Isotope and chemical composition of monthly precipitation collected at Sapporo, northern part of Japan during 2015-2019

Abstract

The aim of this study is to measure tritium concentrations, δ2H, δ18O and ion concentration in monthly precipitation collected at Sapporo, the northern part of Japan and to understand the regional precipitation chemistry. Tritium concentrations of monthly precipitation in Sapporo from July 2015 to the end of 2019 ranged from 0.24 to 1.59 Bq/L with a mean value (±S.D.) of 0.68 ± 0.30 Bq/L. Tritium seasonal patterns were determined with higher tritium concentrations in spring and lower tritium concentrations in summer. It was higher than the reported values in the southern area of Japan. It seemed that tritium concentrations changed with the meteorological conditions depending on the air masses of continental or marine origin and the contribution of cosmogenic tritium from the upper atmosphere. The strong correlation was found between tritium concentrations and NO3− and NH4+ (p < 0.05). It is necessary to accumulate more data as to long-term monitoring for a reliable analysis of ambient tritium concentrations.