Discharge of metals from the St. Lawrence River

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Abstract
The concentrations of dissolved and total Al, Fe, Mn, Co, Ni, Cu, Zn, and Cd in St. Lawrence River water have been measured on a monthly basis over a 2 year period. Riverine suspended particulate matter was also analyzed for nondetrital Mg, Ca, Si, Al, Fe, Mn, Co, Ni, Cu, Zn, and Cd and detrital Mg, Ca, Si, Al, Fe, and Mn. Variability in the concentration of dissolved metals is unrelated to changes in water flow or suspended load. Particulate Al, Fe, Mn, and Zn concentrations are related to water flow. The metal/aluminum ratios of particulate Mn, Cu, Zn, and Cd are elevated with respect to crustal rocks or coastal marine sediments, with the enrichment occurring in the nondetrital, or weak acid soluble, fraction.Annual dissolved metal discharges and nondetrital and total particulate metal discharges that take into account monthly variations in metal concentrations have been calculated for the St. Lawrence River. These discharges have been used to estimate global annual river discharges of metals to the ocean. The calculated discharges are compared with estimates based upon other rivers. The importance of nondetrital particulate metal fluxes is emphasized.