THE IDENTIFICATION OF POINT SOURCES OF HEAVY-METALS IN AN INDUSTRIALLY IMPACTED WATERWAY BY PERIPHYTON AND SURFACE SEDIMENT MONITORING

Periphyton and sediment samples were collected from 12 stations along Bayou d'Inde, a very polluted waterway, in Southwestern Louisiana. The samples were analyzed for Zn, Cu, Pb, Ni, Fe, Cr, Al, Cd, and Ag. When metal concentrations in periphyton or sediment are plotted vs sampling station, the metal distributions clearly indicate a major point source of metals at one station which is located at the mouth of an industrial ditch. Metal levels in periphyton generally parallel those found in surface sediments at the same location, but metal levels in periphyton are generally higher than in sediment from the same location, indicating an enrichment over sediment values. For sediments two types of extraction were investigated using leaching with concentrated HNO3 in a high-pressure decomposition vessel and shaking with 1 N HCI for 2 hr. Both methods correlate well for all metals except Ni, but HNO3 extracted more total metal. Correlations between periphyton and sediment were best for Pb, Fe, and Ag. Poorest correlations were seen for Mn, Ni, and Cd. When periphyton and sediment metal concentrations were normalized to Fe, Mn, and Al, correlation factors for some metals improved while others deteriorated.