Evaluation potentiality of Rhizophora mucronata plantation for pollutants remediation on the Red Sea Coast, Egypt

Abstract

AbstractThe planted Rhizophora mucronata was evaluated in two plant ages (one year and eight years) as a biological tool for reducing the mobility of heavy metals in sediments in Safaga and Hamata, Red Sea Coast, Egypt. It is an important region for tourism and nature reserves; however, this area suffers from various anthropogenic contaminants. The ability of mangrove plantations to reduce sediment contamination through bioaccumulation, phytostabilization, or phytoextraction must be clarified through the investigation of metal behavior in mangrove plants and sediments. All of the studied heavy metals had significantly higher concentrations in the Safaga site's sediments. Elder plants had much lower levels of heavy metals in their sediments than younger plants, also rhizosphere samples were less contaminated than non-rhizosphere ones. The order of remediation efficiency was Mo > Ni > Mn ≥ Co > Al > Cu > Zn ≥ Cr > Fe > V, where the highest % was 99.25, 58.97, 42.64, 42.48, 41.91, 39.47, 37.93, 37.01, 36.89, and 29.44, respectively. R. mucronata parts were more significantly contaminated with Co, Cr, Cu, Mo and Zn in Safaga site, while at the Hamata site, they were more significantly contaminated with Al, Fe, Mn, Ni, and V. The elder plants accumulated higher concentrations than younger ones and the contents of heavy metals in plant samples followed the order of root > aerial roots > shoot. Bioconcentration factor (BCF) values representing the accumulation efficiency of R. mucronata were Ni > Mo > Zn > Cu > Cr > Co > Mn ≥ Al > V > Fe, where their highest values were 17.74, 7.89, 3.95, 3.84, 2.66, 1.91, 1.67, 1.66, 1.6, 1.18, respectively. BCF values exceeded one for all metals and values of translocation factor (TF) were less than unity in all cases, thus Rhizophora mucronata can be considered as a good phytostabilizer of ten studied heavy metals able to reduce their mobility through accumulation by roots, thereby reducing off-site contamination.