Abstract
In order to make clear the influence of detergents on phosphorous loadings to a large river, quantities of water soluble phosphate in the Nagara river and their seasonal variations were studied.
Results are summarized as follows;
1. Amounts of soluble phosphate transported through the Nagara river to Ise Bay varies with seasons. The phosphorus loading is greater from summer to autumn and decreases rapidly towards winter, and reaches a nearly steady state, 350-380 kg/day of phosphorus expressed as P, and the values in winter are only 13-36% of those in summer.
2. In May-September period, 610-690 kg/day of phosphorus as P, over 64% of total loading of phosphorus to the Nagara, sometimes 2, 000 kg/day (over 85%) is loaded to the river by fertilizer and organophosphorus agricultural chemicals in the run off from plowlands in the catchment area of the Nagara river system but phosphorus loading by detergents is less than 8.4-9.4% of total phosphorus loadings.
3. In the Nagara, the amount of phosphorus supplied from effluents of the sewage disposal plants is more than twice the amount from laundry waste water.
