No description available.

No description available.

No description available.

No description available.

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.

The main objective of this research was to understand the fate of naphthalene and n-alkylnaphthalenes during diesel combustion, and an evaluation of their sources in diesel exhaust emissions. This was achieved by the use of a procedure which employed a [14C]radiolabelled PAH technique and a diesel enriched fuel technique (DEFT). The combustion of diesel fuel spiked with [14C]naphthalene has shown unequivocally that 0.5% of the naphthalene contained in diesel fuel survives combustion under the engine conditions studied (2500 rpm and 50 Nm). The survived naphthalene represented 22.8% of the total recovered naphthalene, the other 77.2% was presumably pyrosynthetic in nature. The sources of the pyrosynthesised naphthalene in the emissions was investigated at 2500 rpm and 50 Nm. The previously unreported input of n-methylnaphthalenes to the pyrosynthesised naphthalene was demonstrated by combusting fuel spiked with [14C]2-methylnaphthalene. Radiolabelled 2- methylnaphthalene (0.53% of the original [14C]2-methylnaphthalene) which had survived combustion, and radiolabelled naphthalene (0.02% of the original [14C]2-methylnaphthalene), were recovered in the exhaust extracts. This showed unequivocally that 2-methylnaphthalene was converted to naphthalene in the combustion chamber. The first enrichment experiments (DEFT), in which 1- and 2-methylnaphthalene were added separately to fuel prior to combustion confirmed that demethylation of both species produced naphthalene in small yields (1.9% and 6.1% respectively). The contribution of n-alkylnaphthalenes with the alkyl group greater than methyl in length, to pyrosynthesised naphthalene contained in exhaust emissions was investigated using fuel spiked with non-radiolabelled alkyl-PAH. The major product of combustion of these compounds was 2- vinylnaphthalene, with a 0.08% conversion for 2-butylnaphthalene and a 0.01% conversion for 2- ethylnaphthalene. No dealkylated products were detected in the exhaust emissions. A mechanism for the formation of 2-vinylnaphthalene was proposed. The effect of engine speed and load on the recovery of naphthalene and the contribution of pyrosynthesised and survived naphthalene to recovered naphthalene were established using [14C]naphthalene. At all speeds and loads investigated the pyrosynthesised fraction of recovered naphthalene was shown to be dominant.

No description available.

No description available.

No description available.

No description available.