Biochar amendment changed soil-bound fractions of silver nanoparticles and ions but not their uptake by radish at an environmentally-relevant concentration

Abstract

Plant uptake of silver nanoparticles (Ag NPs) and ions (Ag +) largely depends on their exchangeable and soil-bound fractions in soils, which may be influenced by biochar amendment. This study investigated the effects of biochar amendment (0.1% and 1.0%) on soil sorption of Ag NPs and Ag + , their soil-bound fractions, and their uptake and translocation by radish grown in a loamy sand soil spiked with 1 mg/kg Ag NPs or Ag +. Sorption of Ag + to the soils was much greater than that of Ag NPs, mainly because negatively charged soil particles would attract Ag + , but repel negatively charged Ag NPs. Biochar amendment at 1.0% (by weight) significantly decreased the reducible fraction of Ag + in the soils with and without radish plants and increased the oxidisable fraction of Ag NPs in the soils with radish plants. Biochar amendment had no significant effect on Ag uptake by radish plants (p > 0.05), probably due to low exchangeable Ag fractions in all experimental treatments. In this short-term experiment (35 days), the addition of 1 mg/kg Ag NPs or Ag + did not substantially elevate the level of Ag in radish roots (0.05 ± 0.02-1.06 ± 0.98 mg/kg) and shoots (0.01 ± 0.00-0.03 ± 0.01 mg/kg), compared to the blank control (p > 0.05). Radish uptake of Ag NPs and Ag + at the environmentally-relevant concentration was low with root concentration factors between 0.03 ± 0.03 to 0.29 ± 0.21 and root-to-shoot translocation factors between 0.08 ± 0.10 to 0.89 ± 1.21, which may partially explain the non-significant effect of biochar amendment on Ag uptake.

Fractionation of Heavy Metals in Multi-Contaminated Soil Treated with Biochar Using the Sequential Extraction Procedure

“…To fractionate these metals, many authors have recognized that sequential extraction is a crucial method that could provide useful information on the bioavailability of metals and their transformation forms [ 14 , 18 , 19 , 20 ]. Although several studies confirmed that biochar is an important material for adsorbing HMs from contaminated soil, the mechanism is still unclear [ 4 , 21 ].…”

Probabilistic risk assessment of AgNPs for human health through dietary consumptions of crops

“…However, direct uptake of the particulate form of silver has been observed in plants from a number of studies. 19,68,69 As most of the selected bioaccumulation studies didn't differentiate ionic or particulate silver in crops' edible parts, the oral RfD of silver ions and AgNPs were both considered in this risk assessment. The RfD of pristine AgNPs was adopted due to the lack of the dose response relationship of transformed AgNPs such as sulfurized AgNPs.…”