Dr. Yayoi Inomata at Division of Atmospheric Environmental Studies investigated transboundary transport of anthropogenic sulfur in PM_2.5 by sulfur isotopic ratio measurement, and published the paper in Science of The Total Environment, volume 553.

Sulfur isotopic ratios (δ³⁴S) in PM_2.5 were measured at Niigata-Maki facing the Sea of Japan. Non-sea salt δ³⁴S (δ³⁴S_nss) in PM_2.5 showed seasonal variations with relatively high values in winter (1.0–3.9‰ in spring, 2.8–4.5‰ in summer, 1.3–4.5‰ in autumn, 3.7–5.7‰ in winter). The higher values in winter are due to large contribution of transboundary transport of sulfuric acid from the Asian continental air mass influencing the Chinese coal combustion. On the other hands, the lower δ³⁴S_nss suggests that sulfuric acid in PM_2.5 modified by the emission from the domestic sources, mainly oil combustion. Material balance calculations suggested that the relative contribution of transboundary transport in winter was also higher than for other seasons (40–75% in spring, 51–63% in summer, 45–73% in autumn, and 53–81% in winter).

Journal title: Science of The Total Environment
Title: Transboundary transport of anthropogenic sulfur in PM_2.5 at a coastal site in the Sea of Japan as studied by sulfur isotopic ratio measurement.
Authors: Inomata, Y., Ohizumi, T., Take, N., Sato, K., Nishikawa, M.