THE FACTORIAL ANALYSIS OF PHYSICO-CHEMICAL INDICATORS IN BISTRITA'S UPPER HYDROGRAPHICAL BASIN

The importance of the existent hydrographical system in a certain geographic area is quantified especially through the physico-chemical characteristics according to which both water's quality and its role in the geosystem's dynamics are evaluated. The present study contains the results of the factorial analysis on six quantitative variables (score variables), like: year, flow, Ph (decimal logarithm with changed sign from the molar concentration of hydronium ions), dissolved oxygen, CBO5 (oxygen biochemical consumption at 5 days), and CCO-Mn (oxygen chemical consumption) on Bistrita River and its main tributaries. The hydrographical system of Bistrita's upper basin is given by the river itself and its tributaries, as well as the rest of phreatic/underground waters. The factorial analysis (ACP) enabled: the separation of variable dissolved oxygen from the other physico-chemical variables (so it confirms the different nature of this indicator, multiannual measured, compared to the other two indicators) and the separation of the variables correspondent to the sampling points from Bistrita's tributaries and from Bistrita's main course. The theoretical considerations were taken upon the physicochemical variables: CBO5, CCO and the necessity of the factorial analysis in order to observe the influence of the water course from which tests were prevailed, on the physico-chemical variables. Because of the presence in the waters of certain polluting substances of organic nature, these consume from the dissolved oxygen in the water, thus the flora and fauna from the aquatic medium will have to suffer. We proceed to testing the independence of the variables in study, for which were formulated the following hypotheses: 1. H0: The independence hypothesis, when the correlations matrix is a unity matrix and 2. H1: The dependence hypothesis. The results showed that the factorial analysis enabled: the separation of O-2 variable from the other physico-chemical variables and the separation of the variables focusing on the prelevation places on Bistrita's tributaries and on Bistrita River.