Determination of Potentially Toxic Metals in Mangrove Trees and Associated Sediments Along Saudi Red Sea Coast

Abstract

Monitoring and surveillance of mangrove ecosystem are highly significant, especially in the coastal zones; which receive heavy metal pollutants from the anthropogenic activities. Thus, the determination of toxic metals (Zn, Mn, Cu, Cr, Ni, Pb, Co and Hg) in Avicennia marina ecosystem along the Saudi Arabian Red Sea coast was addressed. to evaluate the level of concentration of the investigated heavy metals. To evaluate the level of concentration of the investigated heavy metals, surface sediment samples as well as roots and leaves were collected from Al-Birk, Almazilif, Jeddah, Zahban, Thuwal Island, Rabigh-I, Rabigh-II, Masturah, Yanbu, and Duba between March and June 2021. The following sequential average concentrations of several trace elements were determined: Mn (258.16±127.06µg g-1) > Cr (51.48 ±16.01 µg g-1) > Zn (39.34 ±17.82 µg g-1) > Ni (30.42±17.88 µg g-1) > Cu (29.51 ±13.62 µg g-1) > Co (11.31±6.95 µg g-1) > Hg (0.98 ±0.20 µg g-1), respectively. While, the higher PETs of Zn (84.19 µg g-1), Mn (495.20 µg g-1), Ni (67.08 µg g-1), and Co (27.41 µg g-1) were greater at the Rabigh-II site. According to the Cd readings, 10% of the sites were moderately contaminated (Cd = 7), while 90% were highly contaminated (Cd = 14). Indices used in ecological risk assessments correlate with the Igeo index. Pb (0.61) > Cu (0.44) > Ni (0.33) > Cr (0.32) > Zn (0.31) > Mn (0.22) > Hg (0.15) > Co (0.11) was the descending average BAF for mangrove leaves, while Pb (0.31) > Ni (0.29) > Cu (0.26) > Hg (0.24) > Cr (0.21) > Zn (0.17) > Co (0.11) > Mn (0.11) was the descending average BAF for roots. This study demonstrated the possibility of developing a framework for managing the Red Sea coast of Saudi Arabia's coastal marine ecosystems.