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17361. 题目: A comparison study of in-situ coagulation and magnetic ion exchange (MIEX) as pre-treatments for ultrafiltration: Evaluating effectiveness of organic matters removals and fouling mitigation
文章编号: N18092613
期刊: Chemosphere
作者: Weiying Xu, Yingying Chen, Huikai Liang, Guoqing Sang, Dong Wei, Dongsheng Wang, Bin Du
更新时间: 2018-09-26
摘要: This work was designed to compare the effectiveness of in-situ coagulation and MIEX as pre-treatments prior to ultrafiltration (UF) to improve organic matter (OM) removal and mitigate membrane fouling. Three kinds of OMs, i.e. salicylic acid (SA), humic acid (HA) and bovine serum albumin (BSA) were employed. The experimental results show that coagulation-UF led to most effective removal of HA (almost 90%), while the SA was uncoagulated and least removable, with the rejection rate of about 55%. Conversely, MIEX present superior ability for removing SA, contributing to additional efficiency of 71.95–77.21% than UF alone. Proper dosage of Al-based coagulants could alleviate flux loss, especially in the cases of HA and BSA. Increasing coagulant dose resulted in continuous decrement of irreversible resistance (R_ir), which dominated the membrane fouling development by the SA water. For HA and BSA waters, alternatively, variations of R_r determined the flux declines. Floc compact degree was the decisive factor for R_r for coagulated SA; while for HA and BSA, R_r was most related to the floc size and foulant-foulant interaction. MIEX was most effective for alleviating flux loss when treating the hydrophilic SA with small molecules and for all the cases, MIEX exerted little influence on the R_r values.
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17362. 题目: Characterizing the roles of organic and inorganic foulants in RO membrane fouling development: The case of coal chemical wastewater treatment
文章编号: N18092612
期刊: Separation and Purification Technology
作者: Shu Wang, Kang Xiao, Xia Huang
更新时间: 2018-09-26
摘要: In this study, various fouling characteristics on the surface of a commercial reverse osmosis (RO) membrane were identified, in terms of different organic and inorganic components. Specifically, a practical secondary wastewater of coal chemical industry was used as the feed solution, and was fractionated into six hydrophobic/hydrophilic acid/base/neutral portions. RO membrane fouling behaviors at different stages were critically described using two characteristic parameters, i.e., initial flux decline rate and final steady-state flux. These parameters were quantified using Michaelis-Menten relation as a model fitting method. In general, the hydrophilic neutral (HIN) and hydrophobic neutral (HON) fractions had the fastest initial fouling rate and the lowest steady-state flux, mainly due to their high contents of polysaccharide. Among the organic constituents (polysaccharide/protein/humic acid), polysaccharide was the most responsible for rapid initial flux decline and low final steady-state flux, as proved by Kendall’s correlation. Among the inorganic constituents (Ca/Mg/Si), Si was found to exert the greatest influence on the final steady-state flux. This indicates that polysaccharide and Si played a combined role in determining the foulant layer permeability at the prolonged fouling stage, and a possible mechanism is that Si might alter the structure of polysaccharide gel layer. Further information on the fouling layers was systematically provided by means of Fourier transform infrared spectroscopy, confocal laser scanning microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy with fractal dimension analysis.
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17363. 题目: Extracellular polymeric substances (EPS) modulate adsorption isotherms between biochar and 2,2′,4,4′-tetrabromodiphenyl ether
文章编号: N18092611
期刊: Chemosphere
作者: Guangxia Liu, Hongjie Sheng, Yuhao Fu, Yang Song, Marc Redmile-Gordon, Yan Qiao, Chenggang Gu, Leilei Xiang, Fang Wang
更新时间: 2018-09-26
摘要: Extracellular polymeric substances (EPS), chars and persistent organic pollutants (POPs) frequently coexist in the environment. However, a knowledge gap exists regarding their interactions. Therefore, we applied 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) as a model POP to investigate the influence of bovine serum albumin (BSA) and sodium alginate (SA) - representing protein and polysaccharide components of EPS - on POP adsorption to biochars. Surface activities of tested biochars were characterised using nuclear magnetic resonance, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The adsorption capacities of BDE-47 on biochars were significantly improved by both EPS analogues: BSA at concentrations of only 5 mg L⁻¹ and SA at 80 mg L⁻¹ at c_e = 1 S_w BDE-47 concentration. However, 80 mg L⁻¹ BSA decreased the BDE-47 adsorption capacities on biochars at the tested BDE-47 concentrations. Chemisorption and pore filling mechanisms appeared to dominate the adsorption process of BDE-47 on maize straw and wheat straw biochars. After adding BSA (or SA), a hydrophobic partition effect was found to best explain the adsorption process and linearity of adsorption was enhanced. These results progress our understanding of bioavailability and migration of POPs: especially relevant to the water industry and biochar/EPS facilitated removal of these contaminants.
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17364. 题目: Influence of physicochemical properties of various soil types on iodide and iodate sorption
文章编号: N18092610
期刊: Chemosphere
作者: Eva Duborská, Martin Urík, Marek Bujdoš, Michaela Matulová
更新时间: 2018-09-26
摘要: Studies that deal with iodine mobility in uncontaminated agricultural soils are scarce and unique. Therefore, in this article, we have evaluated the sorption behavior of two most abundant naturally occurring inorganic iodine species – iodide and iodate – in several soil types. Our results showed that the sorption process is extremely slow with equilibrium achieved after ten days. The sorption of both iodine species is well described by Freundlich isotherm. The affinity of iodine for all investigated soils in the observed concentration range is relatively low. Our results showed that besides iodine speciation, sorption efficiency is highly dependent on soil types and their characteristics. While in mineral soils with low organic carbon content iodide sorption is dominant, organic rich soils are more favorable for iodate sorption. Organic carbon, clay content, pH and the abundance of iron, aluminum and manganese oxides and hydroxides showed to be the most important soil properties controlling iodine sorption. Our results provide new insight into the complex iodine behavior and retention in soils. This is crucial for better understanding of iodine mobility and the ability to enter the food chain.

17365. 题目: Influence of algal organic matter on MS2 bacteriophage inactivation by ultraviolet irradiation at 220 nm and 254 nm
文章编号: N18092609
期刊: Chemosphere
作者: Yulin Wang, Elbashir Araud, Joanna L. Shisler, Thanh H. Nguyen, Baoling Yuan
更新时间: 2018-09-26
摘要: We determined the potential interference of extracellular algal organic matter (EAOM) and intracellular algal organic matter (IAOM) extracted from Microcystis aeruginosa on MS2 bacteriophage inactivation under UV irradiation at two wavelengths (220 and 254 nm). UV irradiation at 220 nm doubled the inactivation rate of MS2 in water containing EAOM than in organic-free phosphate buffered solution. In contrast, EAOM did not change MS2 inactivation by exposure to UV 254 nm. The presence of IAOM did not significantly influence MS2 inactivation by exposure to either UV 254 or UV 220 nm. To achieve 3 log₁₀ inactivation of MS2, UV254 nm required more than double the dose of UV220 nm (45 mJ/cm² vs. 20 mJ/cm²). Linear correlations between the reduction in infectivity and the reduction in genome copies detected by reverse transcription quantitative polymerase chain reaction suggested that genomic damage is the main mechanism responsible for MS2 inactivation in water containing algal organic matter (AOM) by exposure to UV irradiation. These findings suggest that the presence of AOM did not negatively influence MS2 inactivation by either 220 or 254 nm irradiation, and that a lower UV dose of 220 nm irradiation can be used to achieve the same level of inactivation in water containing AOM.

17366. 题目: Marine ammonification and carbonic anhydrase activity induce rapid calcium carbonate precipitation
文章编号: N18092608
期刊: Geochimica et Cosmochimica Acta
作者: S. Krause, V. Liebetrau, C.R. Löscher, F. Böhm, S. Gorb, A. Eisenhauer, T. Treude
更新时间: 2018-09-26
摘要: During Earth’s history, precipitation of calcium carbonate by heterotrophic microbes has substantially contributed to the genesis of copious amounts of carbonate sediment and its subsequent lithification. Previous work identified the microbial sulfur and nitrogen cycle as principal pathways involved in the formation of marine calcium carbonate deposits. While substantial knowledge exists for the importance of the sulfur cycle, specifically sulfate reduction, with regard to carbonate formation, information about carbonate genesis connected to the microbial nitrogen cycle is dissatisfactory. In addition to the established pathways for carbonate mineral formation, also the potential of microbial carbonic anhydrase, a carbonate-relevant, zinc-containing enzyme, is receiving currently increased attention. However, also in this field knowledge is scarce and fragmentary. Here we demonstrate microbial carbonate precipitation as a direct result of the interplay between the microbial nitrogen cycle and a microbially produced enzyme. Using Alcanivorax borkumensis as a model organism, our experiments depict precipitation of a peloidal carbonate matrix within days to weeks, induced by simultaneous ammonification and extracellular carbonic anhydrase activity. The precipitates show similar morphology, mineralogy, δ^44/40Ca, and δ ^88/86Sr to analogs of modern carbonate peloids. The obtained Sr/Ca partition coefficient D_Sr showed no clear deviation from inorganic carbonate phases, indicating that microbially mediated carbonate precipitation, indeed, follows the principles of physico-chemical precipitation. The observed relative enrichment of the precipitates in zinc might help to constrain zinc variations in natural carbonate archives. Our study demonstrates that ammonification, due to intense microbial organic matter degradation, and carbonic anhydrase may play a substantial role for calcium carbonate precipitation in paleo- and recent shallow marine environments.

17367. 题目: Visible-light-driven photocatalytic inactivation of bacteriophage f2 by Cu-TiO₂ nanofibers in the presence of humic acid
文章编号: N18092607
期刊: Journal of Environmental Sciences
作者: Rong Cheng, Mi Kang, Zhi-peng Shen, Lei Shi, Xiang Zheng
更新时间: 2018-09-26
摘要: Pathogenic viruses in drinking water are great threats to public health. Visible-light-driven photocatalysis is a promising technology for virus inactivation. However, the existing photocatalytic antiviral research studies have mostly been carried out in single-component systems, neglecting the effect of natural organic matter, which exists widely in actual water bodies. In this paper, electrospun Cu-TiO₂ nanofibers were prepared as photocatalysts, and their photocatalytic antiviral performance in the presence of humic acid (HA) was comprehensively studied for the first time. The properties of the reaction mixture were measured during the reaction. In addition, the safety, reliability and stability of photocatalytic disinfection in the mixed system were evaluated. The results showed that the virus removal efficiency decreased with the increase of the HA concentration. The type of reaction solution, such as PBS buffer solution or water, did not affect the removal efficiency noticeably. Under acidic conditions, the electrostatic forces between photocatalysts and viruses were strengthened, leading to higher virus removal efficiency. As the reaction time went on, the pH value in the solution increased first and then tended to be stable, the conductivity remained stable, and the dissolved oxygen increased first and then decreased. The safety test showed that the concentration of Cu ions released into the solution was lower than specified by the international standards. No photoreactivation was observed, and the addition of HA significantly reduced the reutilization efficiency of the photocatalysts.
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17368. 题目: Stable carbon isotope records of black carbon on Chinese Loess Plateau since last glacial maximum: An evaluation on their usefulness for paleorainfall and paleovegetation reconstruction
文章编号: N18092606
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Xu Wang, Linlin Cui, Shiling Yang, Jixuan Zhai, Zhongli Ding
更新时间: 2018-09-26
摘要: Stable carbon isotope composition of soil organic matter (δ¹³C_SOM) has been widely used to infer past environmental or vegetation (C₃/C₄) changes. However, as a carbonaceous product of incomplete burning of biomass, the carbon isotope signature of black carbon (BC) has received little study and a limited usage on this purpose. Moreover, the environmental or vegetation indication of BC carbon isotope composition (δ¹³C_BC) in sedimentary records remains ambiguous although the δ¹³C_BC is supposed to reflect carbon isotope composition of vegetation being burnt. This deserves site-specific studies. Here we analyzed δ¹³C_BC and δ¹³C_SOM on loess-paleosol samples from Lijiayuan and Yangling sections on Chinese Loess Plateau (CLP) spanning the last glacial maximum to decipher the environmental (or vegetation) meaning of δ¹³C_BC at each study site. Opposite changing patterns were observed on the δ¹³C_BC values for the two sections. The δ¹³C_BC at Yangling (in southern part of the CLP) varied from − 19.18‰ to − 21.93‰ (mean: − 20.62‰) with more positive values occurred during the middle Holocene than those during the LGM, demonstrating more C₄ plants occupied in the region during the warm-humid middle Holocene. This is consistent with the changing pattern widely-documented in δ¹³C_SOM records over the CLP during the same period. By contrast, the δ¹³C_BC at Lijiayuan (in northwestern part of the CLP) changed within the range of − 21.83‰ ~ − 24.64‰ (mean: − 23.34‰) and displayed more negative values during the early-middle Holocene with respect to the LGM period. The δ¹³C_BC at Lijiayuan were about 2.5‰ lower than those at Yangling, indicating a northward decrease of C₄ plants on the CLP. The anti-phased changes of δ¹³C_BC at Lijiayuan were considered to reflect variations in paleorainfall because the vegetation is dominated by C₃ plants at the study site and carbon isotope compositions of C₃ plants decrease as rainfall increases. Compared with δ¹³C_SOM record at the same profile, δ¹³C_BC seem biased against capturing C₄ signal during mid-Holocene possibly due to dominance of C₃ plants at the study site during fire seasons and a potentially extra source of BC from forest fires occurred on surrounding mountains. By contrast, δ¹³C_BC tend to exaggerate C₄ signal during the LGM attributed to a possible shift of fire season from spring to summer. These findings suggest that we probably underestimate the abundance of C₄ plants during mid-Holocene and overestimate C₄ biomass during the LGM using BC carbon isotope composition.

17369. 题目: Insight into the short- and long-term effects of quinoline on anammox granules: Inhibition and acclimatization
文章编号: N18092605
期刊: Science of The Total Environment
作者: Qian-Qian Chen, Lian-Zeng-Ji Xu, Zao-Zao Zhang, Fan-Qi Sun, Zhi-Jian Shi, Bao-Cheng Huang, Nian-Si Fan, Ren-Cun Jin
更新时间: 2018-09-26
摘要: The short- and long-term influence of quinoline on the properties of anaerobic ammonium oxidation (anammox) biogranules was evaluated. During batch tests, the bioactivity of anammox granules in the presence of different quinoline concentrations was monitored, and the IC₅₀ of quinoline was calculated to be 13.1 mg L⁻¹ using a non-competitive inhibition model. The response of anammox granules to pre-exposure to quinoline was dependent on metabolic status, and the presence of both quinoline and NO₂⁻-N had a rapid detrimental effect, resulting in a 64.5% decrease within 12 h. During continuous-flow experiments, the nitrogen removal rate (NRR) of the reactor decreased sharply within 3 days in the presence of 10 mg L⁻¹ quinoline and then was restored to 2.6 kg N m⁻³ d⁻¹. In the presence of quinoline-induced stress, the specific anammox activity and levels of extracellular polymeric substance and heme c were decreased, while settling velocity persistently increased. After cultivation and acclimation obtained by adding a medium level of quinoline to the influent, the anammox granule sludge was able to tolerate 10 mg L⁻¹ quinoline in 178 days.
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17370. 题目: Effects of biochar on 2, 2′, 4, 4′, 5, 5′-hexabrominated diphenyl ether (BDE-153) fate in Amaranthus mangostanus L.: Accumulation, metabolite formation, and physiological response
文章编号: N18092604
期刊: Science of The Total Environment
作者: Weili Jia, Chuanxin Ma, Jason C. White, Mengfei Yin, Huimin Cao, Jicheng Wang, Cuiping Wang, Hongwen Sun, Baoshan Xing
更新时间: 2018-09-26
摘要: The accumulation and metabolism of 2, 2′, 4, 4′, 5, 5′-hexabrominated diphenyl ether (BDE-153) in Amaranthus mangostanus L. (amaranth) as affected by different concentrations of biochar (1.3 to 26.6 g/L) under hydroponic conditions exposed to 10 μg/L BDE-153 after 10 days were investigated. Biochar significantly reduced BDE-153 shoot and root content by 27.5–61.6% and 73–95.3%, respectively. In general, BDE-153 migration from solution to amaranth decreased with increasing the doses of biochar. BDE-153 metabolites altered with doses of biochar. The ratio of de-BDEs to BDE-153 in root was polynomial correlated to biochar dose (R² = 0.9356**). Root and shoot Fe content was positively correlated with the BDE-153 amounts (R² = 0.948** and 0.822*, respectively). Though the higher biochar dose could obviously control BDE-153 uptake by the vegetable, the toxicity was caused more significantly. For instances, the high concentration of biochar at 26.6 g/L reduced pigment content, increased total ROS, and elevated antioxidant enzyme activity. At the same time, the O₂^– intensity was linearly positively correlated with de-BDEs in root (R² = 0.7324*) while photosynthetic parameter F_v/fm intensity was polynomial correlated to BDEs in shoot (R² = 0.9366*). Transmission electron microscopy (TEM) confirmed that exposure to BDE-153 and high concentration biochar at 26.6 g/L severely altered the chloroplasts in terms of the organelle shape and the presence of starch granules in the chloroplast. Taken together, biochar as a soil amendment could significantly control BDE-153 uptake and enhance BDE-153 metabolism in vegetables, but considering the dose of biochar to avoid its toxicity with higher dose.
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17371. 题目: Aerobic respiration of mineral-bound organic carbon in a soil
文章编号: N18092603
期刊: Science of The Total Environment
作者: Dinesh Adhikari, Sarrah M. Dunham-Cheatham, Dawit N. Wordofa, Paul Verburg, Simon R. Poulson, Yu Yang
更新时间: 2018-09-26
摘要: Associations with minerals can potentially augment soil organic carbon (SOC) stability by reducing the bioavailability and degradation of SOC. However, few studies have directly measured aerobic respiration of mineral-bound SOC. In this study, we investigated the microbial aerobic respiration and bioavailability of ferrihydrite-sorbed glucose (Fh-GLU) and ferrihydrite-sorbed formic acid (Fh-FA) by adding ¹³C-labeled compounds to a soil. During an 11-day incubation, 30.2% of free, non-Fh-sorbed glucose (GLU) and 61.8% of free formic acid (FA) were respired, whereas 4.2% and 27.9% of Fh-GLU and Fh-FA were respired, respectively. Our results demonstrated that Fh-bound GLU/FA had lower bioavailability compared to free organic compounds. Associations with Fh led to greater inhibition in the bioavailability of GLU than that for FA. The priming effects of added compounds on the respiration of native SOC were decreased by their association with Fh. Our results demonstrated that the bioavailability and priming effect of organic compounds depend on their interactions with minerals.
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17372. 题目: New phenolic halogenated disinfection byproducts in simulated chlorinated drinking water: identification, decomposition, and control by ozone-activated carbon treatment
文章编号: N18092602
期刊: Water Research
作者: Yan Huang, Huan Li, Qing Zhou, Aimin Li, Chendong Shuang, Qiming Xian, Bin Xu, Yang Pan
更新时间: 2018-09-26
摘要: Recently, 13 new phenolic halogenated disinfection byproducts (DBPs) were discovered and confirmed in chlorinated drinking water using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry (UPLC/ESI-tqMS), which have been attracting a growing concern due to their higher chronic cytotoxicity, developmental toxicity, and growth inhibition compared with commonly known aliphatic DBPs. In this study, another 12 new phenolic halogenated DBPs were detected and identified in simulated chlorinated drinking water samples, including two monohalo-4-hydroxybenzaldehydes, two monohalo-4-hydroxybenzoic acids, three monohalo-salicylic acids, and five mono/di/trihalo-phenols. Decomposition mechanisms of these new phenolic halogenated DBPs during chlorination were speculated and partially verified by identifying intermediate products. These new DBPs could undergo hydrolysis, halogenation, substitution, addition, decarboxylation, and rearrangement reactions to form a series of decomposition products, including dihaloacetic acids, 2-halomaleic acids, and a group of new heterocyclic DBPs (trihalo-hydroxy-cyclopentene-diones). A bench-scale ozone-granular activated carbon (GAC) treatment unit was designed and set up in the lab. It was found that ozonation and GAC filtration were effective in reducing dissolved organic carbon levels and aromaticity (DBP precursors) of simulated raw water samples, and thus were effective in decreasing the concentrations of these new phenolic DBPs by 82.5% and 88.6%, respectively. Furthermore, four different treatment scenarios (i.e., ozonation, GAC filtration, ozonation followed by GAC filtration, and GAC filtration followed by ozonation) were evaluated and compared. Results showed that ozonation followed by GAC filtration was most effective in precursor removal and could decrease the level of these new phenolic DBPs by up to 97.3%.
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17373. 题目: Insight into carbamazepine degradation by UV/monochloramine: Reaction mechanism, oxidation products, and DBPs formation
文章编号: N18092601
期刊: Water Research
作者: Lingjun Bu, Shiqing Zhou, Shumin Zhu, Yangtao Wu, Xiaodi Duan, Zhou Shi, Dionysios D. Dionysiou
更新时间: 2018-09-26
摘要: UV/monochloramine (NH₂Cl) process has attracted some attention for the elimination of contaminants of emerging concern as a novel advanced oxidation process. However, there is still much uncertainty on the performance and mechanisms of UV/NH₂Cl process because of its complexity and generation of various species of radicals, including NH₂^•, HO^•, Cl^• and other reactive chlorine species (RCS). The mechanism and influence factors of degradation of carbamazepine (CBZ) in the UV/NH₂Cl process were investigated, and a synergistic effect was observed. Degradation of CBZ under all investigated conditions followed pseudo-first order kinetics. The corresponding rate constant increased along with the dosage of NH₂Cl, and was affected significantly by the presence of bicarbonate and natural organic matter. The process has little pH-dependency, while the specific contribution of RCS and HO^• changed with solution pH, and RCS always act as a major contributor to the degradation of CBZ. Eleven byproducts of CBZ were identified and their respective evolution profiles were determined. The participation of UV in chloramination can reduce the formation of nitrogenous DBPs, but promote the formation of carbonaceous DBPs. Furthermore, when influent, sand filtered, and granular activated carbon filtered water was respectively used as background, degradation of CBZ was inhibited to different degree and more disinfection byproducts (DBPs) were generated, compared to deionized water. The electrical energy per order for degradation of CBZ in the UV/NH₂Cl process was also calculated to obtain some preliminary cost information.
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17374. 题目: The impact of varying abiotic humification conditions and the resultant structural characteristics on the copper complexation ability of synthetic humic-like acids in aquatic environments
文章编号: N18092513
期刊: Ecotoxicology and Environmental Safety
作者: Ting Yang, Mark E. Hodson
更新时间: 2018-09-25
摘要: Humic acid (HA) has a high complexation ability with metal ions due to its functional groups. In this study, 11 synthetic humic-like acids (SHLAs) were prepared under varying abiotic humification conditions: precursor species (glycine-catechol and glycine-catechol-glucose), precursor concentrations (from 0.25 M:0.25 M to 1 M:1 M), pH (6–8), temperature (25–45 °C) and mass of MnO2 catalyst (1.3–2.5% w/v). The effect of the varying humification conditions on the complexation ability of the SHLA for Cu2+ were investigated together with the relationships between Cu complexation ability and the structure of the SHLAs (elemental composition, type and content of functional groups, AL/AR, E4/E6). Conditional stability constants (log K) of the SHLAs ranged from 6.00 to 6.42 and complexation capacities ranged from 1.76 mmol/g to 2.61 mmol/g. SHLAs synthesized at lower temperature (25 ℃), pH 8, low precursor concentrations (glycine:catechol= 0.25 M:0.25 M) and a larger proportion of catalyst (2.5% w/v) had a larger copper complexation ability. Log K values of SHLAs had significant positive correlations with carboxylic carbon (r = 0.671, p < 0.01).

17375. 题目: Overvalued allelopathy and overlooked effects of humic acid-like substances on Microcystis aeruginosa and Scenedesmus obliquus competition
文章编号: N18092512
期刊: Harmful Algae
作者: Miaomiao Zhao, Xinyi Chen, Ning Ma, Qiuyue Zhang, Dong Qu, Ming Li
更新时间: 2018-09-25
摘要: To form Microcystis blooms, Microcystis must be competitively dominant to other phytoplankton species to produce enough biomass. The aim of this study was to determine the competition mechanisms between Microcystis aeruginosa and Scenedesmus obliquus. M. aeruginosa and S. obliquus were separately cultured in the filtrate of mono and mixed cultures of M. aeruginosa and S. obliquus with varying treatments concerning N, P and iron availability. The inhibition rate for M. aeruginosa was 20–31% when cultured in mono and mixed culture filtrates enriched with N and P, but this rate was reduced to −15 to 19% when cultured in filtrates enriched with N, P and iron. The inhibition rate for M. aeruginosa decreased from 80 to 100% to 11–39% in dialytic filtrates. However, there were no differences in inhibition rate for S. obliquus, regardless of filtrate or dialytic filtrate treatments. The potential allelochemical, 2-butyl-octanol (0.144 mg L−1), was found to have little inhibitory effect to M. aeruginosa or S. obliquus. Thus, previously reported allelopathy to Microcystis would be overestimated. We also report a new mechanism in phytoplankton competition in this study. The phytoplankton secreted humic acid-like substances that can reduce the bioavailability of iron, resulting in the inhibition of other phytoplankton.

17376. 题目: Oxidation of Reduced Peat Particulate Organic Matter by Dissolved Oxygen: Quantification of Apparent Rate Constants in the Field
文章编号: N18092511
期刊: Environmental Science & Technology
作者: Nicolas Walpen, Maximilian P. Lau, Annika Fiskal, Gordon J. Getzinger, Stefan A. Meyer, Taylor F. Nelson, Mark A. Lever, Martin H. Schroth, Michael Sander
更新时间: 2018-09-25
摘要: Peat particulate organic matter (POM) is an important terminal electron acceptor for anaerobic respiration in northern peatlands provided that the electron-accepting capacity of POM is periodically restored by oxidation with O₂ during peat oxygenation events. We employed push–pull tests with dissolved O₂ as reactant to determine pseudo-first-order rate constants of O₂ consumption (k_obs) in anoxic peat soil of an unperturbed Swedish ombrotrophic bog. Dissolved O₂ was rapidly consumed in anoxic peat with a mean k_obs of 2.91 ± 0.60 h^–1, corresponding to an O₂ half-life of ∼14 min. POM dominated O₂ consumption, as evidenced from approximately 50-fold smaller k_obs in POM-free control tests. Inhibiting microbial activity with formaldehyde did not appreciably slow O₂ consumption, supporting abiotic O₂ reduction by POM moieties, not aerobic respiration, as the primary route of O₂ consumption. Peat preoxygenation with dissolved O₂ lowered k_obs in subsequent oxygen consumption tests, consistent with depletion of reduced moieties in POM. Finally, repeated oxygen consumption tests demonstrated that anoxic peat POM has a high reduction capacity, in excess to 20 μmol electrons donated per gram POM. This work demonstrates rapid abiotic oxidation of reduced POM by O₂, supporting that short-term oxygenation events can restore the capacity of POM to accept electrons from anaerobic respiration in temporarily anoxic parts of peatlands.
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17377. 题目: Groundwater as a source of dissolved organic matter to coastal waters: Insights from radon and CDOM observations in 12 shallow coastal systems
文章编号: N18092510
期刊: Limnology and Oceanography
作者: Jackie R. Webb, Isaac R. Santos, Damien T. Maher, Douglas R. Tait, Tyler Cyronak, Mahmood Sadat‐Noori, Paul Macklin, Luke C. Jeffrey
更新时间: 2018-09-25
摘要: The influence of groundwater and pore‐water exchange on dissolved organic matter (DOM) dynamics in coastal surface waters remains poorly understood. Here, we combine bottom up (i.e., groundwater‐derived flux estimates) and top down (i.e., water column response) evidence to assess whether groundwater exchange drives DOM dynamics in shallow coastal waters. We rely on automated chromophoric DOM (CDOM, a proxy for DOM) and radon (²²²Rn, groundwater proxy) measurements over tidal time scales in 12 shallow systems, including tidal freshwater wetlands, estuaries, mangroves, coral reefs, coastal lakes, a saltmarsh, and a residential canal estate. Groundwater‐derived dissolved organic carbon (DOC) fluxes ranged from 2 ± 2 mmol m⁻² d⁻¹ in a coral reef to 1941 ± 1325 mmol m⁻² d⁻¹ in a mangrove tidal creek. These groundwater fluxes replaced surface water DOC inventories on time scales ranging from ~ 0.5 d to several weeks. Systems with short replacement times displayed positive correlations between radon and CDOM in surface waters. Groundwater exchange diluted surface water DOC in four systems. Using multiple lines of evidence, we interpreted groundwater to be an important source of DOM to surface waters in 4 out of the 12 systems, including an offshore coral reef lagoon with low surface water DOC concentrations. Groundwater discharge was a negligible source of DOM in systems with high surface water DOC and CDOM concentrations such as tidal freshwater wetlands and coastal lakes. This investigation highlights the high variability in groundwater‐derived DOC fluxes and responses in the water column, and demonstrates that submarine groundwater discharge and advective pore‐water exchange should be considered in coastal carbon budgets.

17378. 题目: Factors contributing to aggregate stability at different particle sizes in ultisols from Southern China
文章编号: N18092509
期刊: Journal of Soils and Sediments
作者: Taihui Zheng, Jie Yang, Jie Zhang, Chongjun Tang, Kaitao Liao, Yaojun Liu
更新时间: 2018-09-25
摘要: Purpose: The main objective of this study was to investigate the effects of abiogenic and biogenic factors, and their interaction, on aggregate stability determined at different particle sizes. Materials and methods: Soil samples with the same land use pattern were collected and fractioned into five aggregate sizes: 10–15 mm, 5–10 mm, 2–5 mm, 0.25–2 mm, and < 0.25 mm. Contents of iron/aluminum (Fe/Al) oxides, soil organic carbon (SOC), clay, and mean weight diameter (MWD) values for aggregates at different sizes were determined. The respective contributions of these factors were further estimated using path analysis. Results and discussion: The results showed that SOC contents in A horizon declined with the increase of aggregate size. Highest amorphous iron oxide (Fe_o) contents were observed in 0.25–2 and 2–5 mm aggregates, but highest amorphous aluminum oxide (Al_o) contents were found in 5–10 mm aggregates. Abiotic factors (Fe/Al oxides, clay) played a more important role in determining the formation of < 0.25 mm aggregates, whereas both abiotic and biotic factors play an effective role in stabilizing larger aggregates (0.25–2, 2–5, 5–10, and 10–15 mm). The organo-mineral complexes played a certain role in the stability of soil aggregates, especially the larger aggregates. Conclusions: We conclude that abiotic and biotic factors play variable roles in soil aggregates at different sizes, and more studies are needed to better assess their respective roles to improve our understanding of soil aggregation.

17379. 题目: Estimation of Marine versus Terrigenous Organic Carbon in Sediments off Southwestern Taiwan Using the Bromine to Total Organic Carbon Ratio as a Proxy
文章编号: N18092508
期刊: Journal of Geophysical Research: Biogeosciences
作者: Selvaraj Kandasamy, Baozhi Lin, Jiann‐Yuh Lou, Shuh‐Ji Kao, Chen‐Tung Arthur Chen, Lawrence M. Mayer
更新时间: 2018-09-25
摘要: We measured bromine to total organic carbon (Br:TOC) ratios as an organic source indicator in terrestrial and marine settings of Taiwan, a tectonically active margin that differs from previously studied, passive margins. Terrestrial lake sediments, soils, and river bed and suspended sediments showed Br:TOC ratios ranging from 0.02–2.8 mg‐Br g‐TOC^–1. In ocean margin sediments, Br:TOC ratios ranged from terrigenous values up to 7.6 mg‐Br g‐TOC^–1. A two‐component Br:TOC mixing model for ocean margin sediments indicates roughly equal proportions of terrigenous and marine organic matter (F_T and F_M, respectively). Terrestrial δ¹³C values varied from –31.5 to –24.7‰, a range which is twice the difference between the isotopic terrigenous and marine endmembers used to calculate these proportions. F_T and F_M based on δ¹³C were similar to those using Br:TOC if averaged across all marine sediments, but often differed at the level of individual samples. Depth profiles of amounts of these two forms of organic matter (OC_terr and OC_mar) using Br:TOC ratios show that OC_mar burial is relatively constant while OC_terr and hence TOC vary more strongly; this pattern suggests either episodic terrigenous carbon inputs or winnowing before burial. Variations in TOC:TN and δ¹³C are consistent with this control of TOC by terrigenous carbon. This study validates Br:TOC as a source indicator for terrigenous versus marine‐derived organic matter in sediments derived from mountainous areas in Oceania. As a single parameter source indicator it should have less error than δ¹³C due to less uncertainty of the terrestrial endmember.

17380. 题目: Impact of carbon to nitrogen ratio on the performance of aerobic granular reactor and microbial population dynamics during aerobic sludge granulation
文章编号: N18092507
期刊: Bioresource Technology
作者: Xiaochun Wang, Zhonglin Chen, Jimin Shen, Xia Zhao, Jing Kang
更新时间: 2018-09-25
摘要: Carbon to nitrogen (C/N) ratio is one of the most important factor affecting aerobic granular sludge (AGS) growth and pollutant removal in aerobic granular sludge sequencing batch reactor (AGSBR). For stability of sludge granulation process, AGSs were domesticated in five sequence batch reactors (SBRs) with different C/N ratios (6, 7, 8, 9, and 10), which the ammonia nitrogen concentration of influent was 165 mg/L. The effects of C/N ratio on morphology and property of AGS were studied. The results showed that stable AGS was yielded with good settleability, high pollutant removal efficiency and rich microbial diversity when C/N ratio was 8. AGS yielded had stable structure due to higher protein in extracellular polymeric substances (EPS). High throughput 16S rDNA gene analysis revealed the microbial community diversity increased in AGS under the C/N ratio. The dominant microbes changed at the phylum, class and family three levels with the increasing operation time.
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