Resumen

ESPOSITO, ME et al. Natural pollution (As, F) and eutrofication (N, P) in the basin of El Divisorio stream, Argentina. Phyton (B. Aires) [online]. 2016, vol.85, n.1, pp.51-62. ISSN 1851-5657.

The interrelation between hydrochemistry and hydrodinamics was analyzed in the basin of El Divisorio stream. This was to gain undestanding in the magnitude, distribution of toxic ions (As, F) and behaviour in the discharge of main nutrients (P, N) contributing to the eutrofication of Paso de las Piedras Dam. During two years, 47 sites were sampled determining several parameters: geographical position for each sampling point, phreatic level depth, and As, F, PO₄ and N-NO₃ concentrations. Repeated measures, Fisher test, correlation and regression analysis were applied to all variables. Highly significant space and time diferences (P<0.01) with increments of 0.3 m were detected for isohypses. At every site, diferences with a variable degree of significance were recognized for chemical parameters (As, F, PO₄ and N-NO₃). Hydrodinamics behaves mainly in accord with the seasonal rainfall contribution; run of affects some of the hydrochemical parameters giving rise to a variability that influences water quality. N-NO₃ and PO₄ concentrations are the main factors that cause eutrofcation expressed through algae bloom episodes and deterioration of stored water quality. P is the critical element and in the dry periods the highest contribution is through groundwater flux and to a lesser extent by the continuous discharge of surface water. In the period of greater runof, these elements incorporated to the sedimentary charge as a result of soil erosion, and coming by fertilizers and pesticides are transported in suspension towards the reservoir.

Palabras clave : Pollution; Eutrofication; Hydrochemistry; Hydrodynamics.

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