NATURAL AND ANTHROPOGENIC C-2 TO C-6 HYDROCARBONS IN THE CENTRAL-EASTERN VENEZUELAN ATMOSPHERE DURING THE RAINY-SEASON

The levels of low molecular weight hydrocarbons were measured at prist ine sites and rural locations affected by hydrocarbon emissions from o il and gas producing fields in Venezuela. At the clean sites, lower co ncentrations of C-2 to C-6 alkanes were observed, whereas, in comparis on with remotes sites, very much higher levels were measured at the po lluted sites. Alkenes present relatively high concentrations, with iso prene being the most abundant, all over the study region. The main sou rces of alkenes are likely to be natural, mainly from vegetation. The levels of alkanes recorded at the clean sites and the alkene levels fo und everywhere in the region are in agreement with the values reported for other clean sites in the tropics. The increase of ozone productio n capacity due to the anthropogenic emissions of alkanes from oil and gas fields was estimated. Due to the presence in the atmosphere of imp ortant amounts of naturally emitted isoprene, ethene and propene, whic h makes a substantial contribution to the reactivity of the hydrocarbo n mixture, a small increase (<5%) was estimated to occur in the capaci ty of the ozone production at a regional scale during the rainy season .