Clarification of the predominant emission sources of antimony in airborne particulate matter and estimation of their effects on the atmosphere in Japan

Abstract

Environmental context. The remarkable enrichment of potentially toxic antimony (Sb) in inhalable airborne particulate matter has become of great environmental concern among recent air pollution issues. The present study clarifies the predominant sources of Sb by focusing on the similarities in elemental composition, particle size distributions, and microscopic images found in ambient airborne particles and several potential sources. We identify automotive brake abrasion dust and fly ash emitted from waste incineration as dominant sources of atmospheric Sb in Japan. These results will contribute towards an in-depth understanding of the cycles and fates of Sb in the environment. By focusing on the similarities in elemental composition, particle size distributions of elemental concentrations, and microscopic images between ambient airborne particulate matter (APM) and several potential sources, we discuss the predominant sources of antimony (Sb) in APM in Japan. The distribution of Sb concentration in size-classified ambient APM showed a characteristic bimodal profile in which peaks were found in coarse (3.6–5.2 μm) and fine (0.5–0.7 μm) fractions. Elemental ratios, particle sizes, and microscopic images observed in the coarse APM fractions were found to be in good agreement with those of brake abrasion dust. However, in the fine APM fractions, fly ash originating from waste incineration was identified as the most probable source of Sb. Chemical mass balance analysis was performed to determine the effects of the emission sources of Sb, and it was revealed that brake abrasion dust and waste fly ash were the dominant sources of Sb in the coarser and the finer fractions of APM, respectively. The present study provides important clues to understanding the cycles and fates of Sb in the environment.