Assessment of airborne heavy metal pollution using plant parts and topsoil

Robinia pseudoacacia L. (Fabaceae) was evaluated as a possible bioindicator of airborne heavy metal pollution, which originates from mining and pyrometallurgical copper production in Bor (Eastern Serbia). Concentrations of Cu, Zn, Pb, Cd, As and Hg were determined in different plant organs (washed/unwashed leaves, branches, roots) and topsoil of R. pseudoacacia by ICP-AES and by AAS. Sampling was carried out during 2008 at ten selected sites distributed in five zones with different levels of pollution. Concentrations of Pb, Cd and Hg did not exceeded the maximum allowed concentration (MAC) in soils at any of the sampling sites. Cu and As were present only at two sites within the MAC, whereas Zn exceeded the MAC at two sampling sites. Although present in the soil, As, Cd and Hg were below limit of detection in all parts of R. pseudoacacia. The rest of the studied elements, collected at the sites closest to the copper smelter or in the directions of the prevailing winds, were found to be at high levels. The higest Cu and Zn concentrations were detected in branches of R. pseudoacacia at the site Krivelj in the rural zone (6418.2±355.4 mg kg−1 and 4699.8±320.8 mg kg−1, respectively). Pb was present in similar amounts in all parts of R. pseudoacacia in the concentration ranging from 4.9±0.3 mg kg−1 (in washed leaves, at tourist zone) to 66.9±5.3 mg kg−1 (in roots, at urban-industrial zone). According to the mobility ratio, leaves and branches of R. pseudoacacia acted as excluders of Cu, Zn and Pb, except for the branches which acted as indicators of Zn. Although As is present in high concentrations in the air and topsoil of the examined area, results show that R. pseudoacacia is not a suitable indicator of environmental pollution with As.

Research highlights
► The highest level of heavy metals in soil and plant is in the urban-industrial zone.
► R. pseudoacacia is not a suitable indicator of airborne As, Cd and Hg pollution.
► According to the mobility ratio, leaf and branch acted as excluders of Cu and Zn.
► According to the mobility ratio branches acted as an indicator of Zn.
► Results showed Cu and Zn enrichment in branch and root due to copper production.