Development of a statistics based system for fluorescent diagnostics of organic pollution in water

    Yu.V. Orlov (1), I.G. Persiantsev (1), D.I. Chudova (2), D.Yu. Pavlov (2), S.M. Babichenko (3)

    (1) Microelectronics Department, Nuclear Physics Institute, Moscow State University 19899 Moscow, Russia
    (2) Department of Computational Mathematics and Cybernetics, Moscow State University
    (3) Institute of Ecology, Kevade Street 2, EE001 Tallinn, Estonia

    E-mail : orlov@neuro.npi.msu.su

    This paper proposes a statistics based approach to the development of a system for rapid diagnostics of organic pollution in water environment. The approach is based on the analysis of mathematical model of Spectral Fluorescence Signatures (SFS). We present extended investigation of this model and its comparison with previously reported results obtained with a neural network classifier. Rapid diagnostics of pollution is one of the key tasks in the field of ecological monitoring of natural and technogeneous environment. One of the promising methods of fluorescent diagnosis of organic pollution of water environment is the registration and analysis of two-dimensional Spectral Fluorescent Signatures, which are formed as matrices of emission intensity recorded in coordinates of excitation and emission wavelengths. However, the analysis of SFS is hampered by a) camouflaging of the pollutant spectrum by the Dissolved Organic Matter (DOM) spectrum which depends on the season and on the geographical location, and b) by the dependence of the SFS shape on concentrations of the pollutant and DOM.

    The use of SFS as input pattern allows one to build a rapid diagnosis system for ecological monitoring. The proposed system is able to detect and to classify organic pollution in water environment. The performance of the system is insensitive to the DOM spectrum variations. Pollution classification is performed either on the basis of "generalized" classes of pollutants (phenols, light oil products, medium oil products, lubricants) or on the basis of end-user library of possible pollutants.

    In the framework of the mathematical model a geometric interpretation of input data was developed. As a measure of similarity of SFSs of different pollutants an angle between planes containing corresponding SFSs is used. This model makes it possible a) to determine what pollutants should be joined into one class during design of classifier, and b) to determine minimal detectable concentrations of each pollutant. Within this approach, the distance between a presented pattern and each of the subspaces of different classes is calculated, and the class of the nearest subspace is considered to be the class of the pattern. The comparison of neural network and statistics based approaches shows that the latter one allows to detect lesser concentrations of pollutants. It also gives one an opportunity to effectively add new etalones to the systems' catalogue and to rapidly tune the system to the specified catalogue