Enrichment, leaching, and availability of arsenic in agricultural soils irrigated with contaminated water in central Mexico

Nadia Martínez-Villegasa, C. Y. Cordero-Vázqueza, M. González-Moscosob, O. Delgado-Rodrígueza, A. Juárez-Maldonadob, H. J. Peinado Guevarac, A. E. Marin-Celestinoa, D. M. Meza-Figueroad and B. SenGuptae

a Geociencias Aplicadas, Instituto Potosino de Investigación Científica y Tecnológica, A.C., Mexico

b División de Agronomía, Universidad Autónoma Agraria Antonio Narro, Mexico

c Escuela de ciencias económicas y administrativas, Universidad Autónoma de Sinaloa, Mexico

d Departamento de Geología, Universidad de Sonora, Mexico

e School of Energy, Geoscience, Infrastructure & Society, Heriot-Watt University, United Kingdom

nadia.martinez@ipicyt.edu.mx

Irrigation of agricultural soils with arsenic contaminated water causes arsenic soil enrichment. In the case of permeable aerated soils, arsenic is known to accumulate on iron oxides, causing therefore low leaching and availability. In semi-arid calcareous environments, however, arsenic could be readily mobile and available due to the relatively low content of iron oxides and the solubility of calcite and gypsum. To investigate the leaching and availability of arsenic in agricultural calcareous and gypsic soils with a history of irrigation with arsenic-contaminated water from metallurgical contamination, we collected samples of agricultural surface (0-30 cm) and vertical (0-60 cm) soil to determine total arsenic concentration, water soluble arsenic, and soil mineralogy. Surface soil samples were collected from 0 to 30 cm, while vertical soil samples were collected every 10 cm. We then determined the permeability of the soils by measuring, in-situ, soil moisture using a soil moisture meter and soil electrical resistivity using geophysical methods to further estimate particle size distribution and hydraulic conductivity. Next, we determined the availability of arsenic to maize (Zea mays), sunflower (Helianthus annuus L.), and alfalfa (Medicago sativa) crops in greenhouse experiments. We also determined bioconcentration and translocation of arsenic within the different crops. We found arsenic enrichment in agricultural soils up to 185 mg/kg, which is up to 5 times higher than the background concentrations of 35 mg/kg and 8.5 times higher than Mexican guideline for agricultural soils. Furthermore, we found that arsenic leaches consistently along the soil profile ( 80 mgAs/kg, on average, from 0 to 60 cm) despite being only semipermeable (from 0.002 cm/h to 1.23 cm/h). Arsenic leaching was attributed to a high solubility of arsenic in water (10% of total arsenic, on average), highlighting a risk for arsenic uptake which, in fact, caused high toxicity (necrosis, reduced growth, chlorosis, or death) in sunflower, alfalfa, and maize plants as well as high bioconcentration and translocation. Results from study contribute to understanding leaching and availability of arsenic in semipermeable, semi-arid environments where knowledge is very limited.

results matching ""

    No results matching ""