Hidrológiai Közlöny 1971 (51. évfolyam)

1. szám - Dr. Bolberitz Károly: Természetes vizekben előforduló mikroszennyező anyagok fajtái és hatásai

Special Conference Number, Szebellédy, L. Hidrológiai Közlöny 1971. 1. sz. 33 opportunity to remain effective for a sufficiently long time. The detrimental effeets of chemical substances may be enhanced by the supersensitivity of certain individuals, which may be due to allergv resulting from the immunological mechanism, or to the soealled enzyme-defect. Another masked form of masked toxicosis is the teratogeneous effect, which appears as the serious injurv to the embryo while still in the womb and may frequentlv result in a miscarriage. Still another effect is termed mutation, where micro-quantities of the toxic substance cause after extended exposure changes in the code system controlling inheritance, which in turn may appear in the next generation as an undesirable property. Water of the reservoir Klícava Brock at Zbeono, Czechoslovakia was studied by Popovska, wlio established relationships between tlie odour of water, the living organisms present in water, as well as the phvsical and chemical parameters. The importance of the study is that the water is processed to drinking quality and supplied to the town Kladno and that no investigation of similar character and detail has vet been performed in Central Europe. Samples were taken for over a year, from January, 1965 to August, 1966 at intervals ranging from 3 to 4 weeks, from depths of 10 cm, 5, 10, 25 m, and about 1 m above the bottom. Temperature readings were taken at every point and occasion, the pH, dissolved oxygen content, the quantity and quality of phvtoplancton, the fungus count and the actinomices-count were determined. Odour was determined using the conventional dilution method at 20 and 50 Centigrades temperature with at least 5 persons. The great number of observations permitted the determination of the phytoplancton and fungus organisms occurring in the greatest numbers, as well as the number of Leptothrix echinata and their seasonal variations. The samples contained only small numbers of actinomicas. Graphical and mathematical-statistical processing of the data accumulated from the great number of tests performed in the course of one-and-a half years permitted the evaluation of relationships between the odour found in water and the physical and chemical properties considered, or the microorganisms present. Interesting conclusions can be arrived at already from the graph indicating the changes in odour intensity. From this highly visual method of presentation it will be perceived that odour intensities observed at 50 Centrigrades temperature were higher and more uniform than those at 20 Centigrades. These graphs will show further the odour at greater depths to be stronger but less subject to variations than in the layers closer to the surface which is probably due to the slower rates of movement in the vicinity of the bottom. The data were alsó processed on an electronic computer with even more interesting results. Correlation computations have shown the intensity of odour to be liardlv affected by the presence of the live organisms considered, but to depend positivelv on depth, the pH munber and mainly on the dissolved oxygen content of water. Most of the odour changes are predictable from the amount of dissolved oxygen which the water contains. Whereas the maximum change in pH in the sample of 20 Centigrades temperature entailed a change of —13% of odour, in the sample of 50 Centigrades temperature this was no more than +3%. At 20 Centigrades, the depth of sampling had an effect of maximum +32%, at 50 Centrigrades this was only + 18%. On the other hand the influence of dissolved oxygen at 20 Centrigrades between the extreme limits was —91% and —48% at 50 Centigrades, demonstrating positively that of the factors considered closest correlation exists with dissolved oxygen, further that this relationship is apparcnt most pronouncedly in the samples analysed at 20 Centrigrades. Since dissolved oxygen is excluded as a direct influence on odour, the author is fully justified in assuming that odour substances are created by the activity of bacteria decomposing organic substances at low oxygen content. Toxicological problems related to micro-polluting materials dissolved from plastics used for coating surfaces in contact with water, or from those used in water treatment, are dealt with in the interesting paper of P. Kertai. Although the largemolecule polymers are known to be insoluble in water, several evidences are available for the fact that monomeric residues, the large number of mostly chemicallv active auxiliary materials, the fillers and dyes may be dissolved more, or less and represent a liealth hazard. The toxicological studies of this dissolving capacity are far less advanced than the chemical industry, which serves to under line the importance of similar studies. The difficulties encountered when selecting the method of toxicological testing and evaluating the results obtained are familiar to experts working in this field, and become especially acute when considering substances, wliose detrimental effeets may become apparent after extended exposure only. Four different kinds of methods are applied by Kertai to the investigation of these effeets, which are believed to cover every aspect of the potential liealth hazards causedbv the dissolving substances. For the purpose of these investigations a "standard" solution is prepared by soaking for one week a certain quantity of the substance under consideration in a specified volume of tap water. Actual investigations are performed using diluted batches from the standard solution. All investigations are based, obviouslv, on comparison with reference specimens. The first test is the conventional test of acute toxicity, for which 10 —10 white rats are used for exposures of one week duration. These results are negative, as anticipated, the producers being equally interested that their products should not cause poisoning. The second method aiming at the investigation of semi-acute effeets, is new in the investigation of plastics. It is based on the recognition that the nervous system is the most sensitive in the humán