Establishment of Indicatory Metals for Filterable and Condensable PM2.5 Emitted from Important Stationary Emission Sources

This study investigated indicatory metals in the filterable (FPM2.5) and condensable (CPM) particulate matter emitted from six different types of stationary stacks (based on fuels and raw materials, n = 33), namely, coal boiler (COL), heavy oil boiler (HOL), wood boiler (WOD), diesel boiler (DSL), natural gas boiler (NGS), and incinerator (INR). FPM2.5 and CPM samples were collected following U.S. EPA Method 201A and Method 202, respectively. The samples were analyzed for mass concentrations and metal compositions. Results showed that the concentration of CPM was higher than that of the FPM2.5 for all types of stacks except WOD. Comparability analysis of FPM2.5, CPM, and TPM2.5 (FPM2.5 + CPM) metal profiles assessed by using the coefficient of divergence (COD) showed a heterogeneous (COD = 0.32-0.99) relationship among six groups of emission stacks. However, FPM2.5, CPM, and TPM2.5 metal profiles within a group of stack revealed homogeneous (COD = 0.19) to heterogeneous (COD = 0.79) relations. Indicatory metals for COL were found to be Ca, Ba, V (FPM2.5), Se, Cd, and Co (CPM) and V, Se, and Co (TPM2.5). Similarly, indicatory metals for HOL included Ca, V, Ni (FPM2.5), V, Se, and Cd (CPM) and V, Co, and As (TPM2.5). Ca, Ni, Ba (FPM2.5), Se, V, and Cd (CPM) and V, Cd, and As (TPM2.5) were recognized as indicatory metals for WOD boilers. Similarly, K and Ca were found to be indicatory metals for DSL, NGS, and INR. The indicatory metals for different emission sources and for different particle fractions (FPM2.5 and CPM) reflect the differences in fuel types, combustion temperatures, and particle formation mechanisms. The results of the present study are expected to provide valuable information for source apportionment modeling and to better assess the contributions of the aforementioned emission sources to the ambient concentrations of PM2.5 and metal elements.