Vertical variation of atrazine mineralization capacity in soils

Agriscientia

Barriuso, E.¹  Hang, S.²  Houot, S.¹ 

[1]National Institute of Agronomical Research, Thiverval-Grignon, Francia

[2]U. N. C.

关键词: : Atrazine mineralization;    Adapted sub-soil;    Microbial inactivation;    Bioremediation;   

DOI  :  

学科分类：农业科学（综合）

来源: Universidad Nacional de Cordoba * Facultad de Ciencias Agropecuarias

【 摘 要 】

Se estudió la variación de la capacidad de mineralización de atrazina en dos suelos de la provincia de Córdoba, Argentina. Se seleccionaron dos perfiles de suelos con (suelo adaptado) y sin (suelo no adaptado) historia de aplicación de atrazina. La evolución de atrazina fue caracterizada mediante el balance de la radioactividad del 14C del anillo triazínico identificando las fracciones mineralizada, extractable y no extractable, durante incubaciones en condiciones de laboratorio con suelo tratado con calor (T105) y sin él (Control). La disminución de la capacidad de degradación de atrazina después de la inactivación microbiana y la limitada recuperación de esa capacidad observada en el perfil de suelo adaptado sugirió que los microorganismos degradadores de atrazina estarían distribuidos en todo el perfil siendo los responsables de la mineralización de atrazina en los horizontes subsuperficiales. Contrariamente, en el perfil de suelo no adaptado, la recuperación de la mineralización de atrazina a niveles similares o ligeramente superiores a los del Control corroboró la vía cometabólica del proceso característica de suelos sin historia de uso de atrazina. La capacidad de mineralización de atrazina por los horizontes subsuperficiales, donde tiende a acumularse este herbicida, en suelos con aplicaciones frecuentes de atrazina debiera ser considerada y estimulada como un mecanismo de bioremediación natural.Palabras clave: Mineralización de atrazina; Subsuelo adaptado; Inactivación microbiana; Biorremediación. Fecha de recepción: 01/06/07; fecha de aceptación: 20/12/07 INTRODUCTION Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) is a herbicide that has been banned from the phytosanitary market in some countries due to its pollution risks. However, in other countries such as Argentina and Brazil, it is still widely used (SAGPyA, 2001; Associação Nacional de Defesa Vegetal, 2003). Although atrazine behaviour in soil has been studied for the last 50 years, risks of pollution remain difficult to predict. As with other pesticides, the spatial and temporal variability of biodegradation in soils is probably the main obstacle to adjusting and validating prediction models. During the last ten years, a great amount of experimental evidence has confirmed that some microorganisms or consortia can develop specific enzymatic systems able to mineralize the triazine ring (Mandelbaum et al., 1995; Topp et al., 2000) Identification of such populations both in pure cultures and in soil has led to a distinction between "adapted" and "nonadapted" soils, according to their capacity to mineralize atrazine (Barriuso & Houot, 1996). Currently, the occurrence of this phenomenon is well described (Stolpe & Shea, 1995; Shapir et al., 2000; Ofstrofsky et al., 2002; Smith et al., 2005), as well as the repeated use of atrazine as an initiator of the development of the adapted population (Barriuso & Houot, 1996; Hang et al., 2003). This adapted soil condition is a characteristiCOf the first centimetres of soil reached by herbicide; nevertheless the occurrence of this process has also been described in some subsoil layers (Vanderheyden et al., 1997; Jenks et al. , 1998; Sparling et al., 1998; Hang et al., 2005).Larsen et al., (2000) consider that two factors determine potential subsurface water contamination by a pesticide: its transformation in soil and its ability to be transported through the soil profile. Moreover, Topp et al. (1995) consider that the destruction of pesticides migrating in soils requires microorganisms with suitable degradative capabilities, appropriate environmental conditions for the microorganisms to function, and sufficient residence time for biodegradation to occur. Extractable residues of atrazine tend to accumulate in the first 35-50 cm of the soil profile (Clay et al. , 2000; Asare et al., 2001). Thus, to characterize and quantify the atrazine mineralization capacity of the horizons next to the surface, particularly in soils that receive this herbicide yearly, is an economical and useful tool for selecting agricultural practices that stimulate subsurface biodegradation, for estimating the risk of transport to groundwater and for selecting bioremediation practices. The aim of this work was to evaluate vertical variation of atrazine mineralization capacity in an adapted soil profile with atrazine application history. The occurrence of atrazine-degraders in the soil profile was evaluated by means of soil microbial activity inactivation. The behaviour of 14C-atrazine was studied in laboratory incubations by following the distribution of radioactivity between mineralized, extractable and non-extractable fractions. A nonadapted soil profile was included as a soil control without accelerated atrazine mineralization. MATERIALS AND ME

【 授权许可】

CC BY-NC