论文检索
总访问量：6356985次
总访客量：556207人
所有论文
29101. 题目: Combining the microbial calcite precipitation process with biochar in order to improve nickel remediation
文章编号: N19030206
期刊: Applied Geochemistry
作者: Jing Zhang, Deepika Kumari, Chaolin Fang, Varenyam Achal
更新时间: 2019-03-02
摘要: Microbially induced calcite precipitation (MICP) is a promising technology in the remediation of heavy metals, while biochar is a valuable adsorbent for its removal. In the present study, biochar was added to the MICP process to investigate its effect on the remediation of nickel (Ni). The MICP process immobilized 89% and 66% of Ni2+ at initial concentrations of 50 and 100 mg L−1, respectively. However, biochar had an inhibitory effect on the calcite produced by Bacillus cereus NS4 and suppressed the Ni remediation. The mechanism of suppression by biochar was elucidated by scanning electron microscopy-energy dispersion spectrophotometry, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. Biochar caused weakening of the adsorption bonds responsible for carbonate formation led to dissociation of the carbonate structure. This is the first study to combine biochar with the MICP process and provides reference data for better understanding of the mechanism of suppression of carbonate precipitation by biochar.
29102. 题目: Sorption and leaching behavior of bithionol and levamisole in soils
文章编号: N19030205
期刊: Chemosphere
作者: Xuan Ma, Xueping Liu, Sanglan Ding, Shijun Su, Zhiwei Gan
更新时间: 2019-03-02
摘要: The batch experiments were conducted to understand sorption process of bithionol (BIT) in yellow soil (YS) and red soil (RS), while column leaching experiments were performed to evaluate the leaching behavior of BIT and levamisole (LEV) in the tested soils. The adsorption and desorption data fitted well with the Freundlich isotherms (R2 ≥ 0.94). The distribution coefficient of BIT in the YS and RS were 104 and 98.3 L/kg, respectively. Hysteresis was observed for bithionol desorption in the YS and RS, with hysteresis coefficient of 0.917 and 0.928, respectively. Dissolved organic matter (DOM) addition and acid condition enhanced the adsorption of BIT in the soil. Both BIT and LEV showed poor leaching potential in the tested soils. More than 80% of BIT and LEV remained in the surface soil layer and the amount of the two target compounds in the leachates accounted for less than 1% of overall recovery. DOM showed little influence on the concentration of BIT and LEV in the leachates collected at different time. The results could fill the gap on the behavior of BIT and LEV in soil under laboratory conditions.
29103. 题目: Growth promotion of greenhouse tomatoes with Pseudomonas sp. and Bacillus sp. biofilms and planktonic cells
文章编号: N19030204
期刊: Applied Soil Ecology
作者: Emily Ricci, Timothy Schwinghamer, Di Fan, Donald L. Smith, Valérie Gravel
更新时间: 2019-03-02
摘要: The effects on plants of commercial applications of biofertilizer and biocontrol agents containing planktonic rhizobacteria cells are inconsistent mainly due to an unsuccessful competition with existing endogenous microbial communities. The present study investigated rhizobacteria inoculants in the form of biofilms, which are dense colonies of single or multi-species microbial cells, adherent to either biotic or abiotic surfaces, and encased in a self-produced matrix composed of extracellular polymeric substances. Bacillus sp., Pseudomonas sp., or a mixed inoculum of both bacteria at the planktonic or biofilm stage of growth were applied to greenhouse-grown tomato (Solanum lycopersicum L. cv Trust) plants fertilized with a half strength Hoagland solution or a modified solution lacking phosphate or iron. Based on multivariate analysis of variance, availability of nutrients, bacteria, and stages of bacterial growth significantly affected plant variables known to be contributing factors to greenhouse tomato yield. Results suggest that Bacillus sp. and Pseudomonas sp. biofilms are more effective inoculants than planktonic bacteria cells. Pseudomonas sp. applied as a biofilm increased the height and root dry weight of tomato plants, but it inhibited the positive effects of inoculation on tomato leaf number and tomato root length. Path analysis identified positive causal paths from (Pseudomonas) biofilm and planktonic cells, to the tomato plant growth variables. Presence of Bacillus sp. alone or in a mixture inhibited the positive effects of inoculation on tomato plant leaf area and root dry weight. Nevertheless, the effect of Bacillus sp. on root length was relatively positive. Results suggest that the use of innovative rhizobacteria biofilm technologies could prove advantageous as biofertilizer agents, and alleviate the dependence of greenhouse tomato producers on non-biological agro-chemicals.
29104. 题目: Decomposition of an N-fixing invasive plant compared with a native species: Consequences for ecosystem
文章编号: N19030203
期刊: Applied Soil Ecology
作者: Elizabete Marchante, Hélia Marchante, Helena Freitas, Annelise Kjøller, Sten Struwe
更新时间: 2019-03-02
摘要: Invasion by the Australian Acacia longifolia has significantly altered the characteristics of both vegetation and soil of Portuguese coastal dunes, including the accumulation of a thick litter layer. Although many aspects of impacts by this species in invaded dunes are known, decomposition of the litter is not well studied, but this can be crucial to disentangle both impacts and recovery. In order to better understand the impacts at soil level and the recovery of the system after removal of the invader, decomposition of A. longifolia litter was studied and compared with decomposition of the native Cistus salviifolius, for >3 years. Litterbags were deployed in a coastal sand dune and samples retrieved after 2, 5, 11, 17, 24, 36 and 41 months. At the final sampling, ca. 41% and 48% of the initial litter mass of A. longifolia and C. salviifolius, respectively, remained, showing that in these dunes both species decompose slowly. During the first 17 months, A. longifolia decomposed faster than C. salviifolius, but thereafter the rate slowed down and C. salviifolius was decomposed at a faster rate. In general, throughout decomposition, N and lignin content, lignin/cellulose ratio, cellulase and chitinase activity, and the number of microfungi morphotypes were significantly higher in A. longifolia than in C. salviifolius litter. On the other hand, C/N ratio, cellulose content and the number of microfungal isolates were generally higher in C. salviifolius litter. Mostly for A. longifolia, lignin content and lignin/N ratio increased as the remaining litter mass decreased. Despite high N content and low lignin/N and C/N ratios, almost 43% of the A. longifolia litter is recalcitrant/very slowly decomposed, accumulating on soil surface for long periods. The slow decomposition rate of A. longifolia litter together with the production of much more litter than the native vegetation (ca. 3 times more than C. salviifolius) is reflected in the accumulation of a thick N-rich litter layer on soil surface of invaded areas. This promotes a continuous input of C and nutrients to the soil, and leaves a hidden legacy long after the removal of the invader that, amongst other impacts, prevents the regeneration of native species.
29105. 题目: Impacts of green manure amendment on detritus micro-food web in a double-rice cropping system
文章编号: N19030202
期刊: Applied Soil Ecology
作者: Yunfeng Chen, Ning Hu, Qingzhong Zhang, Yilai Lou, Zhongfang Li, Zheng Tang, Yakov Kuzyakov, Yidong Wang
更新时间: 2019-03-02
摘要: Chinese milk vetch (CMV) is widely used as a green manure due to its efficiency for nutrient preservation and soil fertility improvement, as well for providing more organic substances for soil organisms. Detritus micro-food web drives carbon and nutrient cycling and maintains ecosystem productivity. The effects of CMV amendment on detritus micro-food web were investigated in a six-year field experiment. Compared to the mineral fertilizers (NPK) alone, the fertilizers combined with CMV (NPK + CMV) increased soil organic carbon content, and thus enhanced the biomass of microorganisms, as well as protozoa abundance, while did not change micro-feeding nematode abundance (MN). This indicates a substrate-driven bottom-up effect. However, the green manure application increased omnivores-predators (OP) abundance and the OP/MN ratio, suggesting a top-down effect. Higher F/B ratio indicates a shift of the food web energy structure towards to fungi-dominated channel in the manured soil. Here, the green manure amendment should be encouraged to improve soil detritus micro-food web.
29106. 题目: Effects of land-use change on chemical attributes of a Ferralsol in Brazilian Cerrado
文章编号: N19030201
期刊: CATENA
作者: Fabiane Pereira Machado Dias, Rodrigo Hübner, Flávia de Jesus Nunes, Wilson Mozena Leandro, Francisco Alisson da Silva Xavier
更新时间: 2019-03-02
摘要: The expansion of agriculture in the Brazilian Cerrado biome occurs at the expense of replacing native forest with pasture and/or crops. Negative environmental impacts, such as soil degradation, have been observed during this process. We aimed to evaluate the effect of different agricultural management systems on chemical attributes and soil organic matter fractions of a Ferralsol in an area of Cerrado, in the municipality of Hidrolândia, Goiás, Brazil. The following management systems were evaluated: (a) pasture (PAST), (b) no-tillage system (NT), organic cultivation (ORG) systems with different years of cultivation (2, 6, 8, and 10 years), and (c) a conventional management system (CS). Further, an area under native Cerrado forest (NF) was selected and used as a reference for steady state. Soil cores were collected at 0.0–0.10, 0.10–0.20, and 0.20–0.40 m depths. Macronutrients, total organic C (TOC), particulate organic C (POC), humic substances, and labile-C (Lab-C) were analyzed. The land-use change effect, driven by deforestation with subsequent pasture and/or crop, was evident by principal component (PC) analysis. In the 0.0–0.10 m soil layer, PC2 showed the isolation of NF from agricultural systems, whereas PC1 exhibited similar phenomena for the 0.10–0.20 and 0.20–0.40 m layers. In all cases, the agricultural systems showed weak correlation to TOC, POC, Lab-C and base saturation, suggesting loss of soil chemical fertility compared to NF. The ORG-8 area differed from other managed systems mainly due to high pH, P content, and base saturation. Soil cation exchange capacity was highly correlated to variables associated with soil organic matter, such as TOC, POC, and Lab-C. This result demonstrates that Cerrado soils are highly dependent on soil organic C dynamics. Conversion of Cerrado into agricultural land decreases soil chemical fertility. However, agroecosystems that reduce soil tillage and increase organic inputs, such as organic cultivation and no-tillage, seem to be suitable options for agricultural activity in Brazilian Cerrado.
29107. 题目: The influence of dissolved organic matter on the marine production of carbonyl sulfide (OCS) and carbon disulfide (CS2) in the Eastern Tropical South Pacific
文章编号: N19030110
期刊: Ocean Science Discussions
作者: Sinikka T. Lennartz, Marc von Hobe, Dennis Booge, Henry Bittig, Tim Fischer, Rafael Gonçalves-Araujo, Kerstin B. Ksionzek, Boris P. Koch, Astrid Bracher, Rüdiger Röttgers, Birgit Quack, Christa A. Marandino
更新时间: 2019-03-01
摘要: Oceanic emissions of the climate relevant trace gases carbonyl sulfide (OCS) and carbon disulfide (CS2) are a major source to their atmospheric budget. Their current and future emission estimates are still uncertain due to incomplete process understanding and, therefore, inexact quantification across different biogeochemical regimes. Here we present the first concurrent measurements of both gases together with related fractions of the dissolved organic matter (DOM) pool, i.e. solid-phase extractable dissolved organic sulfur (DOSSPE), chromophoric (CDOM) and fluorescent dissolved organic matter (FDOM) from the Eastern Tropical South Pacific (ETSP). These observations are used to estimate in-situ production rates and identify their drivers. We find different limiting factors of marine photoproduction: while OCS production is limited by the humic-like DOM fraction that can act as a photosensitizer, high CS2 production coincides with high DOSSPE concentration. The lack of correlation between OCS production and DOSSPE may be explained by the active cycling of sulfur between OCS and dissolved inorganic sulfide via OCS photoproduction and hydrolysis. In addition, the only existing parameterization for OCS dark production is validated and updated with new rates from the ETSP and the Indian Ocean. Our results will help to predict oceanic concentrations and emissions of both gases on regional and, potentially, global scales.
29108. 题目: Spatially variable bioturbation and physical mixing drive the sedimentary biogeochemical seascape in the Louisiana continental shelf hypoxic zone
文章编号: N19030109
期刊: Biogeochemistry
作者: Richard Devereux, John C. Lehrter, Giancarlo Cicchetti, David L. Beddick, Diane F. Yates, Brandon M. Jarvis, Jessica Aukamp, Marilynn D. Hoglund
更新时间: 2019-03-01
摘要: Seasonal hypoxia on the Louisiana continental shelf (LCS) has grown to over 22,000 km2 with limited information available on how low oxygen effects the benthos. Benthic macrofaunal colonization and sediment biogeochemical parameters were characterized at twelve stations in waters 10–50 m deep along four transects spanning 320 km across the LCS hypoxic zone in the early fall of 2010 when bottom waters typically return to oxic conditions. Chemical data and sediment profile imaging (SPI) support three primary mechanistic pathways of organic matter degradation on the LCS: (i) metal oxide cycling in depositional muds, (ii) infauna-driven bioturbation delivering oxygen below the sediment–water interface, and (iii) sulfate reduction in sediments where iron oxide availability is limited. The transect nearest the Mississippi River delta had the highest concentrations of porewater and solid phase Mn and Fe with SPI images of recently deposited reddish, mixed muddy sediments suggestive of metal cycling. The deepest stations had high oxidized iron concentrations and rust colored sediments with faunal colonization that suggests sediments are oxidized via bioturbation. Many nearshore and central LCS stations had more black sediments, more disturbed clay layers, lower amounts of oxidized iron, and higher sulfate reduction rates than the deepest stations. Sediment mixing coefficients, DB, determined from chlorophyll-a concentration profiles varied between 33 and 183 cm−2 year−1. DB values were highest at the deepest stations where sediments were colonized. DB were not determined at two nearshore stations where chlorophyll-a concentrations were highly variable in surficial sediments, and on the eastern shelf where sedimentation is high. This study provides a regional view of benthic faunal colonization and sediment biogeochemistry on the LCS, describes regions with potentially different pathways of organic matter degradation, and demonstrates the importance of both bioturbation and physical mixing in processing the large amounts of organic matter in river-dominated continental shelf systems.
29109. 题目: Sonocatalytic degradation of butylparaben in aqueous phase over Pd/C nanoparticles
文章编号: N19030108
期刊: Environmental Science and Pollution Research
作者: Georgios Bampos, Zacharias Frontistis
更新时间: 2019-03-01
摘要: In the present work, the sonocatalytic degradation of butylparaben was investigated using Pd immobilized on carbon black as the sonocatalyst. The presence of 25 mg/L 10Pd/C significantly increased the removal rate of butylparaben and the observed kinetic constant increased from 0.0126 to 0.071 min−1, while the synergy index between sonolysis and adsorption was 70.7%. The BP degradation followed pseudo-first-order kinetics with the apparent kinetic constant decreased from 0.071 to 0.030 min−1 when the initial concentration of butylparaben increased from 0.5 to 2 mg/L. The process was being favored slightly under alkaline conditions. The presence of organic matter (20 mg/L humic acid) reduced the apparent kinetic constant more than two times. The addition of chlorides up to 250 mg/L did not significantly reduce the rate of reaction, while the presence of 250 mg/L bicarbonates reduced the observed kinetic constant from 0.071 to 0.0472 min−1. The prepared catalyst retains the efficiency after five subsequent experiments since the apparent kinetic constant was only slightly decreased from 0.071 to 0.059 min−1.
29110. 题目: Feasibility of agricultural residues and their biochars for plant growing media: Physical and hydraulic properties
文章编号: N19030107
期刊: Waste Management
作者: Golnoosh Banitalebi, Mohammad Reza Mosaddeghi, Hossein Shariatmadari
更新时间: 2019-03-01
摘要: This study was conducted to examine feasibility of using some agricultural residues and their biochars as substitutes for commercial horticultural growing media as cocopeat, sand, perlite, zeolite, pumice, vermiculite and rockwool. Biochars of wheat straw, sawdust, rice hull, sugarcane bagasse and date palm bunches were produced at 300 and 500 °C. Following substrate properties were determined: easily available water (EAW) defined by the difference between water contents (θ) at absolute matric potentials (h) of 10 and 50 hPa (EAW = θ10 − θ50), air after irrigation (AIR = θ0 − θ10), water holding capacity (WHC = θ10), water buffering capacity (WBC = θ50 − θ100), saturated water content (θs), bulk density (BD), total porosity (TP), water drop penetration time (WDPT), pH and electrical conductivity (EC). A classification system was developed to evaluate the substrates as horticultural growing media. Higher pyrolysis temperature produced biochars with higher pH, EC, TP, θs, WHC, EAW, and WBC and lower biochar yield, AIR, BD and WDPT. Sugarcane bagasse biochars had higher θs, TP and WBC and lower BD than other biochars. Comparison among organic residues and inorganic substrates showed that highest TP, θs and EAW were observed in rockwool, whereas, among organic residues, maximum values of these properties were achieved for sugarcane bagasse, wheat straw and sawdust, respectively. Considering pH, EC, BD, TP, EAW, AIR, WBC and WDPT, wheat straw and sawdust were classified as very good substrates similar to cocopeat and rockwool. Other organic residues were placed in good class. Wheat straw and date palm bunches biochars produced at 500 °C and sugarcane bagasse and rice hull biochars were good growing media and can be suitable candidates for amendments or replacements of commercial growing media.
29111. 题目: Evaluation of algal photosynthesis inhibition activity for dissolved organic matter with the consideration of inorganic and coloring constituents
文章编号: N19030106
期刊: Chemosphere
作者: Kentaro Misaki, Yuhei Morita, Kentaro Kobayashi, Yuichi Sugawara, Yoshihisa Shimizu, Taketoshi Kusakabe
更新时间: 2019-03-01
摘要: The effect of waterborne ingredient on ecosystem has been of great interest. In the present study, the evaluation method using algal photosynthesis inhibition assay with dual-channel pulse amplitude modulation (PAM) system was established for a series of water samples to elucidate the potential effect of the total body of organic compounds including natural organic matter (NOM) on aquatic ecosystems. The more sensitive and less time-consuming monitoring method compared with algal growth inhibition assay was suggested, especially considering inorganic and coloring constituents. Algal photosynthesis inhibition activity was detected with high sensitivity for photosystem II (PSII) inhibitors, whereas the IC10 of the other chemicals was over the environmental standard concentration for Chlamydomonas moewusii (Chlorophyceae) and Pheodactylum tricornutum (Diatomea). The photosynthesis inhibition activity of Lake Biwa dissolved organic matter (LBDOM) and fulvic acid (LBFA) was significantly detected at ≥10 times the concentration and >10 mgC L−1, respectively, whereas prominent activity was confirmed for Suwannee River NOM (SRNOM) on the river original concentration (>30 mgC L−1) for both algae. Significant inhibition activity was detected in both algae at least in twice-concentration for water samples from a wastewater treatment pilot plant. There was no great difference in the activity between sewage secondary effluent and its filtrate with ultrafiltration (UF), and physically washing water for the UF membrane.
29112. 题目: Floodplain dynamics in North American permafrost regions under a warming climate and implications for organic carbon stocks: A review and synthesis
文章编号: N19030105
期刊: Earth-Science Reviews
作者: Katherine B. Lininger, Ellen Wohl
更新时间: 2019-03-01
摘要: Although there have been studies on changes to hydrology in permafrost regions and exports of nutrients and organic matter to the Arctic Ocean, little is known about how geomorphic dynamics of rivers in permafrost regions will change in the future under a warming climate and the effects of those changes on floodplains. We focus on river dynamics in the context of channel-floodplain interactions and the implications for organic carbon storage in floodplains. As sites of nutrient processing and storage of sediments and organic matter, changes in channel and floodplain form and process will impact sediment yields, nutrient and organic matter export to the Arctic Ocean, aquatic and riparian habitat, and infrastructure. We present a review of the factors influencing reach-scale river dynamics, using the framework of factors affecting erosive force and erosional resistance of banks and floodplain surfaces, which will change due to a warming climate. We summarize studies indicating how observed and modeled trends in these factors will affect erosive force and erosional resistance in the future. We then hypothesize the net effects that these changes will have on the ratio of erosive force to erosional resistance, and the cascading effects on channel and floodplain form and process. We describe two scenarios that could occur under different conditions in the form of conceptual models, one in which the ratio of erosive force and erosional resistance decreases, and one in which the ratio increases. An increase in the ratio of erosive force to erosional resistance due to a reduction in permafrost extent and depth and an overall increase in discharge would increase bank erosion, bank failures, sediment supply, and lateral channel migration rates, decreasing floodplain turnover time and the age of riparian vegetation. A decrease in the ratio of erosive force to erosional resistance due to a reduction in erosive force relative to sediment supply would cause enhanced deposition within the river corridor. Regardless of which scenario may occur, changes in channel process and form will influence the ratio of lateral to vertical accretion, change the nature and stored amount of floodplain sediment, and change the sources and storage of organic carbon within floodplains.
29113. 题目: The adverse effect of biochar to aquatic algae- the role of free radicals
文章编号: N19030104
期刊: Environmental Pollution
作者: Ying Zhang, Ruixin Yang, Xiaohui Si, Xingwei Duan, Xie Quan
更新时间: 2019-03-01
摘要: The application of biochar in remediation and recovery of heavy metals and/or organic contaminants in water and soil is increasing. However, the adverse effect of biochar to aquatic organisms has not received enough attention. In this study, we conducted a study on the biotoxicity of biochar pyrolyzed from pine needle under oxygen-limited conditions. The toxicity of biochar was expressed with the following endpoints: cell growth, chlorophyll-a (Chl-a), reactive oxygen species (ROS), superoxide dismutase (SOD) content of Scenedesmus obliquus (S. obliquus) and the luminescence of Photobacterium phosphoreum (P. phosphoreum). Here, the effect of free radicals (FRs) contained in biochar was stressed. Our results show that the toxicity of biochar is significantly correlated with the concentration of FRs in biochar particles. Meanwhile, we found the FRs-containing biochar could induce the production of acellular ROS (such as ·OH) in water, which would also induce the production of interior cellular ROS in aquatic organisms. Our findings provide a new insight into the mechanism of toxicity aroused by biochar applications and aid in understanding its potential ecological risk.
图文摘要:
29114. 题目: Dissolved Organic Matter at the Fluvial-Marine Transition in the Laptev Sea Using in situ Data and Ocean Color Remote Sensing
文章编号: N19030103
期刊: Biogeosciences
作者: Bennet Juhls, Pier Paul Overduin, Jens Hölemann, Martin Hieronymi, Atsushi Matsuoka, Birgit Heim, and Jürgen Fischer
更新时间: 2019-03-01
摘要: River water is the main source of dissolved organic carbon (DOC) in the Arctic Ocean. DOC plays an important role in the Arctic carbon cycle and its export from land to sea is expected to increase as ongoing climate change accelerates permafrost thaw. However, transport pathways and transformation of DOC in the land-to-ocean transition are mostly unknown. We collected DOC and aCDOM(λ) samples from 11 expeditions to river, coastal and offshore waters and present a new DOC-aCDOM(λ) model for the fluvial-marine transition zone in the Laptev Sea The aCDOM(λ) characteristics revealed that the DOM in samples of this dataset are primarily of terrigenous origin. Observed changes in aCDOM and its spectral slopes indicate that DOM is modified by microbial- and photo-degradation. Ocean Color Remote Sensing (OCRS) provides the absorption coefficient of colored dissolved organic matter (aCDOM(λ)sat) at λ = 440 or 443 nm, which can be used to estimate DOC concentration at high temporal and spatial resolution over large regions. We tested the statistical performance of five OCRS algorithms and evaluated the plausibility of the spatial distribution of derived aCDOM(λ)sat. The ONNS algorithm showed the best performance compared to in situ aCDOM(440) (r2 = 0.72). Additionally, we found ONNS-derived aCDOM(440), in contrast to other algorithms, to be partly independent of sediment concentration, making ONNS the most suitable aCDOM(λ)sat algorithm for the Laptev Sea region. The DOC-aCDOM(λ) model was applied to ONNS-derived aCDOM(440) and retrieved DOC concentration maps showed moderate agreement to in situ data (r2 = 0.53). The in situ and satellite-retrieved data were offset by up to several days, which may partly explain the weak correlation for this dynamic region. Satellite-derived surface water DOC concentration maps from MERIS satellite data demonstrate rapid removal of DOC within short time periods in coastal waters of the Laptev Sea, which is likely caused by physical mixing and different types of degradation processes. Using samples from all occurring water types leads to a more robust DOC-aCDOM(λ) model for the retrievals of DOC in Arctic shelf and river waters.
29115. 题目: A review of the predictive models estimating association of neutral and ionizable organic chemicals with dissolved organic carbon
文章编号: N19030102
期刊: Science of The Total Environment
作者: Chiara Maria Vitale, Antonio Di Guardo
更新时间: 2019-03-01
摘要: Dissolved organic carbon (DOC) plays a key role in environmental transport, fate and bioavailability of organic chemicals in terrestrial and aquatic ecosystems. Predicting the association of contaminants to DOC is therefore crucial in modelling chemical exposure and risk assessment. The models proposed so far to describe interaction mechanisms between chemicals and DOC and the most influential variables have been reviewed. The single-parameter linear free energy relationships (sp-LFERs) and the poly-parameter linear free energy relationships (pp-LFERs) in the form of linear solvation energy relationships (LSERs) currently available in literature for estimating dissolved organic carbon/water partition (KDOC) and distribution (DDOC) coefficients for organic chemicals were discussed, and limits of the existing approaches explored.For neutral chemicals many predictive equations are currently available in literature, but the quality of the input data on which they are based is often questionable, due to the lack of an unequivocal definition of DOC among different references and to the different and often unreliable KDOC measurement method. For ionizable chemicals instead there is a substantial lack of predictive approaches that need to be fulfilled since just few models are nowadays available to predict DDOC of ionized species. This paper reviews the current approaches for neutral and ionizable chemicals proposing guidelines to select conditions for obtaining reliable data and predictive equations for an improved estimation of KDOC and DDOC.
图文摘要:
29116. 题目: Sialic Acids in the Extracellular Polymeric Substances of Seawater-Adapted Aerobic Granular Sludge
文章编号: N19030101
期刊: Water Research
作者: Danny R. de Graaff, Simon Felz, Thomas R. Neu, Mario Pronk, Mark C.M. van Loosdrecht, Yuemei Lin
更新时间: 2019-03-01
摘要: Sialic acids have been discovered in the extracellular polymeric substances (EPS) of seawater-adapted aerobic granular sludge (AGS). Sialic acids are a group of monosaccharides with a nine-carbon backbone, commonly found in mammalian cells and pathogenic bacteria, and frequently described to protect EPS molecules and cells from attack by proteases or glycosidases. In order to further understand the role of these compounds in AGS, lectin staining, genome analysis of the dominant bacterial species, and shielding tests were done. Fluorescence lectin bar-coding (FLBC) analysis showed an overlap with protein staining, indicating presence of sialoglycoproteins in the EPS matrix. Genome analysis gives a positive indication for putative production of sialic acids by the dominant bacteria Candidatus Accumulibacter. FT-IR analysis shows upon selective removal of sialic acids a decrease in carbohydrates, extension of the protein side chain, and exposure of penultimate sugars. Enzymatic removal of sialic acids results in the removal of galactose residues from the EPS upon subsequent treatment with β-galactosidase, indicating a linkage between galactose and sialic acid at the terminus of glycan chains. This work indicates the importance of sialic acids in the protection of penultimate sugar residues of glycoproteins in EPS, and provides basis for future research in the composition of EPS from biofilms and granular sludge.
图文摘要:
29117. 题目: Composition and vertical flux of particulate organic matter to the oxygen minimum zone of the central Baltic Sea: impact of a sporadic North Sea inflow
文章编号: N19022818
期刊: Biogeosciences
作者: Carolina Cisternas-Novoa, Frédéric A. C. Le Moigne, Anja Engel
更新时间: 2019-02-28
摘要: Particle sinking is a major form of transport for photosynthetically fixed carbon to below the euphotic zone via the biological carbon pump (BCP). Oxygen (O2) depletion may improve the efficiency of the BCP. However, the mechanisms by which O2 deficiency can enhance particulate organic matter (POM) vertical fluxes are not well understood. Here, we investigate the composition and vertical fluxes of POM in two deep basins of the Baltic Sea (GB: Gotland Basin and LD: Landsort Deep). The two basins showed different O2 regimes resulting from the intrusion of oxygen-rich water from the North Sea that ventilated the water column below 140 m in GB, but not in LD, during the time of sampling. In June 2015, we deployed surface-tethered drifting sediment traps in oxic surface waters (GB: 40 and 60 m; LD: 40 and 55 m), within the oxygen minimum zone (OMZ; GB: 110 m and LD: 110 and 180 m) and at recently oxygenated waters by the North Sea inflow in GB (180 m). The primary objective of this study was to test the hypothesis that the different O2 conditions in the water column of GB and LD affected the composition and vertical flux of sinking particles and caused differences in export efficiency between those two basins. The composition and vertical flux of sinking particles were different in GB and LD. In GB, particulate organic carbon (POC) flux was 18 % lower in the shallowest trap (40 m) than in the deepest sediment trap (at 180 m). Particulate nitrogen (PN) and Coomassie stainable particle (CSP) fluxes decreased with depth, while particulate organic phosphorus (POP), biogenic silicate (BSi), chlorophyll a (Chl a) and transparent exopolymeric particle (TEP) fluxes peaked within the core of the OMZ (110 m); this coincided with the presence of manganese oxide-like (MnOx-like) particles aggregated with organic matter. In LD, vertical fluxes of POC, PN and CSPs decreased by 28 %, 42 % and 56 %, respectively, from the surface to deep waters. POP, BSi and TEP fluxes did not decrease continuously with depth, but they were higher at 110 m. Although we observe a higher vertical flux of POP, BSi and TEPs coinciding with abundant MnOx-like particles at 110 m in both basins, the peak in the vertical flux of POM and MnOx-like particles was much higher in GB than in LD. Sinking particles were remarkably enriched in BSi, indicating that diatoms were preferentially included in sinking aggregates and/or there was an inclusion of lithogenic Si (scavenged into sinking particles) in our analysis. During this study, the POC transfer efficiency (POC flux at 180 m over 40 m) was higher in GB (115 %) than in LD (69 %), suggesting that under anoxic conditions a smaller portion of the POC exported below the euphotic zone was transferred to 180 m than under reoxygenated conditions present in GB. In addition, the vertical fluxes of MnOx-like particles were 2 orders of magnitude higher in GB than LD. Our results suggest that POM aggregates with MnOx-like particles formed after the inflow of oxygen-rich water into GB, and the formation of those MnOx–OM-rich particles may alter the composition and vertical flux of POM, potentially contributing to a higher transfer efficiency of POC in GB. This idea is consistent with observations of fresher and less degraded organic matter in deep waters of GB than LD. ]]>
29118. 题目: Contrasted ecological niches shape fungal and prokaryotic community structure in mangroves sediments
文章编号: N19022817
期刊: Environmental Microbiology
作者: P. Luis, G. Saint-Genis, L. Vallon, C. Bourgeois, M. Bruto, C. Marchand, E. Record, M. Hugoni
更新时间: 2019-02-28
摘要: Mangroves are forest ecosystems located at the interface between land and sea where sediments presented a variety of contrasted environmental conditions (i.e. oxic/anoxic, non‐sulfidic/sulfidic, organic matter content) providing an ideal ecosystem to study microbial communities with niche differentiation and distinct community structures. In this work, prokaryotic and fungal compositions were investigated during both wet and dry seasons in New Caledonian mangrove sediments, from the surface to deeper horizons under the two most common tree species in this region (Avicennia marina and Rhizophora stylosa), using high‐throughput sequencing. Our results showed that Bacteria and Archaea communities were mainly shaped by sediment depth while the fungal community was almost evenly distributed according to sediment depth, vegetation cover and season. A detailed analysis of prokaryotic and fungal phyla showed a dominance of Ascomycota over Basidiomycota whatever the compartment, while there was a clear shift in prokaryotic composition. Some prokaryotic phyla were enriched in surface layers such as Proteobacteria, Euryarchaeota while others were mostly associated with deeper layers as Chloroflexi, Bathyarchaeota, Aminicenantes. Our results highlight the importance of considering fungal and prokaryotic counterparts for a better understanding of the microbial succession involved in plant organic matter decomposition in tropical coastal sediments. This article is protected by copyright.
29119. 题目: Earthworm dispersal of plant litter across the surface of agricultural soils
文章编号: N19022816
期刊: Ecology
作者: Visa Nuutinen, Kevin R. Butt
更新时间: 2019-02-28
摘要: When we observed earthworms (Lumbricus terrestris L.; the dew worm or nightcrawler), foraging on patchily distributed plant residues in the laboratory, we noticed an exceptional interaction in their acquisition of dead organic matter. We review this original observation and then relate a subsequent finding which indicates the importance of the phenomenon in the field. This article is protected by copyright. All rights reserved.
29120. 题目: Characterizing organic carbon dynamics during biostimulation of a uranium contaminated field site
文章编号: N19022815
期刊: Biogeochemistry
作者: Martin A. Dangelmayr, Linda A. Figueroa, Kenneth H. Williams, Philip E. Long
更新时间: 2019-02-28
摘要: Uranium contamination of groundwater remains a pressing problem at many former uranium mining and milling operations, such as the Rifle, Integrated Field Research Challenge (IFRC) site. Biostimulation of the subsurface with an organic carbon source such as acetate, followed by the microbially-induced reductive precipitation of uranium has been proposed as an effective remediation strategy. While uranium bioreduction has been studied in several field experiments, the transformation and fate of injected carbon remains poorly understood. This study evaluated the impact of added organic carbon on the long-term biogeochemical attenuation of uranium in the subsurface of a former mill tailings site. Fluorescence and ultraviolet–visible absorbance analyses were used together with dissolved organic carbon (DOC) measurements to track organic carbon dynamics during and post-biostimulation of the 2011 Rifle IFRC experiment. An electron mass balance was performed on well CD01 to account for any unidentified carbon sinks. Measured DOC values increased to 1.76 mM-C during biostimulation, and to 3.18 mM-C post-biostimulation over background DOC values of 0.3–0.4 mM-C. Elevated DOC levels persisted for 90 days after acetate injections ceased. The electron mass balance revealed that assumed electron acceptors would not account for the total amount of acetate consumed. Excitation–emission matrices showed an increase in signals associated with soluble microbial products, during biostimulation, which disappeared post-biostimulation despite an increase in total DOC. Specific ultraviolet absorbance analyses, indicated that DOC present post-biostimulation is less aromatic in nature, compared to background DOC. Our results suggest that microbes convert injected acetate into a form of solid phase organic matter that may be available to sustain iron reduction post-stimulation.