Abstract

SALAZAR-LEDESMA, Maricarmen et al. Susceptibility of soil to human impact: case fo the atrazine herbicide. Bol. Soc. Geol. Mex [online]. 2018, vol.70, n.1, pp.95-119. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2018v70n1a6.

Soil deterioration during the Anthropocene is a result of human activities such as misuse of chemical compounds like herbicides and inadequate agricultural management practices. Atrazine is the most widely used herbicide in maize (Zea mays) crops around the world. Its application is used for improving agricultural yields. However, it also represents a risk factor towards environmental contamination and human health. The objective of this work was to evaluate the adsorption-desorption capacity of atrazine in three types of soils under different agricultural management: (i) Andosol under rainfed agriculture; (ii) Phaeozem under conventional tillage (LC) and under zero tillage (LZ); and (iii) Vertisol under rainfed agriculture (VT), and Vertisols irrigated with raw wastewater during 56 and 100 years (V56 and V100). Standard batch experiments were performed on samples of each soil type with and without organic matter (OM). Adsorption capacity was higher in the soil samples containing OM. The following distribution coefficients (Kd) were obtained: the highest Kd value was obtained in the Andosol (19 L/kg), followed by the Vertisol (3 to 11 L/kg), and the lowest was in the Phaeozem (1 L/kg). We found that the larger affinity of the herbicide for the organic fraction of the soil is not only related to the organic content, but also due to its chemical composition (degree of aromaticity). This depends mainly upon the agricultural management practices such as crop rotation and the incorporation of residues at the end of the crop cycle. Also, the use of wastewater during irrigation and the type of tillage performed are additional factors that affect the quality of soil organic matter. Therefore, the atrazine retention capacity of the soil, contributes to the soil buffering function and to the environmental destination of the herbicide.

Keywords : Atrazine; adsorption-desorption; soil organic matter; agricultural management; Andosol; Phaeozem; Vertisol.

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