Soil Screening by High School Students to Map Lead Contamination From Mining in Peru

Ponce-Canchihuamán J.; Landes F.; Palacios E.; Ponce P.; Languasco J.; da Silva Moura S.; van Geen A. · GeoHealth (2026) · DOI: 10.1029/2025gh001662

Resumen

Soil contamination with toxicants such as lead (Pb) is notoriously patchy and requires considerable effort to map. In the present study of three mining-impacted Peruvian towns, nearly 2,000 students collected and tested 1,500 soil samples using a field kit that combines simulated gastric extraction with visual detection of a purple Pb rhodizonate precipitate. An additional 2,000 soil samples were tested by our team's field staff. The combined results were mapped and compared with total soil Pb concentrations measured by X-ray fluorescence (XRF). The degree of soil contamination varied across sites and within each site. Quality control was provided by reanalyzing a subset of 120 soil samples from the three sites in the laboratory. Overall, total Pb concentrations were highest in Cerro de Pasco with 64% and 30% of samples in the 201–2,000 and 2,001–20,000 mg/kg range, respectively. Total Pb concentrations were somewhat lower in La Oroya with 88% of samples in the 201–2,000 mg/kg range and even lower in Callao with 79% below 200 mg/kg. However, extractable Pb proportions followed an inverse pattern, with the sum of the proportions of medium and high visual readings increasing from 46% to 57% and 69% in Cerro de Pasco, La Oroya, and Callao, respectively. This trend relates more closely to blood-Pb concentrations in children measured at the three sites 2 decades ago than total Pb concentrations. The study demonstrates that student-conducted soil screening can effectively identify Pb contamination patterns while providing valuable science education.

Instituciones: Universidad Peruana Cayetano Heredia