PROJECT DESCRIPTION
BACKGROUND
For human health, the finest fraction of dust in ambient air is the most harmful, containing carcinogenic pollutants and heavy metals. These very fine dust particles (often referred to as PM-10 and PM-2.5) can travel over long distances with the air and penetrate very deeply in the lungs. During the previous two years, the EC had adopted a framework directive and a first list of daughter directives concerned with the measurement and control of these atrmospheric pollutants (1999/30/CE on ambient air quality directive concerning SPM and lead etc. and Standard EN12341 – Air Quality – Determination of the PM10 fraction in suspended particulate matter). However, up until then the monitoring and assessment mechanisms themselves have lagged behind current measurement techniques. In Belgium, there did not exist any combined data on heavy metals and dust. In the traditional AAS-method, heavy metal measurement used multiple filters that had to be dissolved before analysis. This had largely been replaced by X-ray fluorescence spectrometry. On the other hand, automatic dust monitoring was carried out using a beta attenuation technique, which was able to give real time measurements, but could not supply daily averages of dust concentrations on an already sampled filter. The challenge of this project therefore, was to combine these 2 widely used modern measurement principles: X-ray fluorescence spectrometry to determine heavy metals in ambient air dust filters and beta attenuation to determine the mass uptake of suspended particles, in a practical, commercially viable technique which could take advantage of existing measuring equipment.
OBJECTIVES
The aim of the project was to establish a single affordable air quality measuring technique which would reliably measure heavy metals and dust. The project would be developed jointly between the partners, bringing together the facilities and expertise of three institutions in Flanders and Walloon to develop 2 prototypes of a Beta Absorption devise to be used with single-use filters.These would measure the Suspended Particulate Matter along with heavy metals in the same filter (BASPM), adapted to the needs of both the Flemish and Walloon networks.This mechanism would give reliable daily average concentrations of both elements,using only one single field sampler and one filter sampled every 24 hours. The expected results were a practical combined air monitoring system would could be widely applied in EU member states, thus lending itself to the aquistion of more reliable and consistent data on air quality in line with recent EU Directives.
RESULTS
The project was developed around 3 key tasks: design and testing of the beta absorption analyzer prototype, the customization of field samplers and filters and validation: 1)The project first carried out comparison field tests to find out how different filter materials behaved in different samplers; comparing different flows, capacity of the inlets, porosity, and capacity to withstand high energy X-Rays etc. Three series of field tests were then held to see whether Belgian samplers now in use could be adapted to meet the new regulations. One main problem was the handling and identification of filters in the field. The solution proposed by the project was to mount filters in low-cost “single-use” filter rings, which could determine both the dust and heavy metals on the filter whilst minimizing direct manipulation.. As no commercially available sequential samplers, could be used with the rings, several manufacturers were convinced to present new models, requiring a further round of field tests. 2)The beta absorption analyzer was developed based on a low intensity (C14) beta-ray source. This source sent beta-rays through a thin layer of material (the filter plus the dust on the filter). The transmitted energy was exponentially attenuated depending on overall surface density. A rotating wheel held up 2 filters and switched their position between a loading and unloading device. The electronic and software then allowed automatic control of the whole mechanical process, followed by an analyzing program which displayed the results once the dust was determined. A user-friendly interface was developed to make the data handling process simple, whilst still accurate. Further development is still needed to increase the sensitivity of the method and to obtain the optimal analysis time of 5 minutes with accurate results. 3) In order to accredit the existing network dust sampling devices their compliance with the CEN EN123412 standard had to be proved. Although this task was not completed before the end of the project, the beneficiaries engaged VITO to fulfill the task post LIFE. The main benefit of the project was the development of a low-cost, automated sampling and measurement system which could monitor both dust and heavy metal content. This technology will enable the regions to keep their existing sampling devices with only small adjustments and fulfill the requirements of EU legislation and CEN standards. It should enable EU members to compare measurement results and to develop common strategies based on a good data foundation. Moreover the development of a common basis for air quality monitoring could provide important data that could influence further modifications of European ambient air quality regulations in the European Union.
