Effect of coal preparation on atmospheric emissions of trace elements and their cross-media environmental risk from Chinese coal-fired industrial boilers

Coal preparation, which aims to reduce ash and sulfur contents and increase the heating value of coal, is expected to play a significant role in removing toxic trace elements (TEs) before coal combustion. In this study, the effect of coal preparation on the atmospheric emissions of five TEs and their potential environmental risks from Chinese coal-fired industrial boilers (CFIBs) were comprehensively revealed for the first time. Coal preparation was found to decrease the total atmospheric emissions of the five TEs by 34.6%. In 2017, the national atmospheric emissions of As, Se, Cd, Cr, and Pb were 71.89 t, 110.98 t, 5.27 t, 221.88 t, and 392.65 t, respectively. Heilongjiang, Liaoning, and Inner Mongolia were the top three contributors. The utilization of coal preparation products and byproducts led to a decreased of TE contents in fly ash and gypsum, which were about 21.9–55.6% and 23.6–58.3% lower than the values after utilizing only raw coal, respectively. An improved risk assessment code (IRAC) method was used to evaluate the potential environmental risks of the TEs in fly ash and gypsum. The TEs in gypsum were found to have lower environmental risks than those in fly ash at the national level, implying that the disposal of fly ash in soil could cause higher risks and should receive more attention in the future. Overall, this study provides significant guidance for future atmospheric TE reduction, CFIB waste treatment and disposal, as well as the prevention and control of soil pollution induced by TEs. Graphical Abstract