The role of biochar, natural iron oxides, and nanomaterials as soil amendments for immobilizing metals in shooting range soil

Abstract

High concentration of toxic metals in military shooting range soils poses a significant environmental concern due to the potential release of metals, such as Pb, Cu, and Sb, and hence requires remediation. The current study examined the effectiveness of buffalo weed (Ambrosia trifida L.) biomass and its derived biochars at pyrolytic temperatures of 300 and 700 °C, natural iron oxides (NRE), gibbsite, and silver nanoparticles on metal immobilization together with soil quality after 1-year soil incubation. Destructive (e.g., chemical extractions) and non-destructive (e.g., molecular spectroscopy) methods were used to investigate the immobilization efficacy of each amendment on Pb, Cu, and Sb, and to explore the possible immobilization mechanisms. The highest immobilization efficacy was observed with biochar produced at 300 °C, showing the maximum decreases of bioavailability by 94 and 70% for Pb and Cu, respectively, which were attributed to the abundance of functional groups in the biochar. Biochar significantly increased the soil pH, cation exchange capacity, and P contents. Indeed, the scanning electron microscopic elemental dot mapping and X-ray absorption fine structure spectroscopic (EXAFS) studies revealed associations of Pb with P (i.e., the formation of stable chloropyromorphite [Pb5(PO4)3Cl]) in the biomass- or biochar-amended soils. However, no amendment was effective on Sb immobilization.

Role of woody biochar and fungal-bacterial co-inoculation on enzyme activity and metal immobilization in serpentine soil

“…The addition of BC into soils improves plant growth (Jones et al 2012) primarily by increasing nutrient retention (Zheng et al 2013) and by improving microbial activities (Lehmann et al 2011). In recent years, studies have highlighted BC as an effective soil amendment to immobilize heavy metals in soils (Ahmad et al 2012;Ahmad et al 2014a;Rajapaksha et al 2015). Herath et al (2015) documented that the addition of BC to serpentine soil immobilizes Cr, Ni and Mn by reducing heavy metal toxicity in tomato plants.…”

Creation of Technosols to Decrease Metal Availability in Pyritic Tailings with Addition of Biochar and Marble Waste

“…The higher content of carbonates in MSW‐derived biochar promoted increases in soil pH up to 5·5, and the addition of MaW did not contribute to further decrease metal mobility. Previous research has also reported that pH is the main driven factor controlling metal mobility with addition of amendments (Ahmad et al ., ; Rajapaksha et al , ; Paz‐Ferreiro et al ., ). Thus, the addition of warble waste as a source of CaCO 3 is confirmed as a sustainable material for the creation of Technosols from pyritic tailings to decrease metal toxicity, also observed in previous studies (Pardo et al , ; Zornoza et al , ).…”

“…A variety of stabilizing materials have been used such as cement, lime, mussell shell, marble waste (MaW), glacial till, iron oxide, nanomaterials, peat, manure, compost or biochar (Pardo et al , ; Zornoza et al , ; Moon et al ., ; Ahmad et al, ; Rajapaksha et al. , ; Paz‐Ferreiro et al ., ; Smart et al ., ). The primary mechanisms of metal immobilization by stabilizing agents are cation exchange, adsorption, complexation and precipitation (Ahmad et al ., ).…”

“…This goal can be achieved by applying materials with metal stabilization potential, to transform bioavailable metal species into geochemically stable forms (Traina & Laperche, 1999). A variety of stabilizing materials have been used such as cement, lime, mussell shell, marble waste (MaW), glacial till, iron oxide, nanomaterials, peat, manure, compost or biochar (Pardo et al, 2011;Zornoza et al, 2012;Moon et al, 2013;Ahmad et al, 2014;Rajapaksha et al, 2015;Paz-Ferreiro et al, 2016;Smart et al, 2016). The primary mechanisms of metal immobilization by stabilizing agents are cation exchange, adsorption, complexation and precipitation (Ahmad et al, 2014).…”

Integrating EDDS-enhanced washing with low-cost stabilization of metal-contaminated soil from an e-waste recycling site

“…1c&d). It has been shown that Cu, Pb and Zn could be immobilized on the surface of the biochar via formation of surface complexes and precipitates, as well as ion exchange with oxygen-containing functional groups, carboxyl groups (-COOH) in particular (Uchimiya et al, 2011b;Rajapaksha et al, 2015). In addition, electrostatic attraction and cation-p electron donoracceptor interactions could occur on the graphene-like surface of biochar (Qiu et al, 2009;Zhang et al, 2015;Ahmad et al, 2016b).…”