Mercury and selenium in the muscle of piscivorous common mergansers (Mergus merganser) from a selenium-deficient European country.

Although the relationship between mercury (Hg) and selenium (Se) has been studied in wild birds in areas with sufficient or excessive Se levels, little is known about this relationship in areas where the supply of Se is limited. As Hg detoxification is based on the production of biologically inactive Hg-Se complexes, the aim of this study was to investigate the relationships between the concentrations of total mercury (THg), methylmercury (MeHg), inorganic mercury (InHg=THg-MeHg), percent MeHg of THg, Se and molar ratios (THg:Se, MeHg:Se, InHg:Se) in the breast muscle (n=16) of the piscivorous common mergansers (Mergus merganser) from a Se-deficient and moderately Hg-polluted area in Poland. Mergansers were divided into two groups differing in condition (A-very good condition; C-moderate condition). Concentrations of THg, MeHg and Se were determined by atomic absorption spectrometry, modified gas chromatography atomic fluorescence spectroscopy, and spectrofluorometric methods, respectively. In all studied mergansers, mean concentrations of THg, MeHg, InHg, and Se in muscle were 2.63, 1.92, 0.46, and 0.54µgg(-1)dw, respectively. THg and MeHg concentrations in the muscle of group A mergansers were greater than in group C. The ratio of THg:Se was higher in group A than in group C (2.32 vs 1.36; p<0.01), as well as the molar ratio of MeHg:Se (A vs C: 1.98 vs 1.03; p<0.05). Comparisons between mergansers from Poland and Canada showed similar THg and percent MeHg in the muscle, but mergansers from Poland had several times lower Se levels and higher THg:Se ratios (>2.0) than the Canadian mergansers and other European and North American waterbirds. We found statistically significant positive correlations (MeHg-THg, percent MeHg/THg-MeHg, percent InHg/THg-InHg, THg:Se-THg, MeHg:Se-THg, THg:Se-MeHg, MeHg:Se-MeHg, InHg:Se-InHg, MeHg:Se-THg:Se) and some negative correlations (percent InHg/THg-MeHg, percent MeHg/THg-InHg, THg:Se-Se, MeHg:Se-Se). As THg and percent MeHg in the studied mergansers were similar to populations living in non-Se-deficient areas, it is likely that different mechanisms of muscle Hg detoxification have evolved in mergansers populations living in Se-deficient areas.

Hepatic and nephric mercury and selenium concentrations in common mergansers, Mergus merganser, from Baltic Region, Europe.

The subject of the present study was the piscivorous common mergansers (Mergus merganser). The total mercury (THg), methylmercury (MeHg), selenium (Se) inorganic mercury (InHg; THg - MeHg), percentage of THg that is MeHg (%MeHg), molar ratios (THg:Se, MeHg:Se, InHg:Se), and their mutual relations in livers and kidneys were determined in ducks from an Se-deficient area in Poland. The authors verified a hypothesis that, as a result of living in an Se-deficient region, mergansers from Poland should have higher THg:Se ratios than other waterbirds with similar THg tissue levels. Although a comparison of healthy mergansers from Poland and Canada showed similar THg tissue contents, the group in the present study had a few times lower Se levels and higher THg:Se ratios (overall means >1.7 in both livers and kidneys in all studied individuals) than the Canadian group and other European and North American waterbirds. The authors found significant correlations between various relations, including MeHg-THg, InHg-THg, Se-THg, %MeHg-THg, InHg/%THg-THg, %MeHg/THg-InHg, %InHg/THg-InHg, MeHg:Se-THg:Se, InHg:Se-THg:Se, InHg:Se-MeHg:Se in liver and InHg-THg, Se-THg, Se-InHg, %MeHg-THg, %MeHg-InHg, %InHg/THg-InHg, THg:Se-THg, InHg:Se-THg, MeHg:Se-MeHg, THg:Se-InHg, InHg:Se-InHg, and InHg:Se-THg:Se in kidney. It is likely that the main factor responsible for the high value of THG:Se ratio (>1) in mergansers from Poland is Se deficiency in central and northern Europe. Therefore, this element is unlikely to participate in the detoxification of Hg in these birds.

Improvements and application of a modified gas chromatography atomic fluorescence spectroscopy method for routine determination of methylmercury in biota samples.

Improvements to the application of a combined solid-phase microextraction followed by gas chromatography coupled to pyrolysis and atomic fluorescence spectrometry method (SPME-GC-AFS) for methylmercury (MeHg) determination in biota samples are presented. Our new method includes improvements in the methodology of determination and the quantification technique. A shaker instead of a stirrer was used, in order to reduce the possibility of sample contamination and to simplify cleaning procedures. Then, optimal rotation frequency and shaking time were settled at 800 rpm and 10 min, respectively. Moreover, the GC-AFS system was equipped with a valve and an argon heater to eliminate the effect of the decrease in analytical signal caused by the moisture released from SPME fiber. For its determination, MeHg was first extracted from biota samples with a 25% KOH solution (3h) and then it was quantified by two methods, a conventional double standard addition method (AC) and a modified matrix-matched calibration (MQ) which is two times faster than the AC method. Both procedures were successfully tested with certified reference materials, and applied for the first time to the determination of MeHg in muscle samples of goosander (Mergus merganser) and liver samples of white-tailed eagle (Haliaeetus albicilla) with values ranging from 1.19 to 3.84 mg/kg dry weight (dw), and from 0.69 to 6.23 mg kg(-1) dw, respectively.