Assessment of Heavy Metals Concentration in Mangroves Leaves of the Red Sea Coast of Yemen

The present research work focuses on the concentration of Pb, Cd, Cr, Ni, Co, Cu, Zn, Mn, Mg and Fe in mangrove leaves. Samples were collected seasonally at five locations on Yemeni Rea Sea coast: Al-Salif, Al-Urj, Al-Hodeidah, Yakhtol, and Ghorairah, during the months of January, April, August and October 2013, which are chosen to represent the four seasons of a full year. Atomic Absorption Spectroscopy techniques were used to determine concentration of heavy metals in the samples, which extracted using Acid digestion methods. The results showed that heavy metals concentrations (µg/g) in mangrove leaves were in the following order: Mg (987.5-1,743.7) > Fe (201.0-486.0) > Cu (10.2-25.6) > Zn (13.2-23.1) > Mn (8.6-19.1) > Ni (1.9-4.8) > Cr (1.2-3.9) > Co (0.4-2.6) > Pb (ND-3.5) > Cd (ND-0.5). The levels of studied metals in mangrove leaves were comparable with corresponding in other less polluted areas of the world. Concentration of these metals in mangrove leaves were lower than the permissible limits as recommended by WHO, except Mg, Cu, Cr, Pb, and Cd. Relatively high metals concentration at Al-Hodeidah could be due to increasing anthropogenic activities in the vicinity of the site, whereas at Ghorairah may be attributed to the potential contaminants that carried by water currents coming from the Gulf of Aden, through Bab-el-Mandeb Strait. Al-Salif and Yakhtol found to be not polluted by these metals. This might be due to limited influence of anthropogenic activities at these two sites. Higher heavy metals concentration during spring and summer may be associated with increasing biological activities, land run off and rainfall during these seasons. Continuous monitoring of these metals in mangrove habitats to avoid being overcome permissible limits. These findings could be used as database toward future ecological studies, conservation and sustainable management of the Yemeni mangrove habitats located in the Red Sea Coast.