Abstract
Nanoparticles with high reactivity can be applied as amendments to remediate soil metal contaminations by immobilizing toxic elements. Nano-oxides of Fe have been studied but Al and Ti nano-oxides have not been tested for their remediation capacity of toxic metals. The potential of synthesized iron (Fe-O), aluminum (Al-O), and titanium (Ti-O) nano-oxides for stabilizing Cd, Pb, and Zn in mine spoil (Chat) and contaminated soil was compared using adsorption studies and a greenhouse experiment. Chat and soil were amended with nano-oxides at two rates (25 and 50 g·kg−1) and a pot experiment was conducted with sorghum (Sorghum bicolor L. Moench). Leachates were collected twice per week from plant emergence to harvest at maturity and metals were compared against an unamended control. Chat was contaminated with Cd, Pb, and Zn at 84, 1583, and 6154 mg·kg−1, and soil at 15, 1260, and 3082 mg·kg−1, respectively. Adsorption conformed to the Langmuir linear isotherm and adsorption maxima of metals were in the order of Al-O > Ti-O ≥ Fe-O. Nano-oxides reduced Cd concentration by 28% (Fe-O) to 87% (Ti-O) and Zn concentration by 14% (Fe-O) to 85% (Al-O) in plant tissues compared with unamended Chat. Nano-oxides significantly reduced Cd, Pb, and Zn in leachates and available Cd and Zn in Chat/soil relative to the respective unamended controls. Nano-oxides can be used to remediate heavy metal contaminated Chat and soil and facilitate plant growth under proper nutrient supplements. Nano-oxides of Al-O and Ti-O remediated metals more effectively than Fe-O.
Highlights
Soil contamination with toxic elements is both a local and global concern
The initial properties of Chat amended with CaO and manure, and soil were favourable for plant growth, irrespective of their trace metal contents
Phytoavailable metal concentrations evaluated by diffuse gradients in thin films (DGT) showed Cd, 1.67 and 0.15 μg, and Zn, 55 and 24 μg, respectively, for Chat and soil
Summary
Soil contamination with toxic elements is both a local and global concern. There are over 20 million ha of land contaminated by toxic elements with soil concentrations being higher than the geobaseline or regulatory levels (Liu et al 2018). Known as Chat, contaminated with Cd, Pb, and Zn due to the mining of Pb and Zn minerals, were left with a large amount of tailing piles (Pierzynski et al 2002a; Johnson et al 2016) on this site. Vegetative cover establishment is one viable remediation option for such contaminated sites to reduce spreading of toxic materials (Brown et al 2003). In situ stabilization of toxic metals using effective amendments is essential in the process of preparation of Chat and contaminated soil for vegetation
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