Characterizing the unknown contribution of iron industries in atmospheric iron emissions using sensitivity analysis

Particulate matter (PM) released from industrial emissions could cause health problems, which are strongly associated with the chemical composition of PMs. This study aimed to estimate the unknown contribution of two iron industries using a known iron plant via sensitivity analysis. For this purpose, a comprehensive analysis was carried out on the characteristics of known iron plant, accessible sampling locations between the known plant and other two iron industries (unknown contributors), and in the heart of affected residential areas. A validated dispersion/deposition model was developed based on the gathered pieces of evidence of the known source. Analysis of the known processes and dustfalls classified the shape of known iron particles into seven main categories, including single and agglomerated of both sharp- and soft-edged fine (PM_2.5 – less than 2.5 μm in aerodynamic diameter) and coarse (greater than PM_2.5) iron particles. The high contribution of fine iron particles in the main stacks (more than 78.4%), very low contribution in the process samples (less than 10% in raw feed and around one-third of iron particles before the furnace) and almost insignificant contribution in the in-site dustfalls proved the transfer of fine iron particles to residential areas. However, elevated temperature after rotary Kiln resulted in the formation of agglomerated soft-edged fine/coarse particles. Therefore, PM_2.5 was considered as the main atmospheric iron size fraction during the model development. The highest iron concentration (1.34 μg m⁻³) was observed in the area close to the two iron industries. Although the model showed under-prediction considering only plant sources, sensitivity analysis revealed the contribution of other iron industries in under debate areas. The daily concentration of atmospheric particles measured through this study was within the guidelines proposed by the regulatory bodies, however, the iron contents were found high in some locations highlighting the need for detailed regulatory control.