EGU, European Geosciences Union General Assembly, 15-20 April 2007 Wien, Austria. Time series and trends of tropospheric halocarbons in the Mediterranean F. Artuso (1), P. Chamard (1), S. Chiavarini (1), S. Piacentino (2), M. D. Sferlazzo (2)   (1)   ENEA, ACS Department, Via Anguillarese 301, 00123 S. Maria di Galeria, Rome, Italy (2)   ENEA,Climate laboratory, Capo Grecale, 92010 Lampedusa, Italy (florinda.artuso@casaccia.enea.it, tel. +39 06 30483232) Figure 1: CFC-11 weekly time series (blue dots) and 53-week running mean (green line).  INTRODUCTION Measurement of halocarbons in the troposphere is becoming an important task in the climate change investigations because, despite of their low mixing ratios, they have high global warming potentials. Ozone depleting chlorofluorocarbons (CFCs) production has been definitively phased out by 1996 according to the Montreal Protocol (1987) and its Amendaments. The species designed as replacements of CFCs are the partially halogenated hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). In this work we discuss halocompound measurements recorded at the remote site of Lampedusa Island (35.5°N, 12.6°E), in the Mediterranean sea. TRAJECTORY ANALYSIS: THE CASE OF HFC-134a Preliminary combined analysis of backward air mass trajectories (HYSPLIT model) and HFC-134a weekly time series shows that anomalously high mixing ratios correspond to air masses originating from the North-continental area. We associated the deviations of the weekly HFC-134a mixing ratio from the trend line, defined as d, with 5-day air mass back trajectories to better understand the relationship with the air mass origin. Trajectories have been associated to different sectors of origin depending on their permanence time (50% permanence criterion). Four main geographical sectors have been identified: Western Europe (sector W); Eastern Europe and Russia (sector E); Africa (sector A); an oceanic region (sector O), which includes the Mediterranean sea and the Atlantic Ocean. Results are shown in table 1 and in figure 8. According to Edgar (www.mnp.nl/edgar) emission data base air masses originating from Europe and Eastern countries have higher content of HFC-134a than the ones coming from less polluting regions such as North Africa. CFCs Measurements of CFC-11 and CFC-12 atmospheric mixing ratios were started at Lampedusa ENEA station in 1996. The technique used for analysis is conventional gas chromatography with electron capture detection (GC-ECD). Depending upon the atmospheric lifetimes and the rapidity at which the emissions are curtailed the decreasing trend of CFC-11 and CFC-12 follows different behaviors. As reported in literature the concentration of CFC-11 (lifetime= 50 years) was at his maximum around 1993 and then started to slow down. The CFC-11 mixing ratio observed at Lampedusa since January 1997 is decreasing at a rate of about 1.1 ppt/yr and is now at a level of 250.0 ppt (see figure 1). In contrast CFC-12, having a longer lifetime (102 years), was slowly increasing until the end of 2002 and then decreasing in the last 4 years at a rate of 1.8 ppt/yr (figure 2). The actual mixing ratio value recorded at Lampedusa ranges around 534.0 ppt. Figure 2: CFC-12 weekly time series (blue dots) and 53-week running mean (green line). Figure 7: HFC-134a weekly time series (blue dots) and trend (green line). sector number of data average d (ppt) sd (ppt) E 13 (8.9 %) 1.04 0.95 W 19 (13.0 %) 0.92 0.71 O 74 (50.7%) -0.58 0.30 A 11 (7.5 %) -3.01 2.05 U 72 (49.3%)   Table 1- Number (percent) of trajectories, average value of d, and standard deviation of average, sd, satisfying 50% permanence criterion for each geographical sector. U are the unassigned cases. Figure 3: HCFC-22 weekly time series (blue dots) and trend (green line). Figure 4: HCFC-142b weekly time series (blue dots) and trend (green line). O E A W CFC REPLACEMENT COMPOUNDS Since December 2003 several CFC replacement compounds (HCFC-22, HFC-134a, HCFC-141b, HCFC-142b and SF6), are monitored at Lampedusa ENEA station. Samples are collected weekly in 6 L stainless steel canisters and then shipped to the ENEA Casaccia Laboratory (Rome), where they are analysed by gas chromatography-mass spectrometry (GC-MS). According to the data reported by other global monitoring stations of greenhouse gases, all halocompounds show a linear increasing trend. The growth rates recorded for HCFC-22, HCFC-142b, and HFC-134a during the period 2004-2006 are, 4.8, 0.8, and 4.2 ppt/yr respectively (see fig. 3, 4, 7). Measurements of HCFC-141b (fig. 5) and SF6 (fig. 6) during 2004 have not been reported. The growth rates during 2005-2006 are 0.4 and 0.15 ppt/yr respectively. Figure 5: HCFC-141b weekly time series (blue dots) and trend (green line). Figure 6: SF6 weekly time series (blue dots) and trend (green line). Acknowledgements We gratefully acknowledge Dr. Daniela Meloni for her contribution to the trajectory classification and visualization. We also acknowledge the NOAA Air Resources Laboratory (ARL) for provision of the HYSPLIT transport and dispersion model, and of the READY website (http:www.arl.noaa.gov/ready.html), whose results are used in this work. Figure 8: Backward trajectories ending at Lampedusa at 7 UT. Map reports 4 geographical sectors defined in the text above. Trajectory colour indicates measured value of d. Trajectories associated with –2ppt < d <+2ppt have not been reported.