You are here:
Phosphorus Amendment Efficacy for In Situ Remediation of Soil Lead Depends on the Bioaccessible Method
Citation:
Obrycki, J., N. Basta, K. Scheckel, B. Stevens, AND K. Minca. Phosphorus Amendment Efficacy for In Situ Remediation of Soil Lead Depends on the Bioaccessible Method. Elizabeth Guertal, David Myroid, and C. Wayne Smith (ed.), JOURNAL OF ENVIRONMENTAL QUALITY. American Society of Agronomy, MADISON, WI, 45(1):37-44, (2016).
Impact/Purpose:
Developing management recommendations for Pb-contaminated urban soils is necessary to address public questions regarding best practices for using urban soils (Kim et al., 2014). Adding phosphates to Pb-contaminated soils offers one management technique for reducing Pb bioaccessibility as measured by in vitro bioaccessibility tests (Basta et al., 2001; Brown et al., 2007; Scheckel et al., 2013; Zia et al., 2011). This practice has demonstrated reductions in animal and plant Pb uptake. Some forms of phosphate amendments, such as adding large volumes of compost, can reduce Pb exposure due to dilution. Variations in soil Pb response to P amendments depend upon the Pb and P mineral forms. This variation means that phosphate treatments are not always effective in reducing Pb-bioaccessibility and bioavailability. The best case for remediation occurs when soluble P interacts with soluble Pb. This study evaluated phosphate treatment efficacy on two soils collected from Cleveland, OH using EPA Method 1340 and 3 additional extractions that modified the pH and glycine content. The two soils were selected because one was from a garden area and another was from a city lot. Both soils had Pb concentrations >400 mg kg-1 which placed these soils above the EPA screening level for bare soil areas that will be used by children. These soils represented two examples of contaminated soils that are encountered in urban areas where phosphate amendments would likely be considered as a remediation strategy.
Description:
A validated method is needed to measure reductions of in vitro bioaccessible (IVBA) Pb in urban soil remediated with amendments. This study evaluated the effect of in vitro extraction solution pH and glycine buffer on bioaccesible Pb in P-treated soils. Two Pb-contaminated soils (790-1300 mg Pb kg-1), one from a garden and one from a city lot in Cleveland, OH, were incubated in a bench scale experiment for 1 yr. Six phosphate amendments, including bone meal, fish bone, poultry litter, monoammonium phosphate, diammonium phosphate, and triple superphosphate, were added to containers at two application rates. Lead IVBA was assessed using USEPA Method 1340 and three modified versions of this method. Modifications included using solutions with pH 1.5 and 2.5 as well as using solutions with and without 0.4 mol L-1 glycine. Soil amendments were effective in reducing IVBA Pb in these soils as measured by pH 1.5 with glycine buffer. The greatest reductions in IVBA Pb, from 5 to 26%, were found using pH 2.5 extractions. Lead mineral results showed several soil amendments promoted Pb phosphate formation, an indicator of remediation success. A significant negative linear relationship between reduction in IVBA Pb and Pb-phosphate formation was found only for pH 2.5 without glycine extraction solution. A modified USEPA Method 1340 without glycine and using pH 2.5 has the potential to predict P soil treatment efficacy and reductions in bioavailable Pb.
