Vegetation Injury from the Interaction of Nitrogen Dioxide and Sulfur Dioxide

Economic measurement of environment damages

“…With the aid of controlled environmental chambers, Temple (1972) studied exposure of four species of ornamental trees to so 2 • Damages to foliage as high as 95% were found at concentrations of 4 ppm for 6 hours. Tingey et al (1971) and Dunning, Tingey, and Reinert (1970) working with atmospheres of N0 2 and so 2 found that atmospheres of N0 2 below 200 pphm (parts per hundred million) or of so 2 below 50 pphm did not cause leaf injury. dioxide and a combination of -so 2 and N0 2 in portable environmental chambers.…”

Action of Pollutants Individually and in Combination

“…In other studies (Horsman and Wellburn 1975;Jager and Klein 1977), the activity of glutamate dehydrogenase (GDH) has been found to respond to S02 more consistently than any other enzyme indicator. Pollutant mixtures containing both S02 and N0 2 have been shown to be more detrimental to plants than either gas alone (Tingey et al 1971;Ashenden and Mansfield 1978) and to have a more than additive effect on various enzymes (Horsman and Wellburn 1975). A biochemical explanation for the mechanisms behind this synergism was provided by Wellburn et al (1981), who showed that S02 inhibits the normal pathway of N0 2 detoxification so that nitrite and nitrate ions are likely to accumulate to toxic levels in the chloroplasts, where they become involved in free radical reactions and enhance the damaging effects of SOl-ions.…”

Sensitivity of Native Desert Vegetation To SO2and to SO2and NO2Combined

“…9 The possibility of synergism between SO2 and NO2 must be considered near power plants because both SO2 and NO* are emitted. With currently operating coal-fired power plants in the southwest and more under construction, this lack of information on the effects of SO2 and SO2 + NO2 on the native vegetation in the vicinity of these power plants is acute.…”