Geochemical characteristics and quality evaluation of soils in the Mantaro Basin, central Peru

Abstract

In order to enhance the geoscientific collaboration between China and Peru using China’s advanced geochemical investigation and research methods, the China Geological Survey (CGS) and Peru, Instituto Geológico, Minero y Metalúrgico (INGEMMET) jointly conducted a multipurpose geochemical survey in the Mantaro Basin of central Peru. The samples were collected and analyzed in Chinese laboratory according to applicable Chinese national standards. According to the results, the soil of the study area was in general weakly alkaline, with strong enrichment of Au and relatively enriched indicators such as I, C, Corg, Cd, and N. The soil nutrient indicators N and P were relatively abundant, but K was lacking. The comprehensive nutrient grade was mainly “relatively rich” (Grade 2), accounting for 74.1% of the total area, indicating good soil fertility. In terms of soil environmental assessment, Zn and Pb showed slight to severe pollution in a small number of areas, while Cd and As contamination was widespread. The comprehensive grade of soil environment was predominantly “slightly to lightly polluted”, with the polluted areas mainly concentrated within 5 km from either side of the Mantaro River, while the heavily polluted areas were mainly distributed close to the Mantaro River and Huancayo City with large population density. The heavy metal pollution was serious, and the spatial distribution of pollution was closely related to the Mantaro River. The comprehensive geochemical grade of soil quality was mainly “moderate” to “severe”, constituting 83.18% of the area, with only 16.82% of the area graded “good to high quality”. In summary, the Mantaro Basin was found to have relatively rich soil nutrients, severe heavy metal pollution, and a moderate to poor overall soil quality. Recommendations to relevant agencies include strengthening environmental management and control of heavy metal pollution sources in the Mantaro River and its upstream areas.