12761. 题目: Effects of litter source on the dynamics of particulate organic matter fractions and rates of macroaggregate turnover in different soil horizons
期刊: European Journal of Soil Science
作者: C. Parwada, J. Van Tol
摘要: Soil texture influences soil organic matter (SOM) transformation, depletion and reduction in the number of macroaggregates. However, the extent of changes in SOM in response to its quality and mechanisms of stabilization in different types of soil texture is unclear. We evaluated changes in SOM during a 30‐week incubation experiment using seven soils mixed with two sources of litter; Vachellia karroo (Hayne) Banfi & Galasso leaf and Zea mays L. stover. We hypothesized that changes in intraparticulate organic matter (iPOM) is influenced by litter quality ● soil type ● time interactions, which affects rates of turnover of macroaggregates. A completely randomized design was used in arranging soil jars in the incubator. Free light fractions, coarse and fine iPOM within macroaggregates (>250 μm) decreased exponentially from week 1 to 30 and were significantly (P< 0.05) affected by litter source ● soil horizon ● time interactions. Trends of changes in fine iPOM fractions were the same in macroaggregates and microaggregates (P< 0.05). Greatest changes in POM fractions occurred 8 weeks after litter incorporation. Both V. karroo leaf and Z. mays stover stabilized macroaggregates during the first 8 weeks after incubation, thereafter they lost their influence. Therefore, we needed to reapply fresh litter after this period. Changes in iPOM fractions and macroaggregate turnover were specific to a soil type, suggesting that different sources of litter have different stabilizing effects in macroaggregates. Soil macroaggregate stabilization and changes in iPOM could be used as indicators to apply more appropriate management practices for soil protection or productivity.
12762. 题目: Maximizing the production of aromatic hydrocarbons from lignin conversion by coupling methane activation
期刊: Bioresource Technology
作者: Aiguo Wang, Hua Song
摘要: Maximizing the production of aromatic hydrocarbons from lignin conversion by coupling methane activation without solvent was investigated over Zn-Ga modified zeolite catalyst. The co-loading of Zn and Ga greatly improves lignin conversion, arene yield along with BTEX (i.e., benzene, toluene, ethylbenzene, and xylene) selectivity, which gives 37.4 wt% yield of aromatic hydrocarbons with 62.2 wt% selectivity towards BTEX at 400 °C and 3.0 MPa. Methane presence has a negligible impact on lignin conversion, but improves arene yield and BTEX selectivity. Liquid 13C, 1H and 2H NMR investigations confirm the incorporation of methane into the final arene products. The NMR results reveal that methane might be incorporated into both the methyl group and aromatic ring, possibly via methylation of aryl moieties and co-aromatization of alkyl moieties. Pyridine and ammonia as probes for surface acidity analysis of the developed catalysts demonstrate that HZSM5 modification with Zn and Ga species could redistribute BAS (Brønsted acid sites) and LAS (Lewis acid sites) and significantly increase the fraction of weak acidic sites on the catalyst, rendering better catalytic performance on the depolymerization of lignin to arene products with higher BTEX selectivity. The results reported in this work may open a novel route to a promising technique for lignin valorization into aromatics and cost-efficient utilizations of biomass and natural gas resources.
12763. 题目: Magnetic particles modification of coconut shell-derived activated carbon and biochar for effective removal of phenol from water
作者: Zheng Hao, Changhui Wang, Zaisheng Yan, Helong Jiang, Huacheng Xu
摘要: The separation and recovery of pollutant-loaded magnetic carbon materials from organic contaminated environment is recently concerned, but the change of sorption ability and mechanism of activated carbon and biochar caused by magnetic particles modification still need to be explored. Here, the magnetic modification of two coconut shell-, coal-derived activated carbon and one biochar, and its effect on the removal of phenol from water were investigated. Magnetic activated carbon (MAC) and magnetic biochar (MBC) were prepared by co-precipitation. The increase of mass magnetic susceptibilities and energy dispersive X-ray spectroscopy (EDX) analysis showed that magnetic particles were successfully coated on the surface of virgin carbonaceous materials (VCMs). Magnetic modification enhanced the surface area and pore volume of activated carbon, and preserved those structure properties of biochar. Magnetic activated carbon had lower adsorption rates (10.641 g mg−1·min−1) than virgin activated carbon (20.575 g mg−1·min−1) while magnetic biochar exhibited higher adsorption rate (0.618 g mg−1·min−1) compared with virgin biochar (0.040 g mg−1·min−1), which were related to mass transport process. Data from Langmuir model results suggested that maximum adsorption capacities of three carbon adsorbents were increased by magnetic modification. The enhanced removal of phenol after magnetizing process may attribute to the increase of specific surface area and pore volume. Among VCMs/MCCs, magnetic coconut shell-derived carbon material with 951.84 m2/g surface area exhibited the most organic contaminant sorption performance. This finding gives insight into the adsorption mechanism of magnetic AC/BC for phenol, and provides a guidance to choose the appropriate magnetic composites to remove the organic contaminant effectively.
12764. 题目: Influence of extracellular polymeric substances on cell-NPs heteroaggregation process and toxicity of cerium dioxide NPs to Microcystis aeruginosa
期刊: Environmental Pollution
作者: Yangyang Yang, Jun Hou, Peifang Wang, Chao Wang, Xun Wang, Guoxiang You
摘要: The presence of abundant extracellular polymeric substances (EPS) play a vital role in affecting heteroaggregation process and toxicity of nanoparticles (NPs) to Microcystis aeruginosa. Interactions between n-CeO2 and cyanobacteria with/without EPS and the toxicity of n-CeO2 to M. aeruginosa were investigated in this study. Aggregation kinetics of n-CeO2 under both soluble EPS (SEPS) and bound EPS (BEPS) indicated the presence of EPS could induced the formation of EPS-NPs aggregates. Heteroaggregation between cells and n-CeO2 was confirmed through co-settling experiment and SEM-EDS observation. SEPS contributed to the observable heteroaggregation using spectral measurement. Heteroaggregation between cells and n-CeO2 under no BEPS was hardly obtained through spectral measurement, but SEM-EDS observation convinced this process. And the DLVO theory explained this heteroaggregation process under various EPS conditions, where the energy barrier decreased with gradual EPS extraction. In addition, the order for 96 h half growth inhibition concentration (IC50) was Raw M9 > M9-SEPS > M9+BEPS > M9-BEPS. These results revealed that not all heteroaggregation between cell-NPs can lead to the NPs toxicity to cells. BEPS act more important role in buffering against the toxicity of NPs from ambient adverse factors, but SEPS increase the stability of NPs which could aggravate the adverse effects of NPs in the environment.
12765. 题目: Photodegradation of 17β-estradiol on silica gel and natural soil by UV treatment
期刊: Environmental Pollution
作者: Siyuan Wang, Xinghao Wang, Chenguang Li, Xinxin Xu, Zhongbo Wei, Zunyao Wang, Ruijuan Qu
摘要: This paper evaluates the UV photodegradation of 17β-estradiol (E2) on silica gel and in natural soil with different soil components. Silica gel was chosen as a stable and pure support to simulate the photochemical behavior of E2 on the surface of natural soil. Ultraviolet light, rather than visible light, was confirmed to play a decisive role in the photodegradation of E2 on silica gel. The effect of three soil components, including humic acid (HA), inorganic salts, and relative humidity (RH), on the photochemical behavior of E2 on silica gel or soil under UV irradiation was then evaluated. Two HA concentrations (10 and 20 mg g−1) and three salts (ferric sulfate, copper sulfate and sodium carbonate) were observed to obviously inhibit the degradation of E2 on silica gel. Interestingly, nitrate was found to obviously improve the removal efficiency of E2. Both too-dry and too-wet conditions obviously reduced the removal rate of E2, and the optimum relative humidity (RH) value was found to be approximately about 35% (30 °C). Furthermore, twenty intermediate products and two major pathways were proposed to describe the transformation processes of E2 treated by UV irradiation, among which oligomers were found to be the major intermediate products before complete mineralization. The efficient UV removal of E2 on silica gel and natural soil suggested a feasible strategy to remediate E2 contaminated soil.
12766. 题目: Dissolved organic carbon compounds in deep-sea hydrothermal vent fluids from the East Pacific Rise at 9°50’N
期刊: Organic Geochemistry
作者: Krista Longnecker, Stefan M. Sievert, Sean P. Sylva, Jeffrey S. Seewald, Elizabeth B. Kujawinski
摘要: Deep-sea hydrothermal vents are unique ecosystems that may release chemically distinct dissolved organic matter to the deep ocean. Here, we describe the composition and concentrations of polar dissolved organic compounds observed in low and high temperature hydrothermal vent fluids at 9°50’N on the East Pacific Rise. The concentration of dissolved organic carbon was 46 µM in the low temperature hydrothermal fluids and 14 µM in the high temperature hydrothermal fluids. In the low temperature vent fluids, quantifiable dissolved organic compounds were dominated by water-soluble vitamins and amino acids. Derivatives of benzoic acid and the organic sulfur compound 2,3-dihydroxypropane-1-sulfonate (DHPS) were also present in low and high temperature hydrothermal fluids. The low temperature vent fluids contain organic compounds that are central to biological processes, suggesting that they are a by-product of biological activity in the subseafloor. These compounds may fuel heterotrophic and other metabolic processes at deep-sea hydrothermal vents and beyond.
12767. 题目: Thyasira tokunagai as an ecological indicator for the quality of sediment and benthic communities in the East Sea-Byeong, Korea
期刊: Marine Pollution Bulletin
作者: Young-Ryun Kim, Sangjin Lee, Jinhee Kim, Chang-Joon Kim, Ki-Young Choi, Chang-Soo Chung
摘要: The biomass and abundance of molluscan species were identified to evaluate the ecological quality of the surface sediment at the East Sea-Byeong ocean dumping site, Korea. To identify the dominant molluscan species, sediment samples were collected at nine selected stations during five expeditions in 2009, 2012, 2013, 2014, and 2015. In total, 16 molluscan species, including Aplacophora, Gastropoda, Bivalvia, and Scaphopoda, were observed. The bivalve Thyasira tokunagai was the dominant species, accounting for 82.6% of the total abundance of all identified species. This species was also the dominant benthic molluscan in sediments rich in organic matter and with a low manganese content. In addition, environmental variables, including sediment grain size, water depth, total organic carbon, and heavy metals, were found to be critical drivers affecting the spatial distribution of molluscan species.
12768. 题目: Electron donating capacity reduction of dissolved organic matter by solar irradiation reduces the cytotoxicity formation potential during wastewater chlorination
期刊: Water Research
作者: Ye Du, Qian-Yuan Wu, Xiao-Tong Lv, Bei Ye, Xin-Min Zhan, Yun Lu, Hong-Ying Hu
摘要: After treated wastewater is discharged into surface water for unplanned indirect potable reuse, solar irradiation transforms the dissolved organic matter (DOM), which would alter the formation of disinfection byproducts (DBPs) and change the cytotoxicity formation potential (CtFP) during post–chlorination in drinking water treatment plants. This study investigated the effects of solar irradiation on the CtFP and total organic halogen formation potential (TOXFP) of wastewater during post–chlorination. Exposure to natural sunlight decreased the formation potential of cytotoxicity to Chinese Hamster Ovary cells. Under 24 h simulated solar irradiation, CtFP and TOXFP decreased by more than 40%. X–ray photoelectron spectra and Fourier transformation infrared spectra suggested solar irradiation destroyed the key DBP precursors containing phenolic hydroxyl moieties (Ph–OH). The destruction of Ph–OH under solar irradiation was reflected by a decrease in the electron donating capacity (EDC) of DOM and the post–chlorination decreased the EDC further. Increasing the irradiation–consumed EDC abated the chlorine–consumed EDC, while the chlorine–consumed EDC was positively correlated to the CtFP and TOXFP by means of the electrophilic substitution–aromatic ring cleavage. Solar irradiation thus reduced the CtFP and TOXFP in wastewater during post–chlorination. This study revealed that solar irradiation decreased the risks of treated wastewater for unplanned indirect potable reuse and provided a strategy of controlling CtFP and TOXFP via reducing EDC of DOM in pretreatments.
12769. 题目: The dissolution behavior of biogenic calcites in seawater and a possible role for magnesium and organic carbon
期刊: Marine Chemistry
作者: Adam V. Subhas, Nick E. Rollins, William M. Berelson, Jonathan Erez, Patrizia Ziveri, Gerald Langer, Jess F. Adkins
摘要: We present the dissolution kinetics of mixed planktic foraminifera, the benthic foraminifera Amphistegina, the coccolithophore Emiliania huxleyi, and the soft coral Rhythismia fulvum in seawater. Dissolution rates were measured across a large range of saturation states (Ω = 0.99–0.2) by dissolving 13C-labeled calcites in natural seawater undersaturated with respect to calcite. 13C-label was incorporated into biogenic calcite by culturing marine calcifiers in 13C-labeled natural seawater. Net dissolution rates were calculated as the slope of seawater δ13C versus time in a closed seawater-calcite system. All calcites show distinct, nonlinear, dependencies on seawater saturation state when normalized by mass or by specific surface area. For example, coccolith calcite dissolves at a similar rate to inorganic calcite near equilibrium when normalized by surface area, but dissolves much more slowly far from equilibrium. Mass loss from foraminiferal tests is correlated with a decrease in Mg/Ca of the solid, indicating that Mg-rich phases are preferentially leached out at even mild undersaturations. Dissolution also appears to strongly affect test B/Ca. Finally, we provide an interpretation of surface area-normalized biogenic calcite dissolution rates as a function of their Mg and organic carbon content. Near-equilibrium dissolution rates of all calcites measured here show a strong, nonlinear dependence on Mg content. Far-from-equilibrium dissolution rates decrease strongly as a function of organic carbon content. These results help to build a framework for understanding the underlying mechanisms of rate differences between biogenic calcites, and bear important implications for the dissolution of high-Mg calcites in view of ocean acidification.
12770. 题目: Synthesis of a novel tunable lignin-based star copolymer and its flocculation performance in the treatment of kaolin suspension
期刊: Separation and Purification Technology
作者: Zuguang Liu, Xiang Lu, Junkang Xie, Bo Feng, Qiaoning Han
摘要: In current work, lignin-based multi-arm star copolymer phenolated kraft lignin-graft-poly (2-methacryloyloxyethyl) trimethyl ammonium chloride (PKL-g-PDMC) was designed and synthesized as a new kind of cationic flocculant via Steglich esterification of PKL and subsequent RAFT polymerization with DMCs, and its flocculation performance in the removal of kaolin particles from simulated wastewater was evaluated. The star PKL-g-PDMCs with varying graft density and arm length of PDMCs chains were characterized by 1H-NMR, 31P-NMR, GPC and TGA. The effects of graft density and arm length, PKL-g-PDMC dosage, suspension pH and settling time on flocculating performance were investigated by measuring residual turbidity of the settled suspension. The treatment was effective, as demonstrated by 96.4 % efficiency of turbidity removal. Above all, the chemical structure of the copolymers, including graft density and the arm length, can be designable and tunable by simply changing feeding ratios of Steglich esterification and subsequent RAFT polymerization, and thus the best flocculation performance can be obtained. This work provides a blueprint for the design, synthesis and use of novel lignin-based multi-arm star copolymers for wastewater treatment with tunable properties.
12771. 题目: Removal of refractory organic pollutants in reverse-osmosis concentrated leachate by Microwave–Fenton process
期刊: Environmental Science and Pollution Research
作者: Aiping Zhang, Zhepei Gu, Weiming Chen, Qibin Li, Guobin Jiang
摘要: A microwave–Fenton technology was applied to dispose of the reverse-osmosis concentrated leachate. Influential factors on the treatment of concentrated leachate with the pure Fenton and microwave-Fenton method were investigated. For the conventional Fenton process, the removal efficiencies of chemical oxygen demand (CODCr), UV254, and the color number (CN) reached 84%, 87%, and 96%, respectively, with the biodegradability (BOD5/CODCr) increased from 0.13 to 0.51 at an initial pH of 5.0, Fe2+ of 0.04 mol/L, a n(H2O2)/n(Fe2+) ratio of 8 after a reaction time of 3 h. When incorporating the Fenton process with microwave irradiation, a comparative CODCr and UV254, and the CN removal rate of 75%, 83%, and 95%, and a high BOD5/CODCr of 0.62 were achieved under a microwave power of 390 W and an extremely shortened reaction time of only 8 min. Meanwhile, sludge quantity showed a reduction of 24.7%, decreased from 8.50 g/L to 6.40 g/L after the participation of microwave. In addition, molecular-weight fraction (MWF), UV-visible spectrum (UV-vis), and 3D-EEM spectrum tests demonstrated that the macromolecular and complex organic compounds in the wastewater were significantly decomposed into small molecular matters. Our results found that microwave–Fenton is a promising technology for concentrated leachate treatment, with much shorter reaction time, lower sludge production, and enhanced biodegradability, as well as comparative organic matter removal performance.
12772. 题目: Fate of febantel in the aquatic environment—the role of abiotic elimination processes
期刊: Environmental Science and Pollution Research
作者: Sandra Babić, Dragana Mutavdžić Pavlović, Martina Biošić, Danijela Ašperger, Irena Škorić, Mislav Runje
摘要: Febantel is widely used anthelmintic drug active against a range of gastrointestinal parasites in animals. Despite the fact that it has been detected in the aquatic environment, there is no information on its environmental fate. Therefore, abiotic elimination processes of febantel in the aquatic environment have been studied. The results of direct and indirect photodegradation experiments showed that febantel was persistent against solar radiation. Kinetics of hydrolytic elimination was pH and temperature dependent with half-lives in the range from 210 min to 99 days. Febantel metabolites, fenbendazole and fenbendazole sulfone, were found as major degradation products using high-resolution mass spectrometry. The proposed hydrolytic degradation pathway consisted of the base catalyzed hydrolysis followed by consecutive oxidative cyclization to the five-membered ring of the benzo-imidazole derivative. Aquatic toxicity of febantel and its hydrolytic mixture were evaluated toward the luminescence bacteria Vibrio fischeri. Investigation of febantel sorption onto river sediments showed that the best agreement was obtained with the linear model (R2 > 0.99), while the rate of sorption is the best described with the kinetic model of pseudo-second order. The organic carbon-normalized sorption coefficient, KOC, ranged from 1490 to 3894 L kg−1 for five sediment samples. The results of this research demonstrate that febantel persist in the natural waters and potentially could travel far from the source.
12773. 题目: Carbon and nitrogen contents and aggregation index of soil cultivated with onion for seven years using crop successions and rotations
期刊: Soil and Tillage Research
作者: Jucinei José Comin, Lucas Borges Ferreira, Luiz Henrique dos Santos, Leôncio de Paula Koucher, Ludmila Nascimento Machado, Elano dos Santos Junior, Álvaro Luiz Mafra, Claudinei Kurtz, Monique Souza, Gustavo Brunetto, Arcângelo Loss
摘要: Onion is usually cultivated using conventional tillage system (CTS), with excessive soil turning, leaving it with low or no vegetation cover. This favors erosive processes and impacts negatively diverse edaphic attributes. Adopting soil management systems with conservationist bases that use permanent soil coverage and crop rotation can maintain or improve these attributes (for example, soil aggregation and soil organic matter). The objective of this work was to evaluate the total organic carbon (TOC) and total nitrogen (TN) contents, aggregation index, and aggregate mass distribution of a Humic Cambisol cultivated with onions in succession or rotation with other species in no-tillage system (NTS) and CTS. The treatments were: maize/onion (NTS-T1); cover plants (winter)/onion (NTS-T2); maize/winter grasses/onion (NTS-T3); velvet bean/onion (NTS-T4); millet/cover plants (winter)/onion (NTS-T5); velvet bean/rye/onion (NTS-T6); maize/onion (CTS-T7); intercrops cover plants (summer)/onion (NTS-T8). Seven years after the implementation of the experiment, the weighted mean diameter (WMD) of the aggregates, distribution of macroaggregates, mesoaggregates, and microaggregates, and TOC, and TN contents of the soil (0–0.05, 0.05–0.10 and 0.10–0.20 m layers) were evaluated. Periodic soil turning (CTS) in the succession of maize, and onion (T7) reduces TOC and TN contents in the soil surface layer, compared to succession and rotation systems with onion crops in NTS. This negative effect on soil quality is connected to the reduction of aggregate stability, especially the decrease in the amount of macroaggregates. The use of grasses, especially winter grasses in rotation with maize (T3), preceding onion crops in NTS increases TOC content in the soil surface layer. Higher TN accumulation in the surface layer is found in areas with more soil cover plant species in rotation or succession with onion in NTS (T2, T3, T5, T6 and T8). The use of NTS for onion crops generates high soil aggregate stability, with predominance of macroaggregates, regardless of the crop succession or rotation system used. Treatments with no winter soil cover plants (T1, T4 and T7) reduce soil TOC contents and the mass of water-stable macroaggregates and increase the amount of microaggregates in the soil surface layer when compared to the other treatments.
12774. 题目: Exploratory study on modification of sludge-based activated carbon for nutrient removal from stormwater runoff
期刊: Journal of Environmental Management
作者: Chaoyang Yue, Loretta Y. Li, Chris Johnston
摘要: Nutrients (P, N) in stormwater runoff are a major cause of eutrophication and algal blooms. A promising solution to this problem is to amend the rain garden growing medium (RGGM) with sewage sludge-based activated carbon (SBAC). To optimize the SBAC production process, different metals, pyrolysis conditions (temperature, heating time, carrier gas), and post-treatments were explored. When pyrolyzed at 400 °C for two hours, Zn-activated SBAC removed up to 41% of PO4-P (initial concentration of 1 mg/L) and 72% of NO3-N (initial concentration of 2 mg/L), at a dose of 1 g sorbent/L of nutrient-spiked distilled water. When the same dosage was applied to stormwater leachate made from RGGM and spiked with nutrients, the removal efficiencies were reduced to 20% for PO4-P and 38% for NO3-N. These reductions were probably caused by competition from other leachate components. Increasing the dosage to 3 g/L leachate improved PO4-P removal to 31% and NO3-N to 72%, while also resulting in the removal of 46% of total organic carbon. The major energy cost of producing such sorbents is estimated to be ∼$0.76 CAD/kg SBAC.
12775. 题目: Net fractionation of hydrogen isotopes in n-alkanoic acids from soils in the northern boreal forest
期刊: Organic Geochemistry
作者: Aleesha Bakkelund, Trevor J. Porter, Duane G. Froese, Sarah J. Feakins
摘要: Plant-derived n-alkyl lipids are well-preserved in sedimentary archives, and their stable hydrogen isotope ratio (δDwax) is a proxy for precipitation δD and climate. Net fractionation of H isotopes between plant source water and n-alkyl lipids (εwax/water) is the largest uncertainty for interpreting this proxy and depends on plant type and environment. Although popular proxies, n-alkanoic acids (n-acids) are less frequently calibrated in modern environments than n-alkanes. We constrain the net fractionation (εwax/MAP – Mean Annual Precipitation) for the northern boreal forest based on n-C24,26,28 acids in topsoils from a 13-site network in Yukon, Alaska and Northwest Territories (60-68°N). n-Acid homologue distributions for common boreal plants (gymnosperm trees, shrubs, forbs, C3 grasses and mosses) show that soil n-acids are dominated by mosses, but with a reduced carbon preference index compared to fresh mosses, possibly owing to post-depositional degradation. Regionally averaged εwax/MAP values are –93±10‰, –101±11‰ and –95±11‰ for n-C24,26,28 acids, respectively, which are similar to values reported from low and high latitude regions. We find that εwax/MAP for n-C26,28 acids (but not n-C24) is significantly (p≤0.05) smaller with increasing latitude and decreasing mean annual temperature, factors that covary across our network. Since latitude is typically known for ancient deposits, we parsed the dataset to obtain latitude-specific εwax/MAP values for 60-64°N (–107±8‰ for n-C26; and –101±8‰ for n-C28) and 65-68°N (–94±11‰ for n-C26; and –89±10‰ for n-C28). These soil-derived values are relevant for hydroclimate reconstructions using fossil n-acids in paleosols from a comparable paleoflora and latitude.
12776. 题目: Effects of soil deformation on clay dispersion in loess soil
期刊: Soil and Tillage Research
作者: Jerzy Lipiec, Ewa A. Czyż, Anthony R. Dexter, Anna Siczek
摘要: Clay dispersibility is a good indicator of the vulnerability of soil to disperse and therefore of the associated risks of soil water erosion and crusting and subsequent losses of agricultural chemicals in overland flow. The aim of this study was to determine the effect of soil deformation of an erodible soil derived from loess (Haplic Luvisol) on the content of dispersible clay. The soil deformation levels were: non-compacted (NC, 0 tractor pass), moderately compacted (MC, 3 passes), and strongly compacted (SC, 5 passes). The amount of readily-dispersible clay (RDC) was determined using a Hach 2100AN ratio turbidimeter, by measurement of the turbidity of a suspension of soil in water.All the measurements were done with soil from the plough (5–20 cm) and subsoil (25–35 cm) layers. The amount of RDC increased with increasing deformation level and depth. In the plough layer this increase was from 0.786 under NC to 1.216 g 100 g−1 under SC. Corresponding values in the subsoil layer were 1.227 and 1.874 g 100 g−1. Positive correlations were found between readily-dispersible clay and bulk density in both the plough (R2 =0.685) and the subsoil layers (R2 =0.332). The results for clay dispersion are discussed in relation to the different contents of organic carbon in the plough and subsoil layers and the potential mechanisms of soil vulnerability to soil erosion, crusting and deformation.
12777. 题目: Comparing soil inventory with modelling: Carbon balance in central European forest soils varies among forest types
期刊: Science of The Total Environment
作者: Daniel Ziche, Erik Grüneberg, Lutz Hilbrig, Juliane Höhle, Thomas Kompa, Jari Liski, Anna Repo, Nicole Wellbrock
摘要: Forest soils represent a large carbon pool and already small changes in this pool may have an important effect on the global carbon cycle. To predict the future development of the soil organic carbon (SOC) pool, well-validated models are needed. We applied the litter and soil carbon model Yasso15 to 1838 plots of the German national forest soil inventory (NFSI) for the period between 1985 and 2014 to enables a direct comparison to the NFSI measurements. In addition, to provide data for the German Greenhouse Gas Inventory, we simulated the development of SOC with Yasso15 applying a climate projection based on the RCP8.5 scenario. The initial model-calculated SOC stocks were adjusted to the measured ones in the NFSI.On average, there were no significant differences between the simulated SOC changes (0.25 ± 0.10 Mg C ha−1 a−1) and the NFSI data (0.39 ± 0.11 Mg C ha−1 a−1). Comparing regional soil-unit-specific aggregates of the SOC changes, the correlation between both methods was significant (r2 = 0.49) although the NFSI values had a wider range and more negative values. In the majority of forest types, representing 75% of plots, both methods produced similar estimates of the SOC balance. Opposite trends were found in mountainous coniferous forests on acidic soils. These soils had lost carbon according to the NFSI (−0.89 ± 0.30 Mg C ha−1 a−1) whereas they had gained it according to Yasso15 (0.21 ± 0.10 Mg C ha−1 a−1). In oligotrophic pine forests, the NFSI indicated high SOC gains (1.36 ± 0.17 Mg C ha−1 a−1) and Yasso15 much smaller (0.29 ± 0.10 Mg C ha−1 a−1).According to our results, German forest soils are a large carbon sink. The application of the Yasso15 model supports the results of the NFSI. The sink strength differs between forest types possibly because of differences in organic matter stabilisation.
12778. 题目: Temperature Dependence of Dissolved Organic Matter Fluorescence
期刊: Environmental Science & Technology
作者: Garrett McKay, Julie. A. Korak, Fernando L. Rosario-Ortiz
摘要: The temperature dependence of organic matter fluorescence apparent quantum yields (Φf) was measured for a diverse set of organic matter isolates (i.e., marine aquatic, microbial aquatic, terrestrial aquatic, and soil) in aqueous solution and for whole water samples to determine apparent activation energies (Ea) for radiationless decay processes of the excited singlet state. Ea was calculated from temperature dependent Φf data obtained by steady-state methods using a simplified photophysical model and the Arrhenius equation. All aquatic-derived isolates, all whole water samples, and one soil-derived fulvic acid isolate exhibited temperature dependent Φf values, with Ea ranging from 5.4 to 8.4 kJ mol–1 at an excitation wavelength of 350 nm. Conversely, soil humic acid isolates exhibited little or no temperature dependence in Φf. Ea varied with excitation wavelength in most cases, typically exhibiting a decrease between 350 and 500 nm. The narrow range of Ea values observed for these samples when compared to literature Ea values for model fluorophores (∼5–30 kJ mol–1) points to a similar photophysical mechanism for singlet excited states nonradiative inactivation across organic matter isolates of diverse source and character. In addition, this approach to temperature dependent fluorescence analysis provides a fundamental, physical basis, in contrast to existing empirical relationships, for correcting online fluorescence sensors for temperature effects.
12779. 题目: Effects of Biochar and Biosolid on Adsorption of Nitrogen, Phosphorus, and Potassium in Two Soils
期刊: Water, Air, & Soil Pollution
作者: H. Rens, T. Bera, A. K. Alva
摘要: Increasing the retention of nutrients by agricultural soils is of great interest to minimize losses of nutrients by leaching and/or surface runoff. Soil amendments play a role in nutrient retention by increasing the surface area and/or other chemical processes. Biochar (BC) is high carbon-containing by-product of pyrolysis of carbon-rich feedstocks to produce bioenergy. Biosolid is a by-product of wastewater treatment plant. Use of these by-products as amendments to agricultural soils is beneficial to improve soil properties, soil quality, and nutrient retention and enhance carbon sequestration. In this study, the adsorption of NH4-N, P, and K by a sandy soil (Quincy fine sand (QFS)) and a silty clay loam soil (Warden silty loam (WSL)) with BC (0, 22.4, and 44.8 mg ha−1) and biosolid (0 and 22.4 mg ha−1) amendments were investigated. Adsorption of NH4-N by the QFS soil increased with BC application at lower NH4-N concentrations in equilibrium solution. For the WSL soil, NH4-N adsorption peaked at 22.4 mg ha−1 BC rate. Biosolid application increased NH4-N adsorption by the WSL soil while decreased that in the QFS soil. Adsorption of P was greater by the WSL soil as compared to that by the QFS soil. Biosolid amendment significantly increased P adsorption capacity in both soils, while BC amendment had no significant effects. BC and biosolid amendments decreased K adsorption capacity by the WSL soil but had no effects on that by the QFS soil. Ca release with increasing addition of K was greater by the WSL soil as compared to that by the QFS soil. In both the soils, Ca release was not influenced by BC amendment while it increased with addition of biosolid. The fit of adsorption data for NH4-N, P, and K across all treatments and in two soils was better with the Freundlich model than that with the Langmuir model. The nutrients retained by BC or biosolid amended soils are easily released, therefore are readily available for the root uptake in cropped soils.
12780. 题目: The impact of oxygen exposure on long-chain alkyl diols and the long chain diol index (LDI) – a long-term incubation study
期刊: Organic Geochemistry
作者: Sophie Reiche, Sebastiaan W. Rampen, Denise J.C. Dorhout, Jaap S. Sinninghe Damsté, Stefan Schouten
摘要: In recent years, long chain alkyl diols (LCDs) have been increasingly used to study and reconstruct past sea surface temperatures using the long chain diol index (LDI), which is based on changes in the distribution of 1,15-LCDs. However, the impact of diagenesis on LCDs and the LDI is still poorly constrained. Here we studied the impact of oxygen exposure on LCDs and the LDI, by aerobically incubating biomass of the LCD-producing alga Nannochloropsis oculata for 271 days. The concentrations of extractable free- and bound, residually ester-bound and residually-bound glycosidic ether- or amide-bound saturated fatty acids and LCDs were determined. A significant impact of oxygen exposure was observed for C14, C16 and C18 saturated fatty acids and the C20:5 polyunsaturated fatty acid as their concentration decreased significantly over time, irrespective of their mode of binding. LCDs, in contrast, increased significantly in concentration over incubation time, e.g. up to a 30-fold increase in concentrations for residually ester-bound LCDs at day 125 compared to concentrations at the beginning of the experiment. This increase in concentration most likely represents a release of LCDs from the insoluble biopolymer algaenan due to the impact of oxygen exposure. Values of the LDI differed strongly depending on the mode of occurrence of LCDs in the biomass. However, despite the large changes in concentration of LCDs in response to oxygen exposure, the LDI remained relatively stable after prolonged degradation. This suggests that oxygen exposure may not have a substantial impact on the LDI of extractable LCDs used for its determination.