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25141. 题目: Towards a better understanding of the aggregation mechanisms of iron (hydr)oxide nanoparticles interacting with extracellular polymeric substances: Role of pH and electrolyte solution
文章编号: N18071815
期刊: Science of The Total Environment
作者: Di Lin, Peng Cai, Caroline L. Peacock, Yichao Wu, Chunhui Gao, Wanxi Peng, Qiaoyun Huang, Wei Liang
更新时间: 2018-07-18
摘要: Extracellular polymeric substances (EPS) are ubiquitous in the soil and water environment and interact strongly with mineral surfaces. However, these interactions and their impacts on the behavior and fate of minerals remain poorly understood. Here, for a better understanding of the colloidal stability of minerals in the environment, we investigated the aggregation of goethite (α-FeOOH) nanoparticles (NPs) in the presence of EPS from Bacillus subtilis under different environmental conditions (pH, ionic strength and ionic valence). Results showed that the aggregation processes of goethite NPs are determined by the solution chemistry, and the colloidal stability of goethite NPs is strongly influenced by the addition of EPS. In the absence of ionic strength, the addition of EPS promotes the aggregation of goethite NPs only when the pH (pH = 6) is less than the point of zero charge for the goethite nanoparticles (pHpzc ≈ 8). In the presence of ionic strength, the aggregation rate of goethite NPs increases with increasing concentration of NaCl, NaNO3 and Na2SO4 solutions, and after the addition of EPS solution, the critical coagulation concentrations (CCC) of goethite NPs are increased from 43.0, 56.7 and 0.39 mM to 168.0, 304.9 and 126.2 mM in the three electrolyte solutions, indicating that the addition of EPS inhibits the aggregation of goethite NPs. While in Na3PO4 solution, when the concentration of Na3PO4 solution ranged from 0 to 1 mM, the aggregation rate of goethite NPs increases first, followed by a decrease, and with the concentration of Na3PO4 solution exceeding 1 mM, the aggregation rate of goethite NPs increases again, due to the charge screening by sodium counter ions. This study provides a fundamental understanding of the behavior of goethite NPs in natural soil and water environments.

25142. 题目: Carbon-nitrogen removal in a structured-bed reactor (SBRRIA) treating sewage: Operating conditions and metabolic perspectives
文章编号: N18071814
期刊: Journal of Environmental Management
作者: Rafael B. Moura, Carla E.D. Santos, Dagoberto Y. Okada, Tiago H. Martins, Ant?nio Djalma N. Ferraz Júnior, Márcia H.R.Z. Damianovic, Eugenio Foresti
更新时间: 2018-07-18
摘要: The present study evaluated the efficiency of a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) to promote nitrogen and carbon removal from domestic sewage. The intermittent aeration and the recycling rate of 3 keeps the desired mixing degree inside the SBRRIA. Four different operational conditions were tested by varying the hydraulic retention time (HRT) from 12 to 8 h and aerated and non-aerated periods (A/NA) from 2 h/1 h and 3 h/1 h. At the THD of 8 h and A/NA of 2 h/1 h there was a decrease in the nitrification process (77.5%) due to the increase of organic matter availability, affecting the total-N removal performance. However, by increasing the aerated period from 2 h to 3 h, the nitrification efficiency rose to 91.1%, reaching a total-N removal efficiency of 79%. The system reached a maximum total-N loading removed of 0.117 kgN.m 3.d 1 by applying an HRT of 8 h and an intermittent aeration cycle of 3 h, aerated and 1 h non-aerated. The simultaneous nitrification and denitrification (SND) process was related to a complex interplay among microorganisms affiliated mostly to Acidovorax sp., Comamonas sp., Dechloromonas sp., Hydrogenophaga sp., Mycobacterium sp., Rhodobacter sp., and Steroidobacter sp.

25143. 题目: Dynamic contribution of microbial residues to soil organic matter accumulation influenced by maize straw mulching
文章编号: N18071813
期刊: Geoderma
作者: Xiao Liu, Feng Zhou, Guoqing Hu, Shuai Shao, Hongbo He, Wei Zhang, Xudong Zhang, Lijun Li
更新时间: 2018-07-18
摘要: Soil degradation is a serious problem in northeast China due to the routine removal of aboveground crop residues under conventional tillage systems; thus, crop residue retention becomes an essential approach for maintaining and improving soil organic matter (SOM) in this area. However, the impact of returning crop residue on microbial-driven SOM accumulation remains unclear. In this context, an 8-year field experiment with maize straw mulching (SM) was conducted in northeast China to evaluate how maize straw return may influence the dynamic contribution of microbial residues to SOM accumulation. Conventional cultivation was used as a control (CR), in which only 10 cm of aboveground maize biomass remained after the annual harvest. Soil samples (0–10 cm) were collected after the annual harvest for the measurement of soil organic carbon (SOC) and amino sugars (AS). Based on a first-order model, we found that soil microbial residue accumulation in this temperate arable soil might reach a steady state within decades under a specific agricultural management practice. Maize straw mulching both strengthened the retention ability of soil microbial residues and expanded their accumulation capacity. According to the glucosamine to muramic acid ratio, maize straw mulching facilitated the accumulation of fungal residues more than bacterial ones. Compared to maize residue removal, maize straw mulching accelerated the accumulation of microbial residues in SOM and enhanced the contribution of microbial residues to SOM sequestration in the surface soil, likely elucidating the pivotal mechanisms by which the “4/1000” initiative goal for agricultural soil will be met, at least for the first 10 years. Because bacterial residues are actively involved in SOM turnover while fungal residues dominantly contribute to SOM accrual enhanced by maize straw return compared to maize residue removal, we conclude that SOM in this arable field might be stabilized at a higher sequestration capacity under management with maize straw mulching.

25144. 题目: Carbon dynamics in surface and deep soil in response to increasing litter addition rates in an agro-ecosystem
文章编号: N18071812
期刊: Geoderma
作者: Tanvir Shahzad, Faiza Anwar, Sabir Hussain, Faisal Mahmood, Muhammad Saleem Arif, Amna Sahar, Muhammad Farrakh Nawaz, Nazia Perveen, Muhammad Sanaullah, Khadeeja Rehman, Muhammad Imtiaz Rashid
更新时间: 2018-07-18
摘要: Increasing atmospheric CO2 concentration and nitrogen deposition are predicted to increase fresh carbon (C) inputs in soils because of higher net primary productivity. However, relationship between soil C cycling and increased inputs of fresh C in soils is not clear. Moreover, most of the studies on soil organic carbon (SOC) focus on upper 20 cm although >50% SOC is present below this depth. We designed this study to unravel the response of SOC to 0% (control), 0.3%, 0.6%, 1.2% and 2.4% addition of maize litter (C4) to a surface (0–15 cm) and deep layers (55–75 cm) of a C3 soil. The isotopic difference between the maize litter and soil allowed distinguishing soil-derived (native) CO2-C from litter-derived CO2-C and calculating the priming effect (PE). Total respiration was measured over 78 d incubation whereas the PE was determined 39 d and 78 d after incubation. Our results showed that all the litter addition levels induced PE -stimulation of mineralization of the extant SOC in response to availability of fresh organic matter (FOM)- in surface and deep soil layers. Moreover, the PE was significantly higher in the deep than surface soil layer in response to all litter additions, except 2.4% treatment during the 2nd harvest. This result suggests that the deep SOC would mineralize at higher rates under similar supply of FOM to surface and deep soils in this agroecosystem. We also showed a significantly positive linear relationship between PE and litter addition rates for both soils implying continuous loss of SOC under increasing organic matter inputs. In conclusion, our study reveals that the deep soil C would be more vulnerable to priming effect in response to litter addition than the surface soil.

25145. 题目: Influencing factors on the removal of pharmaceuticals from water with micro-grain activated carbon
文章编号: N18071811
期刊: Water Research
作者: Thiago Caique Alves, Alba Cabrera-Codony, Damià Barceló, Sara Rodriguez-Mozaz, Adilson Pinheiro, Rafael Gonzalez-Olmos
更新时间: 2018-07-18
摘要: The removal efficiency of 6 micro-grain AC (μGAC) was examined for 23 selected pharmaceutical compounds, usually found at trace level in municipal wastewater treatment plant (WWTP) effluents. Two different sets of experiments were carried out using distilled water and a real WWTP secondary effluent in order to understand the adsorption mechanisms of pharmaceuticals, including the role of the presence of background organic matter. Physical and chemical properties of μGACs and target pollutants were checked for their potential to predict the pharmaceutical removal. Textural properties of μGACs, and especially the mesopore volume, seemed to play the most important role during the adsorption without background organic matter whereas the chemistry of the μGACs, such as the presence of surface oxygen groups and the point of zero charge, could have more influence in the experiments with WWTP effluent water. Positively charged molecules are better adsorbed due to the influence of the background organic matter and the presence of oxygenated groups in the surface of the μGACs. The UV254 removal correlated well with the pharmaceutical removal and it is confirmed as an indicator to control the performance of pharmaceuticals adsorption with μGACs in tertiary treatment.

25146. 题目: A horizontal permeable reactive barrier stimulates nitrate removal and shifts microbial ecology during rapid infiltration for managed recharge
文章编号: N18071810
期刊: Water Research
作者: Sarah Beganskas, Galen Gorski, Tess Weathers, Andrew T. Fisher, Calla Schmidt, Chad Saltikov, Kaitlyn Redford, Brendon Stoneburner, Ryan Harmon, Walker Weir
更新时间: 2018-07-18
摘要: We present results from field experiments linking hydrology, geochemistry, and microbiology during infiltration at a field site that is used for managed aquifer recharge (MAR). These experiments measured how a horizontal permeable reactive barrier (PRB) made of woodchips impacted subsurface nitrate removal and microbial ecology. Concentrations of dissolved organic carbon consistently increased in infiltrating water below the PRB, but not in un-amended native soil. The average nitrate removal rate in soils below the PRB was 1.5 g/m2/day NO3-N, despite rapid infiltration (up to 1.9 m/d) and a short fluid residence time within the woodchips (≤6 h). In contrast, 0.09 g/m2/day NO3-N was removed on average in native soil. Residual nitrate in infiltrating water below the PRB was enriched in δ15N and δ18O, with low and variable isotopic enrichment factors that are consistent with denitrification during rapid infiltration. Many putative denitrifying bacteria were significantly enhanced in the soil below a PRB; Methylotenera mobilis and genera Microbacterium, Polaromonas, and Novosphingobium had log2 fold-changes of +4.9, +5.6, +7.2, and +11.8, respectively. These bacteria were present before infiltration and were not enhanced in native soil. It appears that the woodchip PRB contributed to favorable conditions in the underlying soil for enhanced nitrate removal, quantitatively shifting soil microbial ecology. These results suggest that using a horizontal PRB could improve water quality during rapid infiltration for MAR.

25147. 题目: Cytostatic drug removal using electrochemical oxidation with BDD electrode: Degradation pathway and toxicity
文章编号: N18071809
期刊: Water Research
作者: Ewa Maria Siedlecka, Aleksandra Ofiarska, Agnieszka Fiszka Borzyszkowska, Anna Bia?k-Bielińska, Piotr Stepnowski, Aleksandra Pieczyńska
更新时间: 2018-07-18
摘要: In the presented study, electrochemical oxidation of five anticancer drugs (5-fluorouracil (5-FU), ifosfamide (IF), cyclophosphamide (CF), methotrexate (MTX), imatinib (IMB)) using boron doped diamond (BDD) electrode was investigated. In the first step the operating parameters of electrolysis were optimized. Studies have demonstrated a significant influence of applying current density, temperature, pH of solution and initial concentration of 5-FU on the process efficiency. A comparison of the decomposition rate of all the tested drugs showed a decrease in the pseudo-first order rate constants in the following order: k(IMB) > k(MTX) > k(CF) ≈ k(IF) > k(5-FU). Mineralization current efficiency (MCE) was determined for all the drugs based on the removal amount of total organic carbon (TOC) and their values decreased in the same order as values of drug degradation rate k. Based on the identified degradation products, electrochemical oxidation pathways of the decomposed drugs were proposed. In the case of CF, IF and 5-FU the degradation process occurred mainly through ketonization, hydroxylation and dehalogenation, while MTX and IMB were decomposed by attack of hydroxyl radicals on benzyl position in parent compounds. An important part of the research was the evaluation of eco-toxicity of electrochemically treated drug solutions against Lemna minor. Toxicity of initial 5-FU and MTX solutions towards L. minor were observed but after electrochemical treatment its toxicity decreased. The opposite trend was observed for CF and IF. In this case no significant toxicity was observed for the initial solutions of these drugs, while after electrochemical treatment an increase in growth inhibition of L. minor was found.

25148. 题目: DOM from mariculture ponds exhibits higher reactivity on photodegradation of sulfonamide antibiotics than from offshore seawaters
文章编号: N18071808
期刊: Water Research
作者: Jieqiong Wang, Jingwen Chen, Xianliang Qiao, Yan Wang, Xiyun Cai, Chengzhi Zhou, Yaoling Zhang, Guanghui Ding
更新时间: 2018-07-18
摘要: Mariculture activities and river inputs lead to coastal seawaters with DOM levels that are comparable to or even higher than those in terrestrial water bodies. However, effects of seawater DOM, and especially of DOM occurring in areas impacted by mariculture, on photodegradation of organic micropollutants, are largely unknown. In this study, simulated sunlight irradiation experiments were performed to probe the effects of DOM extracted from mariculture impacted seawaters and from offshore areas, on photodegradation of three sulfonamide antibiotics (SAs). Results show that the SAs are transformed mainly by indirect photodegradation induced by triplet excited DOM (3DOM*). Compared with DOM from the more pristine coastal waters, the DOM from mariculture impacted areas undergoes less photobleaching, contains higher percentage of humic-like materials and higher proportions of aromatic and carbonyl structures. Thus, the DOM from mariculture areas exhibits higher rates of light absorption, higher formation quantum yields of 3DOM*, higher 3DOM* steady-state concentrations and higher reactivity on photodegradation of the SAs. Photochemistry of the seawater DOM is different from that reported for freshwater lake DOM. This study highlights the importance of probing the effects of DOM from coastal seawaters on photodegradation of organic micropollutants since coastal seawaters are sinks of many aquatic pollutants.

25149. 题目: Leachate from fine root litter is more acidic than leaf litter leachate: A 2.5-year laboratory incubation
文章编号: N18071807
期刊: Science of The Total Environment
作者: Toko Tanikawa, Saori Fujii, Lijuan Sun, Yasuhiro Hirano, Yosuke Matsuda, Kouhei Miyatani, Ryuusei Doi, Takeo Mizoguchi, Nagamitsu Maie
更新时间: 2018-07-18
摘要: Some tree species increase fine root production under soil acidification, thus changing the balance of litter input from leaves and roots. Litter leaches a significant amount of acidic materials during its decomposition, which might facilitate soil acidification. In this context, we focused on dissolved organic matter (DOM) as the major component of acidic materials. We hypothesized that both the quality and quantity of DOM, which control its function (i.e., proton supply), differ between leaf and root litter. To test this hypothesis, we conducted a 2.5-year laboratory incubation experiment using fresh fine roots and fresh green leaves as litter of two coniferous species (Cryptomeria japonica and Chamaecyparis obtusa) and investigated the leachate pH and DOM composition based on the optical properties. After the early stage of decomposition when flash leaching of DOM converged, the amount of dissolved organic carbon (DOC) leached from roots increased again and leachate pH declined. In contrast, DOC concentrations continued to decrease in leaf leachates during the incubation period, and the pH decrease was not as striking as that of root leachates. Optical properties (ultraviolet visible absorption and fluorescence) of DOM revealed that humic-like substances in DOM played a central role in the acidic pH of root leachates. The total amount of protons released from roots of C. japonica and C. obtusa is about 13 and 18 times higher, respectively, than that from leaves. These results imply that the increase of fine root biomass may induce a positive plant–soil feedback in acidic soils, affecting soil biogeochemical functions of terrestrial ecosystems.

25150. 题目: Retention and remobilization mechanisms of environmentally aged silver nanoparticles in an artificial riverbank filtration system
文章编号: N18071806
期刊: Science of The Total Environment
作者: Laura Degenkolb, George Metreveli, Allan Philippe, Anja Brandt, Kerstin Leopold, Lisa Zehlike, Hans-J?rg Vogel, Gabriele E. Schaumann, Thomas Baumann, Martin Kaupenjohann, Friederike Lang, Samuel Kumahor, Sondra Klitzke
更新时间: 2018-07-18
摘要: Riverbank filtration systems are important structures that ensure the cleaning of infiltrating surface water for drinking water production. In our study, we investigated the potential risk for a breakthrough of environmentally aged silver nanoparticles (Ag NP) through these systems. Additionally, we identified factors leading to the remobilization of Ag NP accumulated in surficial sediment layers in order to gain insights into remobilization mechanisms. We conducted column experiments with Ag NP in an outdoor pilot plant consisting of water-saturated sediment columns mimicking a riverbank filtration system. The NP had previously been aged in river water, soil extract, and ultrapure water, respectively. We investigated the depth-dependent breakthrough and retention of NP. In subsequent batch experiments, we studied the processes responsible for a remobilization of Ag NP retained in the upper 10 cm of the sediments, induced by ionic strength reduction, natural organic matter (NOM), and mechanical forces. We determined the amount of remobilized Ag by ICP-MS and differentiated between particulate and ionic Ag after remobilization using GFAAS. The presence of Ag-containing heteroaggregates was investigated by combining filtration with single-particle ICP-MS. Our study indicates that the breakthrough potential of Ag NP in riverbank filtration systems is generally low, but the aging in soil increases their mobility. Remobilization processes are associated to co-mobilization with natural colloids.

25151. 题目: Comparison of n-alkane molecular, carbon and hydrogen isotope compositions of different types of plants in the Dajiuhu peatland, central China
文章编号: N18071805
期刊: Organic Geochemistry
作者: Bingyan Zhao, Yiming Zhang, Xianyu Huang, Ruya Qiu, Zhiqi Zhang, Philip A. Meyers
更新时间: 2018-07-18
摘要: Long chain n-alkanes preserved in peat deposits have been widely used to reconstruct paleoenvironmental and paleoecological changes. However, our knowledge of how the leaf wax molecular and isotopic compositions of peat sequences might respond to changes in plant communities is limited. This study investigates the n-alkane molecular, carbon and hydrogen isotopic compositions of plant species collected from the Dajiuhu peatland, central China. The results show that forb and graminoid plants growing in peatlands have a relatively higher carbon preference index of long-chain n-alkanes than shrubs, ferns and aquatic plants. The δ13C values of individual n-alkanes generally decrease with increasing chain lengths, and different plant groups have similar δ13C values of C31 and C33n-alkanes. An exception is Sphagnum, which has more negative δ13C values of C23 and C25 than those of its longer chain length homologues. Relative to peat pore water δD values in different seasons and different peat depths, the Dajiuhu plants normally exhibit relatively large hydrogen isotope fractionations, and the fractionations gradually increase from graminoid to forb to shrub. Taken together, these results highlight the influence of different kinds of vegetation on the collective molecular and isotopic ratios of n-alkanes in peat deposits.

25152. 题目: Mechanism of oxidation and catalysis of organic matter abiotic humification in the presence of MnO2
文章编号: N18071804
期刊: Journal of Environmental Sciences
作者: Yingchao Zhang, Dongbei Yue, Xu Wang, Wenfang Song
更新时间: 2018-07-18
摘要: Humification plays a critical role in the environmental fate of organic wastes, and MnO2 holds great promise for enhancing this reaction. However, the effects of MnO2 on the enhancement of the humification reaction remain ambiguous. To better reveal the mechanism by which MnO2 enhances the reaction and investigate the fate of the humification products, abiotic humification experiments were performed using increasing concentrations of dissolved organic matter (DOM) to a fixed amount of MnO2. DOM was represented by model humic precursors consisting of catechol, glucose and glycine. The results indicate that the reduction of MnO2 played a dominant role in the formation of fulvic-like acids (FLAs), and the subsequent reduction products, MnOOH and Mn(II), acted as catalysts in the formation of humic-like acids (HLAs). Moreover, CO2 release occurred during the formation of FLAs, and a strong linear correlation between CO2 release and the formation of FLAs was observed (p < 0.01), where 0.73–1.87 mg of CO2 was released per mg dissolved organic carbon (DOC) FLAs. Furthermore, the concentration of MnO2 had a pronounced influence on the product behavior, where a lower MnO2 concentration decreased the quantity of FLAs produced.

25153. 题目: Composition and bioavailability of dissolved organic matter in different water masses of the East China sea
文章编号: N18071803
期刊: Estuarine, Coastal and Shelf Science
作者: Jin-qiang Guo, Sheng-kang Liang, Xiao-jiao Li, Wei Li, Yun-fei Wang, Rong-guo Su
更新时间: 2018-07-18
摘要: The degradation of dissolved organic matter (DOM) is affected by ocean currents, but this influence is poorly understood in the East China Sea (ECS), a dynamic shallow continental shelf characterized by several discrete water masses. This study investigates dissolved organic carbon (DOC), nitrogen (DON) and total dissolved amino acids (TDAA) in different water masses of the ECS. Bioassay experiments were also conducted to determine the labile fraction of DOM. Carbon-normalized yields of TDAA [TDAA (%DOC)] as well as the degradation index (DI) was used to investigate the diagenetic state of organic matter in different water masses. Generally, DOM concentration decreased from the Coastal Current Water (CCW), to the Shelf Mixed Water (SMW), to the Taiwan Warm Current Water (TWCW), and to the Kuroshio Current Water (KCW). DOM in CCW is relatively labile due to inputs from phytoplankton production, while that in the TWCW exhibits low bioavailability, which may be related to nutrient limitation leading to low productivity. The long residence time of the KCW resulted in a high degree of biodegradation associated with nutrient regeneration. Intrusion of nutrient-rich KCW may contribute to the high primary productivity in shelf water, while complex hydrodynamic processes and stratification may control DOM availability in SMW.

25154. 题目: Improved sludge dewaterability using persulfate activated with humic acid supported nanoscale zero-valent iron : Effect on sludge characteristics and reaction mechanisms
文章编号: N18071802
期刊: Environmental Science: Water Research & Technology
作者: Hao Li, Lei Song, Baohong Han, Hongwei Song
更新时间: 2018-07-18
摘要: n this study, nanoscale zero-valent iron (nZVI) supported on humic acid (HA) as a novle nanocomposite (nZVI/HA) was synthesized and characterized by field emission scanning electron microscope (FE-SEM), energy dispersive spectrometry (EDS), Fourier transform infrared (FTIR), and Brunauer–Emmett–Teller method. The nZVI/HA nanocomposite was used as persulfate (PS) activator to enhance sludge dewatering, and the specific resistance to filterability (SRF) of sludge decreased from 2.75×1013 m/kg to 0.217×1013 m/kg after conditioning. Subsequently, variation in extracellular polymeric substances (EPS) under chemical conditioning was investigated concretely to reveal the reaction mechanisms. Analysis of three-dimensional excitation emission matrix (3D-EEM), the reduction of aromatic protein and tryptophan-like protein content in tight-bound extracellular polymers substances (TB-EPS) is conducive for enhancing sludge dewateribility. In addition, the introduction of HA particles effectively decreased sludge compressibility relative to that of raw sludge by forming skeleton structures. The observed sludge microstructure properties clearly indicated that treated sludge floc induced the formation of additional pore structures and water channels.

25155. 题目: Microbial lipid production and organic matters removal from cellulosic ethanol wastewater through coupling Oleaginous yeasts and activated sludge biological method
文章编号: N18071801
期刊: Bioresource Technology
作者: Xueling Zhang, Meng Liu, Xu Zhang, Tianwei Tan
更新时间: 2018-07-18
摘要: In this paper, a novel strategy for lipid production through coupling oleaginous yeasts and activated sludge biological methods by cultivation of Rhodotorula glutinis in cellulosic ethanol wastewater was studied. Under optimal conditions in wastewater medium (dilution ratio of 1:2 and glucose supplement of 40 g/L), the maximum biomass and lipid content as well as the lipid yield reached 11.31 g/L, 18.35% and 2.08 g/L, with the associated removal rates of COD, TOC, NH4+-N, TN and TP reaching 83.15%, 81.81%, 85.49%, 70.52% and 67.46%, respectively. Cellulosic ethanol wastewater treated by the anaerobic-aerobic biological process resulted in removal of COD, NH4+-N, TP and TN reaching 67.55%, 94.17%, 90.16% and 48.89%, respectively. The reused water was used to dilute medium of R. glutinis for microbial lipid production reaching 2.38 g/L and caused positive effects on the accumulation of biomass and lipid.

25156. 题目: Determining phytolith-occluded organic carbon sequestration using an upgraded optimized extraction method: indicating for a missing carbon pool
文章编号: N18071701
期刊: Environmental Science and Pollution Research
作者: Ning Han, Yufei Yang Email, Yang Gao, Zhuo Hao, Jing Tian, Tiantian Yang, Xianwei Song
更新时间: 2018-07-17
摘要: Phytolith-occluded organic carbon (PhytOC) is considered one of the most promising terrestrial carbon (C) sinks. Different methods are used for phytolith extraction from wet-ashing techniques and the subsequent determination of PhytOC content from soil. This is in order to optimize the wet-ashing techniques and to improve estimation accuracy of C sequestration potential of phytoliths from soil. Results show that the organic matter removal and carbonate removal protocol, applying sonication, has a significant effect on phytolith extraction. Namely, the sequential removal of first organic matter and then carbonates applied to such methods could eliminate greater than 17.14, 46.68, and 26.17% extraneous material compared to other methods. Moreover, phytoliths extracted using methods that apply sonication eliminated 7.49, 42.70, and 17.57% more extraneous material than methods that did not. Additionally, the procedure associated with the second oxidation step significantly influenced the determination of PhytOC content, that is, 29.34, 33.75, 26.41, and 64.64% of excess organic C were oxidized during this step. The upgraded optimal method we recommend for phytolith extraction in association with wet-ashing techniques and the subsequent determination of PhytOC content is therefore to first apply sonication, then the second oxidation step, and finally the removal of organic matter. Using this optimal upgraded method, we estimated the C sequestration potential of phytoliths from the soil of slash pine in China at 0.51 Mt. C. Furthermore, using this upgraded optimal method increased the precision of the carbon sequestration potential of phytoliths from soil by up to 63.83%.

25157. 题目: Plant litter quality affects the accumulation rate, composition, and stability of mineral-associated soil organic matter
文章编号: N18071507
期刊: Soil Biology and Biochemistry
作者: S. Carolina Córdova, Dan C. Olk, Ranae N. Dietzel, Kevin E. Mueller, Sotirios V. Archontouilis, Michael J. Castellano
更新时间: 2018-07-15
摘要: Mineral-associated organic matter (MAOM) is a relatively large and stable fraction of soil organic matter (SOM). Plant litters with high rates of mineralization (high quality litters) are hypothesized to promote the accumulation of MAOM with greater efficiency than plant litters with low rates of mineralization (low-quality litters) because litters with high rates of mineralization maximize the synthesis of microbial products and most MAOM is microbial-derived. However, the effect of litter quality on MAOM is inconsistent. We conducted four repeated short-term incubations (46-d each) of four plant litters (alfalfa, oats, maize and soybean) in two low-carbon subsoils (sandy loam and silty loam) with and without nutrient addition. Our short-term incubations focused on the initial stage of litter decomposition during the time when litter quality has a measureable effect on mineralization rates. Plant litter quality had a much greater effect on litter-C mineralization rate and MAOM-C accumulation than did soil type or nutrient addition. Soils amended with high-quality oat and alfalfa litters had greater MAOM-C accumulation than soils amended with low-quality maize and soybean litters. However, soils amended with high-quality litters also had greater litter-C mineralization than soils amended with low-quality litters. As a result, the accumulation of MAOM-C per unit of litter-C mineralization was lower in soils amended with high-vs. low-quality litters (0.65 vs. 1.39 g MAOM-C accumulated g-1 C mineralized). Cellulose and hemicelluose indices of accumulated MAOM were greater for maize and soybean than oats and alfalfa, however, most carbohydrates in MAOM were plant-derived regardless of litter quality. At the end of the incubations, more of the accumulated MAOM-N was potentially mineralizable in soils amended with high quality litters. Nevertheless, most of the litter-C remained as residual litter; just 12% was mineralized to CO2 and 13% was transferred to MAOM. Our results demonstrate several unexpected effects of litter quality on MAOM stabilization including the direct stabilization of plant-derived carbohydrates.

25158. 题目: Plant rhizosphere oxidation reduces methane production and emission in rewetted peatlands
文章编号: N18071506
期刊: Soil Biology and Biochemistry
作者: Svenja Agethen, Michael Sander, Carolin Waldemer, Klaus-Holger Knorr
更新时间: 2018-07-15
摘要: The global loss of peatlands, by drainage or peat extraction, has encouraged measures to restore these ecosystems and their function as carbon sinks. However, there is a potential of high emissions of the potent greenhouse gas CH4 from restored peatlands. Vascular plants, which often dominate restored sites, play a key role in determining the amount of emitted CH4: The plants can either fuel methanogenesis by supplying labile carbon or attenuate methanogenesis by transferring oxygen into the rhizosphere. To quantify the net effect of these counteracting processes, we tested in a two-pronged approach CH4 production, emission, and the underlying processes in (1.) monoliths of three different restored cutover peatlands and in (2.) mesocosms with Eriophorum vaginatum, E. angustifolium and Juncus effusus versus controls with Sphagna and bare peat. Despite waterlogged, and thus persisting anoxic conditions, concentrations of dissolved CH4 remained close to zero in all tested monoliths. We ascribe this finding to two factors: The poor decomposability of the peat material, as determined in anoxic incubations, and the availability of alternative electron acceptors that sustained anaerobic respiration and competitively suppressed methanogenesis. While inorganic electron acceptor pools were small and rapidly diminished, dissolved organic matter provided constant electron acceptor capacity, indicating that reducible moieties in the organic matter were continuously re-oxidized in the rhizosphere of all tested vascular plant species. This continuous re-oxidation of the dissolved organic matter correlated with plant growth rates (R2 = 0.6–0.8), suggesting that supply of oxygen through the aerenchyma of plant roots regenerated electron acceptor capacity in the rhizosphere. Vascular plants may have differential effects on the net ecosystem exchange, however, our findings suggest that CH4 concentrations and emissions may remain low in restored cutover peatlands for months to years. Thus, waterlogging and vascular plant cover of degraded cutover peatlands does not necessarily create hot-spots of CH4 emissions.

25159. 题目: Influence of ancient anthropogenic activities on the mangrove soil microbiome
文章编号: N18071505
期刊: Science of The Total Environment
作者: Luciano F. Huergo, Daniel V. Rissi, Andressa S. Elias, Maria V. Gon?alves, Marcos V. Gernet, Flávio Barreto, Gilson W. Dahmer, Rodrigo A. Reis, Fábio O. Pedrosa, Emanuel M. Souza, Rose A. Monteiro, Valter A. Baura, Eduardo Balsanelli, Leonardo M. Cruz
更新时间: 2018-07-15
摘要: Mangroves are highly productive ecosystems located at the transition between the terrestrial and marine environments. Mangroves play an important role in carbon storage, nutrient cycling and support for the marine food web. Mangrove soils are formed by fine particles rich in organic carbon and are subject to constant fluctuations in oxygen, salinity and nutrient availability due to fresh water flux and tidal variations. Microbes play an important role in nutrient cycling in mangrove soils; however, studies on the mangrove soil microbiome are scarce. Here we compare the microbiome of pristine mangrove soil located in an environmentally protected area in Guaratuba, Southern Brazil, with the microbiome of mangrove soil affected by the presence of carbonaceaous debris eroding from an archeological site known as Sambaqui. We show that although the Sambaqui site has a major effect on soil chemistry, increasing the soil pH by 2.6 units, only minor changes in the soil microbiome were detected indicating resilience of the microbial community to pH variations. The high alpha diversity indexes and predicted metabolic potential suggest that the mangrove soil microbiome not only provides important ecological services but also may host a broad range of microbes and genes of biotechnological interest.

25160. 题目: Probing algogenic organic matter (AOM) by size-exclusion chromatography to predict AOM-derived disinfection by-product formation
文章编号: N18071504
期刊: Science of The Total Environment
作者: Lap-Cuong Hua, Jr-Lin Lin, Shu-Ju Chao, Chihpin Huang
更新时间: 2018-07-15
摘要: High-performance size exclusion chromatography (HPSEC) coupled with peak-fitting technique was used to probe molecular weight (MW) properties of algogenic organic matter (AOM). The qualitative and quantitative MW information derived was used to predict AOM-derived disinfection by-product (DBP) formation. We resolved overlapping HPSEC chromatograms of all AOM samples into six major peaks with R2 > 0.996. This study gave significant insight into the HPSEC profiles of AOM, in which resolved peaks A and B (biopolymers) and peak C (humic substances) showed a strong correlation with the formation of carbonaceous-DBPs (C-DBPs). This likely resulted from the abundance of aromatic structures and conjugated CC double bonds in their chemical nature. Our results also indicated the importance of algal cells, including intra-cellular and cell-bound organic matter, over extra-cellular organic matter as precursors to C-DBP formation. The application of the information extracted from HPSEC profiles associated with the fluorescent components of AOM showed great improvements in the predictability of THMs, HAAs, and C-DBPs with R2 > 0.7 and p < 0.05. The outcome of this study will significantly benefit effective control of AOM-derived DBP formation by the chlorination of eutrophic waters.