Subject Absorption, atmospheric

In real atmospheres a wide array of pollutant combinations may occur. Plant responses described here represent only experimental combinations of major pollutants shown to inhibit CO2 absorption rates. Effects of other important phytotoxic atmospheric pollutants such as ethylene should also be examined along with more complex mixtures. Information regarding the responses of a wider range of plants subjected to varied environmental conditions would further aid in clarifying the problem. 

Tropical upwelling is the main process through which halocarbons are carried up into the stratosphere. Once there, they are distributed polewards along sloped isentiopic surfaces, and subject to photolysis by UV radiation. As Chou [13] have pointed out, UV absorption cross-sections of halocarbons depend strongly on the number of chlorine atoms attached to a particular carbon atom. Hence, stability and thus atmospheric life times increase with increasing number of fluorine replacing chlorine atoms (see 4. and table 1). 

In a study conducted by the Armour Research Foundation (Ref 41) a-Pb azide crystals wrapped in a thin A1 foil were subjected to fast and thermal neutrons in the heavy water pile at Argonne National Laboratory. With a thermal flux rate of about 10l4n/cm2/sec the crystals were irradiated for 8, 17 and 170 hours. The crystals decompd to a brown powder which was identified as Pb carbonate by X-ray techniques and infrared absorption spectra. From a mass spectrographic analysis of the isotopes of carbon and oxygen in the decompn products, it was determined that the mechanism of carbonate formation is a reaction with the atmosphere by broken surface bands produced by the neutrons. Subsequently, Raney (Ref 60) reported... 

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