Tree-ring records of the historic pollution along Novăţ river, Maramureş Mountains, (Romania)

Abstract

Mining activities cause heavy metal pollution of the water, the soil and the air in the affected areas. Metal toxicity, acidic pH and changes in soil structure are supposed to induce a stress on the riparian forest. Coniferous trees affected by this type of human-induced environmental stress react by producing different anatomical changes, commonly the abrupt radial growth decrease and traumatic resin duct production. By analysing growth anomalies formed in tree-rings, it is therefore possible to reconstruct retrospectively the dynamics of forest under environmental polluted, conditions.

On the 10th of March 2000 an ecological disaster occurred in Maramureş Mountains, Romania. A tailing pond of the Baia Borşa mines (district Maramures) burst after heavy precipitations and thawing. About 20 000 t of heavy metal contaminated sludge flooded along Novăţ and Vaser Valleys and then reached the rivers Vişeu and Tisa.

The 2000 event severely pollutes with heavy metals (As, Cd, Cr, Ni, Pb, Zn etc.) the soil and ground water in the riparian forest areas. Moreover, these trees were buried under toxic sediments left after the passage of the flood. Riparian forest stands along Novăţ river are mainly composed by Norway spruce (Picea abies (L) Karst.) trees. This tree species is known to have a high susceptibility to soil pollution, because of the shallow growing roots within the upper part of the soil profile. It has therefore a high potential for dendrochronological studies. In this mining area, so far relations between pollution events and the growth response of Norway spruce have not been tested.