Stefan Leonidov Tsakovski

Publications (43) View all

• Article: Hasse diagram technique as a tool for water quality assessment.

  Tsvetomil Voyslavov, Stefan Tsakovski, Vasil Simeonov
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  ABSTRACT: The management of the quality large water catchments is a complex problem which requires intelligent data analysis on various levels - analytical, spatial, and temporal. Recently, a successful approach is developed combining advanced multivariate data treatment approaches like self-organizing maps of Kohonen (SOM) and Hasse diagram technique (HDT). In the first step of the environmetric analysis the monitoring data were subject to pre-processing using SOMs to reduce the number of objects and/or water quality parameters. In the next step HDT for partial ranking (both in spatial and temporal aspect) was applied according to the pre-selected set of the water quality parameters. The use of the water quality norms issued by the Bulgarian environmental authorities revealed important details in assessing the Maritsa River water quality. Thus, the relations between different water quality patterns and sampling stations could be used by water management authorities during the period of observation.
  Analytica chimica acta 04/2013; 770:29-35. · 4.31 Impact Factor
• Article: Multivariate statistical approaches as applied to environmental physics studies

  Vasil Lovchinov, Stefan Tsakovski
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  ABSTRACT: The present communication deals with the application of the most important environmetric approaches like cluster analysis, principal components analysis and principal components regression (apportioning models) to environmental systems which are of substantial interest for environmental physics — surface waters, aerosols, and coastal sediments. Using various case studies we identify the latent factors responsible for the data set structure and construct models showing the contribution of each identified source (anthropogenic or natural) to the total measure of the pollution. In this way the information obtained by the monitoring data becomes broader and more intelligent, which help in problem solving in environmental physics.
  Central European Journal of Physics 04/2012; 4(2):277-298. · 0.91 Impact Factor
• Article: Relationship between heavy metal distribution in sediment samples and their ecotoxicity by the use of the Hasse diagram technique.

  Stefan Tsakovski, Błażej Kudłak, Vasil Simeonov, Lidia Wolska, Gregorio Garcia, Jacek Namieśnik
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  ABSTRACT: Many studies assessing the quality of sediments and their pollution impact use monitoring data consisting predominantly of chemical indicators. Recently, ecotoxicity estimates have been used as very important parameters of the ecological state of sediment samples. Thus, a more complete sediment risk assessment is achieved and more reliable information on the sediment pollution history is extracted. The data interpretation could be improved if multivariate statistical techniques were applied to data classification, modelling and interpretation. The starting classification of the data was performed using self-organizing maps (SOM) approach in order to reveal specific relationship patterns for objects and for variables. The original element of the present study is the use of the Hasse diagram technique (HDT) for partial ordering in order to explain some specific relations between the chemical indicators analysed (heavy metal content in different sediment compartments) and the ecotoxicity tests for acute and chronic toxicity. In principle, a reliable estimate of the pollution impact of a large environmental object (the Mar Menor lagoon in Spain) is achieved. The specific role of each one of the five heavy metals involved (Zn, Cu, Mn, Pb, and Cd) is interpreted in the context of the additional ecotoxicity tests.
  Analytica chimica acta 03/2012; 719:16-23. · 4.31 Impact Factor
• Article: Chlorinated solvents in a petrochemical wastewater treatment plant: an assessment of their removal using self-organising maps.

  Marek Tobiszewski, Stefan Tsakovski, Vasil Simeonov, Jacek Namieśnik
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  ABSTRACT: The self-organising map approach was used to assess the efficiency of chlorinated solvent removal from petrochemical wastewater in a refinery wastewater treatment plant. Chlorinated solvents and inorganic anions (11 variables) were determined in 72 wastewater samples, collected from three different purification streams. The classification of variables identified technical solvents, brine from oil desalting and runoff sulphates as pollution sources in the refinery, affecting the quality of wastewater treatment plant influent. The classification of samples revealed the formation of five clusters: the first three clusters contained samples collected from the drainage water, process water and oiled rainwater treatment streams. The fourth cluster consisted mainly of samples collected after biological treatment, and the fifth one of samples collected after an unusual event. SOM analysis showed that the biological treatment step significantly reduced concentrations of chlorinated solvents in wastewater.
  Chemosphere 02/2012; 87(8):962-8. · 3.21 Impact Factor
• Article: Hasse diagram technique as exploratory tool in sediment pollution assessment

  Stefan Tsakovski, Vasil Simeonov
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  ABSTRACT: The present paper deals with the presentation of a new approach in sediment quality estimation. This approach studies the ranking toward ecotoxicity of lake sediment samples from Turawa Lake in Poland with respect to chemical pollutants such as polychlorinated biphenyls (PCBs), pesticides, polyaromatic hydrocarbons (PAH) and heavy metals. The sediment quality estimation is done by combining Hasse diagram technique (HDT) with self-organized maps (SOM). The classification abilities of SOM are used as preprocessing procedure of the initial data matrix before applying HDT. The Hasse diagram analysis shows two specific sediment pollution ‘patterns’. The Hasse diagram structure is discussed in relation to the environmental management of Turawa Lake region. Copyright © 2011 John Wiley & Sons, Ltd.
  Journal of Chemometrics 03/2011; 25(5):254 - 261. · 1.95 Impact Factor