C - Lublin

OUTPUT FLUXES OF LEAD IN FOREST ECOSYSTEMS:
SOME APPROACHES TO CALCULATING AND MAPPING
Priputina I., Mikhailov A., Abramychev A.
The input of heavy metals (HM) to terrestrial ecosystems is well known to be a
large scale environmental problem. Aerial deposition because of industrial
emissions is the dominant input of metals to forest ecosystems that can be resulted
in increasing of HM concentrations in the soils as well as in plants and ground
waters. Indications of adverse effects on biota dealt with high levels of metal
accumulation in forest soils are found in many areas in Europe (Curlik et al., 2000).
The methods of calculating of permissible levels of metal inputs to ecosystems
have been continuously developed since the mid of the 1990’s in the framework of
UN/ECE Convention on Long-range Transboundary Air Pollution (De Vries,
Bakker, 1998; UBA, 2003). Critical load approach is widely used under CLRTAP
to be based on steady-state mass balance equation of HM in soil layer. If internal
ecosystem fluxes of HM have been excluded from mass balance equation than
critical load can be accounted as a sum of the harmless metal outputs from the
ecosystem minus natural replenishment through weathering. The main outputs of
HM in forest soils are metal leaching with percolation waters and metal removal
because of growth biomass uptake (only wood biomass is considered). This paper
describes some approaches to calculating and mapping critical loads of Pb in
regional scale on the example of forest ecosystems located in the Centre of the
European Russia.
Leaching estimation. In accordance with (De Vries et al., 2002), metal output flux
from the soils with infiltration water regime can be calculated on the base of
following equation:
M le
= 10 * Q le
* [M] ss (1)
where: Mle – metal leaching from considered soil layer (usually, mineral topsoil),
[g/ha.yr]; Qle – flux of drainage water leaching from soil layer, [m/yr]; [M] ss –
metal concentration in soil solution, [mg/m 3 ]. The factor 10 is needed to convert
the unit from mg/m2.yr to g/ha.yr.
Metal concentration in soil solution ([M] ss ) which depends on main soil properties
(pH, h and clay) and metal concentration in solid phase are accounted using special
transfer functions (UBA, 2003). The results of calculating for the main soil types
from the background sites in the central Russia are presented in Table 1.
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