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25261. 题目: Soil lead immobilization by biochars in short-term laboratory incubation studies
文章编号: N19032909
期刊: Environment International
作者: Avanthi Deshani Igalavithana, Eilhann E. Kwon, Meththika Vithanage, Jörg Rinklebe, Deok Hyun Moon, Erik Meers, Daniel C.W. Tsang, Yong Sik Ok
更新时间: 2019-03-29
摘要: Exchangeable lead (Pb) extracted by ammonium acetate from three independent incubation studies was assessed to understand the influence of feedstock, pyrolysis temperatures, and production conditions on Pb immobilization capacities of different biochars. Vegetable waste biochar, pine cone, wood bark, cocopeat, red pepper stalk, and palm kernel shell were used as feedstocks (food supply and agricultural wastes) to produce biochars at 200–650 °C with and without N₂/CO₂. Biochars were applied at 5 and 2.5% (w w⁻¹) to a Pb contaminated (i.e., 1445 mg kg⁻¹) agricultural soil collected near an old mine. Lead immobilization in biochar treated soils at the end of incubation period was normalized per gram of biochar applied. Biochar produced from vegetable waste at 500 °C showed the highest Pb immobilization (87%) and highest total exchangeable cations (13.5 cmol₍₊₎ kg⁻¹) at the end of the 45 d incubation period. However, on the basis of Pb immobilization per gram of biochar, red pepper stalk biochar produced in CO₂ at 650 °C was the best in Pb immobilization (0.09 mg kg⁻¹ g⁻¹ biochar) compared to the other biochars. The enhanced ability to immobilize Pb by biochar produced in CO₂ could be due to the presence of siloxanes (SiOSi) on biochar surface. Pearson correlation analysis revealed that alkaline pH, ash%, and N% of biochars influence in Pb immobilization and exchangeable cation availability in soil. Biochar production atmosphere considerably change its properties that influence Pb immobilization. Further studies are needed on the modification of properties and Pb immobilization by biochars produced from various feedstocks in CO₂.

25262. 题目: Copper phytoremediation potential of wild plant species growing in the mine polluted areas of Armenia
文章编号: N19032908
期刊: Environmental Pollution
作者: Karen Ghazaryan, Hasmik Movsesyan, Naira Ghazaryan, Beatriz Amanda Watts
更新时间: 2019-03-29
摘要: Nowadays the pollution of soil by trace metals from the mining industry is one of the biggest threats to ecosystems and human health. In this study, sixteen native wild plant species growing in Cu contaminated soils of mining region in Armenia were investigated to reveal their phytoremediation potential for restoration of soils in this area. During the investigation soil main characteristics affecting the Cu accumulation capability of plants were also determined. In roots (dry weight) of dominant plant species growing in Cu contaminated areas the content of copper varied between 55 mg/kg (Hypericum perforatum) and 775 mg/kg (Thymus kotschyanus), and in shoots of plants - in the range from 33 mg/kg (Teucrium orientale) to 243 mg/kg (Phleum pratense). Since the Cu accumulation capability of plants depends both on physiological peculiarities of plants and on the content of Cu_bioavailable in the soil, the studies were carried out in this direction and it was found that the high contents of organic matter and clay in the soil facilitated the decrease of the ratio Cu_bioavailable/Cu_total and as a result - the decrease of Cu accumulation capability of plants. Thymus kotschyanus, Phleum pratense, and Achillea millefolium had the highest phytostabilization potential from all studied plant species due to high bioconcentration factor of root (BCF_root) and low translocation factor (TF) values registered in these plants, and further field and laboratory experiments are planned to confirm this useful ability. The detection of phytoremediation potential of wild plant species growing in areas polluted by trace metals will enable us to use eco-friendly and cost-effective remediation methods, utterly required to clean up the soils in the mining regions of Armenia.
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25263. 题目: The spatial distribution of blue carbon in the coastal wetlands of China
文章编号: N19032907
期刊: Estuarine, Coastal and Shelf Science
作者: Weiqing Meng, Rusty A. Feagin, Beibei Hu, Mengxuan He, Hongyuan Li
更新时间: 2019-03-29
摘要: Coastal wetland losses in China are globally-relevant issues, as formerly sequestered soil organic carbon is released as CO₂ into the atmosphere. Wetland losses also reduce the primary production by plants that would otherwise bury carbon in the future. More than 50% of these ecosystems have been lost globally over the last half century, with this number approaching 58% in China. The negotiation of international accords such as the Paris Climate Agreement rely on the accurate assessment of ecosystem-held carbon quantities. Our objective was to provide the first national scale survey of coastal wetland-based carbon in China. The average soil organic carbon stock (Mg SOC ha⁻¹) across all three types of ecosystems was 236.91, with an average of 344.67 for mangroves, 175.14 for seagrass, and 134.37 for salt marshes. The SOC stock was greatest at 30–60 cm of depth in the case of mangroves, as opposed to 0–20 cm of depth for salt marshes. In terms of the carbon content of the standing aboveground and belowground biomass (Mg C ha⁻¹), mangroves contained by far the most with an average of 253.98 and 83.96, respectively. Carbon burial rates, or the annual flux of SOC into the soil column (Mg C ha⁻¹ yr⁻¹), were 2.26 ± 0.39 for mangroves, 1.38 ± 0.38 for seagrass, and 2.18 ± 0.24 for salt marshes. Through our work, we found a total of 48.12–123.95 Tg of C in China's coastal wetlands (down to 1 m of soil column depth), with an annual burial of 0.84 Tg yr⁻¹. We estimate the average annual emissions of CO₂ to be on the order of 6.83 Tg CO₂ yr⁻¹, due to ongoing and extensive wetland loss and conversion.

25264. 题目: Linking rhizosphere respiration rate of three grassland species with root nitrogen concentration
文章编号: N19032906
期刊: Geoderma
作者: Mao Tang, Daniel C. Keck, Weixin Cheng, Hui Zeng, Biao Zhu
更新时间: 2019-03-29
摘要: Rhizosphere respiration (from roots and rhizosphere microbes utilizing root-derived carbon (C)) is a significant component of soil respiration, and rhizosphere priming effect (RPE, change in soil C decomposition by the presence of living roots in the rhizosphere) is crucial for regulating soil C decomposition. However, the relationships between rhizosphere respiration and RPE and root traits (such as biomass and nitrogen (N) concentration) across plant species and growing conditions are not fully resolved. In this study, we investigated rhizosphere respiration rate and RPE of three grassland species (a grass, a forb and a legume) using a continuous isotope-labeling technique. We found a significantly positive relationship between root-mass-specific rhizosphere respiration rate and root N concentration across the three species and two types of mesocosms (small pots and large buckets), and the scaling exponents were approximately one (indicating isometric scaling). Further, soil organic matter (SOM) decomposition rate was not statistically different between the planted treatments and the unplanted control, suggesting insignificant RPE at the early flowering stage (90 days after seeding) for these three species. Likely, respiration from rhizodeposition (root inputs to soil during the 90-day labeling period) was not included in SOM decomposition by the isotope labeling method, which underestimates SOM decomposition and may partly contribute to the lack of RPE of the three species. Overall, our results show that rhizosphere respiration rate is scalable with root N concentration across different plant species and growing conditions, while RPE of these grassland species at the early flowering stage was insignificant.

25265. 题目: Differences in oxidative potential of black carbon from three combustion emission sources in China
文章编号: N19032905
期刊: Journal of Environmental Management
作者: Rong Li, Yong Han, Lu Wang, Yu Shang, Yingjun Chen
更新时间: 2019-03-29
摘要: Black carbon (BC) is mainly derived from the incomplete combustion of fossil fuels and biomass, and poses a serious threat to human health. Actual BC from extensive emission sources presents a variety of characteristics that are likely associated with different oxidative potentials (OP) and health endpoints. In the present study, BC derived from three main emission sources (residential coal combustion, biomass burning, and diesel engine exhaust) in China was subjected to physiochemical characterization and its OP was tested using dithiothreitol (DTT) assay. In order to obtain actual BC, the water-soluble part (WS) and organic extract (OE) were eluted successively from PM and the residue particle (RP) were reserved. PM from diesel vehicles had the most effective DTT consumption capacity, followed by PM from biomass and coal burning. And the OP of PM was mostly attributed to its RP part which mainly consisted of metals and BC. SEM/TEM, OC/EC, IC, and ICP-MS measurements confirmed that soluble ions and organic compounds were washed off effectively, while some metals were still retained in the RP part. Thus, the OP of BC was evaluated after adding DTPA to inhibit DTT activity caused by metals in the RP. Significant differences in OP and physiochemical characteristics of BC from the three emission sources were observed. BC from diesel exhaust exhibited the highest DTT activity (15.5 ± 12.6 pmol min⁻¹ μg⁻¹) compared to that of BC from biomass (2.5 ± 1.0 pmol min⁻¹ μg⁻¹) and coal (1.3 ± 0.5 pmol min⁻¹ μg⁻¹) burning. Diesel exhaust BC, which was emitted under the highest combustion temperature, had the smallest size. Coal consumption in China contributes to the highest amount of BC mass emission, but our result indicates that diesel exhaust BC has the greatest OP. An emission inventory based on health impacts is urgently needed to control air pollution sources in the future.
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25266. 题目: The distribution of novel bacterial laccases in alpine paleosols is directly related to soil stratigraphy
文章编号: N19032904
期刊: Science of The Total Environment
作者: Shamsudeen U. Dandare, Jonathan M. Young, Brian P. Kelleher, Christopher C.R. Allen
更新时间: 2019-03-29
摘要: Bacterial laccases are now known to be abundant in soil and to function outside of the cell facilitating the bacterial degradation of lignin. In this study we wanted to test the hypotheses that: i) Such enzymes can be identified readily in stratified paleosols using metagenomics approaches, ii) The distribution of these genes as potential ‘public good’ proteins in soil is a function of the soil environment, iii) Such laccase genes can be readily retrieved and expressed in E. coli cloning systems to demonstrate that de novo assembly processes can be used to obtain similar metagenome-derived enzyme activities. To test these hypotheses, in silico gene-targeted assembly was employed to identify genes encoding novel type B two-domain bacterial laccases from alpine soil metagenomes sequenced on an Illumina MiSeq sequencer. The genes obtained from different strata were heterologously cloned, expressed and the gene products were shown to be active against two classical laccase substrates. The use of a metagenome-driven pipeline to obtain such active biocatalysts has demonstrated the potential for gene mining to be applied systematically for the discovery of such enzymes. These data ultimately further demonstrate the application of soil pedology methods to environmental enzyme discovery. As an interdisciplinary effort, we can now establish that paleosols can serve as a useful source of novel biocatalytic enzymes for various applications. We also, for the first time, link soil stratigraphy to enzyme profiling for widespread functional gene activity in paleosols.
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25267. 题目: Synthesis of modified amorphous manganese oxide using low-cost sugars and biochars: Material characterization and metal(loid) sorption properties
文章编号: N19032903
期刊: Science of The Total Environment
作者: Petr Ouředníček, Barbora Hudcová, Lukáš Trakal, Micheal Pohořelý, Michael Komárek
更新时间: 2019-03-29
摘要: In this study, amorphous Mn oxides (AMOs) and their composites with biochar (BC) were synthesized using different sugars (glucose, sucrose, and molasses), and their sorption efficiency toward Zn(II), Cd(II), and As(V) was tested. Additionally, detailed characterization of synthesized materials using various solid-state analysis methods (e.g. XRD, FTIR-ATR, and/or SEM-EDX) was also performed. Despite glucose-based AMOs presented higher sorption efficiency for As(V), i.e., 0.73 mmol g⁻¹ (glucose) > 0.27 mmol g⁻¹ (sucrose and molasses), similar sorption efficiency toward Zn(II), i.e., 0.80 mmol g⁻¹ (glucose and molasses) > 0.66 (sucrose) and Cd(II) (0.71–0.74 mmol g⁻¹ (sucrose and molasses) > 0.36 mmol g⁻¹ (glucose), was observed for sucrose- and molasses-based AMOs under the given conditions. Next, the sorption efficiency of all AMO/BC composites was proportional to their AMO content. Finally, Mn(II) leaching from the structure of the new AMOs was negligible compared to that observed for the glucose-based AMOs, in this study as well as in other similar studies. Moreover, using molasses as reducing agent during AMO synthesis dramatically decreased the total cost of the final materials, which suggested that these new AMOs could represent interesting alternatives for standard remediation technologies. The AMOs synthesized using low-cost sugars could, therefore, be promising materials for real field applications, since the main disadvantages of using standard AMOs are mitigated. Nevertheless, the efficiency and stability of these composites under real-life conditions must be tested prior to their direct application for remediation technologies.
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25268. 题目: Effects of biochar on the earthworm (Eisenia foetida) in soil contaminated with and/or without pesticide mesotrione
文章编号: N19032902
期刊: Science of The Total Environment
作者: Qingming Zhang, Muhammad Saleem, Caixia Wang
更新时间: 2019-03-29
摘要: The plant-derived biochars act as soil conditioners, and thus may influence biological interactions in the soil environment. However, their unintended negative and positive effects on soil organisms remain largely understudied. Therefore, we investigated the effect of 0, 1, 3, and 10% of wheat straw-derived biochar amendments on earthworm (Eisenia foetida) activity in the soil contaminated with and/or without pesticide mesotrione (10 mg/kg dry soil) after 28 days of incubation. The pesticide mesotrione did not affect earthworm growth or reproduction; however, it induced oxidative stress and DNA damage. Although biochar application significantly decreased the concentration of mesotrione in earthworms, it delayed the degradation of pesticide in the soil environment. Compared to zero amendment, the amendment of 1 and 3% of biochar significantly increased (P < 0.05) the earthworm weight and reduced the toxicity effects of mesotrione on earthworms. However, the application of 10% biochar significantly decreased (P < 0.05) earthworm growth and caused DNA damage even in the absence of mesotrione. This study suggests that it is necessary to investigate the effects of different levels of biochar amendments on earthworms and other soil organisms in agricultural fields to develop a broader understanding about the use of biochar and its consequences on soil health.
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25269. 题目: Iodo-trihalomethanes formation during chlorination and chloramination of iodide-containing waters in the presence of Cu²⁺
文章编号: N19032901
期刊: Science of The Total Environment
作者: Jing Liu, Jing Wang, Jie Zhang, Yang Mu
更新时间: 2019-03-29
摘要: In this study, the impact of Cu²⁺ on the formation of iodo-trihalomethanes (I-THMs) during chlorination and chloramination of iodide-containing waters was investigated. Initially, the oxidant consumption and evolution of hypoiodous acid (HOI) were determined during disinfection in the presence of Cu²⁺ and the interaction between natural organic matter humic acid (HA) and Cu²⁺ was also analyzed. Subsequently, the formation of the I-THMs at various Cu²⁺ concentrations was evaluated for chlorination and chloramination. Moreover, in order to explore the possible underlying mechanisms, five model compounds based on the HA structure were used to investigate the I-THMs formation with and without Cu²⁺ during disinfection. The results indicated that the presence of Cu²⁺ markedly affected the conformation of the HA rather than the HOI evolution during disinfection. The concentration of the I-THMs decreased from 34.5 ± 0.8 to 20.9 ± 0.8 nM as the Cu²⁺ concentration increased from 0 to 20 μM during chlorination. In contrast, during chloramination, the total I-THMs concentration decreased from 320.7 ± 7.4 to 267.2 ± 10.7 nM as the Cu²⁺ concentration increased from 0 to 5 μM and then increased to 315.0 ± 1.7 nM when the Cu²⁺ concentration reached 20 μM. The disinfection experiments with the model compounds suggested that the impact of Cu²⁺ on the I-THMs formation largely depended on the organic structures in the HA, thus leading to different results during chlorination and chloramination.
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25270. 题目: Variations in dissolved inorganic carbon species in effluents from large-scale municipal wastewater treatment plants (Qingdao, China) and their potential impacts on coastal acidification
文章编号: N19032811
期刊: Environmental Science and Pollution Research
作者: Xiang-Yu Liu, Xu-Feng Yang, Yun-Xiao Li, Han Zang, Long-Jun Zhang
更新时间: 2019-03-28
摘要: With rapid development of global wastewater treatment plants (WWTPs), acidification and enhanced CO₂ release in receiving waters caused by high-CO₂ treated wastewater input have raised concerns. Insights into the variations in dissolved inorganic carbon (DIC) species in treated wastewater contribute to understanding the mechanisms of the acidification process. Here, we investigated three large-scale municipal WWTPs that discharged into the coast of Qingdao, China, for variations in effluent DIC species and their control mechanisms. The results showed that the effluent DIC concentrations, with a range of 2554–5718 μmol/L, significantly exceeded the concentration in seawater and mainly increased from winter to spring and decreased from summer to autumn. The effluent DIC and its δ¹³C_DIC showed a good negative correlation. The ratios of effluent DIC to total alkalinity (DIC/TAlk) ranged from 1.00 to 1.24, and the proportions of CO₂ in DIC ranged from 0.9 to 19.7%; both sets of values significantly exceeded those in seawater. The proportions of CO₃²⁻ in DIC were only ~ 0.4%. These features determined that the CO₂ concentrations in effluents fluctuated from 3 to 80 times the concentration in seawater, whereas the CO₃²⁻ concentrations were less than 1/15 of those in seawater. Organic matter degradation and nitrogen removal processes made important contributions to the high effluent CO₂ concentrations. The increase in solubility induced by decreased temperature may be the main cause for the higher effluent CO₂ concentrations during winter as well as spring months with low effluent temperatures. Correspondingly, the effluent pH values were significantly lower than the seawater pH values and showed a good negative logarithmic correlation with the DIC/TAlk values, reflecting the control of DIC species on the pH values in treated wastewater. Variations in DIC species in treated wastewater can cause changes in the affected region and the degree of the induced acidification in receiving waters.

25271. 题目: Engineered biochar composites with zeolite, silica, and nano-zerovalent iron for the efficient scavenging of chlortetracycline from aqueous solutions
文章编号: N19032810
期刊: Environmental Science and Pollution Research
作者: Munir Ahmad, Adel R. A. Usman, Muhammad Imran Rafique, Mohammad I. Al-Wabel
更新时间: 2019-03-28
摘要: Date palm waste–derived biochar (DBC) was produced through pyrolysis (600 °C) and modified with zeolite (Z-DBC), silica (S-DBC), or nano-zerovalent iron (nZVI-DBC) to design efficient sorbents. The pristine and engineered biochars were characterized by SEM, XRD, BET, TGA, CHNS-O, and FTIR to investigate the surface, structural, and mineralogical composition. The nZVI-DBC exhibited lowest pH (6.15) and highest surface area (220.92 m² g⁻¹), carbon (80.55%), nitrogen (3.78%), and hydrogen (11.09%) contents compared with other biochars. Isotherm sorption data for chlortetracycline (CTC) removal from aqueous solutions was described well by Langmuir and Redlich–Peterson isotherms showing the highest fitness (R² values in the range of 0.88–0.98 and 0.88–0.99, respectively). Langmuir predicted maximum CTC adsorption capacity was in order of nZVI-DBC (89.05 mg g⁻¹) > S-DBC (45.57 mg g⁻¹) > Z-DBC (30.42 mg g⁻¹) > DBC (28.19 mg g⁻¹). Kinetics adsorption data was best described by power function model (R² = 0.93–0.99), followed by interaparticle diffusion (R² = 0.85–0.96) model. The nZVI-DBC performed outclass by removing 98% of CTC, followed by S-DBC (68%), Z-DBC (35%), and DBC (36%). Chemisorption, H-bonding, and interaparticle diffusion were the operating mechanisms for CTC adsorption onto DBC, S-DBC, and Z-DBC, while π-π electron donor–accepter interactions and redox reactions augmented these mechanisms for highest CTC adsorption onto nZVI-DBC. Therefore, nZVI-DBC may serve as an efficient green technology for the removal of CTC from aqueous solutions and to reduce surface date palm waste pollution.

25272. 题目: Enhanced performance and mechanism of bromate removal in aqueous solution by ruthenium oxide modified biochar (RuO₂/BC)
文章编号: N19032809
期刊: Colloids and Surfaces A: Physicochemical and Engineering Aspects
作者: Chuanglei Fan, Nan Chen, Chuanping Feng, Yuqing Yang, Jibo Qin, Miao Li, Yu Gao
更新时间: 2019-03-28
摘要: The removal of pollutants from water using agricultural waste-based biomaterials is gaining extensive attention. In this study, biochar loading ruthenium oxide (RuO₂/BC), a novel composite for bromate removal from drinking water, has been prepared by the impregnation method. Based on the single-factor design, a Box-Behnken design (BBD) of the response surface methodology (RSM) was applied to access the mutual interactions and effects between the three factors and optimized preparation conditions (activation time is 3.9 h, activation temperature is 612.2 °C and mass ratio of biochar to RuCl₃ is 38.9: 1). The effects of initial solution pH, RuO₂/BC dosage and initial bromate concentration on bromate removal by RuO₂/BC were investigated. The Field Emission Scanning Electronic Microscopy (FESEM), Brunauer-Emmett-Teller (BET), Energy Dispersive X-Ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Zeta potential were used to characterize the properties of prepared composite. Results showed that bromate removal by RuO₂/BC was highly pH dependent and the bromate reduction kinetics followed the pseudo-first-order kinetic model. The detailed mechanism including adsorption and reduction of bromate by the synergistic effect of RuO₂ and biochar (C = C, C = O and -OH) was demonstrated. These results proposed a new approach for the remediation of bromate contaminated water.
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25273. 题目: The role of tephra in enhancing organic carbon preservation in marine sediments
文章编号: N19032808
期刊: Earth-Science Reviews
作者: Jack Longman, Martin R. Palmer, Thomas M. Gernon, Hayley R. Manners
更新时间: 2019-03-28
摘要: Preservation of organic carbon (C_org) in marine sediments plays a major role in defining ocean-atmosphere CO₂ levels, Earth climate, and the generation of hydrocarbons. Important controls over sedimentary C_org preservation include; biological productivity, C_org isolation from oxidants (mainly dissolved O₂) in the overlying water column and sediments, and C_org – mineral association in sediments. Deposition of the products of explosive volcanism (tephra) in the oceans directly enhances C_org burial through all these mechanisms, and indirectly through enhanced formation of authigenic carbonate (C_auth) derived from sedimentary C_org. In the modern oceans, it is suggested that tephra deposition may account for 5–10% of the C_org burial flux and 10–40% of the C_auth burial flux. However, during certain periods in Earth's history, extensive explosive volcanism may have led to enhanced C_auth precipitation on a sufficiently large scale to influence the global ocean-atmosphere carbon cycle. Changes in tephra-related C_org preservation may also have played a role in increasing C_org preservation rates in local marine basins, at the oxic-anoxic boundary and enhanced the generation of hydrocarbon deposits in these settings.

25274. 题目: Effects of dissolved organic matter from different sources on Microcystis aeruginosa growth and physiological characteristics
文章编号: N19032807
期刊: Ecotoxicology and Environmental Safety
作者: Miaomiao Zhao, Dong Qu, Wendi Shen, Ming Li
更新时间: 2019-03-28
摘要: The roles dissolved organic matter play when managing watersheds and controlling cyanobacteria blooms have been overlooked. We assessed the effects of dissolved organic matter extracted from biochar, paddy soil, pectin, and rice husks, at carbon concentrations of 0, 1, 3, 5, and 10 mg L⁻¹ on Microcystis aeruginosa growth, photosynthesis, and physiological characteristics. The dissolved organic matter derived from paddy soil and rice husks increased M. aeruginosa growth by promoting photosynthesis. Biochar at low carbon concentrations (1, 3, and 5 mg L⁻¹) also improved M. aeruginosa growth by increasing the maximum photosynthesis II quantum yield. However, biochar at a high concentration decreased the protein and RNA concentrations in M. aeruginosa and therefore inhibited the increase in M. aeruginosa biomass. Pectin did not affect M. aeruginosa photosynthesis, protein concentration, RNA concentration, or growth. The results suggested that M. aeruginosa growth was improved by the amino acids tryptophan and tyrosine, decreased by abundant humic-acid-like substances, and unaffected by polysaccharides.

25275. 题目: Antecedent precipitation influences the bacterial processing of terrestrial dissolved organic matter in a North Carolina estuary
文章编号: N19032806
期刊: Estuarine, Coastal and Shelf Science
作者: C.L. Osburn, J.N. Atar, T.J. Boyd, M.T. Montgomery
更新时间: 2019-03-28
摘要: Estuaries and coastal waters ultimately receive the terrestrial dissolved organic matter (DOM) exported from coastal watersheds, more directly during extreme precipitation events. Recent work suggests DOM's degradation in coastal waters varies with its quality, which also might vary as a function of precipitation, activating contributions from different sources within a watershed. The aim of this study was to determine the extent to which microbial degradation of terrestrial DOM in the Newport River Estuary, eastern North Carolina, was influenced by precipitation events occurring within the preceding seven days from sampling. We hypothesized that DOM stored in forested wetlands (e.g., pocosins and Cypress swamps) that become connected to the main channel of the Newport River during high precipitation events was more labile than DOM flowing into the estuary under low precipitation events. DOM quality was assessed with optical and stable C isotope (δ¹³C) measurements, while DOM lability was assessed by measurements of bacterial production (BP) and mineralization of ¹⁴C-labeled phenanthrene (Pmin), a polyaromatic tracer compound. Aromatic content of DOM, assessed by specific ultraviolet absorbance at 254 nm (SUVA₂₅₄) was highest in the river with values well over 5.0 L mg C⁻¹ m⁻¹, and decreased with salinity. Antecedent precipitation (AP) of at least 100 mm in the seven days prior to sampling resulted in dissolved organic carbon (DOC) concentrations >20 mg L⁻¹, at salinities <10. Similarly, fluorescence humification index (HIX) values were highest in the estuary after the highest AP. Generally depleted δ¹³C-DOC values (−26 to −28‰) in the estuary up to a salinity of 30 indicated a substantial source of DOM likely originating from the forested swamps and tidal wetlands fringing the estuary. BP exhibited wide variability yet declined with salinity, while median values after higher AP (40 μg C L⁻¹ d⁻¹) were double that under lower AP. By contrast, aromatic mineralization (Pmin) rates increased as both DOC and CDOM concentrations, and SUVA₂₅₄ and HIX values, declined with salinity. However, Pmin rates were highest after the highest AP for the three events sampled. Results indicate that flooding of coastal wetlands mobilizes a large pool of labile DOM which have a large impact on the carbon cycle in estuaries. By altering the quality, as well as quantity of terrestrial organic matter inputs to estuarine systems, extreme events may also affect utilization of aromatic organics by estuarine microbial assemblages, an intriguing research question worthy of further study.
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25276. 题目: The importance of macro- and micro-nutrients over climate for leaf litter decomposition and nutrient release in Patagonian temperate forests
文章编号: N19032805
期刊: Forest Ecology and Management
作者: Lucía Vivanco, Amy T. Austin
更新时间: 2019-03-28
摘要: Temperate forests play an important role in the global carbon (C) cycle. Extensive research on litter decomposition in temperate forests in the Northern Hemisphere have greatly contributed to our conceptual framework of the controls of C cycling, where climate and litter lignin/N ratio have played a dominant role. However, there is a noteworthy lack of basic information on southern temperate forests, which have unique characteristics demonstrated by differences in ecosystem functioning and their response to human impact when compared to their northern counterparts. Patagonian forests are the most extensive temperate forests in South America and offer the opportunity to evaluate the importance of climate and litter traits in old growth forests with relatively little human impact. We compared litter decomposition of 10 dominant native tree species and of two non-native tree species (used as common substrates) in two native forests with varying precipitation and tree species composition: a Nothofagus mesic mixed forest (2200 mm MAP) and an Austrocedrus open dry forest (1350 mm MAP). In addition to rainfall, these forest types differed markedly in tree species composition and leaf litter traits that resulted in 1.5 times larger soil carbon and nitrogen pool in Austrocedrus open dry forest and 5 times higher soil inorganic nitrogen than in Nothofagus mesic forests. Nevertheless, decomposition of common litter substrates was similar between both forest types. In contrast, native tree species litter showed up to 10-fold differences in their decomposition rates in a common forest site. Litter mass loss and nitrogen dynamics were strongly associated with magnesium (Mg) and manganese (Mn) content of the litter, respectively. In contrast to dominant control of climate and litter lignin/N, our results demonstrate that native tree species traits may be more important than climate and its effects on plant-soil interactions in Patagonian forests. Our study also highlights the importance of macro- and micro-nutrients (Mg and Mn) in litter that are generally overlooked as determinants of litter decomposition in terrestrial ecosystems. These native Patagonian forests show distinctive controls of litter decomposition compared with other temperate forests of the world. They also highlight the importance of considering how management that affects tree species identity and composition may have far-reaching effects on ecosystem functioning that are currently not being considered.

25277. 题目: Paired bulk organic and individual amino acid δ¹⁵N analyses of bivalve shell periostracum: A paleoceanographic proxy for water source variability and nitrogen cycling processes
文章编号: N19032804
期刊: Geochimica et Cosmochimica Acta
作者: Nina M. Whitney, Beverly J. Johnson, Philip T. Dostie, Katherine Luzier, Alan D. Wanamaker
更新时间: 2019-03-28
摘要: Developing high resolution, well-dated marine proxies of environmental, climatic, and oceanographic conditions is critical in order to advance our understanding of the ocean’s role in the global climate system. While some work has investigated bulk and compound specific stable nitrogen isotopes (δ¹⁵N) in bivalve shells as proxies for environmental variability, the small concentrations of nitrogen found in the organic matrix of the shell calcium carbonate (CaCO₃) makes developing high resolution records challenging. This study investigates the potential of using the bulk and amino acid δ¹⁵N of bivalve periostracum, the protein layer on the outside of the shell, as a proxy archive of nitrogen cycling processes and water source variability.Bulk δ¹⁵N values were measured on the periostracum, aragonitic CaCO₃, and adductor muscle of Arctica islandica shells collected in the Gulf of Maine. Increased variability of isotopic values across growth lines compared to along growth lines support mechanistic reasoning based on growth processes that periostracum is recording changes in δ¹⁵N over the course of the clam’s lifetime (up to 500 years). In addition, the statistically significant relationship between periostracum δ¹⁵N and contemporaneous carbonate δ¹⁵N of the same shell (r= 0.82, p<.0001, n=40) suggests that periostracum preserves a similar δ¹⁵N signal to that preserved in the carbonate. This finding, coupled with the fact that source amino acid δ¹⁵N values of periostracum are similar to that of the adductor muscle and the particulate organic matter (POM) consumed by the clam, suggests that periostracum bulk δ¹⁵N reflect the δ¹⁵N of the clam’s food source. The isotopic offsets between periostracum, carbonate, and adductor muscle δ¹⁵N values are primarily caused by differences in amino acid composition of the different tissue types, as evidenced by isotope mass balance calculations, although may also be related to differences in δ¹⁵N values of the individual amino acids of the different tissue types, especially the trophic amino acids.Compound specific δ¹⁵N analyses of the periostracum of A. islandica shells were used to determine that the calculated trophic position of the clams in this study (1.4±0.4) did not change significantly between 1783 and 1997. Phenylalanine δ¹⁵N values over the last 70 years show similar trends to that of the bulk record, suggesting that changes in bulk δ¹⁵N of that time period are related to changes in baseline δ¹⁵N. Periostracum δ¹⁵N values from shells collected in the western Gulf of Maine have decreased by ∼1‰ since the mid-1920s. This trend (-0.008‰/year) is not statistically different from the trend of previously published δ¹⁵N values of deep-sea corals from the entrance to the Gulf of Maine over the same time period. This coral record has been shown to indicate a shift in water mass source to the region and therefore the similarity between the two records suggest that changes in periostracum δ¹⁵N values are reflecting broader North Atlantic hydrographic changes. Our study introduces a new, high-resolution and absolutely dated paleoceanographic proxy of baseline δ¹⁵N, presenting the opportunity for future reconstructions of aspects of nitrogen cycling and water source changes in the global oceans.

25278. 题目: Early Silurian δ¹³C_org excursions in the foreland basin of Baltica, both familiar and surprising
文章编号: N19032803
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Emma U. Hammarlund, David K. Loydell, Arne T. Nielsen, Niels H. Schovsbo
更新时间: 2019-03-28
摘要: The Sommerodde-1 core from Bornholm, Denmark, provides a nearly continuous sedimentary archive from the Upper Ordovician through to the Wenlock Series (lower Silurian), as constrained by graptolite biostratigraphy. The cored mudstones represent a deep marine depositional setting in the foreland basin fringing Baltica and we present high-resolution data on the isotopic composition of the section's organic carbon (δ¹³C_org). This chemostratigraphical record is correlated with previously recognized δ¹³C excursions in the Upper Ordovician–lower Silurian, including the Hirnantian positive isotope carbon excursion (HICE), the early Aeronian positive carbon isotope excursion (EACIE), and the early Sheinwoodian positive carbon isotope excursion (ESCIE). A new positive excursion of high magnitude (~4‰) is discovered in the Telychian Oktavites spiralis Biozone (lower Silurian) and we name it the Sommerodde Carbon Isotope Excursion (SOCIE). The SOCIE appears discernible in δ¹³C_carb data from Latvian and Estonian cores but it is not yet widely recognized. However, the magnitude of the excursion within the deep, marine, depositional setting, represented by the Sommerodde-1 core, suggests that the SOCIE reflects a significant event. In addition, the chemostratigraphical record of the Sommerodde-1 core reveals the negative excursion at the transition from the Aeronian to Telychian stages (the ‘Rumba low’), and suggests that the commencement of the EACIE at the base of the Demirastrites triangulatus Biozone potentially is a useful chemostratigraphical marker for the base of the Aeronian Stage.

25279. 题目: Patterns and drivers of meiofaunal assemblages in the canyons Polcevera and Bisagno of the Ligurian Sea (NW Mediterranean Sea)
文章编号: N19032802
期刊: Progress in Oceanography
作者: L. Carugati, M. Lo Martire, R. Danovaro
更新时间: 2019-03-28
摘要: Meiofaunal abundance, assemblage structure and richness of higher taxa were investigated for the first time in two submarine canyons (Polcevera and Bisagno) of the Ligurian Sea and on the adjacent open slope, in relation with the quantity and quality of sedimentary organic matter and other environmental variables, including grain size. Meiofaunal abundance and richness of higher taxa decreased with increasing water depth (from ca. 200 down to ca. 2000-m depth) in the open slope and Polcevera canyon, whereas the highest values were observed at 500 m depth in the Bisagno canyon. The comparison between canyons and the adjacent open slope, showed the lack of significant differences in meiofaunal abundance, at the same depth except for samples collected at 200 and 2000-m depth. Overall the biodiversity was higher in canyons than in the open slope. Phytopigments, utilised as a proxy of the input of primary organic matter, were up to 3 times higher in canyon than in slope sediments and, along with grain size, explained a large portion of the variability in all meiofaunal variables. Canyon and slope showed a high beta diversity (83%), mostly due to the presence of a high portion of rare taxa in the canyons. Some taxa, such as Cladocera, Cumacea, Gastrotricha, Nemertina were exclusively encountered in canyon sediments, whereas Tardigrada were encountered only in the adjacent slope. Results reported here indicated that, differences in meiofaunal assemblages between canyons and slopes are primarily driven by quantity and quality of the available food resources and by the presence of specific topographic features.

25280. 题目: Food web structure and trophodynamics of deep-sea plankton from the Bari Canyon and adjacent slope (Southern Adriatic, central Mediterranean Sea)
文章编号: N19032801
期刊: Progress in Oceanography
作者: I. Conese, E. Fanelli, S. Miserocchi, L. Langone
更新时间: 2019-03-28
摘要: Zooplankton represent a key component of deep-sea ecosystems, linking Particulate Organic Matter (POM) to higher trophic levels through both vertical migrations from the photic zone and being prey of several megafaunal species, including demersal and benthopelagic organisms. Nevertheless, this key group in deep-sea ecosystems is far to be well known, especially concerning trophic aspects. In this study, we aimed to depict the trophic web structure of deep-sea zooplankton collected in sediment traps from the Southern Adriatic, central Mediterranean Sea, and adjacent slope from 600 to 1200 m, and its trophodynamics. To achieve these objectives, we considered a long time-series set of samples, from March 2010 to October 2012 and we used stable isotope analysis of nitrogen and carbon. The area is characterised by cascading events of dense shelf waters, and the possible influence of this periodic phenomenon on seasonal changes in the isotopic composition of deep-sea zooplanktonic species was also analysed. Our results evidenced a complex structure for the deep-sea zooplankton food web with taxa organized in three trophic levels from POM feeders to ultra-specialized carnivores. Temporal changes in the isotopic signatures of deep-sea zooplankton species were observed, although the influence of cascading events was not so clear. The high swimming capability of deep-sea zooplankton and their ability to perform vertical migrations may be the cause of such unclear relationship, with species more relying on vertical fluxes from surface primary production than on lateral advective transport of organic particles.