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Major element, trace element, nutrient, and radionuclide mobility in a mining by-product-amended soil
G Douglas1, J Adeney, K Johnston
1CSIRO Land and Water, WA, Australia. grant.douglas@csiro.au
Journal of Environmental Quality
|November 7, 2012
Summary
Neutralized used acid (NUA), a mineral by-product, significantly reduced phosphorus and nitrogen loss in turf soil. NUA amendment improved soil retention of nutrients, trace elements, and radionuclides, offering agronomic benefits and limiting eutrophication.
Area of Science:
- Environmental Science
- Soil Science
- Agronomy
Background:
- Mineral processing generates by-products like neutralized used acid (NUA), primarily gypsum and Fe-oxyhydroxide.
- Soil amendments are crucial for improving soil health and agricultural productivity.
- Offsite nutrient loss, particularly phosphorus, contributes to eutrophication.
Purpose of the Study:
- To evaluate the efficacy of NUA as a soil amendment in a turf farm setting.
- To assess the impact of NUA on nutrient, trace element, and radionuclide mobility in soil.
- To determine the potential agronomic benefits and environmental implications of NUA application.
Main Methods:
- A 1489-day field trial was conducted on a turf farm.
- Soil was amended with approximately 5% NUA by mass to a depth of 15 cm.
- Subsoil leachates were collected to analyze nutrient (PO4-P, Total Nitrogen) and trace element fluxes.
- Geochemical analysis, including mineral saturation indices and isotopic analysis (Pb, Sr, Nd), was performed.
- Retention of U-Th series radionuclides and radioactivity dose rates were assessed.
Main Results:
- NUA amendment reduced PO4-P and Total Nitrogen fluxes in leachates by 97% and 82%, respectively.
- NUA incorporation led to increased soil saturation of Fe- and Ca-minerals, enhancing assimilation of PO4-P and trace elements.
- Isotopic analysis showed minimal Pb addition from NUA; Sr and Nd isotopes indicated NUA as a Ca source.
- Soils amended with NUA effectively retained U-Th series radionuclides, with limited transfer to leachate or biomass.
- Calculated radioactivity dose rates showed only a minor increase due to NUA.
Conclusions:
- NUA amendment significantly improves soil's capacity to retain nutrients, trace elements, and radionuclides.
- The dissolution of gypsum from NUA promotes the formation of minerals that sequester pollutants.
- NUA application offers potential agronomic benefits, including increased productivity and improved nutrient use efficiency.
- NUA can effectively limit offsite nutrient loss, mitigating eutrophication risks.
- This study demonstrates the viability of using NUA as a sustainable soil amendment for environmental and agricultural benefits.
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