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26021. 题目: Soil organic matter decomposition and carbon sequestration in temperate coniferous forest soils affected by soluble and insoluble spruce needle fractions
文章编号: N19091001
期刊: Soil Biology and Biochemistry
作者: Veronika Jílková, Kateřina Jandová, Allan Sim, Barry Thornton, Eric Paterson
更新时间: 2019-09-10
摘要: Temperate forest soils are important carbon (C) sinks, where the C-stock is largely determined by the balance of leaf inputs and losses through respiration. However, studies dealing with leaf inputs to coniferous forest soils are limited although coniferous forests are widespread through the Northern temperate zone. In this study, we focused on the effects of soluble, insoluble and whole-tissue coniferous needle fractions on soil organic matter (SOM) decomposition and C storage in soil fractions. In addition, the effect of future increased C input was tested by applying a doubled amount of the soluble fraction (whole-tissue + soluble fraction). ¹³C-labelled needles were produced from spruce seedlings in growth chambers and needle fractions were added to the coniferous forest soil in laboratory microcosms. CO₂ respired during incubation from the microcosms was partitioned into needle- and SOM-derived components. After seven months, soils were destructively harvested and analysed for C content in soil fractions and microbial community composition.The soluble, insoluble and whole-tissue fractions resulted in cumulative priming (increased SOM-derived CO₂ relative to unamended controls) of 25 ± 8%, 40 ± 1%, and 39 ± 7%, respectively. The doubled soluble-C addition caused a slightly lower priming (38 ± 2%) than the whole-tissue fraction alone. The addition of needle fractions did not significantly affect the C content of soil fractions. However, the soluble fraction retained in soil was mainly found adsorbed onto mineral particles, whereas the insoluble and whole-tissue fractions occurred mainly as free particulate organic matter or adsorbed onto mineral particles. The insoluble and whole-tissue fraction led to increased fungal abundance and decreased abundance of G⁺ bacteria and actinobacteria. All the fractions were primarily incorporated into fungal biomass after seven months suggesting that fungi were the main consumers of all needle fractions after the labile C had been depleted. When considering all the C gains and losses, the addition of all needle fractions resulted in net soil C increase. This suggests that, although the input of the coniferous needles leads to some C losses through the priming of SOM decomposition, these C losses are compensated by new C storage either in SOM fractions or microbial biomass.

26022. 题目: Improved voltammetric methodology for chromium redox speciation in estuarine waters
文章编号: N19090905
期刊: Analytica Chimica Acta
作者: Jasmin Pađan, Saša Marcinek, Ana-Marija Cindrić, Nicolas Layglon, Veronique Lenoble, Pascal Salaün, Cedric Garnier, Dario Omanović
更新时间: 2019-09-09
摘要: Chromium is a toxic element naturally present in natural waters whose chemical speciation regulates its cycling, mobility and bioavailability. We present here: 1- an improved analytical method for chromium speciation (Cr(VI) vs Cr(III)) in estuarine samples by catalytic adsorptive cathodic stripping voltammetric (cat-AdCSV) and 2- a study highlighting a significant change of redox speciation during summer and winter. Initial measurements first revealed that surface-active substances (SAS) present in estuarine samples strongly influenced the analytical determination of Cr by partially masking the Cr peak through an increase of the background current. We found that the application of a low negative accumulation potential (-1.65 V) resulted in much better voltammograms compared to those obtained using the usual accumulation potential of -1.0 V. Using humic acid (HA) as a model SAS of natural origin, we show that this negative potential clearly prevents adsorption of SAS on the Hg-electrode surface, which in turns benefits the adsorption of the in-situ formed Cr(III)-DTPA complex and the resulting signal. The optimised method was applied to determine chromium redox speciation and distribution along the 23 km long salinity gradient, well oxygenated, Krka River estuary (Croatia). Cr(VI) was found to be the dominant redox species in both summer and winter, with Cr(III) contribution being lower in summer (up to ∼30%, average of ∼5%) than in winter (up to ∼50%, average of ∼30%). In summer, lower concentrations of Cr(VI) were found in the freshwater end-member (2.5 nM) than in the seawater end-member (4-5 nM), while the opposite trend was found in winter. Hexavalent chromium exhibited a non-conservative behaviour along the salinity gradient for both seasons. Chromium predominantly exists in dissolved phase, and contribution of particles reactive Cr(III) was minor.

26023. 题目: An assessment of the tea bag index method as a proxy for organic matter decomposition in intertidal environments
文章编号: N19090904
期刊: Journal of Geophysical Research: Biogeosciences
作者: AnnaClaire R.G. Marley, Craig Smeaton, William E.N. Austin
更新时间: 2019-09-09
摘要: Intertidal wetlands capture and store carbon (C) for long periods of time, helping to reduce the concentration of CO₂ in the atmosphere. Yet the processes which govern the decomposition and subsequent long‐term storage of organic matter (OM) and C in these habitats remains poorly understood. The Tea Bag Index (TBI) uses a standardized OM (green and Rooibos tea) and has the potential to shed light on OM decomposition across habitats, including saltmarshes. Here, we apply the TBI method at two saltmarshes within the same estuary with the aim of (i) reducing the influence of climatic variables and (ii) determining the role of the environment, including the soil characteristics, in the decomposition of OM. We extended the standard (3 months) incubation period over a full year in order to investigate the longer‐term decomposition processes at each site. The initial results partially support previous studies that the early stages of decomposition (leaching of the water‐soluble fraction) is governed by climatic conditions, but may be further enhanced by tidal flushing in saltmarshes. By extending the incubation period, we observed the initiation of mid‐stage OM decomposition (Cellulose degradation) upon which the soil characteristics appear to be the dominant control. These results highlight the importance of long‐term TBI incubations to understand early‐stage OM decomposition. The relationship between tea mass (OM) loss and C loss in these intertidal environments is not straightforward and we would caution the use of the TBI as a direct universal proxy for soil C degradation in such intertidal wetlands.

26024. 题目: Effects of aquatic phototrophs on seasonal hydrochemical, inorganic, and organic carbon variations in a typical karst basin, Southwest China
文章编号: N19090903
期刊: Environmental Science and Pollution Research
作者: Ping’an Sun, Shiyi He, Yaqiong Yuan, Shi Yu, Cheng Zhang
更新时间: 2019-09-09
摘要: Karst processes play an important role in the global carbon cycle. Aquatic phototrophs can transform bicarbonate, which is mainly derived from the weathering of carbonates, into organic carbon. Carbonate mineral weathering coupled with aquatic photosynthesis can be considered a stable and durable carbon sink process. In this study, we addressed seasonal variations in water chemistry in the Lijiang River Basin, which is a typical karst basin, through a comprehensive geochemical study of the river water in four seasons. The parameters were measured in situ, including major ions and isotopes of inorganic and organic carbon. The results showed that (1) DIC was mainly derived from the weathering of carbonates; (2) the transformation from bicarbonate to organic carbon by aquatic phototrophs was evident, and the water chemistry changed, especially in spring and autumn and in the mainstream from Guilin to Yangshuo, which benefited the growth of aquatic phototrophs; and (3) the organic carbon derived from bicarbonates by aquatic phototrophs was nearly half the total organic carbon and 8% of the dissolved inorganic carbon. These results imply that aquatic phototrophs in karst basins can significantly stabilize carbon originating from carbonate rock weathering processes in karst areas.

26025. 题目: Effects of extraction conditions on the redox properties of soil organic matter (SOM) and its ability to stimulate microbial iron(III) mineral reduction by electron shuttling
文章编号: N19090902
期刊: Biogeosciences
作者: Yuge Bai, Edisson Subdiaga, Stefan B. Haderlein, Heike Knicker, and Andreas Kappler
更新时间: 2019-09-09
摘要: Soil organic matter (SOM), including humic substances (HS), is redox-active, can be microbially reduced, and transfers electrons in an abiotic reaction to Fe(III) minerals thus serving as electron shuttle. The standard procedure to extract HS from soil and separate them into humic acids (HA) and fulvic acids (FA) involves alkaline and acidic solutions potentially leading to unwanted changes in SOM chemical and redox properties. To determine the effects of extraction conditions on the redox and electron shuttling properties of SOM extracts, we prepared HS and SOM extracts from a forest soil applying either a combination of 0.1 M NaOH and 6 M HCl, or water (pH 7). Both chemical extractions (NaOH / HCl) and water extractions were done in separate setups under either oxic or anoxic conditions. Furthermore, we applied the NaOH / HCl treatment to a subsample of the water-extracted-SOM. We found that soil extraction with NaOH lead to ca. 100 times more extracted C and the extracted HS had 2–3 times higher electron exchange capacities (EEC) than SOM extracted by water. For water-extracted SOM, anoxic extraction conditions lead to about 7 times more extracted C and 1.5 times higher EEC than under oxic extraction conditions. This difference was probably due to the occurrence of microbial reduction and dissolution of Fe(III) minerals in the soil during the water extraction at neutral pH and the concomitant release of Fe(III) mineral-bound organic matter. NaOH / HCl treatment of the water-extracted SOM lead to 2 times higher EEC values in the HA isolated from the SOM compared to the water-extracted SOM itself, suggesting the chemical treatment with NaOH and HCl caused changes of redox-active functional groups of the extracted organic compounds. Higher EEC of extracts in turn resulted in a higher stimulation of microbial Fe(III) mineral reduction by electron shuttling, i.e. faster initial Fe(III) reduction rates, and in most cases also in higher reduction extents. Our findings suggest that SOM extracted with water at neutral pH should be used to better reflect environmental SOM redox processes in lab experiments and that potential artefacts of the chemical extraction method and anoxic extraction condition need to be considered when evaluating and comparing abiotic and microbial SOM redox processes.

26026. 题目: Transformation of silver ions to silver nanoparticles mediated by humic acid in darkness at ambient temperature
文章编号: N19090901
期刊: Journal of Hazardous Materials
作者: Bin Dong, Guangfei Liu, Jiti Zhou, Jing Wang, Ruofei Jin
更新时间: 2019-09-09
摘要: The conversion of silver materials in environments would impact their toxicity and risk. Previous studies have reported that silver ions (Ag⁺) could be reduced to silver nanoparticles (AgNPs) by natural organic matters (NOM) under sunlight or heating conditions. However, whether such reaction could occur in darkness at ambient temperature and the transformation mechanism were unclear. This study found that Ag⁺ at environmentally relevant concentrations (as low as 1 μg/L) could be reduced to AgNPs by Suwannee River humic acid (SRHA) in darkness at 30 °C. The reaction mechanism probed by X-ray absorption fine structure spectroscopy revealed that Ag⁺ was first bound to the carboxylic groups of SRHA to form Ag⁺-SRHA ligands, which were then reduced to metallic Ag. The increase of pH (6–9) and the coexistence of formate, acetate, carbonate, and sulfate promoted the formation of AgNPs. Besides, the formed AgNPs would coalesce to large aggregates under acidic conditions or in the presence of sulfate. These results suggest that the dark transformation of Ag⁺ to AgNPs mediated by NOM could occur in environments and are important for the better understanding of the natural origin of AgNPs.
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26027. 题目: Hierarchical porous biochar from shrimp shell for persulfate activation: A two-electron transfer path and key impact factors
文章编号: N19090806
期刊: Applied Catalysis B: Environmental
作者: Jiangfang Yu, Lin Tang, Ya Pang, Guangming Zeng, Haopeng Feng, Jiajing Zou, Jingjing Wang, Chengyang Feng, Xu Zhu, Xilian Ouyang, Jisui Tan
更新时间: 2019-09-08
摘要: Herein, hierarchical porous biochar from shrimp shell (PSS-bio) was prepared and applied for persulfate activation for 2,4-dichlorophenol removal. The pyrolysis temperature was found to play an important role in carbon structure and property modulation, where PSS-bio obtained at 800 °C (PSS-800) exhibited the fastest adsorption capacity and the best catalytic activity with the degradation rates 29 times higher than that of PSS-bio obtained at 400 °C (PSS-400). Further analysis demonstrated that hierarchical pores and carbon configuration were two key impact factors of biochar in AOP. Interestingly, the original free-radical dominated pathway in PSS-400 also changed into a non-radical one (direct two-electron transfer path) in PSS-800, whose efficiency could be somewhat disturbed by pH values, humic acid and anions regardless of their concentrations as low as 5 mM or as high as 500 mM, demonstrating its application potential for the treatment of both highly saline water and organic-rich water.

26028. 题目: Bioremediation of gaseous methyl tert-butyl ether by combination of sulfuric acid modified bagasse activated carbon-bone biochar beads and Acinetobacter indicus screened from petroleum contaminated soil
文章编号: N19090805
期刊: Chemosphere
作者: Waleeporn Pongkua, Rujira Dolphen, Paitip Thiravetyan
更新时间: 2019-09-08
摘要: Combination of sulfuric acid modified bagasse activated carbon-bone biochar beads and Acinetobacter indicus screened from petroleum contaminated soil was the best condition for gaseous methyl tert-butyl ether (MTBE) removal. It was found that H₂SO₄ modified bagasse AC in powder form had higher adsorption capacity (989.33 mg g⁻¹) than that in bead form (1.94 mg g⁻¹). In addition, bone biochar in powder form (3.51 mg g⁻¹) also had higher adsorption capacity than that in bead form (1.63 mg g⁻¹). This was the fact that material beads contained high moisture content that inhibited the penetration of gaseous MTBE into the material. And a mixed material of H₂SO₄ modified bagasse AC-bone biochar beads had the highest adsorption capacity (2.22 mg g⁻¹) compared to individual H₂SO₄ modified bagasse AC beads (1.94 mg g⁻¹) and bone biochar beads (1.63 mg g⁻¹) due to a mixed material had more rough surface and high surface area on its material. So, gaseous MTBE can penetrate through this material more easily. Although the maximum adsorption capacity of H₂SO₄ modified bagasse AC in powder form was the highest but microorganism cannot sustain and survive in this form for a long time. Therefore, the material beads were more suitable for microorganism to grow and degrade gaseous MTBE. Microorganism can degrade MTBE and caused no secondary wastes. Moreover, A. indicus was a novel strain for MTBE removal that has not been previously reported. Therefore, a combination of A. indicus-mixed material beads was a good choice for MTBE removal in a biofilter system.
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26029. 题目: Feeding behavior of the ocypodid crab Macrophthalmus japonicus and its effects on oxygen-penetration depth and organic-matter removal in intertidal sediments
文章编号: N19090804
期刊: Estuarine, Coastal and Shelf Science
作者: Bon Joo Koo, Sung-Han Kim, Jung-Ho Hyun
更新时间: 2019-09-08
摘要: This study examined the poorly understood feeding behavior of the ocypodid crab Macrophthalmus japonicus in the field to explore its effects on oxygen-penetration depth (OPD) and organic-matter removal from intertidal sediments. An in situ investigation was conducted on an upper mud flat in the mouth of the Han River estuary, on the western coast of Korea. The behavior of M. japonicus and variation in the OPD within its habitat were surveyed and contents of organic materials such as organic carbon (OC), organic nitrogen (ON) and δ¹⁵N in its feeding pellets were compared as contrasted with non-feeding sediments during the daytime ebb in summer. We continuously recorded the surface activity of the crab during two main feeding periods and during a resting period, when the crabs remain immobile on the surface. Feeding periods exceeded 1 h; crabs fed on sediments more actively during the first feeding period (45 pseudo-pellets individual⁻¹ h⁻¹) than during the second feeding period (19 pseudo-pellets individual⁻¹ h⁻¹). The feeding period duration increased as body size decreased. Adult crabs devoted more of their time to basking in sunlight to dry their bodies, whereas young crabs spent most of their time feeding. Crab feeding activity on the surface generally enhanced the OPD. Conversely, OPD decreased during basking, when most crabs were immobile. Crab feeding greatly altered sediment geochemistry in the intertidal flat. In feeding pellets, OC and ON concentrations decreased to 55% and 60%, respectively, of those in non-feeding sediments. OC and ON were removed at rates of 1.89 mmol C m⁻² h⁻¹ and 0.24 mmol N m⁻² h⁻¹, respectively. The removal rate of OC by crab feeding was three-fold higher than that of OC mineralization by diffusive oxygen uptake (average: 0.56 mmol C m⁻² d⁻¹) and was comparable with the rate of anaerobic carbon mineralization (1.74–3.83 mmol m⁻² h⁻¹) in this region. The increase in the C/N ratio (10.6%–12.5%) and decrease in δ¹⁵N (7.21‰–5.99‰) in feeding pellets compared with non-feeding sediments indicate that M. japonicus removed N more selectively to meet requirements. These results imply that in situ crab activity significantly influenced OC and ON cycles; therefore, it is necessary to consider processes such as macroinvertebrate production and consumption when evaluating the purification function of intertidal sediments.

26030. 题目: Combination of humic acid and clay reduce the ecotoxic effect of TiO₂ NPs: A combined physico-chemical and genetic study using zebrafish embryo
文章编号: N19090803
期刊: Science of The Total Environment
作者: Krupa Kansara, Ashutosh Kumar, Ajay S. Karakoti
更新时间: 2019-09-08
摘要: The series of breakthroughs that have occurred within the realm of nanotechnology have been the source of several new products and technological interventions. One of the most salient examples in this regard is the widespread employment of titanium dioxide (TiO₂) nanoparticles across a range of consumer goods. Given that waste is generated at every stage of the consumer-product cycle (from production to disposal), many items with TiO₂ nanoparticles are likely to end up being discarded into water bodies. In order to understand the interaction of TiO₂ NPs with aquatic ecosystem, the ecological fate and toxicity of TiO₂ NPs was studied by exposing zebrafish embryos to a combination of abiotic factors (humic acid and clay) to assess its effect on the development of zebrafish embryos. The physiological changes were correlated with genetic marker analysis to holistically understand the effect on embryos development. Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to analyze the interaction energy between TiO₂ NPs and natural organic matter (NOM) for understanding the aggregation behavior of engineered nanoparticles (ENPs) in media. The study revealed that combination of HA and clay stabilized TiO₂ NPs, compared to bare TiO₂ and HA or clay alone. TiO₂ NPs and TiO₂ NPs + Clay significantly altered the expression of genes involved in development of dorsoventral axis and neural network of zebrafish embryos. However, the presence of HA and HA + clay showed protective effect on zebrafish embryo development. The complete system analysis demonstrated the possible ameliorating effects of abiotic factors on the ecotoxicity of ENPs.
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26031. 题目: Molecular Composition of Hydrothermal Liquefaction Wastewater from Sewage Sludge and Its Transformation during Anaerobic Digestion
文章编号: N19090802
期刊: Journal of Hazardous Materials
作者: Shilai Hao, Shuang Ren, Nan Zhou, Huihui Chen, Muhammad Usman, Chen He, Quan Shi, Gang Luo, Shicheng Zhang
更新时间: 2019-09-08
摘要: Anaerobic digestion (AD) has shown potential to convert hydrothermal liquefaction wastewater (HTLWW) into biogas in previous studies. However, the identification of refractory components and further insights into the molecular transformations of organics in HTLWW are essential for developing more efficient AD processes. In this study, two HTLWWs were obtained from the temperature-derived hydrothermal liquefaction of sewage sludge at 170 ℃ and 320 ℃. Their molecular compositions, as well as their modifications in the subsequent AD process, were characterized using a suite of advanced molecular tools. The dissolved organic matter (DOM) in the high temperature-derived HTLWW was lower in molecular weight, less saturated, less oxidized, and enhanced in nitrogenous substances. During the AD process, most of the volatile compounds and low molecular weight (LMW) neutrals were removed, while biopolymers were the most refractory. Carboxylic-rich alicyclic molecules (CRAM), particularly those containing 3 to 5 N for low temperature-derived DOM and 1 to 3 N for high temperature-derived DOM, were resistant to anaerobic biodegradation. Meanwhile, compounds with fewer nitrogens and more carboxyl groups were preferentially produced. This molecular characterization of HTLWW-derived DOM and examination of its transformation during AD will contribute to the development of efficient methods for HTLWW treatment in the future.

26032. 题目: Facile inverse micelle fabrication of magnetic ordered mesoporous iron cerium bimetal oxides with excellent performance for arsenic removal from water
文章编号: N19090801
期刊: Journal of Hazardous Materials
作者: Zhipan Wen, Jun Lu, Yalei Zhang, Gang Cheng, Shengnan Huang, Jin Chen, Rui Xu, Yin-an Ming, Yingru Wang, Rong Chen
更新时间: 2019-09-08
摘要: In this study, magnetic ordered mesoporous Fe/Ce bimetal oxides (OMICs) were successfully synthesized via the modified sol-gel-based inverse micelle method. The textural/structure properties, surface chemistry and adsorption behavior of OMICs could be easily adjusted by using the calcination temperature. The sintering of samples would decrease the surface area, while expand the pore and crystallite size, which resulted in the formation of highly ordered inner-connected structure. Compared with pure mesoporous iron oxides (MI) and mesoporous cerium oxides (MC), this ordered mesoporous iron-cerium bimetal oxides (OMIC-3, 450 ℃) exhibited remarkable arsenic adsorption performance. The maximum adsorption capacities of As(III) and As(V) for OMIC-3 were 281.34 and 216.72 mg/g, respectively, and both As(III)/As(V) adsorption kinetics were well described by the pseudo-second order. The ionic strength and coexisting ions (except SiO₃^2- and PO₄^3-) did not affect arsenic removal, while humic acid (HA) significantly influenced on the arsenic removal even at a lower concentration. The adsorption mechanism study revealed that both the surface charge and surface M-OH groups of OMIC-3 were played the key roles in arsenic removal. The reusable property suggested that this magnetic OMIC-3 was a promising excellent adsorbent for decontamination of arsenic-polluted (especially As(III)-polluted) wastewater.
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26033. 题目: Complexation of Arsenite, Arsenate, and Monothioarsenate with Oxygen-Containing Functional Groups of Natural Organic Matter: An XAS Study
文章编号: N19090703
期刊: Environmental Science & Technology
作者: Ashis Biswas, Johannes Besold, Carin Sjöstedt, Jon Petter Gustafsson, Andreas C. Scheinost, Britta Planer-Friedrich
更新时间: 2019-09-07
摘要: Arsenic (As) is reported to be effectively sorbed onto natural organic matter (NOM) via thiol coordination and polyvalent metal cation-bridged ternary complexation. However, the extent of sorption via complexation with oxygen-containing functional groups of NOM is poorly understood. By equilibrating arsenite, arsenate, and monothioarsenate with purified model-peat, followed by As K-edge X-ray absorption spectroscopic analysis, this study shows that complexation with oxygen-containing functional groups can be an additional or alternative mode of As sorption to NOM. The extent of complexation was highest for arsenite, followed by monothioarsenate and arsenate. Complexation was higher at pH 7.0 compared to 4.5 for arsenite and arsenate and vice versa for monothioarsenate because of partial transformation to arsenite at pH 4.5. Modeling of the As K-edge extended X-ray absorption fine structure data revealed that As···C interatomic distances were relatively longer in arsenate- (2.83 ± 0.01 Å) and monothioarsenate-treated peat (2.80 ± 0.02 Å) compared to arsenite treatments (2.73 ± 0.01 Å). This study suggests that arsenite was predominantly complexed with carboxylic groups, whereas arsenate and monothioarsenate were complexed with alcoholic groups of the peat. This study further implies that in systems, where NOM is the major sorbent, arsenate and monothioarsenate can have higher mobility than arsenite.

26034. 题目: As(V) removal using biochar produced from an agricultural waste and prediction of removal efficiency using multiple regression analysis
文章编号: N19090702
期刊: Environmental Science and Pollution Research
作者: Sneh Lata, Roshan Prabhakar, Asok Adak, Sukha Ranjan Samadder
更新时间: 2019-09-07
摘要: Arsenic contamination in drinking water is a matter of concern for many countries. An efficient and low-cost solution for this hazard is essentially needed on urgent basis. Therefore, in this study, banana pith (an agricultural waste) was used for biochar production and later it was modified with iron and applied for arsenic adsorption from aqueous solution. Produced biochar was characterized for proximate, ultimate, and surface analyses. Interestingly, after iron impregnation, the surface area of biochar increased (31.59 m²/g) by nearly 8 times. Morphological analysis showed that iron particles firmly held within the pores after impregnation. Arsenate (As(V)) adsorption behavior of iron-impregnated banana pith biochar was evaluated through a batch study by considering various parameters like dose, concentration, pH, temperature, and competing anions. Compared to impregnated biochar, raw biomass and its biochar showed a lesser affinity for arsenate in aqueous solution. The adsorption isotherm of As(V) on banana pith biochar was covered in the temperature range of 298 to 318 K, and kinetic data of adsorption was experimentally generated at 298 K. Langmuir model for the sorption isotherms and pseudo-second-order kinetic model for the sorption kinetics represented the experimental data. The thermodynamic study showed negative Gibb’s free energy (− 46.88 kJ/mol at 298 K, − 48.58 kJ/mol at 308 K, − 50.73 kJ/mol at 318 K) that suggested spontaneity of the adsorption process. Negative enthalpy (ΔH° = − 10.55 kJ/mol) showed exothermic nature of adsorption of arsenic, while negative entropy (ΔS° = 0.123 kJ/mol.K) suggested enthalpy-driven adsorption process. Mechanism of arsenic adsorption onto iron-impregnated banana pith biochar has also been discussed in detail. Based on the experimental observation, a predictive model for arsenate removal has been developed in this study. The findings of the present study elucidated that iron-impregnated banana pith biochar can be used as a low-cost adsorbing material for As(V) from aqueous solutions.

26035. 题目: A new incubation and measurement approach to estimate the temperature response of soil organic matter decomposition
文章编号: N19090701
期刊: Soil Biology and Biochemistry
作者: Yuan Liu, Nianpeng He, Li Xu, Jing Tian, Yang Gao, Shuai Zheng, Qing Wang, Xuefa Wen, Xingliang Xu, Kuzyakov Yakov
更新时间: 2019-09-07
摘要: A reliable and precise estimate of the temperature sensitivity (Q₁₀) of soil organic matter (SOM) decomposition is critical to predict feedbacks between the global carbon (C) cycle and climate change. In this study, we first summarize two commonly used approaches for estimating Q₁₀ (Approach A: constant temperature incubation and discontinuous measurements, CDM model; Approach B: varying temperature incubation and discontinuous measurements, VDM model). We then introduced a newly developed approach (Approach C, VCM model) that combines rapidly varying temperature incubations and continuous measurements of SOM decomposition rates (R_s) that may be more realistic and suitable for Q₁₀ estimation, especially for large scale estimation. Then, we conducted a 26-day incubation experiment using three different soils to compare the performance of these three approaches for estimating Q₁₀ using R² and P-values as indicators. Our results demonstrate that the fitting goodness of the exponential model was consistently higher for Approach C, with higher R² values, lower confidence intervals, and lower P-values in almost all cases compared with Approaches A and B. Furthermore, results showed that Approaches A and B underestimated the Q₁₀ value by 9.5–13% and 2.9–5.7%, respectively, in three different soils throughout the entire incubation period. Compared with traditional commonly used methods, the newly developed Approach C (VCM model) provides a more accurate and rapid estimation of the temperature response of SOM decomposition and can be used for large-scale estimation of Q₁₀.

26036. 题目: Dissolved organic carbon dynamics in the East China Sea and the northwest Pacific Ocean
文章编号: N19090614
期刊: Ocean Science
作者: Ling Ding, Tiantian Ge, Xuchen Wang
更新时间: 2019-09-06
摘要: Oceanic dissolved organic carbon (DOC) represents one of the largest carbon reservoirs on Earth, and its distribution and biogeochemical cycles play important roles in carbon cycling and other biogeochemical processes in the ocean. We report the distribution and concentrations of DOC for water samples collected from the shelf-edge and slope regions in the East China Sea (ECS) and the Kuroshio Extension (KE) in the northwestern North Pacific during two cruises in 2014–2015. The DOC concentrations were 45–88 µM in the ECS and 35–65 µM in the KE. In addition to biological processes that are estimated to account for 7 % and 8 %–20 % in shaping the DOC distribution in the ECS and KE regions, respectively, the DOC distribution is largely controlled by hydrodynamic mixing of different water masses. By comparing the DOC results with dissolved inorganic carbon (DIC) and dissolved inorganic radiocarbon (Δ14C-DIC) measured from the same water samples, we further demonstrate that the intrusion of the Kuroshio Current could dilute the DOC concentrations at stations in the outer shelf and slope regions of the ECS. The concentrations of DOC in the KE were significantly lower in surface waters than in the ECS, and a relatively low and stable DOC level (∼40 µM) was found in deep water (below 1500 m) at all stations. Based on the previously reported DIC and Δ14C-DIC values for the stations, the observed spatial variations of DOC in the upper 700 m among the stations in the KE were mainly influenced by mixing of the two water masses carried by the Kuroshio and Oyashio, the two dominant western boundary currents in the region. The hydrodynamic processes are thus important factors in the distribution and dynamics of DOC in the KE region.

26037. 题目: Dissolved organic carbon leaching from montane grasslands under contrasting climate, soil and management conditions
文章编号: N19090613
期刊: Biogeochemistry
作者: Jin Fu, Rainer Gasche, Na Wang, Haiyan Lu, Klaus Butterbach-Bahl, Ralf Kiese
更新时间: 2019-09-06
摘要: Grasslands are thought to be more vulnerable than many other ecosystems to climate change since their soils are characterized by high organic carbon contents and warming in montane regions is twice the global average rate. Despite these expected vulnerabilities, little is known about how climate change and management influence dissolved organic carbon (DOC) losses from montane grasslands and how relevant these losses are compared to other ecosystem carbon fluxes. In this study, 36 large (1 m², 140 cm height) grassland lysimeters were filled with undisturbed soil monoliths and operated at three different sites located along an elevational gradient from 860 to 600 m a.s.l. From 2012 to 2014, changes in soil DOC concentrations and DOC leaching losses were quantified under different climate, soil and management (intensive vs. extensive; i.e., differing in the frequency of cutting and manuring events) conditions. The annual DOC leaching losses ranged between 6.6 and 27.5 kg C ha⁻¹ year⁻¹, which was only a minor (< 3%) component of the net ecosystem carbon exchange. DOC leaching losses were not affected by management intensity but were positively correlated with soil organic carbon in the top soil. Climate warming (~ + 2 °C) significantly increased DOC leaching rates for intensive (+ 43%) and extensive management (+ 58%), but only if simultaneous reductions in leachate were moderate. The DOC concentrations in soil water significantly decreased with soil depth. In 10, 30 and 50 cm DOC concentration were positively correlated with aboveground biomass production, indicating that plants play a crucial role in topsoil DOC dynamics. However, this relationship did not occur for DOC in soil water collected at 140 cm, suggesting that adsorption and degradation processes in the subsoil ultimately determine the dynamics of DOC losses below the rooting zone.

26038. 题目: Photocatalytic behavior of biochar-modified carbon nitride with enriched visible-light reactivity
文章编号: N19090612
期刊: Chemosphere
作者: Lirong Meng, Wenhua Yin, Shengsen Wang, Xiaoge Wu, Jianhua Hou, Weiqin Yin, Ke Feng, Yong Sik Ok, Xiaozhi Wang
更新时间: 2019-09-06
摘要: Ultra-thin layered structures and modified bandgaps are two efficient strategies to increase the photocatalytic performance of various materials for the semiconductor industry. In the present study, we combined both strategies in one material to form carbon-doped graphitic carbon nitride (g-C₃N₄) nano-layered structures by the method of melamine thermal condensation, in the presence of different mass ratios of biochar. The characterization showed that the composite with the best ratio retained the g-C₃N₄ polymeric framework and the bond with g-C₃N₄. The biochar was established via π–π stacking interactions and ether bond bridges. The π-conjugated electron systems provided from biochar can elevate charge separation efficiency. The ultra-thin structure also curtailed the distance of photogenerated electrons migrating to the surface and enlarge specific surface area of materials. The presence of carbon narrowed the bandgap and increased light absorption at a wider range of wavelengths of g-C₃N₄. The biochar/melamine ratio of 1:15 presented the best performance, 2.8 and 5 times faster than g-C₃N₄ degradating Rhodamine and Methyl Orange, respectively. Moreover, the catalyst presented a good stability for 4 cycles. In addition to that, biochar from waste biomass can be considered a sustainable, cost-effective, and efficient option to modify g–C₃N₄–based photocatalysts.

26039. 题目: Residual effects of biochar and phosphorus on growth and nutrient accumulation by maize (Zea mays L.) amended with microbes in texturally different soils
文章编号: N19090611
期刊: Chemosphere
作者: Mazhar Rafique, Ibrahim Ortas, Muhammad Rizwan, Hassan Javed Chaudhary, Ali Raza Gurmani, Muhammad Farooq Hussain Munis
更新时间: 2019-09-06
摘要: The purpose of study was to examine the residual effects of two types of biochar amendments, two phosphorus (P) fertilizer levels, phosphorus solubilizing bacteria (PSB) and arbuscular mycorrhizal fungs (AMF) on plant growth, nutrients absorption and root architecture of Zea mays L. in texturally different soils. Biochar signficantly increased nutrients absorption and plant biomass production with P-fertilization and microbial inoculantion. Texturally different soils enhanced the plant biomass and nutrients absorption in their independent capacity on addition of biochar, microbial inoculants and P-fertilization. It was shown that mycorrhizal inoculation had positive influence on plant root and shoot biomass in both soils irrespective to the biochar type used. Root colonization was notably increased in biochar + mycorrhizae (B + M) inocultaed plants. It was shown that mycorrhizal inoculation had positive influence on nutrients absorption by plant roots and it had high content of P, potassium, calcium and magnesium in plants at all biochar and P levels. Without P fertilization, biochar amendments significantly promoted shoot P content and root colonization. The P application significantly influenced soil microbial activity in terms of nutrient concentration and plant growth. Root attributes were significantly inclined by microbial inoculation. Residual effects of biochar and P significantly enhanced the nutreints absorption and maize plant growth. Thus, we concluded that residual biochar and P fertilizer showed positive effects on nutrients absorption and maize plant growth promotion in differently textured soils. Microbial inoculants further stimulated the plant biomass production and nutrients absorption due to effective root colonization.

26040. 题目: Effects of fish culture on particulate organic matter in a reservoir-type river as revealed by absorption spectroscopy and fluorescence EEM-PARAFAC
文章编号: N19090610
期刊: Chemosphere
作者: Hui Wang, Yonghao Wang, Wan-E Zhuang, Wei Chen, Weixin Shi, Zhuoyi Zhu, Liyang Yang
更新时间: 2019-09-06
摘要: Dam construction and fish culture can change the biogeochemical processes in river, yet their impact on the spectral properties of particulate organic matter (POM) remains to be studied. This was investigated in a reservoir-type river (Minjiang river, SE China) using absorption spectroscopy and fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). Five fluorescent components were identified from POM with PARAFAC. Four components C1–C4 were affected by the seasonal variations of rainfall and runoff, indicating the influences of hydrological condition and terrestrial inputs. The Chlorophyll a concentration (Chl a) correlated significantly with the humic-like C3 (p < 0.05) and the protein-like C4 (p < 0.01), indicating phytoplankton was an important source of C3 and C4. The Chl a and fluorescence intensities of C3–C4 were higher in the fish culture zones than in other areas, and the absorption coefficient a₃₀₀ and C1–C4 were lower downstream the dam. These results indicated that fish farming in the reservoir probably promoted the production of POM. The a₃₀₀ and C1 per unit mass of suspended particulate matter (a₃₀₀/TSM and C1/TSM) correlated significantly with the median particle size (p < 0.01), which might be related to the contribution of micro-phytoplankton. The absorption spectra of POM showed a shoulder peak at ∼280 nm, and its intensity correlated significantly and positively with Chl a (p < 0.01). These results indicated that the peak was probably derived from phytoplankton production. Our results have implications for better understanding the influences of human activities on the dynamics of river POM.
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