An analysis of climate change in Nigeria has been carried out. The aim was to investigate the environmental impact of Green house gases. The three zones of the country namely the extreme North, the middle zone and the extreme South have all been separately examined with respect to changes in solar radiation, temperature, precipitation and evaporation. The agricultural productivity for each zone was compiled, and trend plots over time carried out. Correlation tests were done between productivity and climatic changes and it was found that each zonal area reacted differently to changes in climate. The emission of carbon dioxide, methane and the oxides of nitrogen in Nigeria were calculated and trends plotted. A correlation test was also carried out between carbon dioxide emission and temperature change for each zone. The relationship between temperature change and productivity was shown in a regression model. An economic appraisal for Nigeria involving the GDP, pollution and population was examined in terms of the productivity- pollution index. This was also extended to some of the Western countries

This thesis presents precipitation chemistry data from a dense network of 18 bulk and one wet-only precipitation collectors across the Metropolitan County of Greater Manchester, in the North-West of England, between January 1987 and December 1988. The samples were analysed for the major ions in precipitation. The data were used to investigate the spatial and temporal variability of non marine sulphate, nitrate, ammonium, calcium and hydrogen, their sources and potential atmospheric removal processes. This study has demonstrated the significant spatial variability of non marine sulphate, nitrate, ammonium, calcium and hydrogen ion concentrations in bulk precipitation from a dense urban network. The spatial pattern of hydrogen showed a significant inverse relationship with that of calcium, showing the importance of calcium species as the principal buffering agent of urban precipitation chemistry. A significant relationship between calcium and non marine sulphate was found using advanced statistical techniques. Calcium is proposed to principally originate from urban 'dust' particles which react with either sulphur dioxide or sulphate particles to ·produce enhanced concentrations of non marine sulphate in precipitation. A significant relationship was also found between nitrate and ammonium using the same statistical techniques and trajectory analysis. It is proposed that ammonia from sources within the U.K. and the conurbation itself, undergoes gas phase reactions with nitric acid to form ammonium nitrate, and that the spatial variability of nitrate in precipitation is likely to be the result of the strong spatial variability of ammonium. It may also be possible that calcium carbonate, from local sources, reacts with ammonium sulphate particles, liberating ammonia. The temporal variability of non marine sulphate, nitrate, ammonium and hydrogen ion concentrations in precipitation was consistent with patterns observed by other workers. Local and meso scale emissions do not seem to greatly affect the temporal variabi1ity of these ion concentrations, the major controlling factor being meteorology. The temporal variability of ammonium and nitrate deposition is more susceptible to the effects of local and meso scale emissions. Mean network concentrations of non marine sulphate, nitrate, ammonium and hydrogen did not differ great1y to interpolated values from the secondary national network for the year 1988. However, sophisticated statistical analysis comparing selected data from the G.M. network to those from two nearby national network sites revealed important differences regarding the sources of some ions in precipitation and their relative strengths.

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.

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In occupational and public health there is a need for measurement and speciation of chemicals in ambient air to achieve control of air pollution and minimize health risks. In this work two methods of analysis are developed for the analysis of polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) under ambient air conditions. Both methods involve the use of thermal desorption techniques with gas chromatography-mass spectrometry (GC-MS). For the measurement of polycyclic aromatic hydrocarbons (PAHs) airborne particulate samples are obtained by collection on small glass fibre filters. The volatile materials from these are thermally desorbed in two stages and transferred to a Gas Chromatograph-Mass Spectrometer analytical system. Results from studies of particulate samples obtained from sites in the region of Uxbridge, Middlesex are reported for eight selected polycyclic aromatic hydrocarbons (PAHs). Measurements on samples obtained directly from vehicle emission sources with the engine used under different running conditions are also reported. In the method of analysis of volatile organic compounds in air, samples are absorbed into 4mm Carbotrap 300 tubes and thermally desorbed and passed into a gas chromatography-mass spectrometry (GC/MS) or gas chromatography (GC) using helium as carrier gas. The Carbotrap absorbers used, show complete absorb/desorb reversibility, are thermally stable and do not react chemically with injected hydrocarbon standards. To demonstrate the value of the method analytical results obtained under ambient air conditions on the Brunel University campus (Uxbridge, Middlesex) are reported. Six selected low molecular weight aromatic hydrocarbons namely benzene, toluene, ethyl benzene and m-, p- and o-xylene are investigated in detail. The concentrations of these compounds were measured and results related to traffic flow rates and meteorological conditions to establish the fact that vehicle exhaust emissions are the main sources of the volatile organic compounds (VOCs) pollution at the collection sites. A study of volatile organic compounds (VOCs) levels in ambient air in Tehran (Iran) in which 55 hydrocarbons are identified is reported. A detailed study is made of the concentrations of the six hydrocarbons benzene, toluene, ethyl benzene and m-, p- and o-xylene because high concentrations of these pollutants can produce potential health problems. It is shown that the nature of the geographical location and the day time temperature play an important part in determining the composition of the mixture of pollutants in Tehran. Samples obtained directly from internal combustion engines with and without catalytic converters are also analysed using the method developed and the results show that there is a large depletion in aromatic hydrocarbons when toluene is reduced to a greater extent than benzene. The analytical method is also used to compare vehicle emissions from engines under cold start and hot start conditions.