The distribution and variability of heavy metals in a mountainous fir forest ecosystem in two hydrological years

Abstract

The concentrations (for two hydrological years) of the heavy metals As, Cd, Cr, Ni and Pb as well as the isotopic 206Pb/207Pb composition in soil layers were studied in a remote mountainous Bulgarian fir (Abies borisii regis) forest in central Greece. The concentrations of metals in the hydrological cycle (bulk deposition and throughfall) were lower than the respective ones in the past in Europe, especially for Pb. In the litterfall consisting of mosses, lichens, insect frass and pollen the concentrations of all heavy metals were found far higher than those in the needle litterfall. An evidence of dry deposition was that all metals had higher concentrations in older needles than the young ones with the exception of Ni. Ni also had the highest concentration in the trunk wood, whereas all the other metals had a very low one. It is highly probable that Ni has an internal cycle within the fir trees. In all compartments of the standing trees the order of concentrations was Ni>Pb>Cr>Cd>As. The concentrations of metals in the ground vegetation were low with the exception of Cd, Cr and Ni in ferns. The concentrations of metals in the FH horizon and mineral soil followed the order Cr>Ni>Pb>As>Cd, whereas in the L layer Ni had the highest value. Despite the remoteness of the fir forest, the percentages of anthropogenic Pb in the soil reached an appreciable 41% in the FH horizon and lowered to 2% in the 20-40 cm layers.

Macro- and Microelements and the Impact of Sub-Mediterranean Downy Oak Forest Communities on Their Composition in Rainwater

“…Apart from Na, Mg, K, Ca, Fe, Co, Ni, and Sr, the other studied elements had concentrations in rainwater collected in the open area that were lower than in rainwater under the forest canopy. This confirms the fact that the leaf surface has the ability to trap solid particles [31,53].…”

“…However, information on the content of these components in precipitation under tree canopies is scarce. In previous studies, the contents of various elements such as Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, Sr, Ba, etc., in rainwater collected in open areas were considered [3,22,[30][31][32][33]. In this study, we analyzed the concentration of 17 elements in rainwater including Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, Sr, and Ba, which were collected in open areas and under forest canopies.…”