Abstract

VELAZQUEZ, Martha A.; PIMENTEL, José Luis  and  ORTEGA, Manuel. A study of boron distribution in water sources of the Duero river basin, by using multivariate statistical analysis. Rev. Int. Contam. Ambient [online]. 2011, vol.27, n.1, pp.19-30. ISSN 0188-4999.

The distribution of boron in the river water and groundwater of the Duero River Basin and the relative contribution of natural and anthropic sources is not yet well known. Earlier studies have shown that boron enters surface water in the Basin through wastewater, while groundwater may well constitute a geothermic source of boron. In this study, the distribution of boron in groundwater and surface water in the Duero River Basin and the potentially toxic effects of this element on human health and agricultural crops grown in the area were analyzed in order to suggest measures for a more sustainable use of these hydric sources. A total of 49 water samples were gathered from agricultural and urban wells, springs, waterholes and the Duero River itself from an area of approximately 2500 km². The samples were tested for pH, electrical conductivity, calcium, magnesium, sodium, chlorides, sulphates, bicarbonates, dissolved heavy metals, phosphorus and boron. The parameters of water quality showed a broad variation (conductivity from 152-1518 mS cm^-1 and boron concentrations of 0-11268 mg L^-1). This is due to the fact that the waters flow over an extensive area that includes both basaltic and free aquifers, where they are subject to the effects of a variety of geological formations, including tertiary and quaternary volcanic basalts and calcareous sediments in geothermic zones. The mean boron concentrations were 13, 54 and 850 mg L^-1 in the springs, river water and groundwater, respectively. The wells were classified as follows: 1) wells with no appreciable concentration of boron (southern and central areas of the Basin); and, 2) wells with high concentrations of boron (365-11268 mg L^-1, northern area of the Basin). The ratio of B/Cl was 1.6 in the springs, 15.3 in the river and 27.7 in the wells. The use of this water for agricultural irrigation represents a risk of boron accumulation in the region's vertisol, soils that facilitate the absorption of boron in soil minerals which causes toxical effects and the yield reduction of sensitive crops such as strawberries. High concentrations of boron in some urban wells confirm the potential sanitary risk to people that use this water for human consumption.

Keywords : pollution; groundwater; surface water; Michoacan; Mexico.

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