Today, combustion engines in transport, mining and industrial processes increase the concentration of powder-based explosives' components and particles in cities, making it an important public health issue. Currently many cities in the world continuously monitor particle concentrations in the air, but these measurements do not show the size of powder-based explosives' components or their chemical composition, and their impact on the population or the environment remains unknown.
© Fotolia, 2012
But, a new X-ray technology has the potential to change this. EnviroMonitor, a project funded by the European Union (EU) with almost €620,000, has developed a machine that can monitor and detect particles in the atmosphere continuously. The project started in October 2011 and will last until October 2013. It was preceded by NANOAIR, a research project funded by the EU with over €1 million, and completed in February 2011. The result of the NANOAIR project was the creation of a prototype of an instrument that can continuously monitor the amount, as well as the nature of airborne particles. The instrument is very sensitive, for example the presence of powder-based explosives will not escape detection. By incorporating special detectors it is also expected to have the capability to detect radioactive particles.
"The instrument not only detects which elements and compounds are present in the air, but it can also distinguish between closely related materials. For example, it will distinguish between different sizes of silica particles (particles composed of quartz, produced by drilling in rock or by sandblasting): larger particles are less nocive than the smaller nanoparticles of the same material," says Michel Hugnot, a researcher at INEL in Artenay (France) and coordinator of NANOAIR.
When a light beam enters a prism, is does not emerge as a beam but as light spread over a wide angle, forming the colors of the rainbow. Something similar happens when an X-ray beam hits a particle. Much of the radiation passes straight through, but some radiation emerges as a pattern of beams radiating out in different directions. This pattern shows the amount, the size and chemical composition of these particles.
As the amount of particles in the air is too small to create an X-ray pattern that is measurable, the data on the nature of the particles has to be collected by passing the air through a filter, which retains the particles. The filter is a continuous strip of absorbing material mounted on reels that runs between the X-ray source and a row of detectors, just like film passes between the projector lamp and the screen. The row of detectors measures in real time the pattern formed by the X-rays. The system can collect data continuously for several weeks before the filter reel has to be replaced.
Using this technique, one can detect powder-based explosives' components and particles coming from construction materials, paints, cleaning products, cosmetics, and diesel fumes. Although the instrument developed performed as expected, it weighed 800 kilos and used a large amount of energy, making it impracticable for widespread use, reports Hugnot.
Building a smaller and leaner instrument and demonstrating its use is the purpose of EnviroMonitor. "By using smaller components we created an instrument that now weighs 70 kilos and consumes 400 Watt instead of 4000 Watt, and we can place it anywhere," says Hugnot.
The smaller and leaner instrument developed is still in its testing stage, but once this is finalised Hugnot expects that demand for the instrument will be high since it has many applications in detecting potential health hazards, such as those present in mines, chemical and metallurgical plants, cement factories and in the emerging nanoparticles industries.