than for L. perenne, but additional datawould be necessary to draw conclusions
on this.
To infer on the possible accumulation of Hg in plant tissues,
bioaccumulation factors (BAFs, i.e. the root/soil and shoot/soil
concentration ratios for IHg and OrgHg) were calculated (Fig. 4).
The BAFs for IHg varied between 0.030 and 2.2 with mean of 0.49
and median of 0.39 (for roots) and between 0.010 and 1.1 with
mean of 0.19 and median of 0.080 (for shoots). With the exception
of 3 samples (BAFs: 1.2–2.2), the BAFs for IHg were always lower
than 1 suggesting that there is no accumulation of IHg in roots nor
in shoots, relative to soil concentrations.
From Fig. 4 it is clear that the BAFs for IHg in roots and shoots are not
constant. It was possible to establish a clear and significant relationship
between the variation of BAFs of IHg in shoots and the variation of IHg
concentrations in both soils and roots, by linear regression analysis
(Rodrigues et al., 2012b) as described by the following regression