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25741. 题目: Chemical Aging Changed Aggregation Kinetics and Transport of Biochar Colloids
文章编号: N19062611
期刊: Environmental Science & Technology
作者: Yang Wang, Wei Zhang, Jianying Shang, Chongyang Shen, Stephen D. Joseph
更新时间: 2019-06-26
摘要: Little is known about aggregation and transport behaviors of aged biochar colloids in the terrestrial environment. This study investigated aggregation kinetics and transport of biochar colloids from aged (HNO₃ treatment) and pristine pinewood biochars pyrolyzed at 300 and 600 °C (PB300 and PB600) in NaCl and CaCl₂ solutions. In NaCl solutions, critical coagulation concentrations (CCCs) of aged PB300 and PB600 colloids (540 mM and 327 mM) were much greater than the CCCs of pristine biochar colloids (300 mM and 182 mM). This is likely due to substantial increase of negatively charged oxygen-containing functional groups (primarily carboxyl) on aged biochar surfaces. Intriguingly, in CaCl₂ solutions the CCCs of the aged PB300 and PB600 colloids decreased to 25.2 mM and 32.1 mM from 58.6 mM and 41.7 mM for the pristine colloids, respectively. This probably resulted from greater surface charge neutralization and Ca²⁺ bridging for the aged biochar colloids. In salt solutions (e.g., 10 and 50 mM NaCl and 1 and 10 mM CaCl₂), the aged biochar colloids showed higher mobility in porous media than the pristine biochar colloids. This study demonstrated that pristine and aged biochar colloids were stable in the solutions with environmentally relevant ionic strength, and the aging process might substantially increase their mobility in the subsurface.

25742. 题目: Formation of Brominated Organic Compounds and Molecular Transformations in Dissolved Organic Matter (DOM) after Ballast Water Treatment with Sodium Dichloroisocyanurate Dihydrate (DICD)
文章编号: N19062610
期刊: Environmental Science & Technology
作者: Gregory Ziegler, Michael Gonsior, Daniel J. Fisher, Philippe Schmitt-Kopplin, Mario N. Tamburri
更新时间: 2019-06-26
摘要: stuarine water treated with a ballast water management system (BWMS) using a solution of dissolved dichloroisocyanurate dihydrate (DICD) resulted in the formation of newly described brominated disinfection byproducts (Br-DBPs). Analysis of dissolved organic matter (DOM) in untreated water with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) identified 3897 m/z ions and their exact molecular formulas. After DICD treatment, a total of 213 halogenated molecular ions with relative abundance of at least 1% were assigned and confirmed using isotope simulation. Halogenated ions were assigned in four DBP elemental groups including CHOBr (180), CHONBr (13), CHOCl (16), and CHOBrCl (4). Forty-nine of the 197 brominated formulas have not been previously reported. We also were able to tentatively assign possible structures to the formula C₃HBr₃N₂ due to very limited isomeric possibilities. The tentatively assigned compound found at 6.4% relative abundance was identified as either tribromoimidazole or tribromopyrazole. Our results show the formation of complex halogenated DBPs that are formed in the treatment of water with a novel BWMS that employs granular DICD as a biocide. The toxicological and mutagenic properties as well as the fate of these newly identified brominated DBPs are unknown.

25743. 题目: Interaction of zero valent copper nanoparticles with algal cells under simulated natural conditions: Particle dissolution kinetics, uptake and heteroaggregation
文章编号: N19062609
期刊: Science of The Total Environment
作者: Daniel Arenas-Lago, Fazel Abdolahpur Monikh, Martina G. Vijver, Willie J.G.M. Peijnenburg
更新时间: 2019-06-26
摘要: Some metal-based engineered nanoparticles (ENPs) undergo fast dissolution and/or aggregation when they are released in the environment. The underlying processes are controlled by psychochemical/biological parameters of the environment and the properties of the particles. In this study, we investigated the interaction between algal cells and zero valent copper nanoparticles (Cu⁰-ENPs) to elucidate how the cells influence the dissolution and aggregation kinetics of the particles and how these kinetics influence the cellular uptake of Cu. Our finding showed that the concentration of dissolved Cu ([Cu]_dissolved) in the supernatant of the culture media without algal cells was higher than the [Cu]_dissolved in the media with algal cells. In the absence of the cells, dissolved organic matter (DOC) increased the dissolution of the particle due to increasing the stability of the particles against aggregation, thus increasing the available surface area. In the presence of algae, Cu⁰-ENPs heteroaggregated with the cells. Thus, the available surface area decreased over time and this resulted in a low dissolution rate of the particles. The DOC corona on the surface of the particles increased the heteroaggregation of the particles with the cells and decreases the uptake of the particles. Our findings showed that microorganisms influence the fate of ENPs in the environment, and they do so by modifying the dissolution and aggregation kinetics of the Cu⁰-ENPs.
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25744. 题目: The sensitivity of soil organic carbon pools to land management varies depending on former tillage practices
文章编号: N19062608
期刊: Soil and Tillage Research
作者: G.A. Miller, R.M. Rees, B.S. Griffiths, B.C. Ball, J.M. Cloy
更新时间: 2019-06-26
摘要: The rate of change in the relative size of SOC pools (sensitivity) due to land management may vary depending on their level of chemical and/or physical protection from decomposition, but has rarely been directly measured. The availability of archived (1975) soils from an abandoned long term tillage treatment experiment provided a unique opportunity to assess the sensitivity of SOC pools with different levels of stability to uniform land management after divergent tillage treatments. There were four initial treatments (1968–1991): 1) deep plough then no till, 2) shallow plough, 3) reduced till then rotary cultivation and 4) no till. The treatments were followed by uniform long-term grassland management (17 years) and subsequent short-term arable (two years). The sensitivity of SOC to land management was assessed by fractionation and direct comparison of archived soils and soils sampled in 2014 from this site. Both reductions and increases in SOC stocks were observed over time in comparable treatments but the overall effect was a trend towards an equilibration of SOC stocks across all plots. The labile fractions (particulate and dissolved organic matter) were sensitive to land management regardless of initial tillage treatment, but were more sensitive in the reduced till + rotary cultivation and no till treatments (2.3–5.3 times more sensitive than the whole soil) than the deep plough + no till and shallow plough treatments (1.12.2 times more sensitive than the whole soil). The chemically resistant fraction of the soils was surprisingly sensitive to land management (0.9–1.3 times more sensitive than the whole soil). This study shows that the degree of sensitivity of SOC fractions to land management can vary significantly depending on previous tillage management practices.

25745. 题目: A novel clean production approach to utilize crop waste residues as co-diet for mealworm (Tenebrio molitor) biomass production with biochar as byproduct for heavy metal removal
文章编号: N19062607
期刊: Environmental Pollution
作者: Shan-Shan Yang, Yi-di Chen, Ye Zhang, Hui-Min Zhou, Xin-Yu Ji, Lei He, De-Feng Xing, Nan-Qi Ren, Shih-Hsin Ho, Wei-Min Wu
更新时间: 2019-06-26
摘要: Proper management of waste crop residues has been an environmental concern for years. Yellow mealworms (larvae of Tenebrio molitor Linnaeus, 1758) are major insect protein source. In comparison with normal feed wheat bran (WB), we tested five common lignocellulose-rich crop residues as feedstock to rear mealworms, including wheat straw (WS), rice straw (RS), rice bran (RB), rice husk (RH), and corn straw (CS). We then used egested frass for the production of biochar in order to achieve clean production. Except for WS and RH, the crop residues supported mealworms’ life activity and growth with consumption of the residues by 90% or higher and degraded lignin, hemicellulose and cellulose over 32 day period. The sequence of degradability of the feedstocks is RS > RB > CS > WS > RH. Egested frass was converted to biochar which was tested for metal removal including Pb(II), Cd(II), Cu(II), Zn(II), and Cr(VI). Biochar via pyrolysis at 600 °C from RS fed frass (FRSBC) showed the best adsorption performance. The adsorption isotherm fits the Langmuir model, and kinetic analysis fits the Pseudo-Second Order Reaction. The heavy metal adsorption process was well-described using the Intra-Particle Diffusion model. Complexation, cation exchange, precipitation, reduction, deposition, and chelation dominated the adsorption of the metals onto FRSBC. The results indicated that crop residues (WS, RS, RB, and CS) can be utilized as supplementary feedstock along with biochar generated from egested frass to rear mealworms and achieve clean production while generating high-quality bioadsorbent for environment remediation and soil conditioning.
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25746. 题目: Tree species affect soil organic matter stocks and stoichiometry in interaction with soil microbiota
文章编号: N19062606
期刊: Geoderma
作者: Marcel Lorenz, Sören Thiele-Bruhn
更新时间: 2019-06-26
摘要: The purpose of this research was to evaluate tree species effects on quantitative and qualitative soil organic matter (SOM) properties of forest floors and mineral soil layers. Additionally, the contribution of soil microbial biomass to SOM was studied in five forest stands with different dominant tree species.The study was conducted at the afforested spoil heap ‘Sophienhöhe’ located at the lignite open-cast mine Hambach near Jülich, Germany. The 35 year-old afforested sites consisted of monocultural stands of Douglas fir (Pseudotsuga mienziesii), pine (Pinus nigra), beech (Fagus sylvatica) and red oak (Quercus rubra) as well as a mixed deciduous stand site planted mainly with hornbeam (Carpinus betulus), lime (Tilia cordata) and common oak (Quercus robur). There, boundary conditions regarding soil, climate, topography and management were highly similar, equivalent to a common garden experiment but on landscape level. Because the parent material used for site recultivation was free from organic matter or coal material, the SOM accumulation is a result of in situ soil development.Tree species had a significant effect on soil organic carbon (SOC) stocks, stoichiometric patterns of C, hydrogen (H), nitrogen (N), oxygen (O) and sulfur (S) and the microbial biomass carbon (MBC) content in the forest floor and the top mineral soil layers (0–5 cm, 5–10 cm, 10–30 cm). In general, forest floor SOC stocks were significantly higher in coniferous forest stands compared to deciduous tree species. Differences in SOM quantity became less pronounced with increasing depth, while stoichiometric molar ratios of SOM as indices of litter turnover and SOM composition differed also in deeper layers. Differences in H:C and O:C ratios among tree species clearly increased along the depth gradient in mineral soils, indicating that SOM turnover by oxidative processes depends on tree species. Differences in depth gradients of the microbial quotient (MBC to SOC ratio) among tree species emphasized differences in the microbial C turnover. Furthermore, the relationship between the microbial quotient and SOM stoichiometry (C:N and C:S ratio) became stronger with increasing soil depth. This suggests that N and especially S limitation determined the microbial turnover of SOM in deeper mineral soil layers.

25747. 题目: Carbon isotopic analysis of reactive organic matter using a new pyrolysis-cryotrapping- isotope ratio mass spectrometry method: The isotope variation of organic matter within the S1 and S2 peaks of Rock-Eval
文章编号: N19062605
期刊: Organic Geochemistry
作者: M. Dörner, U. Berner, M. Erdmann, T. Barth
更新时间: 2019-06-26
摘要: The source material, the mode of photosynthesis, the organic matter (OM) type, the paleoenvironmental conditions and thermal degradation all determine the isotopic composition of OM. This study presents a novel analytical technique and demonstrates its potential to enhance the understanding of the preservation and maturation-related isotopic compositional changes in OM from different paleoenvironments. A new Rock-Eval type pyrolysis coupled to isotope ratio mass spectrometry (py-IRMS) method has been developed to monitor the isotopic changes during Rock-Eval type pyrolysis while simultaneously recording pyrograms to obtain S1 and S2 peaks compatible with standard Rock-Eval pyrolysis. An automated cryotrapping method allows the sequential sampling of product from defined pyrolysis portions. Each subsample is subsequently transferred to the isotopic ratio mass spectrometer for carbon isotopic measurements. In addition, the cryotrap serves to focus sample peaks, enabling robust and reproducible results even at standard Rock-Eval heating rates. In combination with a standard elemental analyser coupled to an isotopic ratio mass spectrometer (EA–IRMS) it was possible to deconvolute the carbon isotope composition of the reactive components, bitumen and inert components of OM. This allowed us to observe depositional control as well as changes imposed by maturation. Our initial results show the potential of the proposed isotopic screening method to deduce a variety of organic geochemical properties of different OM types based on differences in their carbon isotope compositions. Our results suggest that the ability to produce significant isotopic fractionation during the proposed pyrolysis method is highly dependent on the preservation state of the OM and the thermal maturity.

25748. 题目: Chemical changes during composting of plant residues reduce their mineralisation in soil and cancel the priming effect
文章编号: N19062604
期刊: Soil Biology and Biochemistry
作者: T.Z. Lerch, M.F. Dignac, M. Thevenot, C. Mchergui, S. Houot
更新时间: 2019-06-26
摘要: Applying composts is useful for increasing soil carbon (C) stocks and improving agricultural productivity. In order to understand the effects of composts on soil organic matter (SOM) formation and mineralisation, ¹³C-labelled plant residues, previously composted or not, were incubated in an arable soil. The amount of ¹³C was quantified in the CO₂ evolved, the dissolved organic carbon (DOC) and in the microbial biomass (MB). Composting decreased (from 29 to 9%) the proportion of the plant residue labile pool and increased the residence time of both labile and more stable pools from 21 to 34 days and 1.5–5.5 years, respectively. At the beginning of the incubation, the amounts of ¹³C in the DOC and MB were significantly higher when adding fresh residues than composted ones to the soil. A priming effect on SOM mineralisation (+21% over 3 years) was only observed for non-composted residues. These differences were attributed to changes in the chemical composition of plant materials during composting (less sugars and lipids, more lignins). In terms of C budget, the total loss of CO₂ (including the composting process and the SOM priming by fresh residues) was comparable for both treatments after 600 days of incubation.

25749. 题目: Effect of alpha-hydroxy acids on transformation products formation and degradation mechanisms of carbamazepine by UV/H₂O₂ process
文章编号: N19062603
期刊: Science of The Total Environment
作者: Gang Lu, Jiangyong Hu
更新时间: 2019-06-26
摘要: The role of dissolved organic matters (DOM) in the matrix of water on the degradation of refractory pharmaceutical has aroused broad concerns. However, The effect of alpha-hydroxy acids as vulnerable aliphatic acids in the water on the degradation of Carbamazepine (CBZ) has been lack of research. The decomposition kinetics and transformation products (TPs) of CBZ by UV/H2O2 process were studied in the existence of glycolic acid (GA) and lactic acid (LA) and the degradation pathways were proposed. Both GA and LA had significantly negative effects on the decomposition kinetics and mineralization of CBZ by UV/H₂O₂ process. The declination of steady-state OH concentration in the presence of GA and LA justified the negative effects. GA was demonstrated to be stronger at scavenging and competing OH with CBZ, compared with LA, with the rate constant of slightly less than the common OH scavenger methanol. One-step dosing mode of H₂O₂ was better than multi-step dosing mode for CBZ decomposition, especially in the presence of GA and LA. The identification of TP253a, TP253b, TP271a, TP271b, TP226, and TP180 in the absence and presence of GA and LA were performed by HPLC-MS/MS and two main degradation pathways were presented. Except for TP271a and TP271b, GA and LA retarded the abundance peaks of other four TPs, of which the formation kinetics rates and decay kinetics rates were negatively affected. Tailing peaks of all TPs caused by GA and LA inevitably resulted in the toxicity of the treated effluent of UV/H₂O₂ process even when CBZ was decomposed completely. Therefore, alpha-hydroxy acids play important roles in determining the fate and transformation of refractory pharmaceuticals in AOPs treatment.
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25750. 题目: Formation of iodinated trihalomethanes and noniodinated disinfection byproducts during chloramination of algal organic matter extracted from Microcystis aeruginosa
文章编号: N19062602
期刊: Water Research
作者: Chao Liu, Mahmut S. Ersan, Michael J. Plewa, Gary Amy, Tanju Karanfil
更新时间: 2019-06-26
摘要: The increasing occurrence of harmful algal blooms in surface waters may increase the input of algal organic matter (AOM) to the dissolved organic matter pool. The formation of iodinated trihalomethanes (I-THMs) and noniodinated disinfection byproducts (DBPs) in synthetic water containing AOM extracted from Microcystis aeruginosa was investigated under chloramination (preformed and in-situ formed chloramine, NH₂Cl and Cl₂-NH₂Cl, respectively) and chlorination (Cl₂) processes. AOM is much more favorable for iodine incorporation than natural organic matter (NOM). For example, the formation of I-THM from AOM is much higher than NOM isolate extracted from treated water (e.g., 3.5 times higher in the NH₂Cl process), and thus higher iodine utilization and substitution factors from AOM were observed. Short contact time (2 min) chlorination in Cl₂-NH₂Cl process leading to the formation of halogenated intermediates favored I-THM formation, compared with NH₂Cl process. However, further increasing chlorine contact time from 5 min to 24 h facilitated the conversion from iodide to iodate and thus I-THM formation decreased. Meanwhile, the formation of noniodinated THM4, haloacetonitriles (HANs), and haloacetaldehydes (HALs) increased. Factors including concentrations of AOM and bromide, pH and chlorine/nitrogen ratios influenced the formation of I-THMs and noniodinated DBPs. To evaluate the benefit of mitigating I-THM formation over the risk of noniodinated DBP formation, measured DBPs were weighed against their mammalian cell toxicity indexes. Increasing the chlorine exposure increased the calculated cytotoxicity based on concentrations of measured I-THMs and noniodinated DBPs since unregulated HANs and HALs were the controlling agents.
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25751. 题目: Effects of carbon materials on the formation of disinfection byproducts during chlorination: Pore structure and functional groups
文章编号: N19062601
期刊: Water Research
作者: Min Zhang, Xuan Wang, Tingting Du, Huihui Wang, Huizhi Hao, Yingying Wang, Yao Li, Tianwei Hao
更新时间: 2019-06-26
摘要: Release of carbon materials (CMs) into water and wastewater treatment systems occurs due to their increasing utilization as adsorbents for water treatment. When the CMs, mixed with natural organic matter (NOM), interact with disinfectants used during water treatment (e.g. chlorine), the released CMs can affect the formation of disinfection byproducts (DBPs). In this study, three common CMs were investigated to reveal their possible effects and the mechanisms of DBP formation during the chlorination of NOM. The experimental results indicate that DBPs generation decreased by 10–40% in the presence of CMs when Suwannee River humic acid (SRHA) was chlorinated. The adsorption of SRHA by CMs was hypothesized as the major cause for the DBPs inhibition. CMs could irreversibly adsorb DBP precursors in their mesopores through π-π bonding and hydrophobic effects. OH groups on the surface of CMs were shown to be critical for DBPs inhibition through linking with the OH or COOH groups on the surface of NOM via hydrogen bonding. The study also showed that water chemistry parameters, such as pH and salinity, can affect DBP formation by changing the adsorption of NOM onto CMs. With diverse NOM components, the presence of CMs resulted in decreased formation of trichloromethane from 57.1 μg/L to 23.8, 38.4, and 40.4 μg/L when coal-made activated carbon (CAC), wheat straw-made BC pyrolyzed at 300 °C (WSBC300), and multiwalled carbon nanotubes (MWCNTs), respectively, were added to surface water; and from 30.6 μg/L to 20.0, 19.2, and 13.2 μg/L when CAC, WSBC300, and MWCNTs, respectively, were added to wastewater.

25752. 题目: Deforestation releases old carbon
文章编号: N19062508
期刊: Nature Geoscience
作者: Alf Ekblad, David Bastviken
更新时间: 2019-06-25
摘要: Deep soil carbon in tropical catchments can be rapidly mobilized to rivers upon land-use change to agriculture, suggest analyses of dissolved organic carbon. Such carbon stocks had been thought stable for millennia.

25753. 题目: Impact of different combinations of water treatment processes on the concentration of disinfection by-products and their precursors in swimming pool water
文章编号: N19062507
期刊: Environmental Science & Technology
作者: Bertram Skibinski, Stephan Uhlig, Pascal Müller, Irene Slavik, Wolfgang Uhl
更新时间: 2019-06-25
摘要: To mitigate microbial activity in swimming pools and to ensure hygienic safety for bathers, pool systems have a recirculating water system ensuring continuous water treatment and disinfection by chlorination. A major drawback associated with the use of chlorine as disinfectant is its potential to react with precursor substances present in pool water to form harmful disinfection byproducts (DBPs). In this study, different combinations of conventional and advanced treatment processes were applied to lower the concentration of DBPs and their precursors in pool water by using a pilot-scale swimming pool model operated under reproducible and fully controlled conditions. The quality of the pool water was determined after stationary concentrations of dissolved organic carbon (DOC) were reached. The relative removal of DOC (Δccin–1) across the considered treatment trains ranged between 0.1 ± 2.9% and 7.70 ± 4.5%, where conventional water treatment (coagulation and sand filtration combined with granular activated carbon (GAC) filtration) was revealed to be the most effective. Microbial processes in the deeper, chlorine-free regions of the GAC filter have been found to play an important role in the degradation of organic substances. Almost all treatment combinations were capable of removing trihalomethanes to some degree and trichloramine and dichloroacetonitrile almost completely. However, the results demonstrated that effective removal of DBPs across the treatment train does not necessarily result in low DBP concentrations in the basin of a pool. This raises the importance of the DBP formation potential of the organic precursors, which has been shown to depend strongly on the treatment concept applied. Irrespective of the filtration technique employed, treatment combinations employing UV irradiation as a second treatment step revealed higher concentrations of volatile DBPs in the pool compared to those employing GAC filtration as a second treatment step. In the particular case of trichloramine, results confirm that its removal across the treatment train is not a feasible mitigation strategy because it cannot compensate for the fast formation in the basin.

25754. 题目: Stokes Shift and Specific Fluorescence as Potential Indicators of Organic Matter Hydrophobicity and Molecular Weight in Membrane Bioreactors
文章编号: N19062506
期刊: Environmental Science & Technology
作者: Kang Xiao, Bingjun Han, Jianyu Sun, Jihua Tan, Jinlan Yu, Shuai Liang, Yuexiao Shen, Xia Huang
更新时间: 2019-06-25
摘要: Hydrophobicity and molecular weight (MW) are two fundamental properties of dissolved organic matter (DOM) in wastewater treatment systems. This study proposes fluorescence Stokes shift and specific fluorescence intensity (SFI) as novel indicators of hydrophobicity and MW. These indicators originate from the energy gap and photon efficiency of the fluorescence process and can be readily extracted from a fluorescence excitation–emission matrix (EEM). The statistical linkages between these indicators and hydrophobicity/MW were explored through investigation of DOM across 10 full-scale membrane bioreactors treating municipal wastewater. Stokes shift was found to exhibit a general rule among the hydrophobicity components in the order of hydrophilic substances (HIS) < hydrophobic acids (HOA) < hydrophobic bases (HOB). The Stokes shift of 1.2 μm–1 is a critical border, above which the relative fluorescence correlated significantly with the HOA-related content (Pearson’s r = 0.8). With regard to MW distribution (<1, 1–10, 10–100, and >100 kDa), SFI was found to be the most sensitive to the change of MW of <1 kDa proportion, especially at the excitation/emission wavelengths of 200–320/310–550 nm (r > 0.9). Hydrophobicity-related π conjugation and MW-dependent light exposure might be responsible for the correlations. These fluorescence indicators may be useful for convenient monitoring of DOM in wastewater treatment systems.

25755. 题目: Mobilization of aged and biolabile soil carbon by tropical deforestation
文章编号: N19062505
期刊: Nature Geoscience
作者: Travis W. Drake, Kristof Van Oost, Matti Barthel, Marijn Bauters, Alison M. Hoyt, David C. Podgorski, Johan Six, Pascal Boeckx, Susan E. Trumbore, Landry Cizungu Ntaboba, Robert G. M. Spencer
更新时间: 2019-06-25
摘要: In the mostly pristine Congo Basin, agricultural land-use change has intensified in recent years. One potential and understudied consequence of this deforestation and conversion to agriculture is the mobilization and loss of organic matter from soils to rivers as dissolved organic matter. Here, we quantify and characterize dissolved organic matter sampled from 19 catchments of varying deforestation extent near Lake Kivu over a two-week period during the wet season. Dissolved organic carbon from deforested, agriculturally dominated catchments was older (14C age: ~1.5 kyr) and more biolabile than from pristine forest catchments. Ultrahigh-resolution mass spectrometry revealed that this aged organic matter from deforested catchments was energy rich and chemodiverse, with higher proportions of nitrogen- and sulfur-containing formulae. Given the molecular composition and biolability, we suggest that organic matter from deforested landscapes is preferentially respired upon disturbance, resulting in elevated in-stream concentrations of carbon dioxide. We estimate that while deforestation reduces the overall flux of dissolved organic carbon by approximately 56%, it does not significantly change the yield of biolabile dissolved organic carbon. Ultimately, the exposure of deeper soil horizons through deforestation and agricultural expansion releases old, previously stable, and biolabile soil organic carbon into the modern carbon cycle via the aquatic pathway.

25756. 题目: Seasonal changes in the chemical composition and reactivity of dissolved organic matter at the land-ocean interface of a subtropical river
文章编号: N19062504
期刊: Environmental Science and Pollution Research
作者: Liyang Yang, Qiong Cheng, Wan-E Zhuang, Hui Wang, Wei Chen
更新时间: 2019-06-25
摘要: Dissolved organic matter (DOM) is a critical component in aquatic ecosystems, yet its seasonal variability and reactivity remain not well constrained. These were investigated at the land-ocean interface of a subtropical river (Minjiang River, SE China), using absorption and fluorescence spectroscopy. The annual export flux of dissolved organic carbon (DOC) from the Minjiang River (5.48 × 10¹⁰ g year⁻¹) was highest among the rivers adjacent to the Taiwan Strait, with 72% occurring in spring and summer. The freshwater absorption coefficient a₂₈₀, DOC-specific UV absorbance SUVA₂₅₄ and humification index HIX were higher, while the spectral slope S_275–295 and biological index BIX were lower in summer than in winter. This suggests intensified export of terrestrial aromatic and high molecular weight constituents in the rainy summer season. Six fluorescent components were identified from 428 samples, including humic-like C1–C3, tryptophan-like C4 and C6, and tyrosine-like C5. The freshwater levels of four components (C1, C2, C4, and C6) were lower while that of C5 was higher in the wet season than in the dry season, suggesting contrasting seasonal variations of different constituents. Laboratory experiments were performed to assess the effects of photochemical and microbial degradation on DOM. Photo-degradation removed chromophoric and fluorescent DOM (CDOM and FDOM) effectively, which was stronger (i) for high molecular weight/humic constituents and (ii) during summer under higher solar radiation. Microbial degradation under laboratory controlled conditions generally showed little effect on DOC, and had smaller impact on CDOM and FDOM in winter than in summer. Overall, this study showed notable seasonal changes in the chemical composition and reactivity of DOM at the land-ocean interface, and demonstrated the significant effects of photo-degradation.

25757. 题目: Peatland Volume Mapping Over Resistive Substrates With Airborne Electromagnetic Technology
文章编号: N19062503
期刊: Geophysical Research Letters
作者: Sonia Silvestri, Craig W. Christensen, Asgeir O. K. Lysdahl, Helgard Anschütz, Andreas A. Pfaffhuber, Andrea Viezzoli
更新时间: 2019-06-25
摘要: Despite the importance of peatlands as carbon reservoirs, a reliable methodology for the detection of peat volumes at regional scale is still missing. In this study we explore for the first time the use of airborne electromagnetic (AEM) to detect and quantify peat thickness and extension of two bogs located in Norway, where peat lays over resistive bedrock. Our results show that when calibrated using a small amount of field measurements, AEM can successfully detect peat volume even in less ideal conditions, that is, relatively resistive peat over resistive substrata. We expect the performance of AEM to increase significantly in presence of a conductive substratum without need of calibration with field data. The organic carbon content retrieved from field surveys and laboratory analyses combined with the 3‐D model of the peat extracted from AEM allowed us to quantify the total organic carbon of the selected bogs, hence assessing the carbon pool.

25758. 题目: Impact of prolonged rice cultivation on coupling relationship among C, Fe, and Fe-reducing bacteria over a 1000-year paddy soil chronosequence
文章编号: N19062502
期刊: Biology and Fertility of Soils
作者: Yalong Liu, Yuqi Dong, Tida Ge, Qaiser Hussain, Ping Wang, Jingkuan Wang, Yong Li, Georg Guggenberger, Jinshui Wu
更新时间: 2019-06-25
摘要: Long-term soil chronosequences are valuable model systems for investigating pedogenesis and investigating the process of element coupling. Here, we assessed the coupling relationships among C, Fe, and Fe-reducing bacteria (Anaeromyxobacter, Geobacter, and Shewanella) in a paddy soil chronosequence of approximately 50 to 1000 years. Soils of the chronosequence originated from tidal marsh under nearly identical landscape and climate conditions. During 1000 years of rice cultivation, soil organic carbon (SOC) contents in surface horizons (0–20 cm) increased from 10.4 to 21.8 g kg⁻¹. In contrast, total Fe contents declined from 59.6 to 45.1 g kg⁻¹ during the initial 50 years of paddy rice cultivation and then further decreased at a low rate of 0.004 g kg⁻¹ soil year⁻¹ (equivalent to 10 kg ha⁻¹ soil year⁻¹). Organically complexed Fe oxides (Fe_p) increased from 219 to 642 mg g⁻¹ with increasing time of pedogenesis, but free total Fe oxides (Fe_d) and amorphous Fe oxides (Fe_o) declined at early stage of soil development, followed by a slow accumulation at later stages of the chronosequence. Gene copy numbers of Anaeromyxobacter and Geobacter increased from 4.6 × 10⁵ and 3.6 × 10⁶ copies g⁻¹ to 3.8 × 10⁷ and 3.6 × 10⁷ copies g⁻¹ dry soil with continuous paddy rice cultivation, while concurrently Shewanella gene abundance decreased gradually from 4.5 × 10⁵ to 9.3 × 10⁴ copies g⁻¹ dry soil. Using structural equation modeling (SEM), different coupling relationships were observed among C, Fe, and Fe-reducing bacteria for the first 300 years of paddy chronosequence and thereafter. Overall, all Fe-reducing bacteria did not show consistent variation. With the stable microbial community and iron oxide fractions, the microbially mediated dissimilatory coupling relationship between C and Fe becomes simple during 1000 years of paddy soil development.

25759. 题目: Effect of NaCl on nitrification performance and extracellular polymeric substance characteristic of Klebsiella sp. TN-10
文章编号: N19062501
期刊: Environmental Science and Pollution Research
作者: Dan Li, Yao Jin, Jun Huang, Chongde Wu
更新时间: 2019-06-25
摘要: Klebsiella sp. TN-10, isolated from tannery wastewater, exhibited excellent nitrification ability cultivated in media with NaCl contents ranging from 0 to 35 g/L. Analysis of antioxidative enzyme activities of TN-10 stressed by NaCl showed that the stain produced more superoxide dismutase (SOD) and catalase (CAT) to fight against salt stress conditions. Moreover, the auto-aggregation index of TN-10 decreased with the increment of NaCl contents, which is consistent with results of zeta potentials. Extinction-emission matrix (EEM) and Fourier-transform infrared (FT-IR) spectrum analyses showed that the compositions of extracellular polymeric substances (EPS) by TN-10 after NaCl shock were similar. Furthermore, proteins and polysaccharides were the main components of EPS, and the contents were greatly influenced by salinity. Then, circular dichroism (CD) spectrum was used to calculate the contents of each protein secondary structure. These results provided further insights into the knowledge of nitrification characteristics, auto-aggregation performance, and EPS compositions of TN-10 during NaCl shock.

25760. 题目: Soil Organic Carbon Stocks across Hydrologic Schemes in Freshwater Wetlands of the Chi River Basin, Northeast Thailand
文章编号: N19062403
期刊: Wetlands
作者: Utain Chanlabut, Bhuvadol Gomontean, Akeapot Srifa
更新时间: 2019-06-24
摘要: The role of freshwater wetlands as soil organic carbon (SOC) stocks has been well documented for temperate regions but less is well known in tropical regions. In this study, SOC stocks were compared within three different hydrologic schemes in six freshwater wetlands of the Chi River Basin in tropical Northeast Thailand. The SOC concentration exhibited a decrease with increased depth and significantly differed among the hydrologic schemes (9.15 ± 0.84, 8.66 ± 0.67, and 5.53 ± 0.49 g C kg−1 for the intermittently flooded zone, saturated zone, and permanently flooded zone, respectively). The SOC stocks at 50 cm depth were significantly highest in the intermittently flooded zone (69.05 ± 10.86 Mg C ha−1), followed by the saturated zone and the permanently flooded zone (66.06 ± 7.75 and 43.39 ± 5.83 Mg C ha−1, respectively). Total SOC stocks among wetlands ranged from 123.30 to 291.29 Mg C ha−1. These differences indicate the spatial variability of SOC within wetland locations and among wetlands. The study demonstrates an important ecosystem service of these wetlands as carbon stocks, and it will be useful for management and policy planning of the wetlands in the Chi River Basin.