SEASONAL AND SPATIAL VARIANTIONS STUDY OF MAJOR IONS IN WATER AND SEDIMENT OF IBITINGA RESERVOIR (SÃO PAULO BRAZIL 21°45’S AND 48°50’W)

ABSTRACT

SEASONAL AND SPATIAL VARIANTIONS STUDY OF MAJOR IONS IN WATER AND SEDIMENT OF IBITINGA RESERVOIR (SÃO PAULO BRAZIL 21°45’S AND 48°50’W).

Seasonal and spatial variations in water and sediment of Ibitinga Reservoir was studied from October/89 to November/90, an entire seasonal cycle. Water samples from superficial, middle and bottom column were collected monthly, at 3 sample stations (E-1, E-2 and E-3); including two stations in Jacaré Pepira (EJP) and Jacaré Guaçu (EJG) outfall rivers. At the E-1 and E-2 stations, in the whole period, the cation dominant order was Na⁺ > Ca⁺> K⁺ >Mg⁺, and only in E-2, in the dry period, this order was inverted (Na⁺> Ca⁺⁺> Mg⁺⁺ >K⁺). The anion order was HCO₃^-> SO₄⁼ > Cl^- for reservoir stations for the whole period. In relation to sediment, in Ibitinga Reservoir the dominant order was Ca⁺ >Mg⁺ during the 4 whole period. Jacaré Pepira and Jacaré Guaçú rivers had the dominance of Mg > Ca > K > Na, in the rainy period, and Ca⁺ > Mg⁺ > K⁺ > Na⁺, in the dry period. In relation to ionic dominance, for both rivers, Cl^-was superior to SO ⁼ during the whole period. According to the results, the reservoir ionic content was determined mainly by the Tietê River entrance, and the rain regulation and the tributary rivers were secondary. The Ibitinga Reservoir's water had ionic content double that of Latin America waters, (rain period Tz+: E1 = 26.0 mg/L; E-2 = 31.3 mg/L; E-3 = 31.3 mg/L and TzE-1 = 69.7 mg/L; E-2 = 68.8 mg/L; E-3 = 77.9 mg/L and dry period – Tz=: E-1 = 23.4 mg/L; 23.5 mg/L; 21.9 mg/L and Tz-: E-1 = 60.3mg/L; E-2 = 54.6 mg/L; E-3 = 56.7 mg/L) and the dominant Na⁺ ion suggests an anthropic contribution, through domestic and industrial effluents, and a progressive water quality losts in this reservoir.

KEY WORDS
Reservoir; tropical; major ions; water quality; sediment