Influence of mangrove forestation on heavy metals accumulation and speciation in sediments and phytoremediation capacity of mangrove species of an artificial managed coastal Lagoon at Xiamen in China

This study investigates the heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb) accumulation and speciation in the mangrove and lagoon sediments in the Yundang Lagoon. This also investigates the phytoremediation capacity of the mangrove species in the forestation areas. The result showed that significantly (P < 0.05) higher amount of organic carbon in the mangrove forestation sediments than lagoon sediments. Mangrove forestation increased the accumulation of Cr, Mn, Cu, As, and Zn in the mangrove sediments than lagoon sediments. According to chemical speciation, it revealed that acid-soluble fraction decreased and oxidisable fraction increased in the mangrove sediments than lagoon sediments. Cu, Ni, Cr, and As has considerably increased in oxidisable fraction, and Cd and Pb have increased in the reducible fraction in the mangrove sediment. The bio-concentration factor and translocation factor values indicate that these species of mangroves are not efficient accumulators of heavy metals from the surrounding environment but potential metals translocators. These results suggest that mangrove forestation can increase the circulation of heavy metals resulting in stabilise the polluted environment. Moreover, this study suggests that mangrove forestation has enhanced metals accumulation but decreased their bioavailability and mobility in the sediment.