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23801. 题目: Humic substances from green waste compost: An effective washing agent for heavy metal (Cd, Ni) removal from contaminated sediments 文章编号: N18120504 期刊: Journal of Hazardous Materials 作者: Siyu Zhang, Jia Wen, Yi Hu, Ying Fang, Haibo Zhang, Lang Xing, Yongxu Wang, Guangming Zeng 更新时间: 2018-12-05 摘要: In this study, humic substances (HS) selected from 8 composting groups (peanut straw, sesame straw, corn straw and deciduous leaves, with or without grape marc) were used to remove Cd and Ni from artificially contaminated sediments. Sesame straw compost appeared to have the highest removal capacity for heavy metals through a series comparison on Cd removal efficiency, yield of HS and fulvic acids (FA), and seed germination index. The selected sesame HS was further used to wash two contaminated sediments of varying properties (a clay type for sediment 1 and a silty loam for sediment 2). Batch desorption experiments were conducted to determine the optimum HS concentration, equilibrium time, pH, solid-to-liquid ratio, and washing frequency. Under optimum conditions, a triple washing removed 74.16% of Cd and 42.91% of Ni from sediment 1, and 86.88% of Cd and 43.84% of Ni from sediment 2, respectively, whereas a commercial FA only achieved half of the efficiency. After washing, both sediments were identified with increased contents of total organic matter total nitrogen and phosphorus. Therefore, HS from the sesame straw compost is a cost-effective, efficient and environmental-friendly washing agent to remove heavy metals from contaminated sediments. |
23802. 题目: Exploration of the formation of self-forming dynamic membrane in an upflow anaerobic sludge blanket reactor 文章编号: N18120503 期刊: Separation and Purification Technology 作者: Muhammad Ahmar Siddiqui, Ji Dai, Dao Guan, Guanghao Chen 更新时间: 2018-12-05 摘要: Self-forming dynamic membrane bioreactor (SFDMBR) technology has drawn increased attention recently, especially for its potential application in anaerobic conditions to retain slow growing sludge in the system. To attain maximum sludge retention, quick development of a self-forming dynamic membrane (SFDM) is deemed necessary. A lab-scale upflow anaerobic sludge blanket (UASB) reactor with a side-stream anaerobic SFDMBR was used in this study to investigate the factors affecting the successful formation of a SFDM and identify the indicators of success. The SFDM formed successfully within 60 to 90 min to produce permeates of less than 10 NTU after system optimization. The short formation period and low permeate turbidity provide strong support for the potential of retaining a large amount of sludge in the UASB reactor. The thickness and wet density of the SFDM increased continuously with the decrease in surface area during the formation period. Extracellular polymeric substances (EPS) played an essential role in SFDM formation. Humic acid was the dominant EPS in the sludge, but it did not significantly affect the SFDM formation. Even though polysaccharides only represented 3.7% of the total EPS in sludge, it accumulated on the supporting material as a percentage of the total EPS increased significantly from 6.2% after 60 min to 10.8% after 720 min. Therefore, polysaccharides were the primary reason for the formation of the SFDM. β-polysaccharides were more important because it mainly accumulated on the fiber of the supporting material. 图文摘要:
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23803. 题目: Mineral identity, natural organic matter, and repeated contaminant exposures do not affect the carbon and nitrogen isotope fractionation of 2,4-dinitroanisole during abiotic reduction 文章编号: N18120502 期刊: Environmental Science: Processes Impacts 作者: Matthew J. Berens, Bridget A. Ulrich, Jennifer H. Strehlau, Thomas B. Hofstetter, William A. Arnold 更新时间: 2018-12-05 摘要: The recent development of insensitive munitions, such as 2,4-dinitroanisole (DNAN), as components of military explosives has generated concern for potential subsurface contamination and created a need to fully characterize their transformation processes. Compound specific isotope analysis (CSIA) has proven to be a useful means of assessing transformation pathways according to characteristic stable isotope fractionation patterns. The C and N isotope fractionation of DNAN associated with abiotic and enzymatic hydrolysis was recently assessed. The extent to which DNAN isotope fractionation will be affected by other potentially competing transformation pathways known for nitroaromatic compounds (e.g., reduction) and if previous knowledge can be extrapolated to other environmental matrices remains to be understood. Here, we investigated the C and N isotope fractionation and reaction rate constants of DNAN during abiotic reduction mediated by mineral-associated Fe(II) species as a function of mineral type, natural organic matter presence, and repeated exposures to DNAN. Though rate constants varied, N and C apparent kinetic isotope effects (AKIEs) remained consistent across all experiments (averaged values of 15N-AKIE = 1.0317 ± 0.0064 and 13C-AKIE = 1.0008 ± 0.0005) and revealed significant 15N- and minimal 13C-enrichment in agreement with previous work on nitroaromatic compounds. Moreover, the observed fractionation was clearly distinct from trends for abiotic and enzymatic hydrolysis. This study provides a strengthened basis for the use of CSIA as a robust tool for monitoring DNAN degradation in complex environmental matrices as a component of future remediation efforts. 图文摘要:
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23804. 题目: Soil formation on calcium carbonate-rich parent material in the outer Carpathian Mountains – A case study 文章编号: N18120501 期刊: CATENA 作者: Joanna Beata Kowalska, Tomasz Zaleski, Agnieszka Józefowska, Ryszard Mazurek 更新时间: 2018-12-05 摘要: In this study, ten stratified calcium carbonate–rich soil profiles from the Polish Outer Carpathians were investigated in order to identity the influence of parent material variability and slope processes on soil diversity and their evolution. Moreover, we evaluated the morphological and physico-chemical soil properties to recognize the diagnostic horizons and classification of such soils. While it is usually thought that carbonate-rich soils are considered as formed in situ, these study soils clearly presented layering and contribution of materials, as they were developed from mixed substrates of different origin, e.g. as the result of mass movements and possible aeolian silt contribution. Irrespective of the type of parent material, every investigated soil showed traces of slope processes, resulting in heterogeneous soil profiles. Further, a few different patterns of primary calcium carbonate arrangement were found. In general, the studied soils were characterized by enrichment with calcium carbonate, not only due to inheritance from calcium carbonate–rich parent material but also translocation of calcium carbonate within soil profiles, the latter depending on soil stratification.Based on the obtained results, four pathways of soil evolution were formulated. Leptosols, which represent initial calcium carbonate–rich soils, may evolve in different directions. First, formation of the thick layer suitable for cambic horizon development under deciduous forests, which enables the classification of such soils as Cambisols, depends on slope processes and allochthonous material deposition. In turn, the decrease of mineralization rates for organic matter, delivery of soil material from the upper parts of the slope as well as mixing of organic matter by mesofauna result in the formation of mollic horizons and transformation of Leptosols into Phaeozems. Further erosion and redeposition of fine soil material provide two types of slope sediments: i) those with silt loam texture dominance, and ii) clay loams interstratified with silty substrates. The first type of sediments are more suitable for water percolation, and after carbonate leaching clay dispersion and translocation occur. In such materials, Luvisols may develop. Sediments with a prevalence of clay loam aided Stagnosol formation, in which pools of carbonates were stabilized due to the reduction of water percolation, leading to stagnation. 图文摘要:
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23805. 题目: A conceptual framework to study soil aggregate dynamics 文章编号: N18120410 期刊: European Journal of Soil Science 作者: C. O. Márquez, V. J. García, R. C. Schultz, T. M. Isenhart 更新时间: 2018-12-04 摘要: The objective of this study was to develop a conceptual framework to study soil aggregate dynamics through the integration of aggregation, disruption, stabilization and destabilization processes of soil constituent units. We used aggregate‐size distribution and water stability of macroaggregates to evaluate changes in soil aggregates in two ecosystems where one is the ‘reference’ state and the other is the ‘new’ state. The framework was validated with data from a (i) non‐buffered annual row crop (ARC) system, (ii) no‐till (NT) system and (iii) bare fallow (BF) system. The dynamics of soil aggregates in the ARC were dominated by the disruption of aggregates (the aggregation–disruption index (ADI) was –0.08), in NT by the aggregation process (ADI = 0.03) and in BF by the disruption of aggregates (ADI = –0.20). Three pathways were observed: (i) expression of the aggregation process essential in reestablishing soil structure and functionality, (ii) expression of the disruption process critical in the destruction of soil structure and (iii) prevalence of mixed behaviour where the dominant process depended on the relative rate of aggregation and disruption. The proposed framework and study of the carbon associated with aggregates could pave the way to the development of a methodology for the quantitative study of soil organic carbon (SOC) dynamics, carbon inputs (outputs), soil carbon fractions, and edaphic and biotic conditions that regulate SOC dynamics. |
23806. 题目: Nitrogen removal in response to the varying C/N ratios in subsurface flow constructed wetland microcosms with biochar addition 文章编号: N18120409 期刊: Environmental Science and Pollution Research 作者: Xu Zhou, Shubiao Wu, Ruigang Wang, Haiming Wu 更新时间: 2018-12-04 摘要: Biochar as a substrate has great potential to promote pollutant removal efficiency in subsurface flow constructed wetlands (SSFCWs). However, information about the effect of different influent C/N ratios on treatment efficiency in SSFCWs with biochar is still scarce. In this study, SSFCW microcosms added with and without biochar were performed to investigate comparatively nitrogen removal in response to the domestic wastewater with varying C/N ratios. The results demonstrated that nitrogen removal increased at influent C/N ratios from1 to 3, and then decreased with the rising influent C/N ratios from 3 to 15 in different SSFCWs. Much higher removal efficiencies for COD (92%), NH4+-N (50%), and TN (50%) were obtained in the biochar-added SSFCW especially at the C/N ratio of 3 when comparing to CW without biochar. The higher pollutants removal ability of biochar-added SSFCWs was mainly attributed to the stronger adsorption ability in the porous biochar. However, poor nitrification was observed at various influent C/N ratios in SSFCWs with and without biochar due to lack of enough oxygen. This study supported that the use of biochar could increase the treatment performance in SSFCWs under various influent C/N ratios. |
23807. 题目: Insight into transformation of dissolved organic matter in the Heilongjiang River 文章编号: N18120408 期刊: Environmental Science and Pollution Research 作者: Jianhong Shi, Yue Zhao, Dan Wei, Duoying Zhang, Zimin Wei, Junqiu Wu 更新时间: 2018-12-04 摘要: Heilongjiang is a “browning” river that receives substantial terrestrial organic matter, where reactivity of dissolved organic matter (DOM) may have important effect on ecosystem function and carbon biogeochemical cycle. However, little is known about microbial transformations of different DOM components, which could provide valuable insight into biogeochemical reactivity of DOM. In this study, bioavailability experiments were conducted for 55 days to determine changes of different DOM components by microbial transformations. Labile matter (C1) was detected only in initial DOM, and tryptophan-like substances (C4) were observed from day 5 onwards. Thus, three individual components were identified at each sampling time of the bioavailability experiment. The increase of Fmax in DOM components revealed that microbial humic-like substances (C2), terrestrial humic-like substances (C3), and C4 were produced by microbial transformation, especially in the spring samples. Further, two-dimensional correlation spectroscopy (2D-COS) indicated that shorter wavelength tryptophan-like and microbial humic-like substances can be degraded by microbes or transformed into longer wavelength complex substances. Relatively simple microbial humic-like substances were preferentially produced compared to complex terrestrial humic-like substances. The results make sense to understand the biogeochemical cycling and environmental effects of DOM in the Heilongjiang River. |
23808. 题目: Electronic Structure Modulation of Graphitic Carbon Nitride by Oxygen Doping for Enhanced Catalytic Degradation of Organic Pollutants through Peroxymonosulfate Activation 文章编号: N18120407 期刊: Environmental Science & Technology 作者: Yaowen Gao, Yue Zhu, Lai Lyu, Qingyi Zeng, Xueci Xing, Chun Hu 更新时间: 2018-12-04 摘要: Oxygen-doped graphitic carbon nitride (O–CN) was fabricated via a facile thermal polymerization method using urea and oxalic acid dihydrate as the graphitic carbon nitride precursor and oxygen source, respectively. Experimental and theoretical results revealed that oxygen doping preferentially occurred on the two-coordinated nitrogen positions, which create the formation of low and high electron density areas resulting in the electronic structure modulation of O–CN. As a result, the resultant O–CN exhibits enhanced catalytic activity and excellent long-term stability for peroxymonosulfate (PMS) activation toward the degradation of organic pollutants. The O–CN with modulated electronic structure enables PMS oxidation over the electron-deficient C atoms for the generation of singlet oxygen (1O2) and PMS reduction around the electron-rich O dopants for the formation of hydroxyl radical (•OH) and sulfate radical (SO4•–), in which 1O2 is the major reactive oxygen species, contributing to the selective reactivity of the O–CN/PMS system. Our findings not only propose a novel PMS activation mechanism in terms of simultaneous PMS oxidation and reduction for the production of nonradical and radical species but also provide a valuable insight for the development of efficient metal-free catalysts through nonmetal doping toward the persulfate-based environmental cleanup. 图文摘要:
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23809. 题目: Improvement of mining soil properties through the use of a new bio-conditioner prototype: a greenhouse trial 文章编号: N18120406 期刊: Journal of Soils and Sediments 作者: Manuel Pantoja-Guerra, Ramiro Ramirez-Pisco, Nelson Valero-Valero 更新时间: 2018-12-04 摘要: Purpose: The effect of a prototype of humic bio-conditioner (H-BC) was assessed on the development of edaphic properties and the growth of maize plants in an edaphic material used as topsoil in the rehabilitation of soils in a coal mine in Colombia. Materials and methods: The trial was carried out in a greenhouse, using pots with edaphic material treated with the addition of doses equivalent to 0 (control), 1, 2, and 4 Mg.ha−1 of H-BC; maize seeds were sown and followed up on for 60 days. Plant growth and soil biological, chemical, and physical variables were registered. Results and discussion: The 4-Mg.ha−1 treatment maintained a significantly higher enzymatic activity than the control on day 60. The respiration of the soil treated with H-BC increased significantly, with the 4-Mg.ha−1 treatment standing out. The 2-Mg.ha−1 treatment induced the most noticeable changes in soil metabolic activity profiles. Increases in root and leaf development were observed in the treatment with 4 Mg.ha−1; apparently, this dose improved the absorption of Ca, K, and S by plants; the physical and soil aggregation indices increased significantly with 4 Mg.ha−1. Conclusions: The results indicate that H-BC can be an alternative as an enhancer of the edaphic material used in soil rehabilitation processes. |
23810. 题目: Flocculation-dewatering behavior of waste activated sludge particles under chemical conditioning with inorganic polymer flocculant: Effects of typical sludge properties 文章编号: N18120405 期刊: Chemosphere 作者: Peng Yang, Dandan Li, Weijun Zhang, Ning Wang, Zhaoyi Yang, Dongsheng Wang, Teng Ma 更新时间: 2018-12-04 摘要: The effects of typical sludge properties (solids concentration, soluble extracellular polymeric substances (SEPS) and alkalinity) on waste activated sludge flocculation-dewatering behavior and mechanisms under chemical conditioning with inorganic polymer flocculant-polyaluminum chloride (PACl) were systematically examined in this study. The results indicated that increasing the solids concentration was conductive to sludge dewatering and could greatly decrease the PACl demand in chemical conditioning. Solids concentration had important effects on properties of sludge floc flocculated with PACl, floc structure was more compact and of low EPS concentration at high solids concentrations. High levels of SEPS were adverse to sludge dewaterability after flocculation with PACl, since the SEPS could interact with hydroxy-aluminium through complexation and increase the demand of coagulants. In addition, advantageous speciations of hydroxy-aluminium were rapidly converted into amorphous hydroxides with low flocculation activity at high alkalinity, so the sludge conditioning efficiency was greatly declined. At the same time, the dominant mechanism of chemical conditioning was changed from charge neutralization to sweep coagulation. Finally, this study provides control strategies at complex sludge properties for improving the effectiveness of PACl as a chemical conditioner. 图文摘要:
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23811. 题目: Influence of biochar on physico-chemical and microbial community during swine manure composting process 文章编号: N18120404 期刊: Journal of Environmental Management 作者: Balasubramani Ravindran, Dinh Duc Nguyen, Dhiraj Kumar Chaudhary, Soon Woong Chang, Jaisoo Kim, Sang Ryong Lee, JoungDu Shin, Byong-Hun Jeon, SeokJoo Chung, JaeJoung Lee 更新时间: 2018-12-04 摘要: Excessive nutrients and toxic gas emissions from animal manure management are of great global concern, with negative environmental and economic consequences worldwide. Due to biochar recalcitrance and sorption properties, this study investigated the effect of the biochar(BC) derived from bamboo, amendment on swine manure(SM) composting efficiency through physical, physio-chemical, gaseous emissions, microbiological, and phytotoxic analysis during the 56 day process of in-vessel composting. The treatments were set-up from different ratios of biochar to swine manure mixed with sawdust(SD)(i.e. SM + SD + 3%BC(T1), SM:SD + 5 %BC(T2) and SM:SD + 10 %BC (T3)), while treatment without biochar amendment was used as a control, SM:SD(C). The results showed that, compared to the control, biochar amended compost mixtures had significantly reduced (p ≤ 0.05) bulk density, organic matter(OM), C:N ratio, NH3 emission, pathogenic microorganisms, and phytotoxicity effect (Cress seed, Lepidium sativum Linn.). On the other hand, biochar amendment mixtures had increased total porosity, water holding capacity, rapid thermophilic temperature, and nitrate nitrogen. However, with the most prominent effects in terms of the nutrient quality and degradation rate of compost mixtures, the amendment of 10% biochar is recommended for swine manure management through the composting process. |
23812. 题目: Southern Ocean controls of the vertical marine δ13C gradient – a modelling study 文章编号: N18120403 期刊: Biogeosciences 作者: Anne L. Morée, Jörg Schwinger, and Christoph Heinze 更新时间: 2018-12-04 摘要: δ13C, the standardised 13C∕12C ratio expressed in per mille, is a widely used ocean tracer to study changes in ocean circulation, water mass ventilation, atmospheric pCO2, and the biological carbon pump on timescales ranging from decades to tens of millions of years. δ13C data derived from ocean sediment core analysis provide information on δ13C of dissolved inorganic carbon and the vertical δ13C gradient (i.e. Δδ13C) in past oceans. In order to correctly interpret δ13C and Δδ13C variations, a good understanding is needed of the influence from ocean circulation, air–sea gas exchange and biological productivity on these variations. The Southern Ocean is a key region for these processes, and we show here that Δδ13C in all ocean basins is sensitive to changes in the biogeochemical state of the Southern Ocean. We conduct a set of idealised sensitivity experiments with the ocean biogeochemistry general circulation model HAMOCC2s to explore the effect of biogeochemical state changes of the Southern and Global Ocean on atmospheric δ13C, pCO2, and marine δ13C and Δδ13C. The experiments cover changes in air–sea gas exchange rates, particulate organic carbon sinking rates, sea ice cover, and nutrient uptake efficiency in an unchanged ocean circulation field. Our experiments show that global mean Δδ13C varies by up to about ±0.35‰ around the pre-industrial model reference (1.2‰) in response to biogeochemical change. The amplitude of this sensitivity can be larger at smaller scales, as seen from a maximum sensitivity of about −0.6‰ on ocean basin scale. The ocean's oldest water (North Pacific) responds most to biological changes, the young deep water (North Atlantic) responds strongly to air–sea gas exchange changes, and the vertically well-mixed water (SO) has a low or even reversed Δδ13C sensitivity compared to the other basins. This local Δδ13C sensitivity depends on the local thermodynamic disequilibrium and the Δδ13C sensitivity to local POC export production changes. The direction of both glacial (intensification of Δδ13C) and interglacial (weakening of Δδ13C) Δδ13C change matches the direction of the sensitivity of biogeochemical processes associated with these periods. This supports the idea that biogeochemistry likely explains part of the reconstructed variations in Δδ13C, in addition to changes in ocean circulation. 图文摘要:
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23813. 题目: Small microbialites from the basal Triassic mudstone (Tieshikou, Jiangxi, South China): Geobiologic features, biogenicity, and paleoenvironmental implications 文章编号: N18120402 期刊: Palaeogeography, Palaeoclimatology, Palaeoecology 作者: Hao Yang, Zhong-Qiang Chen, Stephen Kershaw, Wei Liao, Enlü Lü, Yuangen Huang 更新时间: 2018-12-04 摘要: We report small microbialites from the calcareous mudstone slightly above the Permian–Triassic boundary (PTB) in the Tieshikou section, southern Jiangxi Province, South China. The newly found microbialite is a bowl-like structure, which contrasts with the surrounding calcareous mudstone. The small microbialite is composed of columnar forms and fan-shaped structures. Mini-columnar structures resemble mini stromatolites. In plane view, most branches are patchy or strip-shaped, with clotted structures, resembling that of a thrombolite. Fan-shaped cement precipitates are comprised of multiple crystal fans that have a radiating texture and that show distinct growth laminae. The radiating fabrics are represented by rod-shaped filaments under SEM, which are interpreted as calcified trichomes/filaments. Prominent micropores occur within the rods, and they may be the plane views of multiple sheaths of the false branching zone of trichomes. Thus, both the columnar forms and radiating fans are probably microbial in origin. Moreover, three types of nano-sized structures: intraparticle micropores, fibrous biofilms, and filamentous sheaths are also pronounced in both the columnar structures and cement fans of the Tieshikou microbialite, all suggestive of biogenicity. These well-preserved fibrous biofilms probably represent calcified extracellular polymeric substances (EPS), and linear sheaths are interpreted as the traces of bacterial activities during the precipitation of dolomite crystals. The Tieshikou microbialite therefore shares similar biogenetic mechanisms with other PTB microbialites. The combination of the absence of pyrite framboids, slightly negative carbon isotope values, and an association with abundant ammonoids, bivalves, and gastropods indicates oxic conditions during the growth of the Tieshikou microbialite. Moreover, the nodular preservational state resembles widely distributed nodular mudstones or muddy limestones of the Lower Triassic successions worldwide. This implies that nodular mudstone or argillaceous limestones may also have been deposited in microbe-rich environments, in which terrigenous supply was abundant. |
23814. 题目: Biogeochemical controls on black shale deposition during the Frasnian-Famennian biotic crisis in the Illinois and Appalachian Basins, USA, inferred from stable isotopes of nitrogen and carbon 文章编号: N18120401 期刊: Palaeogeography, Palaeoclimatology, Palaeoecology 作者: Benjamin T. Uveges, Christopher K. Junium, Diana L. Boyer, Phoebe A. Cohen, James E. Day 更新时间: 2018-12-04 摘要: The Frasnian-Famennian biotic crisis is marked by two distinct intervals known as the Lower and Upper Kellwasser Events (KWEs) that in many locations are associated with deposition of organic-rich shales. Sedimentary nitrogen and carbon isotopes offer insight into the biogeochemical processing of nutrients, production of organic matter, and palaeoceanographic conditions during the KWEs. Here we present new bulk nitrogen (δ15Nbulk) and organic carbon (δ13Corg) isotope data from the Late Devonian Appalachian and Illinois Basins (AB and IB), with a focus on intervals encompassing the KWEs. Black shales from the IB and AB, including the KWEs, are 15N-depleted (−1.0–+2.0‰) and have significantly lower δ15Nbulk than interbedded grey shales (+0.5–+4.0‰), a trend consistent with many instances of black shale deposition in the Phanerozoic. Organic carbon isotopes exhibit the broad, positive excursions (~+3.5‰ from background) that are typical of the KWEs globally. Superimposed over these positive excursions in δ13Corg are sharp decreases of up to ~3.0‰ within the black shale beds, to as low as −30.5‰. The pattern of δ15Nbulk and δ13Corg values suggests that the depth of the chemocline and the degree of water-column stratification exert a primary control on both δ15Nbulk and δ13Corg during black shale deposition. In the context of the Frasnian-Famennian biotic crisis, the oscillating redox state and changing temperatures would have likely placed extreme stress on organisms within the marine environment of the AB and IB and may potentially have been a contributing factor to diversity loss over this time period. |
23815. 题目: Short-term impacts of high levels of nitrogen fertilization on soil carbon dynamics in a tropical pasture 文章编号: N18120305 期刊: CATENA 作者: Bernardo Melo Montes Nogueira Borges, Ricardo de Oliveira Bordonal, Maria Lucia Silveira, Edson Luiz Mendes Coutinho 更新时间: 2018-12-03 摘要: Bermudagrass (Cynodon spp.) is widely recognized by its ability to respond positively to nitrogen (N) fertilization. Nitrogen often promotes shoot and root growth and, consequently, increase carbon (C) inputs into the soil via above- and below-ground biomass. The objective of this 2-yr field study was to assess the short-term effects of increased N levels on soil C dynamics of a Tifton 85 bermudagrass pasture grown in a tropical soil. Treatments consisted of five levels of N fertilization (0, 60, 120, 180 and 240 kg ha−1 N) applied at each harvest for a total of four harvest events per year. Soil samples were collected at the 0 to 0.1 and 0.1 to 0.2 m depths for determination of soil C content. The latter was also fractionated into free-light (FLF), particulate organic carbon (POC), and mineral-associated organic carbon (C-min) fractions. Results indicated that N levels showed no effect on total C content and distribution among the various size-density fractions. The top layer (0–0.1 m) was more sensitive to changes in soil C for more recalcitrant fractions (POC and C-min) relative to 0.1–0.2 m layer. Our findings suggest that acceleration of the decomposition rate induced by N fertilization may have offset the potential accumulation of soil C associated with high inputs of above- and below-ground biomass, but additional research is warranted to better elucidate long-term impacts of nitrogen fertilization on soil C dynamics in grassland of tropical regions. |
23816. 题目: Alleviation of aluminum phytotoxicity by canola straw biochars varied with their cultivating soils through an investigation of wheat seedling root elongation 文章编号: N18120304 期刊: Chemosphere 作者: Ying Dong, Hui Wang, E Chang, Zhenjie Zhao, Ruhai Wang, Renkou Xu, Jun Jiang 更新时间: 2018-12-03 摘要: The types and amounts of cations and their uptake by plants vary with cultivating soils, which correlates with the carbonates and subsequent alkalis contents in the derived biochars. However, regional differences in the alkaline properties of crop straw biochars are unclear. In the present study, biochars pyrolyzed from canola straws collected from four different regions were used to assess the differences in the alkaline properties among them. The biochars were referred to as YTBC, XCBC, NJBC, and HYBC, respectively, and their feedstocks were collected from four different regions from south to north of China. The NH4OAC exchangeable base cations (K+, Na+, Ca2+, Mg2+) in the biochars were 270.74, 1427.05, 2089.23, and 1516.48 mmol kg−1 for YTBC, XCBC, NJBC, and HYBC, respectively, which were roughly consistent with the exchangeable base cations in the corresponding planting soils (17.57, 28.20, 151.26 and 444.65 mmol kg−1, respectively). The pH, carbonates content, and alkalinity of biochars considerably increased as follows: YTBC < XCBC < NJBC < HYBC. Wheat seedling root elongation experiment indicated that the Al(III) phytotoxicity alleviation effect of the biochars was as follows: HYBC > NJBC > XCBC > YTBC, which was corroborated by the subsequent findings of Evans blue staining, the remnant aluminum (Al(III)) in the reaction solution and Al(III) distribution in the wheat seedling roots. Thus, planting soil had a dominant influence in alleviating Al(III) phytotoxicity, and studies on crop straw biochar properties concerning alkalinities or liming potentials should not only consider crop genera and pyrolysis conditions, but also cultivating conditions. 图文摘要:
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23817. 题目: Quantifying hydrophobicity of natural organic matter using partition coefficients in aqueous two-phase systems 文章编号: N18120303 期刊: Chemosphere 作者: Heyun Fu, Kun Liu, Pedro J.J. Alvarez, Daqiang Yin, Xiaolei Qu, Dongqiang Zhu 更新时间: 2018-12-03 摘要: The hydrophobicity of natural organic matter (NOM) is of great significance for its interfacial processes in natural and engineered systems. However, there is no well-accepted method for the routine determination of NOM hydrophobicity. In this study, the hydrophobicity of NOM spanning a wide range of origins and properties was quantified based on their partition coefficients (KATPS) in poly (ethylene glycol)/potassium citrate aqueous two-phase systems (ATPS). The LnKATPS of NOM correlated well with the elemental, structural, and thermodynamic indices commonly used to characterize NOM hydrophobicity, including (O + N)/C, O/C, aromatic and aliphatic carbon, and the free energy of interactions between molecules (ΔGiwi). A simple linear model was developed to predict NOM hydrophobicity using KATPS. The model was validated using 20 natural water samples collected from rivers and lakes, which suggested good prediction power. ATPS scale system is simple, fast, low-cost, environmentally friendly, and requires little pretreatment and small sample volume. Overall, KATPS can be used as quantitative measure of NOM hydrophobicity that facilitates routinely characterizing the interfacial properties of NOM. 图文摘要:
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23818. 题目: Total Hg and methylmercury dynamics in a river-floodplain system in the Western Amazon: Influence of seasonality, organic matter and physical and chemical parameters 文章编号: N18120302 期刊: Science of The Total Environment 作者: Inacio A. Pestana, Marcelo G. Almeida, Wanderley R. Bastos, Cristina M.M. Souza 更新时间: 2018-12-03 摘要: Total mercury (Hg) and methylmercury (MeHg) circulation in a connected river-floodplain system composed of two black water (a small forest river, igarapé, and Cuniã Lake) and a white water body (Madeira River), located in the Madeira River Basin were evaluated during the rising-water, early and late falling-water periods. We assessed organic matter (C and N composition, (C:N)a; and δ13C isotopic signature), and physical and chemical influences (pH, dissolved O2, electric conductivity) in relationship to Hg and MeHg concentrations. Hg and MeHg concentrations in a sediment profile and three aquatic macrophytes (E. crassipes, E. azuera and Oryza sp.) were measured. Igarapé and Cuniã Lake showed higher Hg and MeHg concentrations (115–709; 10–25 ng g−1) in the suspended particulate matter compared (SPM) compared to the Madeira River (Hg: 5–16; MeHg: 0.2–0.3 ng g−1), partially independent of seasonality (p = 0.06). Total Hg had higher affinity for the SPM (1.75 times) than for dissolved organic matter. Organic matter characteristics correlated with MeHg concentrations (δ13C and (C:N)a; r2 = 0.79; p < 0.0001), as well as physical and chemical parameters of the water column (dissolved O2 and pH; r2 = 0.80; p < 0.0001), demonstrating that physical and chemical changes between the river-floodplain system affect MeHg circulation and production. The inverse correlation of MeHg and SO42− concentrations (r2 = 0.73; p < 0.0001) suggests the action of sulfate-reducing bacteria. Total Hg and MeHg concentrations as well as %MeHg were detected in the sediment profile (Hg: 24–51; MeHg: 0.6–3.2 ng g−1; %MeHg: 1.8–6.2) and aquatic macrophytes (Hg: 1–30; MeHg: 0.3–7.5 ng g−1; %MeHg: 1.6–33.7). We conclude that the highest Hg and MeHg concentrations in Cuniã Lake, compared to the Madeira River, are due to the physical and chemical differences between these environments. 图文摘要:
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23819. 题目: Experimental assessment of occurrences and stability of lead-bearing minerals in bacterial biofilms 文章编号: N18120301 期刊: Chemical Geology 作者: Thaïs Couasnon, Alexandre Gélabert, Georges Ona-Nguema, Sandrine Zanna, Bénédicte Ménez, François Guyot 更新时间: 2018-12-03 摘要: Bio-induced precipitation of lead-bearing minerals is investigated in bacterial biofilms grown by Shewanella oneidensis MR-1 under aerobic conditions. Under the different conditions investigated, thermodynamic calculations establish that the stable mineral phases expected to precipitate are either wulfenite PbMoO4 or cerussite PbCO3. However, observations by electron microscopy show that the first solids precipitated within hours at the experimental solution/biofilm interface are crystals of about 20 nm in diameter of pyromorphite Pb5(PO4)3(OH,Cl). In Mo-bearing systems, the precipitation of the thermodynamically-predicted wulfenite phase is delayed compared to the abiotic experiment and is observed only after 7 days of lead exposure. The initial lead phosphate crystals observed on the extracellular polymeric substances are assumed to result from concurrent local abundances of adsorbed Pb2+ ions and phosphate groups released by metabolically active cells. Scanning electron microscopy observations of samples milled by focused ion beam reveal effective diffusion-limited precipitation of pyromorphite within the well-preserved biofilm porosity. 图文摘要:
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23820. 题目: Easily mineralizable carbon in manure-based biochar added to a soil influences N 2 O emissions and microbial-N cycling genes 文章编号: N18120209 期刊: Land Degradation & Development 作者: Zhongmin Dai, Yong Li, Xiaojie Zhang, Jianjun Wu, Yu Luo, Yakov Kuzyakov, Philip C. Brookes, Jianming Xu 更新时间: 2018-12-02 摘要: Manure‐based biochar is an effective amendment to increase both carbon sequestration and the fertility of degraded soils, while the responses of N2O emissions and microbial‐N cycling genes to its application and the underlying mechanisms are poorly understood. Here, four biochars were produced under two pyrolysis temperatures (300 and 700 °C) and with two organic C extraction procedures (water and acetone extraction). The resulting biochars were either with relative enrichment or depletion in easily mineralizable carbon (EMC) compared to recalcitrant C. We added biochars, with urea and sodium nitrate, to a degraded red soil and incubated the amended soils at moisture levels of 60% and 130% field capacity. All the biochars decreased nitrification gene abundance, i.e. amoA. Biochars with EMC had greater stimulatory effects on the abundance of denitrification genes (nirK, nirS and nosZ) and N2O emission, regardless of moisture level and N form, compared with biochar without EMC. Biochar‐induced microbial activity, biochar aliphatics and alkyl groups correlated positively with N2O emission and denitrification gene abundance. The water dissolved organic C of biochar facilitated the conversion of N2O to N2, whereas the acetone extractable C fraction postponed the completion of denitrification. In conclusion, the N2O emission and denitrification gene abundance increased with decreasing biochar aromaticity and increasing EMC content. Our study emphasizes that the EMC supply in manure‐based biochars also importantly mediates soil N2O emission and microbial N cycling genes, adding to current understanding of influencing factors such as biochar pH, porosity, N availability and redox property. |
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