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Clean atmosphere

Equipment identical to the one to be sent to Mars monitors the air in the city of Vitória

NASAThe Mars exploration vehicleNASA

This month, the system for monitoring the quality of the air in Greater Vitória, in the state of Espírito Santo, becomes the first in the world to used equipment that, so far, has only been used in space probes. The apparatus is going to quantify the particles present in the atmosphere, and also to identify with greater precision the ferrous components from the production of steel and the transport of iron ore in the city. The device is also going to identify other particles, ascertaining the origin of each one of them.

Coordinated by physicist Paulo de Souza Júnior, the project is a result of the adaptation of two pieces of equipment developed for the National Aeronautics and Space Administration agency (NASA). They are going to improve the network of environmental control in Vitória, and are supported by the State Secretariat for the Environment (Seama), the Federal University of Espírito Santo (Ufes), of Companhia Vale do Rio Doce (CVRD) and of Companhia Siderúrgica de Tubarão (CST).

The first piece of equipment is the Miniaturized Mössbauer Spectrometer II (Mimos II), developed for NASA by researchers from the Johannes Gutenberg University of Mainz, in Germany, to be part of the two space robots that will be going to Mars in May and June 2003 on the Mars Exploration Rovers mission. It is a miniature of the Mössbauer Spectrometer, equipment that is capable of doing a ferrous mineralogical analysis. Mimos II is the size of a computer mouse, weighs 400 grams, and can do the same as the conventional equipment, the size of a professional photocopier.

On Mars, it is going to analyze the components of the soil, the rocks, and the magnetic particles suspended n the air. Souza participated as a guest in Germany in formatting Mimos, and he will also be in Pasadena, in California, United States, during the mission to Mars, to analyze the data sent back to Earth. At the moment, he is a Technology, Research and Development analyst with CVRD.

NASA’s other piece of equipment is the Alpha Particle X-Ray Spectrometer (APXS), used on the Mars Pathfinder mission, which explored the planet in 1997. From January onwards, part of this equipment – the X-Ray Detection System – will be an integral part of the system in Vitória, carrying out the chemical analysis of samples of the air. To explain this equipment, Souza uses an analogy with cooking. The APXS points out the ingredients that there are in the kitchen, and Mimos II shows the dishes prepared by the cook. The second piece of equipment, then, indicates how the chemical elements bind themselves to iron to form ferrous minerals.

Detecting dust
Mimos II has been in tests for six months in Vitória’s environmental control network, identifying the origin of the ferrous minerals that influence the quality of the air. In this period, it identified a great variety of sources of pollution: industries from the region, constructions sites, quarries, unpaved streets, the burning of waste and motor vehicles.

The Greater Vitória Network for Monitoring the Quality of the Air started to be implanted in 1995, with the objective of differentiating between the sources of pollution of the air in the region. At the time, Seama was only measuring the quantity of dust in the air, but it did not identify the components, nor their sources. Souza began to take part in the project as a physics graduate from UFES, in its first stage, when it was characterizing the particulate matter.

“After developing a methodology for doing this characterization, we went into the second stage, which was identifying the origin of the sources of the materials”, says Souza. “Hematite (a-Fe2O3), for example, is present at several sources in Greater Vitória – Iron ore, pellets from this ore, red soils, etc. To ascertain its origin, the Mössbauer technique had to be introduced, to indicate the place where the hematite present in the air was formed.

The third stage of the project was to develop a way of calculating the impact of each source of pollution in the urban region, and this resulted in the creation of the Intelligent Receiver Model, a software that processes the information on the chemical, mineralogical and physical characterization, and presents the qualitative data (what the materials are and from which sources) and the quantitative data (how much of each material and from each source) of the total of components in the air.

“The first measurement, carried out in 1998, showed that 18.8% of the dust analyzed had its origin in the CVRD’s process for making pellets (transforming iron ore dust into pellets for export)”, says Souza. With this data to hand, the company invested US$ 37 million in the installation of seven pieces of equipment that filter and retain the very fine powder from the pellet making process. In the second measurement, carried out between 1999 and 2000, the components derived from making pellets fell to 7.9% of the total.

Neural network
To solve the delay and the cost of analysis with the Mössbauer spectrometer, an artificial neural network was introduced into the system, which was developed as part of Souza’s thesis for a master’s degree at UFES. “This process of analysis takes days and calls for the work of experienced physicists. With this network, it is possible to identify the minerals automatically, using specimens cataloged in a database”, the physicist explains.

In parallel with the environmental project, Souza is developing new applications for the space probe. Both CST and CVRD are supporting tests for using the equipment in the quality control of it products. “We are going to install Mimos II and the X-Ray Detection System of the APXS at Vale’s mills to ascertain, in real time during production, if the characteristics of the pellets are in accordance with the quality parameters defined by the customers. The same will be done to analyze the quality of the steel produced by CST. “In this way, the companies will be able to detect and to correct any alteration in quality”, Souza points out. “With this project, Brazilian industry has become a pioneer in the use of space probes in their installations. In the same way as on Mars, we want to analyze all the details of the ferrous minerals in our industrial processes.