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24661. 题目: Changes in biochar properties in typical loess soil under a 5-year field experiment
文章编号: N19080306
期刊: Journal of Soils and Sediments
作者: Lianshuai Tan, Cengceng Sun, Ying Wang, Tongtong Wang, Gao-Lin Wu, Honghua He, Jiyong Zheng
更新时间: 2019-08-03
摘要: Purpose: After biochar is applied to soil as a sustainable soil amendment and a carbon (C) sequestration technique, its physicochemical properties change over time. However, few studies have reported on the changes of biochar properties over the aging process under field conditions. An understanding of such changes can help us to make full use of biochar as a sustainable soil amendment and C sequestration technique. Materials and methods: We used apple tree branches as the raw material to produce biochar and studied the changes in the physicochemical properties of the biochar over a 5-year field experiment. Scanning electron microscopy (SEM), specific surface area (SSA) and micropore area, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy (XPS) were performed. Results and discussion: After 5 years of aging, the SSA of the biochar had increased by 23.91% relative to that of fresh biochar; however, the SSA initially decreased over the first 3 years and then increased over the next 2 years. The reasons for the initial decrease were the destruction and clogging of the existing pore structure, whereas new micropore formation was responsible for the subsequent increase, as verified by micropore area, SEM and XPS analyses. The C content of the biochar was stable over the 5 years, but the surface O content and quantity of oxygen-containing functional groups increased relative to those of fresh biochar, which impacts the adsorption capacity of the biochar. Conclusions: Our findings illustrate that the SSA of the biochar varied with time during the aging process. The stability of the C illustrated the potential of biochar as a C sequestration technique. The increase in oxygen-containing functional groups of the biochar was responsible for the process of nutrient adsorption.

24662. 题目: Engineering of phosphate-functionalized biochars with highly developed surface area and porosity for efficient and selective extraction of uranium
文章编号: N19080305
期刊: Chemical Engineering Journal
作者: Rui Hu, Jiang Xiao, Tianhui Wang, Guangcai Chen, Lin Chen, Xingyou Tian
更新时间: 2019-08-03
摘要: Properly engineering of surface functionality and structural porosity is critical to improve the sorption performance of biochars. Herein, we report a facile one-pot preparation of phosphate group-functionalized biochars (PBs) derived from bamboo sawdust by engineering with phytic acid prior to pyrolysis. High specific surface areas (629, 1298 and 1109 m²·g⁻¹), large pore volumes (0.332, 0.919 and 0.789 cm³·g⁻¹), and abundant phosphorous contents (1.14, 3.32 and 1.53 at.%) are achieved compatibly for the PBs pyrolyzed at given temperatures (i.e., 300, 450 and 600 °C) which are significantly higher than those of pristine biochars. Phytic acid not only releases hydrogen protons to tailor biochar matrixes to make micropores created and further developed, but also provides organic phosphorous-containing moiety to guarantee the surface phosphate functionality. PBs extract U(VI) from aqueous media efficiently, i.e., equilibrium achieved within 8 h, high sorption capacity of 229.2 mg·g⁻¹ (at pH 4.0, T 298 K), and favorable selectivity towards U(VI) against the interference of coexisting metal ions. PBs can be regenerated by 0.1 mol·L⁻¹ Na₂CO₃ and reused well after six recycles. This present work provides a path for the design and synthesis of advanced biochars with favorable potentials in the extraction of U(VI)-containing effluents.
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24663. 题目: Adsorption and Fenton-like removal of chelated nickel from Zn-Ni alloy electroplating wastewater using activated biochar composite derived from Taihu blue algae
文章编号: N19080304
期刊: Chemical Engineering Journal
作者: He Wang, Han Wang, Hui Zhao, Qun Yan
更新时间: 2019-08-03
摘要: A novel biochar composite impregnated with α-Fe₂O₃ in hierarchical porous structures (Fe(III)-ABC-20) was synthesized by means of pyrolysis combining with KOH activation using the yearly bloomed Taihu blue algae as resources. It was found that the biochar activated by KOH obtained the specific surface area of 1657.8 m² g⁻¹, nearly 92.6 times larger than that of the biochar without modification (17.9 m² g⁻¹). Meanwhile, abundant oxygen-containing functional groups such as COOH, OH, etc. are introduced onto the surface of algae biochar. Besides, Fe(III) was successfully loaded onto the porous structure of biochar from combined characterization of XRD, SEM, TEM, FTIR and XPS. Under the optimized operating conditions of pH at 6, Fe(III)-ABC-20 and H₂O₂ dosage of 0.5 g and 20 mM, adsorption equilibrium and Fenton-like reaction time at 20 and 60 min respectively, the biochar composite exhibited 98.87% removal rate of chelated nickel in electroplating wastewater. Moreover, the catalyst exerted better stability after four repeated experiments, as which still remained 93.26% of nickel removal. Meanwhile, electrochemical measurements revealed the presence of ligand to metal charge transfer (LMCT), indicating the promoting of Fenton-like reaction. Noticeably, degradation pathways of N,N,N′,N′-Tetrakis(2-hydroxypropyl) ethylenediamine (EDTP), one of the main complexing agents according to the component identification using mass spectrum within electroplating wastewater are proposed. EDTP might be first degraded to 2-hydroxypropanal or 2-Aminoethyl(ethyl) amine, then further degraded to acetaldehyde or ethylene, and finally oxidized to CO₂ and H₂O. Therefore, the biochar composite developed here could provide a novel route for the resource utilization of blue algae and heavy metal removal in electroplating wastewater containing refractory complexing agent.
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24664. 题目: Revisiting the Great Ordovician Diversification of land plants: Recent data and perspectives
文章编号: N19080303
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Thomas Servais, Borja Cascales-Miñana, Christopher J. Cleal, Philippe Gerrienne, David A.T. Harper, Mareike Neumann
更新时间: 2019-08-03
摘要: Recent molecular clock data suggest with high probability a Cambrian origin of Embryophyta (also called land plants), indicating that their terrestrialization most probably started about 500 Ma. The fossil record of the ‘Cambrian Explosion’ was limited to marine organisms and not visible in the plant fossil record. The most significant changes in early land plant evolution occurred during the Ordovician. For instance, the earliest bryophyte-like cryptospores and the oldest fragments of the earliest land plants come from the Middle and Late Ordovician, respectively. Organic geochemistry studies on biomarker compositions hint at a transition from green algae to land plants during the ‘Great Ordovician Biodiversification Event’ (GOBE). The colonization of the terrestrial realms by land plants clearly had an impact on marine ecosystems. Interactions between the terrestrial and marine biospheres have been proposed and the radiation of land plants potentially impacted on CO₂ and O₂ concentrations and on global climate. In addition, the shift of strontium isotopes during the Ordovician is probably linked to changing terrestrial landscapes, affected by the first massive land invasion of eukaryotic terrestrial life. The land plants seem unaffected by the first global mass extinction at the end of the Ordovician that eliminated many marine invertebrate taxa.

24665. 题目: Response of microbes to biochar strengthen nitrogen removal in subsurface flow constructed wetlands: Microbial community structure and metabolite characteristics
文章编号: N19080302
期刊: Science of The Total Environment
作者: Chaoren Deng, Lei Huang, Yinkun Liang, Hongyu Xiang, Jie Jiang, Qinghua Wang, Jie Hou, Yucheng Chen
更新时间: 2019-08-03
摘要: Four subsurface flow constructed wetlands (SFCWs) were constructed on the basis of the volume ratio of biochar in common gravel (0%, 10%, 20%, and 30%) for the evaluation of microbe and metabolite characteristics response to biochar addition. The results showed that the biochar added SFCWs provided higher removal efficiencies for ammonium (49.69%–63.51%) and total nitrogen (81.83%–86.36%), compared with pure gravel packed SFCWs for ammonium (47.40%) and total nitrogen (80.75%), respectively. Illumina MiSeq sequencing results revealed that the dominant phyla were Proteobacteria, Bacteroidetes, and Firmicutes. Biochar addition can improve the removal of nitrogen by altering microbial community and increasing the relative abundance of Thauera, Candidatus Competibacter, Dechloromonas, Desulfobulbus, Chlorobium, and Thiobacillus. Protein and humic substances were the primary components of extracellular polymeric substance (EPS) in SFCWs. The amount of total EPS considerably decreased with biochar addition, which caused a shift in the EPS functional groups including carbonyl of protein, amide, and hydroxyl groups. Moreover, biochar could enhance the high molecular weight compounds metabolized into low molecular compounds. The results can provide new insights into the use of biochar in the enhancement of nitrogen removal by microbial community and metabolic product characteristics.
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24666. 题目: Modifying effect of ant colonization on soil heterogeneity along a chronosequence of tropical forest restoration on slash-burn lands
文章编号: N19080301
期刊: Soil and Tillage Research
作者: Mei Lu, Shaojun Wang, Zhe Zhang, Minkun Chen, Shaohui Li, Run Cao, Qianbin Cao, Qianqian Zuo, Ping Wang
更新时间: 2019-08-03
摘要: Ants act as ecosystem engineers in regulating soil heterogeneities. Little is known about the degree and direction of these modifications on soils across a restoration chronosequence of tropical forests. Our objectives aimed to explore the effect of belowground-nesting ants on soil characteristics across four forest restoration stages (i.e., 12-, 28-, 42- and 53-yr olds) on slash-burn lands in the tropical Xishuangbanna, southwestern China. We confirmed the hypotheses about a positive effect of ant colonization on soil physical characteristics, and on the enrichment of microbial carbon and mineral nutrients in nest soils across the four restoration stages. Ant nests had the highest enrichment of soil organic matter (103%), readily oxidizable carbon (78%), total nitrogen (114%), available nitrogen (126%), NH₄⁺ (133%) and NO₃– (140%) at the 12-yr old stage compared with the surrounding soils. In contrast, the highest enrichment of microbial carbon (110%) in nest soils was showed at the 53-yr old stage. The enrichment of microbial carbon in nest soils increased with restoration age, but that of soil mineral nutrients would not follow the forest restorations. A higher enrichment of mineral nutrients in nest soils at the early restoration stage can improve soil fertility, which might promote the spontaneous forest restorations. A higher abundance and area of ant nests at the older restoration stage may create a higher bare space for plant development. Therefore, our results suggest that ant colonization can regulate forest restorations, possibly through creating and maintaining higher soil nutrient heterogeneity at earlier stage, and greatly stirring microbial growth and opening up space for plant development at older stage on slash-burn tropical lands.
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24667. 题目: The influence of plankton community structure on sinking velocity and remineralization rate of marine aggregates
文章编号: N19080211
期刊: Global Biogeochemical Cycles
作者: L.T. Bach, P. Stange, J. Taucher, E.P. Achterberg, M. Algueró‐Muñiz, H. Horn, M. Esposito, U. Riebesell
更新时间: 2019-08-02
摘要: Gravitational sinking of photosynthetically fixed particulate organic carbon (POC) constitutes a key component of the biological carbon pump. The fraction of POC leaving the surface ocean depends on POC sinking velocity (SV) and remineralization rate (C_remin), both of which depend on plankton community structure. However, the key drivers in plankton communities controlling SV and C_remin are poorly constrained. In fall 2014, we conducted a 6 weeks mesocosm experiment in the subtropical NE Atlantic Ocean to study the influence of plankton community structure on SV and C_remin. Oligotrophic conditions prevailed for the first 3 weeks, until nutrient‐rich deep water injected into all mesocosms stimulated diatom blooms. SV declined steadily over the course of the experiment due to decreasing CaCO₃ ballast and – according to an optical proxy proposed herein – due to increasing aggregate porosity mostly during an aggregation event after the diatom bloom. Furthermore, SV was positively correlated with the contribution of picophytoplankton to the total phytoplankton biomass. C_remin was highest during a Synechococcus bloom under oligotrophic conditions and in some mesocosms during the diatom bloom after the deep‐water addition while it was particularly low during harmful algal blooms. The temporal changes were considerably larger in C_remin (max. 15‐fold) than in SV (max. 3‐fold). Accordingly, estimated POC transfer efficiency to 1000 m was mainly dependent on how the plankton community structure affected C_remin. Our approach revealed key players and interactions in the plankton food web influencing POC export efficiency thereby improving our mechanistic understanding of the biological carbon pump.

24668. 题目: Alpine glacier shrinkage drives shift in dissolved organic carbon export from quasi‐chemostasis to transport‐limitation
文章编号: N19080210
期刊: Geophysical Research Letters
作者: Marta Boix Canadell, Nicolas Escoffier, Amber J. Ulseth, Stuart N. Lane, Tom J. Battin
更新时间: 2019-08-02
摘要: The export of dissolved organic carbon (DOC) from catchments is considered as an important energy flux through streams and a major connection between terrestrial and aquatic systems. However, the impact that predicted hydrological changes due to glacier retreat and reduction in snow cover changes will have on DOC export from high‐mountain streams remains unclear. In this study, we measured daily runoff and DOC yield during one year in Alpine streams draining catchments with different levels of glacier coverage. DOC yield showed a varied response to runoff across the catchments and varied seasonally as a function of the degree of glaciation and vegetation cover. Using space‐for‐time substitution, our results indicate that the controls on DOC yield from Alpine catchments change from chemostasis to transport‐limitation as glaciers shrink.

24669. 题目: Effects of eddy‐driven subduction on ocean biological carbon pump
文章编号: N19080209
期刊: Global Biogeochemical Cycles
作者: Laure Resplandy, Marina Lévy, Dennis J. McGillicuddy
更新时间: 2019-08-02
摘要: Estimates of the ocean biological carbon pump are limited by uncertainties in the magnitude of the physical injection of particulate (POC) and dissolved (DOC) organic carbon to the ocean interior. A major challenge is to evaluate the contribution of these physical pumps at small spatial and temporal scales (< 100 km and < 1 month). Here, we use a submesoscale permitting bio‐physical model covering a large domain representative of a subpolar and a subtropical gyre to quantify the impact of small‐scale physical carbon pumps. The model successfully simulates intense eddy‐driven subduction hotspots with a magnitude comparable to what has been observed in nature (1000‐6000 mgC m^‐2 d^‐1). These eddy‐driven subduction events are able to transfer carbon below the mixed‐layer, down to 500‐1000 m depth. However, they contribute <5% to the annual flux at the scale of the basin, due to strong compensation between upward and downward fluxes. The model also simulates hotspots of export associated with small‐scale heterogeneity of the mixed‐layer, which intermittently export large amounts of suspended POC and DOC. The mixed‐layer pump contributes ~20% to the annual flux. High resolution measurements of export flux are needed to test models such as this one, and to improve our mechanistic understanding of the biological pump and how it will respond to climate change.

24670. 题目: Bioretention cell incorporating Fe-biochar and saturated zones for enhanced stormwater runoff treatment
文章编号: N19080208
期刊: Chemosphere
作者: Jiaqing Xiong, Sihui Ren, Yifan He, Xiaochang C. Wang, Xuechen Bai, Jiaxuan Wang, Mawuli Dzakpasu
更新时间: 2019-08-02
摘要: Nitrogen (N) and phosphorus (P) removal in conventional bioretention systems is highly variable. Therefore, five novel experimental columns with different media configurations and constituents, and incorporating a saturated zone were developed and assessed to optimize the removal of N, P and other nutrients. Three types of media composed of the conventional mixed sand and soil media (T₁), biochar-amended media (T₂), and iron-coated biochar (ICB)-amended media (T₃) were evaluated. Two of the experimental columns were designed with double-layer configurations, while the other three were of a single-layer structure. Removal efficiencies of nutrients in the experimental columns were evaluated and compared using simulated runoff. Also, the effect of media depth on the retention of P and denitrifying enzyme activity (DEA) in the bioretention columns were evaluated. The experimental column only filled with T₃ showed the best performance for COD, ammonia (NH₄⁺-N) and total phosphorus (TP) removal (94.6%, 98.3% and 93.70%, respectively), whereas columns filled with T₂ performed poorly for TP removal (57.36%). For the removal of nitrate (NO₃⁻-N) and total nitrogen (TN), the columns using a single-layer and only filled with either T₃ or T₂ exhibited the best performance (93% and 97% TN removal, respectively). Overall, this study demonstrates that our proposed single-layered bioretention cell only filled with T₃ and incorporating a saturated zone effectively improves the runoff quality, and can provide a new bioretention cell configuration for efficient stormwater treatment.

24671. 题目: Soil organic matter amount determines the behavior of iron and arsenic in paddy soil with microbial fuel cells
文章编号: N19080207
期刊: Chemosphere
作者: Williamson Gustave, Zhao-Feng Yuan, Raju Sekar, Yu-Xiang Ren, Jinjing-Yuan Liu, Jun Zhang, Zheng Chen
更新时间: 2019-08-02
摘要: Arsenic (As) mobility in paddy soils is mainly controlled by iron (Fe) oxides and iron reducing bacteria (IBR). The Fe reducing bacteria are also considered to be enriched on the anode of soil microbial fuel cells (sMFC). Thus, the sMFC may have an impact on elements’ behavior, especially Fe and As, mobilization and immobilization in paddy soils. In this study, we found dissolved organic matter (DOC) abundance was a major determinate for the sMFC impact on Fe and As. In the constructed sMFCs with and without water management, distinctive behaviors of Fe and As in paddy soil were observed, which can be explained by the low or high DOC content under different water management. When the sMFC was deployed without water management, i.e. DOC was abundant, the sMFC promoted Fe and As movement into the soil porewater. The As release into the porewater was associated with the enhanced Fe reduction by the sMFC. This was ascribed to the acidification effect of sMFC anode and the increase of Fe reducing bacteria in the sMFC anode vicinity and associated bulk soil. However, when the sMFC was coupled with alternating dry-wet cycles, i.e. DOC was limited, the Fe and As concentrations in the soil porewater dramatically decreased by up to 2.3 and 1.6 fold, respectively, compared to the controls under the same water management regime. This study implies an environmental risk for the in-situ application of sMFC in organic matter rich wetlands and also points out a new mitigation strategy for As management in paddy soils.
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24672. 题目: Biochar particle aggregation in soil pore water: influence of ionic strength and interactions with pyrene
文章编号: N19080206
期刊: Environmental Science: Processes Impacts
作者: Stephanie Castan, Gabriel Sigmund, Thorsten Hüffer, Thilo Hofmann
更新时间: 2019-08-02
摘要: The beneficial properties of biochar have led to its increasing application to soils for environmental management. Despite its stability in soil, biochar can physically disintegrate into smaller particles, which can then be relocated from the application area. Biochar transport is strongly dependent on the biochar particle size and aggregation, with the extent of aggregation depending on the chemistry of the soil pore water. Biochar has a strong sorption affinity for polyaromatic hydrocarbons (PAHs) such as pyrene, which can also affect its transport. We therefore investigated biochar particle aggregation in solutions of different ionic strengths (ultrapure water, 0.01 M CaCl2, and 0.1 M CaCl2) with suspensions of biochar particles, and with suspensions of biochar particles loaded with pyrene (0.2, and 3.6 g/kg). Increasing the pyrene concentration in ultrapure water resulted in an increase in biochar particle size, an effect that was more pronounced following equilibration for 28 days than following equilibration for only 24 hours. Biochar particle aggregation in solutions containing both pyrene and 0.01 M CaCl2 was greatly enhanced compared to aggregation in similar solutions with no pyrene. However, the influence of pyrene became negligible at high CaCl2 concentrations (0.1 M CaCl2). To determine fate of biochar in soil the presence of PAHs and the influence of the pore water's ionic strength therefore both need to be taken into account.

24673. 题目: Lignin chemistry of wetland soil profiles in two contrasting basins of the Louisiana Gulf Coast
文章编号: N19080205
期刊: Organic Geochemistry
作者: Weiyang Bi, Jim J. Wang, Syam K. Dodla, Lewis A. Gaston, Ronald D. DeLaune
更新时间: 2019-08-02
摘要: Recent studies indicate that loss of soil organic matter (SOM) from coastal wetlands can contribute to the hypoxia in the northern Gulf of Mexico along the Louisiana coast. In this study, coastal marsh soil profiles of two contrasting basins were investigated for lignin composition in order to assess organic matter source and degradation status under these different wetland formations. The Atchafalaya Basin is undergoing land building whereas the Barataria Basin is experiencing land loss. Lignin monomers were extracted using alkaline CuO oxidation followed by gas chromatography–mass spectrometry characterization. Marsh soil profiles from the Barataria Basin showed strong lignin storage with two-fold higher lignin contents (sum of vanillyl, syringyl, and cinnamyl phenols, Λ₈) than those in the Atchafalaya Basin. Source SOM inputs in the Barataria Basin were non-woody angiosperms, whereas in the Atchafalaya Basin inputs were non-woody angiosperms and some gymnosperm inputs. Principal component analysis (PCA) showed that different soil environmental factors dominated the status of soil organic matter degradation. Soil pH was negatively related to the lignin degradation in the Atchafalaya Basin, whereas high total N contents inhibited lignin degradation in the Barataria Basin. Increasing electrical conductivity inhibited organic matter degradation in the low salinity wetlands of the Atchafalaya Basin, but positively influenced lignin decomposition in the higher salinity marsh soil profiles of Barataria Basin. Despite SOM in the Barataria Basin being more degraded than in the Atchafalaya, the nearly 10-fold greater amount of organic carbon (C) in the Barataria, coupled with net land loss, indicates that it is greater source of oxygen-consuming organic C, thus contributes more to the hypoxia in the Gulf.
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24674. 题目: The interplay of extracellular polymeric substances and oil/Corexit to affect the petroleum incorporation into sinking marine oil snow in four mesocosms
文章编号: N19080204
期刊: Science of The Total Environment
作者: Chen Xu, Peng Lin, Saijin Zhang, Luni Sun, Wei Xing, Kathleen A. Schwehr, Wei-Chun Chin, Terry L. Wade, Anthony H. Knap, Patrick G. Hatcher, Alexandra Yard, Christine Jiang, Antonietta Quigg, Peter H. Santschi
更新时间: 2019-08-02
摘要: Large amounts of oil containing mucous-like marine snow formed in surface waters adjacent to the Deepwater Horizon spill that was implicated in oil delivery to the seafloor. However, whether chemical dispersants that were used increased or decreased the oil incorporation and sedimentation efficiency, and how exopolymeric substances (EPS) are involved in this process remains unresolved. To investigate the microbial responses to oil and dispersants in different oceanic settings, indicated by EPS production, petro- and non-petro carbon sedimentation, four mesocosm (M) experiments were conducted: 1) nearshore seawater with a natural microbial consortia (M2); 2) offshore seawater with f/20 nutrients (M3); 3) coastal seawater with f/20 nutrients (M4); 4) nearshore seawater with a natural microbial consortia for a longer duration (M5). Four treatments were conducted in M2, M3 and M4 whereas only three in M5: 1) a water accommodated fraction of oil (WAF), 2) a chemically-enhanced WAF prepared with Corexit (CEWAF, not in M5), 3) a 10-fold diluted CEWAF (DCEWAF); and 4) controls. Overall, oil and dispersants input, nutrient and microbial biomass addition enhanced EPS production. Dispersant addition tended to induce the production of EPS with higher protein/carbohydrate (P/C) ratios, irrespective of oceanic regions. EPS produced in M4 was generally more hydrophobic than that produced in M3. The P/C ratio of EPS in both the aggregate and the colloidal fraction was a key factor that regulated oil contribution to sinking aggregates, based on the close correlation with %petro-carbon in these fractions. In the short term (4–5 days), both the petro and non-petro carbon sedimentation efficiencies showed decreasing trends when oil/dispersants were present. In comparison, in the longer-term (16 days), petro-carbon sedimentation efficiency was less influenced by dispersants, possibly due to biological and physicochemical changes of the components of the oil-EPS-mineral phase system, which cooperatively controlled the sinking velocities of the aggregates.
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24675. 题目: Comparison of the methane-oxidizing capacity of landfill cover soil amended with biochar produced using different pyrolysis temperatures
文章编号: N19080203
期刊: Science of The Total Environment
作者: Dandan Huang, Luning Yang, Jae Hac Ko, Qiyong Xu
更新时间: 2019-08-02
摘要: The in-situ mitigation of methane (CH₄) in landfill gas using landfill cover soil (LCS) is a cost-effective approach, but its efficiency needs to be enhanced. In this study, we incorporated an enriched methane-oxidizing bacteria (MOB) consortium into LCS and established four biochar-amended LCS groups with biochar produced at 300 °C (BC300), 400 °C (BC400), 500 °C (BC500), and 600 °C (BC600). The purpose was to evaluate the CH₄ oxidation capacity of biochar-amended LCS after inoculation with MOB and to investigate how the physicochemical properties of biochar that are influenced by the pyrolysis temperature affect the performance and microbial activity of biochar-amended LCS. It was found that a 15% volume ratio (representing a mass ratio of 2.49%–2.78%) for biochar amendment in LCS enhanced CH₄ removal efficiency, with the highest removal observed to be 46% for BC400-amended LCS compared to 30% for the original LCS. In addition, CH₄ adsorption by the biochar was not observed, and a 15% mass ratio for biochar in the LCS had no or a negative impact. Besides improving the water-holding capacity and gas permeability of LCS, other possible advantages of biochar amendment in terms of CH₄ oxidization include greater retention of nutrients, electron acceptors, and exchangeable cations, as well as introducing iron ions. It was also found that CH₄ oxidation capacity and the methanotroph activity of biochar-amended LCS did not continue to increase with higher pyrolysis temperatures, even though higher micropore volumes and surface areas were obtained at higher pyrolysis temperatures. From this study, BC400 was identified as the optimal choice for the best performance in terms of enhancing both the CH₄ oxidation capacity of the amended LCS and the growth of type II methanotroph Methylocystaceae, which can possibly be attributed to having the highest cation exchange capacity of the four biochars.
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24676. 题目: Vertical distribution and influencing factors of soil organic carbon in the Loess Plateau, China
文章编号: N19080202
期刊: Science of The Total Environment
作者: Haiyan Yu, Tonggang Zha, Xiaoxia Zhang, Limin Ma
更新时间: 2019-08-02
摘要: Accurate analysis and evaluation of the spatial distribution and the primary factors that affect regional soil organic carbon (SOC) together make an important step in assessing carbon sequestration potential. However, little information is available on distribution of regional SOC in deep soil layers. To analyze the spatial distribution of and factors influencing SOC in a 500 cm soil profile, 1440 soil samples were collected from 90 sites on the Loess Plateau in China. The primary factors dominating the spatial distribution of SOC were quantified using principal component analysis with multiple linear regression (PCA–MLR) analysis. Results showed that the mean SOC of the 500 cm soil profile ranged from 1.20 to 3.37 g kg⁻¹, decreasing with increasing soil depth. The SOC in the deep soil profile decreased across the types of land use in the following order: forestland > cropland > grassland. Based on the factors analyzed in this study, land use accounted for 22% of the variation in SOC and was the dominant factor controlling the spatial distribution of organic carbon in shallow soils (0–100 cm); while soil factors (including soil clay, soil water content, and soil bulk density) were dominant in deep soil layers (200–500 cm), averagely accounting for 44.3%. The SOC stock in the 0–20 cm soil layer was 1.34 kg m⁻², accounting for only a small proportion (8%) of the total carbon in the entire 500 cm soil profile. SOC stock in the 200–500 cm layer was 7.62 kg m⁻², accounting for 40% of the total carbon in the 0–500 cm soil profile. This study demonstrates that a large amount of organic carbon is stored in deep soil, indicating that a better understanding of the reserves and cycles of deep soil carbon is a critical factor in the effective management of terrestrial ecosystems.
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24677. 题目: Soil respiration and organic matter decomposition dynamics respond to legacy fertilizer and weed control treatments in loblolly pine stands
文章编号: N19080201
期刊: Soil Biology and Biochemistry
作者: Praveen Subedi, Eric J. Jokela, Jason G. Vogel
更新时间: 2019-08-02
摘要: Most studies examining how forest soil carbon (C) cycling responds to silvicultural treatments are restricted to a single rotation, with the legacy effects of past management practices being relatively unstudied. Here, we examined soil respiration and organic matter decomposition dynamics (important proxies for C dynamics), climate, and nutrient cycling in a second rotation, 2-year-old loblolly pine (Pinus taeda L.) plantation in north Florida. Carryover (C-) effects of the previous rotation's control (C_C), fertilizer (C_F), weed control (C_W), and combined fertilizer and weed control (C_FW) treatments were examined for residual effects on soil respiration (Rs), heterotrophic respiration (Rh), and substrate decomposition potential. Repeated measurements were made over 13 months. The mean Rs for both the C_F (4.56 μmol CO₂ m⁻² s⁻¹) and C_FW (4.49 μmol CO₂ m⁻² s⁻¹) treatments were increased by 29% and 27%, respectively, compared to the C_C (3.53 μmol CO₂ m⁻² s⁻¹) treatment. The Rh in the C_W (2.97 μmol CO₂ m⁻² s⁻¹) was significantly lower compared to the C_F (4.02 μmol CO₂ m⁻² s⁻¹) and C_FW (3.66 μmol CO₂ m⁻² s⁻¹) treatments, despite having warmer soil temperatures than the C_F treatment, and no differences in soil moisture contents. Soil temperature and Mehlich III soil extractable manganese (Mn) concentrations (0–10 cm) were the only variables that explained variation in Rh. Decomposition rates for a common substrate were also lower in the C_W compared to the C_F, treatment (p = 0.027), potentially because the removal of understory plants in the C_W treatment affected both microclimate and Mn cycling compared to the C_F treatment where understory plants were retained and micronutrients were added as fertilizers. Overall, forest management affected organic matter cycling after replanting and 12 years after the last treatment in the previous rotation, suggesting that long-term studies are needed to understand the effects of silvicultural practices on ecosystem C cycling.

24678. 题目: Contrasting contribution of fungal and bacterial residues to organic carbon accumulation in paddy soils across eastern China
文章编号: N19080116
期刊: Biology and Fertility of Soils
作者: Yinhang Xia, Xiangbi Chen, Yajun Hu, Shengmeng Zheng, Zhao Ning, Georg Guggenberger, Hongbo He, Jinshui Wu, Yirong Su
更新时间: 2019-08-01
摘要: Microbial residues are key components of stable soil organic C (SOC). However, the accumulation patterns of fungal and bacterial residues across climate regions are largely unknown, especially in paddy soils. In this study, the amounts of microbial-derived amino sugars (AS) with their constituents, glucosamine (GlcN), galactosamine (GalN), and muramic acid (MurN, a biomarker of bacterial residues) were quantified in paddy soils, which were collected from mid-temperate, warm-temperate, subtropical, and tropical climate regions across eastern China. The contents of total AS and fungal-derived GlcN (F-GlcN, a biomarker of fungal residues) were lowest in the warm-temperate region, but not significantly different among the other three climate regions. The MurN content and its contribution to SOC accumulation were higher in the warmer and wetter regions (subtropic and tropic) than in the cooler and drier ones (mid-temperate and warm-temperate). Consequently, the ratio of F-GlcN to MurN was lower in the warmer and wetter regions (8.5–15.4) than in the cooler and drier ones (12.8–28.8). These results illustrate that the bacteria participating in SOC transformation and stabilization in paddy soils exerted more prominent activities in the warmer and wetter regions than in the cooler and drier regions. Structure equation models emphasize that the contrasting patterns of fungal and bacterial residues’ contribution to SOC accumulation in paddy ecosystems along the latitudinal gradient were mainly attributed to their different responses to the climate factors of temperature and precipitation.

24679. 题目: Quantitative assessment of microbial necromass contribution to soil organic matter
文章编号: N19080115
期刊: Global Change Biology
作者: Chao Liang, Wulf Amelung, Johannes Lehmann, Matthias Kästner
更新时间: 2019-08-01
摘要: Soil carbon transformation and sequestration have received significant interest in recent years due to a growing need for quantifying its role in mitigating climate change. Even though our understanding of the nature of soil organic matter has recently been substantially revised, fundamental uncertainty remains about the quantitative importance of microbial necromass as part of persistent organic matter. Addressing this uncertainty has been hampered by the absence of quantitative assessments whether microbial matter makes up the majority of the persistent carbon in soil. Direct quantification of microbial necromass in soil is very challenging because of overlapping molecular signature with non‐microbial organic carbon. Here we use a comprehensive analysis of existing biomarker amino sugar data published between 1996‐2018, combined with novel appropriation using ecological systems approach, elemental carbon‐nitrogen stoichiometry, and biomarker scaling, to demonstrate a suit of strategies for quantifying the contribution of microbe‐derived carbon to the topsoil organic carbon reservoir in global temperate agricultural, grassland, and forest ecosystems. We show that microbial necromass can make up more than half of soil organic carbon. Hence, we suggest next‐generation field management requires promoting microbial biomass formation and necromass preservation to maintain healthy soils, ecosystems, and climate. Our analyses have important implications for improving current climate and carbon models, and helping develop management practices and policies.

24680. 题目: Molecular modeling of sorption processes of a range of diverse small organic molecules in Leonardite humic acid
文章编号: N19080114
期刊: European Journal of Soil Science
作者: Drazen Petrov, Daniel Tunega, Martin H. Gerzabek, Chris Oostenbrink
更新时间: 2019-08-01
摘要: Soil organic matter (SOM) is abundant in the environment and plays an important role in several biogeochemical processes including microbial activity, soil aggregation, plant growth and carbon storage. One of its key functions is the retention and release of various chemical compounds, primarily governed by the sorption process, which strongly affects the environmental fate of nutrients and pollutants. Sorption largely depends on the composition of SOM, as well as its structure, dynamics and the thermodynamic conditions. While several approaches are available, experimental characterization of sorption mechanisms is not easy. Computational models for predicting sorption coefficients on the other hand often require a wealth of experimental data for training and are only applicable to compounds and conditions related to the training dataset.