**1. Introduction**

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is the most widely used herbicide around the world. In agricultural soils, approximately 29–34 million kg of atrazine are applied per year [1]. In Mexico, more than 45% of pesticides are categorized as herbicides, and atrazine is one of the most commonly used herbicides in Mexican agriculture [2]. Since 1975, atrazine has been applied to control broadleaf and grass weeds in agricultural crops, including corn, sorghum and sugar cane. Atrazine kills susceptible plants by binding to the quinone protein in photosystem II and inhibiting photosynthetic electron transport [3].

Atrazine is a pre-emergent herbicide and is considered to have low persistence in soil (<12 months). However, its low mobility in soil and its physical and chemical properties contribute towards the contamination of ground and surface waters, which represents a risk to the environment and to human health [4]. In Mexico, atrazine levels in water often exceed the maximum permissible levels for drinking water (0.1 μg L−1) as established by Europe and by the health advisory board of the United States Environmental Protection Agency (EPA) [5, 6]. At a molecular level, atrazine has distinct fates in the environment and may be found in soil, water, biomass (plants) or air. In soil, atrazine is adsorbed by clay particles; however, other adsorption-desorption processes may be involved in its translocation in plants, movement in soil and mobility in aqueous systems, as well as its eventual abiotic or biological degradation [7].

The clean-up of soils contaminated with atrazine is an ecological responsibility, and the discovery of a safe and economical method is a major priority for land management agencies [8]. One such possibility is mycoremediation, or the use of fungal organisms and their enzymes to degrade or transform environmental pollutants [9]. This strategy has been used to degrade pesticides [10], aromatic and polycyclic hydrocarbons [11] and endocrine disruptors [12]. The degradation of environmental pollutants by fungi, specifically by white-rot fungi, is due to their ability to synthesize ligninolytic enzymes, such as laccase, manganese peroxidase and lignin peroxidase, as well as their production of hydrogen peroxide [13, 14].

However, mycoremediation faces several challenges in order to improve the feasibility of this strategy. The following issues, for example, should be addressed: (i) the competition/proliferation of native soil microorganisms (actinomycetes and bacteria) may inhibit the growth of bioremedial fungi; (ii) bioremedial fungi have a limited capacity to produce ligninolytic enzymes. Enzyme production varies depending on the strain and species and is mainly influenced by the content and availability of nutrients (carbon, nitrogen, metal ions, etc.), which stimulate fungal growth and the synthesis of ligninolytic enzymes; finally, (iii) edaphic and environmental factors may adversely affect the establishment and growth of bioremedial fungi [9].

The use of fungal extracts with a proven high activity of ligninolytic enzymes is one means of improving the degradation of pollutants in soil, which may also address some of the aforementioned challenges. Ligninolytic enzymes in white-rot fungi, for example, may be enhanced through the use of fungal co-cultures, although the mechanism by which increased enzyme activity occurs has not yet been described [15]. Given this context, the objectives of the study were: (i) to evaluate the degradation of atrazine in soil microcosms by a white-rot fungus (*Trametes maxima*) and its co-culture with a soil-borne micromycete (*Paecilomyces carneus*) and ii) to determine the absorption-desorption kinetics of atrazine in a clay-loam soil.
