Rethinking soil contamination assessment for urban brownfield management: from total hazard to bioavailability.

Area of Science:

• Environmental Science
• Soil Science
• Ecotoxicology

Background:

• Hazard identification often relies on total potentially toxic element (PTE) concentrations, overestimating risks.
• Bioavailability, not total concentration, determines actual adverse effects and environmental risks.
• Current methods can lead to costly and unnecessary remediation actions.

Purpose of the Study:

• To develop a practical and cost-effective methodology for assessing soil contamination by PTE, incorporating bioavailability.
• To differentiate between total, environmentally available, and bioavailable fractions of PTEs.
• To provide a more accurate and ecologically meaningful assessment of soil hazard for informed decision-making.

Main Methods:

• A three-tiered hazard identification approach: total PTE content, CaCl2 leachable fraction (environmentally available), and plant leaf accumulation (environmentally bioavailable).
• Computation of an Integrated Hazard Excess (IHE) index to aggregate contaminant levels.
• Application of the methodology to a former industrial site, analyzing soil and plant samples for PTEs (As, Cd, Cr, Cu, Ni, Pb, Zn).

Main Results:

• Mapping of IHE values provided a holistic contamination overview of the studied site.
• While total PTE levels were high, mobile and bioavailable fractions were within the range of local urban background levels.
• The study demonstrated that actual environmental risk was significantly lower than suggested by total PTE concentrations.

Conclusions:

• Distinguishing between total, available, and phytoavailable PTE amounts offers a more accurate ecological risk assessment.
• This approach supports decision-making for less disruptive and more sustainable remediation strategies.
• The methodology helps avoid unnecessary excavation and landfill operations, reducing remediation costs.