ALTERATION OF TRACE-METAL GEOCHEMICAL CYCLES DUE TO THE MARINE DISCHARGE OF WASTEWATER

The coastal area investigated of southern California is adjacent to a densely populated, highly industrialized area that injects about 4 × 109l per day of wastewater into the adjacent coastal ocean. The wastewater contains large amounts of Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, Ag and Zn, primarily associated with the solids, which produce trace metal concentrations in the wastewater praticulates of two to three orders of magnitude greater than the natural marine sediment. The injection of this solid waste into the ocean causes large areas (on the order of 130 km2) of the marine sediment adjacent to the outfall systems to become heavily contaminated with trace metals. Less than 10% of the metals injected from the outfall are present in the contaminated marine sediment of the study area. The remaining 90% are either dissolved out of the waste solids suspended in seawater or transported out of the area by currents while still associated with the particulate matter. The effect on the global geochemical system due to wastewater discharge is not as extensive as on a local scale but is perhaps more important. The ocean injection of metals in municipal wastewater by man is now of the same order of magnitude as the injection of the metals by natural weathering. The global consequences of this are unknown; however while the natural rate of trace metal injection is constant, the anthropogenic contribution will increase with time. © 1979.