Lukáš Trakal

Lead and cadmium sorption mechanisms on magnetically modified biochars.

This paper discusses Cd(II) and Pb(II) sorption efficiency of biochars modified by impregnation with magnetic particles. All selected biochar characteristics were significantly affected after the modification. More specifically, the cation exchange capacity increased after the modification, except for grape stalk biochar. However, the changes in the pH value, PZC, and BET surface after modification process were less pronounced. The metal loading rate was also significantly improved, especially for Cd(II) sorption on/in nut shield and plum stone biochars (10- and 16-times increase, respectively). The results indicated that cation exchange (as a metal sorption mechanism) was strengthened after Fe oxide impregnation, which limited the desorbed amount of tested metals. In contrast, the magnetization of grape stalk biochar reduced Pb(II) sorption in comparison with that of pristine biochar. Magnetic modification is, therefore, more efficient for biochars with well-developed structure and for more mobile metals, such as Cd(II).

Geochemical and spectroscopic investigations of Cd and Pb sorption mechanisms on contrasting biochars: engineering implications.

Biochars prepared from nut shells, plum stones, wheat straws, grape stalks and grape husks were tested as potential sorbents for Cd and Pb. Mechanisms responsible for metal retention were investigated and optimal sorption conditions were evaluated using the RSM approach. Results indicated that all tested biochars can effectively remove Cd and Pb from aqueous solution (efficiency varied between 43.8% and 100%). The removal rate of both metals is the least affected by the biochar morphology and specific surface but this removal efficiency is strongly pH-dependent. Results of variable metal removal combined with different optimized conditions explain the different metal sorption mechanisms, where the predominant mechanism is ion exchange. In addition, this mechanism showed very strong binding of sorbed metals as confirmed by the post-desorption of the fully metal-loaded biochars. Finally, these biochars could thus also be applicable for metal contaminated soils to reduce mobility and bioavailability of Cd and Pb.

Sorption behavior of Cd, Cu, Pb, and Zn and their interactions in phytoremediated soil.

The aim of our study was to compare the sorption properties of a contaminated soil before and after two types of phytoremediation (natural phytoextraction vs. phytostabilization with dolomite limestone (DL) application). Soil from a pot experiment in controlled greenhouse conditions performed for two vegetation periods was used for the study. Lead, as the main contaminant in the studied soil, was easily desorbed by Cu, especially due to the increased affinity of Cu for soil organic matter; hence input of Cu to the studied soil can present another environmental risk in soils contaminated with other metals (such as Pb). In addition, the sorption behavior of chosen metals from single-element solutions differed from multi-element solutions. The obtained results proved the different sorption behavior of metals in the single-element solution compared to the multi-element ones. Soil sorption behavior of Cd, Cu, and Zn decreased with the presence of the competitive metals; nevertheless, Pb sorption potential was not influenced by other competitive metals. Natural phytoextraction showed no significant effect on the sorption of Cd, Cu, Pb, and Zn onto the soil. On the other hand, phytostabilization associated with DL application improved the soil sorption efficiency of all chosen metals, especially of Cu.

Phytoextraction of Metals: Modeling Root Metal Uptake and Associated Processes

Because the efficiency of phytoextraction processes is still questionable, various mechanistic and empirical models are needed to better evaluate the suitability of the method. This chapter discusses different aspects of such modeling. First, models predicting the transport of metals and metalloids in the soils and in the roots are presented and discussed in accordance with well-known mechanisms of metal uptake. Because metal (and metalloid) uptake greatly depends on their speciation in the soil solution, several geochemical models providing such information are presented here. This chapter provides an in-depth overview of those models; however, their combination (geochemical, transport, empirical, etc.) will be crucial in order to obtain a robust and transferable model of metal/metalloid uptake and phytoextraction.

Modelling of Cd, Cu, Pb and Zn transport in metal contaminated soil and their uptake by willow (Salix × smithiana) using HYDRUS-2D program

AimsThe main aim of this study was to validate the HYDRUS-2D model for the simulation of Cd, Cu, Pb and Zn transport within a soil column and their accumulation by willows.MethodsA simulation of metal transport and uptake by willow was implemented using the HYDRUS-2D code. Two scenarios of the column experiment were compared: soil (C) and soil with planted willows (V). Seeping water, soil water content and actual transpiration were measured. Metal contents in soil water and willows were analysed.ResultsThe single-porosity model (applied for isotropic soil media) was sufficient for scenario C. The single-porosity (applied for anisotropic soil media) and dual-porosity models (characterizing non-equilibrium water flow) were explored in scenario V. Measured cumulative Cd and Zn uptake showed a 20- and 10-times higher accumulation, respectively, in comparison with the modelled ones. On the other hand, modelled cumulative Pb uptake was reduced by reducing the maximum value of the root uptake concentration cRoot.ConclusionsThe HYDRUS-2D program was usable for modelling of Cd, Cu, Pb and Zn transport and their willow uptake. Additionally, consideration of dual-porosity soil media as well as anisotropy was suitable for the experiment with roots presence in the soil.

Removal of Al, Fe and Mn by Pistia stratiotes L. and its stress response

The influence of different chelates applied in the soil primary on Al and secondary on Fe and Mn mobilization and their removal from solution was investigated. The work compared the efficiency of 10 mM tartaric acid and 3 mM EDTA in soil washing process and accumulation potential of Pistia stratiotes in rhizofiltration process. The plant response on the toxic element Al and other elements Fe and Mn was determined through the nitrogen and free amino acids content in plants. The efficiency of chelates decreased in order 10 mM tartaric acid > deionized water > 3 mM EDTA for all studied elements. P. stratiotes was able to remove up to 90% of elements during the 15 days period. Higher content of toxic element Al and potential toxic elements Fe and Mn were observed in the roots than in the leaves with the increased time. The trend of Al accumulation correlated with Fe accumulation (R2=0.89). Toxicity impact of high level of Al was observed by increased free amino acids (AA) level. Proline, histidine, glutamic acid and glycine were the most synthesised free AA in leaves. Total AA content in leaves was significantly higher under chelates addition compared to control.

Phytoextraction and Assisted Phytoextraction of Metals from Agriculture Used Soil

The clone (Salix × smithiana, Willd.) was cultivated in lysimeter pots to monitor lead (Pb), cadmium (Cd), and zinc (Zn) leachate and to compare the effect of ectomycorrhizal inoculum (ECMI; Paxillus involutus, Bartsch. ex Fr.) on plant growth and metal uptake by willows during two consecutive vegetation periods. The willow clone was able to reduce metal leaching significantly because of its high phytoextraction potential. In addition, ECMI (i) significantly enhanced plant growth; (ii) decreased metal-induced plant stress, which was represented by greater Ntotal in biomass and by greater productions of free amino acids AAfree (from 128 ± 10 to 204 ± 16 μmol kg−1 fresh weight); and (iii) showed no additional effect of metal uptake. Furthermore, treated willows were affected indirectly, probably because of unsuccessful inoculation by Paxillus involutus, Bartsch. ex Fr., caused by high level of volumetric water content (θv) during both vegetation periods (θv = 25%).