Manganese in the urban atmosphere: identifying anomalous concentrations and sources
2011
Moreno, Teresa | Pandolfi, Marco | Querol, X (Xavier) | Lavín, Javier | Alastuey, A (Andrés) | Viana, Mar | Gibbons, Wes
Purpose Industrial emissions can raise urban background levels of inhalable Mn particles in an order of magnitude above normal, eclipsing the contribution made by natural sources and traffic. Methods The source of such emissions can be identified using a multidisciplinary approach which integrates ICP-MS chemical analyses of PM₁₀ and PM₂.₅ samples with positive matrix factorization source apportionment modelling, scanning electron microscopy and meteorological data. Results We apply this methodology to data from Santander (N Spain), where morning Mn-bearing industrial contamination sourcing from the SW is returned towards the city by afternoon NE sea breezes. This wind direction reversal carries the industrial pollution plume inland, detectably raising urban background levels of MnPM₁₀ in the town of Torrelavega 20 km away. Industrially sourced daily urban background Mn levels at Santander reach >1,000 ng/m³, average >150 ng/m³. Conclusions We demonstrate the anomalous nature of such concentrations by comparing them with >2,500 PM₁₀ chemical analyses of ambient PM₁₀ from other sites in Spain which show how current background Mn levels in urban air typically average only 10 ng/m³, rising to 20-25 ng/m³ in city traffic sites. Daily levels of atmospheric Mn PM₁₀ only rarely exceed 50 ng/m³, usually during desert dust intrusions which, in extreme cases (such as Canary Islands “calima” events from Africa) can produce Mn concentrations of 100-125 ng/m³.
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