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

Abstract

Measuring the reduction of in vitro bioaccessible (IVBA) Pb from the addition of phosphate amendments has been researched for more than 20 years. A range of effects have been observed from increases in IVBA Pb to almost 100% reduction. This study determined the mean change in IVBA Pb as a fraction of total Pb (AC) and relative to the IVBA Pb of the control soil (RC) with a random effects meta-analysis. Forty-four studies that investigated the ability of inorganic phosphate amendments to reduce IVBA Pb were identified through 5 databases. These studies were split into 3 groups: primary, secondary, and EPA Method 1340 based on selection criteria, with the primary group being utilized for subgroup analysis and meta-regression. The mean AC was approximately -12% and mean RC was approximately -25% for the primary and secondary groups. For the EPA Method 1340 group, the mean AC was -5% and mean RC was -8%. The results of subgroup analysis identified the phosphorous amendment applied and contamination source as having a significant effect on the AC and RC. Soluble amendments reduce bioaccessible Pb more than insoluble amendments and phosphoric acid is more effective than other phosphate amendments. Urban Pb contamination associated with legacy Pb-paint and tetraethyl Pb from gasoline showed lower reductions than other sources such as shooting ranges and smelting operations. Meta-regression identified high IVBA Pb in the control, low incubated soil pH, and high total Pb with the greater reductions in AC and RC. In order to facilitate comparisons across future remediation research, a set of minimum reported data should be included in published studies and researchers should use standardized in vitro bioaccessibility methods developed for P-treated soils. Additionally, a shared data repository should be created for soil remediation research to enhance available soil property information and better identify unique materials.

Opportunities and Challenges Associated with Bioavailability-Based Remediation Strategies for Lead-Contaminated Soil with Arsenic as a Co-Contaminant—A Critical Review

“…Soil amendment strategies presented in Figs. 1 and A recent meta-analysis review of phosphate amendment studies [51] identified that soluble amendments such as PA showed higher immobilization efficacy than insoluble amendments such as RP. TERs may also vary due to differences in application rates (0.5-10% w/w), P:Pb molar ratios (1:1-5:1), the presence of other soil constituents (e.g., Ca and Zn), which may interact with phosphate, contamination source and the initial concentration of Pb in soils (i.e., highly contaminated mine impacted soils vs. low/ mild elevation as in most urban soils).…”

Estimativa da extensão superficial da contaminação por chumbo (Pb) no solo em uma unidade de conservação de proteção integral no município de São Paulo.

“…. Para diferenciar entre medições in vivo e in vitro, os resultados in vitro são referidos como bioacessíveis(MAYER;BASTA;SCHECKEL, 2022). A bioacessibilidade é uma medida in vitro (IVBA, do inglês in vitro bioacessibility) da solubilidade fisiológica da substância química(US EPA, 2017).…”