A search for an extracellular extractant of Hg for use in the sequential elution technique withPseudoscleropodium purum

Abstract

The extraction efficiency of several metal cations (50 mM CoCl 2 , 20 mM NiCl 2 , 30 mM Pb(NO 3 ) 2 and 50 mM SrCl 2 ) and chelating agents (30 mM dimercaprol, 10 mM EDTA and 50 mM D-penicillamine) was evaluated in order to determine the optimal extracellular extractant for extracting Hg from the moss Pseudoscleropodium purum, by the sequential elution technique (SET). Moss samples were incubated with a high concentration of Hg (40 mg L 21 ) for one hour, and after the intercellular fraction was removed, the samples were subjected to the SET with the above-mentioned extractants. The chelating agents dimercaprol and D-penicillamine displaced most extracellular Hg, probably because both contain -SH groups, which have a high affinity for Hg. Dimercaprol was chosen as the best extractant because it displaced up to 93% of the extracellular metal. This compound was then used to extract Hg in an industrial gradient of Hg contamination, and the concentration of extracellular Hg was calculated relative to the total amount (80%). A new modification to the SET was also proposed. In the new version of the technique, the metals were determined in solid moss samples rather than in extracts. One advantage of the modification is that all of the determinations are carried out with the same analytical technique (direct mercury analysis), thereby minimizing the errors associated with the use of different techniques as in the previous version of the method. It was found that the cell compartment where the metals are located is not always accurately reflected by the SET, and therefore the use of other complementary techniques that show the correct location of the element under study is recommended.

Brachythecium rutabulum and Betula pendula as bioindicators of heavy metal pollution around a chlor-alkali plant in Poland

“…Both species demonstrated the significant lower concentration of this metal at sites at a distance of 6 km relative to the sites at closer distances. This is in agreement with Fernández et al (2000a) and Pérez-Llamazares et al (2009), that mercury contents in mosses is a function of the distance from the pollution source and of the type of industry. Also Grangeon et al (2012) in their investigation around a chlor-alkali factory in Grenoble (France) indicated the highest concentrations (up to 10 mg kg −1 ) of Hg within a radius of 500 m from the factory.…”

Evaluation of the efficacy of the sequential elution technique, by use of electron microscopy methods

“…The modification proposed by Pérez-Llamazares et al (2009) was applied in order to obtain the samples required for analysis by electron microscopy. The technique comprised the following steps: 1. total content (Tot): one third of the material was dried at 45uC for 72 hours for determination of the total concentration of Zn; 2. extracellular extraction: 15 aliquots of between 0.1 and 0.15 g (dry weight) of the remaining moss material were obtained; these were immersed in 10 ml of 20 mM NiCl 2 , with shaking, and in two successive steps (45z30 minutes) with renewal of the extraction medium between each step; 3. intracellular and particulate material (InzPart):…”

“…The extracellular extractant used in the SET was 20 mM NiCl 2 , as this is the most commonly used in such studies (Beckett & Brown, 1984;Branquinho et al, 1997;Vázquez et al, 1999a;Fernández et al, 2007;Pérez-Llamazares et al, 2009). Zinc was chosen for study, because as well as being extracted with NiCl 2 , it is one of the major elements in the moss used in the study, Pseudoscleropodium purum (Carballeira et al, 2002), and therefore was expected to be easily detected by microanalysis.…”

Methodological aspects of moss sample preparation. Effects of freezing and duration of washing on the cellular distribution of elements in Fontinalis squamosa Hedw.

“…Thus, for example, if the samples are washed for too long or energetically, exchangeable extracellular elements will be dislodged and included in the intercellular fraction. Thus, although long washing times were initially used (Bates and Brown, 1974;Brown andBuck, 1978b, 1979), the duration of the washing step was reduced to 30 s in later studies, to prevent alteration of the ionic equilibrium of the extracellular fraction (Wells and Brown, 1990;Vázquez et al, 2000a,b;Pérez-Llamazares et al, 2009). However, if the samples are not washed or the washing step is inefficient, part of the intercellular fraction may be included in the extracellular fraction.…”