The use of zeolite molecular sieves for trapping low concentrations of CO2 from environmental atmospheres

We describe a simple method for trapping low concentrations of CO2 present in gas mixtures, such as air and soil respiration, using a zeolite molecular sieve (type 13x) for environmental carbon isotope studies. We employ reusable molecular-sieve cartridges and a lightweight battery-driven pumping system, developed to enable CO2 collection in difficult and dangerous terrain or under extreme climatic conditions. The results of a small field experiment suggest that CO2 could be quantitatively trapped on and recovered from the 13x molecular sieve, without any fractionation of the stable carbon isotope. The delta(13)C of CO2 was also independent of the amount of air less than or equal to 18 liters and rate at which it was collected, i.e. less than or equal to 1 liter of air/min.