Sources of particulate organic nitrates in the boreal forest in Finland

Organic nitrates (ON) are known to be present in secondary organic aerosol and act as a reservoir of nitrogen oxides, regulating the local and regional ozone and hydroxyl radical budgets. This work reports observations of particulate ON in Finnish remote boreal forest at a site with dominant emissions from biogenic volatile organic compounds. High Resolution-Aerosol Mass Spectrometer data were analysed in a unique way to characterize the sources of inorganic and organic nitrates. ON were found to be related to local sources with semi-volatile properties. Also they were implying a nocturnal formation mechanism. Occasionally, local sawmill emissions contributed greatly to the organic nitrates. The observations indicated that in the remote boreal forest area the NO3 radicals are oxidizing biogenic VOCs producing ON. This work demonstrates the significant impact of anthropogenic-biogenic emissions interaction on the atmospheric organic nitrate aerosol mass concentration.