17281. 题目: Decoupling of priming and microbial N mining during a short-term soil incubation
期刊: Soil Biology and Biochemistry
作者: Birgit Wild, Jian Li, Johanna Pihlblad, Per Bengtson, Tobias Rütting
摘要: Soil carbon (C) and nitrogen (N) availability depend on the breakdown of soil polymers such as lignin, chitin, and protein that represent the major fraction of soil C and N but are too large for immediate uptake by plants and microorganisms. Microorganisms may adjust the production of enzymes targeting different polymers to optimize the balance between C and N availability and demand, and for instance increase the depolymerization of N-rich compounds when C availability is high and N availability low (“microbial N mining”). Such a mechanism could mitigate plant N limitation but also lie behind a stimulation of soil respiration frequently observed in the vicinity of plant roots (“priming effect”). We here compared the effect of increased C and N availability on the depolymerization of native bulk soil organic matter (SOM), and of 13C-enriched lignin, chitin, and protein added to the same soil in two complementary ten day microcosm incubation experiments. A significant reduction of chitin depolymerization (described by the recovery of chitin-derived C in the sum of dissolved organic, microbial and respired C) upon N addition indicated that chitin was degraded to serve as a microbial N source under low-N conditions and replaced in the presence of an immediately available alternative. Protein and lignin depolymerization in contrast were not affected by N addition. Carbon addition enhanced microbial N demand and SOM decomposition rates, but significantly reduced lignin, chitin, and protein depolymerization. Our findings contrast the hypothesis of increased microbial N mining as a key driver behind the priming effect and rather suggest that C addition promoted the mobilization of other soil C pools that replaced lignin, chitin, and protein as microbial C sources, for instance by releasing soil compounds from mineral bonds. We conclude that SOM decomposition is interactively controlled by multiple mechanisms including the balance between C vs N availability. Disentangling these controls will be crucial for understanding C and N cycling on an ecosystem scale.
17282. 题目: Distribution and cycling of terrigenous dissolved organic carbon in peatland-draining rivers and coastal waters of Sarawak, Borneo
作者: Patrick Martin, Nagur Cherukuru, Ashleen S. Y. Tan, Nivedita Sanwlani, Aazani Mujahid, and Moritz Müller
摘要: South-East Asia is home to one of the world's largest stores of tropical peatland and accounts for roughly 10% of the global land-to-sea dissolved organic carbon (DOC) flux. We present the first ever seasonally resolved measurements of DOC concentration and chromophoric dissolved organic matter (CDOM) spectra for six peatland-draining rivers and coastal waters in Sarawak, north-western Borneo. The rivers differed substantially in DOC concentration, ranging from 120–250µmolL−1 (Rajang River) to 3100–4400µmolL−1 (Maludam River). All rivers carried high CDOM concentrations, with a350 in the four blackwater rivers between 70 and 210m−1 and 4 and 12m−1 in the other two rivers. DOC and CDOM showed conservative mixing with seawater except in the largest river (the Rajang), where DOC concentrations in the estuary were elevated, most likely due to inputs from the extensive peatlands within the Rajang Delta. Seasonal variation was moderate and inconsistent between rivers. However, during the rainier north-east monsoon, all marine stations in the western part of our study area had higher DOC concentrations and lower CDOM spectral slopes, indicating a greater proportion of terrigenous DOM in coastal waters. Photodegradation experiments revealed that riverine DOC and CDOM in Sarawak are photolabile: up to 25% of riverine DOC was lost within 5 days of exposure to natural sunlight, and the spectral slopes of photo-bleached CDOM resembled those of our marine samples. We conclude that coastal waters of Sarawak receive large inputs of terrigenous DOC that is only minimally altered during estuarine transport and that any biogeochemical processing must therefore occur mostly at sea. It is likely that photodegradation plays an important role in the degradation of terrigenous DOC in these waters.
17283. 题目: Humic acid removal by gas-liquid interface discharge plasma: performance, mechanism and comparison to ozonation
期刊: Environmental Science: Water Research & Technology
作者: Yanyan Cui, Jianwei Yu, Ming Su, Zeyu Jia, Tingting Liu, Gaku Oinuma, Tokiko Yamauchi
摘要: The removal of natural organic matter (NOM) is a major objective for drinking water treatment. In this study, a novel advanced oxidation process (AOP) based on plasma in gas-liquid interface discharge was investigated for removing humic acid (HA), and ozonation treatment effect was evaluated as comparison. Several index including UV254, dissolved organic carbon (DOC), specific UV absorbance (SUVA), and excitation-emission matrix (EEM) fluorescence spectra were employed to characterize HA transformation. The results showed that typical species including ozone, hydrogen peroxide and HO• were produced in plasma process, which made better removal efficiency than ozonation. Especially, UV254 was removed effectively by 96.5 % and 90.3 % within 15 min by plasma and ozonation, while DOC was 49.2 % and 41.1 %, respectively. HO• radicals were major responsible for the degradation of HA in plasma process, which were mainly generated via reaction of in-situ produced ozone and H2O2 during discharge process. UV/Vis absorbance and EEM results further showed that HA with the large molecular weight fraction was decomposed to small molecular weight fraction. This study indicates that plasma technology has a significant application prospect as a replacement for ozone in drinking water industry.
17284. 题目: Bottom‐up and top‐down effects of browning and warming on shallow lake food webs
期刊: Global Change Biology
作者: Francisco Rivera Vasconcelos, Sebastian Diehl, Patricia Rodríguez, Per Hedström, Jan Karlsson, Pär Byström
摘要: Productivity and trophic structure of aquatic ecosystems result from a complex interplay of bottom‐up and top‐down forces that operate across benthic and pelagic food web compartments. Projected global changes urge the question how this interplay will be affected by browning (increasing input of terrestrial dissolved organic matter), nutrient enrichment and warming. We explored this with a process‐based model of a shallow lake food web consisting of benthic and pelagic components (abiotic resources, primary producers, grazers, carnivores), and compared model expectations with the results of a browning and warming experiment in nutrient‐poor ponds harboring a boreal lake community. Under low nutrient conditions, the model makes three major predictions. (1) Browning reduces light and increases nutrient supply; this decreases benthic and increases pelagic production, gradually shifting productivity from the benthic to the pelagic habitat. (2) Because of active habitat choice, fish exert top‐down control on grazers and benefit primary producers primarily in the more productive of the two habitats. (3) Warming relaxes top‐down control of grazers by fish and decreases primary producer biomass, but effects of warming are generally small compared to effects of browning and nutrient supply. Experimental results were consistent with most model predictions for browning: light penetration, benthic algal production, and zoobenthos biomass decreased, and pelagic nutrients and pelagic algal production increased with browning. Also consistent with expectations, warming had negative effects on benthic and pelagic algal biomass and weak effects on algal production and zoobenthos and zooplankton biomass. Inconsistent with expectations, browning had no effect on zooplankton and warming effects on fish depended on browning. The model is applicable also to nutrient‐rich systems, and we propose that it is a useful tool for the exploration of the consequences of different climate change scenarios for productivity and food web dynamics in shallow lakes, the worldwide most common lake type.
17285. 题目: Ecological risk assessment of heavy metals in surface sediments from the Gorgan Bay, Caspian Sea
期刊: Marine Pollution Bulletin
作者: Mohammad Gholizadeh, Rahman Patimar
摘要: This study was conducted to investigate the amounts of heavy metals in the Gorgan Bay. For this purpose, 12 sediment samples were taken from the Gorgan Bay, and then, the amounts of metals were determined using the ICP-OES spectrometer. Accordingly, the average value of the metals aluminum (Al), arsenic (As), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) was 1.3 ± 0.2%, 8.1 ± 3.8 ppm, 17.9 ± 4.3 ppm, 16.8 ± 4.2 ppm, 16.6 ± 4 ppm, 7.4 ± 1.3 ppm, 17.6 ± 3.7 ppm, and 29.5 ± 6.9 ppm, respectively. According to the Pearson test, a significant correlation was observed among all metals (except arsenic) in this study (P < 0.01), which indicates that the source of the metals (human or natural) is the same in this gulf. There was also a positive correlation between organic matter and all metals (except lead and vanadium) (P > 0.05). This positive correlation probably indicates that these metals enter the aquatic environment along with organic matter or that they are of the same origin (organic matter and metals). On the basis of the PER index, all the measured metals had a low ecological risk at all stations.
17286. 题目: Colored organic matter increases CO2 in meso‐eutrophic lake water through altered light climate and acidity
期刊: Limnology and Oceanography
作者: Anna C. Nydahl, Marcus B. Wallin, Lars J. Tranvik, Carolin Hiller, Katrin Attermeyer, Julie A. Garrison, Fernando Chaguaceda, Kristin Scharnweber, Gesa A. Weyhenmeyer
摘要: Many surface waters across the boreal region are browning due to increased concentrations of colored allochthonous dissolved organic carbon (DOC). Browning may stimulate heterotrophic metabolism, may have a shading effect constraining primary production, and may acidify the water leading to decreased pH with a subsequent shift in the carbonate system. All these effects are expected to result in increased lake water carbon dioxide (CO2) concentrations. We tested here these expectations by assessing the effects of both altered allochthonous DOC input and light conditions through shading on lake water CO2 concentrations. We used two mesocosm experiments with water from the meso‐eutrophic Lake Erken, Sweden, to determine the relative importance of bacterial activities, primary production, and shifts in the carbonate system on CO2 concentrations. We found that DOC addition and shading resulted in a significant increase in partial pressure of CO2 (pCO2) in all mesocosms. Surprisingly, there was no relationship between bacterial activities and pCO2. Instead the experimental reduction of light by DOC and/or shading decreased the photosynthesis to respiration ratio leading to increased pCO2. Another driving force behind the observed pCO2 increase was a significant decrease in pH, caused by a decline in photosynthesis and the input of acidic DOC. Considering that colored allochthonous DOC may increase in a warmer and wetter climate, our results could also apply for whole lake ecosystems and pCO2 may increase in many lakes through a reduction in the rate of photosynthesis and decreased pH.
17287. 题目: Geochemistry of sedimentary organic matter and trace elements in modern lake sediments from transitional karstic land-sea environment of the Neretva River delta (Kuti Lake, Croatia)
期刊: Quaternary International
作者: Maja Ivanić, Sonja Lojen, Dino Grozić, Irena Jurina, Srečo D. Škapin, Tamara Troskot-Čorbić, Nevenka Mikac, Mladen Juračić, Ivan Sondi
摘要: This paper investigates recent sedimentation processes and geochemistry of sedimentary organic matter (SOM) and trace elements in a unique semi-enclosed lacustrine sedimentation system in a transitional land-sea environment of the Neretva River delta. The results have shown that the influence of the Neretva River on the lake sedimentation processes is limited to short-term flood events carrying terrigenous loads, while the authigenic formation of nanostructured calcite is the primary source of sediments in the recent past. The enhanced release of biogenic CO2 into the pore water, deriving from the decomposition of SOM, acts as a major contributor to this process. The occurrence of early formed syngenetic and diagenetic pyrite indicates the existence of oxygen-depleted conditions in the investigated system in the recent past. The input of terrigenous material was identified as the main source of trace elements (Pb, Cu, Zn, Sn) in the lake sediments. The distribution of redox sensitive elements (Mo, Tl, V) particularly depends on the oxygen deficiency and the formation of sedimentary pyrite. The human impact in the study area is negligible, although somewhat elevated concentrations of Sn were found in the surface sediment layers. Finally, the results obtained indicate that the Kuti Lake represents a unique lacustrine environment which can be viewed as an isolated sedimentological and biogeochemical system in the Neretva River delta.
17288. 题目: Evidence of sapropel S1 formation from Holocene lacustrine sequences in Lake Vrana in Dalmatia (Croatia)
期刊: Quaternary International
作者: Koraljka Bakrač, Nikolina Ilijanić, Slobodan Miko, Ozren Hasan
摘要: The sediment core from Lake Vrana (between 1000 and 500 cm) on the eastern Adriatic coast was analyzed using palynological and geochemical approaches to detect environmental changes during the Holocene. The deepest sediments (between 1000 and 967 cm) in Lake Vrana could correspond to Late Pleistocene to Holocene transition. Although this interval is not dated, it is indicated by the palynological record. After that, the Holocene warming is evident and the observed dark layers are identified as Holocene sapropel S1, known in the eastern Mediterranean (10.8–6.1 cal kyr BP). Sapropelic layer S1a in Lake Vrana sediment core is evident between 905 and 790 cm and it ended at 7.9 cal kyr BP. It is formed in a very shallow freshwater ecosystem, dominated by cyanobacteria Gleocapsa and terrigenous detritus as a consequence of runoff. Periodically anoxic condition occurred. The geochemical signature of sapropelic layer S1a from Lake Vrana is consistent with post-depositional oxidation due to transition to the bottom water oxygenation evidenced in elevated Mn and Mn peak at the end of sapropelic layer S1a deposition. Sapropelic layer S1b, deposited between 7.4 and 6.4 cal kyr BP, is characterized by amorphous organic matter. The two sapropelic layers are separated by the horizon at 7.9–7.4 cal kyr BP, corresponding to the drier climate conditions, indicated by the presence of Poaceae, Ericaceae, Juniperus and Pistacia. This horizon reflects regional climatic cooling associated with reduced levels of precipitation that interrupted a period of generally higher precipitation. Based on geochemical data, Total organic carbon (TOC) and Nitrogen (N), the sapropelic layers are characterized by elevated values comparing to the rest of the core.The new records allow reconstruction of paleoenvironmental changes on land, which give insight into the processes and climate conditions that led to the formation of S1. The evidence indicates that: (i) S1 sapropelic layer in Lake Vrana sediments is an organic-poor deposit; (ii) the S1 period in the study area can be divisible into two sub-phases (S1a and S1b). The key factor that initiated the formation of S1 was increased discharge of freshwater into the Lake Vrana basin during warmer and wetter climate in the Early Holocene.
17289. 题目: Mineralogical, organic and isotopic composition as palaeoenvironmental records in the lake sediments of two lakes, the Plitvice Lakes, Croatia
期刊: Quaternary International
作者: Nada Horvatinčić, Andreja Sironić, Jadranka Barešić, Ivan Sondi, Ines Krajcar Bronić, Damir Borković
摘要: Six sediment cores, the top 30–40 cm, from two lakes of different sizes, Lake Prošće and Lake Kaluđerovac, situated in the karst region of the Plitvice Lakes system, Croatia, were studied by mineralogical and structural, C/N and total organic carbon (TOC) and isotopic analyses (a14C and δ13C of carbonate and organic fractions). The study of the two karst lakes where sediment composition is mainly calcite, showed that organic matter (OM) also plays an important role, and that both fractions analysed simultaneously give a good overview of the processes in the lakes. The morphological and structural properties of the calcite particles at micron and submicron levels indicate that the calcite mineral phase is formed by active authigenic precipitation in the studied lake systems. In the small Lake Kaluđerovac, the measured distributions of carbonate and OM fractions, C/N, TOC, and a14C and δ13C values of both fractions along the sediment depth showed similar values for all three cores, with small variations in each core indicating very homogenous precipitation of autochthonous calcite inside the lake, without allochthonous fraction. In the bigger Lake Prošće, the large difference in sediment composition of the three cores indicated different conditions of sediment precipitation inside the lake. Significant fractions of land-derived carbonate and OM were recognized by mineralogical, C/N, a14C and δ13C values in the shallow, coastal area indicating that the sediment was a mixture of allochthonous and autochthonous fractions. In contrast, the composition of the deep-water sediment in the same lake indicated in-situ calcite precipitation and aquatic OM produced in the lake. Sedimentation rates of 0.7 cm/yr and from 0.3 to 0.7 cm/yr for Lake Prošće and Lake Kaluđerovac, respectively, were determined based on the a14C of macrofossils. Extreme hydrological events in 1981 and 2010 were identified by disturbances in carbon isotopes distributions in sediment profiles. No evidence of anthropogenic influence in either lake on the local level was found, but the response to the global 14C contamination was observed by a14C peaks in both, carbonate and organic fractions. Increased bioproductivity in the recent decades was observed in Lake Prošće which can be correlated with a slight increase in lake water temperature in the last three decades. This process can be associated with enhanced eutrophication in Lake Prošće.
17290. 题目: Coupled isotopic evidence for elevated pCO2 and nitrogen limitation across the Santonian-Campanian transition
期刊: Chemical Geology
作者: Hansheng Cao, Alan J. Kaufman, Xuanlong Shan, Huan Cui
摘要: The Santonian–Campanian (S–C) transition notably coincides with the termination of the Cretaceous Normal Superchron, a positive carbon isotope anomaly, and the enhanced preservation of organic matter associated with an oceanic anoxic event at ca. 84 Ma. The driving factors for the OAEs should include global warming, widely believed to be from volcanic sources, the delivery of nutrients to surface oceans from the continents, anoxic sediments and atmosphere, and variations in the configuration of ocean basins. To further investigate this phenomenon and evaluate whether there was a teleconnection between the marine and continental realm, we have studied a lacustrine succession in northeastern China (the Songliao Basin, which is ~3× the size of Lake Superior) that preserves two thick horizons of oil shales and a positive carbon isotope anomaly recorded in ostracode carbonate near the S–C boundary. This freshwater basin is one of the many that formed as a consequence of Mesozoic extensional tectonics in eastern Asia. The stratigraphic trends illustrate broad excursions in the isotopic compositions of carbonate, total organic carbon (including black carbon), and total nitrogen. The carbon isotope data suggest that maximal fractionation (εTOC) at the S–C boundary is caused by enhanced burial of organic carbon and inputs from anoxygenic photoautotrophs and chemoautotrophs, or from the buildup of CO2 in a lake environment. On the other hand, the nitrogen isotope data suggest that the lake became limited in nitrogen immediately before the deposition of the younger oil shale, resulting in the addition of new nitrogen to the system, likely as the result of diazotrophy or ammonium assimilation. To some extent, all of the features we described from the Songliao Basin have been recognized in Jurassic and Cretaceous OAEs. Insofar as climatically-sensitive lakes are typically supersaturated with CO2 relative to the atmosphere, we speculate that nutrient-driven primary productivity in massive lake systems may have released enough greenhouse gas (CO2, CH4, and N2O) into the atmosphere and therefore played a role in enhancing global temperatures and driving widespread anoxia in the Mesozoic oceans.
17291. 题目: Regulation of protist grazing on bacterioplankton by hydrological conditions in coastal waters
期刊: Estuarine, Coastal and Shelf Science
作者: Xiangfu Li, Jie Xu, Zhen Shi, Dapeng Xu, Ruihuan Li, Qian Li, Hongbin Liu
摘要: A series of dilution experiments were conducted along an environmental gradient in coastal waters during April to September 2016, in order to examine the regulation of protist grazing on bacterioplankton by physical processes. Our results suggested that the density gradient in the frontal zone and the pycnocline played a significant role in regulating protist grazing on bacterioplankton in marine environments. The highest bacterial growth rate (1.33 d−1) and grazing rate (1.05 d−1) occurred in the frontal zone along the inshore-offshore transect and in the deep chlorophyll maximum (DCM) that always matched with the pycnocline in terms of the vertical profile in offshore waters. Spatial variability in bacterial growth rate and grazing rate was related to the presence of the density gradient in front and the DCM. The density gradient aggregated phytoplankton and bacterial cells, enhancing their biomass. Meanwhile, high phytoplankton biomass provided more labile organic carbon to bacterioplankton in the front and the DCM, improving bacterial growth. Hence, the density gradient improved bacterial abundance, consequently enhancing the efficiency of protist grazing. Our findings implied that the density gradient improved bacterial carbon converted to high trophic levels and altered carbon flow in microbial food web in marine environments.
17292. 题目: An Integration of Photo-Fenton and Membrane Process for Water Treatment by a PVDF@CuFe2O4 Catalytic Membrane
期刊: Journal of Membrane Science
作者: Tao Wang, Ziyi Wang, Penglei Wang, Yuanyuan Tang
摘要: Membrane fouling always decreases the separation efficiency and shortens the membrane life, which severely hinders the practical application of the membrane technology. The photo-Fenton process can degrade various foulants with the generation of hydroxyl radicals, and its integration with membrane filtration may become an efficient way to improve the antifouling property and filtration performance of the membrane. In this study, the CuFe2O4 particles were synthesized and doped in the PVDF@CuFe2O4 membranes with increasing concentration from 0 to 1.0%. The degradation measurement of methylene blue (MB) solution shows the optimal conditions for the photo-Fenton process as CuFe2O4 concentration of 1.0%, pH of 3.0, and H2O2 dosage of 400 μL. With the photo-Fenton cleaning process, the PVDF@CuFe2O4 membrane (1.0%) exhibits versatile antifouling property to different types of foulants, including organic dyes (e.g. MB and rhodamine B (RhB)), nature organic matter (e.g. humic acid (HA)), and protein (e.g. bovine serum albumin (BSA)). With the integration of photo-Fenton and membrane process, the PVDF@CuFe2O4 membrane (1.0% of CuFe2O4) dramatically enhanced the separation efficiency, with the results of 99.77% to MB, 81.02% to RhB, 36.35% to HA, and 82.94% to BSA. The flux and rejection have been increased respectively to threefold and double of the corresponding data from the membrane filtration alone. Moreover, even after fifteen cycles of experiments, the average MB rejection is still higher than 70%, which further indicates the good stability and reusability of the PVDF@CuFe2O4 membrane. Therefore, this study provides a promising methodology for the successful fabrication of high-performance membrane through the integration of photo-Fenton and membrane process, and further proposes a new strategy on the design and application of functional materials for new generation of catalytic membranes.
17293. 题目: Towards multiproxy, ultra-high resolution molecular stratigraphy: enabling laser-induced mass spectrometry imaging of diverse molecular biomarkers in sediments
期刊: Organic Geochemistry
作者: Lars Wörmer, Jenny Wendt, Susanne Alfken, Jin-Xiang Wang, Marcus Elvert, Verena B. Heuer, Kai-Uwe Hinrichs
摘要: Mass spectrometry imaging (MSI) collects mass spectra of organic compounds from individual micrometer-sized spots and yields high-resolution images of the spatial distribution of target analytes on sample surfaces. MSI can potentially open a new avenue to ultra-high resolution molecular stratigraphy by resolving the fine-scale distribution of molecular biomarkers in geological records. However, ionization of organic molecules within their sediment matrix remains a critical challenge. Building on the recent introduction of MSI of archaeal tetraether lipids, we have extended the analytical spectrum to additional biomarkers and provide guidelines for the generation of multiproxy, ultra-high resolution paleoenvironmental records. We evaluated the addition of artificial matrices to promote ionization, defined the most suitable MS settings, and increased analytical complexity from pure compounds to their investigation in sediment. Most compounds relevant to molecular stratigraphy are not properly ionized in the presence of conventional matrices, but require atypical ones, such as those based on carbon or silver. Sediments serve as a natural matrix, directly allowing detection of many of these compounds. However, the sediment matrix also inhibits some reactions that otherwise promote detection, such as derivatization of alkenones or silver-mediated ionization of n-alkanes. The robustness of MSI-based molecular stratigraphy is enhanced by analysis of target compounds in narrow m/z ranges, and by summation of mass spectra from several coeval measurement spots. We present an initial inventory of compounds readily detected in the sediment tested, including long chain alkenones and diols, sterols, and pigments, and provide an outlook into the use of MSI in multiproxy studies.
17294. 题目: Organic matter accumulation on the Dalong Formation (Upper Permian) in western Hubei, South China: Constraints from multiple geochemical proxies and pyrite morphology
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Weiqing Liu, Jianxin Yao, Jinnan Tong, Yu Qiao, Yao Chen
摘要: Organic-rich black shales in the Upper Permian Dalong Formation are considered excellent source rocks in the western Hubei Basin, South China. However, the mechanisms of organic matter (OM) accumulation remain controversial. Furthermore, the evolution of primary productivity and ocean hypoxia during the Late Permian in the western Hubei Basin is unclear. In this study, we discuss the paleoclimate, paleoceanography, paleoenvironment and the mechanisms of OM accumulation based on geochemical characteristics and pyrite framboid data from drillcore H 1 in Ensi, western Hubei Province. Black shales from the Dalong Formation have high total organic carbon (TOC) contents (2.8–9.3%), while the mudstone samples contain low TOC contents (0.48–1.96%). The weak chemical weathering indicates paleoclimate conditions were relatively cold during black shale deposition, whereas rapid warming occurred during gray mudstone deposition, which may be connected with the Late Permian Changhsingian global climate event. Redox indices, namely, V, U, and Mo concentrations, and the relationship of UEF and MoEF combined with pyrite framboid data suggest that an anoxic to euxinic environment predominated during black shale accumulation. In contrast, oxic to hypoxic marine conditions pervaded the western Hubei Basin during the deposition of mudstone. The primary productivity indices (Cu/Al and Nixs) suggest that high paleoproductivity occurred in the Late Permian, especially during periods of transgression. However, declining primary productivity with enhanced intensity of chemical weathering may indicate that biological extinction was associated with a rapid increase in temperature during the Late Permian. Negative/positive relationships between the TOC contents and Baxs and Nixs values demonstrate that sulfate was consumed by a higher OM input and OM accumulation was mainly controlled by high primary productivity. The study implies that ocean hypoxia and high primary productivity played important roles in OM accumulation. The depositional model shows that high primary productivity possibly resulted from weathering of volcanic ash from land during transgressions and that intense degradation of OM resulted in an euxinic environment.
17295. 题目: Soil carbon stocks under different land uses and the applicability of the soil carbon saturation concept
期刊: Soil and Tillage Research
作者: Songchao Chen, Dominique Arrouays, Denis A. Angers, Manuel P. Martin, Christian Walter
摘要: Increasing soil organic carbon (SOC) stocks via land management has been proposed as a temporary climate change mitigation measure. An upper limit of soil stable SOC storage, which refers to the concepts of SOC saturation has been proposed. Using systematic grid sampling of topsoil in mainland France and an equation that predicts this SOC saturation, we derived estimates of the SOC sequestration potential density (SOCspd) for various land uses. First, using French database and data from the literature we estimated the proportions of the SOC stored in the fine fraction (SOCfine) in total SOC for grassland (69%), cropland (85%) and forest (66%). Then, SOCspd was calculated as the difference between the theoretical SOC saturation value and SOCfine. The SOCspd stocks for French topsoil were estimated at about 1.1 Pg, in which cropland, forest and grassland accounted for 66%, 17% and 17%, respectively. Varying the proportions of SOCfine in the calculations by assuming a possible range of 0.8-0.9 for cropland and 0.6-0.9 for grassland and forest soils led to variations of total SOCspd stocks of about 0.1 Pg for each land use. Most importantly, we demonstrate that the distribution of SOCspd in forest soils is exactly centred at zero, which suggests that on average, forest topsoils are saturated in SOCfine, and thus Hassink’s equation provides a valid estimate for the SOC sequestration potential for French topsoil.
17296. 题目: Improving lignin removal from pre-hydrolysis liquor by horseradish peroxidase-catalyzed polymerization
期刊: Separation and Purification Technology
作者: Zongquan Li, Chenglong Qiu, Jijie Gao, Haowei Wang, Fu yingjuan, Menghua Qin
摘要: The removal of the lignin from the pre-hydrolysis liquor (PHL) of kraft-based dissolved pulp production is essential for the utilization of the saccharides in PHL. Horseradish peroxidase (HRP) was used to treat the PHL, and the treatment conditions for lignin removal were optimized, and the novel combined processes of HRP treatment and flocculation or acidification for lignin removal were proposed and evaluated. The results showed that the HRP treatment caused 33.3% dissolved lignin and 47.7% turbidity removal at the optimized conditions. The weight average molecular weight of the lignin in PHL increased from 1473 to 1719 g/mol with HRP treatment. The lignin polymerization catalyzed by horseradish peroxidase was of great benefit to the lignin removal in the subsequent processes. Compared to the processes of flocculation with poly diallyl dimethyl ammonium chloride (pDADMAC) or acidification, which caused 35.9% and 24.2% dissolved lignin removal, respectively, the combined process of HRP treatment and pDADMAC treatment or acidification at pH 1.5 caused more than 70% dissolved lignin and nearly completely colloidal lignin removal, accompanied by 12–13% saccharides loss.
17297. 题目: Influences of multi influent matrices on the retention of PPCPs by nanofiltration membranes
期刊: Separation and Purification Technology
作者: Rui Xu, Pan Zhang, Qian Wang, Xiaomao Wang, Kaichang Yu, Tao Xue, Xianghua Wen
摘要: Nanofiltration (NF) has great potential in removing trace organic micropollutants in wastewater, especially pharmaceuticals and personal care products (PPCPs). However, little information is available on PPCPs rejections under complex feed water matrices, which better represent real wastewater treatment conditions. In this paper, the PPCPs rejection behaviors and the dominating mechanisms by NF membranes were studied under multi mixed influent matrices which contained various inorganic ions, humic acids and sodium alginate. The results showed that the DF30 membrane had the highest rejection of negatively charged indomethacin (95.4%) and diclofenac sodium (94.1%) in pure water. Our study also showed that electrostatic effect and steric hindrance were the primary rejection mechanisms of PPCPs by DF30 membrane in pure water. The predominant fouling of DF30 membrane could be explained by the complete blocking model in the filtration of mixed influent matrices containing both inorganic ions and organic matters. The components in membrane bioreactor (MBR) effluent was beneficial to retention of positively and neutrally charged PPCPs, but had no significant effects on retention of negatively charged PPCPs. Risk quotients of the six target PPCPs in NF effluent were all lower than 0.1, likely indicating low risk to aquatic organisms. This work has potential implications for a deeper understanding of PPCPs rejections by NF in wastewater treatment.
17298. 题目: Linking bacterial and eukaryotic microbiota to litter chemistry: Combining next generation sequencing with 13C CPMAS NMR spectroscopy
期刊: Soil Biology and Biochemistry
作者: Giuliano Bonanomi, Francesca De Filippis, Gaspare Cesarano, Antonietta La Storia, Maurizio Zotti, Stefano Mazzoleni, Guido Incerti
摘要: Microbial succession over decomposing litter is controlled by biotic interactions, dispersal limitation, grazing pressure, and substrate chemical changes. Recent evidence suggests that the changes in litter chemistry and microbiome during decomposition are interdependent. However, most previous studies separately addressed the microbial successional dynamics or the molecular changes of decomposing litter. Here, we combined litter chemical characterization by 13C NMR spectroscopy with next generation sequencing to compare leaf litter chemistry and microbiome dynamics using 30 litter types, either fresh or decomposed for 30 and 180 days.We observed a decrease of cellulose and C/N ratio during decomposition, while lignin content and lignin/N ratio showed the opposite pattern. 13C NMR revealed significant chemical changes as microbial decomposition was proceeding, with a decrease in O-alkyl C and an increase in alkyl C and methoxyl C relative abundances. Overall, bacterial and eukaryotic taxonomical richness increased with litter age. Among Bacteria, Proteobacteria dominated all undecomposed litters but this group was progressively replaced by members of Actinobacteria, Bacteroidetes, and Firmicutes. Nitrogen-fixing genera such as Beijerinckia and Rhizobium occurred both in undecomposed as well as in aged litters. Among Eukarya, fungi belonging to the Ascomycota phylum were dominant in undecomposed litter with the typical phyllospheric genus Aureobasidium. In aged litters, phyllospheric species were replaced by zygomycetes and other ascomycetous and basydiomycetous fungi. Our analysis of decomposing litter highlighted an unprecedented, widespread occurrence of protists belonging to the Amebozoa and Cercozoa. Correlation network analysis showed that microbial communities are non-randomly structured, showing strikingly distinct composition in relation to litter chemistry. Our data demonstrate that the importance of litter chemistry in shaping microbial community structure increased during the decomposition process, being of little importance for freshly fallen leaves.
17299. 题目: Microtopography Alters Hydrology, Phenol Oxidase Activity and Nutrient Availability in Organic Soils of a Coastal Freshwater Forested Wetland
作者: Kevan J. Minick, Alexia M. Kelley, Guofang Miao, Xuefeng Li, Asko Noormets, Bhaskar Mitra, John S. King
摘要: Hummock-hollow microtopography is a unique feature of wetland ecosystems, but our understanding of its effects on soil carbon and nutrient cycling is limited. We investigated effects of microtopography on hydrology, phenol oxidase activity (POX) and nutrient availability in a freshwater forested wetland of coastal North Carolina. Water table depth (WTD) was measured from September 2012 to August 2013. Ion exchange probes were used to measure nutrient concentrations prior to soil sample collection in August 2013. WTD fluctuated seasonally with maximum and minimum WTD resulting in 92% (September 2012) to 8% (June 2013) of the site in flooded and non-flooded conditions, respectively. Hummocks had greater POX activity (12 ± 2.8 μmol g−1 h−1) compared to hollows (4 ± 0.7 μmol g−1 h−1) and greater concentrations of potassium and sulfur, but lower concentrations of calcium, iron, zinc, boron, and lead. POX was negatively correlated with soil water content. Higher enzyme activity in hummocks likely drives greater rates of carbon and nutrient cycling compared to hollows, consistent with observations that hummocks are hotspots for CO2 fluxes. Microtopography altered site-level hydrologic conditions, phenol oxidase activity and nutrient availability with important implications for understanding carbon and nutrient cycling in forested wetlands and response to changes in hydrology.
17300. 题目: Antagonistic effects of temperature and dissolved organic carbon on fish growth in California mountain lakes
作者: Celia C. Symons, Marika A. Schulhof, Hamanda B. Cavalheri, Jonathan B. Shurin
摘要: Resources and temperature play major roles in determining biological production in lake ecosystems. Lakes have been warming and ‘browning’ over recent decades due to climate change and increased loading of terrestrial organic matter. Conflicting hypotheses and evidence have been presented about whether these changes will increase or decrease fish growth within lakes. Most studies have been conducted in low-elevation lakes where terrestrially derived carbon tends to dominate over carbon produced within lakes. Understanding how fish in high-elevation mountain lakes will respond to warming and browning is particularly needed as warming effects are magnified for mountain lakes and treeline is advancing to higher elevations. We sampled 21 trout populations in the Sierra Nevada Mountains of California to examine how body condition and individual growth rates, measured by otolith analysis, varied across independent elevational gradients in temperature and dissolved organic carbon (DOC). We found that fish grew faster at warmer temperatures and higher nitrogen (TN), but slower in high DOC lakes. Additionally, fish showed better body condition in lakes with higher TN, higher elevation and when they exhibited a more terrestrial δ13C isotopic signature. The future warming and browning of lakes will likely have antagonistic impacts on fish growth, reducing the predicted independent impact of warming and browning alone.