PARENT SESSION

1E - Speciation of chemicals
Poster Hall
8:30 AM - Tuesday, 29 April 2003

(TUP/35) Mercury transformations in the terrestrial isopod Porcellio scaber (Isopoda, Crustacea) and its environment.

Nolde, Nataša¹, Jereb, Vesna¹, Drobne, Damjana², Horvat, Milena¹, ¹ Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia² Department of Biology, University of Ljubljana, Ljubljana, Slovenia

ABSTRACT- Mercury is a highly toxic element and has a distinctive feature to transform into different chemical forms. For example, some microorganisms methylate inorganic mercury to monomethylmercury (MeHg) which is lipofilic and neurotoxic and it biomagnifies in the food chains. In the framework of studies on mercury biogeochemistry in contaminated and polluted sites due to past mercury mining in Slovenia a study on the uptake, distribution and transformation of mercury in the terrestrial isopod Porcellio scaber was innitiated. Some preliminary tests using mercury (Hg²⁺) treated leaves representing food of these animals, indicated that MeHg was formed during the experiment. In order to investigate the origin of MeHg in Porcellio scaber and its environment, experiments were carried out with a radiotracer 203-Hg. Other mercury species, such as 203-Hg²⁺ compounds and 203-Hg⁰, were also measured and preliminary mass balance of mercury in the experiment was calculated. For MeHg and Hg²⁺ determination a radiochemical method with specific separation of 203-Hg²⁺-dithizonate and Me203-Hg-dithizonate by thin layer chromatography and gamma counting was used. For 203-Hg⁰ determination activated carbon traps and gamma counting was used. After two weeks of experiment majority of mercury in animals and their environment remained as 203-Hg²⁺. The net formation of 203-Hg⁰ and Me203-Hg was detected at much lower concentrations. The concentrations of Me203-Hg were higher in the leaves and excrements rather than in the animals. This suggested that the methylation already occurred on the hazelnut leaves and excrements. Based on the quantity of food consumed by the animals, relatively low concentrations of Me203-Hg in the animal and its organs were found. This suggested that demethylation of MeHg could be prevailing process in the digestive system of the animal, a sense of detoxification of MeHg. Further experiments with 14-CH₃Hg will therefore be needed in order to verify this hypothesis. In addition, transformation processes of Hg in excrements should also be addresses as part of the experiment.

Key words: Porcellio scaber, mercury transformations, methylmercury