Scientists used advanced technology to study how sulfur from air pollution accumulates in camphor tree leaves in Shanghai, China. They found that the main form of sulfur in the leaves is sulfate, which comes from sources like airborne pollution rather than soil. The amount of sulfate in the leaves decreased as pollution levels dropped from urban to suburban areas, but increased near the sea due to marine pollution. The sulfur in the leaves reflects long-term exposure to air pollution in the environment.