AI Article Synopsis
- Mangrove sediments modify how metals behave after they settle, acting like natural biogeochemical reactors.
- The study aimed to analyze how various metals (like Fe, Mn, and Cu) are distributed in the sediments and water of Can Gio Mangrove, while also evaluating the ecological risks using a Risk Assessment Code.
- Results showed that most metals originated naturally, likely from upstream soils, and that organic matter in the mudflat influenced metal behavior; manganese posed the highest risk to the ecosystem, highlighting the need to protect mangrove forests from destruction.
Article Abstract
Mangrove sediments act as natural biogeochemical reactors, modifying metals partitioning after their deposition. The objectives of the present study were: to determine distribution and partitioning of metals (Fe, Mn, Ni, Cr, Cu, Co and As) in sediments and pore-waters of Can Gio Mangrove; and to assess their ecological risks based on Risk Assessment Code. Three cores were collected within a mudflat, beneath Avicennia alba and Rhizophora apiculata stands. We suggest that most metals had a natural origin, being deposited in the mangrove mainly as oxyhydroxides derived from the upstream lateritic soils. This hypothesis could be supported by the high proportion of metals in the residual fraction (mean values (%): 71.9, 30.7, 80.7, 80.9, 67.9, 53.4 and 66.5 for Fe, Mn, Ni, Cr, Cu, Co, and As respectively, in the mudflat). The enrichment of mangrove-derived organic matter from the mudflat to the Rhizophora stand (i.e. up to 4.6% of TOC) played a key role in controlling metals partitioning. We suggest that dissolution of Fe and Mn oxyhydroxides in reducing condition during decomposition of organic matter may be a major source of dissolved metals in pore-waters. Only Mn exhibited a potential high risk to the ecosystem. Most metals stocks in the sediments were higher in the Avicennia stand than the Rhizophora stand, possibly because of enhanced dissolution of metal bearing phases beneath later one. In a context of enhanced mangrove forests destruction, this study provides insights on the effects of perturbation and oxidation of sediments on metal release to the environment.
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| http://dx.doi.org/10.1016/j.chemosphere.2018.11.163 | DOI Listing |
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