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.