Total concentration and geoavailability of potentially toxic elements in volcanic soils with agricultural use in the Nevado de Toluca, Mexico

The indiscriminate use of agrochemicals for food production in the Nevado de Toluca, Mexico, has caused negative impacts on the soil, including changes in its physical, chemical and biochemical properties, which implies a potential risk to human health and the environment. Therefore, the objective of the current study was to evaluate the total and geoavailable concentrations of potentially toxic elements (As, Pb, Cd, Zn, Cu and Fe) in agricultural soils of Nevado de Toluca where intensive, semi-intensive and traditional agriculture are practised. Inductively coupled plasma atomic emission spectroscopy was applied to the determination of concentrations of potentially toxic elements. Determination of total arsenic levels was carried out by hydride generation atomic absorption spectrometry. Results show that soils where intensive agriculture and semi-intensive agriculture are practised, total concentration (mg/kg) of potentially toxic elements is greater than in those soils of traditional agriculture. In some of the potentially toxic elements it was observed an evident increase of their geoavailability (mg/L), even though such concentrations are low in absolute terms. The uncontrolled use of agrochemicals is a factor of degradation in agricultural soils of Nevado de Toluca since it modifies their physical and chemical properties, mainly in soils where intensive agriculture and semi- intensive agriculture are practised to cultivate potatoes. The addition of agrochemicals has caused a severe acidification (pH = 2.8 - 4.2) and consequently an accelerated weathering of clay, which has favoured the reduction of the cationic exchange capacity, the decreased organic matter content and the increase of electrical conductivity. Hence, the results of this study demonstrate environmental (soil quality) and human health risks in the long run due to the abuse of agrochemicals.