Heavy metal accumulation by roadside vegetation and implications for pollution control

Abstract

Vehicular emissions cause heavy metal pollution and exert negative impacts on environment and roadside vegetation. Wild plants growing along roadsides are capable of absorbing considerable amounts of heavy metals; thus, could be helpful in reducing heavy metal pollution. Therefore, current study inferred heavy metal absorbance capacity of some wild plant species growing along roadside. Four different wild plant species, i.e., Acacia nilotica L., Calotropis procera L., Ricinus communis L., and Ziziphus mauritiana L. were selected for the study. Leaf samples of these species were collected from four different sites, i.e., Control, New Lahore, Nawababad and Fatehabad. Leaf samples were analyzed to determine Pb2+, Zn2+, Ni2+, Mn2+ and Fe3+ accumulation. The A. nilotica, Z. mauritiana and C. procera accumulated significant amount of Pb at New Lahore site. Similarly, R. communis and A. nilotica accumulated higher amounts of Mn, Zn and Fe at Nawababad and New Lahore sites compared to the rest of the species. Nonetheless, Z. mauritiana accumulated higher amounts of Ni at all sites compared with the other species included in the study. Soil surface contributed towards the uptake of heavy metals in leaves; therefore, wild plant species should be grown near the roadsides to control heavy metals pollution. Results revealed that wild plants growing along roadsides accumulate significant amounts of heavy metals. Therefore, these species could be used to halt the vehicular pollution along roadsides and other polluted areas.

Fig 1. Heavy metal accumulation in different wild plant species growing on roadside in a heavy automobile emission area, means sharing same letters are statistically non-significant (p>0.05).

Fig 2. Iron accumulation in in different wild plant species growing on roadside in a heavy automobile emission area, means sharing same letters are statistically non-significant (p>0.05).

Fig 3. Heavy metal concentrations (mg/g dry weight) in the soil at various sites along Faisalabad-Jhang road.

Fig 4. Physiological attributes of different wild plant species growing on roadside in a heavy automobile emission area.