Speciation of mercury in different environmental compartments. Design, development and optimization of analytical methods and procedures
Date
2009-05-29T10:46:34Z
Authors
Makiese, Julien Lusilao
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Abstract
The widespread use of organometallic compounds and their subsequent release
into the environment has created a great environmental concern about the toxicity
and effects of these pollutants. Mercury pollution is a growing concern worldwide
because its can reach high concentrations in various environmental media and thus
adversely affect humans, wildlife and ecosystem functioning.
Mercury is present in the environment in different molecular forms with specific
biogeochemical transformation and ecotoxicity. Inorganic Hg2+ is the main form in
water and sediment samples. Concentration levels of organomercury species is
very low (usually ng L-1) in aquatic environments but the toxic effect of these
compounds can be significant due to their tendency for bioaccumulation and
biomagnification in the food chain.
The development of a sensitive, reliable, simple, and cost effective procedure for
speciation analysis of mercury in different environmental compartments is
currently one of the principal research challenges in environmental analytical
chemistry. To this end, this study aimed to develop and optimize analytical
methods and procedures for the determination of total mercury and the speciation
of inorganic and organic forms of mercury. The hyphenation of gas chromatography and inductively coupled plasma mass spectrometry (GC-ICP-MS)
was achieved and used successfully.
Rapid and efficient sample preparation procedures based on microwave-assisted
extraction for solid samples were developed. The optimized analytical methods
and procedures were validated by the analysis of environmental certified reference
materials (CRM 015-050 sediment for HgTOT and CRM 463 tuna fish for HgTOT and MeHg). The developed methodologies were finally applied to real environmental samples,
namely soil, sediment, water, fish and human hair, collected in some South
African regions affected by environmental pollution due to reprocessing of old
tailings dumps and chlor-alakali facilities. The study included collection of
ancillary data (pH, redox potential) which are critically important for mercury
monitoring program. Predictive models of mercury speciation in water samples
based on thermodynamic solution equilibria were also established.