Effect of biosolids processing on lead bioavailability in an urban soil

Area of Science:

• Environmental Science
• Soil Science
• Remediation Technologies

Background:

• Urban soils often suffer from lead (Pb) contamination, posing risks to environmental and human health.
• Biosolids, a byproduct of wastewater treatment, are explored for their potential to immobilize heavy metals in soil.
• Different biosolids processing technologies may influence their efficacy in reducing metal bioavailability.

Purpose of the Study:

• To evaluate the effectiveness of biosolids products in reducing lead (Pb) availability in a high Pb urban soil.
• To compare the bioavailability reduction achieved by different biosolids composts, including high iron and high iron + lime variants.
• To correlate in vivo and in vitro methods for assessing Pb bioavailability changes after amendment.

Main Methods:

• Pb-contaminated soil (2000 mg kg(-1) Pb) was amended with biosolids composts (100 g kg(-1)) and incubated for 30 days.
• Pb bioavailability was assessed using in vivo (weanling rat feeding studies) and in vitro (various extraction procedures) methods.
• Conventional (DTPA, Ca(NO3)2) and sequential extractions were employed alongside a rapid in vitro method (pH 2.3).

Main Results:

• Addition of high iron biosolids compost reduced Pb bioavailability by 37% (in vivo) and 43% (in vitro).
• Three out of four tested compost materials reduced Pb bioavailability by over 20%.
• The rapid in vitro (pH 2.3) method showed strong correlation (R=0.9) with in vivo bone Pb results, and sequential extraction indicated Pb partitioning to Fe and Mn oxides.

Conclusions:

• High iron and manganese biosolids composts effectively reduce lead availability in Pb-contaminated urban soils at the tested application rate.
• The rapid in vitro extraction method shows promise as a reliable predictor of in vivo Pb bioavailability.
• Biosolids application represents a viable remediation strategy for lead-contaminated urban soils.