Sinapis alba as a useful plant in bioremediation - studies of defense mechanisms and accumulation of As, Tl and PGEs.

Pollution of the soils with toxic elements is a serious problem all over the world. One of environmentally friendly techniques of their removal is phytoremediation. This paper is a summary of literature data and the results of own studies about the potential of Sinapis alba for bioaccumulation of Tl, As and PGEs, and its usefulness in remediation of polluted environment. S. alba is characterized with low living requirements, BFs ≫ 1 and high TFs, especially for Tl (up to 3). The influence of different forms of studied elements on plants was discussed based on biomass production, morphological changes and the impact on photosynthesis activity. The plants were cultivated in hydroponics and solid media of various composition, for example, in soil supplemented with MnO2, which resulted in BFs lower 6-7 times for leaves, and about 3-4 times for stems, as well as twice lower leaf development. Application of advanced analytical techniques was presented in studies of the detoxification mechanisms, identification of particular chemical forms of the elements and the presence of phytochelatins and their complexes with the investigated elements.Novelty StatementThe paper summarizes both literature and original data on Sinapis alba exposed to such elements as thallium, arsenic and platinum group metals. The influence of different forms of studied elements on white mustard was discussed based on biomass production and morphological changes, as well as the impact on photosynthesis activity. The study covers such aspects as bioaccumulation, phytotoxicity as well as the usefulness of white mustard in remediation of polluted environment.

Simplification of organic matter before voltammetric determination of Tl(I) and Tl(III) in water using nanostructured photocatalyst and solar light.

The crucial point of this study was to verify the hypothesis that both thallium species are not affected by the procedure of photolysis when it is applied as a method of simplification of sample matrix containing surfactants, and that this method of sample pretreatment leads to reliable results of Tl speciation analysis. It is important especially because of high instability of Tl(III), which makes partial reduction of Tl(III)DTPA complex unavoidable. After conservation of Tl speciation by addition of DTPA the photolysis assisted with nanostructured hierarchically organized film was performed using "solar lamp" (Fe2O3/WO3/Fe2O3 film, pH 6, 380-800 nm). The results imply that under proposed photolysis conditions Tl(I) is not oxidized in the presence of water matrix, SDS nor DTPA. Also, even 100-fold excess of Fe(III) ions over Tl(I) ions does not accelerate the oxidation of Tl(I) to Tl(III), and already 2 h of heterogeneous photolysis allow to limit the interferences caused by SDS and obtain reliable results. The data obtained by anodic stripping voltammetry (ASV) were verified using an inter-method comparison with SEC ICP MS. Moreover, after 2 h irradiation the reduction rate of Tl(III)DTPA standard solution increased only slightly from 2-3% to 4-6%. The presence of river water matrix causes a slightly higher (9%) reduction of the trivalent form. These changes are irrelevant in the context of instability of Tl(III) compounds. This study indicates that "soft decomposition" can be applied in speciation analysis of thallium in water matrix.

Organic matter decomposition before arsenic speciation analysis of water sample - "Soft decomposition" using nano-photocatalysts.

The applicability of photolysis in the speciation analysis of arsenic is investigated. The use of nano scale semiconductors (Fe2O3/WO3/Fe2O3 at pH 6) as an active film during solar light irradiation of a water sample, containing some surfactants (SDS), results in the simplification of the organic matter and gives no speciation change in the arsenic. The reproducibility of active layer is shown to be high and the surface roughness of each photoactive sample and photocurrent do not differ by more than 6 and less than 8%, respectively. The procedure of sample pretreatment caused a minimum (8-10%) amount of speciation change, whilst the irradiation is no longer that 2 h. The study indicates that "soft decomposition" can be performed for as long as 4 h, and still give photostable arsenates (III) and methylarsenate species. However, the saturation of the water sample with Ar is required (to reduce the oxygen content) for the longer the decomposition time being applied.

Direct speciation analysis of thallium based on solid phase extraction and specific retention of a Tl(III) complex on alumina coated with sodium dodecyl sulfate.

Alumina (Al2O3) with an average particle size of 63 µm was modified with the anionic surfactant sodium dodecyl sulfate (SDS) and then applied to (i) solid phase extraction and separation of both thallium(I) and thallium(III), and (ii) preconcentration of Tl(III) from waste water samples. Only Tl(III), in the form of its complex with diethylenetriaminepentaacetate (DTPA), was retained on the sorbent, from where it can be eluted with 40 % nitric acid. Thallium species were then quantified by ICP MS. The method was characterized by a LOD of 25 pg of Tl(I) and 160 pg of Tl(III) in 10 mL samples. A large excesses of Tl(I) over Tl(III) was tolerated, and relatively high levels of other metal ions, such as a 500-fold excess of Pb(II) and Cd(II), and a 2000-fold excess of Zn(II), respectively, do not interfere. The sorbent was easily prepared and possesses a high loading capacity, and these properties make it an attractive material for rapid and efficient extraction and speciation of Tl. Graphical abstract:Schematic of the SPE procedure for separation (with preconcentration) of Tl(III) from Tl(I) was developed and applied to direct speciation analysis of thallium in wastewater. Self-made columns packed with alumina coated with SDS were used. The method is resistant to interferences from Pb, Cd, Zn and tolerates a large excess of Tl(I) over Tl(III).

Stability of Tl(III) in the context of speciation analysis of thallium in plants.

The paper presents both "good" and "bad" results obtained during speciation analysis of thallium in plant tissues of a hyperaccumulator of this metal. The object was white mustard - Sinapis alba L. In this plant there were found traces of trivalent thallium. The crucial point of this study (especially in the case of so unstable thallium form as Tl(III)) was to prove that the presence of Tl(III) was not caused by the procedure of sample preparation itself, and that the whole analytical method provides reliable results. Choice of the method for conservation of the initial speciation, extraction with the highest efficiency and proving the correctness of the obtained data were the most difficult parts of the presented study. It was found that: both freezing and drying cause significant changes in the speciation of thallium; quantitative analysis could be performed only with fresh tissues of mustard plants; only short-term storage of an extract from fresh plant tissues is possible; the methodology is not the source of thallium (III); only the presence of DTPA can greatly limit the reduction of TI(III) to TI(I) (up to 1-3%); the UV irradiation results in disintegration of TI(III)DTPA in the presence of plant matrix (reduction up to 90%).