The management and prevention of environmental risks associated with spent telecommunications printed circuit boards (STPCBs) is a concerning issue worldwide. Recycling might be proposed as a proper ...method to overcome this issue. Despite knowing that, choosing a sustainable method is challenging because of STPCBs complexity. This problem was overcome by analyzing STPCBs using different analytical methods and metal speciation. Understanding these data is essential in selection strategies to maximize selective recycling of metals and to minimize environmental impact. This research focused on characterizing STPCBs based on their structural, morphological, physiochemical, surface, and thermal properties. The accurate measurement of metal contents, indicating 187,900 mg kg−1 Cu, 22,540 mg kg−1 Pb, 1320 mg kg−1 Ag, and 205 mg kg−1 Au elements, plus other base metals, revealed a remarkable potential value in STPCBs. The results of structural analyses indicated that the powder has a crystalline structure and consists of Cu, Sn and Pb phases as well as different functional groups. In addition, after evaluating the zeta potential of the sample, the isoelectric pH of the sample was observed to be 5.6, which indicates that the powder particles have a negative surface in an environment with a pH higher than this value. Further, the metal speciation via sequential extraction procedure was performed, which showed that a unique harsh recycling strategy is required due to the stable structure of STPCBs. According to the results of this analysis, the global contamination factor (GCF) value was 83.48, which indicates STPCBs have a high degree of contamination. Leaching tests and environmental criteria were also conducted on this waste. The findings suggest that STPCBs needs pretreatments before landfilling to lower the concentration of toxic metals. Also, waste extraction test was the most aggressive procedure to assess mobility. Achieving this information is considered an essential step to choosing the most efficient recycling methods that minimize environmental impact while maximizing selective recycling of metals.
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•The comprehensive characterization of STPCBs was assessed.•STPCBs were found to contain a significant amount of metallic content.•Fractionation of metals revealed that most metals were in residual fractions.•RAC, CF, GCF, and IR were used to assess environmental risk.•A leaching test showed that STPCBS must not be disposed of in landfills.
Clarifying the occurrence and morphological characteristics of petroleum hydrocarbons (PHs) in soil can facilitate a comprehensive understanding of their migration and transformation patterns in ...soil/sediment. Additionally, by establishing the dynamic transformation process of each occurrence state, the ecological impact and environmental risk associated with PHs in soil/sediment can be assessed more precisely. The adsorption experiments and closed static incubation experiments was carried out to explore the PHs degradation and fraction distribution in aged contaminated soil under two remediation scenarios of natural attenuation (NA) and bioaugmentation (BA) by exogenous bacteria through a new sequential extraction method based on Tenax-TA, Hydroxypropyl-β-cyclodextrin and Rhamnolipid (HPCD/RL), accelerated solvent extractor (ASE) unit and alkaline hydrolysis extraction. The adsorption experiment results illustrated that bioaugmentation could promote the desorption of PHs in the adsorption phase, and the soil-water partition coefficient Kd decreased from 0.153 L/g to 0.092 L/g. The incubation experiment results showed that compared with natural attenuation, bioaugmentation could improve the utilization of PHs in aged soil and promote the generation of non-extractable hydrocarbons. On the 90th day of the experiment, the concentrations of weakly adsorbed hydrocarbons in the natural attenuation and bioaugmentation experimental groups decreased by 46.44% and 87.07%, respectively, while the concentrations of strongly adsorbed hydrocarbons and non-extractable hydrocarbons increased by 77.93%, 182.14%, and 80.91%, and 501.19%, respectively, compared their initial values. We developed a novel dynamic model and inverted the kinetic parameters of the model by the parameter scanning function and the Markov Chain Monte Carlo (MCMC) method based on the Bayesian approach in COMSOL Multiphysics® finite element software combined with experimental data. There was a good linear relationship between experimental interpolation data and model prediction data. The R2 for the concentrations of weakly adsorbed hydrocarbons ranged from 0.9953 to 0.9974, for strongly adsorbed hydrocarbons from 0.9063 to 0.9756, and for non-extractable hydrocarbons from 0.9931 to 0.9982. These extremely high correlation coefficients demonstrate the high accuracy of the parameters calculated using the Bayesian inversion method.
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•Experiment and model for the fraction transformation of total petroleum hydrocarbons in aged soil.•Effects of bioremediation on petroleum hydrocarbons occurrence state in aged soil.•A novel dynamic model.•Bayesian inversion approach based on COMSOL Multiphysics® software.
As global warming intensifies, there will be increased uncertainty as to the environmental behavior and risks from heavy metals in industrial/legacy contaminated sites in permafrost regions. ...Bioavailability has been increasingly used for human health risk assessment of heavy metals in contaminated soils. Soil heavy metal bioavailability depends on soil physicochemical properties, and freeze-thaw affects soil physical, chemical and biological processes. However it is not clear whether freeze-thaw has an effect on the bioavailability of soil heavy metals. In this study, soils contaminated with Pb and As were collected from 10 industrial sites in northeast China. Extractability and bioavailability of soil Pb and As were determined by the Tessier sequential extraction method and four in vitro gastron-intestinal simulation methods under control and freeze-thaw treatments. The aims were: to compare the results of extraction and bioavailability from laboratory experiments which artificially simulate freeze-thaw conditions against control soils; to explore the correlation between bioavailability of Pb/As and soil properties. Freeze-thaw significantly decreased soil pH, and increased the soil weight surface area. Freeze-thaw decreased the percentage in the residual fraction, and increased the percentage of Pb and As in the exchangeable fraction, carbonate-bound fraction, Fe-Mn oxides-bound fraction and organic-bound fraction, relative to control soils. Freeze-thaw significantly increased Pb and As bioavailability compared to the controls. Pb and As released in the gastric phase of the four methods was significantly higher than that in the intestinal phase. Further analysis of correlations between Pb and As bioavailability and soil properties indicated that total concentrations of Al, Fe and Mn, particle size, and weight surface area significantly correlated to Pb and As bioavailability. Overall, this study demonstrated that freeze-thaw did influence the bioavailability of soil heavy metals. It suggests the freeze-thaw action should be comprehensively considered in the human risk assessment of soil pollutants in permafrost regions.
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•Freeze-thaw increased the bioavailability of soil Pb and As.•Changes were detectable under free-thaw treatments using a sequential extraction.•In vitro simulation methods showed differences in freeze-thaw treated soils.•Particle size changes after freeze-thaw were linked to Pb/As bioavailability change.
Understanding the role of N-fixing leguminous trees for phosphorus (P) cycling in highly weathered tropical soils is relevant for the conservation of natural forests as well as the sustainable ...management of agroforests and forest plantations with low P input in the Brazilian Atlantic Forest region. We hypothesized that N-fixing leguminous trees can increase the availability of soil P by exploiting different P sources without causing a depletion of soil organic P due to efficient biogeochemical cycling, but empirical evidence remains scarce. For this purpose, 31P nuclear magnetic resonance spectroscopy (31P NMR) was used for quantifying soil P forms and the Hedley sequential extraction to determine soil P fractions. The studied sites were forestry systems with leguminous trees: mixed forest plantations with different proportions of fast-growing N-fixing leguminous trees; pure plantations, and agroforestry systems with leguminous trees. The results show that all N-fixing leguminous trees and N mineral fertilization positively affected the concentrations of available soil P in relation to the control treatments. There were increases of all P fractions through cycling in all forest sites. 31P NMR spectra clearly identified and quantified that a large amount of phosphomonoesters followed by phosphodiesters in the form of DNA, as well as high reserves of Pi species (ortho-P and pyrophosphate) in the first eleven years of growth at pure plantations, mixed plantations or agroforests. The relations between both ortho-P and DNA with the resin-Pi, NaHCO3-Pi and NaOH-Pi fractions suggest that both analysis methods provide complementary information about the soil P transformations. Thus, the paper highlights the importance of the use of different N-fixing leguminous tree species under different environmental conditions, production systems and management practices for recovering heavily degraded areas, which may be a suitable strategy through efficient management of P in highly weathered tropical soils in the Brazilian Atlantic Forest biome.
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•The leguminous trees increased all soil P-fractions.•31P NMR spectroscopy identified and quantified a large amount of Po and Pi compounds.•Leguminous trees and N fertilization promote Po and Pi accumulation in topsoil (0–10 cm).
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•Effects of extraction condition on AAEM determination in were experimentally studied.•An improved sequential extraction method was proposed with clearly defined conditions.•The new ...method has higher accuracy and is less time consuming.•AAEM occurrence modes and contents in three Zhundong coals were determined by the new method.•Mineral patterns in raw coal and extraction residues were analyzed by XRD.
Zhundong coal is one of the most important coals in China due to its huge reserve, but it causes severe fouling and slagging problems when it is burnt in boilers for its high AAEMs (alkali and alkaline earth metal species) contents. Accurately determination of the occurrence modes and contents of AAEMs in Zhundong coals is a necessary step to overcome the ash-related problems. Nowadays, different researchers used different methods or procedures to determine AAEMs in Zhundong coals, and the data were scattering. Based on a series of experiments on the effects of extraction conditions, an improved extraction method with clearly defined conditions for each extraction step was proposed. 0.1mol/L NH4Cl (pH=8.5) instead of 1mol/L NH4OAc (pH=7) was used to extract the exchangeable AAEMs in Zhundong coals to avoid the high solubility of carbonates in the extraction solution. The improved method was more accurate and took much less time than the conventional one. With the proposed extraction method, the occurrence modes and contents of AAEMs in three Zhundong coals were measured. The results revealed that Na is mainly water soluble (Naw/Natotal=50–85%) which is halite or in the form of surface bound Na+, while Ca and Mg are mainly acid soluble (Caac/Catotal=60–90%, Mgac/Mgtotal=45–90%) which are carbonates together with a little amount of sulfates. Exchangeable AAEMs organically bonded to the coal matrix are not the main occurrence mode of AAEMs. Acid insoluble Ca-species could be rankinite. The amounts of AAEMs in the same occurrence mode could be remarkably different among coals from different Zhundong district. The improved sequential extraction method can be extended to determine AAEMs in high carbonate-containing coals.
Soil nitrogen (N) is controlled by several environmental factors. However, it is unclear how these factors and their interactions affect soil N fractions (SNFs) because of the lack of systematic N ...extraction methods. The Harbin–Dali belt, a transect more than 3,300 km long across China covering various climates, topographies, soil parent materials and vegetation types, was taken as the study area, and the interactive effects on SNFs in largely undisturbed woodlands and grasslands were explored using three SNFs: labile N, moderately stable N and stable N. The soil N fractions were obtained through a novel sequential extraction method that used distilled H2O, 0.5 M CaCl2, 1 M HCl, 6 M HCl, mixed acid (1 M HCl and 5 M HF; MA), concentrated HCl (cHCl) and concentrated H2SO4 as extractive agents to successively separate H2O‐, CaCl2‐, 1 M HCl‐, 6 M HCl‐, MA‐, cHCl‐ and RES‐N fractions. The results showed that increasing mean annual temperature (MAT) directly decreased the concentrations of H2O‐, CaCl2‐ and 1 M HCl‐N, suggesting that warming may reduce available N. The interactions between MAT, parent material, aspect and aridity index also contributed to the three SNFs. Vegetation and its interactions with parent material primarily controlled 6 M HCl‐, cHCl‐ and RES‐N, and climate and topography had indirect effects during these processes. Particularly, more cHCl‐ and RES‐N were accumulated in areas with warm humid climates and rich vegetation species than in other environments. Moreover, soil labile N (H2O‐, CaCl2‐ and 1 M HCl‐N) and cHCl‐N exhibited potential as sensitive indicators for reflecting the changes in MAT and vegetation, respectively. Therefore, the various interactions between climate and other environmental factors controlled the changes in most SNFs. This novel sequential extraction method thus offers a reliable analytical approach to measuring SNFs.
Highlights
Soil nitrogen fractions (SNFs) were fractionated via a novel sequential extraction method.
Increasing MAT decreased the H2O‐, CaCl2‐ and 1 M HCl‐N concentrations.
Interactions of climate, parent material and vegetation affected 6 M HCl‐, MA‐, cHCl‐ and RES‐N.
H2O‐, CaCl2‐, 1 M HCl‐ and cHCl‐N are sensitive SNFs that reflect environmental changes.
Lanthanides (Ln) are considered a type of heavy metals. To analyze Ln host phases in the rock and soil, the sequential extraction method is frequently applied. However, the notable shortcoming of the ...sequential fractionation method is the insufficiently high selectivity of the reagents used and incomplete dissolution of target phases. As a result, a significant part of the host phase is retained in the residue with an unknown composition. Therefore, in the current study, a novel statistical apportioning method for Ln among host phases was developed, taking into account the chemically homogeneous Ln-bearing phases. For this purpose, the statistical analysis is used to determine the Ln content in X phases in the rock and soil based on the analysis of the regression equation of the total content, Ln = f (Xphase). The reliability criterion of the dependence Ln = f (Xphase) is the correlation coefficient ‘r’. This new method is efficient in the case of Ln enrichment of rock and soil when the Ln content is >40% of the Clarke value (i.e., crustal abundance) and r > rcrit. The lower layers of the soil profile are dominated by accessory minerals, and the total P content there reflects the presence of monazite and apatite; the Ti content, the presence of titanite (titanosilicate). The proposed statistical method based on total element analysis provides a significant share of Ti- and P-bearing host phases, which is inaccessible through the dissolution method. Thus, it is concluded that the proposed method is a valuable addition for Ln's extraction for identification of Ln host phases in soils and in rocks.
•Novel statistical apportioning method is developed to analyze homogeneous Ln-bearing phases.•This method provides a significant share of the Ti bearing phases and P bearing phases.•It is significant for Ln's extraction for identification of Ln host phases in soils and in rocks.
Cadmium (Cd) and arsenic (As) soil contamination poses significant problems for crop production worldwide. Zero-valent iron (Fe
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) is a reactive material with reducing power capable of stabilizing ...toxic elements, including heavy metals and metalloids. In this study, we examined the effect of Fe
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application on Cd and As accumulation in spinach (Spinacia oleracea L.) grown in Cd- or As-contaminated soil. Fe
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soil application reduced Cd and As concentrations in spinach shoots and/or roots, and decreased their availability in soil, which may have affected their accumulation in spinach. Additionally, we examined the forms of soil Cd and As using the sequential extraction method. The potential availability of Cd and As forms in soils for plant root is: exchangeable > iron-manganese-oxide-bound > organic-matter-bound > free-oxide-occluded > residual. Fe
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application increased Cd and As distribution in the free-oxide-occluded fraction. Additionally, Fe
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application decreased As distribution in the iron-manganese-oxide-bound fraction while tended to decrease Cd in the organic-matter-bound fraction and increase it in the iron-manganese-oxide-bound fraction. Thus, Fe
0
application can be effective in reducing Cd and As availability in their contaminated soils. Meanwhile, this study showed that Fe
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application inhibited the growth of spinach in Cd-contaminated soil. The unfavorable alterations caused by Fe
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in the contaminated soil should also be investigated in the future.
In this study we have worked on the evaluation of heavy metal contamination in the sediments taken from the Tisza River and its tributaries, and thereby used the sequential extraction method, ...geochemical normalization, the calculation of the enrichment factor (EF), and the methods of statistical analysis. The chemical fractionation of Ni, Cu, Zn, Cr, Pb, Fe, and Mn, carried out by using the modified Tessier method, points to different substrates and binding mechanisms of Cu, Zn and Pb in sediments of the tributaries and sediments of the Tisza River. The similarities in the distributions of Fe and Ni in all types of sediments are the result of geochemical similarity as well as of the fact that natural sources mainly affect the concentration levels of these elements. The calculated enrichment factors (EF, measured metal vs. background concentrations) indicated that metal contamination (Cu, Pb, Zn and Cr) was recorded in the sediments of the Tisza River, while no indications of pollution were detected in the tributaries of the Tisza River and the surrounding pools. The maximum values of the EF were close to 6 for Cu and Pb (moderately severe enrichment) and close to 4.5 for Zn (indicating moderate enrichment). It can be said that the Tisza River is slightly to moderately severely polluted with Cu, Zn, and Pb, and minorly polluted with Cr. It is concluded that sediments of the Tisza serve as a repository for heavy metal accumulation from adjacent urban and industrial areas.
