The Challenge and Its Solution When Determining Biogeochemically Reactive Inorganic Mercury (RHg): Getting the Analytical Method Right

Lian Liang, Milena Horvat, John Alvarez, Lyman Young, Jože Kotnik, Lisa Zhang

Cebam Analytical, Inc., Bothell, USA.
Chevron Energy Technology Company, Richmond, USA.
Department of Environmental Sciences, J. Stefan Institute, Ljubljana, Slovenia.

DOI: 10.4236/ajac.2013.411074                

Abstract

Biogeochemially reactive inorganic mercury (RHg) is an important fraction of Hg. Researchers have attempted to measure RHg when characterizing Hg-impacted sites, conducting research and development of remediation practices, or evaluating remediation efficiency. In these uses, RHg will be the best choice for analysis in ways that total methyl, and other species of Hg cannot duplicate. The fraction has been inadequately measured using the Sn²⁺ reduction method and operationally defined as “Sn²⁺ reducible Hg²⁺”, but the resulting data did not reflect well the nature of the fraction and caused researchers to lose interest, thus limiting the use of RHg in past years. In this work, the problems of using the Sn²⁺ reduction method were discovered to be generating irreproducible and negatively biased results. Negative bias from 20% to 99% was found in different types of waters. To obtain reliable results, an ethylation-based GC-CVAFS method was used to determine RHg. The performance of the method was evaluated by comparing it to the Sn²⁺ reduction method. Biogeochemically meaningful results have been obtained in the application of the method to determine RHg in mercury mine-impacted waters from the Idrijca River in Slovenia.

Keywords

Mercury Speciation; Reactive Hg²⁺; Method Comparison; Ethylation-GC-CVAFS; Sn²⁺ Reduction

Conflicts of Interest

The authors declare no conflicts of interest.

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