Resumen

SANCHEZ BERNAL, Edgar Iván et al. Leaching of alluvial costal soils from Oaxaca, México, using treated wastewaters. Rev. Int. Contam. Ambient [online]. 2012, vol.28, n.4, pp.343-360. ISSN 0188-4999.

The soils of the coastal alluvial plain of Colotepec, Oaxaca, with deficient natural drainage, a shallow water table and irrigated with well-water of moderate salinity, accumulate salts in the top 20 cm of the soil layer. Its tipogenesis form Solonchaks that limit the growth and development of crops. In order to study the movement of salts in the topsoil, it is leached using wastewater as an alternative to sustainable-use water sources to avoid untreated discharge into the intertidal zone and to protect from over-extraction of groundwater used for irrigation. The leaching experiment took place in greenhouse conditions using soil columns collected from the field. A leaching standard of (Qa/Qπ) = 1 was applied, equal to 54.82 m³/ha using the following treat-ments: distilled water (control), well water, treated waste-water and, finally, a mix of well-water and treated waste-water at equal amounts (1:1). Initial salinity of soils was determinated at 5.40 g/L (91.83 Mg/ha). The percentage of exchangeable sodium was superior to 15 % and the pH more than 8.5. The average residual salinity of soil thick-ness (0-30 cm) leached with well-water was 0.67 g/L (11.39 Mg/ha) and the percentage of exchangeable sodium was 2.76 %. With treated waste-water it was determined to be 0.86 g/L (14.62 Mg/ha) and the percentage of exchangeable sodium was 6.53 %. These values indicate adequate levels of salinity and exchangeable sodium. Leaching with both types of water temporarily desalinized the topsoil.

Palabras llave : salinity; sodicity; lixiviation; desalination.