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Homogeneous and heterogeneous aqueous systems of the herbicides of chlorbromuron, atrazine, and alachlor were irradiated with a nonexpensive solar irradiation using a photoreactor with recirculation. Photodegradation of these herbicides occurred in both aqueous systems; however the presence of TiO2clearly accelerated the degradation of the three herbicides in comparison with direct photolysis. Degradation was followed by measuring the chemical oxygen demand (COD) as a function of reaction time for each aqueous system. Over 90% of COD abatement in the heterogeneous aqueous system was obtained in a short time period showing that mineralization of chlorbromuron, atrazine, and alachlor was achieved.

Fe-doped TiO2 was prepared by the sol gel method and characterized by X-ray diffraction. All the Fe-doped TiO2 were composed of an anatase crystal form. The activity of the Fe-doped TiO2 for the degradation of the gesaprim commercial herbicide (which contains atrazine as active compound and formulating agents) was studied by varying the iron content during UV (15 W), visible light and solar irradiations. The visible light came from commercial saving energy lamps (13, 15 and 20 Watts). The gesaprim degradation rate depended on the iron content in the photo catalyst. The Fe-doped TiO2 (0.5% by weight of TiO2) showed higher TOC removal under visible light and was more active than the undoped TiO2 photo catalyst under the light irradiation sources tested. Over 90% of chemical oxygen demand abatement was achieved with both UV and visible light but less time was required to decrease the chemical oxygen demand content by using the catalyst doped with iron at 0.5% under visible light. It was observed that the degradation of gesaprim increased by increasing the iron content in the catalyst under visible light

Palabras clave: herbicida, disponibilidad, vida media RESUMEN La atrazina es ampliamente utilizada en México y el estado de Morelos en la eliminación de maleza de hoja ancha en cultivos de maíz, sorgo, caña de azúcar y piña. Su uso está prohibido en la Unión Europea y restringido en Estados Unidos de América. Hasta el momento sólo se han caracterizado los procesos que influyen en la migración de atrazina sin presencia de emulsificantes y surfactantes. El presente trabajo tiene como objetivo caracterizar la adsorción y la biodegradación de atrazina al 100 % y gesaprim (producto comercial con 43 % atrazina y mezclado con surfactantes y emulsificantes), en diferentes muestras de suelo agrícola del estado de Morelos. Se hicieron muestreos en tres municipios: Moyotepec, Yecapixtla, y Huautla, con base en las diferentes texturas del suelo (arenosos, limosos y arcillosos). Los suelos fueron caracterizados fisica y químicamente, asimismo se obtuvieron las cinéticas de biodegradación con atrazina al 100 % como ingrediente activo y con el producto comercial gesaprim que contiene 43 % de atrazina como ingrediente activo.. Las vidas medias en los suelos Moyotepec, Yecapixtla y Huautla para el gesaprim fueron 126, 18 y 40 d y los porcentajes de biodegradación de 21.4, 71.8 y 50.1 %. Para atrazina al 100 %, fueron de 17, 16 y 6 d y los porcentajes de degradación de 52.7, 72.9 y 65.8 %, respectivamente. Con base en las vidas medias de atrazina al 100 % y gesaprim (43 % atrazina), se observó que la presencia de surfactantes y humectantes disminuye la velocidad de biodegradación y el porcentaje de biodegradación, con lo que se favorecen otros procesos de disipación, debido probablemente a que aumenta la disponibilidad del herbicida.Key words: herbicide, availability, half-life ABSTRACT Atrazine is widely used in Mexico and in the state of Morelos to eliminate broadleaf weeds in maize, sorghum, sugarcane and pineapple crops. Its use is prohibited in the European Union and restricted in the United States of America. So far, only processes that influence atrazine migration without the presence of emulsifiers and surfactants have been characterized. The present work aims to characterize the adsorption and biodegradation of pure atrazine (100%) and gesaprim (commercial product with 43 % atrazine mixed with surfactants and emulsifiers), in different samples of agricultural Rev. Int.