The nature and effects on the environment of heavy metal pollution from a lead smelter near Matlock, Derbyshire
A number of continuous and retrospective passive monitoring techniques have been employed in this study to carry out a comprehensive assessment of heavy metal dispersion and deposition from a secondary lead smelting complex. The principal period of monitoring was designed to coincide with contemporaneous changes in the operation of the complex involving, the incorporation of new smelting and refining centres. The initial phase of the sampling programme began with a preliminary multi-element survey to establish the degree of communality between different metals in smelter emissions and their interrelationships with background factors. Heavy metal deposition was monitored at bimonthly intervals over a two year period at 40 bulk precipitation sites located within an area of 250 km[sup]-2. In a complementary survey suspended moss-bags were collected at bimonthly intervals from 60 sites over a period of one year. Bimonthly levels of Pb deposition at these sites ranged from 7.0 to 1148 g ha[sup]-1 in bulk precipitation and 31 to 1792 mg kg[sup]-1 in moss-bags. The longer term pollution effects resulting from smelter emissions were assessed by determining retrospective heavy metal accumulations in saxicolous lichens and coniferous woodland soil profiles. The results of these surveys have been subjected to a range of interactive computer application packages including statistical analysis, computer mapping and plotting techniques. In the largest of these exercises, a series of 68 two-dimensional and 3-dimensional computer map projections are used to model patterns of heavy metal dispersion and deposition from the smelting complex. The surface profiles produced in these map projections reveal distinctive patterns of severe fugative pollution close to their source region and highly consistent linear stack emission trends largely moderated by the effects of local topographic relief. Local topographic expression is considered to be the most important single determinant influencing the atmospheric dispersion and deposition of heavy metal emissions. The development of locally induced wind patterns appear to largely suppress the vertical dispersion of emissions, leading to higher incident levels of heavy metal pollution within the local system of valleys. Relatively low levels of metal pollution were encountered away from these areas of low elevation during the early monitoring phase, but were later supplanted by more acute pollution effects, up to 500% greater at some outlying sites. On balance, only a marginal increase in pollution is indicated over consecutive yearly monitoring periods.