Soil health alterations with compost additions to natural and remediated heavy metal-contaminated mineland soils

The Oronogo-Duenweg mining belt in southwest Missouri is an EPA Superfund site due to Pb-contaminated soil and groundwater from historic mining and smelting. Remediation has removed Pb-contaminated overburden, uncovering nutrient-deficient C horizons containing elevated Cd and Zn concentrations which impede natural revegetation. This study evaluated compost at rates of 180 and 360 Mg ha-1, monitoring changes in soil properties observed at naturally revegetated sites, native prairie locations (i.e., the soil health benchmark), and areas receiving compost treatments. The Soil Management Assessment Framework (SMAF) was employed to assess physical (bulk density (Bd)), water-stable aggregates (WAS)), chemical (pH, electrical conductivity (EC)), nutrient (plant-available P and K), and biological (soil organic C (SOC)), microbial biomass C (MBC), potentially mineralizable N (PMN), and β-glucosidase activity (BG)) soil health indicators and soil health scores.  Soil metal concentrations were determined using Mehlich-3 and 0.01M CaCl2 extractions, alongside plant total metal concentrations extracted with concentrated HNO¿ and 30% H¿O¿. Compost-treated soils exhibited overall soil health comparable to native prairie; both had greater overall soil health than the natural revegetation site. However, the 360 Mg ha-1 rate led to excessive Mehlich-3 extractable P compared to 180 Mg ha-1. Mehlich-3 extractions revealed that the compost added Cd and Zn to the system, yet Cd and Zn concentrations from the 0.01M CaCl2 extraction were negligible in the compost treated soils.  Plant heavy metal concentrations were below tolerable limits for livestock consumption. A target compost application rate of 180 Mg ha-1, or lower, is suggested for balancing phosphorus and metal concentrations while improving overall soil health.

Impact/Purpose

The Oronogo-Duenweg mining belt in southwestern Missouri, is a designated United States Environmental Protection Agency Superfund site due to lead-contaminated soil and groundwater caused by historic mining and smelting operations. Sites within this area have undergone remediation, which often entails removal of the residual mining wastes and the upper soil horizons (e.g., O, A, and B horizons) to remove the lead contamination to the “clean-up” level of 400 ppm lead.  This leaves subsurface soil layers exposed and incalcitrant to revegetation efforts because of lack of soil development, the presence of coarse fragments or the presence of quantifiable amounts of Zn and Cd.  To improve soil conditions and encourage successful remediated site revegetation this study evaluated compost application at rates of 180 and 360 Mg ha-1.  Changes in soil properties observed at naturally revegetated sites, undisturbed native prairie locations, and remediated soils receiving compost treatments. The Soil Management Assessment Framework (SMAF) was employed to assess physical (bulk density (Bd)), water-stable aggregates (WAS)), chemical (pH, electrical conductivity (EC)), nutrient (plant-available P and K), and biological (soil organic C (SOC)), microbial biomass C (MBC), potentially mineralizable N (PMN), and β-glucosidase activity (BG)) soil health indicators and soil health scores. Compost-amended soils exhibited overall soil health comparable to native prairie and had greater overall soil health than naturally revegetated soils. The 360 Mg ha-1 rate of compost led to excessive extractable P compared to the 180 Mg ha-1 compost treatment. Soils extracted with 0.01M CaCl2 found that extracted Zn and Cd were negligible in the compost treated soils.  Plant heavy metal concentrations were below acceptable limits for livestock consumption. A target compost application rate of 180 Mg ha-1, or lower, is suggested for balancing phosphorus and metal concentrations while improving overall soil health. These results suggest that soil reclamation using biochar and compost can improve mine-impacted soil biogeophysical characteristics, and potentially improve future remediation and revegetation efforts not only in the Oronogo-Duenweg mining belt, but at other mine-impacted sites across the U.S.

Citation

Umeobi, E., T. Ducey, M. Johnson, AND J. Ippolito. Soil health alterations with compost additions to natural and remediated heavy metal-contaminated mineland soils. Ecomed Verlagsgesellschaft AG, Landsberg, GERMANYs11356-025-36602-1, (2025). [DOI: 10.1007/s11356-025-36602-1]

DOI: Soil health alterations with compost additions to natural and remediated heavy metal-contaminated mineland soils