Investigation of heavy metal accumulation in plants growing in contaminated soils (Case study:Qazvin province, Iran)

Abstract

Environmental pollution with heavy metals is a global disaster that is related to human activities. This study was conducted to determine the extent of heavy metals accumulation by plant species in Lia industrial city (Qazvin, Iran) and to investigate the remediative capacity of native plant species grown in the contaminated soils. Soil and industrial wastewater sampling was done radially along transects with 300 m intervals from exit point of wastewater at three sites. In each sampling point, along 100 m transects within 5×2 m plots, the plant samples and soil samples were collected in depth of 0-20 cm and 20-40 cm from rhizosphere zone. Concentration of copper, zinc and chromium in root and shoot of 11 plant species, soil and wastewater were analyzed in three sits for mentioned metals. Bio Concentration factors and translocation factor were determined to ensure phytoremediation availability. Results showed that the concentrations of metals in the soil and wastewater greatly exceeded the threshold limit values. The contents of metals in soils ranged in the order of Cr>Zn>Cu and in wastewater were in the order of Zn>Cr>Cu, respectively. Results showed that Scirpus maritimus L. and Phragmites australis (Cav.) Trin. ex Steudel presented the highest accumulation of Zn, Cu and Cr in their root tissues which were suitable for phytostabilization (with a high BCF couple with low TF). The lowest extractable Zn (7.24 and 3.29 mgkg-1 for shoot and root respectively, BCF=0.07) and extractable Cu (2.56 and 2.80 mgkg-1 for shoot and root respectively, BCF=0.14) were related to Hordeum glaucum L. Moreover, the relatively lowest values of Cr were measured for Taraxacum officinale L. Results indicated that the species, which had low metal bioaccumulation in their roots and high TF, could play important roles for removal of heavy metals through phytoextraction.