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25961. 题目: Manure over crop residues increases soil organic matter but decreases microbial necromass relative contribution in upland Ultisols: Results of a 27-year field experiment
文章编号: N19032101
期刊: Soil Biology and Biochemistry
作者: Guiping Ye, Yongxin Lin, Yakov Kuzyakov, Deyan Liu, Jiafa Luo, Stuart Lindsey, Weijin Wang, Jianbo Fan, Weixin Ding
更新时间: 2019-03-21
摘要: Organic fertilizers increase soil organic matter (SOM) stocks, but the underlying processes depend on the fertilizer type and remain largely unknown. To evaluate the predominant C stabilization mechanisms, upland Ultisols subjected to 27 years of mineral and organic fertilization were analyzed for SOM content, aggregate size classes, and amino sugar composition. The long-term field experiment had seven treatments: no fertilization (Control), mineral NPK fertilizers (NPK), NPK plus lime (NPK + Lime), NPK plus peanut straw (NPK + PeanutStraw), NPK plus rice straw (NPK + RiceStraw), NPK plus radish residue (NPK + RadishResidue), and NPK plus pig manure (NPK + PigManure). The 27-year application of mineral fertilizers (NPK and NPK + Lime), NPK + crop residues, and NPK + PigManure increased SOM content by 11.0–13.2%, 16.3–25.3%, and 44.3%, respectively, compared with the Control. The aliphaticity and recalcitrance indices based on 13C nuclear magnetic resonance spectra of organic fertilizers were higher for pig manure than for crop residues. Both indices were closely correlated with SOM content after 27 years, so higher proportions of recalcitrant C in manure facilitated SOM accumulation. NPK + PigManure increased the mass proportion of large macroaggregates 2.9-fold compared with the Control, and reduced the effective diffusion coefficient of oxygen in the soil. Consequently, NPK + PigManure limited the activity and abundance of aerobes and the accessibility of SOM to microorganisms, in turn facilitating SOM accumulation. The application of mineral fertilizers, NPK + crop residues, and NPK + PigManure increased microbial necromass to 2.85–3.03, 3.21–3.45, and 3.62 g C kg−1, respectively, from 2.63 g C kg−1 in the Control. Compared with crop residues, pig manure did not affect bacterial necromass but increased fungal necromass from 2.19 to 2.39 g C kg−1 to 2.58 g C kg−1, which might associate with increased SOM stability. However, the relative contribution of microbial necromass to SOM was lower under NPK + PigManure than under NPK + crop residues, since more added C was protected in the NPK + PigManure soil. Our results suggest that manure may contribute to SOM accumulation and stabilization in three ways: directly through the input of recalcitrant organic C, indirectly through the stabilization of aggregates and physical protection of C, and to a lesser extent through increasing fungal necromass.
25962. 题目: Liquid chromatographic isolation of individual carbohydrates from environmental matrices for stable carbon analysis and radiocarbon dating
文章编号: N19032016
期刊: Analytica Chimica Acta
作者: Amel Nouara, Christos Panagiotopoulos, Jérôme Balesdent, Kalliopi Violaki, Edouard Bard, Yoann Fagault, Daniel James Repeta, Richard Sempéré
更新时间: 2019-03-20
摘要: Carbohydrates are among the most abundant organic molecules in both aquatic and terrestrial ecosystems; however, very few studies have addressed their isotopic signature using compound-specific isotope analysis, which provides additional information on their origin (δ13C) and fate (Δ14C). In this study, semi-preparative liquid chromatography with refractive index detection (HPLC-RI) was employed to produce pure carbohydrate targets for subsequent offline δ13C and Δ14C isotopic analysis. δ13C analysis was performed by elemental analyzer-isotope ratio mass spectrometer (EA-IRMS) whereas Δ14C analysis was performed by an innovative measurement procedure based on the direct combustion of the isolated fractions using an elemental analyzer coupled to the gas source of a mini carbon dating system (AixMICADAS). In general, four successive purifications with Na+, Ca2+, Pb2+, and Ca2+ cation-exchange columns were sufficient to produce pure carbohydrates. These carbohydrates were subsequently identified using mass spectrometry by comparing their mass spectra with those of authentic standards. The applicability of the proposed method was tested on two different environmental samples comprising marine particulate organic matter (POM) and total suspended atmospheric particles (TSP). The obtained results revealed that for the marine POM sample, the δ13C values of the individual carbohydrates ranged from −18.5 to −16.8‰, except for levoglucosan and mannosan, which presented values of −27.2 and −26.2‰, respectively. For the TSP sample, the δ13C values ranged from −26.4 to −25.0‰. The galactose and glucose Δ14C values were 19 and 43‰, respectively, for the POM sample. On the other hand, the levoglucosan radiocarbon value was 33‰ for the TSP sample. These results suggest that these carbohydrates exhibit a modern age in both of these samples. Radiocarbon HPLC collection window blanks, measured after the addition of phthalic acid (14C free blank), ranged from −988 to −986‰ for the abovementioned compounds, indicating a very small background isotopic influence from the whole purification procedure. Overall, the proposed method does not require derivatization steps, produces extremely low blanks, and may be applied to different types of environmental samples.
25963. 题目: The deep water of Eastern Mediterranean Sea is a hotspot for bacterial activity
文章编号: N19032015
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Eyal Rahav, Jacob Silverman, Ofrat Raveh, Or Hazan, Maxim Rubin-Blum, Christina Zeri, Alexandra Gogou, Martina Kralj, Alexandra Pavlidou, Nurit Kress
更新时间: 2019-03-20
摘要: We investigated the abundance and production of mesopelagic (150–650 m) and bathypelagic (>650 m) bacteria from the poorly-studied Levantine basin (Eastern Mediterranean Sea) during the summers of 2014–2017. We show that the mesopelagic and bathypelagic microbial populations have relatively high cell specific activity, amongst the highest worldwide, likely due to the relatively warm temperatures characterizing these depths in comparison to other oceanic regions. Furthermore, in order to investigate if mesopelagic and bathypelagic microbial populations are limited by the scarce organic carbon substrates in the area, we performed microcosm addition assays of pure glucose (Glu) and/or a mixture of dissolved free amino acids (DFAA). Both the mesopelagic and bathypelagic bacterial populations responded positively to the additions, with bacterial production rapidly increasing within a few hours following the Glu or DFAA amendments. Our results demonstrate that deep-water microbes in the Levantine Basin may be important nutrient recyclers, especially when labile organic carbon is introduced. Our observations may have implications on carbon cycling and sequestration in the oligotrophic Eastern Mediterranean Sea.
25964. 题目: Evaluating CENTURY and Yasso soil carbon models for CO2 emissions and organic carbon stocks of boreal forest soil with Bayesian multi‐model inference
文章编号: N19032014
期刊: European Journal of Soil Science
作者: Boris Ťupek, Samuli Launiainen, Mikko Peltoniemi, Risto Sievänen, Jari Perttunen, Liisa Kulmala, Timo Penttilä, Antti‐Jussi Lindroos, Shoji Hashimoto, Aleksi Lehtonen
更新时间: 2019-03-20
摘要: We can curb climate change by improved management decisions for the most important terrestrial carbon pool, soil organic carbon stock (SOC). However, we need to be confident we can obtain the correct representation of the simultanous effect of the input of plant litter, soil temperature and water (that could be altered by climate or management) on the decomposition of soil organic matter. In this research, we used regression and Bayesian statistics for testing process based models (Yasso07, Yasso15 and CENTURY) with soil heterotrophic respiration (Rh) and SOC, measured at four sites in Finland during 2015 and 2016. We extracted climate modifiers for calibration with Rh. The Rh values of Yasso07, Yasso15 and CENTURY models estimated with default parameterization correlated with measured monthly heterotrophic respiration. Despite a significant correlation, models on average underestimated measured soil respiration by 43%. After the Bayesian calibration, the fitted climate modifier of the Yasso07 model outperformed the Yasso15 and CENTURY models. The Yasso07 model had smaller residual mean square errors and temperature and water functions with fewer, thus more efficient, parameters than the other models. After calibration, there was a small overestimate of Rh by the models that used monotonic moisture functions and a small generic underestimate in autumn. The mismatch between measured and modelled Rh indicates that the Yasso and CENTURY models should be improved by adjusting climate modifiers of decomposition or by accounting for missing controls in e.g. microbial growth.
25965. 题目: Depth-dependent variations of dissolved organic matter composition and humification in a plateau lake using fluorescence spectroscopy
文章编号: N19032013
期刊: Chemosphere
作者: Fanhao Song, Fengchang Wu, Weiying Feng, Shasha Liu, Jia He, Tingting Li, Jin Zhang, Aiming Wu, Dulasiri Amarasiriwardena, Baoshan Xing, Yingchen Bai
更新时间: 2019-03-20
摘要: In aquatic systems, dissolved organic matter (DOM) plays an important role in regulating the reactivity and transport of environmental pollutants. Fluorescence excitation-emission matrix (EEM) analysis combined with fluorescence regional integration (FRI) and parallel factorial analysis (PARAFAC) were applied to investigate the composition, humification degree and depth-dependent variation of DOM in Lake Baihua, China. The results showed that humic-like materials with more than 60% of percentage fluorescence response (Pi,n) were dominant in DOM. The molecular complexity and structural condensation of PARAFAC components showed the order of C1 (humic-like components) > C3 (protein-like components) > C4 (fulvic-like components) > C2 (fulvic-like components). The lower maximum fluorescence intensities (Fmax) of components in surface layers were attributed to photo-oxidation of DOM by radiation. With depths less than 16 m, the Fmax increases and decreases were attributed to accumulation of recalcitrant humic substances and microbial/abiotic degradation of particulate DOM, respectively. A combination of biological and humification indices could be used as indicators for distinguishing different degrees of humification and sources of DOM. DOM from Lake Baihua mainly originated from an aquatic bacterial source that consisted of an important/intermediate autochthonous component with a weak humic character. The fluorescence indices of PI,n/PII,n, PI+II+IV,n/PIII+V,n, C2, C1/C2 and C2/(C3+C4) were more suitable to determine the humification degree. Stronger humic characters and higher humification degree for DOM were present at depths of 10–13 m. The fluorescence spectroscopy combined with fluorescence indices is convenient to investigate depth-dependent DOM characteristics and to assess water quality or pollution risk in lake systems.
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25966. 题目: Synthesis of industrial solid wastes/biochar composites and their use for adsorption of phosphate: from surface properties to sorption mechanism
文章编号: N19032012
期刊: Colloids and Surfaces A: Physicochemical and Engineering Aspects
作者: Bingbing Qiu, Feng Duan
更新时间: 2019-03-20
摘要: This paper demonstrates the synthesis of industrial solid wastes /biochars. The produced materials were characterized by means of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). The composites were investigated for the phosphate removal from the aqueous solution. The effect of pH on removal rate was studied in the range from 3 to 12. The kinetic experimental data for phosphate adsorption was confirmed to follow pseudo-second-order kinetics with R2 > 0.99. Batch adsorption experiments revealed the suitability of the Freundlich model to describe the phosphate adsorption by FAB-F, CGB-F, while Langmuir model was suitable for B-F (where FA: fly ash, CG: coal gangue, B: biochar, and F: ferrite). The maximum adsorption capacities of the three different samples at an initial phosphate concentration of 30 mg/L were 2.39 mg/g with B-F, 3.08 mg/g with FAB-F, and 3.20 mg/g with CGB-F. The experimental results demonstrate that the industrial solid wastes/biochar is a promising alternative material for the restoration of eutrophic water.
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25967. 题目: A potential source of soil ecoenzymes: From the phyllosphere to soil via throughfall
文章编号: N19032011
期刊: Applied Soil Ecology
作者: Taiki Mori, Senhao Wang, Wei Zhang, Jiangming Mo
更新时间: 2019-03-20
摘要: Soil ecoenzymes play an important role in the decomposition and formation of soil organic matter, and are often considered to be derived from soil microbial and plant root activities. This study found another potentially-important source, transfer of ecoenzymes in phyllosphere to soil via throughfall. Throughfall samples were collected in five subtropical forests, and six ecoenzymes were determined therein. Data from this study showed that the ecoenzyme activity in throughfall was significantly higher than that in rainfall. Although this study has the limitation of a single measurement, it is the first report of the potential importance of ecoenzymes in throughfall in forest ecosystems.
25968. 题目: Optimized synthesis of carbon-doped nano-MgO and its performance study in catalyzed ozonation of humic acid in aqueous solutions: Modeling based on response surface methodology
文章编号: N19032010
期刊: Journal of Environmental Management
作者: Ghorban Asgari, Mehdi Salari
更新时间: 2019-03-20
摘要: This research study focused on the optimization of the synthesis of carbon-doped nano-MgO (C-MgO) and the investigation of its catalytic capacity in a catalytic ozonation process (COP) for the removal of humic acid (HA). Characterization analyses, including SEM, EDX, XRD, BET, and photoluminescence test showed that the C-MgO was successfully synthesized. L8 orthogonal arrays according to the Taguchi methodology optimized the synthesis of the C-MgO as follows: sucrose to MgO ratio = 0.5, sonication time = 15 min, calcination temperature = 400 °C and pH = 10.5. A central composite design based on response surface methodology was employed to optimize and model the COP in the removal of HA. A quadratic polynomial model with p-value < 0.0001 and R2 = 0.9988 showed a better fit to experimental responses. The optimum levels of the studied parameters in the COP based on the predictive model were obtained as follows: pH = 9.5, reaction time = 12 min, catalyst dose = 1 g/L, and HA concentration = 5 mg/L. The HA mineralization was determined to be 86.8% at the 100 min reaction time. Additionally, the COP exhibited 34% synergistic effect and the kinetic rate constant of 0.1898 min−1 in the HA removal. The presence of tert-butanol, methanol, salicylic acid, and some anions did not significantly affect the removal of the HA in the COP. From a practical view, this report indicated that the C-MgO catalyst could be potentially applied in the COP for the treatment of the water having high concentrations of HA substances.
25969. 题目: Stable isotopes and geochemical indicators in marine sediments as proxies for anthropogenic impact: A baseline for coastal environments of central Chile (33°S)
文章编号: N19032009
期刊: Marine Pollution Bulletin
作者: Marion Pastene, Eduardo Quiroga, Carlos Felipe Hurtado
更新时间: 2019-03-20
摘要: Stable isotopes and geochemical proxies (TOC/TN and Chla/TOC) in sediments can be used to distinguish organic matter sources (anthropogenic, terrestrial, or marine). This study aims to characterize organic matter (OM) in superficial sediments from three sectors of central Chile (33°S) that are highly influenced by urban and industrial development. Our results show that a substantial fraction of these OM in Quintero Bay is anthropogenic, from industrial and domestic wastewater sources. In contrast, a mixture of terrestrial and anthropogenic OM dominates the isotopic signal of surface sediments from Concón, derived from non-point industrial and agriculture sources associated with the Aconcagua River basin, while Ritoque exhibited a mixture of different OM sources. However, deposition of allochthonous OM in our study area depends on coastal topography, which influences the local currents and well-ventilated waters, promoting the dispersion and assimilation of OM and thus providing an environment with a high capacity for natural remediation.
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25970. 题目: The vertical distribution of Thaumarchaeota in the water column of Lake Malawi inferred from core and intact polar tetraether lipids
文章编号: N19032008
期刊: Organic Geochemistry
作者: Dervla Meegan Kumar, Martijn Woltering, Ellen C. Hopmans, Jaap S. Sinninghe Damsté, Stefan Schouten, Josef P. Werne
更新时间: 2019-03-20
摘要: Several long paleoclimate records generated from Lake Malawi sediments rely on an assumption that the TEX86 paleothermometer reflects annual mean lake surface temperatures. Thaumarchaeota, the producers of the isoprenoid glycerol dialkyl glycerol tetraether (iGDGT) lipids that are the basis of the TEX86 proxy, can occupy a wide range of habitats in the upper water column of lacustrine systems, so it is crucial to specifically constrain the ecology of Thaumarchaeota in Lake Malawi to properly interpret its sedimentary TEX86 record. To investigate the spatial and vertical distribution of Thaumarchaeotal iGDGT production in Lake Malawi, suspended particulate matter (SPM) was collected from the upper water column (>300 m) at three sites spanning the north, central, and south basins of the lake and analyzed for intact polar (IPL) and core (CL) iGDGT lipid abundances. Samples were collected in January during the austral summer when the lake is strongly stratified. Concentrations of the most labile IPL, hexose-phosphohexose (HPH)-crenarchaeol, were greatest just below the deep chlorophyll maximum at ∼50 m water depth in the deeper north and central basins and ∼30 m in the shallow south basin. Maximum CL concentrations occur below the maximum HPH-crenarchaeol concentrations and therefore possibly reflect the accumulation of recently produced IPL GDGT degradation products. If the export of CLs to the sediments is dominated by this CL pool, sedimentary TEX86 would reflect Thaumarchaeota living within the thermocline during the stratified season and therefore may have a cool bias rather than reflecting true surface water temperatures. An increase in abundances of GDGT-2, crenarchaeol isomer, and monohexose (MH)-crenarchaeol at ∼150–200 m suggests that a secondary Thaumarchaeotal population, likely Group I.1b Thaumarchaeota, inhabits the subsurface water column near the anoxic-suboxic boundary. Total production of iGDGTs by this group appears to be much lower than the surface-dwelling clade, but its imprint on sedimentary TEX86 is unknown. An analysis of iGDGT production in the water column throughout the annual cycle is needed to resolve the timing and magnitude of export of CLs to the sediments from these two Thaumarchaeotal populations.
25971. 题目: Methyltrimethyltridecylchromans (MTTCs) in lacustrine sediments in the northern Bohai Bay Basin, China
文章编号: N19032007
期刊: Organic Geochemistry
作者: Kaixi Jiang, Chunming Lin, Li Peng, Xia Zhang, Chunfang Cai
更新时间: 2019-03-20
摘要: Although methyltrimethyltridecylchromans (MTTCs) have been identified and studied for over 30 years in a large number of sediment extracts and crude oils, their origin and palaeosalinity significance are still debated. Here, the geochemical features of MTTCs in 133 organic-rich lacustrine sediments obtained from the northern Bohai Bay Basin are studied in detail. The sediment samples are in an immature to early mature stage and primarily enriched in Types I and II organic matter, which were deposited in lacustrine environments with relatively weakly stratified water columns and anoxic to suboxic conditions. The development of photic zone euxinia (PZE) in the water column was indicated by the occurrence of aryl isoprenoids. MTTCs were detected in all samples and characterized by low abundances of δ-MTTC and high abundances of α-MTTC. Variations in the relative abundance of MTTCs and MTTCI values suggest that selected lacustrine sediments were deposited in normal to semi-saline environments. The ternary diagram of mono-, di- and trimethyl-MTTCs was first established, and shows potential for application to indicate changes in palaeosalinity. Variations in the abundance of MTTCs can effectively indicate palaeosalinity changes in lacustrine environments.
25972. 题目: Biochar potentially mitigates greenhouse gas emissions from cultivation of oilseed rape for biodiesel
文章编号: N19032006
期刊: Science of The Total Environment
作者: Henrik Thers, Sylvestre Njakou Djomo, Lars Elsgaard, Marie Trydeman Knudsen
更新时间: 2019-03-20
摘要: Winter oilseed rape (WOSR) is the main crop for biodiesel in the EU, where legislation demands at least 50% savings in greenhouse gas (GHG) emissions as compared to fossil diesel. Thus industrial sectors search for optimized management systems to lower GHG emissions from oilseed rape cultivation. Recently, pyrolysis of biomass with subsequent soil amendment of biochar has shown potentials for GHG mitigation in terms of carbon (C) sequestration, avoidance of fossil based electricity, and mitigation of soil nitrous oxide (N2O) emissions. Here we analyzed three WOSR scenarios in terms of their global warming impact using a life cycle assessment approach. The first was a reference scenario with average Danish WOSR cultivation where straw residues were incorporated to the soil. The others were biochar scenarios in which the oilseed rape straw was pyrolysed to biochar at two process temperatures (400 and 800 °C) and returned to the field. The concept of avoided atmospheric CO2 load was applied for calculation of C sequestration factors for biochar, which resulted in larger mitigation effects than derived from calculations of just the remaining C in soil. In total, GHG emissions were reduced by 73 to 83% in the two biochar scenarios as compared to the reference scenario, mainly due to increased C sequestration. The climate benefits were higher for pyrolysis of oilseed rape straw at 800 than at 400 °C. The results demonstrated that biochar has a potential to improve the life cycle GHG emissions of oilseed rape biodiesel, and highlighted the importance of consolidated key assumptions, such as biochar stability in soil and the CO2 load of marginal grid electricity.
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25973. 题目: The deposit feeder Capitella teleta has a unique and relatively complex microbiome likely supporting its ability to degrade pollutants
文章编号: N19032005
期刊: Science of The Total Environment
作者: Rebecca Hochstein, Qian Zhang, Michael J. Sadowsky, Valery E. Forbes
更新时间: 2019-03-20
摘要: Capitella teleta is a sediment-dwelling marine polychaete that is often found in high densities in association with organic matter and pollutants. While C. teleta has been reported to transform a variety of aromatic hydrocarbons, the mechanisms by which degradation occurs are unknown. Moreover, there is continuing debate on the role of host and microbiota in degradation activity. The aims of this study were to characterize the gut microbiome of C. teleta and to identify microbiota that could potentially play a role in degradation of organic matter and aromatic hydrocarbons. Sequencing analysis of the 16S rRNA genes from the intestinal tracts of adult worms revealed a unique microbiome that was distinct from that of the worm's sediment food source and fecal pellets. About 66% of the 775 identified OTUs from the C. teleta gut microbiome were found to be unique to the worm and displayed high inter-individual variability. The gut microbiome was dominated by members of the genera Arcobacter, Pseudoalteromonas, Methylobacterium, and Propionibacterium. Functional analyses of microbiota revealed that hydrocarbon treatment led to a proliferation of gene classes involved in chemoheterotrophy and aromatic compound degradation. Of the 18 most abundant taxa identified, 50% were members of genera containing hydrocarbon (PAH)-degrading members, including Acinetobacter, Thalassotalea, and Achromobacter. Data obtained in this study will be useful to understand the biology of this marine polychaete and to elucidate the role that gut bacteria play in worm catabolism and the transformation of sediment organic pollutants.
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25974. 题目: Deep soil water extraction by apple sequesters organic carbon via root biomass rather than altering soil organic carbon content
文章编号: N19032004
期刊: Science of The Total Environment
作者: Huijie Li, Bingcheng Si, Xiaojun Ma, Pute Wu
更新时间: 2019-03-20
摘要: Soil water and carbon stocks have always been research hotspots. However, the interaction between soil water and carbon in deep soil (>1 m below surface) remains poorly understood. The present study used the chronosequence approach to investigate water extraction and carbon input by roots to a depth of 25.2 m in 8-, 11-, 15-, 18-, and 22-year-old afforested apple (Malus pumila Mill.) orchard stands in a sub-humid region of the Chinese Loess Plateau. Three long-term cultivated farmlands were used as a benchmark of soil water and carbon status before land use change. Measurements showed that the apple trees accessed deep soil water reserves by growing deep roots, with the resulting desiccated soil possibly stimulating apple trees to extend their roots into deeper, moister soil. Accordingly, soil water content in the root zone decreased progressively with increasing stand age. For example, the roots of apple trees in the 22-year-old stand extended to 23.2 m below the soil surface and extracted 1530 ± 43 mm deep soil water. Consequently, carbon input from root biomass correlated well with the water storage loss in deep soil (R2 = 0.88). Deep roots accounted for 49 ± 22% of the total root biomass and contributed 0.44 ± 0.15 Mg C ha−1 yr−1 to the deep soil. However, the roots of apple trees did not significantly change the soil organic carbon content in the root zone possibly because there was limited root biomass per unit soil depth and because soil water content in the root zone gradually decreased. These findings demonstrate the importance of deep soil in regulating water and carbon cycles, advancing our understanding of interactions among water, roots, and carbon in this zone.
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25975. 题目: Terrestrial diet influences mercury bioaccumulation in zooplankton and macroinvertebrates in lakes with differing dissolved organic carbon concentrations
文章编号: N19032003
期刊: Science of The Total Environment
作者: Pianpian Wu, Martin Kainz, Staffan Åkerblom, Andrea Garcia Bravo, Lars Sonesten, Brian Branfireun, Anne Deininger, Ann-Kristin Bergström, Kevin Bishop
更新时间: 2019-03-20
摘要: Dietary uptake is a key step in conveying both toxic mercury (Hg; particularly as highly bioavailable methylmercury, MeHg) and essential dietary biochemicals, such as polyunsaturated fatty acids (PUFA), across trophic levels within aquatic food webs. Using stable isotopes and fatty acids we evaluated the role of food sources in size-fractioned plankton and littoral macroinvertebrates for the bioaccumulation of total Hg and MeHg in six oligotrophic and one mesotrophic Swedish lakes with differing concentrations of dissolved organic carbon (DOC). We found that the consumption of both algal and terrestrial diets (assessed by PUFA and long-chain saturated fatty acids, respectively) predicted >66% of the Hg concentration variability in meso- (100–500 μm) and macrozooplankton (>500 μm) in oligotrophic lakes. In the mesotrophic lake, total Hg bioaccumulation in higher trophic level biota, carnivorous macroinvertebrates was also significantly related to terrestrial diet sources (R2 = 0.65, p < 0.01). However, lake pH and DOC correlated to total Hg bioaccumulation and bioconcentration across all lakes, suggesting the consumption of different diet sources is mediated by the influence of lake characteristics. This field study reveals that using dietary biomarkers (stable isotopes and fatty acids) together with the physico-chemical lake parameters pH and nutrients together improve our ability to predict Hg bioaccumulation in aquatic food webs. Fatty acids used as dietary biomarkers provide correlative evidence of specific diet source retention in consumers and their effect on Hg bioaccumulation, while pH and nutrients are the underlying physico-chemical lake parameters controlling differences in Hg bioaccumulation between lakes.
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25976. 题目: Mapping dynamics of soil organic matter in croplands with MODIS data and machine learning algorithms
文章编号: N19032002
期刊: Science of The Total Environment
作者: Di Chen, Naijie Chang, Jingfeng Xiao, Qingbo Zhou, Wenbin Wu
更新时间: 2019-03-20
摘要: As an important indicator of soil quality, soil organic matter (SOM) significantly contributes to land productivity and ecosystem health. Accurately mapping SOM at regional scales is of critical importance for sustainable agriculture and soil utilization management and remains a grand challenge. Many studies used soil sampling data and machine learning algorithms to predict SOM at regional scales for a given year, while few studies mapped SOM for multiple years and examined its temporal dynamics. We compared the performance of four machine learning algorithms: decision tree (DT), bagging decision tree (BDT), random forest (RF), and gradient boosting regression trees (GBRT) in mapping SOM in Hubei province, China over the 18-year period from 2000 to 2017. Our results showed that RF and DT had the highest coefficient of determination (R2) (0.61) and the lowest potential bias (9.48 g/kg), respectively, while GBRT had the lowest mean error (ME) (1.26 g/kg), root mean squared error (RMSE) (5.41 g/kg) and Lin's concordance correlation coefficient (LCCC) (0.72). The SOM map based on GBRT better captured the distribution of the soil sample data than that based on RF. The trained GBRT model and the spatially explicitly data on explanatory variables (e.g., climate, terrain, remote sensing) were used to predict SOM for each 500 m × 500 m grid cell in Hubei for the period from 2000 to 2017. Our results showed that the SOM content of cropland was relatively high in the southeast and relatively low in the north. The SOM content in the topsoil varied from 0.89 to 58.86 g/kg and was averaged at 20.52 g/kg. The mean cropland SOM content of the province exhibited an increasing trend from 2000 to 2017 with an increase of 0. 26 g/kg and a growth rate of 1.28%. Spatially, the SOM content increased in southern Hubei and decreased in central and northern parts of the province. A large portion of the areas with decreasing SOM content in northern Hubei was reclaimed cropland, while a large part of the high-quality cropland with rising SOM content in the east (~0.45 × 104 ha) was lost due to land use change (e.g., urbanization).
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25977. 题目: Aerobic granular sludge membrane bioreactor (AGMBR): Extracellular polymeric substances (EPS) analysis
文章编号: N19032001
期刊: Water Research
作者: Oliver T. Iorhemen, Rania A. Hamza, Mohamed S. Zaghloul, Joo Hwa Tay
更新时间: 2019-03-20
摘要: Aerobic granular sludge membrane bioreactor (AGMBR) has emerged with strong potential to overcome membrane fouling. There have been no extensive studies on extracellular polymeric substances (EPS) in AGMBR. The present work aimed at conducting an in-depth study of EPS and monitoring fouling development in AGMBR using a 22 factorial design having hydraulic retention time (HRT) and total organic carbon (TOC) as independent variables. HRT was tested at three levels of 6, 8 and 10 h while the TOC levels were 104 ± 13, 189 ± 17, and 266 ± 27 mg/L. AGMBR exhibited high proteins (PN) in the tightly-bound EPS (TB-EPS) resulting in high proteins/polysaccharides (PN/PS) ratios of 2–16. The PN in the LB-EPS was low, ranging from 0.01 to 1.92 mg/g MLVSS, but the range of PN/PS ratio was also of 2–16. Despite the high PN/PS ratio, TMP rise was low. Water jet easily sloughed off the developed membrane cake layer. The elimination of chemicals for membrane cleaning has significant cost savings. TOC had a significant main effect on both the PN and PS components of TB-EPS at α < 0.05. TB-EPS PN increased with increase in TOC. TB-EPS PN decreased as HRT increased from 6 h to 10 h at 104 ± 13 mg/L TOC but the change of HRT from 10 h to 6 h at 266 ± 27 mg/L TOC did not affect TB-EPS PN. The TMP increased with increasing HRT at 104 ± 13 and 266 ± 27 mg/L TOC. An increase in sEPS PN correlated well with increase in membrane fouling (r = 0.581). Three runs performed best: 266 ± 27 mg/L TOC and 10 h HRT; 104 ± 13 mg/L TOC and 6 h HR; and 266 ± 27 mg/L TOC and 6 h HRT as TMP was below the 50 kPa threshold. AGMBR achieved 98 ± 1%, 99 ± 1%, 52 ± 33% organics degradation, NH3-N removal, total nitrogen removal, respectively.
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25978. 题目: Lignin catabolic pathways reveal unique characteristics of Dye‐decolorizing peroxidases in Pseudomonas putida
文章编号: N19031910
期刊: Environmental Microbiology
作者: Lu Lin, Xiaopeng Wang, Lanfang Cao, Meiying Xu
更新时间: 2019-03-19
摘要: Lignin is one of the largest carbon reservoirs in the environment, playing an important role in the global carbon cycle. However, lignin degradation in bacteria, especially non‐model organisms, has not been well characterized either enzymatically or genetically. Here, a lignin‐degrading bacterial strain, Pseudomonas putida A514, was used as the research model. Genomic and proteomic analyses suggested that two B subfamily dye‐decolorizing peroxidases (DypBs) were prominent in lignin depolymerization, while the classic O2‐dependent ring cleavage strategy was utilized in central pathways to catabolize lignin‐derived aromatic compounds that were funneled by peripheral pathways. These enzymes, together with a range of transporters, sequential and expression‐dose dependent regulation, and stress response systems coordinated for lignin metabolism. Catalytic assays indicated these DypBs show unique Mn2+ independent lignin depolymerization activity, while Mn2+ oxidation activity is absent. Furthermore, a high synergy between DypB enzymes and A514 cells was observed to promote cell growth (5 x 1012 CFUs/mL) and lignin degradation (27%). This suggested DypBs are competitive lignin biocatalysts and pinpointed limited extracellular secretion capacity as the rate‐limiting factor in bacterial lignin degradation. DypB production was, therefore, optimized in recombinant strains and a 14141‐fold increase in DypB activity (56565 U/L) was achieved, providing novel insights for lignin bioconversion.
25979. 题目: Organic matter content and type variation in the sequence stratigraphic context of the Upper Devonian New Albany Shale, Illinois Basin
文章编号: N19031909
期刊: Sedimentary Geology
作者: Bei Liu, Juergen Schieber, Maria Mastalerz, Juan Teng
更新时间: 2019-03-19
摘要: Organic matter quantity and type are important parameters in conventional source rock evaluation and unconventional shale oil/gas reservoir characterization. Understanding the stratigraphic distribution of organic matter content and type in black shale successions is critical for identifying potentially productive intervals, because organic matter can adsorb large amounts of oil and gas. Detailed examination of total organic carbon content, organic petrographic composition, and high-resolution (8 cm spacing) geochemical proxies in a sequence stratigraphic framework were conducted on an early mature (0.55% Ro) New Albany Shale core of the Illinois Basin to study the influence of relative sea-level fluctuations on paleoproductivity, clastic supply, bottom-water redox conditions, and their combined control on total organic carbon distribution pattern and organic maceral variation. Marine organic matter including amorphous organic matter and alginite (mainly derived from Tasmanites cysts) is the dominant organic matter in the New Albany Shale. Terrestrial organic matter accounts for <10% of total organic matter. Within a sequence stratigraphic context, total organic carbon content increases in transgressive systems tracts, reaches a maximum before the maximum flooding surface, and shows relatively low values in highstand systems tracts. Comparatively, low total organic carbon contents at maximum flooding surfaces reflect a combination of low sedimentation rates, elevated bottom-water oxygenation, and high biogenic silica dilution. Stratigraphically, amorphous organic matter content increases in transgressive systems tracts, reaches a maximum near the maximum flooding surface, and decreases in highstand systems tracts. Enrichment of broken Tasmanites cysts and their detrital infills are an indicator of high-energy environments and could possibly indicate lowstand systems tracts. The stratigraphic distribution of organic matter content and type may result in cyclic stratigraphic variations of hydrocarbon generation potential and oil saturation, and influence the development of secondary organic pores when the New Albany Shale is within the oil and gas windows.
25980. 题目: Interannual variability in the summer dissolved organic matter inventory of the North Sea: implications for the continental shelf pump
文章编号: N19031908
期刊: Biogeosciences
作者: Saisiri Chaichana, Tim Jickells, Martin Johnson
更新时间: 2019-03-19
摘要: We present the distribution and C:N stoichiometry of dissolved organic matter (DOM) in the North Sea in two summers (August 2011 and August 2012), with supporting data from the intervening winter (January 2012). These data demonstrate local variability superimposed on a general pattern of decreasing DOM with increasing distance from land, suggesting concentrations of DOM are controlled on large spatial scales by mixing between the open North Atlantic and either riverine sources or high DOM productivity in nearshore coastal waters driven by riverine nutrient discharge. Given the large size and long residence time of water in the North Sea, we find concentrations are commonly modified from simple conservative mixing between two endmembers. We observe differences in dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations and land–ocean gradients between the two summers, leading to an estimated 10–20 Tg difference in the DOC inventory between the two years, which is of the same order of magnitude as the annual uptake of atmospheric CO2 by the North Sea system, and thus significant for the carbon budget of the North Sea. This difference is not consistent with additional terrestrial loading and is more likely to be due to balancing of mixing and in situ production and loss processes across the North Sea. Differences were particularly pronounced in the bottom layer of the seasonally stratifying northern North Sea, with higher DOC and C:N ratio in 2011 than in 2012. Using other data, we consider the extent to which these differences in the concentrations and C:N ratio of DOM could be due to changes in the biogeochemistry or physical circulation in the two years, or a combination of both. The evidence we have is consistent with a flushing event in winter 2011/12 exchanging DOM-rich, high C:N shelf waters, which may have accumulated over more than 1 year, with deep North Atlantic waters with lower DOC and marginally higher DON. We discuss the implications of these observations for the shelf sea carbon pump and the export of carbon-rich organic matter off the shelf and hypothesise that intermittent flushing of temperate shelf systems may be a key mechanism in the maintenance of the continental shelf pump, via the accumulation and subsequent export of carbon-rich DOM.