Immobilization and phytotoxicity reduction of heavy metals in serpentine soil using biochar

Abstract

Purpose Serpentine soils derived from ultramafic rocks release elevated concentrations of toxic heavy metals into the environment. Hence, crop plants cultivated in or adjacent to serpentine soil may experience reduced growth due to phytotoxicity as well as accumulate toxic heavy metals in edible tissues. We investigated the potential of biochar (BC), a waste byproduct of bioenergy industry in Sri Lanka, as a soil amendment to immobilize Ni, Cr, and Mn in serpentine soil and minimize their phytotoxicity. Materials and methods The BC used in this study was a waste byproduct obtained from a Dendro bioenergy industry in Sri Lanka. This BC was produced by pyrolyzing Gliricidia sepium biomass at 900°C in a closed reactor. A pot experiment was conducted using tomato plants (Lycopersicon esculentum L.) by adding 1, 2.5, and 5 % (w/w) BC applications to evaluate the bioavailability and uptake of metals in serpentine soil. Sequential extractions were utilized to evaluate the effects of BC on bioavailable concentrations of Ni, Cr, and Mn as well as different metal fractionations in BCamended and BC-unamended soil. Postharvest soil in each pot was subjected to a microbial analysis to evaluate the total bacterial and fungal count in BC-amended and BCunamended serpentine soil. Results and discussion Tomato plants grown in 5 % BCamended soil showed approximately 40-fold higher biomass than that of BC-unamended soil, whereas highly favorable microbial growth was observed in the 2.5 % BC-amended soil. Bioaccumulation of Cr, Ni, and Mn decreased by 93-97 % in tomato plants grown in 5 % BC-amended soil compared to the BC-unamended soil. Sequentially extracted metals in the exchangeable fraction revealed that the bioavailabile concentrations of Cr, Ni, and Mn decreased by 99, 61, and 42 %, respectively, in the 5 % BC-amended soil. Conclusions Results suggested that the addition of BC to serpentine soil as a soil amendment immobilizes Cr, Ni, and Mn in serpentine soil and reduces metal-induced toxicities in tomato plants.

Crop response to soils amended with biochar: expected benefits and unintended risks

“…This eventually increases pesticide residual life in soil and negatively affects soil micro-biota. Similarly, absorption capacity of BC has a potential to mitigate the bioavailability of heavy metals in contaminated soils (Beesley et al, 2010;Domene et al, 2015;Fellet et al, 2011Fellet et al, , 2014Herath et al, 2015;Hossain et al, 2015).…”

Amelioration of a degraded ultisol with hardwood biochar: Effects on soil physico-chemical properties and yield of cucumber (Cucumis sativus L)

“…Lehmann and Joseph (2012) have distinguished the term biochar from charcoal in that it is charred organic matter that is applied to soil not only to improve soil properties but also to promote soil remediation or other environmental services while the charcoal is used as fuel or source of heat, as a filter, as a reductant in iron-making or as a colouring agent in industry or art. Researches on biochar are expanding rapidly not only because of its potential for carbon sequestration (Sohi and Shackley, 2009) but also for its several co-benefits as soil amendment, such as increase in crop yield (Akca and Namli, 2015), potential as a technology for immobilizing pollutants (Herath et al, 2015) and increasing soil fertility and nutrient retention in soils. Though previous researchers have really explored the potentials of biochar as soil amendments for agricultural production and improvement of soil quality (Ndor et al, 2015), research on accurate rate of biochar application on a degraded Ultisol and other soil types for specific arable crops is scanty and rather proceeding slowly.…”

Assessing the influence of technosol and biochar amendments combined with Brassica juncea L. on the fractionation of Cu, Ni, Pb and Zn in a polluted mine soil

“…1) Tables 3 and 4). Soil fractions are F1 (water-soluble), F2 (exchangeable), F3 (carbonate bound and specifically sorbed), F4 (associated mainly on Fe and Mn oxides), F5 (organically bound) and F6 (residual) the modification of both organic matter content and soil pH changed the chemical distribution of metal in soils (Herath et al 2014;Khurana and Kansal 2014). As observed for Cu, the higher the amendment rate, the lower the sum of Ni concentrations in the mobile fractions ( Fig.…”