Biochar Amendment Reduces the Availability of Pb in the Soil and Its Uptake in Lettuce

Abstract

The aim of this study was to investigate the ability of biochar amendment to reduce the availability of Pb in the soil and its uptake in lettuce (Lactuca sativa L. var. adela). Seedlings of lettuce were cultivated in Pb-contaminated soils, both with and without 5% biochar (w/w), as well as in a simplified soilless system (hydroponics) at the ecologically relevant Pb concentration of 100 µM, both with and without 1% biochar. Soils amended with biochar resulted in a ca. 50% reduction of the extractable (bioavailable) fraction of Pb, limiting the accumulation of this toxic element in the leaves of lettuce by ca. 50%. A similar behavior was observed for lettuce plants grown hydroponically, even with a much higher reduction of Pb uptake (ca. 80%). Increased cation exchange capacity and pH were likely the main factors limiting the bioavailability of Pb in the soil. Complexation with functional groups and precipitation/co-precipitation both on the biochar surface and in soil aggregates were likely the main mechanisms immobilizing this element.

Metal uptake from iron ore mine tailings by perennial ryegrass (Lolium perenne L.) is higher after wheat straw than wheat straw biochar amendment

“…In present study, compared with the control, decreased metal uptake of Co, Cu, Fe, Mn, Zn, Cr and Ni in the BC 2% treatment was consistent with Fellet et al (2011). The biochar application increased the organic carbon content and pH in the tailings (Table 1), likely increasing metal complexation with organic matter and decreasing a relative proportion of the metallic cations at higher pH, with both of these processes limiting the mobility and availability of Cu ( (Vannini et al 2021). By contrast, shoot metal accumulation increased with increasing rate of wheat straw amendment (Table 3).…”

Effects of Wood-Derived Biochar on Germination, Physiology, and Growth of European Beech (Fagus sylvatica L.) and Turkey Oak (Quercus cerris L.)

“…In line with this assumption, readily amended soils in the present study showed increases in both CEC and pH of 32% and 12%, respectively ( Table S1 ). Moreover, the shift in soil pH from weakly acidic to basic may also have limited the mobility and thus the availability of toxic elements for plants [ 62 , 63 ].…”

Soil Amendments and Foliar Melatonin Reduced Pb Uptake, and Oxidative Stress, and Improved Spinach Quality in Pb-Contaminated Soil

“…Formerly, amending the Pb-polluted soil with BH and MKC reduced Pb uptake in spinach shoots [6]. Similarly, Vannini et al [62] confirmed that the addition of BH (5% w/w) in Pb-contaminated soil effectively reduced soil bioavailable fraction of Pb (up to 50%) and its accumulation in lettuce shoots (up to 50%). The lower availability of Pb in the soil and its uptake by spinach is because of multiple mechanisms associated with BH and MKC in the CIA, which are as follows: (i) the hydration process of MKC within the soil contributed to the conversion of Pb into extremely insoluble Pb-based compounds and struvite-K encapsulation [63] and (ii) the presence of extensive functional groups (like hydroxyl, carboxyl, and phenolic) on BH surfaces efficiently adsorbed Pb 2+ through precipitation, electrostatic interaction, and surface complexation [13].…”