The Nature and Concentration of Organometallics in Natural Waters

Abstract

Certain compounds containing lead atoms bonded to alkyl groups are of much greater toxicity than their non-alkylated analogues. The little research that has been carried out into the occurrence of such compounds in the environment has almost entirely been concerned with atmospheric concentrations. This dissertation seeks to quantify the amounts of alkyl lead compounds in natural waters. The major use of alkyl lead compounds is as anti-knock agents in petrol and since they can subsequently be released to the environment through spillage, evaporation, and exhaust emission, this was considered to be the most probable source of alkyl lead compounds in natural systems. Extraction and estimation procedures for alkyl lead compounds in water and in sediment were developed and spectroscopic studies of pure alkyl lead compounds were made for positive identification. A widely based geographical survey was carried out to determine the normal concentrations of alkyl lead compounds in natural waters and to locate specific sources. Sampling sites were chosen such that all possible types of waters were sampled in a variety of environments. Alkyl lead compounds were only detected in certain road drainage grids, and concentrations significantly above the limits of detection were observed only in grid sediments from forecourts of garages dispensing petrol. Since methylation of inorganic lead salts by micro-organisms could also introduce alkylated lead species into the environment, the ability of various biologically active systems to methylate lead salts was studied. In none of these was biological methylation observed despite the known methylation of mercuric salts under similar conditions. An apparent biological methylation of trimethyl lead salts was shown to proceed by a chemical disproportionation The dissertation concludes that the concentration of alkyl lead compounds in naturel waters does not constitute any hazard to public health.