Metal-Graphene Hybrid Terahertz Metasurfaces for Circulating Tumor DNA Detection Based on Dual Signal Amplification.

Terahertz (THz) spectroscopy has impressive capability for label-free biosensing, but its utility in clinical laboratories is rarely reported due to often unsatisfactory detection performances. Here, we fabricated metal-graphene hybrid THz metasurfaces (MSs) for the sensitive and enzyme-free detection of circulating tumor DNA (ctDNA) in pancreatic cancer plasma samples. The feasibility and mechanism of the enhanced effects of a graphene bridge across the MS and amplified by gold nanoparticles (AuNPs) were investigated experimentally and theoretically. The AuNPs serve to boost charge injection in the graphene film and result in producing a remarkable change in the graded transmissivity index to THz radiation of the MS resonators. Assay design utilizes this feature and a cascade hybridization chain reaction initiated on magnetic beads in the presence of target ctDNA to achieve dual signal amplification (chemical and optical). In addition to demonstrating subfemtomolar detection sensitivity and single-nucleotide mismatch selectivity, the proposed method showed remarkable capability to discriminate between pancreatic cancer patients and healthy individuals by recognizing and quantifying targeted ctDNAs. The introduction of graphene to the metasurface produces an improved sensitivity of 2 orders of magnitude for ctDNA detection. This is the first study to report the combined application of graphene and AuNPs in biosensing by THz spectroscopic resonators and provides a combined identification scheme to detect and discriminate different biological analytes, including nucleic acids, proteins, and various biomarkers.

Rare earth elements applied to phytoremediation: Enhanced endocytosis promotes remediation of antimony contamination with different valence levels in Solanum nigrum L.

Antimony (Sb) pollution poses a noteworthy risk to human health and ecosystem sustainability, therefore effective, eco-friendly, and widely accepted restoration methods are urgently needed. This study introduces a new approach of using La(III) foliar application on Solanum nigrum L. (S. nigrum), a cadmium hyperaccumulator, to improve its photosynthetic and root systems under Sb stress, resulting in a higher biomass. Notably, La(III) also enhances endocytosis in root cells, facilitating efficient and non-selective remediation of both Sb(III) and Sb(V) forms. The absorption of Sb by root cell endocytosis was observed visually with a confocal laser scanning microscope. The subcellular distribution of Sb in the cell wall of S. nigrum is reduced. And the antioxidant enzyme activity system is improved, resulting in an enhanced Sb tolerance in S. nigrum. Based on the existing bibliometric analysis, this paper identified optimal conditions for S. nigrum to achieve maximum translocation and bioconcentration factor values for Sb. The foliar application of La(III) on plants treated with Sb(III), Sb(V), and a combination of both resulted in translocation factor values of 0.89, 1.2, 1.13 and bioconcentration factor values of 11.3, 12.81, 14.54, respectively. Our work suggests that La(III)-enhanced endocytosis of S. nigrum root cells is a promising remediation strategy for Sb-contaminated environments.

Influence of elevated temperature on the species and mobility of chromium in ferrous sulfate-amended contaminated soil.

Ferrous sulfate (FeSO4) combined with acid pretreatment is usually employed to remediate contaminated soils containing Cr(VI). However, the long-term efficiency of this stabilization method is important for its sustainability. In this study, a gradient temperature-elevating exposure test was employed to investigate the stability of Cr in FeSO4-remediated soil when exposed to elevated temperatures (40 °C, 120 °C, and 500 °C), possibly caused by hot weather and/or wildfires. The results of chemical extraction and X-ray absorption near edge structure spectroscopy (XANES) showed that the Cr(VI) in contaminated soil was successfully transformed to Cr(III) after stabilization, resulting in the dramatic decrease of water-leachable Cr(VI). The stabilization efficiency was further improved under 40 °C treatment after 30 days. Subsequently, the 120 °C treatment (7 days) had relatively little effect on the Cr speciation and mobility in soils. However, even one day of 500 °C calcination resulted in the deterioration of stabilization efficiency, and the water-leachable Cr(VI) re-increased and became higher than the Chinese environmental standards (total Cr 15 mg/L, Cr(VI) 5 mg/L) for the classification of hazardous solid wastes. XANES results reflected that heating at 500 °C facilitate the formation of Cr2O3, which was mainly caused by thermal decomposition and dehydration of Cr(OH)3 in the soil. Besides, the transformation of Cr species resulted in the enhanced association of Cr with the most stable residual fraction (88.3%-91.6%) in soil. Based on chemical extraction results, it was suggested that the oxidation of Cr(III) to Cr(VI) contributed to the re-increased mobility of Cr(VI) in soil. However, the XANES results showed that almost no significant re-oxidization of Cr(III) to Cr(VI) happened after heating at 500 °C, which was probably caused by XANES linear combination fits (LCF) uncertainties. Moreover, the changes in soil properties, including a rise in pH to a slightly alkaline range and/or the decomposition of organic matter, possibly contributed to the enhanced mobility of Cr(VI) in soil. This study contributes to clarifying the mobility and transformation of Cr in contaminated soils and provides a support for the sustainable management of remediated soils.

Rapid and sensitive detection of Staphylococcus aureus using a THz metamaterial biosensor based on aptamer-functionalized Fe3O4@Au nanocomposites.

Staphylococcus aureus (S. aureus) poses a serious threat to global public health, necessitating the establishment of rapid and simple tools for its accurate identification. Herein, we developed a terahertz (THz) metamaterial biosensor based on aptamer-functionalized Fe3O4@Au nanocomposites for quantitative S. aureus assays in different clinical samples. Fe3O4@Au@Cys@Apt has the dual advantages of magnetism and a high refractive index in the THz range and was used to rapidly separate and enrich target bacteria in a complex environmental solution. Furthermore, conjugation to the nanocomposites significantly increased the resonance frequency shift of the THz metamaterial after target loading. Our results showed that the shifts in the metamaterial resonance frequency were linearly related to S. aureus concentrations ranging from 1.0 × 103 to 1.0 × 107 CFU/mL, with a detection limit of 4.78 × 102 CFU/mL. The biosensor was further applied to S. aureus detection in spiked human urine and blood with satisfactory recoveries (82.4-109.6%). Our approach also demonstrated strong concordance with traditional plate counting (R2 = 0.99306) while significantly lowering the analysis time from 24 h to <1 h. In conclusion, the proposed biosensor can not only perform culture-free and extraction-free detection of target bacteria but can also be easily extended to the determination of other pathogenic bacteria, rendering it suitable for various bacteria-related disease diagnoses.

Realization of multifunctional transformation based on the vanadium dioxide-assisted metamaterial structure.

In this paper, a multifunctional device and a design method are proposed based on the vanadium dioxide (VO2)-assisted metamaterial structure. The structure comprises several layers arranged from top to bottom, including a VO2 patch layer, a polyimide (PI) dielectric layer, an elliptical metal layer, a VO2 thin film layer, another PI dielectric layer, and a bottom metal layer. The research results show that the metamaterial structure enables linear-to-linear (LTL) polarization conversion and linear-to-circular (LTC) polarization conversion across multiple frequency bands when the VO2 is in the insulating state. Moreover, as the VO2 material undergoes a transition from the insulating state to the metallic state, the multifunctional structure can function as a broadband absorber, exhibiting an absorption rate of over 90% within the frequency range of 1.751-3.853 THz, with a relative bandwidth of 75%. This versatile conversion device holds great potential for applications in terahertz system and smart system fields.

A comprehensive review on the source, ingestion route, attachment and toxicity of microplastics/nanoplastics in human systems.

Microplastics (MPs)/nanoplastics (NPs) are widely found in the natural environment, including soil, water and the atmosphere, which are essential for human survival. In the recent years, there has been a growing concern about the potential impact of MPs/NPs on human health. Due to the increasing interest in this research and the limited number of studies related to the health effects of MPs/NPs on humans, it is necessary to conduct a systematic assessment and review of their potentially toxic effects on human organs and tissues. Humans can be exposed to microplastics through ingestion, inhalation and dermal contact, however, ingestion and inhalation are considered as the primary routes. The ingested MPs/NPs mainly consist of plastic particles with a particle size ranging from 0.1 to 1 µm, that distribute across various tissues and organs within the body, which in turn have a certain impact on the nine major systems of the human body, especially the digestive system and respiratory system, which are closely related to the intake pathway of MPs/NPs. The harmful effects caused by MPs/NPs primarily occur through potential toxic mechanisms such as induction of oxidative stress, generation of inflammatory responses, alteration of lipid metabolism or energy metabolism or expression of related functional factors. This review can help people to systematically understand the hazards of MPs/NPs and related toxicity mechanisms from the level of nine biological systems. It allows MPs/NPs pollution to be emphasized, and it is also hoped that research on their toxic effects will be strengthened in the future.

Lanthanum promotes Solanum nigrum L. growth and phytoremediation of cadmium and lead through endocytosis: Physiological and biochemical response, heavy metal uptake and visualization.

Rare earth elements (REEs) are important to enhance agricultural productivity. The utilization of phytoremediation as a green technology for addressing heavy metal (HMs) contamination in soil and wastewater has gained significant attention. In our research, we conducted indoor hydroponic experiments to examine the impacts of lanthanum (La) on the growth and enrichment capacity of Solanum nigrum L. (S. nigrum). S. nigrum was cultivated in 10 mg·L-1 of cadmium (Cd), 25 mg·L-1 of lead (Pb), and a mixture of both (5 mg·L-1 Cd + 15 mg·L-1 Pb). Additionally, S. nigrum were subjected to foliar spray or hydroponic supplementation of La(III). The treatment with La(III) significantly increased total fresh weight by 17.82 % to 42.20 %, compared to the treatment without La(III). Furthermore, La(III) facilitated the endocytosis of roots and enhanced Cd2+ flux ranging from 15.64 % to 75.99 % when compared to the treatment without La(III). Foliar and hydroponic application of La(III) resulted in an increase in the translocation factors (TF) in plants of Cd and Pb compared to treatments without La(III). These findings can offer valuable insights into the potential of La(III) to enhance the phytoremediation of soil or wastewater polluted with compounds.

Foliar spraying of lanthanum activates endocytosis in lettuce (Lactuca sativa L.) root cells, increasing Cd and Pb accumulation and their bioaccessibility.

Cadmium (Cd) and lead (Pb) accumulate easily in leafy vegetables and can harm human health. Lanthanum (La) have been used to improve agricultural yield and quality, but the effect of La application on Cd/Pb enrichment in leafy vegetables remains incomplete currently. A previous study reported that the endocytosis in lettuce leaf cells can be activated by La, leading to an increase in Pb accumulation in lettuce leaves. However, it has not been investigated whether foliar application of La enhances root cellular endocytosis and promotes its uptake of Cd and Pb. In this study, the influence of La on the uptake of Cd and Pb, Cd bioaccessibility, and the safety risks of cultivating lettuce under Cd and Pb stress were explored. It was found that La increased Cd (16-30 % in shoot, 16-34 % in root) and Pb (25-29 % in shoot, 17-23 % in root) accumulation in lettuce. The increased accumulation of Cd and Pb could be attributed to La-enhanced endocytosis. Meanwhile, La enhanced the toxicity of both Cd and Pb, inhibited lettuce growth, and aggravated the damage to the photosynthetic and antioxidant systems. Finally, gastrointestinal simulation experiments showed that La increased the Cd bioaccessibility in both gastric and intestinal phase by 7-108 % and 9-87 %, respectively. These results offer valuable insights into the safety of REEs for agricultural applications.

Enhancement of wide-band trace terahertz absorption spectroscopy based on microstructures: a review.

Research on the interaction between nanoscale materials and light holds significant scientific significance for the development of fields such as optoelectronic conversion and biosensing. The study of micro- and nano-optics has produced numerous outstanding research achievements by utilizing the dielectric optical coupling mechanism and plasmon effects to enhance the interaction between light and matter. These findings have demonstrated tremendous potential for applications in the field of molecular fingerprint sensing. This review focuses on a retrospective analysis of recent research studies in the enhancement of wide-band trace terahertz absorption spectroscopy. The physical mechanisms of using waveguide structures, dielectric metasurfaces/meta-gratings, and spoof surface plasmon polaritons (SSPs) to improve the interaction between light and trace-amount matters are introduced. The new approaches and methods for enhancing broad-band terahertz absorption spectroscopy of trace samples using microstructure designs are discussed. Additionally, we elucidate the scientific ideas and exploratory achievements in enhancing terahertz fingerprint spectroscopy detection. Finally, we provide an outlook on the research and development direction and potential practical applications of absorption spectroscopy enhancement detection.

Terahertz beam characterization by temporal-spatial mapping with a reflecting echelon.

A terahertz beam imaging method was proposed that involves scanning a reflecting echelon with temporal-spatial mapping inversion based on self-developed translation-scan and rotation-scan temporal-spatial mapping (TTSM and RTSM) algorithms. The beam characteristics of a terahertz time-domain spectroscopy (TDS) system, such as its size, shape, and energy distribution, were obtained. Besides the weak terahertz beam emitted from a TDS system, this scheme is also suitable for imaging large-size terahertz or laser beams in time-domain systems where existing beam imaging is impractical.

A Meta-Analysis of Influencing Factors on the Activity of BiVO4-Based Photocatalysts.

With the continuous advancement of global industrialization, a large amount of organic and inorganic pollutants have been discharged into the environment, which is essential for human survival. Consequently, the issue of water environment pollution has become increasingly severe. Photocatalytic technology is widely used to degrade water pollutants due to its strong oxidizing performance and non-polluting characteristics, and BiVO4-based photocatalysts are one of the ideal raw materials for photocatalytic reactions. However, a comprehensive global analysis of the factors influencing the photocatalytic performance of BiVO4-based photocatalysts is currently lacking. Here, we performed a meta-analysis to investigate the differences in specific surface area, kinetic constants, and the pollutant degradation performance of BiVO4-based photocatalysts under different preparation and degradation conditions. It was found that under the loading condition, all the performances of the photocatalysts can be attributed to the single BiVO4 photocatalyst. Moreover, loading could lead to an increase in the specific surface area of the material, thereby providing more adsorption sites for photocatalysis and ultimately enhancing the photocatalytic performance. Overall, the construct heterojunction and loaded nanomaterials exhibit a superior performance for BiVO4-based photocatalysts with 136.4% and 90.1% improvement, respectively. Additionally, within a certain range, the photocatalytic performance increases with the reaction time and temperature.

Uptake, transport and accumulation of micro- and nano-plastics in terrestrial plants and health risk associated with their transfer to food chain - A mini review.

Waste plastics enter the environment (water, soil, and atmosphere) and degrade into micro- and nano-plastics (MNPs) through physical, chemical, or biological processes. MNPs are ubiquitous in the environment and inevitably interact with terrestrial plants. Terrestrial plants have become important potential sinks, and subsequently, the sources of MNPs. At present, many studies have reported the effects of MNPs on plant physiology, biochemistry, and their phototoxicity. However, the source, detection method, and the absorption process of MNPs in terrestrial plants have not been systematically studied. In order to better understand the continuous process of MNPs entering terrestrial plants, this review introduces the sources and analysis methods of MNPs in terrestrial plants. The uptake pathways of MNPs in terrestrial plants and their influencing factors were systematically summarized. Meanwhile, the transport pathways and the accumulation of MNPs in different plant organs (roots, stems, leaves, calyxes, and fruits) were explored. Finally, the transfer of MNPs through food chains to humans and their health risks were discussed. The aim of this work is to provide significant theoretical knowledge to understand the uptake, transport, and accumulation of MNPs in terrestrial plants and the potential health risks associated with their transfer to humans through food chain.

Using multi-technology to characterize transboundary Hg pollution in the largest presently active Hg deposit in China.

Active Hg mines are primary sources of Hg contamination in the environment of mining districts and surrounding areas. Alleviation of Hg pollution requires knowledge of pollution sources, migration, and transform pathways across various environmental media. Accordingly, the Xunyang Hg-Sb mine, the largest active Hg deposit in China, presently was selected as the study area. GIS, TIMA, EPMA, µ-XRF, TEM-EDS, and Hg stable isotopes were adopted to investigate the spatial distribution, mineralogical characteristics, in situ microanalysis, and pollution sources of Hg in the environment medium at the macro- and micro-levels. The total Hg concentration in samples showed a regional distribution, with higher levels in areas close to the mining operations. The in situ distribution of Hg in soil was mainly associated with the mineralogical phases of quartz, and Hg was also correlated with Sb and S. Hg was also found to be rich mainly in quartz minerals in the sediment and showed different distributions of Sb. Hg hotspots had S abundances and contained no Sb and O. The contributions from the anthropogenic sources to soil Hg were estimated to be 55.35%, among which 45.97% from unroasted Hg ore and 9.38% from tailing. Natural input of soil Hg due to pedogenic processes accounted for 44.65%. Hg in corn grain was mainly derived from the atmosphere. This study will provide a scientific basis for assessing the current environmental quality in this area and minimizing further impacts that affect the nearby environmental medium.

Highly boosted trace-amount terahertz vibrational absorption spectroscopy based on defect one-dimensional photonic crystal.

Although terahertz (THz) spectroscopy demonstrates great application prospects in the fields of fingerprint sensing and detection, traditional sensing schemes face unavoidable limitations in the analysis of trace-amount samples. In this Letter, a novel, to the best of our knowledge, absorption spectroscopy enhancement strategy based on a defect one-dimensional photonic crystal (1D-PC) structure is proposed to achieve strong wideband terahertz wave-matter interactions for trace-amount samples. Based on the Fabry-Pérot resonance effect, the local electric field in a thin-film sample can be boosted by changing the length of the photonic crystal defect cavity, so that the wideband signal of the sample fingerprint can be greatly enhanced. This method exhibits a great absorption enhancement factor, of about 55 times, in a wide terahertz frequency range, facilitating the identification of different samples, such as thin α-lactose films. The investigation reported in this Letter provides a new research idea for enhancing the wide terahertz absorption spectroscopy of trace samples.

Flexible Metamaterial Quarter-Wave Plate and Its Application in Blocking the Backward Reflection of Terahertz Waves.

A terahertz flexible metamaterial quarter-wave plate (QWP) is designed and fabricated using polyimide as the substrate in this paper, with a 3 dB axial ratio bandwidth of 0.51 THz and high polarization conversion efficiency and transmittance. The effect of the incidence angle on the polarization conversion performance of the QWP is discussed by measuring the transmissions at multiple incidence angles. The blocking effect of this QWP combined with a polarizer on the backward reflection of terahertz waves is investigated by terahertz time-domain spectral transmission experiments. By adjusting the angle of the QWP and polarizer with respect to the incident light in the optical path, a blocking efficiency of 20 dB can be achieved at a 20° incidence angle, with a bandwidth of 0.25 THz, a maximum blocking efficiency of 58 dB at 1.73 THz, and an insertion loss of only 1.4 dB. Flexible terahertz metamaterial QWPs and polarizers can effectively block harmful reflected waves in terahertz communication and other systems. They have the advantages of a simple structure, ultra-thinness and flexibility, easy integration, no external magnetic field, and no low-temperature and other environmental requirements, thus having broad application prospects for terahertz on-chip integrated systems.

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.

Foliar application of lanthanum promotes growth and phytoremediation potential Solanum nigrum L.

The hormetic effect of rare earth elements (REEs) has been found in a variety of crops and has been promoting crop growth for decades. Spraying leaves with REEs can enhance the endocytosis of plant roots. The non-selectivity of endocytosis is conducive to the direct absorption of environmental pollutants. The hyperaccumulator Solanum nigrum L. (S. nigrum), as a plant with high biomass and heavy metal tolerance, is a good candidate for phytoremediation. La(III), as a typical light REE, also has an obvious hormetic effect on S. nigrum. At 10 µM La(III), the biomass of S. nigrum reached the maximum, which was 89% greater than the control, and La(III) concentration was much lower than the previously reported optimum of 56 µM for general plants. In the present study, enhanced endocytosis after foliar spraying of La(III) was firstly observed in the root cell of hyperaccumulation plants, and La(III) increased the biomass of S. nigrum by improving the photosynthetic system, and promoting nutrient uptake and root development. The antioxidant defense system improved by La(III) contributed to the tolerance of S. nigrum to heavy metals. Applying a reasonable range of La(III) is beneficial to improving S. nigrum growth and tolerance of heavy metals. Compared with spraying deionized water, the translocation factor and bioaccumulation factor value of S. nigrum to cadmium increased by 15% and 21% respectively when spraying 10 µM La(III). Our findings provide a reference for improving hyperaccumulator plant growth and biomass, which improves phytoremediation efficiency.

Optimize lettuce washing methods to reduce the risk of microplastics ingestion: The evidence from microplastics residues on the surface of lettuce leaves and in the lettuce washing wastewater.

Airborne microplastics have been identified as an emerging contaminant that can adhere to the surface of leafy vegetables, and if not completely removed by washing, there is a high risk that human consumption of these plastics may cause harm to humans. In this study, we simulated atmospheric pollution by spraying microplastic particles (MPs) with particle sizes of 100 nm and 500 nm to determine whether MPs particles would adhere to the lettuce surface and whether different common cleaning methods (water rinsing, ultrasonic vibration cleaning, and edible detergent cleaning) would be effective in removing MPs from the leaf surfaces. We scanned the leaf surface with a laser confocal microscope and examined the wash water with a flow cytometer and found that simple rinsing was not effective in removing plastic particles from lettuce leaves. In comparison, ultrasonic vibratory cleaning showed a better efficiency, 4 times higher than more MPs being washed from the leaves. The most effective method was detergent washing, with the washing efficiency increased by 6.9 times. Ultrasonic vibrations can partially break the chemical bonds between MPs and plant surfaces, and detergents' surfactants can enhance MPs' hydrophilicity. MPs with a particle size of 100 nm were more difficult to clean than those with a particle size of 500 nm. This finding has important implications for the interaction of MPs contamination with vegetables and the cleaning of vegetables.

Leaching of heavy metal(loid)s from historical Pb-Zn mining tailing in abandoned tailing deposit: Up-flow column and batch tests.

This study aims to investigate the water-leaching characteristics of heavy metal(loid)s (HMs) from historical Pb-Zn mine tailing of an abandoned tailing deposit in eastern China. Up-flow column and batch leaching tests were conducted at different liquid-to-solid (L/S) ratios to estimate the releases of HMs and investigate the controlling mechanisms. Calcite and silicate were the dominant minerals in the tailing and the HMs contents followed the order of Zn (2371 mg/kg) > Pb (2061 mg/kg) > Cu (109 mg/kg) > Cr (47.8 mg/kg) > As (15.9 mg/kg) > Cd (5.1 mg/kg). Moreover, considerable fractions of Pb, Zn, and Cd existed in the acid-soluble forms (41-47%). Column and batch leaching tests consistently showed that limited quantities (<0.002%) of HMs could be leached from this historical tailing. In particular, variations in column conditions (e.g., length, flow rate, and initial saturation) significantly affected the release fluxes from the columns but had a relatively limited effect on the leaching mechanisms. The estimated results of HM release suggested that the leaching process was predominantly solubility-controlled and the dissolution of Ca-bearing minerals (e.g., calcite) primarily controlled the release of HMs. The studied tailing had a limited impact on the quality of the surrounding aquatic environments because the water-leaching concentrations of HMs were generally lower than the Chinese standards for drinking water. Only for Pb, the leaching results in column tests were significantly lower than those in batch tests; whereas the results in column tests for other HMs were comparable to those in batch tests to a certain extent. Based on the column test results, the amounts of HMs potentially released from the abandoned tailing deposit (height, 10 m; footprint area, 30,000 m2; tailing dry density, 1.9 × 103 kg/m3) followed a decreasing order of Zn (4.2 × 105 kg) > Cu (2.3 × 104 kg) > Pb (1.4 × 104 kg) > Cr (2.3 × 104 kg) > Cd (1.6 × 103 kg) > As (1.2 × 103 kg) over the 75-year assessment period (corresponding to an L/S ratio of 10 L/kg with an annual precipitation of 1500 mm).

Boosting the terahertz absorption spectroscopy based on the stretchable metasurface.

Terahertz (THz) absorption spectroscopy is widely used for molecular label-free fingerprinting detection, but it is not capable of efficiently analyzing trace-amount sample materials. For improving the efficiency of terahertz absorptance spectroscopy detection, we propose a sensing strategy by treating the geometry sweeping spoof surface plasmon polariton (SSP) of the stretchable metasurface. For the first time, the geometry sweeping can be realized by dynamically stretching the polydimethylsiloxane (PDMS) flexible substrate, leading to the resonant frequency variation of the unit cell. This design provides a significant absorption enhancement factor about 270 times for a 0.1 µm lactose film in a broad terahertz band, enabling the unambiguous identification of different trace-amount samples. The designed method exhibits a novel solution for the enhancement of broad-band terahertz absorption spectroscopy and great application potential in the field of detecting trace-amount samples.