr−1) and 4.4 % yr−1 (2.6 % yr−1–6.4 % yr−1), respectively. Even though the emissions were declining throughout the period, the area including northern France, Belgium, the Netherlands and Luxembourg showed consistently elevated emissions of CFC-11 compared with the surrounding regions. Emissions of CFC-12 were slightly elevated in the same region. CCl4 emissions were the highest in the south of France. France had the highest emissions of all three gases over the period 2008–2021. Emissions from western Europe (2008–2021) were on average 2.4 ± 0.4 Gg (CFC-11), 1.3 ± 0.3 Gg (CFC-12) and 0.9 ± 0.2 Gg (CCl4). Our estimated decline in emissions of CFC-11 is consistent with a western European bank release rate of 3.4 % (2.6 %–4.5 %). This study concludes that emissions of CFC-11, CFC-12 and CCl4 have all declined from 2008 to 2021 in western Europe. Therefore, no evidence is found that western European emissions contributed to the unexplained part of the global increase in atmospheric concentrations of CFC-11 observed in the last decade.

Plant landscape reconstruction above the current timberline at the Monte Cimone and Corno alle Scale mountain areas (Northern Apennines, Italy) during the Late Holocene: The evidence from soil charcoal

This paper presents the first pedoanthracological study carried out on two mountains of the Northern Apennines, Monte Cimone, and Corno alle Scale, where the results provided new palaeoenvironmental data. The pedoantracological sampling followed an elevation gradient from the current timberline to the highest possible elevation, also adapted to the geomorphological characteristics of the study areas. Based on radiocarbon datings (16 at Monte Cimone and 9 at Corno alle Scale), the soil charcoal fragments provided data about the vegetation dynamics and plant landscape reconstruction, primarily indicating the Late Holocene. The landscape over the last 3000 years appears very similar to the current one with very small altitudinal variations of the timberline and treeline. The present study shows a lack of radiocarbon dates for the Middle Holocene and two hypotheses are discussed to explain this finding. Data suggest that past fires were locally linked to periods of climate optimum and possibly with the management of natural resources (especially animal grazing) by human societies. Some questions concerning the absence of Abies alba, today only present as plantation and normally associated with Fagus sylvatica at these latitudes, are discussed.

Abundance and sources of atmospheric halocarbons in the Eastern Mediterranean

Abstract. A wide range of anthropogenic halocarbons is released to the atmosphere, contributing to stratospheric ozone depletion and global warming. Using measurements of atmospheric abundances for the estimation of halocarbon emissions on the global and regional scale has become an important top-down tool for emission validation in the recent past, but many populated and developing areas of the world are only poorly covered by the existing atmospheric halocarbon measurement network. Here we present 6 months of continuous halocarbon observations from Finokalia on the island of Crete in the Eastern Mediterranean. The gases measured are the hydrofluorocarbons (HFCs), HFC-134a (CH2FCF3), HFC-125 (CHF2CF3), HFC-152a (CH3CHF2) and HFC-143a (CH3CF3) and the hydrochlorofluorocarbons (HCFCs), HCFC-22 (CHClF2) and HCFC-142b (CH3CClF2). The Eastern Mediterranean is home to 250 million inhabitants, consisting of a number of developed and developing countries, for which different emission regulations exist under the Kyoto and Montreal protocols. Regional emissions of halocarbons were estimated with Lagrangian atmospheric transport simulations and a Bayesian inverse modeling system, using measurements at Finokalia in conjunction with those from Advanced Global Atmospheric Gases Experiment (AGAGE) sites at Mace Head (Ireland), Jungfraujoch (Switzerland) and Monte Cimone (Italy). Measured peak mole fractions at Finokalia showed generally smaller amplitudes for HFCs than at the European AGAGE sites except for periodic peaks of HFC-152a, indicating strong upwind sources. Higher peak mole fractions were observed for HCFCs, suggesting continued emissions from nearby developing regions such as Egypt and the Middle East. For 2013, the Eastern Mediterranean inverse emission estimates for the four analyzed HFCs and the two HCFCs were 13.9 (11.3–19.3) and 9.5 (6.8–15.1) Tg CO2eq yr−1, respectively. These emissions contributed 16.8 % (13.6–23.3 %) and 53.2 % (38.1–84.2 %) to the total inversion domain, which covers the Eastern Mediterranean as well as central and western Europe. Greek bottom-up HFC emissions reported to the UNFCCC were higher than our top-down estimates, whereas for Turkey our estimates agreed with UNFCCC-reported values for HFC-125 and HFC-143a, but were much and slightly smaller for HFC-134a and HFC-152a, respectively. Sensitivity estimates suggest an improvement of the a posteriori emission estimates, i.e., a reduction of the uncertainties by 40–80 % in the entire inversion domain, compared to an inversion using only the existing central European AGAGE observations.

Comparison of four inverse modelling systems applied to the estimation of HFC-125, HFC-134a, and SF<sub>6</sub> emissions over Europe

Abstract. Hydrofluorocarbons (HFCs) are used in a range of industrial applications and have largely replaced previously used gases (CFCs and HCFCs). HFCs are not ozone-depleting but have large global warming potentials and are, therefore, reported to the United Nations Framework Convention on Climate Change (UNFCCC). Here, we use four independent inverse models to estimate European emissions of the two HFCs contributing the most to global warming (HFC-134a and HFC-125) and of SF6 for the year 2011. Using an ensemble of inverse models offers the possibility to better understand systematic uncertainties in inversions. All systems relied on the same measurement time series from Jungfraujoch (Switzerland), Mace Head (Ireland), and Monte Cimone (Italy) and the same a priori estimates of the emissions, but differed in terms of the Lagrangian transport model (FLEXPART, NAME), inversion method (Bayesian, extended Kalman filter), treatment of baseline mole fractions, spatial gridding, and a priori uncertainties. The model systems were compared with respect to the ability to reproduce the measurement time series, the spatial distribution of the posterior emissions, uncertainty reductions, and total emissions estimated for selected countries. All systems were able to reproduce the measurement time series very well, with prior correlations between 0.5 and 0.9 and posterior correlations being higher by 0.05 to 0.1. For HFC-125, all models estimated higher emissions from Spain + Portugal than reported to UNFCCC (median higher by 390 %) though with a large scatter between individual estimates. Estimates for Germany (+140 %) and Ireland (+850 %) were also considerably higher than UNFCCC, whereas the estimates for France and the UK were consistent with the national reports. In contrast to HFC-125, HFC-134a emissions from Spain + Portugal were broadly consistent with UNFCCC, and emissions from Germany were only 30 % higher. The data suggest that the UK over-reports its HFC-134a emissions to UNFCCC, as the model median emission was significantly lower, by 50 %. An overestimation of both HFC-125 and HFC-134a emissions by about a factor of 2 was also found for a group of eastern European countries (Czech Republic + Poland + Slovakia), though with less confidence since the measurement network has a low sensitivity to these countries. Consistent with UNFCCC, the models identified Germany as the highest national emitter of SF6 in Europe, and the model median emission was only 1 % lower than the UNFCCC numbers. In contrast, the model median emissions were 2–3 times higher than UNFCCC numbers for Italy, France, and Spain + Portugal. The country-aggregated emissions from the different models often did not overlap within the range of the analytical uncertainties formally given by the inversion systems, suggesting that parametric and structural uncertainties are often dominant in the overall a posteriori uncertainty. The current European network of three routine monitoring sites for synthetic greenhouse gases has the potential to identify significant shortcomings in nationally reported emissions, but a denser network would be needed for more reliable monitoring of country-wide emissions of these important greenhouse gases across Europe.

The Possible Influences of the 2012 Modena Earthquakes on the Fluorescence Spectra of Bottled Mineral Water

Two moderate earthquakes with magnitudes of 6.0 and 5.8 occurred in active tectonic crustal structures of the Po Plain in the area of Modena City in Northern Italy. These events generated temporary and/or permanent environmental changes with much damage, leading to 27 deaths. These quakes occurred on May 20, 2012, at 02:03 UTC, and on May 29, 2012, at 07:00 UTC, at depths of 5.5 and 10.1 km, respectively. In order to investigate for effects from the earthquakes on the fluorescence spectra and ion composition of groundwater within the affected area, available mineral water bottled prior to and post the two shocks were collected. Specifically, the regular production lines at the bottling plants of the brands Lieta, Ventasso, Cerelia and Monte Cimone situated in the nearest Appennine chain, contributed to this study. These bottled waters where analyzed for their fluorescence spectra using the synchronous scanning method. Variations of fluorescence intensity a month before the first earthquake of May 20, 2012, appeared to be significant only at Monte Cimone spring, where high density water samples were available. Likewise, variations in ion compositions evidenced peaks at a month before the first earthquake and a month after the second one. pH and conductivity levels of only some springs also shown significant variations at a month before the first earthquake. These findings suggest that a realization of continuous measurement networks in areas prone to incidences by strong earthquakes could be useful for investigating any possible influence of earthquakes on water geochemistry.

Detection and attribution of regional CO2 concentration anomalies using surface observations

In this study, observed episodes of CO2 concentrations at eight Northern Hemisphere (NH) sites from 1993 to 2012 were analyzed. Five-day back trajectories were calculated for a potential source contribution function (PSCF) analysis. A normalized weight factor related to the occurrence of the episodes was applied to derive more reasonable CO2 elevations and sequestrations. Weighted elevated (▵CO2(W_E)) and sequestered (▵CO2(W_S)) CO2 episodes had large spatial discrepancies due to the differentiation of strength and patterns of CO2 emissions/sinks in different regions. The most significant enhancement in CO2 episodes was observed at Asian sites: ▵CO2(W_E) increased by approximately 56% at an annual rate of ∼4% yr−1 from 1995 to 2010 at Waliguan (WLG) and by approximately 39% (∼3% yr−1) from 1997 to 2012 at Yonagunijima (YON). According to the PSCF analysis, these increases are largely attributed to the rapid increase in emissions in China. However, ▵CO2(W_S) was also enhanced by 34.4% with a growth rate of 2.3% yr−1 at WLG from 1995 to 2010 and ∼26.2% (1.7% yr−1) at YON from 1997 to 2012. Both ▵CO2(W_E) and ▵CO2(W_S) showed decreasing or relatively flat trends at Monte Cimone and Schauinsland, indicating reductions in emissions and sinks in central Europe. The different intensities/trends in emissions and sinks observed at different sites in the NH show that estimating future CO2 levels is a complex problem. Atmospheric inverse and process-based ecosystem models should use more regional input data at high temporal and spatial resolutions for future carbon flux estimations.

The front in high alpine rock and ice regions. World War I from an engineering geological point of view

Soon after the Kingdom of Italy declared war on the Austro-Hungarian Empire in May 1915, the hostilities in the high mountains of the Southern Alps began hesitantly and at once solidified to a fierce positional war. For territorial gains, both sides proceeded to a subsurface warfare in hard rock and glacier ice (mining war). Simple mining tools (hammer and chisel), as well as increased technical equipment (drilling by means of pneumatic and electric hammers and blasting) were applied to the mutual tunneling operations (galleries, counter galleries, galleries to locate enemy tunnels and caverns). Until 1918, a total of 34 peak positions were blown up. The impact of engineering geological factors on tunnel driving and blasting success is explained by selected examples (Lagazuoi, Col di Lana and Monte Sief, Marmolada, Monte Cimone and Pasubio).

European emissions of HCFC-22 based on eleven years of high frequency atmospheric measurements and a Bayesian inversion method

HCFC-22 (CHClF2), a stratospheric ozone depleting substance and a powerful greenhouse gas, is the third most abundant anthropogenic halocarbon in the atmosphere. Primarily used in refrigeration and air conditioning systems, its global production and consumption have increased during the last 60 years, with the global increases in the last decade mainly attributable to developing countries. In 2007, an adjustment to the Montreal Protocol for Substances that Deplete the Ozone Layer called for an accelerated phase out of HCFCs, implying a 75% reduction (base year 1989) of HCFC production and consumption by 2010 in developed countries against the previous 65% reduction. In Europe HCFC-22 is continuously monitored at the two sites Mace Head (Ireland) and Monte Cimone (Italy). Combining atmospheric observations with a Bayesian inversion technique, we estimated fluxes of HCFC-22 from Europe and from eight macro-areas within it, over an 11-year period from January 2002 to December 2012, during which the accelerated restrictions on HCFCs production and consumption have entered into force. According to our study, the maximum emissions over the entire domain was in 2003 (38.2 ± 4.7 Gg yr−1), and the minimum in 2012 (12.1 ± 2.0 Gg yr−1); emissions continuously decreased between these years, except for secondary maxima in the 2008 and 2010. Despite such a decrease in regional emissions, background values of HCFC-22 measured at the two European stations over 2002–2012 are still increasing as a consequence of global emissions, in part from developing countries, with an average trend of ca 7.0 ppt yr−1. However, the observations at the two European stations show also that since 2008 a decrease in the global growth rate has occurred. In general, our European emission estimates are in good agreement with those reported by previous studies that used different techniques. Since the currently dominant emission source of HCFC-22 is from banks, we assess the banks' size and their contribution to the total European emissions up to 2030, and we project a fast decrease approaching negligible emissions in the last five years of the considered period. Finally, inversions conducted over three month periods showed evidence for a seasonal cycle in emissions in regions in the Mediterranean basin but not outside it. Emissions derived from regions in the Mediterranean basin were ca. 25% higher in warmer months than in colder months.

Environmental measurements at Monte Cimone GAW station

Continuous atmospheric CO 2 measurements performed by IAFMC at Mt. Cimone Observatory in the period 1980–2009 were analysed in order to select data representing background concentrations. A filtering technique was used to smooth background data and to separate the annual cycle from the long-term increase. The average growth rate of CO 2 was found to be 1.708 ± 0.003 ppm/year, while annual cycle amplitude was 11.42 ± 1.48 ppm. From spectrum analysis of detrended data significant interannual contributions (periods of about four years and of about 2.5 years) were found. Moreover, a strong positive correlation between CO 2 growth rate and global temperature anomalies was found. A statistical model was applied on column ozone data measured in Sestola in the period 1979–2010 in order to separate natural cyclic contributions from the anthropogenic contribution, which is given by a piecewise-linear trend with a turning point in January 1996. We estimated a trend equal to –1.61 ± 0.41 D.U./year before turning point, and a trend of +1.06 ± 1.18 D.U./year after turning point. Finally, a net decrease in annual maximum of near-noon UV index was found from 2005 in Sestola and in the period 1996–2009.

Ten years of continuous observations of stratospheric ozone depleting gases at Monte Cimone (Italy) — Comments on the effectiveness of the Montreal Protocol from a regional perspective

Halogenated gases potentially harmful to the stratospheric ozone layer are monitored worldwide in order to assess compliance with the Montreal Protocol requiring a phase out of these compounds on a global scale. We present the results of long term (2002–2011) continuous observation conducted at the Mt. Cimone GAW Global Station located on the highest peak of the Italian Northern Apennines, at the border of two important regions: the Po Valley (and the Alps) to the North and the Mediterranean Basin to the South. Bi-hourly air samples of CFC-12, CFC-11, CFC-114, CFC-115, H-1211, H-1301, methyl chloroform, carbon tetrachloride, HCFC-22, HCFC-142b, HCFC-124 and methyl bromide are collected and analysed using a gas chromatograph–mass spectrometer, providing multi annual time series. In order to appreciate the effectiveness of the Montreal Protocol from a regional perspective, trends and annual growth rates of halogenated species have been calculated after identification of their baseline values. A comparison with results from other international observation programmes is also presented. Our data show that the peak in the atmospheric mixing ratios of four chlorofluorocarbons, two halons and two chlorocarbons has been reached and all these species now show a negative atmospheric trend. Pollution episodes are still occurring for species like halon-1211, methyl chloroform and carbon tetrachloride, indicating fresh emissions from the site domain which could be ascribed both to fugitive un-reported uses of the compounds and/or emissions from banks. For the hydrofluorocarbons changes in the baseline are affected by emissions from fast developing Countries in East Asia. Fresh emissions from the site domain are clearly declining. Methyl bromide, for which the Mediterranean area is an important source region, shows, in a generally decreasing trend, an emission pattern that is not consistent with the phase-out schedule of this compound, with a renewed increase in the last two years of pollution episodes.

The determination of a “regional” atmospheric background mixing ratio for anthropogenic greenhouse gases: A comparison of two independent methods

Halocarbons are powerful greenhouse gases capable of significantly influencing the radiative forcing of the Earth’s atmosphere. Halocarbons are monitored in several stations which are globally distributed in order to assess long term atmospheric trends and to identify source regions. However, to achieve these aims the definition of background mixing ratios, i.e. the mixing ratio in a given air mass when the recent contribution of local sources is absent, is necessary. This task can be accomplished using different methods. This paper presents a statistical methodology that has been devised specifically for a mountain site located in Continental Europe (Monte Cimone, Italy), characterised by the vicinity of strong sources. The method involves the decomposition of the observed data distribution into a Gaussian distribution, representative of background values, and a Gamma distribution, ascribable to contribution from stronger sources. The method has been applied to a time series from a European marine remote station (Mace Head, Ireland) as well as to time series from Monte Cimone. A comparison of the methodology described in this paper with a well-established meteorological filtering procedure at Mace Head has shown an excellent agreement. A comparison of the baselines at Mace Head, Mt. Cimone and the Swiss alpine station of the Jungfraujoch highlighted the occurrence of a specific background concentration. Although this paper presents the application of the method to three hydrofluorocarbons, the proposed methodology can be extended to any long lived atmospheric component for which a long term time series is available and at any location even if affected by strong source regions.

Stratospheric NO2 trends over the high mountain ‘Ottavio Vittori’ station, Italy

This paper presents an evaluation of the nitrogen dioxide (NO2) trend inferred from UV–visible zenith-sky measurements performed at the ‘Ottavio Vittori’ ground-based research station (http://www.isac.cnr.it/cimone) at Monte Cimone (44.18° N, 10.7° E, 2165 m above sea level (a.s.l.)). Experimental data series are obtained from the measured spectra adopting a retrieval procedure according to differential optical absorption spectroscopy (DOAS) methodology. Data series cover the period from 1993 to 2009, with limited interruptions due to technical maintenance of the instrument or poor meteorological conditions. The NO2 trends are calculated with a linear regression model considering different factors assumed to contribute to NO2 atmospheric content. Before running the model, a procedure for data quality control was applied to reduce or exclude the influence of measurements affected by poor meteorological conditions or the vertical transport of polluted air masses from the lower troposphere. The negative trends obtained for sunrise (a.m.) and sunset (p.m.) NO2 measurements are in good agreement with previous studies accomplished for ground-based stations in the northern hemisphere.

Modeling the transport of Saharan dust toward the Mediterranean region: an important issue for its ecological implications

Airborne particulate matter (PM) is presently an environmental problem of primary concern, whose role in air quality, climatic and ecological issues is well recognized, though still a matter of extensive investigations (Intergovernmental Panel on Climate Change, 2007). It is of great scientific interest to detect sources of atmospheric particulate matter and quantify their influence on the global and local scales. Unfortunately, emissions are usually not directly available, while PM concentration time series are experimentally accessible, so that the problem often consists in inverting these data to determine the region of influence that caused the measured concentration. In this paper we are concerned with an alternative approach to inverse modeling based on backward trajectory analysis (BTA); this approach has the potential to overcome some limitations associated with traditional BTA. We apply this method to the analysis of PM time series from the Monte Cimone observatory, hereafter MCT, a high altitude station on the top of the Italian Northern Apennines, with the aim of estimate the contribution of Saharan dust transport on PM concentration levels registered in the Mediterranean region.

Modeling the transport of Saharan dust toward the Mediterranean region: an important issue for its ecological implications

Airborne particulate matter (PM) is presently an environmental problem of primary concern, whose role in air quality, climatic and ecological issues is well recognized, though still a matter of extensive investigations (Intergovernmental Panel on Climate Change, 2007).It is of great scientific interest to detect sources of atmospheric particulate matter and quantify their influence on the global and local scales. Unfortunately, emissions are usually not directly available, while PM concentration time series are experimentally accessible, so that the problem often consists in "inverting" these data to determine the region of influence that caused the measured concentration. In this paper we are concerned with an alternative approach to inverse modeling based on backward trajectory analysis (BTA); this approach has the potential to overcome some limitations associated with traditional BTA.We apply this method to the analysis of PM time series from the Monte Cimone observatory, hereafter MCT, a high altitude station on the top of the Italian Northern Apennines, with the aim of estimate the contribution of Saharan dust transport on PM concentration levels registered in the Mediterranean region.

Characterization of atmospheric aerosols at Monte Cimone, Italy, during summer 2004: Source apportionment and transport mechanisms

Atmospheric aerosols in the PM10 and PM1 fractions have been sampled at the Global Atmospheric Watch station Mount Cimone, Italy (2165 m above mean sea level) for 3 months during summer 2004, and simultaneous size distributions have been derived by means of an optical particle counter. Samples have been analyzed by X‐ray fluorescence, ion chromatography, and thermal‐optical methodology in order to quantify their elemental, ionic, and carbonaceous constituents. The concentration of PM10 was 16.1 ± 9.8 μg m−3 (average and standard deviation). Source apportionment allowed us to identify, quantify and characterize the following aerosol classes: anthropogenic pollution (10 μg m−3), mineral dust (4 μg m−3), and sea salt (0.2 μg m−3). Pollution has been further split into ammonium sulfate (44%), organic matter (42%), and other compounds (14%). The nitrate/sulfate ratio in the polluted aerosol was 0.1. Fine particles have been completely related to the polluted aerosol component, and they represented 70% in weight of pollution. Coarse particles characterized the dust and salt components, and crustal oxides have been found to be the largest responsible for the aerosol concentration variations that occurred during the campaign. Nitrate has also been found in the coarse particles, representing ∼10% of mineral dust. The analysis of the transport mechanisms responsible for aerosol fluctuations permitted us to identify the origin of the major aerosol components: Pollution has been ascribed to regional transport driven by boundary layer meteorology, whereas mineral dust has been related to long‐range transport events originating in the Sahara and Sahel. A particularly significant Saharan episode has been identified on 10 August 2004 (PM10 daily concentration, 69.9 μg m−3). Average elemental ratios for the African dust events were as follows: Si/Al = 2.31, Fe/Ca = 0.94, Ca/Al = 0.90, K/Ca = 0.44, Ti/Ca = 0.11, and Ti/Fe = 0.12.

CO2 concentrations and δ13C (CO2) values in monthly sets of air samples from downtown Parma and the Parma and Taro river valleys, Emilia-Romagna, Italy†

Monthly sets of discrete air samples were collected from September 2004 to June 2005 in the town of Parma, along North-South and East-West runs (8 plus 8 samples), using four-litre Pyrex flasks. The CO2 concentrations and δ13C values were determined on these samples with the aim of evaluating quantitatively the contribution of domestic heating to the winter atmospheric CO2 pollution in downtown Parma by comparing autumn and spring atmospheric values with winter values. After separation of CO2 from the other air gases in the laboratory, the CO2 concentrations were calculated from the intensity of the 12C16O ion beam in the mass spectrometer, after calibration with artificial air samples whose CO2 concentration was very carefully determined by the Monte Cimone Observatory (Sestola, Modena, Italy). The reproducibility of these measurements was of ∼±0.4 % and, consequently, the most probable error is not higher than±2–3 ppmv and does not affect the magnitude of the gradients between different samples. The standard deviation of δ13C measurements ranges from±0.02 to ±0.04 ‰ (1σ). The results suggest that the contribution of domestic heating to atmospheric CO2 pollution is almost negligible in the case of ground level atmosphere, where the main CO2 pollution is essentially related to the heavy car traffic. This is probably because of the fact that the gases from the domestic heating systems are discharged tens of metres above ground level at a relatively high temperature so that they rise quickly to the upper atmospheric layers and are then displaced by air masses dynamics. Revised version of a paper presented at the VIII IsotopeWorkshop of the European Society for Isotope Research (ESIR), 25–30 June, 2005, Leipzig-Halle, Germany. Monthly sets of discrete air samples were also collected from October 2004 to June 2005 along North-South runs from the town of Parma to the Apennine ridge following the Parma and the Taro river valleys (8 samples and 7 samples per set, respectively) and measured using the same technique. The aim of this study was the comparison between the town samples, the plain country samples and the samples collected on the northern slope of the Apennines. The results reveal huge variations of both CO2 concentration and δ13C through space and time, some of which can be reasonably explained whereas others are rather difficult to understand. The sets of values are discussed and various hypotheses are suggested.

Physical aerosol properties and their relation to air mass origin at Monte Cimone (Italy) during the first MINATROC campaign

Abstract. Aerosol physical properties were measured at the Monte Cimone Observatory (Italy) from 1 June till 6 July 2000. The measurement site is located in the transition zone between the continental boundary layer and the free troposphere (FT), at the border between the Mediterranean area and Central Europe, and is exposed to a variety of air masses. Sub-μm number size distributions, aerosol hygroscopicity near 90% RH, refractory size distribution at 270°C and equivalent black carbon mass were continuously measured. Number size distributions and hygroscopic properties indicate that the site is exposed to aged continental air masses, however during daytime it is also affected by upslope winds. The mixing of this transported polluted boundary layer air masses with relatively clean FT air leads to frequent nucleation events around local noon. Night-time size distributions, including fine and coarse fractions for each air mass episode, have been parameterized by a 3-modal lognormal distribution. Number and volume concentrations in the sub-μm modes are strongly affected by the air mass origin, with highest levels in NW-European air masses, versus very clean, free tropospheric air coming from the N-European sector. During a brief but distinct dust episode, the coarse mode is clearly enhanced. The observed hygroscopic behavior of the aerosol is consistent with the chemical composition described by Putaud et al. (2004), but no closure between known chemical composition and measured hygroscopicity could be made because the hygroscopic properties of the water-soluble organic matter (WSOM) are not known. The data suggest that WSOM is slightly-to-moderately hygroscopic (hygroscopic growth factor GF at 90% relative humidity between 1.05 and 1.51), and that this property may well depend on the air mass origin and history. External mixing of aerosol particles is observed in all air masses through the occurrence of two hygroscopicity modes (average GF of 1.22 and 1.37, respectively). However, the presence of "less" hygroscopic particles has mostly such a low occurrence rate that the average growth factor distribution for each air mass sector actually appears as a single mode. This is not the case for the dust episode, where the external mixing between less hygroscopic and more hygroscopic particles is very prominent, and indicating clearly the occurrence of a dust accumulation mode, extending down to 50 nm particles, along with an anthropogenic pollution mode. The presented physical measurements finally allow us to provide a partitioning of the sub-μm aerosol in four non-overlapping fractions (soluble/volatile, non-soluble/volatile, refractory/non-black carbon, black carbon) which can be associated with separate groups of chemical compounds determined with chemical-analytical techniques (ions, non-water soluble organic matter, dust, elemental carbon). All air masses except the free-tropospheric N-European and Dust episodes show a similar composition within the uncertainty of the data (53%, 37%, 5% and 5% respectively for the four defined fractions). Compared to these sectors, the dust episode shows a clearly enhanced refractory-non-BC fraction (17%), attributed to dust in the accumulation mode, whereas for the very clean N-EUR sector, the total refractory fraction is 25%, of which 13% non-BC and 12% BC.

Size-segregated aerosol mass closure and chemical composition in Monte Cimone (I) during MINATROC

Abstract. Physical and chemical characterizations of the atmospheric aerosol were carried out at Mt. Cimone (Italy) during the 4 June-4 July 2000 period. Particle size distributions in the size range 6nm-10µm were measured with a differential mobility analyzer (DMA) and an optical particle counter (OPC). Size-segregated aerosol was sampled using a 6-stage low pressure impactor. Aerosol samples were submitted to gravimetric and chemical analyses. Ionic, carbonaceous and refractory components of the aerosol were quantified. We compared the sub- and superµm aerosol mass concentrations determined by gravimetric measurements (mGM), chemical analyses (mmCA), and by converting particle size distribution to aerosol mass concentrations (mmSD). Mean random uncertainties associated with the determination of mmGM, mmCA, and mmSD were assessed. The three estimates of the sub-µm aerosol mass concentration agreed, which shows that within experimental uncertainty, the sub-µm aerosol was composed of the quantified components. The three estimates of the super-µm aerosol mass concentration did not agree, which indicates that random uncertainties and/or possible systematic errors in aerosol sampling, sizing or analyses were not adequately accounted for. Aerosol chemical composition in air masses from different origins showed differences, which were significant in regard to experimental uncertainties. During the Saharan dust advection period, coarse dust and fine anthropogenic particles were externally mixed. No anthropogenic sulfate could be found in the super-µm dust particles. In contrast, nitrate was shifted towards the aerosol super-µm fraction in presence of desert dust.

Atmospheric measurements of gas-phase HNO<sub>3</sub> and SO<sub>2</sub> using chemical ionization mass spectrometry during the MINATROC field campaign 2000 on Monte Cimone

Abstract. The EU-project MINATROC (MINeral dust And TROpospheric Chemistry) aims at enabling an estimation of the influence of mineral dust, a major, but to date largely ignored component of tropospheric aerosol, on tropospheric oxidant cycles. Within the scope of this project continuous atmospheric measurements of gas-phase HNO3 and SO2 were conducted in June and July 2000 at the CNR WMO station, situated on Monte Cimone (MTC) (44°11' N --10°42' E, 2165 m asl), Italy. African air transporting dust is occasionally advected over the Mediterranean Sea to the site, thus mineral aerosol emitted from Africa will encounter polluted air masses and provide ideal conditions to study their interactions. HNO3 and SO2 were measured with an improved CIMS (chemical ionization mass spectrometry) system for ground-based measurements that was developed and built at MPI-K Heidelberg. Since HNO3 is a very sticky compound special care was paid for the air-sampling and background-measurement system. Complete data sets could be obtained before, during and after major dust intrusions. For the first time these measurements might provide a strong observational indication of efficient uptake of gas-phase HNO3 by atmospheric mineral-dust aerosol particles.