During a sampling campaign in September 2015, elevated chromium (Cr) concentrations were observed in sediments of industrially exposed sites of the Sava River (stainless steel production and impact ...of metallurgic industry). To verify if sediments also contained hazardous hexavalent Cr (Cr(VI)), there was a need to develop a sensitive and reliable analytical procedure for its determination. In the determination of Cr(VI) in environmental samples, it is necessary to evaluate the suitability of the applied analytical methodology for each individual sample matrix. In these studies, the use of isotopically enriched Cr tracers importantly contribute to the validity of the obtained results. In the present work, an analytical procedure was optimised for the extraction of total Cr(VI) from sediments and the content of Cr(VI) determined by high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). To leach the total amount of Cr(VI) from sediments, an ultrasound-assisted extraction procedure was applied at 80 °C, using 2% NaOH + 3% Na2CO3 as the extraction solution. The addition of 0.4 mol L−1 MgCl2 prevented oxidation of Cr(III) during the extraction step. To control for species interconversion and for an accurate calculation of Cr(VI) concentration by speciated isotope dilution (ID)-ICP-MS, the alkaline extract was doubly spiked with enriched 50Cr(VI) and 53Cr(III). The accuracy of the determination of Cr(VI) was verified by analysing the certified reference material CRM 041 (Cr(VI) in soil), and by spike recovery test. Low limits of detection (LOD) and quantification (LOQ) (1.25 and 4.0 μg Cr(VI) kg−1, respectively) and good repeatability of measurement (relative standard deviation better than ±4.8%) were obtained. The analytical data revealed that Cr(VI) concentrations in sediments of the Sava River did not represent any known environmental hazard.
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•Procedure for the alkaline extraction of total Cr(VI) from sediments was optimised.•50Cr(VI) and 53Cr(III) isotopic tracers enabled to follow species interconversion.•Cr(VI) in Sava River sediments was determined by the speciated ID-ICP-MS.•In most of samples Cr(VI) was not detected, or its content was below 5 μg kg−1.•Concentrations of Cr(VI) in Sava sediments do not represent environmental hazard.
Purpose
River ecosystems are under pressure from several different stressors. Among these, inorganic pollutants contribute to multiple stressor situations and the overall degradation of the ...ecological status of the aquatic environments. The main sources of pollution include different industrial activities, untreated effluents from municipal waste waters and intensive agriculture. In the present study, water, suspended particulate matter (SPM) and sediments of the Sava River were studied in order to assess the pollution status of this river system.
Materials and methods
Sampling was performed during the first sampling campaign of the EU 7th FW funded GLOBAQUA project in September 2014, at 18 selected sampling sites along the Sava River. In 2014, floods predominated from spring to fall. Water samples were collected to determine the total element concentrations, the dissolved (0.45 μm) fraction and element concentrations in SPM. In order to assure comparative results with other river basins, the fraction below 63 μm was analysed in sediments. The extent of pollution was estimated by determination of the total element concentrations and by the identification of the most hazardous highly mobile element fractions (extraction 0.11 mol L
−1
acetic acid) and anthropogenic inputs of elements to sediments (normalization to aluminium (Al) concentration). Concentrations of selected elements were determined by inductively coupled plasma mass spectrometry (ICP-MS).
Results and discussion
Since during sampling campaign the water level was extremely high, water samples contained high amounts of SPM (in general between 80 and 100 mg L
−1
). The data of chemical analysis revealed that concentrations of elements in water, SPM and sediments in general increase along the Sava River from its origin to the confluence with the Danube River. Elevated concentrations of chromium (Cr) and nickel (Ni) in SPM and sediments were observed at industrially exposed sites. Concentrations of Cr and Ni in sediments were up to 320 and 250 mg kg
−1
, respectively. Nevertheless, these elements were present in sparingly soluble forms and hence did not represent an environmental threat. Phosphorus (P) was found in elevated concentrations (up to 1500 mg kg
−1
) at regions with intensive agricultural activities and cities with dense population.
Conclusions
With respect to element concentrations, the pollution of the Sava River is similar to other moderately polluted European rivers. The data from the present study are beneficial for the water management authorities and can contribute to sustainable utilization, management and protection of the Sava River water resources.
Flay ash, cement and electric arc furnace (EAF) dust are frequently mixed in building composites. From them, chromium (Cr), arsenic (As), molybdenum (Mo) and vanadium (V) may be leached. ...Concentrations of V in leachates may be significantly higher than those of Cr, As and Mo, making simultaneous speciation analysis particularly difficult. In this work, a high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) procedure was used for simultaneous speciation of chromate, arsenate, molybdate and vanadate. First, the behaviour of Cr, As, Mo and V species in different oxidation states was studied during their separation under acidic (pH 5) and alkaline (pH 12) conditions. At alkaline pHs chromate, arsenate, molybdate and vanadate were simultaneously separated and eluted at retention times from 390 to 450 s, 230 to 270 s, 340 to 430 s and 270 to 380 s, respectively and detected on-line by ICP-MS, recording m / z 52, 75, 95 and 51, respectively. When V species were leached in significantly higher concentrations than Cr, Mo and As, their detection was possible at the low abundance (0.25%) 50 V isotope, which is also the mass of the 50 Cr isotope (abundance 4.345%), due to selective separation between V and Cr species. Good repeatability of measurement (RSD better than ±3.0%) and quantitative elution of elemental species (column recoveries 99–105%) were obtained. Finally, the procedure was applied in the simultaneous speciation analysis of chromate, arsenate, molybdate and vanadate in highly alkaline aqueous leachates from composites consisting of fly ash, cement and EAF dust that contained a wide range of concentrations of vanadate.
•In NEN 7375 test water is replenished at specific time: diffusion of contaminants prevails.•In modified tests synthetic sea, surface and MilliQ water (no replenishment) were applied.•No ...replenishment of leaching solution: diffusion and dissolution of contaminants.•Synthetic surface and sea water better mimicked environmental conditions.•Contaminants were leached more extensively when leaching solution was not replenished.
The NEN 7375 test has been proposed for evaluating the long-term environmental impacts caused by the release of contaminants from monolithic building and waste materials. Over a period of 64days, at specific points in time, the leaching solution (demineralised water) is replenished. By applying the NEN 7375 test, leaching of contaminants that is based mainly on diffusion is followed. In the present work, the results from modified leaching protocols were evaluated against those obtained by NEN 7375 test. In modified protocols, synthetic sea, surface and MilliQ water were used for the leaching of selected elements and chromate, molybdate and vanadate from compact and ground building composites (98% mixture of fly ash (80%) and cement (20%), and 2% of electric arc furnace (EAF) dust) over 6months. The leaching solutions were not replenished, imitating both the diffusion and the dissolution of contaminants. The data revealed larger extent of leaching when the leaching solution was not replenished. More extensive was also leaching from ground composites, which simulated the disintegration of the material over time. The composition of the leaching solution influenced the release of the matrix constituents from the composites and, consequently, the amount of elements and their chemical species. Synthetic sea and surface water used as leaching solutions, without replenishing, were found to be suitable to simulate the conditions when the building material is immersed in stagnant environmental waters.
Acidolysis is emerging as a promising method for recycling polyurethane foam (PUF) waste. Here, we present highly efficient acidolysis of PUFs with adipic acid (AA) by heating the reaction mixtures ...with microwaves. The influence of experimental conditions, such as reaction temperature, time, and amount of the degradation reagent, on the polyol functionality, molecular weight characteristics, the presence of side products, and the degree of degradation of the remaining PUF hard segments was studied by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS), nuclear magnetic resonance (NMR), size-exclusion chromatography (SEC) coupled to a multidetection system, and Fourier transform infrared (FT-IR) spectroscopy. The purified recycled polyols were used for the synthesis of flexible PUFs. The morphology and mechanical properties of the PUFs show that the degree of functionalization of the polyol by the carboxylic end groups, which is higher for larger amounts of AA used to degrade the PUFs, significantly affects the quality and performance of the flexible PUFs from the recycled polyols.
A fast, robust, and convenient method for quantitative determination of polyamide-6 (PA6) and polyamide-66 (PA66) in plastic wastes is presented. The method includes a straightforward procedure for ...complete hydrolysis of polyamides (PAs) into the constituent monomers and their quantitative determination in hydrolyzates by high-performance liquid chromatography on a mixed-mode column, from which the contents of a particular PA are determined. The method was developed on neat PA6 and PA66 as well as their mixture and was further utilized on PA-based composites and postconsumer wastes (carpet and fishing net wastes) containing PA in different amounts. The information on the content of a particular PA type in plastic wastes is important because it determines the maximum recovery of PA constituent monomer(s) by chemical recycling and consequently suitability of waste as a feedstock. Moreover, the proposed method allows for convenient differentiation between PA6 and PA66 in their mixtures, which is difficult to assess with precision by conventional characterization techniques.
Polyurethane foams (PUFs) are widely used commodity materials, but most of them end up in landfills at the end of their life, which is not in line with the circular economy approach. Here, we ...introduce microwave-assisted aminolysis with amine reagents that contain primary and tertiary amino groups in the structure. These reagents enable complete degradation of the urethane groups in the structure of the flexible PUFs with a much lower amount of degradation reagent than is typically required for solvolysis reactions. The purified, recovered polyols are close equivalents to the corresponding virgin polyols in terms of their structural and molar mass characteristics. Therefore, they can be used for the production of high-quality PUFs without having to adapt the synthesis process. The flexible PUFs made from recovered polyols have comparable mechanical properties to those made from virgin polyols.
•The leaching of Al and Si from steel slag in alkaline solutions was investigated.•Leaching is controlled by the bulk diffusion through the product layer crystals.•CASH gel is reaction product of ...slag leaching in alkaline environment.•Choice of alkali solution greatly influences the Si and Al dissolution.
The dissolution of electric arc furnace steel slag (EAFSS) in highly alkaline MOH solution (M=alkali metal Na or K) has been investigated with emphases on the influence of the initial alkali concentration, solid to liquid (S/L) ratio and temperature on the kinetics of Si and Al dissolution from EAFSS. The shrinking core model (SCM) was used to analyze experimental data and the results have shown that the Si and Al dissolution from EAFSS was greatly influenced by MOH concentration, alkaline ion type and temperature. The dissolution process was controlled by the bulk diffusion through the product layer crystals. The activation energy for Si and Al dissolution was 55.27kJ/mol and 48.05kJ/mol in NaOH solution and 90.68kJ/mol and 33.62kJ/mol in KOH solution, respectively.
Fish from the Sava River are consumed daily by the local people: therefore, concern has been raised about the health implications of eating contaminated fish. In the present study, potentially toxic ...elements (PTE), such as Zn, Cu, Cr, Ni, Cd, Pb, As, Hg, and methylmercury (MeHg), were determined in ichthyofauna that are commonly consumed. PTE were determined in the fish muscle tissue. Fish were sampled at 12 locations from the source of the Sava River to its confluence with the Danube River during two sampling campaigns, namely; in 2014 under high water conditions and in 2015 under normal water conditions. Due to the different water regimes, different fish species were collected for chemical analysis. We observed that the concentrations of elements analysed in the fish muscle tissue were generally very low, except for those of Hg. Moreover, more than 90% of Hg present in the fish was in its most toxic form, namely MeHg. Especially in fish from the 2015 sampling campaign, Hg and MeHg concentrations increased with fish size, trophic level, and in the downstream direction. In addition, for Pb and As, and to some extent for Cd and Cr, spatial differences were detected in both years. The highest concentrations of PTE were detected in fish from sites with intensive industrial and agricultural activities. The consumption of fish in general does not pose a health risk for the PTE studied, except for Hg/MeHg at selected contaminated sites.
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•Potentially toxic elements determined in different fish species from Sava River.•Potentially toxic elements concentrations were generally low, except for As and Hg.•Concentrations of As and Hg in muscle tissue increases in the downstream direction.•90% of Hg was present in its most toxic form, namely MeHg.•Estimated Daily Intake (EDI) for As and Hg exceeded Tolerable DI in the lower Sava
The outbreak of the Coronavirus disease 2019 (COVID-19) pandemic has highlighted the importance of developing antiviral surface coatings that are capable of repelling pathogens and neutralizing them ...through self-sanitizing properties. In this study, a novel coating design based on few-layer graphene (FLG) is proposed and silver-decorated micro copper flakes (CuMF) that exhibit both antibacterial and antiviral properties. The role of sacrificial anode surfaces and intrinsic graphene defects in enhancing the release of metal ions from CuMF embedded in water-based binders is investigated. In silico analysis is conducted to better understand the molecular interactions of pathogen-repelling species with bacterial or bacteriophage proteins. The results show that the optimal amount of CuMF/FLG in the coating leads to a significant reduction in bacterial growth, with reductions of 3.17 and 9.81 log for Staphylococcus aureus and Escherichia coli, respectively. The same coating also showed high antiviral efficacy, reducing bacteriophage phi6 by 5.53 log. The antiviral efficiency of the coating is find to be doubled compared to either micro copper flakes or few-layer graphene alone. This novel coating design is versatile and can be applied to various substrates, such as personal protective clothing and face masks, to provide biocidal activity against both bacterial and viral pathogens.
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