Heavy metals concentration in mangrove tissues and associated sediments and seawater from the north coast of Persian Gulf, Iran: Ecological and health risk assessment

Abstract

We evaluated the concentration of copper (Cu), zinc (Zn), mercury (Hg), nickel (Ni), chromium (Cr), vanadium (V), and cobalt (Co) in the mangrove tissues (leaf and root) and adjusted sediments, as well as seawater samples in the north coast of the Persian Gulf from three counties (Mahshahr, Bord Khun, Asaluyeh). Assaluyeh and Mahshahr were selected because of their proximity to the oil and petrochemical industries and Bord Khun was considered for being away from pollution sources. The metal detected in highest concentration in mangrove leaves and roots was Cu (Asaluyeh: 1.507 μg/g and 1.198 μg/g, Bord Khun: 1.812 and 1.756 μg/g, and Mahshahr: 0.880 and 1.617 μg/g, for leaves and roots, respectively). For sediments, Cr (among the metals) had the highest concentration (1.325 μg/g) in Asaluyeh, whereas in Bord Khun and Mahshahr Ni was predominant: 2.542 and 2.237 μg/g, respectively. For seawater, Cu was the most abundant metal and Hg was the one with the lowest concentration. The bio-concentration factor for Zn and Cu revealed that mangroves in the study areas have suitable potential for phytoremediation of these two metals. Translocation factors from the roots to leaves also indicated higher transportability for Zn and Cu through the plant tissues, compared to the other metals. Ecological indexes quantified the contamination of sediments and revealed a low level of heavy metal accumulation in sediments of the north of the Persian Gulf. Human risk hazards appeared low in all the areas under study. Gas and petrochemical activities can be considered as a potential source of the discharge of heavy metals into the aquatic environment.