h i g h l i g h t s First measurements of 14 C in organic carbon (OC) in the Netherlands. Modern sources dominate OC both at the urban and coastal site. Significantly higher F 14 C(OC) at the coastal site than at the urban site. Clear signature of pollution long-range transport in F 14 C(OC) at the coastal site.

Abstract. We present the set-up and a scientific application of the Stratospheric Air Sub-sampler (SAS), a device to collect and to store the vertical profile of air collected with an AirCore (Karion et al., 2010) in numerous sub-samples for later analysis in the laboratory. The SAS described here is a 20 m long 1/4 inch stainless steel tubing that is separated by eleven valves to divide the tubing into 10 identical segments, but it can be easily adapted to collect smaller or larger samples. In the collection phase the SAS is directly connected to the outlet of an optical analyzer that measures the mole fractions of CO 2 , CH 4 and CO from an AirCore sampler. The stratospheric part (or if desired any part of the AirCore air) is then directed through the SAS. When the SAS is filled with the selected air, the valves are closed and the vertical profile is maintained in the different segments of the SAS. The segments can later be analysed to retrieve vertical profiles of other trace gas signatures that require slower instrumentation. As an application, we describe the coupling of the SAS to an analytical system to determine the 17 O excess of CO 2 , which is a tracer for photochemical processing of stratospheric air. For this purpose the analytical system described by (Mrozek et al., 2015) was adapted for analysis of air directly from the SAS. The performance of the coupled system is demonstrated for a set of air samples from an AirCore flight in November 2014 near Sodankylä, Finland. The standard error for a 25 mL air sample at stratospheric CO 2 mole fraction is 0.

Abstract. This paper presents an analytical system for analysis of all single substituted isotopologues ( 12 C 16 O 17 O, 12 C 16 O 18 O, 13 C 16 O 16 O) in nanomolar quantities of CO 2 extracted from stratospheric air samples. CO 2 is separated from bulk air by gas chromatography and CO 2 isotope ratio measurements (ion masses 45 / 44 and 46 / 44) are performed using isotope ratio mass spectrometry (IRMS). The 17 O excess ( 17 O) is derived from isotope measurements on two different CO 2 aliquots: unmodified CO 2 and CO 2 after complete oxygen isotope exchange with cerium oxide (CeO 2 ) at 700 • C. Thus, a single measurement of 17 O requires two injections of 1 mL of air with a CO 2 mole fraction of 390 µmol mol −1 at 293 K and 1 bar pressure (corresponding to 16 nmol CO 2 each). The required sample size (including flushing) is 2.7 mL of air. A single analysis (one pair of injections) takes 15 minutes. The analytical system is fully automated for unattended measurements over several days. The standard deviation of the 17 O excess analysis is 1.7 ‰. Multiple measurements on an air sample reduce the measurement uncertainty, as expected for the statistical standard error. Thus, the uncertainty for a group of 10 measurements is 0.58 ‰ for 17 O in 2.5 h of analysis. 100 repeat analyses of one air sample decrease the standard error to 0.20 ‰. The instrument performance was demonstrated by measuring CO 2 on stratospheric air samples obtained during the EU project RECONCILE with the high-altitude aircraft Geophysica. The precision for RECONCILE data is 0.03 ‰ (1σ ) for δ 13 C, 0.07 ‰ (1σ ) for δ 18 O and 0.55 ‰ (1σ ) for δ 17 O for a sample of 10 measurements. This is sufficient to examine stratospheric enrichments, which at altitude 33 km go up to 12 ‰ for δ 17 O and up to 8 ‰ for δ 18 O with respect to tropospheric CO 2 : δ 17 O ≈ 21 ‰ Vienna Standard Mean Ocean Water (VSMOW), δ 18 O ≈ 41 ‰ VSMOW (Lämmerzahl et al., 2002). The samples measured with our analytical technique agree with available data for stratospheric CO 2 .

Abstract. We present the setup and a scientific application of the Stratospheric Air Sub-sampler (SAS), a device to collect and to store the vertical profile of air collected with an AirCore (Karion et al., 2010) in numerous sub-samples for later analysis in the laboratory. The SAS described here is a 20 m long 1/4 inch stainless steel tubing that is separated by eleven valves to divide the tubing into ten identical segments, but it can be easily adapted to collect more or less smaller or larger samples. In the collection phase the SAS is directly connected to the outlet of an optical analyzer that measures the mole fractions of CO2, CH4 and CO from an AirCore sampler. The stratospheric part (or if desired any part of the AirCore air) is then directed through the SAS. When the SAS is filled with the selected air, the valves are closed and the vertical profile is maintained in the different segments of the SAS. The segments can later be analyzed to retrieve vertical profiles of other trace gas signatures that require slower instrumentation. As an application, we describe the coupling of the SAS to an analytical system to determine the 17O excess of CO2, which is a tracer for photochemical processing of stratospheric air. For this purpose the analytical system described by Mrozek et al. (2015) was adapted for analysis of air directly from SAS. The performance of the coupled system is demonstrated for a set of air samples from an AirCore flight in November 2014 near Sodankylä, Finland. The standard error for a 25 mL air sample at stratospheric CO2 mole fraction is 0.56 ‰ (1 σ) for δ17O and 0.03 ‰ (1 σ) for both δ18O and δ13C. Measured Δ17O(CO2) values show a clear correlation with N2O in agreement with already published data.

Abstract. This paper presents an analytical system for analysis of all single substituted isotopologues (12C16O17O, 12C16O18O, 13C16O16O) in nanomolar quantities of CO2 extracted from atmospheric air samples. CO2 is separated from bulk air by gas chromatography and CO2 isotope ratio measurements (ion masses 45/44 and 46/44) are performed using isotope ratio mass spectrometry (IRMS). The 17O excess (Δ17O) is derived from isotope measurements on two different CO2 aliquots: unmodified CO2 and CO2 after complete oxygen isotope exchange with cerium oxide (CeO2) at 700 °C. Thus, a single measurement of the 17O excess requires two injections of 1 mL of air with a CO2 mole fraction of 390 μmol mol−1 at 293 K and 1 bar pressure (corresponding to 16 nmol CO2 each). The required sample air size (including flushing) is 2.7 mL of air. A single analysis (one pair of injections) takes 15 min. The analytical system is fully automated for unattended measurements over several days. The standard deviation of the 17O excess analysis is 1.7‰. Repeated analyses of an air sample reduce the measurement uncertainty, as expected for the statistical standard error. Thus, the uncertainty for a group of ten measurements is 0.58‰ for Δ17O in 2.5 h analysis. 270 repeat analyses of one air sample decrease the standard error to 0.20‰. The instrument performance was demonstrated by measuring CO2 on stratospheric air samples obtained during the EU project RECONCILE with the high-altitude aircraft Geophysica. The precision for RECONCILE data is 0.03‰ (1σ) for δ13C, 0.07‰ (1σ) for δ18O and 0.55‰ (1σ) for δ17O for sample of 10 measurements. The samples measured with our analytical technique agree with available data for stratospheric CO2.