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22801. 题目: Novel magnetic biochar as an activator for peroxymonosulfate to degrade bisphenol A: Emphasizing the synergistic effect between graphitized structure and CoFe₂O₄
文章编号: N20012311
期刊: Chemical Engineering Journal
作者: Yi Li, Shuanglong Ma, Shengjun Xu, Haichao Fu, Zhuoqian Li, Kai Li, Kai Sheng, Jinge Du, Xin Lu, Xianghua Li, Shiliang Liu
更新时间: 2020-01-23
摘要: The biochar loaded with CoFe₂O₄ nanoparticles (CoFe₂O₄/HPC) fabricated by pyrolysis exhibited strong magnetic property, hierarchical porous and graphitized structure. CoFe₂O₄/HPC showed much better bisphenol A degradation than CoFe₂O₄ in presence of peroxymonosulfate. The graphitized structure and the synergistic effect between graphitized structure and CoFe₂O₄ were found to be responsible for the superiority of CoFe₂O₄/HPC among all the other catalysts. The prominent role including radical way mainly contributed by SO₄⁻ and non-radical way achieved by ¹O₂, and the secondary role of electron transfer way proceeded by graphitized structure were uncovered. The processes such as redox between Co(III)/Co(II) and Fe(III)/Fe(II), the reduction of Fe(III) by O₂⁻, and the participation of CO in ¹O₂ production were significant to the excellent catalytic performance of CoFe₂O₄/HPC. Considering its excellent separation, stability, adaptability and reusability, CoFe₂O₄/HPC opened up a novel way to develop green catalyst to activate PMS for organic pollutants degradation.
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22802. 题目: Impact of Vacuum UV on natural and algal organic matter from cyanobacterial impacted waters
文章编号: N20012310
期刊: Environmental Science: Water Research & Technology
作者: Flavia Visentin, Siddharth Bhartia, Madjid Mohseni, Sigrid Peldszus, Sarah Dorner, Benoit Barbeau
更新时间: 2020-01-23
摘要: Cyanobacterial blooms are a growing concern around the world. A feasible approach for small treatment plants fed by sources contaminated with cyanobacteria is Vacuum UV (VUV). VUV is a promising advanced oxidation process used to treat water impacted by cyanobacterial blooms, with potential applicability in small and remote communities because of its simplicity. In this work, water samples from three Canadian lakes periodically affected by cyanobacteria were used to assess the impact of natural and algal organic matter (NOM/AOM) on treatment with VUV. NOM and AOM were characterized before and after VUV treatment by size exclusion chromatography (SEC) and fluorescence emission-excitation matrix (FEEM). FEEM spectra were analyzed with the parallel factor analysis (PARAFAC) tool. As a result, we found seven principal components describing the whole dataset. Disinfection by-product (DBP) formation after VUV treatment was analyzed and trihalomethanes (THM) yield was calculated. THM yield increased by 15-20% after VUV treatment. Regarding DBP formation and NOM/AOM fractions from SEC, we found that humic substances are the most important fraction causing the increase in DBP formation with at least 3 higher yield than the other fractions: biopolymers, building blocks, low weight molecular acids, and neutrals.

22803. 题目: Uranium reduction and isotopic fractionation in reducing sediments: Insights from reactive transport modeling
文章编号: N20012309
期刊: Geochimica et Cosmochimica Acta
作者: Kimberly V. Lau, Timothy W. Lyons, Kate Maher
更新时间: 2020-01-23
摘要: Uranium concentrations and isotopic ratios (²³⁸U/²³⁵U, denoted as δ²³⁸U) have been used to provide quantitative information about the degree of oxygenation and de-oxygenation of past oceans. The potential to constrain changes in global redox conditions, in contrast to many other proxies that reflect local conditions, is a particular strength of the uranium isotope approach. Because uranium reduction primarily occurs in sediments underlying anoxic water columns rather than in the anoxic water column itself, the removal of uranium in organic-rich shales is the largest lever on seawater δ²³⁸U. Accordingly, accumulation and isotopic fractionation are modulated by local variations in productivity, basin connectivity, sedimentation rate, and bottom-water redox conditions. To isolate the processes at the sediment-water interface that control δ²³⁸U and uranium accumulation in reducing sediments, we constructed a reactive transport model that couples biogeochemical reactions to diffusive transport and the burial of solutes and minerals.Using the model framework, we test the sensitivity of authigenic uranium isotopic fractionation and accumulation to oxygenation, permeability, sedimentation rate, organic carbon delivery, and basin restriction. Our results demonstrate that these external forcings produce diagnostic patterns in isotopic fractionation. Specifically, the model predicts that authigenic δ²³⁸U is sensitive to productivity because of the associated organic carbon burial rate. Moreover, our results suggest that the isotopic offset does not vary significantly due to changing bottom-water O₂ concentrations, but the amount of accumulation does—a result that differs from previous estimates. Water column uranium reduction adds additional complexity to the ultimate δ²³⁸U value. The predictive patterns derived from model results can offer insight into local depositional conditions, such as sedimentation patterns. Collectively, these effects—including bottom-water redox conditions and related reducing sediments—alter the isotopic signature of the overlying water column according to the authigenic δ²³⁸U value and the diffusive fluxes arising from porewater concentration gradients. More broadly, this work provides important new constraints on the major controls on the δ²³⁸U of sediments while also supporting its use as a proxy for global marine redox conditions.

22804. 题目: Characterisation of shallow groundwater dissolved organic matter in aeolian, alluvial and fractured rock aquifers
文章编号: N20012308
期刊: Geochimica et Cosmochimica Acta
作者: Liza K. McDonough, Helen Rutlidge, Denis M. O'Carroll, Martin S. Andersen, Karina Meredith, Megan I. Behnke, Robert G.M. Spencer, Amy M. McKenna, Christopher E. Marjo, Phetdala Oudone, Andy Baker
更新时间: 2020-01-23
摘要: Groundwater organic matter is processed within aquifers through transformations such as the adsorption of dissolved organic matter (DOM) to minerals and biodegradation. The molecular character of DOM varies according to its source and this can impact its bioavailability and reactivity. Whilst the character of DOM in riverine and oceanic environments is increasingly well understood, the sources, character and ultimately the fate of groundwater DOM remains unclear. Here we examine groundwater DOM from contrasting hydrogeological settings in New South Wales, Australia. For the first time, we identify the distinct molecular composition of three groundwater DOM end-members including a modern terrestrial input, an aged sedimentary peat source, and an aged stable by-product pool. We also identify and characterise the processing pathway of DOM in semi-arid, low sedimentary organic carbon (OC) environments. Based on size exclusion chromatography, ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), isotopic analyses (¹³C, ¹⁴C and ³H) and principle component analysis (PCA), we show that in higher rainfall temperate coastal peatland environments, large amounts of aged sedimentary organic carbon can leach into groundwater resulting in higher molecular weight (500 g mol⁻¹ < molecular weight > 1000 g mol⁻¹) and highly aromatic groundwater DOM with high O / C ratios and low H / C ratios. We show that in semi-arid environments with low rainfall rates and high groundwater residence times, groundwater dissolved organic carbon (DOC) is processed into increasingly low molecular weight (< 350 g mol⁻¹), low aromaticity DOM with low O / C ratios and high H / C ratios by subsurface processing mechanisms such as biodegradation and adsorption. We provide the first comprehensive study of groundwater DOM characterisation based on multiple analytical techniques, and highlight the impact of source inputs and processing on groundwater DOM composition at a molecular level.

22805. 题目: A Chemo-mechanical Snapshot of In-situ Conversion of Kerogen to Petroleum
文章编号: N20012307
期刊: Geochimica et Cosmochimica Acta
作者: Arash Abarghani, Mehdi Ostadhassan, Paul C. Hackley, Andrew E. Pomerantz, Siamak Nejati
更新时间: 2020-01-23
摘要: Organic matter (OM) from various biogenic origins converts to solid bitumen in-situ when it undergoes thermal maturation. It is well documented that during this process, the ratios of both hydrogen and oxygen to carbon will decrease, resulting in an increase in OM aromaticity and molecular chemo-mechanical homogeneity. Although there have been extensive efforts to reveal molecular alteration occurring to OM during conversion, in-situ and continuous observation of such alterations on naturally occurring samples is missing. Therefore, evaluation of previous results cannot be made independent from natural sample variability. In this study, we identified OM particles (Tasmanites) that are evolving in-situ into solid bitumen in the Bakken Formation. This in-situ bituminization allows examination of a continuous transformation in OM molecular structure at micron-scale using AFM based IR spectroscopy applied at the transition/interface zone. Moreover, contact mode in the AFM was employed to reveal and relate changes in mechanical properties at a similar scale of measurement. Understanding these chemical and mechanical alterations is important to understand shale reservoir properties and better explain hydrocarbon generation, expulsion, and migration processes at the microscale.

22806. 题目: Soil degradation and recovery – Changes in organic matter fractions and structural stability
文章编号: N20012306
期刊: Geoderma
作者: Johannes L. Jensen, Per Schjønning, Christopher W. Watts, Bent T. Christensen, Peter B. Obour, Lars J. Munkholm
更新时间: 2020-01-23
摘要: The combination of concurrent soil degradation and restoration scenarios in a long-term experiment with contrasting treatments under steady-state conditions, similar soil texture and climate make the Highfield land-use change experiment at Rothamsted Research unique. We used soil from this experiment to quantify rates of change in organic matter (OM) fractions and soil structural stability (SSS) six years after the management changed. Soil degradation included the conversion of grassland to arable and bare fallow management, while soil restoration comprised introduction of grassland in arable and bare fallow soil. Soils were tested for clay dispersibility measured on two macro-aggregate sizes (DispClay 1–2 mm and DispClay 8–16 mm) and clay-SOM disintegration (DI, the ratio between clay particles retrieved without and with SOM removal). The SSS tests were related to soil organic carbon (SOC), permanganate oxidizable C (POXC) and hot water-extractable C (HWC). The decrease in SOC after termination of grassland was greater than the increase in SOC when introducing grassland. In contrast, it was faster to restore degraded soil than to degrade grassland soil with respect to SSS at macro-aggregate scale. The effect of management changes was more pronounced for 8–16 mm than 1–2 mm aggregates indicating a larger sensitivity towards tillage-induced breakdown of binding agents in larger aggregates. At microscale, SSS depended on SOC content regardless of management. Soil management affected macroscale structural stability beyond what is revealed from measuring changes in OM fractions, underlining the need to include both bonding and binding mechanisms in the interpretation of changes in SSS induced by management.

22807. 题目: Remediation and its biological responses of Cd contaminated sediments using biochar and minerals with nanoscale zero-valent iron loading
文章编号: N20012305
期刊: Science of The Total Environment
作者: Qunqun Liu, Yanqing Sheng, Wenjing Wang, Changyu Li, Guoqiang Zhao
更新时间: 2020-01-23
摘要: Remediation of Cd pollution in sediments is crucial for the safety of aquatic environments and human health. In this study, four effective, common, and low-cost remediation materials (zeolite, sepiolite, red mud (RM), and biochar (BC)) loaded with nanoscale zero-valent iron (nZVI) and themselves were employed to immobilize Cd in sediments. The effects of different materials on sediment properties, immobilization effectiveness, bacterial communities, enzyme activities, and dissolved organic matter (DOM) were investigated. Results showed that sediment properties were significantly changed by the addition of immobilization materials (P < 0.05). The geochemical fraction analysis showed that the labile Cd was partially transformed to the stable fraction after immobilization, with an 11–47% decrease in the acid-soluble fraction and a 50–1000% increase in the residual fraction. The Cd immobilization effectiveness peaked at the nZVI/RM and nZVI/BC treatments, and the Cd toxicity characteristic leaching procedure (TCLP) leachabilities decreased by 42% and 44%, respectively. The modified materials were more effective for immobilizing Cd than the raw materials owing to the presence of nZVI, and the Cd TCLP leachabilities with the modified materials decreased by 15%–22% compared with the raw material treatments. Immobilization-driven reduction of bioavailable Cd enhanced the richness and diversity of bacterial communities and enzyme activities. Moreover, the immobilization treatment promoted the Fe(III)-reducing process by increasing the Fe(III)-reducing bacteria (e.g. Geobacteraceae, Bacillus, and Clostridium), which are conducive to Cd immobilization. Additionally, the DOM composition presented more autogenetic characteristics in treated groups. BC (nZVI/BC) can be selected as the priority material for Cd immobilization in sediments due to higher immobilization effectiveness and lower adverse effects on sediments.
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22808. 题目: Effects of Zn in sludge-derived biochar on Cd immobilization and biological uptake by lettuce
文章编号: N20012304
期刊: Science of The Total Environment
作者: Jia Gao, Tuokun Zhao, Daniel C.W. Tsang, Nan Zhao, Hang Wei, Mingyu Feng, Kunyuan Liu, Weihua Zhang, Rongliang Qiu
更新时间: 2020-01-23
摘要: Considering the high Zn content of municipal sewage sludge and its competition with Cd during plant uptake due to their similar properties, the presence of Zn in sludge-derived biochar (SDBC) may affect Cd immobilization and uptake by plants. To confirm this, SDBC samples with different Zn contents were prepared and characterized. Their Cd immobilization behavior was studied by conducting batch sorption experiments, and their effects on Cd uptake by lettuce were explored by conducting hydroponic experiments. The results reveal that some Zn contained in the sewage sludge was transformed into ZnO during pyrolysis. The Brunauer-Emmett-Teller (BET) surface area of the SDBC samples containing 2324 mg kg⁻¹ Zn (BC-2324) was 18.3 m² g⁻¹, which was 132% larger than that of the samples containing 1438 mg kg⁻¹ Zn (BC-1438). The SDBC samples containing 1901 mg kg⁻¹ (BC-1901) exhibited the highest Langmuir sorption capacity of 3476 mg kg⁻¹, which is 115% higher than that of SB-1438. Furthermore, the lettuce remedied with SB-1901 exhibited 44% more biomass; lower peroxidase, catalase, and malondialdehyde activity; and 18.4% less Cd in the leaves of the lettuce than the lettuce remedied with BC-1438, suggesting the potential benefits of using Zn-rich SDBC for soil amendment.
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22809. 题目: Five decades of declining methylmercury concentrations in boreal foodwebs suggest pivotal role for sulphate deposition
文章编号: N20012303
期刊: Science of The Total Environment
作者: Hans Fredrik Veiteberg Braaten, Markus Lindholm, Heleen A. de Wit
更新时间: 2020-01-23
摘要: Widespread declines in mercury (Hg) in fish in pristine lakes in Fennoscandia since the 1970s are unexplained. Interactions between climate, atmospheric deposition, and elemental cycling of carbon (C), sulphur (S) and Hg are complex and affect Hg bioaccumulation. A parallel significant decline in methyl-Hg (MeHg) concentrations in aquatic macroinvertebrates (Chironomidae) was found between 1976–78 and 2004–15 in an intensely studied, pristine boreal lake (Langtjern, boreal Fennoscandia). Monitoring at Langtjern demonstrated a four-fold decrease in aqueous sulphate concentrations (SO₄, 50-year record), significant lake browning (30-year records), increasing sediment Hg concentrations (50-year record), warming (45-year record) and increased runoff (40-year record). Contrasting Hg trends in biota (downward) and sediment (upward) indicated a disconnect between lake Hg loading and foodweb Hg bioaccumulation. We suggest that reduced SO₄-deposition has 1) constrained substrate availability for SO₄-reducing methylating bacteria (causing reduced foodweb MeHg exposure despite increased Hg loading to the lake), and 2), increased the binding affinity between aqueous organic matter and Hg species (leading to reduced MeHg bioavailability). The downward MeHg trend at the base of the foodweb at Langtjern is mirrored at higher trophic levels by strong declines in perch (Perca fluviatilis) and pike (Esox lucius) Hg concentrations in boreal Fennoscandia. A plausible explanation is that declining SO₄-deposition, rather than climate change or reduced atmospheric Hg, is currently driving reduced MeHg contamination in northern freshwater foodwebs.
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22810. 题目: An in-depth study on the deep-dewatering mechanism of waste activated sludge by ozonation pre-oxidation and chitosan re-flocculation conditioning
文章编号: N20012302
期刊: Science of The Total Environment
作者: Dongdong Ge, Chang Bian, Haiping Yuan, Nanwen Zhu
更新时间: 2020-01-23
摘要: At present, wastewater and sludge management departments are in urgent of the sludge deep-dewatering technique, which can substantially reduce sludge volume, enhance sludge calorific value and save costs. Ozonation pre-oxidation and chitosan (CT) re-flocculation conditioning have been verified to be an efficacious and environmental-friendly approach to realize sludge deep-dewatering. This paper focused on the novel insights into sludge properties under ozonation and CT conditioning. With 60 mg/gTS O₃ and 20 mg/gTS CT, the water content of the conditioned sludge cake satisfied the deep-dewatering level (<60%). The ozone dosage of 60 mg/gTS effectually enhanced the release of soluble COD and retained the inherent organic matters simultaneously, and subsequently, CT could further reduce extracellular biopolymers, especially proteins. Fluorescence analysis indicated that the protein-like substances were largely decomposed into fulvic acid-like and humic acid-like substances after ozonation, and CT could further remove humic acid-like components. Macromolecules were observed to form by CT combining with ozonated extracellular polymers. Low-field NMR technique monitored sludge water states and suggested that water movability weakened after ozonation and enhanced again through CT conditioning. SEM images reflected that CT was available as junction link for ozonated polymers to aggregate into large flocs. Furthermore, the calorific value of conditioned sludge cake increased and sludge cake drying time was saved pronouncedly. The findings provided the systematic and comprehensive insights into the sludge properties in pre-oxidation and re-flocculation conditioning, which would aid in a better understanding of the in-depth dewatering mechanism and developing new dewatering technique.
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22811. 题目: Identification, formation and control of polar brominated disinfection byproducts during cooking with edible salt, organic matter and simulated tap water
文章编号: N20012301
期刊: Water Research
作者: Dan Zhang, Yun Wu, Xiangru Zhang, Wenbin Li, Yan Li, Aimin Li, Yang Pan
更新时间: 2020-01-23
摘要: Edible salt is essential to the health of humans and serves as a seasoning universally. Besides chloride, edible salt also contains other anions such as bromide, fluoride, sulfate, and carbonate due to incomplete removal during raw salt refinement. In a household cooking (e.g., soup making) process, a chlorine/monochloramine residual in tap water could react with bromide in edible salt and organic matter in food (e.g., rice, wheat) to form numerous brominated disinfection byproducts (Br-DBPs) at significant levels, which might induce adverse health effects to human beings. In this study, we solicited 20 edible salts of different types (i.e., sea salts, well and rock salts, lake salts, and bamboo salts) from nine countries and determined their bromide levels to be 67–375 mg/kg, with an average level of 173 mg/kg. A total of 25 polar Br-DBPs were detected and identified with structures/formulae in cooking water samples using ultra performance liquid chromatography/electrospray ionization-triple quadruple mass spectrometry (UPLC/ESI-tqMS) and high-resolution mass spectrometry. Effects of cooking conditions (e.g., disinfectant type and level, edible salt dose, organic matter type and dose, sequence and time interval of adding organic matter and salt, etc.) on the formation of polar Br-DBPs were investigated, and optimized cooking conditions with minimized formation of polar Br-DBPs were determined. Further aided with an Hep G2 cell cytotoxicity assay, it was found that the overall cytotoxicity of chlorinated and chloraminated cooking water samples prepared after cooking condition optimization was reduced by 57% and 22%, respectively, compared with those prepared before cooking condition optimization.
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22812. 题目: Pyrolysis temperature of biochar affects ecoenzymatic stoichiometry and microbial nutrient-use efficiency in a bamboo forest soil
文章编号: N20012222
期刊: Geoderma
作者: Kangying Guo, Yingzhi Zhao, Yang Liu, Junhui Chen, Qifeng Wu, Yifei Ruan, Songhao Li, Jiang Shi, Lin Zhao, Xuan Sun, Chenfei Liang, Qiufang Xu, Hua Qin
更新时间: 2020-01-22
摘要: A microcosm study was performed to investigate changes in soil enzyme activities and microbial C- and N-use efficiencies (CUE and NUE) with amendment of biochars prepared at three pyrolysis temperatures (350, 500 and 700 °C) in an acid bamboo (Phyllostachys praecox) forest soil. The results showed that, compared to the non-amended control, biochars produced at 500 and 700 °C significantly (P < 0.05) increased soil pH, total N, and dissolved N (DN) concentrations, whereas significantly decreased dissolved organic C (DOC) and exchangeable acidity concentrations after three months. The microbial biomass C (MBC) and N (MBN) and the ratio of fungi: bacteria (F:B) were only significantly increased under 350 °C biochar. The ratios of both soil C:N and DOC:DN to MBC:MBN were reduced under 500 and 700 °C biochars, suggesting a lower C:N imbalance between resources and microorganism. The ratio of C- to N-acquiring enzyme activities increased gradually under biochars with increasing temperature. Moreover, microbial CUE increased whereas NUE declined under biochars at 500 and 700 °C, and the threshold elemental ratio (TER) revealed that the microbial nutrient metabolisms were limited by N in soils amended with residue, but were limited by C under biochars at 500 and 700 °C. Structural equation modeling indicated that the C:N imbalance had a great impact on microbial CUE, while changes in F:B ratio and soil pH were closely associated with NUE. This study suggests that changes in microbial nutrient-use efficiency and ecoenzymatic stoichiometry reveals a clear C-limitation, but a N-availability under short-term amendment of biochar produced at a high pyrolysis temperature.

22813. 题目: Biochar addition combined with daily fertigation improves overall soil quality and enhances water-fertilizer productivity of cucumber in alkaline soils of a semi-arid region
文章编号: N20012221
期刊: Geoderma
作者: Xu Zhang, Jisong Qu, Hong Li, Shikai La, Yongqiang Tian, Lihong Gao
更新时间: 2020-01-22
摘要: Crop land degradation is a common phenomenon in most regions of the world, especially in arid and semi-arid regions. To mitigate cropland degradation and further enhance crop productivity, it is crucial to restore soil quality by utilizing efficient soil management practices. Although biochar has been widely used to improve soil conditions, the efficiency of biochar in enhancing crop productivity is often limited by inappropriate agricultural practices (e.g. irrigation and fertilization). Moreover, little information is available regarding the link among availability of water, biochar and productivity. In this study, we measured the effects of biochar addition, daily fertigation and their combination on overall soil quality, crop yield and water-fertilizer productivity in alkaline soils of a semi-arid region, over two years. To comprehensively evaluate soil quality, a wide range of soil physical, chemical, biological and ecological properties were measured and integrated into a soil quality index (SQI). The treatments evaluated were (i) untreated soils managed with traditional irrigation and fertilization (control), (ii) soils treated with biochar and managed with traditional irrigation and fertilization (B), (iii) untreated soils managed with daily fertigation (DF), and (iv) soils treated with biochar and managed with daily fertigation (B + DF). In general, biochar addition enhanced soil quality (expressed by SQI) mainly through increasing soil water content (SWC), available phosphorus (AP), the capacity of soil microbes to utilize miscellaneous (CSM-MI) and microbial biomass carbon (Cmic), and decreasing soil pH and plant-parasitic nematode abundance. Daily fertigation improved soil quality primarily by enhancing SWC, AP, CSM-MI and Cmic. The SQI exhibited strong positive correlations with both plant biomass and fruit yield. In addition, the treatment B + DF showed not only the highest SQI and fruit yield, but also the highest irrigation water-productivity (326.3 and 557.9 kg mm⁻¹ in 2017 and 2018, respectively) and partial factor productivity for fertilizer in both years 2017 and 2018. Our results show that biochar addition combined with daily fertigation can improve overall soil quality, and further enhance cucumber yield and water-fertilizer productivity in alkaline soils.

22814. 题目: Mechanisms underlying the mitigation of both N₂O and NO emissions with field-aged biochar in an Anthrosol
文章编号: N20012220
期刊: Geoderma
作者: Changhua Fan, Pengpeng Duan, Xi Zhang, Haojie Shen, Miao Chen, Zhengqin Xiong
更新时间: 2020-01-22
摘要: The mechanisms associated with N₂O and NO processes following biochar application remain unclear in an Anthrosol under intensively vegetable production. An incubation experiment with ¹⁵N tracing technique and quantitative polymerase chain reaction (qPCR) was performed to investigate the responses of pathways and the microbial mechanisms of N₂O and NO production to the application of wheat biochar (Bw) and swine manure biochar (Bm) field aged for one year in an Anthrosol under 60% water holding capacity. The application of both types of biochar decreased the cumulative N₂O emissions by 12.9–20.0%, with an obvious mitigation effect observed after Bw application. The reduction in N₂O emissions derived from autotrophic nitrification and denitrification induced by biochar were coupled with a decrease in ammonia-oxidizing bacteria (AOB) amoA abundance and the ratio of (nirK + nirS)/nosZ, respectively. Biochar increased the relative contribution of heterotrophic nitrification by 54.2–58.3%, with stronger stimulating effects from the Bm amendment than from the Bw amendment. Moreover, cumulative NO emissions were strongly reduced by an average of 35.5% by biochar, with no differences between Bw and Bm. Furthermore, covariation in NO flux and NO₂⁻–N content, together with the alternations in the abundance of AOB amoA, indicated that nitrifier denitrification might play a vital role in NO emissions. The present study highlights biochar’s promising effects on mitigating N₂O and NO emissions by weakening autotrophic nitrification and denitrification processes. Meantime, heterotrophic nitrification should be taken into consideration when comprehensively assessing the mitigation potential of biochar.
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22815. 题目: Linking biochars properties to their capacity to modify aerobic CH₄ oxidation in an upland agricultural soil
文章编号: N20012219
期刊: Geoderma
作者: María Blanca Pascual, Miguel A. Sánchez-Monedero, Francisco J. Chacón, María Sánchez-García, María L. Cayuela
更新时间: 2020-01-22
摘要: Aerobic soils are the largest biotic sink for atmospheric methane (CH₄). Although agricultural intensification is known to adversely impact soil CH₄ uptake, the application of organic amendments (e.g. composts, green residues) in agricultural soils has been found to stimulate the activity of CH₄ oxidizers. However, little is known about the influence of biochar (a carbonaceous by-product of biomass pyrolysis) on the soil CH₄ sink function. This study analyzes, through a series of laboratory incubation assays, how ten well-characterized biochars with contrasting properties influence CH₄ oxidation rate constants (k) in an aerobic high-pH agricultural soil. Through the use of ¹³C-CH₄, we demonstrated that both CH₄ soil oxidation and CH₄ assimilation were responsible for the decrease in CH₄ concentration. A principal component regression (PCR) of the results suggested that the physico chemical properties of biochars were directly linked to their ability to enhance or inhibit the oxidation of CH₄. Biochars from wood feedstocks and pyrolysed at 600 °C, characterized by a high pore area, led to the highest CH₄ oxidation rates whereas biochars with high ash concentrations and electrical conductivity significantly diminished CH₄ oxidation rates. Biochar redox properties were not found to be relevant for CH₄ oxidation in soil.

22816. 题目: Resilience and microstructural resistance of Archaeological Dark Earths with different soil organic carbon contents in Western Amazonia, Brazil
文章编号: N20012218
期刊: Geoderma
作者: Alan Carlos Batistão, Dörthe Holthusen, José Miguel Reichert, Luís Antônio Coutrim dos Santos, Milton César Costa Campos
更新时间: 2020-01-22
摘要: Archaeological Dark Earths (ADE) are anthropogenic soils with high fertility and excellent physical conditions due to high soil organic carbon (SOC) content. However, climate change, land use and soil management can increase SOC mineralization, resulting in microstructure damage of these soils. To verify the effect of SOC loss, we collected deformed samples from the surface horizon and simulated the reduction of C with the application of 0.2, 0.4 and 0.6 ml of hydrogen peroxide 35% per gram of soil, resulting in three treatments of different oxidation levels and untreated soil. Both original and oxidized soil were submitted to an amplitude sweep test with controlled strain and a thixotropy test, in a compact modular rheometer. To characterize the effect of soil properties on rheology and resilience of ADEs, we performed a correlation analysis with physico-chemical properties from untreated soil. Higher clay and organic matter contents increased the microstructure elasticity of ADEs. The increase in base saturation, mainly due to the high Ca⁺² content, also favors elasticity. The soil’s resilience is a result of the joint effect of particle size distribution, base saturation and SOC content. The microstructure recovers fast, regardless of the disturbance intensity. The SOC loss affected the microstructure differently in each ADE. These differences are not dependent on the amount of SOC lost and mostly labile SOC (as removed by low oxidation intensity) was responsible for soil strength.

22817. 题目: Patterns and environmental controls of soil organic carbon density in Chinese shrublands
文章编号: N20012217
期刊: Geoderma
作者: Jielin Ge, Wenting Xu, Qing Liu, Zhiyao Tang, Zongqiang Xie
更新时间: 2020-01-22
摘要: The soils of shrublands are important for organic carbon storage in terrestrial ecosystems, but geographical patterns and environmental controls of soil organic carbon (SOC) remain largely understudied compared to other terrestrial ecosystems, leaving a significant gap in our understanding of terrestrial ecosystem carbon budgets. Here, we quantified SOC density (SOCD) and its potential determinants based on a comprehensive dataset with a consistent stratified random sampling of extensive soil profiles down to the parent material or to one meter depth across 1211 sites across China. Our up-to-date estimate of SOCD in Chinese shrublands is an average of 8.36 kg m⁻², and ca. 43% of SOC is stored in the upper 20 cm relative to the one meter top soil, which is higher than estimates for shrublands globally. We also observed that SOCD was positively related to shrubland biomass and more so with belowground biomass. Furthermore, SOCD was positively related to mean annual precipitation (MAP), soil total nitrogen (N), phosphorus (P), clay and silt percent, but decreased with increasing mean annual temperature (MAT). Dark felty soils stored the highest SOCD and frigid desert soils stored the lowest. Soil total nitrogen (N), MAP, soil type, MAT, and belowground biomass, soil clay, and pH were the best predictors of total SOCD in Chinese shrublands. We concluded that Chinese shrubland soils store the lowest density of organic carbon so far recorded compared to forests and grasslands, and that the vertical distribution of SOC in Chinese shrublands was much shallower. While both climate (in particular MAP) and soil total N exerted dominant control over geographical patterns of SOCD across Chinese shrublands, soil type also played a significant role. Our study also emphasizes this key role of edaphic variables in determining the SOCD of shrublands and that they should be better incorporated into large-scale assessments of SOC dynamics. Our study extends existing work conducted in forest and grasslands and provides the most up-to-date knowledge on benchmark values for SOCD in Chinese shrublands, with important implications for predicting the fate of C stored in shrubland soils in response to climate change.

22818. 题目: Soil organic carbon, extracellular polymeric substances (EPS), and soil structural stability as affected by previous and current land-use
文章编号: N20012216
期刊: Geoderma
作者: M. Redmile-Gordon, A.S. Gregory, R.P. White, C.W. Watts
更新时间: 2020-01-22
摘要: While soil microbial ecology, soil organic carbon (SOC) and soil physical quality are widely understood to be interrelated — the underlying drivers of emergent properties, from land management to biochemistry, are hotly debated. Biological binding agents, microbial exudates, or ‘extracellular polymeric substances’ (EPS) in soil are now receiving increased attention due to several of the existing methodological challenges having been overcome. We applied a recently developed approach to quantify soil EPS, as extracellular protein and extracellular polysaccharide, on the well-characterised soils of the Highfield Experiment, Rothamsted Research, UK. Our aim was to investigate the links between agricultural land use, SOC, transient binding agents known as EPS, and their impacts on soil physical quality (given by mean weight diameter of water stable aggregates; MWD). We compared the legacy effects from long-term previous land-uses (unfertilised grassland, fertilised arable, and fallow) which were established > 50 years prior to investigation, crossed with the same current land-uses established for a duration of only 2.5 years prior to sampling. Continuously fallow and grassland soils represented the poorest and greatest states of structural integrity, respectively. Total SOC and N were found to be affected by both previous and current land-uses, while extractable EPS and MWD were driven primarily by the current land-use. Land-use change between these two extremes (fallow → grass; grass → fallow) resulted in smaller SOC differences (64% increase or 37% loss) compared to MWD (125% increase or 78% loss). SOC concentration correlated well to MWD (adjusted R² = 0.72) but the greater SOC content from previous grassland was not found to contribute directly to the current stability (p < 0.05). Our work thus supports the view that certain distinct components of SOC, rather than the total pool, have disproportionately important effects on a soil’s structural stability. EPS-protein was more closely related to aggregate stability than EPS-polysaccharide (p values of 0.002 and 0.027, respectively), and ranking soils with the 5 greatest concentrations of EPS-protein to their corresponding orders of stability (MWD) resulted in a perfect match. We confirmed that both EPS-protein and EPS-polysaccharide were transient fractions: supporting the founding models for aggregate formation. We suggest that management of transient binding agents such as EPS —as opposed to simply increasing the total SOC content— may be a more feasible strategy to improve soil structural integrity and help achieve environmental objectives.

22819. 题目: Mapping soil organic carbon and clay using remote sensing to predict soil workability for enhanced climate change adaptation
文章编号: N20012215
期刊: Geoderma
作者: S.S. Paul, N.C. Coops, M.S. Johnson, M. Krzic, A. Chandna, S.M. Smukler
更新时间: 2020-01-22
摘要: Climate change is presenting sizeable challenges for agricultural production around the world. In some regions, shifting precipitation patterns in the spring and fall are negatively impacting farm operation by reducing the number of “workable days” or the days fields can be worked with heavy equipment without damaging soil structure. This can be particularly problematic for farms on clay soils and/or poor drainage. Approximating a water content threshold at which a soil is not workable due to soil structure destruction can be helpful for planning effective farm operations. In this study, we applied advanced remote sensing and machine learning tools to produce digital maps of soil organic carbon (SOC) and clay (CL) content and used them in existing pedotransfer functions (PTFs) to predict a workability threshold (WT) across a study area in Delta, British Columbia, Canada. We combined field data, soil and vegetation indices derived from multiple Landsat satellite images, topographic indices, and soil survey information to digitally map SOC and CL of the agricultural lands in Delta using random forest (RF) and generalized boosted regression model (GBM). When validated against an independent field dataset, the RF model outperformed GBM for all accuracy measures (coefficient of determination – R², concordance correlation coefficient – CCC, and normalized root mean square error – nRMSE). We then spatially applied several PTFs using our digital maps to estimate the plasticity limits of the soil and produce WT map. The WT map was then tested against independent field samples of the soil water content at −10 kPa and we achieved R² of 0.59, CCC of 0.70, and nRMSE of 0.15. Our analysis showed that 40% of the fields in the study area had WT < 30%, a threshold that is already being impacted by reduced workable days. This WT map could be used to improve spatial prioritizations of investments for climate change adaptation at farm to regional scales.

22820. 题目: Climate, carbon content, and soil texture control the independent formation and persistence of particulate and mineral-associated organic matter in soil
文章编号: N20012214
期刊: Geoderma
作者: Michelle L. Haddix, Edward G. Gregorich, Bobbi L. Helgason, Henry Janzen, Benjamin H. Ellert, M. Francesca Cotrufo
更新时间: 2020-01-22
摘要: Understanding the mechanisms controlling the formation and persistence of soil organic matter (SOM) is important for managing soil health and sustainable food production. The formation of SOM and the degree to which it is protected from decomposition are important for determining the long-term persistence of SOM. We used soils collected in a ¹³C-labelled litter decomposition study established at agricultural sites in Canada to understand the formation and persistence of newly-formed SOM. The ten agricultural sites spanned a wide range of soil carbon contents, texture, and climatic conditions. We fractionated the soil to isolate water extractable organic matter (WEOM), free light POM (fPOM), sand-sized and occluded particulate organic matter (oPOM), and silt and clay sized particles, referred to as mineral-associated organic matter (MAOM). Quantitative isotope tracing was used to determine the litter-derived C in all fractions. We performed these analyses early (six months after incubation) and later (five years after incubation) in the decomposition process to evaluate factors that control the formation and persistence of POM and MAOM. After six months litter-derived C was found in all fractions, but after five years it had declined in all fractions except the MAOM. Formation of MAOM was related to high mean annual precipitation and low sand content, whereas occluded POM formation was related to high soil C content. Persistence of MAOM and POM during the incubation were associated with low soil temperature and high soil C content. There was no consistent indication that formation of MAOM occurred from the decomposition of POM, suggesting that MAOM and POM are formed by two separate pathways. This has important implications for SOC models, which assume that plant-derived C passes through a sequence of pools, becoming more stable along the way.