Atmospheric Pollution in the Ponderosa Pine Blight Area

Abstract

The ponderosa pine trees in the industrialized area north of Spokane, Washington, have exhibited a characteristic reddening of the needles since 1943, known locally as ponderosa pine blight. The blighted area now embraces approximately 50 square miles, and the trees within a 3-square mile area near the center are dead. As a portion of a comprehensive investigation, the concentrations of gaseous fluorine and sulfur compounds in the air during the growing season of 1950 have been determined through operation of twelve air-sampling stations and a mobile air-analysis laboratory. Analysis of rain-water samples obtained during each rainy period throughout October and November 1950 at 82 locations established the points of origin of the contaminants and the extent of their dispersion. Meteorological and topographical conditions in the ponderosa pine blight area, which control the dispersion of pollutants and explain the damage and pollutant concentration-patterns, are discussed. Concentrations of gaseous fluorine compounds in the atmosphere of the area will serve as a guide in controlled fumigation of ponderosa pine.