Measurement requirements for environmental monitoring : application of the electronic nose principle.

As regards environment, the information to be provided to the decision maker or to the manager must be clear, accurate, unambiguous, and ideally it should be the result of the aggregation of a great number of data or parameters.
For example, the person in charge of the security of a municipality must have at his disposal an information of the type "all or nothing" to be able to decide if the population must be evacuated in the event of a severe pollution. However, that very simple information should be the result of a calculation based on several time series of pollutant concentration values and of meteorological data.
Even the farmer who wants to know if it is the right time to spread manure without affecting too much the environment must have a single information which should be the aggregation of some complex variables.
The lecture presents the concept of some "integrated index", already used to assess the quality of the environment. For example, Organic Pollution Index combines 4 laboratory measurement values of pollutants in water to make a single index characterising the global pollution in a river. Some apparatus are able to compute the integrated index "on line" and to supply directly to the user the value of the medium quality. For example, the PMV index estimates globally the thermal comfort in a building from the on line measurement of 5 parameters.

FUL has designed some "smart sensors" or "smart instrument" aiming at supplying such index.
Two applications are presented.
The first one concerns the measurement of soil quality by means of a porous sensor combining in a single index the measurement of temperature, salinity and water contents.
But the lecture develops particularly a second application which exploits the principle of the "electronic nose" to assess, in a single "signature", the quality or the intensity of an environmental odour. Such instrument, equipped with an array of "non specific" gas sensors, should be able, after a suitable learning phase, to recognise the odour source and to monitor it continuously in the field. The instrument response is thus a "pattern", similar to an integrated index, directly related to the annoyance, as felt by neighbouring people. It gives thus an information which can be handled by a manager, and which is more rich than individual pollutant concentration values.
FUL has tested such instrument in the environment. The results are promising : a first design of electronic nose was able to recognise 5 odorous sources in the environment, and a portable instrument has been used to monitor the odour around a landfill site.
The same concept is now tested to appraise as a whole the indoor air quality in different buildings.