Using phosphate amendments to reduce bioaccessible Pb in contaminated soils: A meta-analysis

Area of Science:

• Environmental Science
• Geochemistry
• Soil Science

Background:

• Lead (Pb) contamination in soil poses risks to human health and ecosystems.
• In vitro bioaccessible (IVBA) lead is a key metric for assessing exposure risk.
• Phosphate amendments are widely studied for their potential to reduce Pb IVBA.

Purpose of the Study:

• To determine the mean reduction in IVBA Pb using phosphate amendments through meta-analysis.
• To identify factors influencing the effectiveness of phosphate amendments in reducing Pb IVBA.
• To provide recommendations for standardizing future soil remediation research.

Main Methods:

• A random effects meta-analysis was conducted on 44 studies.
• Studies were categorized into primary, secondary, and EPA Method 1340 groups.
• Subgroup analysis and meta-regression were used to identify significant factors.

Main Results:

• Phosphate amendments, on average, reduced IVBA Pb by approximately -12% (AC) and -25% (RC) in primary/secondary groups.
• Reductions were less pronounced in the EPA Method 1340 group (-5% AC, -8% RC).
• Soluble amendments, phosphoric acid, and specific contamination sources (e.g., shooting ranges) showed greater Pb IVBA reduction.

Conclusions:

• Phosphate amendments are effective in reducing soil lead IVBA, with variations based on amendment type and contamination source.
• Factors like high initial IVBA Pb, low soil pH, and high total Pb correlate with greater reductions.
• Standardized methods and data sharing are crucial for advancing soil remediation research.