论文检索

总访问量：6130410次

总访客量：494056人

所有论文

31541. 题目: Differential responses of carbon‐degrading enzymes activities to warming: implications for soil respiration
文章编号: N18071903
期刊: Global Change Biology
作者: Ji Chen, Yiqi Luo, Pablo García‐Palacios, Junji Cao, Marina Dacal, Xuhui Zhou, Jianwei Li, Jianyang Xia, Shuli Niu, Huiyi Yang, Shelby Shelton, Wei Guo, Kees Jan van Groenigen
更新时间: 2018-07-19
摘要: Extracellular enzymes catalyze rate‐limiting steps in soil organic matter decomposition, and their activities (EEAs) play a key role in determining soil respiration (SR). Both EEAs and SR are highly sensitive to temperature, but their responses to climate warming remain poorly understood. Here, we present a meta‐analysis on the response of soil cellulase and ligninase activities and SR to warming, synthesizing data from 56 studies. We found that warming significantly enhanced ligninase activity by 21.4% but had no effect on cellulase activity. Increases in ligninase activity were positively correlated with changes in SR, while no such relationship was found for cellulase. The warming response of ligninase activity was more closely related to the responses of SR than a wide range of environmental and experimental methodological factors. Furthermore, warming effects on ligninase activity increased with experiment duration. These results suggest that soil microorganisms sustain long term increases in SR with warming by gradually increasing the degradation of the recalcitrant carbon pool.

31542. 题目: Effect of contrasting tillage and cropping systems on soil aggregation, carbon pools and aggregate‐associated carbon in rainfed Vertisols
文章编号: N18071902
期刊: European Journal of Soil Science
作者: J. Somasundaram, R. S. Chaudhary, D. Awanish Kumar, A. K. Biswas, N. K. Sinha, M. Mohanty, K. M. Hati, P. Jha, M. Sankar, A. K. Patra, R. Dalal, S. K. Chaudhari
更新时间: 2018-07-19
摘要: Worldwide, conservation agriculture practices involving minimal soil disturbances and retention of crop residue (>30%) have been practised increasingly and recognized to enhance soil health by optimizing key soil attributes. However, little information is available on the short‐term effects of conservation agriculture practices on soil properties under rainfed Vertisols of Central India. Thus, our aim was to study the short‐term effects of contrasting tillage treatments and cropping systems on soil aggregation, aggregate‐associated carbon (C), carbon pools and crop productivity. This study comprised three tillage systems (TS), reduced tillage (RT), no tillage (NT) with retention of crop residue and conventional tillage (CT), together with four cropping systems (CS), namely soya bean (Glycine max L.) + pigeon pea (Cajanus cajan L.) (2:1), soya bean–wheat (Titricum durum L.), maize (Zea mays L.) + pigeon pea (1:1), and maize–chickpea Cicer arietinum L.). The experiment was laid out in a split‐plot design with three replicates. Soil samples were collected at four depths: 0–5, 5–15, 15–30 and 30–45 cm from the experimental field after completion of four crop cycles. Results indicated that at depths 0–5 and 5–15 cm, tillage and cropping system had a significant effect on aggregate mean weight diameter (MWD). The MWDs of 0.97 and 0.94 mm were larger for NT than CT (0.77 and 0.83 mm) at 0–5‐ and 5–15‐cm depths, respectively. Water‐stable aggregates (WSAs) were also larger for NT (70.74%) and RT (70.09%) than CT (59.50%) at 0–5 cm. Tillage practice, cropping system and their interaction had a greater effect (P < 0.05) on the content of aggregate‐associated C for large macroaggregates (LM). There was more aggregate‐associated C for NT and RT at 0–5‐cm depth than for CT. Cropping system also had a significant effect (P < 0.05) on aggregate‐associated C at 0–5‐cm depth. Soil organic C (%) fractions were in the order of non‐labile >very labile >less labile >labile for 0–5‐ and 5–15‐cm depths after four crop cycles. Less labile and non‐labile C fractions contributed >50% of TOC, indicating a more recalcitrant form of carbon present in the soil. Tillage had no significant effect (P > 0.05) on crop yields after four crop cycles. Conservation agriculture can have a positive effect on aggregate stability, aggregate‐associated C and different carbon pools in a Vertisol.

31543. 题目: Ash and fire, char, and biochar in the environment
文章编号: N18071901
期刊: Land Degradation & Development
作者: Yakov Kuzyakov, Agustin Merino， Paulo Pereira
更新时间: 2018-07-19
摘要: Fire is an extreme event leading to rapid and dramatic losses of carbon (C), nutrients, and ballast elements from ecosystems and leaving ash and char on the soil surface. This affects soil processes, properties, and functions. Similar effects can be induced by applying biochar—the product of artificial pyrolysis of plant materials and organic wastes. The nutrients in ashes remaining after a fire or in biochar after pyrolysis will be leached within a few years, and only the highly condensed material will remain in the soil over centuries and millennia. This Special Issue (SI) is devoted to ash, fire, char, and biochar in the environment, with a special focus on soil processes and properties. We begin by comprehensively summarizing the positive and negative effects of fire, ash, char, and biochar on the physical, chemical, and biological properties of soils. We then review the 15 papers contributing to this SI. The first group of studies focuses on reconstructing fires during the Holocene and then linking them to human activities and land use. These studies clearly concluded that the fire frequency strongly increased with human invasion and occupation, and that charcoal properties are useful in reconstructing anthropogenic activities. The second group of studies is mainly devoted to changes in physical, chemical, and biological soil properties as well as to interactions between soil functions depending on fire, ash, and char properties. The final group describes the effects of biochar on soil properties and functions such as nutrient availability, C sequestration, microbial diversity and community structure, and heavy metal fixation. The overall conclusion is that fire and the remaining ash and char as well as the application of biochar have short‐ and long‐term consequences for soil. Despite the dramatic effects of fire on vegetation, these factors have many positive effects on soil properties and functions, whereby the influences extend from local, landscape, and regional scales to the global scale.

31544. 题目: Quantification of lipid biomarkers in sedimentary contexts: comparing different calibration methods
文章编号: N18071817
期刊: Organic Geochemistry
作者: Antonio V. Herrera-Herrera, Carolina Mallol
更新时间: 2018-07-18
摘要: The analysis of lipid biomarkers has gained increasing importance within environmental and archaeological fields because they are representative of particular plant and animal sources. Accurate quantification of such compounds is essential to obtaining significant information. In this paper, accuracy in the quantification of n-alkanes (as model compounds) in sedimentary contexts was studied using three different approaches: proportions of areas with regards to an internal standard, instrumental calibration and matrix-matched calibration. Alkanes were extracted by ultrasonic assisted solid-liquid extraction and analyzed by gas chromatography coupled to mass spectrometry. Instrumental calibration curves were obtained with determination coefficients (R2) higher than 0.9900. The matrix effect was studied (in the range between -100% and 140%) and matrix-matched calibration curves with R2 above 0.9904 were obtained. Matrix matched calibration provided the best results (percentages in the range 10-130%) when compared with instrumental calibration (1-142%) and no calibration (2-274%). Four sediment samples from an archaeological Neanderthal site were analyzed with the three quantification methods and a Student s t test demonstrated that the results obtained were significantly different: Concentrations were non-uniformly under- or overestimated, and the highest peak and the alkane profile varied with the different methods. According to these data, matrix-matched calibration should be the preferred method for quantification since results are more accurate with only a small amount of extra work. This method requires that control sediment samples are collected at the site under consideration.

31545. 题目: Influence of new agromining cropping systems on soil bacterial diversity and the physico-chemical characteristics of an ultramafic soil
文章编号: N18071816
期刊: Science of The Total Environment
作者: Ramez F. Saad, Ahmad Kobaissi, Guillaume Echevarria, Petra Kidd, Magdalena Calusinska, Xavier Goux, Emile Benizri
更新时间: 2018-07-18
摘要: Most of the research dedicated to agromining has focused on cultivating a single hyperaccumulator plant, although plant diversity has been shown to positively modify soil characteristics. Hence, we compared the effect of cropping a nickel-hyperaccumulator Alyssum murale with a legume (Vicia sativa) to A. murale's mono-culture, on the bacterial diversity and physico-chemical characteristics of an ultramafic soil. A pot experiment with 5 replicates was conducted in controlled conditions for 11 months. The treatments studied were: co-cropping and rotation vs. mineral fertilization controls and bare soil. The introduction of legumes induced a clearly positive effect on the soil's microbial biomass carbon and nitrogen. Arylsulfatase and urease activities tended to be enhanced in the co-cropping and rotation treatments and to be lessened in the mineral fertilization treatments. However, β-glucosidase and phosphatase activities were seen to decrease when legumes were used. Our results showed that the rotation treatment induced a higher organic matter content than the fertilized control did. Actinobacteria was the most-represented bacterial phyla and had lower relative abundance in treatments associating legumes. Conversely, the relative abundance of Acidobacteria and Gemmatimonadetes phyla increased but not significantly in treatments with legumes. The relative abundance of Chloroflexi phylum was shown to be significantly higher for the fertilized rotation control. The relative abundance of β-Proteobacteria subphylum increased but not significantly in treatments with legumes. NMDS analysis showed a clear separation between planted treatments and bare soil and between co-cropping and rotation and fertilized controls. Shannon index showed reduction in microbial diversity that was mainly due to chemical inputs in the soil. This study showed that these new cropping systems influenced both the bacterial diversity and the physico-chemical characteristics of an ultramafic soil. In addition, this study provides evidence that mineral fertilization can negatively impact bacterial communities and some of their functions linked to biogeochemical cycles.

31546. 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.

31547. 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.

31548. 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.

31549. 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.

31550. 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.

31551. 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.

31552. 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.

31553. 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.

31554. 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.

31555. 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.

31556. 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.

31557. 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.

31558. 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.

31559. 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.

31560. 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.