Lead transfer in the soil-root-plant system in a highly contaminated Andean area

Abstract

Lead (Pb) is highly toxic heavy metal that is detrimental to the food system. There are large mining and metallurgical companies in the central highlands of Peru that have been active for almost a century and contribute to air, water, and soil pollution, affecting food quality and causing damage to the environment and human health. Our study, conducted in 2018, assessed the content and transfer of lead in the soil-root-plant system in the high Andean grasslands in a geographical area near the metallurgical complex of La Oroya. Lead levels were measured in 120 samples of top soil (0-20 cm), roots, and grass shoots by flame atomic absorption spectroscopy. No significant differences were found between the soil pH, organic matter content, and lead among the samples evaluated (P > 0.05). Mean Pb concentrations decreased in the order of soil > root > shoot (P < 0.01) (212.36 ± 38.40, 154.65 ± 52.85 and 19.71 ± 2.81 mg/kg, respectively). The soil-to-root Pb bioconcentration factor, root-to-shoot translocation factor, and soil-to-shoot bioaccumulation factor values were 0.74 ± 0.26, 0.14 ± 0.06 and 0.10 ± 0.03, respectively. Lead in the soil was 3.03 times higher than the maximum limit for agricultural soil, and was 1.97 times higher than the value limit for fodder. Our findings are important and show that soils and pasture in this geographical area have high Pb levels due to metallurgical emissions that have been occurring since 1922. Such pollution negatively impacts health and the socio-economic status of the exposed populations.

Keywords: Bioaccumulation factor; Contaminated soil; Forage quality; Heavy metals; Highland Andes Peru; Lead bioaccumulation; Lead in plans; Smelting; Soil pH.

Figure 1. Partial map of La Oroya-Peru, research area (3,900–4,500 m. a.s.l).

La Oroya-Peru research area partial map (3900-4500 m asl). (A)The road from the La Oroya mining-metallurgical complex to the study area (20 km). (B) The study site and the distribution of soil and pasture sampling points (1 m2/sample) in two periods.