Saturday, 15 July 2006

Distribution of Man Induced Mineral Salts and Arsenic in the Irrigated Lands of Semi-Arid North Ethiopia.

Fassil Kebede Yimamu, Mekelle Univ, -, -, Mekelle, 231, Ethiopia

Appearance of white salt patches on the irrigated fields of Tigray, north Ethiopia with high concentrations of soluble salts may be toxic on saline and sodic soils by increasing the solute suctions, reducing the availability of air and water to plants. For appropriate reclamation of such soils, it is imperative to diagnose the salt types in the irrigated fields where the problem is aggravated. Thus, this study was attempted to examine and identify the salt types and arsenic distribution. Salt, soil and water specimens were collected from southern, central and eastern Tigray having major small-scale irrigation activities. The samples were analyzed using X-Ray Diffractometry and other standard techniques. Accordingly, Gypsum (17.2%), Calcite (14.1%) and Gismodine (2.8%) were found to be the major saline forming mineral types in irrigated fields of the Korir and Wukro dams, respectively. In irrigated field of the Gumselasa Dam, southern Tigray, Calcite (31.4%), Anorthite (10.8%), and Gypsum (7.5%) were predominant. In irrigated field of the May Delle dam, Central Tigray, Thenardite (44.3%), Calcite (9.8%), Halite (9.2%), Zincobloedite (5.6%) and Gypsum (2.5%) were found in order of importance. Besides, the mineral types in the May Negus dam in Axum are Anorthoclase (63.7%) and Gypsum (9.5%), merely. In addition, the Arsenic distribution ranged between 260-440, 260-300 and 260-460 ppm in Korer, Kelamino and Gumselesa irrigated fields, respectively. Keywords: man induced, mineral salts, Arsenic, irrigated lands, Ethiopia.

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