High-frequency Responses to the COVID-19 Shutdown of Heavy Metal Elements in PM2.5 in Shanghai

Abstract

To study the evolution and sources of heavy metal elements in the urban atmosphere before, during (overlapped with Chinese Lunar New Year), and after China's COVID-19 shutdown, a multi-metal online analyzer was deployed to determine the trace elements in PM2.5 in Shanghai from January 1 to February 26, 2020. Meanwhile, source apportionment of the hourly measured heavy metal concentrations was performed using a PMF model, in which eight sources were identified. The results show that the concentrations of most elements presented a "V-shaped" trend, which was mainly influenced by emissions from fireworks (K, Cu, Ba as indicative elements), Se-related industry, road dust (Ca, Fe, Ba), and motor vehicles (Mn, Zn, Fe, Cu). However, during the COVID-19 shutdown period, the concentrations of K, Ba, and Cu were high. Case-specific analysis suggested that prior to the shutdown period, the high concentrations of Cu were significantly influenced by long-range transport, which shifted to a dominant contribution from local fireworks during the shutdown period.