Thesis (Ph. D.)--University of Oregon, 1999. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 59-60). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948027.

Chlorosis and premature loss of pine needles was observed in the Delamere Forest, N. Cheshire in late 1992. Fears that the local environment had suffered, and was continuing to suffer, from acid rain or mist 'episodes' as a result of airborne pollutants, led to an analysis of pine needles for total foliar element concentrations in early 1994. Analysis by X-ray Fluorescence Analysis (XRF) revealed levels of foliar sulphur (0.35%) and chloride (0.32%) that suggested deposition of these chemicals as a result of emissions from nearby sources, including a local power station , Ince 'B', a scenario later confirmed by the local environment agency. A monthly programme designed to monitor tree health in Delamere Forest in relation to local levels of atmospheric S02 took place between June 1994 and April 1996, using fixed populations of Scots Pine (P. sylvestris L.) and Corsican Pine (P. nigra var. maritima (Ait.) Melville) to differentiate between short-term acute pollution events and long-term chronic ambient deposition, and to attempt to pinpoint pollution sources. The results revealed complex seasonally affected inter-relationships between atmospheric (dry deposited) sulphur dioxide, rainfall, wind direction and fluctuations in concentrations of foliar elements such as sulphur and magnesium. Average monthly atmospheric S02 levels during this programme were 20 ug/m-3 and foliar S 0.096% total dry weight. The average foliar magnesium level was low at 0.02%. Peaks of atmospheric SO2 were recorded of over 100 ug/m-3, with a maximum of 127 ug/m-3. The initial findings were used as part of a local governmental enquiry that contributed to the decision process which eventually led to the eventual closure of Ince 'B' in 1997. In order to monitor any subsequent changes in tree health as a result, further sampling took place from June 1998 to February 1999. Atmospheric sulphur dioxide levels fell significantly after the closure of of the power station (average 9l ug/m-3) and this change in air quality was reflected in a similarly significant fall in overall concentrations of foliar sulphur (average 0.064% total dry weight). Foliar Mg levels had risen during this period to 0.032%. Recent observations of continued damage to pine foliage in Delamere suggested that although the fall in atmospheric S02 in this area and the subsequent improvement in air quality had followed national trends, Delamere Forest has an ongoing health problem derived from other locally emitted atmospheric pollutants including sporadic emissions of chlorine. It is likely, due to the nature and close proximity of petro-chemical industries, that other pollutants in the immediate local atmosphere such as ozone and ammonia also influence tree health in Delamere Forest and the surrounding environment. Analysis by XRF clearly demonstrated a quick and accurate method of determining foliar element concentrations that could be used to monitor tree health affected by atmospheric pollution. This technique could successfully be used to identify local pollution sources which could prove important in the light of the reduction in local atmospheric pollution monitoring sites since 1999.

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Two series of experiments have been carried out to study the relative contributions of both dry deposition wash off and crown leaching, including H<SUP>+ </SUP>-cation exchange, to the change in chemistry of rain passing over the leaves of Sitka spruce (<i>Picea sitchensis</i> (Bong.) Carr.). In the first experiments detached needles and small trees were washed under several conditions with artificial acid rain water, following various pretreatments. Increases in Na and Mg in the canopy drip were found to be due, predominantly, to washed off dry deposition whereas about 50% of the K and Ca increases on washing with solutions of pH less than 4 were considered to be due to leaching of neutral salts and H<SUP>+ </SUP>-cation exchange. In a second series of experiments the unidirectional membrane fluxes of ions across the needle surface were studied by compartmental analysis, using <SUP>36</SUP>Cl, <SUP>45</SUP>Ca and <SUP>42</SUP>K. There appears to be a net loss of all these elements when artificial rain water solution of pH 4.3 was used for elution. Neutral salt leaching over 24 h may result in as much as 5% of total K present in needle being lost, making it the most readily leached cation. Ca is not readily available for exchange as it is bound within the vacuole and cell wall. It was determined that about 15% of total Ca is available for exchange, of which 1.5-3% is considered to be leached as neutral salts. The elution of <SUP>45</SUP>Ca from needles attached to twigs suggested that leached Ca may be readily replaced by movement from the translocation stream to the cytoplasm. Although Cl in canopy drip is generally considered to be due predominantly to washed off dry deposition, about 12.5% of the total Cl content of needles was estimated to be leached over 24 h.

The main objective of this work was to determine the quantum yields for the production of alkoxy radicals via the near U-V photolysis of alkyl nitrites. Alkoxy radical reactions, including their isomerization, are important in both clear and polluted atmospheres. Alkyl nitrites were used as a photolytic source of alkoxy radicals (1). The extent of the of photolysis for the nitrites was determined by measuring the yield of either ketone or aldehyde product produced from the decomposition of the alkoxy radical, as a result of the dissociation of the nitrite concerned. Experiments were carried out at elevated temperatures (393K) in order to ensure that every alkoxy radical that was formed, dissociated via reaction (3), rather than recombine with nitric oxide to reform the nitrite (2). Care was taken to search for any other products via the primary step. RONO = (+ hv) RO &43 NO (1); RO + NO &61 RONO (2); RO = Products (Ketone or Aldehyde) (3) The experimental determination of azomethane, t-butyl, s-butyl, t-pentyl and 2-pentyl nitrite molecular electronic absorption spectrums were carried out using ultraviolet and near ultraviolet spectrophotometry (U.V.). Spectrophotometric measurements were made using certain nitrite pressure at 393 K with a 9.3 cm length cell. The average absorption at each nanometer of 5 runs were plotted against the absorption range (328 - 383 nm). The absorption cross section (σ) and the absorption rate (J_a) for the azomethane and the four nitrites were measured and calculated in the range 328 - 283 nm and at 393 K.

Effects of acid rain on the dry weight, nitrogen and sulfur content of radish plants were determined. They were exposed to distilled water acidified with a 7:3 ratio of sulfuric acid and nitric acid and adjusted to pH levels 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.7. A control group, exposed to distilled water only, was also used. Four hundred plants, divided in eight groups, were grown under laboratory conditions. At four, seven and ten week intervals, an equal number of plants of each pH level were removed from the soil.Plants exposed to water of lower pH values were found to be significantly higher (p < .05) in dry weight, percentage of nitrogen, and weight of sulfur per plant than crops at more neutral pH levels. The increased weight may be due to the greater availability of nitrates and sulfates at lower pH levels. These compounds probably contributed to better growth and greater dry weight of the plants at low pH levels.