eesti teaduste
akadeemia kirjastus
Estonian Journal of Ecology
Modelling the hydrochemical status of small stratified Lake Verevi (Estonia); 87–105

Henno Starast, Tõnu Möls, Katrin Ott, Aini Lindpere, Marina Haldna
A survey is given of the vertical distribution and seasonal changes of the chemical composition of water in Lake Verevi. The majority of data consist of 166 to 1011 measurements per parameter from 1984–2001. Statistical analysis was performed with the SAS system, Release 8.1, using a 64-parameter linear model with independent factors ‘sampling year’, ‘sampling day within the year’, and ‘sampling depth’. The depth intervals where the chemical composition of water changed significantly, confidence limits, and predicted mean values were estimated using specific contrasts tailored for the General Linear Models (GLM) procedure of the SAS program package. The hydrochemical state of the lake in summer, autumn, and winter is characterized on the basis of 18 parameters. Stratification is the strongest in summer when water temperature, dissolved oxygen, oxygen saturation, and pH decrease towards the bottom. At the same time, alkalinity, the sum of Ca and Mg, conductivity, Si, CODCr and CODMn increase in the same direction. The most significant increase towards the bottom was shown by total P, PO3-4 total N, and NH+4 The concentrations of SO2-4 NO-2 and NO-3 show relatively constant values from surface to bottom. In autumn, at the time of convective mixing, differences in the water composition from surface to bottom persist but become less pronounced. According to chemical composition, the water in L. Verevi is stratified all the year round.

Alekin, O. A. 1959. Methods for investigation of physical and chemical properties of water. In Vital Functions of Fresh Water in the Soviet Union, vol. 4(2) (Pavlovski, E. N. & Zhadin, V. I., eds), pp. 213–300. Izdatel¢stvo Akademii Nauk SSSR, Moskva–Leningrad (in Russian).

Crumpton, W. G., Isenhart, T. M. & Mitchell, P. D. 1992. Nitrate and organic N analyses with second-derivative spectroscopy. Limnol. Oceanogr., 37(4), 907–913.

Fall, M. J. 1996. JENWAY Model 4150 Conductivity Meter Manual. Jenway Ltd., Dunmow, Essex.

Gubachek, Z. & Artamoshkina, F. M. (eds) 1977. Standardized Methods for the Investigation of Water Quality. Moskva (in Russian).

Hansen, H. P. & Koroleff, F. 1999. Determination of nutrients. In Methods of Seawater Analysis (Grasshoff, K., Kremling, K. & Ehrhardt, M., eds), pp. 159–226 . WILEY-VCH, Weinheim.

Hellat, K., Mashirin, A., Mei, L. & Tenno, T. 1986. Metrological guaranteeing of devices for measuring oxygen in the water. Acta Comment. Univ. Tartu., 757, 184–193 (in Russian).

Koroleff, F. 1982. Total and organic nitrogen. In Methods of Seawater Analysis (Grasshoff, K., ed.), pp. 162–168. Verlag Chemie.

Mäemets, A. 1977. Eesti NSV järved ja nende kaitse. Valgus, Tallinn.

Mäemets, A., Ott, K. & Parts, M. 1991. Hüdrokeemia. In Verevi järve seisund (Timm, H., ed.), pp. 44–68. Tartu.

Milius, A., Saan, T., Starast, H. & Lindpere, A. 1991. Total phosphorus in Estonian lakes. Proc. Estonian Acad. Sci. Ecol., 1, 122–130.

Möls, T. 2005. Lineaarsed statistilised meetodid Eesti mageveekogude vee ja elustiku analüüsi­miseks. Eesti Looduseuurijate Seltsi Kirjastus, Tartu.

Ott, I. & Kõiv, T. (eds) 2005. Lake Verevi, Estonia – A Highly Stratified Hypertrophic Lake. Springer, Netherlands.

Reports of the Baltic Intercalibration Workshop. 1977. Kiel.

Riikoja, H. 1940. Zur Kenntnis einiger Seen Ost-Eestis, insbesondere ihrer Wasserchemie. In Tartu Ülikooli Loodusuurijate Seltsi Aruanded, 46 (Lepik, E., ed.), pp. 168–329. Tartu Ülikooli juures oleva Loodusuurijate Seltsi Kirjastus.

Simm, H. 1975. Eesti pinnavete hüdrokeemia. Valgus, Tallinn.

Timm, H. (ed.) 1991. Verevi järve seisund. Estonian Academy Publishers, Tartu.

Wetzel, R. G. 1983. Limnology. Saunders College Publishing.

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