AN ASSESSMENT OF METALS IN AN ESTUARINE WETLANDS ECOSYSTEM

Biotic and abiotic samples from two physically proximate, temperate, e stuarine Hackensack River wetlands (New Jersey) located in highly urba nized areas were analyzed for chromium (total and hexavalent), copper, and lead. The study was performed to determine if chromite ore proces sing residues (COPR) in fill material surrounding one of the two sites (i.e., the ''Study Site'') were associated with statistically signifi cant higher total chromium concentrations in the biotic media at the S tudy Site relative to the other site (i.e., the ''Reference Site''). C opper and lead concentrations were evaluated to determine whether othe r metals may have accumulated at the Study Site due to factors other t han COPR. Concentrations of the three metals were evaluated in samples of water, sediment, plant tissue (Phragmites root and shoot tissues), fish tissue (Fundulus sp. whole body tissue), and blue crab tissues ( Callinectes sapidus muscle and hepatopancreas tissues). Physical and c hemical characteristics of the two sites that could have influenced th e environmental fate and bioavailability of the metals were also evalu ated. Concentrations of each of the three metals were approximately an order of magnitude higher in sediment samples from the Study Site. Co ncentrations of ''total'' and ''dissolved'' metals, however, were simi lar between the water samples collected at the two sites. Tidal flushi ng of the Study Site was restricted by tidal gates, and the higher met al concentrations in the sediments were attributed to factors resultin g from the restricted tidal flushing. Statistically significant higher biota metal concentrations were found at the Study Site only for tota l chromium in blue crab hepatopancreas tissue and for lead in Phragmit es shoot tissue. Tissues from the Study Site contained statistically s ignificant lower concentrations of copper in all the biotic samples an d of lead in blue crab hepatopancreas tissue than corresponding tissue s from the Reference Site. Despite the Study Site sediments containing metal concentrations three to nine times greater than those in the Re ference Site's sediments, no pattern of higher metal concentrations in biotic samples from the Study Site was found. The metals, including t otal chromium, were tightly bound to the sediments and therefore not b ioavailable. Study Site sediment characteristics apparently limiting m etal bioavailability included high organic carbon content, reducing co nditions, high sulfide concentrations, high specific surface areas ass ociated with a high proportion of silt and clay components, and high c ation content.