Accumulation of Heavy Metals in the Urban Soils of Natural Monument “Bunardzhik” (Plovdiv, Bulgaria)

Progressing urbanization makes soils structurally altered and that results in their degradation, so we aimed to analyze the content of some heavy metals in urban soils of the park zone of Natural monument “Bunardzhik”, situated in the real center of the city of Plovdiv (Bulgaria). Soil samples were collected from the surface layers of urban soils located to the Western and Eastern park zones of the Bunardzhik Hill, according to transects starting from the main communication routes. Soil content of As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sr, V, U, Zn was determined by inductively coupled plasma–mass spectrometry (ICP–MS). The content of V, Mn, Cr, Cu, Zn and Pb is noticeably reduced in the Western park zone (p<0.05), leaving from the route and reaching the middle of the park zone. Urban soils from the Eastern park zone are more polluted and there no significant decreases in their content with increasing the distance from the main road artery have been found. All studied heavy metals and toxic elements could be arranged as follows: Mn (436 mg/kg) > Zn (81 mg/kg) > V (40 mg/kg) > Pb (39.7 mg/kg) > Sr (38.3 mg/kg) > Cu (31.3 mg/kg) > Cr (23.7 mg/kg) > Ni (22.0 mg/kg) > As (3.3 mg/kg) > U (1.9 mg/kg) > Cd (0.36 mg/kg) in the Western park zone and Mn (552 mg/kg) > Zn (84 mg/kg) > V (62 mg/kg) > Pb (52.3 mg/kg) > Cr (36.3 mg/kg) > Sr (33.7 mg/kg) > Cu (28.7 mg/kg) > Ni (28.3 mg/kg) > As (6.0 mg/kg) > U (3.1 mg/kg) > Se (1.6 mg/kg) > Cd (0.55 mg/kg) > Hg (0.23 mg/kg) in the Eastern park zone, respectively. The results obtained for the two studied park zones allow for their use for recreational purposes but some exceedance of the precautionary limits should be adressed.