Spectroscopic study of corona discharges on coniferous trees

A woody as well as herbal plant is a producer of substances creating their bodies and also of substances-certain secondary metabolites-that are released to the environment. The metabolites released from plants in the form of gases or vapours, as volatile aromatic hydrocarbons (especially terpenes) are not confined to their close surroundings and become an ecological factor even in a distant environment. Contaminated atmospheric air in the surroundings area of the corona discharge contains various chemical species and such species influence the corona discharge in return. Terpenes are typical secondary metabolites of plants. They are a natural species widespread in the plants with carbon frame created by various forms of isoprene. Terpenes are contained particularly in coniferous species. Under natural conditions in the forest ecosystem, terpenes occur partly in the mixtures contained in the plant tissues as liquid resins, partly (following their release from the tissues and evaporation from the plant surfaces) as a vapour in the atmosphere. The mixture of terpenes in the form of vapour is of importance mainly from the ecological point of view. The concentration of monoterpene hydrocarbons (C5H8)(2) (alpha-pinene, beta-pinene, Delta(3)-carene, limonene) in the open air of forest ecosystems is relatively low and varies from 0,1 mg/m(3) in the stands of pine, cryptomeria and cypress to 6 mg/m(3) in the stands of pine and oak, respectively. Neither their behaviour in discharge nor their reactions with other species (espepially ozone) axe not fully known. The aim of the paper is to present FTIR spectra of the corona discharge on needles of pine showing the presence of terpenes and their destruction in negative corona discharge. Furthermore, the generation of ozone in the corona discharge is observed and possible products of the reaction of ozone with terpenes are discussed.