Conocarpus biochar as a soil amendment for reducing heavy metal availability and uptake by maize plants

Abstract

The objective of this study was to assess the use of Concarpus biochar as a soil amendment for reducing heavy metal accessibility and uptake by maize plants (Zea mays L.). The impacts of biochar rates (0.0, 1.0, 3.0, and 5.0% w/w) and two soil moisture levels (75% and 100% of field capacity, FC) on immobilization and availability of Fe, Mn, Zn, Cd, Cu and Pb to maize plants as well as its application effects on soil pH, EC, bulk density, and moisture content were evaluated using heavy metal-contaminated soil collected from mining area. The biochar addition significantly decreased the bulk density and increased moisture content of soil. Applying biochar significantly reduced NH4OAc- or AB-DTPA-extractable heavy metal concentrations of soils, indicating metal immobilization. Conocarpus biochar increased shoot dry biomass of maize plants by 54.5-102% at 75% FC and 133-266% at 100% FC. Moreover, applying biochar significantly reduced shoot heavy metal concentrations in maize plants (except for Fe at 75% FC) in response to increasing application rates, with a highest decrease of 51.3% and 60.5% for Mn, 28% and 21.2% for Zn, 60% and 29.5% for Cu, 53.2% and 47.2% for Cd at soil moisture levels of 75% FC and 100% FC, respectively. The results suggest that biochar may be effectively used as a soil amendment for heavy metal immobilization and in reducing its phytotoxicity.

Effect of thermal conversion of pig manure and poultry litter on the content and mobility of Mn and Fe in biochars and in soil after their application

“…Undoubtedly, the considerable increase in soil pH as a result of application of organic materials (especially biochars) contributed to this. The obtained research results on the decrease in Mn mobility find confirmation in the results published by Al-Wabel et al (2015). Reduction of acidification led to formation of poorly soluble Mn compounds in the soil.…”

“…It has been shown that the content of Fe and Mn extracted with 0.025 M C 10H22N4O8 was higher than the content of these elements extracted with 1 M NH4NO3, mainly due to different extraction force of the solutions (Al-Wabel et al, 2015). The obtained results indicate that the amendment of organic materials to the soil did not have much effect on the content of Fe and Mn in the organic fraction (Table 6).…”

“…It should also be highlighted that the highly porous structure of biochar and the presence of functional groups did not have a significant impact on adsorption of Fe and Mn. According to Al-Wabel et al (2015), amendment of biochar to soil has an effect on the content of available forms of both Fe and Mn. Fellet et al (2011) also showed that biochar reduces the mobility of trace elements.…”

Using bamboo biochar with compost for the stabilization and phytotoxicity reduction of heavy metals in mine-contaminated soils of China

“…The root uptake of Zn, Pb, Cd and Cu was reduced by as much as 19%, 30%, 50 and 28%, respectively, in T4 in the case of FC soil and 13%, 14%, 19 and 32%, respectively, in TG soil compared to their respective controls. Similarly, 28, 60 and 53.2% reductions in Zn, Cu and Cd, respectively were reported after 10% biochar application to soil 24 . These results further illustrated that the reduction in the bioavailable fraction in FC and TG soil decreased the uptake of HMs in Brassica roots.

Figure 4Effect of bamboo biochar on root uptake (mg kg −1 DW) of TEs in Brassica juncea .

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A comparison of technologies for remediation of heavy metal contaminated soils

“…Biochar is a carbon rich, porous, purpose-produced charcoal manufactured during the pyrolysis of organic residues such as municipal waste, animal wastes, wood, crop residues, and biosolids. Several studies revealed that addition of biochars to soil greatly enhanced the sorption of heavy metal(loid)s and significantly reduced their mobility and phytoavailability (Al-Wabel et al, 2015;Puga et al, 2015). Addition of biochar to soil changes chemical, physical, and biological properties of soil.…”