[Vertical Migration Characteristics and Fate of Heavy Metals from Zinc Smelting Slag in Soil Profile].

To investigate the influence of heavy metals in smelting waste residue on the quality of soil and groundwater, a simulation column experiment was conducted to study the migration characteristics of heavy metals from the leaching solution of zinc volatilizing kiln residue in the site soil profile under continuous or intermittent leaching for 90 days. The concentrations of Cd, Cu, Pb, and Zn in leachate and their accumulation, chemical fractions, and particle size distribution characteristics in the soil profile were analyzed, and the retention mechanism of heavy metals was also discussed. The results showed that the concentration of heavy metals in the soil column leachate decreased rapidly after reaching the peak at the earlier leaching stage, and the Cd concentration far exceeded the threshold limit of 0.1 mg·L-1(class Ⅳ) of the Quality Standard for Groundwater(GB/T 14848-2017), indicating that there was Cd pollution risk of groundwater. The soil profile had a great adsorption capacity for heavy metals in the waste residue. Cd, Cu, Pb, and Zn were predominately accumulated in the shallow soil depth(0-10 cm), which was 237-429, 1.25-16.2, 1.38-2.31, and 1.79-3.17 times of the content of corresponding heavy metals in the soil profile before leaching, respectively. The migration distance of heavy metals in the slag under continuous leaching was longer than that under intermittent leaching, and Cd was significantly accumulated in the deep layer of the soil column. The contribution of soil coarse particles(0.5-2.0 mm) to the total cumulative amount of Cd, Cu, and Zn was larger, whereas Pb was more prone to accumulate in the particle size of<0.25 mm. The results of BCR sequential extraction fraction showed that the accumulated Cd, Cu, and Zn in shallow soil depth were mainly present in the weak acid extraction, accounting for 62.4%-76.7%, 72.0%-95.8%, and 67.6%-85.8% of total content, respectively. The X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FTIR) analysis showed that exogenous heavy metals in slag entering the soil would not form a stable mineral phase within 90 days, and the soil hydroxyl(-OH) and carbonyl(C=O) functional groups and iron aluminum silicate oxides were the main retention factors.

[Solid-solution Partitioning Coefficients and Environmental Risk of Cd and Pb in Soil in Chang-Zhu-Tan Area].

The leaching risk of heavy metals in soil has a large spatial variability on a regional scale. Taking the Chang-Zhu-Tan area as the research object, this work studied the distribution and influencing factors of available contents and solid-solution partition coefficient (Kd) of Cd and Pb in soil with land uses and clarified the environmental risk of heavy metals in soil based on Kd values measured by CaCl2 (soil-to-water ratio, 1:0.5). The results showed that the contents of available Cd and Pb in soil followed the order of forest land>suburban farmland>urban green space>industrial green space. The average Kd of Cd in soil was 449.79 L·kg-1, and that of Pb was 27604.07 L·kg-1, indicating that the mobility of Cd in the soil was significantly higher than that of Pb. The Kd values of forest soil were significantly lower than that in the other land uses. The Kd values were mainly affected by soil pH and the total content of heavy metals in soil. Adopting the available content of heavy metals measured by CaCl2 (soil-to-water ratio, 1:10) as a dependent variable, the multiple regressions effectively predicted the Kd values of Cd and Pb in soil, with R2 values of 84.2% and 67.6%, respectively. The environmental risk assessment indicated that the leaching risk in 93.8%-96.1% of the sampling sites could be ignored, whereas a few sampling sites near factories with low pH may pose a risk to the groundwater environment. The mobility of heavy metals in soil and the distribution of pollution sources determined the leaching risk of heavy metals. The results provide a method and theoretical support for preventing the environmental risk of heavy metals in soil on a regional scale.

[Component Properties and Heavy Metal Accumulation Characteristics of Contaminated Rice Straw Biochar During Oxygen-controlled Pyrolysis].

Pyrolysis is an important technology to achieve the harmlessness and recycling of contaminated biomass. In this study, the effects of oxygen-controlled atmosphere on the component properties and heavy metal accumulation characteristics of contaminated rice straw biochar were studied. The results showed that low-oxygen pyrolysis could effectively produce biochar using contaminated rice straw and improve the stability of heavy metals in biochar. Under the nitrogen atmosphere, the yield of rice straw biochar was 29.4%-34.9%. The aromatization index (SUVA254) of dissolved organic matter (DOM) increased first and then decreased with the increase in pyrolysis temperature, whereas the fluorescent components were mainly humic-like acid substances. Meanwhile, Ca mainly existed in the form of CaCO3 in biochar. Compared with the pure nitrogen condition, the biochar yield was reduced by 5.6%-13.5% and 14.9%-15.7% under the pyrolysis atmosphere containing 10% and 20% oxygen content, respectively. Ca existed in the form of CaO in biochar, which increased the pH value of the biochar by more than 0.5 units. The oxygen of the pyrolysis atmosphere accelerated the degradation of the lignin component, resulting in the gradual decrease in SUVA254 of DOM. With the increase in oxygen content in the pyrolysis atmosphere, humic-like acid substances in DOM were transformed into fulvic-like acid substances. Under the conditions of 400℃ and a 10% oxygen-containing atmosphere, the exchangeable fractions of Cu, Cd, Pb, Ni, and As in biochar were decreased by 5.2%, 3.7%, 1.7%, 0.8%, and 0.7%, respectively, indicating that heavy metals are transformed into more stable states. The results suggested that the higher biochar yield and heavy metal stability could be obtained by introducing a proper amount of nitrogen into the air (controlling the oxygen content of approximately 10%) for pyrolysis treatment of contaminated rice straw, providing an economic and feasible technology for the achievement of harmlessness and recovery of contaminated rice straw.

[Characteristics and Risk Assessment of Heavy Metals in the Soil Around Copper Smelting Sites].

Copper smelting can cause heavy metal pollution in surrounding soil and threaten human health. This study examined the characteristics, distribution, and health risk of heavy metals in soil with different land uses around 40 copper smelting sites at home and abroad by collecting published literature data. The results showed that the mean values of ω(As), ω(Cd), ω(Cu), ω(Pb), and ω(Zn) in the soil around the copper smelting sites were 196, 10.5, 1948, 604, and 853 mg·kg-1, respectively. The order of Igeo was Cd(5.63)>Cu(3.88)>As(2.96)>Pb(2.30)>Zn(1.27), and the accumulation of Cd and Cu was the most serious. High Nemero index (NIPI) values were found in the soil around smelting sites with a long history of smelting, outdated process, and insufficient environmental protection measures. Significant correlations were found between the concentrations of heavy metals in the soil, which decreased with the sampling distance. The heavy metals mainly accumulated within 2-3 km from the smelting sites. Compared with the smelting history, scale, and process, land use type had a lower effect on soil heavy metal concentrations. The heavy metals in the soil around copper smelters may pose carcinogenic and non-carcinogenic risks on residents. The high health risks were mainly caused by As and Pb in smelting production areas, and Pb in woodland. These results may guide the risk prevention of heavy metal pollution in the soil around smelting sites.

[Potential of Intercropping Pennisetum purpureum Schum with Melia azedarach L. and Broussonetia papyrifera for Phytoremediation of Heavy-metal Contaminated Soil around Mining Areas].

In order to study the potential of intercropping Pennisetum purpureum Schum with Melia azedarach L. and Broussonetia papyrifera for phytoremediation of heavy-metal contaminated soil around mining areas, a pot experiment was conducted to investigate the effects of intercropping on plant biomass, heavy metal accumulation, dynamic changes in heavy metal content in soil solution, and response characteristics of the rhizosphere microbial community. The results indicated that the shoot biomass of P. purpureum and M. azedarach from their intercropping system (KX) was increased by 26.5% and 13.2%, respectively, and the shoot biomass of B. papyrifera from the intercropping system of P. purpureum and B. papyrifera (GX) was increased by 13.5% compared with their corresponding monoculture systems. The shoot Cd content of M. azedarach in the KX treatment was significantly increased by 24.9% (P<0.05), and their Cd and Pb accumulation in shoots were also significantly increased. The shoot contents and accumulations of Cd and Pb from P. purpureum in the GX treatment were significantly increased; however, those in B. papyrifera shoots were decreased. The total accumulations of Cd and Pb in each pot from intercropping systems were higher than that from the monoculture treatment, with that from the KX treatment being the highest at 1065 µg·pot-1. During the 150-day cultivation process, the pH value and dissolved organic carbon (DOC) content in the soil solution under the intercropping systems of KX and GX were higher than those of original soil (CK). After 150 d cultivation, the DOC contents of the soil solution under the KX and GX treatments were significantly increased by 40.5% and 33.1% in comparison with that under CK (P<0.05), respectively. Compared with those from CK and P. purpureum and B. papyrifera monoculture treatments, the Cd content in soil solution from the KX treatment was significantly decreased by 56.1%, 35.5%, and 46.5%, and that in the GX treatment was decreased by 54.5%, 33.2%, and 44.6% (P<0.05), respectively. The Shannon and Chao1 indices of rhizosphere microorganisms under the intercropping systems were significantly higher than those under CK. The number of unique OTUs in intercropping systems was significantly higher than that in CK and the M. azedarach and B. papyrifera monocultures. Intercropping improved the abundance of dominant bacteria such as Actinobacteriota and Acidobacteriota, and the abundance of Actinobacteriota increased by 31.6%, 20.9%, and 25.3% in the KX treatment and by 32.3%, 21.5%, and 25.9% in the GX treatment, respectively, in comparison with those in CK and the P. purpureum and M. azedarach monocultures. It was concluded that intercropping P. purpureum with wood plants could increase their shoot biomass and the accumulations of Cd and Pb, as well as soil environmental quality, whereas the availability and migration risk of heavy metals in soil were reduced. Moreover, the intercropping of P. purpureum and M. azedarach was more beneficial to the remediation of polymetallic-contaminated soil around mining areas.

[Effect of Butyl Xanthate on Pb2+ and Cd2+ Adsorption by Soil Around a Dressing Plant].

Flotation agents can enter the soil and water environment around mining areas through beneficiation wastewater discharge and overflow from tailings ponds. The adsorption of Pb2+ and Cd2+ on soil around a lead-zinc dressing plant was investigated in the presence of potassium butyl xanthate (PBX). Batch experiments were conducted with different initial pH, PBX, Pb2+, and Cd2+solution concentrations. The fractions of lead and cadmium were altered after treatment with different concentrations of PBX. The results showed that adsorption of Pb2+and Cd2+ on soil was seriously inhibited by PBX. When PBX concentration was 40 mg·L-1, the adsorption capacity of Pb2+ and Cd2+ decreased from 3540 mg·kg-1 and 387 mg·kg-1 to 3085 mg·kg-1 and 100 mg·kg-1, respectively. The Pb2+ and Cd2+ adsorption kinetic process was best fitted by the quasi-second-order kinetic model, which indicated that the adsorption process of Pb2+ and Cd2+ on soil was mainly chemical adsorption. The formation of a hydrophobic and insoluble complex and competitive adsorption between PBX, Pb2+, and Cd2+ on the soil surface was the main reason for reducing the adsorption capacity. The results showed that PBX could increase the mobility of Pb2+ and Cd2+ on soil. The degree of impact improved with increasing initial concentration of PBX and pH but decreased with increasing initial concentration of Pb2+ and Cd2+, and the adsorption isotherms conformed to the Freundlich isotherm. Under low PBX content (100 mg·kg-1), exchangeable and reducible cadmium contents in the soil increased, which could lead to the activation of cadmium in soil. However, the addition of PBX to the treated soil could reduce the content of exchangeable and reducible lead. As the concentration of PBX increased, the reduction effect also increased, which was related to the stronger complex stability of Pb(C4H9OCS2)2 than that of Cd(C4H9OCS2)2. The results showed that residual flotation reagents in beneficiation wastewater may increase the potential ecological risk of heavy metals such as Pb and Cd in soil, and the prevention and control of the potential ecological risk should be strengthened.

Screening of acetylcholinesterase inhibitory and antioxidant active compounds from Terminalia chebula fruits by spectrum-effect relationship and liquid chromatography-mass spectrometry analysis.

Screening and identification of active components from traditional Chinese medicines is rather challenging due to the diversity and complexity of chemical components. Herein, a comprehensive strategy based on a spectrum-effect relationship model and LC-MS analysis was developed to screen active components from Terminalia chebula fruits. The water extract of T. chebula fruits was subjected to macroporous resin column and then eluted successively with water and 30%, 50%, 70%, and 95% ethanol. The 30% ethanol eluate fractions of eighteen batches from T. chebula fruits were used for the spectrum-effect relationship study. The IC50 values for acetylcholinesterase inhibitory and 2,2-diphenyl-1-picrylhydrazyl scavenging activities were measured, LC fingerprints were established, and 15 common peaks were specified. The spectrum-effect relationship between common peaks and IC50 values was investigated by principal component analysis, gray relational analysis, partial least square and multiple linear regression. The 30% ethanol eluate fraction was further characterized by LC-MS analysis. The chromatographic peaks (Peaks 1, 2, 3, 5, 12, 14, 15) making great contributions to the efficacy were screened through a spectrum-effect relationship model, and sixteen components were further identified. The results suggested that the proposed strategy is simple and effective for acquiring active components from a complex matrix.

Cellulose filter paper immobilized α-glucosidase and its application to screening inhibitors from traditional Chinese medicine.

In this study, α-glucosidase was successfully immobilized on cellulose filter paper and further applied to screening inhibitors from traditional Chinese medicines combined with capillary electrophoresis analysis. For α-glucosidase immobilization, a cellulose filter paper was used as the carrier and grafted with amino groups by coating chitosan, then α-glucosidase was covalently bonded on the amino-modified carrier via epoxy ring-opening reaction using polyethylene glycol diglycidyl ether as the crosslinker. Several parameters influencing the enzyme immobilization were optimized and the optimal values were enzyme concentration of 4 U/mL, polyethylene glycol diglycidyl ether concentration of 1.25%, chitosan concentration of 7.5 mg/mL, immobilization pH 7.0, crosslinking time of 4 h and immobilization time of 2 h. The immobilized α-glucosidase exhibited good batch-to-batch reproducibility (RSD = 2.1%, n = 5), excellent storage stability (73.5% of its initial activity after being stored at 4°C for 15 days), and reusability (75% of its initial activity after 10 repeated cycles). The Michaelis constant of immobilized α-glucosidase and half-maximal inhibitory concentration of acarbose were calculated to be 1.12 mM and 0.38 µM, respectively. Finally, the immobilized α-glucosidase was used for screening inhibitors from 14 kinds of Traditional Chinese Medicine extracts, and Sanguisorbae Radix showed the strongest inhibitory effect on α-glucosidase.

Screening and identification of α-glucosidase inhibitors from Cyclocarya paliurus leaves by ultrafiltration coupled with liquid chromatography-mass spectrometry and molecular docking.

Cyclocarya paliurus, as an important edible and medicinal product, has shown a good prospect in the prevention of diabetes mellitus (DM). However, it is unclear which active compounds derived from C. paliurus play a significant role in inhibiting α-glucosidase activity. In present study, affinity-based screening assay was developed to screen and identify potential α-glucosidase inhibitors from C. paliurus leaves based on affinity ultrafiltration coupled with ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) and molecular docking. After being enriched by D-101 macroporous resin, five eluent fractions with different polarity were obtained and their inhibitory activities on α-glucosidase were evaluated by an enzyme inhibition assay in vitro. The result showed that 70% ethanol fraction of C. paliurus leaves exhibited remarkable α-glucosidase inhibitory activity with the IC50 value of 17.81 µg/mL. The 70% ethanol fraction was incubated with α-glucosidase and then active compounds would form enzyme-inhibitor complexes. The complexes could be separated from inactive components by the interception ability of ultrafiltration membrane under centrifugation. A total of 36 active compounds were screened from C. paliurus leaves and the chemical structures were further characterized by UPLC-QTOF-MS/MS. Furthermore, molecular docking was performed to investigate possible inhibitory mechanisms between active compounds and α-glucosidase. The docking result showed that cyclocarioside I, pterocaryoside B, arjunolic acid, cyclocarioside Z5, cypaliuruside D and cyclocarioside N could be embedded well into the active pocket of α-glucosidase, and had significant affinity interactions with critical amino acid residues by forming hydrogen bonds, hydrophobic interactions and van der Waals, and affinity energies ranged from -9.3 to -6.7 kJ/mol. The results indicated that the developed method is rapid and effective for high throughput screening of potential α-glucosidase inhibitors from complex mixtures. Moreover, C. paliurus exhibited a remarkable inhibitory activity on α-glucosidase, making it a promising candidate for the prevention of DM.

[Characteristics and Risk Assessment of Heavy Metals in Urban Soils of Major Cities in China].

The rapid urbanization in China may lead to heavy metal pollution in urban soil, threatening the health of residents. By collecting literature data published in the last 15 years, the characteristics and risks of heavy metals in the urban soils of 52 cities in China were analyzed. The results showed that the average ω(Pb), ω(Cd), ω(Cu) and ω(Zn) in the urban soils of China were 58.5, 0.49, 42.1, and 156.3 mg·kg-1, respectively, and the average Igeo values were ordered as follows Cd(1.10) > Zn(0.36) > Pb(0.28) > Cu(0.13). The high concentrations of heavy metals in the urban soils were mainly found in cities located in coastal economically developed provinces (such as Jiangsu, Zhejiang, etc.) and resource-based provinces (such as Hunan, Henan, Inner Mongolia, etc.). The cities of Kaifeng, Yangzhou, Hohhot, Taiyuan, and Xiangtan had relatively high Igeo values for heavy metals in the soils. The concentrations of heavy metals in soils from industrial areas and roadsides were significantly higher than those from residential areas and parks, suggesting that heavy traffic and developed heavy industry were the main causes of heavy metal accumulation in the urban soils. No significant correlations between the average concentrations of heavy metals in urban soil and urban economic and environmental indicators[such as permanent population, GDP, ρ (PM10), ρ(PM2.5), and SO2 emissions] were found. The concentrations of heavy metals in urban soils showed large spatial heterogeneity, and hence the average concentrations may not reflect the overall accumulation level in a city. The non-carcinogenic risks for children posed by heavy metals in urban soils were generally low, and the main risk contributor was Pb. However, the exposure to heavy metals in soils in cities with developed smelting industries is worthy of attention.

α-Glucosidase inhibitors screening from Cyclocarya paliurus based on spectrum-effect relationship and UPLC-MS/MS.

Cyclocarya paliurus is an edible and medicinal plant exhibiting significant hypoglycemic effect. However, its active components are still unclear and need further elucidation. In this research, the active components of the leaves of C. paliurus responsible for the α-glucosidase inhibitory activity were screened and identified based on a spectrum-effect relationship study in combination with ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) analysis. The 70% ethanol eluate fraction of the leaves of C. paliurus with the strongest α-glucosidase inhibitory activity was obtained after extraction and purification with macroporous resin. Their chromatographic fingerprints (15 batches) were established by UPLC analysis and 32 common peaks were specified by similarity analysis. Their IC50 values for α-glucosidase inhibition were measured by an enzymatic reaction. Several multivariate statistical analysis methods including hierarchical cluster analysis, principal component analysis, partial least square analysis and gray relational analysis were applied to explore the spectrum-effect relationship between common peaks and IC50 values, and the chromatographic peaks making a large contribution to efficacy were screened out. To further elucidate the active components of leaves of C. paliurus, the 70% ethanol eluate fraction was characterized by UPLC-MS/MS analysis, and 10 compounds were identified. This study provides a valuable reference for further research and development of hypoglycemic active components of C. paliurus.

[Adsorption Characteristics and Mechanism of Cd and Pb in Tiered Soil Profiles from a Zinc Smelting Site].

Vertically tiered soil profiles, comprising miscellaneous fill (S1), plain fill (S2), silty clay (S3), and completely weathered slate (S4), were collected from a zinc smelter site in Zhuzhou City, Hunan Province, and their Cd and Pb adsorption characteristics were examined. Static batch experiments were conducted with different initial Cd and Pb solution concentrations, at temperatures of 288-308 K and pH values of 2-6. The results showed that a pseudo first-order model could be fitted to the kinetics of Cd/Pb adsorption in these soils. The soil profiles had a large retention capacity for Cd and Pb. The Cd and Pb adsorption isotherms for these soils conformed to the Freundlich isotherm, with maximum adsorption at 298 K of 2097-4504 mg ·kg-1 for Cd and 4376-10564 mg ·kg-1 for Pb, based on the Langmuir isotherm. The adsorption capacity of Cd and Pb increased with an increase in initial pH and temperature. The Cd and Pb adsorption process were a spontaneous physical and chemical process, and the soil profiles were ranked by their Cd and Pb adsorption capacities in the following order:completely weathered slate (S4)>miscellaneous fill (S1)>silty clay (S3)>plain fill (S2). The variation in adsorption capacities resulted from the differences in physical and chemical properties of the soil, mainly Fe/Al content and cation exchange capacity. Fourier transform infrared and SEM-EDS analysis showed that the main adsorption mechanism is the exchange of Cd and Pb with Fe/Al, while -OH/C＝O sites in soils were the predominant adsorption sites for Cd and Pb. In the study area, exogenous Cd and Pb discharged by smelting activity accumulated predominantly in surface soil, and their concentration gradually decreased with depth. These results provide a scientific basis for the prevention and control of heavy metal pollution in the soil and groundwater of a smelting site.

[Effect of Calcium Magnesium Phosphate on Remediation Paddy Soil Contaminated with Cadmium Using Lime and Sepiolite].

The combined application of amendments, such as hydroxyhistidine and zeolite, can effectively reduce both the bioavailability of heavy metals in soil and the bioaccumulation of heavy metals by rice, thus improving the safety of agricultural products. In this work, the effect of calcium magnesium phosphorus fertilizer on the content of available Cd in paddy soil and Cd accumulation in various parts of rice by lime combined with sepiolite was studied using a plot experiment. The results show that calcium magnesium phosphorus fertilizer can significantly promote the remediation effect of lime combined with sepiolite. Compared with the treatment with lime combined with sepiolite, the application of calcium magnesium phosphorus fertilizer significantly decreases the available Cd content in the soil and the Cd accumulation in the brown rice. With calcium magnesium phosphorus fertilizer of 2250 kg·hm-2, Cd2+ in soil formed less soluble cadmium phosphate, the content of extractable, reducible and oxidizable Cd was reduced, and the percentage of available Cd content in the soil was significantly (P<0.05) reduced by 46.97%. Meanwhile, the Cd content in brown rice was decreased to 0.04 mg·kg-1, which is far lower than the level required by the National Standard for Food Safety (GB 2762-2017) (0.2 mg·kg-1). In addition, the production of brown rice was increased by 28.34%. Correlation analysis shows that the Cd content in rice roots, straw, and brown rice was positively correlated with the available Cd content in soil (P<0.01), and between the Cd content in brown rice and in roots and straw (P<0.01). In general, the results indicate that the available Cd content in soil was the key factor affecting the Cd content in brown rice. The application of calcium magnesium phosphorus fertilizer can improve the amendment of lime combined with sepiolite for available Cd in soil and reduce the Cd absorption of rice roots and straw so that the Cd content in brown rice is reduced. The results show that the application of calcium magnesium phosphorus fertilizer enhances the effect of reducing the Cd content in brown rice by lime combined with sepiolite. Finally, it can both meet the safety requirements of brown rice quality and increase the yield of brown rice in Cd-contaminated paddy soil.

[Mechanism of Synergistic Adsorption of Arsenic and Cadmium by Aluminium-substituted Ferrihydrites].

The synergistic process and mechanism of aluminum (Al)-substituted ferrihydrites on arsenic[As(Ⅴ)] and cadmium[Cd(Ⅱ)] were studied under laboratory conditions. The results showed that synergistic adsorption and coprecipitation of As and Cd by Al-substituted ferrihydrites was clearly affected by both the pH of solution and the order in which heavy metals were added. The solution in which As co-existed with Cd for 72 hours, at a pH of 6.0 to 6.5, the As and Cd adsorption capacity of Al-substituted ferrihydrites containing 20% Al (AF20) reached 60.9 mg·g-1 and 17.1 mg·g-1, respectively. The removal rates of As and Cd were 96.0% and 73.0%, respectively. Arsenic and Cd were synergistically adsorbed into the internal pores of AF20 particles, and the synergistic adsorption effect of AF20 on As and Cd was clear. Adding Cd to the solution containing As, for 72 hours, and with a pH of 6.1 to 6.5, the As and Cd adsorption capacity of AF20 was 58.1 mg·g-1 and 12.4 mg·g-1, respectively. The removal rates of As and Cd were 96.0% and 48.3%, respectively. Adsorption of As limited the fixation of Cd by AF20. When adding As to the solution containing Cd, for 72 hours, with a pH of 9.5 to 9.8, fixed amounts of As and Cd on AF20 were 20.9 mg·g-1 and 24.4 mg·g-1, respectively. The removal rates of As and Cd were 38.8% and 98.9%, respectively. The coprecipitation of As and Cd by AF20 was clear. The resulting insoluble As and Cd compounds distributed the Cd distribution in a sparse strip and impeded the further adsorption of As. The results show that Al-substituted ferrihydrites can synergistically adsorb and coprecipitate As and Cd in contaminated environmental media.

[Distribution and Accumulation of Cadmium in Paddy Soil and Rice Affected by Pollutant Sources Control and Improvement Measures].

The objective of this study was to determine the effect of five scenarios on the accumulation of Cd in the soil-rice system, including the return of straw to the field and the lack of the return, atmospheric deposition control, use of clean water for irrigation, and the use of lime. For the field experiments, three typical paddies were selected and divided into five plots (5 m×6 m) in Xiangtan, Zhuzhou, and Liling in the Hunan province from April to October 2016. The results showed that the application of lime can increase pH by 0.87, while the available Cd concentration in the soil was decreased by 33.7%. The accumulations of Cd in roots, stems, and brown rice were decreased by 47.9%, 46.7%, and 54.8%, respectively, with a decrease in the corresponding bioconcentration factors. Irrigating with clean water and liming tended to increase the soil pH by 0.44 and 0.49, respectively, while the available Cd concentration in the soil was decreased by 18.2% and 14.5%, respectively. The Cd concentrations in roots, stems, and brown rice were decreased by 32.6%, 24.2%, and 18.0%, and 17.6%, 11.3%, and 25.4% with decreased bioconcentration factors under both treatments (irrigating with clean water and liming). The available Cd concentration in the soil was increased by 6.1% and the Cd accumulation in the rice plants also increased with the return of straw to the soil. The bioconcentration factors of the rice plants were also increased when the paddy straw was returned to the fields. The results showed that the measures, such as the use of lime, atmospheric deposition control, use of clean water for irrigation, and lack of the return of straw to the paddy soil, should be helpful for the safe production of brown rice. The possible long-term risks associated with returning straw to the paddy field should be evaluated scientifically.

Release of cadmium in contaminated paddy soil amended with NPK fertilizer and lime under water management.

Agricultural soils contaminated with cadmium (Cd) pose a risk to receiving surface water via drainage or runoff. A 90-day laboratory incubation experiment was conducted to investigate the release characteristics and transformation of Cd from contaminated paddy soil amended with agrochemical (NPK fertilizer) and lime (L) under water management regimes of continuous flooding (F) and drying-wetting cycles (DW). The result showed that the dissolved Cd concentrations in overlying water of the fertilizer treatment under flooding (NPK+F) and drying-wetting (NPK+DW) reached up to 81.0 µg/L and 276 µg/L, and were much higher than that from the corresponding controls without NPK fertilizer addition at the end of experiment. The Cd concentration showed significantly negative correlation with overlying water pH, but positive correlation with soil redox potential and concentrations of dissolved total nitrogen, sulfate and manganese in overlying water (P < 0.05), indicating that drying-wetting cycles and N fertilizer addition may enhance soil Cd release. The Cd concentrations in overlying water from all treatments except NPK+L+F treatment exceeded the Cd threshold limit of Chinese Environmental Quality Standards for Surface Water (10 µg/L Grade V) and poses potential risk to surface water quality. Meanwhile, the proportion of Cd in the acid-soluble fraction from all incubated soil except NPK+L+F treatment increased compared to before incubation. The results indicated that continuous flooding was a reasonable water management candidate coupled with lime addition for immobilizing soil Cd.

[Intercropping Arundo donax with Woody Plants to Remediate Heavy Metal-Contaminated Soil].

A greenhouse experiment was conducted to study the potential of intercropping Arundo donax with Broussonetia papyrifera or Morus alba to remediate heavy metal-contaminated soil. The results showed that intercropping the herbaceous plant A. donax with woody plants B. papyrifera or M. alba was beneficial for plant growth on heavy metal-contaminated soil. This can effectively enhance the comprehensive enrichment capacity of heavy metals and improve soil enzyme activities. The photosynthetic pigment contents in the leaves of A. donax, B. papyrifera, and M. alba decreased along with remediation time under monoculture treatment for each plant. However, compared with 90 d cultivation, the chlorophyll-a and carotenoid contents in B. papyrifera leaves and chlorophyll-b and carotenoid contents in M. alba leaves under intercropping treatment after 270 d cultivation were only slightly changed. Furthermore, chlorophyll-a, chlorophyll-b, and carotenoid contents in M. alba leaves under intercropping treatment were significantly (P<0.05) increased by 99.1%, 177.1%, and 119.9%, respectively, compared with monoculture-treated M. alba, and the total biomass of M. alba increased significantly (P<0.05) by 26.1%. Compared with monoculture-treated A. donax, the total accumulation amounts of Pb and Zn in the shoots of combined plants was significantly (P<0.05) enhanced by 171% and 124% under intercropping treatment of A. donax with B. papyrifera. Compared with monoculture-treated M. alba and A. donax, the total accumulation amounts of As and Pb in the shoots of intercropped plants were significantly (P<0.05) enhanced by 150% and 76.5%, respectively, under intercropping treatment of A. donax with M. alba. Moreover, the fractions of As, Cd, Pb, and Zn in contaminated soil slightly changed under intercropping treatment of A. donax with B. papyrifera or M. alba, and soil urease, acid phosphatase, and total phosphatase activity was superior to part of the monoculture treatments after 270 d cultivation. The results further suggested that intercropping A. donax with B. papyrifera or M. alba could be effectively used for heavy metal-contaminated soil remediation, while simultaneously improving the biological quality in contaminated soil.

New evidence guiding extent of lymphadenectomy for esophagogastric junction tumor: Application of Ber-Ep4 Joint with CD44v6 staining on the detection of lower mediastinal lymph node micrometastasis and survival analysis.

For Siewert type II adenocarcinoma of the esophagogastric junction (AEJ), the optimal surgical approach and extent of lymph nodes dissection remain controversial. Immunohistochemistry (IHC) has been reported to be available for identifying lymph node micrometastasis (LNMM) in patients with AEJ. This was a prospective case series of patients who underwent R0 resection and lower mediastinal lymphadenectomy from January 2010 to June 2015 in Fujian Medical University Union Hospital for Siewert type II AEJ. The outcomes were analyzed retrospectively. A total of 1325 lymph nodes were collected from 49 patients, grouped into 3 groups: lower mediastinal, paracardial, and abdominal. The former 2 groups were examined by monoclonal antibodies against Ber-Ep4 and CD44v6. The incidence of LNMM in mediastinal group was 37% (18/49) for Ber-Ep4 and 33% (16/49) for CD44v6. While in routine histological diagnosis, the number of patients with the positive lymph nodes was 7 (14%). When combining IHC with histopathology (HE) staining, the incidence of positive mediastinal lymph nodes was increased to 24%, with a total number of 37 lymph nodes from 28 patients (57%). Micrometastases indicated by Ber-Ep4 and CD44v6 were associated with the depth of tumor invasion (P = 0.020 and 0.037, respectively), histopathological nodal status (P = 0.024 and 0.01, respectively), and Lauren classification (P = 0.038 and, respectively). Expression of CD44v6 and Ber-Ep4 was positively correlated (r = 0.643, P < 0.001). The 3- and 5-year survival rates for all patients were 66% and 50%, respectively. The patients with LNMM had a lower 3-year survival rate of 51%, compared to 80% from no LNMM group; 5-year survival rate was also lower in LNMM group, which is 29% versus 68% (P = 0.006) in the no LNMM group. Patients with positive Ber-Ep4 cells had a lower survival, but not statistically significant (P = 0.058). CD44v6-positive group had a significantly reduced survival (P < 0.001). In patients group with negative lower mediastinal lymph nodes, patients without LNMM obtained a significant survival benefit (P = 0.021). Our study demonstrated that routine test for LNMM is necessary for patients with negative lymph nodes. As a positive prognostic factor, thorough lower mediastinal lymphadenectomy in an invasive approach should be considered when necessary. Ber-Ep4 and CD44v6 were shown to be great markers for detecting LNMM.

Response of soil microbial activities and microbial community structure to vanadium stress.

High levels of vanadium (V) have long-term, hazardous impacts on soil ecosystems and biological processes. In the present study, the effects of V on soil enzymatic activities, basal respiration (BR), microbial biomass carbon (MBC), and the microbial community structure were investigated through 12-week greenhouse incubation experiments. The results showed that V content affected soil dehydrogenase activity (DHA), BR, and MBC, while urease activity (UA) was less sensitive to V stress. The average median effective concentration (EC50) thresholds of V were predicted using a log-logistic dose-response model, and they were 362mgV/kg soil for BR and 417mgV/kg soil for DHA. BR and DHA were more sensitive to V addition and could be used as biological indicators for soil V pollution. According to a polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, the structural diversity of the microbial community decreased for soil V contents ranged between 254 and 1104mg/kg after 1 week of incubation. As the incubation time increased, the diversity of the soil microbial community structure increased for V contents ranged between 354 and 1104mg/kg, indicating that some new V-tolerant bacterial species might have replicated under these conditions.

Phytostabilisation potential of giant reed for metals contaminated soil modified with complex organic fertiliser and fly ash: A field experiment.

An orthogonal field experiment of giant reed (Arundo donax) modified with organic complex fertiliser (OCF), and OCF and fly ash (O&F), at different planting densities was carried out in metal-contaminated soil. The available percentage of arsenic (As) and lead (Pb) in soil decreased from 8.45% to 2.19% and from 29.6% to 13.5% by OCF, respectively, and that of cadmium (Cd) was reduced from 25.3% to 6.49% by O&F. The total biomass of giant reed was 631g per individual following application of O&F in contaminated soil. The accumulation of As, Cd, and Pb in giant reed was 1.57, 4.06, and 11.25mg per individual. Urease and sucrase activity were 87.4NH4-Nµg/gd and 63.1glucosemg/gd in response to the treatments modified using OCF, while the highest dehydrogenase activity was 101 TPF (triphenyltetrazolium formazan) µg/gd in the treatments modified using O&F. Dominant bacteria (frequency>50%) were enriched with increasing planting density of giant reed. These results indicate that the phytostabilisation of metal-contaminated soil by giant reed could be improved by the application of O&F or OCF.