Zinc contamination in surface water of the Umeda River, Japan

Abstract

Due to the adverse effects of zinc (Zn) on the aquatic organisms, environmental quality standards (EQS) for zinc of 0.03 mg/L in surface water has been enacted in Japan since 2003. However, “zinc elevated sites” persist, including Aichi Prefecture. This study aims to assess the spatial and temporal variability of zinc contamination for 14 months in surface water of the Umeda River, Aichi Prefecture. The water samples were analyzed using Flame Atomic Absorption Spectrometry. The zinc concentrations tended to be higher in a downstream direction. The concentration means of nine sampling stations in surface water in August 2019 to July 2020 varied from 0.011 to 0.031 mg/L. The annual mean concentration value has already exceeded the EQS. Meanwhile, the yearly concentration means of the industrial wastewater were 0.036 to 0.079 mg/L, lower than the National Effluent Standards of 2 mg/L in Japan. All sampling points had relatively high concentrations ranged from 0.021 to 0.062 mg/L in February during the winter season. The reduced precipitation causing low river discharges might consequently elevate the zinc concentrations. The total zinc load at the most downstream section was approximately 0.012 t/km2/year. According to this study, the Umeda River has been affected by anthropogenic activities.