(Autodepuration of Rio Grande í  Rio Grande í  SP Brazil). Major ions and chlorophyll a)

Authors

  • Mithine TAKINO Pesquisador Cientí­­fico -  Seção de Limnologia - Divisão de Pesca Interior - Instituto de Pesca - Bolsista CNPq
  • Maria Helena MAIER Pesquisador Cientí­­fico -  Seção de Limnologia - Divisão de Pesca Interior - Instituto de Pesca - Bolsista CNPq

Keywords:

NíO CONSTA

Abstract

This paper is part of a research on the depuration process of Rio Grande Reservoir (23°46'S and 46°38'W, altitude 746.5 m), aiming the determination of the physiographic and anthropic influences in this process. The results of monthly samplings of the water column (October 1982 to September 1983) at 3 sampling stations showed the cationic and anionic proportions Na > Ca > Mg > K and Cl > HC03 > S04 (meq/L), which were also previously found in 1979. Changes in the cation concentrations led to small changes in the M/D, D/D and M/M relations (M: monovalent, D: divalent). The chlorophyll a content showed a considerable reduction, for the median (4.91 µg/L) was approximately 10 times lower than that obtained in 1979. The median values for each station were quite similar. The reduction of the chlorophyll a content could be a result of the effect of the intensive treatment with algicides which the reservoir periodically receives. The salinity suffered a dilution along the major axis of the reservoir (from the spring to the dam), showing changes if compared to previous studies (1979).

Published

2018-06-25

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