Investigation of an Optimal Sampling Resolution to Support Soil Management Decisions for Urban Plots

Area of Science:

• Environmental Science
• Geospatial Analysis
• Soil Science

Background:

• Lead pollution in urban soils poses risks to community reuse projects.
• The U.S. Environmental Protection Agency (USEPA) updated lead (Pb) soil thresholds in January 2024.
• Urban settings present unique challenges for soil lead remediation due to multiple contaminant sources.

Purpose of the Study:

• Determine the optimal soil sampling density for identifying lead pollution hotspots in urban community reuse sites.
• Evaluate the trade-off between sampling resolution and labor efficiency.
• Inform soil management decisions for urban land redevelopment.

Main Methods:

• In situ X-ray Fluorescence (pXRF) was used to measure soil lead concentrations.
• Inverse distance weighted geospatial interpolation was applied to analyze sampling data.
• Various grid sampling resolutions (3-m to 12-m) were compared.

Main Results:

• A 6-meter grid resolution (approximately 1/36-m² density) was identified as the largest effective resolution for detecting lead hotspots.
• Higher sampling densities (smaller grids) are required to meet the 100-mg/kg threshold in urban areas, often necessitating extensive excavation.
• The 200-mg/kg threshold was used for analysis due to the impracticality of the 100-mg/kg threshold in the studied urban context.

Conclusions:

• A 6-meter grid sampling strategy provides an effective balance for identifying lead pollution hotspots in urban soils for community reuse.
• Efficient soil screening protocols are crucial for managing environmental risks and facilitating land redevelopment.
• The findings support informed soil management practices in urban environments facing lead contamination.