Terpenes Emitted to Air from Forestry and the Forest Industry

Doctoral thesis, 1992

A major environmental concern with respect to hydrocarbon emissions is the formation of phytotoxic photooxidants. The work reported in this thesis focusses on the poorly studied anthropogenic terpene emissions from the industrial use of softwood. The advanced analytical determinations were made by adsorption sampling followed by thermal desorption and gas chromatography in the laboratory. Monoterpenes from forestry were analyzed for Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Near to a harvester, the total monoterpene concentrations reached ~1000 mg/m3, whereas the background level was ~1 mg/m3. Prominent monoterpenes were a-pinene, b-pinene, 3-carene, camphene, limonene, b-phellandrene, myrcene and terpinolene. Local formation of phytotoxic photooxidants may occur because of the short lifetimes of terpenes in air. Terpenes in process emissions and plumes from kraft pulp industries were found to have a uniform composition similar to that of pulpwood and of recovered sulphate turpentine. Predominant monoterpenes were a-pinene and 3-carene from Scots pine. The emitted terpenes give rise to photooxidants and to oxidation of co-emitted sulphur and nitrogen oxides. The monoterpenes in emissions from industries producing stone groundwood and thermomechanical pulp were similar in composition to that of the processed pulpwood from Norway spruce. The major monoterpenes were a-pinene (>50%) and b-pinene (~25%). The process emissions from a sulphite mill consisted mainly of p-cymene, formed from spruce monoterpenes by acid rearrangements. The terpene emissions from the barking of timber and pulpwood differed somewhat in composition from that of the wood. Increased proportions of b-phellandrene and myrcene were observed for Norway spruce. Oxidative decomposition and acid rearrangements of monoterpenes in the sampling cartridges were studied as major analytical difficulties. Pretreatment with thiosulphate and hydrogencarbonate prevented unwanted reactions of the terpenes.