Enrichment mechanisms of Mo in soil in the karst region Guangxi, China.

Soils developed in karst regions have naturally high background values of molybdenum (Mo) due to geological factors. However, the enrichment mechanism of Mo in these soils are not fully understood, making it challenging to assess their ecological risk and utilize Mo-rich land resources. To shed light on this issue, this study collected and analyzed data from the 1:50,000 geochemical survey in Guangxi, including 536,503 sets of soil data and 3043 sets of rock data, as well as 40 sets of carbonate rock-soil from typical karst regions. The results showed that soil Mo enrichment is highly correlated with the distribution of carbonate rocks in karst regions. The carbonate rocks in these regions contain Mo ranging from 0.03 to 1.06 mg·kg-1 (with a mean of 0.22 mg·kg-1). In comparison, the soil Mo derived from carbonate rocks can reach up to 6.00 mg·kg-1 (with a mean of 2.75 mg·kg-1), representing an average enrichment of soil Mo that is 24 times higher compared to the carbonate parent rock. The enrichment of soil Mo in karst regions is primarily controlled by secondary enrichment during the weathering process of carbonate. During the insoluble residue accumulation process, the dissolution of carbonate leads to a dramatic reduction in bedrock volume, and the adsorption of clay minerals and Fe minerals in insoluble residues plays an essential role in Mo enrichment during these stages. During the soil-forming stage of the insoluble residue, most Mo leaches into the water body due to the mineral transformation of insoluble residue. Consequently, as Fe-Mn nodules in soils become more enriched with increasing weathering intensity, some Mo is absorbed and passivated by iron and manganese oxides (hydroxides). Accordingly, the contribution of Fe-Mn nodules and the degree of leaching were closely related to the enrichment of soil Mo in karst regions. This study provides insights into the enrichment mechanisms of Mo in soils developed in karst regions, which will help to evaluate their ecological risk in these environments.

Identification of high ecological risk areas with naturally high background value of soil Cd related to carbonate rocks.

The characteristics of high concentrations or high activity levels of heavy metals, especially Cd, in soils caused by the pedogenesis of rocks are attracting increased attention. Carbonate rocks and black shales often coexist during geological deposition, but the risk characteristics of heavy metals are different after their weathering into the soil. The purpose of this study was to investigate the element concentrations of a naturally high background value area, to identify patterns of different risk areas, and to make recommendations for the safe usage of farmland. The results showed that, compared with the soil in the carbonate rock area, the soil in the black shale area was more acidified and most of the heavy metal elements were leached. Based on the soil pH value and the heavy metal concentrations, an identification method for land risk areas within naturally high background values was established, and land planning was carried out using this method. The exceeding rates of Cd in rice for the preferential protection area and strict control area were 0.0 and 50.0%, respectively. Therefore, in naturally high background area, the identified lithology can apply to maximize the use of farmland resources. This method provides a basis for preliminary ecological risk screening in naturally high background value areas using the results of the soil survey. A suggestion for the prevention and control of soil pollution in areas with naturally high background values was put forward. In carbonate rock areas, the soil should be closely monitored to prevent soil acidification.

Identification of the spatial patterns and controlling factors of Se in soil and rice in Guangxi through hot spot analysis.

Selenium (Se) is essential to human health, anti-cancer, possessing antioxidant, and antiviral properties. In this study, the spatial patterns of rice Se and their varying relationship with soil Se on a regional scale were studied using hot spot analysis for the agricultural soils in Guangxi. According to the hot and cold spot maps, rice Se correlates positively with soil Se in Guangxi agricultural soils. High rice Se accompanies high soil Se in the central part of Guangxi (e.g., Liuzhou, Laibin), and low rice Se is in line with low soil Se in the western part (e.g., Baise). However, the hot spot analysis maps indicate that southwestern Guangxi exhibits a special characteristic of low rice Se with high soil Se (e.g., Chongzuo). This special pattern is strongly associated with the high concentrations of Fe2O3 (ferromanganese nodules) in the carbonate rock area. The hot spot analysis proves useful in revealing the spatial patterns of rice Se in Guangxi and identifying the hidden patterns.

Transfer mechanism and bioaccumulation risk of potentially toxic elements in soil-rice systems comparing different soil parent materials.

Although the accumulation of potentially toxic elements in soil and crops has attracted widespread attention, the characteristics of the transfer and accumulation of potentially toxic elements in soil-crop systems with different soil parent materials are still not clear. Soil and crop samples were collected from agricultural regions with different soil parent materials in Guangxi, China. This study analyzed the concentrations of Cd, Zn, and Fe in the roots, straws, and seeds of rice (Oryza sativa L.) and soils with Quaternary sediments and clastic rocks as the parent materials. The concentration of several potentially toxic elements in rice tissue from the two areas followed the order of Croot> Cstraw> Cseed. The transport capability of Cd and Zn from roots to straws is higher than straws to seeds, and Fe showed a strong capability for transport from straws to seeds. In general, the transfer capacity of potentially toxic elements in the soil-rice system in the Quaternary sediments area was stronger than that in the soil-rice system in the clastic rocks area. Soil pH and minerals, which were represented by major elements, were the main factors affecting the transfer of metals from soil to seeds. This approach could help to evaluate the bioaccumulation risk of potentially toxic elements in crops in different areas quantitatively.

Potential Ecological Risk Assessment of Heavy Metals in the Fe-Mn Nodules in the Karst Area of Guangxi, Southwest China.

We investigated the concentration of heavy metals in the Fe-Mn nodules in soils derived from the carbonate rocks of typical karst areas in Guangxi, Southwest China. Compared with the soil background values in Guangxi, heavy metals are substantially enriched in the following order: Cd (268.13) > Pb (39.46) > Cr (11.80) > Zn (8.43) > Ni (6.16) > Cu (3.65). CaCl2 extraction results indicate that heavy metals in the nodules are substantially stable, while the proportions of the metals released to the surrounding environment are extremely low (≤ 0.003%). Moreover, pH-static leaching experiments indicate that heavy metals can hardly be dissolved into the surrounding soil environment under natural conditions (pH 6-8). However, once the soil environment is acidified, heavy metals incorporated in the nodules will gradually release into the surrounding environment, thereby causing potential ecological risks.

Soil Threshold Values for Zn Based on Soil-Rice System and Health Risk Assessment in a Typical Carbonate Area of Guangxi.

Zinc (Zn) is enriched in carbonate area related to geological genesis. To ensure safety of rice, soil threshold values of Zn in soil-rice systems were assessed based on analysis of soil-rice Zn concentration in relation to human health risk. Models for the prediction of Zn concentration of early-season and late-season rice grain were accurately established on the basis of significant partial correlations between log10 (BAFs) and log10 (soil properties). The rice threshold value ranged from 10.67 to 37.90 mg/kg, which might not suitable for male and urban residents. The soil safety threshold of early-season rice and late-season rice in carbonate area ranged from 148-200 mg/kg, 119-200 mg/kg with pH below 6.5, 148-250 mg/kg, 119-250 mg/kg with pH ranging from 6.5 to 7.5; 148-300 mg/kg, 119-300 mg/kg with pH above 7.5, respectively.

Volumetric enhancement of Raman scattering for fast detection based on a silver-lined hollow-core fiber.

Fast detection and identification of chemicals are of utmost importance for field testing and real-time monitoring in many fields. Raman spectroscopy is the predominant technique in principle, but its wide application is limited on account of weak scattering efficiency. Surface Enhanced Raman Spectroscopy (SERS) technique provides a solution for signal enhancement, but may not good at fast detection due to cross contamination and bulky instruments. Hollow-core fiber-based Raman cell with long interaction length can achieve high detection sensitivity, but it also suffers from low flow rate, bulky high-pressure equipment and light coupling structure, which also restricts its application for fast detection. In order to solve those problems, we proposed a portable Raman cell, by using metal-lined hollow-core fibers (MLHCF) with large bandwidth, good field confinement, extremely large numerical aperture and arbitrary length. With our proposed fiber inserted light coupling and light reflecting method, a Raman cell of 3.1 cm in length provides nearly 50 times of signal enhancement compared with direct detection using bare fiber tip. Furthermore, the sample exchange rate could be as fast as 1 second even under normal pressure without any cross contamination. At last, we also demonstrated the underlying general mechanism of signal enhancement and summarized it as volumetric enhancement of Raman scattering (VERS). Both the experiment results and the theoretical analysis demonstrated that our device has the potential for fast online Raman detection, which also possesses high-sensitivity and high-accuracy.

Source identification and exposure risk management for soil arsenic in urban reclamation areas with high background levels: A case study in a coastal reclamation site from the Pearl River Delta, China.

Urbanization involving the excavation and reuse of arsenic-bearing geological materials may pose human health risks. We investigated the distribution and sources of soil arsenic at a coastal reclamation site in the Pearl River Delta, China, and proposed risk management strategies. Analysis of 899 soil samples revealed an average of 58.97 mg/kg arsenic, with a maximum of 1450 mg/kg, mainly in fill material obtained from a local island. Integrative analysis combining reclamation history, regional geology, and bedrock mineralogy conclusively identified hydrothermally altered arsenic-bearing sulfide minerals within extensively fractured bedrock as the primary source of arsenic. Physical weathering and anthropogenic rock blasting produced discrete arsenic-rich particles that were directly transported into soils during land reclamation and accumulated to potential hazardous levels. Oral, dermal, and inhalation pathways were identified as primary exposures for future populations. Integrated engineering and institutional controls, coupled with long-term monitoring, were recommended to mitigate risks. The results highlight the importance of identifying specific geogenic and anthropogenic sources that contribute to heavy metal enrichment of soils in reclaimed areas where native bedrock naturally contains elevated level of metals, supporting evidence-based best practices for risk management and future land use.

Characteristics and numerical simulation of chromium transportation, migration and transformation in soil-groundwater system.

Understanding chromium (Cr) migration and dispersion patterns in the soil-groundwater system is critical for the control and remediation of subsurface Cr contamination. In this study, a typical Cr-contaminated site from the Pearl River Delta (PRD) in China was simulated with a three-dimensional (3D) sandbox experiment to investigate the migration and transformation behavior of Cr. Results revealed that under the combined influence of rainfall and groundwater flow, a complex flow field favorable for 3D migration and solute dispersion was formed. The flow field characteristics were influenced by water-table depth, which in turn affected Cr behavior in the system. Moreover, downward flow field expansion under low water-table conditions led to Cr vertical migration range expansion, causing greater contamination in the deep soil. The migration process was accompanied with Cr(VI) reduction, during which approximately 75 % of the total Cr was immobilized in soils. The reactive transport model achieved a good fit for Cr retention and morphological distribution in the solid phase. The model indicates that Cr is more readily transported and dispersed with groundwater, and Cr migrated and spread downstream by 15 m during the eighth year. Therefore, managing water-table depth could be a strategy to minimize the Cr vertical migration and contamination.

Carbonate rocks as natural buffers: Exploring their environmental impact on heavy metals in sulfide deposits.

Carbonate rocks are closely related to the genesis and spatial distribution of polymetallic sulfide deposits. The natural buffering of carbonate rocks can reduce the ecological impact of heavy metals produced by mining and smelting. Ignoring the buffering effect of carbonate rocks on the heavy metals in the mine environment leads to inaccurate ecological risk assessment, wasting land resources and funds. This study investigates Cd, Zn, and Pb distribution and speciation in the water and soil-rice system in the polymetallic sulfide deposit at Daxin, Guangxi. The study aims to reveal the effects of the natural buffering of carbonate rocks on the migration and transformation of heavy metals. The results show that the water Zn and Cd concentrations decreased from 1857.0 to 0.9 mg L-1 to 0.16 and 0.001 mg L-1, respectively, from the mining area to 4 km downstream. The natural buffering of carbonate increases the water pH from 2.80 to 7.64, resulting in a tendency for Cd, Zn, and Pb to separate from the aqueous phase and enrich the sediments. Soil Cd content in the mining area reached 110.0 mg kg-1 (mean value 55.88 mg kg-1), and rice Cd seriously exceeded the maximum limit. However, the weathering of carbonate reduces the migration ability and bioavailability of Cd. Soil Cd is mainly in the Fe-Mn bound and carbonate-bound fractions, resulting in lower Cd content in downstream soils (mean value 2.73 mg kg-1). Soil CaO, tFe2O3, and Mn hindered the uptake of soil Cd by rice rendering a lower exceedance of Cd in downstream rice. Therefore, this study recommends a farmland management plan under the premise of rice Cd content and integrated soil Cd content, which ensures food safety and fully utilizes farmland resources. This result provides a scientific basis for ecological risk assessment, mine environmental protection, and management in the carbonatite sulfide mine environment.

Spatially varying relationships of soil Se concentration and rice Se concentration in Guangxi, China: A geographically weighted regression approach.

In recent years, the biogeochemical behavior and environmental impact of Selenium (Se) on soil-plant systems have received widespread attention, and traditional statistical methods reveal generally positive correlations between rice Se and soil Se. However, that initial positive relationship may have been obscured by local external factors. Using local scale data from the geochemical evaluation of land quality project, this work employed geographically weighted regression (GWR) to examine the spatial variation of rice Se (as the dependent variable) and soil Se (as the independent variable) in Guangxi. Strong and weak correlation coefficients occur between rice Se and soil Se, thereby indicating that their relationships are spatially varying. Guangxi is characterized by significantly positive correlations in most areas, with weak correlations mostly found in the south-western and central-eastern regions. Areas with weak correlation can be divided into two patterns: high soil Se with low rice Se and high rice Se with low soil Se. The unique patterns are correlated with distinct natural factors, particularly the abundance of Fe-rich soils in the carbonate area; by contrast, sandstone areas in central Guangxi may have been affected by anthropogenic activities. To reveal the spatially varying relationships at the local scale, we employed GWR, an effective tool that allowed us to identify the association between environmental variables and influencing factors and explore spatially varying relationships between them. This study breaks through the existing understanding that soil Se is completely positively correlated with rice Se for the first time, and concludes that their correlation is spatially variable, providing an effective approach for the study of complex relationships.

Transferability of heavy metal(loid)s from karstic soils with high geochemical background to peanut seeds.

Globally distributed karstic soils are characterized by the high accumulation of heavy metal(loid)s, such as Cd. Biogeochemistries and transferability of metal(loid)s in such soils are notably different from that in soils of anthropogenic pollution as evidenced by increasing studies about rice and maize. To solve the question about metal(loid) background and transferability in the system of karstic soils and crops with underground fruits, we designedly collected 246 paired soil-peanut seed samples in a world-famous karstic region in Southwestern China covering an area of 98,700 km2. The concentrations of eight regulatory metal(loid)s (Cd, As, Cr, Cu, Hg, Ni, Pb, and Zn) in soil samples exceeded current standards to different degrees, demonstrating a typical high background. However, the transferability of metal(loid)s from soils to peanut seeds is quite low, resulting in a low exceedance rate of metal(loid)s (Cd, 12.2% and Pb, 1.2%) in seeds ("seed metal(loid)s"), in accordance with the results that metal(loid)s in soils mostly distributed in the inert/residual fractions. Based on the distinct response characteristics of peanut seed metal(loid)s to soil status from rice/maize grain metals, a model was further developed for effectively predicting the concentration of Cd in peanut seeds. Collectively, this study provides a basis for the assessment of soil environmental quality and safety zoning of upland field in karst areas.

Diagnostic Performance of Vascular Permeability and Texture Parameters for Evaluating the Response to Neoadjuvant Chemoradiotherapy in Patients With Esophageal Squamous Cell Carcinoma.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is an aggressive type of cancer, associated with poor prognosis. The development of an accurate and non-invasive method to evaluate the pathologic response of patients with ESCC to chemoradiotherapy remains a critical issue. Therefore, the aim of this study was to assess the importance of vascular permeability and texture parameters in predicting the response to neoadjuvant chemoradiotherapy (NACRT) in patients with ESCC. METHODS: This prospective analysis included patients with T1-T2 stage of ESCC, without either lymphatic or metastasis, and distant metastasis. All patients underwent surgery having received two rounds of NACRT. All patients underwent dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) twice, i.e., before the first NACRT and after the second NACRT. Patients were assessed for treatment response at 30 days after the second NACRT. Patients were divided into the complete response (CR) and partial response (PR) groups based on their responses to NACRT. Vascular permeability and texture parameters were extracted from the DCE-MRI scans. After assessing the diagnostic performance of individual parameters, a combined model with vascular permeability and texture parameters was generated to predict the response to NACRT. RESULTS: In this study, the CR and PR groups included 16 patients each. The volume transfer constant (Ktrans), extracellular extravascular volume fraction (ve), and entropy values, as well as changes to each of these parameters, extracted from the second DCE-MRI scans, showed significant differences between the CR and PR groups. The area under the curve (AUC) of Ktrans, ve, and entropy values showed good diagnostic ability (0.813, 0.789, and 0.707, respectively). A logistic regression model combining Ktrans, ve, and entropy had significant diagnostic ability (AUC=0.977). CONCLUSIONS: The use of a combined model with vascular permeability and texture parameters can improve post-NACRT prognostication in patients with ESCC.

Geogenic cadmium pollution in multi-medians caused by black shales in Luzhai, Guangxi.

Cadmium (Cd) concentration was investigated in parent rocks, surrounding soil of black shales outcrop, stream water, stream sediments, paddy soil as well as rice plants. Leaching test and sequential extraction procedure were applied to evaluate Cd mobility and bioavailability in soil samples. This study aims to emphasize ecological risk of Cd induced by black shales by combining various natural medias in black shales area and control area. The black shales parent rocks have elevated Cd concentration and act as a source of Cd. The liberated Cd from black shales outcrop temporarily accumulated in the acidized surrounding soil and could arise potential adverse impacts on environment due to rainfall. Although high concentration of Cd was not detected in stream water, Cd concentrated stream sediment was a hidden toxin for surface water system. Cd in paddy soil was primarily from geogenic source and effected little by anthropogenic source. The concentration as well as mobility and bioavailability of Cd were high in paddy soil in black shales area, which lead to elevated Cd concentration in roots, shoots and grains of rice. As a result, residents in black shales area suffer increased non-carcinogenic risk of Cd via food chain.

The Preliminary Study on Procurement Biliary Convergence from Donors with Complicated Bile Duct Variant in Emergency Right Lobe Living Donor Liver Transplantation.

BACKGROUND: The incidence of biliary complications after living donor adult liver transplantation (LDALT) is still high due to the bile duct variation and necessity reconstruction of multiple small bile ducts. The current surgical management of the biliary variants is unsatisfactory. We evaluated the role of a new surgical approach in a complicated hilar bile duct variant (Nakamura type IV and Nakamura type II) under emergent right lobe LDALT for high model for end-stage liver disease score patients. METHODS: The common hepatic duct (CHD) and the left hepatic duct (LHD) of the donor were transected in a right-graft including short common trunks with right posterior and anterior bile ducts, whereas the LHD of the donor was anastomosed to the CHD and the common trunks of a right-graft bile duct and the recipient CHD was end-to-end anastomosed. RESULTS: Ten of 13 grafts (Nakamura types II, III, and IV) had two or more biliary orifices after right graft lobectomy; seven patients had biliary complications (53.8%). Later, the surgical innovation was carried out in five donors with variant bile duct (four Nakamura type IV and one type II), and, consequently, no biliary or other complications were observed in donors and recipients during 47-53 months of follow-up; significant differences (P < 0.05) were found when two stages were compared. CONCLUSION: Our initial experience suggests that, in the urgent condition of LDALT when an alternative live donor was unavailable, a surgical innovation of cutting part of the CHD trunks including variant right hepatic ducts in a complicated donor bile duct variant may facilitate biliary reconstruction and reduce long-term biliary complications.

Feasibility of liver graft procurement with donor gallbladder preservation in living donor liver transplantation.

OBJECTIVE: Cholecystectomy is routinely performed at most transplant centers during living donor liver transplantation (LDLT). This study was performed to evaluate the feasibility of liver graft procurement with donor gallbladder preservation in LDLT. METHODS: Eighty-nine LDLTs (from June 2006 to Dec 2012) were retrospectively analyzed at our hospital. The surgical approach for liver graft procurement with donor gallbladder preservation was assessed, and the anatomy of the cystic artery, the morphology and contractibility of the preserved gallbladder, postoperative symptoms, and vascular and biliary complications were compared among donors with or without gallbladder preservation. RESULTS: Twenty-eight donors (15 right and 13 left-liver grafts) successfully underwent liver graft procurement with gallbladder preservation. Among the 15 right lobectomy donors, for 12 cases (80.0 %) the cystic artery originated from right hepatic artery. From the left hepatic artery and proper hepatic artery accounted for 6.7 % (1/15), respectively. Postoperative symptoms among these 28 donors were slight, although donors with cholecystectomy often complained of fatty food aversion, dyspepsia, and diarrhea during an average follow-up of 58.6 (44-78) months. The morphology and contractibility of the preserved gallbladders were comparable with normal status; the rate of contraction was 53.8 and 76.7 %, respectively, 30 and 60 min after ingestion of a fatty meal. Biliary and vascular complications among donors and recipients, irrespective of gallbladder preservation, were not significantly different. CONCLUSIONS: These data suggest that for donors compliant with anatomical requirements, liver graft procurement with gallbladder preservation for the donor is feasible and safe. The preserved gallbladder was assessed as functioning well and postoperative symptoms as a result of cholecystectomy were significantly reduced during long-term follow-up.

Tunable ternary (N, P, B)-doped porous nanocarbons and their catalytic properties for oxygen reduction reaction.

Heteroatom (N, P, and B)-codoped nanocarbons (NPBC) with nanoporous morphology are fabricated via a facile one-step pyrolysis method and exhibit good electrocatalytic activity, durability, and selectivity for the oxygen reduction reaction (ORR) in alkaline media. The ORR activity of NPBC is better than single- (nitrogen-doped carbon (NC)) or dual-doped (nitrogen and phosphorus codoped carbon (NPC) or nitrogen and boron codoped carbon (NBC)) catalysts in terms of onset potential and current density. This synthetic approach is efficient and suitable for large-scale fabrication of metal-free carbon-based catalysts.