Basin Response to Detergent-Phosphorus Control in Southern Ontario

Abstract

The role of phosphorus in the cultural eutrophication of the lower Great Lakes has been the subject of intensive study and regulative action. Phosphorus reduction has been carried out primarily by reduction of phosphorus in domestic laundry detergent and by removal in sewage handling facilities. Consequently, reductions of phosphorus in point source drainage systems are commonly cited as 40–60%. The response of in-stream processes in whole drainage basins is less well known. River- mouth data for the period 1969–1974, for 78 point and nonpoint source drainage systems in southern Ontario, permit an evaluation of basin response to phased reduction in detergent phosphorus and to imposition of a 1 mg·l⁻¹ sewage effluent standard. It was postulated that diffuse source systems, which should reflect naturally occurring concentration/dilution effects, would provide an index against which to evaluate point source system response. However, phosphorus in nonpoint source drainage also underwent substantial reduction of up to 65% and 73% for total and soluble forms, respectively. Several alternative analytical procedures support the conclusion that reductions of phosphorus in detergent in Ontario has had a widespread beneficial effect that is not limited to those basins having point sources nor influenced by specific or unique land uses in nonpoint source basins.