The fate of sewage phosphorus input to a subarctic lake chain

The subarctic iron-mining town of Schefferville, Quebec discharges some 6.6 t P annually from sewage into a lake chain. P concentrations in the receiving lake build up during the winter, ice-cover period and the lake waters become anoxic. Spring flushing is rapid and pronounced, and throughout the summer lake P concentrations remain relatively low. Iron-rich groundwater inflow to the lakes promotes sedimentation of P as Fe-phosphates in the spring when lake waters are re-oxygenated. Sedimentation in the receiving lake accounts for 80% of the annual sewage P load, and only 12% passes out of the three-lake chain studied.