Adsorptive preconcentration technique including oxidant scavenging for the measurement of reactive natural hydrocarbons in ambient air

An analytical methodology for sampling and determination of airborne biogenic non-methane hydrocarbons (NMHCs) was checked in laboratory- and field studies with regard to its suitability for the measurement of reactive natural NMHCs, such as isoprene and terpenes in remote areas. The experiments have shown that ozone scrubbing prior to the preconcentration step is necessary; otherwise a serious underestimation of some natural alkenes is unavoidable. The decomposition of trapped species during the sampling complicates a reliable determination of the plant emissions, especially if the mixing ratios of the hydrocarbons are low in comparison to the concentrations of atmospheric photooxidants, as usually observed in forested areas. Thus, a simple oxidant scavenger was included in the sampling device. In addition, results from field measurements of biogenic NMHCs in a tropical rain forest are presented, indicating the importance of high molecular weight terpenes, such as sesquiterpenes, as plant emissions under special environmental conditions.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday