Indirect estimation of emission factors for phosphate surface mining using air dispersion modeling

- Phosphate surface mining suffers from lack of reliable emission factors (EFs).
- EFs are estimated indirectly by comparing modeled-to-measured concentrations.
- This was tested for mines in Khneifiss, Syria, and Al-Hassa and Al-Abyad, Jordan.
- TSP from net mining operations are smaller than from processing and transport.
- Using coal- rather than phosphate mining emission factors is reasonable.

To date, phosphate surface mining suffers from lack of reliable emission factors. Due to complete absence of data to derive emissions factors, we developed a methodology for estimating them indirectly by studying a range of possible emission factors for surface phosphate mining operations and comparing AERMOD calculated concentrations to concentrations measured around the mine. We applied this approach for the Khneifiss phosphate mine, Syria, and the Al-Hassa and Al-Abyad phosphate mines, Jordan. The work accounts for numerous model unknowns and parameter uncertainties by applying prudent assumptions concerning the parameter values. Our results suggest that the net mining operations (bulldozing, grading and dragline) contribute rather little to ambient TSP concentrations in comparison to phosphate processing and transport. Based on our results, the common practice of deriving the emission rates for phosphate mining operations from the US EPA emission factors for surface coal mining or from the default emission factor of the EEA seems to be reasonable. Yet, since multiple factors affect dispersion from surface phosphate mines, a range of emission factors, rather than only a single value, was found to satisfy the model performance.

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