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22841. 题目: Characterization of Organic Matter in Water from Oil and Gas Wells Hydraulically Fractured with Recycled Water
文章编号: N19042503
期刊: Journal of Hazardous Materials
作者: Seongyun Kim, Pinar Omur-Ozbek, Ken Carlson
更新时间: 2019-04-25
摘要: Liquid chromatography quadrupole time-of-flight mass spectrometry was performed to understand how frac fluid with recycled water (RWA) and frac fluid with fresh water (FWA) compare when subjected to downhole temperature and oxidation conditions. Ethylene oxide and propylated glycol functional units were quantified from both RWA and FWA. Qualitative analysis was performed using Agilent qualitative analysis software B.06.00 based on the exact mass of the chemical compound. Acetone, aldol, alkoxylated phenol formaldehyde resin, diethylbenzene, dipropylene glycol, d-Limonene, ether salt, ethylbenzene, n-dodecyl-2-pyrrolidone, dodecylbenzenesulfonate isopropanolamine, polyethylene glycol, and triethylene glycol were detected in FWA and RWA samples. In the van Krevelen diagram, FWA and RWA show a low degree of oxidation and highly saturated organic compounds. Kendrick mass defect (KMD) analysis was applied using ethylene oxide and propylated glycol units. KMD analysis based on ethylene oxide was scattered between 0 and 0.1, while some KMD analyses based on the propylated glycol are close to 1. FWA had an average carbon number of 32.3 and double bond equivalent (DBE) of 9.8 while RWA had average carbon number of 31.5 and DBE of 9.5. RWA contained predominantly C₂₁-C₄₀ compounds, while FWA had a higher concentration in the over C₄₁ range.
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22842. 题目: Soil solid-phase organic matter-mediated microbial reduction of iron minerals increases with land use change sequence from fallow to paddy fields
文章编号: N19042502
期刊: Science of The Total Environment
作者: Wenbing Tan, Ying Yuan, Xinyu Zhao, Qiuling Dang, Ye Yuan, Renfei Li, Dongyu Cui, Beidou Xi
更新时间: 2019-04-25
摘要: The microbial reduction of Fe(III) minerals (MRF) is an important process in paddy soil because it can affect the biogeochemical cycles of many major and trace elements. Natural organic matter (NOM) that mainly exists in the form of solid phase in soil can mediate MRF through electron shuttling functionality. However, whether a link exists between solid-phase NOM-mediated MRF in soil and the age of paddy field since the reclamation on fallow is unclear. Here, we use microbial reduction method to assess the solid-phase NOM-mediated MRF of paddy soils with different reclamation ages. The results show that solid-phase NOM-mediated MRF exhibits a positive response to land use change sequence from fallow to paddy field, indicating that the long-term natural development of paddy field favors the electron shuttling of NOM between cells and Fe(III) minerals. This increase in the electron shuttling of NOM is not due to the increase in the redox functional groups of NOM, but may be attributed to the formation of NOM-mineral complex through the synergistic increases in NOM content and transformation of soil texture from clay loam to loam. The decrease in the redox potential of Fe(III) minerals in soil caused by decreased pH and the increase in Fe content in the organic matter-complexed form may also partly facilitate electron transfer from NOM to Fe(III) minerals. Our work is useful in predicting the role of soil solid-phase NOM in mediating MRF in the context of long-term reclamation of paddy field and provides guidance for the environmental management of paddy fields.
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22843. 题目: An improved method to identify osmium-stained organic matter within soil aggregate structure by electron microscopy and synchrotron X-ray micro-computed tomography
文章编号: N19042501
期刊: Soil and Tillage Research
作者: Miwa Arai, Go-Ichiro Uramoto, Maki Asano, Katsuyuki Uematsu, Kentaro Uesugi, Akihisa Takeuchi, Yuki Morono, Rota Wagai
更新时间: 2019-04-25
摘要: Organic matter (OM) in surface soil is largely present within porous mineral-dominant clusters called aggregates. Recent studies have shown the localization of OM within large macroaggregate structure based on synchrotron X-ray micro-computed tomography (μCT) coupled with a vapor-phase, osmium (Os)-staining pretreatment. Here we developed a new approach to identify OM locations within submillimeter-sized aggregates at higher spatial resolution and assessed its applicability using a well-characterized surface volcanic soil, an allophanic Andisol, under no-tillage with leaf compost addition. Water-stable aggregates (500–800 μm in diameter) were embedded in agarose, chemically fixed, and repeatedly stained by osmium tetroxide and thiocarbohydrazide, followed by gradual dehydration with ethanol and resin fixation. Scanning electron microscopy and μCT observation showed no signs of physical alteration during sample preparation. Energy-dispersive X-ray spectroscopy analysis of the microtome-cut surface of the aggregate identified plant detritus highly enriched in Os and much smaller amorphous OM (<10 μm) that were high in Fe, Al, and Si as well as Os. Synchrotron μCT imaging by photon energies above and below Os L₃ X-ray absorption edge (10.87 keV) and subsequent image calculation showed the distribution of Os-stained voxels down to micrometer scale. The improved resolution compared to previous studies was partly attributable to liquid-state staining and thiocarbohydrazide bridging. Other advantages and some cautions of the proposed method were discussed.

22844. 题目: Co-transport behavior of nano-ZnO particles in the presence of metal-nanoparticles through saturated porous media
文章编号: N19042409
期刊: Journal of Environmental Chemical Engineering
作者: Dibyanshu Trishikhi Raychoudhury
更新时间: 2019-04-24
摘要: The objective of this study is to evaluate the co-transport behavior of nZnO (193.0 nm) along with other metal-based ENPs [i.e., nTiO2 (198.6 nm), nAg (167.9 nm), and nFexOy (178.5 nm)] through saturated porous media in the presence and absence of humic acid (HA) under varying pH (8, 6.5 and 5). To achieve this objective a series of column experiments are performed where the nZnO particles are injected in the porous media in the presence of other metal ENPs. After each column experiment, the column was sectioned, and the retained mass of nZnO and the porosity along the length of the column were measured. The size and surface charge of ENPs were also assessed. The study indicates that negligible amount of nZnO get transported in the absence of HA whether injected as a single entity or along with other ENPs. However, in the presence of HA and at pH 8, significant amounts (C/C0 = 0.57 to 0.68) of nZnO get transported. The surface charge of nZnO or mix-ENPs is positive or close to neutral. While in the presence of HA, surface charge of nZnO or mix-ENPs becomes highly negative (-40.6 ± 0.9 mV), which probably resulted in unfavorable condition for particle deposition in the presence of HA. Presence of nAg and nTiO2 does not influence the transport efficiency of nZnO. However, in the presence of nFexOy and under HA medium a decrease in the eluted concentration of nZnO is observed. With a decrease in pH (within a range of 6.5 to 5), co-transport efficiency of nZnO particles (α = 0.38-1.00, C/C0 = 0.03-0.0) has reduced drastically even when suspended in HA medium. This is probably controlled by surface charge of ENPs. The study also indicates that the hyper-exponential retention of ENPs has insignificant implication on the alteration of porosity of the media. Overall it could be stated that the presence of HA and the solution pH are mainly controlling the transport behavior of nZnO within the experimental condition adopted in this study.

22845. 题目: Structural characteristics of humic substances in buried ancient paddy soils as revealed by 13C NMR spectroscopy
文章编号: N19042408
期刊: Environmental Geochemistry and Health
作者: Pei Liu, Weijun Zhou, Haojie Cui, Jie Tan, Sheng Cao
更新时间: 2019-04-24
摘要: The study of organic matter in ancient paddy soils is helpful for understanding the influence of human activities on soil carbon sequestration and global climate change. However, little information on the spatial distribution and structural characteristics of the humic substances (HS) in ancient paddy soils is available. The spatial distributions of humic acids (HAs) and fulvic acids (FAs) in ancient paddy soils and modern cultivated paddy soils at the Shanlonggang site on the Liyang Plain were investigated, and the associated structures were characterized by using 13C nuclear magnetic resonance (NMR). The 13C NMR spectra revealed the following carbon types in HAs and FAs in both types of paddy soil in order of decreasing abundance: O-alkyl carbon (ranging from 39.7 to 51.8% and from 42.6 to 50.9%, respectively) ≥ alkyl carbon (ranging from 16.8 to 23.5% and from 15.7 to 22.4%, respectively) ≈ carboxyl carbon (ranging from 13.3 to 19.3% and from 16.9 to 22.0%, respectively) > aromatic carbon (ranging from 12.8 to 23.5% and from 10.0 to 17.2%, respectively). Moreover, the degree of aromaticity of HA was higher than that of FA in both soil samples. The humic constituents of the buried ancient paddy soils were less aromatic and oxidized than those of the modern cultivated paddy soils. The organic carbon in the ancient paddy soils was also less aromatic and oxidized than that in the modern cultivated paddy soils, suggesting that the structures of the HS in the ancient paddy soils were relatively simple. The results of this study provide new insights into the effect of secondary paddy soil formation on the spatial distribution, structural characteristics, and stability mechanisms of the HS in ancient paddy soils.

22846. 题目: Low-Molecular-Weight Organic Acid Complexation Affects Antimony(III) Adsorption by Granular Ferric Hydroxide
文章编号: N19042407
期刊: Environmental Science & Technology
作者: Xiaochen Li, Tatiana Reich, Michael Kersten, Chuanyong Jing
更新时间: 2019-04-24
摘要: Antimony(III) mobility in natural aquatic environments is generally enhanced by dissolved organic matter. Tartaric acid is often used to form complexes with and stabilize dissolved Sb(III) in adsorption studies. However, competition between such low-molecular-weight organic acid complexation and adsorption of Sb(III) has received little attention, which prompted us to measure Sb(III) adsorption by iron oxyhydroxide adsorbents commonly used in water treatment plants. Sb K-edge X-ray absorption fine structure (EXAFS) spectra gave Sb–O and Sb–Fe distances and coordinations compatible with a bidentate binuclear inner-sphere complex with trigonal Sb(O,OH)₃ polyhedra sharing corners with Fe(O,OH)₆ octahedra and a bidentate mononuclear inner-sphere complex but with Sb(O,OH)₄ tetrahedra at alkaline pH. Experimental batch titration data were fitted using the charge-distribution multisite surface complexation (CD-MUSIC) model, constrained by the EXAFS molecular level information and taking competitive effects by the organic ligand into consideration. The proportion adsorbed at acid to neutral pH decreased as the Sb(III) concentration increased. The CD-MUSIC adsorption model indicates that this was solely caused by strong competition from tartrate complexation in solution, which leads to adsorption constants higher than those derived without taking this competition into account. The adsorption model results allow for calculating a pe–pH predominance diagram using the USGS PhreePlot code. The study provides consistent surface complexation stability constants, allowing the new database to be used also to reliably model adsorption of toxic oxyanions in anoxic aqueous environments: for example, to accurately simulate competition between Sb(III) and As(III).
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22847. 题目: Sunlight-Mediated Lead and Chromium Release from Commercial Lead Chromate Pigments in Aqueous Phase
文章编号: N19042406
期刊: Environmental Science & Technology
作者: Han Gao, Peiyun Wei, Huiting Liu, Mingce Long, Heyun Fu, Xiaolei Qu
更新时间: 2019-04-24
摘要: Lead chromate pigments are included in a group of the most widely used pigments, which account for 3% of worldwide lead consumption. This study reports the photoactivity of commercial lead chromate pigment (i.e., chrome yellow) under simulated sunlight. It underwent photodissolution in the presence of organic acid and dissolved organic matter in the aqueous phase, releasing Pb(II) and Cr(III). Pb(II) was released more readily than Cr(III) which mainly formed hydroxides and oxides. The photodissolution can be activated by light with a wavelength <514 nm. The reaction is mediated by the reduction of Cr(VI) in the pigment by self-generated electrons. The kinetics were mainly affected by the electron-hole separation efficiency which can be enhanced by electron donors. The reaction rate decreases with increasing solution pH as the photodissolution process consumes protons. The photodissolution of the chrome yellow pigment was further confirmed in a river water sample under natural sunlight, with 11.28% of lead and 2.56% of chromium released in 7 h. This study highlights the importance of considering photochemical processes in risk assessments and regulations of commercial semiconductor pigments, which are currently based on their solubility.
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22848. 题目: Enhanced Permanganate Oxidation of Sulfamethoxazole and Removal of Dissolved Organics with Biochar: Formation of Highly Oxidative Manganese Intermediate Species and in Situ Activation of Biochar
文章编号: N19042405
期刊: Environmental Science & Technology
作者: Shi-Qi Tian, Lu Wang, Yu-Lei Liu, Tao Yang, Zhuang-Song Huang, Xian-Shi Wang, Hai-Yang He, Jin Jiang, Jun Ma
更新时间: 2019-04-24
摘要: Sulfamethoxazole (SMX) is a broad-spectrum antibiotic and was largely used in breeding industry. The reaction rate of SMX with KMnO₄ is slow, and the adsorption efficiency of biochar for SMX was inferior (less than 11% in 30 min). By adding biochar powder into SMX solution with the addition of permanganate, the oxidation ratio of SMX surged to 97% in 30 min, and over 58% of the total organic carbon (TOC) was simultaneously removed. KMnO₄ interacted with biochar and resulted in the formation of highly oxidative intermediate manganese species, which transformed SMX into hydrolysis products, oxygen-transfer products, and self-coupling products. Brunauer–Emmett–Teller (BET) analysis showed that surface area, total pore volume, and micropore volume of biochar increased by 32.1%, 36.4%, and 80.6%, respectively, after reaction process. This in situ activation of biochar with KMnO₄ enhanced its adsorption capacity and led to great improvement of TOC removal. Besides KMnO₄ oxidation, biochar also enhanced TOC removal in Mn(III) oxidation (KMnO₄+ bisulfite) and ozonization of SMX. Considering that KMnO₄ could react with biochar and result in the formation of intermediate manganese species, while biochar can be simultaneously activated and exhibit high capacity for organic adsorption, the combination of biochar with the chemical/advanced oxidation could be a promising process for the removal of environmental pollutants.
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22849. 题目: Role of tidal wetland stability in lateral fluxes of particulate organic matter and carbon
文章编号: N19042404
期刊: Journal of Geophysical Research: Biogeosciences
作者: Neil K. Ganju, Zafer Defne, Tracy Elsey‐Quirk, Julia M. Moriarty
更新时间: 2019-04-24
摘要: Tidal wetland fluxes of particulate organic matter and carbon (POM, POC) are important terms in global budgets, but remain poorly constrained. Given the link between sediment fluxes and wetland stability, POM and POC fluxes should also be related to stability. We measured POM and POC fluxes in eight microtidal salt marsh channels, with net POM fluxes ranging between ‐121±33 (export) and +102±28 (import) g OM m^‐2 y^‐1 and net POC fluxes ranging between ‐52±14 and +43±12 g C m^‐2 y^‐1. A regression employing two measures of stability, the unvegetated‐vegetated marsh ratio (UVVR) and elevation, explained >95% of the variation in net fluxes. The regression indicates that marshes with lower elevation and UVVR import POM and POC while higher elevation marshes with high UVVR export POM and POC. We applied these relationships to marsh units within Barnegat Bay, New Jersey, USA, finding a net POM import of +2,355±1,570 Mg OM y^‐1 (+15±10 g OM m^‐2 y^‐1) and a net POC import of +1,263±632 Mg C y^‐1 (+8±4 g C m^‐2 y^‐1). The magnitude of this import was similar to an estimate of POM and POC export due to edge erosion (‐2,535 Mg OM y^‐1 and ‐1,291 Mg C y^‐1), suggesting that this system may be neutral from a POM and POC perspective. In terms of a net budget, a disintegrating wetland should release organic material, while a stable wetland should trap material. This study quantifies that concept, and demonstrates a linkage between POM/POC flux and geomorphic stability.

22850. 题目: Large fine‐scale spatiotemporal variations of CH4 diffusive fluxes from shrimp aquaculture ponds affected by organic matter supply and aeration in Southeast China
文章编号: N19042403
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ping Yang, Yan Zhang, Hong Yang, Yifei Zhang, Jin Xu, Lishan Tan, Chuan Tong, Derrick Y.F. Lai
更新时间: 2019-04-24
摘要: Mariculture shrimp ponds are important CH₄ sources to the atmosphere. However, the spatiotemporal variations of CH₄ concentration and flux at fine spatial scales in mariculture ponds are poorly known, particularly in China, world largest aquaculture producer. In this study, the plot‐scale spatiotemporal variations of water CH₄ concentration and flux, both within and among ponds, were researched in shrimp ponds in Shanyutan wetland, Min River Estuary, Southeast China. The average water CH₄ concentration and diffusion flux across the water‐air interface in the shrimp ponds over the shrimp aquaculture period varied from 2.29 ± 0.29 to 50.48 ± 20.91 μM and from 0.09 ± 0.01 to 2.32 ± 0.95 mmol m^‐2 h^‐1, respectively. The CH₄ emissions from the estuarine ponds varied greatly in seasonal dynamics, with peaks in August and September, which was similar to the trend of water temperature and dissolved oxygen (DO) concentrations. There was no remarkable difference in CH₄ concentration and flux between shrimp ponds, but significantly spatiotemporal differences in CH₄ concentration and flux within the ponds. Significantly higher emissions occurred in the feeding zone, accounting for approximately 60% of total CH₄ emission flux, while much lower CH₄ emissions appeared in aeration zone, contributing 14% to total flux. This study suggests the importance of considering spatiotemporal variation in the whole‐pond estimates of CH₄ concentration and flux. In light of such high spatial variation within ponds, improving aeration and feed utilization efficiency would help to mitigate CH₄ emissions from mariculture ponds.

22851. 题目: Effect of iron and manganese on ammonium removal from micro-polluted source water by immobilized HITLi7^T at 2 °C
文章编号: N19042402
期刊: Bioresource Technology
作者: Zejia Zheng, Weiguang Li, Duoying Zhang, Wen Qin, Yi Zhao, Longyi Lv
更新时间: 2019-04-24
摘要: In this study, trace metals (Fe & Mn) were applied to enhance NH₄⁺-N removal in source water at 2 °C, and 22.7% of initial 2.20 mg/L NH₄⁺-N was removed by pre-treating granular activated carbon (GAC) with Fe & Mn before immobilizing Acinetobacter harbinensis HITLi7^T to form biological activated carbon (BAC). Biomass and dehydrogenase activity (DHA) on this modified BAC were 2.80 × 10⁸ CFU/g-DW C and 0.50 mg/L/g-DW C, respectively, both the highest. Additionally, 4.76 times more biomass and 9.76 times higher DHA of HITLi7^T were observed in the cultivation with Fe & Mn dosing. Extracellular polymeric substances (EPS) measurements found Fe & Mn dosing could increase total EPS amount (44.3% higher) and polysaccharide (PS) ratio (1.50% higher) secreted by HITLi7^T. According to the results of 3D-excitation-emission matrix (3D-EEM) fluorescence spectra and infrared spectra (FTIR) analysis, Fe and Mn promoted the secretion of tryptophan-like substances and changed functional groups COH, COC, CO and COOH, which are associated with protein and PS.
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22852. 题目: Carbon dioxide as a carrier gas and biomass addition decrease the total and bioavailable polycyclic aromatic hydrocarbons in biochar produced from sewage sludge
文章编号: N19042401
期刊: Chemosphere
作者: Magdalena Kończak, Yanzheng Gao, Patryk Oleszczuk
更新时间: 2019-04-24
摘要: Organic-solvent extractable (C_tot) and freely dissolved (C_free) polycyclic aromatic hydrocarbons (PAHs) (US EPA 16 PAHs) were determined in biochars produced from the mixture of sewage sludge and sewage sludge and willow (8:2 or 6:4, w/w). The pyrolysis was carried out at 500, 600, and 700 °C using two different carrier gases (N₂ or CO₂). Addition of willow and the change of carrier gas from N₂ to CO₂ reduced C_tot PAHs (from 7.0 to 52%) and C_free PAHs (15–29%) content. Co-application of willow and SSL and the use of CO₂ as a carrier gas also beneficially affected the PAHs profile. The biochars produced with willow addition and/or in a CO₂ atmosphere were characterized by a lower (from 9.0 to 62.8%) percentage of 3-6-ring PAHs (C_tot) than the biochars derived from sewage sludge alone in N₂ atmosphere. The contribution of individual C_free PAHs did not differ significantly between biochars. The presence of willow during pyrolysis influenced the direction of the changes in the C_tot PAH content depending on the pyrolysis temperature. For SSL alone, regardless of the carrier gas used, the content of C_tot PAHs was observed to decrease with increasing temperature, whereas in the presence of willow temperature did not affect significantly (P ≥ 0.05) the C_tot PAHs content. The change of carrier gas from N₂ to CO₂ increased the affinity of the biochars to PAHs as confirmed by the distribution coefficients log K_TOC.
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22853. 题目: Biochar combined with compost to reduce the mobility, bioavailability and plant uptake of 2,2',4,4'-tetrabrominated diphenyl ether in soil
文章编号: N19042305
期刊: Journal of Hazardous Materials
作者: Leilei Xiang, Hongjie Sheng, Chenggang Gu, Redmile-Gordon Marc, Yu Wang, Yonrong Bian, Xin Jiang, Fang Wang
更新时间: 2019-04-23
摘要: Biochar application to soil is recognised for its capacity to immobilise pollutants (through sorption) while composted inputs can accelerate the biodegradation of organic pollutants. However, little is known about the influence of combined incorporation on plant uptake of organic pollutants. Therefore, we investigated the effects of maize straw-derived biochar (MSB), compost derived from maize straw and pig manure (SMC), and their combination (MSB-SMC) as soil amendments on bioavailability of 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) and carrot (Daucus carota L.) uptake in a horticultural soil. We found that biochar alone performed well in reducing BDE-47 bioavailability, but was less effective at degrading the pollutant. Conversely, addition of compost stimulated BDE-47 biodegradation. MSB-SMC enhanced BDE-47 biodegradation in soil, reduced contamination of carrot roots, and caused significant reductions in soil extractable BDE-47. The combination of contrasting approaches to remediation thus resulted in the most favorable outcome for a contaminated soil: immobilisation of contaminant from vegetable crops (via biochar) with simultaneous bioremediation of the growing medium. These findings point towards an effective strategy for reducing plant uptake of PDBEs through the combined use of biochar and compost as soil amendment – reducing mobility and facilitating degradation of the accessible contaminant fractions.
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22854. 题目: Carbon isoscapes of rodent diets in the Great Plains USA deviate from regional gradients in C₄ grass abundance due to a preference for C₃ plant resources
文章编号: N19042304
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Andrew W. Haveles, David L. Fox, Kena Fox-Dobbs
更新时间: 2019-04-23
摘要: Diet is an ecological attribute that species may adjust to cope with changing environments and may indicate how a population responds to changes in resource availability. In the Great Plains, plants utilizing the C₄ photosynthetic pathway may increase in abundance in the future because of their high tolerance for warm and dry environments, which are projected to increase. How increased C₄ abundance will influence grassland food webs remains unknown.Here, we evaluate how rodent diets vary relative to C₄ plant biomass at the regional scale of the southern Great Plains in the U.S. We measured δ¹³C values of hair from 534 individuals of 14 rodent species. Resulting isoscapes of δ¹³C values were statistically compared to three proxies for local abundance of C₄ grasses across the region.Overall, diets of most rodent species were dominated by C₃-derived resources with a few species relying on C₄ resources. Ordinary least squares linear regressions indicate that proxies for regional abundance of C₄ grasses explain very little of the variance in δ¹³C values in hair for the entire rodent community, however the isoscape of rodent hair δ¹³C values does broadly correspond to that for δ¹³C values of soil organic matter. The difference between median δ¹³C values of granivores and folivores is significantly and highly correlated with SOM δ¹³C values.Results from this study can be used as a baseline for characterizing dietary shifts in response to environmental change both in the geological past and in the future, and they identify which dietary categories may be most sensitive to future changes in the regional abundance of C₄ grasses.

22855. 题目: Synergistic effects of urban tributary mixing on dissolved organic matter biodegradation in an impounded river system
文章编号: N19042303
期刊: Science of The Total Environment
作者: Most Shirina Begum, Inae Jang, Jung-Min Lee, Han Bin Oh, Hyojin Jin, Ji-Hyung Park
更新时间: 2019-04-23
摘要: Dams and wastewater may greatly perturb riverine fluxes of dissolved organic matter (DOM) and CO₂, yet little is known about the relationships between altered DOM quality and CO₂ emission in eutrophic impounded river systems. A basin-wide field survey of surface water CO₂ and dissolved organic carbon (DOC) was combined with laboratory incubations to examine how dams and urban tributaries delivering treated wastewater influence longitudinal patterns in DOM properties and CO₂ along the impounded Han River traversing Seoul metropolitan area. Fluorescent DOM indices including parallel factor analysis (PARAFAC) components were used to characterize DOM in relation to biodegradable DOC (BDOC). Compared with distinct downstream increases in DOC and CO₂, BDOC concentration and its proportion in DOC (%BDOC) were highly variable along the mainstem and peaked at urban tributaries. Longitudinal increases in fluorescence index (FI), biological index (BIX), and two PARAFAC components (C2 and C3) contrasted with general decreases in humification index (HIX) and C1, reflecting increasing downstream inputs of anthropogenic DOM. During a 5-day incubation employing continuous CO₂ measurements, the cumulative production of CO₂ in the mainstem water mixed with urban tributary water was significantly higher than the level expected for conservative mixing of the two samples, indicating a synergistic enhancement of DOM biodegradation. Molecular formulas identified by Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) revealed more consumed molecules in the mainstem water and more newly produced molecules in the tributary water over the 5-day incubation, implying abundant labile components in the mainstem water discharged from the upstream dam and highly processed tributary DOM limited in immediately biodegradable organic materials. Downstream increases in CO₂ and DOC along the Han River, combined with the synergistic effect observed in the mixed water, suggest that mixing wastewater-derived DOM with labile autochthonous DOM can enhance CO₂ production in the river system perturbed by impoundment and wastewater.
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22856. 题目: Sediment alkaline-extracted organic matter (AEOM) fluorescence: An archive of Holocene marine organic matter origins
文章编号: N19042302
期刊: Science of The Total Environment
作者: Carolina P. Funkey, Daniel J. Conley, Colin A. Stedmon
更新时间: 2019-04-23
摘要: Organic matter (OM) is comprised of a complex mixture of substrates, which are difficult to fully characterize. Therefore a range of analytical approaches is applied to provide a better understanding of the dynamics and biogeochemical cycling of aquatic system. One approach is UV–Visible spectroscopy, which includes measurements of spectral absorption and fluorescence of colored and fluorescent fractions of dissolved OM (DOM, CDOM and FDOM). In this study OM fluorescence is characterized by excitation-emission matrix spectroscopy on alkaline extracted DOM from a Baltic Sea sediment core that spanned 8500 years and fluctuating levels of hypoxia. Our results showed that three underlying fluorescence components had strong correlations with carbon, nitrogen content and δ¹⁵N. Our results demonstrate that optical properties of extracted OM from sediments reveal information about OM quality and quantity similar to those of biomarkers, which can be a useful additional tool for investigating OM deposition.
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22857. 题目: N₂ fixation impacted by carbon fixation via dissolved organic carbon in the changing Daya Bay, South China Sea
文章编号: N19042301
期刊: Science of The Total Environment
作者: Danyang Li, Jiaxing Liu, Run Zhang, Min Chen, Weifeng Yang, Junjie Li, Ziming Fang, Bo Wang, Yusheng Qiu, Minfang Zheng
更新时间: 2019-04-23
摘要: We present the first concurrent measurements of N₂ fixation rates (¹⁵N₂ uptake), primary production (¹⁴C uptake), dissolved organic carbon (DOC) concentrations, and diazotrophic community composition derived from nitrogenase (nifH) abundance in the subtropical Daya Bay (DB) of the coastal northern South China Sea (NSCS) from 2015 to 2017. N₂ fixation rates ranged from n.d. - 4.51 nmol N L⁻¹ h⁻¹. Such values were generally higher than those reported in the neighbouring NSCS open waters and several well-studied oligotrophic waters, thereby suggesting that N-replete conditions do not prevent N₂ fixation in coastal waters. N₂ fixation rates were positively and significantly correlated with the primary production and the concentration of DOC in DB in the spring and summer. Combined with other lines of evidence, we suggest that N₂ fixation may be facilitated by non-diazotrophic phytoplankton via a probable regulation of the quantity and quality (bioavailability) of DOC in DB. Since DB represents a suitable site that has experienced dramatic human-induced changes in environmental conditions, our results likely provide insights in understanding how N₂ fixation and relevant biogeochemical processes may respond to intensified global anthropogenic forcing in similar coastal settings.
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22858. 题目: Revealing the impact of pyrolysis temperature on dissolved organic matter released from the biochar prepared from Typha orientalis
文章编号: N19042203
期刊: Chemosphere
作者: Haiming Wu, Yanshan Qi, Lu Dong, Xin Zhao, Hai Liu
更新时间: 2019-04-22
摘要: Biochars derived from wetland biomass have been extensively applied in water and wastewater treatments. This study investigated the quantity and chemical quality of dissolved organic matter (DOM) released from the biochar prepared from the typical wetland plant (Typha orientalis) at different pyrolysis temperatures (300–700 °C) by using fluorescence excitation-emission (EEM) spectrophotometry with parallel factor analysis (PARAFAC) and UV–Visible spectroscopy. The results showed that the content of DOM released from biochars at low pyrolysis temperatures (300–500 °C) was higher than that observed at high pyrolysis temperatures (600–700 °C). The distribution of DOM components (mainly including three humic acid-like substances, one fulvic acid-like substance and one tyrosine-like substance) varied significantly due to the increase of pyrolysis temperatures. The fulvic acid-like material was the key DOM component at the low pyrolysis temperature while the humic acid-like material became dominant at the high temperature. DOM quality indices also indicated that the percentage of the low molecular-weight DOM increased with the decreasing DOC concentration due to the higher temperatures. The results obtained in this study would be beneficial to guide the rational application of biochars in waste treatments.
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22859. 题目: Fate of Triclocarban (TCC) in aquatic and terrestrial systems and human exposure
文章编号: N19042202
期刊: Chemosphere
作者: Vimalkumar Krishnamoorthi, Sangeetha Seethappan, Arivalagan Pugazhendhi
更新时间: 2019-04-22
摘要: Triclocarban(TCC) is considered as contaminant of emerging concern (CEC), and ranked in the top 10 CEC occurrence. TCC is a high production volume synthetic chemical used extensively in various personal care products. This chemical will be released into the environment via incomplete wastewater treatment and untreated wastewater discharge. TCC and its transformation products (4,4’-dichlorocarbilide (DCC),1-(3-chlorophenyl)-3-phenylurea (MCC) and carbanilide (NCC),2’-OH-TCC, 3’-OH-TCC) were detected in the environmental matrices. Sediment organic carbon will influence TCC concentrations in suspended and bed sediments. TCC is an antimicrobial agent and also emerging endocrine disruptor that can cause immune dysfunction and affect human reproductive outcomes. Furthermore, TCC alters the expression of proteins related to binding and metabolism, skeletal muscle development and function, nervous system development and immune response. TCC has potential health risks in wildlife and humans. Several animal studies illustrate that it can cause various adverse effects, which can be monitored by antioxidant biomarkers (CAT, GST and LPO). Accumulation of TCC in organisms depends on the lipophilicity and bioavailability of TCC in sediment and water. TCC was continuously detected in aquatic system. TCC is a lipophilic compound, which can efficiently bind with lipid content. Women are more vulnerable to TCC due to substantially higher frequency and extended exposure to TCC. This review provides basic information of occurrence of TCC and the exposure levels in aquatic organisms. Several literatures have shown the higher usage and human exposure levels of TCC, which provides useful information for the chemical management approaches.

22860. 题目: Effect of co-existing Co²⁺ ions on the aggregation of humic acid in aquatic environment: Aggregation kinetics, dynamic properties and fluorescence spectroscopic study
文章编号: N19042201
期刊: Science of The Total Environment
作者: Liqiang Tan, Chaofeng Zhao, Xiaoli Tan, Xin Wang, Jinghua Feng, Ming Fang, Yuejiex Ai, Tasawar Hayat, Lu Sun, Xiangke Wang
更新时间: 2019-04-22
摘要: The fate and transport of humic substances in the aquatic environments depend significantly on their interactions with co-existing ions. Herein, we employed dynamic light scattering (DLS) measurement, molecular dynamic (MD) simulation and fluorescence spectrometry to investigate the aggregation of humic acid (HA) in the presence of Co²⁺ ions. The aggregation kinetics was depicted by hydrodynamic diameter (<D_h>) and the attachment efficiency (α) of HA aggregates. α increases gradually in the reaction-limited (slow) regime due to the decrease of the double layer repulsion, and the energy barrier is eliminated to a certain extent in the diffusion-limited reaction while α close to unity. The complexation between functional groups (i.e. carboxylic and phenolic groups) of HA and Co²⁺ ions contributes significantly to the aggregation process of HA. MD simulation and density functional theory (DFT) calculation demonstrate that the aggregation process of HA can be promoted by Co²⁺ through several inter- or intra-molecular interactions between HA and the Co²⁺ ions. The results provide a pathway for insight into the interactions between HA and metal ions, which is important for deeply understanding the environmental behaviors of HA in natural aqueous systems.
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