Reactions of Organolead Compounds Under Natural Conditions

Abstract

Certain compounds containing lead atoms bonded to alkyl groups are of much greater toxicity than their non-alkylated analogues. The tetra-alkyl lead compounds are used as anti-knock additives in petrol and are discharged into the atmosphere by exhaust emission, spillage, and evaporation. Because of their toxicity, the concentration and reaction of such compounds in natural waters is of great importance. Little data is available on the concentration and properties of organolead compounds in the environment, and the information which is available is concerned mainly with the concentration of tetra-alkyl lead compounds in the atmosphere. This dissertation seeks to establish the fate of organolead compounds washed from the atmosphere into natural water systems. Procedures for the extraction and estimation of alkyl lead compounds in water and on sediment were developed. The reactions of soluble organolead compounds in aqueous systems under conditions of light, dark, and added metal ions were studied, as were the reactions of alkyl lead compounds adsorbed on silica. Some exploratory work on the biological methylation of inorganic and alkyl lead ions was carried out to substantiate studies by other workers, and it was concluded that the reported results could, in many cases, be explained by a chemical disproportionation mechanism involving sulphide ions rather than a biological mechanism. This dissertation concludes that it is unlikely that any organolead compounds entering natural waters will remain dissolved and unreacted for any length of time, and that all reactions lead to a reduction in total alkyl lead content of the system with inorganic lead as the final product.