Assessing Heavy Metal Accumulation in Urban Plants: Implications for Environmental Health and Traffic-Related Pollution in Al-Diwaniyah City, Iraq

This study aimed to compare the ability of five plant species, including (Conocarpus erectus, Acacia sensu lato (s.l.), Melaleuca viminalis, Dodonaea viscosa and Lantana camara) to absorb and accumulate heavy elements in their tissues, which were grown in the central islands in the city of Diwaniyah. This included areas of street in front of the medical college, Umm Al Khail First Street, Umm Al-Khail Street, near Abbas Attiwi Bridge, Al-Adly Street in the Euphrates District, and Clock Field Street, respectively. Results showed that soil samples S1 and S3 were contaminated by Pb, and the rest of the sites were contaminated with nickel only. This indicates through the table findings a rise in these heavy metals’ concentrations with a rise in traffic momentum. Thus, the Pb concentrations in the growing plants’ shoot parts with respect to this research had surpassed the allowed critical limit of 5.00 mg.kg-1 dry matter, in which the highest value was recorded at the site with respect to S3 as well as S2. Meanwhile, the findings indicate that Cd concentrations in S3 and S1 had increased and exceeded the allowable limit of 0.20 mg.kg-1 dry matter. In the meantime, the nickel concentrations were within the permissible limits of 67.90 mg.kg-1 dry matter. The Zn concentration exceeded the permitted limits of 60.00 mg.kg-1 dry matter except for plants (Acacia s.l. and Lantana camara) in sites S5 and S2. The results confirmed that the values of Heavy Metals Bioaccumulation Coefficient (BAC) for most of the study elements had recorded the highest value in the Dodonaea plant for Zn, Cd, and Pb, except for Ni. It was more accumulated in the Melaleuca viminalis plant, which indicates the superiority of the Dodonaea plant in accumulating Pb, Cd, and Zn over the rest of the study plants, as they took the following order: Lantana camara < Acacia s.l. < Conocarpus erectus < Melaleuca viminalis < Dodonaea viscosa. The best plants accumulated nickel in the following order: Acacia s.l. < Lantana camara < Conocarpus erectus < Dodonaea viscosa < Melaleuca viminalis.