Secondary substances from NOx of the upper reaches of the Takahashi River, Okayama Prefecture

Abstract

Secondary NOx concentrations in the upper reaches of the Takahashi River in Okayama Prefecture were investigated, and O₃ concentrations averaged 24.0 ppb, 0.87 times that of Tokyo Tower. The high O₃ concentration was attributed to transboundary pollution from the Asian continent. The NO₃^- concentration in the stream water was 5.68 micromol/L. Although the NO₃^- concentration in the stream water was time-representative, this catchment was dominated by cedar, cypress, and sawara plantations (89.8%).