Patterns of accumulation and baseline values for metals in agricultural soils from a copper mining region in southern Peru

Abstract

As global copper demand surges, it’s vital to conduct a thorough analysis of metal concentrations in the agricultural soils of mining districts. This is especially pertinent for the Andean region, where, in the face of clear soil degradation, there’s a notable lack of in-depth research. This study is the first attempt to characterize variations in the concentration of 17 metals in the agricultural soils of Moquegua – a region with a long history of mining activity that contributes significantly to Peru’s position as the world’s second-largest producer of copper. The surface horizons of 336 agricultural soils under vegetable crops were sampled between 9 and 3,934 m above sea level (m.a.s.l.) to determine the total content of metal nutrients (MNs) (Ca, Mg, K, Na, Fe, Cu, Mn, Zn) and heavy metals (HMs) (Cd, Cr, Ni, Pb, As, Co, Ba, V, Al) by inductively coupled plasma-optical emission spectrometry (ICP-OES). The accumulation of metals was found to increase with altitude. The study identified hotspots with a high concentration of metals and spatial patterns in their geographic distribution. The observed median values for As (70.9 mg/kg), Cd (7.1 mg/kg), and Pb (89.7 mg/kg) represent the highest metal concentrations among the identified clusters. Notably, these values surpass the Environmental Quality Standards (ECA) set for agricultural soils in Peru. As there are no local standards for all the metals studied, our results can serve as reference values for guiding land management practices, particularly in the context of copper mining.