Speciation of scandium and gallium in soil

A critical review of the occurrence of scandium and yttrium in mushrooms

Scandium (Sc) and Yttrium (Y) along with the other rare earth elements (REE) are being increasingly extracted to meet the escalating demand for their use in modern high technology applications. Concern has been voiced that releases from this escalating usage may pollute environments, including the habitats of wild species of mushrooms, many of which are foraged and prized as foods. This review collates the scarce information on occurrence of these elements in wild mushrooms and also reviews soil substrate levels, including forested habitats. Sc and Y occurred at lower levels in mushrooms (<1.0-1000 µg kg-1 dw for Sc and<1.8-1500 µg kg-1 dw for Y) compared to the corresponding range for the sum of the lanthanides in the same species (16-8400 µg kg-1 dw). The reported species showed considerably more variation in Y contents than Sc which show a narrow median distribution range (20-40 µg kg-1 dw). Data allowing temporal examination was very limited but showed no increasing trend between the 1970s to 2019, nor were any geographical influences apparent. The study of the essentiality, toxicity or other effects of REE including Sc and Y at levels of current dietary intake are as yet undefined. High intake scenarios using the highest median concentrations of Sc and Y, resulted in daily intakes of 1.2 and 3.3 μg respectively from 300 g portions of mushroom meals. These could be considered as low unless future toxicological insights make these intake levels relevant.

Mining minerals and critical raw materials from bittern: Understanding metal ions fate in saltwork ponds

Seawater represents a potential resource for raw materials extraction. Although NaCl is the most representative mineral extracted other valuable compounds such as Mg, Li, Sr, Rb and B and elements at trace level (Cs, Co, In, Sc, Ga and Ge) are also contained in this "liquid mine". Most of them are considered as Critical Raw Materials by the European Union. Solar saltworks, providing concentration factors of up-to 20 to 40, offer a perfect platform for the development of minerals and metal recovery schemes taking benefit of the concentration and purification achieved along the evaporation saltwork ponds. However, the geochemistry of these elements in this environment has not been yet thoroughly evaluated. Their knowledge could enable the deployment of technologies capable to achieve the recovery of valuable minerals. The high ionic strengths expected (0.5-7 mol/kg) and the chemical complexity of the solutions imply that only numerical geochemical codes, as PHREEQC, and the use of Pitzer model to estimate the activity coefficients of the different species in solution can be adopted to provide valuable description of the systems. In the present work, for the first time, PHREEQC Pitzer code database was extended to include the target minor and trace elements using Trapani saltworks (Sicily, Italy) as a case study system. The model was able to predict: i) the purity in halite and the major impurities contained, mainly Ca, Mg and sulphate species; ii) the fate of minor components as B, Sr, Cs, Co, Ge and Ga along the evaporation ponds. The results obtained pose a fundamental step in critical raw materials mining from seawater brine, for process intensification and combination with desalination.

Reproducibility of elemental profile across two vintages in Pinot noir wines from fourteen different vineyard sites

The reproducibility of elemental profile in wines produced across vintages of 2015 and 2016 has been studied using grapes from a single scion clone of Vitis vinifera L. cv. Pinot noir. Grapevines were grown on fourteen different vineyard sites, from Oregon to southern California in the U.S.A., which span distances from approximately hundreds of meters to 1450 km, while elevations range from near sea level to nearly 500 m. The number of elements quantified in the wines made from the 2016 vintage was thirty, by using inductively coupled plasma mass spectrometry (ICP-MS). These data were compared with the twenty-seven elements quantified and previously reported in wines made from 2015 vintage, including twenty-four elements reported in both vintages. The composition of each element was analyzed by analysis of variance with main effect of vineyard. Wines were classified according to vineyard origin and environmental growing site with a combination of factors correlated with the wine elemental profile. The low variability (< 25%) of certain elements in wines from at least eight sites across both vintages, including Group 1 (Cs, K, Na and Rb), Group 2 (Ba, Ca, Mg and Sr), Group 3B (Eu), Group 13 (Al, B and Ga), Group 15 (As and P) and Co, Fe, Mn, Ni and V, demonstrated the reproducibility over the seasons analyzed (2015 and 2016). The comparison of elemental profile of wines across growing seasons demonstrates the opportunity to reproduce one key aspect of wine chemistry across vintages.

Mobility and retention of indium and gallium in saturated porous media

Transport of indium and gallium is reported in laboratory column experiments using quartz sand as a model porous medium representative of a groundwater system. With increased use of indium and gallium in recent years, mainly in the semiconductor industry, concerns arise regarding their environmental effects. The transport and retention behavior of these two metals were quantified via batch and column experiments, and numerical modeling. The effect of natural organic matter on indium and gallium mobility was studied by addition of humic acid (HA). Measured breakthrough curves from column experiments demonstrated different binding capacities between indium and gallium, stronger for indium, with the presence of HA affecting retention dynamics. For indium, the binding capacity on quartz decreases significantly in the presence of HA, leading to enhanced mobility. In contrast, gallium exhibits slightly higher retention and lower mobility in the presence of HA. In all cases, the binding capacity of gallium to quartz is much weaker than that of indium. These results are consistent with the assumption that indium and gallium form different types of complexes with organic ligands, with gallium complexes appearing more stable than indium complexes. Quantitative modeling confirmed that metal retention is controlled by complex stability.

Scandium, yttrium, and lanthanide contents in soil from Serbia and their accumulation in the mushroom Macrolepiota procera (Scop.) Singer

The mobility (fractionation) of rare earth elements (REEs) and their possible impacts on ecosystems are still relatively unknown. Soil samples were collected from two sites in central Serbia, an unpolluted mountain region (site 1) and a forest near a city (site 2). In order to investigate REE fractions (acid-soluble/exchangeable, reducible, oxidizable, and residual) in soils, BCR sequential extraction was performed. Additionally, the content of REEs was also determined in stipes and caps of the mushroom Macrolepiota procera, growing in the observed sites. Sc, Y, and lanthanide contents were determined by inductively coupled plasma mass spectrometry (ICP-MS), and results were subjected to multivariate data analysis. Application of pattern recognition technique revealed the existence of two distinguished clusters belonging to different geographical sites and determined by greater levels of Sc, Y, and lanthanides in Goč soil compared to Trstenik soil. Additionally, PCA analysis showed that REEs in soil were concentrated in two groups: the first consisted of elements belonging to light REEs and the second contained heavy REEs. These results suggest that the distribution of REEs in soils could indicate the geographical origin and type of soil. The bioconcentration factors and translocation factors for each REE were also calculated. This study provides baseline data on the rare earth element levels in the wild edible mushroom M. procera, growing in Serbia. In terms of bioconcentration and bioexclusion concept, Sc, Y, and REEs were bioexcluded in M. procera for both studied sites.

The mobility and plant uptake of gallium and indium, two emerging contaminants associated with electronic waste and other sources

Gallium (Ga) and indium (In) are increasingly susceptible to soil contamination via disposal of electronic equipment. Chemically similar to aluminium (Al), these elements may be mobile and bioavailable under acidic conditions. We sought to determine extent and nature of Ga and In mobility in the soil - plant system and thus their potential to enter the food chain. Batch sorption experiments on a high fertility silt loam (pH 5.95, CEC 22 meq 100 g^-1) showed strong retention of both elements to the soil matrix, with mean distribution coefficient (K_D) values of 408 and 2021 L kg^-1 for Ga and In respectively. K_D increased with concentration, which we attributed to precipitation of excess ions as insoluble hydroxides. K_D decreased with increased pH as Ga/In(OH)²⁺ and Ga/In(OH)₂⁺ transitioned to Ga/In(OH)₄^-. Movement into the aboveground portions of perennial ryegrass (Lolium perenne L.) was low, with bioaccumulation factors of 0.0037 for Ga and 0.0002 for In; foliar concentrations peaked at 11.6 mg kg^-1 and 0.015 mg kg^-1 respectively. The mobility of Ga and In in the soil - plant system is low compared to other common trace element contaminants such as cadmium, copper, and zinc. Therefore, Ga and In are likely to accumulate in soils and soil ingestion, either directly, via inhaled dust, or dust attached to food, will be the largest pathway into the food chain. Future work should focus on the effect of redox conditions on Ga and In, as well as uptake into acidophilic plants such as Camellia spp., which accumulate Al.

Pollution characteristics and potential health risk of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in soil/sediment from Baiyin City, North West, China

In order to better understand the environmental behaviors of persistent organic pollutants, the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were investigated in twenty-three soil/sediment samples from Baiying City, Northwest China, in 2008. The possible sources and potential health risk of PCDD/Fs were also discussed. The concentrations of PCDD/Fs in nineteen soil samples varied between 20.13 and 496.26 pg/g dry weight (dw.), with an average value of 125.59 pg/g dw. The highest International Toxic Equivalent (I-TEQ) of PCDD/Fs (8.34 pg/g dw.) in soil was found at sample S1 collected from proximity to a copper metallurgy plant. The concentrations of PCDD/Fs in four sediment samples ranged from 37.69 to 491.49 pg/g dw., with an average value of 169.95 pg/g dw. The highest I-TEQ of PCDD/Fs (8.56 pg/g dw.) in sediment was found at sample S12 collected from the East big ditch with waste water discharged into the Yellow River. The results indicated that PCDD/Fs contamination of soil/sediment is originated from three sources: chlorine-containing chemicals, non-ferrous metal industrial PCDD/Fs emission and coal burning. The health risk exposure to PCDD/Fs through soil, dust ingestion and dermal absorption ranged from 0.0006 to 0.0134 pg/kg/day Word Health Organization's toxic equivalent in 1998 (WHO1998-TEQ) with mean values 0.0032 pg WHO1998-TEQ for adults and varied between 0.0012 and 0.0256 pg/kg/day WHO1998-TEQ with mean values 0.006 pg/kg/day WHO1998-TEQ for children, respectively. These results indicated that health risk of PCDD/Fs for children should be paid more attention.

Distribution patterns of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sediments of the Xiangjiang River, China

We investigated the occurrence and distribution patterns of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in six sediment samples from the Xiangjiang River, Hunan Province, People's Republic of China. Total concentrations of PCDD/Fs ranged from 876 to 497,759 (mean 160,766) ng/kg dw, the highest of which exceeded that have ever been reported for sediment samples. World Health Organization total toxicity equivalent (WHO-TEQ) concentrations in three out of six samples were significantly higher than the guidance level (21.5 ng WHO-TEQ/kg dw) suggested by Canadian Sediment Quality Guideline. A predominance of octachlorodibenzo-p-dioxin (OCDD) was observed with an average contribution of 90.8% to the total PCDD/F concentrations, while 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) was the major contributor to the PCDD/F WHO-TEQ concentrations in most of the sites. Such high levels of OCDD and HpCDD may be attributed to the presence of PCP/PCP-Na pollution, although MB-WW, agricultural straw open burning, and boilers-hazardous wastes were also the potential sources of PCDD/Fs. This is the first report for the concentrations and congener profiles of PCDD/Fs in sediment samples from the Xiangtan, Zhuzhou, and Changsha sections of the Xiangjiang River, providing scientific evidence for establishing priorities to reduce ecological risks posed by PCDD/Fs in the rapidly developing areas of Hunan Province and elsewhere.

Extraction-spectrophotometric investigations on two ternary ion-association complexes of gallium(III)

Complex formation and liquid-liquid extraction were studied in systems containing Ga(III), azoderivative of resorcinol {4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR)}, 2,3,5-triphenyltetrazolium chloride (TTC), water and chloroform. The optimum conditions w.r.t. pH, extraction time, concentration of ADR and concentration of TTC for the extraction of Ga(III) as an ion-associate complex were found.. The composition of the extracted complexes, (TT+)[Ga(PAR)2] (I), (TT+)[Ga(TAR)2] (II) or (TT+)2[Ga(OH)(TAR)2] (III), and the constants of association (β) between 2,3,5-triphenyltetrazolium cation (TT+) with corresponding anionic chelates were established by several methods. The constants of distribution (KD) and extraction (Kex) of the principal species I and III were determined as well. The apparent molar absorptivities of the chloroform extract at the optimum extraction-spectrophotometric conditions were ɛ′510=9.5×104 L mol−1 cm−1 (I) and ɛ′530=4.6×104 L mol−1 cm−1 (III). The validity of Beer’s law was checked and analytical characteristics that were calculated are reported herein.

Levels of PCDD/Fs in agricultural soils near two municipal waste incinerators in Shanghai, China

A study was conducted on polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) in agricultural soils at 41 sites within a radius of 3 km from two municipal solid waste incinerators in Shanghai. The PCDD/F concentrations ranged from 71.32 to 3,881.44 pg g⁻¹ (0.64-61.15 pg I-TEQ g⁻¹). The highest PCDD/F concentrations were found approximately 1,000 m from the municipal solid waste incinerators. The PCDD/F homologue profiles of all soil samples were compared with the profiles from suspected PCDD/F sources by multivariate statistical analysis. The results showed that, the PCDD/F pollutions in some soil samples can be attributed to emissions from the municipal solid waste incinerators.