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To improve the resource utilization of chromium-containing solid waste in cement-based materials, the leaching rate, valence state, and microscopic morphology of hexavalent chromium in Portland cement-based materials were studied. The results indicate that the stabilization rate of hexavalent chromium in cement reaches 95% for specimens containing 0.5% potassium chromate by mass after 60 days. However, when the potassium chromate content is increased to 5%, the stabilization rate drops below 90%. Analysis through photoelectron spectroscopy elucidates that chromium mainly exists in two valence states within the cement paste: trivalent chromium, present as Cr(OH)3 and CrOOH, and hexavalent chromium, existing in the forms of CaCrO4 and K2CrO4. After curing for 28 days, the ratio of trivalent chromium to hexavalent chromium is approximately 7:13, with the main hexavalent chromium compound CaCrO4 constituting about 21.4% of the total chromium content. Microscopic phase tests further intricate interactions between calcium ions and hexavalent chromium ions in a low water-cement ratio matrix, resulting in the additional CaCrO4 whose quality steadily increased with age. The rise in ion content leads to a continuous augmentation in the diffraction peaks density of ettringite (AFt). This is attributed to the slightly larger spatial position of CrO42- compared to SO42-, facilitating its partial replacement in the columnar structure lattice of the ettringite hydration product.

During the drying and processing of raisins, the presence of foreign matter such as fruit stems, branches, stones, and plastics is a common issue. To address this, we propose an enhanced real-time detection approach leveraging an improved YOLOv8 model. This novel method integrates the multi-head self-attention mechanism (MHSA) from BoTNet into YOLOv8’s backbone. In the model’s neck layer, selected C2f modules have been strategically replaced with RFAConv modules. The model also adopts an EIoU loss function in place of the original CIoU. Our experiments reveal that the refined YOLOv8 boasts a precision of 94.5%, a recall rate of 89.9%, and an F1-score of 0.921, with a mAP reaching 96.2% at the 0.5 IoU threshold and 81.5% across the 0.5–0.95 IoU range. For this model, comprising 13,177,692 parameters, the average time required for detecting each image on a GPU is 7.8 milliseconds. In contrast to several prevalent models of today, our enhanced model excels in mAP0.5 and demonstrates superiority in F1-score, parameter economy, computational efficiency, and speed. This study conclusively validates the capability of our improved YOLOv8 model to execute real-time foreign object detection on raisin production lines with high efficacy.

Chromium (Cr) is mainly found in the form of organic-Cr(III) complexes in the natural environment and industrial waste. The widespread existence of composite contaminants composed of organic matter (OM) and Cr pose a serious ecological threat, and its potential interaction and removal need to be further summarised. Organic ligands, such as carbohydrates, nitrogen compounds, phenolic compounds, humus substances (HS), and low molecular weight organic acids (LMWOAs), play an important role in governing the speciation, mobility, and absorption and desorption of Cr in the environment. Moreover, growing evidence indicates that oxygen-containing functional groups (e.g., carboxyl, hydroxyl, and phosphate) are closely related to the complexation of Cr(III). Advanced oxidation processes (AOPs) are efficient and widely applicable technologies. However, the re-complexation of oxidation intermediates with Cr(III) and the formation and accumulation of much more toxic Cr(VI) species hinder the possible utilisation of AOPs. In this paper, the sources and harmful effects of organic-Cr(III) complexes are reported in detail. The complexation behaviour and structure of the organic-Cr(III) complexes are also described. Subsequently, the application of AOPs in the decomplexation and degradation of organic-Cr(III) complexes is summarised. This review can be helpful for developing technologies that are more efficient for organic-Cr(III) complex removal and establishing the scientific background for reducing Cr discharge Cr into the environment.

BackgroundDespite the continuing effort in investigating the preventive therapies for stroke-associated pneumonia (SAP), which is closely associated with unfavorable outcomes, conclusively effective therapy for the prevention of SAP is still lacking. Remote ischemic conditioning (RIC) has been proven to improve the survival in the sepsis model and inflammatory responses have been indicated as important mechanisms involved in the multi-organ protection effect of RIC. This study aimed to assess the safety and the preliminary efficacy of RIC in the prevention of SAP in patients with acute ischemic stroke.MethodsWe performed a proof-of-concept, pilot open-label randomized controlled trial. Eligible patients (age > 18 years) within 48 h after stroke onset between March 2019 and October 2019 with acute ischemic stroke were randomly allocated (1:1) to the RIC group and the control group. All participants received standard medical therapy. Patients in the RIC group underwent RIC twice daily for 6 consecutive days. The safety outcome included any adverse events associated with RIC procedures. The efficacy outcome included the incidence of SAP, changes of immunological profiles including mHLA-DR, TLR-2, and TLR-4 as well as other plasma parameters from routine blood tests.ResultsIn total, 46 patients aged 63.1 ± 12.5 years, were recruited (23 in each group). Overall, 19 patients in the RIC group and 22 patients in the control group completed this study. No severe adverse event was attributed to RIC procedures. The incidence of SAP was lower in the remote ischemic conditioning group (2 patients [10.5%]) than that in the control group (6 patients [27.3%]), but no significant difference was detected in both univariate and multivariate analysis (p = 0.249 and adjusted p = 0.666). No significance has been found in this pilot trial in the level of immunological profiles HLA-DR, TLR4 and TLR2 expressed on monocytes as well as blood parameters tested through routine blood tests between the two groups (p > 0.05). The IL-6 and IL-1β levels at day 5 after admission in the RIC group were lower than those in the control group (p < 0.05).InterpretationThis proof-of-concept pilot randomized controlled trial was to investigate RIC as a prevention method for SAP. Remote ischemic conditioning is safe in the prevention of SAP in patients with acute ischemic stroke. The preventive effect of RIC on SAP should be further validated in future studies.

Cement solidification was a widely used method to broaden the resource utilization of dredged sludge. However, the organic matter in sludge limit the application of cement solidification. The fulic acid (FA) was used to simulate the natural organic matter in sludge. With the increase in FA content, the sludge gradually changed from low-liquid-limit clay to high-liquid-limit clay. The unconfined compression test showed that the strength of cement-solidified dredged sludge (CDS) decreased with FA content. The influence mechanism of the FA on cement solidification was revealed by a water content test, a hydration heat test, scanning electron microscopy, and thermogravimetric analysis. FA hindered the conversion of pore water to combined water and reduced the hydration heat inside CDS. The FA in sludge weakened the internal bond within CDS by hindering the development of C-S-H gel from spheroidal to flake. At the same time, the final amount of hydrates such as C-S-H, C-A-H and AFt also decreased in the CDS containing FA. The weakening mechanism of FA on the strength of CDS can be attributed to three aspects: (1) FA adsorbed on the surface of cement minerals and hindered the contact between cement minerals and pore water; (2) acidic FA reduced the pH of the pore liquid in CDS; (3) the carboxyl and hydroxyl functional groups of FA adsorbed calcium ions in pore liquid through ion coordination.

The unconfined compressive strength (UCS) of sludge with different consistency limits solidified by cement was investigated. The results showed that under the condition of constant initial water content, a higher liquid index of soil resulted in higher UCS. A novel strength-evaluation model based on the ratio of the liquid index to the cement content was developed, and the prediction deviation of the model was within 30%. The influence mechanism of the consistency limit of sludge on the cement solidification was revealed by scanning electron microscopy, mercury intrusion porosimetry, X-ray diffractometer and thermogravimetric analysis. For the cement-solidified dredged sludge (CDS) with a lower liquid index, a large amount of hydrate was interlaced with each other and wrapped soil particles, promoting the formation of a dense structure. For the CDS with a higher liquid index, hydrates such as C-S-H and ettringite challenged each other to play the role of “cementing particles” and “filling pores”, resulting in the formation of the porous structure. The mineralogical analyses confirmed that more C-S-H gels and ettringites were generated in the CDS with a lower liquid index, but less calcite was formed due to its denser structure. In engineering applications, reducing the liquid index by adjusting the consistency limit can improve the strength performance of CDS.

Hot dry rock (HDR) geothermal energy has many advantages, such as being renewable, clean, widely distributed, and without time and weather limitations. Hydraulic fracturing is usually needed for the exploitation of HDR geothermal energy. It has many hidden faults in the reservoir/caprock sequences. Injecting fluid into underground formations during hydraulic fracturing often induces fault slip and leads to earthquakes. Therefore, to well understand the induced fault slip and earthquakes is important for the applications and development of HDR geothermal exploitation. In this study, we investigated the hazardous injection area of the induced earthquakes during hydraulic fracturing. The study was based on a hydraulic fracturing test in Qiabuqia geothermal field in China. According to the field, a fault-surrounding rock-fracturing region system was developed to study the influences of fluid injection on the stability of the specific fault. A total of 60 hydraulic fracturing regions and 180 numerical experiments were designed. The results revealed that the hazardous injection regions that threaten the fault’s stability were near to the fault and concentrated on the following four areas: (a) above the top of the fault in underlying strata; (b) above the top of the hanging wall of the fault in underlying strata; (c) near to the fault planes in both footwall and hanging wall; (d) at the bottom of the footwall of the fault in underlying strata. The hazardous injection area can be controlled effectively by adjusting the injection pressure.

Hot dry rock (HDR) geothermal energy has become promising resources for relieving the energy crisis and global warming. The exploitation of HDR geothermal energy usually needs an enhanced geothermal system (EGS) with artificial fracture networks by hydraulic fracturing. Fault reactivation and seismicity induced by hydraulic fracturing raise a great challenge. In this paper, we investigated the characteristics of fault slip and seismicity by numerical simulation. The study was based on a hydraulic fracturing project in the geothermal field of Yishu fault zone in China. It revealed that fluid injection during hydraulic fracturing can cause the faults that exist beyond the fluid-pressurized region to slip and can even induce large seismic event. It was easier to cause felt earthquakes when hydraulic fracturing was carried out in different layers simultaneously. We also examined the effects of the location, permeability, and area of the fracturing region on fault slip and magnitude of the resulting events. The results of the study can provide some useful references for establishing HDR EGS in Yishu fault zone.

A rapidly growing body of evidence supports that neuroinflammation plays a major role in epileptogenesis and disease progression. The capacity to identify pathological neuroinflammation in individuals with epilepsy is a crucial step on the timing of anti-inflammatory intervention and patient selection, which will be challenging aspects in future clinical studies. The discovery of noninvasive biomarkers that are accessible in the blood or molecular neuroimaging would facilitate clinical translation of experimental findings into humans. These innovative and noninvasive approaches have the advantage of monitoring the dynamic changes of neuroinflammation in epilepsy. Here, we will review the available evidence for the measurement of neuroinflammation in patients with epilepsy using noninvasive techniques and critically analyze the major scientific challenges of noninvasive methods. Finally, we propose the potential for use in clinical applications.

Cement-stabilized dredged sediment (CDS) when used as a new road construction material cannot only solve the problem of abandoned sediment disposal, but also effectively save natural soil resources. This study aimed to evaluate the strength and permeability of CDS and establish corresponding prediction models from the perspective of a stabilization mechanism. The soil–water composition and pore size distribution were investigated by the nuclear magnetic resonance (NMR) technique. The results demonstrated that more liquid pore water inside the CDS specimen transformed into combined water with cement hydration. The amount of combined water, which essentially characterized the hydration process of cement, presented a linear relationship with log (t). The cementation and filling action of hydrates resulted in the transformation of large pores into smaller ones, hence the optimal pore size decreased with an increasing curing period and cement content. The stress–strain curves and hydraulic conductivity were determined based on unconfined compression and flexible wall penetration tests, respectively. The unconfined compressive strength increased exponentially with the amount of combined water, and the functional correlations of hydraulic conductivity and micropore parameters were established. The reliability of the NMR technique as a new method to study the microscopic evolution mechanism of the strength and permeability of CDS was further verified by scanning electron microscopy and mercury intrusion porosimetry tests.

This study examined the correlation between non-metallic organic tanning agents (NOTAs) and wastewater containing double-triazine (bistriazine). Specifically, high-throughput sequencing was used to analyze how the physical and chemical properties of the bistriazine-containing wastewater affected the microbial community. In total, 9995 operating taxonomy units (OTUs) were detected at a similarity level of 97%. According to the taxonomy results and relative bacterial richness, the non-metallic organic tanning agent (NOTA) wastewater communities showed significant differences. Clostridium sensu stricto and Turicibacter bacteria were dominant in NOTA T2, T3, and the blank control (KB) wastewater; Trichococcus and Aeromonas were dominant in NOTA T4; and Pseudomonas was dominant in T2, T4, and the blank control (KB). Thus, the addition of bistriazine ring derivatives altered the composition of the bacterial community. Furthermore, Spearman’s correlation analysis revealed a substantial correlation in the composition of the communities and the physicochemical properties of the wastewater. Acidocella and norank c Cyanobacteria correlated positively with Total Phosphorus (TP) (p ≤ 0.001) and Mycobacterium showed a positively held correlation with pH (p ≤ 0.05). Conversely, norank_f__Elev-16S-1332 indicated a negative correlation with TP, Total Nitrogen (TN), and Total Organic Carbon (TOC) (p ≤ 0.05), whereas Zoogloea correlated negatively with NH3–N, TOC, and TN (p ≤ 0.05). Regarding water quality, a significant correlation between microbial communities and the physicochemical properties of bistriazine wastewater was also observed (p ≤ 0.05). We concluded that Trichococcus, Clostridium sensu stricto, Turicibacter, Pseudomonas, Intestinibacter, Acidocella, Bacillus, and Tolumonas showed a high tolerance for bistriazine wastewater, which could offer insight into its bioremediation.

Based on the concept of microbial community multi-processing in integrated spatial bacterial succession (ISBS), this study constructs a highly efficient cellular fixed-bed bioreactor that follows the growth of biological flora in the wastewater treatment process. The reactor is organically partitioned based on synergistic laws and in accordance with environmental and microbial metabolic changes, and sewage is subjected to unitized and specialized biological treatment under direct current conditions. The results show that the ISBS reactor exhibits stable nitrogen removal performance under a low-carbon source. Compared with traditional sewage biochemical treatment technology, the microbial concentration is increased by 2–3 times and even up to 12 times, and the ammonia nitrogen removal rate is maintained at 99%. The removal rate reaches 90% (hydraulic retention time of 14 h). High-throughput sequencing analysis based on 16S rDNA reveals the microbial community structure succession at different depths of the same section of the reactor. The microbial community is rich under the influence of environmental factors and exhibits different responses. The intervals vary. An analysis of the microbial community function explains why the ISBS reactor has high nitrogen removal efficiency.

Polymer nanocomposites have been widely used in the preparation of coating agents in the leather industry. Considering the complex bio-effect and ecological risk of nanomaterial, research on the biodegradability and biocompatibility of polyacrylate/metal nanocomposites in activated sludge system is of specific significance. We investigated the change of the bacterial community and diversity of activated sludge fed with polyacrylate/ZnO nanocomposites in both low (500 mg COD /L) and high (1000 mg COD/L) doses. COD removal, dehydrogenase activity, and total protein of activated sludge system were monitored in all treatments over 30 days. The results demonstrated that the exposure to both polyacrylate/ ZnO nanocomposite and polyacrylate decreased the dehydrogenase activity at early stage comparing to the control, but had no significant influence on COD removal. Overall, the bacterial communities in activated sludge were resistant to polyacrylate/ZnO nanocomposites, and had higher levels of metabolic activity, protein accumulation and bioavailability when exposed to these chemicals comparing to the control especially at later stages of incubation (15-30 days), which indicated that these polyacrylate/ZnO nanocomposites of certain amount were biocompatible to activated sludge system.

Conventional biochemical processes have unsatisfactory effects on refractory wastewater treatment. Thus, a technically feasible and economical treatment should be established. In the conventional culture of microorganisms, adding exogenous nutrients to a medium can effectively promote micro-organism growth. Therefore, using exogenous nutrients in wastewater treatment may enhance microbial activity, subsequently speeding up the removal of contaminants. In this study, nutrients with different carbon and nitrogen (C/N) ratios were added to activated sludge and a chemical oxygen demand (COD) of 1000 mg/L was considered the benchmark for carbon source in the activated sludge process. Results showed that wastewater COD was reduced below 130 mg/L, and the removal rate reached 90% when the C/N ratio was 5:1. Along with the results from the study on F/M, dehydrogenase activity, content of extracellular polymeric substances, and microbial community in the wastewater treatment process, our findings indicated that adding exogenous nutrients increase microbial community diversity and promote the activity of microorganisms, thereby wastewater COD was reduced to 130 mg/L after 12 h and the removal rate reached approximately 90%. Simultaneously, analysis results on microbial community structure indicated that Proteobacteria, Firmicutes, and Bacteroidetes were the dominant species of bacteria. The addition of exogenous nutrients may increase the abundances of Pseudomonas and Bacillus species, which were essential in COD removal. [ABSTRACT FROM AUTHOR]

A novel porous tablet material (PTM) was developed from zirconium pillared montmorillonite (Zr-MMT) by dry pressing technique combined with sacrificial template (polymethylmethacrylate). The developed PTM can be effectively separated from water. The layered structure of montmorillonite was still intact and the three-dimensional interconnected porosity of PTM was evenly distributed, which means that PTM has good permeability. The specific surface area and total pore volume of PTM were 80.04 m²/g and 0.28 m³/g, respectively, indicating that the PTM can provide a large number of vacant surface active sites. The saturated adsorption capacity to Pb(II) was 215.52 mg/g, which was much higher than that of montmorillonite type clay adsorbents. These findings demonstrate that PTM could be used as separable adsorbent for Pb(II) removal from aqueous solution. [ABSTRACT FROM AUTHOR]

Emission of CO2 resulting from mineralization of organic carbon in agricultural soil is main pathways of greenhouse gas emission. In this research, effect of biochar on humus, organic carbon accumulation, and metabolic quotient of soil were investigated. Different contents of biochar were added in two kinds of soil with different fertility. According to the results, biochar played a positive role on promoting the formation of soil humus. Contents of humic acids (HAs), fulvic acids (FAs), and humins (HMs) in treatment with biochar increased obviously, which was benefit to the stability of soil organic carbon pool. After 210 days incubation, content of HAs increased 9.8% to 13.6%; content of FAs increased 17.2% to 20.8%; content of HMs increased 20.5% to 22.6% compared with control. Biochar promoted the accumulation of nutrient elements thereby improved the soil quality. In addition, biochar accelerated the formation of carbohydrate, esters, aromatics and other organic macromolecules, which is difficult to decompose by soil microbial, resulting in the stability increase of organic carbon. Moreover, after 210 -days incubation, metabolic quotient ( qCO2) in soils with 8% biochar decreased 5% to 10% compared with control, suggesting that biochar has positive effect on the ecological function of soil. Therefore, it can be concluded that biochar can affect on soil carbon cycle by changing soil carbon characteristics. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1467-1472, 2015 [ABSTRACT FROM AUTHOR]

This work set out to study the effects of cadmium (Cd) in sediments on the antioxidant enzyme activities in the digestive gland of Asian clam Corbicula fluminea and to explore the potential for applying these responses to evaluate the Cd-contaminated sediment. Additionally, diffusive gradients in thin-films (DGT) technique was used to predict the response of its antioxidant defense system. The sediments, collected from Taihu Lake, were spiked with Cd at different concentrations (0.72, 0.91, 1.62, 2.59, 11.2, 20.4 and 40.6 mg kg-1, dry weight). Asian clam was cultivated for 28 days. Concentrations of Cd in the body of Asian clam had a good relationship with concentrations of Cd in overlying water and sediments, as measured by DGT. Cd affected these biochemical parameters significantly, especially for superoxide (SOD), peroxidase (POD) and glutathione (GSH), which began to show higher sensitivity and have a significant difference in low dosage (0.91 mg Cd kg-1) compared with blank. Contents of MDA and MT, which were induced by Cd, increased with the increasing Cd concentration in sediments and reached peak values at 11.2 and 20.4 mg kg-1, respectively, after 28 days exposure. All of these results suggested that biochemical responses cooperated in detoxifying and maintaining cellular metabolic homeostasis. The R² of regression analysis between the contents of MT and the concentrations of Cd measured by DGT, in sediments and soft body were 0.71, 0.94 and 0.88 after 28 days exposure. This suggested that DGT measurement could predict the response of MT. Cd accumulation, GSH and MT were indispensable biomarkers and the MDA content and DGT appeared to be promising biomarkers. The results clearly indicated that Cd could induce oxidative stress in the digestive gland of Asian clam. The combination of biomonitors with DGT can obtain different information about Cd bioavailability and confirm the significance of applying a suite of biomarkers rather than a selective index to assess the sublethal effect. It also offered theoretical methods for the prediction of sediment Cd pollution. [ABSTRACT FROM AUTHOR]

Polyaniline adsorbent prepared by chemical oxidation was developed to remove the humic acid (HA) in aqueous solution. The adsorbents showed the high adsorption capacity for aqueous HA with the maximum adsorption amount 126.58 mg g-1, and the adsorption isotherm obeyed the Langmuir model. The adsorption kinetics followed an initial diffusion-controlled and then an attachment-controlled adsorption process. The HA adsorption was not much impacted in the presence of Na+, K+, while Ca2+ ion in aqueous solution can evidently enhance the HA adsorption. The HA adsorption on polyaniline decreased with increasing solution pH owing to the electrostatic interaction between imine and amine of polyaniline and disassociated HA. The HA molecules adsorbed on the polyaniline can be effectively desorbed in 0.1 M NaOH solution, and regenerated adsorbent can be repeatedly used in the subsequently adsorption-regeneration cycles. [ABSTRACT FROM AUTHOR]

Heavy metal pollution and their fractionations in the sediments of Changjiang River in Nanjing Reach was monitored for cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), and copper (Cu). Moreover, the biological enrichment of metals by riverine plants was studied. The results demonstrated there were highly significant variations among different sampling stations for the concentrations of tested metals. The highest range was for Cu (38.8-120.4 mg kg), followed by Cr (74.4-120.0 mg kg), Zn (80.9-121.1 mg kg), Ni (26.0-55.5 mg kg), Pb (15.8-46.7 mg kg) and Cd (0.28-0.48 mg kg). Cd was the element with highest biological enrichment factor (BEF). The highest BEF of Cd in Erigeron bonariensis reached 3.0, indicating a significant Cd enrichment in this aquatic plant. In addition, 60% of Cd was found in reducible fraction and exchangeable and acid-soluble fraction, which was consistent with its high mobility. The consistency of Cd fraction in sediment and suspended particle indicated they came from the same source. Accumulated Cd concentration calculated according to the release curve showed significant relativity with the total Cd concentration in the sediment. [ABSTRACT FROM AUTHOR]

Microorganism communities and chemical characteristics in sludge-bamboo charcoal composting system were investigated to find the effect of bamboo charcoal on composting. According to a plate count test, abundances of bacteria, fungi and actinomycetes in the treatment with bamboo charcoal were several times higher than those in treatment without bamboo charcoal. In addition, terminal restriction fragment length polymorphism (TRFLP) analysis indicated that the bacterial community diversity in treatment with bamboo charcoal was greater than that of the control. Both results demonstrated that amendment with bamboo charcoal can increase microorganism population and microorganism community diversity in a sludge composting system. Moreover, the results of FTIR spectroscopy disclosed that aerobic composting can promote the formation of surface acid groups on bamboo charcoal. These surface acid groups may deprotonate and react with NH4+ to form stable complexes. Therefore, the increase of functional groups accompanied with greater assimilation of nitrogen by microorganisms could reduce nitrogen loss in sludge composting. [ABSTRACT FROM AUTHOR]

Six stations in the lower reach region of Changjiang River within Baguazhou Island, Nanjing reach were chosen to investigate the toxic metals pollution characteristic in suspended particle material (SPM). SPM concentration, as well as reflectance spectroscopy characteristic, toxic metal concentrations, and lead isotopes of suspended particle material were studied. SPM concentrations were obtained from fluvial cross-sectional sampling near the surface (20 cm) and the study presents the cross-sectional averages. SPM concentrations varied around 170-300 mg L. Reflectance spectroscopy measurements differed from each other over each cross-section but no common pattern characterizing the cross-sectional behavior of the measurements was observed. The metal concentrations in the SPM decreased in the sequence: Mn > Zn > Cu > Cr > Pb > Cd. The result of lead isotopes analysis proved that lead isotopes composition in SPM are mainly produced by natural contributions and influenced by anthropogenic activity at the same time. [ABSTRACT FROM AUTHOR]

Conventional methods for investigating heavy metal contamination in soil are time consuming and expensive. In this study, we (i) explored reflectance spectroscopy as an alternative method for assessing heavy metals, and (ii) further explored the physiochemical mechanism that allows estimation of heavy metals with the reflectance spectroscopy method. We first investigated the spectral response of changing concentrations of heavy metals in soils. The results indicated that only at very high concentration can transition elements exhibit their inherent absorption features. In spite of this observation, we successfully predicted low levels of heavy metals in agricultural soils. The best prediction accuracies were obtained for the siderophile elements Ni, Cr, and Co. The poorest prediction was for Cd. The order of prediction accuracy for metals was approximately the same as the order of their correlation coefficients with Fe. Complementary to some previous studies that found that the intercorrelation between heavy metals and active soil components (such as Fe oxides, organic matter, and clay) is the major predictive mechanism, in the present study we concluded that the correlation with total Fe (including active and residual Fe) is the major mechanism. This conclusion was further supported by both correlation analysis and chemical sequential extraction. Correlation analysis showed that all metals are negatively correlated with reflectance while positively correlated with the absorption depth at about 500 nm, a feature resulting from goethite. The chemical forms of heavy metals, which showed that besides the crystalline Fe oxide and organic matter fractions, heavy metals have significant amounts in the residual fraction, also strengthened the conclusion. [ABSTRACT FROM AUTHOR]

Atmospheric nitrogen (N) deposition has rapidly increased during the last few decades; however, the seasonal responses of leaf N:P stoichiometry to N deposition remain unclear. In 2008, a simulated N deposition experiment (0, 30, 60, and 120 kg·N·ha−1·yr−1) was conducted in an old-growth temperate forest in Northeast China. In 2014, the leaves of 17 woody species and soil were sampled in spring, summer, and autumn in each treatment, and N:P stoichiometry was assessed. Community N and P in summer were significantly lower than that in spring and autumn. Unlike broadleaved species, conifers showed no significant variation among the three seasons. N addition significantly enhanced community N and soil available P but decreased soil total P in summer and autumn, and decreased community P, as well as the P concentration of three life forms (conifer, tree, and shrub), in autumn. Our results emphasize the importance of multiple sampling across seasons in temperate forests. Arguing against the traditional consensus, the productivity of the old-growth temperate forests is limited by both N and P.

Magnetically separable polyaniline (Fe3O4@SiO2-PANI) was prepared by in situ chemical polymerization of aniline on the surface of silica-coated Fe3O4 nanoparticles, and characterized by FTIR spectroscopy, powder X-ray diffraction, elemental analysis, transmission electron microscopy, vibrating sample magnetometry and X-ray photoelectron spectroscopy. Characterization results showed that Fe3O4@SiO2-PANI with amino groups of 1.78mmol/g and the average diameter of 21.6nm are superparamagnetic. Adsorption behavior of Fe3O4@SiO2-PANI nanoparticles for humic acid (HA) was investigated by batch experiments and adsorption kinetic tests. HA adsorption amount on the adsorbent decreased with increasing solution pH and the presence of Ca2+ resulted in the enhanced HA adsorption. HA adsorption on Fe3O4@SiO2-PANI could be well described by Langmuir model and the maximum adsorption amount of the adsorbent for HA at 25°C was 36.36mg/g. HA adsorption process on the adsorbent obey pseudo-second-order kinetics and the adsorption rates decrease with increasing initial HA concentration. The XPS analysis verified that HA adsorption over the adsorbent could be attributed to the surface complexation between the disassociated HA molecules and the protonated nitrogen of polyaniline on the adsorbent. HA loaded adsorbent could be magnetically separated and easily desorbed in 0.01mol/L NaOH solution. Regeneration tests indicated that Fe3O4@SiO2-PANI could be used repeatedly. [ABSTRACT FROM AUTHOR]