Acid-soluble Fraction Research Articles

Geochemical controls on the distribution and bioavailability of heavy metals in sediments from Yangtze River to the East China Sea: Assessed by sequential extraction versus diffusive gradients in thin-films (DGT) technique

This study conducted a comprehensive investigation on the distribution and bioavailability of heavy metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) in sediments along two typical transects from Yangtze River to the East China Sea continental shelf that spanning large physicochemical gradients. Heavy metals were mainly associated with the fine-grained sediments (enriched with organic matter), exhibiting decreasing trends from nearshore to offshore sites. The turbidity maximum zone showed the highest metal concentrations, which evaluated as polluted for some tested metals (especially Cd) using the geo-accumulation index. Based on the modified BCR procedure, the non-residual fractions of Cu, Zn and Pb were higher within the turbidity maximum zone, and significantly negatively correlated with bottom water salinity. The DGT-labile metals all positively correlated with the acid-soluble metal fraction (especially for Cd, Zn and Cr), and negatively correlated with salinity (except Co). Therefore, our results suggest salinity as the key factor controlling metal bioavailability, which could further modulate metal diffusive fluxes at the sediment-water interface. Considering that DGT probes could readily capture the bioavailable metal fractions, and reflect the impacts of salinity, we suggest DGT technique can be used as a robust predictor for metal bioavailability and mobility in estuary sediments.

Toxic metals and the risks of sludge from the treatment of wastewater from beryllium smelting

The release of highly toxic beryllium in sludge (BCS) produced by physico-chemical treatment of beryllium-containing wastewater from Be smelting production has become a growing concern with the widespread use of Be in the defense industry. This work investigated the potential mobility of Be in BCS. The toxicity characteristic leaching procedure (TCLP) of BCS showed that the amount of leached Be was up to 202 mg L−1, which exceeded the regulated limit by nearly 10,000 times. The chemical fractionation analysis further revealed that the excessive amount of Be leached from BCS was contributed to the high content of acid-soluble fraction and reducible fraction of Be, which accounted for over 70% of the Be content. The results obtained from mineralogical automatic analyzer (MLA) showed that gypsum (23.23%) and epidote (19.55%) were the two major mineralogical phases of BCS. Both were small and loosely structured agglomerated particles with a D50 of 6.61 μm and 3.31 μm. ToF-SIMS results revealed that the Be distribution on the surface of BCS particles was relatively dispersed, with no aggregation or encapsulation. Be co-precipitated with gypsum and chlorite in the form of unstable Be(OH)2, which attached to the surface of these small particles. The unstable state of Be and the small size, loose structure and high liberation of the host material phases are the main reasons for the high leaching mobility of Be. The results of the risk assessment indicated that BCS posed an extremely high potential ecological risk, with Be being the most significant contributor.

Biochar assists phosphate solubilizing bacteria to resist combined Pb and Cd stress by promoting acid secretion and extracellular electron transfer

Microorganisms have difficulty surviving and performing remediation functions in mixed systems with high concentrations of Pb and Cd. Biochar has the potential to assist microorganism remediation as an excellent adsorbent for heavy metals. In this study, pig manure biochar (PMB) was used to assist phosphorus solubilizing bacteria (PSB) to explore the mineralization protection and biofeedback mechanism of biochar on PSB under mixed stress of 1000 mg/L Pb2+ and 500 mg/L Cd2+. The adsorption results showed that the removal of Pb2+ and Cd2+ by PMB+PSB was 148.77% and 72.27% higher than that by PSB. Meanwhile, the non-bioavailable fraction of Cd2+ and acid-soluble fraction of Pb2+ in PMB+PSB were increased by 9% and 3%, respectively. Mineralogical and microbial secretion results confirm that showed that the acidic soluble fraction and non-bioavailable fraction were mostly Pb/Cd-carbonate and Pb/Cd-phosphate. The pore adsorption and precipitation (carbonate) of biochar were able to reduce the exposure of PSB to Pb/Cd and the background stress concentration, thus stimulating the biological positive feedback effect of PSB and forming a microenvironment in the cell periphery. The vesicle detoxification and extracellular polymeric substance protection mechanism of PSB were improved under biochar protection, and the individual size and activity of PSB cells were enhanced. Besides, citric acid release from PSB (28.85% increase) accelerated the dissolution of unstable Cd-carbonate, thereby releasing a large amount of Cd2+ to compete with Pb2+ for PO43-. Thus, the protection of biochar and the positive feedback effect of PSB could reduce the biotoxicity of Cd2+ in the stress system by preferentially forming a stable Cd-phosphate. In addition, the excellent electrical conductivity and organic material adsorption of biochar increased the extracellular electron transport rate of microorganisms, which further accelerated the mineralization and immobilization of Pb2+ and Cd2+, so as to ensure the repair effect of PSB on heavy metals.

Chemical Composition of Thoracic Dust at Workplaces During Cement Production.

Cement belongs to the most used building materials. Clinker is the major constituent of cement, and it is believed that the strong increase of pH after hydration of clinker minerals is responsible for the observed decline in lung function of cement production workers. Information on clinker exposure at workplaces in the cement production industry is scarse. The aims of this study are to determine the chemical composition of thoracic dust and to quantify workplace exposure to clinker in cement production. The elemental composition of 1250 personal thoracic samples collected at workplaces in 15 plants located in 8 different countries (Estonia, Greece, Italy, Norway, Sweden, Switzerland, Spain, Turkey) was determined by inductively coupled plasma optical emission spectrometry (ICP-OES), separately for water- and acid-soluble fraction. Positive matrix factorization (PMF) was used to determine the contribution of different sources to the dust composition and to quantify the clinker content in 1227 of the thoracic samples. In addition, 107 material samples were analysed to facilitate interpretation of the factors obtained by PMF. The median thoracic mass concentrations varied for individual plants between 0.28 and 3.5 mg/m3. PMF with 8 water-soluble and 10 insoluble (i.e., acid-soluble) element concentrations yielded a five-factor solution: Ca, K, Na sulfates; silicates; insoluble clinker; soluble clinker-rich; and soluble Ca-rich. The clinker content of the samples was calculated as sum of the insoluble clinker and soluble clinker-rich factors. The median clinker fraction of all samples was 45% (range 0-95%), and varied between 20% and 70% for individual plants. The 5-factor solution of PMF was selected on the basis of several mathematical parameters recommended in the literature as well as the mineralogical interpretability of the factors. In addition, interpretation of the factors was supported by the measured apparent solubility of Al, K, Si, Fe, and to a lesser extent Ca in material samples. The total clinker content obtained in the present study is considerably lower than estimates based on the Ca concentrations in a sample, and somewhat lower than estimates based on Si concentrations after selective leaching with a methanol/maleic acid mixture. The clinker abundance in workplace dust of one plant investigated in the present contribution was also estimated in a recent study by electron microscopy, and the good agreement between both studies gives confidence in the results of PMF. The clinker fraction in personal thoracic samples could be quantified from the chemical composition by positive matrix factorization. Our results allow for further epidemiological analyses of health effects in the cement production industry. As these estimates are more accurate for clinker exposure than aerosol mass, stronger associations with respiratory effects are expected if clinker is the main cause of these effects.

Mechanochemical treatment with red mud added for heavy metals solidification in municipal solid waste incineration fly ash

The effective stabilization of heavy metals municipal solid waste incineration fly ash (FA) is very important for the disposal of FA, due to that heavy metals leaching from FA will induce environmental risks to a content. In this study, Red mud (RM) was used as an additive for the stabilization of heavy metals in FA during the mechanochemical process. The results demonstrated that the addition of RM significantly reduce the leaching of Pb, Cr and Zn from FA. In the conditions of 30 wt% of red mud, 0.1 g L−1 of solid-to-liquid ratio and 24 h of ball-milling time, the leaching concentration of Pb, Cr and Zn decreased by 99%, 81.18% and 100%, respectively. Meanwhile, the residue fraction of Pb, Cr and Zn increased, part of the reducible Cr is changed into acid-soluble fraction of Cr due to oxidation. Moreover, FA was broken into small particles and then agglomerated into larger ones after mechanochemical treatment. The main reasons accounting for the solidification of heavy metals were ascribed to the precipitation and sealing by the fine particles, capture by new phases, dissolution and elution of soluble salt. RM play a key role in forming new phases (include hydrocalumite, andradite and aluminosilicate minerals) which in favor of solidification of heavy metals. This work provides a good method for the effective heavy metals stabilization in FA and presents a new sight into the reuse of RM.

A double-edged sword: Reductive soil disinfestation changes the fates of trace metal elements in soil

Although the effects of reductive soil disinfestation (RSD) in soil sterilization have been proven in several countries, the potential risks of trace metal elements (TMEs) caused by RSD require further assessment. Here, freshly Cd-spiked soil and historically contaminated greenhouse soil were exposed to RSD and the fates of TMEs, Cd, Co, Cu, Ni, Pb, and Zn, were investigated. All RSD treatments lasted for 21 days and subsamples were collected at different time intervals. Samples were open-air incubated for another 7 days until day 28 to simulate the situation after drainage. The bioavailability and geochemical fractionation of TMEs were investigated based on single and sequential extraction procedures and the environmental risks were assessed. The results showed that RSD increased the relative abundance of Firmicutes and Bacteroidetes, and the content of functional groups, including Fe, Mn, and S compounds respirations increased after RSD, highlighting the possible reductive dissolution of FeMn oxides and precipitation of TMEs. The dissolution decreased the reducible fractions of TMEs and increased the acid-soluble fractions of Co, Ni, Pb, and Zn, in the European Community Bureau of Reference results, reflecting the activation of TMEs in soils. However, the precipitation of sulfate resulted in the stabilization of Cd and Cu in two types of soils, increased their residual fractions, and decreased their acid-soluble fractions and bioavailabilities. After drainage, because the influence caused by precipitation rapidly disappeared and the impact of FeMn oxides dissolution remained, the acid-solubility of TMEs was greater than their initial status in the two soils. Furthermore, as a highly toxic metal, the activation of Cd at 28 days caused the rapid increase of ecological risks, which is particularly concerning. The results suggest that RSD temporarily increases the potential risks of TMEs and that certain measures must be taken.

Migration and distribution characteristics of soil heavy metal(loid)s at a lead smelting site

Heavy metal(loid)s contamination is a constant issue at smelting sites. It is essential to investigate the spatial distribution and migration characteristics of heavy metal(loid)s in the soil for environmental management and remediation strategies of non-ferrous smelting sites. In this study, 203 soil samples from 57 sites were collected in a typical lead smelting site. The findings demonstrated that there were significant Pb, Zn, Cd, and As contamination in soil samples. The spatial distribution of heavy metal(loid)s showed strong spatial heterogeneity, the contaminated soil areas of Pb, As, Cd, and Zn were 99.5%, 98.9%, 85.3%, and 72.4%, respectively. Pb, Cd, and As contamination of the soil reached a depth of 5 m, which migrated from the surface to deep soil layers. The leaching contents of Zn, Pb, and As decreased obviously in 3-4 m soil layer, but the leaching content of Cd was still high, which indicated the high migration of Cd. With the increase of depth, the proportion of acid soluble fraction of heavy metal(loid)s decreased, and the residual fraction increased. The acid soluble fraction of Cd accounted for a higher proportion, and As mainly existed in reducible and residual fractions in soil. According to the calculation of the migration factor, the migration of heavy metal(loid)s in soils were ordered as Cd > Zn > Pb > As. The outcomes are advantageous for risk reduction and site remediation for non-ferrous metal smelting sites.

Spatial Distribution and Risk Assessment of Heavy Metals in Surface Sediments from the Middle and Upper Reaches of the Yangtze River

The hydrological regime of rivers significantly changes after dam impoundment, which in turn affects the particle composition and heavy metal fractions of the river sediments. From June to July 2019, the sediments from 26 sampling sections were collected along the main stream of the Yangtze River from Panzhihua City in the upper reaches of the Yangtze River to Hukou City in the middle reaches of the Yangtze River. The concentrations and fractions of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn were measured using the BCR three-step extraction procedure. The pollution status and potential ecological risk of heavy metals in sediments were evaluated using the geo-accumulation index, the sediment quality guideline, and the risk assessment coding method (RAC). The results showed that the average particle size of sediments in the upper reaches of the Yangtze River (Jinsha River cascade reservoir section and the Three Gorges reservoir section) decreased from upstream to downstream, the total concentrations of As and Zn increased, and the variation trend in the middle reaches was not obvious. The content of clay particles was significantly positively correlated with the acid-soluble fraction concentrations of Cd and Ni. Cd was mainly in the residual fraction (59.26%) and acid-soluble fraction (24.67%). Large parts of Cr and Ni were residual fractions accounting for 92.41% and 83.41%, respectively. As, Co, Cu, Pb, and Zn were mainly in the residual fraction and the reducible fraction. The order of decrease for the pollution degree (Igeo) of As, Cd, Co, Cr, Ni, and Zn was the Jinsha River, the middle reaches of the Yangtze River, and the Three Gorges Reservoir. The decrease order of bioavailability (RAC) of Cd, Co, Cr, Cu, Ni, and Zn was the Three Gorges Reservoir, the Jinsha River, and the middle reaches of the Yangtze River. The bioavailability of As and Pb decreased in the order of the middle reaches of the Yangtze River, the Three Gorges, and the Jinsha River. According to the classification of the RAC, Cd in the Three Gorges Reservoir area exhibited a high risk with the RAC accounting for 48.44%. Cu, Ni, and Zn showed a low or medium risk.

Combining the advantages of Rhizophagus intraradices and Serendipita indica to reduce the risk of Cd on soybean safety and environmental pollution

The discharge of industrial wastes and improper application of fertilizers have caused Cd pollution in farmland soil. Combined microbial and plant remediation is an environmentally friendly method for Cd pollution remediation, but single microbial colonization cannot meet the dual needs of safe production and remediation in Cd pollution. Therefore, we designed an 85 days pot experiment to investigate the effect of compound or single arbuscular mycorrhizal fungi (AMF: Rhizophagus intraradices, RI) and Serendipita indica (SI) with similar physiological and ecological functions, on the soybean physiological parameters, soil factors, and soil Cd fractions. Their effects were analyzed on the Cd accumulation and transport ability and the soil contamination degree/risk in different Cd stress. The results showed that under different concentrations of Cd stress, Both RI and SI could not only increase the chlorophyll content of soybean to promote photosynthesis, thereby increasing the stem length and biomass index to promote growth, but also reduce the malondialdehyde content and increase the proline content to reduce the Cd-mediated oxidative damage. In addition, they cannot only increase soil pH and available phosphorus, but also improve soil urease and catalase activities. Furthermore, compound inoculant can reduce the Cd content in soybean by 55.96% (aerial), 72.61% (underground), and convert the Cd acid-soluble fraction into a more stable chemical fraction to reduce the risk of soil Cd pollution. It was found that SI had a more positive impact on soybean physiology, while RI was on soil quality. In conclusion, the compound inoculant combining the advantages of the two fungi is suitable for farmland under different concentrations of Cd stress.

Particle size of biochar significantly regulates the chemical speciation, transformation, and ecotoxicity of cadmium in biochar

The pyrolysis of biomass containing excessive heavy metals is likely to produce heavy metal contaminated biochar (BC). Although multiple lines of evidence indicate that higher charring temperature leads to enhanced immobilization of heavy metals in BC, we find that particle size could also play a critical role in the content of heavy metals in BC and BC ecotoxicity. Here, BC derived from cadmium (Cd) enriched rice straw was prepared at different temperatures (300–600 °C) and divided into macro-, colloidal-, and nano-sized fractions, respectively. The content and chemical forms of Cd in BC fractions as well as related algal toxicity were examined. The results show that for the same temperature BC the content of Cd followed an order of colloidal-BC > macro-BC > nano-BC; and the residual fractions of Cd significantly decreased (3.47–16.08%) while that of acid soluble and reducible fractions significantly increased (4.13–16.51% and 0.24–1.71%, respectively) with decreasing particle size of BC. Consistently, colloidal-BC exhibited the highest ecotoxicity for Scenedesmus obliquus. The acid soluble fractions of Cd in macro- and colloidal-BC played a dominating role in their algal toxicity (p < 0.05). However, the ecotoxicity of nano-BC was more dependent on the total content of Cd than specific fractions probably due to the phagocytosis by algal cells. These results indicate that the chemical forms and ecotoxicity of Cd in BC could be remarkably modified by its particle size, which has profound implications for understanding the behavior and potential risk of heavy metal contaminated BC in the environment.

Efficient lead immobilization by bio-beads containing Pseudomonas rhodesiae and bone char

Mineralization of lead ions (Pb2+) to pyromorphite using phosphorus-containing materials is an effective way to remediate lead (Pb) contamination. Bone char is rich in phosphorus, but its immobilization of Pb2+ is limited by poor phosphate release. To utilize the phosphorus in bone char and provide a suitable growth environment for phosphate-solubilizing bacteria, bone char and Pseudomonas rhodesiae HP-7 were encapsulated into bio-beads, and the immobilization performance and mechanism of Pb in solution and soil by bio-beads were investigated. The results showed that 137 mg/g of phosphorus was released from bone char in the presence of the HP-7 strain. Pb2+ removal efficiency reached 100 % with an initial Pb2+ concentration of 1 mM, bone char content of 6 g/L, and bio-bead dosage of 1 %. Most Pb2+ was immobilized on the surface of the bio-beads as Pb5(PO4)3Cl. The soil remediation experiments showed a 34 % reduction in the acid-soluble fraction of Pb. The bio-beads showed good stability in long-term (30 d) soil remediation. The present study shows that bone char can be turned into an efficient Pb immobilization material in the presence of phosphate-solubilizing bacteria. Thus, bio-beads are expected to be used in the remediation of Pb-contaminated environments.

Technical note: simultaneous determination of amino thiols in pig tissue by ultra-high performance liquid chromatography with fluorescence detection.

Sulfur amino acid nutrition and metabolism are linked to animal disease. While validated methods for the determination of amino thiol levels in plasma or serum are available, there is a dearth of validated methods for their measurement in tissue. A robust and reproducible ultra-high performance liquid chromatography method has been validated for the simultaneous determination of concentrations of cysteine (Cys), cysteinylglycine (CysGly), homocysteine (Hcys), γ-glutamylcysteine (γ-GluCys), and glutathione (GSH) in pig tissue. Tissue was homogenized and deproteinized with trichloroacetic acid. Amino thiols in the acid-soluble fraction of the tissue homogenate were reduced with tris-(2-carboxyethyl)-phosphine hydrochloride and derivatized with 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (ABD-F). Amino thiols were resolved under reversed-phase gradient conditions on a Waters Acquity BEH C18 column (1.7 µm, 2.1 mm × 100 mm) within 4.5 min and detected with fluorescence. The peak area ratio of analyte to 2-mercaptopropionylglycine internal standard, added to external calibration standards and samples, was used to develop linear calibration curves. Linear calibrations were performed over the range of 15-1,500 nmol/g for Cys, CysGly, Hcys, and γ-GluCys and 150-15,000 nmol/g for GSH. Linearity, lower limit of detection, lower limit of quantitation, accuracy, precision, sample stability, and carryover were evaluated. We demonstrate excellent linearity for all analytes within their respective concentration range (r2 > 0.99) and excellent recovery of amino thiols from spiked samples (mean ± SD across tissues; Cys, 100.0 ± 2.2%; CysGly, 95.4 ± 5.1%; Hcys, 96.6 ± 2.0%; γ-GluCys, 102.2 ± 2.7%; and GSH, 100.6 ± 3.3%). The intra-day and inter-day precisions did not exceed 5% and 10%, respectively. Repeated freezing and thawing of tissue homogenate did not affect measured amino thiol concentrations, ABD-labeled amino thiols were stable for 1 wk after derivatization, and there was no sample carryover across consecutive injections. We confirm the identity of each ABD-labeled amino thiol with Orbitrap mass spectrometry. Finally, we apply the method to the determination of amino thiol concentrations in liver and jejunum tissues in newly weaned pigs and show that despite elevated Cys and maintained GSH concentrations in liver, both γ-GluCys and GSH decline in jejunum of weaned pigs.

New insights into the decrease in Cd2+ bioavailability in sediments by microplastics: Role of geochemical properties.

Microplastics (MPs) are considered to influence the bioavailability of heavy metals through direct adsorption, but this neglects the distribution of heavy metal chemical speciation indirectly influenced by MPs by altering geochemical properties. The present study aims to explore the link between the fractionation distribution of cadmium (Cd2+) and changes in geochemical properties in sediments induced by polyethylene terephthalate microplastics (PET-MPs). The PET-MPs reduced the acid-soluble fraction of Cd2+ in sediments and increased its organically bound fraction. In addition, the concentration of bioavailable Cd2+ in the sediment decreased by 4.09-25.96 % with increasing PET-MPs doses and aging. Whereas the thermal aging of PET-MPs led to a decrease in the molar ratio of oxygen-containing functional groups and the BET surface area, which is not favorable for improving the adsorption capacity of PET-MPs. On the other hand, the correlation analysis demonstrated the key role of PET-MPs in increasing the content of sediment organic matter and its humification level, which indirectly led to a decrease in Cd2+ bioavailability. The microbial analysis demonstrated that PET-MPs increase the relative abundances of Chloroflexi, hexokinase, and 6-phosphofructose kinase in sediments, thereby increasing the humification level of sediment organic matter. The present study provides a new perspective for understanding the environmental risks of MPs-altered heavy metals.

Chemical association of copper and selenium in coals of Sindh by time saving single step strategy and their impact on groundwater.

The aim of the present study is to estimate the different chemical fractionations of copper (Cu) and selenium (Se) in coal samples of different coal mining areas. The Cu and Se bound to various chemical fractions of coal collected from two mining fields of Sindh, Pakistan, have been determined by BCR sequential extraction scheme (BCR-SES). The long duration of the BCR sequential scheme (51h) was reduced by a time-saving shaking device (ultrasonic bath) termed as ultrasonic-assisted extraction (USE) depending on the same operating conditions and extracting solutions used for BCR sequential extraction scheme. The both trace elements were determined in aquifer water, sampled from different depth of both coal mining fields. In addition, the groundwater of dug well in the vicinity of coal mining areas were also analyzed for Cu and Se using reported extraction methodologies. The partitioning of Cu and Se bound with different chemical fractions of coal was successfully made by proposed USE, within 2h as compared to long duration of BCR-SES (51h). The Cu and Se concentrations in acid-soluble fractions of coal samples were > 10%, enhanced by USE extraction procedure than those values gained via BCR-SES (p < 0.01). About 67 to 69% of Cu were found in the first three fractions, whereas their remaining amount corresponding to 31 to 33%, respectively bound with crystalline/residual fraction, while up to 66.1 to 71.1% of total Se contents extracted in three extractable phases, followed up to 28.9 to 33.8% of it was bound with residual phase. The concentrations of Cu and Se in groundwater of different aquifers were found in decreasing order as AQ1 > AQII > AQIII; the same trend was observed for two aquifers of Lakhra coal mining, whereas the groundwater samples have two to three folds higher levels of Se than WHO limit. The Cu levels in water samples were significantly lower than the recommended limit of WHO for drinking water (p < 0.01).

Analysing Objects to Tailor Environmental Preventive Conservation

This work explores the potential of analyzing individual objects to improve their preventive conservation. Previously, environmental recommendations have been based on an average or worst response of material groups. Cultural heritage objects are extremely variable and within a group such as archaeological iron a very wide range of responses are shown. Characterizing a single object’s response allows its environment to be tailored to its requirements and can enable significant resource and carbon footprint savings. Three main approaches are considered with a material explored in detail including preventive conservation ramifications. Composition analysis is investigated through the stability of limestones. The critical concentrations of soluble salts causing surface deterioration in one environment has been explored. A more rapid method of analyzing clays in acid insoluble fractions from drillings and undertaking that analysis non-invasively has been developed. Measuring deterioration rates is explored through oxygen consumption analyses of archaeological iron. The distributions of previously published data are explored and the changes in rates examined. A scheme for parchment based on shrinkage temperatures and observations is presented for the first time and its use illustrated with a newly acquired letter. The type of work required to produce these schemes is explored with leather.

Soil pH restricts the ability of biochar to passivate cadmium: A meta-analysis

Soil acidification is the main cause for aggravation of soil cadmium (Cd) pollution. Biochar treatment can increase the soil pH and decrease the Cd availability in soils. However, there is limited information in literature on the comprehensive assessment of the response of Cd fractions to biochar. Therefore, in the present meta-analysis study, we evaluate the response of Cd fractions to biochar application in soils with different pH and to further examine the effect of physicochemical properties of biochar on Cd. Results from the overall analysis indicated that biochar treatment increased the soil pH by 7.0%, thereby decreasing the amount of available Cd (37.3%). In acidic soil, biochar significantly reduced the acid-soluble fraction (Acid-Cd) of Cd by 36.8%, while Oxidizable fraction of Cd (Oxid-Cd, 20.9%) and Residual fraction of Cd (Resid-Cd, 22.2%) were significantly increased. In neutral soils, only Acid-Cd was significantly reduced (33.0%) in the presence of biochar. In alkaline soils, biochar caused significant reduction in Acid-Cd of 12.4% and an increase in Oxid-Cd and Resid-Cd of 26.6% and 47.8%, respectively. Further, our findings showed that biochar with cation exchange capacity >100 cmol+/kg effectively decreased Acid-Cd (32.4%), while biochar with the percentage of hydrogen <2% was more contributory in increasing Resid-Cd (64.3%). These results demonstrate the importance of soil pH in regulating the biological effectiveness of Cd in soil and the complexation between the functional groups of biochar and Cd, and provide key information for the remediation of Cd pollution in soils with different pH by biochar.

Bioaccumulation and retention of Po-210 and Pb-210 in two species of mosses from the zone of influence of the former radium-extracting plants.

The presented study was aimed at assessing the ability to accumulate and retain 210Po and 210Pb in two species of the mosses Sphagnum girgensohnii Russow and Pleurozium schreberi (Willd. ex Brid.) Mitt. Mosses were collected in the zone of influence of the former radium-extracting plants (Komi Republic, Russia). 210Po and 210Pb activity concentrations in S. girgensohnii varied from 131 ± 15.4 to 221 ± 18.3Bqkg-1, and from 164 ± 18.6 to 309 ± 26.1Bqkg-1 respectively. In P. schreberi corresponding activity concentrations ranged from 107 ± 18.8 to 328 ± 29.2Bqkg-1 and from 117 ± 13.2 to 399 ± 31.1Bqkg-1. Activity concentrations of 210Po and 210Pb in autumn were higher than in summer. In the young parts of the mosses, they were lower than in the old parts. To assess the ability to retain accumulated radionuclides, watersoluble (distilled H2O), exchangeable (1M CH3COONH4), and acidsoluble (0.1M H2SO4) fractions of 210Po and 210Pb were isolated from the studied mosses by the method sequential extraction. It was revealed that these fractions in total contained up to 26% of 210Po and 39% of 210Pb. The results showed that the studied moss species are a good biogeochemical barrier and long-term storage for 210Pb and 210Po.

Insights into the heavy metal adsorption and immobilization mechanisms of CaFe-layered double hydroxide corn straw biochar: Synthesis and application in a combined heavy metal-contaminated environment

Biochar is an emerging eco-friendly and high-efficiency heavy metal (HM) adsorbent that exhibits satisfactory HM remediation effects in both water and soil environments. However, few studies have investigated the mechanisms and application of biochar in the remediation of combined HM-contaminated environments. Therefore, in the present study, a novel corn straw biochar-loaded calcium-iron layered double hydroxide composite (CaFe-LDH@CSB) was synthesized via the coprecipitation method and applied as a remediation adsorbent to remove HMs in both water and soil environments. The results indicated that the HM adsorption mechanism of CaFe-LDH@CSB in the aquatic phase involved a chemical endothermic adsorption process of functional group-complexed monolayers, dominated by precipitation, ion exchange, complexation and π bond interactions. The maximum adsorption capacity for Cd(II), Pb(II), Zn(II) and Cu(II) in the aqueous phase reached 24.58, 240.96, 57.57 and 39.35 mg g−1, respectively. In addition, application of CaFe-LDH@CSB in the combined HM-contaminated soil treatment helped to increase the soil pH, which increased by 5.1–17.9% in low-contamination (LC) soil and by 7.0–13.9% in high-contamination (HC) soil. Moreover, application of CaFe-LDH@CSB effectively decreased the acid-soluble fraction of HMs and increased the HM residual fraction. The immobilization mechanism of CaFe-LDH@CSB in the soil was concluded to involve pore filling, functional group action and electrostatic interactions. Overall, this study provided a novel LDH biochar composite that can be effectively applied in the remediation of combined HM-contaminated water and soil environments.

Chimeric Phagocytic Receptors (CPR) to target Alzheimer’s disease pathology

AbstractBackgroundBased on the premise that protein aggregation and accumulation in AD and many other neurodegenerative disorders is a key, causal, pathologic event, therapeutic strategies need to focus on i) prevention of aggregate formation ii) enhancement of clearance of the aggregate or iii) neutralization of “toxic” signaling by the aggregate. Enhancing clearance of the target protein via phagocytic mechanisms is the most direct way to test the hypothesis that enhancing clearance will be beneficial. We cloned two novel chimeric phagocytic receptors (CPRs), fused to a previously characterized anti‐Abeta scFv. The present work aims to explore whether astrocyte expressed CPRs targeting Aβ enhance phagocyte clearance and alter the target pathology, when delivered into the brain of the Alzheimer’s disease mouse model, CRND8, as a prevention paradigm, before the pathology develops, or after amyloid aggregation already occurred.MethodAnti‐Abeta recombinant scFvs fused to two most promising CPRs were packaged in AAV under astrocytic GFAP promoter and delivered into the brains of newborn CRND8 mice (prevention paradigm) as well as older mice with preexisting pathology (treatment paradigm). Amyloid burden and Aβ levels in the soluble, SDS soluble and SDS‐insoluble, Formic Acid soluble fractions, as well as the state of astrocytosis and astrogliosis were compared between various cohorts. Backbone of the CPR without the scFv as well as pAAV‐EGFP served as controls.ResultInitially we evaluated expression, amyloid burden and GFAP and IBA staining in mice that were injected with 2 CPRs, pAAV‐MRC1‐GFAP‐scFv9, pAAV‐FCRG‐GFAP‐scFv9, as well as pAAV‐MRC1‐BB (backbone control) and pAAV‐EGFP control. Amyloid staining revealed a significant clearance of amyloid staining in the area around the injection site, which overlapped with the expression of CPR. Additionally, expression of CPRs resulted in increased astrocytes and microglia burden.ConclusionThese results suggest a significant amyloid alteration by chosen CPRs. Future studies will optimize brain delivery as well as determine therapeutic potential of CPRs following transplantation of the CPR expressing microglia/monocytes into the brain mice with preexisting pathology.

The effects of washing solvents on the properties of ceramsite and heavy metal immobilization via the cosintering of municipal solid waste incineration fly ash and Cr-containing waste glass

Various washing solvents are being extensively researched to remove chlorides from municipal solid waste incineration fly ash (FA) and they have significant impacts on the recycling and reutilization of FA. The cosintering of FA and waste glass (WG) containing chromium (Cr) was explored in this study, as well as the effects of washing solutions (water [W-FA], phosphoric acid [P-FA], and sodium carbonate [Na-FA]) on the treated FA compositions, ceramsite characteristics, and heavy metals speciation. The findings demonstrated that washing process increased calcium oxide (CaO) content while reducing soluble salt level. The particle strength increased from 290.50 N to 926.78 N at 800–1050 °C, while increased from 228.68 N to 820.23 N when WG increased from 20% to 60%. Raw-FA ceramsite had a lower sintering temperature than treated FA ceramsite due to the higher particle strength and lower water absorption rate. At 1000 °C, the acid-soluble fraction of Cr of Na-FA and P-FA ceramsite was 64.72% and 9.07%, showing a promoted and inhibited effect on Cr leaching, respectively. The ecological risk index for P-FA and Na-FA ceramsite, both of which were produced at 1100 °C, were 30.61 and 46.68, respectively, indicating low environmental risk. Wollastonite was the dominating mineral phase in W-FA and Na-FA ceramsite, whereas chlorapatite and halite predominated in P-FA and Raw-FA ceramsite. Chlorine in P-FA ceramsite was combined with phosphates and calcium to generate stable minerals. Washing pretreatment reduced the environmental risk of ceramsite, and introduction of phosphorus could enhance heavy metal immobilization.