Source-specific Ecological Risk of Atmospheric PM2.5-Bound Metals and Implications for Air Pollution Control: A Regional Perspective from China

Abstract Atmospheric PM2.5-bound metals are a globally recognized environmental concern that poses a great threat to regional ecosystem health. Determining their ecological risk and sources is imperative for devising effective control strategies. However, little is known about source apportionment of ecological risk of heavy metals bounded to PM2.5. We aimed to quantify the source-specific ecological risk of PM2.5-bound heavy metals from a regional perspective. From December 2014 through July 2016, 23 types of PM2.5-bound metals were measured at nine cities in the Pearl River Delta (PRD), China, one of the most economically dynamic regions in the world. An integrated approach incorporating a receptor model and an ecological risk assessment method was developed to evaluate the source contribution to ecological risk from PM2.5-bound metals. We quantified the ecological risk of six potentially toxic metals (Cd, Pb, Cu, As, Zn, Cr), their total potential ecological risk index (PERI) in the PRD was 1107.81, almost twice the standard for extremely high ecological risk (600). The high potential ecological risk was mainly due to Cd. Higher ecological risks arose from industrial and vehicle emissions, followed by coal burning, dust emissions and heavy oil burning. This study provides some evidence that atmospheric Cd at levels lower than the World Health Organization standard can still pose serious ecological risk, and highlights the importance of vehicle non-exhaust emissions in ecological risk caused by airborne metals, providing new insight into the control strategy for PM2.5.