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24801. 题目: Montmorillonite clay and humic acid modulate the behavior of copper oxide nanoparticles in aqueous environment and induces developmental defects in zebrafish embryo
文章编号: N19101004
期刊: Environmental Pollution
作者: Krupa Kansara, Archini Paruthi, Superb K. Misra, Ajay S. Karakoti, Ashutosh Kumar
更新时间: 2019-10-10
摘要: Copper oxide nanoparticles (CuO NPs) is one of the most commonly used metal oxide nanoparticles for commercial and industrial products. An increase in the manufacturing and use of the CuO NPs based products has increased the likelihood of their release into the aquatic environment. This has attracted major attention among researchers to explore their impact in human as well as environmental systems. CuO NPs, once released into the environment interact with the biotic and abiotic constituents of the ecosystem. Hence the objective of the study was to provide a holistic understanding of the effect of abiotic factors on the stability and aggregation of CuO NPs and its correlation with their effect on the development of zebrafish embryo. It has been observed that the bioavailability of CuO NPs decrease in presence of humic acid (HA) and heteroagglomeration of CuO NPs occurs with clay minerals. CuO NPs, CuO NPs + HA and CuO NPs + Clay significantly altered the expression of genes involved in development of dorsoventral axis and neural network of zebrafish embryos. However, the presence of HA with clay showed protective effect on zebrafish embryo development. These findings provide new insights into the interaction of NPs with abiotic factors and combined effects of such complexes on developing zebrafish embryos genetic markers.
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24802. 题目: Rapid urbanisation threatens fertile agricultural land and soil carbon in the Nile delta
文章编号: N19101003
期刊: Journal of Environmental Management
作者: Sameh K. Abd-Elmabod, Alice C. Fitch, Zhenhua Zhang, Ramadan R. Ali, Laurence Jones
更新时间: 2019-10-10
摘要: Agriculture land in Egypt represents only 3.8% of the total area. The Nile delta provides two thirds of Egypt's agriculture land, but is threatened by urban sprawl. The paper aims to quantify urban expansion over a 45 year period using 6 time points from 1972 to 2017, and its impacts on agricultural potential, soil organic carbon stocks, and implications for water use. The study used multi-temporal satellite data and remote sensing techniques (Maximum Likelihood supervised classification, and NDVI), soil sampling and analysis, data on water irrigation, and agroecological system and ecosystem services model (MicroLEIS, InVEST) to assess the effects of land use change.Urban area increased by a factor of 5, from 452 km2 in 1972 to 2644 km2 in 2017. The greatest losses occurred to the fertile Vertic Torrifluvent soils on the older delta, which lost 1734 km2. Soil organic carbon (0–75 cm depth) lost as a result of soil sealing from urbanisation rose from 25,000 to 141,000 Mg C over the 45 years. As a result of increased pressure on delta land, agriculture expanded into the higher desert areas outside the delta, on marginal land sustained by intensive fertiliser use and irrigation, which in turn puts pressure on water use. Therefore, rapid urban expansion has resulted in a loss of soil carbon and a shift in agriculture from fertile soils to marginal soils, requiring more capital inputs, which is ultimately less sustainable. Modelling suggested that soil management improvement could make better use of fertile soils within the Delta currently affected by high salinity and poor drainage.Future planning should encourage urban expansion on the less fertile soils outside of the delta, while improving suitability of existing agricultural land and minimising land degradation within the delta.

24803. 题目: Competitor and substrate sizes and diffusion together define enzymatic depolymerization and microbial substrate uptake rates
文章编号: N19101002
期刊: Soil Biology and Biochemistry
作者: Jinyun Tang, William J. Riley
更新时间: 2019-10-10
摘要: Diffusion limitations of extracellular enzymes and soluble monomers have been recognized as important mechanisms controlling soil organic matter (SOM) dynamics. Here we combine diffusion limitation with the geometric sizes of extracellular enzymes, polymer particles, monomers, and bacterial cells to derive testable relationships of SOM kinetic parameters, including (1) maximum reaction rates and (2) binding half saturation constants (also known as substrate affinity parameters). We integrate the relevant mechanisms with the Equilibrium Chemistry Approximation (ECA) kinetics, which has been shown to reasonably represent these complex competitive interactions in soils, and then evaluate the reverse and forward Michaelis-Menten kinetics approximations under different conditions. We found: (1) due to the size contrast between larger organic polymer particles and smaller enzyme molecules, depolymerization is limited by the abundance of enzyme binding sites supplied by polymer particles, making the reverse Michaelis-Menten kinetics a better approximation to the ECA kinetics for depolymerization, and (2) due to the size contrast between larger microbial cells and smaller monomer molecules, monomer uptake is limited by accessible microbial cell transporters, making the forward Michaelis-Menten kinetics a better approximation to ECA kinetics for microbial monomer substrate uptake. These results may explain conflicting applications in the literature associated with using reverse and forward Michaelis-Menten kinetics to represent SOM dynamics. Further, the size contrast between litter particles and extracellular enzymes suggests that litter fragmentation by soil fauna and fungi is an important process to be included in models of organic matter decomposition and challenges soil enzyme assays to accurately measure enzyme abundances in order to properly derive the kinetic parameters.

24804. 题目: Alleviating reverse osmosis membrane fouling caused by biopolymers using pre-ozonation
文章编号: N19101001
期刊: Journal of Membrane Science
作者: Zhonglong Yin, Tiancheng Wen, Yan Li Aimin, Li, Chao Long
更新时间: 2019-10-10
摘要: Pre-ozonation prior to membrane filtration was widely investigated for the mitigation of membrane fouling by biopolymers, nevertheless, the application of ozone pre-treatment on reverse osmosis (RO) membrane is limited. In this work, bovine serum albumin (BSA) and sodium alginate (SA) were selected as representatives of protein and polysaccharides, respectively. RO fouling by BSA, SA and BSA + SA (weight ratio = 1:1) solutions was investigated before and after pre-ozonation with ozone dose ranging from 0.05 to 0.25 mg O₃/mg DOC (dissolved organic carbon). The results showed the fouling alleviation was limited for filtration of all foulants at ozone dose of 0.05 mg O₃/mg DOC. When ozone dose was higher than 0.10 mg O₃/mg DOC, however, pre-ozonation effectively increased the permeate flux and decreased the irreversible fouling. The improvement of the permeate flux and reversible fouling was due to the increase in electrostatic (EL) repulsion and decrease in hydrophobic interaction between biopolymer and RO membrane, resulting from the increase in negative charge and hydrophilicity of BSA and SA after pre-ozonation. In addition, the results of in-situ streaming potential measurement showed that pre-ozonation reduced the deposition of BSA and SA on RO membrane and weakened the adhesive force between BSA (or SA) and membrane surface, resulting in an increase in reversible fouling. In summary, organic fouling of RO membrane caused by biopolymers could be mitigated efficiently by pre-ozonation.
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24805. 题目: Molecular Interaction of Aqueous Iodine Species with Humic Acid Studied by I and C K-Edge X-ray Absorption Spectroscopy
文章编号: N19100904
期刊: Environmental Science & Technology
作者: Dien Li, Chen Xu, Chris M. Yeager, Peng Lin, Wei Xing, Kathleen A. Schwehr, Ning Chen, Zachary Arthur, Daniel I Kaplan, Peter H. Santschi
更新时间: 2019-10-09
摘要: Iodine-129 is one of three key risk drivers at several US Department of Energy waste management sites. Natural organic matter (NOM) is thought to play important roles in the immobilization of aqueous iodide (I–) and iodate (IO3–) in the environment, but molecular interactions between NOM and iodine species are poorly understood. In this work, we investigated iodine and carbon speciation in three humic acid (HA)-I systems using I K-edge XANES and EXAFS and C K-edge XANES spectroscopy: (1) I– in the presence of laccase (an oxidase enzyme) and a mediator, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) in a pH 4 buffer, (2) I– in the presence of lactoperoxidase (LPO) and H2O2 in a pH 7 buffer, and (3) IO3– in a pH 3 groundwater. Both oxidase and peroxidase systems could oxidize I– to I2 or hypoiodide (HOI) leading to organo-I formation. However, the laccase-ABTS mediator was the most effective and enhanced I– uptake by HA up to 13.5 mg/g, compared to 1.9 mg/g for the LPO–H2O2. IO3– was abiotically reduced to I2 or HOI leading to an organo-I formation. Pathways for HA iodination include covalent modification of aromatic-type rings by I2 / HOI or iodine incorporation into newly formed benzoquinone species arising from the oxidation of phenolic C species. This study improves our molecular-level understanding of NOM–iodine interactions and stresses the important role that mediators may play in the enzymatic reactions between iodine and NOM.

24806. 题目: Interaction between chlortetracycline and calcium-rich biochar: Enhanced removal by adsorption coupled with flocculation
文章编号: N19100903
期刊: Chemical Engineering Journal
作者: Qi Xu, Qin Zhou, Minmin Pan, Lichun Dai
更新时间: 2019-10-09
摘要: A high residual concentration of antibiotics in the environment represents a to the animal and human health, thus, removal of these antibiotics is an urgent problem in need of a solution. In this study, calcium-rich biochar (CRB) pyrolyzed from a natural organic-inorganic-composite (i.e., crab shell) was investigated for its significant efficiency in removing efficiency of chlortetracycline (CTC) from aqueous solution. Batch experiments were conducted to explore the interaction between CRB and CTC to characterize the ability of CRB to remove CTC. Results showed that the equilibrium pH of the system decreased as the initial concentration of CTC increased, resulting in a complicated CTC removal process. Specifically, at a low initial concentration of CTC, the predominantly occurred through adsorption, which is well-described by the Freundlich isotherm model. The adsorption capacity of CRB for CTC reached 1432.3 mg g⁻¹ at 298 K. Adsorption rates were estimated by kinetic models, and the pseudo-second-order model displays a good fit for the kinetic data at various concentrations. Adsorption and flocculation were responsible for the removal of CTC at a high initial concentration. The maximum removal capacity was 5048 mg g⁻¹ at 298 K. Microcosmic characterization and macroscopic results demonstrated that cation bridging, π-π interaction, electrostatic interaction and hydrogen bonding could be involved in the removal process, which varied with the initial concentration of CTC. Therefore, based on the high-efficiency and low-cost of CRB, this material promises to be an ideal candidate to remove antibiotics (e.g., CTC) from wastewater and control their transport within the environment.
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24807. 题目: Activity and stability of biochar in hydrogen peroxide based oxidation system for degradation of naphthenic acid
文章编号: N19100902
期刊: Chemosphere
作者: Parmila Devi, Ajay K. Dalai, S.P. Chaurasia
更新时间: 2019-10-09
摘要: This study investigated the stability and catalytic activity of wheat straw biochar (WS), hardwood biochar (HW) and commercial activated carbon (AC) in hydrogen peroxide (H₂O₂) based oxidation system for degradation of model naphthenic acids compound, 1-methyl-1- cyclohexane carboxylic acid (MCCA). WS showed excellent catalytic activity for decomposition of H₂O₂ and MCCA degradation as demonstrated by high H₂O₂ decomposition rate (2.0*10⁻⁴ M⁻¹s⁻¹), amount of hydroxyl (OH) radicals generated (182 mg/L) and degradation efficiency of MCCA (100% at C_o – 100 mg/L). 2-Methyl pentatonic acid was identified as reaction intermediate and 99% mineralization of MCCA was obtained within 4 h. The real wastewater conditions were simulated by addition of chloride (Cl⁻) and bicarbonate ions (HCO₃⁻) and found that lower concentrations of Cl⁻ and HCO₃⁻ have minimal influence on MCCA removal. Overall, biochar catalyzed H₂O₂ based oxidation process has great potential and can be applied for degradation of NAs in oil-sand processed water.
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24808. 题目: Biomarkers as indicators of sedimentary organic matter sources and early diagenetic transformation of pentacyclic triterpenoids in a tropical mangrove ecosystem
文章编号: N19100901
期刊: Estuarine, Coastal and Shelf Science
作者: Mukesh Kumar, Tomasz Boski, Francisco P. Lima-Filho, Francisco H.R. Bezerra, Francisco J. González -Vila, Md Khurshid Alam Bhuiyan, José A. González-Pérez
更新时间: 2019-10-09
摘要: Mangrove vegetation covers extensive areas along Brazilian tropical coasts and accumulates large amounts of organic carbon in the intertidal sediments. We have investigated the molecular biomarker composition of mangrove sediments from the Potengi estuary North-East Brazil. To characterise sources and fate of sedimentary organic matter (OM), a direct analytical pyrolysis approach was used. The sediment pyrolysates yielded homologous series of aliphatic compounds (n-alkane/n-alkene doublets, n-alkanoic acid and n-alkan-2-ones), triterpenoids and lignin-derived methoxphenols, indicating that most of the sedimentary OM input originates from terrestrial vascular plants. High abundance of long-chain n-alk-1-ene series with an even carbon number predominance peaking at C_28:1 ―most likely originated from local mangrove vegetation― is found co-eluted with the saturated odd carbon n-alkane series. The occurrence of lignin and n-alkan-2-one biomarkers in the sediments has provided parallel information about the input from vascular plants dominating the intertidal zone. This was further corroborated by the presence of the triterpenols (β-amyrin, and germanicol), that provided chemotaxonomic information on mangrove derived leaf wax in sedimentary OM. The unsaturated triterpenoid including teraxerol acetate, olean-12-ene, olean-18-ene, oleana-11, 13(18)-diene, a-neoursa-3(5), 12-diene and aneooleana-3(5), 12-diene, were also observed in sediment pyrolysates. The presence of these unsaturated pentacyclic triterpenoids revealed an early diagenetic alteration of terrestrial OM in the sediments. This study has demonstrated that routine application of analytical pyrolysis may provide important insight into the sources of sedimentary OM and its diagenetic fate in mangrove intertidal sediments.
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24809. 题目: Variability in Dissolved Organic Matter Composition and Biolability across Gradients of Glacial Coverage and Distance from Glacial Terminus on the Tibetan Plateau
文章编号: N19100804
期刊: Environmental Science & Technology
作者: Yongqiang Zhou, Lei Zhou, Xiaoting He, Kyoung-Soon Jang, Xiaolong Yao, Yang Hu, Yunlin Zhang, Xiangying Li, Robert G. M. Spencer, Justin Dean Brookes, Erik Jeppesen
更新时间: 2019-10-08
摘要: Globally, alpine glaciers hold a large quantity of dissolved organic matter (DOM) and are headwaters of numerous rivers supporting downstream heterotrophic metabolism. However, it remains unclear how glacial coverage and distance from the glacial terminus affect the fate of DOM. Here, we elucidate DOM variability in glacial-fed streams on the Tibetan Plateau using field sampling and bioincubation experiments and compare our findings with the existing literature. We found that dissolved organic carbon, DOM absorption a(254), DOM aromaticity, and the relative abundance of lignin compounds in glacial-fed streams and rivers all increased with increasing distance from the glacial terminus and with decreasing glacial coverage. We also found that contribution of protein-like components, the relative abundance of aliphatic compounds, and DOM biolability increased with increasing glacial coverage and with decreasing distance from the glacial terminus. The ratio of glacial coverage to the logarithmic transformed distance from the glacial terminus was better than that of actual glacial coverage and distance from the glacial terminus in tracing the variability of glacial-fed stream DOM. Microbes in surface ice can produce biolabile DOM that is exported downstream with meltwater. This glacial-fed stream and river DOM is an important source of the highly bioavailable material fueling downstream heterotrophic activity.

24810. 题目: Influence of land use and hydrologic variability on seasonal dissolved organic carbon and nitrate export: insights from a multi-year regional analysis for the northeastern USA
文章编号: N19100803
期刊: Biogeochemistry
作者: Erin Seybold, Arthur J. Gold, Shreeram P. Inamdar, Carol Adair, W. B. Bowden, Matthew C. H. Vaughan, Soni M. Pradhanang, Kelly Addy, James B. Shanley, Andrew Vermilyea, Delphis F. Levia, Beverley C. Wemple, Andrew W. Schroth
更新时间: 2019-10-08
摘要: Land use/land cover (LULC) change has significant impacts on nutrient loading to aquatic systems and has been linked to deteriorating water quality globally. While many relationships between LULC and nutrient loading have been identified, characterization of the interaction between LULC, climate (specifically variable hydrologic forcing) and solute export across seasonal and interannual time scales is needed to understand the processes that determine nutrient loading and responses to change. Recent advances in high-frequency water quality sensors provide opportunities to assess these interannual relationships with sufficiently high temporal resolution to capture the unpredictable, short-term storm events that likely drive important export mechanisms for dissolved organic carbon (DOC) and nitrate (NO₃⁻–N). We deployed a network of in situ sensors in forested, agricultural, and urban watersheds across the northeastern United States. Using 2 years of high-frequency sensor data, we provide a regional assessment of how LULC and hydrologic variability affected the timing and magnitude of dissolved organic carbon and nitrate export, and the status of watershed fluxes as either supply or transport controlled. Analysis of annual export dynamics revealed systematic differences in the timing and magnitude of DOC and NO₃⁻–N delivery among different LULC classes, with distinct regional similarities in the timing of DOC and NO₃⁻–N fluxes from forested and urban watersheds. Conversely, export dynamics at agricultural sites appeared to be highly site-specific, likely driven by local agricultural practices and regulations. Furthermore, the magnitude of solute fluxes across watersheds responded strongly to interannual variability in rainfall, suggesting a high degree of hydrologic control over nutrient loading across the region. Thus, there is strong potential for climate-driven changes in regional hydrologic cycles to drive variation in the magnitude of downstream nutrient fluxes, particularly in watersheds where solute supply and/or transport has been modified.

24811. 题目: Drivers of seasonal and event scale DOC dynamics at the outlet of mountainous peatlands revealed by high frequency monitoring
文章编号: N19100802
期刊: Biogeosciences
作者: Thomas Rosset, Stéphane Binet, Jean-Marc Antoine, Emilie Lerigoleur, François Rigal, and Laure Gandois
更新时间: 2019-10-08
摘要: Peatlands store about 20 % of the global soil organic carbon stock and are an important source of dissolved organic carbon (DOC) for inland waters. Recent improvements for in situ optical monitoring revealed that the DOC concentration in streams draining peatlands is highly variable, showing seasonal variation and short and intense DOC concentration peak periods. This study aimed to determine the variables driving stream DOC concentration variations at seasonal and event scales. Two mountainous peatlands (one fen and one bog) were monitored in the French Pyrenees to capture their outlet DOC concentration variability at a high frequency rate (30 min). Abiotic variables including precipitation, stream temperature and water level, water table depth and peat water temperature were also monitored at high frequency and used as potential predictors to explain DOC concentration variability. Results show that at both sites, DOC concentration time series can be decomposed into a seasonal baseline interrupted by many short and intense peaks of higher concentrations. The DOC concentration baseline is driven, at the seasonal scale, by peat water temperature. At the event scale, DOC concentration increases are mostly driven by water table increases within the peat at both sites. Univariate linear models between DOC concentration and peat water temperature or water table increases show greater efficiency at the fen site. Water recession times were derived from water level time series using master recession curve coefficients. They vary greatly between bog and fen but also within one peatland site. They partly explain the differences between DOC dynamics in the studied peatlands, including porewater DOC concentrations and the links between stream DOC concentration and water table rise. This highlights that peatland complexes are composed of a mosaic of heterogeneous peat units distinctively producing or transferring DOC to streams.

24812. 题目: Impact of phosphate, silicate and natural organic matter on the size of Fe(III) precipitates and arsenate co-precipitation efficiency in calcium containing water
文章编号: N19100801
期刊: Separation and Purification Technology
作者: Arslan Ahmad, Sam Rutten, Martijn Eikelboom, Luuk de Waal, Harry Bruning, Prosun Bhattacharya, Albert van der Wal
更新时间: 2019-10-08
摘要: Removal of arsenic (As) from water by co-precipitation with Fe(III) (oxyhydr)oxides is a widely used technique in water treatment. Nevertheless, As removal efficiency appears to be sensitive to the composition of the water matrix. The aim of this study was to gain a deeper understanding of the independent and combined effects of silicate (Si), phosphate (P), natural organic matter (NOM) and calcium (Ca) on arsenate [As(V)] co-precipitation efficiency and the size of Fe(III) precipitates. We found that, in complex solutions, containing multiple solutes and high levels of Ca, (variations in) Si and P concentrations reduce As(V) removal to some extent, mainly due to a decreased adsorption of As(V) onto Fe(III) precipitates. On the other hand, NOM concentrations reduced As(V) removal to a much greater extent, due to possible formation of mobile Fe(III)–NOM complexes that were difficult to remove by filtration. These findings have a great significance for predicting As(V) removal as a function of seasonal and process-related water quality changes at water treatment plants.

24813. 题目: Colloidal Organic Matter and Metal(loid)s in Coastal Waters (Gulf of Trieste, Northern Adriatic Sea)
文章编号: N19100705
期刊: Aquatic Geochemistry
作者: Katja Klun, Ingrid Falnoga, Darja Mazej, Primož Šket, Jadran Faganeli
更新时间: 2019-10-07
摘要: Large volumes of seawater were sampled in the Gulf of Trieste (northern Adriatic Sea) in order to study the interactions between colloidal organic matter (COM) and metal(loid)s (Me) in coastal waters. COM (> 5 kDa) was isolated by ultrafiltration and characterized using 1H NMR spectroscopy and elemental Corg. and Ntot. analyses. COM in the gulf represents about one quarter of the dissolved organic carbon (DOC), and according to 1H NMR analysis, it is composed of polysaccharides (30–45%), lipids (30–55%), proteins and carboxyl-rich alicyclic molecules (CRAM) (15–20%), and humics (< 1%). An accumulation of COM was observed in the late spring–early summer. The polysaccharide and lipid fractions increased up to twofold and the protein fraction decreased, reflected in a higher Corg./Ntot. (28, molar) ratio. Higher concentrations of humics were observed due to local freshwater discharges in spring. COM from the Isonzo/Soča River differed from the marine COM exhibiting higher protein/CRAM and higher humic contents. COM from the Isonzo/Soča mouth at salinities 16–33 was compositionally similar to marine COM. Analysis of Me, performed by ICP-MS and CVAFS (Hg), showed that Hg (nearly 100%), Cu (20%), Cr (10%), and Se (10%) have the highest Me affinity to colloids. Similar to COM, Hg and Cu rapidly increased till summer due to their sequestration in accumulated COM (transfer to particulate phase). The observed Me/Corg. ratios (Co, Cd, Hg < U, Cr, Ni, Mn < As, Zn, Cu, V < Se, Al, Fe) differ somewhat from those of the Irving–Williams series and can be explained by the composition of COM and variable background concentrations of studied Me in the northern Adriatic. Data from the salinity gradient in the metal-contaminated (especially Hg, Pb, Zn) Isonzo/Soča mouth showed flocculation of Al and Ba and desorption of V, Co, As, Se, Cs, U, and Hg, from the riverine particles with increasing ionic strength, while Fe, Mn, Cu, Cr, Ni, Zn, Cd, and Pb did not correlate with salinity.

24814. 题目: Inhibitory Effect of Dissolved Organic Matter on the Transformation of Selected Anilines and Sulfonamide Antibiotics Induced by the Sulfate Radical
文章编号: N19100704
期刊: Environmental Science & Technology
作者: Silvio Canonica, Ursula Schönenberger
更新时间: 2019-10-07
摘要: Dissolved organic matter (DOM) has been shown to inhibit the oxidation of aromatic amines initiated by excited triplet states, an effect that was attributed to the reduction of oxidation intermediates back to their parent compounds. The present study focuses on the quantification of an analogous inhibitory effect of DOM on aqueous oxidations induced by the sulfate radical (SO4·–). Second-order rate constants for the SO4·–-induced transformation of selected anilines and sulfonamide antibiotics were determined by competition kinetics in the presence and absence of DOM from three different isolates at pH 8. In the presence of 1 mgC L–1 of DOM, a significant reduction in the rate constant was observed for most of the compounds compared to DOM-free solutions, but for two electron-rich anilines, increases in the rate constant were measured. For 4-cyanoaniline and sulfamethoxazole, the DOM concentration dependence of the rate constant consisted of a sharp decrease up to ∼1.0 mgC L–1 of DOM followed by a region of slight changes or even increases for higher DOM concentrations (up to 5 mgC L–1). This behavior was attributed to the occurrence of the aforementioned inhibitory effect and a counteracting accelerated transformation of the contaminants due to reactions with secondary radical oxidants resulting from DOM oxidation by SO4·–. Both effects of inhibition and secondary oxidants should be considered when assessing the abatement of aromatic amines in SO4·–-based advanced oxidation processes.

24815. 题目: Aggregation kinetics of different surface-modified polystyrene nanoparticles in monovalent and divalent electrolytes
文章编号: N19100703
期刊: Environmental Pollution
作者: Sujuan Yu, Mohai Shen, Shasha Li, Yueju Fu, Dan Zhang, Huayi Liu, Jingfu Liu
更新时间: 2019-10-07
摘要: The intentional production and degradation of plastic debris may result in the formation of nanoplastics. Currently, the scarce information on the environmental behaviors of nanoplastics hinders accurate assessment of their potential risks. Herein, the aggregation kinetics of different surface-modified polystyrene nanoparticles in monovalent and divalent electrolytes was investigated to shed some light on the fate of nanoplastics in the aquatic environment. Three monodisperse nanoparticles including unmodified nanoparticles (PS-Bare), carboxylated nanoparticles (PS–COOH) and amino modified nanoparticles (PS–NH₂), as well as one polydisperse nanoparticles that formed by laser ablation of polystyrene films (PS-Laser) were used as models to understand the effects of surface groups and morphology. Results showed that aggregation kinetics of negatively charged PS-Bare and PS-COOH obeyed the DLVO theory in NaCl and CaCl₂ solutions. The presence of Suwannee river natural organic matters (SRNOM) suppressed the aggregation of PS-Bare and PS-COOH in monovalent electrolytes by steric hindrance. However, in divalent electrolytes, their stability was enhanced at low concentrations of SRNOM (below 5 mg C L⁻¹), while became worse at high concentrations of SRNOM (above 5 mg C L⁻¹) due to the interparticle bridging effect caused by Ca²⁺ and carboxyl groups of SRNOM. The cation bridging effect was also observed for PS-laser in the presence of high concentrations of divalent electrolytes and SRNOM. The adsorption of SRNOM could neutralize or even reverse surface charges of positively charged PS-NH₂ at high concentrations, thus enhanced or inhibited the aggregation of PS-NH₂. No synergistic effect of Ca²⁺ and SRNOM was observed on the aggregation of PS-NH₂, probably due to the steric repulsion imparted by the surface modification. Our results highlight that surface charge and surface modification significantly influence aggregation behaviors of nanoplastics in aquatic systems.
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24816. 题目: The soil priming effect: Consistent across ecosystems, elusive mechanisms
文章编号: N19100702
期刊: Soil Biology and Biochemistry
作者: Xiao-Jun Allen Liu, Brianna K. Finley, Rebecca L. Mau, Egbert Schwartz, Paul Dijkstra, Matthew A. Bowker, Bruce A. Hungate
更新时间: 2019-10-07
摘要: Organic matter input to soils can accelerate the decomposition of native soil carbon (C), a process called the priming effect. Priming is ubiquitous and exhibits some consistent patterns, but a general explanation remains elusive, in part because of variation in the response across different ecosystems, and because of a diversity of proposed mechanisms, including microbial activation, stoichiometry, and community shifts. Here, we conducted five-week incubations of four soils (grassland, piñon-juniper, ponderosa pine, mixed conifer), varying the amount of substrate added (as ¹³C-glucose, either 350 or 1000 μg C g⁻¹ week⁻¹) and either with no added nitrogen (N), or with sufficient N (as NH₄NO₃) to bring the C-to-N ratio of the added substrate to 10. Using four different ecosystems enabled testing the generality of mechanisms underlying the priming effect. The responses of priming to the amount and C-to-N ratio of the added substrate were consistent across ecosystems: priming increased with the rate of substrate addition and declined when the C-to-N ratio of the substrate was reduced. However, structural equation models failed to confirm intermediate responses postulated to mediate the priming effect, including responses postulated to be mediated by stoichiometry and microbial activation. Specifically, priming was not clearly associated with changes in microbial biomass or turnover, nor with extracellular enzyme activities or the microbial C-to-N ratio. The strongest explanatory pathways in the structural equation models were the substrate, soil, and C-to-N ratio treatments themselves, with no intermediates, suggesting that either these measurements lacked sufficient sensitivity to reveal causal relationships, or the actual drivers for priming were not included in the ancillary measurements. While we observed consistent changes in priming caused by the amount and C-to-N ratio of the added substrate across a wide array of soils, our findings did not clearly conform to common models offered for the priming effect. Because priming is a residual flux involving diverse substrates of varying chemical composition, a simple and generalizable explanation of the phenomenon may be elusive.

24817. 题目: Biological ion exchange as an alternative to biological activated carbon for drinking water treatment
文章编号: N19100701
期刊: Water Research
作者: Zhen Liu, Kim Maren Lompe, Madjid Mohseni, Pierre R. Bérubé, Sébastien Sauvé, Benoit Barbeau
更新时间: 2019-10-07
摘要: Biological ion exchange (BIEX) has proved to remove natural organic matter (NOM) better than biological activated carbon (BAC). This raises the question if BIEX can be integrated into a full-scale drinking water treatment plant to remove NOM and ammonia. In this study, a pilot plant consisting of one BIEX filter, three GAC filters and one BAC filter was set up as second-stage filtration at the Sainte-Rose drinking water treatment plant (Laval, Canada). The pilot plant was operated for a period of nine months without regeneration of the ion exchange resins. The influent water showed low DOC (2.5 mg/L) and high sulfate concentrations (28.2 mg/L). Except of a short peak of DOC released at about 1 000 BV, the BIEX filter achieved a nearly constant removal of 29–36% over the whole study period. The DOC removals of GAC were similar to BIEX at < 8000 BV but then stabilized at 13–24% after 8 000 BV. Most DOC removal in the BIEX filter was achieved at the top 30 cm layer (81%) compared to 62–66% removal in the GAC/BAC filters in the same layer. After the rapid exhaustion of the primary ion exchange capacity (<1 000 BV), sulfate displaced the fraction of NOM with lower affinity than sulfate, corresponding to the initial DOC release in the BIEX filter. The fraction of NOM with higher affinity than sulfate can still replace sulfate, which explains the good long-term performance of the BIEX filter. BIEX released ammonia with an average of 15% in warm water condition, probably related to the small diameter of the column which limited backwash effectiveness.
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24818. 题目: Soil structure and nutrient supply drive changes in soil microbial communities during conversion of virgin desert soil to irrigated cropland
文章编号: N19100613
期刊: European Journal of Soil Science
作者: Long‐Fei Chen, Zhi‐Bin He, Wen‐Zhi Zhao, Ji‐Liang Liu, Hai Zhou, Jing Li, Yang‐Yang Meng, Li‐Sha Wang
更新时间: 2019-10-06
摘要: Soil microorganisms are critical to soil health and environmental functions; however, the dynamics of microbial communities and their response to soil variables following conversion of desert soils to oasis farmland have not been well documented. We used high‐throughput pyrosequencing to investigate the dynamics of soil microbial communities along an irrigated cultivation chronosequence (cultivation for 16, 33, 45 and 60 years) and in adjacent non‐cultivated soil in a desert‐oasis ecotone in northwestern China. Additionally, we explored which soil variables may be responsible for shifts in microbial communities. Generally, cultivation in desert soil increased microbial community abundance and diversity; however, bacterial abundance and diversity increased along the cultivation chronosequence, while fungal abundance and diversity initially increased and then decreased. Continuous crop cultivation also resulted in a shift in microbial community composition, notably with a decrease in nitrogen (N)‐fixing microbes (Proteobacteria and Cyanobacteria) and an increase in ammonia‐oxidizing (Nitrosomonadales) and nitrite‐oxidizing microbes (Nitrospirae). Redundancy analysis showed that soil organic carbon, total N, available N, available phosphorus and bulk density explained over 80% of the variation in both bacterial and fungal communities; this indicated the critical roles of nutrient supply and soil structure in shaping the composition and diversity of microbial communities during the conversion of native desert soils to irrigated croplands.

24819. 题目: Combined soil and foliar ZnSO4 application improves wheat grain Zn concentration and Zn fractions in a calcareous soil
文章编号: N19100612
期刊: European Journal of Soil Science
作者: A.Q. Zhao, B.N. Wang, X.H. Tian, X.B. Yang
更新时间: 2019-10-06
摘要: Dietary zinc deficiency is a common micronutrient deficiency in humans. Zinc fertilization has been proved to be an effective approach to improve grain Zn concentration in wheat and alleviate Zn deficiency in humans. To maximize the potential of Zn fertilization, it is necessary to select appropriate Zn fertilizer forms and application methods. Here, combined soil and foliar application of ZnSO₄, rather than Zn‐ethylenediaminetetraacetate (Zn‐EDTA), effectively increased grain Zn concentration in winter wheat (Triticum aestivum L. cv. “Xiaoyan 22”) grown in a calcareous soil. However, neither ZnSO₄ nor Zn‐EDTA, when applied to the soil or the foliage alone, had any significant effect on grain Zn concentration. The fractions of Zn loosely bound to organic matter, carbonate‐bound Zn, and manganese oxide‐bound Zn in the rhizosphere soil changed dynamically over the course of the wheat growth period, with the highest levels found at the jointing stage. The residual ZnSO₄ fertilizer had a positive effect on grain Zn concentration in the subsequent wheat crop due to increased storage of phytic acid in wheat grains and high concentrations of Zn loosely bound to organic matter and carbonate‐bound Zn in the soil. In comparison, Zn‐EDTA applied to the soil only increased the exchangeable‐Zn fraction, and had little residual effect on any other Zn fraction. Repeated soil applications of Zn‐EDTA would be effective to improve grain Zn concentration in wheat plants in subsequent years.

24820. 题目: Conceptualizing soil organic matter into particulate and mineral‐associated forms to address global change in the 21st century
文章编号: N19100611
期刊: Global Change Biology
作者: Jocelyn M. Lavallee, Jennifer L. Soong, M. Francesca Cotrufo
更新时间: 2019-10-06
摘要: Managing soil organic matter (SOM) stocks to address global change challenges requires well‐substantiated knowledge of SOM behavior that can be clearly communicated between scientists, management practitioners, and policy makers. However, SOM is incredibly complex and requires separation into multiple components with contrasting behavior in order to study and predict its dynamics. Numerous diverse SOM separation schemes are currently used, making cross‐study comparisons difficult and hindering broad‐scale generalizations. Here we recommend separating SOM into particulate (POM) and mineral‐associated (MAOM) forms, two SOM components that are fundamentally different in terms of their formation, persistence, and functioning. We provide evidence of their highly contrasting physical and chemical properties, mean residence times in soil, and responses to land use change, plant litter inputs, warming, CO₂ enrichment, and N fertilization. Conceptualizing SOM into POM versus MAOM is a feasible, well‐supported, and useful framework that will allow scientists to move beyond studies of bulk SOM, but also use a consistent separation scheme across studies. Ultimately, we propose the POM versus MAOM framework as the best way forward to understand and predict broad‐scale SOM dynamics in the context of global change challenges and provide necessary recommendations to managers and policy makers.