Six C10H16 monoterpenes, p-cymene, and isoprene, all known or thought to be emitted to the atmosphere by vegetation, were irradiated in the presence of NOx. The terpenes studied included one acyclic triolefin (myrcene), two monocyclic diolefins (d-limonene, terpinolene), and three bicyclic monolefins (alpha-pinene, beta-pinene, and delta-carene). Propylene was also studied since this olefin serves as a point of reference with other chamber studies. Results showed that monoterpenes and isoprene promoted the oxidation of NO to NO2 and were themselves consumed at rates comparable to or greater than propylene; p-cymene was decidedly slow in these respects. The monoterpenes however did not permit the buildup of ozone due to their rapid reaction with ozone. The ozone suppression was particularly noticeable at high carbon/NOx ratios. Deciduous forests, isoprene emitters, are coniferous forests. Coniferous forests may in fact function as a sink for ozone. Reported ambient concentrations of isoprene and terpenic hydrocarbons in forested areas are too low to account for more than a few ppb of ozone even if NOx is available.

"September 1979." Includes bibliographical references (pages 60-66).