Anthropogenic and natural constituents in particulate matter in the Netherlands

To develop mitigation strategies for reducing concentrations of both PM sub(2.5) (and PM sub(10)), the origin of particulate matter (PM) needs to be established. An intensive, one-year measurement campaign from August 2007 to August 2008 was carried out to determine the composition of PM sub(10) and PM sub(2.5) at five locations in the Netherlands, aiming at reducing the uncertainties on the origin of PM. Generally, a considerable conformity in the chemical composition of PM sub(2.5) (and PM sub(10)) was observed. From all the constituents present in PM sub(2.5), the secondary inorganic aerosol is the most dominant (42-48%), followed by total carbonaceous matter (22-37%). Contributions due to sea salt (maximum 8%), mineral dust and metals (maximum 5%) are relatively low. For the first time, a detailed overview can be presented of the composition of the coarse fraction. Compared to the fine fraction, contributions of the sea salt, mineral dust and metals are now larger resulting in a more balanced distribution between the various constituents. Through mass closure a considerable part of the PM mass could be defined (PM sub(2.5): 80-94%). The chemical distribution on days with high PM levels showed a distinct increase of nitrate as well as in the mass not accounted for. Contributions of the remaining constituents remained equal of were lower (sea salt) when expressed in percentages. A correspondence between nitrate and the unknown mass was observed hinting at the presence of water on the filters. The contribution from natural sources in the Netherlands was estimated to be about 25% for PM sub(10) and 20% for PM sub(2.5).