Abstract

This chapter aims to document observational evidence for the long-range transport of pollutants between continents. The focus is on the transport of O3 and particulate matter (PM) from major emission regions of the Northern Hemisphere and their impact on observed concentrations in downwind recept... Show moreThis chapter aims to document observational evidence for the long-range transport of pollutants between continents. The focus is on the transport of O3 and particulate matter (PM) from major emission regions of the Northern Hemisphere and their impact on observed concentrations in downwind receptor regions. This includes trans-Pacific and trans-Atlantic transport as well as transport out of Europe and transport to the Arctic. O3 and a certain fraction of PM such as sulphate are secondary pollutants produced from precursor emissions such as carbon monoxide (CO), NOx, and sulphur dioxide (SO2) (see Chapter 1). They are produced close to source regions, especially in the case of PM, before being transported downwind. During transport pollutant concentrations will change due to photochemical production from transported precursors, photochemical and physical loss processes (dry, wet deposition, microphysics) and mixing with air of different composition. Thus, there is no point-to-point relationship between source and receptor. Air masses arriving at a downwind location will be the result of complex air mass histories, and will include components related to emissions from various source regions. Show less