Measurements of biogenic hydrocarbons and carbonyl compounds emitted by trees from temperate warm Atlantic rainforest, Brazil

Abstract

This study is part of a three-year project on biogenic volatile organic compound (VOC) emissions from trees of the temperate warm Atlantic rainforest found in the metropolitan area of São Paulo City (MASP). No study of VOC emission rates from plant species has been carried out in the temperate warm Atlantic rainforest of Brazil prior to this work. Eleven species were selected (Alchornea sidifolia, Cupania oblongifolia, Cecropia pachystachia, Syagrus romanzoffiana, Casearia sylvestris, Machaerium villosum, Trema micrantha, Croton floribundus, Myrcia rostrata, Solanum erianthum and Ficus insipida) and some of them were studied in urban, sub-urban and forest areas inside the MASP in order to evaluate biogenic VOC composition at sites characterized by different emission sources. Biogenic VOC emissions were determined by placing branches of plants in a dynamic enclosure system, an all-Teflon cuvette, and by sampling the compounds in the air leaving the cuvette. Pre-concentration using adsorbents to retain the VOC, followed by GC-MS after thermal desorption of the sample, was employed to determine the amount of biogenic hydrocarbons. The collection of carbonyl compounds on a 2,4-dinitrophenylhydrazine coated silica followed by HPLC-UV was used to analyze low molecular weight carbonyl compounds. Emission rates of isoprene, α-pinene, camphene and limonene ranged from 0.01 to 2.16 μg C h⁻¹ g⁻¹ and emission rates of aldehydes (C₂–C₆), acrolein, methacrolein and 2-butanone ranged from 1.5 × 10⁻² to 2.3 μg C h⁻¹ g ⁻¹. Ambient and leaf temperatures, relative humidity, light intensity, O₃ and NO_x levels in the local atmosphere were monitored during experiments. It was possible to identify different biogenic VOCs emitted from typical plants of temperate warm Atlantic rainforest. The emission rates were reported as a function of the type of site investigated and were only provided for compounds for which quantification was feasible. Other biogenic compounds were only identified.