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30421. 题目: Distribution, dynamics and determinants of antibiotics in soils in a peri-urban area of Yangtze River Delta, Eastern China
文章编号: N18080203
期刊: Chemosphere
作者: Fangkai Zhao, Liding Chen, Lei Yang, Shoujuan Li, Long Sun, Xinwei Yu
更新时间: 2018-08-02
摘要: Antibiotics are increasingly recognized as anthropogenic contaminants in soils, and they can persist through a complex vicious cycle of transformation and bioaccumulation. In this study, we quantified 11 quinolones (QNs), 5 sulfonamides (SAs), 5 macrolides (MLs), and 4 tetracyclines (TCs) in soils at three soil layers (0–10, 10–20, 20–40 cm) in a typical peri-urban catchment in the Yangtze River Delta, Eastern China. The results showed that total antibiotic levels were significantly higher in cropland topsoil (p < 0.05) compared to orchards and forests (p < 0.05). Moreover, a significant seasonal variation for antibiotic concentrations in croplands’ topsoil were observed in the summer (50.59 ± 84.55 ng/g) and winter (112.44 ± 140.58 ng/g). Chlortetracycline (15.30 ± 45.44 ng/g), enrofloxacin (0.43 ± 0.93 ng/g), sulfamethazine (0.05 ± 0.02 ng/g) and clarithromycin (0.03 ± 0.03 ng/g) were detected with the highest frequencies within TCs, QNs, SAs, and MLs, respectively. Concentrations of TCs, QNs, and SAs decreased with increasing soil depth. The concentrations of TCs, QNs, and SAs were significantly affected by the intensity of human activities. According to the results of redundancy analysis (RDA), anthropogenic effects on the distribution of antibiotics in soils in winter were so strong that they dwarfed the effects of environmental factors. In summer, human activities and their interactions with environmental factors were the dominant contributors to variations in soil antibiotics. In addition, the results of RDA suggested that soil pH and organic matter closely correlated with the levels of antibiotics, and Actinobacteria was the predominant contributor to the biodegradation of antibiotics in this study area.
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30422. 题目: Visible-light-driven photocatalytic degradation of ciprofloxacin by a ternary Mn₂O₃/Mn₃O₄/MnO₂ valence state heterojunction
文章编号: N18080202
期刊: Chemical Engineering Journal
作者: Jianhui Zhao, Zhiwei Zhao, Ning Li, Jun Nan, Ruixin Yu, Jinying Du
更新时间: 2018-08-02
摘要: Valence state heterostructure exhibits great potential for contaminants remediation from water and wastewater with effective charge separation and little energy loss. However, the preparation process commonly shows complex with uncontrolled manner, forming undesired valence states, which hinders the advancement of valence state heterostructure. Herein, an Oxone induced strategy is established to controllably design manganese-based valence state heterostructure for the first time. A superior Mn₂O₃/Mn₃O₄/MnO₂ (molar ratio of 3:1:2) photocatalyst with dual Ⅱ heterostructures was generated by Oxone (0.3 mM) induced Mn₂O₃ (0.2 g/L) under visible light. The Mn₂O₃/Mn₃O₄/MnO₂ heterojunction achieved 95.6% removal and 63.9% mineralization of ciprofloxacin (cipro) under visible light irradiation for 40 min. The excellent catalytic performance was derived from the improved surface area, decreased isoelectric point, enhanced light absorption and efficient charge separation of the Mn₂O₃/Mn₃O₄/MnO₂ heterostructure. Moreover, the radicals trapping experiment and Electron paramagnetic resonance (EPR) measurement revealed the dominant roles of holes and superoxide radicals for cipro degradation. Furthermore, the reusable Mn₂O₃/Mn₃O₄/MnO₂ could remove cipro selectively with co-existing natural organic matters and inorganic ions, which exhibited high practicability in real waters. Impressively, this work provides an innovative approach for controllable design of valence state heterostructure and fabricates a promising photocatalyst towards antibiotics degradation.
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30423. 题目: Influence of organic management on As bioavailability: Soil quality and tomato As uptake
文章编号: N18080201
期刊: Chemosphere
作者: Silvia Rita Stazi, Roberto Mancinelli, Rosita Marabottini, Enrica Allevato, Emanuele Radicetti, Enio Campiglia, Sara Marinari
更新时间: 2018-08-02
摘要: The research studied the effects of organic vs. conventional management of soil quality and tomato yield quality, cultivated in a geogenic arsenic contaminated soil. The chemical and biochemical properties were analyzed to evaluate soil quality, arsenic mobility and its phyto-availability, as well as arsenic accumulation in the tomato plant tissues and if tomatoes cultivated in arsenic rich soil represents a risk for human health. A general improvement of tomato growth and soil quality was observed in the organic management, where soil organic carbon increased from 1.24 to 1.48% and total nitrogen content. The arsenic content of the soil in the organic management increased from 57.0 to 65.3 mg kg⁻¹, probably due to a greater content of organic matter which permitted the soil to retain the arsenic naturally present in irrigation water. An increase of bioavailable arsenic was observed in the conventional management compared to the organic one (7.05 vs 6.18 mg kg⁻¹). The bioavailable form of metalloid may affect soil microbial community structure assessed using El-FAME analysis. The increase of the total arsenic concentration in the organic management did not represent a stress factor for soil microbial biomass carbon (Cmic), which was higher in the organic management than in the conventional one (267 vs. 132 μg Cmic g⁻¹). Even if the organic management caused an increase of total arsenic concentration in the soil due to the enhanced organic matter content, retaining arsenic from irrigation water, this management mitigates the arsenic uptake by tomato plants reducing the mobility of the metalloid.

30424. 题目: The interplay between natural organic matter and bromide on bromine substitution
文章编号: N18080110
期刊: Science of The Total Environment
作者: Mahmut S. Ersan, Chao Liu, Gary Amy, Tanju Karanfil
更新时间: 2018-08-01
摘要: This study examined the interplay between bromide and DOM characteristics, described with SUVA₂₅₄, in terms of formation and speciation of selected DBPs [trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles (HANs)] during chlorination under various water treatment conditions. Cytotoxicity evaluations were also conducted based on the types and amounts of DBPs formed and their corresponding cytotoxicity index values. The results showed that the formation of THMs and HAAs increased as the specific UV absorbance at 254 nm (SUVA₂₅₄) of the waters increased; however, there was no clear trend for HANs. THM and HAN formation increased with increasing bromide levels, while there was no bromide effect on the HAA formation. Lower HAA5 (monochloroaceticacid, monobromoaceticacid, dichloroaceticacid, trichloroaceticacid, dibromoaceticacid) to HAA9 (monochloroaceticacid, monobromoaceticacid, dichloroaceticacid, trichloroaceticacid, dibromoaceticacid, bromochloroaceticacid, bromodichloroaceticacid, dibromochloroaceticacid, tribromoaceticacid) ratios, independent of SUVA₂₅₄, were observed with increasing bromide levels. Bromine substitution factor (BSF) values were in the order of BSF_DHAN > BSF_THAA > BSF_THM ≈ BSF_DHAA. BSF values for all class of DBPs decreased with increasing SUVA₂₅₄. TOX formation increased with increasing SUVA₂₅₄ without an impact of bromide concentration. UTOX/TOX ratios were higher in treated low SUVA₂₅₄ waters than raw waters having higher SUVA₂₅₄ values, and they decreased with increasing initial bromide concentration in all sources. Increasing bromide concentration from 0.5 μM to 10 μM elevated the calculated cytotoxicity index values of waters. Despite their much lower (approximately ~10 times) formation as compared to THMs and HAAs, HANs controlled the calculated cytotoxicity of studied waters.
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30425. 题目: The influence of aging on the comparative terrestrial ecotoxicity potential of copper and zinc in soils
文章编号: N18080109
期刊: Environmental Science and Pollution Research
作者: Aiju Liu, Qiang Liao, Mingzhu Li, Menghong Li, Zilin Meng, Qian Zhang, Huansheng Cao
更新时间: 2018-08-01
摘要: Metal exposure to terrestrial organism is influenced by the reactivity of the solid-phase metal pool. Aging is one of the important factors that control the reactivity of the solid-phase metal pool in soil. In this study, the selected 13 soils were collected from different locations of China, representing different soil types. The reactivity variation of spiked Cu and Zn with aging was assessed in these 13 soils, and their comparative toxicity potentials (CTPs) were also calculated. The median reactive fractions (f_reactive) of Cu and Zn with 95% confidence intervals were 1.6 × 10⁻² (3.5 × 10⁻⁶ to 2.2 × 10⁻¹) and 0.10 (9.1 × 10⁻⁴ to 0.44) kg_reactive/kg_total, and the median CTPs for Cu and Zn were 2.09 (8.1 × 10⁻⁴ to 2.2 × 10⁴) and 0.85 (8.5 × 10⁻⁴ to 7.2 × 10²) m³/kg day, respectively. The statistical analysis indicated that aging variability in the CTP of Cu and Zn was mainly associated with the variability in soil organic carbon and pH. These results stress the importance of dealing with aging in the calculation of CTPs for terrestrial ecotoxicity of metals.

30426. 题目: Vertical and seasonal variations of soil carbon pools in ginkgo agroforestry systems in eastern China
文章编号: N18080108
期刊: CATENA
作者: Jing Guo, Bo Wang, Guibin Wang, Yaqiong Wu, Fuliang Cao
更新时间: 2018-08-01
摘要: Agroforestry provides opportunities to decrease the levels of carbon dioxide (CO₂) released into the atmosphere by increasing the carbon (C) stored in agricultural systems. In agroforestry systems, soil C pools serve as the most important and stable C sink, but there is limited information on the vertical and seasonal variations of soil C pools. In this study, the vertical and seasonal variations of soil organic C (SOC) and its labile pools were measured in five planting systems: a pure ginkgo (Gingko biloba. L) planting system, a pure wheat (Triticum aestivum L.) field, a pure metasequoia (Metasequoia glyptostroboides Hu et Cheng) seedling system, a ginkgo and wheat agroforestry system, and a ginkgo and metasequoia seedling agroforestry system. Among these systems, the ginkgo and wheat system had a significantly higher SOC content than the other systems throughout the year, particularly at depths of 0–10 cm and 10–20 cm. Additionally, the pure ginkgo and pure metasequoia systems had lower SOC contents than the other planting systems, and this decrease was attributed to the relatively limited tree litter input and lower fine root biomass. Microbial biomass C (MBC) and soil readily oxidizable C (ROC) exhibited similar vertical and seasonal variations and reached minimum values in winter. The highest MBC and ROC contents were observed in the ginkgo and wheat system at a depth of 0–10 cm, i.e., 127.3 mg kg⁻¹ and 4.49 g kg⁻¹, respectively. The highest water-soluble organic carbon (WSOC) content was observed in summer at a depth of 0–10 cm, i.e., 472.2 mg kg⁻¹. A Pearson correlation analysis indicated that soil properties were significantly correlated with SOC and labile C fractions. The results suggested that an agroforestry system resulted in a greater increase in the soil C sink; in particular, the ginkgo and wheat system achieved the best results. Basic soil properties played key roles in soil carbon formation. These results provide important information about SOC and labile C fraction dynamics resulting from planting systems and depth variations and strengthen our understanding of soil C sequestration in agroforestry systems.

30427. 题目: Effects of mixed surfactants on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in crops and the bioremediation of contaminated farmlands
文章编号: N18080107
期刊: Science of The Total Environment
作者: Zhiheng Li, Wei Wang, Lizhong Zhu
更新时间: 2018-08-01
摘要: Given the widespread contamination of polycyclic aromatic hydrocarbons (PAHs) in farmland, it is necessary to develop a technology to ensure the safety of agricultural productions and remediate the contaminated soils. In this study, a series of mixed surfactants were utilized to reduce the uptake of PAHs by crops in farming period and enhance the plant-microbe associated biodegradation in fallow period. During the farming period, the mixtures of cetyltrimethyl ammonium bromide (CTMAB) and Tween 80 were attached on soil by cationic-exchange and hydrogen bond, respectively, which increased soil organic matter to partition the bio-available fraction of PAHs. The maximum reduction of phenanthrene and pyrene was 88.6% and 94.9% for chrysanthemum (Chrysanthemum coronarium L.), and 90.6% and 91.9% for raphanus (Raphanus sativus L.), respectively. During the fallow period, sodium dodecyl benzene sulfonate (SDBS) reduced the adsorption loss of Tween 80 on soil to enhance desorption of PAHs. The mixtures of SDBS and Tween 80 increased the water-soluble fraction of PAHs in soils, modified bacterial community structure, and enriched the functional genes involved cell motility and signal transduction. Removal efficiencies of phenanthrene and pyrene in soils were high to 86.7% and 90.7%. This systematic technology provided an effective solution to remediate and plant on PAH-contaminated farmlands.
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30428. 题目: Framework for Cost-Effective Prediction of Unregulated Disinfection By-Products in Drinking Water Distribution Using Differential Free Chlorine
文章编号: N18080106
期刊: Environmental Science: Water Research & Technology
作者: Gyan Chhipi Shrestha, Manuel J. Rodriguez, Rehan Sadiq
更新时间: 2018-08-01
摘要: Unregulated disinfection by-products (U-DBPs) in drinking water are formed primarily by the reaction of disinfectants (e.g., chlorine) and natural organic matter (NOM). The formation can be dictated by basic water quality and operational parameters. This purpose of this study was to develop a cost-effective framework for predicting U-DBP concentration in water distribution networks (WDNs) based on changes in free chlorine in the WDN with respect to that at the water treatment plant (WTP) outlet (called differential free chlorine, i.e., Cl2). Under the framework, mixed-effects models were developed to predict U-DBP families: haloacetonitriles (HANs) and haloketones (HKs) and individual compounds: chloropicrin (CPK), dichloroacetonitrile (DCAN), borochloroacetonitrile (BCAN), and 1,1,1 trichloropropanone (TCP). Common water quality parameters at the WTP outlet were also included to increase the effectiveness of the models. The models developed were applied successfully to two applications: a single large-sized and combined medium-sized water systems with the R2 of predictive models up to 0.95 and a 95% confidence interval of percent difference in the predictions of -27% to 32%. These applications show that Cl2 only or with basic water quality parameters at WTP are effective parameters for estimating U-DBP concentration in WDNs. The proposed framework can be used by water utilities as a low-cost method to develop models for their water systems to identify potential locations to monitor U-DBPs. Moreover, the frameworks can be used by public health organizations to assess population exposure to U-DBPs in drinking water.

30429. 题目: No difference in ectomycorrhizal morphotype composition between abandoned and inhabited nests of wood ants (Formica polyctena) in a central European spruce forest
文章编号: N18080105
期刊: Geoderma
作者: Veronika Jílková, Martin Vohník, Ondřej Mudrák, Hana Šimáčková, Jan Frouz
更新时间: 2018-08-01
摘要: In temperate forest ecosystems, ectomycorrhizal (EcM) fungi substantially support coniferous trees by nutrients, but importance of EcM for tree nutrition might be lower in nutrient-rich hotspots, such as in wood ant nests. In this study, we focused on differences in EcM morphotype composition between natural nutrient-rich hot spots of various quality (inhabited vs. abandoned wood ant nests) and the surrounding forest floor. In a secondary Norway spruce forest typical for central Europe, we took samples from different belowground parts of five inhabited and five abandoned nests (centre and rim) as well as from the forest floor 20 cm from the nests (run-off zone) and >3 m from the nests (forest soil). The substrates were subjected to analyses of the EcM morphotype composition, moisture and nutrient contents. Wood ant nest substrates had several times increased nutrient contents compared to the forest soil, but there were no significant differences in moisture. Available nutrient contents were higher in inhabited nests than in abandoned nests. The EcM morphotype composition differed between the nest samples and the forest floor samples but not between the inhabited and abandoned nests suggesting that, apart from the level of nutrient enrichment and their availability, moisture is another important factor affecting EcM community composition.

30430. 题目: Biochars mediated degradation, leaching and bioavailability of pyrazosulfuron-ethyl in a sandy loam soil
文章编号: N18080104
期刊: Geoderma
作者: Suman Manna, Neera Singh
更新时间: 2018-08-01
摘要: Burning of crop residues after harvest is a quick, cheap and an easy way to manage the large quantities of agricultural biomass for timely preparation of the field for next crop. Conversion of the crop harvest residues into biochars and incorporating them back in the same field can address the issue of land clearing, waste utilization and nutrient conservation but, any amendment to the soil changes its physico-chemical characteristics and can affect the fate of soil applied herbicides. The present study reports the effect of low (400 °C) and high (600 °C) temperature wheat (WBC) and rice (RBC) straw biochar's amendment on leaching, degradation and bioavailability of pyrazosulfuron-ethyl (PYRAZO) in a sandy loam soil. The PYRAZO was poorly retained in the control soil column where 78% of the soil-applied herbicide leached out of the control soil column. Biochars addition (0.02 and 0.05 g kg⁻¹) significantly reduced the PYRAZO leaching by affecting herbicide's breakthrough time and its maximum concentration in leachate.
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30431. 题目: Characterizing dissolved organic matter in eroded sediments from a loess hilly catchment using fluorescence EEM-PARAFAC and UV–Visible absorption: Insights from source identification and carbon cycling
文章编号: N18080103
期刊: Geoderma
作者: Chun Liu, Zhongwu Li, Asmeret Asefaw Berhe, Haibing Xiao, Lin Liu, Danyang Wang, Hao Peng, Guangming Zeng
更新时间: 2018-08-01
摘要: The chemical characteristics of dissolved organic matter (DOM) in soils that experience erosion and deposition are key to the biogeochemical cycle of carbon on the earth's surface. However, data related to the transport and fate of DOM from soils that experience erosion and different management practices are scarce, particularly at catchment scales. In this study, soil samples (uppermost 10 cm) were collected from uplands representing four land use types (cropland, fallow, grassland, and forests) as well as gullies, and sediment samples (100 cm sampled at 10 depths) were collected from sediments retained by a check dam. Chemical characteristics of DOM in soils and sediments, as well as subsequent source identification, were inferred from UV–Visible absorption and fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC) as well as principal component analysis (PCA). The results indicated higher aromaticity, hydrophobic fraction, and molecular size in DOM from forest soils than those from other land use types and gullies. These factors were also higher in soils at the eroding sites than in sediments. EEM-PARAFAC analysis demonstrated that more protein-like components (tyrosine-like and tryptophan-like combined, accounting for >42.77%) were present in sediments compared to soils with terrestrial humic-like substances. PCA results revealed that approximately 72% of the variance in the DOM characteristics was explained by the first two principal components and that the DOM in upland and gully soils had a negligible contribution to DOM in sediments. Combined our results indicate that, despite the large amount of sediment-associated carbon that is transported by erosion and trapped in check dams, DOM is likely mineralized during soil transport. Furthermore, biological production of new organic compounds (autochthonous sources) are likely the major source of sediment DOM in depositional settings.

30432. 题目: Anaerobic organic carbon mineralization in tidal wetlands along a low-level salinity gradient of a subtropical estuary: Rates, pathways, and controls
文章编号: N18080102
期刊: Geoderma
作者: Min Luo, Wenfeng Zhu, Jiafang Huang, Yuxiu Liu, Xun Duan, Jie Wu, Chuan Tong
更新时间: 2018-08-01
摘要: To examine how the rates and pathways of anaerobic organic carbon mineralization (AOCM) of tidal freshwater wetlands change with low-level increases in salinity, we investigated the rates and controls of microbial iron and sulfate reduction, methane production, and total AOCM in tidal wetlands along a freshwater to oligohaline (0.1–3.3 ppt) gradient in the Min River Estuary in southeastern China. Porewater chloride was found to be strongly correlated with total organic carbon (TOC), carbon to nitrogen (C:N) ratios, and porewater geochemistry (sulfate, pH, ammonium, and dissolved methane levels). Furthermore, a higher plant biomass, larger iron oxides pool, and lower sulfide levels were observed in the oligohaline wetlands. The contribution of microbial sulfate reduction to AOCM increased from 16% to 67%. In contrast, the contribution of microbial iron reduction and methane production declined from 52% to 22% and 12% to 2%, respectively, along the increasing salinity gradient. No consistent changes were found in the total AOCM rates. The rates of methane production were primarily controlled by the C:N ratios and concentrations of porewater ammonium and amorphous iron oxides, while the microbial sulfate and iron reduction rates were mainly controlled by belowground biomass, water content, and concentrations of porewater chloride and sulfate. Our findings provide insight into the potential consequences of modest saltwater intrusion; these may not alter the rates of AOCM in the Min River Estuary, but could change the dominant AOCM pathway from microbial iron reduction to sulfate reduction and accelerate sulfidic effects in this historically freshwater wetland ecosystem.
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30433. 题目: The occurrence, distribution and degradation of antibiotics by ionizing radiation: An overview
文章编号: N18080101
期刊: Science of The Total Environment
作者: Jianlong Wang, Run Zhuan, Libing Chu
更新时间: 2018-08-01
摘要: Antibiotics have been extensively applied, making them ubiquitous in aquatic environment. As emerging contaminants, the occurrence and distribution of antibiotics in the environment has received increasing attention due to their potential adverse effects on human health and ecosystem. However, antibiotics cannot be effectively removed in conventional biological treatment processes, and their natural biodegradation is also ineffective. In this review, the occurrence and distribution of antibiotics in aquatic environments, including surface water, wastewater and effluent of wastewater treatment plants, were analyzed and summarized. Recent progress of antibiotics degradation by ionizing radiation was reviewed. The various influencing factors, such as absorbed dose, initial concentration, inorganic anions and organic matters, on the removal efficiency of antibiotics were introduced and discussed. To improve their removal efficiency, several advanced oxidation processes (AOPs) such as H₂O₂, Fe²⁺, Fe²⁺/H₂O₂, as well as biological treatment processes, are combined with ionizing radiation. Some suggestions for future studies of antibiotics degradation by ionizing radiation were proposed. Ionizing radiation may be a promising technology for removal of antibiotics from water and wastewater.
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30434. 题目: Climate and plant controls on soil organic matter in coastal wetlands
文章编号: N18073118
期刊: Global Change Biology
作者: Michael J. Osland, Christopher A. Gabler, James B. Grace, Richard H. Day, Meagan L. McCoy, Jennie L. McLeod, Andrew S. From, Nicholas M. Enwright, Laura C. Feher, Camille L. Stagg, Stephen B. Hartley
更新时间: 2018-07-31
摘要: Coastal wetlands are among the most productive and carbon‐rich ecosystems on Earth. Long‐term carbon storage in coastal wetlands occurs primarily belowground as soil organic matter (SOM). In addition to serving as a carbon sink, SOM influences wetland ecosystem structure, function, and stability. To anticipate and mitigate the effects of climate change, there is a need to advance understanding of environmental controls on wetland SOM. Here, we investigated the influence of four soil formation factors: climate, biota, parent materials, and topography. Along the northern Gulf of Mexico, we collected wetland plant and soil data across elevation and zonation gradients within 10 estuaries that span broad temperature and precipitation gradients. Our results highlight the importance of climate–plant controls and indicate that the influence of elevation is scale and location dependent. Coastal wetland plants are sensitive to climate change; small changes in temperature or precipitation can transform coastal wetland plant communities. Across the region, SOM was greatest in mangrove forests and in salt marshes dominated by graminoid plants. SOM was lower in salt flats that lacked vascular plants and in salt marshes dominated by succulent plants. We quantified strong relationships between precipitation, salinity, plant productivity, and SOM. Low precipitation leads to high salinity, which limits plant productivity and appears to constrain SOM accumulation. Our analyses use data from the Gulf of Mexico, but our results can be related to coastal wetlands across the globe and provide a foundation for predicting the ecological effects of future reductions in precipitation and freshwater availability. Coastal wetlands provide many ecosystem services that are SOM dependent and highly vulnerable to climate change. Collectively, our results indicate that future changes in SOM and plant productivity, regulated by cascading effects of precipitation on freshwater availability and salinity, could impact wetland stability and affect the supply of some wetland ecosystem services.

30435. 题目: Performances and mechanisms of efficient degradation of atrazine using peroxymonosulfate and ferrate as oxidants
文章编号: N18073117
期刊: Chemical Engineering Journal
作者: Shaohua Wu, Huiru Li, Xiang Li, Huijun He, Chunping Yang
更新时间: 2018-07-31
摘要: In this study, the degradation efficiencies and mechanisms of atrazine, a recalcitrant herbicide, were thoroughly investigated using ferrate (Fe(VI))/peroxymonosulfate (PMS) process. In comparison with Fe(VI) or PMS alone, Fe(VI)/PMS process significantly enhanced the degradation of atrazine, and its degradation efficiency was higher than that of Fe(VI)/persulfate or Fe(VI)/H₂O₂ process at pH 6.0. Complete degradation of atrazine at an initial concentration of 46.5 µM could be achieved within 20 min at initial concentrations of 6.0 mM Fe(VI), 5.0 mM PMS, pH 6.0, and 25 °C. Fe(VI)/PMS could efficiently degrade atrazine within a wide range of pH values (5–9). NOM concentration lower than 4.0 mg/L was favorable for atrazine degradation. Results of electron spin resonance and quenching studies indicated that both hydroxyl radical and sulfate radical were generated in the Fe(VI)/PMS process, while sulfate radical was the dominant reactive radical responsible for atrazine degradation. The mechanisms of PMS activation were elucidated on the basis of the results of XRD and XPS. In addition, fourteen intermediates from atrazine degradation were identified by LC/MS/MS, and consequently pathways for the degradation were proposed.

30436. 题目: Bioavailability and preservation of organic phosphorus in lake sediments: Insights from enzymatic hydrolysis and ³¹P nuclear magnetic resonance
文章编号: N18073116
期刊: Chemosphere
作者: Yuanrong Zhu, Weiying Feng, Shasha Liu, Zhongqi He, Xiaoli Zhao, Yong Liu, Jianyang Guo, John P. Giesy, Fengchang Wu
更新时间: 2018-07-31
摘要: Bioavailability and preservation of organic P (P_o) in the sediment profiles (DC-1 and DC-2) from Lake Dianchi, a eutrophic lake in China, were investigated by a combination of enzymatic hydrolysis and solution ³¹P nuclear magnetic resonance (NMR) spectroscopy. Results showed that large of P_o could be extracted by NaOH-EDTA (NaOH-EDTA P_o), with little P_o in residues after extraction with NaOH-EDTA. Bioavailability and preservation of NaOH-EDTA P_o provide key information for biogeochemical cycling of P_o in sediments. The details of P species and their bioavailability in NaOH-EDTA P_o showed that 54.8–70.4% in DC-1 and 54.6–100% in DC-2, measured by ³¹P NMR, could be hydrolyzed by the phosphatase. Whereas, some proportion of NaOH-EDTA P_o could not be hydrolyzed by the phosphatase, and decreased with sediment depth. Interaction between P_o and other organic matter (e.g., humic acids) is likely an important factor for preservation of these P_o in the sediment profiles. Simulation experiments of hydrolysis of model P_o compounds adsorbed by minerals, such as goethite and montmorillonite, further indicated that adsorption to minerals protected some P_o, especially phytate-like P, from enzymatic hydrolysis, thus preserving these forms of P_o in sediments. Interactions of P_o with organic matter and minerals in the sediments are two important factors determining biogeochemical cycling of P_o in lakes. Intervention to break the cycle of FeP and bioavailable P_o (e.g., labile monoester P) in the history of eutrophication is important way to control algal blooming.
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30437. 题目: Redistribution of methane emission hot spots under drawdown conditions
文章编号: N18073115
期刊: Science of The Total Environment
作者: Stephan Hilgert, Cristovão Vicente Scapulatempo Fernandes, Stephan Fuchs
更新时间: 2018-07-31
摘要: In the context of reservoirs, sediment trapping, and aquatic greenhouse gas (GHG) production, knowledge about the distribution of hot and low spots is essential for improved measurement strategies. It is also a key to a precise assessment of the GHG emissions of each reservoir. Large numbers of reservoirs are used mainly for hydroelectric power generation and, hence, affected by strong changes in water level. Drawdown events may lead to significant changes in spatial sediment and organic carbon distribution and, consequently, strongly alter the GHG emission patterns of the water body. We combined hydroacoustic sediment classification, sediment magnitude detection, and ebullition flux assessment with in-situ pore water investigations and sediment coring to detect ebullition distribution patterns after strong reservoir drawdown. The research was conducted in the Capivari Reservoir in the southeast of Brazil, which was affected by up to 15 m of drawdown within the last 10 years.
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30438. 题目: Iron-organic matter complexes accelerate microbial iron cycling in an iron-rich fen
文章编号: N18073114
期刊: Science of The Total Environment
作者: Stefan Kügler, Rebecca E. Cooper, Carl-Eric Wegner, Jan Frieder Mohr, Thomas Wichard, Kirsten Küsel
更新时间: 2018-07-31
摘要: The accessibility of iron (Fe) species for microbial processes is dependent on solubility and redox state, which are influenced by complexation with dissolved organic matter (DOM) and water-extractable organic matter (WEOM). We evaluated the complexation of these pools of organic matter to soluble Fe(II) and Fe(III) in the slightly acidic Schlöppnerbrunnen fen and subsequent effects on Fe(II) oxidation and Fe(III) reduction. We found the majority of soluble Fe(II) and Fe(III) is complexed to DOM. High-resolution mass spectrometry identified potential complexing partners in peat-derived water extracts (PWE), including compound classes known to function as ligands or electron shuttles, like tannins and sulfur-containing compounds. Furthermore, we observed clear differences in the stability of Fe(II)- and Fe(III)-DOM, with more labile complexes dominating the upper, oxic layers (0–10 cm) and more stable complexes in lower, anoxic layers (15–30 cm). Metal isotope-coded profiling identified a single potential chemical formula (C₄₂H₅₇O₁₃N₉Fe₂) associated with a stable Fe-DOM complex. Fe(III) reduction and Fe(II) oxidation incubations with Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1 or Sideroxydans CL-21, respectively, were used to determine the influence of Fe-DOM complexes on Fe cycling rates. The addition of PWE led to a 2.3-fold increase in Fe(III) reduction rates and 0.5-fold increase in Fe(II) oxidation rates, indicating Fe-DOM complexes greatly influence microbial Fe cycling by potentially serving as electron shuttles. Molecular analyses revealed Fe(III)-reducing and Fe(II)-oxidizing bacteria co-exist across all depths, in approximately equal proportions (representing 0.1–1.0% of the total microbial community), despite observed changes in redox potential. The activity of Fe(III)-reducing bacteria might explain the presence of the detected Fe(II) stabilized via complexation with DOM even under oxic conditions in upper peat layers. Therefore, these Fe(II)-DOM complexes can be recycled by microaerophilic Fe(II)-oxidizers. Taken together, these results suggest Fe-DOM complexation in the fen accelerates microbial-mediated redox processes across the entire redox continuum.
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30439. 题目: Enhanced nitrate removal and high selectivity towards dinitrogen for groundwater remediation using biochar-supported nano zero-valent iron
文章编号: N18073113
期刊: Chemical Engineering Journal
作者: Anlei Wei, Jing Ma, Jingjing Chen, Yan Zhang, Jinxi Song, Xiangyang Yu
更新时间: 2018-07-31
摘要: We prepared nano zero-valent iron/biochar composites (nZVI/BC) to remove nitrate from groundwater with harmless products. Results show nZVI/BCs derived from different mass ratios of Fe(0) to biochar exhibited different nitrate removal efficiencies, and the mass ratio of 1:2 developed the nZVI/BC with optimum nitrate removal. The nZVI/BC maintained preferable nitrate removal (75.0%–97.0%) over a wide pH range 2–12. Nitrate removal amount declined due to serious corrosion and clogging of nZVI/BC’s surface when initial nitrate concentration exceeded 40 mg/L. The nitrate removal process followed a first-order kinetic reaction. As regards real groundwater, the nZVI/BC removed more nitrate than both pure Fe(0) nanoparticles and biochar. Reaction product analysis revealed 60.1% of removed nitrate selectively became dinitrogen. X-ray photoelectron spectroscopy measurements suggested that nitrate-oxidized Fe(0) resulted in significant increase of magnetite on the surface of nZVI/BC. The redox potential and pH of long duration in reaction changed around −210 mV and 8–9, respectively. These changes facilitated the selective reduction of nitrate to dinitrogen. We also proposed that biochar may provide favorable circumstances for nitrate reduction by directly mediating redox potential, pH and electron transfer, which establishes a possible mechanism for the enhanced removal and selective reduction of nitrate. Our study suggests that nZVI/BC would be a promising alternative for the remediation of nitrate-contaminated groundwater.
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30440. 题目: Sodium hypochlorite assisted membrane cleaning: Alterations in the characteristics of organic foulants and membrane permeability
文章编号: N18073112
期刊: Chemosphere
作者: Shu Zhai, Weiming Zhang, Ting Li, Wenbin Zhang, Lu Lv, Bingcai Pan
更新时间: 2018-07-31
摘要: Chemical cleaning is an important approach for alleviating severe fouling in membrane separation processes. In this study, lysozyme (LYS) was exposed to sodium hypochlorite (NaClO) with varied concentrations (0–2000 ppm) to understand the changes in the physicochemical properties and functional groups as well as the variations in membrane permeabilities. The results showed that membrane filterability exhibited an obvious ‘U-shaped’ trend, and the valley existed when the ratio of Cl/C (the ratio of NaClO and TOC concentrations in feed water) is among 1.35–3.09. Upon exposure to low dose NaClO, three-dimensional fluorescence excitation-emission matrix (3D-EEM) spectra showed that tryptophan protein substances were transformed to more hydrophobic humic-like substances. Fourier transform infrared (FTIR) analysis further confirmed that exposure to low dose NaClO promoted the breakage of aromatic substituents, leading to the formation of hydrophobic condensed aromatic substances. On the contrary, at high NaClO loads, protein structures were destroyed completely and almost no obvious fluorescent intensities could be detected, which promoted the recovery of membrane filterabilities. Notably, the chemical cleaning mechanisms of fouled membranes with NaClO were understood in depth in this study. These results provide new information about the oxidation products of LYS and the cleaning efficiency upon exposure to NaClO.
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