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

Elevated Urbanization-Driven Plant Accumulation of Metal(loid)s Including Arsenic Species and Assessment of the Kłodnica River Sediment Contamination

The impact of water and bottom sediment pollution of a river subjected to a strong industrial anthropogenic pressure of metal(loid) (including arsenic and its species) accumulation in riverbank plants such as Solidago virgaurea L., Phragmites L. and Urtica dioica L. was investigated. The high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) technique was used to study organic and inorganic arsenic species in selected plants and their response to heavy metal and arsenic contamination. The modified BCR extraction results showed that arsenic was mainly bound to the mobile reducible and organic-sulfide fractions in the Kłodnica River bottom sediments. Research has shown that the bottom sediments of the Kłodnica River are contaminated with metals, including Pb, Zn, Ni, As, and among arsenic species, the As(V) form dominated quantitatively, with its highest concentration being 49.3 mg kg^-1 and the organic species occurred extremely rarely. The highest concentration of arsenic, among the tested plants, occurred in Phragmites communis L. The evaluation of the bottom sediment pollution was performed using Sb/As factor, geoaccumulation index (I_geo), enrichment factor (EF) and pollution load index (PLI). The ability of the plant to assimilate metals from the substrate was studied by calculation of the bioaccumulation factor (BAF). Values of the I_geo change in a wide range from class 1 (uncontaminated to moderately polluted for Cu and Zn) at the first sampling point, to 5 (highly to extremely polluted for Ba and Fe) at the K4 sampling point. The I_geo results show an increase in the contamination with elements toward the runoff of the Kłodnica River.

Water and soil contaminated by arsenic: the use of microorganisms and plants in bioremediation

Owing to their roles in the arsenic (As) biogeochemical cycle, microorganisms and plants offer significant potential for developing innovative biotechnological applications able to remediate As pollutions. This possible use in bioremediation processes and phytomanagement is based on their ability to catalyse various biotransformation reactions leading to, e.g. the precipitation, dissolution, and sequestration of As, stabilisation in the root zone and shoot As removal. On the one hand, genomic studies of microorganisms and their communities are useful in understanding their metabolic activities and their interaction with As. On the other hand, our knowledge of molecular mechanisms and fate of As in plants has been improved by laboratory and field experiments. Such studies pave new avenues for developing environmentally friendly bioprocessing options targeting As, which worldwide represents a major risk to many ecosystems and human health.

Variations of arsenic forms and the role of arsenate reductase in three hydrophytes exposed to different arsenic species

In order to understand the mechanisms of arsenic (As) accumulation and detoxification in aquatic plants exposed to different As species, a hydroponic experiment was conducted and the three aquatic plants (Hydrilla verticillata, Pistia stratiotes and Eichhornia crassipes) were exposed to different concentrations of As(III), As(V) and dimethylarsinate (DMA) for 10 days. The biomass, the surface As adsorption and total As adsorption of three plants were determined. Furthermore, As speciation in the culture solution and plant body, as well as the arsenate reductase (AR) activities of roots and shoots, were also analyzed. The results showed that the surface As adsorption of plants was far less than total As absorption. Compared to As(V), the plants showed a lower DMA accumulation. P. stratiotes showed the highest accumulation of inorganic arsenic but E. crassipes showed the lowest at the same As treatment. E. crassipes showed a strong ability to accumulate DMA. Results from As speciation analysis in culture solution showed that As(III) was transformed to As(V) in all As(III) treatments, and the oxidation rates followed as the sequence of H. verticillata>P. stratiotes>E. crassipes>no plant. As(III) was the predominant species in both roots (39.4-88.3%) and shoots (39-86%) of As(III)-exposed plants. As(V) and As(III) were the predominant species in roots (37-94%) and shoots (31.1-85.6%) in As(V)-exposed plants, respectively. DMA was the predominant species in both roots (23.46-100%) and shoots (72.6-100%) in DMA-exposed plants. The As(III) contents and AR activities in the roots of P. stratiotes and in the shoots of H. verticillata were significantly increased when exposed to 1 mg·L^-1 or 3 mg·L^-1 As(V). Therefore, As accumulation mainly occurred via biological uptake rather than physicochemical adsorption, and AR played an important role in As detoxification in aquatic plants. In the case of As(V)-exposed plants, their As tolerance was attributed to the increase of AR activities.

Multi-mode Sample Introduction System (MSIS) as an interface in the hyphenated system 2 HPLC-MSIS-ICP-OES in simultaneous determination of metals and metalloids species

The paper presents a usage of a new hyphenated technique, wherein a Multi-mode Sample Introduction System (MSIS) was applied as an interface of two high pressure liquid chromatography units and inductively coupled plasma optical emission spectrometry (2 HPLC-MSIS-ICP-OES). Simultaneous separation and detection of non-hydride forming and hydride forming elements was possible due to the application of two different HPLC column, cation-exchange and anion-exchange respectively. The method was able to determine 15 elements quantitatively with a distinction of three arsenic and two iron species and it was validated obtaining acceptable LODs (2.67-28.7 μg L^-1) and recoveries (80-120%). The method applicability was presented and confirmed on 5 varied sample matrix types i.e. post-glacial sediments, yerba mate (Ilex paraguariensis), soil samples located in the proximity of industry wastes disposal site, river sediments, and archaeological pottery. In addition to the above, unknown Cu, Fe, Mn and Zn species were detected in real samples (qualitative speciation analysis) and the identification was attempted according to the literature.

Arsenic uptake, speciation and physiological response of tree species (Acer pseudoplatanus, Betula pendula and Quercus robur) treated with dimethylarsinic acid

The aim of the study was to evaluate the effect of dimethylarsinic acid (DMA) on growth parameters and levels of stress-related metabolites in Acer pseudoplatanus, Betula pendula and Quercus robur. The increase of DMA concentration in the solution led to a notable growth retardation of trees. An intense As accumulation (mainly As(III) and As(V)) expressed as BCF and TF > 1 was recorded only for Q. robur. Generally a decrease in contents of cellulose, hemicellulose and holocellulose with a simultaneous increase in lignin content were recorded. Phenolic composition of leaf extracts was modified by DMA, while root and rhizosphere extracts were poor in phenolics. Toxicity of DMA leads to a significant drop in salicylic acid content in leaves observed at lower doses. Higher DMA levels caused a second, probably ROS-derived depletion of the metabolite accompanied with a severe growth retardation, most pronounced in the case of B. pendula. DMA caused the inhibition of LMWOA biosynthesis in roots of A. pseudoplatanus, B. pendula and their exudation into the rhizosphere, while in Q. robur roots and leaves a stimulation of their accumulation was observed. Disturbances in the activity of enzymatic antioxidants were observed for all the species following the increasing level of DMA.

Profile and concentration of the low molecular weight organic acids and phenolic compounds created by two-year-old Acer platanoides seedlings growing under different As forms

Two-year-old seedlings of Acer platanoides were cultivated during a three-month hydroponic experiment in modified Knop solution enriched with inorganic (As(III), As(V)) and organic (dimethylarsinic acid - DMA) arsenic forms at 0.06 mM, 0.6 mM and their combinations. The profile and content of low molecular weight organic acids (LMWOAs) and phenolic compounds were also determined in the rhizosphere, roots and leaves. Arsenic (As) treatment caused an elevated creation of the above mentioned metabolites, which was higher in leaves than in the rhizosphere or roots, and their overall content was correlated with the concentration of As in A. platanoides organs. The addition of all As forms strongly induced the exudation of citric and oxalic acids into the rhizosphere, while malonic, acetic, citric and malic acids were formed in the roots. The most differential profile of roots was confirmed for As(V) 0.06 mM (4-hydroxybenzoic (4-HBA), syringic, 2,5 dihydroxybenzoic (2,5-DHBA), caffeic, chlorogenic, ferulic, p-coumaric and sinapic acids and catechin). The obtained results indicate that the presence of particular As forms has a significant impact on the content and profile of exuded and created LMWOAs and phenolic compounds, and can also have a decisive influence on the activation of appropriate detoxification mechanisms.

Influence of environmental factors on arsenic accumulation and biotransformation using the aquatic plant species Hydrilla verticillata

Hydrilla verticillata (waterthyme) has been successfully used for phytoremediation in arsenic (As) contaminated water. To evaluate the effects of environmental factors on phytoremediation, this study conducted a series of orthogonal design experiments to determine optimal conditions, including phosphorus (P), nitrogen (N), and arsenate (As(V)) concentrations and initial pH levels, for As accumulation and biotransformation using this aquatic plant species, while also analyzing As species transformation in culture media after 96-hr exposure. Analysis of variance and the signal-to-noise ratio were used to identify both the effects of these environmental factors and their optimal conditions for this purpose. Results indicated that both N and P significantly impacted accumulation, and N was essential in As species transformation. High N and intermediate P levels were critical to As accumulation and biotransformation by H. verticillata, while high N and low P levels were beneficial to As species transformation in culture media. The highest total arsenic accumulation was (197.2 ± 17.4) μg/g dry weight when As(V) was at level 3 (375 μg/L), N at level 2 (4 mg/L), P at level 1 (0.02 mg/L), and pH at level 2 (7). Although H. verticillata is highly efficient in removing As(V) from aquatic environments, its use could be potentially harmful to both humans and the natural environment due to its release of highly toxic arsenite. For cost-effective and ecofriendly phytoremediation of As-contaminated water, both N and P are helpful in regulating As accumulation and transformation in plants.

Phytoextraction of arsenic forms in selected tree species growing in As-polluted mining sludge

The aim of this study was to determine the phytoextraction of inorganic (As(III), As(V)) and organic arsenic (As_org) forms in six tree species: Acer platanoides, Acer pseudoplatanus, Betula pendula, Quercus robur, Tilia cordata and Ulmus laevis. Plants were grown in a pot experiment using As-polluted mining sludge for 90 days. Arsenic (As_total) was accumulated mainly in the roots of all six tree species, which were generally thinner, shorter and/or black after the experiment. The highest concentration of As(III) and As(V) was determined in the roots of A. pseudoplatanus and A. platanoides (174 and 420 mg kg^-1, respectively). High concentrations of As(III) were also recorded in the shoots of B. pendula (11.9 mg kg^-1) and As(V) in the aerial parts of U. laevis and A. pseudoplatanus (77.4 and 70.1 mg kg^-1). With some exceptions, the dominant form in the tree organs was As_org, present in mining sludge in low concentration. This form has a decisive influence on As phytoextraction by young tree seedlings even though its BCF value was the only one lower than 1. The obtained results highlight the important role of speciation studies in assessing the response of plants growing in heavily polluted mining sludge.

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.