Background and Purpose: The concentration of heavy metals in the environment has increased due to, among other reasons, the influence of human activity. An increase in concentration is not at the same level for all metals and depends mainly on the amount and the way of transmission, aswell as the source of pollution. The way that any heavy metal moves within an ecosystem depends on the biogeochemical cycle. There are a number ofways of circulation between the atmosphere, hydrosphere, geosphere and biosphere. The transmission of heavy metals can be observed through atmospheric flows in the form of gases as well as sedimentation of dry and wet deposits in the forest ecosystem.
Materials and Methods: The following heavy metals were monitored:
lead (Pb) copper (Cu), zinc (Zn) and cadmium (Cd). Sampling was performed by means of funnels (throughfall) and the amount of precipitation was measured in rain gauges with a surface opening of 60 cm2. Rain gauges and funnels were placed diagonally by 6–9 items, each on 30x30m plot. On a control plot, where the impact of vegetation was excluded, funnels (bulks) were placed in a random order or circularly. Plastic zero tension lysimeters were placed in the soil at the depth of 20 cmor beneath the humus layer and in mineral part of the soil at the depth of 100 cm. They collected the seeped
liquid (seepage) in the soil. Sampling was carried out once a month. According to data obtained by monitoring, our forests and soils absorb more deposited heavy metals (wet and dry sedimentation) compared to the control samples in the open area.
Results: Concentration of lead and cadmium in some samples in lysimeters at a depth of 10 cm was increased and according to drinking water standards in Croatia (Pb>2.0 μgL–1, Cd>0.20 μgL–1) was t0o high. In lysimetric liquids, a slightly increased amount of heavy metals was observed. The average content of cadmium in lysimeters (spring, summer and autumn) was 0.13–0.36–0.37 μgL–1, lead 4.3–4.2–5.1 μgL–1, copper 3.3–5.3–4.6 μgL–1, zinc12.7–8.9–17.6 μgL–1, respectively.
Conclusions: The forest ecosystems of Pedunculate oak and common
hornbeam, with its bio-mass surface, allow increased dry deposition of substances which, by means of precipitation, become leached through tree-crowns. These results are in agreement with other investigations (Bretchel,1989; Van Breemen at al. 1988; Lindberg at al.1988;) which demonstrate that the deposition under forest tree-crowns is greater than in a open space, away from the influence of vegetation. This influences forest soils and soil solution in forest soils. There was an increased input of heavy metals intoour forest ecosystem at all monitored sites. At control locations (bulks), where impact of vegetation is excluded, the amounts of heavy metals are always lower. On the basis of these investigations it can be concluded
that problems of constant accumulation of heavy metals in soils are present in the region of lowland forests. In this processthe types of soil play a significant role in buffering deposition substances which fall as precipitation
