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24901. 题目: Quantifying degradative loss of terrigenous organic carbon in surface sediments across the Laptev and East Siberian Sea
文章编号: N19010708
期刊: Global Biogeochemical Cycles
作者: Lisa Bröder, August Andersson, Tommaso Tesi, Igor Semiletov, Örjan Gustafsson
更新时间: 2019-01-07
摘要: Ongoing permafrost thaw in the Arctic may remobilize large amounts of old organic matter. Upon transport to the Siberian shelf seas, this material may be degraded and released to the atmosphere, exported off‐shelf or buried in the sediments. While our understanding of the fate of permafrost‐derived organic matter in shelf waters is improving, poor constraints remain regarding degradation in sediments. Here, we use an extensive dataset of organic carbon concentrations and isotopes (n=109) to inventory terrigenous organic carbon (terrOC) in surficial sediments of the Laptev and East Siberian Seas (LS+ESS). About 55 % of these ~2.7 Tg terrOC appear resistant to degradation on a millennial timescale. A first‐order degradation rate constant of 1.5 kyr‐1 is derived by combining a previously established relationship between water depth and cross‐shelf sediment‐terrOC transport time with mineral‐associated terrOC loadings. This yields a terrOC degradation flux of ~1.7 Gg yr‐1 from surficial sediments during cross‐shelf transport, which is orders of magnitude lower than earlier estimates for degradation fluxes of dissolved and particulate terrOC in the water column of the LS+ESS. The difference is mainly due to the low degradation rate constant of sedimentary terrOC, likely caused by a combination of factors: (i) the lower availability of oxygen in the sediments compared to fully oxygenated waters, (ii) the stabilizing role of terrOC‐mineral associations and (iii) the higher proportion of material that is intrinsically recalcitrant due to its chemical/molecular structure in sediments. Sequestration of permafrost‐released terrOC in shelf sediments may thereby attenuate the otherwise expected permafrost carbon‐climate feedback.

24902. 题目: Dissolved organic matter chemistry and transport along an Arctic tundra hillslope
文章编号: N19010707
期刊: Global Biogeochemical Cycles
作者: Laurel M. Lynch, Megan B. Machmuller, Claudia M. Boot, Timothy P. Covino, Christopher D. Rithner, M. Francesca Cotrufo, David W. Hoyt, Matthew D. Wallenstein
更新时间: 2019-01-07
摘要: Permafrost thaw is projected to restructure the connectivity of surface and subsurface flowpaths, influencing export dynamics of dissolved organic matter (DOM) through Arctic watersheds. Resulting shifts in flowpath exchange between both soil horizons (organic‐mineral) and landscape positions (hillslope‐riparian) could alter DOM mobility and molecular‐level patterns in chemical composition. Using conservative tracers, we found relatively rapid lateral flows occurred across a headwater Arctic tundra hillslope, as well as along the mineral‐permafrost interface. While pore waters collected from the organic horizon were associated with plant‐derived molecules, those collected from permafrost‐influenced mineral horizons had a microbial origin, as determined by fluorescence spectroscopy. Using high‐resolution NMR spectroscopy, we found that riparian DOM had greater structural diversity than hillslope DOM, suggesting riparian soils could supply a diverse array of compounds to surface waters if terrestrial‐aquatic connectivity increases with warming. In combination, these results suggest integrating DOM mobilization with its chemical and spatial heterogeneity can help predict how permafrost loss will structure ecosystem metabolism and carbon‐climate feedbacks in Arctic catchments with similar topographic features.

24903. 题目: Detection of transient denitrification during a high organic matter event in the Black Sea
文章编号: N19010706
期刊: Global Biogeochemical Cycles
作者: Clara A. Fuchsman, Barbara Paul, James T. Staley, Evgeniy V. Yakushev, James W. Murray
更新时间: 2019-01-07
摘要: N₂ production by denitrification can occur in anoxic water or potentially inside organic particles. Here we compare data from the Black Sea, a permanently anoxic basin, during two organic matter regimes: suspended particulate organic matter concentrations were high in the oxycline after the spring bloom in March 2005 compared to lower organic matter concentrations in June 2005, May and October 2007, July 2008 and May 2001. For all cruises, N₂ gas had a maximum in the suboxic zone [O₂ <10 μmol L^‐1]. During the high organic matter event [March 2005], an additional shallower N₂ gas and δ¹⁵N‐N₂ maxima occurred above the suboxic zone in the oxycline where oxygen concentrations were 30‐50 μmol L^‐1. Examination of 16S rRNA indicated that anammox bacteria were not present in the oxycline. The δ¹⁵N of biologically produced N₂ in the oxycline in March 2005 was significantly enriched (+7 to +38‰), not depleted, as would be expected from water column fractionation. A simple diffusion calculation indicated that ammonium produced from remineralization inside particles could be oxidized to nitrate and then completely consumed by denitrification inside the particle. In this calculation, half of denitrified N atoms originated from organic N [δ¹⁵N = 11‰] and half of N atoms originated from ambient nitrate [δ¹⁵N = 5‐7‰], producing enriched δ¹⁵N‐N₂ values. We suggest that denitrifiers were active in microzones inside particulates in hypoxic waters above the suboxic zone of the Black Sea. Denitrification in particles may also explain previous data from the oxycline above ocean oxygen deficient zones.

24904. 题目: Impacts of wise grazing on physicochemical and biological features of soil in a sandy grassland on the Tibetan Plateau
文章编号: N19010705
期刊: Land Degradation & Development
作者: Nan Nan Zhang, Geng Sun, Bo Zhong, En Tao Wang, Chun Zhang Zhao, Yan Jie Wang, Wei Cheng, Ning Wu
更新时间: 2019-01-07
摘要: Desertification is a serious environmental problem on the Tibetan Plateau and various strategies, such as long‐term fencing and grazing management, have been implemented in that region to control the soil degradation. However, little is known about the role of interactions among the soil aggregate, microbial communities, and nutrient traits in the soil restoration. In this study, we compared the effects of different restoration strategies on the formation of aggregates, the amount and distribution of soil nutrients, as well as the abundance and diversity of bacteria in a sandy soil of grassland at the Tibetan Plateau. The results demonstrated that both the grazing exclusion (GE: artificial planting and nutrient addition) and wise grazing (WG: artificial planting and nutrient addition with controlled grazing) treatments significantly increased the proportion of macroaggregates (4.0 and 5.2 times, P < 0.05) compared with the control. Increased soil organic carbon (SOC), total carbon (TC), total nitrogen (TN), and total phosphorus (TP) were found in the aggregates of WG treatment, but not in the GE samples. In addition, WG significantly changed the bacterial composition and increased bacterial abundance in soil. This study evaluated WG as an efficient management for restoration of degraded sandy grassland in the Tibetan Plateau since it significantly enriched the soil nutrients, improved the soil structure and increased bacterial abundance. This is the first study to relate the aggregates with nutrient accumulation and bacterial community during the soil restoration in the Tibetan Plateau.

24905. 题目: The effect of redox capacity of humic acids on hexachlorobenzene dechlorination during the anaerobic digestion process
文章编号: N19010704
期刊: Environmental Science and Pollution Research
作者: Dongyang Li, Beidou Xi, Yingjun Li, Xiaowei Wang, Tianxue Yang, Hong Yu, Caihong Huang, Jianchao Zhu, Qi Li, Xing Peng, Zhifei Ma
更新时间: 2019-01-07
摘要: Hexachlorobenzene (HCB) dechlorination affected by humic acids (HA) was evaluated in terms of HA redox capacity, HA concentrations, and microbial community, as well as the correlation between HA redox capacity values and HCB concentrations. With addition of HA in the initial stage, redox capacity values increased by 2.19 meq/L (80 mg/L of HA addition, HA₈₀), 2.51 meq/L (120 mg/L of HA addition, HA₁₂₀), and 3.64 meq/L (200 mg/L of HA addition, HA₂₀₀), respectively. The addition of HA could prominently enhance the HCB degradation rate. However, the concentration and the redox capacity of HA decreased during the anaerobic digestion process. Illumina MiSeq sequencing showed that microbial community affected by HA. Bacillus, Comamonas, and Pseudomonas were the predominant genera during the HCB dechlorination treatment. Moreover, Bacillus and Pseudomonas can improve HA electron transfer capability and promote the dechlorination of HCB.

24906. 题目: Non-additive responses of soil C and N to rice straw and hairy vetch ( Vicia villosa Roth L. ) mixtures in a paddy soil
文章编号: N19010703
期刊: Plant and Soil
作者: Guopeng Zhou, Weidong Cao, Jinshun Bai, Changxu Xu, Naohua Zeng, Songjuan Gao, Robert M. Rees
更新时间: 2019-01-07
摘要: Aims: We studied the effects of mixing rice straw and hairy vetch plant residues in a subtropical paddy soil, on subsequent carbon (C) and nitrogen (N) dynamics. Methods: Using a theoretical framework, we designed two groups of experiments (involving equal amounts of residual C or N addition, referred to as either C or N treatments). Each experiment included mixed residues of rice straw and hairy vetch at different mixing ratios. Soils together with residues were incubated at 25 °C under waterlogged conditions for 100 days. Greenhouse gas (GHG) emissions and soil C and N fractions were measured continuously. Results: Both C and N treatments affected soil C and N dynamics, and these dynamics were quantitatively dependent on residue C/N ratios. The effect of residue mixtures on C and N dynamics could not be predicted from single residues, since there were non-additive effects of residue mixtures. Synergistic effects were generally more frequent than antagonistic effects. Residue mixtures tended to enhance CO₂ and CH₄ emissions in both C and N treatments but decreased N₂O emissions in the N treatment. In the N treatment, dissolved organic C (DOC), dissolved organic N (DON), and microbial biomass C (MBC) concentrations increased. DOC and DON concentrations decreased in the C treatment. Residue mixtures enhanced the global warming potentials (GWP) of greenhouse gases (GHG) emitted from soil by non-additive synergistic effects. The C/N ratio of residue mixtures affected the non-additive responses of soil C and N dynamics, for example mixtures with a C/N ratio of 25 had higher CO₂ emissions and DOC concentrations than those with a C/N ratio of 35 as a consequence of non-additive effects, however, CH₄ emissions and MBC concentrations were higher in mixtures with a C/N ratio of 35 than in mixtures with a C/N ration of 25. Conclusions: These results indicated that non-additive effects can impact soil C and N dynamics and that residue C/N ratios play an important role in influencing non-additive effects. Applying a single residue to paddy soils may be better than residue mixtures from a GWP mitigation perspective.

24907. 题目: Efficient removal of Cd(II), Cu(II), Pb(II), and Zn(II) from wastewater and natural water using submersible device
文章编号: N19010702
期刊: Environmental Science and Pollution Research
作者: Boris S. Smolyakov, Alexei K. Sagidullin, Roman E. Romanov, Nadezhda I. Yermolaeva
更新时间: 2019-01-07
摘要: In this study, a simple submersible device was tested to remove and recover Cd(II), Cu(II), Pb(II), and Zn(II) from model wastewater and real natural water. To obtain this device, fine particles (< 0.1 mm) of a new hybrid adsorbent based on the mesoporous carbon and Fenton-modified humic acids were fixed onto a highly porous polymeric matrix. The hybrid adsorbent was characterized by various methods. The main mechanism for Cd(II), Cu(II), Pb(II), and Zn(II) adsorption by the hybrid adsorbent is chemosorption by surface functional groups, the total concentration of which was found to be 1.56 mmol g⁻¹. The adsorption capacity depends on pH, and at pH 6.0, it has the following order (mmol g⁻¹): Cu(II) (1.14) > Pb(II) (0.86) > Zn(II) (0.59) > Cd(II) (0.50). The possibility of applying a submersible device for the removal and recovery of these metals from multi-metal wastewaters and reservoirs was studied. A high efficiency of metal removal (95–99.9%) and recovery (85–99%) from wastewater remained in at least six consecutive adsorption–desorption cycles. Effective removal of metals from the water of a contaminated reservoir contributed to the rapid restoration of the phytoplankton organisms after their oppression by metals. Thus, the use of a submerged device with the new hybrid adsorbent can be an effective way of remediating wastewaters and natural waters contaminated with metals.

24908. 题目: Adsorption and regeneration characteristics of phosphorus from sludge dewatering filtrate by magnetic anion exchange resin
文章编号: N19010701
期刊: Environmental Science and Pollution Research
作者: Mingyang Song, Min Li
更新时间: 2019-01-07
摘要: Removal and recovery of phosphorus (P) from sewage are essential for sustainable development of P resource. Based on the water quality determination of sludge dewatering filtrate from a wastewater treatment plant in Beijing, this study investigated the adsorption and regeneration characteristics of P by magnetic anion exchange resin (MAEX). The experiments showed that the P adsorption capacity of MAEX could reach a maximum of 2.74 mg/mL when initial P concentration was 25 mg/L and dosage of MAEX was 8 mL/L. The P adsorption on MAEX resin was suitable for large temperature range (283–323 K). However, the adsorption capacity was reduced in various degrees due to the interference of different anions (Br⁻, SO₄²⁻, Cl⁻, NO₃⁻, HCO₃⁻, CO₃²⁻) and organic compounds (bovine serum albumin, humic acid). Kinetics studies indicated that the P adsorption process followed the pseudo-second-order model. The MAEX resin had a rapid P adsorption rate and the P adsorption capacity at 30 min could reach 97.7–99.3% of q_e. Increase of temperature was favorable to P adsorption on MAEX, and the adsorption isotherm data fitted to Langmuir model more than Freundlich model. Meanwhile, the thermodynamics parameters were calculated; it was shown that the adsorption process was an endothermic reaction. Desorption and regeneration experiments showed that NaHCO₃ was a suitable regenerant, and the P adsorption capacity could reach 90.51% of the original capacity after 10 times of adsorption-desorption cycles; this indicated that MAEX resin has an excellent regeneration performance and thus has a very good application prospect of P removal and recovery. Fourier transform infrared spectroscopy (FTIR) analysis confirmed that ion exchange, charge attraction, and hydrogen bonding affected the removal of P by the MAEX resin. The vibrating sample magnetometer (VSM) analysis revealed that MAEX resin was a kind of soft magnetic materials with good magnetism.

24909. 题目: Effect of tobacco stem-derived biochar on soil metal immobilization and the cultivation of tobacco plant
文章编号: N19010614
期刊: Journal of Soils and Sediments
作者: Jin Zhang, Jianyun Zhang, Minyan Wang, Shengchun Wu, Hailong Wang, Nabeel Khan Niazi, Yu Bon Man, Peter Christie, Shengdao Shan, Ming Hung Wong
更新时间: 2019-01-06
摘要: Purpose: Tobacco stems collected from tobacco cultivation fields were pyrolyzed to produce value-added biochar that was used to remediate metal-contaminated soil which was then used for tobacco cultivation. The feasibility of the scheme was evaluated. Materials and methods: A pot experiment was carried out to assess the impacts of tobacco stem-derived biochar (TSB 0, 2, 4, and 8%) on tobacco growth and leaf yields, soil properties, the availability of soil Cr, Cu, and Pb, and the accumulation of the three metals in tobacco plants. Results and discussion: Soil pH, organic matter content, and available phosphorus content increased with increasing application of TSB from 2 to 8% compared to the control (no biochar addition). In contrast, the acid-soluble and the reducible fractions of soil Cu and the reducible fraction of soil Pb and Cr decreased markedly, and the oxidizable fraction of the metals increased significantly with increasing application of TSB. This indicates that adding more TSB led to increasing immobilization of all three metals in the soil. Furthermore, both the number of tobacco leaves and the foliar biomass increased significantly with the addition of TSB to the soil. Based on our data, 4% is an economically suitable application rate of TSB for decreasing metal accumulation in plants and increasing tobacco leaf yields. Conclusions: The results indicate that it is feasible to use biochar derived from tobacco stem waste to remediate metal-contaminated soils which can then be used for tobacco cultivation. This is very useful in the recycling of the waste biomass and for remediation of soil metal pollution.

24910. 题目: Redox characterization of humins in sediments from the Yangtze Estuary to the East China Sea and their effects on microbial redox reactions
文章编号: N19010613
期刊: Journal of Soils and Sediments
作者: Chunfang Zhang, Shaohong You, Hongyue Dang, Zhiling Li, Qinglin Xie, Dongdong Zhang
更新时间: 2019-01-06
摘要: Purpose: Humins, as solid-phase redox mediators, are important for enhancing anaerobic biotransformation processes. Although humins are broadly distributed in estuarine and marine sediments, to date, their electron transfer capacity (ETC) from marine sediments has been poorly characterized. This study determined the potential of humins as redox mediators for microbial redox metabolic reactions in sediments along a transect from the Yangtze Estuary to the adjacent East China Sea and analyzed their electron-mediating characteristics. Materials and methods: Comparative analyses of humins in sediments along this transect were conducted to investigate their ETC as redox mediators for microbial redox metabolic reactions, namely dissimilatory iron reduction (DIR) and dissimilatory nitrate reduction to ammonium (DNRA), using Shewanella oneidensis MR-1. Elemental composition, electrochemical, and Fourier transform infrared analyses were performed to better understand the functional redox groups in humins. Results and discussion: All the humins functioned as solid-phase redox mediators and enhanced DIR and DNRA by Shewanella oneidensis, although with varying efficacy. The humins extracted from sampling site P1 (P1-HM), located close to the Yangtze Estuary, most effectively enhanced iron and nitrate reduction without nitrite accumulation. Electrochemical analysis confirmed the highest redox activity and ETC in P1-HM and a weakening trend of ETC with increasing distance from the estuary. Fourier transform infrared analysis suggested that quinone moieties might serve as key redox functional groups in humins. Conclusions: Considering their high yield and ETC, P1-HM could be important redox mediators that influence microbial redox metabolic reactions in sedimentary ecosystems of the Yangtze Estuary. Thus, this study provides insights into the distribution of humins, their ECT, and their potential role as redox mediators for microbial redox reactions, which could improve understanding of elemental biogeochemical cycling processes involving microorganisms in the Yangtze Estuary and East China Sea sedimentary ecosystems and provide important reference information for researches on other estuary areas.

24911. 题目: Organic micropollutants’ distribution within sludge organic matter fractions explains their dynamic during sewage sludge anaerobic digestion followed by composting
文章编号: N19010612
期刊: Environmental Science and Pollution Research
作者: Quentin Aemig, Nicolas Doussiet, Alice Danel, Nadine Delgenès, Julie Jimenez, Sabine Houot, Dominique Patureau
更新时间: 2019-01-06
摘要: The simultaneous fate of organic matter and 4 endocrine disruptors (3 polycyclic aromatic hydrocarbons (PAHs) (fluoranthene, benzo(b)fluoranthene, and benzo(a)pyrene) and nonylphenols (NP)) was studied during the anaerobic digestion followed by composting of sludge at lab-scale. Sludge organic matter was characterized, thanks to chemical fractionation and 3D fluorescence deciphering its accessibility and biodegradability. Total chemical oxygen demand (COD) removal was 41% and 56% during anaerobic digestion and composting, respectively. 3D fluorescence highlighted the quality changes of organic matter. During continuous anaerobic digestion, organic micropollutants’ removal was 22 ± 14%, 6 ± 5%, 18 ± 9%, and 0% for fluoranthene, benzo(b)fluoranthene, benzo(a)pyrene, and nonylphenols, respectively. Discontinuous composting allowed to go further on the organic micropollutants’ removal as 34 ± 8%, 31 ± 20%, 38 ± 10%, and 52 ± 6% of fluoranthene, benzo(b)fluoranthene, benzo(a)pyrene, and nonylphenols were dissipated, respectively. Moreover, the accessibility of PAH and NP expressed by their presence in the various sludge organic matter fractions and its evolution during both treatments was linked to both the quality evolution of the organic matter and the physicochemical properties of the PAH and NP; the presence in most accessible fractions explained the amount of PAH and NP dissipated.

24912. 题目: Magnetic nanoferromanganese oxides modified biochar derived from pine sawdust for adsorption of tetracycline hydrochloride
文章编号: N19010611
期刊: Environmental Science and Pollution Research
作者: Jie Liang, Yilong Fang, Yuan Luo, Guangming Zeng, Jiaqin Deng, Xiaofei Tan, Ning Tang, Xuemei Li, Xinyue He, Chunting Feng, Shujing Ye
更新时间: 2019-01-06
摘要: In this study, a new type of composite material, namely modified biochar (MBC), was synthesized by loading the magnetic ferromanganese oxide nanoparticles on pine biochar. BET, SEM, and FTIR were employed to analyze the surface properties and pore structures of MBC. In addition, XRD was adopted to examine the crystal structure of MBC. Characterization results showed that the surface area and porosity of MBC have been greatly improved, and the functional groups have been introduced by ferromanganese oxides. Adsorption experiments of tetracycline hydrochloride (TC) including kinetics, isotherms, thermodynamics as well as the influence of pH, salt ion strength, and the environmental risk of MBC, were evaluated. The results revealed that the experimental data conformed to the pseudo-second-order kinetic model and the Freundlich isotherm model. In the adsorption process, MBC showed excellent adsorption ability (maximum capacity for TC 100.74 mg g⁻¹) to BC (33.76 mg g⁻¹). In isotherm experiments, the maximum adsorption capacity of TC by MBC reached 177.71 mg g⁻¹. Toxicity studies showed that the MBC had no harm to the environment. To conclude, MBC has great potential for applications in removing TC from water.

24913. 题目: Composition and settling properties of suspended particulate matter in estuaries of the Chesapeake Bay and Baltic Sea regions
文章编号: N19010610
期刊: Journal of Soils and Sediments
作者: Paul A. Bukaveckas, Marija Katarzyte, Anne Schlegel, Renalda Spuriene, Todd Egerton, Diana Vaiciute
更新时间: 2019-01-06
摘要: Purpose: Our goal was to understand how differences in source material (allochthonous vs. autochthonous) and phytoplankton communities (diatoms vs. cyanobacteria) influence composition and settling properties of suspended particulate matter. Materials and methods: We characterized the composition and settling properties of suspended particulate matter in two systems—one which has a high hydrologic loading factor (watershed to surface area ratio), and a diatom-dominated phytoplankton community (James River Estuary, USA), and a second, where hydrologic inputs are proportionally smaller, and the summer phytoplankton community is dominated by cyanobacteria (Curonian Lagoon, Lithuania). Results and discussion: In the James, we found that TSS concentrations were positively related to discharge, whereas POC concentrations were negatively correlated with discharge and positively correlated with Chl-a. We infer that suspended particulate matter in this system was largely derived from allochthonous inputs, but that the organic matter fraction was derived from autochthonous production. In the Curonian Lagoon, TSS concentrations were correlated with Chl-a, but not discharge, indicating that suspended particulate matter was largely of autochthonous origin. In the James, the proportion of settleable materials was greater during high TSS concentrations, indicating that high discharge events delivered heavier particulates. In the Curonian Lagoon, we observed a seasonal decline in settling rates associated with the shift from mixed (diatoms and chlorophytes) to cyanobacteria-dominated phytoplankton, which we attribute to the presence of positively buoyant cyanobacteria. Conclusions: We found that a comparative approach yielded useful insights regarding sources, composition, and settling properties of suspended particulate matter in two estuaries that differ in hydrologic loading and phytoplankton community composition. Our findings suggest that the presence of positively buoyant cyanobacteria favors export losses of particulate C, N, and P to marine waters over retention through sedimentation in transitional zones.

24914. 题目: Post fire litters are richer in water soluble carbon and lead to increased microbial activity
文章编号: N19010609
期刊: Applied Soil Ecology
作者: E. Stirling, L.M. Macdonald, R.J. Smernik, T.R. Cavagnaro
更新时间: 2019-01-06
摘要: Under conditions of increased fire season length and area affected by fire, stocks of carbon stored in forests are at increased risk of burning. While much research has investigated the immediate loss of above ground and below ground carbon stocks through combustion during a fire, there has been little research on subsequent organic matter cycling in post-fire environments. Fire can introduce new organic matter to the litter layer through the formation of a post-fire litter layer composed of debris from fire induced plant stress or death. This litter may have different chemistry and decomposition dynamics to the pre-fire litter due to the changed pathway from plant to ground and the narrow age range of the debris. In this study, litters collected from two vegetation types (Pinus and Eucalyptus dominated) and from adjacent areas either fire affected (FA) or not fire affected (NFA) were incubated as litter, or as water extracts of litter, in soils to determine fire induced changes in nutrient pools, microbial biomass and microbial activity. Post-fire litters contained more labile C (15 and 30 mg C g native/pine litter⁻¹, respectively) than litters unaffected by fire (4 mg C g litter⁻¹). Increased labile C concentration correlated (r² > 0.95) with increased microbial activity without a concurrent change in nitrogen (microbial) or phosphorus (resin and microbial) pools. Our results suggest that labile C in post-fire litter can alter microbial carbon cycling and that effects may be more pronounced under pine compared to native forest.

24915. 题目: Respective roles of Fe-oxyhydroxide dissolution, pH changes and sediment inputs in dissolved phosphorus release from wetland soils under anoxic conditions
文章编号: N19010608
期刊: Geoderma
作者: Sen Gu, Gérard Gruau, Rémi Dupas, Patrice Petitjean, Qingman Li, Gilles Pinay
更新时间: 2019-01-06
摘要: The development of anoxic conditions in riparian wetland (RW) soils is widely known to release dissolved phosphorus (DP), but the respective roles of reductive dissolution of Fe-oxyhydroxide, pH changes and sediment inputs in this release remain debated. This study aimed to identify and quantify these respective roles via laboratory anaerobic/aerobic incubation of RW soils with and without the addition of sediment. The investigated soils came from two RWs with contrasting P status and organic matter (OM) content in their soils, while the added sediment came from an adjacent cultivated field. Results showed that the amount and speciation of the DP released during anaerobic/aerobic incubations were controlled by soil P status and soil OM content. During anaerobic incubation, DP release in the soil with high extractable P and low OM contents was controlled by reductive dissolution of Fe-oxyhydroxides (83%), whereas that released in the soil with low extractable P and high OM contents was controlled by an increase in pH (88%). Anaerobic incubation of a mixture of eroded sediments and RW soils increased the release of DP, dissolved organic carbon and Fe(II) (by 16%, 4% and 18%, respectively) compared to the simple addition of the amounts released during their separate incubations. Management practices should decrease soil erosion from upland fields to avoid deposition of P-rich sediments on RW soils. Management efforts should focus preferentially on RWs whose Fe:P molar ratios in the soil solution during reduction are the lowest, since they indicate a high risk that the DP released will be transferred to watercourses.
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24916. 题目: Impacts of land use change on soil organic matter chemistry in the Everglades, Florida - a characterization with pyrolysis-gas chromatography–mass spectrometry
文章编号: N19010607
期刊: Geoderma
作者: Zhongsheng Zhang, Jian Jim Wang, Xianguo Lyu, Ming Jiang, Jehangir Bhadha, Alan Wright
更新时间: 2019-01-06
摘要: Reclamation of marshlands for agricultural land use is widespread. An example of large-scale land use shifts is evident in the Everglades Agricultural Area of Florida where freshwater wetlands were converted to sugarcane (Saccharum officinarum) production. Such land-use shifts can markedly influence soil organic matter cycling and processes. The effect of such land use change on molecular characteristics of soil organic carbon is unknown. In this study, three surface soils cores (0–5 cm, 5–10 cm, and 10–19 cm) from a representative marsh and a sugarcane field in the Florida Everglades with known land use history and management practices were characterized using pyrolysis-gas chromatography–mass spectrometry (Py-GC/MS) to investigate molecular characteristics of soil organic matter. Soil organic carbon (SOC), total nitrogen, total sulfur, and water extractable organic carbon contents in sugarcane soil were 37.02%, 2.44%, 0.46% and 0.11%, while they were 44.57%, 2.62%, 0.73% and 0.38%, respectively. On the whole, marshland reclamation to sugarcane caused increase of aromatics (from 11.37% to 13.20%), polyaromatic hydrocarbon (from 0% to 1.63%), n-alkanes (from 8.90% to 16.17%), n-alkenes (from 25.10% to 28.77%), other aliphatics (from 7.33% to 11.77%) and fatty acids (from 1.93% to 3.87%) in pyrolysis products of soil organic matter (SOM), whereas this shift reduced lignin (from 12.87% to 2.47%), phenols (from 23.33% to 16.13%), polysaccharides (from 2.40% to 1.03%), benzofuran (from 1.67% to 0.27) and nitrogen containing compounds (from 5.07% to 4.67%), respectively. Overall, the conversion of marsh to sugarcane land use not only reduced total SOC contents but also altered molecular features of SOM with significant increases in aliphatic fractions and almost complete exhaustion of lignin fractions, signifying SOC dynamic shift due to land change in the Everglades.

24917. 题目: Controls on mineral-associated organic matter formation in a degraded Oxisol
文章编号: N19010606
期刊: Geoderma
作者: Chenglong Ye, Steven J. Hall, Shuijin Hu
更新时间: 2019-01-06
摘要: Oxisols are the dominant soil type in humid tropical and subtropical regions and are subjected to both drying–rewetting (DRW) cycles and fluctuating oxygen (O₂) availability driven by warm temperatures and abundant rainfall in surface layers. Drying-rewetting cycles and O₂ fluctuations may critically affect the microbial transformation of plant litter and subsequent stabilization as mineral-associated organic carbon (MAOC), but experimental data are still limited. We examined the impacts of DRW cycles, and variable O₂ regimes with constant moisture, on carbon (C) and iron (Fe) dynamics in a degraded Oxisol (under long-term fallow) with added plant residues. In laboratory incubations (>3 months), both DRW cycling and fluctuating O₂ availability induced a flush of respiration and a temporary increase in microbial biomass C (MBC) following soil rewetting or O₂ exposure, although MBC was consistently suppressed in these treatments relative to the control (60% water holding capacity under constantly aerobic condition). Consequently, DRW cycles significantly increased but O₂ fluctuations significantly decreased cumulative C mineralization relative to the control. Concentrations of short-range-ordered Fe oxides peaked immediately after litter addition and decreased five-fold during the remainder of the experiment. Mineral-associated C (defined as the chemically dispersed <53 μm soil fraction) increased 42–64% relative to initial values but was significantly lower under DRW cycling and fluctuating O₂ relative to the control. Correspondingly, these treatments had greater fine particulate organic C (53–250 μm), despite increased CO₂ production under DRW cycling. Our data indicate the potential for rapid and significant accrual of MAOC in a degraded Oxisol, but environmental factors such as DRW cycling and fluctuating O₂ can inhibit the conversion of plant litter to MAOC—possibly by suppressing microbial biomass formation and/or microbial transformations of organic matter.
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24918. 题目: The role of water column stability and wind mixing in the production/export dynamics of two bays in the Western Antarctic Peninsula
文章编号: N19010605
期刊: Progress in Oceanography
作者: Juan Höfer, Ricardo Giesecke, Mark J. Hopwood, Vania Carrera, Emilio Alarcón, Humberto E. González
更新时间: 2019-01-06
摘要: During January and February 2017 massive phytoplankton blooms (chlorophyll > 15 mg m^-3) were registered in surface waters within two bays in the Western Antarctic Peninsula (WAP). Reflecting these intense blooms, surface waters exhibited high pH (up to 8.4), low pCO₂ (< 175 µatm) and low nitrate concentrations (down to 1.5 µM). These summer phytoplankton blooms consisted mainly of diatoms and were associated with the presence of shallow, surface freshwater plumes originating from glacier-melt outflow which contributed both to stratification and to iron supply, thus facilitating pronounced nitrate and CO₂ drawdown. These findings suggest that with future increases in freshwater discharge around the WAP, phytoplankton blooms in the northern WAP may become more dominated by large cells, resembling the blooms occurring further south along the Peninsula. Fresher surface waters enhanced water column stability in both bays, enabling phytoplankton populations to attain high growth rates. Phytoplankton was observed to double their biomass in 2.3 days, consistent with the high net primary production rates recorded in both bays (1.29 - 8.83 g C m^-2 d^-1). Phytoplankton growth rates showed a direct mechanistic relationship with changes in water column stability, suggesting that this is a main driver of primary productivity in near-shore Antarctic coastal ecosystems, which agrees with previous findings. After wind induced mixing, the organic matter produced within both bays did not settle inside them, suggesting that it was laterally advected out of the bays. Thus, we hypothesize that highly productive near-shore bay areas in Antarctica may supply organic matter to oceanic waters.

24919. 题目: Efficient and controllable alcoholysis of Kraft lignin catalyzed by porous zeolite-supported Nickel-Copper catalyst
文章编号: N19010604
期刊: Bioresource Technology
作者: Liping Kong, ChunZe Liu, Ji Gao, Yuanyuan Wang, Liyi Dai
更新时间: 2019-01-06
摘要: The alcoholysis of Kraft lignin was catalyzed by bimetallic Ni-Cu supported on H-Beta, HZSM-5, MAS-7, MCM-41 and SAPO-11 zeolite materials in isopropanol solvent. Results showed that a higher bio-oil yield of 98.80 wt.% and monomer yield of 50.83 wt.% without obvious char were achieved at 330°C for 3 h over Ni-Cu/H-Beta catalyst. Isopropanol was found to be more effective in H₂ generation and facilitated to the hydrodeoxygenation of lignin-derived phenolic compounds. Moreover, the composition of liquid products was also influenced by the acidity and pore structure of catalyst. The superior cycloalkanes yield was produced over Ni-Cu/H-Beta with larger pore size and more acidity. In contrast, a large number of cyclic ketones/alcohols and alkanes were obtained over other zeolites supported catalysts with smaller pore size and less acid content. Besides, the temperature, time and solvent effect on the lignin depolymerization were also researched.
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24920. 题目: Is microbial reduction of Fe (III) in podzolic soils influencing C release?
文章编号: N19010603
期刊: Geoderma
作者: Marie-Liesse Vermeire, Steeve Bonneville, Benoit Stenuit, Bruno Delvaux, Jean-Thomas Cornélis
更新时间: 2019-01-06
摘要: Fe(III) oxides stabilize soil organic matter by forming Fe organo-mineral associations (Fe-OMA). Under anoxic conditions, Fe-OMA may be destabilized by microbial dissimilatory iron reduction that releases aqueous Fe(II) and also possibly adsorbed or co-precipitated organic matter. Soil spodic horizons that accumulate Fe-OMA are ideal natural materials to study such impact. Here, we study three spodic horizons from pedons (P) of increasing age: P-270 yrs, P-330 yrs and P-530 yrs. Their contents of total carbon and short range ordered (SRO) Fe oxides increase with soil age from, respectively, 1486 to 3618 and 13 to 249 μmol g⁻¹. The samples were incubated for 96 h under anoxic conditions, with and without Shewanella putrefaciens (a model dissimilatory Fe(III)-reducing bacteria) in a minimal medium devoid of any pH buffer and external electron donor. The concentration of dissolved Fe(II), total Fe and organic C was monitored at 9 time steps. With increasing age, both the rate and extent of microbial Fe(III) reduction increased after S. putrefaciens addition. In P-270 yrs, P-330 yrs and P-530 yrs, respectively, the microbial reduction rates were 0.004, 0.026 and 0.114 fmol Fe(II) h⁻¹ cell⁻¹ while the amounts of released Fe(II) were 0.23, 0.32 and 1.98 μmol Fe(II) g⁻¹, both being strongly correlated with SRO Fe oxides content. Dissolved organic carbon (DOC) was released with or without S. putrefaciens in all samples (up to 73 μmol OC g⁻¹ after 96 h in P-530 yrs). Adding S. putrefaciens significantly increased DOC release, but only in P-270 yrs. Podzol development thus increases the impact of anoxia on Fe(II) release since organic matter accumulation impedes Fe oxide crystallization, thereby amplifying Fe availability for Fe reducing microbes. The evolution of Fe oxide content and crystallinity thus affects the fate of both C and Fe in soils.