Diminishing Heavy Metal Hazards of Contaminated Soil via Biochar Supplementation

Abstract

Depending on the geochemical forms, heavy metal (HM) accumulation is one of the most serious environmental problems in the world and poses negative impacts on soil, plants, animals, and humans. Although the use of biochar to remediate contaminated soils is well known, the huge quantities of waste used and its recycling technique to sustain soil in addition to its use conditions are determinant factors for its characteristics and uses. A pot experiment was conducted in a completely randomized block design to evaluate metal forms and their availability under the application of garden waste biochar (GB) pyrolyzed at different temperatures, and a sequential extraction procedure was designed to fractionate Pb, Cd, Zn, and Cu of the contaminated soil. The results show that the TCLP-extractable Pb, Cd, Zn, and Cu were significantly decreased depending on the biochar addition rate, pyrolysis temperature, and tested metal. The acid extractable fraction was significantly decreased by 51.54, 26.42, 16.01, and 74.13% for Pb, Cd, Zn, and Cu, respectively, at the highest application level of GB400 compared to untreated pots. On the other hand, the organic matter bound fraction increased by 76.10, 54.69, 23.72, and 43.87% for the corresponding metals. The Fe/Mn oxide bound fraction was the predominant portion of lead (57.25–62.84%), whereas the acid fraction was major in the case of Cd (58.06–77.05%). The availability of these metals varied according to the application rate, pyrolysis temperature, and examined metals. Therefore, the GB is a nominee as a promising practice to reduce HM risks, especially pyrolyzed at 400 °C by converting the available fraction into unavailable ones.

Lead and zinc chemical fraction alterations in multi-metal contaminated soil with pomelo peel biochar and biochar/apatite incubation

“…However, when applied with PPB500, the rate of 5:5% (PPB5A5) had a better effect on reducing F1-Pb than only 5% (PPB5:5) biochar, while the rate of 3:3% (PPB5A3) had a worse impact on reducing F1-Pb than 3% biochar (PPB5:3). The decrease in the exchangeable fraction of lead in contaminated soil when the biochar application rates increases was reported in previous studies [1,7,18].…”

“…However, identifying the chemical speciation of HMs offers more comprehensive information regarding their availability, movement, and toxicity. It is vital to understand their chemical speciation to comprehend the bioavailability and chemical form of HMs, which significantly impact their fate and redistribution [7]. Sequential extraction and fractionation procedures have been popularly used as valuable tools that may provide more comprehensive knowledge about the source, bioavailability, and toxicity of HMs [28].…”

Appraisal of Heavy Metals Accumulation, Physiological Response, and Human Health Risks of Five Crop Species Grown at Various Distances from Traffic Highway

“…We also found a strong positive correlation between proline accumulation in plants with both Pb and Cd concentrations. Proline prevents the inactivation of key enzymes by toxic metal ions [66,67]. In addition, proline acts as an osmoregulator and scavenger of free radicals thus protecting plants from oxidative injuries [68].…”

Impact of Biochar Application on Ammonia Volatilization from Paddy Fields under Controlled Irrigation

“…Through the background of climate change, environmental pollution, energy shortage, and agricultural sustainable development in recent years, biochar has attracted wide attention for its carbon sequestration and emission reduction, soil improvement [8], and environmental remediation [9][10][11][12][13]. Biochar is a solid product derived from the pyrolysis of bio-organic materials (also known as biomass) in an anaerobic or hypoxic environment [14].…”