No description available.

No description available.

Though nitrogen oxides (NOx ) emissions from aircraft make a relatively small contribution to the overall NOx emissions when compared to surface emissions, they constitute the only man-made pollutant at high altitude. Excessive NOx emissions might cause ozone depletion in the stratosphere and ozone increases in the troposphere, both topics of increasing environment concern in recent years. To tackle the problem of NOx emissions and their effects upon the environment, the spatial distribution of NOy (NOx + RN03) needs to be fully understood. The most significant source of NOx emissions is due to long range civil subsonic aircraft during their cruise phase. Detailed studies were performed for seven cases, including five single flight and two global scale scenarios, using the most widely used B747-400 aircraft which are powered by 4 three-shaft turbofan engines. Using models of aircraft performance, cruise phase NOx emissions are derived and employed as input to run a three-dimensional chemistry transport model. In order to achieve realistic results, all scenarios were carried out using a one-year period of simulation to study the transport and dispersion of NOy emitted from aircraft exhausts. For a better understanding of the atmospheric behaviour of NOy , two other cases were also carried out, a one-month simulation during both summer and winter situations. The results show that the upper troposphere may certainly be perturbed by aircraft NOx emissions at cruise altitude. The relative increase in NOx concentration is estimated to be of the order of 40% in the meridional average and up to 160% in regions covered with heavy air traffic such as Europe, the USA and the North Atlantic. This thesis investigates the quantity of long range civil subsonic aircraft NOx pollutants at cruise altitude and their subsequent implications for the upper troposphere. It discusses the concept of atmospheric NOy pollution chemistry, using computer programs developed for both total aircraft performance and 3-D chemistry transport modelling, and combinations thereof. Simulations have been conducted to predict the relationship between the NOx emissions and the environment. In addition, the thesis highlights the most important variables and derives a procedure to model the emissions from subsonic aircraft flight and to assess their impacts upon the atmosphere. Finally, some complicated problems which need further work are also mentioned.

This thesis presents precipitation, streamwater and soil chemistry from three upland catchments in Scotland situated upon granite parent material and receiving different deposition loadings. Marine ions are identified as important components of precipitation and streamwater at the two coastal sites (Bealach and Cardoon) and lesser importance at the inland site (Allt a'Mharcaidh). Similar ratios of Na:Ca:Mg in precipitation and streamwater indicate the importance of catchment hydrology and organic soils in controlling streamwater chemistry. Input/output budgets indicate SO4-S and H+ loss from the Cardoon (a region of high acid deposition inputs) compared with the other two less polluted sites which exhibit SO4-S and H + retention. The SO4-S loss from the Cardoon is also associated with a high DOC flux in streamwater. In all three catchments differences were found between published critical load values and those calculated as part of this study. Seasonal and annual variations in critical loads for freshwaters at all sites indicate sampling for the national mapping exercise does not reflect the most acid-sensitive periods. Streamwater was also more sensitive than standing waters, with lower critical load values. Soil critical load values were lower than published soil critical load values as well as freshwater critical loads calculated in this study. Inclusion of marine-derived base-cations in PROFILE calculations of soil critical loads increased values markedly (1 keq ha-1yr -1) at the 2 coastal sites. Soil critical load varied little between horizons, suggesting that the identification of hydrologically important mineral horizon was not important. Lowest critical load values for freshwaters were controlled by the organic horizons which are not considered in PROFILE calculations. The implications of the omission of organic horizons from critical load calculations for soil in upland catchments are discussed and the use of critical loads at a catchment based level addressed.

This paper gives a description of three well known clustering methods, and discusses the advantages and disadvantages of each. Then, the results of these three clustering methods are compared through examining them on a specific set of data.

A novel system for leaching of reconstituted cores of soils taken from horizons of <I>Calluna</I> moorland podzol profiles derived from granites has been used to see if absolute, or at least, relative, weathering rates assessed by simple leaching techniques and by using the PROFILE model agreed. Initial base cations are first removed by leaching with ammonium acetate. Agreement was reasonable, but the results highlighted problems posed by mineralization effects in column-based procedures. A successful attempt was made to develop a procedure to overcome this problem, based upon pre-oxidation with H₂O₂. This procedure was tested on a selection of B and C horizon soils from podzol profiles, and shown to give weathering rates which correlated well with those derived using the PROFILE model. The equilibrated soil cores remaining at the end of the study were then used for testing the effect of acidification of infiltrating water upon weathering rates of base cations. Weathering rate did not increase regularly to combat the acid input. Intact soil core microcosms, fitted with rhizon samplers at three depths and subjected to appropriate simulated precipitation, have been used to elucidate how land use influences the mobility of copper and zinc. Three land uses were considered, improved pasture, semi-improved pasture, and <I>Calluna</I> moorland. Copper and zinc concentrations were also measured in river water samples collected at 59 points from throughout the River Dee network under diverse flow conditions, with a view to elucidating catchment factors influencing the mobilisation of these two elements into river water. The results demonstrated large inputs of copper arising as a consequence of arable land use, and suggested that TOC in drainage water from moorland soils mobilises copper from mineral sediments in the river network. Both zinc and copper concentrations were increased under high discharge conditions.

Thesis (M.A.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 72-75). Also available via the Internet.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 157-169).

No description available.

Three-way median polish is used to model the monthly concentrations of three kinds of ions in precipitation, namely sulphate, nitrate and hydrogen ions. In contrast to previous findings that the wet acid deposition had decreased from late 70's to early 80's, the results suggest that there is a V-shaped trend for wet acid deposition during the period of 1980 -1986 with the change point around 1983. Strong seasonality is also discovered by the analysis. Nonparametric monotone trend tests are performed on the data collected from 1980 to 1986 and on the data collected from 1983 to 1986 separately. The results are consistent with the findings from the median polish approach. A nonparametric slope estimate of the trend is obtained for each monitoring station. Based on these estimates, the slope estimate is obtained by Kriging interpolation for each integer degree grid point of longitude and latitude across the 48 conterminous states in the United States. Also, a geographical pattern in the data is suggested by hierarchical clustering and by median polishing. / Science, Faculty of / Statistics, Department of / Graduate