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25701. 题目: Hurricane pulses: Small watershed exports of dissolved nutrients and organic matter during large storms in the Southeastern USA
文章编号: N19070202
期刊: Science of The Total Environment
作者: Shuo Chen, YueHan Lu, Padmanava Dash, Parnab Das, Jianwei Li, Krista Capps, Hamed Majidzadeh, Mark Elliott
更新时间: 2019-07-02
摘要: Extreme weather events, such as hurricanes, can cause ecological disturbances that alter energy and nutrients across terrestrial-aquatic boundaries. Yet, relatively few studies have considered the impacts of extreme weather events on biogeochemical dynamics in watersheds at larger spatial scales. Here, we assessed the effects of Hurricanes Harvey and Irma on the export of dissolved organic matter (DOM) and nutrients in ten watersheds from five southeastern states of the United States. We quantified the magnitude of dissolved organic carbon (DOC) and nutrients exported during the storms and assessed the changes in DOM sources and bioreactivity after storms. Our results show that the storm-mobilized DOC and nutrients fluxes were primarily driven by water discharge. The proportions of terrestrial, humic-like DOM compounds increased, and percent autochthonous, protein-like DOM decreased during high flows. Percent bioreactive DOC decreased with increasing discharge. Bioreactivity increased with increasing nitrate concentration, but decreased as percent terrestrial humic-like DOM, aromaticity, and molecular weight increased. These observations suggest that storms may have shifted flow paths to shallower depths that promoted the addition of biorefractory organic matter from topsoils into the water column. Notably, the total flux of bioreactive DOC was at least nearly twice as high at peak discharge, indicating materials transported by large storm flows could strongly enhance microbial activity in streams, although the position of storm-mediated microbial hotspots would depend on the flow rate and other instream parameters. Additionally, compared to forest-dominated watersheds, urban watersheds exported high loads of nutrients and bioreactive DOC, and a wetland-dominated watershed had a prolonged, but relatively subdued export of DOC and nutrients. Together, our findings highlight the ecological significance of extreme weather and climate events in leading to rapid, large-magnitude changes in energy and nutrient availability within drainage networks, and the potential interactions between land use and climate change on watershed biogeochemistry.
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25702. 题目: Molecular characterization of dissolved organic matters in winter atmospheric fine particulate matters (PM_2.5) from a coastal city of northeast China
文章编号: N19070201
期刊: Science of The Total Environment
作者: Cuiping Ning, Yuan Gao, Haijun Zhang, Haoran Yu, Lei Wang, Ningbo Geng, Rong Cao, Jiping Chen
更新时间: 2019-07-02
摘要: Dissolved organic matters (DOMs) in fine particulate matters (PM_2.5) play a crucial role in global climate change and carbon cycle. However, the chemical components of DOMs are poorly understood due to its ultra-complexity. In this study, DOMs in atmospheric PM_2.5 collected during the heating period in coastal city Dalian were analyzed with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometer, and the molecular composition was characterized. A large number of monoisotopic molecular formulas were assigned to DOMs, which could be classified into CHO, CHNO, CHOS, and CHNOS subgroups. A total of 4228 molecular formulas were identified in DOMs collected in hazy days, while only 2313 components were found in DOMs collected in normal days. CHO group was the dominated components in normal days, whereas CHNO group gave significantly higher contributions in hazy days. The S-containing (CHOS and CHNOS) groups posed the highest relative percentages in both normal and hazy days. In addition, potential emission sources were discussed according to the chemical component analysis. The van Krevelent diagram illustrated that lignin-like and protein/amino sugar family species were the most abundant subclasses in DOMs; and 78% and 94% of DOMs in atmospheric PM_2.5 collected from Dalian could come from biogenic origins in hazy and normal days, respectively. More compounds in hazy days were derived from anthropogenic emissions.
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25703. 题目: Glycerol dialkyl glycerol tetraethers (GDGT) distributions from soil to cave: refining the speleothem paleothermometer
文章编号: N19070103
期刊: Organic Geochemistry
作者: Andy Baker, Alison J. Blyth, Catherine N. Jex, James A. Mcdonald, Martijn Woltering, Stuart J. Khan
更新时间: 2019-07-01
摘要: The glycerol dialkyl glycerol tetraether (GDGT) paleothermometer has potential application as a speleothem paleoclimate proxy. However, the source of GDGTs found in speleothems is poorly understood, with multiple potential sources of GDGTs from the soil to the speleothem surface. Here we analyse GDGTs in soils, soil leachates, in-cave surfaces and cave drip waters at two Australian montane caves. We observe significantly different GDGT distributions between soils, soil leachates, in-cave surfaces and drip waters, and significant spatial differences in in-cave GDGT distributions. Comparison with published modern in-cave and karst groundwater GDGT datasets from Australia, Europe and China shows that speleothem GDGT distributions are different from those of all potential sources. We hypothesise that speleothem surfaces have a calcifying, alkaline, oxic, wet, carbon-available environment that supports a microbial community that is different from other possible karst GDGT sources. We propose that the presence of GDGTs related to anoxic or methanogenic conditions, and observed in cave drip water and on in-cave surfaces, can be used to identify GDGTs from these sources. We confirm that TEX86 based paleothermometers are robust speleothem GDGT paleothermometers, whose calibration can be further refined through improved understanding and measurement of cave temperatures.
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25704. 题目: Metabolic profiling of Daphnia magna exposure to a mixture of hydrophobic organic contaminants in the presence of dissolved organic matter
文章编号: N19070102
期刊: Science of The Total Environment
作者: Vera Kovacevic, André J. Simpson, Myrna J. Simpson
更新时间: 2019-07-01
摘要: The hydrophobic organic contaminants triclosan, triphenyl phosphate (TPhP) and diazinon sorb to dissolved organic matter (DOM) and this may alter their bioavailability and toxicity. ¹H nuclear magnetic resonance (NMR)-based metabolomics was used to investigate how DOM at 1 and 5 mg organic carbon/L may alter the metabolome of Daphnia magna from exposure to equitoxic mixtures of triclosan, TPhP and diazinon. These contaminants have different modes of action toward D. magna. The contaminant concentrations in each mixture were an equal percentage of their lethal concentration to 50% of the population (LC₅₀) values, which equates to 1250 μg/L TPhP, 330 μg/L triclosan and 0.9 μg/L diazinon. The ternary mixture exposure at 1% LC₅₀ values did not alter the D. magna metabolome. Contaminant mixture exposures at 5%, 10%, and 15% LC₅₀ values decreased glucose, serine and glycine concentrations and increased asparagine and threonine concentrations, suggesting disruptions in energy metabolism. The contaminant mixture had a unique mode of action in D. magna and DOM at 1 and 5 mg organic carbon/L did not change this mode of action. The estimated sorption of triclosan, TPhP or diazinon to DOM at 1 or 5 mg organic carbon/L in this experimental design was calculated to be <50% for each contaminant. This suggests that the mode of action of the contaminant mixture was not altered by DOM because the two environmentally relevant concentrations of DOM may have not substantially altered contaminant bioavailability. Our results indicate that DOM may not inevitably mitigate or alter the sub-lethal toxicity of a mixture of hydrophobic organic contaminants. This indicates the complexity of predicting the molecular-level toxicity of environmental mixtures. For adequate risk assessment of freshwater ecosystems, it is vital to account for the combined sub-lethal toxicity of an environmental mixture of contaminants.
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25705. 题目: Coating magnetic biochar with humic acid for high efficient removal of fluoroquinolone antibiotics in water
文章编号: N19070101
期刊: Science of The Total Environment
作者: Jing Zhao, Guiwei Liang, Xiaoli Zhang, Xuewei Cai, Ruining Li, Xiaoyun Xie, Zhaowei Wang
更新时间: 2019-07-01
摘要: As antibiotics are widely consumed, fluoroquinolones (FQs) behave to have huge hidden danger to human health. Various agricultural residues have potential to produce biochar rich in porous structure for adsorption of contaminants. In this study, potato leaves and stems were pyrolyzed at 500 °C under anoxic condition for biochar (BC) preparation. At the same conditions, magnetic biochar (MBC) and humic acid (HA) coated magnetic biochar (HAB) were also prepared. In particular, characterizations of HAB showed the extensive coating of HA on MBC surface and introducing more oxygen-containing groups, which may promote the adsorption capacity of biochar. Three typical FQs (ciprofloxacin (CIP), norfloxacin (NOR) and enrofloxacin (ENR)) were used as target contaminants to further investigate the adsorption property of HAB. Compared with BC and MBC, novel adsorbent HAB due to introduction of HA exhibited better FQs adsorption ability, and its maximum adsorption capacity for CIP, NOR and ENR were 1.80, 1.67 and 1.70 times higher than those of MBC and were 3.40, 2.88, 2.96 times higher than those of raw BC, respectively. Pseudo-second-order kinetic model and Langmuir isotherm model could describe the process of FQs adsorbed on HAB more appropriately, and thermodynamic results illustrated that the sorption process was spontaneous and endothermic. In addition, FQs adsorption by HAB was increased with initial solution pH from 3.0 to 10.0, while it was slightly decreased with ionic strength rising (0.001–0.1 M CaCl₂). Combined with FTIR results, high FQs removal efficiency could be attributed to electrostatic, hydrophobic, H-bond and π-π EDA interactions.
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25706. 题目: Monitoring the kinetics of reactions between natural organic matter and Al(III) ions using differential absorbance spectra
文章编号: N19063003
期刊: Chemosphere
作者: Mingquan Yan, Tingting Luo, Na Li, Gregory V. Korshin
更新时间: 2019-06-30
摘要: This study examined the kinetics of the binding of Al(III) ions by natural organic matter (NOM) exemplified by Suwannee River humic acid (SRHA). This processes was studied for a 5–8 pH range and environmentally relevant concentrations of the system components. Al(III)-NOM interactions were quantified using differential absorbance spectra whose intensity and shape depended on pH and reaction time. In all cases the differential spectra had four bands with maxima located at 245, 275, 320, 380 nm. These bands were assigned to the engagement of the carboxylic-like and/or phenolic-like groups, as well as electrostatic gel in NOM. Several parameters of the absorbance spectra (e.g., spectral slopes of log-transformed spectra in wavelength range 260–270 and 350–400 nm, ΔS_260-270 and ΔS_350-400 respectively) were linearly correlated (R² = 0.98) with concentrations of carboxylic-like groups and total NOM-bound Al(III) ions predicted based on the NICA-Donnan model. The binding of Al(III) ion by NOM at all pHs was modeled assuming the presence of three kinetically distinct sites. This study demonstrates that differential absorbance spectroscopy can be used to quantify the kinetics and mechanisms of NOM-metal ions interactions and monitor them in practically important system including water treatment operations.

25707. 题目: Similar temperature sensitivity of soil mineral-associated organic carbon regardless of age
文章编号: N19063002
期刊: Soil Biology and Biochemistry
作者: Kristiina Karhu, Emmi Hilasvuori, Marko Järvenpää, Laura Arppe, Bent T. Christensen, Hannu Fritze, Liisa Kulmala, Markku Oinonen, Juha-Matti Pitkänen, Pekka Vanhala, Jussi Heinonsalo, Jari Liski
更新时间: 2019-06-30
摘要: Most of the carbon (C) stored in temperate arable soils is present in organic matter (OM) intimately associated with soil minerals and with slow turnover rates. The sensitivity of mineral-associated OM to changes in temperature is crucial for reliable predictions of the response of soil C turnover to global warming and the associated flux of carbon dioxide (CO₂) from the soil to the atmosphere. We studied the temperature sensitivity of C in <63 μm fractions rich in mineral-associated organic matter (MOM) and of C in >63 μm fractions rich in particulate organic matter (POM). The fractions were isolated by physical separation of two light-textured arable soils where the C4-plant silage maize had replaced C3-crops 25 years ago. Differences in ¹³C abundance allowed for calculation of the age of C in the soil-size fractions (old C, C3–C > 25 years; recent C, C4–C < 25 years). We incubated bulk soils (<2 mm) and size fractions sequentially at 6, 18, 26 and 34 °C (ramping up and down the temperature scale) and calculated the temperature sensitivity of old and recent C from ¹²CO₂ and ¹³CO₂ evolution rates. The temperature sensitivity was similar or slightly higher for POM than for MOM. Within the POM fraction, old C3–C was more sensitive to changes in temperature than recent C4–C. For the MOM fraction, the temperature sensitivity was unrelated to the age of C. Quantitative PCR analysis indicated that the proportions of bacteria, archaea and fungi did not change during incubation. Our results suggest that while OM stabilizing mechanisms affect the temperature sensitivity of soil C, temperature sensitivity appears unrelated to the age of mineral-associated OM.

25708. 题目: Glycerol dialkyl glycerol tetraethers (GDGTs) in high latitude Siberian permafrost: Diversity, environmental controls, and implications for proxy applications
文章编号: N19063001
期刊: Organic Geochemistry
作者: Stephanie Kusch, Maria Winterfeld, Gesine Mollenhauer, Silke T. Höfle, Lutz Schirrmeister, Georg Schwamborn, Janet Rethemeyer
更新时间: 2019-06-30
摘要: Archaeal and bacterial glycerol dialkyl glycerol tetraethers (GDGTs) are globally abundant in soils under various climatic conditions, but little is known about their sources, relative distribution, and environmental controls on their diversity in high latitude permafrost deposits. Thus, constraints on GDGT-based proxies such as methylation of branched GDGTs (MBT) or cyclization of branched GDGTs (CBT) used to infer mean annual temperature or soil pH are also sparse. We investigate the GDGT diversity in typical North Siberian permafrost deposits including the active layer of polygonal tundra soils (seasonally frozen ground), fluvial terrace/floodplain sediments, Holocene and Pleistocene thermokarst sediments, and late Pleistocene Ice Complex (Yedoma). Our data show that isoprenoid GDGTs are produced by both methanotrophic and methanogenic Euryarchaeota as well as Thaumarchaeota, but their abundance does not seem to be controlled by the investigated physicochemical parameters including %TOC, %TN, and soil pH. Branched GDGTs (brGDGTs) show similar distributional changes to what has been observed in other high latitude soil samples, i.e., a dominance of pentamethylated and hexamethylated brGDGTs likely reflecting the adaptation to low temperatures and a positive correlation of the degree of cyclization with soil pH. Specifically, brGDGT-IIIa correlates positively with %TOC and %TN and negatively with soil pH, while brGDGT-Ib and brGDGT-IIb correlate negatively with %TOC and %TN and positively with pH. Moreover, we observe a negative correlation between 5-methyl and 6-methyl brGDGTs without cyclopentane moieties (except brGDGT-IIIa), but this anticorrelation does not seem to be related to the investigated physicochemical parameters. The observed brGDGT distribution yields a permafrost-specific soil pH calibration, pHPFCBTPF(r²=0.60, RMSE=0.074; n=109).The different investigated deposit types show some distinct GDGT distributional changes and appear to be distinguishable based on crenarchaeol relative abundance, GDGT-0/(crenarchaeol+GDGT-0) ratios, and CBT’_PF values, although we also observe strong heterogeneity for each deposit type. In particular, Yedoma and the active layer of polygonal tundra soils represent distinct endmembers, which differ from each other as well as from fluvial terrace/floodplain sediments and thermokarst sediments, while the latter two deposit types have similar GDGT fingerprints that are not easily distinguishable. Yet, the observed GDGT distributional differences have implications for GDGT proxies analyzed in aquatic suspended matter and sediments. Quantitative estimates of permafrost erosion as well as soil pH inferred using BIT indices or CBT’_PF, respectively, may be biased by changing relative contributions of different deposit types (carrying their respective GDGT signals) to the exported permafrost OC, particularly from Yedoma and the active layer of polygonal tundra soils.

25709. 题目: DOC Transport and Export in a Dynamic Tropical Catchment
文章编号: N19062905
期刊: Journal of Geophysical Research: Biogeosciences
作者: R. Sánchez‐Murillo, L. G. Romero‐Esquivel, J. Jiménez‐Antillón, J. Salas‐Navarro, L. Corrales‐Salazar, J. Álvarez‐Carvajal, S. Álvarez‐McInerney, D. Bonilla‐Barrantes, N. Gutiérrez‐Sibaja, M. Martínez‐Arroyo, E. Ortiz‐Apuy, J. Salgado‐Lobo, J. Villalobos‐Morales, G. Esquivel‐Hernández, L. D. Rojas‐Jiménez, C. Gómez‐Castro, Q. Jiménez‐Madrigal, O. Vargas‐Gutiérrez, C. Birkel
更新时间: 2019-06-29
摘要: Dissolved organic carbon (DOC) transport and export from headwater forests into freshwaters in highly dynamic tropical catchments are still understudied. Here we present a DOC analysis (2017) in a pristine and small (~2.6 km²) tropical catchment of Costa Rica. Storm flows governed a rapid surface and lateral allochthonous DOC transport (62.2% of the annual DOC export). Cross‐correlation analysis of rainfall and stream discharge indicated that DOC transport occurred on average ~1.25 hr after the rainfall maxima, with large contributions of event water, ranging from 42.4±0.3% up to 98.2±0.3% of the total discharge. Carbon export flux (annual mean=6.7±0.1 g C · m^‐2 · year^‐1) was greater than values reported in subtropical and temperate catchments. Specific ultraviolet absorbance indicated a mixture of hydrophobic humic and hydrophilic nonhumic matter during both baseflow and storm events. Our results highlight the rapid storm‐driven DOC transport and export as well as low biogeochemical attenuation during baseflow episodes in a climate sensitive hot spot. By understanding the key factors controlling the amount of organic carbon transported to streams in dynamic tropical landscapes, better global‐ and catchment‐scale model assessments, conservation practices, and water treatment innovations can be identified.

25710. 题目: Soil organic carbon components in inner Mongolian shrub-encroached grasslands
文章编号: N19062904
期刊: Plant and Soil
作者: Luhong Zhou, Haihua Shen, Yunping Xu, He Li, Leiyi Chen, Yinghui Wang, Pujin Zhang, Xia Zhao, Taoyu Liu, Huifeng Hu, Jingyun Fang
更新时间: 2019-06-29
摘要: Aims: Shrub encroachment has profound influences on regional carbon cycling. However, few studies have examined the changes in soil organic carbon (SOC) components at the molecular level along a climate gradient. In this study, we aimed to investigate the effects of biotic and abiotic factors on the patterns of SOC components in the shrub patches and the grassy matrix. Methods: We analyzed the distribution and controlling factors of SOC components (including free lipids, bound lipids, and lignin-derived phenols) in the topsoil of shrub-encroached grasslands along natural climate gradients in Inner Mongolia, China. Results: We found that the concentrations of bound lipids and lignin-derived phenols were significantly higher and the vanillic acid to vanillin ratio ((Ad/Al)_v) was significantly lower in the shrub patches than in the grassy matrix (p < 0.05). After excluding variables exhibiting collinearity, redundancy analysis showed that shrub patch cover and soil pH were the most important variables that influenced SOC composition in the shrub patches, while herb characteristics and shrub density were the most important in the grassy matrix. Structural equation modeling showed that shrub characteristics at the plot scale greatly contributed to the variance in all components in the grassy matrix, whereas soil properties were more important in the shrub patches. Conclusions: Our results highlight that although the topsoil carbon content did not change, shrub encroachment altered the SOC components and their drivers in the Inner Mongolian grasslands.

25711. 题目: Soil fungal communities vary with invasion by the exotic Spartina alternifolia Loisel. in coastal salt marshes of eastern China
文章编号: N19062903
期刊: Plant and Soil
作者: Wen Yang, Nasreen Jeelani, Lu Xia, Zhihong Zhu, Yiqi Luo, Xiaoli Cheng, Shuqing An
更新时间: 2019-06-29
摘要: Aims: Soil fungal communities play a critical role in ecosystem carbon (C) and nitrogen (N) cycling. Although the effect of plant invasions on ecosystem C and N cycling is well established, its impact on soil fungal communities is not fully understood. The objective of this study was therefore to understand the variations in soil fungal communities as affected by plant invasion, and the mechanisms that drive these changes. Methods: We examined the impacts of invasive Spartina alternifolia Loisel. (SA) on soil fungal abundance, diversity, community composition, trophic modes and functional groups in comparison with bare flat (BF) and native Suaeda salsa (Linn.) Pall. (SS), Scirpus mariqueter Tang et Wang (SM), and Phragmites australis (Cav.) Trin. ex Steud. (PA) communities in coastal salt marshes of eastern China, based on analyses of the quantitative polymerase chain reaction (qPCR) and Illumina MiSeq DNA sequences of fungal internal transcribed spacer (ITS) region. Results: SA invasion increased the soil fungal abundance and diversity compared to BF, SS, SM, and PA soils. The increased soil fungal abundance and diversity were highly related to soil organic carbon (C) and nitrogen (N), water-soluble organic carbon (WSOC), litter C:N ratio, and root C:N ratio. Soil fungal community composition was shifted following SA invasion. Specifically, SA invasion significantly enhanced the relative abundance of Basidiomycota, and reduced the relative abundance of Ascomycota compared with BF, SS, SM, and PA soils. Additionally, SA invasion changed soil fungal trophic modes and functional groups. The relative abundance of saprotrophic fungi significantly increased, while the relative abundances of symbiotic and pathotrophic fungi decreased following SA invasion. Conclusions: Our data revealed that SA invasion altered soil fungal abundance, diversity, community composition, trophic modes and functional groups, which were primarily driven by the quality and quantity of plant residues, soil nutrition substrates, as well as soil physicochemical properties. The changes in soil fungal communities, especially their trophic modes and functional groups following SA invasion would greatly affect soil C and N decomposition and accumulation with potential feedback on climate change.

25712. 题目: Organic carbon within soil aggregates under forestry systems and pasture in a southeast region of Brazil
文章编号: N19062902
期刊: CATENA
作者: Laís Carvalho Vicente, Emanuela Forestieri Gama-Rodrigues, Antonio Carlos Gama-Rodrigues
更新时间: 2019-06-29
摘要: The location of organic matter within the aggregate is a key factor for stabilizing and storing soil organic carbon (SOC). In this context, the purpose of this study was to answer the following question: How much is the contribution of aggregate associated-C in total SOC accumulation up to 1 m under different land uses in the Atlantic rainforest zone of Brazil The experimental areas were: a secondary-forest; 3 and 5-year-old eucalyptus plantation; 35-year-old rubber tree plantation; and 50-year-old unfertilized pasture. Soil samples were collected at six different depths (0–10, 10–20, 20–40, 40–60, 60–80 and 80–100 cm), air dried and separated by wet-sieving into three fraction-size classes (2000–250 μm; 250–53 μm and <53 μm) – corresponding to macroaggregate, microaggregate and silt-and-clay size fraction, respectively. The ultrasonic method was used to quantify the C physically-protected in macro and microaggregates. Macroaggregates accumulated higher amounts of C (C_Ma) than microaggregates (C_Mi). The amount of C_Ma stock in all land-use systems ranged from 33 to 8 Mg ha⁻¹, and the C_Mi ranged from 11 to 7 Mg ha⁻¹. This represents around 22 to 4% and 7 to 4%, respectively, of physically protected C in the SOC storage up to 100 cm. The amount of C_Ma + C_Mi up to 1 m was 43 Mg ha⁻¹ and 36 Mg ha⁻¹ under 3- and 5-year-old eucalyptus plantations; 30 Mg ha⁻¹ in the in secondary forest; and 19 Mg ha⁻¹ in the rubber plantation and pasture. The C stabilization within aggregates represents a significant mechanism of C protection in these soils.

25713. 题目: Reuse of shale gas flowback and produced water: Effects of coagulation and adsorption on ultrafiltration, reverse osmosis combined process
文章编号: N19062901
期刊: Science of The Total Environment
作者: Wei Shang, Alberto Tiraferri, Qiping He, Naiwen Li, Haiqing Chang, Chao Liu, Baicang Liu
更新时间: 2019-06-29
摘要: The shale gas flowback and produced water (FPW) from hydraulic fracturing in the Sichuan province of China has relatively low to moderate levels of total dissolved solids (<20 g/L) and organics (<50 mg/L of dissolved organic carbon). As such, a combined ultrafiltration (UF), reverse osmosis (RO) system can be successfully applied to desalinate this feed water with the goal of reuse. However, the concentration of influent organic matter and particulates in the UF and RO stage is high, and the overall ionic and organics composition is highly complex, so that the membrane processes do not perform well, also due to fouling. To ensure the long-term and efficient operation of the UF-RO stages, a combined pretreatment of the FPW with coagulation and adsorption was investigated. The effect of different parameters on the performance on the system was studied in detail. Overall, the coagulation-adsorption pre-treatment greatly reduced fouling of the membrane processes, thanks to the high removal rate of turbidity (98.8%) and dissolved organic carbon (86.3%). The adsorption of organic matter by powdered activated carbon was best described by the Freundlich equilibrium model, with a pseudo second-order model representing the adsorption kinetics. Also, the various ions had competitive removal rates during the adsorption step, a phenomenon reported for the first time for FPW treatment. Also, an optimal dose of activated carbon existed to maximize fouling reduction and effluent quality. The overall treatment system produced a high-quality water streams, suitable for reuse.
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25714. 题目: Humic surface waters of frozen peat bogs (permafrost zone) are highly resistant to bio- and photodegradation
文章编号: N19062811
期刊: Biogeosciences
作者: Liudmila S. Shirokova, Artem V. Chupakov, Svetlana A. Zabelina, Natalia V. Neverova, Dahedrey Payandi-Rolland, Carole Causserand, Jan Karlsson, Oleg S. Pokrovsky
更新时间: 2019-06-28
摘要: In contrast to the large number of studies on humic waters from permafrost-free regions and oligotrophic waters from permafrost-bearing regions, the bio- and photolability of DOM from the humic surface waters of permafrost-bearing regions has not been thoroughly evaluated. Following standardized protocol, we measured biodegradation (at low, intermediate and high temperatures) and photodegradation (at one intermediate temperature) of DOM in surface waters along the hydrological continuum (depression → stream → thermokarst lake → Pechora River) within a frozen peatland in European Russia. In all systems, within the experimental resolution of 5 % to 10 %, there was no bio- or photodegradation of DOM over a 1-month incubation period. It is possible that the main cause of the lack of degradation is the dominance of allochthonous refractory (soil, peat) DOM in all waters studied. However, all surface waters were supersaturated with CO2. Thus, this study suggests that, rather than bio- and photodegradation of DOM in the water column, other factors such as peat pore-water DOM processing and respiration of sediments are the main drivers of elevated pCO2 and CO2 emission in humic boreal waters of frozen peat bogs.

25715. 题目: Direct Observations of the Occlusion of Soil Organic Matter within Calcite
文章编号: N19062810
期刊: Environmental Science & Technology
作者: Jialin Chi, Wenjun Zhang, Lijun Wang, Christine V. Putnis
更新时间: 2019-06-28
摘要: Global soil carbon cycling plays a key role in regulating and stabilizing the earth’s climate change because of soils with amounts of carbon at least three times greater than those of other ecological systems. Soil minerals have also been shown to underlie the persistence of soil organic matter (SOM) through both adsorption and occlusion, but the microscopic mechanisms that control the latter process are poorly understood. Here, using time-resolved in situ atomic force microscopy (AFM) to observe how calcite, a representative mineral in alkaline soils, interacts with humic substances, we show that following adsorption, humic substances are gradually occluded by the advancing steps of spirals on the calcite (1014) face grown in relatively high supersaturated solutions, through the embedment, compression, and closure of humic substance particles into cavities. This occlusion progress is inhibited by phytate at high concentrations (10–100 μM) due to the formation of phytate-Ca precipitates on step edges to prevent the step advancement, whereas phytate at relatively low concentrations (≤1 μM) and oxalate at high concentrations (100 μM) have little effect on this process. These in situ observations may provide new insights into the organo–mineral interaction, resulting in the incorporation of humic substances into minerals with a longer storage time to delay degradation in soils. This will improve our understanding of carbon cycling and immobilization in soil ecological systems.

25716. 题目: Molecular-Level Composition and Acute Toxicity of Photosolubilized Petrogenic Carbon
文章编号: N19062809
期刊: Environmental Science & Technology
作者: Phoebe Zito, David C. Podgorski, Joshua Johnson, Huan Chen, Ryan P. Rodgers, François Guillemette, Anne M. Kellerman, Robert G. M. Spencer, Matthew A. Tarr
更新时间: 2019-06-28
摘要: To examine the molecular-level composition and acute toxicity per unit carbon of the petroleum-derived dissolved organic matter (DOM_HC) produced via photo-oxidation, heavy and light oils were irradiated over seawater with simulated sunlight. Increases in dissolved organic carbon concentrations as a function of time were associated with changes in the DOM_HC composition and acute toxicity per unit carbon. Parallel factor analysis showed that the fluorescent dissolved organic matter (FDOM) composition produced from the heavy oil became more blue-shifted over time, while the light oil produced a mixture of blue- and red-shifted components similar to FDOM signatures. Ultrahigh-resolution mass spectrometry reveals that the composition of the DOM_HC produced from both heavy and light oils was initially relatively reduced, with low O/C. With time, the composition of the DOM_HC produced from the heavy oil shifted to unsaturated, high-oxygen compounds, while that produced from the light oil comprised a range of high O/C aliphatic, unsaturated, and aromatic compounds. Microtox assays suggest that the DOM_HC initially produced is the most toxic (62% inhibition); however, after 24 h, a rapid decrease in toxicity decreased linearly to 0% inhibition for the heavy DOM_HC and 12% inhibition for the light DOM_HC at extended exposure periods.

25717. 题目: Reduced catalytic activity of an exogenous extracellular β-D-glucosidase due to adsorption on a model humic-clay complex and different soils under wetting and drying cycles
文章编号: N19062808
期刊: Biology and Fertility of Soils
作者: Pierluigi Mazzei, Alessandro Piccolo
更新时间: 2019-06-28
摘要: To ascertain the role of extracellular enzymes in soil biochemical reactions, we followed the changes in catalytic activity of an exogenous β-glucosidase (GLU) enzyme after its adsorption on a synthetic model humic-clay complex, composed by a lignite humic acid coupled by Al bridges to a Ca-montmorillonite (HM), and on three sterilised soils (DS, ISC and IST) with different properties. Either HM or the selected soils enabled a stable GLU adsorption that induced a significant decrease of GLU activity. In the case of soils, both the largest GLU adsorption and reduction of catalytic activity was observed for the clayey and organic matter-rich ISC soil. When the GLU-soil adducts were subjected to wetting and drying (W/D) cycles for 3 and 6 weeks, the enzyme activity was further largely reduced after the first 3 weeks of W/D, while the decrease progressed more slowly during the following 3 weeks. This was attributed to the increasing modification of the enzyme conformational structure due to formation of dispersive and hydrogen bonds with the inorganic and organic components of HM and soils. Our results showed that an exogenous extracellular enzyme, such as GLU, is quantitatively immobilised on model and real soil aggregates, and that the catalytic activity is significantly and progressively reduced by soil physical-chemical changes, thereby implying that soil biochemical transformations are to be accounted more to intracellular than extracellular enzymes.

25718. 题目: Identifying the Molecular Signatures of Agricultural Expansion in Amazonian Headwater Streams
文章编号: N19062807
期刊: Journal of Geophysical Research: Biogeosciences
作者: Robert G.M. Spencer, Anne M. Kellerman, David C. Podgorski, Marcia N. Macedo, KathiJo Jankowski, Darlisson Nunes, Christopher Neill
更新时间: 2019-06-28
摘要: Agricultural impacts on aquatic ecosystems are well studied; however, most research has focused on temperate regions, whereas the forefront of agricultural expansion is currently in the tropics. At the vanguard of this growth is the boundary between the Amazon and Cerrado biomes in Brazil, driven primarily by expansion of soybean and corn croplands. Here we examine the impacts of cropland expansion on receiving lowland Amazon Basin headwater streams in terms of dissolved organic carbon (DOC) concentration and dissolved organic matter (DOM) composition via ultrahigh‐resolution mass spectrometry. Streams draining croplands had lower DOC concentrations and DOM molecular signatures enriched in N‐ and S‐containing formula in comparison to forested streams. Cropland streams were also enriched in aliphatic, peptide‐like, and highly unsaturated and phenolic (low O/C) compound categories in comparison to forest streams (enriched in polyphenolics, condensed aromatics, and highly unsaturated and phenolic [high O/C] compound categories) indicative of the shifting of sources from organic‐rich surface soils and litter layers to autochthonous and more microbial biomass. Distinct molecular assemblages were strongly correlated with cropland and forest catchments, highlighting headwater streams as sentinels for detecting change. On investigation of unique molecular formulae present in only cropland sites, four cropland markers provided the ability to track agricultural impacts in the region. Overall, these patterns indicate reduced organic matter inputs in croplands and greater microbial degradation at these sites leading to declining DOC concentrations, and DOM of more microbial character in receiving streams that is more biolabile, with clear ramifications for downstream ecology and biogeochemical cycles.

25719. 题目: Removal of tylosin and copper from aqueous solution by biochar stabilized nano-hydroxyapatite
文章编号: N19062806
期刊: Chemosphere
作者: Zhen Li, Miao Li, Tongli Zheng, Yandan Li, Xiang Liu
更新时间: 2019-06-28
摘要: Antibiotics and heavy metals are frequently detected simultaneously in water environment. Effective elimination methods for antibiotics and heavy metals pollution should deserve our attention. This study investigates the adsorption performance of biochar modified with nano-hydroxyapatite (nHAP) on tylosin (TYL) and Cu from water simultaneously. Composite adsorbents of nHAP and biomass, derived from three waste residues, which were wood-processing residues (WR), wheat straw (WS) and Chinese medicine residues (CMR), were prepared. According to the results of orthogonal experiment, the degree of influence of the three factors on TYL and Cu were the pyrolysis temperature > the proportion of nHAP and biomass > the sources of biomass, and pyrolysis temperature> the sources of biomass> the proportion of nHAP and biomass, respectively. The optimum conditions for nHAP@biochar were screened. At pH < 7.0, the adsorption quality of TYL increased with pH increased, while at pH > 7.0, the adsorption quality of TYL changed slightly. At low pH, Cu and TYL could compete for the same adsorption sites on nHAP@biochars. The adsorption amount of TYL and Cu were both increased with increasing of the temperature. Compared with Langmuir model, Freundlich model could better fit the TYL adsorption on nHAP@biochars, with K_f values of TYL 62.35 (mmol/kg) (L/mmol)ⁿ (WR1) and 4.84 (mmol/kg) (L/mmol)ⁿ (CMR1), respectively.

25720. 题目: Detection of DNA damage formation by natural organic matter using EGFP-fused MDC1-expressing cells
文章编号: N19062805
期刊: Chemosphere
作者: Kentaro Misaki, Shun Matsuda, Tomonari Matsuda, Taketoshi Kusakabe, Yoshihisa Shimizu
更新时间: 2019-06-28
摘要: Studies have been conducted on the genotoxicity and carcinogenicity of disinfection by-products formed from natural organic matter (NOM) and mitigation effect for mutagens and clastogens by NOM. Whereas, reportedly, synthetic humic acid in high concentration has induced genotoxicity in human cells, and NOM samples have provoked mild oxidative and other physiological responses in aquatic organisms. Our group developed a novel detection method for DNA damage formation, namely enhanced green fluorescent protein (EGFP)-fused mediator of DNA damage checkpoint 1 (MDC1)-expressing human cells as simple and high-sensitive system. By using this method, a significant increase in the foci area was observed after 3 h, but not 24 h for 130 mgC L⁻¹ Suwannee River fulvic acid (SRFA), 38 mgC L⁻¹ humic acid (SRHA), and 19 mgC L⁻¹ NOM (SRNOM). The SRNOM concentration is the original environmental one; therefore, it was suggested that the formation and repair of DNA damage associated with γ-H2AX, a biomarker for DNA double-strand breaks by mild oxidative stress, in Suwannee River (SR) were detected for the first time. The increase in the foci area was not observed for 18 mgC L⁻¹ Lake Biwa fulvic acid (LBFA) and 50 mg L⁻¹ catechin after both 3 h and 24 h. The difference between the SR and Lake Biwa (LB) samples may result from the differences in their electron-accepting capacity. The application of this methodology is expected to elucidate oxidative stress and toxicological effects shortly and in detail for many water samples.