Pb remobilization by bacterially mediated dissolution of pyromorphite Pb5(PO4)3Cl in presence of phosphate-solubilizing Pseudomonas putida

Abstract

Remediation of lead (Pb)-contaminated sites with phosphate amendments is one of the best studied and cost-effective methods for in situ immobilization. In this treatment, a very stable mineral, pyromorphite Pb5(PO4)3Cl, is formed. Several studies propose to improve this treatment method with the addition of phosphate-solubilizing bacteria (PSB). The effect of bacteria on solubilization of pyromorphite is unknown. In this study, the effect of the soil microorganisms on the stability of pyromorphite Pb5(PO4)3Cl has been investigated in a set of batch solution experiments. The mineral was reacted with Pseudomonas putida, a common soil microorganism. Dissolution of pyromorphite was enhanced by the presence of P. putida, resulting in an elevated Pb concentration in the solution. This occurred even when the bacteria were provided with an additional source of phosphate in the solution. Pyromorphite has been shown to be a potential source of nutrient phosphorus for common soil bacteria. Thus, the use of PSB in remediation treatments of Pb contaminated sites may have adverse long-term impacts on Pb immobilization. Conscious phosphate management is suggested for long-term sustainability of the in situ Pb immobilization by pyromorphite formation.

Remediation of Heavy Metal-Contaminated Agricultural Soils Using Microbes

“…In general, organic acids can bind heavy metal ions in the soil solution through the complex formation, but the stability of organic acid ligand-metal complexes is dependent on the following factors: (1) organic acids' nature (number of carboxylic groups and their position), (2) ligand-metal complex form type and (3) soil solution pH (Zaidi et al 2006 ;Jones 1998 ;Ryan et al 2001 ;Sultana et al 2014 ). The organic acids biosynthesized by microbes play an important role in the complexation of toxic and essential metal ions and increase their mobility for plant uptake (Han et al 2006 ;Sánchez-Marín and Beiras 2012 ;Fomina et al 2004 ;Martino et al 2003 ;Uroz et al 2009 ;Topolska et al 2014 ). The effect of the Pseudomonas putida inoculation on the solubility of pyromorphite Pb 5 (PO 4 ) 3 Cl has been investigated in a set of batch solution experiments.…”

“…The effect of the Pseudomonas putida inoculation on the solubility of pyromorphite Pb 5 (PO 4 ) 3 Cl has been investigated in a set of batch solution experiments. Solubilization of pyromorphite was enhanced by the presence of P. putida , resulting in an elevated Pb concentration in the solution (Topolska et al 2014 ). An endophytic bacterial strain JN27 isolated from roots of Zea mays displayed high tolerance and mobilization to Cd and was identifi ed as Rahnella sp.…”

Phosphatase‐mediated bioprecipitation of lead by soil fungi

“…Under general geochemical conditions, the pyromorphite family Pb5(PO4)3X, where X = F, Cl, Br, OH, are the most stable environmental Pb compounds (Pb5(PO4)3F, Ksp = 10 −71.6 , Pb5(PO4)3Cl, Ksp = 10 −84.4 , Pb5(PO4)3Br, Ksp = 10 −78.1 and Pb5(PO4)3OH, Ksp = 10 −76.8 ) over a wide range of conditions (Chen et al, 2007;Chrysochoou et al, 2007). mycogenic organic acids, can affect pyromorphite stability (Sayer et al, 1999;Fomina et al, 2004;Manecki and Maurice, 2008;Debela et al, 2010;Topolska et al, 2014). mycogenic organic acids, can affect pyromorphite stability (Sayer et al, 1999;Fomina et al, 2004;Manecki and Maurice, 2008;Debela et al, 2010;Topolska et al, 2014).…”

“…Microbes can import phosphate from phosphate-containing organic compounds by first cleaving C-O-P ester bonds with phosphatases that release Pi (Hýsek and Šarapatka, 1997;Hayes et al, 2000;Yadav and Tarafdar, 2001;Bull et al, 2002). apatites and other phosphates (Sayer et al, 1995;Di Simine et al, 1998;Whitelaw, 2000;Jacobs et al, 2002a,b;Fomina et al, 2004;2005;Ahemad et al, 2009;Topolska et al, 2014) but can also release phosphate from organic phosphate sources through phosphatase activity (Aickin et al, 1979;Macaskie et al, 1992;1994;2000;Yong and Macaskie, 1995;Boswell et al, 1999;Dick et al, 2011). apatites and other phosphates (Sayer et al, 1995;Di Simine et al, 1998;Whitelaw, 2000;Jacobs et al, 2002a,b;Fomina et al, 2004;2005;Ahemad et al, 2009;Topolska et al, 2014) but can also release phosphate from organic phosphate sources through phosphatase activity (Aickin et al, 1979;Macaskie et al, 1992;1994;2000;Yong and Macaskie, 1995;Boswell et al, 1999;Dick et al, 2011).…”

“…However, it has been clearly demonstrated that certain microbial metabolites, e.g. mycogenic organic acids, can affect pyromorphite stability (Sayer et al, 1999;Fomina et al, 2004;Manecki and Maurice, 2008;Debela et al, 2010;Topolska et al, 2014). The formation of lead oxalate from pyromorphite by several free-living and mycorrhizal fungi has been demonstrated (Sayer et al, 1999;Fomina et al, 2004).…”