Decreasing Lead Bioaccessibility in Industrial and Firing Range Soils with Phosphate‐Based Amendments

Abstract

In-situ stabilization using phosphate (P) amendments, such as P-based fertilizers and rock, are a potentially cost-effective and minimally disruptive alternative for stabilizing Pb in soils. We examined the effect of time (0-365 d), in vitro extraction pH (1.5 vs. 2.3), and dosage of three P-based amendments on the bioaccessibility (as a surrogate for oral bioavailability) of Pb in 10 soils from U.S. Department of Defense facilities. Initial untreated soil bioaccessibility consistently exceeded the U.S. Environmental Protection Agency default value of 60% relative bioavailability, with higher bioaccessibility consistently observed at an in vitro extraction pH of 1.5 vs. 2.3. Although P-based amendments statistically (P < 0.05) reduced bioaccessibility in many instances, with reductions dependent on the amendment and dosage, large amendment dosages (approximately 20-25% by mass to yield 5% P by mass) were required to reduce average bioaccessibility by approximately 25%. For most amendment combinations, reductions continued to occur for periods up to 1 yr, indicating that the observed reductions were not merely experimental artifacts of the in vitro extraction procedure. Although our results indicated that reductions in Pb bioaccessibility with P amendments are technically feasible, relatively large amendment masses were required to achieve relatively modest reductions in bioaccessibility. The cost and potential environmental implications of adding such large amounts of P may limit the practicality of in situ immobilization for some Pb-contaminated soils, industrial and firing range soils in particular.

An inter-laboratory trial of the unified BARGE bioaccessibility method for arsenic, cadmium and lead in soil

“…The key contaminants included in this work are arsenic (As), lead (Pb) and cadmium (Cd) as they are potentially harmful to human health (ATSDR, 2007b;ATSDR, 2007a;ATSDR, 2008) and the most common elements undergoing bioaccessibility research Ruby et al, 1993;Ruby et al, 1996;Albores et al, 2000;Oomen et al, 2002;Marschner et al, 2006;Chan et al, 2007;Datta et al, 2007;Drexler and Brattin, 2007;Finzgar et al, 2007;Hansen et al, 2007;Juhasz et al, 2007aJuhasz et al, , 2007bLjung et al, 2007;Sarkar et al, 2007;Subacz et al, 2007;Turner and Ip, 2007;Van de Wiele et al, 2007;Beak et al, 2008;Moseley et al, 2008;Girouard and Zagury, 2009;Morman et al, 2009;Nagar et al, 2009;Poggio et al, 2009;Smith et al, 2009;Zhang et al, 2009;Demetriades et al, 2010;Juhasz et al2010). …”

Firing Range Soils Yield a Diverse Array of Fungal Isolates Capable of Organic Acid Production and Pb Mineral Solubilization

“…This firing range was previously part of a study by Moseley et al (35) in which the soils (soils 7, 8, and 9) were reported to contain between 1,000 and 4,000 mg Pb kg Ϫ1 , an average of 1.63% total carbon, 1.31% total organic carbon, a pH of around 6, and an average of 20.6%, 31.7%, and 47% sand, silt, and clay, respectively. These soils were found to have high levels of Pb bioaccessibility ranging from 75.7% up to 95.7%, indicating that significant proportions of Pb in these soils are readily exchangeable and bioavailable despite their clay-rich texture and limestone mineral origin (35).…”

“…These soils were found to have high levels of Pb bioaccessibility ranging from 75.7% up to 95.7%, indicating that significant proportions of Pb in these soils are readily exchangeable and bioavailable despite their clay-rich texture and limestone mineral origin (35).…”

Toxicity characteristic leaching procedure over- or under-estimates leachability of lead in phosphate-amended contaminated soils

“…Phosphate materials are effective amendments for immobilizing heavy metals in contaminated soils (Hafsteinsdóttir et al, 2015;Moseley et al, 2008). For example, immobilization tests of Cd and Cu by NH 4 H 2 PO 4 over 35 days yielded the minerals Cd 5 H 2 (PO 4 ) 4 Á4H 2 O, Cu 3 (OH) 3 PO 4 and CuNH 4 PO 4 (Ayati and Lundager Madsen, 2000).…”