Nonanthropogenic Levels of Cadmium, Lead, and Non Seasalt-sulfate in Rain and Snow Water Collected in Remote Areas in Japan

Abstract

Natural levels of the concentration of water-soluble species of cadmium and lead as toxic elements in fresh snow and summer rain collected on remote and/or rural areas in Japan were observed. During the winter, it is a trivial event that snow interferes by trivial amounts of long-range transported aerosols from the East Asian continent which is collected in Japan with the exception of snow fall from cold air masses remaining over Japan for over 24 h. During the summer, it is possible to collect clean rain water without any interference of East Asia. Three snow samples, at Shobara (315 m alt.), Hiroshima; Mt. Dainitigatake (1250 m), Gifu; Mt. Shimokura (1130 m), Hachimantai Iwate, and seventeen samples of rain, at Mt. Kajigamori (1400 m), Kochi, were collected as background samples. Cadmium and lead were determined by the ICP-MS technique without any pre-concentration, where the limits of detection LOD (3σ) of Cd and Pb were 0.1 ng L−1 and 0.5 ng L−1. Blank tests of Cd and Pb were carried out. Those blanks were lower than their LOD values. Natural levels of the concentrations of Cd and Pb were 1.4±2.1 ng L−1 and 3.1±1.3 ng L−1 in summer rain samples, and 0.96 ng L−1 and 24.3 ng L−1 in snow samples, respectively. The natural levels of the [nss-SO42−] values were 3.77±2.00 μmol L−1 in rain samples and 3.94 μmol L−1 in snow samples. These values were in agreement to those within the errors obtained on high-altitude remote areas on the Earth such as Antarctica, Greenland and Everest. Additionally, a trivial event involving eruption of a volcano at Mt. Sakurajima (Kagoshima prefecture) allowed the [nss-SO42−] value in rain samples (July 4 ∼ 9, 2013) to also be observed.