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17461. 题目: Projected trends of soil organic carbon stocks in Meghalaya state of Northeast Himalayas, India. Implications for a policy perspective
文章编号: N19090602
期刊: Science of The Total Environment
作者: Gaurav Mishra, Krishna Giri, Abhishek Jangir, Rosa Francaviglia
更新时间: 2019-09-06
摘要: Agricultural and forestry activities can affect soil organic carbon (SOC) levels and CO2 emissions from terrestrial ecosystems due to land use changes. In Northeast Himalayas, studies on the effects of forest conversion to temporary agricultural lands (jhum) on the loss of SOC and soil quality degradation have received the attention of policy makers and scientific research. Presently, local communities are now oriented towards the settled plantations systems with modern cash crops such as tea and rubber, that could act as potential SOC sinks. However, no information on SOC dynamics and simulation studies after land-use change from temporary agricultural lands (jhum) to settled cultivations and under climate change (CC) conditions are available for the Meghalaya state. Applying the RothC model, we focused on four different scenarios including the conversion from jhum to settled cultivation (rubber plantations and tea gardens), as well as continuous jhum cultivation and jhum to jhum with a period of secondary succession. Simulations under CC conditions indicated that SOC stocks significantly increased by 1.20 t C ha−1 yr−1 in tea gardens compared to rubber and jhum scenarios. Conversely, SOC stocks slightly decreased by 0.07 t C ha−1 yr−1 in rubber plantations, while the regrowth of a natural vegetation cover as secondary succession following the abandonment of the jhum fields, showed a lower SOC decrease (0.18 t C ha−1 yr−1) compared to the continuous jhum cultivation (0.24 t C ha−1 yr−1). Thus, for CC mitigation in a policy perspective, tea gardens could represent the best land use to store increasing amounts of SOC in the long-term perspective and optimize farmers' incomes, while in rubber plantations SOC storage is limited in time. Jhum cultivation can benefit in terms of productivity and profitability by extending the duration of the secondary succession period.
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17462. 题目: Autochthonous dissolved organic matter potentially fuels methane ebullition from experimental lakes
文章编号: N19090601
期刊: Water Research
作者: Yongqiang Zhou, Lei Zhou, Yunlin Zhang, Javier Garcia de Souza, David C. Podgorski, Robert G.M. Spencer, Erik Jeppesen, Thomas A. Davidson
更新时间: 2019-09-06
摘要: Shallow lakes are hotspots for carbon processing and important natural sources of methane (CH4) emission. Ebullitive CH4 flux may constitute the overwhelming majority of total CH4 flux, but the episodic nature of ebullition events makes determining both quantity and the controlling factors challenging. Here we used the world's longest running shallow-lake mesocosm facility, where the experimental treatments are low and high nutrients crossed with three temperatures, to investigate the quantity and drivers of CH4 ebullition. The mean CH4 ebullition flux in the high nutrient treatment (41.5 ± 52.3 mg CH4–C m−2 d−1) mesocosms was significantly larger than in the low nutrient treatment (3.6 ± 5.4 mg CH4–C m−2 d−1) mesocosms, varying with temperature scenarios. Over eight weeks from June to August covered here warming resulted in a weak, but insignificant enhancement of CH4 ebullition. We found significant positive relationships between ebullition and chlorophyll-a, dissolved organic carbon (DOC), biodegradable DOC, δ2H, δ18O and δ13C-DOC, autochthonous dissolved organic matter (DOM) fluorescent components, and a fraction of lipids, proteins, and lignins revealed using ultrahigh-resolution mass spectrometry, and a negative relationship between ebullitive CH4 flux and the percentage volume inhabited of macrophytes. A 24 h laboratory bio-incubation experiment performed at room temperature (20 ± 2 °C) in the dark further revealed a rapid depletion of algal-DOM concurrent with a massive increased CH4 production, whereas soil-derived DOM had a limited effect on CH4 production. We conclude that eutrophication likely induced the loss of macrophytes and increase in algal biomass, and the resultant accumulation algal derived bio-labile DOM potentially drives enhanced outgassing of ebullitive CH4 from the shallow-lake mesocosms.
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17463. 题目: Characterization of activated sludge flocs in membrane bioreactor: stable and unstable flocs
文章编号: N19090515
期刊: Environmental Science and Pollution Research
作者: Yifei Sang, Shengli Wang, Lianfa Song, Jingbo Guo, Lanhe Zhang, Haifeng Zhang
更新时间: 2019-09-05
摘要: In this study, the properties of unstable and stable flocs were investigated under the steady operation of a membrane bioreactor (MBR). The extracellular polymeric substances (EPS) composition, surface charge, and hydrophobicity of unstable and stable flocs were examined and compared. Interfacial interactions of the membrane with unstable flocs, unstable flocs themselves, and unstable and stable flocs were assessed using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) models. Cake layer resistance was found to contribute more than 80% of total resistance under steady operating conditions. Compared with stable flocs, unstable flocs possessed a higher level of EPS, more diverse protein, more negative charge, weaker hydrophobicity, and higher fouling potential. Thermodynamic analyses showed that unstable flocs had a higher adhesive strength (− 63.4 mJ/m2) with the membrane, lower self-cohesive strength (− 18.3 mJ/m2), and higher cohesive strength (− 54.3 mJ/m2) with stable flocs. Therefore, some unstable flocs remained on the membrane surface to form the cake layer due to their poor cohesion strength.

17464. 题目: Warm Events Induce Loss of Resilience in Organic Carbon Production in the Northeast Pacific Ocean
文章编号: N19090514
期刊: Global Biogeochemical Cycles
作者: Mariana B. Bif, Leo Siqueira, Dennis A. Hansell
更新时间: 2019-09-05
摘要: Between 2013 and 2016, a series of warm events induced by ocean‐atmosphere oscillations negatively impacted productivity in the northeast Pacific Ocean. For two consecutive winters (2013‐2014 and 2014‐2015), suppressed wind stress and warm near‐surface ocean temperature anomalies restricted vertical mixing between the surface and underlying nutrient‐enriched waters. Here we assess historical data of sea surface temperature and sea level pressure, along with nearly a decade of biogeochemical float data to evaluate the impact of these warm events on organic carbon production. The first stratified winter experienced little apparent impact on the magnitude of net organic carbon production in the growing season relative to prior years, suggesting an immediate resilience from reduced new nutrients, apparently depending on recycled iron. However, the subsequent winter experienced virtually zero net production; a loss of resilience, perhaps due to net iron removal with export, was evident. We find that consistently enhanced winter stratification decreased carbon production much more so than a single warm winter. This study highlights the sensitivity of marine productivity to ocean‐atmosphere oscillations, reducing deep ocean carbon sequestration with prolonged ocean warming and stratification.

17465. 题目: Influence of biogenic organics on the chemical composition of Arctic aerosols
文章编号: N19090513
期刊: Global Biogeochemical Cycles
作者: J.H. Choi, E. Jang, Y.J. Yoon, J.Y. Park, T.‐W. Kim, S. Becagli, L. Caiazzo, D. Cappelletti, R. Krejci, K. Eleftheriadis, K.‐T. Park, K.S. Jang
更新时间: 2019-09-05
摘要: We use an ultrahigh‐resolution 15 Tesla Fourier transform ion cyclotron resonance mass spectrometer (15T FT‐ICR MS) to elucidate the compositional changes in Arctic organic aerosols collected at Ny‐Ålesund, Svalbard, in May 2015. The FT‐ICR MS analysis of airborne organic matter provided information on the molecular compositions of aerosol particles collected during the Arctic spring period. The air mass transport history, combined with satellite‐derived geographical information and chlorophyll concentration data, revealed that the molecular compositions of organic aerosols drastically differed depending on the origin of the potential source region. The protein and lignin compound populations contributed more than 70% of the total intensity of assigned molecules when the air masses mainly passed over the ocean region. Interestingly, the intensity of microbe‐derived organics (protein and carbohydrate compounds) was positively correlated with the air mass exposure to phytoplankton biomass proxied as chlorophyll. Furthermore, the intensities of lignin and unsaturated hydrocarbon compounds, typically derived from terrestrial vegetation, increased with an increase in the advection time of the air mass over the ocean domain. These results suggest that the accumulation of dissolved biogenic organics in the Arctic Ocean possibly derived from both phytoplankton and terrestrial vegetation could significantly influence the chemical properties of Arctic organic aerosols during a productive spring period. The interpretation of molecular changes in organic aerosols using an ultrahigh‐resolution mass spectrometer could provide deep insight for understanding organic aerosols in the atmosphere over the Arctic and the relationship of organic aerosols with biogeochemical processes in terms of aerosol formation and environmental changes.

17466. 题目: Hydrologic shifts create complex transient distributions of particulate organic carbon and biogeochemical responses in beach aquifers
文章编号: N19090512
期刊: Journal of Geophysical Research: Biogeosciences
作者: Kyra H. Kim, Holly A. Michael, Erin K. Field, William J. Ullman
更新时间: 2019-09-05
摘要: Biogeochemical reactions within intertidal zones of coastal aquifers have been shown to alter the concentrations of terrestrial solutes prior to discharge to surface waters. In organic‐poor sandy aquifers, the input of marine organic matter from infiltrating seawater supports active biogeochemical reactions within the sediments. However, while the seasonality of surface water organic carbon concentrations (primary production) and groundwater mixing have been documented, there is limited understanding of the transience of various organic carbon pools (porewater particulate, dissolved, sedimentary) within the aquifer and how these relate to the location and magnitudes of biogeochemical reactions over time. To understand the relationship between changes in groundwater flow and the seasonal migration of geochemical patterns, beach porewater and sediment samples were collected and analyzed from six field sampling events spanning two years. While the seasonally‐dynamic patterns of aerobic respiration closely followed those of salinity, redox conditions and nutrient characteristics (distributions of N and P, denitrification rates) were unrelated to contemporaneous salinity patterns. This divergence was attributed to the spatial variations of reactive particulate organic carbon distributions, unrelated to salinity patterns, likely due to filtration, retardation, and immobilization dynamics during transport within the sediments. Results support a “carbon memory” effect within the beach, with the evolution and migration of reaction patterns relating to the distribution of these scattered carbon pools as more mobile solutes move over less mobile pools during changes in hydrologic conditions. This holds important implications for the prediction and quantification of biogeochemical reactions within beach systems.

17467. 题目: Response of organic carbon fractions and microbial community composition of soil aggregates to long-term fertilizations in an intensive greenhouse system
文章编号: N19090511
期刊: Journal of Soils and Sediments
作者: Lihong Tong, Ling Zhu, Yizhong Lv, Kun Zhu, Xiayan Liu, Rui Zhao
更新时间: 2019-09-05
摘要: Purpose: Soil organic carbon (SOC) content and stability, which are regulated by microbial communities, vary depending on aggregate size. The objectives of this study were to investigate the distribution of the SOC fraction and microbial community composition within soil aggregates when subjected to different fertilization treatments. Materials and methods: This study used high-throughput sequencing technology to analyze the soil microbial community distribution in different-sized aggregate fractions [> 2 mm (large macro-aggregates), 2–0.25 mm (small macro-aggregates), and < 0.25 mm (microaggregates)] when they were subjected to different fertilization treatments in a 16-year greenhouse experiment. The three treatments were chemical fertilizer (CF), 50% organic fertilizer + 50% chemical fertilizer (MF), and organic fertilizer (OF). Results and discussion: The results showed that the application of organic fertilizer significantly increased the soil organic carbon (SOC), dissolvable organic carbon (DOC), and microbial biomass carbon (MBC) contents and changed microbial community composition in all the different-sized soil aggregates. We observed that OF significantly reduced the relative abundance of bacterial communities in all aggregates and significantly increased the relative abundances of fungal communities in small macro-aggregates. The larger fungal communities in small macro-aggregates could promote soil aggregation and C sequestration. Conclusions: Organic fertilization increased the substrate contents in soil aggregates and enhanced soil aggregation and microbial activity in macro-aggregates, which are critical factors that facilitate C transformation and sequestration. These improvements resulted in significantly improved soil fertility and increased vegetable yield in the greenhouses.

17468. 题目: Evaluation of caffeine adsorption by MgAl-LDH/biochar composite
文章编号: N19090510
期刊: Environmental Science and Pollution Research
作者: Pollyanna Vanessa dos Santos Lins, Danielly Carlos Henrique, Alessandra Honjo Ide, Carmem Lúcia de Paiva e Silva Zanta, Lucas Meili
更新时间: 2019-09-05
摘要: In the present work, the composite MgAl-LDH/biochar using activated carbon from bovine bone as support for the layered double hydroxide particles was successfully synthesised and used as an alternative adsorbent for caffeine removal from water. Kinetic studies showed that the equilibrium was achieved in only 20 min of contact between the adsorbent and the adsorbate. The pseudo-first-order model represented the experimental data more satisfactorily (R2 = 0.95), suggesting a physical adsorption process. The isotherms were performed at three temperatures, in which it was observed the decrease in the adsorption in higher temperatures. It was obtained a maximum adsorption capacity of 26.219 mg/g at 40 °C, and the experimental data were better adjusted by Redlich–Peterson, R2 > 0.9942. In short, the study demonstrated that the composite was satisfactorily synthesised and its use in the caffeine removal was quite attractive, being a potential adsorbent for water treatment applications.

17469. 题目: Variations in the rate of accumulation and chemical structure of soil organic matter in a coastal peatland in Sarawak, Malaysia
文章编号: N19090509
期刊: CATENA
作者: Faustina E. Sangok, Yuki Sugiura, Nagamitsu Maie, Lulie Melling, Toshio Nakamura, Kosuke Ikeya, Akira Watanabe
更新时间: 2019-09-05
摘要: To determine the variation in the rate of accumulation and chemical structure of soil organic matter (SOM) in a tropical coastal peatland, series of soil cores samples were collected in the Maludam National Park, Sarawak, Malaysia and analyzed. Duplicate soil core samples were collected from three phasic communities in the peat swamp forests, Mixed Peat Swamp (MPS; depth of 50–450 cm), Alan Batu (ABt; depth of 200–700 cm), and Alan Bunga (ABg; depth of 200–800 cm), which were located at outer, middle, and inner sites on the peat dome. The 14C age of the SOM was determined at depths of every 50 or 100 cm and 4–6 samples from each profile were subjected to ramp cross polarization/magic angle spinning 13C nuclear magnetic resonance (NMR) analysis. The 14C age of SOM ranged from 1602 to 5162 years before the present (yBP), 1134–4043 yBP, and 928–3376 yBP in the cases of the MPS, ABt, and ABg forests, respectively. Those after calibration were in the ranges of 1482–5958 (MPS), 1322–4603 (ABt), and 837–3629 (ABg) yBP. The relationship between calibrated 14C age and soil depth, when regressed to a linear function with the constraint that the age of surface sediment is 0 year, showed that the rate of peat accumulation was 0.60 ± 0.01 (MPS), 1.5 ± 0.0 (ABt), and 1.9 ± 0.1 (ABg) mm y−1. However, in the case of the MPS forest, this rate was not constant but decreased toward the present. The 13C NMR results showed the decrease in the relative abundance of alkyl C and an increase in that of carbohydrate C with soil age/depth in the MPS forest soil profiles, suggesting an acceleration in the decomposition of SOM as the cause of the decrease in the rate of accumulation of the peat. Variations in the C composition of the other two forest soils with soil age were small. The relative content of aromatic C remained relatively constant, indicating that aromatic C is consistently a major component of the C pool throughout the peat soil layers.

17470. 题目: Comprehensive study on the formation of brominated byproducts during heat-activated persulfate degradation
文章编号: N19090508
期刊: Chemical Engineering Journal
作者: Ziying Wang, Yisheng Shao, Naiyun Gao, Bin Xu, Na An, Xian Lu
更新时间: 2019-09-05
摘要: Applying the highly oxidative sulfate radical (SO4) to pollutant degradation may cause it to react with the coexisting bromide (Br) to form undesired byproducts. This study investigated the transformation of Br during the degradation process of a contaminant (diethyl phthalate (DEP)) via heat-activated persulfate (PS). Dibromoacetonitrile and bromoform formed with Br and natural organic matter (NOM) in the solution, while only bromoform was detected without NOM. The formation of these brominated disinfection byproducts (Br-DBPs) can be ascribed to the reactions between the phenolic groups of DEP degradation intermediates or NOM and reactive bromine species (free bromine and radical bromine) generated through the oxidation of Br by SO4. Br-DBPs were degraded by excessive SO4, which indicates that organic bromine is a temporary phase during the turnover of Br. The time-dependent formation of organic and inorganic bromines suggests that Br may have cycled several times between organic and inorganic forms before eventually turning into bromate. The bromate formation showed a lag phase before continuously increasing. Generally, increasing the temperature, PS dosage, and Br and organic matter (DEP and NOM) concentrations increased the maximum concentration of Br-DBPs. Additionally, these reaction parameters facilitated bromate formation except for organic matter, whose inhibitory effect is probably due to the consumption of reactive species by organic matter and the generated superoxide anion. The total organic carbon concentration of the solution exhibited a relatively quick reduction followed by a slow decrease. These results highlight the potential risks of PS activation technologies and can help prevent such risks in actual practice.
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17471. 题目: Effect of swine biogas slurry application on soil dissolved organic matter (DOM) content and fluorescence characteristics
文章编号: N19090507
期刊: Ecotoxicology and Environmental Safety
作者: Lilong Yan, Qingping Liu, Cong Liu, Yue Liu, Mingyue Zhang, Yudan Zhang, Ying Zhang, Wanrong Gu
更新时间: 2019-09-05
摘要: The application of biogas slurry as an organic fertilizer is a promising method for utilizing breeding manure wastewater. At present, the impact of biogas slurry on the properties of organic matter in soil is not clear. In this study, a pot experiment in which chemical fertilizers were replaced with biogas slurry from a swine farm was performed. The fluorescence spectra combined with parallel factor (PARAFAC) analysis and principal component analysis (PCA) were used to explore the influence of biogas slurry on the protein and humic substance contents in the dissolved organic matter (DOM) in soil. The results showed that there were two proteins (component 3 (C3) and component 4 (C4)) and two humic substances ( component 1 (C1) and component 2 (C2)) in the DOM of the experimental soil. The application of swine biogas slurry can significantly increase the content of DOM in soil, but the increase was weakened with extended time. Compared with the CKA, the biogas slurry significantly increased the C1, C2, C3 and C4 contents in the initial stage by 116.17%, 76.41%, 578.71% and 278.13%, respectively. Within 28 days of planting corn, proteins with simple molecular structure in the DOM in the soil began to be transformed into humic substances with high molecular weight and more complex molecular structures. On the 60th day, the contents of C1 and C2 in the DOM of the treated treatments soil increased by 13.72%–34.40% and 5.05%–17.78% respectively, and tyrosine content decreased by 90.11%–94.41%. This study provides a new perspective on the effects of biogas slurry application on soil properties and sustainable utilization of soil.
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17472. 题目: The main factors controlling spatial variability of soil organic carbon in a small karst watershed, Guizhou Province, China
文章编号: N19090506
期刊: Geoderma
作者: Yunxing Bai, Yunchao Zhou
更新时间: 2019-09-05
摘要: Soil organic carbon (SOC) is an important component of the global carbon pool. Assessment of SOC in a karst mountainous area is a great challenge due to the high spatial heterogeneity in topography, land use and soil. This study used 2755 soil samples from a karst watershed in southwestern China to quantitatively study the spatial variability in SOC in this small karst watershed. The effects of parent soil material, soil type, land use, slope position, slope orientation and rock exposure rate on the spatial distributions of SOC in the karst watershed were compared by statistical modelling. The results showed that the SOC content in the study area was 25.01 g/kg, and the coefficient of variation was 55.26%, indicating moderate-intensity variation. The nugget coefficient C0/(C0 + C) was >0.70, and the spatial distribution of SOC was mainly affected by structural factors. Parent soil material, soil type, land use, slope position, slope direction and rock exposure rate had significant effects on the SOC (p < 0.001). The independent interpretation of SOC spatial variation by influencing factors is as follows: soil family level (37.40%) > land use (23.10%) > rock exposure rate (22.10%) > soil group level (17.50%) > parent material (10.90%) > slope position (7.20%) > slope direction (5.10%). Soils in the lower soil categories of the soil classification system were better able to reflect SOC spatial distributions. When soil family levels, land uses and rock exposure rates are used as predictors, 56.60% of SOC variability can be explained. Therefore, it is advisable to use a combination of soil family levels, land uses and rock exposure rates as the main controlling factor for predicting or assessing SOC spatial distributions in karst areas.
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17473. 题目: Biochar increases 15N fertilizer retention and indigenous soil N uptake in a cotton-barley rotation system
文章编号: N19090505
期刊: Geoderma
作者: Zhi Wang, Zhen Wang, Ying Luo, Ya-nan Zhan, Ya-li Meng, Zhi-guo Zhou
更新时间: 2019-09-05
摘要: Biochar amendments can modify fertilizer nitrogen (N) availability in soil and crop N uptake. However, how biochar addition affects crop N uptake and fertilizer N recovery under various N levels is not yet well understood. To address this question, we conducted a two-season [cotton (Gossypium hirsutum L.)-barley (Hordeum vulgare L.) rotation] pot experiment that included four N fertilizer rates (0, 75, 150, and 300 kg N ha1, supplied as urea-15N) combined with two straw-biochar rates (0 and 15 t ha−1). Soil properties, plant root morphology, N uptake, and biomass yield were studied. Biochar addition decreased soil inorganic N content but increased urea-N retention at cotton harvest, leading to 32% of the applied urea-N accumulating in soil compared with 27% without biochar, averaged across fertilizer N rates. Use of 15N fertilizer showed that biochar increased plant uptake of indigenous soil N, not fertilizer N. An obvious decrease in urea-15N recovery induced by biochar was observed at 75 kg N ha1, but not at 150 or 300 kg N ha1. The efficiency of urea-15N recovery by plants (15NRE, 34–45%), measured using the tracer method, was much lower than that measured using the traditional non-isotope method (NRE, 67–96%). At barley harvest, 2–5% of the urea-N, applied in the first season, was taken up by plants, and 12–19% remained in soils receiving biochar. We concluded that straw-biochar addition increased soil 15N fertilizer retention and plant N uptake of indigenous soil N, not fertilizer N, and the increased indigenous soil N uptake persisted into the second cropping season.
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17474. 题目: Glomalin-related soil protein affects soil aggregation and recovery of soil nutrient following natural revegetation on the Loess Plateau
文章编号: N19090504
期刊: Geoderma
作者: Hongfei Liu, Xiukang Wang, Chutao Liang, Zemin Ai, Yang Wu, Hongwei Xu, Sha Xue, Guobin Liu
更新时间: 2019-09-05
摘要: The glomalin-related soil protein (GRSP) is an important fraction of soil organic carbon (SOC) and soil nitrogen (N), and is important for stabilization of SOC and soil aggregates. However, the effects of natural restoration on the concentration and allocation of GRSP differ for different soil aggregate sizes, and how size further affects SOC and soil N restoration, and stabilization of SOC and soil aggregates is not well understood. Here, we present the first characterization of the distribution of GRSP fractions and soil nutrients in soil aggregates following natural restoration by choosing fields of 0, 7, 12, 17, 22, 32 years after cropland abandonment, and a natural grassland as reference. GRSP concentration increased most in microaggregates after 32 years of natural restoration. The processes of rapid accumulation of GRSP (22 to 32 years) occurred simultaneously with the formation of macroaggregates, reduction of microaggregates, and rapid increase of mean weight diameter (22 to 32-years). The soil aggregate stability and contents of GRSP, SOC, labile carbon, total N and phosphorus in each soil aggregate fraction significantly increased in the late stage of natural restoration (22 to 32 years). The most recalcitrant carbon fraction in microaggregates significantly increased between 7 and 32 years (0.887 g kg1). Our study suggests that abandoning farmland is effective for the restoration of GRSP, soil nutrients and structure and that microaggregates promote the accumulation of recalcitrant carbon and increase the stability of SOC largely through its ability to retain GRSP.

17475. 题目: Effects of intensities and cycles of heating on mineralization of organic matter and microbial community composition of a Mollisol under different land use types
文章编号: N19090503
期刊: Geoderma
作者: Andong Shi, Xuan Zhou, Shuihong Yao, Bin Zhang
更新时间: 2019-09-05
摘要: Soil heating at high temperatures was often found in greenhouse agriculture and high temperature extremes are predicted to occur more frequently in future climate. Yet, the influences of soil heating on soil organic matter decomposition, N mineralization, and the shift in microbial community composition are not well studied, particularly over multiple heating cycles and among different land use types. The main objectives of this study were 1) to investigate the effects of multiple heating cycles on soil respiration, N mineralization and soil microbial community composition, 2) to explore the relationships between soil microbial functions and community composition following heating cycles, and 3) to examine the influence of different land use types on soil microbial functions and community composition. The soils were sampled from an arable land, a forestland, and a grassland, and subjected to 25 °C constantly and to 40 or 50 °C for 18 h before being kept at 25 °C within 10 days for 3 cycles. At all temperature treatments, the forestland and the grassland had higher soil respiration rates, microbial biomasses and soil mineral N concentrations, compared to the arable land. In addition, the forestland and the grassland showed similar patterns of soil microbial community composition characterized by phospholipid fatty acid profiles (PLFA), but differed from that in the arable land. The soil respiration rates were enhanced by the increases in heating temperatures, and soil microbial biomass carbon (C) and N concentrations was reduced after heating at 40 °C, compared to these in the control treatment, and the reduction became more pronounced in heating treatment at 50 °C. With the increasing number of heating cycles, the soil respiration rate decreased after heating, but soil mineral N concentration was gradually enhanced, particularly in heating treatment at 50 °C. The principal component analysis of PLFAs demonstrated that soil microbial community composition shifted dramatically between days 21 and 30 (cycle 3), and between days 11 and 21 (between cycles 2 and 3, respectively), compared to that between days 1 and 11 (between cycles 1 and 2). The shift was consistent for all the land use types via PC1, but differed between the arable land and other land use types via PC2. Therefore, our findings suggested that cyclic heating drove changes in microbial composition, uncoupled soil C and N cycling during soil organic matter decomposition and could lead to a rapid decline of soil fertility and environmental quality under heating stresses.

17476. 题目: Removal of Arsenic(III) from water using magnetite precipitated onto Douglas fir biochar
文章编号: N19090502
期刊: Journal of Environmental Management
作者: Chanaka M. Navarathna, Akila G. Karunanayake, Sameera R. Gunatilake, Charles U. Pittman, Felio Perez, Dinesh Mohan, Todd Mlsna
更新时间: 2019-09-05
摘要: Magnetic Fe3O4/Douglas fir biochar composites (MBC) were prepared with a 29.2% wt. Fe3O4 loading and used to treat As(III)-contaminated water. Toxicity of As(III) (inorganic) is significantly greater than As(V) and more difficult to remove from water. Removal efficiency was optimized verses pH, contact time and initial concentration. Column sorption and regeneration were also studied. Adsorption kinetics data best fitted the pseudo second order model (R2 > 0.99). Adsorption was analyzed with three isotherm models at 20, 25 and 40 °C. The Sips isotherm showed the best fit at 25 °C with a 5.49 mg/g adsorption capacity, which is comparable with other adsorbents. MBC gave faster kinetics (~1–1.5 h) at pH 7 and ambient temperature than previous adsorbents. The Gibbs free energy (ΔG) of this spontaneous As(III) adsorption was −35 kJ/mol and ΔH = 70 kJ/mol was endothermic. Experiments were performed on industrial and laboratory wastewater samples in the presence of other co-existing contaminants (pharmaceutical residues, heavy metals ions and oxi-anions). The composite reduced the arsenic concentrations below the WHO's safe limit of 0.2 mg/L for waste water discharge. X-ray photoelectron spectroscopy (XPS) studies found As(III) and less toxic As(V) on Fe3O4 surfaces indicating adsorbed (or adsorbing) As(III) oxidation occurred upon contact with O2 and possibly dissolved Fe(III) or upon drying under oxic conditions. Under anoxic conditions magnetite to maghemite transformation drives the oxidation. A pH-dependent surface chemisorption mechanism was proposed governing adsorption aided by XPS studies vs pH.
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17477. 题目: pH and exchangeable aluminum are major regulators of microbial energy flow and carbon use efficiency in soil microbial communities
文章编号: N19090501
期刊: Soil Biology and Biochemistry
作者: Davey L. Jones, Emily C. Cooledge, Frances C. Hoyle, Robert I. Griffiths, Daniel V. Murphy
更新时间: 2019-09-05
摘要: The microbial partitioning of organic carbon (C) into either anabolic (i.e. growth) or catabolic (i.e. respiration) metabolic pathways represents a key process regulating the amount of added C that is retained in soil. The factors regulating C use efficiency (CUE) in agricultural soils, however, remain poorly understood. The aim of this study was to investigate substrate CUE from a wide range of soils (n = 970) and geographical area (200,000 km2) to determine which soil properties most influenced C retention within the microbial community. Using a 14C-labeling approach, we showed that the average CUE across all soils was 0.65 ± 0.003, but that the variation in CUE was relatively high within the sample population (CV 14.9%). Of the major properties measured in our soils, we found that pH and exchangeable aluminum (Al) were highly correlated with CUE. We identified a critical pH transition point at which CUE declined (pH 5.5). This coincided exactly with the point at which Al3+ started to become soluble. In contrast, other soil factors [e.g. total C and nitrogen (N), dissolved organic C (DOC), clay content, available calcium, nitrogen, phosphorus (P) and sulfur (S), total base cations] showed little or no relationship with CUE. We also found no evidence to suggest that nutrient stoichiometry (C:N, C:P and C:S ratios) influenced CUE in these soils. Based on current evidence, we postulate that the decline in microbial CUE at low pH and high Al reflects a greater channeling of C into energy intensive metabolic pathways involved in overcoming H+/Al3+ stress (e.g. cell repair and detoxification). The response may also be associated with shifts in microbial community structure, which are known to be tightly associated with soil pH. We conclude that maintaining agricultural soils above pH 5.5 maximizes microbial energy efficiency.
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17478. 题目: Peroxymonosulfate Oxidizes Amino Acids in Water without Activation
文章编号: N19090417
期刊: Environmental Science & Technology
作者: Mercedes Ruiz, Yi Yang, Christian A. Lochbaum, Daniel Graham Delafield, Joseph J. Pignatello, Lingjun Li, Joel A. Pedersen
更新时间: 2019-09-04
摘要: A variety of peptidic and proteinaceous contaminants (e.g., proteins, toxins, pathogens) present in the environment may pose risk to human health and wildlife. Peroxymonosulfate is a strong oxidant (EH0 = 1.82 V for HSO5–, the predominant species at environmental pH values) that may hold promise for the deactivation of proteinaceous contaminants. Relatively little quantitative information exists on the rates of peroxymonosulfate reactions with free amino acids. Here, we studied the oxidation of 19 of the 20 standard proteinogenic amino acids (all except cysteine) by peroxymonosulfate without explicit activation. Reaction half-lives at pH 7 ranged from milliseconds to hours. Amino acids possessing sulfur-containing, heteroaromatic, or substituted aromatic side chains were the most susceptible to oxidation by peroxymonosulfate, with rates of transformation decreasing in the order methionine > tryptophan > tyrosine > histidine. The rate of tryptophan oxidation did not decrease in the presence of an aquatic natural organic matter. Singlet oxygen resulting from peroxymonosulfate self-decomposition, while detected by electron paramagnetic resonance spectroscopy, was unlikely to be the principal reactive species. Our results demonstrate that peroxymonosulfate is capable of oxidizing 19 amino acids without explicit activation and that solvent-exposed methionine and tryptophan residues are likely initial targets of oxidation in peptides and proteins.

17479. 题目: Antimonite Binding to Natural Organic Matter: Spectroscopic Evidence from a Mine Water Impacted Peatland
文章编号: N19090416
期刊: Environmental Science & Technology
作者: Johannes Besold, Anne Eberle, Vincent Noël, Katharina Kujala, Naresh Kumar, Andreas C Scheinost, Juan Lezama Pacheco, Scott Fendorf, Britta Planer-Friedrich
更新时间: 2019-09-04
摘要: Peatlands and other wetlands are sinks for antimony (Sb), and solid natural organic matter (NOM) may play an important role in controlling Sb binding. However, direct evidence of Sb sequestration in natural peat samples is lacking. Here, we analyzed solid phase Sb, iron (Fe), and sulfur (S) as well as aqueous Sb speciation in three profiles up to a depth of 80 cm in a mine water impacted peatland in northern Finland. Linear combination fittings of extended X-ray absorption fine structure spectra showed that Sb binding to Fe phases was of minor importance and observed only in the uppermost layers of the peatland. Instead, the dominant (to almost exclusive) sequestration mechanism was Sb(III) binding to oxygen-containing functional groups, and at greater depths, increasingly Sb(III) binding to thiol groups of NOM. Aqueous Sb speciation was dominated by antimonate, while antimonite concentrations were low, further supporting our findings of much higher reactivity of Sb(III) than Sb(V) toward peat surfaces. Insufficient residence time for efficient reduction of antimonate to antimonite currently hinders higher Sb removal in the studied peatland. Overall, our findings imply that Sb(III) binding to solid NOM acts as an important sequestration mechanism under reducing conditions in peatlands and other high-organic matter environments.

17480. 题目: Natural groundwater nutrient fluxes exceed anthropogenic inputs in an ecologically impacted estuary: lessons learned from Mobile Bay, Alabama
文章编号: N19090415
期刊: Biogeochemistry
作者: Daniel Montiel, Alexander F. Lamore, Jackson Stewart, W. Joe Lambert, Jacob Honeck, Yuehan Lu, Olivia Warren, Dini Adyasari, Nils Moosdorf, Natasha Dimova
更新时间: 2019-09-04
摘要: In this study we evaluated the magnitude and seasonal variations of natural and anthropogenic fluxes of inorganic (NO3, NH4+, and PO43−) and organic (DON and dissolved organic carbon) nutrients delivered by submarine groundwater discharge (SGD) and rivers to the fourth largest estuary in the USA, Mobile Bay in Alabama. To identify the sources of SGD-nutrient in the estuary and their subsurface biogeochemical transformation, we applied a multi-method approach that combines geochemical nutrient (N and P) mass-balances, stable isotopes (nitrate (updelta^{15} { ext{N}}_{{{ ext{NO}}_{3} }}) and (updelta^{18} { ext{O}}_{{{ ext{NO}}_{3} }}) and sediment organic matter δ13Corg and δ15Norg) signatures, microbial sequencing analyses, dissolved organic matter source-composition, and shallow estuarine sediment lithological analyses. We found that during dry seasons SGD delivered nearly a quarter of the total nutrient inputs to Mobile Bay. These SGD fluxes were anoxic and N was delivered to the bay almost entirely as NH4+ and DON, which represented more than half of the total NH4+ and almost one fifth of the total DON inputs to the bay. We further observed that these significant SGD-derived N fluxes occurred exclusively to the east shore of Mobile Bay, historically impacted by hypoxia and large-scale fish kills known as “Jubilees”. We demonstrate here that although the Mobile Bay coastal area is largely developed and anthropogenic influences are well documented, a shallow peat layer identified only on the east shore serves as the main source of the exceptionally high NH4+ and DON fluxes. We found that the high groundwater NO3 concentrations observed further inland from over-fertilization also identified by previous studies, decreased dramatically as groundwater percolated through the intertidal zone of the coastal aquifer. The microbial community identified in the coastal sediments suggests that denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were the main processes responsible for this extensive removal and transformation of anthropogenic N, respectively. Furthermore, we found no significant anthropogenic inputs from manure or sewage waste to the bay. These findings show that natural sources of nutrients can outcompete anthropogenic inputs despite extensive development of the coastal area. We hypothesize that similar subsurface biogeochemical nutrient transformations can occur in other shallow estuaries of the northern Gulf of Mexico and worldwide.

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