ABSTRACT
Cities and industrialized areas were often installed in the proximity of salt marshes in estuaries and coastal lagoons. In these cases, flooding transports large quantities of contaminants in both dissolved and suspended particulate forms to the salt marsh areas. Anthropogenic metals are incorporated in the sediments, decreasing their availability in the water column. Several studies have proposed that salt marshes act as natural sinks for metals (10-12). However, a number of factors may cause postdepositional mobilization of metals from industrial and urban origin. Diagenetic reactions related to oxidation of organic matter that usu ally occurs in high levels in salt marshes and oxidation of metal sulfides in the rooting zone (13) lead to the mobilization of metals. Complex interactions be tween salt marsh plants and sediments result in the redistribution of metals in the sediment-root system (14). Metals are taken up by the roots and translocated to the above-ground parts of the plants; when the plants die the biosynthesized organic matter is oxidized and the metals returned to the sediments. Since roots accumulate larger quantities of metals (15,16), the interactions between below ground biomass and sediments are extremely effective and may have a strong influence on the form and concentrations of metals in the rhizosphere (7). Re moval or substitution of degradation products by the flooding water that perco-
lates the upper sediment layers during the flood tide (17) forces the export of material to the water column.
