Discovery of a transalkylation mechanism – Identification of ethylmercury⁺ at a tetraethyllead-contaminated site using sodiumtetrapropylborate, GC-AED and HPLC-AFS

Abstract

Although organolead as a gasoline additive is banned in most countries, contamination by organolead compounds is still present. Little is known about transformation reactions of organolead compounds and especially transalkylation reactions with other metals. Laboratory experiments to clarify transalkylation reactions between organolead and inorganic mercury, and investigations of sites, where organolead compounds were emitted, are reported. Under laboratory conditions, inorganic mercury is ethylated to ethylmercury⁺ in presence of tetraethyllead. These transalkylations take place very fast and almost completely. In soil samples from an industrial site contaminated with organolead compounds and inorganic mercury, EtHg⁺ was clearly identified in high concentrations (up to 46 mg Hg/kg dw). Furthermore, methylmercury⁺ was found in concentrations up to 27 mg Hg/kg dw. It is the first time, that a transethylation of an organolead compound to an organomercurial compound in the environment is reported. It must be assumed, that this transalkylation takes place at sites, where organolead compounds occur and Hg²⁺ is available. Thus, it will be necessary to assess the risk of these sites.