THE EFFECTS OF RED CLAY EROSION ON ORTHOPHOSPHATE LEVELS IN SOUTHWESTERN LAKE SUPERIOR

Abstract

The effects of the erosion of red clay deposits along the northwestern Wisconsin shoreline area on orthophosphate inputs into Lake Superior was in­vestigated. Using clay soil and river particulate samples, exchange and leach­ing of orthophosphate in Lake Superior water was studied. The results indi­cate inputs of 240 metric tons of P04 from soil entering Lake Superior an­nually from shoreline erosion and 63 metric tons of P04 from river particulates. These values are affected by orthophosphate inputs from other sources in the area and microbial uptake. The clay exhibits a buffering effect on the aqueous system and a net removal of orthophosphate by suspended particulates may result in locations where high aqueous orthophosphate levels occur.