International Journal of Marine Science, 2017, Vol.7, No.26, 260-271
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environmental conditions could cause release of loosely bound mercury from the iron monosulfides, carbonates of
iron and manganese (Lechler et al., 1997; Filgueiras et al., 2002; Bloom et al., 2003). Hence F1 and F2 are more
mobile and bioavailable than any other forms and can be transported by natural processes later made available for
methylation (Ullrich et al., 2001; Boszke et al., 2003). Studies on mercury fractionation was meagre in polar
ecosystems, hence comparison is very difficult. High percentage (7.8%) of F2 was noticed from mining areas
(Miller et al., 1995) whereas the mean value of the present study was high (20.47%). The mean value of F1 was
also comparably higher than the reported values (Kot and Matyushkina, 2003; Ramasamy et al., 2012).
Even though the total concentration was low, the bioavailable mercury bound to first and second fraction was
slightly high in the system. The cumulative percentage of these two fractions of Hg in the sediments was plotted
(Figure 5) and assessed based on the different risk assessment code (RAC) classes (Ramasamy et al., 2012; Navya
et al., 2015). Among the samples analysed, four samples (26% of the samples) are in very high risk (>50%) and
more than 52% of the samples are under high to very high risk class. This indicated the potential availability of
mercury for the biota as well as for the chemical and biological transformations like methylation in the system.
Figure 5 Percentage of first two easily available fractions of mercury in the sediments
Organic chelated mercury (F3) fraction was the second smallest among the five fractions. This fraction is mainly
influenced by the presence of organic matter. The mercury bound to organic ligands like humic and fulvic acids,
amino acids etc. through reduced sulphur species (Xia et al., 1999). Oxygen and nitrogen atoms can also act as
binding sites for mercury (Hesterberg et al., 2001). Apart from this a very small amount of mercury associated
with living and dead biota and methyl mercury can also found in this fraction (Bloom et al., 2003; Ramasamy et
al., 2012; Navya et al., 2015). The methylation potential is high for F3 compared with F4 and F5 (Frohne et al.,
2012). The sediments of Kongsfjorden have low F3 content and such transformations may comparatively less.
However at the same time bioavailable fractions are high.
Mercury bound to sulphide (F5) fraction is normally not available for methylation. The F5 fractions showed a
very low concentration in Kongsfjorden sediments. However, if conditions become aerobic ionic mercury could
be released and which in turn can undergo methylation (Ullrich et al., 2001; Boszke et al., 2003). The reducing
conditions favours the mercury bound to sulphide fraction in aquatic sediments (Lechler et al., 1997; Beldowski
and Pempkowaik, 2003). This fraction generally represents the residual Hg and the presence of Hg sulphide in
sediments is normally related to natural occurrences of the metal (Lechler et al., 1997). Hence it is evident that the
mercury present in the sediments was of anthropogenic origin.
The fractionation results showed that more mobile fractions are there in the outer fjord, however a few samples
from inner fjord also showed the presence of mobile fractions. This might be due to the deposition of mercury
through melted water from glaciers. Grain size may also play a vital role in the adsorption of mercury as it is
evident from the sites 12 (very near to glacier) and 14 (very near to the stream mouth) where coarse sediments
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