Arsenic (As) contamination in sediments has been reported worldwide. However, few studies have investigated As contamination on a national scale in China. This study aims to address this gap by ...analyzing the existing literature on As contamination and sediment samples collected from ten main river basins: the Songhua River Basin (SRB), Liao River Basin (LRB), Hai River Basin (HRB), Yellow River Basin (YRB), Huai River Basin (HuRB), Yangtze River Basin (YtRB), Pearl River Basin (PRB), Southeastern River Basin (SeRB), Southwestern River Basin (SwRB), and Northwestern River Basin (NwRB). Regional geochemical baseline (RGB) values of As in the sediments of river basins were calculated to estimate human contributions of As using normalization and cumulative frequency distribution curves. The established RGB values in the SRB, YtRB, and PRB were higher than the corresponding regional soil background (RSB), possibly because of the high intensity of human activities in the SRB, YtRB, and PRB. Taking RGB and RSB values as the background references, contamination assessment yielded important information on As contamination in China. With high As contributions from Yunnan province, the PRB suffered from the highest level of contamination, and the mean human contribution of As in the PRB was 64.4%. The contamination levels in the less developed southwestern regions were even higher than in some river basins in economically developed regions (e.g., YRB). In addition, As in the PRB and YtRB was found to be partially contributed by industrial wastewater discharge, and the response of As contamination in sediments to industrial wastewater discharge was analyzed. The temporal change (2004–2016) of As in sediments from the PRB, YtRB, and YRB corresponded well with that of As discharged in wastewater within the corresponding river basins. This study thus serves as a valuable foundation for policies focused on ameliorating As contamination in China.
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•A national-scale assessment and a review were conducted on As in sediments in China•The PRB showed high As levels, with 64.4% from human contributions.•The RGB values in the SRB, YtRB, and PRB were higher than the corresponding RSB.•As contamination was significant even in undeveloped southwestern river basins.•Temporal changes of As in three major basins matched with that of As in wastewater.
•Micro/nanoscale motors(MNMs) have been regarded as promising tools in the field of engineered regeneration. Herein, a review on the advancements of MNMs in the area of engineered regeneration is ...presented, covering aspects from their propulsion mechanisms to their frontiers in engineered regeneration, listing the revolutionary applications in biosensing, medical imaging, drug delivery and tissue engineering. Finally, challenges and future directions of MNMs are finally discussed on the basis of the achievements.•We review the advancements of MNMs in engineered regeneration, covering from their propulsion mechanisms to theirfrontiers.
Micro/nanoscale motors(MNMs) have been regarded as promising tools in the field of engineered regeneration due to unique property of autonomous motion. Herein, a review on the advancements of MNMs in the area of engineered regeneration is presented, covering aspects from their propulsion mechanisms to their frontiers in engineered regeneration, listing the revolutionary applications in biosensing, medical imaging, drug delivery and tissue engineering. Finally, challenges and future directions of MNMs are finally discussed on the basis of the achievements.
Chromium (Cr) is a widespread pollutant with high toxicity and mobility. However, the diffusion–resupply kinetics of Cr(VI) between the solid phase and solution in the soils remain unclear. Here, we ...quantified the contributions of the soil solution and solid phase to the diffusion–resupply process of Cr(VI) in the contaminated soils using the diffusive gradients in thin-films (DGT) and DGT-induced fluxes in soils model. Based on the solution extraction result, Cr(VI) was the main available Cr species in the contaminated soils. Comparing the two diffusion–resupply stages of the kinetic process, the potential hazards due to the resupply from the solid phase can reach 10.71–50.66 %, although the soil solution accounted for the largest proportion of the effective concentration of Cr(VI) (49.34–89.29 %), which was ignored in the traditional equilibrium method. The kinetic parameters can be used to interpret the dynamic process. The resupply ability of the solid phase was closely related to the response time (Tc). The longer Tc was consistent with the low desorption constant, indicating a kinetic limitation. The magnitude of the resupply from the solid phase was related to labile pool size of Cr(VI) and soil organic carbon content. This study established a new quantification method for assessing diffusion-resupply kinetics of Cr(VI) in the soil， indicating the underestimation of Cr(VI) risk based on the use of traditional equilibrium methods. Our data provided a scientific basis for ecological risk assessment, pollution prevention, surface- and groundwater control, and environmental governance in areas with Cr contaminated soil.
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•Dynamic transport behavior of Cr(Ⅵ) was studied using DGT and DIFS.•Contribution of solid and solution in the kinetics process of Cr(Ⅵ) was quantified.•The resupply of Cr(Ⅵ) from the solid phase was considerable (10.71–50.66 %).•The contribution of the solid phase can be interpreted using the response time.•The major factors influencing response time were labile pool size and TOC content.
The 1–3 connectivity epoxy resin modified cement based piezoelectric composites were developed to meet the requirement of concrete structural heath monitoring. The piezoelectric ceramic volume ...fraction on piezoelectric, dielectric and electromechanical coupling properties of the composites were discussed. The results showed that the relative permittivity of the piezoelectric composites increases linearly with increasing the PZT piezoelectric ceramic volume fraction, but the dielectric loss of the piezoelectric composites is a little bit larger than that of the PZT ceramic. The piezoelectric strain constant
d
33
of the piezoelectric composites is mainly contributed by PZT ceramic and is in proportion to PZT volume fraction, however, the piezoelectric voltage constant
g
33
show the opposite variation. When PZT volume fraction decreases to 27.7%,
g
33
value of the piezoelectric composites reaches to 75.0 (mV)·m·N
−1
.
When PZT ceramic volume fraction is 62.33%, the thickness electromechanical coupling coefficient
k
t
of the piezoelectric composites is the largest of 66.73%. The acoustic impedance
Z
of the piezoelectric composite is close to that of the concrete when PZT ceramic volume fraction is less than 44.44%.
•Embedded piezoelectric ultrasonic transducers were developed.•Corrosion of reinforcement concrete was monitored based on the ultrasonic method.•Three corrosion periods can be obtained based on the ...acoustic parameters.
The corrosion behavior of steel in concrete is an engineering issue that needs to be monitored to ensure structural safety. Novel cement/polymer-based piezoelectric composites were used to fabricate embedded ultrasonic transducers. This study investigated the corrosion development of reinforcement bar in concrete by employing ultrasonic transmission technique. The transmitted ultrasonic wave and acoustic parameters were extracted to reveal the corrosion process of steel. Results show that ultrasonic time- and frequency-domain spectra have weak amplitude attenuation when the corrosion rate of steel is less than 1%. Corrosion then weakens further when the corrosion rate is higher than 5%. A similar variation is observed on the frequency-domain spectrum. Variations in the corrosion rates of steel bars in concrete can be categorized into three periods based on the acoustic parameters, namely, the initial corrosion period when the corrosion rate is less than 1%, rapid corrosion period at a corrosion rate of 1%–6%, and corrosion development period when the corrosion rate is higher than 6%.
The Three Gorges Reservoir (TGR) is the largest reservoir in China. Cadmium (Cd) is a primary pollutant in the TGR, and its speciation and bioavailability have attracted extensive attention since TGR ...submergence. In this study, Chelex-100 DGT (diffusive gradient in thin films) and the sequential extraction method were used to investigate the bioavailable Cd in sediments obtained from a typical tributary (Meixi) and mainstream (Yangtze) in the TGR. The total Cd concentrations in sediments of the four stations were also determined. In comparison to the concentrations of labile Cd measured by DGT (CDGT-Cd) in four profiles, CJ and MX-upstream/downstream were at potential risk for Cd release from surface sediments using the apparent diffusion flux across the interface numerical model. The order of CDGT-Cd in surface sediments was as follows: CJ > MX-downstream > MX-upstream > MX-midstream. Additionally, a positive correlation was demonstrated between CDGT-Cd and Cd in the exchangeable fraction (F1) in the surface sediments, indicating that Cd in the exchangeable fraction was readily captured by DGT. A negative correlation was observed between CDGT-Cd and CDGT-Fe, CDGT-Mn in the sediment-water-interface (SWI), suggesting that Fe/Mn oxides did not control the release of labile-Cd from sediments. Furthermore, a positive correlation existed between the CDGT-Cd in the surface sediments and Cd in the oxidizable fraction (F3), illustrating that Cd sorbed or bound with organic matter or sulfide was labile and released into the water phase from the surface sediments. A dark area was found in the AgI gel, which further demonstrated that Cd simultaneously was released with sulfide in this area.
•DGT-labile Cd was used to assess sediment coresina typical tributary and mainstream in the TGR.•Fe/Mn oxides did not control the release of labile Cd in sediments.•Organic matter and sulfides governed the mobility of labile Cd in surface sediments.•A dark area was found in AgI gel indirectly demonstrated Cd combining with sulfide to release.•Labile Cd in the sediments has the potential to release into the overlying water.
DGT-labile Cd was positively correlated with Cd in exchangeable and oxidizable fraction in the TGR tributary sediments.
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•B concentrations in sediments slightly increased as periodic water-level fluctuation.•Distribution of B exhibited relatively high spatial heterogeneity in TGR sediments.•Dam ...construction facilitated the sediments redistribution along the TGR area.•Small amount of B originated from anthropogenic source removing sediment size effect.•Accumulation of B in TGR sediments exhibited low potential ecological risk.
Hydropower dam construction can alter the continuity of the river flow, thereby influencing geochemical cycle of seldom monitored trace elements due to the change of hydrological regime by reservoir regulation. Here, we investigated the response of hydrological regime on migration of boron (B) in the sediments of Three Gorges Reservoir (TGR) using multiple geochemical approaches. Although B concentrations in TGR sediments increased slightly during five consecutive water seasons, the potential ecological risk exhibited relatively low. The spatial distribution patterns of B with high heterogeneity in TGR sediments were influenced by periodic water-level fluctuation. This high spatial heterogeneity significantly correlated with the distribution of fine-grain sediments, which was attributed to the change of hydrological regime (including the decrease of water flow velocity, sediment accumulation, and extended residence time of suspended fine-grain sediments). In order to remove the sediment size effect, the geochemical normalization approach was applied, and revealed that the slope of normalization curve remarkably decreased from 0.9402 to 0.3682. This indicated that a small amount of B was still accumulated in the mid- and downstream of TGR after removing the hydrological regime effect. Further source identification using geochemical baseline model and principal component analysis, exposed that this slight accumulation of B in sediments originated from the anthropogenic input (8.45%). Our findings provide a geochemical insight on the environmental impacts of reservoir operation on toxic element cycling, with potential implications for ecological assessment of hydropower worldwide.
Heart‐on‐a‐chip plays an important role in revealing the biological mechanism and developing new drugs for cardiomyopathy. Tremendous efforts have been devoted to developing heart‐on‐a‐chip systems ...featuring simplified fabrication, accurate imitation and microphysiological visuality. In this paper, the authors present a novel electroconductive and anisotropic structural color hydrogel by simply polymerizing non‐close‐packed colloidal arrays on super aligned carbon nanotube sheets (SACNTs) for visualized and accurate heart‐on‐a‐chip construction. The generated anisotropic hydrogel consists of a colloidal array‐locked hydrogel layer with brilliant structural color on one surface and a conductive methacrylated gelatin (GelMA)/SACNTs film on the other surface. It is demonstrated that the anisotropic morphology of the SACNTs could effectively induce the alignment of cardiomyocytes, and the conductivity of SACNTs could contribute to the synchronous beating of cardiomyocytes. Such consistent beating rhythm caused the deformation of the hydrogel substrates and dynamic shifts in structural color and reflection spectra of the whole hybrid hydrogels. More attractively, with the integration of such cardiomyocyte‐driven living structural color hydrogels and microfluidics, a visualized heart‐on‐a‐chip system with more consistent beating frequency has been established for dynamic cardiomyocyte sensing and drug screening. The results indicate that the electroconductive and anisotropic structural color hydrogels are potential for various biomedical applications.
An electroconductive and anisotropic structural color hydrogel by simply polymerizing non‐close‐packed colloidal arrays on super aligned carbon nanotube sheets (SACNTs) is presented. With the integration of such cardiomyocyte‐driven living structural color hydrogels and microfluidics, a visualized heart‐on‐a‐chip system with more consistent beating frequency has been established for dynamic cardiomyocyte sensing and drug screening.
•Novel embedded piezoelectric sensor for SHM of concrete structure was developed.•Influence of temperature on EMI method were studied at different frequency ranges.•The electromechanical impedance ...responds differently to load from orthotropic direction.
A kind of embedded impedance-based piezoelectric sensor was fabricated by using mixture of cement powder and epoxy resin as packaging layer. Effects of temperature and load on impedance and conductance spectra of the sensor were investigated. The results show that the baseline of conductance spectra shifts with increasing temperature, and the resonance peaks in the conductance spectra show obvious temperature dependence. The impedance spectra of the embedded sensor under external load from different direction was discussed. The results indicate that the sensor is sensitive to the initial load when the external load is parallel to the thickness direction of the sensor. When the load is along the planar direction of the sensor, the impedance spectra of the sensor show good correlation with the load variation. The root mean square deviation (RMSD) index was also employed here to intuitively indicate the impedance variation of the embedded PZT sensor under temperature and load.
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