Influence of Climate and Topography on Oxidant Air Pollution Concentrations That Damage Conifer Forests in Southern California

Wien

1972

S. 585-607

3 Abb., 1 Tab., 13 Lit. Ang.

Unselbständiges Werk

200144688

The concentration gradient of the total oxidant component of photochemical air pollution was measured from an urban basin east of Los Angeles, California, up to the forested crest of nearby mountains. Four ground stations at elevations from 442 m to 1725 m continuously measured oxidant, temperature, relative humidity, and winds on a slope having two distinct Vegetation zones. During June, July, and August 1969, the polluted air was confined below 1525 m until midday by a temperature inversion layer. Highest oxidant concentrations in the conifer forest occurred at 1600 PST following transport of polluted air upslope by convection currents and onshore breezes. At higher elevations, the daily oxidant maximum occurred later than the temperature and vapor pressure gradient maxima. The longest daily duration of oxidant above 10 pphm was at the 1725 m Station in June and at the 817 m Station during July and August. Oxidant measurements by aircraft in late June - early July consistently localized the greatest concentrations at 915 m next to the variable depth and inland penetration of the polluted layer of marine air and the extent of airflow up the mountain slope determine dosage of total oxidant received by vegetation in elevational zones.