Relationships Between Heavy Metal Concentrations in Japanese Knotweed (Reynoutria Japonica Houtt.) Tissues and Soil in Urban Parks in Southern Poland

This study focuses on the concentrations of trace elements and macroelements in soils, leaves, stems, rhizome and seed of Reynoutria japonica in 5 urban parks with different levels of disturbance (high, medium, low). The sampling locations within each park were chosen along river banks or forest edges. The soil samples were taken only in the humus horizon which averaged about 15 cm in thickness. Concentrations of Ca, Mg, K, Na, Fe, Al, Zn, Cd, Pb, P, S, Cr, Cu and Ni in plant material and soil were analyzed. The orders of average heavy-metal abundances found are Zn>Cu>Pb>Cr>Ni>Cd in leaves and Zn>Cu>Pb>Ni>Cr>Cd in a park soils showing a high levels of disturbance. In cases of low disturbance levels, the orders of average abundances for leaves are Zn>Cu>Cd>Ni>Pb>Cr and, for soil, Zn>Cr>Ni>Pb>Cu>Cd. The highest enrichments noted for Zn in topsoil was about 581.2 mg/kg in soil and, in leaves, 594 mg/kg. On all of the sites, both in the case of soil and plant materials, Zn was a dominant element and its concentration ranged from 44.6 to 581.2 mg/kg in soils and from 38.6 to 541.7, leafs (38-594 mg/kg), stems (115.8 -178.4mg/kg). The lowest concentrations of Cd (0.14-0.21 mg/kg, Cu (5.9-6.9 mg/kg) and Ni (4.6-14.5 mg/kg) in soil were observed in a parks with low levels of disturbance. Similar patterns of regularity were also observed in leaves, stems and rhizome. Different concentrations of metals in each park result from the degree of diversity of the parent rocks on which soil was formed. In the case of soil material transported from elsewhere, the concentrations of heavy metals are higher than in soils formed from local rocks. In a park located near a road, the concentrations of metals found also reflect traffic emissions and other sources of pollution. The results showed that R. japonica has a high capability to accumulate heavy metals. The stems contain more accumulated Zn than leaves, seed and rhizome.