Zinc Speciation Research Articles

Zinc speciation in fly ash from MSWI using XAS - novel insights and implications

The chemical forms of zinc in fly ash from municipal solid waste incineration (MSWI) crucially affect ash management, influencing both material recovery options and the risk of unwanted leaching into ecosystems. The zinc speciation was investigated in fly ash samples sourced from full-scale MSWI plants, including four grate fired boilers (GB) and one fluidized bed boiler (FB). We applied X-ray Absorption Spectroscopy (XAS), and the spectra were analyzed against a unique library of over 30 relevant compounds, tailored to the nuances of zinc chemistry of fly ash. Nano-XANES and sequential leaching were employed as complementary analytical methods. Multiple chemical forms of zinc were found in the ash, whereof potassium zinc chloride salts (K2ZnCl4) emerged as the predominant form in GB fly ash representing 41–64 % of the zinc content, while less for FB fly ash (19 %). The mere exposure to humidity in the air during storage resulted in hydroxylation of the alkali zinc chlorides into Zn5(OH)8Cl2·H2O. Other forms of zinc in the ash were Zn4Si2O7(OH)2·H2O, ZnFe2O4, ZnAl2O4, surface adsorbed zinc, and Zn5(CO3)2(OH)6. Notably, the proportion of zinc in spinel forms (ZnFe2O4 and ZnAl2O4) increased threefold in FB ash compared to GB ash, representing ∼60 % and ∼10–20 % of the zinc, respectively.

PET microplastics influenced microbial community and heavy metal speciation in heavy-metal contaminated soils

Co-occurrence of microplastics and heavy metals is common in soils. The interactions between microplastics and heavy metals have received increasing attention in recent years, particularly for revealing the mechanisms underpinning their interactions. In the present study, Polyethylene Terephthalate (PET) microplastics are added in soil, which have led to variations in soil physicochemical properties, enzymatic activity, microbial community structure, and chemical speciation of chromium (Cr), cadmium (Cd), copper (Cu), and zinc (Zn) in heavy metal contaminated soils. Soil physicochemical properties (pH, SWC and SOC) and enzymatic activities (urease and dehydrogenase) alter as result of PET addition, which promoted the transformation of heavy metal chemical speciation from bioavailable fraction to oxidizable and residual fraction. The results suggested that PET microplastics in heavy metal contaminated soil may reduce the heavy metal bioavailability by altering the properties of the soil microenvironment. The significant variations in microbial community have been observed. The relative abundance of Gp6, Gaiella, Nocardia, Herbaspirllum and Gp16 changed dramatically throughout the incubation period, which were either heavy metal tolerant or played crucial roles in modifying the chemical composition of heavy metals. This work contributes to an in-depth understanding of the effects of microplastics on the biochemical transformation of heavy metal contaminated soils, which will be valuable to the development of clean up strategy for soils with co-contaminant of microplastics and heavy metals.

Zinc speciation in highly weathered tropical soils affected by large scale vegetable production

Agriculture in highly weathered tropical soils often requires considerable application of lime and fertilizers to ensure satisfactory plant nutrient levels. The consequences of these continue long-term applications is not well understood may induce changes in soil chemical properties, the abundance, and speciation of potentially toxic trace element and as well as of micronutrients in agriculture soils. In this study, we evaluated the adsorption (at pH 5) and speciation of Zn in tropical soils (both agricultural and native vegetation) as a function of fertilization and contact time using chemical fractionation analyses and X-ray absorption spectroscopy. The soils overall had high Zn adsorption capacities (∼ 700 mg kg-1), but the agricultural soil was approximately 30 % higher than of the soil under native vegetation, and the proportion of Zn in the mobile fraction was 35 % in native vegetation and 21 % in agricultural soils. Zn speciation via linear combination analysis showed a strong relationship with soil mineralogical composition and reveled that Zn associated with organic matter decreased while Zn associated with P increased after the conversion of soils from native vegetation to highly fertilized soil. Aluminosilicate soil minerals were identified as major sinks of soil Zn, accounting for 34 % of total Zn retention regardless of soil origin and land use. Association of Zn with phosphate (i.e., hopeite) was observed in the agricultural soil samples, which might be an unexpected Zn-bearing mineral in highly weathered tropical soils and could have impacts on Zn plant nutrition.

Speciation, distribution and relationship of zinc and cadmium in summer coastal seawater of northern China

Considering that zinc (Zn) is essential for marine phytoplankton growth and cadmium (Cd) can replace Zn as a cofactor of mutual conversion and regulate the effect of carbonic anhydrase, we here presented the concentration, chemical speciation and relationship of Zn and Cd collected from three consecutive voyages (2019–2021) in summer coastal seawater of northern China. Dissolved Zn and Cd concentrations were determined using inductively coupled plasma mass–spectrometry (ICP–MS) and ranged from 0.37 to 3.09 μM and 1.88–13.66 nM, respectively. Natural labile Zn and Cd were determined using a highly automated electrochemical detection system and ranged from below detection limit-1.11 μM and below detection limit-5.23 nM, respectively. The speciation, distribution and interrelationships of Zn and Cd were compared with the distribution of the diatoms community, and studied by the correlation with pH and dissolved inorganic carbon (DIC). Finally, the Zn and Cd labile and inert chemical species concentrations were compared with those of the open sea and the coast. The results indicated that the dissolved Zn and Cd concentrations in surface seawater were higher than those in bottom seawater, possibly due to the dominance of exogenous inputs compared to phytoplankton uptake. Higher phytoplankton abundance was associated with lower natural labile Zn and Cd concentrations, but this was not the main factor affecting the distribution of natural labile Zn and Cd. Unlike the open ocean, there was no potential for Zn limitation of certain phytoplankton groups in this region, but both Zn and Cd played important roles in the fixation of carbon dioxide, and Cd might result in mitigating Zn uptake. Activities such as ocean currents, which bring limiting nutrient trace metals (e.g., Zn) from the coast into the open ocean, could regulate the structure of primary producers. This study has great potential for the investigation of the biogeochemical cycling of Zn and Cd and their role in marine carbon fixation in coastal seawater.

Sp-ICP-MS and HR–CS–GFAAS as useful available techniques for the size characterization and speciation of ionic and nanoparticular zinc in cosmetic and pharmaceutical samples

The use of zinc oxide nanoparticles (ZnO NPs) in cosmetic and pharmaceutical industry has been increased in recent years due to their good properties as solar radiation filters and antibacterial agent. According to the literature, the potential toxicity of these NPs could be size-dependent and the amount of solubilized metal. This work investigates new reliable and straightforward methodologies that enables the determination of ZnO NPs, discriminating them from ionic zinc in cosmetic samples. Two different techniques of analysis have been applied in this study: high-resolution continuum source graphite furnace atomic absorption spectrometry (HR–CS–GFAAS), and “single particle” inductively coupled plasma mass spectrometry (sp-ICP-MS). Triton X-100 has been used as a surfactant for the formation of homogeneous and stable slurries which allowed the determination of the concentration and sizes of ZnO NPs and Zn2+ in baby creams, eyeshadows, and lotions. A central composite design (CCD) was performed for the two techniques to optimize the concentration of Triton X-100 and sonication time. For validation purpose, the results of Zn2+ and ZnO NPs contents achieved by HR–CS–GFAAS were compared with the total Zn content obtained by acid digestion of the samples. A size comparison of the ZnO NPs was also carried out with the data obtained through the two methodologies and validated with transmission electron microscopy (TEM). In the case of TEM analysis, two different media were tried to study possible agglomerates and interactions between the particles and the matrix.

Speciation and Pollution Assessment of Chromium and Zinc in Landfill Soils of Brazzaville: Physico-Chemical Analyses and Heavy Metal Contamination

Speciation and Pollution Assessment of Chromium and Zinc in Landfill Soils of Brazzaville: Physico-Chemical Analyses and Heavy Metal Contamination

Speciation of toxic pollutants in Pb/Zn smelter slags by X-ray Absorption Spectroscopy in the context of the literature

Pb/Zn smelter slag is a hazardous industrial waste from the Imperial Smelting Process (ISP). The speciation of zinc, lead, copper and arsenic in the slag controls their recovery or fate in the environment but has been little investigated. X-ray Absorption Spectroscopy (XAS) was applied to this complex poorly crystalline material for the first time to gain new insights about speciation of elements at low concentration. Zn, Cu, As K-edge and Pb L3-edge XAS was carried out for a Pb/Zn slag from a closed ISP facility in England, supported by Fe, S and P K-edge XAS. Results are presented in the context of a full review of the literature. X-ray fluorescence showed that concentrations of Zn, Pb, Cu and As were 8.4, 1.6, 0.48 and 0.45 wt%, respectively. Wüstite (FeO) was the only crystalline phase identified by X-ray diffraction, but XAS provided a more complete understanding of the matrix. Zn was found to be mainly present in glass, ZnS, and possibly solid solutions with Fe oxides; Pb was mainly present in glass and apatite minerals (e.g., Pb5(PO4)3OH); Cu was mainly speciated as Cu2S, with some metallic Cu and a weathering product, Cu(OH)2; As speciation was likely dominated by arsenic (III) and (V) oxides and sulfides.

Application of zincon analysis to investigate the zinc speciation in aqueous media for further understanding of ZnO solubility

The environmental accumulation and toxicity potential of metal oxide nanoparticles because of their increasing use in various commercial products have increased the interest in understanding the behavior of these materials in the aquatic environment. For example, zinc oxide (ZnO) is used in various industrial applications but exhibits partial solubility in aqueous media, therefore it has potential aquatoxic action. ZnO dissolves in water by releasing Zn2+ ions; thus, understanding the complexation behavior of these ions with water is crucial to be able to give a complete description of the fate of ZnO in aquatic environment. In this study, we propose application of a reliable and facile route based on the zincon analysis to further understand the Zn2+ complexation when ZnO is placed in aqueous media. To evaluate this, eight Zn2+ standards at a certain concentration were first prepared in the pH range between 7.0 and 10.0. Samples were analyzed via Inductive Coupled Plasma-Mass spectrometry (ICP-MS/MS) and the zincon analysis by monitoring their UV absorbance maximum at 620 nm. Analysis before and after centrifugation aided the investigation of the pH dependent complexation of Zn2+. In the centrifuged samples, the measured zinc ion fraction decreased, suggesting precipitation of zinc as zinc hydroxide (Zn(OH)2(s)) in the solid form from the solution when the pH was increased from 7.0 to 10.0. However, there was no significant decrease in the non-centrifuged samples in the same pH range. These results show that the zincon analysis can be used to quantify both Zn2+(aq) ions and Zn(OH)2. Moreover, the zincon results were consistent with the results of ICP-MS/MS analyses. The centrifugation helps to sediment solid hydroxide particles enabling one to predict fraction of the ions and the hydroxides. Solid hydroxide precipitate was characterized by FTIR, XRD, SEM and EDX; and formation of orthorhombic Zn(OH)2 phase was confirmed.

Design of Flame‐Made ZnZrOx Catalysts for Sustainable Methanol Synthesis from CO2 (Adv. Energy Mater. 14/2023)

Methanol Synthesis In article number 2204122, Javier Pérez-Ramírez and co-workers apply flame spray pyrolysis to design superior ZnZrOx catalysts for methanol synthesis from CO2. Synthesis-structure-performance relationships are established, revealing that zinc speciation and location determine catalyst architecture, the nature of catalytic ensembles, and the corresponding reactivity.

Zinc Speciation and Propane Dehydrogenation in Zn/H-ZSM-5 Catalysts

Zn/H-ZSM-5 catalysts have been frequently investigated for propane dehydrogenation (PDH); however, the active site remains unresolved due to the complexity of the system. We employed in situ FTIR spectroscopy and a kinetics method to correlate the Zn speciation and PDH activity in Zn/H-ZSM-5 with two Si/Al ratios (15 and 39) and a range of Zn/Al ratios (0–1.7). Incremental additions of zinc show that Zn2+ sites are preferentially formed on H-ZSM-5 over a fraction of paired Al sites followed by [Zn-O-Zn]2+ and [ZnOH]+ sites and then ZnOx clusters. The [Zn-OH]+ and [Zn-O-Zn]2+ sites in H-ZSM-5 are more active and selective than isolated Zn2+ for PDH. [Zn-OH]+ species sublimate over time on stream, leading to catalyst deactivation, while [Zn-O-Zn]2+ species are stable even after high-temperature reduction (750 °C for 60 min). Three distinct Zn sites ([Zn-O-Zn]2+, Zn2+, and [ZnOH]+) show a similar propane reaction order (close to 1) and H2 reaction order (close to 0). Combined with the lack of Zn hydride when propane flows over the catalyst at 550 °C, it is concluded that propane adsorption and dissociation is a rate-determining step and H2 desorption is fast. This work indicates that the preparation of H-ZSM-5 with abundant Al pairs may be a strategy to form stable and selective Zn/H-ZSM-5 catalysts for propane dehydrogenation. It is also highlighted that examining the effect of both metal/Al ratios and Al distribution of the zeolite is crucial in identifying the metal cations in metal–zeolite systems.

Contrasting impact of soil amendments on bioavailability, mobility and speciation of zinc in an acidic sandy loam soil

Contrasting impact of soil amendments on bioavailability, mobility and speciation of zinc in an acidic sandy loam soil

Selenium toxicity and bioaccumulation in selenium-enriched fly (Chrysomya megacephala) maggots.

Selenium (Se) is an essential trace element for human health, and as a potential animal feed, the Chrysomya megacephala (Fabricius) fly is rich in protein and fat. By using different concentrations of sodium selenite (0, 30, 50, 70mgkg-1), the possibility of biological Se enrichment in C. megacephala (Fabricius) maggots (CMMs) was investigated. The accumulation, Se speciation, enzymatic activity, and concentrations of copper (Cu), zinc (Zn), chromium (Cr), and cadmium (Cd) in the maggots were also determined. Transcriptomics was also used to investigate the mechanism of the Se response to CMM genes. The results showed that the CMMs had a survival rate of > 80% at Se exposure concentrations ranging from 0 to 100mgkg-1. The optimal concentration of sodium selenite for CMM growth was 50mgkg-1, and the weight, protein content, and total Se accumulation of the larvae (10.8g, 53.5%, and 72.6 ± 3.36mgkg-1 (DW), respectively) were considerably higher than the control and other exposure doses (p < 0.05). In addition, Se improved the ability of maggots to absorb Cu and Zn, decreased malondialdehyde (MDA) and lipid peroxidation, but improved the antioxidant activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX). Furthermore, Se negatively affected the absorption of Cd and Cr. According to the transcriptomic findings, Se supplementation can boost protein synthesis and control both antioxidant and non-antioxidant enzyme activity in CMMs. Therefore, our findings showed that Se-enriched CMMs may counteract the toxicity of Cd and Cr, and Se is an effective supplement for improving the consumption safety of cultured animals fed containing CMMs.

Zinc speciation and desorption kinetics in a mining waste impacted tropical soil amended with phosphate

Mining is an important component of the Brazilian economy. However, it may also contribute to environmental problems such as the pollution of soils with zinc and other potentially toxic metals. Our objective was to evaluate changes in the chemical speciation and mobility of Zn in a soil amended with phosphate. Soil samples were collected from a deactivated mining area in the state of Minas Gerais, Brazil, and amended with NH4H2PO4 saturated with deionized water to 70 % of maximum water retention and incubated at 25 ± 2 °C in open containers for 60 days. The soil was chemically and mineralogically characterized, and sequential extraction, desorption kinetics, and speciation were carried out using synchrotron bulk-sample and micro–X-ray Absorption Near-Edge Structure (XANES/μ-XANES) spectroscopy at the Zn K-edge, and X-ray fluorescence microprobe analysis (μ-XRF). The combination of μ-XRF and μ-XANES techniques made it possible to identify Zn hotspots in the main species formed after phosphate remediation. The best fit combination for bulk XANES and μ-XANES was observed in Zn-montmorillonite, Zn-kerolite, Zn-ferrihydrite, and gahnite. In the course of phosphate treatment, gahnite, Zn layered double hydroxides (Zn-LDH), Zn3(PO4), and ZnO were identified by bulk XANES, while Zn-ferrihydrite, Zn-montmorillonite, and scholzite were identified by μ-XANES. Zinc in the phosphate-amended soil had the strongest partial correlations (r′ > 0.05) with Ni, Co, Fe, Cr, Mn, Si, P, Cd, Pb, and Cd, while the unamended soil showed the strongest correlation with Cu, Pb, Fe, and Si. The application of NH4H2PO4 altered Zn speciation and favored an increase in Zn desorption. The most available Zn contents after phosphate amendment were correlated with the release of exchangeable Zn fractions, associated with carbonate and organic matter.

The Effect of Zinc Speciation and Its Concentration on Bioaccumulation in Pomfret (Colossoma macropomum) and Sepat Fish (Trichogaster Trichopterus)

Heavy metal Zinc is still a pollutant from various industrial and domestic activities whose waste is directly dumped into the waters. The presence of biota in the waters can be used as a bioindicator to identify the presence of heavy metal contaminants. The kinetics of the Zinc bioaccumulation process through the freshwater route using pomfret (Colossoma macropomum) and sepat fish (Trichogaster trichopterus) as bioindicators have been investigated by analyzing the effect on variations in concentration and pH. This research was conducted by determining Zinc speciation's effect and concentration on the bioaccumulation process. The results showed an increase in concentration would also increase the rate of uptake and elimination rate of Zinc by pomfret and sepat, obtained concentration factors (CF) at variations of Zinc concentration in pomfret was 2.56 - 22.97 mL.g–1 and 2.14 - 56.87 mL.g–1 in sepat fish. While the value of the concentration factor (CF) in the variation of pH for pomfret is 0.65 - 13.15 mL.g–1 and for sepat fish is 0.93 - 15.29 mL.g–1, and ZnCl42– was the dominant species containing Zn in most of the electrolytes in fresh water and from each concentration variation. This method is expected to provide information that can be used for environmental studies and against toxic effects for food safety. HIGHLIGHTS The kinetics of the Zinc bioaccumulation process through the freshwater route as bioindicators have been investigated This research was conducted by determining Zinc speciation's effect and concentration on the bioaccumulation process Provides information on the accumulation of Zinc in Pomfret ( macropumum) and Sepat Fish (T. trichopterus) to be used as an environmental study and for food safety purposes GRAPHICAL ABSTRACT

Analysis of hydrochemical parameters and dissolved zinc interaction by using PHREEQC simulation

Zinc is frequently reacting with inorganic species in water to form zinc species. Thus, the chemical speciation of Zinc in the aquatic environment has become a significant concern nowadays due to its adverse effect on humans and its potential toxicity in the water system. In this study, to investigate the interaction between dissolved zinc and hydro-chemical factors and to estimate the Zn speciation form, samples of river water were collected spatially from the Umeda River mainstream and tributaries in different seasons for one year. The hydrochemistry and dissolved zinc pollution characteristics of the samples were analyzed. Zn speciation was assessed by PHREEQC simulation. The result show that the main form of Zn speciation was Zinc free ion (Zn2+) in all seasons. However, in summer and spring season, the ZnCO3 and ZnOH+ concentration was higher than the other season. These speciation form may be attributed to the activities around the river in different season according to the similarities in downstream and upstream areas by the hierarchical cluster analysis result.

Speciation and isotopic analysis of zinc in size-fractionated aerosol samples related to its source and chemical processes

Zinc (Zn) in aerosols plays important roles for biological activity and attracts public attention from the perspective of environmental measures. Because of its high volatility and water solubility, Zn is readily released into the atmosphere by human activities and supplied to natural water. To explore the origin and formation process of Zn in atmospheric aerosols, it is important to investigate isotopic (= δ66Zn) and speciation information of Zn in size-fractioned aerosols. We measured light δ66Zn (e.g., δ66ZnIRMM = −1.32‰ as the lowest value; IRMM-3702 is used for the normalization in this study) mainly for the particles ranging from 0.65 to 4.7 μm for the samples collected at Tsukuba, Chiba, and a motorway tunnel (Yasumiyama Tunnel in Hiroshima) in particular for the samples collected in 2002, but δ66ZnIRMM in the particle sizes increased above −0.8‰ for the samples collected in 2011 and 2016. Zn species in aerosols were estimated based on X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, suggesting that (i) Zn oxalate and sulfate and (ii) Zn oxide, sulfide, and carbonate are main Zn species in fine and coarse particles, respectively. In particular, Zn chloride was found mainly in the middle particle size range (2.1–4.7 μm), which corresponds to the range with light δ66Zn, suggesting that the light δ66Zn was caused by emission of Zn chloride during artificial combustion processes in accordance with other studies. The origins of Zn in aerosols are assumed to have three endmembers; (A) tire and brake wears and road dust, (B) industrial emissions, and (C) vehicular exhaust. Their formation mechanisms are related to vaporization and mixing processes based on the results of combined analysis of atmospheric concentration, speciation, and isotopic composition of Zn with different particle sizes. These trends could be successfully interpreted by species-specific δ66Zn values: component (A) consisting mainly of Zn oxide and sulfide with relatively heavier δ66Zn, component (B) Zn chloride and sulfate secondarily formed in the droplet mode having lightest δ66Zn among all the species, and (C) Zn oxalate with δ66Zn closer to 0‰ due to its emission by the complete combustion in vehicle engines. Species-specific Zn isotope data obtained by the simultaneous application of speciation and isotopic analyses of Zn in size-fractionated aerosols complementary provide novel information on the initial generation and secondary processes for the formation of Zn species in the aerosols.

Impacts of wet-dry alternations on cadmium and zinc immobilisation in soil remediated with iron oxides

Chemical immobilisation is extensively used for in-situ remediation of heavy metals contaminated soil. Immobilised heavy metals could be reactivated by multiple factors such as pH, moisture, temperature, rainfall, etc., among which rainfall is very important, especially acid rain in southern China. Wet-dry alternations were used to simulate the leaching of metals by rainwater. The variation of cadmium (Cd) and zinc (Zn) speciation distribution in soil immobilised with iron oxides (goethite (GE) and 2-line ferrihydrite (GLS)) was investigated. The impacts of wet-dry alternations on the properties of the soil and amendments were also assessed. In the soil without amendments (OS) and amended with GE (GS), the stable fractions were reactivated and transformed into labile fractions under wet-dry alternations. In the soil amended with GLS (LS), the exchangeable and carbonate-bound Cd decreased while the soluble, Fe–Mn oxide bound and organic bound Cd increased. The carbonate-bound Zn was transformed into the Fe–Mn oxide-bound Zn. Transformation from the amorphous iron oxide into crystalline iron oxide in GS and LS were 4.9% and 5.3%. The Pearson correlation analysis showed that the soil pH and the iron-oxide speciation were strongly correlated with Cd/Zn fractions in the soil. The specific surface area, pore volume and adsorption capacity of the iron oxides decreased by 9.26%, 38.89% and 62–73% (for GE), 1.88%, 22.22% and 26–55% (for GLS). The altered soil properties and morphological differences between the two iron oxides under wet-dry alternations were important reasons for Cd/Zn reactivation.

Speciation and risk assessment of Zn, Pb, and Cd in bottom sediments of two small upland dam reservoirs, Poland

Sediments of two small dam reservoirs in Poland, Zalew Zemborzycki (ZZ) and Brody Iłżeckie (BI), were studied. Sediments from both reservoirs were sampled at 17 sites in the transects perpendicular to the shoreline, at the river inflow and the frontal dam and analysed using the BCR procedure for speciation of zinc (Zn), lead (Pb) and cadmium (Cd). The risk assessment code (RAC) and the individual contamination factor (ICF) were determined. In BI, the sediments were removed from the considerable part of the reservoir, creating an opportunity to study the effect of dredging on the speciation of trace metals. Trace metals partitioning was differentiated according to the transect/site and in the case of BI sediments also on the transect location in the dredged or undredged part of the reservoir. Considering ZZ sediments, the order of fractions for Zn, Pb and Cd according to a decreasing overall mean percentage contribution to total metal content was the same: F4 (residual) >F3 (oxidisable) >F2 (reducible) >F1 (acid soluble). In sediments of ZZ at most sites, the RAC for Zn, Pb and Cd revealed low or medium risk and ICF low or moderate contamination. For BI sediments, the order of fractions for Pb was similar while for Zn and Cd quite the opposite compared to the sediments of ZZ and it was: Pb–F4>F3>F1>F2, Zn–F1>F3>F2>F4, Cd–F1>F2>F3>F4. For BI sediments, RAC values for Zn, on average, indicated high and very high ecological risk; for Pb low and moderate risk and for Cd – high risk in the initial part and dredged part and according to the average value in the reservoir, while a medium risk in undredged part sediments. The ICF index showed high contamination with Cd for all BI sediments. The sequential analysis showed that Pb is poorly mobile as in sediments of both reservoirs residual fractions accounted, on average, for about 60% of the total content.

Online and In Situ Monitoring of the Exchange, Transmetalation, and Cross-Coupling of a Negishi Reaction

We have developed a reaction monitoring method which provides quantitative information through exchange, transmetalation (TM), and cross-coupling for a Negishi reaction. Online HPLC and ReactIR were used as orthogonal techniques to corroborate time-course data through each step. Excellent agreement between the two techniques was observed through monitoring the magnesium/bromine exchange. Quantitative information regarding the TM was gathered via a novel, inline quenching technique facilitated by online HPLC. Quenching reaction aliquots with the electrophile 4-chlorobenzaldehyde allowed us to determine the extent of TM because of its selectivity for reacting with organomagnesiums. After TM, the Negishi reaction was performed and monitored using online LC. Titrating ZnCl2 into a solution of arylmagnesium allowed us to gain insights into zinc speciation in situ. Less than 1 equiv of ZnCl2 was needed to achieve complete TM, evidencing the presence of diorganozincs/arylzincates. Additionally, using substoichiometric quantities of ZnCl2 resulted in higher rates of catalysis for the Negishi reaction.

Determination of zinc speciation in soil using synchrotron radiation and its effects on cellular organelles of Phragmites australis

It is necessary to apply modern approaches to prevent the spread/toxic effects of pollution caused by a changing climate; especially metal pollutants to the soil. Thus, the present investigation was aimed to examine chemical speciation of soil samples collected from the River floodplain and its effects on native plant species; Phragmites australis. Synchrotron radiation (SR) tools for Zn speciation in soil and scanning electron microscopy for anatomical changes in plants were applied. Speciation of Zn was a dominant pollutant in Technosols. Two local surroundings were observed for Zn corresponding to its coordination by O and by S, close to ZnS. Whereas, the mixed local surrounding was noted with Zn–S and Zn–O bonds. The analysis of X-ray absorption fine structure results revealed that Technosols contained 70 and 30% of Zn–S and Zn–O bonds, respectively. SR results could be summarized that the main contribution in Technosols was from the authigenic minerals of metals with S: würtzite (hexagonal ZnS), sphalerite (cubic ZnS), bornite (Cu5FeS4), and covellite (CuS). The investigation on growth and modifications in the ultrastructure of P. australis roots and stems showed changes in cellular tissues such as in epidermis and mesoderm, and in subcellular organelles: mitochondria, chloroplast, cell membrane, etc. It is established that the soil contamination with exceeded limits slows down the ontogenetic developments of P. australis. Our findings could provide insight into the physiochemical characteristics of polluted soil as well as information on the toxic effects of pollutants on plants based on non-destructive approaches.