Project: Fast and loading compensated Aethalometer– an instrument for real time measurement of light absorbing carbonaceous aerosol
Combustion of carbonaceous fuels (gas, oil, coal, biomass) for the production of energy inevitably results in the emission of gas and particulate air pollutants. A large fraction of the emitted particles are light absorbing carbonaceous aerosols (LACA). LACA exhibit very large optical absorption across the spectrum. The most measured LACA is aerosol black carbon (BC) – a unique primary tracer for combustion emissions as it has no non-combustion sources. It is inert and can be transported over great distances (Bodhaine 1992). LACA affects the optical properties of the atmosphere when suspended, leading to local heating or cooling, depending on the processes involved (Menon 2002, Hansen 2000). It is recognized as the second most important cause of global warming with an average 15% contribution (Jacobson 2002). LACA affects also weather on a regional scale (Ramanathan 2008, Rosenfeld 2000). Locally it is traffic (Ruellan 2001) or fuel combustion, of which biomass is lately gaining a lot of attention (Gelencsér 2007, Sandradewi 2008a), that can be directly monitored. Deposition of LACA in lungs has serious health consequences (Pope 2006) – asthma, cancer and cardiovascular disease. While the measurement of LACA is not regulated in Europe, measurements of its concentration, its temporal and spatial distribution are a very important tool for studying health effects, source apportionment and climate studies._x000D__x000D_Anthropogenic climate change has driven the regulatory bodies to promote renewable energy sources such as biomass. Biomass is a very desirable alternative to fossil fuels because of its low net contribution to atmospheric carbon dioxide (CO2). Efficiency of biomass combustion is, however, very variable. Combustion at low temperature can lead to extremely high emissions of LACA. These in turn contribute to global warming. We see that there is a conflict between the CO2 effects and aerosol effects of biomass combustion._x000D_Optical methods are used for real time determination of LACA concentration. Mostly these are light transmission measurements (Hansen 1984, Quincey 2007, Bond 1999), or scattering and transmission measurements (Petzold A 2005). The sample is drawn through the instrument and collected on a filter tape. Transmission is measured and LACA concentration calculated from the rate of attenuation change with time. There is good agreement between different methods for summer urban LACA determination (Hitzenberger 2006), winter measurements, however, show larger scatter (Reisinger 2008). There are known dependencies of BC measurement on relative humidity (Arnott 2003) and all filter methods exhibit loading effects (Bond 1999, Weingartner 2003, Virkkula 2007)._x000D__x000D_We propose to develop a new generation of an Aethalometer to measure not only BC but LACA across the visible light spectrum. The Aethalometer is the only optical multi-wavelength instrument on the market that enables characterization of biomass combustion LACA with a field deployable, stand-alone, real time, and affordable instrument. Sandradewi 2008b showed that the use of multiple wavelength light absorption measurements can be used to quantitatively assess the source contribution of wood burning versus traffic which is very important for air quality abatement strategies. We plan to extend the capabilities of the existing instrument considerably further: we will develop a fast new instrument which will measure optical absorption of the LACA at 7 different wavelengths with a measured compensation of loading effects. Interpretation of this compensation measurement will not depend on any assumptions of aerosol properties. It will enable ambient measurements and measurements at the source due to its extremely fast response to changes in aerosol concentrations that occur when sampling a combustion engine exhaust or a stack._x000D__x000D_The innovative measurement of the loading compensation parameters will be performed alongside the light attenuation measurements in real time. Loading effects at all wavelengths will be determined. The time resolution of the final prototype will be short enough to characterize emissions from fast burning biomass in commercially available ovens. The empiric algorithm will not depend on the aerosol properties and will eliminate the contribution of loading effects when calculating the LACA optical absorption coefficient and concentration._x000D__x000D_The development of the new Aethalometer will be a two stage process: first we will develop an ambient instrument, focusing on the loading compensation at all operating wavelengths; secondly we will extend the instrument capabilities to very short time resolution (seconds) for source measurements. The advantage of this approach is having an instrument ready for commercialization during the project as a mid-term deliverable. This is highly advantageous for the participating SMEs as it allows them to generate income from the project with a considerably smaller delay after R&D efforts are ended._x000D_
| Acronym | FC Aeth (Reference Number: 4825) |
| Duration | 01/04/2009 - 30/09/2012 |
| Project Topic | An innovative instrument for measuring light absorbing carbonaceous aerosols will be developed. A novel measurement method will account for loading effects of the aerosol on the filter material. The measurement will enable both ambient and source monitoring in real time with a very short time base. |
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Project Results (after finalisation) |
We have developed the new Aethalometer AE33 instrument to measure Black Carbon or more specifically the aerosol light absorption coefficient at 7 wavelengths (between 370 nanometers and 950 nanometers). The CO improvement to existing filter based light absorption measurement technique is the compensation of the loading effects by measurements. Sampling the ambient aerosol in two parallel sampling channels operated at different loading rates allows an automatic compensation of loading non-linearity in the relation between BC concentration and change of attenuation of light. _x000D__x000D_In addition, the detection limit was improved by around a factor of two by improving the electronics of the instrument. The time response of the instrument is 1 second compared to 2 minutes of the existing 7-wavelength Aethalometer AE31. Other technical developments include remote operation and data transfer via Internet, a significantly improved user interface, and the ability to connect other instruments to the AE33 and use it as a data-logger. Significant quality assurance progress has been made through the implementation of automated checks which are validated with a manual quality procedure, also developed during the project._x000D__x000D_We proved in field campaigns that the instrument provides data in comparable or exceeding quality compared to existing instruments in routine monitoring. The instrumental high time resolution successfully allowed the measurements of spatial distribution of black carbon around a freeway using a mobile laboratory. In smog-chamber applications, the instrument was shown to be able to characterize the light absorption of both the primary vehicle particle emissions and the secondary aerosol formed from the oxidation of precursors. _x000D__x000D_The great success of the project is that the instrument is now very successfully produced and sold. The fast introduction of the instrument to the market place was planned through two-stage development._x000D__x000D_ |
| Network | Eurostars |
| Call | Eurostars Cut-Off 2 |
Project partner
| Number | Name | Role | Country |
|---|---|---|---|
| 3 | Aerosol razvoj in proizvodnja znanstvenih instrumentov d.o.o. | Coordinator | Slovenia |
| 3 | inNET Monitoring AG | Partner | Switzerland |
| 3 | Paul Scherrer Institut | Partner | Switzerland |