Complete ammonia oxidation (comammox) at pH 3-4 supports stable production of ammonium nitrate from urine.

This study developed a new process that stably produced ammonium nitrate (NH4NO3), an important and commonly used fertilizer, from the source-separated urine by comammox Nitrospira. In the first stage, the complete conversion of ammonium to nitrate was achieved by comammox Nitrospira. In this scenario, the pH was maintained at 6 by adding external alkali, which also provided sufficient alkalinity for full nitrification. In the second stage, the NH4NO3 was produced directly by comammox Nitropsira by converting half of the ammonium in urine into nitrate. In this case, no alkali was added and pH automatically dropped and self-maintained at an extremely acidic level (pH 3-4). In both scenarios, negligible nitrite accumulation was observed, while the final product of the second stage contained ammonium and nitrate at the molar ratio of 1:1. The dominance of comammox Nitrospira over canonical ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was systematically proved by the combination of 16S rRNA gene amplicon sequencing, quantitative polymerase chain reaction, and metagenomics. Notably, metagenomic sequencing suggested that the relative abundance of comammox Nitrospira was over 20 % under the acidic condition at pH 3-4, while canonical AOB and NOB were undetectable. Batch experiments showed that the optimal pH for the enriched comammox Nitrospira was ∼7, which could sustain their activity in a wider pH range from 4 to 8 surprisingly but lost activity at pH 3 and 9. The findings not only present an application potential of comammox Nitrospira in nitrogen recovery from urine wastewater but also report the survivability of comammox bacteria in acidic environments.

Prospective association of comorbid hypertension and depressive symptoms with C-reactive protein in older adults.

BACKGROUND: Hypertension and depressive symptoms often occur together in the older population, and each has been separately linked to elevated C-reactive protein (CRP). This study investigated the prospective association between comorbid hypertension and depressive symptoms and high-sensitivity CRP (hs-CRP) in a Chinese older population. METHODS: This study used data from 4978 participants aged 50 and above, who took part in two waves (2011 and 2015) of the China Health and Retirement Longitudinal Study (CHARLS). Hypertension, depressive symptoms and hs-CRP were measured. Logistic regressions adjusted for confounding variables were used to examine the association between the baseline comorbidity of hypertension and depressive symptoms and the change in hs-CRP levels. RESULTS: Hypertension and depressive symptoms did not show independent associations with an elevated level of hs-CRP. Participants with comorbid hypertension and depressive symptoms were more likely to develop a higher level of hs-CRP at follow-up (OR = 1.39, 95 % CI: 1.12-1.74) even after adjusting for covariates. Sex- and age-stratified analyses indicated that the association between the comorbidity and higher levels of hs-CRP were prone to be observed in women (OR = 1.55, 95 % CI: 1.16-2.08) and older adults (OR = 1.74, 95 % CI: 1.20-2.52). CONCLUSIONS: Comorbid hypertension and depressive symptoms is related to a higher risk of elevated hs-CRP levels. This association appears to be more pronounced among women and older adults compared to their counterparts. LIMITATION: Depression was self-reported by participants, which might be considered less unreliable than clinical diagnoses.

Development and external validation of a quantitative diagnostic model for malignant gastric lesions in clinical opportunistic screening: A multicenter real-world study.

BACKGROUND: Clinical opportunistic screening is a cost-effective cancer screening modality. This study aimed to establish an easy-to-use diagnostic model serving as a risk stratification tool for identification of individuals with malignant gastric lesions for opportunistic screening. METHODS: We developed a questionnaire-based diagnostic model using a joint dataset including two clinical cohorts from northern and southern China. The cohorts consisted of 17,360 outpatients who had undergone upper gastrointestinal endoscopic examination in endoscopic clinics. The final model was derived based on unconditional logistic regression, and predictors were selected according to the Akaike information criterion. External validation was carried out with 32,614 participants from a community-based randomized controlled trial. RESULTS: This questionnaire-based diagnostic model for malignant gastric lesions had eight predictors, including advanced age, male gender, family history of gastric cancer, low body mass index, unexplained weight loss, consumption of leftover food, consumption of preserved food, and epigastric pain. This model showed high discriminative power in the development set with an area under the receiver operating characteristic curve (AUC) of 0.791 (95% confidence interval [CI]: 0.750-0.831). External validation of the model in the general population generated an AUC of 0.696 (95% CI: 0.570-0.822). This model showed an ideal ability for enriching prevalent malignant gastric lesions when applied to various scenarios. CONCLUSION: This easy-to-use questionnaire-based model for diagnosis of prevalent malignant gastric lesions may serve as an effective prescreening tool in clinical opportunistic screening for gastric cancer.

Mathematical modeling and experimental validation of a novel Circulating Oxygenation Biofilm Equipment (COBE) for the management of decentralized wastewater treatment.

The difficulties of management were the key barriers to the promotion of decentralized wastewater treatment in remote areas. In this study, a novel decentralized Circulating Oxygenation Biofilm Equipment (COBE) and its remote management potential based on mathematical modeling were investigated. The COBE is an integrated biofilm reactor that employs drippage aeration and enables oxygenation, filtration, and effluent processes to be controlled, thus providing convenience for controlling. The model for the COBE describing drippage aeration, comprehensive ammonia-related microbes, and corncob carbon source release process was studied to uncover the impacts of operational conditions on decentralized wastewater treatment in the COBE system. The equipment regulation parameter (circulating oxygenation ratio) was found to be linearly correlated with the oxygen mass transfer coefficient. This discovery enabled highly accurate prediction of COD, NH4-N, and TN concentrations in the equipment effluent at various scenarios. The comprehensive ammonia oxidation biological model indicated that the model could duplicate the actual situation of the succession of ammonia metabolizing related microorganisms. Comammox and ammonia-oxidizing archaea (AOA) dominated ammonia metabolism in this equipment rather than conventional ammonium-oxidizing bacteria (AOB). This study could contribute to the Internet of Things system construction of decentralized wastewater treatment equipment, and provide a solution for timely decentralized equipment management in remote areas.

Multiple Hydrogen Bonding-Assisted High-Strength Hydrogel of Silica/Polyacrylamide Nanocomposite Cross-Linked with Polyethylenimine.

The nanocomposite gel system has been successfully applied as a water shutoff agent to enhance oil recovery (EOR) or for plugging to control lost circulation events. In this study, the silica/polyacrylamide nanocomposite was synthesized via in situ free radical polymerization of acrylamide (AM) monomers in the presence of silica nanoparticles. The composite was cross-linked with polyethylenimine to prepare a high-strength hydrogel. The viscosity test was conducted to determine the gelation time of the gel. Rheological measurements and sand pack breakthrough pressure tests were carried out to measure the gel strength. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and scanning electron microscopy (SEM) tests were adopted to characterize the structure and morphology of the gel. The results show that compared to polyacrylamide (PAM) gel, the gelation time of the nanocomposite gel will decrease with increasing gel elasticity modulus, and the breakthrough pressure of the nanocomposite gel is 29.82 MPa, which increased by 65%. As shown in the ATR-FTIR test, this can be attributed to the presence of multiple hydrogen bonds for the PAM molecule with both silica and quartz sand particles. In the composite gel, hydrogen bonding mainly forms between the O atoms of PAM and the H atom on the surface of silica, enhancing gel strength and elasticity modulus with more cross-linking density and less porosity. Moreover, H bonding between additional -NH2 of PAM and quartz sand particles helps improve gel plugging pressure. However, in the silica and PAM mixture gel, the H bonding of silica occupies -NH2 of PAM, which became unavailable to attach on the sand surface, reducing the breakthrough pressure by 30%, although it can enhance the rheological strength. This study suggests that in situ composite of silica in PAM can not only greatly improve gel rheological strength but also help maintain the strong adhesion of PAM molecules onto quartz sand, resulting in better plugging performance in the sand reservoir.

Shared and distinct neural correlates of first and second language morphological processing in bilingual brain.

While morphology constitutes a crucial component of the human language system, the neural bases of morphological processing in the human brain remains to be elucidated. The current study aims at exploring the extent to which the second language (L2) morphological processing would resemble or differ from that of their first language (L1) in adult Chinese-English bilinguals. Bilingual participants were asked to complete a morphological priming lexical decision task drawing on derivational morphology, which is present for both Chinese and English, when their electrophysiological and optical responses were recorded concurrently. Functional near-infrared spectroscopy (fNIRS) revealed a neural dissociation between morphological and semantic priming effects in the left fronto-temporal network, while L1 Chinese engaged enhanced activation in the left prefrontal cortex for morphological parsing relative to L2 English. In the early stage of lexical processing, cross-language morphological processing manifested a difference in degree, not in kind, as revealed by the early left anterior negativity (ELAN) effect. In addition, L1 and L2 shared both early and late structural parsing processes (P250 and 300 ~ 500 ms negativity, respectively). Therefore, the current results support a unified competition model for bilingual development, where bilinguals would primarily employ L1 neural resources for L2 morphological representation and processing.

[Potential Ecological Risk Assessment and Source Analysis of Heavy Metals in Soil-crop System in Xiong'an New District].

In order to evaluate the distribution characteristics of fluorine geochemistry in the surface soil and human health risk in Xiong'an New District, GIS spatial analysis and correlation analysis were used to analyze the depleted and enriched features and influencing factors of soil fluoride and to carry out the soil fluoride health risk assessment. The uncertainty of the health risk assessment results was studied based on the Monte Carlo stochastic simulation. The results showed that the average content of fluorine was 641 mg·kg-1, which was 1.34 times the background value of the national A-layer soil. The excess fluorine and high-grade samples accounted for more than 85%, and the overall soil fluorine content was relatively high. The average content of fluoride of the irrigation water samples was 0.85 mg·L-1, the spatial distribution characteristics of which were affected by the hydrochemical type and flow direction of shallow groundwater. The vertical spatial variation of soil fluoride, mainly affected by the vertical distribution of soil physicochemical properties such as soil organic carbon and texture, was not obvious. The depletion and enrichment of topsoil fluorine was mainly controlled by the geological background, and its spatial distribution was affected by external inputs, such as human factors (agricultural irrigation water, fertilization, and atmospheric dry and wet deposition). The soil fluoride content was significantly correlated with the iconic indicators of the geomorphological environment, including the content of Al2O3, Fe2O3, MgO, K2O, soil organic carbon (Corg.), cation exchange capacity (CEC), clay, and silt (P<0.01). The results of human health risk assessment showed that oral intake was the main exposure risk route of soil fluoride. The non-carcinogenic health risk index HQ of adults was less than 1, and the harm could be ignored. The probability of non-carcinogenic health risk exceeding the threshold for adults and children was 34.3% and 27.6%, respectively, and daily soil intake was the most sensitive parameter.

Element distribution of grading in red mud at different temperatures based on TIMA and EDS analysis.

In this paper, element distribution patterns of red mud particles with different grading temperatures were explored based on TIMA and EDS, and alkali removal performance of different particle sizes under high temperature grading was compared. The results show that non-clay phases in the particles coagulate with the clay phases of different sodium contents during stacking process, thus forming a mixture phase containing clay phase and other impurities. The potential of grading utilization of red mud is displayed by process mineralogy studies. The elements and phases of different particle sizes of red mud cannot be effectively separated by grading at room temperature. Due to high-temperature grading, red mud is divided into three particle sizes, namely, a (above 100 µm), b (38-100 µm), and c (below 38 µm), with Na2O contents of 3.25%, 2.31%, and 8.13%, respectively, decreasing to 1.00%, 0.27%, and 2.99% after alkali removal. The different elements and phases of red mud can be effectively separated by high-temperature grading, which promotes the classification of different particle sizes and the comprehensive utilization of red mud.

Design of NiS@Ni3S2/CdS heterostructure with intimate contact interface for sensitive photoelectrochemical detection of lincomycin.

Owing to their internal electric field effect and abundant photo-induced carriers, photoactive heterostructured materials are considered a feasible approach to improve the sensitivity of a photoelectrochemical (PEC) sensor. Herein, a novel NiS@Ni3S2/CdS heterostructure composite is derived from Ni-loaded zeolitic imidazolate framework (Ni-ZIF). The PEC experiments showed the NiS@Ni3S2/CdS composite exhibits superior photocurrent response than NiS@Ni3S2 and CdS. This is attributed to the fact that the type II heterojunction of NiS@Ni3S2/CdS with a tightly connected interface reduces the transport distance of carriers and facilitates electron-hole separation. Next, using the NiS@Ni3S2/CdS modified electrode, an aptamer/glutaraldehyde/chitosan/NiS@Ni3S2/CdS/ITO PEC biosensor is developed, which exhibits excellent sensitivity for lincomycin (Lin) detection with a wide linear range (0.0001 âˆ¼ 1.25 nM) and a low detection limit of 0.067 pM. The prepared sensor is further employed to monitor Lin in the actual milk. The results confirm that the prepared sensing electrode displays good selectivity, repeatability and stability.

Study on thermal insulation cement and its thermal insulation characteristics for geothermal wells.

Reducing the heat loss in wellbore is the key for efficient development of geothermal resource. It is a reliable solution to establish a long-term stable wellbore with good thermal insulation through cementing. In this paper, the cement-based composite thermal insulation material was prepared by using cement as the cementing material, hollow glass beads, foaming agent and stabilizer as main raw materials, and other conventional admixtures. Foams and hollow glass beads can introduce gas with low thermal conductivity into cement, so as to improve the thermal insulation of composite material. Foams are produced by chemical forming process, using foaming agent, which is prepared according electrochemistry and thermodynamics, and the foam stabilizer helps foam distribute in cement slurry stably and uniformly. 10-13% hollow glass beads can significantly reduce the thermal conductivity of hardened cement, without significant adverse effects on the rheology and strength of the material. The thermal conductivity of the composite thermal insulation material can be as low as 0.2998 W·(m·K)-1, which is 62% lower than that of conventional cement, while the compressive strength is 6.10 MPa, meeting the engineering requirement. A thermal-conductivity prediction method is proposed correspondingly based on Maxwell model, and the prediction error of the newly established model is within 2%. This research can provide technical support for efficient development of geothermal resources.

3D-crumpled graphitic carbon nitride achieving promoted visible-light-driven molecular oxygen activation for phenol degradation.

Boosting optical absorption and charge transfer of g-C3N4 is of great importance but a challenging task for developing metal-free high-performance photocatalyst. Herein, 3D-crumpled g-C3N4 (DCN) is synthesized through a direct top-down thermal etching strategy. The thermal exfoliation of layered bulk g-C3N4 (BCN) in air atmosphere induces partial distortion of heptazine-based g-C3N4 nanosheet, which further self-assemble into 3D-crumpled network structure. Spectroscopic and photoelectrochemical characterization demonstrate that the unique DCN can not only remarkably extend the visible-light response region to 600 nm by awakening the n-π* electron transition, but also significantly promote O2 activation for selective H2O2 generation owing to the intensified electron delocalization and charge transport ability. Thus, DCN catalyst realizes an excellent photocatalytic phenol degradation rate under visible light irradiation (0.690 h-1), far (4.4-fold) out from the BCN counterparts. This work enables synergistic optimization of optical absorption, charge transport and surface-active sites by constructing a 3D-crumpled structure, which expands the engineering toolbox of metal-free skeleton photocatalyst for developing practical and economical catalysts for environmental remediation.

Thoracic Jia-Ji electro-acupuncture mitigates low skeletal muscle atrophy and improves motor function recovery following thoracic spinal cord injury in rats.

OBJECTIVES: The goal of this study was to determine whether electro-acupuncture (EA) stimulation might protect the motor endplate, minimize muscle atrophy in the hind limbs, and enhance functional recovery of rats with spinal cord injury (SCI). METHODS: Sprague-Dawley adult female rats (n = 30) were randomly assigned into Sham, SCI, and EA + SCI groups (n = 10 each). Rats in the Sham and SCI groups were bound in prone position only for 30 min, and rats in the EA + SCI group were treated with electro-acupuncture. The EA was conducted from the first day after surgery, lasted for 30 mins, once every day for 28 consecutive days. RESULTS: EA significantly prevented motor endplate degeneration, improved electrophysiological function, and ameliorated hindlimb muscle atrophy after SCI. Meanwhile, EA upregulated Tuj-1 expression, downregulated GFAP expression, and reduced glial scar formation. Additionally, after 4 weeks of EA treatment, the serum of SCI rats exhibited a reduced inflammatory response. CONCLUSION: These findings suggest that EA can preserve the motor endplate and reduce muscular atrophy. In addition, EA has been shown to improve the function of upper and lower neurons, reduce glial scar formation, suppress systemic inflammation, and improve axon regeneration.

Temperature-Dependent Absorption of Ternary HfS2-xSex 2D Layered Semiconductors.

In this study, we present the investigation of optical properties on a series of HfS2-xSex crystals with different Se compositions x changing from 0 to 2. We used the chemical-vapor transport method to grow these layered ternary compound semiconductors in bulk form. Their lattice constants and crystal properties were characterized by X-ray diffraction, high-resolution transmission electron microscopy, and Raman spectroscopy. We have performed absorption spectroscopies to determine their optical band-gap energies, which started from 2.012 eV with x = 0, and gradually shifts to 1.219 eV for x = 2. Furthermore, we measured the absorption spectroscopies at different temperatures in the range of 20-300 K to identify the temperature dependence of band-gap energies. The band-gap energies of HfS2-xSex were determined from the linear extrapolation method. We have noticed that the band-gap energy may be continuously tuned to the required energy by manipulating the ratio of S and Se. The parameters that describe the temperature influence on the band-gap energy are evaluated and discussed.

The Sealing Effect Improvement Prediction of Flat Rubber Ring in Roller Bit Based on Yeoh_Revised Model.

In a roller bit, the flat rubber ring (FRR) often needs to apply a certain amount of compression to ensure that its rotation and static sealing surfaces can be stably sealed. For the predicted Mises stress, values smaller than the actual Mises stress due to soft single-axis compression (SAC) stress are predicted by the Yeoh (N = 3) model. To more reasonably predict stress under the static compression of the FRR in the roller bit, the sealing effect of the FRR based on the SAC contact stress and the calculated Mises stress was evaluated by the Yeoh_revised model. Based on the assumption that hydrogenated nitrile-butadiene rubber (HNBR) is isotropic and incompressible, first, we derived the fitting formulas for three types of constitutive models and the Jacobi matrix of the Yeoh_revised model and developed hyperelastic constitutive subroutines. Simultaneously, the accuracy of three models (Yeoh, Yeoh_revised and Ogden) was evaluated by the goodness of fit (R2) to data from three kinds of tensile experiment tests. The highest R2 is 0.9771 with the Yeoh_revised model, which merges the advantages of the other two fitting models and effectively improves the Yeoh model's soft property of SAC contact stress. Additionally, by measuring on-site FRR wear, the maximum Mises stress on the sealing surface calculated based on the Yeoh_revised model is about twice that of the Yeoh model, and the maximum Mises stress on the rotation contact sealing surface is higher than that on the outside (static sealing) surface, which makes the aging of the rotation surface more severe. Thus, it was demonstrated that, on the premise of ensuring FRR sealing contact stress, the Yeoh_revised model can more reasonably predict the sealing effect of the FRR to more precisely calculate Mises stress than the Yeoh model. This also contributes to FRR structure optimization to prolong the service life of the FRR in the roller bit.

Comammox Nitrospira Bacteria Are Dominant Ammonia Oxidizers in Mainstream Nitrification Bioreactors Emended with Sponge Carriers.

Complete ammonia oxidation (i.e., comammox) is a newly discovered microbial process performed by a subset of the Nitrospira genus, and this unique microbial process has been ubiquitously detected in various wastewater treatment units. However, the operational conditions favoring comammox prevalence remain unclear. In this study, the dominance of comammox Nitrospira in four sponge biofilm reactors fed with low-strength ammonium (NH4+ = 23 ± 3 mg N/L) wastewater was proved by coupling 16S rRNA gene amplicon sequencing, quantitative polymerase chain reaction (qPCR), and metagenomic sequencing. The results showed that comammox Nitrospira dominated in the nitrifying guild over canonical ammonia-oxidizing bacteria (AOB) constantly, despite the significant variation in the residual ammonium concentration (0.01-15 mg N/L) under different sets of operating conditions. This result indicates that sponge biofilms greatly favor retaining comammox Nitrospira in wastewater treatment and highlights an essential role of biomass retention in the comammox prevalence. Moreover, analyses of the assembled metagenomic sequences revealed that the retrieved amoA gene sequences affiliated with comammox Nitrospira (53.9-66.0% read counts of total amoA gene reads) were always higher than those (28.4-43.4%) related to ß-proteobacterial AOB taxa. The comammox Nitrospira bacteria detected in the present biofilm systems were close to clade A Candidatus Nitrospira nitrosa.

In Vitro and In Vivo Evaluation of Injectable Strontium-Modified Calcium Phosphate Cement for Bone Defect Repair in Rats.

Calcium phosphate cement (CPC) has been widely studied, but its lack of osteoinductivity and inadequate mechanical properties limit its application, while strontium is able to promote bone formation and inhibit bone resorption. In this study, different proportions of tristrontium silicate were introduced to create a novel strontium-modified calcium phosphate cement (SMPC). The physicochemical properties of SMPC and CPC were compared, and the microstructures of the bone cements were characterized with scanning electron microscopy assays. Then, the effect of SMPC on cell proliferation and differentiation was examined. Furthermore, local inflammatory response and osteogenesis after SMPC implantation were also confirmed in the study. Finally, a rat model of isolated vertebral defects was used to test the biomechanical properties of the cements. The results showed that SMPC has better injectability and a shorter setting time than CPC. Meanwhile, the addition of tristrontium silicate promoted the mechanical strength of calcium phosphate cement, and the compressive strength of 5% SMPC increased to 6.00 ± 0.74 MPa. However, this promotion effect gradually diminished with an increase in tristrontium silicate, which was also found in the rat model of isolated vertebral defects. Furthermore, SMPC showed a more preferential role in promoting cell proliferation and differentiation compared to CPC. Neither SMPC nor CPC showed significant inflammatory responses in vivo. Histological staining suggested that SMPCs were significantly better than CPC in promoting new bone regeneration. Importantly, this osteogenesis effect of SMPC was positively correlated with the ratio of tristrontium silicate. In conclusion, 5% SMPC is a promising substitute material for bone repair with excellent physicochemical properties and biological activity.

Tracking differentiator based back-stepping control for valve-controlled hydraulic actuator system.

Back-stepping design method is widely used in high-performance tracking control tasks As is known to all, the controller based on back-stepping design will become complex as the model order increases, which is the so called "explosion of terms" problem. In this paper, a tracking differentiator (TD) based back-stepping controller is proposed to handle the "explosion of terms" problem. Instead of calculating the derivatives of intermediate control variables through tedious analytical expressions, for the proposed method, the tracking differentiator is embedded into each recursive procedure to generate the substitute derivative signal for every intermediate control variable. As a result, the complexity of implementation procedure of back-stepping controller is significantly reduced. The discrepancies between the derivative substitutes and the real derivatives are considered. And the effects on control performances caused by the discrepancies are analyzed. In addition to giving the theoretical results and the stability proofs with Lyapunov methods, the developed controller design method is evaluated through a series of experiments with a hydraulic robot arm position serve system. The control performance of the proposed controller is verified by the experiments results.

Temperature Dependent Excitonic Transition Energy and Enhanced Electron-Phonon Coupling in Layered Ternary SnS2-xSex Semiconductors with Fully Tunable Stoichiometry.

In this study, a series of SnS2-xSex (0 ≤ x ≤ 2) layered semiconductors were grown by the chemical-vapor transport method. The crystal structural and material phase of SnS2-xSex layered van der Waals crystals was characterized by X-ray diffraction measurements and Raman spectroscopy. The temperature dependence of the spectral features in the vicinity of the direct band edge excitonic transitions of the layered SnS2-xSex compounds was measured in the temperature range of 20-300 K using the piezoreflectance (PzR) technique. The near band-edge excitonic transition energies of SnS2-xSex were determined from a detailed line-shape fit of the PzR spectra. The PzR characterization has shown that the excitonic transitions were continuously tunable with the ratio of S and Se. The parameters that describe the temperature variation of the energies of the excitonic transitions are evaluated and discussed.

[Characteristics and Origins of Heavy Metals in Soil and Crops in Mountain Area of Southern Sichuan].

Excessive heavy metals in soils and crops will affect the human living environment and health. In order to study the enrichment characteristics and causes of heavy metals in soils and crops in a mountainous area of southern Sichuan, 1699 cultivated soil samples, 30 rice seed samples, 31 corn seed samples, 15 tea samples, and 76 crop root soil samples were collected. The enrichment characteristics and origins of heavy metals in the soil were studied using mathematical statistics, principal component analysis, and correlation analysis. The enrichment characteristics of heavy metals in crops and their correlations with root soil were discussed. The results showed that the content of heavy metals in cultivated soil was higher than the national soil background value, and many sampling points exceeded the risk screening value. Among them, 770 points of Cd, 176 points of Cu, 116 points of Cr, and 106 points of Ni exceeded the standard. Combining the factor analysis results, it was found that Cd, Cr, Cu, Ni, and Zn in cultivated soil mainly originated from the geological background, and Cd was also affected by soil organic matter and pH. Meanwhile, Hg and Pb were mainly related to human activities. The results showed that the contents of heavy metals in the crops were lower than the national standards; the enrichment coefficients of heavy metals in crops were generally small, and were mainly in the following order: tea > rice > corn. The correlation analysis of the heavy metal contents in the root soil and crops showed that there was no significant correlation among them. Thus, the heavy metals in the soil generally had a high content and low activity, which did not affect the quality and safety of the three crops. However, Cu in corn and CaO in root soil, As in corn seed and Fe2O3 in root soil, and Ni in corn seed and Fe2O3 in root soil showed significant correlations, whereas As in rice seed and CaO in root soil and Hg in rice seed and MgO in root soil showed significant correlations, and no significant correlations were found in tea.

[Geochemical Survey Method of Land Quality in Land Parcel Scale City: A Case Study of the Initial Area of the Xiong'an New District].

In order to evaluate the land quality geochemical survey achievement in the service of the accurate management of urban land resources, the initial area of the Xiong'an New District as urbanization pathfinder in China is chosen as the research subject. The sample points were set by differential classification, and the spatial interpolation accuracy of the soil elements at a plot scale and a quantitative assessment of the consistency of the land plot (pattern spot) prediction evaluation were studied under the conditions of different sampling densities. The regional geochemical variation values randomly distributed on the plane can be reflected quantitatively by differential classification sampling, which can meet the basic demand of the quality attribute of a single plot (map spot) by the accurate management of urban land resources. The spatial variability of soil elements is mostly middle to moderate, and Cd, Cu, Pb, Hg, Se, N, P, and other elements of high spatial variability are affected by human industrial and agricultural production activities. Under the same sampling density, the larger the element variation coefficient, the worse the spatial interpolation accuracy. Although the interpolation accuracy of the same element index is affected by the sampling density, the increase in the sampling density could not identify the continuous component on the structure of the soil element content. The soil environment is clean, and the heavy metal content is lower than the GB15618-2018 standard. The interpolation results are basically consistent with the grading results of the measured values, while the contents of N, P, and K of the nutrient indices vary greatly, and the predicted and measured geochemical grades of the plots (map spot) differ substantially under the influence of factors such as human disturbance and spatial variability. The quantitative evaluation of the six different sampling densities indicates that the 16 points·km-2 sampling density adopted in the geochemical survey and evaluation of urban land quality can satisfy the needs of an accurate control of urban land resources in the study area and similar areas. The research can provide key technologies to support and serve the accurate management of urban land resources for geochemical surveys and the evaluation of land quality in land parcel scale cities.