Redox-induced Mobilization of Rare Earth Elements in Musa Estuary Sediment, Southwest of Iran

In aquatic environments, metals tend to sink into sedimentary beds, but under different redox conditions they might be released to the water column. Oxic and anoxic microcosm experiments were conducted using an automatic microcosm apparatus to investigate how redox potential (Eh) affects the release of rare earth elements (REEs) in an estuary sediment sample. Results indicated that REEs mobility increases in both oxic and anoxic conditions although the average amount of REEs mobilization was higher in oxic conditions than anoxic conditions. Lu and Sm were the most mobile elements while Ce showed the lowest amount of release. REEs release is influenced by a mix of controlling factors including dissolution of Fe-Mn oxyhydroxides, low pH condition, and increase in dissolved organic carbon (DOC) under anoxic condition. An increase in Eh caused a decreasing pH from 8.08 to 6.80 and increasing DOC from 18.93 to 425 mg/l which resulted in the release of REEs. Enrichment factors (EFs) revealed that Musa estuary is threatened with Ce, Dy, La, Nd, Pr, and Sm. The high ecotoxicology effects of soluble REEs calling for potential environmental risks in Musa estuary.

Mercury contamination in some marine biota species from Khuzestan shore, Persian Gulf

In this study, concentrations of mercury (Hg) were analyzed in some marine biota species (fish, shrimp, and crab) from Khuzestan shore, north part of the Persian Gulf. It was also our intention to evaluate potential risks to human health associated with seafood consumption. The results indicated that concentrations of Hg in the fish and crustacean were different among the species and tissues. Liver in fish and hepatopancreas in crustacean exhibited higher Hg concentration than the other tissues. The highest concentration of Hg was detected in Acanthopagrus latus liver (1.37 µg/g), followed by Labeo rohita (0.87 µg/g), Johnius belangerii (0.79 µg/g), and Barbus grypus (0.69 µg/g), respectively. Also the highest Hg concentrations were detected in shrimp species, Penaeus semisulcatus hepatopancreas (0.95 µg/g), followed by blue crab Portunus pelagicus (0.76 µg/g) and Metapenaues affinis (0.64 µg/g), respectively. The comparison indicated that benthic species were more contaminated than were other pelagic species. The results indicated that highest concentrations of Hg between different stations were detected in Musa estuary. The Hg concentration in all species were low than standards, expect in A. latus and P. semisulcatus collected from Musa estuary (S4). The variation in Hg levels among the species is likely to have resulted from metal bioavailability, changes in tissue composition, habitat,s and locations.