Examining heavy metals in guava: Soil quality and climatic effects

Guava (Psidium guajava L.) is a key crop for food security and economic livelihoods in Colombia, where it supports thousands of families and holds a designation of origin for its derived products. However, heavy metal (HM) contamination in soils poses risks to agricultural productivity, food safety, and export potential. The objective was to determine how soil factors and environmental conditions influence the accumulation of heavy metals, particularly cadmium, arsenic, mercury, and lead in guava production areas. Soil and plant tissue samples were collected from various regions, assessing soil biological activity through basal respiration and dehydrogenase activity, while heavy metal concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS). Random Forest models and principal component analysis were also employed to analyze the influence of edaphic, climatic, and remote sensing variables. Heavy metal concentrations varied significantly across matrices, with soils showing the highest levels (up to 7.76 mg kg⁻¹ Cd in Guavatá and 1.46 mg kg⁻¹ Cr in Puente Nacional), while fruits maintained uniformly low concentrations except for Cd in Guavatá. Soil microbial activity (SMA) peaked in Vélez and Guavatá (156–154 kg ha⁻¹ d⁻¹ at 24 h), whereas dehydrogenase activity was highest in Puente Nacional (64 µg TTF g⁻¹ 24 h⁻¹). Random Forest and PCA revealed that precipitation, soil density, and clay content drove Cd distribution, with SMA exhibiting a strong negative correlation (R² = 0.86; 15.2% Cd reduction per 10-unit SMA increase). Spatially, Cd clustered in Guavatá-Vélez (29% of area > 1.47 mg kg⁻¹), while high SMA zones (161 kg ha⁻¹ d⁻¹) predominated in central-western regions, underscoring their inverse relationship. Heavy metal concentrations in guava fruits and soils complied with safety limits, supporting safe consumption and export. Soil microbial activity significantly reduced Cd bioavailability (− 15.2% per 10-unit SMA increase), highlighting its role in mitigating contamination. Precipitation and soil density were critical environmental drivers. These findings provide actionable insights for sustainable guava production and soil management in Santander, Colombia.