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Copper is an attractive candidate for sensing ammonia. Here, an electrodissolution mechanism for measuring liquid-phase ammonia was developed via a novel three-dimensional rosette-like structure of copper nanoparticles (CuNPs) integrated onto carbon cloth (CuNPs/CC). A one-step hydrothermal synthetic procedure was employed to construct the metallic CuNPs with a stereo rosette-like pattern on flexible CC substrate. The morphology, composition and sensing performance of the as-prepared composite were characterised in detail. The CuNPs/CC composite showed excellent sensing performance to ammonia, which is attributed to the electrodissolution of CuNPs being promoted by ammonia to form a stabilised copper-ammonia complex. This electrochemical response occurs without the electro-oxidation of ammonia, thus avoiding the energy barrier of the N–N bond and the toxicity of N-adsorbates, which is advantageous for ammonia detection. In addition, the sensor also shows very high sensitivity to ammonia with a low detection limit, as well as good anti-interference performance, repeatability and stability. The high accuracy and precision for the quantification of ammonia concentration in a variety of real samples indicate that the CuNPs/CC composition has potential in the development of high-performance ammonia sensors. Image 1 • Novel consequences on the development of ammonia sensor. • Ideal 3D CuNPs/CC with easy preparation and good reproducibility. • A reliable electrodissolution mechanism with strong and fast response for successful application. [ABSTRACT FROM AUTHOR]

Calcium ions (Ca2+) play crucial roles as second messengers in living cells and are associated with the onset and development of chronic brain diseases, including epilepsy. Dynamic and real‐time imaging of extracellular calcium levels ([Ca2+]ex) in the brain holds great potential for identifying disease foci. Magnetic resonance imaging (MRI) is a powerful non‐invasive tool for Ca2+ imaging with unlimited depth penetration. However, current available Ca2+ MR sensors lack the sensitivity to monitor small [Ca2+]ex alterations associated with chronic brain diseases in vivo. In this study, a highly sensitive Ca2+‐dependent T2‐T1 switchable magnetic nanosensor is reported, consisting of Ca2+‐specific ligands engineered near‐paramagnetic iron oxide nanoparticles. Surface ligand modifications can be adjusted to regulate the interaction energy between sensors and Ca2+, allowing for customizable response range and sensitivity to fulfill the in vivo imaging requirements. The optimized sensors enable non‐invasive visualization of early‐stage seizure focus in mice undergoing epilepsy. [ABSTRACT FROM AUTHOR]

Ultra‐high field (UHF) magnetic resonance imaging (MRI) has emerged as a focal point of interest in the field of cancer diagnosis. Despite the ability of current paramagnetic or superparamagnetic smart MRI contrast agents to selectively enhance tumor signals in low‐field MRI, their effectiveness at UHF remains inadequate due to inherent magnetism. Here, we report a ligand‐mediated magnetism‐conversion nanoprobe (MCNP) composed of 3‐mercaptopropionic acid ligand‐coated silver‐gadolinium bimetallic nanoparticles. The MCNP exhibits a pH‐dependent magnetism conversion from ferromagnetism to diamagnetism, facilitating tunable nanomagnetism for pH‐activatable UHF MRI. Under neutral pH, the thiolate (−S−) ligands lead to short τ′m and increased magnetization of the MCNPs. Conversely, in the acidic tumor microenvironment, the thiolate ligands are protonated and transform into thiol (−SH) ligands, resulting in prolonged τ′m and decreased magnetization of the MCNP, thereby enhancing longitudinal relaxivity (r1) values at UHF MRI. Notably, under a 9 T MRI field, the pH‐sensitive changes in Ag−S binding affinity of the MCNP lead to a remarkable (>10‐fold) r1 increase in an acidic medium (pH 5.0). In vivo studies demonstrate the capability of MCNPs to amplify MRI signal of hepatic tumors, suggesting their potential as a next‐generation UHF‐tailored smart MRI contrast agent. [ABSTRACT FROM AUTHOR]

Ultra‐high field (UHF) magnetic resonance imaging (MRI) has emerged as a focal point of interest in the field of cancer diagnosis. Despite the ability of current paramagnetic or superparamagnetic smart MRI contrast agents to selectively enhance tumor signals in low‐field MRI, their effectiveness at UHF remains inadequate due to inherent magnetism. Here, we report a ligand‐mediated magnetism‐conversion nanoprobe (MCNP) composed of 3‐mercaptopropionic acid ligand‐coated silver‐gadolinium bimetallic nanoparticles. The MCNP exhibits a pH‐dependent magnetism conversion from ferromagnetism to diamagnetism, facilitating tunable nanomagnetism for pH‐activatable UHF MRI. Under neutral pH, the thiolate (−S−) ligands lead to short τ′m and increased magnetization of the MCNPs. Conversely, in the acidic tumor microenvironment, the thiolate ligands are protonated and transform into thiol (−SH) ligands, resulting in prolonged τ′m and decreased magnetization of the MCNP, thereby enhancing longitudinal relaxivity (r1) values at UHF MRI. Notably, under a 9 T MRI field, the pH‐sensitive changes in Ag−S binding affinity of the MCNP lead to a remarkable (>10‐fold) r1 increase in an acidic medium (pH 5.0). In vivo studies demonstrate the capability of MCNPs to amplify MRI signal of hepatic tumors, suggesting their potential as a next‐generation UHF‐tailored smart MRI contrast agent. [ABSTRACT FROM AUTHOR]

In this study, the hydrochemical characteristics of groundwater were assessed based on 64 shallow groundwater samples collected in the Guanzhong Basin, China, and the health risk of nitrate (NO3-) in drinking water was assessed. In addition, the spatial distributions of major water quality indicators were investigated, while bivariate plots, saturation index, and stable isotopes were used to reveal the processes controlling groundwater hydrogeochemistry. The results showed that groundwater in the study area was mostly fresh water. However, the maximum and average NO3– concentrations were 397.0 and 92.9 mg/L, respectively, indicating serious groundwater NO3– pollution. The percolation of contaminated river water exhibited considerable impacts on groundwater quality. Carbonate dissolution was the major process controlling the hydrochemical characteristics of groundwater, while human activities were responsible for the high concentrations of groundwater pollutants, especially NO3–. Evaporation fraction of groundwater in the study area revealed by stable hydrogen and oxygen isotopes ranged from 4 to 13% and 4 to 11%, respectively. High non-carcinogenic health risks of NO3– to adults and children were observed in about 46.88 and 75% of the collected groundwater samples, respectively. The risk value ranges were 0-6.00 and 0-14.06, with average values of 1.36 and 3.19, for adults and children, respectively. [ABSTRACT FROM AUTHOR]

The soil is the primary source of selenium intake for humans and animals. Investigating selenium's migration from soil to crops and the human body holds significant scientific value in assessing agroecosystems and human well-being. This study analyzes selenium levels in soils, crops, and human hair in Aksu, Xinjiang, a selenium-rich farmland, focusing on the Selenium-Crop-Hair System (SCHS). In Aksu's selenium-rich farmland, soil selenium ranged from 0.09 to 4.60 mg/kg, averaging 0.356 mg/kg. Among crops, average selenium content ranked as follows: wheat (0.084 mg/kg) > rice (0.079 mg/kg) > maize (0.065 mg/kg) > carrot (0.058 mg/kg) > walnut (0.044 mg/kg) > apple (0.042 mg/kg) > jujubes (0.039 mg/kg). Human hair displayed selenium content ranging from 0.34 to 0.57 mg/kg, averaging 0.46 mg/kg. Overall, selenium levels in soils, crops, and human hair fall within selenium-moderate to selenium-sufficient ranges. Comparatively, bioaccumulation factors (BAF) of rice/soil (0.22) and hair/soil (1.28) in Aksu surpass those in other Chinese regions, indicating higher selenium bioavailability in the northwestern, China. Rice and carrots, under intense irrigation, exhibited a strong correlation in selenium content among crops, rhizosphere soil, and background soil. Conversely, weak correlations were observed between the edible part of apples, walnuts, jujubes, wheat, maize, rhizosphere soil, and background soil. Intensively irrigated farmland showed higher selenium content in rhizosphere soil and crops compared to rainfed fields, suggesting that irrigation, potentially coupled with intercropping and residue management, may enhance selenium migration and circulation in soils. However, crop selenium content may be more influenced by biological absorption characteristics. • Northwest China has higher selenium bioavailability. • Irrigation is beneficial for the circulation of selenium in farmland. • Selenium content in root soil is controlled by cultivation mode. • The selenium content of crops depends on their biological species. [ABSTRACT FROM AUTHOR]

Herein, a novel electrochemical sensor for glucose and hydrogen peroxide (H2O2) detection was successfully developed through the use of Cu nanoflowers (CuNFs) combined with flexible carbon cloth (CC) substrate. The 3D flower‐like CuNFs in size uniformly and firmly grow on CC substrate by a facile, scalable, one‐step hydrothermal strategy. Morphology, size and surface property of the prepared CuNFs/CC were examined by SEM, EDS and TEM, respectively. The electrochemical mechanism of CuNFs/CC for glucose and H2O2 detection was investigated by cyclic voltammetry. High electrochemical performances were displayed with amperometric i‐t curves including a wide linear range from 1.0 nM to 6.0 mM for glucose and from 1.0 μM to 36.66 mM for H2O2, respectively. Good sensitivity, repeatability, and stability, as well as anti‐interference ability, the carbon cloth‐supported CuNFs will be the promising materials for fabricating practical non‐enzymatic glucose and H2O2 sensors. [ABSTRACT FROM AUTHOR]

Despite numerous advances in the field of nonenzymatic glucose detection, monitoring glucose in physiological applications is still a challenge and is mostly limited to electrode surface modification. This study proposes a simple method for electrodepositing cotton-like gold microspheres (CGMs) on a carbon cloth (CC) flexible electrode, with the potential for the functional supporting substrate to monitor glucose in a neutral environment. It was demonstrated that the voltammetric response of glucose oxidation increased with increases in glucose concentration in the 3D functional flexible substrate; moreover, the amperometric response of glucose oxidation increased over time. The results indicate that the functional flexible electrode—made of gold microspheres-based carbon cloth with a predefined geometry and pore-architecture network to promote the medium-permeation and synergetic effects between CGMs and CC—can be a suitable platform for measuring glucose variation in environments with neutral pH. This is particularly relevant because the oxygen-containing functional groups on the CC surface increase the dehydrogenation rate of glucose oxidation in neutral phosphate-buffered saline. [Display omitted] • The carbon cloth-supported CGMs were firstly fabricated and directly used as the flexible glucose sensor. • The flexible glucose sensor can be easily manufactured in 1 h and displayed long service life. • The CGMs/CC realized the detection of glucose under physiological conditions and successfully applied to sweat and blood. [ABSTRACT FROM AUTHOR]

Intercropping has gained widespread adoption among farmers due to its ability to yield higher outputs. The primary reasons behind the yield advantage of intercropping systems are the border effects. Among various factors influencing the inter-species relationship, nitrogen (N) plays a crucial role. However, yield and border effects of wheat/maize intercropping at different N levels have been poorly studied, especially under rainfed conditions with different rainfall year types. The objective of this study was to compare the contribution of different crop strips to yield at different N levels and to explore the impact of different precipitation on crop physiological characteristics and water use of intercropping systems in rainfed areas. A field experiment was conducted between 2019 and 2021 in Yangling, Shaanxi Province, adopting a two-factor design, with the main treatment as planting pattern (sole wheat; sole maize; wheat/maize intercropping), and the secondary treatment as three N levels (0, 180, 300 kg ha−1 for wheat and 0, 235, 360 kg ha−1 for maize). Results showed that, intercropping increased total yield and land productivity, with a land equivalent ratio of 1.05–1.15. The intercropping system led to increased water consumption during crop growth, however, it also exhibited a notable improvement in water use efficiency, with a 5.2–16.9% increase compared to sole wheat cultivation. During the symbiotic period, intercropping wheat showed competitive advantages, resulting in yield increments of 16.4–31.2% over the two-year period. Border row wheat contributed 63.7% of the total production, with the increase in yield mainly attributed to an increase in the number of spikes and 1000-kernel weight. On the other hand, the intercropping maize showed a competitive disadvantage during the symbiotic period. The leaf area index, net photosynthetic rate, and yield of border row maize were comparatively lower than those of inner maize. However, no significant differences were observed between the yield of inner row maize and that of sole maize. After the wheat harvest, the intercropping maize resumed growth. The growth of intercropping maize was constrained by N and moisture conditions. In 2020 (Precipitation: 572.8 mm), the yield of intercropping maize increased by 3.2% compared to sole maize under N2 treatment, but in 2021 (Precipitation: 251.4 mm), the yield of intercropping maize decreased by 1.1%− 4.3%. Wheat/maize intercropping has clear advantages in land use in the Northwest China due to the availability of more resources for wheat/maize intercropping, especially in the border rows of wheat. The recovery of late-sown crops is limited by water and nitrogen, and increasing the water and nitrogen supply of late-sown crops can better play the advantages of intercropping. This study demonstrates that the contribution of intercropping system component crops to yield, and provides practical guidance for improving the productivity of wheat/maize intercropping systems in Northwest China. • The border effects of wheat/maize strip intercropping were studied. • Border wheat rows received better light, nutrition and moisture conditions. • The border wheat contributed 63.7% of the total wheat output. • The recovery growth of maize was affected by nitrogen and precipitation. • Wheat/maize intercropping improved land productivity in Northwest China. [ABSTRACT FROM AUTHOR]

While the Healthy China strategy is being implemented, the China Geological Survey has proposed and deployed a health geological survey project, starting a new journey of health geological survey and evaluation to support and serve the construction of Healthy China. However, there are still many urgent problems to be solved in this project, such as the survey vision, the framework of the evaluation indicators, the risk identification method, and the service scopes of the potential achievements. Therefore, in this paper, a framework for health geological survey and evaluation was proposed, which includes regional health geological survey zoning and local ecological risk identification. At regional scale, the framework of indicators, grading standard, score calculation, zoning method of health geological survey, identification of beneficial and harmful health geological factors, and application of achievements were proposed. These contents were presented based on the core evaluation indicators (e.g., the chemical composition, physicochemical properties, topography, and climate of the crustal surface environment caused by geological evolution processes) and the optional evaluation indicators (e.g., sanitary condition, economic level and geo-environment). At local scale, the selection of evaluation area, workflow, risk identification and the application of achievements were proposed to avoid the ecological risks of harmful trace elements and develop beneficial health geological resources. • Proposal of the framework of health geology survey and evaluation. • Presentation of regional health geological survey zoning evaluation indicator and method. • Establishment of the criterion for ecological risk evaluation at a local scale. [ABSTRACT FROM AUTHOR]

This study aims to investigate the selenium (Se) distribution in the soils of the vast cultivated areas of Aksu Prefecture in mid-Western Xinjiang of Northwest China. The study of the origin and enrichment mechanism of Se in the soils of alluvial fans of these areas (also known as oasis areas) are of great importance for the conservation and development of Se-rich resources. Geological genetic analyses and elemental abundance comparisons confirmed that the Se-rich basement rocks (i.e., the Xiyu Group) are the primary source material of Se in the oasis farmlands. The study, carried out on samples taken along two transects that cross each other, showed that, from the peripheral to the core farmland of the investigated area, the Se concentration increases significantly, accompanied by a decrease in pH and increases in organic matter and clay particles. The peripheral farming land in Aksu showed low median Se concentration of 0.19 mg/kg that represent the regional soil background, high alkalinity (pH = 8.1–9.4), high silica content (SiO 2 = 47.8–72.0 wt%) and low organic matter content (OrgC = 0.17–0.76 wt%). The core farming land, representing the intensely cultivated farmland, showed a median Se content of 0.56 mg/kg, and is characterized by low alkalinity (pH = 7.3–8.5) and silica content (SiO 2 = 33.5–52.5 wt%), and is rich in organic matter (OrgC = 0.87–9.8 wt%). Based on the vertical soil section investigation, we found that the soil mineralogical and geochemical variations from the deep to the shallow soil layers is similar to that from the peripheral to the core farming land. Thanks to soil acidification and accumulation of organic matters and clay particles, the oasis-type farming activities transfer Se from the Se-enriched parts of the peripheral farming land and the deep soil layers to the upper soil layers of the core farming land. This Se-enrichment mechanism made the core farming land and its topsoil the most Se-rich part of the investigated area. • Basement strata are the selenium's provenance of the selenium-rich farmland. • Significant increase in selenium from the periphery to the core of the farming land. • Organic matter, clay particle, and soil acidification cause the selenium enrichment. [ABSTRACT FROM AUTHOR]