Open    Access



First Measurements of Biogenic Hydrocarbons in Air in a Tropical Cloudy Forest, Monteverde, Costa Rica



Author(s)

Germain Esquivel-Hernández¹, Sergio Madrigal-Carballo², Rosa Alfaro-Solís¹, José Pablo Sibaja-Brenes¹ and Juan Valdés-González¹

Full-Text PDF XML     140 Views

DOI:10.17265/1934-7375/2011.12.005

1. Atmospheric Chemistry Laboratory, National University, Escuela de Quimica, Heredia 86-3000, Costa Rica
2. Polymers Research Group, National University, Escuela de Quimica, Heredia 86-3000, Costa Rica

Measurements of biogenic hydrocarbons in ambient air were carried out during 2008 ina cloudy tropical forest in Monteverde, Costa Rica. Isoprene, α-pinene, β-pinene, 3-carene, d-limonene and γ-terpinene were sampled by adsorption cartridges filled with graphitized carbon and Tenax TA and analyzed by GC-FID. Parallel samples were collected using2 literscanisters and analyzed by GC-MS. In situ ozone measurements were done by using a UV absorption instrument. Increasing mixing ratios of isoprene, related to photosynthetic activity and ambient temperature, were observed during the morning and afternoon hours. Maximum isoprene’s mixing ratio reached 30 ppbv in March. An increment in the emissions of monoterpenes during high humidity periods and after rain events was also observed. Average mixing ratios of monoterpenes were between 0.3 and 3 ppbv. During the dry season (December to April), most abundant hydrocarbons were isoprene and d-limonene, whereas in the rainy season (May to November) isoprene and α-pinene were dominant. Hydrocarbons mixing ratios were used to estimate the OH and NO₃ densities. Average OH density was calculated in (4.87 ± 0.17) × 10⁶ mol/cm³. Average NO₃ density was calculated in (1.39 ± 0.09) × 10⁸ mol/cm³. Average O₃ mixing ratio was 30.9 ppbv.

Biogenic hydrocarbons, ambient air, atmospheric oxidation, cloudy forest.