138
Basile et al. 2012; González and Pokrovsky 2014), which leads to the increase of
their intracellular concentration independent of the previously existent intracellular
concentration (González and Pokrovsky 2014). There are numerous sources and
factors that can influence the contents of heavy metals in bryophytes. Metals from
the atmosphere can reach the surface of terrestrial bryophytes in solution (precipitation) or in the form of dry deposition that can later be solubilized or washed away
(Fernandez et al. 2012; Stankovic et al. 2018). Even though terrestrial bryophytes
take most of the substances from the atmosphere, soil dust particles contribute significantly to some toxic metal contents (Berg and Steinnes 1997). The bioavailability of the elements and their mobility in soil are significantly correlated to the
concentration of the hydrogen ions in soil solution, the organic compounds, and the
chemical composition (Salemaa et al. 2004). Windblown particles from the ground
containing heavy metals can also influence the amounts of heavy metals in bryophytes (Berg and Steinnes 1997; Salemaa et al. 2004). The retention of these particles on moss surface depends on the particle size and the surface structure
(Salemaa et al. 2004; Stankovic et al. 2018). Metal transport from soil to bryophyte
depends mainly on the local climatic conditions (Salemaa et al. 2004). Besides
these, other sources, such as natural trace element cycling processes and leaching
of the heavy metals that were previously accumulated in vascular plants through
their root system, may also contribute to the heavy metal content in bryophytes
(Salemaa et al. 2004; Stankovic et al. 2018). Water also has a significant role in the
heavy metal uptake by bryophytes. For the aquatic bryophytes, it is their living
environment and the primary source of all the minerals, including the heavy metals
(Salemaa et al. 2004). In the case of terrestrial bryophytes, water can bring or dissolve particles that are already deposited on the bryophyte surface facilitating the
uptake of heavy metals by the plant, but it can also wash out the deposited pollutants and lower down the uptake of these elements (Fernandez et al. 2007). The
quantity, intensity, and duration of the precipitation determine the amount of accumulated and leached heavy metals from the terrestrial bryophytes. Leaching can
significantly influence the uptake of almost all investigated heavy metals. While the
uptake efficiencies for metals such as Pb and Ni remain generally stable, leaching
process may influence the uptake efficiencies for metals such as Cd, Cu, and Zn or
even be a dominant factor in the case of Mn and Cr. The chemical composition of
the medium in contact with the bryophyte surface dominantly influences which
heavy metal and what amount of it is going to be absorbed and retained by the plant.
Different heavy metals differ in their affinities for the binding sites of the cell walls
of bryophytes (Rühling and Tyler 1970), indicating that competition effects may
significantly alter the uptake kinetics of a specific heavy metal (Wolterbeek 2002;
Stankovic et al. 2018).
The concentrations of metals in the environment are usually not high enough to
cause the occupation of the majority of the extracellular exchange sites. Conversely,
the concentration of protons in strongly acidic environments is high enough and
may prevent the binding of different heavy metals by bryophytes or even lead to the
leaching of different heavy metals from their cell wall (Salemaa et al. 2004). Wells
and Brown (1987) have shown that in the moss Rhytidiadelphus squarrosus (Hedw.)
B. Balabanova et al.
Basile et al. 2012; González and Pokrovsky 2014), which leads to the increase of
their intracellular concentration independent of the previously existent intracellular
concentration (González and Pokrovsky 2014). There are numerous sources and
factors that can influence the contents of heavy metals in bryophytes. Metals from
the atmosphere can reach the surface of terrestrial bryophytes in solution (precipitation) or in the form of dry deposition that can later be solubilized or washed away
(Fernandez et al. 2012; Stankovic et al. 2018). Even though terrestrial bryophytes
take most of the substances from the atmosphere, soil dust particles contribute significantly to some toxic metal contents (Berg and Steinnes 1997). The bioavailability of the elements and their mobility in soil are significantly correlated to the
concentration of the hydrogen ions in soil solution, the organic compounds, and the
chemical composition (Salemaa et al. 2004). Windblown particles from the ground
containing heavy metals can also influence the amounts of heavy metals in bryophytes (Berg and Steinnes 1997; Salemaa et al. 2004). The retention of these particles on moss surface depends on the particle size and the surface structure
(Salemaa et al. 2004; Stankovic et al. 2018). Metal transport from soil to bryophyte
depends mainly on the local climatic conditions (Salemaa et al. 2004). Besides
these, other sources, such as natural trace element cycling processes and leaching
of the heavy metals that were previously accumulated in vascular plants through
their root system, may also contribute to the heavy metal content in bryophytes
(Salemaa et al. 2004; Stankovic et al. 2018). Water also has a significant role in the
heavy metal uptake by bryophytes. For the aquatic bryophytes, it is their living
environment and the primary source of all the minerals, including the heavy metals
(Salemaa et al. 2004). In the case of terrestrial bryophytes, water can bring or dissolve particles that are already deposited on the bryophyte surface facilitating the
uptake of heavy metals by the plant, but it can also wash out the deposited pollutants and lower down the uptake of these elements (Fernandez et al. 2007). The
quantity, intensity, and duration of the precipitation determine the amount of accumulated and leached heavy metals from the terrestrial bryophytes. Leaching can
significantly influence the uptake of almost all investigated heavy metals. While the
uptake efficiencies for metals such as Pb and Ni remain generally stable, leaching
process may influence the uptake efficiencies for metals such as Cd, Cu, and Zn or
even be a dominant factor in the case of Mn and Cr. The chemical composition of
the medium in contact with the bryophyte surface dominantly influences which
heavy metal and what amount of it is going to be absorbed and retained by the plant.
Different heavy metals differ in their affinities for the binding sites of the cell walls
of bryophytes (Rühling and Tyler 1970), indicating that competition effects may
significantly alter the uptake kinetics of a specific heavy metal (Wolterbeek 2002;
Stankovic et al. 2018).
The concentrations of metals in the environment are usually not high enough to
cause the occupation of the majority of the extracellular exchange sites. Conversely,
the concentration of protons in strongly acidic environments is high enough and
may prevent the binding of different heavy metals by bryophytes or even lead to the
leaching of different heavy metals from their cell wall (Salemaa et al. 2004). Wells
and Brown (1987) have shown that in the moss Rhytidiadelphus squarrosus (Hedw.)
B. Balabanova et al.