Long-term changes of metal contents in two metallophyte species (Olkusz area of Zn-Pb ores, Poland)

The authors present the changes of the As, Cd, Fe, Mn, Pb and Zn contents in two plant-considered metallophytes: common bent Agrostis capillaris (blades) and birch Betula pendula (leaves and seeds), recorded in a Zn-Pb industrial region of Olkusz (Poland) in 1994 and 2014. The highest amounts of Cd (12 ppm) and Zn (2524 ppm) in the common bent occur in the vicinity of the mining and metallurgical works ‘Bolesław’ in Bukowno. However, these values are significantly lower than those in 1994: Cd by 87 % and Zn by 52 %. The highest contents of Fe (2674 ppm), Mn (130 ppm) and Pb (334 ppm) in this grass species are in the vicinity of the closed Olkusz mine. These contents have increased in comparison with the 1994 figures: Fe by 56 %, Mn by 120 % and Pb by 6 %. In the birch leaves, the metal contents averaged for four sites are the following: As 2.1, Cd 6.5, Fe 261, Mn 110, Pb 70 and Zn 1657 ppm, being lower from the figures in 1994. The highest As, Fe and Pb contents of birch leaves occur in the habitat closest to the former Olkusz mine, while those of Cd, Mn and Zn in the habitat distant at 100 m from the active plant in Bukowno. The common bent grass generates better resistance mechanisms against the metals than does the birch. In the birch leaves, the contents of the metals are significantly lower than those of the grass blades, but higher from those of the birch seeds collected from the same tree individuals. It is a proof of good functioning of the mechanisms preventing excessive metal amounts from the cell metabolism and of the presence of physiological barriers protecting birch seeds as the generative organs.