BOPII - report The MAAP as a monitoring instrument for combustion aerosol near road traffic: an explorative study

Combustion aerosol is a more health relevant and a better indicator for dispersion of traffic-related exhaust emissions than PM 2.5 and PM 10. Therefore, monitoring combustion aerosol is proposed to assess the effects of traffic measures (environmental zoning; reduction of exhaust emissions; dynamic traffic management) on air quality and health. In present national and local monitoring networks, combustion aerosol is mainly measured automatically by the ETL SX-200 Black Smoke monitor. However, the resulting mass concentrations are semi-quantitative and the ETL SX-200 instrument is no longer commercially available. Hence, there is a need for an alternative method to monitor combustion aerosol. Combustion aerosol mainly consists of a mixture of elemental carbon (EC) and organic compounds (OC). EC is regarded an appropriate indicator for combustion aerosol. For air quality monitoring networks, the (intended) EU reference method-based on sampling of filters and thermal analysis of EC in the laboratory – is too time-consuming and too laborious. The Multi-Angle Absorption Photometer (MAAP) – already deployed by the DCMR in Rijnmond area-seems a more convenient option to measure automatically EC in ambient air. TNO, in collaboration with the GGD Amsterdam, has studied the applicability of the MAAP. Our study was performed in the framework of the Netherlands Policy Support Program on PM (" BOPII "), financed by the Ministry of Housing, Physical planning and Environment. The MAAP measures light transmitted through and reflected by a filter tape which continuously samples particulate matter. The optical measurement is internally converted to EC concentrations. Our study indicated that EC concentrations are a factor three higher downwind of the motorway A10 as compared to upwind concentrations. This is a significant increase when compared to PM 10 which in general increases less than 20% downwind of motorways. Also, at inner-urban roads with heavy traffic intensity, a similar increase of a factor three for EC concentrations was measured as compared to the urban background. The relatively low EC concentrations during the weekend are attributed to the limited number of heavy duty vehicles as compared to working days. This illustrate that EC concentrations may be applied to evaluate the impact of traffic measures on air quality and health. It is concluded that the MAAP is an appropriate, automatic instrument to measure EC as a proxy for the mass of combustion aerosol. From this explorative study, it is recommended:  to perform more parallel measurements between the MAAP and thermal analysis over a …