John T. Middleton

Contribution of burning of agricultural wastes to photochemical air pollution

Agricultural wastes from orchards, grain fields, and range lands are burned each year in California as the most practical means of ridding the land of these wastes. In order to determine the relative contribution of the burning of such material to photochemical air pollution, the effluent from 1 23 fires of known weights of range brush, both dry and green, barley and rice stubble, and prunings from various fruit and nut trees were monitored in a special tower which provided an open burning situation. Analyses were made for total hydrocarbon, expressed as C, by flame ionization detection, and for 24 individual hydrocarbons by gas chromatography, as well as for CO and CO2 by infrared spectroscopy. A few analyses were made for oxides of nitrogen. These data, coupled with temperature and airflow measurements, allowed calculations to be made on pounds of effluent per ton of material burned and demonstrated that the emissions from agricultural burning are much less than those from the automobile, a principal so...

Damage to Vegetation from Polluted Atmospheres

Damage to vegetation from polluted atmospheres has been recognized for more than a century. Sulfur dioxide was the first pollutant recognized as causing significant damage to vegetation, and fluorine is the most important halogen which causes damage. The other halogens and hydrogen sulfide, ammonia, and carbon monoxide do not cause significant damage to vegetation because these contaminants usually arise from accidental losses from specific sources and usually do not occur in sufficiently high concentrations.

Air Quality Criteria and Standards for Agriculture

Many food, fiber, forage, and forest crops and a number of animals are adversely affected by a variety of air pollutants. The more important and generally occurring of these pollutants are ethylene, fluorides, ozone, peroxyacyl nitrates (PAN), and sulfur oxides. Their effects upon animals and plants can best be judged by criteria which describe the reaction of biologic materials to pollutant concentration and exposure time. Four criteria are recognized: (1) interference with enzyme systems; (2) change in cellular chemical constituents and physical structure; (3) retardation of growth and reduction in production from altered metabolism; and (4) acute immediate tissue degeneration. Information on tissue degenerative effects due to these pollutants is the most common; there are some reports on growth and productivity reduction; but little data are available on cellular alterations and interference with enzymes. Determination and measurement of the latter two criteria are essential to the ultimate definition ...

Time-resolved photon echo and fluorescence anisotropy study of organically doped sol-gel glasses

We present the first time resolved photon echo measurements of homogeneous dephasing of organic dopants in an inorganic sol-gel glass and compare these results with recent hole- burning experiments. In addition, energy transfer mechanisms and chromophore spatial distributions are investigated by time-resolved fluorescence anisotropy measurements.