Nutrient and trace element leaching following mine reclamation with biosolids

Area of Science:

• Environmental Science
• Soil Science
• Water Quality Management

Background:

• Mine reclamation often uses biosolids to enhance revegetation success.
• Excessive nutrient addition from biosolids can lead to nutrient leaching and water contamination.
• Understanding the water quality impacts of high biosolids application rates is crucial.

Purpose of the Study:

• To monitor water quality changes over three years at a Pennsylvania mine site reclaimed with biosolids.
• To assess the impact of biosolids application at a maximum permitted loading rate (134 Mg ha(-1)) on leachate composition.
• To evaluate the potential for increased leaching of nitrate (NO3) and other biosolids constituents.

Main Methods:

• A three-year water quality monitoring study was conducted on a reclaimed mine site.
• Zero-tension lysimeters were installed at 1-m depth in biosolids-treated and control areas.
• Percolate water samples were analyzed for pH, acidity, nitrate (NO3), and heavy metals (Al, Mn, Cu, Ni, Pb, Zn).

Main Results:

• Biosolids application resulted in lower pH and higher acidity in percolate water compared to the control area.
• Maximum first-year leachate nitrate (NO3) concentrations reached approximately 300 mg L(-1), decreasing in the second year.
• Leaching of acidity and metals (Al, Mn, Cu, Ni, Pb, Zn) correlated with increased acidity, indicating mobilization due to lower pH.

Conclusions:

• High application rates of low C/N ratio biosolids can negatively impact water quality through increased acidity and metal leaching.
• Estimated inorganic nitrogen (N) leaching loss was substantial (2327 kg N ha(-1)) in the first two years post-application.
• Biosolids reclamation practices should be modified to mitigate potential adverse effects on water quality, particularly concerning application rates and nutrient management.