A Study of Lead Alkylation in Natural Systems

  • Andrew P. Whitmore

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

A thesis presented by Andrew Peter Whitmore for the degree of Doctor of Philosophy in the University of Aston in Birmingham. Organic derivatives of heavy metals are rather more toxic to the higher forms of life than their inorganic counterparts. Following the discovery that microorganisms on sediment sludges are capable of methylating inorganic salts of mercury to the neurotoxin methylmercury, a great deal of attention has been focussed upon the biological methylation of other heavy metals: notably lead.

Tetramethyllead has been found in low concentrations on sediments and in fish, in both coastal and inland waters. At the same time, several workers have investigated the effects of natural sediments on solutions of lead salts and reached the conclusion that sporadic biological methylation of lead takes place.

In contrast, data presented in the following chapters suggests a number of possible reasons for the apparent methylation of lead. No such biological methylation was observed during the present study, and a thorough evaluation of all analytical methods was carried out.

In addition a number of unstable monoalkyl and monoaryllead compounds were prepared in order to investigate the biological alkylation of lead (IV) salts.

The behaviour of dialkyl and trialkyllead compounds on natural and artificial sediments was also followed. Conclusions drawn from the comparison of the two systems may help to cast light upon the apparent biological methylation of partially alkylated lead salts.

Finally conditions are set out for the chemical methylation of inorganic lead in natural waters. Iodomethane, a substance present in seawater was found to react in dilute aqueous solution, with lead metal or its salts to yield organolead compounds.

Although aquatic organisms are known to concentrate alkyllead compounds, it is suggested that the environmental methylation processes outlined here do not present a danger to public health.
Date of Award1981
Original languageEnglish
Awarding Institution
  • Aston University

Keywords

  • lead alkylation
  • natural systems

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