Arsenic(III) sequestration by terrestrial-derived soil protein: Roles of redox-active moieties and Fe(III).

Glomalin-related soil protein (GRSP) has demonstrated significant potential for water purification and remediation of heavy metals in soils; however, its redox reactivity for As(III) sequestration and the corresponding redox-active component are still poorly understood. This study investigated the photochemical properties of GRSP and its mechanism of oxidation/adsorption of As(III). The results showed that UV irradiation triggered electron transfer and the production of reactive oxygen species (ROS) in GRSP, thereby facilitating As(III) oxidation with promotion rates ranging from 43.34 % to 111.1 %. The oxidation of As(III) occurred both on the GRSP photoforming holes and in the ROS reaction from the oxygen reduction products of the photoforming electrons. OH• and H2O2 played an important role in the oxidation of As(III) by GRSP, especially under alkaline conditions. Moreover, the presence of Fe(III) in GRSP facilitated the formation of OH• and its the oxidation capacity towards As(III). The binding of As(III) to the -COOH, -OH, and -FeO groups on the GRSP surface occurred through surface complexation. Overall, these findings provided new insights into the roles of the redox-active moieties and Fe(III) on GRSP in the promoted oxidation of As(III), which would help to deepen our understanding of the migration and transformation of As(III) in soils.

Comparative analysis of size-fractional eukaryotic microbes in subtropical riverine systems inferred from 18S rRNA gene V4 and V9 regions.

Eukaryotic microbes play key ecological roles in riverine ecosystems. Amplicon sequencing has greatly facilitated the identification and characterization of eukaryotic microbial communities. Currently, 18S rRNA gene V4 and V9 hypervariable regions are widely used for sequencing eukaryotic microbes. Identifying optimal regions for the profiling of size-fractional eukaryotic microbial communities is critical for microbial ecological studies. In this study, we spanned three rivers with typical natural-human influenced transition gradients to evaluate the performance of the 18S rRNA gene V4 and V9 hypervariable regions for sequencing size-fractional eukaryotic microbes (>180 µm, 20-180 µm, 5-20 µm, 3-5 µm, 0.8-3 µm). Our comparative analysis revealed that amplicon results depend on the specific species and microbial size. The V9 region was most effective for detecting a broad taxonomic range of species. The V4 region was superior to the V9 region for the identification of microbes in the minor 3 µm and at the family and genus levels, especially for specific microbial groups, such as Labyrinthulomycetes. However, the V9 region was more effective for studies of diverse eukaryotic groups, including Archamoebae, Heterolobosea, and Microsporidia, and various algae, such as Haptophyta, Florideophycidae, and Bangiales. Our results highlight the importance of accounting for potential misclassifications when employing both V4 and V9 regions for the identification of microbial sequences. The use of optimal regions for amplification could enhance the utility of amplicon sequencing in environmental studies. The insights gained from this work will aid future studies that employ amplicon-based identification approaches for the characterization of eukaryotic microbial communities and contribute to our understanding of microbial ecology within aquatic systems.

Excretion characteristics of main compounds of Yigong San in urine, feces, and bile of rats.

Yigong San (YGS) is a traditional Chinese medicine formula used for pediatric anorexia, chronic atrophic gastritis, and irritable bowel syndrome. In this study, the excretion of eight main compounds, including liquiritin; isoliquiritin; hesperidin; ginsenosides Rb1, Re, and Rg1; and atractylenolides I and II, in rat urine, feces, and bile, was investigated by ultra-high performance liquid chromatography-tandem mass spectrometry. The results showed that the cumulative excretion rates of the compounds in rat urine, feces, and bile were 0.018-1.15%, 0.024-19.89%, and 0.0025-0.72%, respectively. Among the eight compounds detected, liquiritin was the richest in urine, and ginsenosides Re and Rg1 and atractylenolide I were mainly found in feces and bile. In summary, the main components of YGS are excreted via multiple approaches. Liquiritin is mainly through urine, whereas isoliquiritin; hesperidin; ginsenosides Rb1, Re, and Rg1; and atractylenolides I and II are mainly through feces. The excretion of these compounds in bile is usually positively correlated with that in feces. This study lays a foundation for further pharmacological research and application of YGS.

Microplastics emerge as a hotspot for dibutyl phthalate sources in rivers and oceans: Leaching behavior and potential risks.

Dibutyl phthalate (DBP) as a plasticizer has been widely used in the processing of plastic products. Nevertheless, these DBP additives have the potential to be released into the environment throughout the entire life cycle of plastic products. Herein, the leaching behavior of DBP from PVC microplastics (MPs) in freshwater and seawater and its potential risks were investigated. The results show that the plasticizer content, UV irradiation, and hydrochemical conditions have a great influence on the leaching of DBP from the MPs. The release of DBP into the environment increases proportionally with higher concentrations of additive DBP in MPs, particularly when it exceeds 15 %. The surface of MPs undergoes accelerated oxidation and increased hydrophilicity under UV radiation, thereby facilitating the leaching of DBP. Through 30 continuous leaching experiments, the leaching of DBP from MPs in freshwater and seawater can reach up to 12.28 and 5.42 mg g-1, respectively, indicating that MPs are a continuous source of DBP pollution in the aquatic environment. Moreover, phthalate pollution index (PPI) indicates that MPs can significantly increase DBP pollution in marine environment through land and sea transport processes. Therefore, we advocate that the management of MPs waste containing DBP be prioritized in coastal sustainable development.

EEG power spectra parameterization and adaptive channel selection towards semi-supervised seizure prediction.

BACKGROUND: The seizure prediction algorithms have demonstrated their potential in mitigating epilepsy risks by detecting the pre-ictal state using ongoing electroencephalogram (EEG) signals. However, most of them require high-density EEG, which is burdensome to the patients for daily monitoring. Moreover, prevailing seizure models require extensive training with significant labeled data which is very time-consuming and demanding for the epileptologists. METHOD: To address these challenges, here we propose an adaptive channel selection strategy and a semi-supervised deep learning model respectively to reduce the number of EEG channels and to limit the amount of labeled data required for accurate seizure prediction. Our channel selection module is centered on features from EEG power spectra parameterization that precisely characterize the epileptic activities to identify the seizure-associated channels for each patient. The semi-supervised model integrates generative adversarial networks and bidirectional long short-term memory networks to enhance seizure prediction. RESULTS: Our approach is evaluated on the CHB-MIT and Siena epilepsy datasets. With utilizing only 4 channels, the method demonstrates outstanding performance with an AUC of 93.15% on the CHB-MIT dataset and an AUC of 88.98% on the Siena dataset. Experimental results also demonstrate that our selection approach reduces the model parameters and training time. CONCLUSIONS: Adaptive channel selection coupled with semi-supervised learning can offer the possible bases for a light weight and computationally efficient seizure prediction system, making the daily monitoring practical to improve patients' quality of life.

TRPC4 aggravates hypoxic pulmonary hypertension by promoting pulmonary endothelial cell apoptosis.

Pulmonary hypertension (PH) is a devastating disease that lacks effective treatment options and is characterized by severe pulmonary vascular remodeling. Pulmonary arterial endothelial cell (PAEC) dysfunction drives the initiation and pathogenesis of pulmonary arterial hypertension. Canonical transient receptor potential (TRPC) channels, a family of Ca2+-permeable channels, play an important role in various diseases. However, the effect and mechanism of TRPCs on PH development have not been fully elucidated. Among the TRPC family members, TRPC4 expression was markedly upregulated in PAECs from hypoxia combined with SU5416 (HySu)-induced PH mice and monocrotaline (MCT)-treated PH rats, as well as in hypoxia-exposed PAECs, suggesting that TRPC4 in PAECs may participate in the occurrence and development of PH. In this study, we aimed to investigate whether TRPC4 in PAECs has an aggravating effect on PH and elucidate the molecular mechanisms. We observed that hypoxia treatment promoted PAEC apoptosis through a caspase-12/endoplasmic reticulum stress (ERS)-dependent pathway. Knockdown of TRPC4 attenuated hypoxia-induced apoptosis and caspase-3/caspase-12 activity in PAECs. Accordingly, adeno-associated virus (AAV) serotype 6-mediated pulmonary endothelial TRPC4 silencing (AAV6-Tie-shRNA-TRPC4) or TRPC4 antagonist suppressed PH progression as evidenced by reduced right ventricular systolic pressure (RVSP), pulmonary vascular remodeling, PAEC apoptosis and reactive oxygen species (ROS) production. Mechanistically, unbiased RNA sequencing (RNA-seq) suggested that TRPC4 deficiency suppressed the expression of the proapoptotic protein sushi domain containing 2 (Susd2) in hypoxia-exposed mouse PAECs. Moreover, TRPC4 activated hypoxia-induced PAEC apoptosis by promoting Susd2 expression. Therefore, inhibiting TRPC4 ameliorated PAEC apoptosis and hypoxic PH in animals by repressing Susd2 signaling, which may serve as a therapeutic target for the management of PH.

Immobilization mechanisms of Sr(II), Ni(II), and Cd(II) on glomalin-related soil protein in mangrove sediments at the microscopic scale.

Glomalin-related soil protein (GRSP) is a significant component in the sequestration of heavy metal in soils, but its mechanisms for metal adsorption are poorly known. This study combined spectroscopic data with molecular docking simulations to reveal metal adsorption onto GRSP's surface functional groups at the molecular level. The EXAFS combined with FTIR and XPS analyses indicated that the adsorption of Cd(II), Sr(II), and Ni(II) by GRSP occurred mainly through the coordination of -OH and -COOH groups with the metal. The -COOH and -OH groups bound to the metal as electron donors and the electron density of the oxygen atom decreased, suggesting that electrostatic attraction might be involved in the adsorption process. Two-dimensional correlation spectroscopy revealed that preferential adsorption occurred on GRSP for the metal in sequential order of -COOH groups followed by -OH groups. The presence of the Ni-C shell in the Ni EXAFS spectrum suggested that Ni formed organometallic complexes with the GRSP surface. However, Sr-C and Cd-C were absent in the second shell of the Sr and Cd spectra, which was attributed to the adsorption of Sr and Cd ions with large hydration ion radius by GRSP to form outer-sphere complexes. Through molecular docking simulations, negatively charged residues such as ASP151 and ASP472 in GRSP were found to provide electrostatic attraction and ligand combination for the metal adsorption, which was consistent with the spectroscopic analyses. Overall, these findings provided new insights into the interaction mechanisms between GRSP and metals, which will help deepen our understanding of the ecological functions of GRSP in metal sequestration.

A bacteriophage against Citrobacter braakii and its synergistic effect with antibiotics.

A bacteriophage BD49 specific for Citrobacter braakii was screened out and purified by double-layer plate method. It consists of a polyhedral head of 93.1 ± 1.2 nm long and 72.9 ± 4.2 nm wide, tail fibers, collar, sheath and baseplate. The bacteriophage was identified by morphology observed with transmission electron microscope (TEM), whole genome sequencing carried out by Illumina next generation sequencing (NGS) technique, and gene annotation based on Clusters of Orthologous Groups of proteins (COG) database. It was identified primarily as a member of Caudovirales by morphology and further determined as Caudovirales, Myoviridae, and Citrobacter bacteriophage by alignment of its whole genome sequence with the NCBI database and establishment of phylogenetic tree. The bacteriophage showed good environmental suitability with optimal multiplicity of infection (MOI) of 0.01, proliferation time of 80 min, optimum living temperature of 30-40 °C, and living pH of 5-10. In addition, it exhibited synergistic effect with ciprofloxacin against C. braakii in antibacterial tests.

Enhanced Cr(VI) stabilization by terrestrial-derived soil protein: Photoelectrochemical properties and reduction mechanisms.

Glomalin-related soil protein (GRSP) is a stable iron-organic carbon mixture that can enhance heavy metal sequestration in soils. However, the roles of GRSP in the transformation and fate of Cr(VI) have been rarely reported. Herein, we investigated the electrochemical and photocatalytic properties of GRSP and its mechanisms in Cr(VI) adsorption and reduction. Results showed that GRSP had a stronger ability for Cr(VI) adsorption and reduction than other biomaterials, with the highest adsorption amount of up to 0.126 mmol/g. The removal efficiency of Cr(VI) by GRSP was enhanced (4-7%) by ultraviolet irradiation due to the hydrated electrons produced by GRSP. Fe(II) ions, persistent free radicals, and oxygen-containing functional groups on the GRSP surface as electron donors participated in the reduction of Cr(VI) under dark condition. Moreover, Cr(III) was mainly adsorbed on the -COOH groups of GRSP via electrostatic interactions. Based on 2D correlation spectroscopy, the preferential adsorption occurred on the GRSP surface for Cr(VI) in the sequential order of CO → COO- → O-H → C-O. This work provides new insights into the Cr(VI) adsorption and reduction mechanism by GRSP. Overall, GRSP can serve as a natural iron-organic carbon for the photo-reduction of Cr(VI) pollution in environments.

Establishment of Highly Efficient Plant Regeneration, Callus Transformation and Analysis of Botrytis cinerea-Responsive PR Promoters in Lilium brownii var. viridulum.

Lilium brownii var. viridulum, commonly called Longya lily, is a well-known flower and vegetable plant in China that has poor tolerance to Botrytis fungal disease. The molecularimprovement has mainly been restricted to an efficient regeneration and transformation system. In this study, the highly efficient regeneration of Longya lily was established through the optimization of embryogenic callus, adventitious shoot and rooting induction. The major factors influencing transformation (antibiotics, Agrobacterium concentration, infection time, suspension solution and coculture medium) were examined. The expression responses of PR promoters (ZmPR4 and BjCHI1) to B. cinerea were assessed in transgenic calli. The results showed that Murashige and Skoog (MS) medium with 1.0 mg·L-1 picloram (PIC) and 0.2 mg·L-1 1-naphthaleneacetic acid (NAA) under light conditions and MS with 0.5 mg·L-1 6-benzylaminopurine (6-BA) and 1.0 mg·L-1 NAA under darkness were optimal for embryogenic callus induction (64.67% rate) and proliferation (3.96 coefficient). Callus inoculation into MS containing 2.0 mg·L-1 thidiazuron (TDZ), 0.4 mg·L-1 NAA, 1.0 mg·L-1 TDZ and 0.5 mg·L-1 NAA led to shooting induction (92.22 of rate) and proliferation (3.28 of coefficient) promotion, respectively. The rooting rate reached 99.00% on MS with 0.3 mg·L-1 NAA. Moreover, a transformation rate of 65.56% was achieved by soaking the callus in Agrobacterium at an OD600 of 0.4 for 10 min in modified MS without NH4NO3 as the suspension solution and coculture medium before selecting 75 mg·L-1 hygromycin and 300 mg·L-1 cefotaxime. Only the BjCHI1 promoter was obviously expressed in transgenic calli. These results could facilitate the generation of Longya lily transgenic plants with improved B. cinerea resistance.

Combined use of positive matrix factorization and 13C15N stable isotopes to trace organic matter-bound potential toxic metals in the urban mangrove sediments.

Coastal sediments act as sinks of sediment organic matter (SOM) and metals because of their special land-sea location and depositional properties. However, there are few reports on the correlation between the sources of organic matter (OM) and associated potential toxic metals (PTMs). In this study, we combined CN stable isotope analysis and positive matrix factorization to identify the matter and metal sources of OM and glomalin-related soil protein (GRSP) in an estuary under several decades of urbanization. The results of the positive matrix factorization (PMF) reveal a correlation between the sources of total sediment metals and the sources of OM-related metals. The sources of both SOM-bound PTMs and GRSP-bound PTMs are significantly related to the sources of total PTMs. OM sources were elucidated through 13C-15 N stable isotopes, and the potential sources of different types of OM differed. In addition, there is a significant correlation between OM-associated PTMs and organic matter sources. Interestingly, the functional groups of SOM were mainly influenced by multiple PTM sources but no OM source, while the functional groups of GRSP were regulated by a single metal source and OM source. This study deepened the understanding of the coupling between PTMs and SOM. The possibility of combined use of positive matrix factorization and 13C-15 N stable isotope tracing of metals as well as the sources of each metal fractions has been evaluated, which will provide new insights for the transportation of PTMs.

Sequestration of strontium, nickel, and cadmium on glomalin-related soil protein: Interfacial behaviors and ecological functions.

Glomalin-related soil protein (GRSP) is a widespread recalcitrant soil protein complex that promotes the immobilization of metals in soils. Herein, we combined indoor simulation and field investigation to reveal the interfacial behaviors and ecological functions of GRSP to the three typical metals (Sr(II), Ni(II), and Cd(II)). The kinetic and isotherm data suggested that GRSP had a strong ability to adsorb the metals, which was closely related to the Hard-Soft-Acid-Base theory and the film diffusion mechanisms. Regarding environmental factors, the higher solution pH was beneficial to the adsorption of the metals onto GRSP, while the adsorption capacity decreased at lower or higher salinity due to the salting-out and Na+ competition effects. Moreover, Sr(II), Ni(II), and Cd(II) showed competitive adsorption onto GRSP, which was associated with the spatial site resistance effect. By comparing the retention factors of seven natural and artificial particles, GRSP had elevated distribution coefficients in high metal concentration, while its retention factors showed a relatively lower decrease, suggesting that GRSP had excellent buffer performance for a potential metal pollution emergency. Through the continental-scale coastal regions investigation, GRSP sequestered 1.05-3.11 µmol/g Ni, 0.31-1.49 µmol/g Sr, and 0.01-0.06 µmol/g Cd with 0.54-0.91 % of the sediment mass, demonstrating its strong ability to adsorb the metals. Therefore, we advocate that GRSP, as a recalcitrant protein complex, can be considered an effective tool for buffering capacity of metal pollution and environmental capacity within coastal wetlands.

Uncovering the disposable face masks as vectors of metal ions (Pb(â ¡), Cd(â ¡), Sr(â ¡)) during the COVID-19 pandemic.

The demand for disposable face masks (DFMs) increased sharply in response to the COVID-19 pandemic. However, information regarding the underlying roles of the largely discarded DFMs in the environment is extremely lacking. This study focused on the pristine and UV-aged DFMs as vectors of metal ions (Pb(Ⅱ), Cd(Ⅱ), and Sr(Ⅱ)). Further, the aging mechanism of DFMs with UV radiation as well as the interaction mechanisms between DFMs and metal ions were investigated. Results revealed that the aging process would help to promote more metal ions adsorbed onto DFMs, which was mainly attributed to the presence of oxygen-containing groups on the aged DFMs. The adsorption affinity of pristine and aged DFMs for the metal ions followed Pb(Ⅱ) > Cd(Ⅱ) > Sr(Ⅱ), which was positively corrected with the electronegativity of the metals. Interestingly, we found that even if DFMs were not disrupted, DFMs had similar or even higher adsorption affinity for metals compared with other existing microplastics. Besides, regarding environmental factors, including salinity and solution pH played a crucial role in the adsorption processes, with greater adsorption capacities for pristine and aged DFMs at higher pH values and low salinity. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory further confirmed that the pristine DFMs interacted with the metals mainly through electrostatic interaction, while electrostatic interaction and surface complexation jointly regulated the adsorption of the metals onto aged DFMs. Overall, these findings would help to evaluate environmental behaviors and risks of DFMs associated with metals.

Enhanced heavy metal adsorption on microplastics by incorporating flame retardant hexabromocyclododecanes: Mechanisms and potential migration risks.

Microplastics (MPs) are known to act as carriers of heavy metals; however, little is known about the intrinsic chemical additives of MPs, such as hexabromocyclododecane (HBCD), in terms of the adsorption behaviors and migration risks of heavy metals on MPs. Here, we reported the potential mechanisms and risks of HBCD inherent in polystyrene (PS) MPs with Cu(II), Ni(II), and Zn(II) adsorption/desorption. A comparison of the adsorption capacity of the metals onto HBCD/PS composites (HBCD/PS) MPs (10.31-20.76 µmol/g), pure MPs (0-3.60 µmol/g), and natural minerals (0.11-13.88 µmol/g) showed that the addition of HBCD significantly promoted the metals adsorption onto the HBCD/PS MPs, and even exceeded that of natural particles. Isotherms and thermodynamic data suggested that the adsorption process of the metals onto the HBCD/PS MPs was spontaneous and endothermic, and that the adsorption was a mainly multi-ion process with an inclined direction. Furthermore, the results of SEM-EDS, FTIR, and XPS analyses, as well as density functional theory well explained that the metals were mainly adsorbed on the -O and -Br groups of the HBCD/PS MPs via electrostatic interactions and surface complexation. More importantly, by comparing the desorption activity with natural river water and seawater, HBCD inherent in MPs can enhance the long-range transfer of metals carried by the HBCD/PS MPs from contamination sources to potential sink like oceans. Thus, the HBCD/PS MPs with high loading of Cu(II), Ni(II), and Zn(II) could be potential secondary sources of these metals in seawater. Overall, these findings revealed the potential risks of flame retardant in MPs associated with metal migration, and advocated that flame retardant-related waste MPs should be included in coastal sustainable development.

Primary intracranial extraskeletal myxoid chondrosarcoma: A case report and review of literature.

BACKGROUND: Primary intracranial extraskeletal myxoid chondrosarcoma (EMC) is an extremely rare low- to intermediate-grade malignant soft tissue sarcoma, and only 15 cases have been reported in the literature. Due to its rarity, clinical data and research on this tumor type are extremely limited, the pathogenesis and histological origin are still unclear, and the diagnostic and standard clinical treatment strategies for intracranial EMC remain controversial and undefined. CASE SUMMARY: We reported a case of a 52-year-old male who was admitted to the hospital with headache and dizziness for 1 mo, and his health status deteriorated during the last week. CT of the head showed a well-defined low-density lesion situated in the left cavernous sinus. Brain magnetic resonance imaging (MRI) showed a 3.4 cm × 3.0 cm sized, well-defined, round-shaped and heterogeneously enhanced lesion located in the left cavernous sinus. The entire lesion was removed via supratentorial craniotomy and microsurgery. Postoperative pathological diagnosis indicated primary intracranial EMC. Subsequently, the patient underwent 45 Gy/15 F stereotactic radiotherapy after discharge. At present, it is 12 mo after surgery, with regular postoperative follow-up and regular MRI examinations, that there are no clinical symptoms and radiographic evidence indicating the recurrence of the tumor, and the patient has returned to normal life. CONCLUSION: Currently, the most beneficial treatment for primary intracranial EMC is gross total resection combined with postoperative radiotherapy. Long-term follow-up is also necessary for patients.

Assessment of Clinical Diagnostic Efficacy of Pulmonary Function Test Based on DBN-SVM of Pediatric Asthma and Cough Variant Asthma.

The diagnosis of asthma depends on the unprejudiced proof of the varying airflow obstruction. The pulmonary function tests are carried out to evaluate the clinical value of different types of respiratory diseases in children or infants. This study is focused on the clinical evaluation of the pulmonary function tests in the diagnosis of pediatric asthma and cough variant asthma. A differential diagnosis method for chronic obstructive pulmonary disease (COPD) and asthma-COPD overlap with complementary diagnostic value is proposed. For the pulmonary function tests, the COPD gene dataset was selected and feature selection was performed using the DBN-SVM scoring method. For analysis and comparison, the differential diagnosis models were built using ROC curves for the accuracy of the deep belief network model and the support vector machine model. The sensitive features associated with COPD and ACO classification using the deep belief network model were found to be in good agreement with known clinical diagnostic strategies. The clinical diagnosis tests for pulmonary pediatric asthma and cough variant asthma were conducted on two groups of children, with both groups containing a basis of comparison. 80 cases of pediatric asthma and cough variant asthma were admitted from 2013 to 2014 and 80 cases of children with a healthy physical examination. The results of the two groups were compared. The results showed that the levels of FEV1, PEF, and FVC were significantly lower (P < 0.05), in healthy children, and FEV1/FVC%, RV, and RV/TCL% were significantly higher (P < 0.05) in children with asthma and cough variant asthma during acute exacerbation and chronic persistence. There were no statistically significant differences in the duration of clinical remission (P > 0.05). Thus, the study suggests that confirmed cases of the diagnosis of pediatric asthma and cough variant asthma by pulmonary function tests were significantly higher than those of conventional tests (P < 0.05). From this study, we can conclude that pulmonary function tests can accurately diagnose pediatric asthma and cough variant asthma, and also accurately reflect the development of the child's disease, which is of high clinical value.

Spatial heterogeneity in chemical composition and stability of glomalin-related soil protein in the coastal wetlands.

GRSP is widely distributed in coastal wetlands, and there is a tendency for it to degrade with increasing burial depth. However, the dynamic changes in the chemical composition and stability of GRSP during the burial process are still unclear. The purpose of this study is to clarify the chemical composition and accumulation characteristics of GRSP during the burial process in the Zhangjiang estuary. In a field study, soil cores to the depth of 100 cm were collected in the estuary from mangrove forests dominated by Kandelia obovata and Avicennia marina, and from mudflat. The results showed that the concentration of GRSP in mangrove forest soil was significantly higher than that in the mudflat (p < 0.05), and the C/N ratio of GRSP increased with depth at all sites. Analysis of Fourier transform infrared (FTIR) data showed that the degradation rates of the GRSP's compositions varied with increasing burial depth, with microbial action and pH possibly being the main factors affecting degradation. Values of recalcitrance index (RI) showed that the stability of GRSP increased with increasing depth, and the contribution of GRSP to soil organic carbon (SOC) also increased. This suggests that the burial process plays a role in screening and storing the stable components of GRSP. Overall, our findings suggest that the concentration and chemical composition of GRSP vary dynamically according to habitat and burial processes. In addition, the improved stability of GRSP could contribute to carbon sequestration in coastal wetlands.

Extraction and purification of glomalin-related soil protein (GRSP) to determine the associated trace metal(loid)s.

Glomalin-related soil protein (GRSP) is recalcitrant compound in the soil and sediment and plays a crucial role in metal transportation. However, potential metal speciation changes during GRSP extraction remain unreported. Here, a feasible GRSP extraction and purification procotol is described for robust determination of GRSP-bound metal(loid)s. Several spectrum patterns measured before and after GRSP extraction indicate that the GRSP extraction process does not significantly affect the mineral state of the samples. Potential bias generated by simultaneous metal release during GRSP extraction can be effectively eliminated by applying complete and independent dialysis.•Na signal appeared in the X-ray photoelectron survey spectrum after GRSP extraction, suggesting that Na exchange may be a critical process in releasing metal(loid)s.•Element maps obtained using secondary ion mass spectroscopy exhibited different distribution of C-N and Fe after GRSP extraction, thus suggesting that uncoupling of the Fe-organic framework occurred during GRSP extraction, which could result in the release of organic matter and metal(loid)s.•European Community Bureau of Reference (BCR) subsequent extraction reveals that most of the metal(loid)s were extracted from the acid-exchangeable and residual fraction during GRSP extraction. Remarkable differences in the GRSP-bound metal content before and after dialysis implied that the dialysis could remove most metal(loid)s.

Immobilization of lead(â ¡) and zinc(â ¡) onto glomalin-related soil protein (GRSP): Adsorption properties and interaction mechanisms.

Glomalin-related soil protein (GRSP), a microbial product that can be used as a bioflocculant, is critical to metal sequestration in the ecosystem. However, the relationship between GRSP and heavy metal has not been well explored. In this study, the adsorption behaviors and mechanisms of Pb(II) and Zn(II) ions on GRSP were investigated. Results reveal that the Pb(II) and Zn(II) adsorption closely conform to the pseudo second-order model, which indicates that the chemisorption of GRSP occurred after intra-particle diffusion. The adsorption process is influenced by the degree of pollution, pH value, GRSP content in the environment. In addition, scanning electron microscopy coupled with microanalysis (SEM-EDX) reveals that the surface structure of GRSP is irregularly blocky or flaky and metal ions are uniformly distributed on the surface of GRSP. Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analysis show that the carboxyl and nitro groups on GRSP act as ligands to form complexes with two divalent metal ions. The interaction between GRSP and the metals is mainly surface complexation. This research further reveals the dynamic response of its structural components when GRSP sequestrates heavy metals in mangrove sediment and aqueous ecosystems, demonstrating a new perspective for the transport and transformation of heavy metals onto GRSP.