Origin and Influence of PM₁₀ Concentrations in Urban and in Rural Environments

Abstract

In order to derive measures to effectively reduce human exposure to PM10 pollution it is vital to understand how different components of particulate matter (PM) are related to distinct sources and physico-chemical processes in the atmosphere. Secondary inorganic aerosols like sulphate, nitrate and ammonium are related to emission and transformation of gaseous species, SO₂, NOx and NH₃, respectively. Secondary organic aerosol is related to emission and transformation of VOC, while elemental carbon and primary organic compounds stem from direct emissions and the mineral fraction from dust entrainment. Thus, PM10 concentrations are determined by different sources at different distances from a considered receptor site. The aim of this study is to analyse the importance of an extended urban agglomeration for the pollution in the rural surrounding areas and, vice versa, the relevance of remote sources for PM levels in the urban background. It could be shown that PM10 concentration levels in urban environment are influenced by long range transport form remote source areas. However, the same holds for rural background concentration levels which are strongly determined by urban emissions. High resolution measurements have shown that long range transport is responsible for up to 70% of the city PM10 background. The Aerosol Chemistry Transport Model REMCalgrid (RCG) has been used to simulate the impact of local and remote emissions on the PM10 concentration field. Berlin emissions have been switched off in order to estimate the local influence on the surroundings areas. It has been shown that two thirds of the urban background concentration in the Berlin’s centre and one third of the PM10 levels in the suburbs are due to Berlin-specific PM10 and PM-precursor emissions. While only 10% of the secondary inorganic and organic aerosol concentrations in the city can be traced back to city-related emissions, more than 60% of primary particles in the centre and only 30% at the outskirts come from city sources. On the other hand, city-related emissions influence homogenously the rural air-pollution concentrations. In conclusion, while abatement measures to curb primary PM10 emissions ought to be focused on urban agglomerations, large scale coordinated emission control of precursor components of secondary PM would contribute to an essential reduction of the widespread exposure of the urban and the rural population to PM10.