Measuring the perception and metacognition of time.

The ability of humans to identify and reproduce short time intervals (in the region of a second) may be affected by many factors ranging from the gender and personality of the individual observer, through the attentional state, to the precise spatiotemporal structure of the stimulus. The relative roles of these very different factors are a challenge to describe and define; several methodological approaches have been used to achieve this to varying degrees of success. Here we describe and model the results of a paradigm affording not only a first-order measurement of the perceived duration of an interval but also a second-order metacognitive judgement of perceived time. This approach, we argue, expands the form of the data generally collected in duration-judgements and allows more detailed comparison of psychophysical behavior to the underlying theory. We also describe a hierarchical Bayesian measurement model that performs a quantitative analysis of the trial-by-trial data calculating the variability of the temporal estimates and the metacognitive judgments allowing direct comparison between an actual and an ideal observer. We fit the model to data collected for judgements of 750 ms (bisecting 1500 ms) and 1500 ms (bisecting 3000 ms) intervals across three stimulus modalities (visual, audio, and audiovisual). This enhanced form of data on a given interval judgement and the ability to track its progression on a trial-by-trial basis offers a way of looking at the different roles that subject-based, task-based and stimulus-based factors have on the perception of time.

Transport behavior of microplastics in soil‒water environments and its dependence on soil components.

Microplastic (MP) pollution has become a global concern, and the transport behavior of MPs in soil-water systems is vital in determining their distribution and potential risks to the subsurface environment. To reveal the role of various soil components on MP migration, the downward transport behavior of polystyrene (PS) MPs were explored in this study via column experiments with mono or multi-soil components as porous media. Compared with the selected soil mineral volcanic rock (VR) and fine river sand (RS), condensed soil organic matter (SOM) resulted in higher transport efficiencies for PS microparticles, with greater than 90% total mass recovery under the experimental conditions. The more surface charges of SOM than minerals contribute to the high migration efficiency of PS MPs, and electrostatic repulsion is assumed a significant driving mechanism in the migration of negatively charged PS particles in soils. The ionic strength of porewater influenced the PS migration behaviors by altering the electrostatic interactions between the MPs and soil grains. The uniform mixing of SOM with mineral grains significantly enhanced the transport efficiency of PS MPs in the columns. The results provide supports for the prediction and prevention of the risks of MPs to the subsurface environment.

Heterogeneous photo-Fenton degradation of acid orange 7 activated by red mud biochar under visible light irradiation.

The heterogeneous photo-Fenton process is an effective technology for degrading organic contaminants in wastewater, and Fe-based catalysts are recently preferred due to their low biotoxicity and geological abundance. Herein, we synthesized a Fe-containing red mud biochar (RMBC) via one-step co-pyrolysis of red mud and shaddock peel as a photo-Fenton catalyst to activate H2O2 and degrade an azo dye (acid orange 7, AO7). RMBC showed excellent AO7 removal capability with a decolorization efficiency of nearly 100% and a mineralization efficiency of 87% in the heterogeneous photo-Fenton process with visible light irradiation, which were kept stable in five successive reuses. RMBC provided Fe2+ for H2O2 activation, and the light irradiation facilitated the redox cycle of Fe2+/Fe3+ in the system to produce more reactive oxygen species (ROS, i.e., •OH) for AO7 degradation. Further investigation revealed that •OH was the predominant ROS responsible for AO7 degradation in the light-free condition, while more ROS were produced in the system with light irradiation, and 1O2 was the primary ROS in the photo-Fenton process for AO7 removal, followed by •OH and O2•-. This study provides insight into the interfacial mechanisms of RMBC as a photo-Fenton catalyst for treating non-degradable organic contaminants in water through advanced oxidation processes under visible light irradiation.

Release of microplastics from disposable cups in daily use.

Global concern over microplastics (MPs) is increasing because of the potential threat these substances pose to ecosystem and human health. Disposable cups, frequently used as containers of beverages, are typically made of plastic or plastic-coated paper. The release of MPs from disposable cups during use may provide a direct exposure pathway for humans. In this study, the MP release capacities of 90 batches of commercial disposable cups, including polyethylene (PE)-coated paper cups, polypropylene (PP) cups, and polystyrene (PS) cups, were investigated under daily use conditions, and the properties of released MP particles are characterized with Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The MPs release into containing beverages is detected for each of the tested cups in this study. The released MPs particles are in irregular shapes and dominantly smaller than 20 µm. The quantities of released MPs are in the range of 675-5984, 781-4951, and 838-5215 particles/L for PE-coated paper cups, PP cups and PS cups, respectively, when containing pure water at 95 °C for 20 min. No significant difference in the quantity of MP released is observed among the three types of the cups in the experimental conditions. High temperature is found to promote the release of MPs from disposable cups. The MP release is notable when the cups are used for a second time, although at a slightly lower level than the first use. Acidic carbonated beverages obviously enhance MP release from PE-coated cups over that of ultrapure water.

Synergistic role of inherent calcium and iron minerals in paper mill sludge biochar for phosphate adsorption.

Phosphate adsorption using metal-based biochar has awakened much attention and triggered extensive research. In this study, novel Ca/Fe-rich biochars were prepared via a one-step process of pyrolyzing paper mill sludge (PMS) at various temperatures (300, 500, 700, and 800 °C) under a CO2 atmosphere for phosphate removal. Batch adsorption experiments showed that the biochar obtained at 800 °C (PB-800), which could be easily separated magnetically, exhibited the best phosphate adsorption capacity in a wide range of solution pH (5-11). Based on the Langmuir model, the maximum phosphate adsorption capacity for PB-800 was 17.33 mg/g. Besides, the effects of ambient temperature as well as coexisting ions on phosphate removal were also investigated. Kinetic and thermodynamic analysis revealed that chemisorption dominated the adsorption process. The calcium carbonate and ferric salts in the sludge were converted into CaO and Fe3O4 through pyrolysis at 800 °C. The CaO inherent in PB-800 was proved to serve as active sites for the chemical precipitation, showing its synergistic effect with iron oxide compounds (i.e., Fe3O4, α-Fe2O3) on phosphate removal through chemical precipitation, ligand exchange, and complexation. This study not only provides a feasible waste-to-wealth strategy for converting PMS into a Ca/Fe-rich magnetic biochar that can be used as an effective phosphate adsorbent, but also offers new insights into the synergistic effect of calcium and iron species for the adsorption of phosphate using biochar.

Functionalizing biochar by Co-pyrolysis shaddock peel with red mud for removing acid orange 7 from water.

Biochar modification by metal/metal oxide is promising for improving its adsorption capability for contaminants, especially the anions. However, conventional chemical modifications are complicated and costly. In this study, novel Fe/Fe oxide loaded biochars (RMBCs) were synthesized from a one-step co-pyrolysis of red mud (RM) and shaddock peel (SP), and their potential application for removing anionic azo dye (acid orange 7, AO7) from the aqueous environment was evaluated. Fe from red mud was successfully loaded onto biochars pyrolyzed at 300-800 °C, which presented from oxidation form (Fe2O3) to the reduction forms (FeO and Fe0) with increasing pyrolysis temperature. The RMBC produced at 800 °C with RM:SP mass ratio of 1:1 (RMBC8001:1) exhibited the best capability for AO7 removal (∼32 mg/g), attributed to both adsorption and degradation. The higher surface area of RMBC8001:1 and its greater affinity for AO7 led to the higher adsorption. In addition, RMBC8001:1-induced degradation of AO7 was another key mechanism for AO7 removal. The reduction forms of Fe (FeO or Fe0) in RMBC8001:1 may provide electrons for breaking down the azo bond in AO7 molecules and result in degradation, which is further enhanced in acid conditions due to the participation of readily release of Fe2+ and the available H+ in AO7 degradation. Furthermore, RMBC8001:1 can be easily separated from the treated water by using magnetic field, which significantly benefits its separation in wastewater treatment.

Retention and transport behavior of microplastic particles in water-saturated porous media.

Microplastic (MP) pollution has become a global concern given its wide occurrence and potential ecological risks. The retention/transport features of MPs in porous media govern the fate and risks of MPs in subsurface environments. Polystyrene (PS) microspheres are employed as representative MPs to explore the migration behaviors in water-saturated quartz sand columns. The hydrodynamic size mainly determines the deposition and size exclusion straining of MPs in porous media, and further the attachment efficiency. PS50 (PS with 50 nm diameter) shows a total migration rate greater than 85% in each of the studied conditions. In contrast, PS500 commonly exhibits slower migration velocities and higher attachment efficiencies than those of PS50 and PS100. The ionic strength, pH, and dissolved organic matter content of the solution show obvious effects on the retention/transport of PS MPs. The influences of solution chemical properties are consistent with the prediction of Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The results in this study clarify the size-dependent migration characteristics of MPs in porous media and provide a basis for risk assessment of MPs in terrestrial environments.

Removal of phosphate from water by paper mill sludge biochar.

Biochar modification by metals and metal oxides is considered a practical approach for enhancing the adsorption capacity of anionic compounds such as phosphate (P). This study obtained paper mill sludge (PMS) biochar (PMSB) via a one-step process by pyrolyzing PMS waste containing ferric salt to remove anionic P from water. The ferric salt in the sludge was transformed into ferric oxide and zero-valent-iron (Fe0) in N2 atmosphere at pyrolysis temperatures ranging from 300 to 800 °C. The maximum adsorption (Qm) of the PMSBs for P ranged from 9.75 to 25.19 mg P/g. Adsorption is a spontaneous and endothermic process, which implies chemisorption. PMSB obtained at 800 °C (PMSB800) exhibited the best performance for P removal. Fe0 in PMSB800 plays a vital role in P removal via adsorption and coprecipitation, such as forming the ≡Fe-O-P ternary complex. Furthermore, the possible chemical precipitation of P by CaO decomposed from calcite (CaCO3; an additive of paper production that remains in PMS) may also contribute to the removal of P by PMSB800. Moreover, PMSBs can be easily separated magnetically from water after application and adsorption. This study achieved a waste-to-wealth strategy by turning waste PMS into a metal/metal oxide-embedded biochar with excellent P removal capability and simple magnetic separation properties via a one-step pyrolysis process.

Enhanced removal of ammonium from water using sulfonated reed waste biochar-A lab-scale investigation.

The removal of excessive ammonium from water is vital for preventing eutrophication of surface water and ensuring drinking water safety. Several studies have explored the use of biochar for removing ammonium from water. However, the efficacy of pristine biochar is generally weak, and various biochar modification approaches have been proposed to enhance adsorption capacity. In this study, biochar obtained from giant reed stalks (300, 500, 700 °C) was modified by sulfonation, and the ammonium adsorption capabilities of both giant reed biochars (RBCs) and sulfonated reed biochars (SRBCs) were assessed. The ammonium adsorption rates of SRBCs were much faster than RBCs, with equilibrium times of ∼2 h and ∼8 h for SRBCs and RBCs, respectively. The Langmuir maximum adsorption capacities of SRBCs were 4.20-5.19 mg N/g for SRBCs, significantly greater than RBCs (1.09-1.92 mg N/g). Physical-chemical characterization methods confirmed the increased levels of carboxylic and sulfonic groups on sulfonated biochar. The reaction of ammonium with these O-containing functional groups was the primary mechanism for the enhancement of ammonium adsorption by SRBCs. To conclude, sulfonation significantly improved the adsorption performance of biochar, suggesting its potential application for ammonium mitigation in water.

Highly effective adsorption of antibiotics from water by hierarchically porous carbon: Effect of nanoporous geometry.

Pharmaceutical antibiotics have recently become emerging environmental contaminants. To enhance the removal efficiency of antibiotics in water, hierarchically porous carbons (HPCs) with designed porous patterns are used in both batch and column mode adsorption processes in this study, and the role of their nanoporous geometry in the adsorption dynamics are explored. THPC (HPC with trimodal pores) and DHPC (HPC with bimodal pores) exhibit remarkably superior adsorption performances to the selected antibiotics than those of commercial activated carbon (AC) with similar surface area, especially in column mode adsorption. The effective treatment volumes of the HPC-columns remain up to 8-10 times those of the AC-columns for the removal of tetracycline and 4-6 times for the removal of tylosin. The mass transfer rates of the carbon-based columns present the order of THPC > DHPC > AC. As comparison, the columns based on monomodal mesoporous carbon (MEC) and microporous carbon (MAC) exhibit low effective treatment volumes although their high mass transfer speed. The interconnected meso/macropores in HPCs benefit the intraparticle mass transfer of guest molecules and the accessibility of adsorption sites. The micropores linking to the meso/macropores not only provide adsorption sites but also facilitate adsorption affinity.

Ammonium removal using a calcined natural zeolite modified with sodium nitrate.

Ammonium is one of the key factors responsible for the eutrophication of water bodies. The purpose of this study was to remove ammonium from water using a natural zeolite (NZ) modified with sodium nitrate (NaNO3) by impregnation and calcination. The ability of the NZ to remove ammonium from water was determined by single calcination; however, its efficiency was significantly enhanced by impregnation with a NaNO3 solution. Zeolite modified with 3.00 M NaNO3 and calcination at 673 K yielded the best ammonium removal efficiency, which was 39.88 % higher than the NZ alone. The zeolites that were regenerated over six times maintained a removal rate of 79.35-84.79 % by mixing 25.0 mg of the NZ into 50 mL of a 5.0 mg/L ammonium solution. The improved performance of the modified zeolite (qm, 16.96 mg/g) was mainly attributed to its relatively elevated mesopore volumes and higher ion-exchange capacity that results from nitrate decomposition, oxygen release, and sodium-ion exchange. The adsorption kinetics and isotherms are best described by the pseudo-first-order (PFO) and Freundlich model, respectively, and the process was endothermic. The effects of other factors, including coexisting ions, pH, and dosage, on ammonium adsorption were also determined.

Organo-layered double hydroxides for the removal of polycyclic aromatic hydrocarbons from soil washing effluents containing high concentrations of surfactants.

Disposal of soil washing effluent (SWE) resulting from the surfactant-enhanced remediation of soil containing hydrophobic organic contaminants (HOCs)is complicated because of the presence of high levels of surfactants. The synthesized layered double hydroxides (LDHs), modified with sodium dodecyl sulfonate (SDS) in different loading amounts (organo-LDHs),were evaluated in this study as sorbents for the removal of two typical HOCs, phenanthrene (PHE) and pyrene (PYR),from a simulative SWE. The results showed that the organo-LDHs can effectively sorb PHE and PYR from the SWE within an equilibrium time of 2 h. All isotherms were linear and the sorption capabilities of the organo-LDHs increased almost linearly with the increase in the amount of SDS loaded on the LDHs. Besides, the surface areas of the organo-LDHs decreased sharply with the increase in SDS loading owing to the hindrance of the exposed surface of the LDHs by the incorporated SDS. These findings indicated that partitioning dominated the sorption process rather than adsorption, and the strong affinity of HOCs towards the organic phase in LDHs assisted in the effective removal of polycyclic aromatic hydrocarbons (PAHs) from the SWE. Furthermore, the sorption capabilities of organo-LDHs towards PHE and PYR at the higher loading amounts of SDS were much greater than that of commercial activated carbon at the higher concentration ranges of PAHs.

[Spatial heterogeneity of community structure of Picea crassifolia forest in Qilian Mountains, China].

We selected the grid of 5 m x 5 m in a dynamic monitoring plot (340 m x 300 m) as the sampling unites and chose 5 structural characteristics (density, average crown breadth, coverage, conspicuousness and average height) to study the spatial heterogeneity of community structure of Picea crassifolia forest in Dayekou Basin of Qilian Mountains by the fractal geometry and geostatistics methods. The results showed that the order of spatial variation in these characteristics was: density > average crown breadth > conspicuousness > coverage > average height, with the variation coefficient ranging from 43.7% to 79.6%. Moran's I index indicated that the structural variables had different degrees of spatial autocorrelation, and the order of autocorrelation was density > average height> coverage > average crown breadth > conspicuousness, with the range of -0.047-0.382. The exponential semivariation model well fitted the spatial variability in different structural features, and the range was 24.6-68.1 m. The variables displayed moderate spatial autocorrelation except for coverage, while the other variables had strong spatial autocorrelation, and the fractal dimension of the variables was close to 2, indicating a low spatial dependence among variables. The variables presented a superposing characteristic of zonal and patchy structures except for density and coverage, while the other variables presented strong patchiness property. Density and coverage had a certain spatial dependence on average crown breadth, conspicuousness and average height. Density and coverage for the spatial heterogeneity of community structural of P. crassifolia forests were 10 m and 0.5 hm2, respectively.

Structures of OTMA- and DODMA-bentonite and their sorption characteristics towards organic compounds.

Illuminating the factors that influence the organic carbon content normalized sorption coefficient (K(oc)) of organoclays towards hydrophobic organic compounds (HOCs) is meaningful for predicting and optimizing the sorption capacity of organoclay. In this paper, the structures and sorption characteristics towards HOCs of organobentonites synthesized with octadecyltrimethylammonium chloride (OTMAC) and dioctadecyldimethylammonium chloride (DODMAC) were studied in order to further account for the variation of K(oc). The conformations of bentonite-sorbed OTMA(+) and DODMA(+) transformed from disorder to order as surfactant loading increasing. The packing densities of DODMA(+) aggregates were higher than those of OTMA(+) aggregates at low surfactant loadings. At high surfactant loading region (1.0-1.4CEC for OTMA-Bent and 0.5-0.7CEC for DODMA-Bent), similar paraffin-type bilayer arrangements were adopted by sorbed OTMA(+) and DODMA(+), and their packing densities were close under the same f(oc) in dry state organobentonites. It was found that loading forms of surfactant onto bentonite had important effect on the structure of organobentonite in water-saturated state, and further to influence the sorption characteristics of organobentonite towards HOCs. When the loading exceeded 0.8CEC, OTMAC in salt molecule form appeared in the clay interlayer via hydrophobic interaction. The strong hydration of surfactant ammonium heads and the counterions (Cl(-)) in aqueous system interfered the hydrophobic interaction of the OTMA(+) clusters and destroyed the close packing in clay galleries. As a result, the sorption capacity of organobentonite towards HOCs was sharply reduced.