Actions of PO₄^3-, Fe²⁺ and Al³⁺ of surface water in the region of the Inawashiro Lake

Abstract

Hot spring in the Inawashiro lake catchment contained high concentrations of Fe and Al ions and carried them down the stream. Fe and Al ions reached 40 and 55 mg/l respectively. However, most of Fe and Al ions were gradually precipitated with oxidation and increase of pH. As the same time, PO₄^3-in the river and the lake was thought to be precipitated as Fe and Al phosphates. In particular, Fe ions in the Nagase River were thought to be precipitated as Fe (OH) ₃ down the stream and then the deposit contained phosphorus. When the Nagase River flowed into the Inawashiro lake, Al ions change to Al (OH) ₃ and Al (OH) ₃ was thought to be precipitated with phosphorus in the lake. Therefore, PO₄^3- concentration was thought to be very low in the Inawashiro lake although the catchment was contaminated by fertilizer from rice field, orchard and house sewage.