Arsenite phytoextraction and its influence on selected nutritional elements in one-year-old tree species

Ecotoxicological monitoring of potentially toxic elements contamination in Eucalyptus forest plantation subjected to long-term irrigation with recycled wastewater

Afforestation is an evergreen technology for restraining greenhouse gases (GHGs) emission and improving soil carbon sink in arid and semi-arid regions. Nonetheless, the long-term impact of woody forests irrigation using recycled wastewater resources remains inconclusive so far. For this purpose, the ecological risk benchmarks of potentially toxic elements (PTEs) were investigated on Eucalyptus forest plantation in order to gauge their bioavailability in the rhizospheric layer of Typic Torripsammentsoil and their accretion capacity in the biosphere. Water quality guidelines pointed to a moderate degree of restriction on use with elevated levels of PTEs. Notably, concentrations of As, B, Cd, Cr, Cu, Mn, Ni, V and Zn were above the permissible limits for irrigation. The geospatial mapping of PTEs concentration in soil pointed to elevated levels of most PTEs, particularly in the deforestated areas. Some of PTEs (Cd, Cu, Hg and Zn) showed values above the permissible limits. A spectrum of ecological risk indices showed considerable to high degree of contamination. Among PTEs, the water-soluble and exchangeable fractions showed high values of As, Cd and Hg (20.7, 17.2 and 11.0%, respectively). Sequential extraction showed variations among PTEs in their tendency to bind with different soil geochemical fractions: (i) carbonate (Cd, Zn and Cu), (ii) Fe-Mn oxides (Pb, Zn and Mn) and (iii) organic matter (B, Pb and Hg). Eight fungal species including Aspergillus flavus, Fusarium solani, Cephalosporimsp., Penicilliumsp., Rhizoctonia solani, Aspergillus niger, Botrytissp. and Verticilliumsp. were dominated in soil. Meanwhile, Agrobacteriumsp., phosphate solubilizing bacteria, nitrogen fixing bacteria and Escherichia coli were the dominant bacterial strains. Values of bioaccumulation index varied among PTEs, wherein B (5.15), Ni (1.98), Mn (1.62) and Cd (1.02) exhibited higher phytoextraction potentials. Other PTEs, however, exhibited values below 1.0 confirming their low phytoextraction potentials. Findings of this investigation, therefore, provide insights into biochemical signals of PTEs contamination in woody forest plantations and the urgent need to contextualize the large-scale utilization of recycled wastewater resources in such vulnerable areas.

Time-dependent changes of arsenic and its selected forms in a hydroponic experiment with Quercus robur L

Mutual transformations of particular As forms are dynamic. Therefore hydroponic experiments need to account for this variation. For this reason, the aim of the study was to determine the time-dependent changes of As_total and selected forms of this metalloid (As(III), As(V), DMA or the sum of other organic forms) in modified Knop's solution and organs (root, low and high stem) of 2-year-old Quercus robur L. seedlings within a 33-day long hydroponic experiment. The results indicate the varying speed of As uptake and transport to aerial plant parts. A decrease in contents of As forms in organs of seedlings exposed to individual As forms varied, which indicates simultaneous transformations of As forms both in Knop's solution and plant organs. The obtained results indicate the need to analyse the main forms of As both in the nutrient solution and plant organs to assess the actual effectiveness of As phytoextraction by plants. It is necessary because, as demonstrated in this work, the addition of a specific As form does not mean that the capacity of a given plant relative to this form specifically is assessed. Capsule: The form of arsenic added to the medium undergoes dynamic changes affecting the phytoextraction of this metalloid in Quercus robur L. organs.

Arsenate phytoextraction abilities of one-year-old tree species and its effects on the nutritional element content in plant organs

The aim of the study was to evaluate the As phytoextraction potential of four tree species: Acer pseudoplatanus L., Betula pendula Roth., Quercus robur L., and Ulmus laevis Pall. in light of their prospective use in the phytoremediation of arsenate [As(V)] contaminated soils. The content of nutritional elements: B, Ca, K, Mg, Na, Si, P, and S was also analyzed. The trees were grown for 1 month in hydroponic cultures (Knop medium) supplemented with As(V), (1 mM). The results showed that the highest As accumulation efficiency was characterized by B. pendula (BCF = 0.87) and Q. robur (BCF = 0.5). Betula pendula accumulated about 80% of As in its roots (TF = 0.22) whereas Q. robur accumulated more than 60% of As in its shoots (TF = 1.60). The other tree species accumulated significantly lower amounts of As, more than 60% of which collected in their shoots. As(V) phytoextraction led to a significantly lower level of P and S in the roots of all tested tree species. Betula pendula seems promising for phytostabilisation and Q. robur for phytoextraction of As(V) from contaminated soils. The obtained results confirm the accumulation and translocation of As(V), as well as the acquisition of nutritional elements by the selected tree species.

Arsenic content in two-year-old Acer platanoides L. and Tilia cordata Miller seedlings growing under dimethylarsinic acid exposure-model experiment

The presence of cacodylic acid (dimethylarsinic acid, DMA) can be an important factor in limiting the abilities of young tree seedlings to adapt to unfavorable environmental conditions. For this reason, the aim of the study was to estimate the influence of different DMA additions (from 0.01 to 0.6 mM) to modified Knop solution to arsenic (As) and selected forms of this metalloid (As(III), As(V), DMA) phytoextraction by two-year-old Acer platanoides L. and Tilia cordata Miller seedlings. Additionally, the biomass and other elements important in As transport in plants were analyzed. Seedlings of both tree species were able to grow in all experimental systems except the one with the highest DMA concentration (0.6 mM). Exposure of tree seedlings was related to a general decrease in plant biomass. Phytoextraction of As in roots, stems, and leaves increased with a rise of DMA concentration in solution to the highest content of As in A. platanoides and T. cordata roots growing under 0.3 mM (135 ± 13 and 116 ± 14 mg kg^-1 dry weight). Arsenic was accumulated mainly in roots, thereby confirming bioconcentration factor values BCF > 1 for all tree seedlings treated with DMA. Exposure of plants to low DMA concentrations (0.01 and 0.03 mM) was related to the transport of this element to aboveground parts, while increased DMA concentration in other experimental systems led to the limitation of As transport to stems, as confirmed by translocation factor values TF < 1. Changes in many other elements such as boron, silicon, phosphorus, or sulfur concentration indicated the possible influence of DMA on the transport of As from roots to leaves. The obtained results show that DMA can be an important factor in modulating As phytoextraction in the studied tree species.

Arsenic forms in phytoextraction of this metalloid in organs of 2-year-old Acer platanoides seedlings

The aim of the study was to estimate the significance of the role of arsenite (As(III)), arsenate (As(V)), and dimethylarsinic acid (DMA) presence in modified Knop medium in the efficiency of phytoextraction of arsenic (As) in Acer platanoides root, stem, and leaves. The addition of particular As forms in single, double, and triple experimental systems was associated with a lower increase of seedling biomass compared to control plants (system free of As forms addition). Depending on As forms and their concentration in solution, negative symptoms from slight visible changes (inorganic forms separately or jointly), through smaller and discolored leaves (after DMA addition), and finally to their withering (after high DMA addition) were observed. Changes of color and shape for root systems exposed to particular As forms separately or jointly were also observed, in spite of the fact that there were no significant changes in biomass of seedlings growing in all experimental systems. The highest mean concentrations of As in root, stem, and leaves (590, 70, and 140 mg kg^-1 dry weight (DW), respectively) were observed in plants growing under different experimental systems. The highest bioconcentration factor values were 10.8 for plants exposed to 0.06 mM of As(III) and DMA, while the highest translocation factor (1.0) was recorded for plants growing under the same As forms (0.6 and 0.06 mM, respectively). The obtained results indicate that the presence of particular As forms not only determines As phytoextraction and transport of this metalloid form but also has a decisive influence on plant morphology and survivability. As regards the practical aspects of phytoremediation, the kind of As forms present in substrate are more important than their total concentration.