Abstract
Abstract. We present setup, testing and initial results from a new automated system for stable carbon isotope ratio measurements on C2 to C6 atmospheric hydrocarbons. The inlet system allows analysis of trace gases from air samples ranging from a few liters for urban samples and samples with high mixing ratios, to many tens of liters for samples from remote unpolluted regions with very low mixing ratios. The centerpiece of the sample preparation is the separation trap, which is used to separate CO2 and methane from the compounds of interest. The main features of the system are (i) the capability to sample up to 300 l of air, (ii) long term (since May 2009) operational δ13C accuracy levels in the range 0.3–0.8 ‰ (1-σ), and (iii) detection limits of order 1.5–2.5 ngC (collected amount of substance) for all reported compounds. The first application of this system was the analysis of 21 ambient air samples taken during 48 h in August 2009 in Utrecht, the Netherlands. Results obtained are generally in good agreement with those from similar urban ambient air studies. Short sample intervals allowed by the design of the instrument help to illustrate the complex diurnal behavior of hydrocarbons in an urban environment, where diverse sources, dynamical processes, and chemical reactions are present.
Highlights
A significant amount of the total reactive carbon input to the atmosphere consists of non-methane hydrocarbons (NMHCs)
These are emitted to the atmosphere through many processes, both natural as a product of vegetative growth, decay and natural combustion of plant material, and anthropogenic including biomass burning for energy or heating, fossil fuel combustion, and industrial processes
Ethylene, propyne, and propylene originate primarily from combustion processes such as fossil fuel combustion and biomass burning; alkanes mainly stem from natural gas leakage and petroleum product evaporation, with significant transportation sources as well; and aromatic compounds mainly from transportation sources and solvent evaporation (Goldstein and Shaw, 2003; Redeker et al, 2007)
Summary
A significant amount of the total reactive carbon input (estimated as near 1150 Tg yr−1, Guenther et al, 1995) to the atmosphere consists of non-methane hydrocarbons (NMHCs). Development of the coupled gas chromatography – (combustion interface) – isotope ratio mass spectrometer (IRMS), as pioneered by Matthews and Hayes (1978) for CO2 and N2 isotope work, substantially improved upon earlier techniques based on dual-inlet isotope ratio mass spectrometers by greatly reducing necessary sample size and eliminating the need to extract individual compounds from a sample, which is a difficult and time-consuming task This breakthrough allowed significant research work into the stable isotopic ratios of carbon, nitrogen, oxygen and hydrogen containing compounds in the atmosphere. Development of instrumentation able to accomplish compound specific measurement of carbon isotope ratios of NMHC is somewhat newer (Rudolph et al, 1997; Goldstein and Shaw, 2003; Brenninkmeijer, 2009). Sample injection into the GC occurs by extracting and heating the FOC trap to a temperature of over 100 ◦C within 30 s, at a flow rate of 2.1 ml min−1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
