Translocation of Heavy Metals in Herbs under Urban Anthropogenic Pollution Conditions

Abstract

This study aims to examine the translocation of heavy metals from urban soils to herbs in Tyumen (Russian Federation). The mobile and acid-soluble heavy metal fractions in soils, as well as the heavy metal contents in plants, were determined by atomic absorption spectrophotometry. The bioconcentration factor was estimated as the ratio of the amount of heavy metals in soils to that in plants. Heavy metal concentrations in urban soils were higher than those at the control site by 20% and by up to 10 times. The greatest heavy metal accumulation in both soils and plants was found at the battery manufacturing and metallurgical plants, exceeding the control levels of Pb and Fe by 2–17 times. The Cu, Fe and Mn contents in soil were positively correlated with those in plants. Heavy metal translocation by the plants was species-specific. The percentages of the mobile heavy metal fractions decreased in the following order: Mn > Zn > Cu > Fe. Heavy metal accumulation in Poa pratensis, Trifolium rubens, Vicia cracca, Matricaria chamomilla and Tussilago farfara in the urban sites compared to that at the control site decreased in the following order: Fe > Zn > Cu > Mn > Pb > Cd. Tussilago farfara exhibited the highest Fe, Mn and Zn accumulation, which exceeded the control levels by 17, 5 and 3.5 times, respectively. The heavy metal bioconcentration factors, indicators of translocation, decreased in the following order: Cu > Zn > Cd > Pb > Mn > Fe. The heavy metal translocation suggests the need to relocate industrial facilities to areas outside the city. Future monitoring of the study area is needed to ensure its long-term ecological safety. • The heavy metal concentration in urban soils was elevated indicating ecological risk • Iron was the most accumulated metal in all examined plant species • Heavy metal translocation in coltsfoot was higher than that in the four herb species